WO2025019354A2 - Management of process water in gasification - Google Patents

Abstract

Gasification processes are disclosed, implementing one or more strategies for managing the requirements of water utilization for a number of purposes. These include cooling of the gasifier effluent and conditioning it for subsequent operations, such as by removing solids and water-soluble contaminants. Advantageously, the needs for gasifier effluent purification are integrated with its cooling (e.g., quenching, including full quenching) requirements, optionally further in combination with other water-utilizing operations such as water treatment and/or steam generation systems. Some benefits may be further realized according to the manner in which the gasifier effluent is cooled, such as by full quenching through direct contact with quench water, to provide a cooled, saturated gasifier effluent. The overall effect of these strategies may be reduced capital, utility, and operating costs, with simplified control/instrumentation.

Description

MANAGEMENT OF PROCESS WATER IN GASIFICATION

CROSS REFERENCE TO RELATED APPLICATION

[01] This application claims the benefit of priority to U.S. Provisional Application No. 63/526,705, filed July 14, 2023, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[02] Aspects of the invention relate to gasification processes, and more particularly the effective utilization of process water in such processes for a number of purposes including cooling, solids and water-soluble contaminant removal, and steam generation.

DESCRIPTION OF RELATED ART

[03] 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, such as by direct and/or indirect heat exchange. Synthesis gas from gasification must also be 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 its hydrogen content to be increased, relative to that obtained from gasification alone.

[04] Undesired tar components in the gasifier effluent, which can include fused ring molecules such as naphthalene and pyrene, pose significant challenges in terms of the tendency of such high boiling-temperature molecules 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. For these 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.

[05] Regarding the need to increase the bRCO molar ratio of the synthesis gas for its subsequent use in a number of reactions, the exothermic water-gas shift (WGS) reaction gas according to:

CO + H₂O H₂ + CO₂ is widely exploited. The thermodynamics of this reaction govern an equilibrium shift toward hydrogen production at lower temperatures, which are generally unfavorable from the standpoint of reaction kinetics. Operations conducted to purify the gasifier effluent, or synthesis gas, in preparation for the catalytic WGS reaction, include scrubbing to remove water-soluble contaminants. The scrubbing operation, however, generally requires a reduction in both temperature and moisture content of the resulting scrubbed gasifier effluent, thereby directionally reducing its suitability in these respects for the WGS operation. Overall, the economics of biomass gasification and the effective utilization of the produced synthesis gas for obtaining desired end products are impacted by a number of complex and interacting processing objectives, as well as the associated equipment requirements. The present state of the art would benefit from improvements in gasification technology, relating to the management of the significant requirements for process water, associated with carrying out such objectives.

SUMMARY OF THE INVENTION

[06] 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 managing the requirements of water utilization for a number of purposes. These include cooling of the gasifier effluent and conditioning it for subsequent operations, such as by removing solids and water-soluble contaminants. Advantageously, processes have been discovered whereby the needs for gasifier effluent purification are integrated with its cooling (e.g., quenching, including full quenching) requirements, optionally further in combination with other water-utilizing operations such as water treatment and/or steam generation systems. Certain aspects and embodiments of the invention relate to processes in which the gasifier effluent is cooled in a particular manner, such as by full quenching, involving direct contact with quench water, to provide a cooled, saturated gasifier effluent. Advantages may thereby reside in any one of more of (1) reduced equipment costs, compared to alternative cooling options that utilize a radiant syngas cooler (RSC), a convective syngas cooler (CSC), and/or a partial quench system; (2) elimination of utilities and equipment needed for soot blowing with nitrogen and/or CO2 of such coolers and/or a syngas filter; (3) heat removal from high temperature syngas being very simple and economical; (4) substitution of at least a portion of otherwise expensive, high quality makeup quench water with available process effluent water; (5) significant savings in capital, operations, and maintenance costs; and (6) simplified temperature control of syngas to downstream operations/equipment. Other advantages may reside in the removal of operating constraints, in order to provide greater processing flexibility. For example, one or more of the requirements for (a) syngas filtration; (b) maintenance of the syngas, upstream of the scrubbing operation, at a temperature above its dewpoint (saturation temperature); and (c) utilizing startup steam for boiler circulation and warmup, may be reduced or eliminated completely.

[07] Some aspects of the invention relate to addressing certain problems of gasification processes, such as high utility consumption, significant capital costs, and operational complexity (e.g., associated with operating and control loops). With respect to utility consumption, processes that rely on syngas cooling via an RSC, partial quench system, or combination of these can often consume high rates of utilities including expensive boiler feed water (high quality makeup quench water) and nitrogen/CCh for soot blowing and instrument purging. With respect to capital costs and complexity, these same cooling strategies, in addition to the use of a convective syngas cooler (CSC), may involve significant expense and control requirements (e.g., VO control loops). Certain embodiments described herein may deviate from “carryover” coal/petroleum coke conversion technologies, including those involving gasification and intended for the production of high pressure steam, as needed for power generation. In this regard, these steam/power utilities are generally not an important consideration in facilities for converting syngas to renewable products such as bio-derived methanol, bio-derived hydrocarbons (e.g., gasoline and jet fuel), renewable natural gas (RNG). Certain embodiments described herein are therefore better aligned with more cost- effective solutions that may include the generation of low and/or medium pressure steam for chemical production and general use.

[08] Overall advantages relating to certain embodiments include the simplicity and costeffectiveness by which solid and water-soluble contaminants may be managed and effectively integrated with cooling, such as by full quenching of the gasifier effluent. Further integration with steps and associated equipment for solids -containing water treatment may also be realized. Aspects of the invention are thereby associated with the management of water requirements of gasification processes for various purposes including cooling, steam generation, and purification (e.g., slag/fly ash removal and wet scrubbing). Such management may result in significantly reduced requirements for high quality makeup process water, such as boiler feed water. The complexity of control systems, needed for alternative cooling strategies, may be diminished.

