Integrated cleaning operations for the treatment of synthesis gas from gasification.

Abstract

A process for the gasification of carbonaceous feeds, preferably biomass, is disclosed that can implement one or more strategies for removing contaminants, particularly chlorides and ammonia, while reducing adverse impacts on overall processing objectives. These objectives can include obtaining a synthesis gas product with sufficient purity and hydrogen content or H:CO molar ratio to favor downstream conversion and / or separation operations, as needed, to generate value-added products (e.g., hydrocarbons, alcohols such as methanol, RNG, or renewable purified hydrogen). According to certain embodiments, heat and / or material integration of (i) contaminant removal and (ii) other operations in the gasification process can lead to additional efficiencies. Metallic material requirements can be reduced compared to conventional processes.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 437,199, filed January 5, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] Aspects of the present invention relate to a gasification process in which water soluble contaminants such as chlorides and ammonia present in the gasifier effluent are removed by scrubbing operations, which may include chloride scrubbers and ammonia scrubbers integrated upstream and downstream, respectively, of a water gas shift operation. [Background technology]

[0003] Coal gasification has been carried out industrially for over 100 years to produce synthesis gas (syngas), which can be further processed into transportation fuels. More recent efforts to develop energy independence with reduced greenhouse gas emissions have led to significant interest in using biomass as a gasification feed and thereby a potential alternative source of synthesis gas and its downstream conversion products. Generally, biomass gasification is carried out by partial oxidation in the presence of a suitable oxidizing gas containing oxygen and possibly other components, such as steam. Gasification at high temperatures and pressures, optionally in the presence of a catalytic material, produces a waste stream containing hydrogen and oxides of carbon (CO, CO), and hydrocarbons such as methane. This waste stream, often referred to as synthesis gas because of its H and CO content, must be significantly cooled and treated to remove many undesirable components. These include particulates and by-products of gasification, commonly referred to as tar and oil, which have a tendency to condense, coat and foul the interior surfaces of process piping and equipment.

[0004] Furthermore, downstream conversion of syngas to value-added products often requires an increase in the hydrogen content relative to that available from gasification alone. As an alternative to the expense of adding pure hydrogen, the H:CO molar ratio of the syngas can be increased for use in a number of subsequent reactions by performing the following exothermic water-gas shift (WGS) reaction gas:

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[0005] Purification of syngas is necessary not only for WGS operations, but also to prevent deactivation of catalysts used in downstream conversion operations, including Fischer-Tropsch synthesis to produce hydrocarbons, conversion of syngas to methanol, and methanation for the production of renewable natural gas (RNG) or biomethane. To this end, removal of contaminants arising from small amounts of heteroatoms (e.g., Cl, N, and S) found in carbonaceous feeds, and generally hydrogenated forms of such contaminants (e.g., HCl, NH, HS), must be carefully controlled at each stage of the overall gasification process. In this regard, current approaches utilize a single scrubber vessel after gasification (e.g., via partial oxidation) followed by tar removal and filtration. The scrubbed syngas exiting this vessel is in a non-ideal condition for subsequent operations due to its depleted heat and water content, as discussed above.

[0006] Thus, many technical challenges exist with respect to the requirements for heating, cooling, removal of tars and other contaminants, and adjustment of the H:CO molar ratio necessary to obtain a syngas product suitable for subsequent conversion to higher value products. The additional requirement for contaminant removal adds another layer of complexity in view of the associated changes in syngas quality resulting from conventional purification means. The current state of the art would benefit from improved contaminant management to reduce or eliminate certain adverse effects on the purified syngas that complicate downstream processing. Summary of the Invention

[0007] Aspects of the present invention relate to the discovery of a gasification process that utilizes a carbonaceous feed, preferably biomass, that enables one or more strategies for removing contaminants, particularly chlorides and ammonia, while reducing adverse impacts on overall processing objectives. Such objectives can include obtaining a syngas product with sufficient purity and hydrogen content or H:CO molar ratio to favor downstream conversion and / or separation operations, as needed, to generate value-added products (e.g., hydrocarbons, alcohols such as methanol, RNG, or renewable purified hydrogen). According to certain embodiments, (i) contaminant removal and (ii) heat and / or material integration with other operations in the gasification process can lead to further efficiency gains; in either event, improvements in overall process economics can be realized.

