Integrated gasification and electrolysis process

Abstract

Aspects of the invention relate to improved flexibility in being able to supply oxygen and hydrogen, for example from electrolysis, to a process having both gasification and methanation steps, and how that process operates in response to variations in the carbonaceous feedstock. Any offset between the ideal amount of hydrogen and the amount available from a particular source can be offset by adjusting one or more operations in the process, particularly those that ultimately affect the amount of CO and / or CO available downstream of the gasifier for conversion to methane in the RNG product stream. [Selected Figure] Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 62 / 697,540, filed Jul. 13, 2018, which is incorporated herein by reference in its entirety.

[0002] Technical Field Aspects of the present invention relate to a gasification process for producing renewable natural gas (RNG), which process is integrated with electrolysis to provide a supply of oxygen and hydrogen.

Background Art

[0003] The gasification of coal has been carried out industrially for over a century in the production of synthesis gas that can be further processed into transportation fuels. Recent goals of reducing greenhouse gas emissions and developing energy self - sufficiency have led to strong interest in using biomass as a gasification feedstock, thereby leading to potential sources of renewable natural gas (RNG). According to a multi - step process, the gasification of biomass is first carried out by partial oxidation in the presence of an oxidant gas containing other possible components such as oxygen and steam. The gasification at high temperature and pressure produces emissions containing methane, carbon oxides (CO, CO 2 ), and hydrogen. This emission may be called synthesis gas from the perspective of its CO and H 2 content and is usually processed to remove many undesirable components such as particulate matter, alkali metals, sulfur compounds, and tar (referring to organic compounds generally having a boiling point higher than benzene). This treatment step makes the gasifier emissions suitable for downstream conversion of high - concentration H 2 and CO / CO 2 by catalytic methanation to increase the methane content of the resulting RNG stream.

[0004] As can be understood from the atomic composition of wood and other forms of biomass, gasifier emissions typically lack sufficient hydrogen to fully convert the supplied carbon content to methane, resulting in excessive CO and CO 2 that must be considered in the economics of the overall process. Therefore, the addition of hydrogen to enable more complete utilization of biomass carbon in methane production is quite interesting. Hydrogen can often be obtained as a product from steam reforming of methane and / or other hydrocarbons by technologies that are very stable but require significant amounts of energy. Also, using fossil methane to produce such hydrogen defeats the purpose of obtaining natural gas from purely renewable resources. The integration of hydrogen from electrolysis as a potential source to enable more complete methanation of gasifier emissions has been proposed by Non-Patent Document 1 and Non-Patent Document 2. Nevertheless, further development of biomass gasification to improve its economics compared to fossil-derived natural gas production is necessary to realize its commercial-scale implementation in RNG production.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

[0006] Aspects of the present invention relate to the discovery of a gasification process for producing methane, having improved efficiency in the management of the feedstocks input into the process and / or the energy obtained from the process. By supplying electrolytic oxygen and hydrogen to this process, the overall carbon footprint (carbon dioxide emissions) associated with the production of RNG from carbonaceous feedstocks such as coal and biomass can be advantageously reduced. For example, electrolytic oxygen can be used to increase the amount supplied from a conventional air separation unit (ASU) to a gasifier, while the co-produced electrolytic hydrogen can be supplied to a methanation reactor to improve the utilization of carbon in the feedstock for methane production. This then creates further opportunities for integration, particularly with respect to the additional heat generated from the exothermic methanation reaction that can be recovered in the form of steam and ultimately electricity to power the electrolyzer.

[0007] Certain aspects relate to an improvement in flexibility to be able to supply the oxygen and hydrogen of an electrolyzer to a process having both gasification and methanation steps, and an improvement in how to operate the process in response to variations in carbonaceous feedstocks. In this regard, typical ASUs are associated with high capital and operating costs, and their production capacity often does not match the need for pure oxygen in a gasifier. This can occur, for example, when the ASU is not available in an economically appropriate size and / or when an oxygen supply source such as pressure swing adsorption (PSA) cannot provide sufficient purity. Both ASUs and PSAs are recognized as having the potential to produce oxygen but also produce nitrogen, which is not always easily utilized or monetized. Hydrogen may be available from conventional reforming, but this production method is energy intensive and typically based on fossil-derived hydrocarbons. Thus, electrolysis may address many of the deficiencies associated with the production of purified oxygen and / or hydrogen by other means, in addition to providing improvements in overall feed carbon utilization (e.g., methane yield) and heat integration.

[0008] The amount of electrolytic oxygen can be determined primarily or completely by the amount and type of carbonaceous feedstock to the gasifier, regardless of whether it is supplied in combination with another source such as ASU oxygen or PSA oxygen. However, the amount of corresponding electrolytic hydrogen produced in satisfying this oxygen demand is usually not optimal for the complete conversion of CO and CO 2 in the downstream methanation reactor. Advantageously, such an offset between the ideal amount of hydrogen and the amount available as the stoichiometric amount from the electrolysis of water that satisfies the oxygen demand of the gasifier can be offset by adjusting one or more operations of the process, particularly the operations available downstream of the gasifier for converting to methane in the RNG product stream, in terms of the amount of CO and / or CO 2 that ultimately affect it. The operation to be adjusted can alternatively or additionally affect the CO / H 2 molar ratio and / or the CO 2 / H 2 molar ratio downstream of the gasifier. In another way, if sufficient electrolytic hydrogen is available, a typical process including gasification and methanation can completely eliminate such operations, thereby simplifying RNG production and reducing associated costs.

[0009] Embodiments of the present invention are directed to a process for producing methane, for example, as an RNG product, the process including both gasification and methanation. Gasification refers to contacting a carbonaceous feedstock in a gasifier (or, more specifically, the gasification reactor of the gasifier) with an oxygen-containing gasifier feed to provide a gasifier effluent containing CO, CO 2 , H 2 , and / or H 2 O, and usually all of these components. The electrolytic hydrogen obtained from the electrolyzer can be combined with the gasifier effluent at a point upstream of the methanation reactor or, alternatively, within the methanation reactor. The additional or supplemented electrolytic hydrogen, or at least a portion thereof, reacts with CO and / or CO in the gasifier effluent within the methanation reactor 2react with at least a portion thereof to form methane, thereby improving the utilization of carbon in the carbonaceous feedstock in the production of RNG. Advantageously, one or more of a series of operations performed on the operation of the process, for example, the gasifier effluent downstream of the gasifier and upstream of the methanation reactor, can be adjusted according to the make-up amount or flow rate of electrolytic hydrogen to improve the overall process efficiency. The operation to be adjusted is an operation that affects the concentration of CO and / or CO 2 in the feed to the methanation reactor, and typical operations are sour shift operations or acid gas removal operations. Alternatively or additionally, the operation to be adjusted is the CO / H 2 molar ratio and / or CO 2 / H 2 molar ratio in the feed to the methanation reactor and can affect the molar ratio.

