Gasification processes including recycle of products from syngas purification

Abstract

Gasification processes utilizing carbonaceous feeds and preferably biomass are disclosed, which can implement one or more strategies for integration of products, such as CO2-enriched products, that are generated from syngas purification, and into which CO2 and possibly other acid gases are preferentially rejected. Such products, which necessarily result as a consequence of obtaining a purified syngas product that is desirably substantially free of components other than H2 and CO, are often provided at different pressures and with corresponding, different compositions. Advantageously, these products can be effectively "matched" or "tailored" to the process and utility needs in the overall production of renewable products (e.g., liquid hydrocarbons or purified hydrogen). Important advantages relate to the discovery of economically attractive solutions for reducing potential CO emissions in CO2 that is vented to the atmosphere.

Description

GASIFICATION PROCESSES INCLUDING RECYCLE OF PRODUCTS FROM SYNGAS PURIFICATIONCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 608,373, filed December 11, 2023, which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] Aspects of the invention relate to gasification processes, and more particularly such processes comprising a syngas purification (e.g., acid gas removal) operation, in which one or more products (e.g., CO2-enriched products) of this operation are recycled.DESCRIPTION OF RELATED ART

[0003] The gasification of coal has been performed industrially for over a century in the production of synthesis gas (syngas) that can be further processed into transportation fuels and other valuable end products. More recent efforts toward developing energy independence with reduced greenhouse gas emissions have led to a strong interest in using biomass as a gasification feed, and thereby an alternative potential source of synthesis gas, as well as its downstream conversion products. Generally, biomass gasification is performed by partial oxidation in the presence of a suitable oxidizing gas containing oxygen and other possible components such as steam. Gasification at elevated temperature and pressure, optionally in the presence of a catalytic material, produces an effluent with hydrogen and oxides of carbon (CO, CO2), as well as hydrocarbons such as methane. This effluent, which is often referred to as synthesis gas in view of its H2 and CO content, must be cooled significantly and also treated to remove a number of undesired components that can include particulates, alkali metals, halides, and sulfur compounds, in addition to byproducts of gasification that are generally referred to as tars and oils. Furthermore, downstream conversion of the synthesis gas to value-added products often requires conditioning to remove CO2 and other acid gas contaminants that include H2S and COS.

[0004] Undesired tar components in the gasifier effluent, such as fused ring molecules (e.g., naphthalene and pyrene), pose significant challenges in terms of the tendency of such high boiling-temperature species to condense from the vapor phase onto lower-temperature surfaces encountered downstream of the gasifier. Physical deposition of tars and oils is known to cause fouling / clogging of process lines, valves, reactors, and other equipment. Forthese reasons, the thermal destruction of tar is commonly practiced, but this, in turn, requires temperatures of about 1300°C, well exceeding those of the gasifier and sufficient to cause melting and / or slagging of ash that is also present in tar-laden syngas stream or gasifier effluent. The molten material or slag is itself a source of potential fouling and plugging, due to deposition at cooler downstream temperatures, such as encountered in equipment for upgrading of synthesis gas to end products. To mitigate these problems, the use of a sufficiently large-sized radiant syngas cooler (RSC) is viewed as a possible way to separate slag via a quench chamber at the bottom of this apparatus.

[0005] Regarding the need for acid gas removal, absorptive techniques such as those utilizing a physical or chemical solvent, or otherwise separations based on solid adsorbents (e.g., molecular sieves) or membranes, are typically implemented. In conjunction with a refined syngas product, the removed acid gases are often provided in separate streams from distinct separation stages performed under differing operating pressures. Overall, the economics of biomass gasification are significantly impacted by a number of complex and interacting objectives in performing syngas purification, in addition to other operational steps, as well as by the associated equipment requirements. In view of this, effective integration of available heat and material streams that are needed for many process- and utility-related functions, in achieving an economical pathway for downstream conversion and / or separation of the produced synthesis gas to obtain desired end products, represents an important area for ongoing investigation. The present state of the art would benefit from improvements in gasification technology, relating to usage of products generated from syngas purification operations, including such products that might otherwise require specialized handling to avoid hazardous and / or greenhouse gas emissions.SUMMARY OF THE INVENTION

[0006] Aspects of the invention are associated with the discovery of gasification processes utilizing carbonaceous feeds and preferably biomass, which can implement one or more strategies for valuable integration of products, such as CO2-enriched products, that are generated from syngas purification, and into which CO2 and possibly other acid gases are preferentially rejected. Such products, which necessarily result as a consequence of obtaining a purified syngas product that is desirably substantially free of components other than H2 and CO, are often provided at different pressures and with corresponding, different compositions. Advantageously, these products can be effectively “matched” or “tailored” to the process and utility needs in the overall conversion of carbonaceous feeds to renewable products (e.g.,liquid hydrocarbons or purified hydrogen), considering their pressure and composition characteristics. Specific strategies and associated process configurations, for routing and / or combining products of syngas separation operations may be based on a number of considerations, such as the ability to (i) consolidate certain operations (e.g., compression) and associated equipment, (ii) avoid venting of hazardous components and / or greenhouse gases, and / or (iii) compensate for the overall direct material needs, as well as heat and / or utility requirements, of individual operations, which include the syngas separation operation itself and other operations involved in gasification.

[0007] For example, a relatively high purity CCh-enriched product, from a given syngas separation operation, may contain a relatively low concentration of CO (e.g., 1000 mol-ppm or less). In this case, such product may be more appropriately directed to functions that can involve release to the atmosphere. Particular embodiments are therefore directed to processes comprising recycling at least a portion of a high purity CO2-enriched product for use as a utility for one or more operations upstream of the syngas purification operation, including the gasifier. Such utilities may include, for example, inertization to reduce fire / explosion hazards, pressurization, and solid particulate removal. In some embodiments, all or substantially all of such high purity CCh-enriched product may be either recycled for use as a utility or otherwise removed from the environment, such as sequestered (e.g., underground) to remove CO2 from the atmosphere and thereby reduce global greenhouse gases. In this regard, sequestration generally requires CO2 having specific quality standards, depending on the classification and construction of the particular sequestration well. Otherwise, for example in the case of a low purity or medium purity CO2-enriched product, this may contain a more significant concentration of CO (e.g., 0.5 mol-% or more) and, for this reason, may be more appropriately directed to functions that are less susceptible to release. Therefore, other particular embodiments may comprise recycling at least a portion, and preferably all or substantially all, of a low purity or medium purity CO2-enriched product for use directly in one or more operations upstream of the syngas purification operation, including the gasifier. In the case of direct use in the gasifier, this may be as a feed to the gasifier, such as a fluidizing gas of this operation. In the case of direct use in a tar removal operation, this may be as a fuel to a hot oxygen burner of this operation.

[0008] Of further significance is the recognition that the pressure at which a given gaseous product (e.g., a low purity CO2-enriched product or a medium purity CO2-enriched product) is obtained may be varied or adjusted and thereby serve as a “handle” to regulate the amountand / or composition of this product, thereby further customizing a given syngas purification operation to the needs of the overall gasification process. Increasing pressure, for example, may lead directionally to lower amounts and lower product purities, and may cause relatively more absorbed CO2 to require desorption at a stage operating at a lower pressure.

[0009] Related aspects of the invention are associated with advantages derived from the recycle of gases obtained from the purification of a gasifier effluent, particularly in the case of utilizing purification operations (e.g., acid gas removal) that involve pressure changes to separate and recover various contaminants (e.g., CO2). Importantly, product losses may be reduced, and process economics improved, in some cases by staging the desorption and recycling of lower purity, acid gas -containing products back to the feed of the syngas purification operation or possibly to other operations. Such recycle may be used to supplement, or augment, existing process material and utility requirements, including those of, for example, a tar removal operation (e.g., fuel for a hot oxygen burner), a radiant syngas cooler or convective syngas cooler (e.g., gas for soot blowers), a filtration operation (e.g., gas for a filter back pulsing system), or any other operation that could benefit from gas addition (e.g., to control a gas flow).

[0010] Particular aspects relate to the ability, in some cases, to reduce product losses that might otherwise result as a consequence of syngas purification. Such reduction may be achieved, for example, by recycling higher pressure and / or lower purity, CCh-cnrichcd product streams, and / or by combining such product streams with others being recycled to the gasifier or its associated downstream processing steps and utilities, which together make up a complex that can be referred to as a “Gasification Island” (GI). Other particular aspects relate to operational performance improvements and decreases in cost (both capital and equipment) that may be realized by combining recycle streams that have been found suitable, in terms of their composition, pressure, and / or other characteristics, for a common purpose. Still other particular aspects relate to the reduction in potential hazardous or greenhouse gas emissions by routing certain products to uses that are internal to the gasifier and other operations, thereby avoiding venting to the atmosphere and / or greater sequestration requirements. Advantages may be gained over a baseline proposition, according to which lower purity products (e.g., CO2-enriched products) are recycled as a feed to a syngas purification operation (e.g., based on absorptive acid gas removal using a physical or chemical solvent, or adsorptive separation), whereas “cleaner” products are returned to the GI.

[0011] Important advantages may therefore reside in a number of strategies associated with managing products obtained in syngas purification. These strategies include the sharing of resources, such as by combining two compressors (each constituting an expensive rotating equipment apparatus) into a single compressor to decrease capital and operating costs. Such strategies also include reducing the material throughput of the syngas purification operation. For example, the return of all low-quality products to this operation, as a base case, would significantly increase its required capacity. By diverting at least a portion of these products for purposes (e.g., utilities for operations upstream of syngas purification) that are already at least partially satisfied by other non-condensable gas-containing streams, this capacity and the associated equipment sizing needs may be mitigated.

[0012] Strategies further include the elimination of redundant equipment and process streams that are conventionally separated. This is particularly applicable to separation processes used in purifying syngas, in which systems are employed that exploit differences of gaseous mixture components, with respect to their absorption / desorption efficiencies at different pressures. In such systems, multiple vessels or columns are utilized to provide product fractions at the corresponding, multiple pressures. If two potential discharge streams can be combined, the performance requirements typically attained using two vessels, such as one “high” pressure vessel and one “low” pressure vessel, may be relaxed and separation may instead be performed sufficiently through the use of a single vessel, such as a “medium” pressure vessel. This equipment reduction can further translate to an overall compressor duty reduction, since the low-pressure vessel is generally sized for a higher flowrate, thereby providing a benefit that outweighs the detriment of losing the high-pressure vessel operation. Yet other strategies extend to those based on reducing emissions of gaseous components that are hazardous or that contribute to atmospheric greenhouse gas emissions. In this regard, gas streams provided from the GI have, as significant components, H2 and CO, the latter of which is hazardous and therefore raises significant concerns relating to its projected emission in gasification processes. Gas purification techniques are typically specified according to a tradeoff between increased product purity / lower potential emissions, and the associated, greater operating and capital expenditures. By accepting a lower purity of a gaseous product but with the intent to use this toward satisfying already existing, substantial, recycle requirements in the GI, the potential for CO emissions can be greatly reduced, with little or no impact on economics.

[0013] In some embodiments of the invention directed to gasification processes described herein, therefore, advantages may reside in flowing or routing, such as by recycling, at least oneproduct (e.g., a CCh-enriched product) obtained from a synthesis gas purification operation (e.g., an acid gas removal operation), to that operation and / or to an upstream operation (e.g., a gasifier or operation downstream of the gasifier and upstream of the synthesis gas purification operation). According to other embodiments directed to gasification processes described herein, advantages may reside in adjusting a pressure of a syngas purification operation (e.g., an acid gas removal operation), such as by adjusting the operating pressure at which a first- stage separated gaseous fraction, or other CCh-cnrichcd product, is removed from a separation vessel (e.g., a flash vaporizer or column of the syngas purification operation), in response to an amount of the CCh-cnrichcd product that may be desired, utilized in, or required for, the syngas purification operation and / or an upstream operation. Advantages that may be realized include the simplification of process flows, reduced capital and operating costs, improved product yields (e.g., based on total carbon) due to reduced material losses, and a reduction in emissions of hazardous components and / or greenhouse gases. Overall, aspects and associated advantages of the invention, as defined by particular processes described and claimed herein, relate to the discovery of economically attractive solutions for reducing potential CO emissions in CO2 that is vented to the atmosphere.

[0014] These and other embodiments, aspects, and advantages relating to the present invention are apparent from the following Detailed Description.BRIEF DESCRIPTION OF THE DRAWING

[0015] A more complete understanding of the exemplary embodiments of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying figures, in which the same reference numbers are used to indicate the same or similar features.

[0016] FIG. 1 depicts a flowscheme illustrating an embodiment of a process for the gasification of a carbonaceous feed, which process employs a number of possible features as described herein, including a syngas purification operation (e.g., an acid gas removal operation) and various possibilities for recycling products of this operation to various points throughout the overall process.

[0017] FIG. 2 depicts more details of a specific syngas purification operation, in terms of equipment and process streams that may be used to provide a purified syngas product, in addition to CO2-enriched products of varying purity that are removed from different stages operating at different pressures.