[0008] Certain aspects of the present invention relate to the use of separate scrubbers to contact synthesis gas with an aqueous medium to remove (i) primarily chlorides (e.g., in the form of HCl) and (ii) primarily ammonia. The former chloride scrubber may be positioned upstream of a water-gas shift (WGS) operation, while the latter ammonia scrubber may be positioned downstream of such a WGS operation. The efficiency of the scrubbers and the overall gasification process may be improved through integration of (i) the scrubbers with each other and / or (ii) the scrubbers with other process operations. For example, (i) may be implemented by utilizing the aqueous product of the ammonia scrubber as at least a portion of the aqueous feed to the chloride scrubber. This can improve the removal efficiency of chloride contaminants through acid-base chemistry, such as through the production of ammonium chloride, given that the aqueous product of the ammonia scrubber is basic. Another benefit may result from ammonia acting as a buffer against the strongly acidic HCl, thereby reducing the overall acidity of the aqueous chloride scrubber product (e.g., contained in and exiting the lower section of the chloride scrubber). Case (ii) may be implemented, for example, by utilizing the aqueous product of either the chloride scrubber or the ammonia scrubber directly or indirectly to cool the gasifier effluent (e.g., directly in a quench operation or indirectly in a convective or radiative syngas cooler).

[0009] A further aspect relates generally to the recognition of advantages derived from operating separate scrubbers under separate conditions, such as utilizing higher temperatures for a chloride scrubber upstream of a WGS operation compared to an ammonia scrubber downstream of the WGS operation. Importantly, typical catalysts used in WGS operations may be tolerant of ammonia but not chloride, and therefore "split" scrubbing of water-soluble contaminants, i.e., primarily via separate steps upstream of the WGS operation to remove chlorides and primarily via separate steps downstream of the WGS operation, respectively, provides advantages. These relate to "focused" removal of contaminants upstream of the WGS operation that are most detrimental to the WGS operation (e.g., the catalyst used in this operation) without requiring extensive dehydration of the scrubbed gas that is subsequently subjected to the WGS reaction. In particular, the desirably high moisture level and temperature of the chloride-depleted syngas exiting the chloride scrubber can be maintained for processing via the catalytic WGS reaction prior to ammonia removal. Increasing the moisture level, or HO concentration, thermodynamically favors the production of hydrogen via the WGS reaction. The higher operating temperature of the chloride scrubber may particularly refer to the temperature at or near the gas outlet of this vessel, since the temperature of the chloride-depleted syngas exiting the chloride scrubber will govern the moisture level of the process stream, depending also on the overall operating pressure. In some embodiments, the temperature of the chloride scrubber gas outlet exceeds the temperature of the ammonia scrubber gas outlet, and may even exceed the overall temperature of the ammonia scrubber (e.g., the temperature everywhere in this vessel).

[0010] By maintaining a desirably high moisture level and temperature of the chloride-depleted syngas, at least a portion of which may be fed to a WGS operation, advantages are obtained over conventional gas scrubbing (e.g., generally to remove water-soluble contaminants), which may involve the use of low scrubber temperatures and, consequently, the need to add steam, or relatively large amounts of steam, prior to the WGS operation. For example, for a feed to a WGS operation having a desired 1:1 HO:syngas molar ratio (i.e., a moisture level of 50% by volume), conventional gas scrubbing upstream of this operation may require supplemental steam to the feed, i.e., the scrubbed effluent, in an amount equivalent to most of the required moisture. By utilizing a "split" scrubbing of water-soluble contaminants as described herein, this supplemental steam amount may be reduced or even eliminated. Such a reduction in steam consumption can be realized in the case of WGS operations conducted either as a "sweet shift" under low sulfur concentrations or as a "sour shift" under high sulfur concentrations, the latter operation typically requiring at least about 300 ppm by volume of total sulfur due to the sulfidation treatment required to maintain the activity of the sour WGS catalyst. The sour shift is acceptable because sulfur removal occurs primarily in the ammonia scrubber downstream of the WGS operation due to the lower scrubber operating temperatures relative to chloride scrubber temperatures. Thus, compared to conventional scrubbing, the HS loading, as well as the steam loading, can be reduced for sour shift operations in the case of split scrubbing. This is important for biomass gasification processes where added flexibility for sour shift operation is realized, for improved management of sulfur contaminants (e.g., HS, COS) in the gasifier effluent, and for providing an overall more robust design for handling carbonaceous feeds of different qualities. In either event, the processes described herein can advantageously utilize the residual heat of gasification (e.g., in the gasifier effluent after cooling and filtration) for the purpose of vaporizing water in the chloride scrubber, thereby providing a higher moisture content feed to the WGS operation.

[0011] More specifically regarding the importance of the temperature at or near the gas outlet of the chloride scrubber, adjusting the temperature can be particularly beneficial in adjusting the moisture level of the chloride-depleted syngas exiting this vessel, in view of the fact that at least a portion of the syngas is fed to a WGS operation, which, as discussed above, is thermodynamically influenced by HO concentration. Considering that the chloride-depleted syngas is saturated at the gas outlet of the chloride scrubber, its moisture level, or volume percentage of water vapor, should provide a water vapor partial pressure (volume percentage of water vapor multiplied by the total operating pressure) equivalent to the vapor pressure of pure water at the temperature of the chloride-depleted syngas at or near the gas outlet of the chloride scrubber. Accordingly, certain embodiments of the present invention are directed to a gasification process that includes adjusting the temperature of the chloride-depleted syngas obtained from the chloride scrubber (e.g., the temperature at or near its gas outlet) to control (e.g., maintain) a set moisture level (humidity) of the chloride-depleted syngas.

