Patent Application
20220119269
The present disclosure relates to the use of renewable energy in ammonia synthesis; more particularly, the present disclosure relates to the electrification of an ammonia synthesis plant; still more particularly, the present disclosure relates to a reduction in environmental emissions, such as carbon dioxide, by reducing the combustion of hydrocarbons (e.g., natural gas/fossil fuels) for fuel in an ammonia synthesis plant.
Chemical synthesis plants are utilized to provide a variety of chemicals. Often, a dedicated fuel is burned or ‘combusted’ to provide heat of reaction for chemical synthesis, energy to heat one or more process streams, energy to vaporize liquids (e.g., boil water used as a diluent), energy to do work (e.g., drive a compressor or pump), or energy for other process operations throughout the chemical synthesis plant. Such burning or combustion of fuels results in the production of flue gases, which can be harmful to the environment, and also results in a loss of energy efficiency of the process. Likewise, steam is often conventionally utilized as a plant-wide heat and/or energy transfer fluid within chemical synthesis plants. The steam utilized for the heat and/or energy transfer is often produced via the combustion of a fuel, resulting in the production of additional flue gas and further energy efficiency losses during the chemical synthesis. Additionally, the use of a material that could otherwise be utilized as a reactant for combustion as a fuel also reduces an amount of the desired chemical product produced in the chemical synthesis plant from a given amount of the material. Accordingly, a need exists for enhanced systems and methods of chemical synthesis whereby an amount of fuels, especially fossil fuels, burned to provide energy is reduced or eliminated. Desirably, such systems and methods also provide for an increase in energy efficiency and/or a decrease in emissions, such as emissions of greenhouse gases (GHG), by the chemical synthesis plant.
Herein disclosed is an ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream comprising natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or a combination thereof; a syngas generation section comprising one or more reformers operable to reform the feed stream to produce a reformer product stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer product stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that, relative to a conventional ammonia synthesis plant, more of the energy required by the ammonia synthesis plant, the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
Also disclosed herein is an ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream comprising a carbon-containing material, such as natural gas, methane, propane, butane, LPG, naphtha, coal and/or petroleum coke; a syngas generation section comprising one or more reformers operable to the pretreated feed stream to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising at least one shift reactor operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising at least one ammonia synthesis reactor operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy required by the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by electricity.
Further disclosed herein is an ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no steam is utilized for mechanical work.
Also disclosed herein is an ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no flue gas is produced.
Further disclosed herein is an ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured for no combustion other than optionally within an autothermal reformer (ATR) of the syngas generation section.
Also disclosed herein is an ammonia synthesis plant comprising an electrically heated steam reformer operable to provide hydrogen and an electrically powered air separation unit (ASU) operable to provide nitrogen for the ammonia synthesis.
Further disclosed herein is an ammonia synthesis plant comprising: a purification section operable to receive a hydrogen stream and a stream of nitrogen, wherein the stream of nitrogen is optionally from a source disparate from a source of the hydrogen stream, optionally remove at least one component from the hydrogen stream and/or the nitrogen stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy supplied for compression and heating within the purification section, the ammonia synthesis section, or the entire ammonia synthesis plant, is supplied from a non-carbon based energy source, a renewable energy source, electricity, and/or renewable electricity.
For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.
It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed compositions, methods, and/or products may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated hereinbelow, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.
While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently disclosed subject matter belongs.
As utilized herein, an ‘intermittent energy source’ or ‘IES’ is any source of energy that is not continuously available for conversion into electricity and outside direct control because the used energy cannot be stored or is economically undesirable. The availability of the intermittent energy source may be predictable or non-predictable. A renewable intermittent energy source is an intermittent energy source that is also a source of renewable energy, as defined hereinbelow. ‘Intermittent electricity’ refers to electricity produced from an IES.
As utilized herein, ‘renewable energy’ and ‘non-fossil based energy (ENF)’ includes energy derived from a sustainable energy source that is replaced rapidly by a natural, ongoing process, and nuclear energy. Accordingly, the terms ‘renewable energy’ and ‘non-fossil based energy (ENF)’ refer to energy derived from a non-fossil fuel based energy source (e.g., energy not produced via the combustion of a fossil fuel such as coal or natural gas), while ‘non-renewable’ or ‘fossil based energy (EF)’ is energy derived from a fossil fuel-based energy source (e.g., energy produced via the combustion of a fossil fuel). Fossil fuels are natural fuels, such as coal or gas, formed in the geological past from the remains of living organisms. Accordingly, as utilized herein, ‘renewable’ and ‘non-fossil based energy (ENF)’ include, without limitation, wind, solar power, water flow/movement, or biomass, that is not depleted when used, as opposed to ‘non-renewable’ energy from a source, such as fossil fuels, that is depleted when used. Renewable energy thus excludes fossil fuel based energy (EF) and includes biofuels.
As utilized herein, ‘non-carbon based energy (ENC)’ is energy from a non-carbon based energy source (e.g., energy not produced via the combustion of a carbon-based fuel such as a hydrocarbon), while carbon based energy (EC) is energy from a carbon-based energy source (e.g., energy produced via the combustion of a carbon-based fuel such as a hydrocarbon). Nuclear energy is considered herein a renewable, non-fossil (ENF) based energy and a non-carbon based energy (ENC). Carbon-based energy (EC) can thus be renewable (e.g., non-fossil fuel based) or non-renewable (e.g., fossil fuel-based). For example, various carbon-based biofuels are herein considered renewable, carbon-based energy sources.
As utilized herein, ‘renewable electricity’ indicates electricity produced from a renewable energy source, while ‘non-renewable electricity’ is electricity produced from a non-renewable energy source. As utilized herein ‘non-carbon based electricity’ indicates electricity produced from a non-carbon based energy source, while ‘carbon-based electricity’ is electricity produced from a carbon-based energy source.
For example, in embodiments, renewable electricity and/or heat throughout the herein-disclosed ammonia synthesis plant can be provided by the combustion of renewable hydrocarbons that come from renewable (e.g., biological) sources. For example, renewable electricity can, in embodiments, be produced via the combustion of an ENF/EC energy source comprising methane produced in a digester fed with agricultural wastes. Likewise, in embodiments, an ENF/EC energy source comprising synthesis gas produced using short cycle carbon waste materials can be utilized as a fuel (e.g., combusted to produce renewable electricity and/or heat). Desirably, the carbon dioxide generated by such combustion is recaptured (e.g., by the growth of a new crop).
As utilized herein, ‘externally’ combusting a fuel refers to combusting a fuel outside of a reactor, e.g., in a furnace. Combustion as a part of the primary reaction (e.g., combustion which takes place with reforming in autothermal reforming (ATR)) would not be considered ‘externally’ combusting. As utilized herein, a ‘dedicated’ fuel is a fuel or portion of a feed stream introduced solely to provide fuel value (e.g., combustion heat) and not be converted into product.
As utilized herein, ‘heat transfer steam (SHT)’ indicates steam produced solely or primarily as an energy or heat transfer medium (e.g., steam not utilized as a diluent and/or reactant).
As utilized herein, ‘net’ heat input or removal refers to heat input or removal that results in primary energy consumption, e.g., heat input or removal not provided from another section or stream of the plant, e.g., not provided via heat exchange with another process stream. Similarly, ‘net’ energy refers to energy that results in primary energy consumption, e.g., energy not provided from another section or stream of the plant, e.g., thermal energy not provided via heat exchange with another process stream.
As utilized herein, ‘powering’ indicates supplying with mechanical and/or electrical energy.
As utilized herein, ‘heating’ indicates supplying with thermal energy. As utilized herein ‘cooling’ indicates the removal of thermal energy therefrom. As utilized herein, ‘direct’ heating or cooling refer to heating or cooling without the use of a heat transfer medium/fluid; ‘indirect’ heating or cooling refer to heating or cooling via a heat transfer medium/fluid.
As utilized herein, ‘most’ or ‘a majority’ indicates more than 50% or more than half.
As utilized herein, a ‘desired’ parameter (e.g., desired temperature) may refer to an intended or target value for the parameter, for example a predetermined value such as a set-point value used for process control.
Amount of electricity consumed: References to consumption of electricity may refer to a rate at which electricity is used (e.g., in MW), as measured at a particular location. For example, a rate may be calculated at the boundary of each electrified furnace or at an overall olefin synthesis plant boundary. This calculation may consider all electricity used within that location.
Flue gas: A mixture of gases that may be produced by the burning of fuel or other materials in a power station and/or industrial plant, where the mixture of gases may be extracted via ducts.
Flue gas heat recovery: Flue gas heat recovery may refer to the extraction of useful thermal energy from hot flue gases, for example by passing said hot flue gas over one or more heat exchangers to raise the temperature of a cooler process fluid and/or change the phase of said fluid (e.g., boil water to raise steam). Any energy remaining in the flue gas after any flue gas heat recovery may be termed flue gas (energy) loss. A flue gas heat recovery section may be the equipment and corresponding location of said equipment used to recover flue gas heat. A lack of flue gas heat recovery section may mean there is no equipment or area where heat is recovered from hot flue gases.
Convection section: A convection section may be a portion of a furnace (e.g., steam cracking furnace or reforming furnace) where heat is recovered from hot flue gases by convective heat transfer. A lack of convection section may mean that there is no equipment or area where heat is recovered by convective heat transfer from hot flue gases.
“Steam-free” or “Substantially Steam-free”: “Steam free” may refer to a process where steam is not used to transfer energy from one process operation to another, or to bring energy into the process from outside. “Substantially steam-free” may mean that the use of steam to transfer energy from one process operation to another or to bring energy into the process from outside has been minimized such that the sum of all energy transfers using steam amount to less than approximately 10%, approximately 20%, or approximately 30% of the net energy provided. Steam used as a reactant, a diluent, obtained as a product, or directly mixed with a process stream may be termed “process steam” and is not included in this definition.
Primary energy transfer medium: A primary energy transfer medium may be a substance that is used to move energy in the form of thermal energy from one process operation to another, or to bring energy into a process. Note that a substance may serve more than one purpose in a process such as acting as a reactant or reaction diluent whilst also acting as a medium to transfer heat from one process operation to another. In such instances, the use of steam as reactant or diluent may be considered primary and the effect of also transferring heat may be considered secondary.
Resistive heating: Resistive heating may be heating by means of passing electric current through resistive units.
Inductive heating: Induction heating may be a process of heating an electrically conducting object (usually a metal) by electromagnetic induction.
Radiant heating: Radiant heating may be a process of heating an object via radiation from one or more hotter objects.
Externally combusting: Externally combusting may mean burning fuel to generate heat and transferring this heat to a process fluid across a surface (e.g., a tube wall) such that combustion products do not mix with the process fluid.
Thermoelectric device: A thermoelectric device may be a device for the direct conversion of temperature differences to electric voltage (or vice versa) across a thermocouple.
Isothermal operation: Isothermal operations may be operations at a constant temperature. Isothermal operation can keep temperature within 0.5%, 1%, 2%, 3%, 4%, 5% up to 10% of the predetermined operation temperature.
Convective heat transfer: Convective heat transfer may be the movement of heat from one place to another by the movement of a fluid or fluids.
Although the majority of the above definitions are substantially as understood by those of skill in the art, one or more of the above definitions can be defined hereinabove in a manner differing from the meaning as ordinarily understood by those of skill in the art, due to the particular description herein of the presently disclosed subject matter.
The unit operations used to effect this transformation require significant amounts of energy. Conventionally, this energy is primarily supplied by burning a fuel, often natural gas, to generate heat, denoted in
Electricity is usually only a small external input into most chemical production processes. Internal electrical requirements, such as for lighting or control, are usually so small as to be negligible, and in those few processes which require large amounts of electricity, for example, electrochemical reactors (e.g., the chlor-alkali process to make chlorine (Cl2) and sodium hydroxide (NaOH)), this electricity is commonly generated within the plant boundaries by the combustion of hydrocarbons, and, even when not generated within the plant boundaries, if the electricity is obtained by the combustion of hydrocarbons rather than renewably, such use of electricity is equivalent in terms of energy efficiency and CO2 emissions to on-site production of the electricity via hydrocarbon combustion.
Within most chemical production processes, energy consumption can conveniently be divided into three main categories. In the first such broad category, referred to herein as first category C1, heat is supplied directly as thermal energy by the combustion of a fuel (e.g., natural gas/fossil fuels) in a furnace. (As utilized, here, ‘directly’ indicates the absence of an intermediate heat transfer medium, such as steam.) These furnaces are often operated at high temperature and require large heat fluxes. The energy efficiency of such furnaces is limited by the heat losses in the furnace flue gas. Even where these heat losses are minimized by the cooling of the flue gas to recover energy, for example to generate steam or provide process heating, the conversion of the chemical energy contained in the fuel to usable thermal energy generally does not exceed 85 to 90%, even with substantial investment and loss of design and operating flexibility.
The second broad category, referred to herein as second category C2, of energy consumption in chemical processes comprises the heating of various chemical streams, primarily either to raise the temperature thereof to a desired reaction temperature or to provide energy for separations, most commonly distillation. Although some of this heat can be obtained by exchange with other chemical streams, it is most typically provided either by steam generated directly by the combustion of hydrocarbon fuels (e.g., natural gas/fossil fuels) or by heat transfer from the flue gas from high-temperature furnaces (e.g., from category C1). Most modern chemical processes include a relatively complicated steam system (or other heat transfer fluid system which will generically be referred to herein for simplicity as a steam heat transfer system) to move energy from where it is in excess to where it is needed. This steam system may include multiple pressure levels of steam to provide heat at different temperatures, as well as a steam and condensate recovery system, and is subject to corrosion, fouling, and other operational difficulties, including water treatment and contaminated condensate disposal. The fraction of the energy contained in the steam that can be used to heat process streams is generally limited to 90 to 95% by practical constraints on heat transfer, steam condensation, and boiler water recycle. If the steam was generated by an on-purpose external boiler, at most 80 to 85% of the chemical energy contained in the fuel will be used as heat by the chemical process, since an additional 10 to 15% or more will be lost to flue gas as in first category C1.
The third major category, referred to herein as third category C3, of energy usage in chemical processes is energy utilized to perform mechanical work. This work is primarily utilized for pressurizing and moving fluids from one place to another, and is used to drive rotating equipment such as pumps, compressors, and fans. This third category C3 also includes refrigeration equipment, since it is primarily powered by compression. In most chemical facilities, the energy for this work is provided by steam, obtained either by heat transfer with hot process streams, by heat transfer with partially-cooled flue gas streams from a furnace (e.g., in the convection section) in category C1, or directly from the combustion of hydrocarbons (e.g., natural gas/fossil fuels) in an on-purpose external boiler. Because of limitations on the conversion of thermal energy to mechanical work, the energy efficiency of these uses relative to the contained chemical energy of the hydrocarbons used as fuel is low, typically only 25 to 40%.
It has been unexpectedly discovered that using electricity (e.g., renewable and/or non-renewable electricity) to replace energy obtained from a hydrocarbon fuel in a chemical process can improve the process by increasing overall energy efficiency, while decreasing carbon dioxide emissions. In some cases, using electricity (e.g., renewable and/or non-renewable electricity) to replace energy obtained from a hydrocarbon fuel in a chemical process can also improve reliability and operability, decrease emissions of, for example, NOx, SOx, CO, and/or volatile organic compounds, and/or decrease production costs (e.g., if low-cost electricity is available).
According to embodiments of this disclosure, heat conventionally supplied as thermal energy by the combustion of a fuel (e.g., natural gas/fossil fuels) in a furnace and/or other heating in first category C1 is replaced by electrical heating. Electrical heat, electrical heating, generating heat electrically, electrical heater apparatus, and the like refer to the conversion of electricity into thermal energy available to be applied to a fluid. Such electrical heating includes, without limitation, heating by impedance (e.g., where electricity flows through a conduit carrying the fluid to be heated), heating via ohmic heating, plasma, electric are, radio frequency (RF), infrared (IR), UV, and/or microwaves, heating by passage over a resistively heated element, heating by radiation from an electrically-heated element, heating by induction (e.g., an oscillating magnetic field), heating by mechanical means (e.g. compression) driven by electricity, heating via heat pump, heating by passing a relatively hot inert gas or another medium over tubes containing a fluid to be heated, wherein the hot inert gas or the another medium is heated electrically, or heating by some combination of these or the like.
According to embodiments of this disclosure, the utilization of steam (or another heat transfer fluid) as in second category C2 is eliminated and/or any steam (or other fluid) utilized solely as an intermediate heat transfer medium is electrically produced or heated (e.g., via electrical heating of water).
According to embodiments of this disclosure, conventional rotating equipment (e.g., steam turbines) utilized in third category C3 is replaced with electrically driven apparatus. According to embodiments of this disclosure, heat removal in third category C3 is replaced by electrically-powered heat removal, e.g., cooling and/or refrigeration. Electrical cooling, electrical coolers, removing heat electrically, electrical cooling or refrigeration apparatus, and the like refer to the removal of thermal energy from a fluid. Such electrical cooling includes, without limitation, cooling by electrically powered apparatus. For example, and without limitation, electrical cooling can be provided by powering a refrigeration cycle with electricity, wherein a refrigerant is compressed by an electrically powered compressor. As another example, electrical cooling can be provided by powering a cooling fan that blows air, wherein the air cools a process fluid or element. In embodiments, electrical heating and cooling can be effected by any electrical source.
One of the main advantages to supplying needed energy via (e.g., renewable) electricity can be that the energy efficiency of the process will increase. Table 1 shows the energy efficiency of unit operations exemplifying the three categories of energy use in a chemical plant described above as C1, C2, and C3. It can be seen from Table 1 that the efficiency of each of the three categories of energy consumption is greater when electrical power is used. The gain can be greatest when steam drives for rotating equipment are replaced, according to embodiments of this disclosure, with electrical motors (as in third category C3, discussed hereinabove), which can operate with as much as three times the energy efficiency of steam drives. These gains are only realized when the electricity is derived from non-carbon based renewable sources, since the generation of electricity from carbon-based fuel combustion is only 30 to 45% energy efficient. Energy efficiency gains when using renewable electricity for heating applications (as in first category C1 and second category C2, discussed hereinabove) are smaller, but still significant. The net result is that less total energy will be used if renewable energy is used in place of carbon-based fuels (e.g., natural gas or other hydrocarbons).