[09] Particular embodiments of the invention are directed to a process for gasification of a carbonaceous feed. The process comprises, in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent, such as a raw gasifier effluent exiting the gasifier directly or a tar-depleted gasifier effluent exiting an intervening tar removal operation, with this gasifier effluent (or syngas) comprising H2, CO, solids (e.g., slag and/or fly ash) and water-soluble contaminants. The process further comprises, in a full quenching operation, contacting at least a portion of the gasifier effluent, optionally following one or more intervening operations, with quench water to remove at least a portion of the solids and provide a cooled, saturated gasifier effluent. In addition, the process comprises feeding at least a portion of the cooled, saturated gasifier effluent (e.g. , as a scrubber feed) to a scrubbing operation to remove at least a portion of the water-soluble contaminants and provide a scrubbed gasifier effluent.

[10] Other particular embodiments of the invention are directed to a process for gasification of a carbonaceous feed, which process includes contacting the carbonaceous feed with an oxygencontaining gasifier feed, in a gasifier and under gasification conditions, to provide a gasifier effluent as described above (e.g. , a raw gasifier effluent exiting the gasifier directly or a tar- depleted gasifier effluent exiting an intervening tar removal operation). The gasifier effluent (or syngas) comprises H2, CO, solids (e.g., slag and/or fly ash) and water-soluble contaminants. The process further comprises, in a quenching operation, contacting at least a portion of the gasifier effluent, optionally following one or more intervening operations, with quench water to remove at least a portion of the solids and provide a cooled gasifier effluent. The quenching operation may be, more particularly, a full quenching operation according to the embodiment above, which provides a cooled, saturated gasifier effluent, but more broadly may be any quenching operation utilizing water for direct cooling of the gasifier effluent, with such water utilization being advantageously integrated with one or more other operations that consume process makeup water and/or produce process effluent water. Particular operations of this type include scrubber feed cooling and the scrubbing operation itself. Accordingly, representative processes may comprise feeding at least a portion of the cooled gasifier effluent (e.g., a cooled, saturated gasifier effluent in the case of the quenching operation being a full quenching operation), optionally following one or more other intervening operations, to a scrubbing operation to provide a scrubbed gasifier effluent and a scrubber effluent water comprising at least a portion of the water-soluble contaminants. In more particular embodiments, for example in which the one or more other intervening operations may comprise scrubber feed cooling, representative processes may comprise (a) feeding at least a portion of the cooled gasifier effluent to a scrubber feed cooler for generation of steam from heat in the cooled gasifier and for providing a scrubber feed, and (b) feeding at least a portion of the scrubber feed to a scrubbing operation to provide a scrubbed gasifier effluent and a scrubber effluent water comprising at least a portion of the water-soluble contaminants.

[11] In any of the above embodiments, integration with water utilization may be advantageously achieved according to a processing step in which at least a portion of the scrubber effluent water is recycled to the quenching operation (e.g., for contacting with the at least portion of the gasifier effluent) and/or used for another operation of the process, such as in a solids- containing water treatment system for treating solids -containing water provided from the quenching operation. Alternatively, or in combination, in any of the above embodiments, integration with water utilization may be advantageously achieved if process makeup water supplies water requirements of (internal and/or external to) the process, and (a) a first portion of the process makeup water is fed to the quenching operation, together with (e.g., for contacting with) the at least portion of the gasifier effluent; (b) a second portion of the process makeup water is fed to the scrubber feed cooler, for uptake of heat in (e.g., for heat exchange with) the cooled gasifier effluent and generation of steam; and/or (c) a third portion of the process makeup water is fed to the scrubbing operation, for uptake of the at least portion of the water-soluble contaminants. [12] These and other embodiments, aspects, and advantages relating to the present invention are apparent from the following Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

[13] 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 identify the same or similar features.

[14] 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 quenching (e.g., full quenching) and scrubbing operations, which may be further integrated with utilization of process makeup water and/or process effluent water.

[15] FIG. 2 depicts a representative quenching operation, connected to an adjacent solids- containing water treatment system.

[16] For the sake of simplicity, multiple features are illustrated and described in each of the figures, with the understanding that not all features (e.g., not all individual operations and their associated process streams and equipment) are required and that various specific features can be implemented independently of others.

[17] In order to facilitate explanation and understanding, FIGS. 1 and 2 provide an overview of these and other features for use 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 to the implementation or understanding of the various aspects of the invention. Such equipment would be readily apparent to those skilled in the art, having knowledge of the present disclosure. Other processes for producing syngas and/or its conversion products such as renewable liquids, 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

[18] 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 (i.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.

[19] 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.

[20] 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 “treating the solids-containing water in one or more solids-containing water treatment systems” should be understood to mean treating all or a portion of the solids-containing water in such solids-containing water treatment system(s). 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.

[21] 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 the cooled gasifier effluent and scrubbed gasifier effluent, as well as the bulk WGS product flow, 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. Therefore, for example, one or more “operations downstream of the gasifier” can refer, according to a specific embodiment, to 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 and/or a filtration operation that follow the tar removal operation, as an intervening operation, 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.

[22] Specific processes described herein are defined by a gasifier, a quenching operation downstream of the gasifier, and a scrubbing operation e.g., wet scrubber) downstream of the quenching operation, as well as optionally a WGS operation downstream of the scrubbing operation. The gasifier provides a “gasifier effluent” and the WGS operation provides a “WGS product.” 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 WGS operation. The “gasifier effluent” may be more particularly designated as an “un-scrubbed gasifier effluent” or a “scrubbed gasifier effluent,” which are also general terms but add specificity in terms of characterizing the gasifier effluent depending on whether or not it has been subjected to the scrubbing operation.