[0012] Locating the WGS operation between separate scrubbers can enable further improvements in process flexibility and integration by bypassing a portion of the effluent from a first scrubber (e.g., a chloride scrubber) through the WGS operation to control the hydrogen content and / or H:CO molar ratio of the treated syngas product obtained after passing through both scrubbers. This bypass can also be used to provide additional temperature control, for example, of the H-enriched syngas fed to a second scrubber (e.g., an ammonia scrubber) by coupling with feed / effluent heat exchange around the WGS operation. In this regard, scrubber performance is temperature dependent, and ammonia scrubbers typically operate more efficiently (i.e., with increased ammonia removal, when all other process variables are held constant) at lower temperatures within the practical temperature range of interest. When feed / effluent heat exchange is implemented, heat from the exothermic WGS reaction can be advantageously recovered to provide at least a portion of the heat requirements of the feed, such as saturated, chloride-depleted syngas, to the WGS operation. It combines the H2-enriched syngas obtained from the WGS operation with the heat of gasification.

[0013] Consistent with these findings, certain embodiments of the present invention are directed to gasification processes that include feeding at least a first portion of a chloride-depleted syngas to a WGS operation to provide an H-enriched syngas, and contacting the H-enriched syngas with an aqueous ammonia scrubber feed in an ammonia scrubber to provide a treated syngas product. Other certain embodiments are directed to such processes that include feeding at least a first portion of the chloride-depleted syngas to a WGS operation to provide an H-enriched syngas, and feeding at least a second portion of the chloride-depleted syngas (e.g., directly) to an ammonia scrubber, where the second portion is not subjected to a WGS operation, i.e., bypasses the WGS operation, without increasing the H content of the second portion (enriching the second portion with H).

[0014] Yet another advantage of "split" cleaning of water-soluble contaminants according to the embodiments described herein is the avoidance of multiple layers of pumps and heat exchangers that would be required if only a single scrubber were used. With separate scrubbers serving primarily separate purposes, the lower section of each scrubber can utilize simple liquid level control (e.g., blowdown vacuum) with a discharge, as opposed to the more complex circulating water loops traditionally used to separate scrubber operations. In this way, the risk of chlorides coming into contact with pumps and other equipment associated with ammonia scrubbers is significantly reduced. This eases the equipment requirements in hydrochloric acid applications, which are associated with high-grade metal materials that can entail significant costs. Maintenance costs can also be reduced, as the lower scrubber pumps and heat exchangers typically have the highest concentrations of metal ions, which cause wear and reduce the useful life of these equipment. Therefore, the use of separate scrubbers, as opposed to a single connected scrubber, can result in cost savings in terms of both capital expenditures (equipment) (e.g., due to lower metal material / corrosion resistance requirements) and operating costs.

[0015] An overall advantage of the various embodiments described herein relates to increased process flexibility associated with removing contaminants from syngas through the use of separate scrubbers and associated operating conditions that can be adjusted to achieve desired process parameters (e.g., moisture levels and temperatures). These and other embodiments, aspects, and advantages of the present invention will become apparent from the detailed description that follows. [Brief explanation of the drawings]

[0016] Exemplary embodiments of the present invention and their advantages may be more fully understood by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numerals are used to identify like features, and in which:

[0017] [Figure 1]1 depicts a flow diagram illustrating one embodiment of a process for gasification of a carbonaceous feed, the process employing multiple possible features as described herein, including scrubbing to remove water-soluble contaminants. [Figure 2] 1 depicts a flow diagram illustrating in more detail certain aspects, such as the flow of aqueous streams around the chloride scrubber and ammonia scrubber, as well as supplemental heaters and coolers that may be used.

[0018] For simplicity, multiple features are illustrated and described in each of the figures, but it should be understood that not all features (e.g., every individual operation and its associated process streams and equipment) are required, and that various specific features can be implemented independently of other features.

[0019] For ease of explanation and understanding, Figures 1 and 2 provide an overview of these and other features for implementation in a gasification process. Some associated equipment, such as specific vessels, heat exchangers, valves, instrumentation, and utilities, is not shown because their specific description is not essential to the implementation or understanding of various aspects of the present invention. Such equipment will be readily apparent to one of ordinary skill in the art with knowledge of this disclosure. Other processes for producing conversion products, such as synthesis gas and / or renewable liquids, according to other embodiments within the scope of the present invention, and for having components configured and partially determined according to specific processing objectives, will likewise be apparent. DETAILED DESCRIPTION OF THE INVENTION

[0020] In this specification, the expressions "wt %" and "vol %" are used to denote weight percentage and volume percentage, respectively. The expressions "ppm by weight" and "ppm by volume" denote parts per million by weight and volume, respectively. For an ideal gas, "vol %" and "ppm by volume" correspond to molar percentage (mol %) and molar parts per million (mol ppm), respectively.

