Patent Application
20140072480
None.
This disclosure relates to systems and methods for the fast pyrolysis of organic matter to produce transportation fuel. More specifically, it relates to the rapid removal of entrained char particulates from pyrolysis vapors, and optionally, catalytic modification of pyrolysis vapors created during the fast pyrolysis of organic matter to create a hydrocarbon transportation fuel or a component thereof.
The U.S. Renewable Fuel Standards (RFS) mandate requires increasing volumes of advanced biofuels to be produced. One method being developed to meet this mandate is the fast pyrolysis of biomass. Conventional biomass fast pyrolysis involves the rapid heating of biomass in the presence of little or no oxygen. Conventional fast pyrolysis produces oxygenated pyrolysis vapors that are highly reactive, along with a solid carbonaceous char particles that retain the vast majority of metals (e.g. Na, K, Mg) present in the biomass feedstock. Pyrolysis vapor product compounds comprise radicals that often lead to rapid, uncontrolled oligomerization or polymerization, which is facilitated by entrainment of metal-impregnated char particles that can serve as catalysts for these addition reactions. If left unchecked, large molecular weight compounds rapidly form that are extremely difficult to upgrade to transportation fuels. Conventional processes typically avoid this result by rapidly quenching the pyrolysis vapors to form a liquid pyrolysis oil. However, this typically 1) fails to remove all entrained char and metals, 2) delays upgrading of the product 3) decreases process efficiency by condensing to liquid pyrolysis oil, then later re-vaporizing for catalytic conversion to an industrial or transportation fuel. Additionally, conventional processes typically remove entrained char particles via cyclones (incomplete particulate removal) or conventional filtration that requires ongoing maintenance.
There is a need to improve fast pyrolysis technology for the production of hydrocarbons having molecular weights and characteristics fungible with current hydrocarbon transportation fuels. Such methods and systems must rapidly stabilize raw pyrolysis vapors to prevent uncontrolled polymerization, while also quickly and efficiently removing entrained char particulates and associated catalyst poisons to prevent them from contacting the stabilizing or upgrading catalysts.
Conventional pyrolysis methods and systems have suffered from either 1) char carry-over in the pyrolysis vapors, leading to deactivation of downstream upgrading catalysts, or 2) use of separation devices such as conventional filter and cyclones to remove char from pyrolysis vapors, which results in an undesirable delay prior to either quenching or catalytically upgrading the pyrolysis vapors. Such delay can allow undesirable secondary reactions to occur that produce excessively large molecular weight products that are difficult to further upgrade into a transportation fuel.
The inventive processes and systems disclosed herein provide a solution to the problem of catalyst fouling and poisoning over time, as well as the plugging of catalyst beds that receive raw pyrolysis vapors carrying entrained char particles. The processes and systems disclosed herein also minimize the delay between production of the pyrolysis vapors and catalytic upgrading to products that are fungible with petroleum-derived transportation fuels, or a component thereof.
A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings in which:
The invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale. It should be understood that the drawings and their accompanying detailed descriptions are not intended to limit the scope of the invention to the particular form disclosed, but are illustrative only of specific embodiments.
Pyrolysis vapors are known to be highly reactive, and can rapidly form high molecular weight compounds that are above the boiling-point range of typical hydrocarbon transportation fuels (i.e., a carbon number greater than about 35). Examples of typical addition reactions between compounds typically found in pyrolysis vapors are shown in Schemes 1-3 below:
The methods and systems described herein allow rapid filtration/removal of solid char particles from raw pyrolysis vapors by immediately directing the vapors through a moving bed granular filter (MBGF) comprising a heated heat carrier as the granular filter material. The heated heat carrier slowly passes through the MBGF and is conveyed along with char filtrate to the pyrolysis reactor to facilitate heat transfer to the biomass feedstock.
The granular material within the moving bed also serves as the granular heat carrier that assists in rapidly transferring heat to the biomass in the pyrolysis reactor. Char that is removed from the pyrolysis vapors and retained within the MBGF is then immediately conveyed along with the heat carrier to the pyrolysis reactor.
In certain embodiments, the granular material comprising the moving bed of the MBGF also comprises at least one catalyst. One or more catalysts may be included in a mixture with the heat carrier. In certain embodiments, the heat carrier itself possess catalytic activity or be impregnated with one or more catalysts.