[23] The terms “gasifier effluent” and “un-scrubbed gasifier effluent” encompass 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 (i.e., a “cooled gasifier effluent” in the case of a quenching operation generally, and a “cooled, saturated gasifier effluent” in the case of a full quenching operation more particularly), having a lower temperature and higher moisture (H2O) concentration relative to the raw gasifier effluent, resulting from direct quenching (e.g., partial quenching or full quenching) with water, (iv) 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,” (v) the raw gasifier effluent having been subjected to removal of heat, and which may provide all or a part of a “scrubber feed,” having a lower temperature relative to the raw gasifier effluent, resulting from heat removal (e.g., to generate steam), and (vi) the raw gasifier effluent having been subjected to any other operation upstream of the scrubbing operation, whether or not specifically described herein.

[24] Likewise, the terms “gasifier effluent” and “scrubbed gasifier effluent” encompass more specific terms that designate (vii) the raw gasifier effluent or un-scrubbed gasifier effluent having been subjected to a scrubbing operation to reduce its content of water-soluble contaminants (e.g., chlorides), and (viii) the raw gasifier effluent or scrubbed gasifier effluent having been subjected to any other operation downstream of the scrubbing operation, whether or not specifically described herein. The terms “gasifier effluent,” “un-scrubbed gasifier effluent,” and “scrubbed gasifier effluent,” and any of the more specific examples (i)-(viii) of these terms, encompass products (e.g., flow streams) that are upstream of, and optionally may be fed to, the WGS operation.

[25] The term “WGS product” is a general term that refers to a product of the WGS operation, all or a portion of which may, according to particular embodiments, be fed to a syngas conversion operation or a syngas separation operation to provide as a value-added product, a renewable syngas conversion product or a renewable syngas separation product. The term “WGS product” encompasses all or a portion of the product provided directly by the WGS operation, or otherwise such product after having been subjected to heating, cooling, pressurization, depressurization, and/or purification, such as acid gas removal. The terms “syngas,” “synthesis gas,” or “synthesis gas product,” insofar as they relate to streams comprising H2 and CO, are used herein to generally refer to the gasifier effluent, whether an un-scrubbed gasifier effluent or a scrubbed gasifier effluent as defined above, or the WGS product.

[26] 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). 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 synthesis reaction stage, or a methanation reaction stage) or a syngas separation operation (e.g., comprising a hydrogen purification stage, such as in the case of syngas separation by pressure swing adsorption (PSA) and/or the use of a membrane). Any such syngas conversion operation or syngas separation operation is preferably performed on the WGS product that can yield an increased, and more favorable, HiiCO molar ratio, in terms of efficiently performing the desired conversion or separation. 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.

[27] Representative gasification processes described herein are defined by various possible operations, occurring downstream of the gasifier which may include a tar removal operation; operations for cooling, such as a quenching operation (e.g., a full quenching operation), and optionally an RSC and/or a CSC; a filtration operation; a scrubber feed cooler, such as by using a boiler; a scrubbing operation; a WGS operation; and a syngas conversion operation. Certain possible features of the gasifier, as well as these downstream operations and their associated process streams and conditions, whether used alone or in any combination, according to preferred embodiments and otherwise any embodiments as defined in the claims, as well as the embodiments illustrated in FIGS. 1 and 2, are provided in the following description.

Gasifier

[28] 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.

[29] 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- fossil-derived) substances derived from organisms living above the earth’s surface or within the 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, com 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).

[30] 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., steam generated in a scrubber feed cooler, RCS-generated steam, and/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 typically from about 816°C (1500°F) to about 1038°C (1900°F). These temperatures may be characteristic of the raw gasifier effluent obtained from the gasifier. 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).

[31] 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.

[32] In addition to gasifier effluent tar, the raw gasifier effluent comprises 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 (e.g., solids such as slag and/or fly ash, as well as water-soluble contaminants), 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.

[33] 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 Fh:CO molar ratio of the gasifier effluent may be suitable for use in downstream syngas conversion operations (reactions or separations), such as (i) the conversion to a renewable syngas conversion product comprising higher molecular weight hydrocarbons and/or alcohols of varying carbon numbers via Fischer-Tropsch conversion or (ii) the conversion to a renewable syngas conversion product comprising methanol via a catalytic methanol synthesis reaction, or (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. More typically, however, a WGS operation is needed to achieve a favorable FhiCO molar ratio, and/or a favorable H2 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 of obtaining purified hydrogen as a renewable syngas separation product (e.g., by utilizing one or more PSA and/or membrane separation stages).

[34] Independently of, or in combination with, the representative amounts (concentrations) of H2 and CO above, the gasifier effluent 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 gasifier effluent 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 CH4 may account for substantially all of the composition of the gasifier effluent. That is, these non-condensable gases 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

[35] 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, or syngas conversion operations, for upgrading synthesis gas to higher value products, which perform optimally (e.g., from the standpoint of stability) with pure feed gases.

[36] 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.

[37] 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, the conversion 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)). [38] 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.

[39] 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.

[40] 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 as bio-oil liquor, to extract the tars and oils based on their preferential solubility. The liquid adsorbent may be combusted after it has become spent.

[41] 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, and Optional Solids Removal

[42] Hot gasifier effluent, for example the tar-depleted gasifier effluent exiting the tar removal operation, can be cooled by various techniques that include direct, radiant, and/or convective heat exchange. In the case of direct heat exchange by physical mixing of materials present in process streams (e.g., the gasifier effluent and quench water), at least one quenching operation, such as a full quenching operation or a partial (dry) quenching operation may be used. In either case, quench 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 (i.e., to provide an increased H2:CO molar ratio and an increased H2 concentration). The quench water added may include process makeup water, or a portion thereof that may be referred to as quenching operation makeup water, optionally in combination with water obtained or recycled from elsewhere in the process, such as with all or a portion of scrubber effluent water obtained from a scrubbing operation as described herein for the removal of water-soluble contaminants from an un-scrubbed gasifier effluent.