[0010] Another embodiment of the present invention relates to an integrated gasification, methanation, and electrolysis process for producing RNG. A typical process involves contacting biomass with an oxygen-containing gasifier feed in a gasifier in a gasification zone to provide CO, CO 2 , H 2 , and / or H 2 O, and a gasification zone effluent that typically contains all of these components. The oxygen-containing gasifier feed contains electrolytic oxygen obtained from the electrolysis of water in an electrolytic cell. This process further includes converting at least a portion of the CO and / or CO 2 in the gasification zone effluent to methane in a methanation reactor in the methanation zone. RNG is obtained as the methanation zone effluent, or RNG is recovered from the methanation zone (e.g., any of the following one or more purification steps). The gasification zone or the methanation zone or both include at least one operation that affects the CO concentration or the CO 2 concentration, or causes such a concentration change from the feed to the operation to the product of the operation. Alternatively or in combination, the gasification zone or the methanation zone or both include the CO / H 2 molar ratio and / or CO2 / H 2 including at least one operation that affects the molar ratio or causes such a change in the molar ratio in the product of the operation from the feed to the operation. The process can further include adjusting at least one operation in response to the replenishment amount or flow rate of electrolytic hydrogen. This replenishment amount may be the total flow rate of electrolytic hydrogen added to the process at one or more locations between the gasification device and the methanation reactor (e.g., added to either or both of the gasification zone or the methanation zone), and a part or all of this replenishment amount reacts to form methane in the methanation reactor. This replenishment amount of electrolytic hydrogen may be substantially stoichiometric in the oxygen-containing gasification device feed, or may be substantially twice the molar flow rate of electrolytic oxygen added to the gasification device. This can include one or more separate gas feed streams.

[0011] The gasification zone and / or the methanation zone can include one or more operations as described herein that can affect, cannot affect, or at least substantially affect the CO concentration or the CO 2 concentration in the methanation reactor feed or inlet. Alternatively or in combination, the gasification zone and / or the methanation zone can include one or more operations as described herein that can affect, cannot affect, or at least substantially affect the CO / H 2 molar ratio and / or the CO 2 / H 2 molar ratio in the methanation reactor feed or inlet. The gasification zone can be separated from the methanation zone by a compression stage.

[0012] Another embodiment of the present invention is directed to a process for producing methane, the process comprising gasifying a carbonaceous feedstock to produce CO, CO 2 , H 2 , and / or H 2O, and providing a gasifier effluent that typically contains all of these components. The process also involves introducing a make-up amount of hydrogen upstream of the methanator or into the methanator to react at least a portion of the make-up hydrogen with at least a portion of the CO and / or CO 2 in the gasifier effluent to form methane. The process can further include adjusting the operation of the process according to the make-up amount of hydrogen. Otherwise, advantageously, a typical process can exclude at least one processing step that would affect the feed to the methanator, or the methanator inlet, the CO concentration or the CO 2 concentration. Otherwise, instead or in combination, the process can exclude at least one processing step that would affect the methanator feed, or the methanator inlet, the CO / H 2 molar ratio and / or the CO 2 / H 2 molar ratio. This effect on the concentration or molar ratio can be caused, for example, in the case of a sour shift operation, by the reaction during operation (i.e., throughout the process) consuming or producing CO and / or CO 2 . Otherwise, the processing step to be excluded can, for example, in the case of an acid gas removal operation, add CO and / or CO 2 to, or remove CO and / or CO 2 from, the methanator feed or the methanator inlet, the CO concentration or the CO 2 concentration. Otherwise, the processing step to be excluded can, by such addition or removal of CO and / or CO 2 in the operation (i.e., throughout the process), instead or additionally affect the methanator feed or the methanator inlet, the CO / H 2 molar ratio and / or the CO 2 / H 2 molar ratio.

[0013] These and other embodiments, aspects, and advantages of the present invention will become apparent from the following detailed description.

[0014] Brief Description of the Drawings A more complete understanding of the exemplary embodiments of the present invention and their advantages can be obtained by reference to the following description in conjunction with the accompanying drawings, in which like reference numerals are used to identify like features.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0016] Between FIGS. 1 and 2, the same or similar elements are denoted by the same numbers. For ease of explanation and understanding, these figures provide a simplified overview. Associated equipment such as vessels, heat exchangers, valves, instrumentation, and utilities are not shown because their specific description is not essential for the implementation or understanding of the various aspects of the present invention. Such equipment will be readily apparent to those skilled in the art having the knowledge of the present disclosure. Another process for producing methane having a configuration and components that are partially determined according to the purpose of a specific process according to another embodiment within the scope of the present invention will be similarly apparent.

[0017] Detailed Description The expressions "weight % (wt%)" and "mole % (mol%)" are used herein to denote weight percent and mole percent, respectively. The expressions "weight ppm (wt ppm)" and "mole ppm (mol ppm)" denote weight and mole parts per million, respectively. In the case of an ideal gas, "mol%" and "mol ppm" are equal to volume percent and volume parts per million, respectively.

[0018] Embodiments of the present invention are directed to a process for producing methane from a carbonaceous feedstock by gasification and methanation, respectively, carried out in a gasification and methanation reactor. Here, a supplemental hydrogen source is added to the process to improve the overall utilization of carbon in the carbonaceous feedstock in producing methane (i.e., improve the methane yield based on the carbon content of the carbon supplied). When the source of the supplemental hydrogen is obtained from the electrolysis of water, advantageously, in contrast to hydrogen produced from steam reforming of fossil hydrocarbons, this reactant is a carbon-free resource that does not contribute to the carbon footprint associated with the methane produced. Thus, according to some embodiments, methane can be produced primarily from renewable feeds including biomass, air and / or electrolytic oxygen as the carbonaceous feedstock, and electrolytic hydrogen. Further, some or all of the electrical energy required for electrolysis can be obtained as heat recovered from the gasifier or the exothermic methanation reactor.

[0019] In a gasifier (or, more specifically, the gasification reactor of a gasifier), the carbonaceous feedstock is subjected to partial oxidation in the presence of an oxygen-containing gasifier feed at a feed rate limited to only 20 to 70% of the oxygen that would normally be required for complete combustion. The oxygen-containing gasifier feed can also contain another oxygenated gasification component containing H 2 O and / or CO 2 . CO, CO 2 , and methane (CH 4 ) derived from the carbon present in the carbonaceous feedstock, and H 2 and / or H 2Gasification plant emissions containing O (usually both) and other components at low concentrations are produced. The carbonaceous feedstock can include coal (e.g., high-quality anthracite or bituminous coal, or low-quality sub-bituminous coal, lignite or peat), petroleum coke, asphaltenes, and / or liquid petroleum residues, or other fossil-derived materials. In a preferred embodiment, the carbonaceous feedstock can include biomass. The term "biomass" refers to renewable (not fossil-derived) materials derived from organisms living on the surface of the earth or in the seas, rivers, and / or lakes of the earth. Representative biomass can include any plant material such as hardwoods (e.g., whitewood trees), softwoods, softwood or softwood bark, lignin, algae, and / or seaweed (kelp), or a mixture of plant materials. Energy crops, or other agricultural residues (e.g., logging residues) or other types of plant waste or plant-derived waste can also be used as plant materials. Specific exemplary plant materials include "intentional" energy crops such as switchgrass, miscanthus, and algae, as well as corn fiber, corn stover, and sugarcane bagasse. Products of short-rotation forestry such as energy crops include beech, ash, southern beech, oak, eucalyptus, poplar, willow, hornbeam, Australian blackwood, silver maple, and varieties of elm. Another example of suitable biomass includes organic waste such as vegetable oil, carbohydrates (e.g., sugars), old paper, buildings, demolition waste, digested sludge, and biosludge. Thus, representative carbonaceous feedstocks include any of these types of biomass (or contain them). Specific carbonaceous feedstocks containing biomass include products derived from municipal solid waste (MSW) such as municipal solid waste (MSW) or refuse-derived fuel (RDF). The carbonaceous feedstock can include a combination of fossil-derived materials and renewable materials including those described above.