[0018] Whereas the figures illustrate multiple possible features that may be implemented individually or in any combination, not all features (e.g., not all individual operations and their associated process streams and equipment) are required in, or essential to, the practice of various inventive embodiments described herein. For example, according to some embodiments, various intervening operations, between gasifier 50 and syngas purification operation 85, as shown in FIG. 1, may be omitted. Likewise, second stage CO2 separator 400, as shown in FIG. 2, may be omitted in some embodiments. It should be understood that various specific features can be implemented independently of others.

[0019] In order to facilitate explanation and understanding, the figures provide overviews of various features for implementation in gasification processes. Some associated equipment such as certain vessels, heat exchangers, valves, instrumentation, and utilities, are not shown, as their specific description is not essential with respect to the practice of various inventive embodiments. In the case of FIG. 2, for example, a number of auxiliary process streams connecting absorber 200 and CO2 separators 300, 400, as well as additional equipment and heat exchange that may be implemented between pairs of these auxiliary streams, are not shown. Such details would be apparent to those skilled in the art, having knowledge of the present disclosure. Other processes for producing syngas and / or its conversion products, according to other embodiments within the scope of the invention and having configurations and constituents determined, in part, according to particular processing objectives, would likewise be apparent.DETAILED DESCRIPTION

[0020] The expressions “wt-%” and “mol-%,” are used herein to designate weight percentages and molar percentages, respectively. The expressions “wt-ppm” and “mol-ppm” designate weight and molar parts per million, respectively. For ideal gases, “mol-%” and “mol-ppm” are equal to percentages by volume and parts per million by volume, respectively. The terms “barg” and “psig,” when used herein, designate gauge pressures (z.e., pressure in excess of atmospheric pressure) in units of bars and pounds per square inch, respectively, whereas the terms “bar” and “psi,” when used herein, designate absolute pressures. For example, gauge pressures of 0 barg and 0 psig are approximately equivalent to absolute pressures of 1 bar and 14.5 psi, respectively.

[0021] The term “substantially,” as used herein, refers to an extent of at least 95%. For example, the phrase “substantially all” may be replaced by “at least 95%. ” The phrases “all or a portion”or “at least a portion” are meant to encompass, in certain embodiments, “at least 50% of,” “at least 75% of,” “at least 90% of,” and, in preferred embodiments, “all.” Likewise, designated portions, such as a “first portion” or “second portion” may represent these percentages (but not all) of the total, and particularly these percentages (but not all) of the total process stream to which they refer. Reference to any starting material, intermediate product, or final product, which are all preferably process streams in the case of continuous processes, should be understood to mean “all or a portion” of such starting material, intermediate product, or final product, in view of the possibility that some portions may not be used, such as due to sampling, purging, diversion for other purposes, mechanical losses, etc. Therefore, for example, the phrase “recycling... at least one CCL-enriched product” should be understood to mean “recycling all or a portion of...at least one CCh-cnrichcd product.” In fact, in particular embodiments in which such CCh-cnrichcd product is recycled to two or more locations (e.g., to both a syngas purification operation and an upstream operation such as the gasifier), portions of this product are necessarily recycled to each location. As in the case of “all or portion” being expressly stated, when “all or a portion” is the understood meaning, this phrase is should further be understood to encompasses certain and preferred embodiments as noted above.

[0022] Representative processes described herein for the gasification of a carbonaceous feed may comprise a number of unit operations, with one of such operations stated as being performed or carried out “before,” “prior to,” or “upstream of’ another of such operations, or with one of such operations being performed or carried out “after,” “subsequent to,” or “downstream of,” another of such operations. These quoted phrases, which refer to the order in which one operation is performed or carried out relative to another, are in reference to the overall process flow, as would be appreciated by one skilled in the art having knowledge of the present specification. More specifically, the overall process flow can be defined by the bulk gasifier effluent flow, including bulk flows of both the un-scrubbed gasifier effluent and scrubbed gasifier effluent, as such flow(s) is / are subjected to operations as defined herein. Insofar as the quoted phrases are used to designate order, in specific embodiments these phrases mean that one operation immediately precedes or follows another operation, whereas more generally these phrases do not preclude the possibility of intervening operations.

[0023] Therefore, for example, one or more “operations downstream of the gasifier” can refer, according to a specific embodiment, an operation that immediately follows the gasifier, such as in the case of a tar removal operation according to the embodiment illustrated in FIG. 1.However, this phrase more generally, and preferably, refers to any of, or any combination of, operations that follow the gasifier, whether or not intervening operations are present, such as in the case of any one or more of a quenching operation, a radiant syngas cooler (RSC) or convective syngas cooler (CSC), a filtration operation, a scrubber feed cooler, and / or a scrubbing operation that follow the tar removal operation, as an intervening operation, according to the embodiment illustrated in FIG. 1. In the same manner, “an upstream operation” relative to “the syngas purification operation” can refer, according to a specific embodiment, to an operation that immediately precedes the syngas purification operation, such as in the case of the scrubbing operation noted above and according to the embodiment illustrated in FIG. 1. However, “an upstream operation” relative to “the syngas purification operation” in this context more generally, and preferably, refers to any of, or any combination of, operations that include the gasifier and also follow the gasifier, but nonetheless precede the syngas purification operation, whether or not intervening operations are present. Therefore, “an upstream operation” relative to “the syngas purification operation” may include, for example, a gasifier, a tar removal operation, a quenching operation, a radiant syngas cooler (RSC) or convective syngas cooler (CSC), a filtration operation, a scrubber feed cooler, and / or a scrubbing operation, as noted above and according to the embodiment illustrated in FIG. 1. Therefore, to the extent that representative processes described herein are defined as including certain unit operations, unless otherwise stated or designated (e.g., by using the phrase “consisting of’), such processes do not preclude the use of other operations, whether or not specifically described herein.

[0024] The terms “syngas,” or alternatively “synthesis gas,” insofar as they relate to streams comprising H2 and CO, are used herein to generally refer to the gasifier effluent, whether or not having been subjected to one or more operations downstream of the gasifier and upstream of the syngas purification operation (e.g., acid gas removal operation). Characteristics of the gasifier effluent, in terms of its composition, including its H2:C0 molar ratio, are described herein and are applicable to any “syngas,” or alternatively “synthesis gas,” as described herein. The term “purified syngas product” generally refers to the product of a syngas purification operation as described herein, such as an acid gas removal operation according to the embodiment illustrated in FIG. 2. Characteristics of a purified syngas product, in terms of its composition, including its H2:C0 molar ratio, are as described herein with respect to any “gasifier effluent,” “syngas,” or alternatively “synthesis gas,” but excluding all orsubstantially all acid gases, which encompass CO2 as well as sulfur-containing gases such as H2S and COS.

[0025] The term “gasifier effluent” is a general term that refers to the effluent of the gasifier, whether or not having been subjected to one or more operations downstream of the gasifier and upstream of the syngas purification operation (e.g., acid gas removal operation). The term “gasifier effluent” therefore encompasses more specific terms that designate (i) the effluent provided directly by the gasifier, i.e., the “raw gasifier effluent,” (ii) the raw gasifier effluent having been subjected to at least a tar removal operation, i.e., a “tar-depleted gasifier effluent,” having a lower concentration of tars and oils relative to the raw gasifier effluent, (iii) the raw gasifier effluent having been subjected to at least a quenching operation (e.g., a dry quenching operation or a full quenching operation), i.e., a “quenched gasifier effluent,” having a lower temperature and higher moisture (H2O) concentration relative to the raw gasifier effluent, resulting from direct quenching (e.g., partial quenching or complete quenching) with water, (iv) the raw gasifier effluent having been subjected to at least a radiant syngas cooler (RSC) or at least a convective syngas cooler (CSC), i.e., a “cooled gasifier effluent” having a lower temperature relative to the raw gasifier effluent, resulting from heat transfer for external steam generation, (v) the raw gasifier effluent having been subjected to at least a filtration operation, i.e., a “filtered gasifier effluent,” having a lower solid particle content relative to the raw gasifier effluent, and which may provide all or part of a “heated scrubber feed,” or otherwise all or part of a “scrubber feed,” (vi) the raw gasifier effluent having been subjected to removal of heat, i.e., a “scrubber feed” or a “further cooled gasifier effluent,” having a lower temperature relative to the raw gasifier effluent, resulting from heat removal (e.g., to generate steam), (vii) the raw gasifier effluent or un-scrubbed gasifier effluent having been subjected to a scrubbing operation, i.e., a “scrubbed gasifier effluent,” having a lower content of water-soluble contaminants (e.g., chlorides), relative to the raw gasifier effluent, and (viii) the raw gasifier effluent having been subjected to any other operation downstream of the gasifier and upstream of the syngas purification operation, whether or not specifically described herein.

[0026] A “purified syngas product,” refers to a product of a syngas purification operation, such as an acid gas removal operation, having an increased concentration of syngas and / or its components (e.g., H2 and / or CO) relative to that of a feed to that operation, such as a gasifier effluent as described herein (e.g., a scrubbed gasifier effluent). The syngas purification operation may, in some embodiments, be part of an overall syngas conditioning stage thatmay include any one or more of (a) compression, (b) acid gas removal, and (c) a water-gas shift (WGS) operation, preferably in this order but possibly in any other order, such that the purified syngas product may correspond to a “conditioned syngas product” having been conditioned for a downstream syngas conversion operation or syngas separation operation. A conditioning stage in this regard may perform various operations that provide the conditioned syngas product with characteristics that are more favorable for a given downstream conversion or separation, such as a higher pressure, a lower acid gas (e.g., lower CO2) concentration, and / or an increased FhiCO molar ratio.

[0027] Whether or not the syngas purification operation is part of an overall syngas conditioning stage, representative processes may further comprise feeding all or a portion of the purified syngas product to a downstream syngas conversion operation (e.g., a biomethanol synthesis operation) or a syngas separation operation to provide as a value-added product, a renewable syngas conversion product (e.g., purified biomethanol product) or a renewable syngas separation product. Particular examples of renewable syngas conversion products and renewable syngas separation products include both renewable liquid products (e.g., liquid hydrocarbons or methanol) and renewable gaseous products (e.g., renewable natural gas (RNG) or renewable hydrogen).

[0028] The modifiers “syngas conversion” and “syngas separation,” as well as the modifiers “conversion” and “separation,” as used in the terms “renewable syngas conversion product,” “renewable syngas separation product,” “gaseous conversion byproduct,” “liquid conversion byproduct,” and “gaseous separation byproduct” are meant to more specifically designate the origin of these products and byproducts, as being obtained from either a syngas conversion operation (e.g., comprising a Fischer-Tropsch reaction stage, a methanol (or biomethanol) synthesis reaction stage, or a methanation reaction stage) or a syngas separation operation (e.g., comprising a hydrogen purification (or hydrogen recovery) stage, such as in the case of syngas separation by pressure swing adsorption (PSA) and / or the use of a membrane). The use of the modifiers “separation” and “conversion” in the terms noted above to modify products and byproducts does not preclude such products and byproducts being obtained from a combination of separation and conversion, in either order. For example, in the particular case of a biomethanol synthesis operation, as a particular syngas conversion operation, a gaseous byproduct of this operation may provide all or a portion of a feed to a downstream hydrogen recovery operation, as an example of a syngas separation operation,which in turn provides an H -cnrichcd off gas, which may be considered an example of either a syngas conversion product (or byproduct) or a syngas separation product (or byproduct).

[0029] Any syngas conversion operation or syngas separation operation may be performed on a WGS product, obtained from a WGS operation as part of a syngas conditioning stage, as described above, with such WGS operation providing an increased, and more favorable, H2:C0 molar ratio, in terms of efficiently performing the desired conversion or separation.

[0030] Particular embodiments of the invention are directed to a process for gasification of a carbonaceous feed. The process comprises: (a) in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent comprising H2, CO, and CO2; (b) optionally following one or more intervening operations, feeding at least a portion of the gasifier effluent to a syngas purification operation to provide (i) a purified syngas product having a CO2 concentration lower than that of the gasifier effluent and (ii) at least one CO2-enriched product having a CO2 concentration higher than that of the gasifier effluent. In addition to having a lower CO2 concentration relative to that of the gasifier effluent, the purified syngas product may have a combined concentration of H2 and CO, and / or a concentration of H2 and / or CO alone, that is higher than that of the gasifier effluent (e.g., a scrubbed gasifier effluent), which is the feed to the syngas purification operation. Likewise, in addition to having a higher CO2 concentration relative to the gasifier effluent, a given CO2-enriched product may have a concentration of H2 and CO in combination, and / or a concentration of H2 and / or CO alone, that is lower than that of the gasifier effluent (e.g., a scrubbed gasifier effluent), which is the feed to the syngas purification operation.

[0031] Representative processes may further comprise (c) routing or flowing, such as recycling, at least a portion of the at least one CO2-enriched product to the syngas purification operation, such as by combining the CO2-enriched product, or portion thereof, with the gasifier effluent (e.g., a scrubbed gasifier effluent) that is fed to the syngas purification operation. Alternatively, or in combination, step (c) may comprise routing or flowing, such as recycling, at least a portion of the at least one CO2-enriched product to an upstream operation (e.g., to the gasifier and / or an operation as described herein, which is downstream of the gasifier and upstream of the syngas purification operation).