According to this disclosure, non-carbon based energy, renewable energy, and/or electricity (e.g., from renewable and/or non-renewable sources) can be utilized rather than conventional energy sources in categories C1, C2, and/or C3 described hereinabove. In embodiments, electrification is utilized for a majority of or substantially all utilities. In embodiments, electrification is utilized for a majority of or substantially all unit operations. In embodiments, electrification is utilized for a majority of or substantially all utilities and unit operations. In embodiments, electrification is utilized for a majority of or substantially all process applications, engines, cooling and/or heating (e.g., electrically driven heat pumps, refrigeration, electrical heating), radiation, storage systems, or a combination thereof.
In embodiments, the non-carbon based and/or renewable energy source comprises wind, solar, geothermal, hydroelectric, nuclear, tide, wave, ocean thermal gradient power, pressure-retarded osmosis, or a combination thereof. In embodiments, the non-carbon based energy source comprises hydrogen. In embodiments, electricity for electrification as described herein is produced from such a renewable and/or non-carbon based energy source. In embodiments, some or all of the electricity is from a non-renewable and/or carbon-based source, such as, without limitation, combustion of hydrocarbons (e.g., renewable or non-renewable hydrocarbons), coal, or hydrogen derived from hydrocarbons (e.g., renewable or non-renewable hydrocarbons).
The majority of the CO2 emitted from most chemical plants is a result of fossil fuel combustion to provide energy for the plant. An additional benefit of using renewable energy in chemical synthesis as per embodiments of this disclosure is that the amount of greenhouse gases emitted will be significantly (e.g., by greater than or equal to at least 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100%) reduced relative to an equivalent conventional chemical synthesis plant or method in which hydrocarbons and/or fossil fuel(s) may be combusted. The burning of hydrocarbons (e.g., natural gas, methane) to generate energy results in the production of carbon dioxide (CO2); this production can be reduced or avoided by the use of renewable energy according to embodiments of this disclosure. In embodiments of this disclosure, the amount of CO2 produced per ton of product produced is reduced to less than or equal to about 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.75, 0.50, 0.30, 0.25, 0.20, 0.10, 0.05, or 0 tons CO2 per ton chemical product (e.g., ammonia). Furthermore, in embodiments of this disclosure, the use of renewable energy frees up these hydrocarbons (e.g., natural gas, methane) typically burned for fuel for use as a chemical feedstock (e.g., to make ammonia), which is a higher value use.
The use of renewable electricity in the production of chemicals can also lead to operational advantages. For example, in embodiments, electric power can be utilized to provide a more accurate and tunable input of heat, for example to control the temperature profile along a reactor or to change the temperature of specific trays in a distillation column. In embodiments, the use of electric heating in a reaction section (e.g., in a pyrolysis reaction section) leads to better controlled decoking and/or faster decoking. Without limitation, other examples include the use of electric powered refrigeration units to increase the efficiency of separations, and the replacement of inefficient stand-by gas-fired boilers with quick-acting on-demand electrical heaters and steam generators and for other utility uses. The use of electricity may also allow for significant operational advantages during start-up or shut-down, or to respond to process variability. In general, electricity as an energy source can be applied in specific locations and in precise and tunable amounts with a rapid response to process changes, leading to a variety of advantages over the use of thermal/combustion energy.
The use of renewable electricity according to embodiments of this disclosure can also increase the energy efficiency of utilities that supply energy to more than one chemical plant (e.g., an ammonia synthesis plant and a nearby methanol synthesis plant or an ammonia synthesis plant and a nearby olefin synthesis plant). For example, if the compressors in an air separation unit that provides oxygen and nitrogen to several different production facilities are powered with renewable electricity, significant energy gains can be achieved relative to supplying this power with steam derived from the combustion of natural gas.
Energy recovery may be provided, in embodiments, via high temperature heat pumps or vapor recompression. The plant may further comprise heat and/or energy storage, for example, for use when an intermittent energy source (IES) is utilized. In embodiments, waste heat can be upgraded to usable temperature levels via electrically driven heat pumps. In other embodiments, energy can be recovered as electricity when process stream pressures are reduced by using a power-generating turbine instead of a control valve. In other embodiments, energy can be recovered as electricity using thermoelectric devices.
The use of renewable electricity to replace natural gas or other hydrocarbons as a source of energy, according to embodiments of this disclosure, can be done as part of a retrofit of an existing chemical process (e.g., an existing ammonia synthesis plant) or as an integral component of the design of a new chemical plant (e.g., a new ammonia synthesis plant). In a retrofit, opportunities for using renewable energy can depend on elements of the existing design, such as the steam system; in a retrofit, careful examination of the entire energy balance and steam system will be required, as electrifying individual pieces of equipment without regard to these considerations may result in energy inefficiencies. In embodiments, as seen in Table 1, the highest efficiency gains are achieved by replacing steam drives for rotating equipment (e.g., in third category C3) with electric motors. However, differing objectives may lead to different choices in partial electrification; in embodiments, in some instances greater CO2 reductions at the expense of smaller increases in energy efficiency may sometimes be realized by first replacing hydrocarbon-fired furnaces (e.g., in first category C1). In embodiments, if thermal energy and/or steam are obtained from more than one hydrocarbon source, the most advantageous operation can be achieved by eliminating the most expensive and/or polluting fuel sources first. How much renewable energy can be included and to what extent existing fuel consumption and carbon dioxide (CO2) emissions can be decreased can vary depending on the application, and will be within the skill of those of skill in the art upon reading this disclosure.
In embodiments, planning for the use of renewable energy in the design of a grass-roots chemical facility (e.g., a grass-roots ammonia synthesis plant) can allow for more significant opportunities for better energy efficiency and lower CO2 emissions. In embodiments, powering all rotating equipment (e.g., in third category C3) with electricity is utilized to realize large gains in energy efficiency. In embodiments, substantially all (or a majority, or greater than 40, 50, 60, 70, 80, or 90%) electric heating (e.g., in first category C1 and/or second category C2) is utilized, and the inefficiencies due to the loss of heat in flue gas are substantially reduced or even avoided. In embodiments, the use of steam generated via the combustion of a fossil fuel (e.g., in second category C2) can be minimized or avoided altogether. In embodiments, a change in catalyst and/or a modification of reactor operating conditions is utilized to allow for less heat generation in a reactor and/or the production of fewer byproducts that are burned. In embodiments, a plant (e.g., ammonia synthesis plant) design based on the use of renewable electricity allows for enhanced optimization of separations operations, since the relative costs of compression and refrigeration are changed via utilization of renewable electricity as per this disclosure. Such enhanced separations can, in embodiments, also allow for further capture of minor byproducts from vent streams, freeing these minor products up for further use as feedstocks or products. Furthermore, the use of low-cost electricity, according to embodiments of this disclosure, may allow for the introduction of novel technologies such as, without limitation, hybrid gas and electric heaters, variable speed compressor drives, distributed refrigeration, heat pumps, improved distillation columns, passive solar heating of fluids, precise control of reactor temperature profiles, new materials of construction, and quench or cooling using electrically refrigerated diluents. If the cost of electricity is sufficiently low, utilization of such electricity as taught herein may favor the introduction of new electrochemical processes. For new construction, it may be less capital intensive to drive processes electrically, due, for example, to the lack of a (e.g., plant-wide) steam distribution system.
According to embodiments of this disclosure, non-carbon based energy, renewable energy, and/or electricity (renewable, non-renewable, carbon-based, and/or non-carbon based electricity) can be used in the production of nearly every chemical, including but not limited to methanol, ammonia, olefins (e.g., ethylene, propylene), aromatics, glycols, and polymers. Non-carbon based energy, renewable energy, and/or electricity can also be used, in embodiments, in the preparation of feedstocks for chemicals and for fuels production, such as in methyl tert-butyl ether (MTBE) synthesis, cracking, isomerization, and reforming. In such embodiments, some (e.g., at least about 10, 20, 30, 40, or 50%), a majority (e.g., at least about 50, 60, 70, 80, 90, or 95%), or all (e.g., about 100%) of the heating throughout the plant/process or a section thereof can be provided by electrical heating and/or some (e.g., at least about 10, 20, 30, 40, or 50%), a majority (e.g., at least about 50, 60, 70, 80, 90, or 95%), or all (e.g., about 100%) of the cooling throughout the plant/process or a section thereof can be provided by electrical cooling as described hereinabove. Disclosed hereinbelow is the use of renewable energy, non-carbon based energy, and/or electricity in ammonia synthesis applications.
The disclosures of U.S. Provisional Patent Application Nos. 62/792,612 and 62/792,615, entitled Use of Renewable Energy in Olefin Synthesis, U.S. Provisional Patent Application Nos. 62/792,617 and 62/792,619, entitled Use of Renewable Energy in Ammonia Synthesis, U.S. Provisional Patent Application Nos. 62/792,622 and 62/792,627, entitled Use of Renewable Energy in Methanol Synthesis, and U.S. Provisional Patent Application Nos. 62/792,631, 62/792,632, 62/792,633, 62/792,634, and 62/792,635, entitled Use of Renewable Energy in the Production of Chemicals, which are being filed on Jan. 15, 2019, are hereby incorporated herein for purposes not contrary to this disclosure.
This disclosure describes an ammonia synthesis plant for producing ammonia configured such that a majority of the net energy required by one or more sections, units, groups of like units, or unit operations of the ammonia synthesis plant is provided by non-carbon based energy (ENC) from a non-carbon based energy source (e.g., not produced via the combustion of a carbon-based fuel such as a hydrocarbon), from renewable energy (e.g., from non-fossil fuel derived energy (EN)), and/or from electricity. The ENC or EN source may, in embodiments, comprise, primarily comprise, consist essentially of, or consist of electricity. The ENC or EN source may, in embodiments, comprise, primarily comprise, consist essentially of, or consist of renewable electricity. In embodiments a portion (e.g., greater than or equal to about 5, 10, 20, 30, 40, 50), a majority (e.g., greater than or equal to about 50, 60, 70, 80, 90, or 95%), or all (e.g., about 100%) of the net energy needed by the overall ammonia synthesis plant, a section of the plant (e.g., a feed pretreating section, a syngas generation section, generally known and also referred to herein at times as a reforming section, a shift conversion section, a hydrogen and nitrogen purification section (sometimes referred to herein simply as a ‘hydrogen purification section’ or simply a ‘purification section’), and/or an ammonia synthesis and/or separation section (sometimes simply referred to as an ‘ammonia synthesis section’)), a unit or group of like units (e.g., compressors, power providing units, reboilers, heating units, cooling units, refrigerators, separators, distillation/fractionation columns, reformers, shift reactors) or unit operations (e.g., compressing, powering, reacting (e.g., reforming), separating, heating, cooling) of the plant, or a combination thereof is provided by electricity, renewable energy (e.g., non-fossil fuel derived energy (ENF)), and/or non-carbon based energy (ENC). In embodiments, electricity is provided from a renewable energy source, such as, without limitation, wind (e.g., via wind turbines), solar (e.g., photovoltaic (PV) panels or solar thermal), hydroelectric, wave, geothermal, nuclear, tide, biomass combustion with associated capture of CO2 in replacement crops, or a combination thereof. In embodiments a portion (e.g., greater than or equal to about 5, 10, 20, 30, 40, 50), a majority (e.g., greater than or equal to about 50, 60, 70, 80, 90, or 95%), or all (e.g., about 100%) of the electricity, renewable energy (e.g., non-fossil fuel derived energy (ENF), or non-carbon based energy (ENC) needed by the overall ammonia synthesis plant, a section of the plant (e.g., a feed pretreating section, a syngas generation section, a shift conversion section, a hydrogen and nitrogen purification section, and/or an ammonia synthesis section and/or ammonia separation section), a unit or a group of like units (e.g., compressors, power providing units, heating units, reboilers, cooling units, refrigerators, separators, distillation/fractionation columns, reactors, shift reactors) or unit operations (e.g., compressing, powering, reacting, separating, heating, cooling) of the ammonia synthesis plant, or a combination thereof, and conventionally provided in a similar ammonia synthesis plant via combustion of a fuel, a carbon-based fuel, and/or a fossil fuel and/or the use of steam (e.g., that was itself generated via the combustion of such a fuel) as an intermediate heat (and/or energy) transfer fluid, is provided without combusting a fuel, a carbon-based fuel, and/or a fossil fuel and/or without the use of steam generated by the combustion of such a fuel as an intermediate heat (and/or energy) transfer fluid. In embodiments, the net energy for the overall plant or one or more sections, units or groups of like units of the plant is provided by electricity from a renewable energy source. For example, in embodiments, heating is electrically provided via resistive heating or otherwise converting electrical energy into thermal energy and/or mechanical energy.
In embodiments, an ammonia synthesis plant of this disclosure is configured such that a majority (e.g., greater than 50, 60, 70, 80, or 90%) of the net energy needed for powering, heating, cooling, compressing, or a combination thereof utilized via the feed pretreating system, one or more syngas generators (e.g. steam reformers), a shift conversion system, a hydrogen purification system, an ammonia synthesis system, or a combination thereof, as described hereinbelow, is provided by electricity.
In embodiments, an ammonia synthesis plant according to embodiments of this disclosure is a large plant having a production capacity for ammonia of greater than or equal to about 100,000 tons per year, 500,000 tons per year, or 2,500,000 tons per year. At the larger sizes anticipated in this disclosure, the amount of energy provided by a non-carbon based energy source, a renewable energy source and/or electricity will be correspondingly large. In embodiments, a partially or completely electrified plant according to the methods of this disclosure will consume at least 25, 50, 100, 150, 200, 300, 400, or 500 MW of electricity.
Although a specific embodiment of an ammonia synthesis plant will be utilized to describe the electrification of an ammonia synthesis plant, as disclosed herein, it is to be understood that numerous arrangements of units and a variety of ammonia synthesis technologies can be electrified as per this disclosure, as will be obvious to those of skill in the art upon reading the description herein.
With reference to
As indicated in the ammonia synthesis block flow diagram of
H2O+CO→H2+CO2, (1)
and provide shifted reformer product 35. A hydrogen and nitrogen purification section 40 is operable to produce an ammonia synthesis feed stream (also referred to herein as a purified reformer product) 45 comprising purified hydrogen and nitrogen. An ammonia synthesis section 50 is operable to produce ammonia from the ammonia synthesis feed 45 and thus provide an ammonia product 55. In embodiments, substantially pure nitrogen is introduced just prior to introduction of the ammonia synthesis feed into ammonia synthesis section 50/150. It is to be understood that, in such embodiments, the gas purified in hydrogen and nitrogen purification section 40/140 does not comprise nitrogen.
As mentioned above and depicted in
According to this disclosure, when cooling process streams, as much heat as possible should be used to heat other process streams. However, below a certain temperature, further heat transfer is no longer effective or useful, and blowers, cooling water, and/or refrigeration (which require an energy input for heat removal) are utilized. In such embodiments, for example, heat exchangers, refrigeration units, or a combination thereof for altering the temperature of process streams may be powered electrically. In embodiments, steam is not utilized solely as an intermediate heat and/or energy transfer stream, and the plant or section(s) thereof do not comprise an elaborate steam system such as conventionally employed for energy transfer. In embodiments, steam is used as a heat transfer fluid and is not used to do mechanical work, for example to drive a pump or compressor. In embodiments, heating is provided via resistive heating. In embodiments, heating is provided via inductive heating.
Although not intending to be limited by the examples provided herein, a description of some of the ways an ammonia synthesis plant can be electrified according to embodiments of this disclosure will now be provided with reference to the exemplary ammonia synthesis block flow diagram of ammonia synthesis plant II of
As noted hereinabove with reference to the embodiment of
H2+RSH→RH+H2S(gas) (2).
The gaseous hydrogen sulfide can then be adsorbed and removed by passing it through beds of, for example, zinc oxide, where it is converted to solid zinc sulfide via the Equation (3):
H2S+ZnO→ZnS+H2O (3).
Feed purification apparatus utilized in feed pretreating section 10 can be any suitable contaminant/poison removal apparatus known to those of skill in the art. In embodiments, the pretreating section 10/110 is operable to provide the feed at a desired operating temperature and/or pressure for the downstream syngas generation or reforming section 20/120.
According to embodiments of this disclosure, feed pretreating can be effected with a reduced usage of non-carbon based energy, the use of renewable energy, and/or the use of electricity (e.g., electricity from renewable and/or non-renewable source(s)). For example: compressors of the pretreating section can be operated with electric motors rather than gas or steam driven turbines, heat input or removal needed in feed pretreating can be electrically provided, or a combination thereof. In embodiments, pressure reduction is utilized to generate electricity. In embodiments, feed pretreatment catalysts are regenerated using electrical heating and/or electrically-heated gas.
An ammonia synthesis plant according to this disclosure comprises a syngas generation section operable to reform the carbon-containing feed to produce hydrogen and carbon monoxide. The syngas generation section can include steam methane reforming, autothermal reforming, or both. In embodiments, a syngas generation section 120 comprises a steam methane reformer or bed, an autothermal reforming reactor or bed, and an adiabatic steam methane reforming reactor or bed.
Syngas generation section 20/120 can be operable to effect catalytic steam reforming of the (e.g., sulfur-free) methane feed to form hydrogen plus carbon monoxide via the reversible and equilibrium limited Equation (4):
CH4+H2O⇄CO+3H2 (4).
The syngas generation section 120 of the embodiment of
At autothermal reforming 120B, air 106 is added (e.g., via compressor or compression section C1) to the partially converted stream indicated at 121 and the oxygen in the air combusts with methane to generate carbon oxides, water, and heat. The exit temperature of the autothermal reformer at 120B can be about 1000° C., although some hotter and cooler zones may exist in the reactor. In the embodiment of
In the embodiment of
Conventionally, a fuel (e.g., natural gas, methane, purge gas from the ammonia synthesis section) is burned to provide heat Q1 needed to attain a desired reforming temperature. In embodiments of this disclosure, a desired steam reforming temperature is attained without burning a fuel. In embodiments of this disclosure, a desired steam reforming temperature is attained without burning a carbon-based fuel. Desirably, no natural gas or methane is burned as a fuel, as such natural gas or methane conventionally burned as a fuel can then be utilized as a feed to produce additional ammonia product according to embodiments of this disclosure.
In embodiments, steam reforming can be effected with a reduced usage of non-carbon based energy, the use of renewable energy, and/or the use of electricity (e.g., electricity from renewable and/or non-renewable source(s)). For example: compressors of the reforming section (such as compressor C1) can be operated with an electric motor, an electricity-driven turbine, and/or a turbine driven by electrically-produced steam rather than via a gas or steam driven turbine or a turbine driven by steam produced via the combustion of a fuel; the heat input Q1 required to attain and maintain a desired reforming temperature and provide the endothermic heat of reaction (in a steam methane reformer 120A and/or an adiabatic steam methane reformer 120C) can be electrically provided; or a combination thereof. In embodiments, the steam reformer(s) are heated with resistive or inductive heating. In embodiments, the steam reformer(s) are heated by means of radiative panels that are heated electrically (e.g., via resistive heating, inductive heating, ohmic heating, or the like.)