[0020] Downstream of the gasifier, the methane product can be obtained directly from the methanator effluent or, if not, recovered from this effluent after additional purification and / or treatment. The carbon utilization for methane production throughout the process, and thus the resulting methane yield, is improved by adding make-up hydrogen (e.g., improved compared to a baseline process without make-up hydrogen). For example, the carbon utilization and / or methane yield (e.g., based on the carbon present in the biomass or another carbonaceous feedstock) may increase by at least about 3%, at least about 5%, or at least about 10% compared to a baseline process without the addition of make-up hydrogen (e.g., electrolytic hydrogen). For comparison purposes, the baseline process is maintained the same for all parameters of the gasifier or gasification zone, while the methanator or methanation zone can be operated to maximize the methane yield according to the baseline process.

[0021] Importantly, the processes described herein can be operated to address the constraints associated with the use of electrolytic hydrogen and oxygen, and the required amount of electrolytic oxygen can be managed in whole or mainly by the amount and type of carbonaceous feedstock being gasified. On the other hand, the corresponding amount of electrolytic hydrogen produced may be sub-optimal for converting all of the CO and CO 2 obtained from the gasifier to methane. In this case, one or more operations of the process that affect the CO and / or CO 2 concentration at the methanator inlet can be adjusted or controlled (e.g., by continuous feedback) to reduce waste and improve the economics of the overall process. The one or more operations to be adjusted can alternatively or additionally affect the CO / H 2 and / or CO 2 / H 2 molar ratio at the methanator inlet.

[0022] In some embodiments, this adjustment or control is advantageously used to maintain the CO and / or CO 2Maintain complete or substantially complete conversion and directly obtain or recover high-quality methane products (e.g., having characteristics to make it "pipeline quality" as understood in the art), or RNG products when derived from typical methane products or renewable carbonaceous feedstocks such as biomass can be any one or any combination of the following: (i) a methane concentration of at least about 90 mol% (e.g., about 90 mol% to about 99 mol%) or at least about 95 mol% (e.g., about 95 mol% to about 98 mol%); (ii) a concentration of hydrocarbons other than methane of less than about 5 mol%, or less than about 3 mol% (e.g., C 2 -C 6 total hydrocarbon concentration); (iii) a hydrogen concentration of less than about 0.05 mol%, or less than about 0.01 mol%; (iv) a CO 2 concentration of less than about 2 mol%, or less than about 1 mol%; and / or (v) a sulfur concentration of less than about 10 mol ppm, or less than about 5 mol ppm. Another characteristic of methane products or RNG products suitable for pipeline transportation includes having a heating value within 5% of pure methane and being free of water and toxic or corrosive contaminants. In some embodiments, this product may have a hydrogen concentration of up to about 4 mol% (e.g., about 1 mol% to about 4 mol%), but nevertheless can be considered pipeline quality. Typically, the CO concentration of this product is less than about 1 mol%, e.g., less than about 0.1 mol%.

[0023] Typical operations that can be adjusted by the effect on the amount and / or concentration of CO and / or CO 2 at the methane reformer inlet (e.g., in the total methanation reactor feed or gas entering this reactor), or otherwise by the effect on the molar ratio of CO / H 2 and / or CO 2 / H 2 at the methane reformer inlet can include the following operations: (i) generating or consuming CO and / or CO 2 in the process (e.g., generating or producing CO and / or CO 2 by reaction in the process, or otherwise CO and / or CO 2reacting to thereby consume or expend one or both of these components from the process); or, (ii) adding and / or removing CO or CO 2 from the process (e.g., adding an additional source of CO and / or CO 2 , or introducing a feed containing CO and / or CO 2 into the process, or otherwise separating a stream containing one or both of these components from the process). This operation can cause a change (increase or decrease) in the absolute concentration or relative amount of CO and / or CO 2 from the inlet of the operation to the outlet of the operation (usually at least about 2% (e.g., about 2% to about 30%), typically at least about 5% (e.g., about 5% to about 35%), and often at least about 10% (e.g., about 10% to about 30%)) (excluding the flow bypassing the operation). More specifically, this operation can be adjusted according to the amount or flow rate of hydrogen (e.g., electrolytic hydrogen) at least a portion of which then reacts in the methanation reactor.

[0024] Thus, in the case of an operation that produces or otherwise adds CO and / or CO 2 , that operation can be enhanced or increased with a relatively large amount of make-up hydrogen and decreased or reduced with a relatively small amount of make-up hydrogen. Conversely, in the case of an operation that consumes or otherwise removes CO and / or CO 2 , that operation can be decreased or reduced with a relatively large amount of make-up hydrogen and enhanced or increased with a relatively small amount of make-up hydrogen. The ability to adjust, i.e., enhance or decrease, one or more operations that affect (i) the concentration or total amount of CO and / or CO 2 at the methanation reactor inlet, and / or (ii) the CO / H 2 and / or CO 2 / H 2 molar ratio at the methanation reactor inlet constitutes an important aspect of the present invention from the perspective of improving the carbon utilization of biomass or other carbonaceous feedstocks.

[0025] Enhancement or increase in an operation can include increasing the ability, for example, by increasing the flow rate of a solvent or extractant for contacting the feed to the operation, or otherwise by increasing the amount of solid bed material such as an adsorbent or catalyst available for such contact (e.g., by operating an additional vessel containing the material). Alternatively, enhancement can include increasing the degree of operation, for example, by increasing the operating temperature and / or pressure, and / or otherwise by increasing the residence time (e.g., decreasing the space velocity). Conversely, reduction or decrease in an operation can include decreasing the ability, for example, by decreasing the flow rate of a solvent or extractant for contacting the feed to the operation, or otherwise by decreasing the amount of solid bed material such as an adsorbent or catalyst available for such contact (e.g., by removing a vessel containing the material). Alternatively, decrease can include decreasing the degree of operation, for example, by decreasing the operating temperature and / or pressure, and / or otherwise by decreasing the residence time (e.g., increasing the space velocity). Also, a particular operation can be enhanced or decreased by adjustment that bypasses all or at least a portion of the feed to the operation, for example, by bypassing around the operation. In the case of a bypass, the feed to the bypassed operation becomes part of the feed to a downstream operation such as the next successive operation normally carried out in the process. In the case of a complete bypass of all the feed to a particular operation, the process either operates essentially without that operation or excludes that operation.