[0021] As used herein, the term "substantially" refers to an extent of at least 95%. For example, the phrase "substantially all" can be substituted with "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." Similarly, designated portions such as a "first portion" or a "second portion" can represent these percentages of the whole (but not all), and particularly these percentages of the whole (but not all) process stream to which they refer.

[0022] Reference to any starting material, intermediate product, or final product, preferably all of which is a process stream, in the case of a continuous process, should be understood to mean "all or a portion" of such starting material, intermediate product, or final product, with the understanding that some portion may not be used due to sampling, purging, diversion for other purposes, mechanical losses, etc. Thus, for example, the phrase "contacting the gasifier effluent with the aqueous chloride scrubber feed" should be understood to mean "contacting all or a portion of the gasifier effluent with all or a portion of the aqueous chloride scrubber feed." When so understood, this phrase encompasses the specific and preferred embodiments set forth above, just as if "all or a portion" were explicitly stated.

[0023] The exemplary processes described herein for the gasification of a carbonaceous feed may include multiple unit operations, with one of such operations being performed or carried out "before," "prior to," or "upstream of" other such operations, or one of such operations being performed or carried out "after," "following," or "downstream of" other such operations. These bracketed phrases, which refer to the order in which one operation is performed or carried out relative to another, refer to the overall process flow, as would be understood by one of ordinary skill in the art with the knowledge of this disclosure. More specifically, with reference to the drawings, the overall process flow can be defined by the bulk flow of gasifier effluent, which encompasses the bulk flows of streams designated "gasifier effluent" (e.g., "filtered gasifier effluent"), "syngas" (e.g., "chloride-depleted syngas"), and "WGS" (e.g., "WGS feed"), which streams are subjected to operations as defined herein. To the extent that the parenthetical phrases above are used to indicate sequence, in specific embodiments, these phrases mean that one operation immediately precedes or follows another operation, but more generally, these phrases do not exclude the possibility of intervening operations. Thus, for example, a description or illustration in a drawing that a filtration operation is downstream of a quench operation refers to the filtration operation following the quench operation immediately, according to specific embodiments. However, this description or illustration more generally and preferably means that one or more intervening operations (e.g., a convective synthesis gas cooler (CSC), according to the embodiment illustrated in the drawing) may be performed or carried out between these operations. Thus, to the extent that the representative processes described herein are defined as including particular unit operations (e.g., by using the term "directly" or the phrase "consisting of"), unless otherwise stated or specified (e.g., by using the term "directly" or the phrase "consisting of"), such processes do not exclude the use of other operations, whether or not specifically described herein.

[0024] The specific process described herein is defined by a gasifier, a chloride scrubber downstream of the gasifier, and a WGS operation downstream of the chloride scrubber. The gasifier provides a "gasifier effluent," the chloride scrubber provides a "chloride-depleted syngas," a portion of which may provide a "WGS feed," and the WGS operation provides an "H-enriched syngas." The term "gasifier effluent" is a general term that refers to the gasifier effluent, regardless of whether it has been subjected to one or more operations downstream of the gasifier and upstream of the chloride scrubber.

[0025] The term "gasifier effluent" therefore includes (i) effluent provided directly by a gasifier, i.e., "raw gasifier effluent", (ii) raw gasifier effluent that has been subjected to at least a tar removal operation, having a lower concentration of tar and oil relative to the raw gasifier effluent, i.e., "tar-depleted gasifier effluent", (iii) raw gasifier effluent that has been subjected to at least a dry quench operation, having a lower temperature and a higher water (H2O) concentration relative to the raw gasifier effluent, resulting from direct quenching (e.g., partial quenching) with water, i.e., "quenched gasifier effluent", (iv (v) raw gasifier effluent that has been subjected to at least a filtration operation, having a low solid particle content relative to the raw gasifier effluent, i.e., "filtered gasifier effluent," and (vi) raw gasifier effluent that has been subjected to any other operation upstream of the chloride scrubber, whether or not specifically described herein.

[0026] Similarly, the term "WGS feed" may encompass more specific terms designating (i) the portion of the chloride-depleted syngas provided directly by the chloride scrubber and directed to the WGS operation, i.e., the "WGS feed portion," (ii) the WGS feed portion that has been subjected to heating at least upstream of the WGS operation, e.g., heated by indirect heat exchange with H-enriched syngas provided by the WGS operation, i.e., the "heated WGS portion," (iii) the WGS feed portion that has been subjected to at least supplemental chloride removal upstream of the WGS operation, e.g., by treatment with a chloride guard bed, and (iv) the WGS feed portion that has been subjected to any other operation upstream of the WGS operation, whether or not specifically described herein. The term "H-enriched syngas" can refer to hydrogen-enriched syngas provided directly by a WGS operation (e.g., the reactor effluent of that operation), which has been subjected to at least cooling upstream of the ammonia scrubber, e.g., by indirect heat exchange with a WGS feed portion, i.e., "cooled H-enriched syngas," and which has been subjected to any other operation upstream of the ammonia scrubber, whether or not specifically described herein. The terms "syngas" or alternatively "syngas product," insofar as they relate to streams comprising H and CO, are used herein to generally refer to any of the "gasifier effluent," "WGS feed," and "H-enriched syngas" as described above, in addition to the "processed syngas product."