[0032] In the case of routing or flowing, such as recycling, to an upstream operation according to step (c), this includes embodiments in which the at least one CO2-enriched product, or portionthereof, is used directly in that upstream operation, as a process stream. This direct use as a process stream refers to the CO2 and optionally other components of the at least one CO2- enriched product, or portion thereof, being contained in the gasifier effluent exiting the operation in which it is directly used. For example, according to an embodiment in which at least a portion of a CCh-enriched product is used directly as a fuel for a tar removal operation, such as more specifically for a hot oxygen burner of this operation, the CO2 originally present in this product, as a relatively inert component, may be removed from this operation in the tar-depleted gasifier effluent, even if other components (e.g., CO) originally present in the CO2-enriched product become converted (e.g., oxidized). According to other embodiments in which a CO2-enriched product is used directly in an upstream operation, the gasifier provides an example of such operation, with direct use as a feed to this operation (e.g., as a fluidizing gas to aid in fluidization) being a more specific example.

[0033] In the case of routing or flowing, such as recycling, to an upstream operation according to step (c), this also includes embodiments in which the at least one CCh-cnrichcd product, or portion thereof, is used as a utility for the upstream operation. In some cases, this use as a utility does not result in the CO2 and optionally other components of the at least one CO2- enriched product, or portion thereof, being contained, to any appreciable extent, in the gasifier effluent exiting the operation in which it is used. For example, less than about 5%, or even less than about 1% of the CO2 in a given CC -enriched product that is used as a utility, may be present in the effluent of a given operation for which that product is used as a utility. In other cases, this use as a utility may result in at least some of the CO2 and optionally other components of the at least one CCh-cnrichcd product being contained in the gasifier effluent exiting the operation in which it is used. For example, at least about 50%, or even at least about 85%, of the CO2 in a given CCh-enriched product that is used as a utility, may be present in the effluent of a given operation for which that product is used as a utility. An example of a utility for an upstream operation is any utility that comprises solid particulate removal, such as in the case of at least a portion of CCh-enriched product being used for gas of (i) a blower (e.g., a soot blower) for a gasifier effluent cooler (e.g., an RSC or CSC) or (ii) a filter back pulsing system for a filtration operation. Often, the characteristics of a given CO2-enriched product, in terms having an elevated pressure and temperature, as well as a low content of, or substantial lack of, components (e.g., nitrogen) that would be undesirable if allowed to mix with the effluent of a given operation, are particularly advantageous for use as a utility. According to other embodiments in which a CO2-enriched product is used as autility for an upstream operation, the gasifier provides an example of such operation, with use for inertization (e.g., prevention or mitigation of fire and / or explosion hazards) and / or pressurization (e.g., blanketing of vessels and / or solids transport equipment) being more specific examples.

[0034] As an alternative to a step (c) described above, of routing or flowing, such as recycling, at least a portion of the at least one CCh-cnrichcd product, according to other embodiments a step (c) of processes described herein may comprise adjusting a pressure of the syngas purification operation, responsive to an amount of the at least one CCh-cnrichcd product, provided to, or possibly required in (e.g., as determined periodically or possibly continuously, such as according to a control set point) the syngas purification operation and / or an upstream operation. The amount provided to, or required in, the upstream operation, may be such amount that is used directly in that operation and / or otherwise used for a utility for that operation, as described above. Adjusting the pressure of the syngas purification operation may, more particularly, comprise adjusting an operating pressure at which a gaseous fraction, at least a portion of which is contained in the CCh-cnrichcd product, is separated from the syngas purification operation. In more particular embodiments, the operating pressure may be that of a single vapor- liquid equilibrium stage separation vessel (e.g., a flash vaporizer) or that of a multiple vapor-liquid equilibrium stage separation vessel (e.g., a column). For example, the at least one CCh-enriched product may be characteristic of a medium purity CO2-enriched product that comprises a first stage-separated gaseous fraction, such as a fraction that is provided (e.g., as an overhead or light fraction) from a first stage CO2 separator (e.g., flash vaporizer or column). In this case, the step of adjusting the pressure of the syngas purification operation may comprise, more specifically, adjusting a pressure of the first stage CO2 separator.

[0035] As described herein, prior to (c) routing or flowing, such as recycling, at least a portion of the at least one CCh-cnrichcd product to the syngas purification operation, or otherwise (c) adjusting a pressure of the syngas purification operation, representative processes comprise feeding at least a portion of the gasifier effluent to the syngas purification operation, optionally following one or more intervening operations. These intervening operations may include, more specifically, any one or more of (i) a tar removal operation to remove at least a portion of gasifier effluent tar from the gasifier effluent, (ii) a quenching operation comprising direct contact of the gasifier effluent with quench water, (iii) a radiant syngas cooler (RSC) or convective syngas cooler (CSC) implementing heat-exchanging contact ofthe gasifier effluent with boiler feed water, (iv) a filtration operation to remove solid particles from the gasifier effluent, (v) a scrubber feed cooler for further cooling of the gasifier effluent, and / or (vi) a scrubbing operation to remove at least a portion of the water-soluble contaminants from the gasifier effluent. The gasifier effluent, or portion thereof, that is fed to the syngas purification operation may therefore be, according to more specific embodiments, respectively (i) a tar-depleted gasifier effluent, (ii) a quenched gasifier effluent, (iii) cooled gasifier effluent, (iv) a filtered gasifier effluent, (v) a further cooled gasifier effluent, or (vi) a scrubbed gasifier effluent.Syngas Purification Operation

[0036] A syngas purification operation is used to improve the quality of the gasifier effluent (e.g., scrubbed gasifier effluent), such as for subsequent or downstream syngas conversion or syngas separation operations, as described herein. This quality improvement generally involves the removal of impurities such as CO2 and possibly other contaminants such as sulfur-containing gases (e.g., H2S and COS) that may likewise be considered acid gases. In preferred embodiments, the syngas purification operation is more particularly an acid gas removal operation. In view of this description, a given syngas purification operation may broadly be used to provide (i) a purified syngas product and (ii) one or more CO2-enriched products, with (i) having (a) a higher concentration of syngas and / or its components (e.g., H2 and / or CO) relative to that of the gasifier effluent and the one or more CO2-enriched products, and (b) a lower concentration of CO2 relative to that of the gasifier effluent and the one or more CO2-enriched products. Likewise, the (ii) one or more CO2-enriched products may each have (a) a lower concentration of syngas and / or its components (e.g., H2 and / or CO) relative to that of the gasifier effluent and the purified syngas product, and (b) a higher concentration of CO2 relative to that of the gasifier effluent and the purified syngas product.

[0037] In some embodiments, the at least one CO2-enriched product may include both a medium purity CO2-enriched product and a high purity CO2-enriched product, whereas in more particular embodiments, the at least one CO2-enriched product may include a low purity CO2- enriched product, a medium purity CO2-enriched product, and a high purity CO2-enriched product. The different CO2-enriched products may be obtained from stages (or separation vessels of stages, such as flash vaporizers or columns) operating at different pressures to provide different fractions at the different purity levels. Particular separations in a syngas purification operation, providing such fractions, may be based on absorption (e.g., absorptive acid gas removal using a physical or chemical solvent), adsorption using a solid adsorbent ormolecular sieve (e.g., pressure swing adsorption (PSA)), or the use of a membrane. For example, a syngas purification operation based on absorption may utilize (i) an absorption column, such as a CO2 absorber, operating at high pressure to increase absorption efficiency of CO2 and provide an absorber overhead fraction, at least a portion of which fraction is contained in the purified syngas product. At least a portion of a bottoms fraction of this CO2 absorber, i.e., an absorber bottoms fraction, may be contained in a low purity CCh-cnrichcd product. The absorption column (i) may be followed by (ii) a first stage desorption column, such as a first stage CO2 separator operating at medium pressure for desorption of at least a portion of the absorbed CO2 into a first stage overhead fraction, at least a portion of which fraction may be contained in a medium purity CCh-enriched product, and optionally further followed by (iii) a second stage desorption column, such as a second stage CO2 separator operating at low pressure for desorption of at least a further portion of the absorbed CO2 into a second stage overhead fraction, at least a portion of which fraction may be contained in a high purity CCh-cnrichcd product.

[0038] The terms “low purity,” “medium purity,” “high purity,” are meant to designate purities of one product relative to another product, and likewise the terms “low pressure,” “medium pressure,” and “high pressure” are meant to designate pressures of one stage (or of a separation vessel of such stage) relative to another stage (or of a separation vessel of such stage). By varying pressures of the stages at which various products are obtained, the compositions of the corresponding CC -enriched products, as well as the composition of the purified syngas product, can likewise be varied. Particular concentrations of components of representative low purity, medium purity, and high purity CCh-cnrichcd products are described herein. With respect to particular pressures of an absorption column (e.g., a CO2 absorber), such pressures may be in a range from about 10 bar to about 100 bar, such as from about 25 bar to about 70 bar. With respect to particular pressures of a first stage desorption column, such as a first stage CO2 separator, such pressures may be in a range from about 2 bar to about 10 bar, such as from about 2 bar to about 6 bar. With respect to particular pressures of a second stage desorption column, such as a second stage CO2 separator, such pressures may be in a range from about 1 bar to about 10 bar, such as from about 1 bar to about 5 bar. In representative embodiments, the various CCh-cnrichcd products described herein may have, or be available at, pressures corresponding to columns or other separation vessels from which they are obtained. That is, a low purity CCh-cnrichcd product may have a pressure as described above with respect to an absorption column (e.g., a CO2 absorber), amedium purity CCri-cnrichcd product may have a pressure as described above with respect to a first stage desorption column, such as a first stage CO2 separator, and / or a high purity CO2- enriched product may have a pressure as described above with respect to a second stage desorption column, such as a first stage CO2 separator. In general, the characteristics of a given CO2-enriched product, in terms of having an elevated or above-ambient pressure (e.g., at least about 2 bar, or at least about 5 bar) and / or an elevated or above-ambient temperature (e.g., at least about 35°C (95°F), or at least about 50°C (122°F)), are favorable for use as a process stream or as a utility. Such uses may be particularly advantageous, in some embodiments, in view of low contents of certain components of a given CC -enriched product that might otherwise reduce the performance and / or efficiency of the gasification process overall, including downstream conversion and / or separation operations. These components include non-reactive gases such as nitrogen, and, according to exemplary embodiments, a CCh-cnrichcd product may, for example, have an N2 concentration of generally less than about 5 mol-%, typically less than about 2 mol-%, and often less than about 1 mol-%. Uses of a CCh-cnrichcd product may also be particularly advantageous, in some embodiments, in view of low contents of certain components that might otherwise pose an increased flammability / explosion risk. According to exemplary embodiments, a CO2- enriched product may, for example, have an O2 concentration, an H2 concentration, or a combined O2 and H2 concentration, of generally less than about 5 mol-%, typically less than about 2 mol-%, and often less than about 1 mol-%. Such concentration(s) of O2 and / or H2, may be in combination with a low concentration of N2 as described above.

[0039] The terms “overhead fraction” and “bottoms fraction” are likewise relative terms. Whereas an “overhead” fraction refers to a fraction is obtained as a lighter, lower-boiling, or more volatile fraction from a vessel (e.g., a flash vaporizer or column), relative to a feed to that vessel, a “bottoms” fraction refers to a fraction is obtained as a heavier, higher-boiling, or less volatile fraction from a vessel (e.g., a flash vaporizer or column), relative to a feed to that vessel. In more specific embodiments, an overhead fraction is obtained as the vapor fraction of a flash vaporizer or above a topmost theoretical or actual contacting stage of a column, whereas a bottoms fraction is obtained as the liquid fraction of a flash vaporizer or below the bottommost theoretical or actual contacting stage of a column.

[0040] In terms of particular concentrations, according to certain embodiments and preferably those in which the syngas purification operation is based on absorption of CO2 as an acid gas, a low purity CO2-enriched product may have a CO2 concentration of generally less than about 95mol-% (e.g., from about 40 mol-% to about 95 mol-%), typically less than about 90 mol-% (e.g., from about 50 mol-% to about 90 mol-%), and often less than about 75 mol-% (e.g., from about 60 mol-% to about 75 mol-%). Optionally in combination with such CO2 concentration, the low purity CO2-enriched product may have an H2 concentration of generally greater than about 2 mol-% (e.g., from about 2 mol-% to about 25 mol-%), typically greater than about 5 mol-% (e.g., from about 5 mol-% to about 20 mol-%), and often greater than about 10 mol-% (e.g., from about 10 mol-% to about 15 mol-%). Optionally in combination with such CO2 concentration and / or H2 concentration, the low purity CO2-enriched product may have a CO concentration of generally greater than about 5 mol-% (e.g., from about 5 mol-% to about 35 mol-%), typically greater than about 10 mol-% (e.g., from about 10 mol-% to about 30 mol-%), and often greater than about 15 mol-% (e.g., from about 15 mol-% to about 25 mol-%). Optionally in combination with such CO2 concentration, H2 concentration, and / or CO concentration, the low purity CO2-enriched product may have a total concentration of sulfur-containing gases (e.g., H2S and COS) of generally at least about 10 mol-ppm (e.g., from about 10 mol-ppm to about 2000 mol-ppm), typically at least about 50 mol-ppm (e.g., from about 50 mol-ppm to about 1000 mol-ppm), and often at least about 200 mol-ppm (e.g., from about 200 mol-ppm to about 500 mol-ppm).