[0026] CO and / or CO 2 For an operation of generating, or otherwise adding, more CO and / or CO 2 is generated or added in one direction. For an operation of consuming, or otherwise removing, CO and / or CO 2 more CO and / or CO 2 is consumed or removed in one direction. Conversely, for CO and / or CO 2In the case of an operation to generate or otherwise add, the decrease or reduction is less CO and / or CO 2 is generated or added in one direction. CO and / or CO 2 In the case of an operation to consume or otherwise remove, the decrease or reduction is less CO and / or CO 2 is consumed or removed in one direction.

[0027] With the knowledge of the present disclosure, those skilled in the art will readily understand the full range of adjustments that can be made to a desired operation, as necessary, to enhance or degrade its performance, based on the amount of hydrogen (e.g., electrolytic hydrogen) added to the process.

[0028] Also, certain aspects of the present invention relate to process control, whereby one or more operations of the process that affect the concentration or total amount of CO and / or CO 2 at the methanation reactor inlet, and / or the CO / H 2 and / or CO 2 / H 2 molar ratio at the methanation reactor inlet can be adjusted in response to a change in the hydrogen makeup or flow rate. For example, the control may be such that a particular composition at the methanation reactor inlet is to be maintained as a setpoint, the composition being one that enables high utilization of CO and / or CO 2 in the conversion to methane. The setpoint composition can be based on, for example, the concentration of H 2 in the feed or inlet to the methanation reactor relative to the concentration of CO and / or CO 2 A particular setpoint can be a concentration ratio (or molar ratio) given by [H 2 / (3·[CO]) or [H 2 / (3·[CO]+4·[CO 2 ) (the parentheses are used to denote component concentrations). The control can be this ratio, and / or the CO and / or CO 2Some other measure related to the efficiency at which it is utilized can be maintained at a value of 1 or approximately 1 (e.g., typically within a range of about 0.7 to about 1.5, typically within a range of about 0.8 to about 1.3, and many within a range of about 0.9 to about 1.1). Depending on the deviation of this ratio or another measured value from the set point, operations that affect the concentration or total amount of CO and / or CO 2 at the methanation reactor inlet described herein can be adjusted automatically or manually.

[0029] For example, depending on the deviation from the set point indicating an excess concentration of hydrogen (e.g., due to an increased amount or flow rate of supplemental hydrogen), the operation of generating or otherwise adding CO and / or CO 2 may be enhanced or increased, or the operation of consuming or otherwise removing CO and / or CO 2 may be decreased or reduced. Conversely, depending on the deviation from the set point indicating a deficiency in hydrogen concentration (e.g., due to a decreased amount or flow rate of supplemental hydrogen), the operation of generating or otherwise adding CO and / or CO 2 may be decreased or reduced, or the operation of consuming or otherwise removing CO and / or CO 2 may be enhanced or increased. Adjustments for enhancing or reducing the operation can follow any of those specifically described herein, and the degree of such enhancement or reduction can be controlled automatically or manually. (Example: For example, the degree to which the feed is diverted from the operation by bypassing the feed can be adjusted automatically or manually depending on the deviation from the set point related to the efficiency at which CO and / or CO 2 is utilized in the methanation reactor.)

[0030] A specific operation that affects the concentration of CO and / or CO 2 at the methanation reactor inlet is the sour shift operation, which refers to the operation of performing a catalytic water gas shift (WGS) reaction in the presence of sulfur compounds. Therefore, a sulfur-tolerant WGS catalyst is used in the WGS reactor of this operation. The sour shift operation is CO + H 2 O → CO2 +H 2 According to 2 , it is used to generate hydrogen by the WGS reaction. Therefore, any WGS operation that can usually be used in the process, either in the sour shift operation or downstream of the gasifier and upstream of the methanation reactor, consumes CO and CO 2 and H 2 to produce both. According to the above types of operations, for the purpose of characterizing the sour shift operation or the general WGS operation, this can be considered as "an operation that consumes or otherwise removes CO and / or CO 2 ". When this operation is adjusted, it usually decreases or reduces in response to excess hydrogen and strengthens or increases in response to insufficient hydrogen due to the co-production of H 2 by the WGS reaction. In the case of the reverse WGS operation, regardless of whether it is carried out in the presence or absence of sulfur compounds, this can conversely be considered as "an operation that produces or adds CO and / or CO 2 ". Another specific operation that affects the CO and / or CO 2 concentration at the methanation reactor inlet is the acid gas removal operation, which is "an operation that consumes or otherwise removes CO and / or CO 2 since CO is removed in this operation while the amount of CO is usually not affected from the feed to the product. Yet another specific operation that can be considered as "an operation that produces or adds CO and / or CO 2 " is the gasifier. When this operation is adjusted, it usually strengthens or increases in response to excess hydrogen and decreases or reduces in response to insufficient hydrogen. This operation results in H 2 as a result of the gasification reaction. 2is co-produced, but this component is usually produced in a sub-stoichiometric ratio to CO according to the methanation reaction. In certain examples of adjusting the operation of the gasifier, the feed can be bypassed from the gasifier such that the operation decreases or reduces with a relatively small amount of make-up hydrogen (e.g., in response to a deviation from a setpoint indicating a lack of hydrogen concentration). The feed can include all or part of the oxygen supplied to the process (e.g., included in the oxygen make-up), and the oxygen can be an oxygen-containing gasifier feed including electrolytic oxygen and / or oxygen separated from air.

[0031] (i) the concentration or total amount of CO and / or CO 2 at the methanator inlet, and / or (ii) the CO / H 2 and / or CO 2 / H 2 molar ratio at the methanator inlet, for any particular WGS (e.g., water-gas shift), reverse WGS, acid gas removal, or operation of the gasifier, or any other operation of the normal process that affects the same, such operation can be conveniently adjusted, for example, by bypassing at least a portion of the feed from such operation as described above (e.g., using manual or automatic control). In the case of a sufficient make-up amount or flow rate of hydrogen (e.g., electrolytic hydrogen), it would be advantageous to reduce any operation that consumes or otherwise removes CO and / or CO 2 until such operation is no longer used at all. For example, when achieving the desired utilization of carbon in the carbonaceous feedstock, the water-gas shift operation and / or acid gas removal can be completely bypassed. Accordingly, embodiments of the present invention are directed to the processes described herein for the gasification of a carbonaceous feedstock (e.g., biomass) followed by methanation, in which a make-up hydrogen source is added to the process, and the process excludes one or both of a water-gas shift operation or an acid gas removal operation, such that, for example, in this process, upstream of the methanator (i) the amount of CO and / or CO 2 in the gasifier effluent is not substantially adjusted, and / or (ii) the CO / H 2and / or CO 2 / H 2 includes not substantially adjusting the molar ratio of. That is, the relative amounts of CO and / or CO 2 in the gasifier effluent can vary by less than about 10%, less than about 5%, or even less than about 2% (e.g., the number of moles of any of these components can increase or decrease) due to the absence of operations that substantially produce, add, consume, and / or remove CO and / or CO 2 . More specifically, due to the absence of operations that consume and / or remove CO and / or CO 2 . Alternatively, or additionally, the relative CO / H 2 molar ratio and / or the relative CO 2 / H 2 molar ratio can be varied within these percentage ranges. In this way, advantageously, substantially all of the CO and / or CO 2 produced in the gasifier is fed to the methanation reactor for the production of methane products (e.g., RNG) and can preferably be utilized there.