In embodiments, steam for the reforming reaction can be generated with electrical heating. In embodiments, the steam is generated using an electrode boiler or a resistive immersion heater. In embodiments, preheating of the feed is effected by the injection of steam that is at a higher temperature than the feed stream to be heated. In embodiments, this steam is superheated electrically. The air 106 introduced to the autothermal reformer can be electrically heated. In embodiments, the steam methane reforming reactor at 120A is electrically heated to give a controlled temperature profile such that the extent of reaction is increased. In embodiments, this controlled profile more closely approximates isothermal operation. In embodiments, the feed to the autothermal reformer comprises oxygen, rather than air, and nitrogen is introduced later in the process, e.g., between steps C2 and B2. In embodiments, this oxygen and nitrogen are obtained from an air separation unit (ASU). In embodiments, the air separation unit is operated using renewable electricity. In embodiments the syngas generation section 20/120 does not contain an autothermal reformer, and nitrogen is introduced as a pure nitrogen stream produced in an electrically powered air separation unit. In embodiments, the syngas exiting a primary reformer may be heated (e.g., via the use of electrical energy/heating) to a temperature at which it can be further converted in an adiabatic steam reforming reactor. Nitrogen (e.g. from an electrically powered ASU) may be introduced either before or after the adiabatic reformer. In embodiments in which the nitrogen is introduced before the adiabatic steam reformer, this nitrogen stream may be preheated (e.g., electrically) so as to provide some or all of the additional heat required to raise the temperature of the syngas inlet to the adiabatic reformer.
As noted above, an ammonia synthesis plant of this disclosure can comprise a shift conversion or ‘shifting’ section 30/130. The shift conversion section 30/130 can comprise a high temperature shift reactor, a low temperature shift reactor, a first shift reactor, a final shift reactor, or a combination thereof. The shift conversion section can include cooling upstream and/or downstream of the high temperature shift reactor, the low temperature shift reactor, or both, wherein the heat removed can be transferred either directly or indirectly to another process stream.
After the syngas generation is complete, the syngas product stream 125 is subjected to water gas shifting in the shift conversion section 30/130 to produce additional hydrogen via the water gas shift (WGS) reaction of Equation (1) above. The shifting can be effected via any suitable methods known in the art, in embodiments, so long as the energy for the ammonia synthesis plant I/II or the shifting section 30/130 is provided as detailed herein. For example, shifting can comprise high temperature shift, low temperature shift, or both, as in the embodiment of
Shifting section 130 can further comprise cooling of the high temperature shifted stream 132 in a second cooling step or unit(s) A2 (with heat removal indicated by Q3), whereby the stream is cooled to provide cooled, high temperature shifted stream 133.
Shifting section 130 of the embodiment of
A third cooling step A3 (with heat removal indicated by Q4) can be employed to reduce the temperature of the low temperature shifted reformer product 134, and provide a cooled, shifted reformer product stream 135. In embodiments, the cooled, shifted reformer product stream 135 has a temperature suitable for feeding to the hydrogen and nitrogen purification section 40/140. Such a temperature may be between ambient temperature and 100° C.
According to embodiments of this disclosure, shifting can be effected with a reduced usage of non-carbon based energy, the use of renewable energy, and/or the use of electricity (e.g., electricity from renewable and/or non-renewable source(s)). For example: the heat removal (such as heat removal Q2 for cooling A1 prior to shifting, the heat removal Q3 for cooling A2 between a high temperature shift 130A and a low temperature shift 130B, the heat removal Q4 for cooling A3 after a low temperature shift 130B) required to provide a desired shift temperature can be electrically provided, or a combination thereof. In embodiments, heat removal is matched with heat inputs so that recovered thermal energy is used for heating other process streams. In embodiments, Q2, Q3, and Q4 are used to supply thermal energy to Q1 Q5, and/or Q7, and the remaining energy is supplied electrically. In embodiments, reactors (for one or more steps, sometimes including reforming) can have a temperature profile imposed by electric heating. In embodiments, thermoelectric devices and/or heat pumps are used to move energy from Q2, Q3, and/or Q4 to other places where the energy can be utilized.
As noted above, an ammonia synthesis plant of this disclosure can comprise a hydrogen and nitrogen purification section 40/140. The hydrogen and nitrogen purification section 40/140 can be operable to remove one or more components (e.g., carbon dioxide, water, carbon monoxide, or a combination thereof) from the shifted syngas product in stream 35/135. The hydrogen and nitrogen purification section 40/140 can comprise a carbon dioxide removal apparatus, a methanation apparatus, a water condensing/cooling apparatus, heating apparatus, compression apparatus, or a combination thereof, as described further hereinbelow.
As noted above, the hydrogen and nitrogen purification section 40/140 can comprise a carbon dioxide removal apparatus. As noted above, in embodiments, after shifting, the shifted reformer product stream is cooled and much of the steam present in this stream is condensed. In the embodiment of
As noted above, the hydrogen and nitrogen purification section 40/140 can comprise a methanation apparatus. Due to the nature of the (typically multi-promoted magnetite) catalyst used in the ammonia synthesis reaction of ammonia synthesis section 50/150 described below, only very low levels of oxygen-containing (especially CO, CO2 and H2O) compounds can be tolerated in the ammonia synthesis feed gas stream(s) or purified reformer product in stream 45/145 (e.g., in the hydrogen and nitrogen mixture). In embodiments, after carbon dioxide removal 140A, the carbon dioxide-reduced stream 141 may be heated, as mentioned further hereinbelow and indicated at B1 (with heat input indicated at Q5) prior to methanation 140B in a methanator. Methanation is operable to remove residual carbon monoxide and carbon dioxide via reaction with hydrogen to form methane and water according to Equations (5) and (6):
CO+3H2→CH4+H2O (5)
CO2+4H2→CH4+2H2O (6).
An alternative to the use of a methanator is to convert the trace levels of CO into CO2 by the addition of a stoichiometric quantity of oxygen from an oxygen containing stream and passing this mixed stream over a bed of a selective CO oxidation catalyst (e.g., highly dispersed gold). In this way CO can be reacted with O2 according to Equation (7):
CO+½O2→CO2 (7).
When this alternative CO removal process is employed, it should be carried out prior to the CO2 removal step. An advantage of this alternative process is that, in contrast to methanation, no hydrogen is consumed. Suitable oxygen containing streams include air, oxygen-enriched air produced in an air separation plant and pure oxygen produced in an air separation plant (which may be electrically powered, in embodiments).
As noted above, the hydrogen and nitrogen purification section 40/140 can comprise a water removal or “water condensing” apparatus. In the embodiment of
As noted above, the hydrogen and nitrogen purification section 40/140 can comprise compression C2. For example, in the embodiment of
As noted above, the hydrogen and nitrogen purification section 40/140 can comprise heating apparatus. Heating can be provided upstream of methanation; downstream of compression and upstream of ammonia synthesis section 150; or both. For example, after carbon dioxide removal 140A, the carbon dioxide-reduced stream 141 may be heated, as mentioned further hereinbelow and indicated at B1 (with heat input indicated at Q5) prior to methanation 140B in a methanator. The compressed dry gas in purified reformer product stream 145 can be heated B2 (with heat input indicated at Q7) after compression C2 and prior to ammonia synthesis in ammonia synthesis section 150. The purified reformer product in compressed, dry gas stream 145 can be heated, for example, to a temperature in the range of from about 100° C. to about 350° C. (in stream 146) prior to ammonia synthesis.
According to embodiments of this disclosure, hydrogen and nitrogen purification can be effected with a reduced usage of non-carbon based energy, the use of renewable energy, and/or the use of electricity (e.g., electricity from renewable and/or non-renewable source(s)). For example: carbon dioxide removal 140A can be electrified by electrifying solvent regeneration. Methanation 140B can be electrified, for example, by electrically heating gas 141 at B1 and/or by electrically heating the methanation reactor at 140B. Hydrogen and nitrogen drying (e.g., at A4) may be electrified, for example, by electrically heating the regeneration gas stream. In embodiments, the heat input Q5 required to attain a desired methanation temperature by heating B1 can be electrically provided; the heat removal Q6 required to effect water condensing A4 can be electrically provided; the compressing utilized at C2 can be effected via an electric motor, an electricity-driven turbine, and/or a turbine driven by electrically produced steam rather than a gas-driven turbine and/or a steam turbine driven by steam produced from combustion of a fuel; the heat input Q7 needed to reach a desired ammonia synthesis temperature at heating B2 can be electrically provided; or a combination thereof. In embodiments, heat removal is matched with heat inputs so that recovered thermal energy is used to heat other process streams. In embodiments, the energy recovered in Q6 is applied to energy input Q5, and the balance is supplied electrically. In embodiments, hydrogen obtained from another source is added to the process in the hydrogen purification section 40/140. In embodiments, this hydrogen is obtained from a process that uses renewable electricity. In embodiments, some or all of the nitrogen needed for ammonia synthesis is added near the end of the hydrogen purification section 40/140 (for example via nitrogen line 266 depicted in
In embodiments, enough hydrogen is available from outside sources (e.g., from a steam cracker, from refinery sources, and/or from water electrolysis) that the reforming and shift conversion sections are no longer needed. Nitrogen of the appropriate purity from other sources (e.g., from an air separation unit) is then added to this hydrogen prior to compression C2. Heating B2, ammonia synthesis 150A, cooling A5/A6 and separation then proceed as described below. In embodiments, all hydrogen is produced using a non-carbon based energy source, a renewable energy source, electricity, and/or renewable electricity. In embodiments, the nitrogen is obtained from an air separation unit powered mostly or entirely by electricity. In embodiments, the compressor of compression C2, recycle compressor C3, and/or the compressor(s) used for refrigeration A6 are driven electrically. In embodiments, a majority, 60%, 70%, 80%, 90%, or all external energy for heating B2, ammonia synthesis 150A, cooling A5/A6 and separation is supplied using a non-carbon based energy source, a renewable energy source, electricity, and/or renewable electricity.
In embodiments, the hydrogen and nitrogen stream from which carbon dioxide has been removed (e.g., stream 144), may be further purified to reduce or eliminate contamination with methane, for example using a pressure swing adsorption (PSA) system, generating a purified hydrogen and nitrogen stream low in methane and a separate methane stream. In embodiments, said separate methane stream may be recycled to the syngas generation section 20/120 whereas the low in methane purified hydrogen and nitrogen stream may be fed to the ammonia synthesis loop. This approach can, in embodiments, reduce the need for loop purging and improve the overall efficiency of the process.
In embodiments, a PSA type system can be used to remove methane, CO and CO2 from the hydrogen and nitrogen stream ahead of the ammonia synthesis loop of ammonia synthesis section 50/150, or optionally ahead of a methanator of 140B. In such embodiments, the hydrogen and nitrogen stream can be fed to the synthesis loop whereas the mixed carbon oxides and methane stream can be further processed to produce relatively pure CO2 and methane streams. In embodiments, the relatively pure CO2 and methane streams can be fed to a urea plant and recycled to the synthesis gas generation sections of the ammonia plant, respectively.
As noted above, an ammonia synthesis plant of this disclosure can comprise an ammonia synthesis section 50/150. The ammonia synthesis section 50/150 can comprise one or more ammonia synthesis reactors or catalyst beds for carrying out the ammonia synthesis 150A; cooling apparatus A5/A6 operable to remove heat after each of the one or more ammonia synthesis reactors or catalyst beds; compression apparatus (also referred to herein as a recycle compressor) C3 operable to recycle nitrogen and hydrogen to the one or more ammonia synthesis reactors; a purge gas system 150B operable to purge gas (e.g., methane, argon, nitrogen, and/or CO2) from the ammonia synthesis section 50/150; or a combination thereof, as described further hereinbelow.
In the ammonia synthesis section 50/150, nitrogen (N2) and hydrogen (H2) are reacted to make ammonia (NH3). In embodiments, to produce the desired ammonia end-product, the purified hydrogen is catalytically reacted with nitrogen to form ammonia according to equilibrium limited Equation (8):
3H2+N2±2NH3. (8).
The nitrogen for the ammonia synthesis reaction may already in the purified syngas generation section product stream 45/145 (e.g., derived from process air at 106 as in the embodiment of
As noted above, the ammonia synthesis section 50/150 can comprise one or more ammonia synthesis reactor(s) and/or catalyst bed(s). The ammonia synthesis reaction can be carried out in one or more ammonia synthesis reactors or catalyst beds of ammonia synthesis section 50/150. The ammonia synthesis reaction of Equation (8) is exothermic and conversion is equilibrium limited. In embodiments, the ammonia synthesis reaction is carried out at about 200 to 500° C. In embodiments, the reaction is carried out over a series of (e.g., three) catalyst beds/reactors and heat is removed in between the beds (heat removal from the ammonia synthesis section 50/150 between and/or after the ammonia synthesis reactor(s)/catalyst bed(s), indicated at Q8 in
As noted above, in embodiments, the ammonia synthesis section 50/150 comprises cooling apparatus operable to remove heat after each of the one or more ammonia synthesis reactors or catalyst beds and to enable separation of ammonia from the effluent gas stream obtained from the ammonia synthesis reactor(s). This cooling may occur in one or more steps. In embodiments, the post-ammonia-synthesis cooling comprises two steps: a first step comprising thermal cooling (where heat can be extracted) and a second step, which requires an energy input (primarily refrigeration). In a first post-ammonia-synthesis cooling, as indicated at A5 (with energy removal indicated at Q8), the cooling is operated to extract heat and/or energy from ammonia in line 151 that can be used elsewhere in the process (e.g., via heat exchange). In a second post-ammonia-synthesis cooling, as indicated at A6, energy input (e.g., work in driving a compressor) is required to further cool the product stream 151′ from the first cooling A5 such that ammonia is condensed and removed via ammonia product stream 155. In this second cooling, the product stream can be cooled and then chilled to a range of about −10 to about 5° C. at a high pressure (e.g. close to ammonia synthesis loop pressure) such that the ammonia is condensed and removed as a liquid. The remaining vapor, containing a majority of the unreacted hydrogen and nitrogen and a minority of the ammonia, is recycled via line 152 and recycle compressor C3 to the ammonia synthesis loop (e.g., via recycle stream 153), whereas the liquid stream (e.g., ammonia stream 155), containing the majority of the ammonia and a minority of the unconverted hydrogen and nitrogen, can be further chilled and depressurized for further purification thereof, if desired, and the ammonia product stored, sold, or etc.
As noted above, in embodiments, the ammonia synthesis section 50/150 comprises compression apparatus (also referred to herein as a recycle compressor) C3 operable to recycle nitrogen and hydrogen to the one or more ammonia synthesis reactors. In the embodiment of
As noted above, in embodiments, the ammonia synthesis section 50/150 comprises a purge gas system operable to purge gas (e.g., methane, nitrogen (N2), hydrogen (H2), argon (Ar) and/or impurities) from the ammonia synthesis section 50/150. In embodiments, to handle build-up of residual methane and inerts in the recycle gas in recycle stream 153, methane and inerts are purged from the recycle gas via a purge gas system 150B. In the embodiment of
According to embodiments of this disclosure, ammonia synthesis 150 can be effected with a reduced usage of non-carbon based energy, the use of renewable energy, and/or the use of electricity (e.g., electricity from renewable and/or non-renewable source(s)). In embodiments, the heat removal Q8 required to attain a desired ammonia synthesis temperature within or downstream of one or more ammonia synthesis reactors (e.g., via cooling A5) is transferred to other streams via heat exchange, or this energy is otherwise utilized by conversion to electricity; the compressing utilized at recycle compressor C3 can be effected via an electric motor, an electricity-driven turbine, and/or a turbine driven by electrically produced steam rather than via a gas-driven turbine and/or a turbine driven by steam produced via combustion of a fuel; the heat removal Q9 needed by purge gas system 150B can be electrically provided; or a combination thereof. In embodiments, the cooling/refrigeration system for obtaining product ammonia (A6) is driven such that energy input is provided by electricity. In embodiments, the higher efficiency of electrically-driven compressors utilized at C2 and C3 allow for a higher than normal pressure in the ammonia synthesis reactor at 150A to be achieved economically and results in a higher per-pass yield of ammonia. In embodiments, this higher pressure allows for the reactor temperature to be lowered and results in a higher per-pass yield of ammonia. In embodiments, the higher efficiency of the electrically-driven compressors in the refrigeration system at A6 allows for economical separation of ammonia at a lower temperature, enabling a more complete separation. In embodiments, a combination of higher pressure, lower temperature, and/or higher yield allow ammonia to be condensed against cooling water rather than a colder refrigerant at A6.
In embodiments, a majority, greater than 20, 30, 40, 50, 60, 70, 80, or 90%, or substantially all of the net heat input or removal (Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, and/or Q9) needed within the ammonia synthesis plant is provided from a non-carbon based energy source, from a renewable energy source, such as renewable electricity, and/or from electricity (e.g., electricity from renewable and/or non-renewable source(s)).
In embodiments, a majority, greater than 20, 30, 40, 50, 60, 70, 80, or 90%, or substantially all of the energy needed for compression (e.g., at air compressor C1, dry gas stream compression C2, and/or recycle compressor C3) within the ammonia synthesis plant is provided from a non-carbon based energy source, from a renewable energy source, such as renewable electricity, and/or from electricity (e.g., electricity from renewable and/or non-renewable source(s)). For example, an electric motor, an electrically-driven turbine, and/or a turbine driven by steam produced electrically may be utilized to provide compression throughout the ammonia synthesis plant or one or more sections thereof. In embodiments, a majority, greater than 20, 30, 40, 50, 60, 70, 80, or 90%, or substantially all of the compressors are replaced by or utilize an electric motor, an electrically-driven turbine, and/or a turbine driven by steam produced electrically.
In embodiments, electricity is utilized to produce slightly colder (e.g., 2, 5, 10 or 15° C. colder) cooling water than conventional. In embodiments, electricity is utilized to supply the energy needed for the refrigeration system.
In embodiments, electricity can be used to provide the motive force for fluids. For example, electricity can be used to power pumps to move and/or pressurize liquids, and/or to power air blowers and/or fans. In embodiments, a fraction, a majority, or all (e.g., 20, 30, 40, 50, 60, 70, 80, 90, or 100%) of the number of pumps utilized in the ammonia synthesis plant are electrified.