[0041] A medium purity CCh-cnrichcd product may have a CO2 concentration of generally greater than about 90 mol-%, typically greater than about 95 mol-%, and often greater than about 98 mol-%. Optionally in combination with such CO2 concentration, the medium purity CO2- enriched product may have an H2 concentration of generally less than about 5 mol-%, typically less than about 2 mol-%, and often less than about 1 mol-%. Optionally in combination with such CO2 concentration and / or H2 concentration, the medium purity CO2- enriched product may have a CO concentration of generally less than about 15 mol-%, typically less than about 10 mol-%, and often less than about 5 mol-%. Optionally in combination with such CO2 concentration, H2 concentration, and / or CO concentration, the medium purity CO2-enriched product may have a total concentration of sulfur-containing gases (e.g., H2S and COS) of generally less than about 1000 mol-ppm, typically less than about 500 mol-ppm, and often less than about 100 mol-ppm.

[0042] A high purity CO2-enriched product may have a CO2 concentration that is greater than that of the medium purity CO2-enriched product and / or one or both of an H2 concentration and a CO concentration that is less than that of the medium purity CO-enriched product. Optionally in combination with these relative CO2, H2, and / or CO concentrations, the high purity CO2-enriched product may have a total concentration of sulfur-containing gases (e.g., H2S and COS) that is less than that of the medium purity CO-enriched product. The high purity CO2- enriched product may have a CO2 concentration of generally greater than about 95 mol-%, typically greater than about 99 mol-%, and often greater than about 99.9 mol-%. Optionally in combination with such CO2 concentration, the high purity CO2-enriched product may have an H2 concentration of generally less than about 1 mol-%, typically less than about 5000 mol- ppm, and often less than about 1000 mol-ppm. Optionally in combination with such CO2 concentration and / or H2 concentration, the high purity CO2-enriched product may have a CO concentration of generally less than about 1 mol-%, typically less than about 1000 mol-ppm, and often less than about 200 mol-ppm. Optionally in combination with such CO2 concentration, H2 concentration, and / or CO concentration, the high purity CO2-enriched product may have a total concentration of sulfur-containing gases (e.g., H2S and COS) of generally less than about 500 mol-ppm, typically less than about 100 mol-ppm, and often less than about 25 mol-ppm.

[0043] The effective removal of contaminants from the feed to the syngas purification operation, such as a scrubbed gasifier effluent, may result in the purified syngas product being substantially free of components other than the syngas components H2 and CO. In certain embodiments, H2 and CO may be present in the purified syngas product in a combined concentration of at generally least about 90 mol-%, typically at least about 95 mol-%, and often at least about 99 mol-%. Typically, the tkiCO molar ratio of the purified syngas product does not change appreciably from that of the feed to the syngas purification operation, such as a scrubbed gasifier effluent, and may be the same or substantially the same as that of such feed. In particular embodiments, the purified syngas product may have, optionally in combination with a combined concentration of H2 and CO as described above, an H2:CO molar ratio of from about 0.5 to about 3.5, from about 1.0 to about 3.0, or from about 1.5 to about 2.5. In embodiments in which the syngas purification operation is part of an overall syngas conditioning stage that further includes a water-gas shift (WGS) operation, this latter operation may be used to increase the tkiCO molar ratio of the purified syngas product, for example in a downstream WGS product, to improve its suitability for a downstream syngas conversion operation and / or syngas separation operation. In certain embodiments, and particularly those in which the syngas purification operation is used for the removal of acid gases, the CO2 concentration of the purified syngas product may be generallyless than about 5 mol-%, typically less than about 1 mol-%, and often less than about 1000 mol-ppm.

[0044] A syngas purification operation, such as acid gas removal operation, may therefore be used to separate one or more CCh-enriched products from a gasifier effluent, for example the scrubbed gasifier effluent directly exiting the scrubbing operation or optionally this scrubbed gasifier effluent following compression to provide a compressed, scrubbed gasifier effluent. The one or more CCh-cnrichcd products may also, in some cases, be characterized as H2S- enriched products (e.g., having higher H2S concentrations compared to that of the scrubbed gasifier effluent or compressed, scrubbed gasifier effluent). The one or more CCh-enriched products may also be enriched in other sulfur compounds, such as COS and / or SO2, as well as enriched in overall sulfur content (concentration), relative to corresponding concentrations of these contaminants in the feed to the syngas purification operation, such as a scrubbed gasifier effluent or compressed, scrubbed gasifier effluent.

[0045] An absorber (e.g., CO2 absorber) of a syngas purification operation may be a column utilizing multiple stages of contacting with a physical solvent, such as in the case of Rectisol® or Selexol® acid gas removal operations, in which the respective physical solvents are cold methanol or dimethyl ethers of polyethylene glycol. The physical solvent used in Selexol® may generally be suitable for temperatures up to 175°C (347°F). Suitable solvents (e.g., physical and chemical solvents) are typically characterized by having selective solubility for acid gases including CO2 as well as sulfur-containing gases (e.g., H2S and COS). This selective solubility is often enhanced in the case of physical solvents by the use of elevated pressure. Such solvents may be regenerated (e.g., after having reached substantially a capacity for the removal of acid gases), together with desorbing or release of separated acid gases, upon reducing pressure in a vessel (e.g., a flash vaporizer or column) in one or more desorption (e.g., CO2 separation) stages. In the case of using cold temperatures to promote acid gas absorption (e.g., into cold methanol), a combined feed / product heat exchanger can improve economics associated with heat integration. In addition, desorption of acid gases may be facilitated by increased temperature in the desorption stage(s) and / or the use of a stripping gas such as N2.

[0046] A syngas purification operation, such as an acid gas removal operation, may also utilize one or more stages of contacting with a chemical solvent, examples of which are amine solvents such as monoethanolamine, diethanolamine, methyldiethanolamine (MDEA), diisopropylamine, or diglycolamine. In the case of a chemical solvent, acid gases includingC02as well as sulfur-containing gases (e.g., H2S and COS) are selectively absorbed by chemical interactions, and the solvent may be regenerated, together with desorbing or release of a separated acid gases, upon heating. Other solvents, such as potassium carbonate, a solution of sodium salts of amino acids, etc. can also be used to remove at least a portion of such acid gases initially present in the feed to the syngas purification operation (e.g., scrubbed gasifier effluent or compressed, scrubbed gasifier effluent).Other Operations of Representative Processes

[0047] Representative gasification processes described herein are defined by various possible operations, occurring downstream of the gasifier and upstream of the syngas purification operation. These intervening operations may include a tar removal operation; operations for cooling, such as a quenching operation, an RSC and / or a CSC; a filtration operation; a scrubber feed cooler, such as by using a boiler; and a scrubbing operation. As also described above, the syngas purification operation may be part of an overall syngas conditioning stage that further includes compression (e.g., upstream of the syngas purification operation), and / or a WGS operation (e.g., downstream of the syngas conversion operation). Representative processes may also include a syngas conversion operation or a syngas separation operation, downstream of the syngas purification operation or overall syngas conditioning stage. Certain possible features of the gasifier, these intervening operations, additional operations of a syngas conditioning stage (other than the syngas purification operation), and downstream syngas conversion and syngas separation operations, as well as process streams and conditions associated with any of these operations, according to preferred embodiments and otherwise any embodiments as defined in the claims and / or illustrated in FIG. 1, are provided in the following description.Gasifier

[0048] Representative processes comprise, in a gasifier, contacting a carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent (e.g., a raw gasifier effluent) comprising synthesis gas.

[0049] The carbonaceous feed may comprise coal (e.g., high quality anthracite or bituminous coal, or lesser quality subbituminous, lignite, or peat), petroleum coke, asphaltene, and / or liquid petroleum residue, or other fossil-derived substance. In a preferred embodiment, the carbonaceous feed may comprise biomass. The term “biomass” refers to renewable (non- fos sil-derived) substances derived from organisms living above the earth’s surface or withinthe earth’s oceans, rivers, and / or lakes. Representative biomass can include any plant material, or mixture of plant materials, such as a hardwood (e.g., whitewood), a softwood, a hardwood or softwood bark, lignin, algae, and / or lemna (sea weeds). Energy crops, or otherwise agricultural residues (e.g., logging residues) or other types of plant wastes or plant- derived wastes, may also be used as plant materials. Specific exemplary plant materials include corn fiber, corn stover, and sugar cane bagasse, in addition to “on-purpose” energy crops such as switchgrass, miscanthus, and algae. Short rotation forestry products, such as energy crops, include alder, ash, southern beech, birch, eucalyptus, poplar, willow, paper mulberry, Australian Blackwood, sycamore, and varieties of paulownia elongate. Other examples of suitable biomass include vegetable oils, carbohydrates (e.g., sugars), organic waste materials, such as waste paper, construction, demolition wastes, digester sludge, and biosludge. Representative carbonaceous feeds therefore include, or comprise, any of these types of biomass. Particular carbonaceous feeds comprising biomass include municipal solid waste (MSW) or products derived from MSW, such as refuse derived fuel (RDF). Carbonaceous feeds may comprise a combination of fossil-derived and renewable substances, including those described above. A preferred carbonaceous feed is wood (e.g., in the form of wood chips).

[0050] In the gasifier (or, more particularly, a gasification reactor of this gasifier), the carbonaceous feed is subjected to partial oxidation in the presence of an oxygen-containing gasifier feed, added in an amount generally limited to supply only 20-70% of the oxygen that would be necessary for complete combustion. The oxygen-containing gasifier feed will generally comprise other oxygenated gaseous components including H2O and / or CO2 that may likewise serve as oxidants of the carbonaceous feed. The oxygen-containing gasifier feed can refer to all gases being fed or added to the gasifier, or otherwise can refer to gas that is separate from other gases being fed or added, whether subsequently combined upstream of, or within, the gasifier. For example, the oxygen-containing gasifier feed may be introduced to the gasifier, along with steam, or a portion of steam, generated elsewhere in the process (e.g., RSC- generated steam or CSC-generated steam) and used as a separate feed. Contacting of the carbonaceous feed with the oxygen-containing gasifier feed in the gasifier provides a gasifier effluent, and more particularly a raw gasifier effluent as the product directly exiting the gasifier. One or more reactors (e.g., in series or parallel) of the gasifier may operate under gasification conditions present in such reactor(s), with these conditions including a temperature of generally from about 500°C (932°F) to about 1000°C (1832°F), and typicallyfrom about 816°C (1500°F) to about 1038°C (1900°F). Other gasification conditions may include atmospheric pressure or elevated pressure, for example an absolute pressure generally from about 0.1 megapascals (MPa) (14.5 psi) to about 10 MPa (1450 psi), and typically from about 1 MPa (145 psi) to about 3 MPa (435 psi), or from about 0.5 MPa (72 psi) to about 2 MPa (290 psi).

[0051] Gasification reactor configurations include counter-current fixed bed (“up draft”), co-current fixed bed (“down draft”), and entrained flow plasma. Different solid catalysts, having differing activities for one or more desired functions in gasification, such as tar reduction, enhanced Fh yield, and / or reduced CO2 yield, may be used. Limestone may be added to a gasification reactor, for example, to promote tar reduction by cracking. Various catalytic materials may be used in a gasification reactor, including solid particles of dolomite, supported nickel, alkali metals, and alkali metal compounds such as alkali metal carbonates, bicarbonates, and hydroxides. Often, a gasifier is operated with a gasification reactor having a fluidized bed of particles of the carbonaceous feed (and optionally particles of solid catalyst), with the oxygen-containing gasifier feed, and optionally separate, fluidizing H2O- and / or CO2-containing feeds, being fed upwardly through the particle bed. Exemplary types of fluidized beds include bubbling fluidized beds and entrained fluidized beds.

[0052] The raw gasifier effluent comprises, as main constituents, CO, CO2, and methane (CH4) that are derived from the carbon present in the carbonaceous feed, as well as H2 and / or H2O, and generally both, together with other components in minor concentrations. For example, the raw gasifier effluent may further comprise gasifier effluent tar and / or water-soluble contaminants, as undesired impurities, as described below. According to the embodiment illustrated in FIG. 1, the raw gasifier effluent 16 may be obtained directly from gasifier 50, prior to further operations as described herein.

