Patent Application
20240208808
The present invention provides a method and system for producing blue ammonia, providing for a higher percentage of carbon capture. The method and system of the invention may be used in any ammonia plant.
Blue ammonia is a fossil fuel-based product produced with minimum emission of CO2 to the atmosphere. It is seen as a transition product between conventional fossil fuel-based ammonia and green ammonia produced from green or renewable power and air. The CO2 resulting from a blue ammonia production shall be stored permanently or converted into other chemicals. The main steps for producing blue ammonia are essentially the same as for producing conventional fossil fuel-based ammonia, the difference being that more of the carbon stemming from the carbon fuel is captured, providing a possibility for further processing.
The key here is that the blue ammonia does not release any carbon dioxide when used as fertilizer or burned. Currently available technology traps nearly all CO2 generated during the conversion process making this fuel one of the first carbon free fuel options for mass use. Blue ammonia is considered an environmental friendly product which can be used until sufficient renewable or green power is available for producing green ammonia.
If we can continue to diversify our power generation methods and create more and more renewable or green energy, the potential rises that we can perfect a method of green energy that produces hydrogen and ammonia as byproducts giving us a completely clean and safe power cycle.
Document WO2018/149641 discloses a process for the synthesis of ammonia from natural gas comprising conversion of a charge of desulphurized natural gas and steam, with oxygen-enriched air or oxygen, into a synthesis gas (11), and treatment of the synthesis gas (11) with shift reaction and decarbonation, wherein a part of the CO2-depleted synthesis gas, obtained after decarbonation, is separated and used as fuel fraction for one or more furnaces of the conversion section, and the remaining part of the gas is used to produce ammonia.
The present invention is different from the setup disclosed in that document in that the present invention recovers a flash gas from the CO2 removal step and enables the use of a more carbon depleted fuel, thereby achieving a higher carbon recovery (more than 99%) compared to the cited document.
The present invention refers to a method, system and plant for producing ammonia with a high percentage of carbon capture, preferably >99% of carbon capture, when compared to the standard method where optimally between about 90-93% of carbon capture is achieved.
The method of the present invention provides for the following advantages:
Said advantages are provided by a set of features, comprising:
References used to represent the different steps of in the method of the present invention are:
Blue Ammonia is ammonia that is created from using fossil fuel where at least 90% of the Carbon in the fossil fuel is captured to be used in other products and processes or to be stored.
Catalyst poison means a substance that reduces the effectiveness of a catalyst in a chemical reaction. In theory, because catalysts are not consumed in chemical reactions, they can be used repeatedly over an indefinite period of time. In practice, however, poisons, which come from the reacting substances or products of the reaction itself, accumulate on the surface of solid catalysts and cause their effectiveness to decrease. For this reason, when the effectiveness of a catalyst has reached a certain low level, steps are taken to remove the poison or replenish the active catalyst component that may have reacted with the poison. Commonly encountered poisons include carbon on the silica-alumina catalyst in the cracking of petroleum; sulfur, arsenic, or lead on metal catalysts in hydrogenation or dehydrogenation reactions; and oxygen and water on iron catalysts used in ammonia synthesis.
Contaminant means any substances or elements which are not desirable. Within the context of the present invention, contaminants comprise catalyst poisons.
Flash gas means an intermediate gas stream obtained during desorption of CO2 in a solvent based CO2 removal step.
Green Ammonia is ammonia that is produced by using green electricity, water and air.
Green Electricity is electricity produced from renewable resources such as wind, solar, Hydro or geothermal energy
Ammonia synthesis catalysts mean, within the context of the present invention, any catalysts suitable for synthesizing ammonia and also suitable for cracking ammonia. These catalysts are preferably iron (Fe) based, but may also comprise other catalysts suitable for the same purpose and operating at similar conditions.
Electrolysis of water means decomposition of water into oxygen and hydrogen gas due to the passage of an electric current.