[0032] Typical operations that can be adjusted according to the hydrogen feed amount can exclude operations used mainly to remove components other than CO and / or CO 2 , but still minimize the change in the amount and / or concentration of CO and / or CO 2 from the inlet of the operation (or the input of the feed to the operation) to the outlet of the operation (or the product removed from the operation). Such operations that can be excluded (i.e., operations not adjusted as described herein) include operations used for the removal of tar, solid particles, and sulfur, and specific operations are tar conversion operations, gas filtration / scrubbing operations, additional washing operations, and sulfur removal operations. This will be described in detail below. All of these operations can be performed on the gasifier effluent before introducing it into the methanation reactor, regardless of whether they are considered to belong to the gasification zone or the downstream methanation zone.

[0033] Figure 1 shows the integration of an electrolyzer 35, a gasification zone 100, and a methanation zone 200 for the production of methane in general. This methane, i.e., is present in the methanation reactor effluent 25 from the methanation zone 200 and is produced from the carbon in the carbonaceous feedstock 10 supplied to the gasifier in the gasification zone 100. Also supplied to this zone is a make-up amount of oxygen 14, which can be obtained entirely as electrolytic oxygen 19 or, if not, provided as a combination of electrolytic oxygen 19 and any air separation unit (ASU) oxygen 32 obtained from the separation of make-up air 40 in the ASU 45. The ASU 45 can include, for example, any technique for separating pure or substantially pure oxygen, such as to obtain ASU oxygen 32 having an oxygen concentration of at least about 90 mol%, preferably at least about 95 mol%, and / or a make-up amount of oxygen 14. Thus, the ASU can include or comprise pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA), membrane separation, and / or molten salt-based oxygen separation. The use of the ASU 45 to remove inert nitrogen from the make-up air 40 can be beneficial in terms of reducing the size of the equipment, including the gasifier and equipment associated with downstream processing operations, and improving the heating value of the gasifier effluent and downstream products (exemplary downstream operations and products described herein).

[0034] The make-up amount of oxygen 14 can be determined at least in part (e.g., mostly or exactly entirely) based on the make-up amount of the carbonaceous feedstock 10. According to some embodiments, the make-up amount of oxygen 14 can be determined based on both the make-up amount and type of the carbonaceous feedstock (especially when significant changes in the properties of the carbonaceous feedstock 10, e.g., its carbon content, occur during a particular operation). For example, the make-up amount of oxygen can be set to the amount required for a desired degree of oxidation of the carbon present in the carbonaceous feedstock, such as the percentage of stoichiometric oxygen required for oxidation to CO 2 and so on. In representative embodiments, the make-up amount of oxygen can typically be, for example, about 20% to about 95% of this stoichiometric requirement, typically about 30% to about 90%, and often about 40% to about 80%.

[0035] As clearly shown by FIG. 2, as the oxygen-containing gasifier feed 14a, all or part of the supply amount of oxygen 14 can be supplied to the gasifier 105 in the gasification zone 100, and any part 14b of this supply amount can be used for the tar conversion operation 110. Therefore, the oxygen-containing gasifier feed 14a can contain the electrolytic oxygen 19 obtained from the electrolytic cell 35, and optionally can further contain the ASU oxygen 32 obtained from the ASU 45. The oxygen-containing gasifier feed 14a can refer to all the gases supplied or added to the gasifier 105, regardless of whether they are mixed upstream or inside the gasifier 105. For example, the oxygen-containing gasifier feed 14a can be mixed with the electrolytic oxygen 19 and / or the ASU oxygen 32 upstream of the gasifier 105, or another H 2 O and / or CO 2 containing feed 12 is introduced into the gasification zone 100 or more specifically into the gasifier 105 as H 2 O and / or CO 2 and can further contain another oxygenated gas component such as this.

[0036] As further shown in the more general flow scheme of FIG. 1, in addition to electrolytic oxygen 19, the electrolytic cell also produces electrolytic hydrogen 18 in a stoichiometric amount relative to the electrolytic oxygen (e.g., 2 moles of electrolytic hydrogen per mole of electrolytic oxygen) from, for example, the electrolysis of added water 30. The electrolytic hydrogen 18 can be mixed with at least a portion of the gasification zone effluent 16 to provide a combined methanation zone feed 20. Alternatively, the electrolytic hydrogen 18 can be combined with a feed to any or any combination of the operations of the methanation zone 200, such as the operation shown in the more detailed flow scheme of FIG. 2, within the methanation zone 200. According to a preferred embodiment, the electrolytic hydrogen 18 is combined with the methanation reactor feed 212 or otherwise added directly to the methanation reactor 225. Regardless of where the electrolytic hydrogen 18 is added to the process (e.g., a feed to the gasification zone 100 or any of its constituent operations 105, 110, 115, 120 and / or 125, or a feed to the methanation zone or any of its constituent operations 210, 215, 220 and / or 225), the electrolytic hydrogen 18 can improve the yield of methane obtained in the methanation reactor effluent 25 by reaction with the carbon oxides (CO and / or CO 2 ) produced from the gasification of the carbonaceous feedstock 10.

[0037] According to FIG. 1, further process integration can be achieved by recovering the gasification zone energy 15 from the gasification zone 100 and / or the methanation zone energy 17 from the methanation zone 200. This energy can be provided to the electrolyzer 35 in the form of electrical energy and can satisfy some or all of the required amount of the electrolyzer 35. As shown in FIG. 2, considering the high temperature used in the gasification device 105, in addition to the highly exothermic reaction occurring in the methanation reactor 225, heat can be recovered from the products downstream of these operations 105, 225. For example, the gasification device heat recovery operation 115 (e.g., equipped with a heat exchanger) can be used to recover the heat 118 of the gasification device in the form of high-pressure steam passed to the generator 121 that generates electrical energy in the form of the gasification zone energy 15. Similarly, the methanation reactor heat recovery operation 230 (e.g., equipped with a heat exchanger) can be used to recover the heat 218 of the methanation reactor in the form of high-pressure steam passed to the generator 221 that generates electrical energy in the form of the methanation zone energy 17. In the embodiment shown in FIG. 2, the gasifier heat recovery operation 115 recovers heat from the high-temperature tar conversion product 106. On the other hand, the methanation reactor heat recovery operation 230 recovers heat from the high-temperature methanation product 216. Heat and a lot of low-quality heat can be recovered from the process using, for example, the gasification device heat recovery operation 115 and / or the methanation reactor heat recovery operation 230 for the purpose of preheating and / or pretreating the water 30 used for electrolysis. Those skilled in the art with knowledge of the present disclosure will understand that various forms of heat can be recovered and utilized from any of several streams of the integrated process described herein. Yet another possibility for process integration can arise from recovering water from the process, such as water supplied to and / or generated in the gasification device 105. Such water can be recovered (e.g., condensed) more specifically from the emissions of any of the operations described herein, including the high-temperature methanation product 216 and / or the methanation reactor effluent 25 (e.g., as a result of the methanation reactor heat recovery operation 230).The recovered water can advantageously provide all or part of the water 30 used for electrolysis, for example, in a way that no external water is required in the process (i.e., the process is self - sufficient in terms of sufficient water recovery to meet the required water consumption).