[0053] The raw gasifier effluent, or any gasifier effluent having been subjected to one or more operations as described herein, may comprise synthesis gas, i.e., may comprise both H2 and CO, with these components being present in various amounts (concentrations), and preferably in a combined amount of greater than about 25 mol-% (e.g., from about 25 mol-% to about 95 mol-%), greater than about 50 mol-% (e.g., from about 50 mol-% to about 90 mol-%), or greater than about 65 mol-% (e.g., from about 65 mol-% to about 85 mol-%). With respect to any such combined amounts (concentrations), the FLiCO molar ratio of the gasifier effluent may be suitable for use in downstream syngas conversion operations or syngas separation operations), such as (i) the conversion to a renewable syngas conversion product comprisinghigher molecular weight hydrocarbons and / or alcohols of varying carbon numbers via Fischer-Tropsch conversion, (ii) the conversion to a renewable syngas conversion product comprising methanol via a catalytic methanol synthesis reaction (e.g., performed in a biomethanol synthesis operation or stage), (iii) the conversion to a renewable syngas conversion product comprising renewable natural gas (RNG) via catalytic methanation that increases the methane content in a resulting RNG stream, or (iv) the separation of a renewable syngas separation product comprising purified hydrogen. For example, the gasifier effluent, or any “syngas” or “synthesis gas product” that has not been subjected to a water-gas shift (WGS) reaction, may have an FhiCO molar ratio from about 0.5 to about 3.5, from about 1.0 to about 3.0, or from about 1.5 to about 2.5. More typically, however, such a WGS operation is needed to achieve a favorable FhiCO molar ratio, and / or a favorable Fh concentration, for these or other downstream syngas conversion and separation operations. For example, the WGS operation may include parameters (e.g., reactor temperatures and / or catalyst types) for obtaining the highest yield / concentration of hydrogen, through consumption of CO present in the syngas upstream of this operation, in the case obtaining purified hydrogen as a renewable syngas separation product (e.g., by utilizing one or more PSA and / or membrane separation stages). Relative to a feed to a WGS operation (e.g., the gasifier effluent, or any “syngas” or “synthesis gas product” that has not been subjected to a WGS reaction), a WGS product may have an FhiCO molar ratio that is increased by at least about 0.25, at least about 0.5, or at least about 1.0.

[0054] Independently of, or in combination with, the representative amounts (concentrations) of H2 and CO above, the raw gasifier effluent, or any gasifier effluent having been subjected to one or more operations as described herein, may comprise CO2, for example in an amount of at least about 2 mol-% (e.g., from about 2 mol-% to about 30 mol-%), at least about 5 mol-% (e.g., from about 5 mol-% to about 25 mol-%), or at least about 10 mol-% (e.g., from about 10 mol-% to about 20 mol-%). Independently of, or in combination with, the representative amounts (concentrations) of H2, CO, and CO2 above, the raw gasifier effluent, or any gasifier effluent having been subjected to one or more operations as described herein, may comprise CH4, for example in an amount of at least about 0.5 mol-% (e.g., from about 0.5 mol-% to about 15 mol-%), at least about 1 mol-% (e.g., from about 1 mol-% to about 10 mol-%), or at least about 2 mol-% (e.g., from about 2 mol-% to about 8 mol-%). Together with any water vapor (H2O), these non-condensable gases H2, CO, CO2, and CPU may account for substantially all of the composition of the gasifier effluent. That is, these non-condensablegases and any water may be present in the gasifier effluent in a combined amount of at least about 90 mol-%, at least about 95 mol-%, or even at least about 99 mol-%.Tar Removal Operation

[0055] The raw gasifier effluent, obtained directly from the gasifier, will generally comprise gasifier effluent tar, such that a tar removal operation is typically necessary for further processing. This gasifier effluent tar can include compounds that are referred to in the art as “tars” and “oils” and are more particularly hydrocarbons and oxygenated hydrocarbons having molecular weights greater than that of methane, which may be present in the gasifier effluent at concentrations ranging from several wt-ppm to several wt-%. Certain types of these compounds, having relatively high molecular weight, are further characterized by being problematic due to their tendency to condense at lower temperatures and coat internal surfaces of processing equipment, downstream of the gasifier, causing undesirable fouling, corrosion, and / or plugging. These compounds also interfere with subsequent processing steps, including syngas conversion operations and syngas separation operations, for upgrading synthesis gas to higher value products, which operations perform optimally (e.g., from the standpoint of stability) with pure feed gases.

[0056] Particular compounds that are undesirable for these reasons include hydrocarbons and oxygenated hydrocarbons having six carbon atoms or more (C6+hydrocarbons and oxygenated hydrocarbons), with benzene, toluene, xylenes, naphthalene, pyrene, phenol, and cresols being specific examples. These compounds are typically present in the raw gasifier effluent in a total (combined) amount from 1-100 g / Nm3. The removal (e.g., by conversion) of these organic compounds is therefore generally necessary to avoid serious problems caused by their deposition over time. Other types of tars and oils, such as ethane, ethylene, and acetylene, will not condense from the gasifier effluent but will nonetheless “tie up” hydrogen and carbon, with the effect of reducing the overall yield of H2 and CO as the desired components of synthesis gas.

[0057] Depending on the specific tar removal operation, tars and oils in the raw gasifier effluent can be converted, either catalytically or non-catalytically, by oxidation, cracking, and / or reforming to provide, in the tar-depleted gasifier effluent, additional H2 and CO. The tar conversion reaction(s) can utilize available O2 or oxygen sources (e.g., H2O and / or CO2) that are present in, and / or added to, the synthesis gas. In view of the gasifier effluent tar, together with methane, containing a significant portion of the energy of the raw gasifier effluent, theconversion of these compounds can increase the overall yield of synthesis gas substantially. The tar removal operation, which may therefore, according to certain embodiments, be more specifically a tar conversion operation, can effectively reduce the concentration of compounds present as tar in the raw gasifier effluent, having been produced in the gasifier. In general, tar removal, and more particularly tar conversion reactions, may be performed under higher temperatures compared to those used in the gasifier, such that the tar-depleted gasifier effluent, obtained directly from the tar removal operation, may have a temperature of greater than about 1000°C (e.g., from about 1000°C (1832°F) to about 1500°C (2732°F), such as from about 1204°C (2200°F) to about 1427°C (2600°F)).

[0058] According to one embodiment, the tar removal operation may be used for the conversion (e.g., reforming) of tar and methane through non-catalytic partial oxidation (Pox) in a reactor used for this operation. The efficiency of this specific operation can be promoted using hot oxygen burner (HOB) technology, according to which an excess of oxygen is mixed with a small amount of fuel (e.g., natural gas, propane, or recycled synthesis gas). Combustion of this fuel within the reactor can result in a temperature increase to above 1100°C (2012°F), causing the combustion products and excess oxygen to accelerate to sonic velocity through a nozzle, thereby forming a turbulent jet that enhances mixing between the tar / methane containing synthesis gas and the reactive hot oxygen stream. An HOB-based system can effectively improve synthesis gas yields. As described herein, one possible source of fuel is a recycled, CCh-enriched product, such as a low purity CCh-cnrichcd product containing combustible components (e.g., CO).

[0059] In the case of a tar removal operation that utilizes catalytic conversion of tar and methane, this operation may include a reactor containing a bed of catalyst comprising solid or supported Ni, solid or supported Fe, and / or dolomite, for example in the form of a secondary fluidized bed downstream of the gasifier. Other catalysts for tar conversion include olivine, limestone, zeolites, and even metal-containing char produced from the gasification. As in the case of non-catalytic processes that may be performed in a tar removal operation, catalytic tar conversion may likewise include the introduction of supplemental oxygen and / or steam reactants, into a reactor used for this operation.

[0060] According to other particular embodiments, the tar removal operation may utilize a suitable liquid or solid adsorbent, to selectively adsorb tars and oils from the raw gasifier effluent. For example, the tar removal operation may be performed with an oil washing system, whereby the raw gasifier effluent is passed through (contacted with) a liquid medium such asbio-oil liquor, to extract the tars and oils based on their preferential solubility. The liquid adsorbent may be combusted after it has become spent.

[0061] Regardless of the particular method by which the tar removal operation is performed, the raw gasifier effluent may comprise tars and oils (e.g., present as compounds described above) in an amount, or combined amount, from about 0.01 wt-% to about 5 wt-%, such as from about 0.1 wt-% to about 3 wt-% or from about 0.5 wt-% to about 2 wt-%. The tar removal operation may be effective to substantially or completely remove this gasifier effluent tar. For example, the tar-depleted gasifier effluent exiting, or obtained directly from, this operation, may comprise tars and oils in an amount, or combined amount, of less than about 0.5 wt-%, less than about 0.1 wt-%, or less than about 0.01 wt-%. Representative levels of removal of tars and oils (e.g., by conversion), measured across the tar removal operation, may be at least about 90%, at least about 95%, or even at least about 99%, resulting in a tar- depleted gasifier effluent that may be substantially or completely free of tar.Quenching Operation

[0062] Hot gasifier effluent, for example the tar-depleted gasifier effluent exiting the tar removal operation, can be cooled by various techniques that include radiant and / or convective heat exchange. In representative embodiments, at least one quenching operation, such as a dry quenching operation or a full quenching operation, may be used, in which water is added directly to the gasifier effluent and contributes to its overall moisture content, thereby favoring H2 production via the equilibrium-limited WGS reaction (z.e., to provide an increased H2:CO molar ratio and an increased H2 concentration). A dry or partial quenching operation utilizes the sensible heat of the gasifier effluent to vaporize the injected water, which is sufficient for obtaining the resulting quenched gasifier effluent at a desired, cooler temperature. A full or complete quenching operation uses sufficient water to saturate the quenched gasifier effluent. In the case of using dry or full quenching without the further use of an RSC or CSC, the quenched gasifier effluent may have a temperature from about 250°C (482°F) to about 600°C (1112°F), and preferably from about 275°C (527°F) to about 350°C (662°F) to allow for further processing. Representative processes can otherwise include, however, sufficient further cooling (e.g., using an RSC or a CSC) as required upstream of a subsequent filtration operation (passage through a filter) to remove solid particles (e.g., dust). In preferred embodiments, only a partial quench is used in the quenching operation, as opposed to a full quench, such that the quenched gasifier effluent exiting, or obtained directly from, the dry quenching operation is above its dewpoint, i.e., not saturated. In general, thedry quenching operation can promote rapid and efficient cooling through direct contact between hot gasifier effluent and water or other aqueous quenching medium.Radiant Syngas Cooler (RSC) or Convective Syngas Cooler (CSC)

[0063] As described herein, according to representative embodiments, a combination of a quenching operation characterized by direct contact of a synthesis gas (e.g., the tar-depleted gasifier effluent exiting the tar removal operation) and a quenching medium such as water, together with an RSC or a CSC, can provide effective cooling for further downstream operations. An RSC may also be effective for removal of ash and formed slag. For example, an RSC or a CSC may be used to cool a quenched gasifier effluent exiting the quenching operation to provide a cooled gasifier effluent having a temperature within a range as described above, with respect to a quenched gasifier effluent that does not require further cooling for downstream processing. In this case, the quenched gasifier effluent may have an intermediate temperature, such as 400°C (752°F) to about 900°C (1652°F), and preferably from about 538°C (1000°F) to about 816°C (1500°F). An RSC or a CSC may operate by indirect heat transfer, such as in the case of having a shell and tube configuration, typically with the generation steam from some of the heat recovered from the gasifier and tar removal operation. According to more particular embodiments, an RSC or CSC may operate as a boiler (e.g., a fire tube boiler or water tube boiler) for the production of medium and / or high pressure steam. In the case of using a CCh-enriched product as a utility for an RSC or a CSC, such as for solid particulate removal, certain characteristics of this product may be advantageous. These include an elevated pressure, an elevated temperature, and / or a low N2 concentration as described above. One specific utility, in the case of solid particulate removal, is a blower for a gasifier effluent cooler (e.g., an RSC or CSC). A CO2-enriched product having above-ambient pressure and temperature is beneficial, for example, in the case of soot blowing for the cleaning of cooling tubes, and a low N2 concentration ensures that this component will not contaminate, to any appreciable extent, the syngas exiting a gasifier effluent cooler and thereby reduce efficiency of a downstream conversion operation (e.g., to produce chemicals) or a downstream separation operation (e.g., to purify hydrogen).Filtration Operation

[0064] A filtration operation, using any suitable filter, may be used to remove solid particles (particulates) from the gasifier effluent, for example the quenched gasifier effluent as described above, exiting a dry or full quenching operation, or the cooled gasifier effluent asdescribed above, exiting an RSC or a CSC. In the case of biomass gasification, these solid particles can include char, tar, soot, and ash, any of which can generally contain alkali metals such as sodium. Corrosive and / or harmful species such as chlorides, arsenic, and / or mercury may also be contained in such solid particles. A high temperature filtration, for example using bundles of metal or ceramic filters, may generally be sufficient to reduce the content of solid particles in the gasifier effluent, such as to provide a filtered gasifier effluent exiting, or obtained directly from, the filtration operation and having less than 1 wt-ppm, and possibly less than 0.1 wt-ppm of solid particles. In representative embodiments, the filtered gasifier effluent may have a temperature in a range as described above to allow for the filtration, such as a temperature from about 250°C (482°F) to about 600°C (1112°F), and preferably from about 275°C (527°F) to about 350°C (662°F). That is, the filtration operation may involve little or no cooling of the gas stream being filtered. In the case of using a CCh-cnrichcd product as a utility for a filtration operation, such as for solid particulate removal, certain characteristics of this product may be advantageous, in the same or similar manner as with respect to its use as a utility for a gasifier effluent cooler (e.g., an RSC or CSC). These characteristics include an elevated pressure, an elevated temperature, and / or a low N2 concentration as described above. One specific utility, in the case of solid particulate removal, is a filter back pulsing system for a filtration operation. A CO2-enriched product having above-ambient pressure and temperature is beneficial, for example, in the case of filter back-pulsing for the cleaning of filter elements, and a low N2 concentration ensures that this component will not contaminate, to any appreciable extent, the syngas exiting a filtration operation and thereby reduce efficiency of a downstream conversion operation (e.g., to produce chemicals) or a downstream separation operation (e.g., to purify hydrogen).