[0027] The term "treated syngas product" is a general term that refers to the product obtained by scrubbing in both the chloride scrubber and the ammonia scrubber to remove specified contaminants, and in certain embodiments may refer to the product provided directly by the ammonia scrubber or to such a product that has otherwise been subjected to another operation, for example, upstream of the syngas conversion operation. Thus, all or a portion of the treated syngas product may, in certain embodiments, be fed to a syngas conversion operation or a syngas separation operation to provide a value-added product, a renewable syngas conversion product, or a renewable syngas separation product.

[0028] Specific 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). A typical syngas conversion operation to obtain a syngas conversion product may include a Fischer-Tropsch reaction stage, a methanol synthesis reaction stage, or a methanation reaction stage. A typical syngas separation operation to obtain a syngas separation product may include a hydrogen purification stage, such as in the case of syngas separation by pressure swing adsorption (PSA) and / or the use of membranes. Any such syngas conversion or syngas separation operation is preferably performed downstream of a WGS operation, where the H:CO molar ratio may be increased and more favorable from the standpoint of efficiently carrying out the desired conversion or separation.

[0029] In achieving various objects and related advantages described herein, certain embodiments of the present invention are directed to a process for the gasification of a carbonaceous feed to produce a syngas product, and / or, optionally, a process for producing downstream renewable syngas conversion products (e.g., liquid hydrocarbons or methanol) or downstream renewable syngas separation products (e.g., purified hydrogen) following reaction or separation of the syngas product. An exemplary process includes contacting a carbonaceous feed with an oxygen-containing gasifier feed under gasification conditions in a gasifier to provide a gasifier effluent containing syngas, H, CO, and water-soluble contaminants. Such contaminants may include chlorides (e.g., HCl) and nitrogen-containing compounds (e.g., ammonia) derived from trace amounts of Cl and N present in the carbonaceous feed. As noted above, this gasifier effluent may be characterized as any one of, among others, raw gasifier effluent, tar-depleted gasifier effluent, quenched gasifier effluent, cooled gasifier effluent, or filtered gasifier effluent.

[0030] The process may further include contacting the gasifier effluent with an aqueous chloride scrubber feed in a chloride scrubber to provide a chloride-depleted syngas that exits a gas outlet of the chloride scrubber. An exemplary process may further include adjusting or maintaining a temperature of the chloride-depleted syngas, such as the temperature at or near the gas outlet, to control (e.g., maintain) a set moisture level (humidity) of the chloride-depleted syngas. Such moisture level may be one that provides favorable performance characteristics (e.g., conversion to hydrogen) in subsequent WGS operations. An exemplary set moisture level may be any discrete value within a range of about 20% to about 80% by volume, such as about 30% to about 70% by volume (e.g., a set moisture level of 50% by volume). Typical temperatures of the chloride-depleted syngas to achieve such moisture levels may be in the range of about 100°C (212°F) to about 250°C (482°F), such as about 120°C (248°F) to about 200°C (392°F), and generally depend on the operating pressure of the chloride scrubber, and more particularly, the pressure at the gas outlet of the chloride scrubber.

[0031] Advantageously, adjusting or controlling the temperature of the chloride scrubber gas outlet allows for control of the moisture level of the chloride-depleted syngas. This temperature may be adjusted or controlled, for example, by an external heat source providing indirect heating and / or cooling, or may otherwise be adjusted or controlled by varying the flow rate of the aqueous feed to the chloride scrubber (e.g., entering the chloride scrubber at an axial height near the gas outlet, e.g., in the case of a counterflow scrubber, at or near the top of the chloride scrubber) in response to the temperature of this aqueous feed. As further described herein, this aqueous feed may include the aqueous product of the ammonia scrubber.

[0032] For example, the set moisture level may be an estimated level based on the relationship between temperature and water vapor pressure, which in turn corresponds to the partial pressure of water (volume percentage of water vapor multiplied by the total operating pressure) in the chloride-depleted syngas exiting the chloride scrubber. This partial pressure corresponds to the vapor pressure of pure water. For example, for a set moisture level of 50% by volume and an operating pressure of 11 bar absolute, the temperature of the chloride-depleted syngas at or near the gas outlet of the chloride scrubber should be adjusted to or maintained at a temperature corresponding to the boiling point of water at 5.5 bar absolute, or approximately 156°C (312°F). In view of this description, it can be understood that, directionally, at any given operating pressure, or more specifically, at the pressure at the gas outlet of the chloride scrubber, the higher the temperature of the chloride-depleted syngas, the higher the moisture level. Additionally, higher operating pressures of the vessel require directionally higher outlet temperatures to achieve a given moisture level. Such higher temperatures may in turn lead to higher quality heat availability for steam generation or heat integration within the overall process.