Pyrolysis vapors filtered by the MBGF optionally contact the at least one catalyst within the MBGF, which catalytically upgrades and/or stabilizes the chemical species within the pyrolysis vapors to prevent unwanted secondary reactions that produce products that are difficult to upgrade to a transportation fuel (or component thereof). In certain embodiments, the heat carrier itself may possess catalytic activity, or one or more catalyst(s) may be impregnated on the heat carrier. Alternatively, the heat carrier may be mixed with one or more catalysts that are either supported or unsupported.
Immediately directing raw pyrolysis vapors from a pyrolysis reactor into a MBGF comprising at least one catalyst minimizes the time between production of the pyrolysis vapors and subsequent upgrading while simultaneously removing char particles that 1) cause harmful secondary reactions that limit the upgradability of the vapors and 2) poison downstream equipment and catalytic upgrading. The present inventive disclosure also improves efficiency by eliminating the heated container that pre-heats the granular heat carrier in a conventional pyrolysis system prior to entry of the heat carrier into the pyrolysis reactor. The heat carrier is instead heated within the MBGF.
Rapid heating of the biomass feedstock in an atmosphere containing little or no oxygen results in the thermal breakdown of the feedstock, producing oxygenated hydrocarbon vapors that are hereinafter termed “pyrolysis vapors”. The pyrolysis reactor utilized to produce these pyrolysis vapors is compatible with any known pyrolysis reactor configuration or technology, including, but not limited to, bubbling bed, circulating bed, moving or fluidized bed, ablative, vacuum, microwave heated, plasma-heated, counter-current, auger or combinations of one or more of these configurations. The pyrolysis reactor used preferably utilizes a solid heat carrier and transfers heat to the biomass feedstock primarily through solid-solid contact. Preferably, the reactor comprises at least one auger that assists in rapidly and evenly distributing heat to the feedstock, as well as helping to convey the feedstock and optional heat carrier through the pyrolysis reactor. A reactor comprising at least one auger is also more efficient in char removal than, for example, a fluidized bed reactor that produces char fines by attrition of larger char particles that then elutriate into the produced pyrolysis vapors.
The pyrolysis vapors rise and may be driven by a carrier gas (or optionally, a pressure differential) toward an optional disengagement zone that allows separation of the vapors from entrained char, heat carrier, and metals while avoiding vapor condensation. The pyrolysis vapors then exit the pyrolysis reactor via at least one outlet. Preferably, the at least one outlet is located at (or near) the top of the pyrolysis reactor to minimize entrainment of char particles in the pyrolysis vapors passing through the outlet(s). The large majority of char created by pyrolysis of the feedstock may be eliminated from the reactor in a variety of ways, depending upon the pyrolysis technology and configuration utilized. Preventing entrainment of char prevents fouling/poisoning of catalyst(s) located downstream that are utilized to catalytically stabilize and/or catalytically upgrade the pyrolysis vapors.
The pyrolysis vapors passing through the outlet are directed into the MBGF that is kept in close proximity in order to remove entrained particulates from the pyrolysis vapors as rapidly as possible. The pyrolysis vapors are maintained at all times above a temperature that would allow condensation of the vapors to liquid phase. Preferably, this temperature is between 250° C. to 500° C., and is accomplished in part by heating of the granular filter material within the MBGF. The pyrolysis vapors may contact the moving bed of granular material in co-current flow, cross-current flow, or counter-current flow. In certain embodiments, the pyrolysis vapors may contact multiple MBGF within a single container, or multiple containers. One or more of the moving beds of granular material may then serve as the heated heat carrier within the pyrolysis reactor. Preferably, heat carrier fed to the pyrolysis reactor has been pre-heated in the heated container to a temperature of at least 480° C. in order to effectively transfer sufficient heat to the biomass feedstock to facilitate pyrolysis of the feedstock.
In certain embodiments, at least one MBGF may comprise a catalyst or mixtures of more than one catalyst. In embodiments where more than one MBGF are utilized, each MBGF may comprise a different catalyst or different combinations of catalyst. In some embodiments, pyrolysis vapors may contact an initial MBGF comprising heat carrier alone, immediately followed by a second bed comprising one or more upgrading catalysts. In such embodiments, the upgrading catalyst(s) maintain even greater isolation from char particles entrained in the pyrolysis vapors.