As noted above, when utilizing electricity from a renewable source that has a potentially or known intermittent supply (e.g., an intermittent energy source or IES), various steps can be taken to maintain operation of the ammonia synthesis plant, according to embodiments of this disclosure. Such handling of an IES can be as described in U.S. Provisional Patent Application Nos. 62/792,636 and 62/792,637, entitled Use of Intermittent Energy in the Production of Chemicals, which are being filed on Jan. 15, 2019, the disclosure of each of which is hereby incorporated herein for purposes not contrary to this disclosure. For example, in embodiments, compressed hydrogen is stored for intermittency of electric supply. Alternatively or additionally, recovered hydrogen separated from the purge gas can be pressurized and stored when electricity is available and used to generate electricity using a fuel cell during times of low electric supply. Alternatively or additionally, one or more cryogenic liquids can be stored for intermittency of electric supply. Alternatively or additionally, heat can be stored for intermittency of electric supply.
In embodiments, when a methane steam reformer is utilized in syngas generation section 20/120, heat may be stored in the insulating material lining the internals of the reforming furnace, thereby increasing the heat storage capacity of the furnace such that temporary loses of electrical power to the heating elements therein would result in only a small drop in the temperature of the reforming tubes which are heated largely through radiation from the surface of surrounding insulating material. Alternatively or additionally, batteries can be kept for intermittency of electric supply. Backup power for key components may be provided; non-renewable electricity may be utilized as a back-up for intermittent renewable electricity. For example, such backup power may be produced via apparatus driven by compressed gas or a flywheel. Alternatively or additionally, natural gas feed, hydrogen, or nitrogen can be stored for intermittency of electric supply. Alternatively or additionally, stored compressed gases can be used to generate electricity as they are depressurized. Alternatively or additionally, cooled ammonia product can be stored for use as a refrigerant for intermittency of electric supply.
Electrification of the ammonia synthesis plant of this disclosure can be provided via an electricity supply that can be high voltage or low voltage. The electric devices can be operable or operated on alternating (single or multiphase) or direct current.
In embodiments, steam generated by the combustion of fuels or produced solely for heat and/or energy transfer is not utilized in an ammonia synthesis system and method of this disclosure (e.g., in the pretreating section 10/110, the syngas generation/reforming section 20/120, the shift conversion section 30/130, the hydrogen and/or nitrogen purification section 40/140, and/or the product purification section 50/150). In this manner, an ammonia synthesis plant according to this disclosure can be operated, in embodiments, without an elaborate steam heat and/or energy transfer system (which may be conventionally utilized in an ammonia synthesis plant). In some applications, for example where steam is utilized within a reactor as a feed component and/or diluent, such steam may be produced via heat transfer with a process stream within the ammonia synthesis plant and/or may be produced electrically. In embodiments, steam generated via heat transfer with a process stream may be superheated using electricity. In embodiments, steam is not utilized throughout the ammonia synthesis plant as a commodity or utility. In embodiments, an ammonia synthesis plant of this disclosure is essentially steam-free, or utilizes substantially less steam (e.g., uses at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 volume percent (vol %) less steam) than a conventional plant for producing ammonia. For example, a conventional plant for producing ammonia may utilize steam production for reboilers of distillation columns of the feed pretreating section 10/110 and/or the hydrogen and/or nitrogen purification section 40/140, may utilize steam production to drive steam turbines for compressing process and/or recycle streams, or may utilize steam production to drive steam turbines for refrigeration. In embodiments, steam is not produced for these operations in an ammonia plant according to this disclosure, or substantially less steam is produced (e.g., at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 volume percent (vol %) less steam). In embodiments, steam is used as a heat transfer fluid, but is not used to do mechanical work (e.g., to drive a compressor or pump.) In embodiments, the steam generated for these operations is primarily (e.g., of the total steam utilized, the greatest percentage is electrically produced), mainly (e.g., greater than 50% of the steam is electrically produced) or substantially all electrically produced. In embodiments, the steam utilized as a reactant or diluent is primarily (e.g., of the total steam utilized, the greatest percentage is electrically produced), mainly (e.g., greater than 50% of the steam is electrically produced) or substantially all electrically produced.
In embodiments, in an ammonia synthesis plant or process of this disclosure, more energy is utilized directly ‘as-is’, for example, utilizing heat from a hot product effluent stream to heat a feed stream, rather than being transformed, e.g., via the generation of steam and the conversion of the thermal energy to mechanical energy via a steam turbine. According to embodiments of this disclosure, the use of energy directly can increase the energy efficiency of the ammonia synthesis plant, for example by reducing energy efficiency losses that occur when heat is converted to mechanical energy.
As energy consumption is a large fraction of the operating costs of a traditional ammonia synthesis plant, increasing energy efficiency (e.g., via electrification) as per this disclosure and/or utilizing natural gas conventionally burned to provide heat for syngas generation (e.g. by reforming) and/or burned for compression (e.g., burned to produce steam for a steam turbine or burned for a gas turbine) to produce additional ammonia may provide economic advantages over a conventional ammonia synthesis plant. Concomitantly, the reduction of the burning of fossil fuels (e.g., natural gas, methane) as a fuel enabled via this disclosure provides for reduced greenhouse gas (GHG) emissions relative to a conventional ammonia synthesis plant in which hydrocarbons are burned as fuel. In embodiments, GHG emissions resulting from the provision of energy for the process (e.g., carbon dioxide emissions) are reduced by at least 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% relative to a conventional ammonia synthesis plant in which hydrocarbons are burned as fuel. In embodiments of this disclosure, the amount of CO2 produced per ton of ammonia produced is reduced to less than 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, or 1.0 tons CO2 per ton ammonia. In embodiments, aspects of this disclosure can lead to an increase in carbon efficiency of a process, i.e. to a fraction of carbon consumed in the process that reappears as a useful product, and/or a reduced specific energy consumption (e.g., the energy utilized to synthesize a quantity of chemical product).
Conventionally, the energy required for unit operations in chemical processes is generally provided by the burning of fossil fuels, especially natural gas. Herein-disclosed are systems and methods by which this energy input can be reduced or replaced, in embodiments, with non-carbon based energy, renewable energy, such as renewable electricity, and/or by electricity from any source (e.g., renewable and/or non-renewable), such that energy efficiency is improved (e.g., energy losses are reduced). In embodiments, energy efficiency (e.g., reduced energy losses) is increased by a decrease in or elimination of the use of steam to do mechanical work. In embodiments, the energy efficiency of the process is increased such that the specific energy consumption (the total net energy input, including fuel and electricity, but not including any contribution of the heat of reaction, feed, or byproduct credits, to the process divided by the production rate) is less than 12, 11, 10, 9, 8, or 7 GJ/ton of ammonia produced, where the specific energy consumption is calculated using the higher heating value of the fuel. In embodiments, the total amount of methane and/or natural gas used as feed and fuel is less than 0.65, 0.60, 0.55, 0.50, 0.45, or 0.40 tons per ton of ammonia produced. In embodiments, the total amount of methane and/or natural gas used as fuel is less than 0.20, 0.15, 0.10, 0.05, or 0 tons per ton of ammonia produced. The herein-disclosed use of non-carbon based energy, renewable energy, and/or electricity in the production of chemicals, such as the production of ammonia via steam methane reforming, increases energy efficiency of and/or decreases and/or eliminates carbon dioxide emissions from and fossil fuel consumption within the ammonia synthesis process.
The embodiments having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims in any manner.
A process simulation was performed to determine the heat and mass flows for a typical process III for the production of ammonia. The process simulation utilized in this Comparative Example 1 was made using Aspen Plus®. It does not represent a specific operating plant, but it is representative of a typical plant as described hereinbelow with reference to
Process III of Comparative Example 1 utilizes primary and secondary (autothermal) reforming (i.e., ATR) and is configured to produce 125 metric tons per hour of ammonia. If operated for a typical 8000 hours in a year, this would result in the production of one million tons of ammonia, although variations in downtime due to upsets and maintenance could increase or reduce this output. This size is typical of large ammonia plants being built today.
As shown in
There are four major energy consumers in the conventional process III of this Comparative Example 1: (1) regeneration of the amine solution in CO2 removal 240A, (2) power (e.g., to provide work W1, W2, W3) to drive the three large compressors via compressor turbines 265 including air compressor C1, synthesis loop compressor(s) C2/C3, and refrigeration compressor at A6, (3) heating to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating of the feed (e.g., at heating B2) before the first ammonia synthesis reactor of 250A. As is common, very little electricity is consumed, primarily for some smaller pumps. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat the methanation reactor feed (e.g., at heating B1) can be obtained from heat removed when cooling at A4 the product gases 243 from the same reactor), but the rest must be supplied externally and is conventionally generated by burning fuel. In Comparative Example 1, external energy is supplied in two places: the primary reformer furnace of primary reformer 220A, and the auxiliary boiler 260. The primary reformer furnace consumes 7.3 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 111 MW. Auxiliary boiler 260 consumes 40.5 t/hr of natural gas with a contained chemical energy of 617 MW. In addition, although some of the reactions are endothermic (e.g., steam reforming), the net set of reactions for Comparative Example 1 is exothermic and generates roughly 70 MW of energy that can be used elsewhere. How to most efficiently allocate this energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Comparative Example 1 a strategy was utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. For example, in the process of Comparative Example 1, this wasted energy amounts to 147 MW. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 2 shows energy use values for the process of Comparative Example 1. As seen in Table 2, an amount of 728 MW of energy is supplied through the combustion of natural gas in the reformer furnace of primary reformer 220A and the auxiliary boiler 260. An additional 70 MW is obtained as the net exothermic heat of reaction. The total net energy input to the process is 798 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 111 MW consumed in the primary reformer furnace at 220A, the radiant section is used to provide 57 MW to further heat the gases and supply the heat of reaction; an additional 31 MW is transferred in the convection section to preheat the feed water/methane mixture 215. The remaining 23 MW is lost to the atmosphere in the flue gas. An amount of 617 MW is supplied to the auxiliary boiler 260, of which 68 MW is used to supply heat for CO2 removal at 240A and 424 MW provides the power for the three large compressors, air compressor C1, synthesis loop compressor(s) C2/C3, and the refrigeration compressor at A6; 124 MW is lost to the atmosphere in the flue gas. In total, 147 MW, or 18% of the net external energy supplied, is lost in the flue gas from the reformer furnace at primary reformer 220A and auxiliary boiler 260.
As further seen in the data in Table 2, the total fuel gas consumption is 382,000 tons per year. The combustion of this fuel results in the atmospheric emissions 1.05 million tons of CO2 annually. An additional 1.23 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 2.28 million tons per year. Specific energy consumption including the fuel as well as the heat of reaction is 22.9 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel inputs is 20.9 GJ per ton of ammonia produced. An amount of 40% of the total supplied energy (318 MW out of 798 MW) is lost due to inefficiencies in the conversion of steam to mechanical work; another 18% (147 MW) of the total supplied energy is lost to the atmosphere from the stack gas.
Example 1 is a partial electrification process IV as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 1. In process IV, partial electrification is provided by electric compressors. The key elements of this electrified plant or process IV are shown in
There are four major energy consumers in the partially electrified process IV of this Example 1: (1) regeneration of the amine solution in CO2 removal 240A, (2) power (e.g., for work W1, W2, W3) to drive the three large compressors, air compressor C1, synthesis loop compressor(s) C2/C3, and refrigeration compressor at A6, (3) heating to raise the temperature of the feed gases (e.g., at 110) and provide the heat of reaction for the primary reformer 220A, and (4) preheating of the feed (e.g., at heating B2) before the first ammonia synthesis reactor at 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat the methanation reactor feed (e.g., at heating B1) can be obtained from heat removed when cooling at A4 the product gases 243 from the same reactor), but the rest must be supplied externally. In Example 1, external energy is supplied in three places: the primary reformer furnace at 220A, the auxiliary boiler 260, and renewable electricity used to power the three large compressors (e.g., C1, C2/C3, and a refrigeration compressor at A6). The primary reformer furnace at 220A consumes 7.3 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 111 MW. Auxiliary boiler 260 consumes 5.6 t/hr of natural gas with a contained chemical energy of 85 MW. An amount of 114 MW of electricity is supplied to three large compressors; at an efficiency of 93%, this performs the same work that required 424 MW of high pressure steam 263 in Comparative Example 1. In addition, although some of the reactions are endothermic (e.g., steam reforming), the net set of reactions for Example 1 is exothermic and generates roughly 70 MW of energy that can be used elsewhere. How to most efficiently allocate this energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 1 a strategy was utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. In the process of Example 1, this wasted energy amounts to only 40 MW, a reduction of 73% over Comparative Example 1. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 2 shows energy use values for the process of Example 1. As seen in Table 2, an amount of 196 MW of energy is supplied through the combustion of natural gas in the reformer furnace of primary reformer 220A and the auxiliary boiler 260, a reduction of 73% over Comparative Example 1. An amount of 114 MW of renewable electricity is supplied, and an additional 70 MW is obtained as the net exothermic heat of reaction. The total net energy input to the process is 380 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 111 MW consumed in the primary reformer furnace at 220A, the radiant section is used to provide 57 MW to further heat the gases and supply the heat of reaction; an additional 31 MW is transferred in the convection section to preheat the feed water/methane mixture 215. The remaining 23 MW is lost to the atmosphere in the flue gas. An amount of 85 MW is supplied to the auxiliary boiler 260, of which 68 MW is used to supply heat for CO2 removal at 240A and 17 MW is lost to the atmosphere in the flue gas. In total, 40 MW, or 10.5% of the net external energy (e.g., energy conventionally provided via burning of a fuel) supplied, is lost in the flue gas from the reformer furnace at 220A and auxiliary boiler 260.
As further seen in the data in Table 2, total fuel gas consumption is 103,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.28 million tons of CO2 annually. An additional 1.23 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.51 million tons per year, a decrease of 33% over Comparative Example 1. Specific energy consumption, including the fuel, electricity, and heat of reaction, is 10.9 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 8.9 GJ per ton of ammonia produced. An amount of 10.5% of the total supplied energy is lost in the stack gas and none is lost due to inefficiencies in the conversion of steam to mechanical work, in contrast to Comparative Example 1 where 18% and 40%, respectively, of the energy was lost in these ways.
Example 2 is a further partial electrification process V as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 1. In process V, partial electrification is provided by an electric furnace in addition to the electric compressors of Example 1. The key elements of this electrified plant/process V are shown in
There are four major energy consumers in the partially electrified process V of this Example 2: (1) regeneration of the amine solution in CO2 removal 240A, (2) power (e.g., W1, W2, W3) to drive the three large compressors, air compressor C1, synthesis loop compressor(s) C2/C3, and refrigeration compressor at A6, (3) heating to raise the temperature (e.g., at feed pretreatment 110) of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating of the feed (e.g., at heating B2) before the first ammonia synthesis reactor 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat the methanation reactor feed (e.g., at heating B1) can be obtained from heat removed when cooling the product gases from the same reactor (e.g., at A4)), but the rest must be supplied externally. In Example 2, external energy is supplied in three places: the primary reformer 220A, the auxiliary boiler 260, and power for the three large compressors (e.g., C1, C2/C3, and refrigeration compressor at A6). The primary reformer 220A is heated electrically; 72 MW of renewable electricity are used to generate 68 MW of heat. In contrast to Comparative Example 1, there is no convection section in the primary reformer furnace and no flue gas losses from this heating. Auxiliary boiler 260 consumes 7.0 t/hr of natural gas with a contained chemical energy of 107 MW. An amount of 114 MW of electricity is supplied to three large compressors; at an efficiency of 93%, this performs the same work that required 424 MW of high pressure steam 263 in Comparative Example 1. In addition, although some of the reactions are endothermic (e.g., steam reforming at 220A), the net set of reactions for Example 2 is exothermic and generates roughly 70 MW of energy that can be used elsewhere. How to most efficiently allocate this energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 2 a strategy was utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from this boiler contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. In the process of Example 2, this wasted energy amounts to only 22 MW, a reduction of 84% over Comparative Example 1. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 2 shows energy use values for the process of Example 2. As seen in Table 2, an amount of 107 MW of energy is supplied through the combustion of natural gas in the auxiliary boiler 260, a reduction of 84% over Comparative Example 1. An amount of 186 MW of renewable electricity is supplied, and an additional 70 MW is obtained as the net exothermic heat of reaction. The total net energy input to the process V is 363 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 72 MW supplied to the primary reformer at 220A, all is supplied to the reactor; there is no convection section in the primary reformer furnace and no flue gas in this embodiment. An amount of 107 MW is supplied to the auxiliary boiler 260, of which 86 MW is used to supply heat for CO2 removal 240A and 21 MW is lost to the atmosphere in the flue gas. In total, 22 MW, or 6.10% of the net external energy supplied, is lost in the flue gas from the auxiliary boiler 260. An additional 12 MW, or 3.3% of the net external energy supplied, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 2, total fuel gas consumption is 56,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.155 million tons of CO2 annually. An additional 1.23 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.38 million tons per year, a decrease of 39% over Comparative Example 1. Specific energy consumption including the fuel, electricity and heat of reaction is 10.5 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 8.4 GJ per ton of ammonia produced. An amount of 9.4% of the total supplied energy is lost in the stack gas and due to electrical inefficiencies; none is lost, in this embodiment, due to inefficiencies in the conversion of steam to mechanical work.