[43] A full quenching operation utilizes the sensible heat of the gasifier effluent to vaporize a portion of the injected quench water, with a sufficient amount of this quench water being added or present, such that the cooled gasifier effluent exits the quenching operation in a saturated condition (i.e., as a cooled, saturated gasifier effluent). A dry or partial quenching operation, in contrast, results in complete vaporization of the quench water, with the cooled gasifier effluent being unsaturated, or above its dewpoint. In preferred embodiments, the quenching operation is a full quenching operation and the cooled gasifier effluent is a cooled, saturated gasifier effluent.

[44] In the case of using either full quenching or partial (dry) quenching without the further use of an RSC or a CSC, the cooled, saturated gasifier effluent, or respectively the cooled gasifier effluent, may have a temperature from about 400°C (752°F) to about 900°C (1652°F), and preferably from about 538°C (1000°F) to about 816°C (1500°F) for further processing. In the case of certain downstream operations such as subsequent filtration, or in the case of preferred embodiments in general, the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) exiting the quenching operation may have a lower temperature to reduce further cooling requirements, such as a temperature within a range as described above. In some embodiments, the cooled 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).

[45] Representative processes can include, after the quenching operation, or after sufficient further cooling (e.g., using an RSC or a CSC), a subsequent filtration operation (passage through a filter) to remove solid particles (e.g., dust). In preferred embodiments as described above, the use of a full quenching operation with the cooled gasifier effluent exiting, or obtained directly from, this operation being saturated (i.e., being a cooled, saturated gasifier effluent obtained substantially at its dewpoint), can lead to important advantages. Such advantages include the ability to obviate the need for (or avoid) a downstream filtration operation, due to the full quenching operation being compatible with a solids-containing water treatment system, such as a flash and/or solids settling system. Such advantages further include, alternatively or in combination, the ability to obviate the need for (or avoid) an RSC and/or CSC and the associated, significant costs, with the potential consequence of losing the capability of generating high pressure steam in the process. Accordingly, in preferred embodiments, processes described herein utilize a full quenching operation without an RSC or CSC, and also without a filtration operation, to provide a cooled, saturated gasifier effluent that may be further processed in a scrubbing operation, with optional further cooling occurring in a scrubber feed cooler (e.g., a boiler). In general, the quenching operation (e.g., full quenching operation or dry quenching operation) can promote rapid and efficient cooling through direct contact between hot gasifier effluent and water or other aqueous quenching medium.

[46] Optionally, a full quenching operation may conveniently perform solids removal from the gasifier effluent, such as in the case of this solids-containing gas stream being dispersed within a liquid level to provide a solids-containing water, or water product. This may be treated in one or more solids-containing water treatments systems, for example employing a vaporizer and/or solids settler, to concentrate solids such as slag and less dense fly ash (or “fly slag”) that initially become entrained in the gasifier effluent.

[47] In the case of biomass gasification, solid particles contained in the gasifier effluent (e.g., raw gasifier effluent or tar-depleted gasifier effluent), and which may be absent in the cooled gasifier effluent or cooled, saturated gasifier effluent, by virtue of a connected (an integrated), solids-containing water treatment system, 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 suitable solids-containing water treatment system (e.g., including a vaporizer and/or solids settler), may advantageously reduce the content of solid particles in the gasifier effluent, such as to provide a cooled gasifier effluent or cooled, saturated gasifier effluent exiting, or obtained directly from, the quenching operation and having less than 1 wt-ppm, and possibly less than 0.1 wt-ppm of solid particles. Such effective solids removal, or degree of solids removal, may thereby advantageously avoid the need for supplemental filtration and its associated complexities that include cleaning/soot blowing.

Radiant Syngas Cooler (RSC) or Convective Syngas Cooler (CSC)

[48] In some embodiments, a combination of a quenching operation as described above and 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. If used, an RSC may effectively remove formed slag and ash from the gasifier effluent, or such removal may be performed by both a full quenching operation and an RSC. The combination of a quenching operation and a downstream RSC or CSC, to cool the quenched gasifier effluent exiting the quenching operation, may provide a cooled gasifier effluent having a temperature within any of the ranges described above for further processing, such as to allow a subsequent filtration operation, or to reduce further cooling requirements in general.

[49] 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.

Filtration Operation

[50] A filtration operation, using any suitable filter, may be used to remove solid particles (particulates) from the gasifier effluent, for example the cooled gasifier effluent as described above, exiting the quenching operation. The filtration operation may therefore be used in conjunction with a full quenching operation for substantially complete solids removal, or in preferred embodiments the quenching operation (e.g., full quenching operation) alone may provide sufficient solids removal for processing needs, including a degree of removal of the types of solid particles, as well as the corrosive and/or harmful species contained in these solid particles, as described above. That is, a separate filtration operation may be avoided in preferred embodiments. [51] In representative embodiments, the filtered gasifier effluent may have a temperature in a range as described above, and/or a content of solid particles as described above, with respect to the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent). Gas filtration at elevated temperatures may be carried out, for example, using bundles of metal or ceramic filters. 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 particle 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).

[52] A 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 a carbon 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

[53] Prior to the scrubbing operation, heat may be removed from the gasifier effluent, such as the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) described above and exiting, or obtained directly from, the quenching operation, or possibly 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 the scrubber, in which case both the heated and cooled streams may comprise an un-scrubbed gasifier effluent, such as the cooled gasifier effluent or filtered gasifier effluent. It can therefore be appreciated that, according to specific embodiments, the “heated scrubber feed” may correspond to, or may comprise, the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) or possibly the filtered gasifier effluent. Also, the heated scrubber feed/cooled 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 upstream cooling occurring in the quenching operation (e.g., full quenching operation) to provide a cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) for direct use in the scrubbing operation. In such cases, the “scrubber feed” may correspond to, or may comprise, the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent).