Following initial upgrading and/or stabilization of the pyrolysis vapors within the MBGF, additional upgrading may be performed. Following upgrading, the product molecules have molecular weights that are within the boiling range of a transportation fuel, such as, but not limited to gasoline, diesel and gasoil. Without upgrading, the product compounds may be still be suitable for use as a component of a hydrocarbon transportation fuel (for example, as a blend component at up to about 5-10% (by vol.). With sufficient oxygen removal (and optionally other upgrading reactions that increase molecular size), the product optimally comprises a hydrocarbon fuel that is fungible with petroleum-derived transportation fuels. In certain embodiments, for example, additional oxygen, nitrogen, and sulfur may be removed by conventional hydrotreating processes to produce a finished transportation fuel (as detailed further below). Each portion of pyrolysis vapors is maintained in vapor phase both prior to, and during the upgrading process.
Optimally, the final product of the process does not include a significant quantity of product molecules having a carbon number greater than about 35 carbons, more preferably no greater than about 30 carbons. Hydrocarbons larger than this are typically unsuitable for use as a transportation fuel or a component thereof, and would have a boiling point above the boiling point range of gasoline, kerosene or jet fuel, diesel #1, #2 or #4 and light fuel oil.
The length and or volume of the reaction zone or reactor where the upgrading occurs is at least partly determined by the kinetics of the reactions occurring between the catalyst(s) and the portion of raw pyrolysis vapors. These kinetics can be determined by conventional methodology, such as by analyzing the molecular composition of mixtures of partially-upgraded pyrolysis vapors and raw pyrolysis vapors over time at a given temperature and pressure using conventional gas chromatography/mass spectrometry. The size of the reaction zone is optimized such that the average carbon number of product molecules leaving the reaction zone is between 6 and 35, more preferably between 6-30, or within the carbon number range of molecules in the boiling range of transportations fuels such as gasoline, kerosene, jet fuel, diesel #1, #2 or #4 and light fuel oil. Optimization of the average carbon number of the product can be performed based upon the desired specifications of the product fuel.
In certain embodiments, a portion of the product of the reacting (e.g., products with a carbon number below 6, excess hydrogen, etc.) or a portion of one or more of the pyrolysis vapor portions may be returned to the pyrolyzer or to any of the upgrading reactors to be further upgraded or utilized in the upgrading of the pyrolysis vapors.
The low particulate vapors leaving the MBGF may optionally be further upgraded by hydrotreating, which is familiar to those having skill in the art and further reduces oxygen content of the products while also removing residual sulfur and nitrogen to levels that meet government mandates for a finished transportation fuel. Hydrotreating can be performed in one-step or multiple steps in the presence of conventional hydrotreating catalyst(s) or via other known methods, such as thermal deoxygenation in the presence of a metal hydroxide (e.g., CaOH).
Each portion of pyrolysis vapors may be diluted with a carrier gas that may be the same carrier gas at was utilized in the pyrolysis reactor, or a different gas added downstream from the pyrolysis reactor. The carrier gas may be an inert gas or a reactive gas. If the carrier gas is a reactive gas, it may also serve to facilitate one or more upgrading reactions.
Examples of biomass feedstock used in the present invention include, but are not limited to, oil-containing biomass, such as jatropha plant, macroalgae or microalgae. Carbohydrate-based biomass may also be used as feedstock, where carbohydrate-based refers to biomass where at least a fraction of its composition is made of carbohydrates. Carbohydrate-based biomasses are available from a variety of sources including cellulosic biomass and algal biomass. Specific examples of feedstock useful in the current invention include, but are not limited to: sugars, carbohydrates, fatty acids, proteins, oils, eucalyptus oil, forest residues, dead trees, branches, leaves, tree stumps, yard clippings, wood chips, wood fiber, sugar beets, miscanthus, switchgrass, hemp, corn, corn fiber, poplar, willow, sorghum, sugarcane, palm oil, corn syrup, algal cultures, bacterial cultures, fermentation cultures, paper manufacturing waste, agricultural residues (e.g., corn stover, wheat straw and sugarcane bagasse), dedicated energy crops (e.g., poplar trees, switchgrass, and miscanthus giganteus sugarcane) sawmill and paper mill discards, food manufacturing waste, meat processing waste, animal waste, biological waste and/or municipal sewage.