Example 3 is a different partial electrification process VI as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 1. In process VI, partial electrification is provided by an electric reboiler (of CO2 removal 240A) in addition to the electric compressors of Example 1. The key elements of this electrified plant VI are shown in
There are four major energy consumers in the partially electrified process VI of this Example 3: (1) regeneration of the amine solution in CO2 removal 240A, (2) power (e.g., for work W1, W2, W3) to drive the three large compressors, air compressor C1, synthesis loop compressor(s) C2/C3, and refrigeration compressor at A6, (3) heating to raise the temperature of the feed gases (e.g., at feed pretreatment 110) and provide the heat of reaction for the primary reformer 220A, and (4) preheating of the feed (e.g., at heating B2) before the first ammonia synthesis reactor 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat the methanation reactor feed (e.g., at heating B1) can be obtained from heat removed when cooling (e.g., at A4) the product gases 243 from the same reactor), but the rest must be supplied externally. In Example 3, external energy is supplied in three places: the primary reformer 220A, electric heating for regeneration of the amine stripping solution in the CO2 removal system at 240A, and power for the three large compressors. The primary reformer furnace of primary reformer 220A consumes 7.3 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 111 MW. An amount of 72 MW of electricity is supplied to the CO2 removal system 240A, generating 68 MW of heat at an efficiency of 95%. An amount of 114 MW of electricity is supplied to three large compressors; at an efficiency of 93%, this performs the same work that required 424 MW of high pressure steam 263 in Comparative Example 1. In addition, although some of the reactions are endothermic (e.g., steam reforming at 220A), the net set of reactions for Example 3 is exothermic and generates roughly 70 MW of energy that can be used elsewhere. How to most efficiently allocate this energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 3 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from this furnace contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. In the process of Example 3, this wasted energy amounts to only 23 MW, a reduction of 84% over Comparative Example 1. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 2 shows energy use values for the process of Example 3. As seen in Table 2, an amount of 111 MW of energy is supplied through the combustion of natural gas in the secondary reformer furnace at 220A, but no energy is supplied through an auxiliary boiler. An amount of 186 MW of renewable electricity is supplied. An additional 70 MW is obtained as the net exothermic heat of reaction. The total net energy input to the process is 367 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. In total, 23 MW, or 6.3% of the net external energy supplied, is lost in the flue gas (e.g., from the reformer furnace at 220A). An additional 12 MW, or 3.3% of the net external energy supplied, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 2, total fuel gas consumption is 58,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.160 million tons of CO2 annually. An additional 1.23 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.39 million tons per year, a decrease of 39% over Comparative Example 1. Specific energy consumption including the fuel, electricity, and heat of reaction is 10.6 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 8.6 GJ per ton of ammonia produced. 9.5% of the total supplied energy is lost in the stack gas and due to electrical inefficiencies; none is lost, in this embodiment, due to inefficiencies in the conversion of steam to mechanical work.
Example 4 is a near-complete electrification process VII as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 1; no external energy is supplied from combustion, although there is still some combustion inside the process due to the oxidation of methane, carbon monoxide, and hydrogen in the secondary autothermal reformer at 220B. In process VII, near-complete electrification is provided by electric compressors (as in Examples 1-3), an electric furnace in primary reformer 220A (as in Example 2), and an electric reboiler (as in Example 3). The key elements of this electrified plant or process VII are shown in
There are four major energy consumers in the electrified process of this Example 4: (1) regeneration of the amine solution in CO2 removal 240A, (2) power (e.g., W1, W2, W3) to drive the three large compressors, air compressor C1, synthesis loop compressor(s) C2/C3, and refrigeration compressor at A6, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating (e.g., at heating B2) of the feed before the first ammonia synthesis reactor at 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed when cooling (e.g., at A4) the product gases from the same reactor), but the rest must be supplied externally. In Example 4, external energy is supplied in three places: the primary reformer at 220A, heating for regeneration of the amine stripping solution in the CO2 removal system at 240A, and power for the three large compressors. All of this energy is supplied electrically in Example 4. The primary reformer at 220A is heated electrically; 72 MW of renewable electricity are used to generate 68 MW of heat. In contrast to Comparative Example 1, there is no convection section in the primary reformer furnace and no flue gas losses from this heating. An amount of 72 MW of electricity is supplied to the CO2 removal system 240A, generating 68 MW of heat at an efficiency of 95%. An amount of 114 MW of electricity is supplied to the three large compressors; at an efficiency of 93%, this performs the same work that required 424 MW of high pressure steam 263 in Comparative Example 1. In addition, although some of the reactions are endothermic (e.g., steam reforming at 220A), the net set of reactions for Example 4 is exothermic and generates roughly 70 MW of energy that can be used elsewhere. How to most efficiently allocate this energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 4 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. In the process of Example 4, there are no flue gas losses, a reduction of 100% over Comparative Example 1. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor 250A
Table 2 shows energy use values for the process VII of Example 4. As seen in Table 2, 276 MW of renewable electricity are supplied. An additional 70 MW is obtained as the net exothermic heat of reaction. The total net energy input to the process is 347 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Only 16 MW, or 4.6% of the net external energy supplied, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 2, no fuel gas is consumed in Example 4. Because of this, the only CO2 emitted is the 1.23 million tons of CO2 formed by the process chemistry itself; this represents a decrease of 46% over Comparative Example 1. Specific energy consumption including the electricity and the heat of reaction is 10.0 GJ per ton of ammonia produced; specific energy consumption calculated only on the electrical inputs is 8.0 GJ per ton of ammonia produced. The amount of energy lost due to inefficiencies in energy use, 16 MW, is only about one-thirtieth of the energy lost to flue gas and steam-to-mechanical energy conversion in Comparative Example 1.
A process simulation was performed to determine the heat and mass flows for a process VIII for the production of ammonia. The process simulation utilized in this Comparative Example 2 was made using Aspen Plus®. The process of Comparative Example 2, shown in
The process VIII of Comparative Example 2 is configured to produce 125 metric tons per hour of ammonia. If operated for a typical 8000 hours in a year, this would result in the production of one million tons of ammonia, although variations in downtime due to upsets and maintenance could increase or reduce this output. This size is typical of large ammonia plants being built today.
As shown in
There are four major energy consumers in the conventional process VIII of this Comparative Example 2: (1) regeneration of the amine solution in CO2 removal 240A, (2) power to drive the two large compressors via compressor turbines 265: synthesis loop compressor(s) C2/C3 and refrigeration compressor at A6, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating (e.g., at heating B2) of the feed before the first ammonia synthesis reactor 250A. As is common, very little electricity is consumed, primarily for some smaller pumps. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed when cooling (e.g., at A4) the product gases from the same reactor), but the rest must be supplied externally and is conventionally generated by burning fuel. In Comparative Example 2, external energy is supplied in two places: the primary reformer furnace of primary reformer 220A, and the auxiliary boiler 260. The primary reformer furnace consumes 21.1 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 322 MW. Auxiliary boiler 260 consumes 29.9 t/hr of natural gas with a contained chemical energy of 455 MW. In addition, although some of the reactions are exothermic (e.g., ammonia synthesis at 250A), the net set of reactions for Comparative Example 2 is endothermic and requires roughly 67 MW of energy to be provided. (In contrast, the net set of reactions for Comparative Example 1 was exothermic.) How to most efficiently allocate the available energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Comparative Example 2 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. For example, in the process of Comparative Example 2, this wasted energy amounts to 155 MW. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor 250A.
Table 3 shows energy use values for the process VIII of Comparative Example 2. As seen in Table 3, an amount of 777 MW of energy is supplied through the combustion of natural gas in the reformer furnace of primary reformer 220A and the auxiliary boiler 260. Of this energy, 67 MW is required to supply the net endothermic heat of reaction. After subtracting this, the available net energy input to the process for other uses is 710 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 322 MW consumed in the primary reformer furnace, the radiant section is used to provide 168 MW to further heat the gases and supply the heat of reaction; an additional 90 MW is transferred in the convection section to provide process heat. The remaining 64 MW is lost to the atmosphere in the flue gas. An amount of 455 MW is supplied to the auxiliary boiler 260, of which 15 MW is used to supply heat for CO2 removal 240A and 349 MW provides the power for the two large compressors, synthesis loop compressor(s) C2/C3, and the refrigeration compressor at A6; 91 MW is lost to the atmosphere in the flue gas. In total, 155 MW, or 22% of the net available energy supplied, is lost in the flue gas from the reformer furnace at primary reformer 220A and auxiliary boiler 260.
As further seen in the data in Table 3, the total fuel gas consumption is 448,000 tons per year. The combustion of this fuel results in the atmospheric emissions 1.23 million tons of CO2 annually. An additional 1.1 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 2.33 million tons per year. Specific energy consumption after subtracting the heat of reaction from the fuel inputs is 19.2 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel inputs is 21.0 GJ per ton of ammonia produced. An amount of 37% of the net available energy (262 MW out of 710 MW) is lost due to inefficiencies in the conversion of steam to mechanical work; another 22% (155 MW) of the total supplied energy is lost to the atmosphere from the stack gas.
Example 5 is a partial electrification process IX as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 2. In process IX, partial electrification is provided by electric compressors. The key elements of this electrified plant IX are shown in
As shown in
There are four major energy consumers in the conventional process IX of this Example 5: (1) regeneration of the amine solution in CO2 removal at 240A, (2) power to drive the two large compressors, synthesis loop compressor(s) C2/C3 and refrigeration compressor at A6, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating of the feed (e.g., at heating B2) before the first ammonia synthesis reactor 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed (e.g., at A4) when cooling the product gases 243 from the same reactor), but the rest must be supplied externally. In Example 5, external energy is supplied in three places: the primary reformer furnace at primary reformer 220A, the auxiliary boiler 260, and renewable electricity used to power the large compressors. The primary reformer furnace consumes 21.1 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 322 MW. Auxiliary boiler 260 consumes 1.2 t/hr of natural gas with a contained chemical energy of 18 MW. An amount of 94 MW of electricity is supplied to the two large compressors; at an efficiency of 93%, this performs the same work that required 349 MW of high pressure steam 263 in Comparative Example 2. In addition, although some of the reactions are exothermic (e.g., ammonia synthesis at 250A), the net set of reactions for Example 5 is endothermic and requires roughly 67 MW of energy to be provided. How to most efficiently allocate the available energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 5 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. For example, in the process of Example 5, this wasted energy amounts to 68 MW, a reduction of 56% over Comparative Example 2. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 3 shows energy use values for the process IX of Example 5. As seen in Table 3, an amount of 340 MW of energy is supplied through the combustion of natural gas in the reformer furnace of primary reformer 220A and the auxiliary boiler 260, a reduction of 56% over Comparative Example 2. An additional 94 MW of energy is supplied as electricity. Of the total energy, 67 MW is required to supply the net endothermic heat of reaction. After subtracting this, the available net energy input to the process for other uses is 367 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 322 MW consumed in the primary reformer furnace, the radiant section is used to provide 168 MW to further heat the gases and supply the heat of reaction; an additional 90 MW is transferred in the convection section to provide process heat. The remaining 64 MW is lost to the atmosphere in the flue gas. An amount of 18 MW is supplied to the auxiliary boiler 260, of which 15 MW is used to supply heat for CO2 removal 240A; 91 MW is lost to the atmosphere in the flue gas. In total, 68 MW, or 19% of the net available energy supplied, is lost in the flue gas from the reformer furnace of primary reformer 220A and auxiliary boiler 260.
As further seen in the data in Table 3, the total fuel gas consumption of process IX is 179,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.49 million tons of CO2 annually. An additional 1.1 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.59 million tons per year, a decrease of 32% over Comparative Example 2. Specific energy consumption after subtracting the heat of reaction from the fuel and electricity inputs is 9.9 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 11.8 GJ per ton of ammonia produced. An amount of 19% of the total available energy is lost to the atmosphere from the stack gas, but none is lost due to inefficiencies in the conversion of steam to mechanical work, in contrast to Comparative Example 2 where 22% and 37%, respectively, of the energy was lost in these ways.
Example 6 is a partial electrification process X as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 2. In process X, partial electrification is provided by an electric furnace of primary reformer 220A in addition to the electric compressors of Example 5. The key elements of this electrified plant X are shown in
As shown in
There are four major energy consumers in the process X of this Example 6: (1) regeneration of the amine solution in CO2 removal 240A, (2) power to drive the two large compressors, e.g., work W2 and W3 required for synthesis loop compressor(s) C2/C3 and refrigeration compressor at A6, respectively, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer 220A, and (4) preheating (e.g., at heating B2) of the feed before the first ammonia synthesis reactor 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed when cooling (e.g., at A4) the product gases from the same reactor), but the rest must be supplied externally. In Example 6, external energy is supplied in three places: the primary reformer furnace of primary reformer 220A, the auxiliary boiler 260, and renewable electricity used to power the two large compressors. The primary reformer 220A is heated electrically in this embodiment; 210 MW of renewable electricity are used to generate 200 MW of heat. In contrast to Comparative Example 2, there is no convection section in the primary reformer furnace and no flue gas losses from this heating. Auxiliary boiler 260 consumes 5.5 t/hr of natural gas with a contained chemical energy of 84 MW. An amount of 94 MW of electricity is supplied to the two large compressors; at an efficiency of 93%, this performs the same work that required 349 MW of high pressure steam 263 in Comparative Example 2. In addition, although some of the reactions are exothermic (e.g., ammonia synthesis at 250A), the net set of reactions for Example 6 is endothermic and requires roughly 67 MW of energy to be provided. How to most efficiently allocate the available energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 6 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. For example, in the process of Example 6, this wasted energy amounts to 17 MW, a reduction of 89% over Comparative Example 2. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 3 shows energy use values for the process of Example 6. As seen in Table 3, an amount of 84 MW of energy is supplied through the combustion of natural gas in the auxiliary boiler 260, a reduction of 89% over fuel consumption in Comparative Example 2. An additional 304 MW of energy is supplied as electricity. Of the total energy, 67 MW is required to supply the net endothermic heat of reaction. After subtracting this, the available net energy input to the process for other uses is 321 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 72 MW of renewable electricity supplied to the primary reformer 220A, all is supplied to the reactor; there is no convection section and no flue gas produced in primary reformer 220A of this embodiment. An amount of 84 MW is supplied to the auxiliary boiler 260, of which 67 MW is used to supply heat for CO2 removal 240A; 17 MW, or 5.3% of the net external energy available, is lost to the atmosphere in the flue gas. An additional 17 MW, or 5.3% of the net external energy available, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 3, the total fuel gas consumption is 44,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.12 million tons of CO2 annually. An additional 1.1 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.22 million tons per year, a decrease of 48% over Comparative Example 2. Specific energy consumption after subtracting for the heat of reaction from the fuel and electricity inputs is 8.7 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 10.5 GJ per ton of ammonia produced. Only 5% of the total available energy is lost to the atmosphere from the stack gas, but none is lost due to inefficiencies in the conversion of steam to mechanical work, in contrast to Comparative Example 2 where 22% and 37%, respectively, of the energy was lost in these ways.
Example 7 is a partial electrification process XI as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 2. In process XI, partial electrification is provided by an electric reboiler (as in Example 3) in addition to the electric compressors of Example 5. The key elements of this electrified plant XI are shown in
As shown in
There are four major energy consumers in the process XI of this Example 7: (1) regeneration of the amine solution in CO2 removal 240A, (2) power to drive the two large compressors, e.g., work W2 and W3 for synthesis loop compressor(s) C2/C3 and refrigeration compressor at A6, respectively, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer at 220, and (4) preheating (e.g., at heating B2) of the feed before the first ammonia synthesis reactor 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed when cooling (e.g., at A4) the product gases 243 from the same reactor), but the rest must be supplied externally. In Example 7, external energy is supplied in three places: the primary reformer furnace at primary reforming 220A, an electric heater for the CO2 removal system at 240A, and renewable electricity used to power the two large compressors. The primary reformer furnace consumes 21.1 t/hr of natural gas with a contained chemical energy (high-heating value, or HHV) of 322 MW. 16 MW of electricity is supplied to the CO2 removal system 240A, generating 15 MW of heat at an efficiency of 95%. An amount of 94 MW of electricity is supplied to the large compressors; at an efficiency of 93%, this performs the same work that required 349 MW of high pressure steam 263 in Comparative Example 2. In addition, although some of the reactions are exothermic (e.g., ammonia synthesis at 250A), the net set of reactions for Example 7 is endothermic and requires roughly 67 MW of energy to be provided. How to most efficiently allocate the available energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 7 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. For example, in the process of Example 7, this wasted energy amounts to 64 MW, a reduction of 59% over Comparative Example 2. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor at 250A.
Table 3 shows energy use values for the process XI of Example 7. As seen in Table 3, an amount of 322 MW of energy is supplied through the combustion of natural gas in the reformer furnace at primary reformer 220A; in contrast to Comparative Example 2, there is no auxiliary boiler. An additional 110 MW of energy is supplied as electricity. Of the total energy, 67 MW is required to supply the net endothermic heat of reaction. After subtracting this, the available net energy input to the process for other uses is 365 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. Of the 322 MW consumed in the primary reformer furnace, the radiant section is used to provide 168 MW to further heat the gases and supply the heat of reaction; an additional 90 MW is transferred in the convection section to provide process heat. The remaining 64 MW is lost to the atmosphere in the flue gas; this represents 18% of the total net available energy. An additional 7 MW, or 1.9% of the net external energy available, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 3, the total fuel gas consumption is 169,000 tons per year. The combustion of this fuel results in the atmospheric emissions 0.47 million tons of CO2 annually. An additional 1.1 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.57 million tons per year, a decrease of 33% over Comparative Example 2. Specific energy consumption after subtracting the heat of reaction from fuel and electricity inputs is 9.9 GJ per ton of ammonia produced; specific energy consumption calculated only on the fuel and electricity inputs is 11.7 GJ per ton of ammonia produced. An amount of 18% of the total available energy is lost to the atmosphere from the stack gas, but none is lost due to inefficiencies in the conversion of steam to mechanical work, in contrast to Comparative Example 2 where 22% and 37%, respectively, of the energy was lost in these ways.
Example 8 is a near-complete electrification process XII as per an embodiment of this disclosure of the ammonia synthesis process described in Comparative Example 2. In process XII, near-complete electrification is provided by electric compressors (as in Examples 5-7), an electric furnace in primary reformer 220A (as in Example 6), and an electric reboiler (as in Example 7). The key elements of this electrified plant XII are shown in
As shown in
There are four major energy consumers in the process XII of this Example 8: (1) regeneration of the amine solution in CO2 removal 240A, (2) power to drive the two large compressors, e.g., to provide work W2 and W3 for synthesis loop compressor(s) C2/C3 and refrigeration compressor at A6, respectively, (3) heating (e.g., at feed pretreatment 110) to raise the temperature of the feed gases and provide the heat of reaction for the primary reformer at 220A, and (4) preheating (e.g., at heating B2) of the feed before the first ammonia synthesis reactor of 250A. Smaller amounts of energy are used for a variety of other purposes. Some of the energy required for these operations can be obtained by heat exchange with streams that are being cooled (for example, much of the heat required to preheat (e.g., at heating B1) the methanation reactor feed can be obtained from heat removed when cooling (e.g., at A4) the product gases 243 from the same reactor), but the rest must be supplied externally. In Example 8, external energy is supplied in three places: the electric heating of the primary reformer at 220A, an electric heater for the CO2 removal system at 240A, and renewable electricity used to power the two large compressors; all of this external energy is supplied by renewable electricity in this embodiment. The primary reformer 220A is heated electrically; 210 MW of renewable electricity are used to generate 200 MW of heat. In contrast to Comparative Example 2, there is no convection section in the primary reformer furnace and no flue gas losses from this heating. In Example 8, 71 MW of electricity is supplied to the CO2 removal system 240A, generating 67 MW of heat at an efficiency of 95%. An amount of 94 MW of electricity is supplied to the two large compressors; at an efficiency of 93%, this performs the same work that required 349 MW of high pressure steam 263 in Comparative Example 2. In addition, although some of the reactions are exothermic (e.g., ammonia synthesis at 250A), the net set of reactions for Example 8 is endothermic and requires roughly 67 MW of energy to be provided. How to most efficiently allocate the available energy to the various consumers of energy in the process with the highest efficiency is an engineering problem that can be addressed by one of skill in the art upon reading this disclosure via careful matching of temperatures, types of energy, and energy content. Energy can be transferred directly via heat exchange or it can be converted to steam that can either be used for heat exchange or to do mechanical work, such as to drive a compressor. In Example 8 a strategy has been utilized that maximizes heat exchange between the various process streams; assuming that available heat can be moved efficiently from where it is available to where it is needed at a corresponding temperature. This represents a maximal heat integration strategy and minimizes external energy inputs, but other arrangements are possible, as will be obvious to one skilled in the art. The use of combustion to supply some of the external energy input needed for the process comes with a concomitant disadvantage—the stack or flue gas from these furnaces and boilers contains energy that cannot be usefully recovered because of its low temperature and difficulties in condensing water. However, in the process of Example 8, no energy is lost in the flue gas. Energy is also lost in several process steps where streams are cooled but the heat cannot be usefully recovered, for example in the final cooling of the product stream from ammonia synthesis reactor of 250A.