[54] The scrubber feed cooler may be used to perform indirect heat transfer between the gasifier effluent (e.g., cooled gasifier effluent exiting the quenching operation) and process makeup water (e.g., boiler feed water), or a portion thereof that may be referred to as scrubber feed cooler makeup water, to provide generated steam (e.g., low or medium pressure steam). In representative embodiments, the scrubber feed, whether or not having been cooled in a scrubber feed cooler, may have been cooled generally (e.g., in the quenching operation or downstream of this 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 embodiment 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 cooled 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

[55] A scrubbing operation may be used to remove water and water-soluble contaminants from an un-scrubbed gasifier effluent, such as the cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) exiting the quenching operation, optionally following the cooling of this stream by a scrubber feed cooler as described above. For example, the cooled 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. As described above, this scrubber feed cooler, in performing indirect heat exchange to further cool the cooled gasifier effluent, may also generate steam (e.g., low and/or medium pressure steam) from a portion of the process makeup water, such as boiler feed water.

[56] Otherwise, in the absence of a scrubber feed cooler, the cooled gasifier effluent, at substantially the temperature exiting the quenching operation, or possibly the filtered gasifier effluent at substantially the temperature exiting the filtration operation, may serve as a feed to the scrubbing operation. Either with or without a scrubber feed cooler, the scrubbing operation itself may provide further cooling of the scrubber feed (e.g., cooled gasifier effluent or filtered gasifier effluent). 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 43°C (110°F) to about 66°C (150°F).

[57] 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.

[58] According to embodiments as described herein, the scrubbing operation may also provide an aqueous product stream, or scrubber effluent water, into which at least a portion of the water- soluble contaminants, as described above and initially present in the gasifier effluent, are dissolved and thereby removed from this effluent. The scrubbing operation may generally require, as an input or feed, makeup process water or a portion thereof that may be referred to as scrubber makeup water, whereas the scrubber effluent water may advantageously be provided to other operations as described herein to improve water integration.

WGS Operation

[59] The water gas shift (WGS) operation reacts CO present in a gasifier effluent, for example the scrubbed gasifier effluent immediately exiting the scrubbing operation, with steam to increase H2 concentration (as well as CO2 concentration). In this manner, the scrubbed gasifier effluent may be characterized as a feed to the WGS operation (WGS feed). Following the tar removal operation, quenching operation, optional filtration operation, and scrubbing operation, the scrubbed gasifier effluent/feed to the WGS operation may have favorable properties for use in this operation, in terms of its being free or substantially free of water- soluble contaminants as described above, as well as tars and particulates. [60] According to some embodiments, the scrubbed gasifier effluent/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 H2:CO 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 the steam generation (e.g., using a boiler) as described above. For example, at least a portion of steam (e.g., low or medium pressure steam) generated in the boiler 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.

[61] 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 (i.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-Cr2Oa catalysts).

[62] 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 a more 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.

[63] 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 H2:C0 molar ratio and increased th concentration, relative to the feed to the WGS operation or the synthesis gas obtained from upstream operations (e.g., filtered gasifier effluent or cooled gasifier effluent). For example, the immediate WGS product may have an F iCO 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 F S which can be recycled and more easily removed elsewhere in the process, such as in an acid gas removal operation or possibly, at least to some extent, in the scrubbing operation.

Syngas Conversion or Separation Operations

[64] 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. 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 process the 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. [65] In the case of methanol production, the syngas conversion operation may comprise a methanol 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.

[66] 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.

[67] 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 and consequently 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-%).

Further exemplary embodiments of gasification processes

[68] FIG. 1 depicts a flowscheme illustrating an embodiment of a process including operations as described above, including quenching and scrubbing operations having water inputs and outputs that may be advantageously integrated to improve efficiency. 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 a gasifier effluent comprising th, CO, solids (e.g., comprising slag and fly ash) and water-soluble contaminants. 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-%. The gasifier effluent may be any process stream downstream of gasifier 50 and upstream of quenching operation 60, including raw gasifier effluent 16 exiting gasifier 50 or tar-depleted gasifier effluent 18 exiting tar removal operation 55. The process may further comprise, in quenching operation 60, which may be a full quenching operation, contacting at least a portion of the gasifier effluent with quench water 20 to remove at least a portion of the solids and provide cooled gasifier effluent 22, which in the case of a full quenching operation may be, more particularly, a cooled, saturated gasifier effluent. The process may still further comprise feeding at least a portion of cooled gasifier effluent 22, for example as scrubber feed 28 in embodiments in which filtration operation 70 is excluded, to scrubbing operation 80 to remove at least a portion of the water-soluble contaminants and provide scrubbed gasifier effluent 30.

[69] 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 absence of both scrubber feed cooler 75 and upstream filtration operation 70, the scrubber feed may correspond to, or may comprise, cooled gasifier effluent 22, which may be, more particularly, a cooled, saturated gasifier effluent 22, such as in the case of quenching operation being a full quenching operation. In the case utilizing scrubber feed cooler 75, an un-scrubbed gasifier effluent or portion thereof may be fed to this cooler, for example as cooled gasifier effluent/heated scrubber feed 26, or optionally filtered gasifier effluent/heated scrubber feed 26. In some embodiments, cooler 75 may provide steam generation from heat in this heated scrubber feed, 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, a cooled gasifier effluent that is at a higher temperature relative to this scrubber feed. Therefore, cooled gasifier effluent 22 may have the same composition as heated scrubber feed 26 and/or scrubber feed 28.