[0033] In achieving various other objects and related advantages described herein, other specific embodiments of the present invention are directed to a process for the gasification of a carbonaceous feed to produce a synthesis gas product, and / or, optionally, a process for producing downstream renewable synthesis gas conversion products (e.g., liquid hydrocarbons or methanol) or downstream renewable synthesis gas separation products (e.g., purified hydrogen) following reaction or separation of the synthesis gas product. An exemplary process includes contacting a carbonaceous feed with an oxygen-containing gasifier feed under gasification conditions in a gasifier, as described herein, to provide a gasifier effluent containing synthesis gas, H, CO, and water-soluble contaminants, as also described herein. The process may further include contacting the gasifier effluent with an aqueous chloride scrubber feed in a chloride scrubber to provide a chloride-depleted synthesis gas that exits the chloride scrubber gas outlet. Additionally, such a process may further include feeding at least a first portion of the chloride-depleted synthesis gas to a water-gas shift (WGS) operation to provide a H-enriched synthesis gas. These processes may still further include (a) contacting the H-enriched syngas with an aqueous ammonia scrubber feed in an ammonia scrubber to provide a treated syngas product, and / or (b) feeding at least a second portion of the chloride-depleted syngas to an ammonia scrubber (e.g., directly) without subjecting the second portion to a WGS operation (e.g., by bypassing a WGS operation without increasing the H content in / enriching the second portion with H).

[0034] The exemplary gasification process described herein is defined by various possible operations downstream of the gasifier, which may include tar removal operations, cooling operations such as quenching and / or CSC, filtration operations, chloride scrubbers, WGS feed / effluent heat exchange, chloride guard beds, WGS operations, ammonia scrubbers, and syngas conversion operations. Specific possible features of the gasifier, as well as these downstream operations and their associated process streams and conditions, are provided in the following description, according to preferred embodiments and any alternative embodiments defined in the claims and the embodiments illustrated in Figures 1 and 2.

[0035] Gasifier An exemplary process includes contacting a carbonaceous feed with an oxygen-containing gasifier feed under gasification conditions in a gasifier and providing a gasifier effluent (e.g., neat gasifier effluent) comprising synthesis gas.

[0036] The carbonaceous feed may include coal (e.g., high-quality anthracite or bituminous coal, or lesser-quality subbituminous, lignite, or peat), petroleum coke, asphaltenes, and / or mobile petroleum residues, or other petroleum-derived materials. In a preferred embodiment, the carbonaceous feed may include biomass. The term "biomass" refers to renewable (non-petroleum-derived) material derived from living organisms that live on the Earth's surface or in the Earth's oceans, rivers, and / or lakes. Exemplary biomass may include any plant material or mixture of plant materials, such as hardwood (e.g., whitewood), softwood, hardwood or softwood bark, lignin, algae, and / or lemna (seaweed). Energy crops or otherwise other agricultural residues (e.g., logging residues), or other types of plant or plant-derived waste, may also be used as plant material. Specific exemplary plant materials include corn fiber, corn stover, and sugarcane bagasse, in addition to "target" energy crops such as switchgrass, miscanthus, and algae. Short-rotation forest products, such as energy crops, include alder, ash, Antarctic beech, birch, eucalyptus, poplar, willow, paper mulberry, Australian blackwood, sycamore, and various oak trees. Other examples of suitable biomass include vegetable oils, carbohydrates (e.g., sugars), organic waste materials such as waste paper, structures, demolition waste, digested sludge, and biosludge. Thus, exemplary carbonaceous feeds include or comprise any of these types of biomass. Specific carbonaceous feeds containing biomass include municipal solid waste (MSW) or MSW-derived products, such as refuse-derived fuel (RDF). Carbonaceous feeds can include combinations of petroleum-derived materials and renewable materials, including those described above. A preferred carbonaceous feed is wood.