Table 3 shows energy use values for the process XII of Example 8. As seen in Table 3, an amount of 375 MW of energy is supplied as electricity. Of the total energy, 67 MW is required to supply the net endothermic heat of reaction. After subtracting this, the available net energy input to the process for other uses is 308 MW, although a large amount (>400 MW) of energy is also transferred internally from the cooling of hot product streams to the heating of feed streams. In contrast to Comparative Example 2, no energy is lost in Example 8 in the conversion of steam to mechanical work or to the atmosphere in the flue gas. An amount of 21 MW, or 6.8% of the net external energy available, is lost due to inefficiencies in the use of electricity.
As further seen in the data in Table 3, there is no fuel gas consumption in process XII Example 8. Because of this, the combustion of fuel does not result in the atmospheric emission of CO2. 1.1 million tons of CO2 are emitted from the process chemistry itself, giving total CO2 emissions of 1.1 million tons per year, a decrease of 53% over Comparative Example 2. Specific energy consumption after subtracting the heat of reaction from the electricity inputs is 8.3 GJ per ton of ammonia produced; specific energy consumption calculated only on the electricity inputs is 10.2 GJ per ton of ammonia produced. In contrast to Comparative Example 2, no energy is lost to the atmosphere from the stack gas and no energy is lost in the conversion of steam to mechanical work.
As depicted in dashed lines in
To the process XII described in Example 8, we further add a pressure swing adsorption (PSA) gas separation unit 267 to purify the purge gas stream 205′. With a flowrate of 16.7 t/hr, this purge gas stream 205′ contains of 11 weight % hydrogen. The gas separation unit 267 consumes 2 MW of electricity, and yields a product stream 268 of essentially pure hydrogen. The resulting 1.84 t/hr of purified hydrogen is compressed by compressor C4 and stored in storage vessel 280 for use when the availability of renewable electricity is lower, or when it is more expensive. When needed, the stored hydrogen in storage vessel 280 is combined with the hydrogen in 268 being produced at that time by the process, and both are converted to electricity 272 using a fuel cell 270. When to use the stored hydrogen for electricity production will be determined by a variety of factors. As one possibility, if some renewable electricity was available on a diurnal basis, 22.1 tons hydrogen could be collected and stored over a twelve hour period. When released over the next twelve hours and combined with the 1.84 t/hr hydrogen in line 268 still being produced by the process, this would result in approximately 64 MW of electricity 272 being available continuously for the twelve hours. This could supply 170% of the 375 MW of electricity required for the operation of the process XII.
While various embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the subject matter disclosed herein are possible and are within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, RL and an upper limit, RU is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=RL+k*(RU-RL), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc.
Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present disclosure. Thus, the claims are a further description and are an addition to the embodiments of the present disclosure. The discussion of a reference is not an admission that it is prior art to the present disclosure, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein.
The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. While compositions and methods are described in broader terms of “having”, “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim.
Numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an”, as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents, the definitions that are consistent with this specification should be adopted.
Embodiments disclosed herein include:
A: An ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream comprising natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or a combination thereof; a syngas generation section comprising one or more reformers operable to reform the feed stream to produce a reformer product stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer product stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that, relative to a conventional ammonia synthesis plant, more of the energy required by the ammonia synthesis plant, the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
B: An ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream comprising a carbon-containing material, such as natural gas, methane, propane, butane, LPG, naphtha, coal and/or petroleum coke; a syngas generation section comprising one or more reformers operable to the pretreated feed stream to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising at least one shift reactor operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising at least one ammonia synthesis reactor operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy required by the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by electricity.
C: An ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no steam is utilized for mechanical work.
D: An ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no flue gas is produced.
E: An ammonia synthesis plant comprising: a feed pretreating section operable to pretreat a feed stream; a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen; a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream; a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured for no combustion other than optionally within an autothermal reformer (ATR) of the syngas generation section.
F: An ammonia synthesis plant comprising an electrically heated steam reformer operable to provide hydrogen and an electrically powered air separation unit (ASU) operable to provide nitrogen for the ammonia synthesis.
G: An ammonia synthesis plant comprising: a purification section operable to receive a hydrogen stream and a stream of nitrogen, wherein the stream of nitrogen is optionally from a source disparate from a source of the hydrogen stream, optionally remove at least one component from the hydrogen stream and/or the nitrogen stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy supplied for compression and heating within the purification section, the ammonia synthesis section, or the entire ammonia synthesis plant, is supplied from a non-carbon based energy source, a renewable energy source, electricity, and/or renewable electricity.
Each of embodiments A, B, C, D, E, F, and G may have one or more of the following additional elements: Element 1: wherein the non-carbon based energy source comprises electricity. Element 2: wherein the electricity is produced from a renewable energy source. Element 3: wherein the renewable energy source comprises wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof. Element 4: wherein a desired reforming temperature within at least one of the one or more reformers can be attained without externally (e.g., in a furnace) combusting a fuel or a carbon-based fuel. Element 5: wherein the one or more reformers are heated to the desired reforming temperature via heating from electricity or renewable electricity and including associated convective, radiant or other heat transfer means. Element 6: wherein the one or more reactors are heated resistively or inductively. Element 7: wherein, other than the production of steam for use in a steam methane reformer and/or a pre-reformer, steam is not utilized as a primary energy transfer medium, and/or wherein steam is not utilized for mechanical work. Element 8: wherein: a majority, some, or all of the steam utilized in a steam methane reformer, a pre-reformer, or a combination thereof is produced electrically. Element 9: further comprising an electrode boiler and/or an immersion heater for the production of steam. Element 10: wherein the pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof comprises one or more compressors, and wherein at least half or a majority of the one or more compressors are configured for non-gas-driven and/or non-steam-driven operation and/or are configured for operation via steam produced without burning a fuel or a carbon-based fuel. Element 11: wherein at least one of the one or more compressors are configured for bifunctional operation via both electric motor-driven and gas-driven or both electric motor-driven and steam driven operation, and/or comprise at least one electric motor-driven compressor and at least one gas-driven or steam-driven compressor. Element 12: comprising dual compressors for one or more compression step of the feed pretreating section, the syngas generation section, the shift conversion section, the hydrogen purification section, the ammonia synthesis section, or a combination thereof, such that the compression step can be effected via a first of the dual compressors that is online when a second of the dual compressors is offline, and vice versa, wherein the first of the dual compressors is electric motor-driven, and the second of the dual compressors is steam-driven or combustion-driven. Element 13: wherein configuration of the plant enables operation of one or more compression step via renewable electricity, when available, and operation via steam or combustion, when renewable electricity is not available. Element 14: wherein the renewable electricity is provided by wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof. Element 15: comprising apparatus for cooling or heating a process stream, wherein a fraction or a majority of the heating apparatus, the cooling apparatus, or both provide heating or cooling electrically. Element 16: wherein the fraction or the majority of the cooling apparatus comprises cooling apparatus downstream of each of the one or more reformers; cooling apparatus downstream of a final of the one or more reformers; cooling apparatus downstream of a high temperature shift reactor, a low temperature shift reactor, or both; cooling apparatus downstream of a methanator and configured to condense water out of a methanator product stream; cooling apparatus downstream one or more of the one or more ammonia synthesis reactors; or a combination thereof. Element 17: wherein the fraction or the majority of the heating apparatus comprises heating apparatus before the one or more reformers; between a carbon dioxide removal apparatus and a methanator of the purification section; heating apparatus upstream of the one or more ammonia synthesis reactors; or both. Element 18: wherein energy is stored using compressed hydrogen, compressed natural gas feed, cryogenic liquids, thermal batteries (including high thermal mass furnace lining material), electric batteries, or a combination thereof, such that the stored energy from the hydrogen, the natural gas, the cryogenic liquids, the thermal batteries, and/or electricity can be utilized when renewable electricity is not available. Element 19: further comprising electricity production apparatus configured to produce electricity from pressure or heat within the ammonia synthesis plant. Element 20: wherein the electricity production apparatus comprises an expander, a thermoelectric device, or a combination thereof. Element 21: wherein: the syngas generation section comprises a steam methane reformer upstream of an autothermal reformer, wherein a compressor is utilized to compress air for introduction into the autothermal reformer; the shift conversion section comprises a high temperature shift reactor upstream of a low temperature shift reactor, with cooling apparatus before and after the high temperature shift reactor and after the low temperature shift reactor; the hydrogen purification section comprises a carbon dioxide removal apparatus upstream of a methanator and separated therefrom via a heating apparatus, and a water condensing apparatus, one or more compressors, and a heating apparatus downstream of the methanator; the ammonia synthesis section comprises one or more ammonia synthesis reactors with heat removal apparatus, a recycle compressor downstream from a last of the one or more ammonia synthesis reactors, and a purge gas system, wherein the purge is taken upstream of the recycle compressor, wherein a majority of a net heat input needed by the steam methane reformer; a net heat input provided by the heating apparatus; a net heat removal effected by the cooling apparatus, the water condensing apparatus, and/or the purge gas system; or a combination thereof is provided by electricity; and/or wherein a majority of the compressors selected from the compressor utilized to compress the air, the one or more compressors downstream of the methanator, and the recycle compressor are electric-motor driven and/or driven by electrically-produced steam. Element 22: comprising no ATR, and further comprising an inlet line for nitrogen downstream of the one or more reformers of the syngas generation section. Element 23: comprising no autothermal reformer (ATR). Element 24: further comprising a nitrogen inlet line fluidly connecting the ASU with the one or more ammonia synthesis reactors, whereby the nitrogen from the ASU can be introduced as a component of a feed to the one or more ammonia synthesis reactors. Element 25: wherein the purification section further comprises a methanator, wherein the nitrogen inlet line is downstream of the methanator. Element 26: wherein an ammonia synthesis loop of the ammonia synthesis plant is operable with a lower amount of purging than a conventional ammonia synthesis plant.
The following are non-limiting, specific embodiments in accordance with the present disclosure:
A first embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream comprising natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or a combination thereof, a syngas generation section comprising one or more reformers operable to reform the feed stream to produce a reformer product stream comprising carbon monoxide and hydrogen, a shift conversion section comprising one or more shift reactors operable to subject the reformer product stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen, and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that, relative to a conventional ammonia synthesis plant, more of the energy required by the ammonia synthesis plant, the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
A second embodiment, which is the ammonia synthesis plant of the first embodiment, wherein the non-carbon based energy source comprises electricity.
A third embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream comprising a carbon-containing material, such as natural gas, methane, propane, butane, LPG, naphtha, coal and/or petroleum coke, a syngas generation section comprising one or more reformers operable to the pretreated feed stream to produce a reformer gas stream comprising carbon monoxide and hydrogen, a shift conversion section comprising at least one shift reactor operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen, and/or an ammonia synthesis section comprising at least one ammonia synthesis reactor operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy required by the feed pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof, is provided by electricity.
A fourth embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein the electricity is produced from a renewable energy source.
A fifth embodiment, which is the ammonia synthesis plant of the fourth embodiment, wherein the renewable energy source comprises wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof.
A sixth embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein a desired reforming temperature within at least one of the one or more reformers can be attained without externally (e.g., in a furnace) combusting a fuel or a carbon-based fuel.
A seventh embodiment, which is the ammonia synthesis plant of the sixth embodiment, wherein the one or more reformers are heated to the desired reforming temperature via heating from electricity or renewable electricity and including associated convective, radiant or other heat transfer means.
An eighth embodiment, which is the ammonia synthesis plant of the seventh embodiment, wherein the one or more reactors are heated resistively or inductively.
A ninth embodiment, which is the ammonia synthesis plant of the second or the third embodiment wherein, other than the production of steam for use in a steam methane reformer and/or a pre-reformer, steam is not utilized as a primary energy transfer medium, and/or wherein steam is not utilized for mechanical work.
A tenth embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein a majority, some, or all of the steam utilized in a steam methane reformer, a pre-reformer, or a combination thereof is produced electrically.
An eleventh embodiment, which is the ammonia synthesis plant of the tenth embodiment further comprising an electrode boiler and/or an immersion heater for the production of steam.
A twelfth embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein the pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof comprises one or more compressors, and wherein at least half or a majority of the one or more compressors are configured for non-gas-driven and/or non-steam-driven operation and/or are configured for operation via steam produced without burning a fuel or a carbon-based fuel.
A thirteenth embodiment, which is the ammonia synthesis plant of the twelfth embodiment, wherein at least one of the one or more compressors are configured for bifunctional operation via both electric motor-driven and gas-driven or both electric motor-driven and steam driven operation, and/or comprise at least one electric motor-driven compressor and at least one gas-driven or steam-driven compressor.
A fourteenth embodiment, which is the ammonia synthesis plant of the twelfth embodiment comprising dual compressors for one or more compression step of the feed pretreating section, the syngas generation section, the shift conversion section, the hydrogen purification section, the ammonia synthesis section, or a combination thereof, such that the compression step can be effected via a first of the dual compressors that is online when a second of the dual compressors is offline, and vice versa, wherein the first of the dual compressors is electric motor-driven, and the second of the dual compressors is steam-driven or combustion-driven.
A fifteenth embodiment, which is the ammonia synthesis plant of the twelfth, the thirteenth, or the fourteenth embodiment, wherein configuration of the plant enables operation of one or more compression step via renewable electricity, when available, and operation via steam or combustion, when renewable electricity is not available.
A sixteenth embodiment, which is the ammonia synthesis plant of the fifteenth embodiment, wherein the renewable electricity is provided by wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof.
A seventeenth embodiment, which is the ammonia synthesis plant of the second or the third embodiment comprising apparatus for cooling or heating a process stream, wherein a fraction or a majority of the heating apparatus, the cooling apparatus, or both provide heating or cooling electrically.
An eighteenth embodiment, which is the ammonia synthesis plant of the seventeenth embodiment, wherein the fraction or the majority of the cooling apparatus comprises cooling apparatus downstream of each of the one or more reformers; cooling apparatus downstream of a final of the one or more reformers; cooling apparatus downstream of a high temperature shift reactor, a low temperature shift reactor, or both; cooling apparatus downstream of a methanator and configured to condense water out of a methanator product stream; cooling apparatus downstream one or more of the one or more ammonia synthesis reactors; or a combination thereof.
A nineteenth embodiment, which is the ammonia synthesis plant of the seventeenth embodiment, wherein the fraction or the majority of the heating apparatus comprises heating apparatus before the one or more reformers; between a carbon dioxide removal apparatus and a methanator of the purification section; heating apparatus upstream of the one or more ammonia synthesis reactors; or both.
A twentieth embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein energy is stored using compressed hydrogen, compressed natural gas feed, cryogenic liquids, thermal batteries (including high thermal mass furnace lining material), electric batteries, or a combination thereof, such that the stored energy from the hydrogen, the natural gas, the cryogenic liquids, the thermal batteries, and/or electricity can be utilized when renewable electricity is not available.
A twenty-first embodiment, which is the ammonia synthesis plant of the second or the third embodiment further comprising electricity production apparatus configured to produce electricity from pressure or heat within the ammonia synthesis plant.
A twenty-second embodiment, which is the ammonia synthesis plant of the twenty-first embodiment, wherein the electricity production apparatus comprises an expander, a thermoelectric device, or a combination thereof.
A twenty-third embodiment, which is the ammonia synthesis plant of the second or the third embodiment, wherein the syngas generation section comprises a steam methane reformer upstream of an autothermal reformer, wherein a compressor is utilized to compress air for introduction into the autothermal reformer, the shift conversion section comprises a high temperature shift reactor upstream of a low temperature shift reactor, with cooling apparatus before and after the high temperature shift reactor and after the low temperature shift reactor, the hydrogen purification section comprises a carbon dioxide removal apparatus upstream of a methanator and separated therefrom via a heating apparatus, and a water condensing apparatus, one or more compressors, and a heating apparatus downstream of the methanator, the ammonia synthesis section comprises one or more ammonia synthesis reactors with heat removal apparatus, a recycle compressor downstream from a last of the one or more ammonia synthesis reactors, and a purge gas system, wherein the purge is taken upstream of the recycle compressor, wherein a majority of a net heat input needed by the steam methane reformer; a net heat input provided by the heating apparatus; a net heat removal effected by the cooling apparatus, the water condensing apparatus, and/or the purge gas system; or a combination thereof is provided by electricity, and/or wherein a majority of the compressors selected from the compressor utilized to compress the air, the one or more compressors downstream of the methanator, and the recycle compressor are electric-motor driven and/or driven by electrically-produced steam.
A twenty-fourth embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream, a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen, a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen, and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no steam is utilized for mechanical work.
A twenty-fifth embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream, a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen, a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that no flue gas is produced.
A twenty-sixth embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream, a syngas generation section comprising one or more reformers operable to reform methane to produce a reformer gas stream comprising carbon monoxide and hydrogen, a shift conversion section comprising one or more shift reactors operable to subject the reformer gas stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and/or an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured for no combustion other than optionally within an autothermal reformer (ATR) of the syngas generation section.
A twenty-seventh embodiment, which is the ammonia synthesis plant of the twenty-sixth embodiment comprising no ATR, and further comprising an inlet line for nitrogen downstream of the one or more reformers of the syngas generation section.