The pyrolysis reactor utilized is compatible with any known pyrolysis reactor configuration or technology that may benefit from the use of a heat carrier. Examples of such configurations may include, but are not limited to, bubbling bed, circulating bed, moving or fluidized bed, vacuum, microwave heated, plasma-heated, counter-current, auger, free-fall or combinations of one or more of these configurations.
During pyrolysis of the biomass feedstock 12 in the pyrolysis reactor 20, the large majority of produced char and granular heat carrier is removed near the bottom of the reactor via outlet 22. After separation of the granular heat carrier from the char 25 in separation device 24, the separated granular heat carrier 23 is conveyed to a heated container 31, which encloses a moving bed granular filter (MBGF) 33 that utilizes the separated granular heat carrier 23 as granular filter material. The separated granular heat carrier 23 that is recycled to heated container 33 may be supplemented or replaced by fresh granular heat carrier 32 either continuously or periodically. The heated container 31 may periodically also serve as a regenerator for the granular heat carrier in the MBGF 31 by heating the granular heat carrier and optional catalyst(s) to a temperature that is high enough to remove deposits of coke and any other catalyst poison, reactivate catalytic activity, or both.
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The pyrolysis reactor is typically operated to exclude most oxygen or air by the introduction of a carrier gas. In the embodiment shown in
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Heated granular heat carrier containing filtered char 94 leaves the heated container 98 via an outlet near the bottom of the heated container 98 and is separated from the char in separation device 95 to produce separated char 96 and the heated granular heat carrier 75 that is then conveyed to the pyrolysis reactor 80.
Further referring to
The granular filter material (granular heat carrier) of the MBGF 149 may optionally comprise mixtures of more than one catalyst, or multiple beds of catalyst (either moving or fixed) that contact the pyrolysis vapors in series or in parallel. The granular filter material is kept inside the heated container 151 long enough to allow heating of the granular filter material to become the heated granular heat carrier. Used granular filter material carrying char particles removed from the pyrolysis vapors 137 within the MBGF 149 leaves the heated container 151 via conduit 154 and is conveyed to the granular heat carrier inlet 127.
To reduce granular heat carrier entrainment that would lead to granular heat carrier entrainment in the pyrolysis vapors, the median granular heat carrier particle size is greater than about 100 microns, preferably greater than about 250 microns and most preferably greater than 300 microns. For similar reasons, the bulk density of the granular heat carrier particles is typically at least 500 kg/m3, and preferably greater than about 1,000 kg/m3.
While a significant quantity of heat for performing pyrolysis of the feedstock is derived from the heated granular heat carrier, the temperature within the pyrolysis reactor may be maintained via one or more additional mechanisms, such as heating of the reactor walls, heating of the at least one auger, microwave or inductive heating, addition of a heated carrier gas and microwave heating. Regardless of the heating mechanism utilized, preferably the pyrolysis reactor and its contents are maintained at a temperature of at least 315° C.
Heat carrier may be composed of a variety of materials that are capable of retaining heat. Preferably, the granular heat carrier is also efficient in absorbing heat as well as transferring heat to a biomass feedstock.
As previously mentioned, in certain embodiments a carrier gas is employed that may comprise one or more of many gases that are either inert or reactive. For example, the carrier gas may comprise gases such as nitrogen, helium, argon, hydrogen, methane and mixtures thereof. If the carrier gas comprises a reactive gas, the reactive gas may optionally react with the biomass during pyrolysis, may serve as a reactant when the pyrolysis products are upgraded by contacting the upgrading catalyst(s), or both. The carrier gas may be injected into the system at more than one point, or injected simultaneously at multiple points. One point may comprise combining the carrier gas with the feedstock prior to entering the pyrolysis reactor, while another may comprise injecting the carrier gas directly into the pyrolysis reactor proximal to the biomass feedstock inlet. A third point may comprise injecting the carrier gas proximal to the first outlet of the pyrolysis reactor. This may be preferable if the carrier gas is to be used as a reactant during upgrading of the primary pyrolysis product.