[0065] In some embodiments, a filtration operation may be performed upstream of (prior to) the tar removal operation to allow the latter to operate more effectively. The removal of solid particles of varying average particles sizes, using filtration or other techniques, may be performed at any of a number of possible stages within the overall process. For example, coarse solids removal by centrifugation may be performed directly downstream of the gasifier, and / or may even be performed in situ in the gasifier (e.g., using internal cyclones, for removal of solid particles, positioned in a headspace above a fluidized particle bed).

[0066] The filtration operation may be followed by, or integrated with, a supplemental cleaning operation to further purify the gasifier effluent, such as to further reduce its tar and overall hydrocarbon content, for example by contact with a solid “polishing” material such as acarbon bed. This can provide for more thorough removal of benzene, naphthalene, pyrene, toluene, phenols, and other condensable species that could otherwise be detrimental to downstream operations, such as by deposition onto equipment.Scrubber Feed Cooler

[0067] Prior to the scrubbing operation, heat may be removed from the gasifier effluent, such as the filtered gasifier effluent described above and exiting, or obtained directly from, the filtration operation. According to some embodiments, a boiler and / or an air cooler (employing fans) may be used as a scrubber feed cooler to carry out indirect heat exchange. Regardless of the particular type, this cooler may more specifically perform cooling of a heated scrubber feed to provide the scrubber feed (or cooled scrubber feed) that is input directly to the scrubber, in which case both the heated and cooled streams may comprise an un-scrubbed gasifier effluent, such as the filtered gasifier effluent. It can therefore be appreciated that, according to specific embodiments, the “heated scrubber feed” may correspond to, or may comprise, the “filtered gasifier effluent.” Also, the heated scrubber feed / filtered gasifier effluent and the scrubber feed / cooled scrubber feed may be specific examples of an “un-scrubbed gasifier effluent.” In some embodiments, a scrubber feed cooler may be absent, such as in the case of sufficient cooling occurring upstream of the filtration operation for direct use of the filtered gasifier effluent in the scrubbing operation. In such cases, the “scrubber feed” may correspond to, or may comprise, the “filtered gasifier effluent.”

[0068] In representative embodiments, the scrubber feed, whether or not having been cooled in a scrubber feed cooler, may have been cooled generally, upstream and / or downstream of the filtration operation, to a temperature from about 200°C (392°F) to about 450°C (842°F), and preferably from about 225 °C (437 °F) to about 325 °C (617 °F). Such temperature may correspond to the scrubber gas inlet temperature or scrubber operating temperature. In the case of using a scrubber feed cooler downstream of the filtration operation, as illustrated in FIG. 1, the heated scrubber feed, directly upstream of this cooler, may have a temperature within the ranges given above with respect to the filtered gasifier effluent, which may be from about 250°C (482°F) to about 600°C (1112°F), and preferably from about 275°C (527°F) to about 350°C (662°F).Scrubbing Operation

[0069] A scrubbing operation may be used to remove water and water-soluble contaminants from an un-scrubbed gasifier effluent, such as the filtered gasifier effluent exiting the filtrationoperation, optionally following the cooling of this stream by a scrubber feed cooler. For example, the filtered gasifier effluent may serve as a feed to a boiler that, following indirect heat exchange, provides a cooled effluent upstream of the scrubbing operation, all or at least a portion of which effluent may provide the scrubber feed to the scrubbing operation. Otherwise, in the absence of a scrubber feed cooler, the filtered gasifier effluent, at substantially the temperature exiting the filtration operation, may serve as a feed to the scrubbing operation. In either case, the scrubbing operation itself may provide further cooling of the scrubber feed. For example, the scrubbed gasifier effluent exiting the scrubber may have a temperature from about 35°C (95°F) to about 100°C (212°F), and preferably from about 35°C (95°F) to about 66°C (150°F).

[0070] The scrubbing operation, such as wet scrubbing, may be effective for removing, as water- soluble contaminants, chlorides (e.g., in the form of HC1), ammonia, and HCN, as well as fine solid particles (e.g., char and ash). For example, in the case of using a wet scrubber, an un-scrubbed gasifier effluent, such as the scrubber feed obtained optionally following cooling, may be fed to a trayed column to perform co-current or counter-current contacting with water or an aqueous solution. Further cooling in this column, such as to a temperature below 100°C (212°F) can aid in droplet condensation for improving the contaminant removal effectiveness. The scrubbing operation can be used to provide a scrubbed gasifier effluent exiting, or obtained directly from, this operation and having a combined amount of chloride, ammonia, and solid particles of less than 1 wt-ppm, and possibly less than 0.1 wt-ppm. The scrubbing operation also generally serves to remove water, such that the moisture content of the scrubbed gasifier effluent is reduced, relative to that of the scrubber feed.WGS Operation

[0071] The water gas shift (WGS) operation reacts CO present in a gasifier effluent (e.g., the scrubbed gasifier effluent exiting the scrubbing operation, or the compressed, scrubbed gasifier effluent exiting a compressor), or may react CO present in the purified syngas product exiting the syngas purification operation, with steam to increase H2 concentration (as well as CO2 concentration). In this manner, the scrubbed gasifier effluent, optionally after being subjected to compression and / or syngas purification (e.g., acid gas removal), may be characterized as a feed to the WGS operation (WGS feed). Following the tar removal operation, filtration operation, and scrubbing operation, the scrubbed gasifier effluent, or any downstream feed to the WGS operation, may have favorable properties for use in thisoperation, in terms of its being free or substantially free of water-soluble contaminants as described above, as well as tars and particulates.

[0072] According to some embodiments, the scrubbed gasifier effluent, or any feed to the WGS operation, may be heated and / or supplemented with moisture (steam) to further improve its properties for kinetically and / or thermodynamically favoring the WGS reaction that desirably increases the tkiCO molar ratio and / or H2 concentration of the WGS product relative these characteristics of the WGS feed. For example, this feed may be heated to a temperature from about 225°C (437°F) to about 475°C (887°F), and preferably from about 260°C (500°F) to about 399°C (750°F), prior to its input to the WGS operation. The moisture content of this feed may be augmented utilizing a supplemental source of steam, such as at least a portion of the generated steam provided from steam generation (e.g., using a boiler) in any cooling operation described above. For example, at least a portion of steam (e.g., low or medium pressure steam) generated in the scrubber feed cooler, RSC (as RSC-generated steam), or CSC (as CSC-generated steam) may be fed or added to the WGS operation (e.g., to one or more reactors used in this operation), thereby improving overall heat balancing / integration. In the WGS operation, the use of steam in excess of the stoichiometric amount may be beneficial, particularly in adiabatic, fixed-bed reactors, for a number of purposes. These include driving the equilibrium toward hydrogen production, adding heat capacity to limit the exothermic temperature rise, and minimizing side reactions, such as methanation.

[0073] Reactors used in a WGS operation may contain a suitable catalyst, such as those comprising one or more of Co, Ni, Mo, and W on a solid support, particular examples of which are Co / Mo and Ni / Mo catalysts that exhibit sulfur tolerance. Other catalysts for use in this operation (z.e., contained within one or more WGS reactors) include those based on copper- containing and / or zinc-containing catalysts, such as Cu-Zn-Al; chromium-containing catalysts; iron oxides; zinc ferrite; magnetite; chromium oxides; and any combination thereof (e.g., Fe2O3-Cr2O3 catalysts).

[0074] In a typical WGS operation, two or more reactors with interstage cooling are used in view of the thermodynamic characteristics of the WGS reaction. For example, a high-temperature shift (HTS) reactor may operate with a temperature of the reactor inlet from about 310°C (590°F) to about 450°C (842°F), with more favorable reaction kinetics but a less favorable equilibrium conversion. The effluent from the HTS may then be cooled to a temperature suitable for the reactor inlet of a low-temperature shift (LTS) reactor, such as from about 200°C (392°F) to about 250°C (482°F), for providing less favorable reaction kinetics but amore favorable equilibrium conversion, such that the combined effect of the HTS and LTS reactors results in a high conversion to H2 with a favorable residence time. In some cases, it may be desirable to use three or more reactors, or catalyst beds, to perform the WGS reaction, again with cooling between consecutive reactors or catalyst beds.

[0075] In this manner, the WGS operation may be used to provide an immediate WGS product exiting, or obtained directly from, this operation and having an increased FhiCO molar ratio and increased H2 concentration, relative to the feed to the WGS operation or the synthesis gas obtained from upstream operations (e.g., synthesis gas product, scrubbed gasifier effluent (optionally following compression), filtered gasifier effluent, or cooled gasifier effluent). For example, the immediate WGS product may have an FhiCO molar ratio from about 0.5 to about 3.5, from about 1.0 to about 3.0, or from about 1.5 to about 2.5 and / or a hydrogen concentration of at least about 35 mol-% (e.g., from about 35 mol-% to about 80 mol-%), at least about 40 mol-% (e.g., from about 40 mol-% to about 70 mol-%), or at least about 45 mol-% (e.g., from about 45 mol-% to about 65 mol-%). These characteristics of the immediate WGS product may be controlled by bypassing the WGS operation to a greater or lesser extent (e.g., diverting a smaller or larger portion of the feed to this operation, around this operation to provide a portion of the immediate WGS product). The WGS operation may be further beneficial in terms of converting carbonyl sulfide (COS) to H2S which can be recycled and more easily removed elsewhere in the process, such as in the syngas purification operation (e.g., acid gas removal operation) or possibly, at least to some extent, in the scrubbing operation.Syngas Conversion or Separation Operations

[0076] In some embodiments, processes described herein may also include a syngas conversion operation or syngas separation operation to produce a respective renewable syngas conversion product or renewable syngas separation product, such as liquid hydrocarbons, methanol, or RNG as examples of conversion products, and purified hydrogen as an example of a separation product. According to particular embodiments, the feed to a syngas conversion operation or syngas separation operation may be the purified syngas product, following the syngas purification operation, or optionally a WGS product, following a WGS operation downstream of the syngas purification operation.

[0077] In the case of liquid hydrocarbon production, the syngas conversion operation may comprise a Fischer-Tropsch (FT) reaction stage. One or more reactors in this stage are used to processthe synthesis gas mixture of hydrogen (H2) and carbon monoxide (CO) by successive cleavage of C-0 bonds and formation of C-C bonds with the incorporation of hydrogen. This mechanism provides for the formation of hydrocarbons, and particularly straight-chain alkanes, with a distribution of molecular weights that can be controlled to some extent by varying the FT reaction conditions and catalyst properties. Such properties include pore size and other characteristics of the support material. The choice of FT catalyst and its active metals (e.g., Fe or Ru) can impact FT product yields in other respects, such as in the production of oxygenates.

[0078] In the case of methanol production, the syngas conversion operation may comprise a methanol synthesis reaction stage, or more specifically a biomethanol synthesis reaction stage. One or more reactors in this stage are used to form methanol according to the catalytic reaction:Representative catalysts for the synthesis of methanol by this route are characterized by “CZA,” which is a reference to copper and zinc on alumina, or Cu / ZnO / AhOa. Alternatively, or in combination, various other catalytic metals and their oxides may be used, including one or more of W, Zr, In, Pd, Ti, Co, Ga, Ni, Ce, Au, Mn, and their combinations.

[0079] In the case of methane production as a syngas conversion operation to provide a renewable natural gas (RNG) product, one or more methanation reactors (e.g., in series or parallel) may be used to react CO and / or CO2 with hydrogen and thereby provide a hot methanation product having a significantly higher concentration of methane relative to that initially present (e.g., in the WGS product). Catalysts suitable for use in a methanation reactor include supported metals such as ruthenium and / or other noble metals, as well as molybdenum and tungsten. Generally, however, supported nickel catalysts are most cost effective. Often, a methanation reactor is operated using a fixed bed of the catalyst.