A twenty-eighth embodiment, which is an ammonia synthesis plant comprising an electrically heated steam reformer operable to provide hydrogen and an electrically powered air separation unit (ASU) operable to provide nitrogen for the ammonia synthesis.
A twenty-ninth embodiment, which is the ammonia synthesis plant of the twenty-eighth embodiment comprising no autothermal reformer (ATR).
A thirtieth embodiment, which is the ammonia synthesis plant of the twenty-ninth embodiment further comprising a nitrogen inlet line fluidly connecting the ASU with the one or more ammonia synthesis reactors, whereby the nitrogen from the ASU can be introduced as a component of a feed to the one or more ammonia synthesis reactors.
A thirty-first embodiment, which is the ammonia synthesis plant of the thirtieth embodiment, wherein the purification section further comprises a methanator, wherein the nitrogen inlet line is downstream of the methanator.
A thirty-second embodiment, which is the ammonia synthesis plant of the twenty-eighth embodiment, wherein an ammonia synthesis loop of the ammonia synthesis plant is operable with a lower amount of purging than a conventional ammonia synthesis plant.
A thirty-third embodiment, which is an ammonia synthesis plant comprising a purification section operable to receive a hydrogen stream and a stream of nitrogen, wherein the stream of nitrogen is optionally from a source disparate from a source of the hydrogen stream, optionally remove at least one component from the hydrogen stream and/or the nitrogen stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen; and an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein the ammonia synthesis plant is configured such that a majority of the net external energy supplied for compression and heating within the purification section, the ammonia synthesis section, or the entire ammonia synthesis plant, is supplied from a non-carbon based energy source, a renewable energy source, electricity, and/or renewable electricity.
A thirty-fourth embodiment, which is an apparatus and/or a method of producing ammonia via the apparatus as described herein and recited in any of the first through the thirty-third embodiments or any of the embodiments described in this disclosure.
The following are non-limiting, specific embodiments in accordance with the present disclosure:
Embodiments disclosed herein include:
A: A method of producing ammonia, the method comprising: (a) introducing a feed comprising a carbon containing material selected from natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or combinations thereof to a synthesis gas generation section such as steam reforming or partial oxidation to produce a synthesis gas product comprising hydrogen and carbon monoxide, where the energy required for the synthesis gas generation section is supplied by a heat input Q1; (b) cooling the reformer product to produce a cooled synthesis gas by effecting a heat removal Q2; (c) shifting the cooled synthesis gas to produce a shifted synthesis gas product; (d) cooling the shifted synthesis gas by effecting a heat removal Q3 to produce a cooled, shifted synthesis gas; (e) purifying the cooled, shifted synthesis gas by: removing carbon dioxide from the cooled, shifted synthesis gas; heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas; methanating the heated carbon-dioxide reduced gas to produce a methanator product; and cooling and condensing water from the methanator product by a heat removal Q5 to provide a purified gas; (f) compressing the purified gas; (g) heating the compressed, purified gas by a heat input Q6 to provide a heated gas; (h) providing an ammonia synthesis feed comprising the heated gas, wherein the ammonia synthesis feed comprises hydrogen and nitrogen, wherein the nitrogen is present in the synthesis gas or subsequently added thereto; (i) producing a product comprising ammonia from the ammonia synthesis feed; (j) cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen; (k) compressing the gas stream comprising nitrogen and hydrogen via a recycle compressor; and/or (l) purging via a purge gas system, wherein further cooling is effected by a heat removal Q8, wherein, relative to a conventional method of producing ammonia, more of the net energy required by the method or in (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k), (l), or a combination thereof (e.g., net thermal energy required (e.g., Q1+Q4+Q6−Q2−Q3−Q5−Q7−Q8) and/or the net energy needed for mechanical work) is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
B: A method of producing ammonia, the method comprising: (a) subjecting a feed comprising a carbon containing material selected from natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or combinations thereof to reforming in a reformer of a synthesis gas generation section to produce a reformer product comprising synthesis gas containing hydrogen and carbon monoxide, wherein a reforming temperature is maintained by a heat input Q1; (b) cooling the reformer product to produce a cooled reformer product by effecting a heat removal Q2; (c) shifting the reformer product to produce a shifted synthesis gas; (d) cooling the shifted synthesis gas by effecting a heat removal Q3; (e) purifying the cooled, shifted synthesis gas by: removing carbon dioxide from the cooled, shifted synthesis gas; heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas; methanating the heated carbon-dioxide reduced gas to produce a methanator product; and cooling and condensing water from the methanator product by removing a heat removal Q5 to provide a purified gas; (f) compressing the purified gas; (g) heating the compressed, purified gas by a heat input Q6 to provide a heated gas; (h) providing an ammonia synthesis feed comprising the heated gas, wherein the ammonia synthesis feed comprises hydrogen and nitrogen; (i) producing a product comprising ammonia from the ammonia synthesis feed; (j) cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen; (k) compressing the gas stream comprising nitrogen and hydrogen; and/or (l) purging via a purge gas system, wherein purging is effected by a heat removal Q8, wherein a majority of the net thermal and/or mechanical energy required by the method or one or more of (a)-(l) is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
C: A method of producing ammonia, the method comprising: (a) reacting (e.g., via processes such as steam reforming, partial oxidation and of gasification), a carbon containing material such as natural gas, methane, propane, butane, LPG, naphtha, coal or petroleum coke to produce a synthesis gas comprising carbon monoxide and hydrogen; (b) shifting the synthesis gas to produce a shifted product comprising increased amount of hydrogen; (c) purifying the shifted product to produce a purified gas comprising a smaller amount of non-hydrogen components; and (d) synthesizing ammonia from the purified gas and optionally additional nitrogen to provide an ammonia product, wherein a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed in (a), (b), (c), (d), or a combination thereof is provided by a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof.
D: A method of producing ammonia, the method comprising: introducing a feed comprising a carbon containing material such as natural gas, methane, propane, butane, LPG, naphtha, coal or petroleum coke to a synthesis gas generation section such as steam reforming or partial oxidation to produce a synthesis gas product comprising hydrogen and carbon monoxide, where the energy required for the synthesis gas generation section is supplied by a heat input Q1; cooling the synthesis gas product to produce a cooled synthesis gas by effecting a heat removal Q2; shifting the cooled synthesis gas to produce a shifted synthesis gas product; cooling the shifted synthesis gas product by effecting a heat removal Q3 to produce a cooled, shifted synthesis gas; purifying the cooled, shifted synthesis gas by: removing carbon dioxide from the cooled, shifted synthesis gas; heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas; methanating the heated carbon-dioxide reduced gas to produce a methanator product; and cooling and condensing water from the methanator product by removing a heat removal Q5 to provide a purified gas; compressing the purified gas; heating the compressed, purified gas by a heat input Q6 to provide a heated gas; providing an ammonia synthesis feed comprising the heated gas and optionally added nitrogen; producing a product comprising ammonia from the ammonia synthesis feed; cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen; compressing the gas stream comprising nitrogen and hydrogen via a recycle compressor; and/or purging via a purge gas system, wherein further cooling is effected by a heat removal Q8, wherein a majority or substantially all of the heat removed in cooling and water condensation (e.g., Q2, Q3, Q5, Q7, and/or Q8) is used only for heating other streams (e.g., Q1, Q4, and/or Q7) and/or is converted to electricity.
Each of embodiments A, B, C, and D may have one or more of the following additional elements: Element 1: wherein the non-carbon based energy source comprises electricity. Element 2: wherein the electricity is produced from a renewable energy source. Element 3: wherein the renewable energy source comprises wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof. Element 4: wherein the energy required for the synthesis gas generation section is supplied without combusting a fuel or a carbon-based fuel. Element 5: wherein the non-carbon based energy source comprises or the electricity is produced via an intermittent energy source (IES), and further comprising maintaining the temperature of one or more reactors in the synthesis gas generation section without combusting a fuel or a carbon-based fuel when the IES is available, and maintaining the temperature of one or more reactors in the synthesis gas generation section via a stored supply of energy from the IES or by combusting a fuel or a carbon-based fuel when the IES is not available. Element 6: wherein the synthesis gas generation is carried out in one or more steam reformers and the necessary energy is supplied via inductive or resistive heating from electricity or renewable electricity and including associated convective, radiant or other heat transfer means. Element 7: wherein, other than the optional production of steam for use in the synthesis gas generating section, steam is not utilized as a primary energy transfer medium; and/or steam is not utilized for mechanical work. Element 8: wherein a majority, some, or all of the steam utilized in the synthesis gas generating section, one or more, a majority, or all steam turbines of the plant, or a combination thereof is produced electrically. Element 9: wherein removing heat does not comprise the production of steam for use for mechanical work. Element 10: wherein compressing the purified gas, compressing the gas stream comprising nitrogen and hydrogen, compressing air for introduction into the process, or a combination thereof comprises compressing with a compressor driven by electric motor, an electrically-driven turbine, or a turbine driven by steam produced electrically in at least one, most, or all compressors utilized. Element 11: further comprising utilizing a thermoelectric device to convert some of the heat removed at Q2, Q3, Q5, Q7, and/or Q8 to electricity. Element 12: further comprising utilizing electric heating to control a temperature profile of any or all of a number of reactors of the synthesis gas generation section, shifting reactors utilized for shifting, methanation reactors utilized for the methanating, and ammonia synthesis reactors utilized for producing the product comprising ammonia from the ammonia synthesis feed. Element 13: wherein at least one of a number of reactors of the synthesis gas generation section is operated to at least approximate isothermal operation. Element 14: wherein a system for removing carbon dioxide comprises amine recovery, and wherein the amine recovery is effected with electric heating. Element 15: wherein the electric heating is performed by an immersion heater. Element 16: further comprising providing some or all of the heat Q1 needed to achieve a reaction temperature in (a) via feeding steam to one or more reactors of the synthesis gas generation section, wherein the steam is superheated electrically. Element 17: further comprising providing the nitrogen in the ammonia synthesis feed via an air separation unit (ASU) powered by renewable electricity, whereby the ammonia synthesis feed has a reduced amount of argon and/or other inert species relative to conventional operation. Element 18: wherein the reduced amount of argon and/or other inerts reduces a purging of an ammonia synthesis loop of the ammonia synthesis relative to conventional ammonia synthesis. Element 19: further comprising providing the nitrogen in the ammonia synthesis feed by introducing nitrogen from the renewable electrically powered ASU during or after the purifying of the cooled, shifted synthesis gas. Element 20: further comprising removing methane from the purified gas prior to compressing the purified gas, wherein removing methane from the purified gas reduces an amount of purging in (l) of an ammonia synthesis loop utilized to produce the product comprising ammonia from the ammonia synthesis feed. Element 21: further comprising removing the methane from the purified gas via a renewable electrically powered methane removal process. Element 22: wherein the renewable electrically powered methane removal process comprises pressure swing adsorption (PSA). Element 23: further comprising storing natural gas when electricity is available and/or below a threshold price, and utilizing the stored natural gas as a component of the feed and/or to generate electricity when electricity is unavailable or above the threshold price. Element 24: further comprising storing a refrigerant when electricity is available or below a threshold price and utilizing the refrigerant for cooling to provide heat removal Q2, Q3, Q5, Q7, and/or Q8 when electricity is unavailable or above the threshold price. Element 25: wherein the refrigerant comprises ammonia. Element 26: further comprising separating hydrogen from a purge gas stream and combusting at least a portion of the separated hydrogen to provide heat, high-temperature steam for use as a reactant in syngas generation, or both. Element 27: further comprising separating hydrogen from a purge gas stream, and optionally storing at least a portion of the separated hydrogen and converting the stored at least a portion of the hydrogen to electricity when other sources of electricity are not readily available and/or are not available at a desirable price. Element 28: wherein one or more fuel cells is used for the conversion of hydrogen to electricity. Element 29: wherein the amount of electricity consumed is greater than or equal to about 25 MW. Element 30: wherein the amount of CO2 produced per ton of ammonia is less than or equal to about 1.6 tons CO2 per ton of ammonia produced. Element 31: wherein the specific energy consumption is less than or equal to about 12 GJ per ton of ammonia produced. Element 32: wherein the total consumption of methane and/or natural gas for both feed and fuel is less than or equal to about 0.65 tons per ton of ammonia produced. Element 33: wherein the total consumption of methane and/or natural gas for fuel is less than or equal to about 0.20 tons per ton of ammonia produced. Element 34: wherein a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed for heat removal, heat input, compression, or a combination thereof in (a), (b), (c), (d), or a combination thereof is provided by a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof. Element 35: wherein (a) synthesis gas generation is effected without burning a fuel and/or a carbon-based fuel. Element 36: wherein utilizing a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof to provide a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed in (a), (b), (c), (d), or the combination thereof results in a reduction of at least 5, 10, 20, 30, or 40% in greenhouse gas emissions relative to a conventional method of producing ammonia.
The following are non-limiting, specific embodiments in accordance with the present disclosure:
A first embodiment, which is a method of producing ammonia, the method comprising (a) introducing a feed comprising a carbon containing material selected from natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or combinations thereof to a synthesis gas generation section such as steam reforming or partial oxidation to produce a synthesis gas product comprising hydrogen and carbon monoxide, where the energy required for the synthesis gas generation section is supplied by a heat input Q1, (b) cooling the reformer product to produce a cooled synthesis gas by effecting a heat removal Q2, (c) shifting the cooled synthesis gas to produce a shifted synthesis gas product, (d) cooling the shifted synthesis gas by effecting a heat removal Q3 to produce a cooled, shifted synthesis gas, (e) purifying the cooled, shifted synthesis gas by removing carbon dioxide from the cooled, shifted synthesis gas, heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas, methanating the heated carbon-dioxide reduced gas to produce a methanator product, and cooling and condensing water from the methanator product by a heat removal Q5 to provide a purified gas, (f) compressing the purified gas, (g) heating the compressed, purified gas by a heat input Q6 to provide a heated gas, (h) providing an ammonia synthesis feed comprising the heated gas, wherein the ammonia synthesis feed comprises hydrogen and nitrogen, wherein the nitrogen is present in the synthesis gas or subsequently added thereto, (i) producing a product comprising ammonia from the ammonia synthesis feed, (j) cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen, (k) compressing the gas stream comprising nitrogen and hydrogen via a recycle compressor, and/or (l) purging via a purge gas system, wherein further cooling is effected by a heat removal Q8, wherein, relative to a conventional method of producing ammonia, more of the net energy required by the method or in (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k), (l), or a combination thereof (e.g., net thermal energy required (e.g., Q1+Q4+Q6−Q2−Q3−Q5−Q7−Q8) and/or the net energy needed for mechanical work) is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
A second embodiment, which is the method of the first embodiment, wherein the non-carbon based energy source comprises electricity.
A third embodiment, which is a method of producing ammonia, the method comprising (a) subjecting a feed comprising a carbon containing material selected from natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or combinations thereof to reforming in a reformer of a synthesis gas generation section to produce a reformer product comprising synthesis gas containing hydrogen and carbon monoxide, wherein a reforming temperature is maintained by a heat input Q1, (b) cooling the reformer product to produce a cooled reformer product by effecting a heat removal Q2, (c) shifting the reformer product to produce a shifted synthesis gas, (d) cooling the shifted synthesis gas by effecting a heat removal Q3, (e) purifying the cooled, shifted synthesis gas by removing carbon dioxide from the cooled, shifted synthesis gas, heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas, methanating the heated carbon-dioxide reduced gas to produce a methanator product, and cooling and condensing water from the methanator product by removing a heat removal Q5 to provide a purified gas, (f) compressing the purified gas, (g) heating the compressed, purified gas by a heat input Q6 to provide a heated gas, (h) providing an ammonia synthesis feed comprising the heated gas, wherein the ammonia synthesis feed comprises hydrogen and nitrogen, (i) producing a product comprising ammonia from the ammonia synthesis feed, (j) cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen, (k) compressing the gas stream comprising nitrogen and hydrogen, and/or (l) purging via a purge gas system, wherein purging is effected by a heat removal Q8, wherein a majority of the net thermal and/or mechanical energy required by the method or one or more of (a)-(l) is provided by a non-carbon based energy source, a renewable energy source, and/or electricity.
A fourth embodiment, which is the method of the second or the third embodiment, wherein the electricity is produced from a renewable energy source.
A fifth embodiment, which is the method of the fourth embodiment, wherein the renewable energy source comprises wind, solar, geothermal, hydroelectric, nuclear, tide, wave, or a combination thereof.
A sixth embodiment, which is the method of the second or the third embodiment, wherein the energy required for the synthesis gas generation section is supplied without combusting a fuel or a carbon-based fuel.
A seventh embodiment, which is the method of the sixth embodiment, wherein the non-carbon based energy source comprises or the electricity is produced via an intermittent energy source (IES), and further comprising maintaining the temperature of one or more reactors in the synthesis gas generation section without combusting a fuel or a carbon-based fuel when the IES is available, and maintaining the temperature of one or more reactors in the synthesis gas generation section via a stored supply of energy from the IES or by combusting a fuel or a carbon-based fuel when the IES is not available.
An eighth embodiment, which is the method of the second or the third embodiment, wherein the synthesis gas generation is carried out in one or more steam reformers and the necessary energy is supplied via inductive or resistive heating from electricity or renewable electricity and including associated convective, radiant or other heat transfer means.
A ninth embodiment, which is the method of the second or the third embodiment wherein, other than the optional production of steam for use in the synthesis gas generating section, steam is not utilized as a primary energy transfer medium, and/or steam is not utilized for mechanical work.
A tenth embodiment, which is the method of the second or the third embodiment, wherein a majority, some, or all of the steam utilized in the synthesis gas generating section, one or more, a majority, or all steam turbines of the plant, or a combination thereof is produced electrically.
An eleventh embodiment, which is the method of the second or the third embodiment, wherein removing heat does not comprise the production of steam for use for mechanical work.
A twelfth embodiment, which is the method of the second or the third embodiment, wherein compressing the purified gas, compressing the gas stream comprising nitrogen and hydrogen, compressing air for introduction into the process, or a combination thereof comprises compressing with a compressor driven by electric motor, an electrically-driven turbine, or a turbine driven by steam produced electrically in at least one, most, or all compressors utilized.
A thirteenth embodiment, which is the method of the second or the third embodiment further comprising utilizing a thermoelectric device to convert some of the heat removed at Q2, Q3, Q5, Q7, and/or Q8 to electricity.