In certain embodiments, a gas may be injected just upstream of the pyrolysis reactor first outlet in order to 1) assist in preventing entrained char and heat carrier particles from leaving the pyrolysis reactor, 2) quench the primary pyrolysis product to a lower temperature, 3) heat the primary pyrolysis product to a higher temperature, or combinations thereof. In embodiments where the carrier gas serves to quench the primary pyrolysis product, such quenching may prevent coking. Embodiments where the carrier gas serves to heat the primary pyrolysis product may prevent formation of char and secondary pyrolysis reactions that may reduce the subsequent upgradability of the primary pyrolysis product to a bio-derived fuel. However, quenching is limited such that the quenched primary pyrolysis product does not condense prior to contacting the upgrading catalyst(s). Typically, this requires that the quenched pyrolysis vapors maintain a temperature of at least 250° C. to prevent condensation to liquid phase.
The volumetric flow rate, or “standard gas hourly space velocity” (SGHSV) of the carrier gas is adjusted to minimize the time between pyrolysis and catalytic upgrading, such that the upgrading catalyst (or optionally, catalysts) contacts primary products of pyrolysis and not larger secondary products that are more difficult to upgrade to a bio-derived transportation fuel. Volumetric flow rate for a given embodiment depends upon factors including, but not limited to, the volume of the pyrolysis reactor, the temperature and pressure at which the pyrolysis reactor is maintained, the feed rate of the biomass feedstock to the pyrolysis reactor, and the type of feedstock utilized. A paper by J. N. Brown, et al. provides one example of how these variables can be adjusted to determine an optimal volumetric flow rate for a desired pyrolysis outcome, including, for example, the pyrolysis liquid to pyrolysis gas ratio, and the relative percentage of the feedstock converted to char.
The pressure maintained within the pyrolysis reactor is generally within a range of about 0 psig to 3000 psig. Preferably, the pyrolysis reactor is maintained at a pressure in the range of 100 psig to 500 psig to increase throughput of biomass feedstock, and in certain embodiments, facilitate catalytic upgrading of the primary pyrolysis product. The pyrolysis reactor operates at a temperature between 300° C. and 700° C. and pressures between 0 psig and 2500 psig. The carrier gas for the pyrolyzer may be any mixture of gases with less than 22 vol % molecular oxygen, but preferably less than 0.5 vol % molecular oxygen. Preferably gases are hydrogen, nitrogen, methane, carbon dioxide, carbon monoxide, or some combination thereof. Gases from the pyrolysis process may also be recycled to serve as part or all of the carrier gas.
The physical distance between the pyrolysis reactor and the upgrading catalyst(s) may vary, but is preferably minimized, taking into consideration the space velocity of the primary pyrolysis vapors (optionally in a mixture with a carrier gas) out of the pyrolysis reactor. Minimizing this distance assists in decreasing the time between production of the primary pyrolysis vapors and subsequent contacting with one or more upgrading catalyst(s). Through optimizing the variables of distance and space velocity, the inventive processes and systems described herein assures that the upgrading catalyst contacts and catalytically upgrades primary pyrolysis vapor compounds produced from pyrolysis and not subsequent secondary products created by non-preferred reactions as little as 0.25 seconds after production of the pyrolysis vapors. Generally, the distance between the pyrolyzer and the upgrading catalyst(s) is less than 4 ft. More preferably, this distance is less than 1 ft., and most preferably, less than 6 inches.
Optionally, a disengagement zone is located near the at least one outlet of the pyrolysis reactor that may include additional features to limit reactivity of the pyrolysis vapors prior to contact with the upgrading catalyst(s). Such features may include, but are not limited to, temperature control, introduction of a gas or fluid to quench the primary pyrolysis product (as mentioned previously), flow control through judicious choices in geometry (preferably, a geometry minimizing bends and small orifices to decrease the potential for vapor condensation, the presence of a pre-catalyst (such as zeolite monolith, or any of the above-mentioned upgrading catalysts) at the interface between reactors.
After exiting the pyrolysis reactor along with produced char, the granular heat carrier, optionally comprising one or more catalysts, may be periodically or continuously passed through a regenerator for de-coking as needed, then returned to the container comprising the MBGF. The heat carrier could optionally be diverted from other points in the system for regeneration. Fresh heat carrier, optionally comprising one or more catalysts, may be added on a periodic or continuous basis to the system to compensate for catalyst attrition, deactivation or both.