[0038] Figure 2 provides a more detailed description of the process shown in Figure 1 and shows the operations carried out downstream of the gasification unit 105 and upstream of the methanation reactor 225. This is, i.e., a continuous operation that is considered to be carried out on the gasification unit effluent 103 and provides the methanation reactor feed 212. Each operation can be considered in relation to the feed and product streams of each operation where at least one characteristic (e.g., composition, temperature, and / or pressure) of the product of that operation is changed compared to the feed to that operation. Also, the result of one operation can be considered as the feed to the next operation. As described above, the operations may or may not affect, or may or may not substantially affect, the CO and / or CO 2 concentration (methanation reactor inlet CO concentration or methanation inlet CO 2 concentration), or may or may not substantially affect the CO / H 2 molar ratio and / or CO 2 / H 2 molar ratio (methanation reactor inlet CO / H 2 molar ratio or methanation inlet CO 2 / H 2 molar ratio or methanation inlet CO 2 / H molar ratio) (e.g., they may, within the above - mentioned ranges, cause an absolute concentration or a change (increase or decrease) in the relative amount of CO and / or CO from the inlet of the operation to the outlet of the operation (excluding the stream bypassing the operation)). Alternatively, or further, the operations may or may not affect, or may or may not substantially affect, the CO / H 2 and / or CO2 / H 2 may cause a change (increase or decrease) in the absolute molar ratio or relative molar ratio of

[0039] In the embodiment of FIG. 2, some operations are shown to be performed in the gasification zone 100, while other operations are shown to be performed in the methanation zone 200. The boundary between these zones 100 and 200 is the compressor 205, whereby the process pressure increases from the pressure related to the conditions of the gasification device 105 (subtracting the pressure loss occurring in the equipment between the gasification device 105 and the compressor 205) to the pressure related to the conditions of the methanation reactor 225 (adding the pressure loss occurring in the equipment between the compressor 205 and the methanation reactor 225). Thus, according to some embodiments, the operations in the gasification zone 100 can be performed at a relatively low pressure, for example, at an absolute pressure of typically about 0.1 megapascal (MPa) (14.5 psi) to about 3 MPa (435), while the operations in the methanation zone 200 can be performed at a relatively high pressure, for example, at an absolute pressure of about 2 MPa (290 psi) to about 6.5 MPa (943 psi). However, those skilled in the art with the knowledge of the present disclosure will recognize that one or more of the operations shown in the gasification zone 100 can alternatively be performed in the methanation zone 200, and vice versa. The operations may be performed in an order different from the order shown and may be excluded. Further, the illustrated operations do not preclude the possibility of one or more additional steps or operations occurring upstream and / or downstream of a particular illustrated operation (e.g., reactions (e.g., COS hydrolysis), heat input or recovery, water removal, mixing with an auxiliary feed stream, separation of an intermediate product stream (e.g., NH 3 for removal), bypassed one or more operations using a part of the process, and / or recycling of a part of the process stream back to the same or an upstream operation).

[0040] Accordingly, representative processes can include one or more of the specific operations shown in FIG. 2, which depend at least in part on the characteristics of the carbonaceous feedstock 10 and the conditions (both affecting) within the gasifier 105, as well as the composition of the gasifier effluent 103, and subsequent processing operations to provide an appropriate composition of the methanation reactor feed 212 required in the gasification zone 100 and / or the methanation zone 200. In the specific embodiment shown in FIG. 2, as shown in FIG. 2, (i) alternatively, the gasifier effluent 103, which is a tar conversion feed, is processed in a tar conversion operation 110 to provide a high-temperature tar conversion product 106 with a reduced tar concentration; (ii) alternatively, the high-temperature tar conversion product 106, which is a gasifier heat recovery feed, is cooled in a gasifier heat recovery operation 115 to provide a gasifier heat recovery product 109 having a lower temperature, in addition to the heat 118 of the gasifier, as described above; (iii) alternatively, the gasifier heat recovery product 109, which is a gas filtration / scrubbing feed, is processed in a gas filtration / scrubbing operation 120 to provide a gas filtration / scrubbing product 112 with a reduced solid particle content; (iv) alternatively, the gas filtration / scrubbing product 112, which is an additional washing feed, is processed in an additional washing operation 125 to provide an additional washing product 16 as a gasification zone effluent with a reduced concentration of condensable hydrocarbons (e.g., benzene and / or naphthalene), as described above; (v) alternatively, the gasification zone effluent 16, which is a methanation zone feed (or, when mixed with at least a portion of the electrolytic hydrogen 18, the combined methanation zone feed 20 as described above), is compressed in a compressor 205 to provide a compressed product 203 having a higher pressure; (vi) alternatively, the compressed product 203, which is a sour shift feed, is processed in a sour shift operation 210 to provide a sour shift product 206 having a higher H 2 concentration; (vii) alternatively, the sour shift product 206, which is a sulfur removal feed, is processed in a sulfur removal operation 215 to remove sulfur compounds (e.g., H 2providing a sulfur removal product 209 with a reduced concentration of S and / or COS; and (viii) alternatively, the sulfur removal product 209, which is an acid gas removal feed, is produced in the acid gas removal operation 220 and, for example, as described above, as the methanation reactor feed 212, CO 2 providing an acid gas removal product with a lower concentration. As described above, the methanation reactor feed 212 is processed in the methanation reactor 225 to convert CO and CO 2 to H 2 reacting it to provide a hot methanation product 216 having a higher concentration of methane. Downstream of the methanation reactor 225, alternatively, the hot methanation product 216, which is a methanation reactor heat recovery feed, is cooled in the methanation reactor heat recovery operation 230 to provide a methanation reactor effluent 25 at a lower temperature in addition to the heat 218 of the methanation reactor as described above. The hot methanation product 216 and / or the methanation reactor effluent 25 can be subjected to drying, and the water removed in the drying step can be recovered and used as described above to provide all or part of the water 30 for electrolysis.