Fuel systems comprise fuel systems for supply of fuel to the combustion side of tubular reformers and/or fired heaters and/or auxiliary boilers and/or gas turbines. These systems comprise one or more burners in which the incoming fuel streams are burned together with air at variable temperature and pressure.
High-pressure electrolysis (HPE) is the electrolysis of water by decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to the passing of an electric current through the water at elevated pressure, typically above 10 bar.
Make-up ammonia or Traded Ammonia comprises ammonia (NH3) and water (H2O), preferably between 0.2 to 0.5% of water content. It is usually supplied as a liquid but may also be a solution comprising different physical states. The effect of water comprised in ammonia feedstock in the ammonia decomposition process is primarily that due to poisoning the process, which usually has to take place at a high temperatures. This will increase process cost for ammonia decomposition as well as cost of construction materials in the plant. According to National Bureau of Standards ammonia shall conform to the following properties: minimum purity of 99.98% (wt), maximum 0,0005% (wt) oil and maximum 0.02% (wt) moisture.
Nitridation means the formation of nitrogen compounds through the action of ammonia.
PSA means pressure swing adsorption.
Shift means Water-gas shift reaction (WGSR) or Shift reaction, the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen:
The WGSR is an important industrial reaction that is used in the manufacture of ammonia, hydrocarbons, methanol, and hydrogen. It is also often used in conjunction with steam reforming of methane and other hydrocarbons. In the Fischer-Tropsch process, the WGSR is one of the most important reactions used to balance the H2/CO ratio. The water gas shift reaction is a moderately exothermic reversible reaction. Therefore, with increasing temperature the reaction rate increases but the carbon dioxide production becomes less favorable. Due to its exothermic nature, high carbon monoxide percentage is thermodynamically favored at low temperatures. Despite the thermodynamic favorability at low temperatures, the reaction is faster at high temperatures.
Shift unit or section means a process step where the shift reaction is performed.
Reducing CO2 emission has become a bound task in the chemical industry. Production of ammonia using hydrocarbons as feedstock inevitably results in CO2 formation which typically ends up in at least two CO2 containing process streams, one almost pure CO2 stream (1) extracted from the syngas cleaning section and one or more flue gas streams (2). The CO2 stream (1) can be utilized for further chemical processing or stored. The CO2 in the flue gas stream (2) needs to be recovered before it can find similar use. The flue gas recovery process has a high operating and capital cost. It is therefore an advantage to limit the CO2 content in the flue gas.
It is well known that CO2 in the flue gas can be avoided by using carbon free fuels. In general hydrocarbons such as natural gas and carbon containing off gases originating from the process are used as fuels. The advantage of this invention is that the main part of these fuels are replaced by an internal hydrogen rich stream and that the unavoidable off gas are recycled to the process. By applying this invention it is possible to reduce the CO2 content in the flue gas streams by more than 90%. Provided the pure CO2 stream (1) is utilized or stored, then the product ammonia will be considered to be blue.
Table 1 shows the benefits of the proposed layout in the present invention, in terms of carbon recovery (%).
Traditional ammonia production involves utilization of off gases from ammonia recovery and syngas preparation steps to supplement natural gas as main fuels for fired heater/process furnaces. This would result in carbon emissions from flue gas stack which could partly be recovered by using a solution based carbon capture technology. The recovery rate for such a plant, including carbon recovery from flue gases would not be higher than 90% and is a capital intensive process. With the proposed layout including firing of hydrogen rich fuel and utilization of off gases in the main process results in significant carbon emission reduction, more than 99% recovery. This process will be significantly cheaper and would require minimum steps and will have lower footprint on plot.
Wherein at least part of the off-gas (4,8) removed in step e) i) and e) ii) or at least part of recovered CH4 (10) stemming from synthesis gas in step e) iii) are compressed and sent to step a) or b).
The shift reaction in step c) is CO+H2O=CO2+H2.
A tubular reformer is also known as a steam reformer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21170905.0 | Apr 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP22/59091 | 4/6/2022 | WO |