[0080] In the case of purified hydrogen production, the syngas separation operation may comprise a renewable hydrogen separation stage that can utilize, for example, (i) an adsorbent in the case of separation by PSA or (ii) a membrane. Combinations of such stages may be used in a given syngas separation operation. In any such operation, a gaseous separation byproduct is also provided that is generally enriched in the non-hydrogen components of syngas, such as CO, CO2, and / or H2O. This byproduct may be, for example, a PSA tail gas or otherwise a membrane permeate or retentate, depending on the particular membrane used andconsequently whether the renewable hydrogen separation product is recovered as the membrane retentate or permeate. This hydrogen, obtained as a result of utilizing a syngas separation operation downstream of the WGS operation, may, in some embodiments, be characterized as high purity hydrogen (e.g., having a purity of at least about 99 mol-% or more, such as at least 99.9 mol-% or at least 99.99 mol-%).

[0081] According to other embodiments, the syngas conversion operation may comprise a methanol synthesis reaction stage, or more specifically a biomethanol synthesis reaction stage, which, in addition to a raw biomethanol product, may provide a separated, gaseous byproduct. This gaseous byproduct may, in turn, be beneficially subjected to a hydrogen recovery operation, as a syngas separation operation described above. The hydrogen recovery operation may utilize, for example, (i) an adsorbent in the case of separation by PSA or (ii) a membrane, to further separate the gaseous byproduct into both an H -cnrichcd off gas and an H -dcplctcd tail gas, optionally having properties that are characteristic of a renewable hydrogen separation product and a tail gas (e.g., PSA tail gas) as described above. These H -cnrichcd and H2-depleted gas streams may optionally be further utilized in the process as described herein.Further exemplary embodiments of gasification processes

[0082] FIG. 1 depicts a flowscheme illustrating an embodiment of a process including operations as described above, and more particularly including a syngas purification operation, providing CO2-enriched products that may be recycled to that operation, and / or to an upstream operation.

[0083] With reference to FIG. 1, and with the understanding that embodiments disclosed herein do not necessarily require all of the illustrated features, such embodiments may be directed to a process for gasification of a carbonaceous feed (e.g., wood) generally. The process may comprise, in gasifier 50, contacting carbonaceous feed 10 (which may be a dried carbonaceous feed, following drying) with oxygen-containing gasifier feed 14 (and optionally a separate source of steam) under gasification conditions to provide an un- scrubbed gasifier effluent comprising H2, CO, and CO2. Oxygen-containing gasifier feed 14 alone (or possibly in combination with a separate source of steam), may comprise H2O and O2, as well as optionally CO2, in a combined concentration of at least about 90 mol-%, at least about 95 mol-%, or at least about 99 mol-%. An un-scrubbed gasifier effluent may be any process stream downstream of gasifier 50 and upstream of scrubbing operation 80, including rawgasifier effluent 16, tar-depleted gasifier effluent 18, quenched gasifier effluent 22, cooled gasifier effluent 24, filtered gasifier effluent 26, or scrubber feed 28.

[0084] The process may further comprise feeding at least a portion of the un-scrubbed gasifier effluent, for example as scrubber feed 28, to scrubbing operation 80 to remove at least a portion of the water-soluble contaminants and provide scrubbed gasifier effluent 30. In the absence of scrubber feed cooler 75, the scrubber feed may correspond to, or may comprise, filtered gasifier effluent 26, which may be fed directly to scrubbing operation 80. In the case utilizing scrubber feed cooler 75, an un-scrubbed gasifier effluent or portion thereof may be fed, for example as filtered gasifier effluent / heated scrubber feed 26, to cooler 75. In some embodiments, cooler 75 may provide generated steam 33 from heat in this heated scrubber feed being transferred to boiler feed water 31, as well as provide scrubber feed 28 (which may also be referred to as a cooled scrubber feed in such embodiments). It can therefore be appreciated that either or both of heated scrubber feed 26 and scrubber feed 28 may correspond to, or may comprise, an un-scrubbed gasifier effluent, such as in the particular case of an un-scrubbed gasifier effluent, that, as a heated scrubber feed, is at a higher temperature relative to this un-scrubbed gasifier effluent, as a scrubber feed. The unscrubbed gasifier effluent, as heated scrubber feed 26 and scrubber feed 28, may have the same composition.

[0085] In exemplary embodiments, the un-scrubbed gasifier effluent, which is optionally fed to cooler 75 as heated scrubber feed 26 or directly fed to scrubbing operation 80 as scrubbed feed 28, may be a filtered gasifier effluent, having been subjected to filtration operation 70, as an intervening operation, to remove solid particles. More particularly, in addition to having been subjected to filtration operation 70, the filtered gasifier effluent may have been further subjected to one or more other operations downstream of gasifier 50 and upstream of filtration operation 70. For example, such operations may include one or more of (i) tar removal operation 55 to remove at least a portion of gasifier effluent tar (e.g., and provide tar-depleted gasifier effluent 18), (ii) quenching operation 60 (which may be a partial or full quenching operation) comprising direct contact with quench water 20 (e.g., and provide quenched gasifier effluent 22), and (iii) radiant syngas cooler 65 (RSC) or convective syngas cooler (CSC) 65, implementing heat-exchanging contact with, respectively, RSC feed water or CSC feed water (e.g., and provide cooled gasifier effluent 24). The RSC feed water or CSC feed water may be, for example, boiler feed water 25 which, following heat exchange in RSC 65 or CSC 65, provides RSC-generated steam 23 or CSC-generated steam 23,respectively. Optionally in combination with any of these particular intervening operations, other intervening operations may include both filtration operation 70 and scrubber feed cooler 75 downstream of this operation. In this case, the un-scrubbed gasifier effluent, at least a portion of which is fed as a scrubber feed to scrubbing operation 80, according to any exemplary process as described herein, may be more particularly a filtered and cooled gasifier effluent, having been subjected to filtration operation 70 to remove solid particles and also to scrubber feed cooler 75.

[0086] With respect to various features of representative processes, therefore, raw gasifier effluent 16 produced in gasifier 50 is fed to tar removal operation 55, to provide tar-depleted gasifier effluent 18, having a lower amount of tar relative to raw gasifier effluent 16. Generally, processes comprise recovering a synthesis gas product from tar-depleted gasifier effluent 16, with such synthesis gas product possibly including any of those downstream of tar-depleted gasifier effluent 16 as illustrated in FIG. 1. For example, the synthesis gas product may be recovered as purified syngas product 34, optionally following one or more intervening operations performed on the gasifier effluent, downstream of the gasifier and upstream of the syngas purification operation. Such intervening operations can include one or more of (i) tar removal operation 55 to removal at least a portion of gasifier effluent tar, (ii) quenching operation 60 comprising direct contact of the gasifier effluent with quench water 20, (iii) radiant syngas cooler (RSC) 65 or convective syngas cooler (CSC) 65, implementing heatexchanging contact of the gasifier effluent with RSC feed water or CSC feed water (e.g., boiler feed water), as the case may be (iv) filtration operation 70 to remove solid particles from the gasifier effluent, (v) scrubber feed cooler 75 to further remove heat from (for further cooling of) the gasifier effluent (e.g., and thereby control the temperature of the downstream scrubbing operation), and (vi) scrubbing operation 80 to remove water-soluble contaminants from the gasifier effluent. In combination, gasifier 50, tar removal operation 55, quenching operation 60, RSC 65 or CSC 65, filtration operation 70, scrubber feed cooler 75, and scrubbing operation 80, may be characterized as a “gasification island” upstream of syngas purification operation 85.

[0087] According to exemplary embodiments, quenching operation 60, may be more particularly a partial dry quench (PDQ) operation. Representative processes may further comprise, in any order but preferably in the following order: in the PDQ operation, contacting (e.g., by direct contact) tar-depleted gasifier effluent 18 with quench water 20 to provide quenched gasifier effluent 22; in the RSC 65 or CSC 65, further cooling quenched gasifier effluent 22 toprovide cooled gasifier effluent 24 and, respectively, RSC-generated steam 23 or CSC- generated steam 23; in filtration operation 70, removing solid particles from cooled gasifier effluent 24 to provide filtered gasifier effluent 26; and in scrubber feed cooler 75, cooling filtered gasifier effluent 26 to provide scrubber feed 28, to the scrubbing operation 80. Generally, according to certain embodiments as illustrated in FIG. 1, quenching operation 60 provides quenched gasifier effluent 22, having a temperature that is decreased relative to that of tar-depleted gasifier effluent 18. The process may additionally comprise, in radiant syngas cooler (RSC) 65 or convective syngas cooler (CSC) 65, further cooling quenched gasifier effluent 22, such as by indirect, heat-exchanging contact with RSC feed water or CSC feed water, respectively. This provides cooled gasifier effluent 24, which may then be subjected to filtration operation 70, heat removal in scrubber feed cooler 75, and scrubbing operation 80, with particular details of these operations as described herein.

[0088] Representative processes may further comprise feeding at least a portion of scrubbed gasifier effluent 30 to syngas purification operation 85 that provides purified syngas product 34 that may, relative to scrubbed gasifier effluent 30, have characteristics that are more favorable for downstream syngas conversion operations and / or downstream syngas separation operations. Such characteristics may include a lower acid gas (e.g., lower CO2) concentration, resulting from acid gas removal, as described herein. In embodiments, syngas purification operation 85 may be part of an overall syngas conditioning stage that may include one or more other operations, in addition to purification, that are performed on scrubbed gasifier effluent 30, with these including any one or more of compression (e.g., using compressor) and a WGS operation. These may be performed in any order relative to syngas purification operation 85, but preferably compression is performed upstream of this operation and / or a WGS operation is performed downstream of this operation.

[0089] In addition to purified syngas product 34, syngas purification operation may provide one or more CO2-enriched products 32a, 32b, 32c as described herein, having a CO2 concentration that is higher than that of scrubbed gasifier effluent 30, and / or having a concentration of H2 and / or CO that is lower than that of gasifier effluent 30, which in the embodiment illustrated in FIG. 1 is the feed to syngas purification operation. Representative compositions of CO2- enriched products 32a, 32b, 32c are described above. In achieving various benefits as described herein, according to the specific embodiment illustrated in FIG. 1, processes may comprise recycling one or more CO2-enriched products 32a, 32b, 32c to syngas purification operation 85 (e.g., by combining with scrubbed gasifier effluent 30) and / or to an upstreamoperation, such as any of gasifier 50, tar removal operation 55, quenching operation 60, RSC 65 or CSC 65, filtration operation 70, scrubber feed cooler 75, or scrubbing operation 80. In the case of recycling to an upstream operation, as described above, this may be for use directly in that upstream operation (e.g., as a process stream) or for use as a utility for that upstream operation.

[0090] In particular embodiments, at least one CC -enriched product 32a, 32b, 32c may be recycled to syngas purification operation 85 in a syngas purification recycle amount that represents an excess, above that utilized in, or required for, gasifier 50 and / or gasifier utilities 50a. In this case, therefore, the at least one CC -enriched product 32a, 32b, 32c may be recycled to both syngas purification operation 85 and to the gasifier. Any excess of such product(s), beyond the amount(s) needed for processing in gasifier 50 and / or for use in gasifier utilities 50a, may be recycled to syngas purification operation 85. Alternatively, in the case of recycling at least one CCh-cnrichcd product 32a, 32b, 32c to the gasifier, an excess may be sequestered, i.e., a sequestration amount may represent the excess of a gasifier recycle amount that is utilized in, or required for, gasifier 50 and / or gasifier utilities 50a. Whether an excess amount of a given CCh-enriched product is recycled to the syngas purification operation or otherwise sequestered may depend, for example, on the composition of that particular product. For example, it may be preferable to recycle a low and / or medium purity CCh-cnrichcd product, having a more significant concentration of CO as described above, in order to maintain this CO within the process. On the other hand, it may be preferable to sequester a high purity CO2-enriched product, having a less significant concentration of CO, in view of the reduced environmental concerns.

[0091] The at least one CO2-enriched product may, for example, include both medium purity CO2- enriched product 32b and high purity CO2-enriched product 32c, or, in more particular embodiments, may include all three of low purity CO2-enriched product 32a, medium purity CO2-enriched product 32b and high purity CO2-enriched product 32c, as better illustrated in FIG. 2 with respect to the manner in which these CO2-enriched products may be obtained, in addition to purified syngas product 34, from syngas purification operation 85. In the embodiment of FIG. 2, this operation may be configured more particularly as an acid gas removal operation comprising CO2 absorber 200 for absorbing CO2 from scrubbed gasifier effluent 30, as well as first stage CO2 separator 300 and second stage CO2 separator 400, for separating or desorbing CO2 that is absorbed in CO2 absorber, and more particularly absorbed in liquid solvent exiting the bottoms of this column and subsequently passed to first andsecond stage CO2 separators 300, 400. In view of the favorability of low temperatures for promoting CO2 absorption into a solvent such as methanol, feed / product heat exchanger 100 may be used to improve heat integration / transfer, for example in the cooling of the feed to syngas purification operation 85, such as scrubbed gasifier effluent 30. As illustrated, this feed may be cooled through heat exchange with any of purified syngas product 34, medium purity CO2-enriched product 32b, and / or high purity CCh-cnrichcd product 32c. The CO2 absorber 200 and first and second stage CO2 separators 300, 400 may operate at respective high, medium, and low pressures (relative to one another), with values of these pressures typically being within ranges as described above.