[0041] As shown in FIG. 2, electrolytic hydrogen 18, as an exemplary source of make-up hydrogen, can be combined with the gasification zone effluent 16 so that only a single compressor 205 is required downstream for methanation. Alternatively, as described above, electrolytic hydrogen 18 can be combined with, for example, any of the compressed product 203, the sour shift product 206, the sulfur removal product 209, and / or the methanation reactor feed 212 using an additional compression source (not shown). For example, combining electrolytic hydrogen 18 with the sour shift product 206 can improve the conversion to hydrogen in the sour shift operation 210 considering the equilibrium limit of the WGS reaction. Combining electrolytic hydrogen 18 with either the sulfur removal product 209 and / or the methanation reactor feed 212 reduces the overall flow through the sulfur removal operation 215 and / or the acid gas removal operation 220, thereby reducing the size of the equipment corresponding to these operations and thus reducing the capital cost and the operating cost.

[0042] The gasification zone 100 can include one or more gasification devices (e.g., operating in series or in parallel) that operate under the conditions of a gasification device (e.g., the conditions present in a gasification reactor) typically having a temperature of about 500 °C (932 °F) to about 1000 °C (1832 °F), and typically about 750 °C (1382 °F) to about 950 °C (1742 °F). In many cases, the gasification device is operated in a gasification reactor having a fluidized bed of particles of a carbonaceous feedstock, and an oxygen-containing gasification device feed, and optionally H 2 O and / or CO 2 -containing feeds are supplied upward through the particle bed. Other configurations of gasification reactors include countercurrent fixed beds (“upflow”), co-current fixed beds (“downflow”), and entrained plasmas. The conditions of the gasification device also include atmospheric pressure or high pressure, e.g., typically an absolute pressure of about 0.1 megapascal (MPa) (14.5 psi) to about 10 MPa (1450 psi), typically about 1 MPa (145 psi) to about 3 MPa (435 psi). A variety of catalyst materials can be used in the gasification reactor, including solid particles of dolomite, supported nickel, alkali metals, and alkali metal compounds such as alkali metal carbonates, bicarbonates, and hydroxides. A variety of catalysts having different activities for one or more desired functions in gasification, such as tar reduction, H 2 -yield improvement, and / or CO 2 -yield reduction, can be used. Limestone can be added to the gasification reactor, for example, to promote the reduction of tar by decomposition. The gasification device effluent, also called syngas, typically contains CO, CO 2 2, H 2 2, water, methane, sulfur compounds (such as H 2 2S and / or COS), nitrogen compounds (such as NH 3 3), tar, and solid particulates. According to a representative embodiment, the H 2 2 concentration of the gasification device effluent is typically about 10 mole % to about 55 mole %, and typically about 20 mole % to about 45 mole %. CO and CO 2The concentrations are each typically from about 5 mol% to about 50 mol%, and typically from about 15 mol% to about 35 mol%. The methane concentration is typically from about 1 mol% to about 15 mol%, and typically from about 2 mol% to about 10 mol%. The gasifier effluent mainly (e.g., at a total concentration of at least about 75 mol%, at least about 80 mol%, or at least about 85 mol%) comprises the components CO, CO 2 , water, and H 2 and may contain.

[0043] The tar conversion operation 110 can be used to reduce the concentration of tar (organic compounds having a boiling point temperature higher than the boiling point temperature of benzene) in the gasifier effluent produced by gasification. Compounds removed by tar conversion or tar reforming include C 6 + hydrocarbons (e.g., toluene and / or naphthalene) and oxygenates such as phenol. In the absence of tar conversion, the amount of tar produced by biomass gasification may, over time, be sufficient to cause serious problems in downstream equipment such as corrosion and / or clogging. The tar conversion operation can include a separate reactor, for example in the form of a secondary fluidized bed downstream of the gasifier, comprising a catalyst bed containing solid or supported Ni, solid or supported Fe, and / or dolomite. Other catalysts for tar conversion include cancrinite, limestone, zeolite, and even metal-containing carbides produced from gasification. Alternatively, the tar can be converted by non-catalytic partial oxidation. According to one embodiment, the tar is converted by both cracking and steam reforming, often while maintaining the yield of methane initially obtained, and beneficially increasing the yield of H 2 and CO 2 initially obtained from gasification. The tar conversion reaction can be carried out at a temperature higher than the temperature used in the gasifier, for example above 1000 °C (e.g., from about 1000 °C (1832 °F) to about 1250 °C (2282 °F)).

[0044] The gas filtration / scrubbing operation 120 can be used to remove solid particles (fine particles) in the gasifier effluent. In the case of biomass gasification, the solid particles formed include carbides, tars, soot, and ash, any of which may usually contain alkali metals such as sodium. Corrosive and / or harmful species such as chlorides, arsenic, and / or mercury may also be contained in the fine particles. For example, high-temperature filtration using a bundle of metal or ceramic filters may usually be sufficient to reduce the content of fine particles in the gasifier effluent to less than 1 weight ppm, and in some cases less than 0.1 weight ppm. In some embodiments, the gas filtration / scrubbing operation 120 can be performed upstream (before) the tar conversion operation 110 to enable the latter to operate more effectively.

[0045] The additional washing operation 125 can be used to further reduce the tar and overall hydrocarbon content of the gasifier effluent, for example, by contacting it with a solid "polishing" material such as a carbon bed. This can provide more complete removal of benzene, naphthalene, toluene, phenol, and other condensable species that may be harmful to the operation of the compressor 205 in another respect and / or may deposit on the catalyst used in the methanation reactor, thereby causing deactivation of the catalyst (e.g., by blocking the catalytically active Ni sites of the catalyst).

[0046] The sour shift operation 210 can be used to perform the WGS reaction in the presence of sulfur compounds, thereby increasing the concentration of H 2 (or the H 2 :CO molar ratio) compared to the concentration in the initial gasifier effluent obtained from the gasifier. This operation uses a catalyst such as a cobalt-molybdenum catalyst for H 2One or more WGS reactors (e.g., operating in series or in parallel) having a suitable catalyst that is resistant to deactivation in the presence of S and / or COS can be included. Another catalyst for this purpose includes those based on copper-containing and / or zinc-containing catalysts, such as Cu-Zn-Al; chromium-containing catalysts; iron oxide; zinc ferrite; magnetite; chromium oxide; and any combination thereof (e.g., Fe 2 O 3 -Cr 2 O 3 catalyst). The conditions for the catalytic WGS reaction include a temperature of about 150 °C (302 °F) to about 400 °C (752 °F).

[0047] The sulfur removal operation 215 can be used to reduce the concentration of sulfur compounds including H 2 S, COS, and / or SO 2 in the gasifier effluent. These compounds due to the presence of trace amounts of sulfur in the carbonaceous feedstock containing biomass can be harmful (e.g., poisonous) to the catalyst used in the methanation reactor, for example, due to the formation of nickel sulfide at the catalytically active Ni sites of the catalyst. The sulfur removal operation can include contacting the gasifier effluent with a guard bed suitable to obtain a product essentially sulfur-free (e.g., total sulfur less than 1 weight ppm, e.g., less than 0.1 weight ppm) at any stage of the process (e.g., downstream of the sour shift operation shown in Figure 2). Suitable guard bed materials include iron-containing adsorbent (iron "sponge") materials and / or materials used in water treatment such as zinc oxide.