[0037] In the gasifier (or, more specifically, the gasification reactor of the gasifier), the carbonaceous feed undergoes partial oxidation in the presence of an oxygen-containing gasifier feed, typically added in a limited amount to provide only 20-70% of the oxygen required for complete combustion. The oxygen-containing gasifier feed generally includes other oxygenated gaseous components, including HO and / or CO, which may act as oxidizers for the carbonaceous feed. The oxygen-containing gasifier feed may refer to all gases fed to or added to the gasifier, or may refer to gases that are separate from other gases being fed or added, whether or not they are subsequently combined substantially upstream or within the gasifier. For example, the oxygen-containing gasifier feed may be introduced into the gasifier along with steam or a portion of steam generated elsewhere in the process (e.g., steam generated in a CSC) and used as a separate feed. Contacting the carbonaceous feed with the oxygen-containing gasifier feed in the gasifier provides gasifier effluent, and more specifically, neat gasifier effluent as a direct product from the gasifier. One or more reactors (e.g., in series or parallel) of the gasifier may operate under gasification conditions present in such reactors, which generally include temperatures from about 500°C (932°F) to about 1000°C (1832°F), typically from about 816°C (1500°F) to about 1038°C (1900°F). Other gasification conditions may include atmospheric or elevated pressures, such as, for example, absolute pressures of generally from about 0.1 megapascals (MPa) (14.5 psi) to about 10 MPa (1450 psi), 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).

[0038] Gasification reactor configurations include countercurrent fixed bed ("updraft"), cocurrent fixed bed ("downdraft"), and entrained plasma. Various solid catalysts may be used with different activities for one or more desired functions during gasification, such as tar reduction, H yield enhancement, and / or CO yield reduction. Limestone may be added to the gasification reactor, for example, to promote tar reduction by cracking. Various catalyst materials may be used in the gasification reactor, including dolomite, supported nickel, alkali metals, and solid particles of alkali metal compounds such as alkali metal carbonates, bicarbonates, and hydroxides. Gasifiers are often operated with a gasification reactor having a fluidized bed of particles of carbonaceous feed (and, optionally, particles of solid catalyst), with the oxygen-containing gasifier feed and, optionally, a separate fluidized H2O- and / or CO2-containing feed fed upward through the particle bed. Exemplary types of fluidized beds include bubbling fluidized beds and entrained fluidized beds.

[0039] In addition to gasifier effluent tar, the raw gasifier effluent contains CO, CO, and methane (CH) derived from carbon present in the carbonaceous feed, and H and / or H, generally both, along with trace concentrations of other components, as described below. According to the embodiment illustrated in the figures, raw gasifier effluent 16 may be obtained directly from the gasifier 50 prior to further operations described herein.

[0040] Gasifier effluent, either as is, or any gasifier effluent that has been subjected to one or more of the operations described herein, may contain syngas, i.e., may contain both H and CO, with these components present in various amounts (concentrations) and preferably in a total 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 such total amount (concentration), the H:CO molar ratio of the gasifier effluent may be suitable for use in downstream syngas conversion operations (reaction or separation), such as (i) conversion via a Fischer-Tropsch conversion to renewable syngas conversion products comprising higher molecular weight hydrocarbons and / or alcohols of varying carbon numbers, or (ii) conversion to renewable syngas conversion products comprising methanol via a catalytic methanol synthesis reaction, or (iii) conversion to renewable syngas conversion products comprising renewable natural gas (RNG) via catalytic methanation to increase the methane content in the resulting RNG stream, or (iv) separation of renewable syngas separation products comprising purified hydrogen. More typically, however, WGS operations are required to achieve a preferred H:CO molar ratio and / or preferred H concentration for these or other downstream syngas conversion and separation operations. For example, a WGS operation may include parameters (e.g., reactor temperature and / or catalyst type) to obtain maximum yield / concentration of hydrogen through consumption of CO present in the syngas upstream of this operation when purified hydrogen is obtained as a renewable syngas separation product (e.g., by utilizing one or more PSA and / or membrane separation stages).

[0041] Independently of or in combination with the exemplary amounts (concentrations) of H and CO listed above, the gasifier effluent may contain CO in an amount of, for example, at least about 2 mol% (e.g., about 2 mol% to about 30 mol%), at least about 5 mol% (e.g., about 5 mol% to about 25 mol%), or at least about 10 mol% (e.g., about 10 mol% to about 20 mol%). Independently of or in combination with the exemplary amounts (concentrations) of H, CO, and CO listed above, the gasifier effluent may contain CH in an amount of, for example, at least about 0.5 mol% (e.g., about 0.5 mol% to about 15 mol%), at least about 1 mol% (e.g., about 1 mol% to about 10 mol%), or at least about 2 mol% (e.g., about 2 mol% to about 8 mol%). These non-condensable gases, H, CO, CO, and CH, along with any water vapor (H, O), may account for substantially all of the composition of the gasifier effluent. That is, these non-condensable gases, and optionally 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 %.

[0042] Tar removal operation Raw gasifier effluent obtained directly from a gasifier generally contains gasifier effluent tar, which typically requires a tar removal operation for further processing. This gasifier effluent tar can contain compounds referred to in the art as "tar" and "oil," more specifically, 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 ppm to several percent by weight. Certain types of these compounds, which have relatively high molecular weights, are characterized as problematic due to their tendency to condense at low temperatures and coat the internal surfaces of processing equipment downstream from the gasifier, causing undesirable fouling, corrosion, and / or clogging. These compounds can also interfere with subsequent processing steps or syngas conversion operations to upgrade the syngas to higher-value products, which are best performed (e.g., from a stability standpoint) using a high-purity feed gas.