[70] In exemplary embodiments, the gasifier effluent such as cooled gasifier effluent 22, which is optionally fed to cooler 75 as heated scrubber feed 26 or directly fed to scrubbing operation 80 as scrubber feed 28, may have been subjected to one or more intervening operations downstream of gasifier 50 and upstream of quenching operation 60, which intervening operations may include tar removal operation 55 to remove at least a portion of gasifier effluent tar (e.g., and provide tar-depleted gasifier effluent 18). Alternatively or in combination, the gasifier effluent such as cooled gasifier effluent 22 or other un-scrubbed gasifier effluent, may be subjected to one or more intervening operations downstream of quenching operation 60 and upstream of scrubbing operation 80. For example, such intervening operations may include one or more of a radiant syngas cooler (RSC) or a convective syngas cooler (CSC), implementing indirect heat-exchanging contact with, respectively, RSC feed water or CSC feed water. Optionally in combination with such RSC or CSC, other intervening operations may include both filtration operation 70 and/or scrubber feed cooler 75, downstream of RSC and/or CSC. In this case, the cooled gasifier effluent (e.g., the cooled, saturated 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 further cooled gasifier effluent, having been subjected to filtration operation 70 to remove solid particles and also to scrubber feed cooler 75.

[71] In addition to scrubbed gasifier effluent 30, from which water-soluble contaminants present in the gasifier effluent have been removed by scrubbing operation 80, this operation may also provide scrubber effluent water 34 comprising at least a portion of these contaminants (e.g., having been removed, more particularly, from cooled, saturated gasifier effluent 22). Representative processes may comprise using at least a portion of scrubber effluent water 34 in, such as recycling this to, an operation of the processes, in achieving various benefits and advantages as described herein. As illustrated in FIG. 1, particular operations in this regard include quenching operation (e.g., full quenching operation) 60 and/or solids -containing water treatment system 65a, 65b, to which respective first portion 34a and/or second portion 34b of scrubber effluent water 34 may be fed. Solids-containing water treatment system 65a, 65b may operate in conjunction (be in fluid communication) with quenching operation 60 and may more particularly be, or comprise, a flash and/or solids-settling system that may include a respective vaporizer 65a and/or solids settler 65b. In general, solids-containing water treatment system 65a, 65b may be integrated with a sump or slag water system of quenching operation 60. With respect to utilizing the scrubber effluent water 34 in the process, embodiments of interest therefore more generally include adding at least a portion of this product to a sump of the process (e.g., sump of the quenching operation or other cooling operation), a slag water system of the process (e.g., slag water system of the quenching operation or other cooling operation), and/or a cooler of the process for heat removal via direct or indirect heat exchange. Representative processes may therefore comprise recovering from scrubbing operation 80 (e.g., following at least a first scrubber contacting stage), scrubber effluent water 34. All or at least first portion 34a of scrubber effluent water 34 may be recycled to quenching operation 60 for contacting with the gasifier effluent, such as in the case of being fed together with at least a portion of the gasifier effluent, and also optionally together with first portion 32a of process makeup water. Alternatively or in combination, all or at least second portion 34b of scrubber effluent water may be fed to solids -containing water treatment system 65a, 65b. As further illustrated in FIG. 1, quench water 20 may comprise both at least a portion (e.g., first portion 34a) of scrubber effluent water, in addition to at least a portion (e.g., first portion 32a) of process makeup water, being namely quenching operation makeup water.

[72] In this regard, FIG. 2 illustrates additional details with respect to quenching operation 60, which may utilize quenching vessel 650, into which the gasifier effluent, such as raw gasifier effluent 16 or tar-depleted gasifier effluent 18, may be fed through gasifier effluent inlet 601. The gas temperature at this inlet may be within the ranges as described above with respect to the raw gasifier effluent obtained directly from the gasifier 50 or the tar-depleted gasifier effluent obtained directly from the tar removal operation 55. The temperature at gasifier effluent inlet 601 to quenching operation 60 may, in particular embodiments, be from about 1093°C (2000°F) to about 1649°C (3000°F), and typically from about 1371°C (2500°F) to about 1510°C (2750°F). FIG. 2 more particularly illustrates a specific embodiment of a full quenching operation, in which contacting between the gasifier effluent 16, 18 and quench water 20 comprises dispersing this effluent below liquid level 602 of the quench water, i.e., within the liquid itself. In the case of a full quenching operation, the gas stream being output as a cooled gasifier effluent 22, through cooled gasifier effluent outlet 603, is more particularly a cooled, saturated gasifier effluent. With respect to liquid level 602, this may be provided by at least a portion of the scrubber effluent water, such as first portion 34a, and below this liquid level 602 at least a portion of the gasifier effluent may be dispersed, such as through gas distributor 605. With reference to FIG. 1, quench water 20, which may comprise one or both of quenching operation makeup water 32a (e.g., as a first portion of process makeup water) and recycled scrubber effluent water or a portion 34a thereof, may comprise, or represent, a net amount of water as needed to fully saturate the gasifier effluent.

[73] According to the embodiment illustrated in FIG. 2, in addition to cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) 22, quenching operation (e.g., full quenching operation) 60 further provides solids-containing water 600, which may be referred to as a solids -containing water product that contains solids such as slag and fly ash, in an amount corresponding to that removed from the gasifier effluent (e.g., the difference between the amount of solids initially present in the gasifier effluent, fed to the quenching operation, and the amount remaining in the cooled gasifier effluent, exiting the quenching operation). In this manner, quenching operation 60 may serve to effectively remove solids present in the gasifier effluent, with a high removal efficiency, for example, as described above and possibly being characteristic of a filtration operation. Therefore, it can be appreciated that quenching operation 60, such as a full quenching operation, can provide both effective solids removal, as well as effective cooling. For example, in some embodiments, the solids removed in the quenching operation (e.g., full quenching operation), or the at least portion of solids present in the gasifier effluent that is fed to this operation and removed by it, is sufficient to avoid a filtration operation, downstream of the quenching operation. Alternatively or in combination, heat removed from the gasifier effluent in the quenching operation (e.g., full quenching operation) is sufficient to avoid a radiant syngas cooler (RSC) and/or the generation of high pressure steam.