[0092] The same or analogous principles in the recycling of CCh-enriched products, for example those obtained at different stages under different operating pressures, can likewise be applied to other types of syngas purification operations, such as those based on adsorption using a solid adsorbent or molecular sieve (e.g., pressure swing adsorption (PSA)) or those based on using semi-permeable membranes. The implementation of these and other gas purification operations in the practice of the present invention would be would be apparent to those skilled in the art, having knowledge of the present disclosure.

[0093] As further illustrated in FIG. 2, purified syngas product 34 and low purity CCh-enriched product 32a may comprise absorber-separated gaseous fractions, such as in the case of purified syngas product 34 comprising at least a portion of absorber overhead fraction 340 and low purity CC -enriched product 32a comprising at least a portion of absorber bottoms fraction 320, optionally withdrawn from an overhead of flash drum 250 that provides at least a single vapor / liquid separation stage, allowing solvent in the liquid phase to pass to first and second stage CO2 separators 300, 400 for recovery of absorbed CO2. In addition, medium purity CO2-enriched product 32b may comprise a first stage- separated gaseous fraction, such as in the case of this product comprising first stage overhead fraction 322, and high purity CO2-enriched product 32c may comprise a second stage-separated gaseous fraction, such as in the case of this product comprising second stage overhead fraction 323. According to some embodiments, the medium purity CCh-cnrichcd product may comprise a mixture of an absorber-separated gaseous fraction and a first stage- separated gaseous fraction. For example, as further illustrated in FIG. 2, a first- stage- separated gaseous fraction, namely first stage overhead fraction 322, is mixed with an absorber-separated gaseous fraction, namely absorber bottoms fraction 320, optionally withdrawn from an overhead of flash drum 250. In this case, medium purity CO2-enriched product 32b comprises first stage overhead fraction322 that is mixed with (i) portion 321 of absorber bottoms fraction 320, upstream of feed / product heat exchanger 100, as well as (ii) a second portion of this absorber bottoms fraction 320, namely that portion provided as low purity CCh-enriched product 32a, downstream of feed / product heat exchanger 100.

[0094] This combining of CCh-cnrichcd products represents one possibility for product consolidation, such that syngas purification operation 85 provides only a medium purity CO2- enriched product and a high-purity CCh-enriched product. Whereas the former may be more suitable for recycle in the process (z.e., for use directly in an upstream operation) to capture its fuel value and carbon content without significant concern for release into the environment, the latter may be more suitable for recycle for utilities and / or sequestration, given the reduced concentrations of detrimental impurities that may be released. For example, optional portion 325 of high purity CCh-enriched product 32c may be sequestered. In general, given the differences in the compositions of low purity CCh-enriched product 32a, medium purity CO2- enriched product 32b (whether or not combined as described above), and high purity CO2- enriched product 32c, which differences may arise from the conditions (e.g., pressure) at which these products are obtained from syngas purification operation 85, in representative embodiments processes may comprise (i) recycling at least a portion of medium purity CO2- enriched product 32b to the gasifier as the upstream operation, either for use directly in the upstream operation or for use as a utility; (b) recycling all or substantially all of the medium purity CO2-enriched product 32b to an upstream operation, namely one or more operations upstream of syngas purification operation 85, whereas in the case of high purity CO2- enriched product 32c, at least a portion of this may be sequestered; or (c) recycling at least a portion, and possibly all or substantially all, of low purity CCh-cnrichcd product 32a for use directly in an upstream operation, namely one or more operations upstream of syngas purification operation 85, such as in the case of use as a feed to gasifier 50, for example as a fluidizing gas, or in the case of use in a tar removal operation, for example as a fuel to a hot oxygen burner of this operation.

[0095] According to further representative embodiments, processes may comprise recycling at least a portion of high purity CCh-enriched product 32c for use as a utility for one or more upstream operations, namely one or more operations upstream of syngas purification operation 85. To the extent that high purity CCh-cnrichcd product 32c may have a less significant concentration of CO and possibly other impurities, for example according to representative compositions described above, the recycle and use of this product for utilities,which may involve releases to the atmosphere, can mitigate environmental risks. In more particular embodiments, processes may comprise recycling all or substantially all of high purity CO2-enriched product 32c for use as a utility for an upstream operation or for sequestration, such that this high purity product is essentially confined to applications in which the potential for emissions is more pronounced. For representative upstream operations, particular utilities include those comprising solid particulate removal. An example of such utility is a blower (e.g., soot blower) for a gasifier effluent cooler, such as RSC 65 or CSC 65. Another example is a filter back pulsing system for filtration operation 70. In general, any CCF-cnrichcd product, and particularly such product having elevated pressure and temperature, in view of further having a low content of nitrogen or other components that may be detrimental if introduced into process streams, may have characteristics that are advantageous for solid particulate removal. In embodiments in which the upstream operation is the gasifier, exemplary utilities for this operation, included in gasifier utilities 50a, comprise inertization or pressurization, such as in the case of blanketing of vessels and solids transport equipment (e.g., lock hoppers) to mitigate fire and explosion hazards.

[0096] According to embodiments described herein, feeding at least a portion of scrubbed gasifier effluent 30, provided from scrubbing operation 80, to syngas purification operation 85, provides purified syngas product 34 having an acid gas (e.g., CO2) concentration that is decreased relative to that of raw gasifier effluent 16, and / or syngas exiting subsequent operations, such as tar-depleted gasifier effluent 18, quenched gasifier effluent 22, cooled gasifier effluent 24, filtered gasifier effluent 26, scrubber feed 28, or scrubbed gasifier effluent 30. Representative processes may further comprise feeding at least a portion of purified syngas product 34, optionally following a WGS operation (not shown) to provide a WGS product, to a syngas conversion operation or a syngas separation operation, thereby providing a respective renewable syngas conversion product or renewable syngas separation product. According to more specific embodiments, for example, (i) a syngas conversion operation may comprise a Fischer-Tropsch reaction stage, such that the renewable syngas conversion product comprises liquid hydrocarbons and / or oxygenates (e.g., alcohols) of varying carbon numbers, (ii) a syngas conversion operation may comprise a catalytic methanol synthesis reaction stage, such that the renewable syngas conversion product comprises methanol, or (iii) a syngas conversion operation may comprise a catalytic methanation reaction stage, such that renewable syngas conversion product comprises RNG.According to other more specific embodiments, a syngas separation operation may comprise a renewable hydrogen separation stage, such that renewable syngas separation product comprises purified hydrogen.

[0097] Further embodiments of the invention are directed to a process for purifying a gasifier effluent. The process comprises feeding the gasifier effluent to a syngas purification operation to provide, in addition to (i) a purified syngas product having a CO2 concentration lower than that of the gasifier effluent (and also generally having a concentration of H2 and / or CO higher than that of the gasifier effluent, which is a feed to the syngas purification operation), (ii) two or more CO2-enriched products at different pressures and with different CO2 concentrations that are each higher than that of the gasifier effluent. The processes further comprise recycling at least one of the two or more CO2-enriched products to (i) the syngas purification operation (e.g., by combining the CO2-enriched product(s) with a gasifier effluent, such as scrubbed gasifier effluent, that is fed to that operation), (ii) a gasifier that provides the gasifier effluent, and / or (iii) to an operation upstream of the syngas purification operation and downstream of the gasifier.

[0098] Overall, aspects of the invention relate to the implementation of strategies for valuable integration of products, such as CO2-enriched products, that are generated from syngas purification, and into which CO2 and possibly other acid gases are preferentially rejected. Those skilled in the art, having knowledge of the present disclosure, will recognize that various changes can be made to these processes in attaining advantages described herein, as well as other advantages, without departing from the scope of the present disclosure. As such, it should be understood that the features of the disclosure are susceptible to modifications and / or substitutions, and the specific embodiments described herein are for illustrative purposes only, and not limiting of the invention as set forth in the appended claims.

Claims

CLAIMS:

1. A process for gasification of a carbonaceous feed, the process comprising:(a) in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent comprising H2, CO, and CO2;(b) optionally following one or more intervening operations, feeding at least a portion of the gasifier effluent to a syngas purification operation to provide (i) a purified syngas product having a CO2 concentration lower than that of the gasifier effluent and (ii) at least one CO2-enriched product having a CO2 concentration higher than that of the gasifier effluent; and(c) recycling the at least one CCh-cnrichcd product to the syngas purification operation and / or to an upstream operation.

2. The process of claim 1, wherein step (c) comprises recycling the at least one CO2- enriched product to the syngas purification operation in a syngas purification recycle amount that represents an excess of a gasifier recycle amount required for said gasifier.

3. The process of claim 1, wherein step (c) comprises sequestering the at least one CO2- enriched product in a sequestration amount that represents an excess of a gasifier recycle amount required for said gasifier.

4. The process of claim 1, wherein the at least one CCh-cnrichcd product includes both a medium purity CCh-cnrichcd product and a high purity CCh-cnrichcd product.

5. The process of claim 4, wherein step (c) comprises recycling at least a portion of the high purity CO2-enriched product for use as a utility for an upstream operation.

6. The process of claim 4 or claim 5, wherein all or substantially all of the high purity CO2- enriched product is either recycled for said use as a utility for an upstream operation or sequestered.

7. The process of claim 5 or claim 6, wherein the utility for the upstream comprises solid particulate removal.

8. The process of claim 7, wherein the utility for the upstream operation is a blower for a gasifier effluent cooler or a filter back pulsing system for a filtration operation.

9. The process of any one of claims 5 to 8, wherein the upstream operation is the gasifier, and wherein the utility for the upstream operation comprises inertization or pressurization.

10. The process of any one of claims 4 to 9, wherein the medium purity CCh-cnrichcd product comprises a mixture of an absorber-separated gaseous fraction and a first stage- separated gaseous fraction.

11. The process of claim 10, wherein the first stage-separated gaseous fraction is mixed with the absorber-separated gaseous fraction, both upstream and downstream of a feed / product heat exchanger of the syngas purification operation.

12. The process of any one of claims 4 to 11, wherein step (c) comprises recycling at least a portion of the medium purity CCh-cnrichcd product to the gasifier as the upstream operation.

13. The process of any one of claim 4 to 12, wherein step (c) comprises recycling all or substantially all of the medium purity CCh-cnrichcd product to an upstream operation.

14. The process of any one of claims 1 to 13, wherein the at least one CCh-enriched product includes a low purity CCh-cnrichcd product, a medium purity CCh-cnrichcd product, and a high purity CCh-cnrichcd product.

15. The process of claim 14, wherein (c) comprises recycling at least a portion of the low purity CO2-enriched product for use directly in the upstream operation.

16. The process of claim 14 or claim 15, wherein:(i) the low purity CCh-cnrichcd product has a CO2 concentration of less than about 95 mol-% and / or a CO concentration of greater than about 5 mol-%,(ii) the medium purity CO2-enriched product has a CO2 concentration of greater than about 90 mol-% and / or a CO concentration of less than about 5 mol-%, and / or(iii) the high purity CCri-cnrichcd product has a CO2 concentration greater than that of the medium purity CCri-cnrichcd product and / or a CO concentration less than that of the medium purity CO2-enriched product.

17. A process for gasification of a carbonaceous feed, the process comprising:(a) in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent comprising H2, CO, and CO2;(b) optionally following one or more intervening operations, feeding at least a portion of the gasifier effluent to a syngas purification operation to provide (i) a purified syngas product having a CO2 concentration lower than that of the gasifier effluent and (ii) at least one CO2-enriched product having a CO2 concentration higher than that of the gasifier effluent; and(c) adjusting a pressure of the syngas purification operation, responsive to an amount of said at least one CCh-cnrichcd product required in the syngas purification operation and / or an upstream operation.

18. The process of claim 17, wherein said at least one CCh-cnrichcd product includes a medium purity CCh-cnrichcd product that comprises a first stage-separated gaseous fraction, said first stage- separated gaseous fraction being provided from a first stage CO2 separator, and wherein step (c) comprises adjusting a pressure of the first stage CO2 separator.

19. The process of any one of claims 1 to 18, wherein the one or more intervening operations includes one or more of (i) a tar removal operation to remove at least a portion of gasifier effluent tar from the gasifier effluent, (ii) a quenching operation comprising direct contact of the gasifier effluent with quench water, (ii) a radiant syngas cooler (RSC) or convective syngas cooler (CSC) implementing heat-exchanging contact of the gasifier effluent with boiler feed water, (iii) a filtration operation to remove solid particles from the gasifier effluent, (iv) a scrubber feed cooler for further cooling of the gasifier effluent, and (v) a scrubbing operation to remove at least a portion of the water-soluble contaminants from the gasifier effluent.

0. A process for purifying a gasifier effluent, the process comprising: feeding the gasifier effluent to a syngas purification operation to provide, in addition to (i) a purified syngas product having a CO2 concentration lower than that of the gasifier effluent, (ii) two or more CCh-enriched products at different pressures and with different CO2 concentrations that are each higher than that of the gasifier effluent, and recycling at least one of the two or more CCh-enriched products to the syngas purification operation, to a gasifier that provides the gasifier effluent, and / or to an operation upstream of the syngas purification operation and downstream of the gasifier.

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