Additional upgrading catalysts may be employed in separate catalyst beds located downstream from the MBGF. Optionally, multiple upgrading catalyst beds may be placed within a single reactor and operated in series, or as a mixture of upgrading catalysts. In certain embodiments, multiple upgrading catalyst beds may be operated in different reactors, in parallel or series to facilitate different upgrading pathways. If multiple upgrading reactors are utilized, different conditions may be maintained in each reactor in order to facilitate a given catalytic reaction. To facilitate flow of the pyrolysis vapors through multiple reactors, a pressure differential may be maintained wherein the pressure in each successive reactor progressively decreases. These upgrading beds may utilize any known configuration including, but not limited to, fixed bed, bubbling bed or circulating bed to remove residual particulates. Such methods may be as described in U.S. Pat. No. 8,268,271, which is hereby incorporated by reference.
Examples of some upgrading catalysts that may be useful for the present invention, along with typical reaction conditions are disclosed in U.S. patent application Ser. No. 13/416,533, although any catalyst known to catalyze the conversion of biomass-derived pyrolysis products to a fuel range hydrocarbon or an intermediate compound may be utilized. The upgrading catalyst(s) may include, but are not limited to, zeolites, metal modified zeolites, and other modified zeolites. Other catalysts may include forms of alumina, silica-alumina, and silica, unmodified or modified with various metals, not limited to but including, Nickel, Cobalt, Molybdenum, Tungsten, Cerium, Praseodymium, Iron, Platinum, Palladium, Ruthenium and Copper and mixtures thereof. Still other catalysts may include unsupported metals, supported or unsupported metal oxides or metal phosphides, and mixtures thereof. Catalyst types include deoxygenation catalysts, hydrogenation catalysts, hydrodesulfurization catalysts, hydrodenitrogenation catalysts, hydrocracking catalysts, water-gas-shift catalysts, and condensation catalysts. Catalysts may be sulfided or un-sulfided.
In certain embodiments employing a hydrogenation catalyst as an upgrading catalyst, the hydrogenation catalyst may selected from the group consisting of ceria (Ce), magnesium (Mg), nickel (Ni), cobalt (Co), gold (Au), iridium (Ir), osmium (Os), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru) and combinations thereof. In certain embodiments employing a condensation catalyst as an upgrading catalyst, the catalyst is selected from the group consisting of alumina, silica, silica-alumina, zirconia, titania, ceria, manganese oxide, magnesium, praseodymium oxide, samarium oxide, and combinations thereof. Optionally, the condensation catalyst comprises a promoter metal selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), Iron (Fe), gold (Au), iridium (Ir), osmium (Os), palladium (Pd), platinum (Pt), rhodium (Rh), and combinations thereof. In certain embodiments employing a polishing catalyst as an upgrading catalyst, the polishing catalyst is selected from the group consisting of molybdenum (Mo), tungsten (W), cobalt (Co), nickel (Ni), NiW, NiMo, NiMoW, CoMo and combinations thereof. The polishing catalyst may be associated with a solid support material that may include carbon, alumina, silica, zeolite, ceramic, Al2O3, and other known solid support materials.
The catalytic upgrading of the pyrolysis vapors may result in product that is less reactive, has a lower or higher molecular weight, a lower oxygen content, a lower water content, an altered range of organic chemical species or combinations of more than one of these effects when compared to pyrolysis vapors that have not been catalytically upgraded.
The residence time of the pyrolysis vapors in the MBGF and each upgrading reactor generally ranges from 0.01 sec to 1000 sec. Preferably, the residence time is in a range from 0.05 sec to 400 secs. More preferably, the residence time is in a range from 0.1 sec to 200 sec. Most preferably, the residence time is in a range from 0.1 sec to 100 sec.
The temperature maintained within the MBGF and each upgrading reactor is generally in the range from 72° F. to 1500° F. Preferably, the temperature is in the range from 100° F. to 1000° F., although if multiple upgrading reactors are used, the MBGF and each upgrading reactor each may be maintained at a different temperature within this range.
Certain upgrading reactions are advantageously conducted at a pressure that is greater than atmospheric pressure. The pressure that is maintained in the MBGF and each one or more upgrading reactors may range from 0-3000 psig, although a preferred pressure range is zero to 1000 psig. In certain embodiments, the pressure may range from 10 to 800 psig, from 20 to 650 psig, from 100 to 500 psig. An exemplary pressure might be 400 psig. If multiple upgrading reactors are used, the MBGF and each upgrading reactor may be maintained at a different pressure within this range, although the pressure within the MBGF will typically match the pressure within the pyrolysis reactor to facilitate the flow of materials and gases between them.