[74] Further with reference to FIG. 2, representative processes may comprise treating solids- containing water 600 in one or more solids-containing water treatment systems. For example, solids-containing water treatment system(s) 65a, 65b may be used to treat solids- containing water product 600, withdrawn through solids/water outlet 604. More particularly, such treating may process solids-containing water product 600, in order to separate or concentrate solids 606 comprising slag and/or fly ash from solids separation effluent water 607, with the former product 606 being enriched in slag and/or fly ash relative to solids- containing water product 600 and the latter product 607 being depleted in these solids relative to solids-containing water product 600. The separating or concentrating of solids and residual water in the various products 606, 607 may be achieved, in particular embodiments, with suitable equipment such as a vaporizer 65a and/or solids settler 65b. Advantageously, to further improve overall water utilization, representative processes may also comprise using (e.g., recycling) at least a portion of solids separation effluent water 607 e.g., separated as a result of treating solids -containing water product 600 in solids-containing water treatment system(s) 65a, 65b) in an operation of the process. For example, solids separation effluent water 607 may be used in, or recycled to, any one of more of quenching operation 60, scrubbing operation 80, or scrubber feed cooler 75 to meet some or all of the water requirements of these operations. For example, utilization of this product in, or recycle of this product to, scrubber feed cooler 75 may involve its conversion to generated steam 33 by indirect heat exchange with the cooled gasifier effluent obtained from quenching operation 60, and optionally following filtration.

[75] For integration and balancing of water consumption in and water discharge from, both the process as a whole and individual operations of the process, process makeup water (e.g., boiler feed water) may supply the water requirements of the process, both internally (e.g., as in the case of direct cooling using quench water 20 in quenching operation 60) and externally (e.g., as in the case of indirect cooling using water provided to scrubber feed cooler 75). Process effluent water may represent water discharged or removed from the process. The overall quantity discharged or removed may advantageously be reduced by recycling at least a portion of water discharged or removed from individual operations, to other individual operations, as described herein and/or illustrated in FIG. 1. With further reference to this figure, (a) first portion 32a of the process makeup water may be fed to quenching operation 60 together with (and for contacting with) at least a portion of the gasifier effluent fed to this operation, (b) second portion 32b of the process makeup water may be fed to scrubber feed cooler 75, for the uptake of heat in (or indirect heat exchange with) the cooled gasifier effluent provided from the quenching operation 60, thereby providing generated steam 33 (low and/or medium pressure steam) from this second portion 32b, and/or (c) third portion 32c of the process makeup water may be fed to scrubbing operation 80, for the uptake of the at least portion of the water-soluble contaminants removed by this operation from the scrubber feed (e.g., corresponding to, or comprising at least a portion of, cooled gasifier effluent 22).

[76] Generally, processes described herein comprise recovering a synthesis gas product from a gasifier effluent, for example raw gasifier effluent 16 or tar-depleted gasifier effluent 18, with such synthesis gas product possibly including any of those downstream of tar-depleted gasifier effluent 18 as illustrated in the FIG. 1. For example, the synthesis gas product may be recovered as water-gas shift (WGS) product 36 of WGS operation 90, optionally following one or more intervening operations performed on the gasifier effluent, downstream of the tar removal operation and upstream of the WGS operation. Such intervening operations can include one or more of (i) quenching operation 60 comprising direct contact of the gasifier effluent with quench water 20, (ii) optionally a radiant syngas cooler (RSC) or a convective syngas cooler (CSC) implementing heat-exchanging contact of the gasifier effluent with RSC feed water or CSC feed water, as the case may be (iii) filtration operation 70 to remove solid particles from the gasifier effluent, (iv) scrubber feed cooler 75 to further remove heat from the gasifier effluent and control the temperature of the downstream scrubbing operation, and (v) scrubbing operation 80 to remove water-soluble contaminants from the gasifier effluent.

[77] As more particularly illustrated in the FIG. 1, a representative process comprises, in quenching operation 60, which may be more particularly a full quenching operation or a partial dry quenching (PDQ) operation, contacting (e.g., by direct contact), tar-depleted gasifier effluent 18 with quench water 20, which may comprise at least a portion 34a of scrubber effluent water 34. The quenching operation provides cooled gasifier effluent 22 e.g., cooled, saturated gasifier effluent), having a temperature that is decreased relative to that of tar-depleted gasifier effluent 18, with particular details of quenching operation 60 as optionally illustrated in FIG. 2. The process may optionally comprise, or may otherwise forego the use of, a radiant syngas cooler (RSC) and/or a convective syngas cooler (CSC), to provide further cooling of the cooled gasifier effluent 22, such as by indirect, heatexchanging contact with RSC feed water or CSC feed water, respectively. Cooled gasifier effluent (e.g., cooled, saturated gasifier effluent) 22 may be subjected to, other otherwise the process may forego, (i) filtration operation 70 and/or (ii) heat removal in scrubber feed cooler 75. Scrubbing operation 80 may be used for removal of water-soluble contaminants from the gasifier effluent, prior to feeding at least a portion of scrubbed gasifier effluent 30, provided from scrubbing operation 80, to WGS operation 90. This provides WGS product 36 having a H2:CO molar ratio that is increased relative to that of raw gasifier effluent 16, and/or syngas exiting any of intervening operations, such as tar-depleted gasifier effluent 18 exiting tar removal operation 55, cooled gasifier effluent 22 exiting quenching operation 60, filtered gasifier effluent 26 exiting filtration operation 70, or scrubbed gasifier effluent 30 exiting scrubbing operation 80.