[0048] The acid gas removal operation 220 is for each initial concentration in the gasifier effluent obtained from the gasifier and / or for each concentration obtained in the sour shift product, for CO 2 and / or another acid gas (e.g., H 2It can be used to reduce the concentration of (S). The acid gas removal operation can utilize one or more steps of contacting with a physical solvent such as Selexol (trademark) (dimethyl ether of polyethylene glycol), Rectisol (trademark) (cold methanol), or a combination thereof. One or more amine solvents such as monoethanolamine, diethanolamine, methyldiethanolamine, diisopropylamine, or diglycolamine, or methanol, potassium carbonate, a solution of sodium salt of amino acid, etc. can also be used to remove at least a part of the acid gas. The acid gas removal product upstream of the methanation reactor usually has a CO concentration of about 2 mol% to about 40 mol%, typically about 5 mol% to about 20 mol%. 2 It may have a concentration, and the total sulfur concentration may be less than about 0.1 mol-ppm.

[0049] The methanation zone 200 includes one or more methanation reactors (for example, operating in series or in parallel), and CO and / or CO 2reacted with hydrogen, thereby providing a methanation reactor effluent having a significantly higher methane concentration compared to the initial methane concentration in the hot methanation product and / or, ultimately, the gasifier effluent obtained from the gasifier. Catalysts suitable for use in the methanation reactor include supported metals such as ruthenium and / or another noble metal, and molybdenum and tungsten. However, generally, supported nickel catalysts are the most cost-effective. In many cases, the methanation reactor is operated using a fixed bed of catalyst. Other conditions suitable for the methanation reactor typically include temperatures from about 250 °C (482 °F) to about 600 °C (1112 °F), and typically from about 350 °C (662 °F) to about 500 °C (932 °F). Methanation conditions typically also include absolute pressures from about 1.4 (MPa) (203 psi) to about 6.9 MPa (1000 psi), and typically from about 2.8 MPa (406 psi) to about 5.5 MPa (798 psi). The concentration of methane in the methanation reactor effluent (e.g., RNG product), or in the product recovered from this effluent, is typically at least about 60 mol% (e.g., from about 60 mol% to about 99.9 mol%), and typically at least about 80 mol% (e.g., from about 80 mol% to about 99 mol%). The effluent and / or product may have other characteristics of "pipeline quality" methane, as described above.

[0050] Overall, aspects of the invention relate to the improved utilization of electrolytic hydrogen as a source supplied to an integrated gasification and methanation process for the production of methane, e.g., in combination with hydrogen, such as stoichiometric amounts of electrolytic oxygen. Those skilled in the art having the knowledge of this disclosure will recognize that various changes can be made to these processes to achieve these and other advantages without departing from the scope of this disclosure. That is, the features of this disclosure are susceptible to modification and / or substitution, and the specific embodiments illustrated and described herein are for illustrative purposes only and are not intended to limit the invention as recited in the appended claims.

Claims

1. A process for producing methane, comprising the following steps: In a gasification apparatus, a carbonaceous feedstock is contacted with an oxygen-containing gasification apparatus feed to provide a gasification apparatus effluent containing CO, CO ２ and H ２ ; a step of providing a gasification apparatus effluent containing; In a methanation reactor, electrolytic hydrogen obtained from an electrolytic cell is reacted with at least a part of CO and / or CO ２ in the gasifier effluent to form methane, Adjust the operation of the process carried out on the gasifier effluent downstream of the gasifier and upstream of the methanation reactor, and according to the replenishment amount of the electrolytic hydrogen generated in the electrolyzer, the CO concentration at the methanation reactor inlet or the CO at the methanation reactor inlet ２ affect the concentration to control the composition of the setpoint of the feed or inlet to the methanation reactor, The operation is a water gas shift (WGS) operation that generates H ２ during the process, or the operation is an acid gas removal operation that removes CO ２ during the process.

2. The process according to claim 1, further comprising obtaining the methane product as the methanation reactor effluent or recovering the methane product from the methanation reactor effluent.

3. The WGS operation consumes CO in the presence of a sulfur compound and generates CO ２ in an acidic WGS operation during the process, the process according to claim 1 or 2.

4. The process according to any one of claims 1 to 3, wherein the operation is adjusted by bypassing at least a portion of the feed to the operation.

5. The composition of the set point is [H ２ / (3·[CO]) or [H ２ / (3·[CO] + 4·[CO ２ ) at the methanation reactor inlet ratio according to any one of claims 1 to 4.

6. The process according to any one of claims 1 to 5, wherein the carbonaceous feedstock comprises coal or biomass.

7. The process according to any one of claims 1 to 6, wherein the oxygen-containing gasifier feed comprises electrolytic oxygen obtained from an electrolyzer.

8. The process according to claim 7, wherein the oxygen-containing gasifier feed further comprises ASU oxygen obtained from an air separation unit.

9. The process according to claim 8, wherein the electrolytic oxygen and the ASU oxygen provide an oxygen feed rate that is at least partially determined based on the replenishment rate of the carbonaceous feedstock.

10. wherein the oxygen-containing gasification device feed further comprises H ２ O and / or CO ２ The process according to any one of claims 1 to 9.

11. The process according to any one of claims 1 to 10, further comprising one or more additional operations downstream of the gasifier and upstream of the methanation reactor, the one or more operations each performing one or more additional treatment steps on the gasifier effluent, the treatment steps being selected from the group consisting of tar conversion, heat recovery, filtration / scrubbing, additional washing, and sulfur removal.

12. The process according to any one of claims 1 to 11, wherein the electrolytic hydrogen increases the methane yield based on the carbon present in the carbonaceous feedstock by at least 10% compared to a baseline process performed without the addition of electrolytic hydrogen.

13. The process according to claim 2, wherein the methane product is pipeline-quality gas.

14. The composition of the set point is the H of the feed or inlet to the methanation reactor with respect to the CO concentration and / or CO ２ concentration, and the process according to any one of claims 1 to 13. ２ concentration-based.

15. The process according to claim 2, wherein the methane product has a methane concentration of at least 90 mol%.

16. The process according to claim 2, wherein the methane product has a concentration of hydrocarbons other than methane of less than 5 mol%.

17. The process according to claim 9, wherein the amount of oxygen is determined based on both the replenishment rate of the carbonaceous feedstock and the properties of the carbonaceous feedstock.

18. The process according to claim 17, wherein the property of the carbonaceous feedstock is the carbon content of the carbonaceous feedstock.

19. The process according to claim 13, wherein the gas of the pipeline quality has a calorific value within 5% of the calorific value of pure methane.

20. A process according to any one of claims 1 to 19, wherein heat from the gasifier or the methanation reactor is recovered to generate electric power used in the electrolytic cell.

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