The flow of pyrolysis vapors within the MBGF may be horizontal if encountering the moving bed in a cross-flow configuration, or preferably upward if encountering the moving bed filter in a counter-current flow configuration. The flow of pyrolysis vapors within each upgrading reactor is preferably upward, although downward or lateral gas flow may also be utilized.
Upon exiting the final upgrading reactor, the upgraded product may be directed to a condensation system that functions to reduce the temperature to a temperature that is at or below the dew point for at least one component of the product, thereby allowing condensation and collection of that component as a liquid transportation fuel or transportation fuel component that may be utilized as blendstock to make a finished transportation fuel. Typically, the quenching conditions utilized do not result in the condensation of methane, but preferably will condense hydrocarbons containing four or more carbons. Hydrogen may be separated from the non-condensable gas by a variety of conventional methods and recycled as at least a portion of the carrier gas, thereby also serving as a source of reducing equivalents for pyrolysis vapor upgrading reactions. In certain embodiments, recycled hydrogen may be added directly into, or just upstream from, an upgrading reactor to facilitate one or more upgrading reactions. Alternatively, the entirety, or some fraction, of the bulk non-condensable gas is used for this same purpose. In another embodiment, the entirety, or some fraction, of the bulk of the non-condensable gas is sent to a combustor or hydrogen generation unit (e.g., a reformer) to generate either heat or hydrogen, respectively. The resulting heat or hydrogen may then be partially or entirely recycled back to the process.
Upon combining and reacting at least one partially-upgraded stream of pyrolysis vapors with a stream of non-upgraded pyrolysis vapors, a series of reactions take place that increase the molecular weight and carbon number of the product compounds. Chemical reactions taking place may include condensation, dimerization, oligomerization, and alkylation, among others. The increase in average molecular weight resulting from the reacting of these streams is limited by the relative abundance of reactive functional groups in the partially-stabilized streams of pyrolysis vapors. Examples of such reactive functional groups include, but are not limited to, aldehydes, ketones, alcohols. Olefins also are conducive to reactions leading to products of increased molecular weight in the inventive process. The reaction pathways provided in Scheme 1-3 (see above) are intended as non-limiting examples demonstrating how certain oxygenated hydrocarbons present in primary pyrolysis vapors can be converted to molecules having molecular weights in the gasoline, diesel and gasoil boiling range and suitable for use as a hydrocarbon transportation fuel.
As used herein, the term “entrainment” is defined as transport of a solid particle by a gas stream. Entrainment of a given solid particle typically occurs when the local velocity of a gas stream exceeds the terminal falling velocity of the particle.
As used herein, the term “standard gas hourly space velocity” or “SGHSV” refers to the gas hourly space velocity of a gas stream measured at standard conditions.
As used herein, the term “fuel component” is defined as a mixture of chemical compounds suitable for blending with, and comprising at least a portion of, a finished transportation fuel.
As used herein, the terms “stabilize” and “stabilizing” are defined as removing at least a portion of the reactive functional groups or moieties present on the chemical compounds found in pyrolysis vapors.
As used herein, the term “transportation fuel” is defined as fuels having carbon numbers within the range of molecules suitable for use in hydrocarbon transportation fuels, including gasoline, kerosene, jet fuel, diesel #1, #2 or #4 and light fuel oil.
As used herein, the term “upgrading catalyst” is defined as any catalyst that facilitates chemical reactions within the molecules present in pyrolysis vapors (resulting from fast-pyrolysis of biomass) that converts them to products suitable for use in a transportation fuel, a transportation fuel component, or that converts them to intermediate products (including stabilized, less reactive intermediate products) that are more easily further converted to a transportation fuel or transportation fuel component.
In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present disclosure, in particular, any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as an additional embodiment of the present invention.
Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those having skill in the art may be able to study the preferred embodiments and identify additional variants of the invention that are not exactly as described herein, but that remain within the scope of the claims. The description, abstract and drawings are not intended to limit the scope of the invention. Instead, the invention is specifically intended to be as broad as the claims below and their inventive equivalents.
All of the references cited herein are expressly incorporated by reference. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication data after the priority date of this application. Incorporated references are listed again here for convenience:
This application is a non-provisional application which claims benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/699,000 filed Sep. 10, 2012, entitled “Generating Deoxygenated Pyrolysis Vapors,” which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61699000 | Sep 2012 | US |