A fourteenth embodiment, which is the method of the second or the third embodiment further comprising utilizing electric heating to control a temperature profile of any or all of a number of reactors of the synthesis gas generation section, shifting reactors utilized for shifting, methanation reactors utilized for the methanating, and ammonia synthesis reactors utilized for producing the product comprising ammonia from the ammonia synthesis feed.
A fifteenth embodiment, which is the method of the second or the third embodiment, wherein at least one of a number of reactors of the synthesis gas generation section is operated to at least approximate isothermal operation.
A sixteenth embodiment, which is the method of the second or the third embodiment, wherein a system for removing carbon dioxide comprises amine recovery, and wherein the amine recovery is effected with electric heating.
A seventeenth embodiment, which is the method of the sixteenth embodiment, wherein the electric heating is performed by an immersion heater.
An eighteenth embodiment, which is the method of the second or the third embodiment further comprising providing some or all of the heat Q1 needed to achieve a reaction temperature in (a) via feeding steam to one or more reactors of the synthesis gas generation section, wherein the steam is superheated electrically.
A nineteenth embodiment, which is the method of the second or the third embodiment further comprising providing the nitrogen in the ammonia synthesis feed via an air separation unit (ASU) powered by renewable electricity, whereby the ammonia synthesis feed has a reduced amount of argon and/or other inert species relative to conventional operation.
A twentieth embodiment, which is the method of the nineteenth embodiment, wherein the reduced amount of argon and/or other inerts reduces a purging of an ammonia synthesis loop of the ammonia synthesis relative to conventional ammonia synthesis.
A twenty-first embodiment, which is the method of the twentieth embodiment further comprising providing the nitrogen in the ammonia synthesis feed by introducing nitrogen from the renewable electrically powered ASU during or after the purifying of the cooled, shifted synthesis gas.
A twenty-second embodiment, which is the method of the second or the third embodiment, further comprising removing methane from the purified gas prior to compressing the purified gas, wherein removing methane from the purified gas reduces an amount of purging in (l) of an ammonia synthesis loop utilized to produce the product comprising ammonia from the ammonia synthesis feed.
A twenty-third embodiment, which is the method of the twenty-second embodiment further comprising removing the methane from the purified gas via a renewable electrically powered methane removal process.
A twenty-fourth embodiment, which is the method of the twenty-third embodiment, wherein the renewable electrically powered methane removal process comprises pressure swing adsorption (PSA).
A twenty-fifth embodiment, which is the method of the second or the third embodiment further comprising storing natural gas when electricity is available and/or below a threshold price, and utilizing the stored natural gas as a component of the feed and/or to generate electricity when electricity is unavailable or above the threshold price.
A twenty-sixth embodiment, which is the method of the second or the third embodiment further comprising storing a refrigerant when electricity is available or below a threshold price and utilizing the refrigerant for cooling to provide heat removal Q2, Q3, Q5, Q7, and/or Q8 when electricity is unavailable or above the threshold price.
A twenty-seventh embodiment, which is the method of the twenty-sixth embodiment, wherein the refrigerant comprises ammonia.
A twenty-eighth embodiment, which is the method of the second or the third embodiment further comprising separating hydrogen from a purge gas stream and combusting at least a portion of the separated hydrogen to provide heat, high-temperature steam for use as a reactant in syngas generation, or both.
A twenty-ninth embodiment, which is the method of the second or the third embodiment, further comprising separating hydrogen from a purge gas stream, and optionally storing at least a portion of the separated hydrogen and converting the stored at least a portion of the hydrogen to electricity when other sources of electricity are not readily available and/or are not available at a desirable price.
A thirtieth embodiment, which is the method of the twenty-ninth embodiment, wherein one or more fuel cells is used for the conversion of hydrogen to electricity.
A thirty-first embodiment, which is the method of the second or the third embodiment, wherein the amount of electricity consumed is greater than or equal to about 25 MW.
A thirty-second embodiment, which is the method of the first, the second, or the third embodiment, wherein the amount of CO2 produced per ton of ammonia is less than or equal to about 1.6 tons CO2 per ton of ammonia produced.
A thirty-third embodiment, which is the method of the first, the second, or the third embodiment, wherein the specific energy consumption is less than or equal to about 12 GJ per ton of ammonia produced.
A thirty-fourth embodiment, which is the method of the first, the second, or the third embodiment, wherein the total consumption of methane and/or natural gas for both feed and fuel is less than or equal to about 0.65 tons per ton of ammonia produced.
A thirty-fifth embodiment, which is the method of the first, the second, or the third embodiment, wherein the total consumption of methane and/or natural gas for fuel is less than or equal to about 0.20 tons per ton of ammonia produced.
A thirty-sixth embodiment, which is a method of producing ammonia, the method comprising (a) reacting (e.g., via processes such as steam reforming, partial oxidation and of gasification), a carbon containing material such as natural gas, methane, propane, butane, LPG, naphtha, coal or petroleum coke to produce a synthesis gas comprising carbon monoxide and hydrogen, (b) shifting the synthesis gas to produce a shifted product comprising increased amount of hydrogen, (c) purifying the shifted product to produce a purified gas comprising a smaller amount of non-hydrogen components, and (d) synthesizing ammonia from the purified gas and optionally additional nitrogen to provide an ammonia product, wherein a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed in (a), (b), (c), (d), or a combination thereof is provided by a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof.
A thirty-seventh embodiment, which is the method of the thirty-sixth embodiment, wherein a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed for heat removal, heat input, compression, or a combination thereof in (a), (b), (c), (d), or a combination thereof is provided by a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof.
A thirty-eighth embodiment, which is the method of the thirty-sixth embodiment, wherein (a) synthesis gas generation is effected without burning a fuel and/or a carbon-based fuel.
A thirty-ninth embodiment, which is the method of the thirty-sixth embodiment, wherein utilizing a non-carbon based energy source, a renewable energy source, electricity, or a combination thereof to provide a majority or greater than or equal to about 40, 50, 60, 70, 80, or 90% of the net energy needed in (a), (b), (c), (d), or the combination thereof results in a reduction of at least 5, 10, 20, 30, or 40% in greenhouse gas emissions relative to a conventional method of producing ammonia.
A fortieth embodiment, which is a method of producing ammonia, the method comprising introducing a feed comprising a carbon containing material such as natural gas, methane, propane, butane, LPG, naphtha, coal or petroleum coke to a synthesis gas generation section such as steam reforming or partial oxidation to produce a synthesis gas product comprising hydrogen and carbon monoxide, where the energy required for the synthesis gas generation section is supplied by a heat input Q1, cooling the synthesis gas product to produce a cooled synthesis gas by effecting a heat removal Q2, shifting the cooled synthesis gas to produce a shifted synthesis gas product, cooling the shifted synthesis gas product by effecting a heat removal Q3 to produce a cooled, shifted synthesis gas, purifying the cooled, shifted synthesis gas by removing carbon dioxide from the cooled, shifted synthesis gas, heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas, methanating the heated carbon-dioxide reduced gas to produce a methanator product, and cooling and condensing water from the methanator product by removing a heat removal Q5 to provide a purified gas, compressing the purified gas, heating the compressed, purified gas by a heat input Q6 to provide a heated gas, providing an ammonia synthesis feed comprising the heated gas and optionally added nitrogen, producing a product comprising ammonia from the ammonia synthesis feed, cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen, compressing the gas stream comprising nitrogen and hydrogen via a recycle compressor, and/or purging via a purge gas system, wherein further cooling is effected by a heat removal Q8, wherein a majority or substantially all of the heat removed in cooling and water condensation (e.g., Q2, Q3, Q5, Q7, and/or Q8) is used only for heating other streams (e.g., Q1, Q4, and/or Q7) and/or is converted to electricity.
The following are non-limiting, specific embodiments in accordance with the present disclosure:
A first embodiment, which is an ammonia synthesis plant comprising a feed pretreating section operable to pretreat a feed stream comprising natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or a combination thereof, a syngas generation section comprising one or more reformers operable to reform the feed stream to produce a reformer product stream comprising carbon monoxide and hydrogen, a shift conversion section comprising one or more shift reactors operable to subject the reformer product stream to the water gas shift reaction, to produce a shifted gas stream comprising more hydrogen than the reformer gas stream, a purification section operable to remove at least one component from the shifted gas stream, and provide an ammonia synthesis feed stream comprising hydrogen and nitrogen, and an ammonia synthesis section comprising one or more ammonia synthesis reactors operable to produce ammonia from the ammonia synthesis feed stream, wherein ammonia synthesis plant consumes greater than or equal to about 25 MW of electricity, wherein the amount of CO2 produced per ton of ammonia is less than or equal to about 1.6 tons CO2 per ton of ammonia produced, and wherein the specific energy consumption is less than or equal to about 12 GJ per ton of ammonia produced.
A second embodiment, which is the ammonia synthesis plant according to the first embodiment, wherein the ammonia synthesis plant has no flue gas heat recovery section.
A third embodiment, which is the ammonia synthesis plant according to the first or the second embodiment, wherein a predetermined reforming temperature within at least one of the one or more reformers can be attained without externally combusting a fuel or a carbon-based fuel, and wherein the one or more reformers are heated to the predetermined reforming temperature via heating from electricity and including associated convective, radiant or other heat transfer means.
A fourth embodiment, which is the ammonia synthesis plant according to any of the first through the third embodiments, wherein the one or more reactors are heated inductively.
A fifth embodiment, which is the ammonia synthesis plant according to any of the first through the fourth embodiments, wherein other than the production of steam for use in a steam methane reformer or a pre-reformer, steam is not utilized as a primary energy transfer medium.
A sixth embodiment, which is the ammonia synthesis plant according to any of the first through the fifth embodiments, wherein at least 25% of mechanical work performed in the ammonia synthesis plant is accomplished without use of steam. In an aspect, which is the ammonia synthesis plant according to the sixth embodiment, at least 25, 30, 40, 50, 60, 70, 80, 90, 99, or 100% of mechanical work performed in the ammonia synthesis plant is accomplished without use of steam, for example via one or more electrified compressors. In an aspect, which is the ammonia synthesis plant according to the sixth embodiment, at least 50, 60, 70, 80, 90, 99, or 100% of mechanical work performed in the ammonia synthesis plant is accomplished without use of steam, for example via two or more electrified compressors. In an aspect, which is the ammonia synthesis plant according to the sixth embodiment, at least 50, 60, 70, 80, 90, 99, or 100% of mechanical work performed in the ammonia synthesis plant is accomplished without use of steam, for example via three or more electrified compressors using equal to or greater than about 100, 110, or 120 MW of electricity.
A seventh embodiment, which is the ammonia synthesis plant according to any of the first through the sixth embodiments, wherein at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 100% of the steam utilized in a steam methane reformer, a pre-reformer, or a combination thereof is produced by electric heating.
An eighth embodiment, which is the ammonia synthesis plant according to any of the first through the seventh embodiments, wherein the pretreating section, the syngas generation section, the shift conversion section, the purification section, the ammonia synthesis section, or a combination thereof comprises one or more compressors, and wherein at least half of the one or more compressors are configured for non-gas-driven or non-steam-driven operation or are configured for operation via steam produced without burning a fuel.
A ninth embodiment, which is the ammonia synthesis plant according to any of the first through the eighth embodiments, wherein energy is stored using compressed hydrogen, compressed natural gas feed, cryogenic liquids, thermal batteries, high thermal mass furnace lining material, electric batteries, or a combination thereof, such that the stored energy from the hydrogen, the natural gas, the cryogenic liquids, the thermal batteries, and electricity can be utilized in the ammonia synthesis plant when renewable electricity is not available.
A tenth embodiment, which is the ammonia synthesis plant according to any of the first through the ninth embodiments, further comprising electricity production apparatus configured to produce electricity from pressure or heat within the ammonia synthesis plant, and wherein the electricity production apparatus comprises an expander, a thermoelectric device, or a combination thereof.
An eleventh embodiment, which is the ammonia synthesis plant according to any of the first through the tenth embodiments, comprising (a) an electrically heated steam reformer operable to provide hydrogen and an electrically powered air separation unit (ASU) operable to provide nitrogen for the ammonia synthesis, (b) no autothermal reformer (ATR), and (c) a nitrogen inlet line fluidly connecting the ASU with the one or more ammonia synthesis reactors, whereby the nitrogen from the ASU can be introduced as a component of a feed to the one or more ammonia synthesis reactors.
A twelfth embodiment, which is a method of producing ammonia, the method comprising (a) introducing a feed comprising a carbon containing material selected from natural gas, methane, propane, butane, LPG, naphtha, coal, petroleum coke, or combinations thereof to a synthesis gas generation section such as steam reforming or partial oxidation to produce a synthesis gas product comprising hydrogen and carbon monoxide, where the energy required for the synthesis gas generation section is supplied by a heat input Q1, (b) cooling the reformer product to produce a cooled synthesis gas by effecting a heat removal Q2, (c) shifting the cooled synthesis gas to produce a shifted synthesis gas product, (d) cooling the shifted synthesis gas by effecting a heat removal Q3 to produce a cooled, shifted synthesis gas, (e) purifying the cooled, shifted synthesis gas by removing carbon dioxide from the cooled, shifted synthesis gas, heating by a heat input Q4 to produce a heated carbon-dioxide reduced gas, methanating the heated carbon-dioxide reduced gas to produce a methanator product, and cooling and condensing water from the methanator product by a heat removal Q5 to provide a purified gas, (f) compressing the purified gas, (g) heating the compressed, purified gas by a heat input Q6 to provide a heated gas, (h) providing an ammonia synthesis feed comprising the heated gas, wherein the ammonia synthesis feed comprises hydrogen and nitrogen, wherein the nitrogen is present in the synthesis gas or subsequently added thereto, (i) producing a product comprising ammonia from the ammonia synthesis feed, (j) cooling the product comprising ammonia by a heat removal Q7 to remove ammonia from the product comprising ammonia and provide a recycle gas stream comprising nitrogen and hydrogen, (k) compressing the gas stream comprising nitrogen and hydrogen via a recycle compressor, and (l) purging via a purge gas system, wherein further cooling is effected by a heat removal Q8, wherein the method consumes greater than or equal to about 25 MW of electricity per day, wherein the amount of CO2 produced per ton of ammonia is less than or equal to about 1.6 tons CO2 per ton of ammonia produced, and wherein the specific energy consumption is less than or equal to about 12 GJ per ton of ammonia produced.
A thirteenth embodiment, which is the method according to the twelfth embodiment, wherein the total consumption of methane and natural gas for both feed and fuel is less than or equal to about 0.65 tons per ton of ammonia produced.
A fourteenth embodiment, which is the method according to the twelfth or the thirteenth embodiment, wherein the total consumption of methane and natural gas for fuel is less than or equal to about 0.20 tons per ton of ammonia produced.
A fifteenth embodiment, which is the method according to any of the twelfth through the fourteenth embodiments, wherein the energy required for the synthesis gas generation section is supplied without combusting a fuel.
A sixteenth embodiment, which is the method according to any of the twelfth through the fifteenth embodiments, wherein the non-carbon based energy source comprises or the electricity is produced via an intermittent energy source (IES), and further comprising maintaining the temperature of one or more reactors in the synthesis gas generation section without combusting a fuel or a carbon-based fuel when the IES is available, and maintaining the temperature of one or more reactors in the synthesis gas generation section via a stored supply of energy from the IES or by combusting a fuel or a carbon-based fuel when the IES is not available.
A seventeenth embodiment, which is the method according to any of the twelfth through the sixteenth embodiments, further comprising utilizing electric heating to control a temperature profile of at least one reactor of the synthesis gas generation section, shifting reactors utilized for shifting, methanation reactors utilized for the methanating, and ammonia synthesis reactors utilized for producing the product comprising ammonia from the ammonia synthesis feed.
An eighteenth embodiment, which is the method according to the seventeenth embodiment, wherein at least one of a reactors of the synthesis gas generation section are operated to at least approximate isothermal operation.
A nineteenth embodiment, which is the method of according to any of the twelfth through the eighteenth embodiments, further comprising providing some or all of the heat Q1 needed to achieve a reaction temperature in (a) via feeding steam to one or more reactors of the synthesis gas generation section, wherein the steam is superheated electrically.
A twentieth embodiment, which is the method according to any of the twelfth through the nineteenth embodiments, further comprising removing methane from the purified gas prior to compressing the purified gas, wherein removing methane from the purified gas reduces an amount of purging in (l) of an ammonia synthesis loop utilized to produce the product comprising ammonia from the ammonia synthesis feed, wherein the removing the methane from the purified gas via a renewable electrically powered methane removal process, and wherein the renewable electrically powered methane removal process comprises pressure swing adsorption (PSA).
A twenty-first embodiment, which is the method according to any of the twelfth through the twentieth embodiments, further comprising storing natural gas when electricity is available and below a threshold price, and utilizing the stored natural gas as a component of the feed or to generate electricity when electricity is unavailable or above the threshold price.
A twenty-second embodiment, which is the method according to any of the twelfth through the twenty-first embodiments, further comprising storing a refrigerant when electricity is available or below a threshold price and utilizing the refrigerant for cooling to provide heat removal Q2, Q3, Q5, Q7, and Q8 when electricity is unavailable or above the threshold price, and wherein the refrigerant comprises ammonia.
A twenty-third embodiment, which is the method according to any of the twelfth through the twenty-second embodiments, further comprising separating hydrogen from a purge gas stream, and storing at least a portion of the separated hydrogen and converting the stored at least a portion of the hydrogen to electricity when other sources of electricity are not readily available or are not available at a desirable price, wherein one or more fuel cells is used for the conversion of hydrogen to electricity.
A twenty-fourth embodiment, which is the method according to any of the twelfth through the twenty-third embodiments, wherein a system for removing carbon dioxide comprises amine recovery, and wherein the amine recovery is effected with electric heating.
While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the teachings of this disclosure. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention.
Numerous other modifications, equivalents, and alternatives, will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such modifications, equivalents, and alternatives where applicable. Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the detailed description of the present invention. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/013522 | 1/14/2020 | WO | 00 |
| Number | Date | Country | |
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| 62792612 | Jan 2019 | US | |
| 62792615 | Jan 2019 | US | |
| 62792617 | Jan 2019 | US | |
| 62792619 | Jan 2019 | US | |
| 62792622 | Jan 2019 | US | |
| 62792627 | Jan 2019 | US | |
| 62792631 | Jan 2019 | US | |
| 62792632 | Jan 2019 | US | |
| 62792633 | Jan 2019 | US | |
| 62792634 | Jan 2019 | US | |
| 62792635 | Jan 2019 | US | |
| 62792636 | Jan 2019 | US | |
| 62792637 | Jan 2019 | US |