[78] Representative processes may further comprise feeding at least a portion of WGS product 36 to syngas conversion operation 95 or syngas separation operation 95 to provide respective renewable syngas conversion product 40 or renewable syngas separation product 40. According to more specific embodiments, for example, (i) syngas conversion operation 95 may comprise a Fischer-Tropsch reaction stage, such that renewable syngas conversion product 40 comprises liquid hydrocarbons and/or oxygenates (e.g., alcohols) of varying carbon numbers, (ii) syngas conversion operation 95 may comprise a catalytic methanol synthesis reaction stage, such that renewable syngas conversion product 40 comprises methanol, or (iii) syngas conversion operation 95 may comprise a catalytic methanation reaction stage, such that renewable syngas conversion product 40 comprises RNG. According to other more specific embodiments, syngas separation operation 95 may comprise a renewable hydrogen separation stage, such that renewable syngas separation product 40 comprises purified hydrogen.

[79] Overall, aspects of the invention relate to gasification processes implementing strategies for efficient water utilization in, and water usage integration among, operations such as a full quenching operation, scrubber feed cooler, and/or scrubbing operation, as needed to achieve processing requirements with respect to heating, cooling, and purification. Those skilled in the art, having knowledge of the present disclosure, will recognize that various changes can be made to these processes in attaining these and 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: in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent comprising H2, CO, solids, and water-soluble contaminants; in a full quenching operation, contacting at least a portion of the gasifier effluent, optionally following one or more intervening operations, with quench water to remove at least a portion of the solids and provide a cooled, saturated gasifier effluent; and feeding at least a portion of the cooled, saturated gasifier effluent, to a scrubbing operation to remove at least a portion of the water-soluble contaminants, and provide a scrubbed gasifier effluent.

2. The process of claim 1, wherein, in addition to the cooled, saturated gasifier effluent, the full quenching operation further provides a solids-containing water.

3. The process of claim 2, further comprising treating the solids-containing water in one or more solids-containing water treatment systems.

4. The process of claim 3, wherein the one or more solids-containing water treatment systems includes a vaporizer and/or a solids settler.

5. The process of claim 3 or claim 4, wherein the treating separates slag and/or fly ash from solids separation effluent water.

6. The process of claim 5, further comprising using at least a portion of the solids separation effluent water in an operation of the process.

7. The process of claim 6, wherein the operation is the full quenching operation, the scrubbing operation, a scrubber feed cooler, or a combination thereof.

8. The process of any one of claims 1 to 7, wherein the contacting in the full quenching operation comprises dispersing the gasifier effluent below a liquid level of the quench water.

9. The process of any one of claims 1 to 8, wherein, in addition to the scrubbed gasifier effluent, the scrubbing operation provides a scrubber effluent water comprising the at least portion of water-soluble contaminants.

10. The process of claim 9, further comprising using at least a portion of the scrubber effluent water in an operation of the process.

11. The process of claim 10, wherein the operation is the full quenching operation or a solids- containing water treatment system.

12. The process of any one of claims 1 to 11, wherein the at least portion of the solids removed in the full quenching operation is sufficient to avoid a filtration operation, downstream of the full quenching operation.

13. The process of any one of claims 1 to 12, wherein heat removed from the gasifier effluent in the full quenching operation is sufficient is avoid a radiant syngas cooler (RSC) and/or the generation of high pressure steam.

14. The process of any one of claims 1 to 13, further comprising feeding at least a portion of the scrubbed gasifier effluent to a water-gas shift (WGS) operation, to provide a WGS product having an thiCO molar ratio that is increased, relative to that of the scrubbed gasifier effluent.

15. A process for gasification of a carbonaceous feed, the process comprising: in a gasifier, contacting the carbonaceous feed with an oxygen-containing gasifier feed, under gasification conditions, to provide a gasifier effluent comprising H2, CO, solids, and water-soluble contaminants; in a quenching operation, contacting at least a portion of the gasifier effluent, optionally following one or more intervening operations, with quench water to provide a cooled gasifier effluent; feeding at least a portion of the cooled gasifier effluent, to a scrubber feed cooler for generation of steam from heat in the cooled gasifier effluent and for providing a scrubber feed; and feeding at least a portion of the scrubber feed to a scrubbing operation to provide a scrubbed gasifier effluent and a scrubber effluent water comprising at least a portion of the water-soluble contaminants, wherein at least a portion of the scrubber effluent water is recycled to the quenching operation.

16. The process of claim 15, wherein the quenching operation is a full quenching operation and the cooled gasifier effluent is a cooled, saturated gasifier effluent.

17. The process of claim 15 or claim 16, wherein the at least portion of the scrubber effluent water is fed to a quenching vessel of the quenching operation to provide a liquid level of the quench water, below which the at least portion of the gasifier effluent is dispersed.

18. The process of any one of claims 15 to 17, wherein the quench water comprises both the at least portion of the scrubber effluent water and process makeup water.

19. The process of any one of claims 15 to 18, wherein process makeup water supplies water requirements of the process, and further wherein:

(a) a first portion of the process makeup water is fed to the quenching operation, together with the at least portion of the gasifier effluent;

(b) a second portion of the process makeup water is fed to the scrubber feed cooler, for uptake of said heat in the cooled gasifier effluent and generation of said steam; and/or

(c) a third portion of the process makeup water is fed to the scrubbing operation, for uptake of said at least portion of the water-soluble contaminants.

20. The process of any one of claims 15 to 19, wherein the at least portion of the scrubber effluent water recycled to the quenching operation is a first portion that is fed together with the at least portion of the gasifier effluent, and wherein a second portion of the scrubber effluent water is fed to a solids-containing water treatment system of the process.