[0043] Certain compounds that are undesirable for this reason include hydrocarbons with six or more carbon atoms and oxygenated hydrocarbons (C6 + These compounds typically occur in concentrations of 1-100 g / Nm3 in the raw gasifier effluent. 3 Therefore, removal of these organic compounds (e.g., by conversion) is generally necessary to avoid serious problems caused by their buildup over time. Other types of tar and oil, such as ethane, ethylene, and acetylene, do not condense from the gasifier effluent but nevertheless "bind" hydrogen and carbon, with the effect of reducing the overall yield of H and CO as desired components of syngas.

[0044] Depending on the specific tar removal operation, tar and oil in the raw gasifier effluent can be converted by oxidation, decomposition, and / or reforming, either catalytically or non-catalytically, to provide additional H and CO in the tar-depleted gasifier effluent. Tar conversion reactions can utilize available O or oxygen sources (e.g., HO and / or CO) present in and / or added to the syngas. In terms of gasifier effluent tar, converting these compounds, along with methane, which contains the majority of the energy in the raw gasifier effluent, can substantially increase the overall syngas yield. Thus, according to certain embodiments, a tar removal operation, which may more specifically be a tar conversion operation, can effectively reduce the concentration of compounds present as tars in the raw gasifier effluent produced in the gasifier. Generally, tar removal, and more specifically, tar conversion reactions, may be carried out at 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 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)).

[0045] According to one embodiment, a tar removal operation can be used for the conversion (e.g., reforming) of tars and methane through non-catalytic partial oxidation (POX) in a reactor used for this operation. The efficiency of this particular operation can be enhanced using hot oxygen burner (HOB) technology, in which excess oxygen is mixed with a small amount of fuel (e.g., natural gas, propane, or recycled syngas). Combustion of this fuel in the reactor can result in a temperature increase of over 1100°C (2012°F), causing the combustion products and excess oxygen to accelerate to sonic speeds through a nozzle, thereby forming a turbulent jet that improves mixing between the tar / methane-containing syngas and the reactive hot oxygen stream. HOB-based systems can effectively improve syngas yields by converting methane and tars to additional H and CO, along with the generation of heat.

[0046] In the case of tar removal operations utilizing catalytic conversion of tar and methane, the 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 charcoal produced from gasification. As with non-catalytic processes that may be practiced in tar removal operations, catalytic tar conversion may also include introducing additional oxygen and / or steam reactants into the reactor used in the operation.

[0047] According to other specific embodiments, the tar removal operation may utilize a suitable liquid or solid sorbent to selectively adsorb tar and oil from the raw gasifier effluent. For example, the tar removal operation may be carried out in conjunction with an oil absorption system, whereby the raw gasifier effluent is passed through (contacted with) a liquid medium, such as a bio-oil liquid, to extract the tar and oil based on their selective solubility. The liquid sorbent may be combusted after consumption.

[0048] Regardless of the particular manner in which the tar removal operation is performed, the raw gasifier effluent may contain tar and oil (e.g., present as compounds described above) in an amount of about 0.01% to about 5% by weight, e.g., about 0.1% to about 3% by weight, or about 0.5% to about 2% by weight, or in a combined amount. The tar removal operation may be effective to substantially or completely remove the gasifier effluent tar. For example, the tar-depleted gasifier effluent emerging from or obtained directly from the operation may contain tar and oil in an amount of less than about 0.5% by weight, less than about 0.1% by weight, or less than about 0.01% by weight, or in a combined amount. Exemplary levels of tar and oil removal (e.g., by conversion), as measured over 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.

[0049] Quenching operation High-temperature gasifier effluent, e.g., tar-depleted gasifier effluent emerging from a tar removal operation, can be cooled by a variety of techniques, including radiant and / or convective heat exchange. In an exemplary embodiment, at least one quenching operation, and preferably a dry quenching operation, is used, in which water is added directly to the gasifier effluent to contribute to its overall water content, thereby favoring H production via the equilibrium-limited WGS reaction (i.e., to provide an increased H:CO molar ratio and increased H concentration). The dry quenching operation utilizes the sensible heat of the gasifier effluent to vaporize the injected water, which is sufficient to obtain a resulting quenched gasifier effluent at the desired cooling temperature. According to a preferred embodiment, when the use of an RSC is avoided, the quenched gasifier effluent has a temperature of about 400°C (752°F) to about 900°C (1652°F), and preferably about 538°C (1000°F) to about 816°C (1500°F), to allow for further processing. This may include, after sufficient further cooling (e.g., using a CSC), a subsequent filtration operation (passing through a filter) to remove solid particles (e.g., dust). In a preferred embodiment, only partial quenching, rather than complete quenching, is used in the quenching operation, such that the quenched gasifier effluent exiting or obtained directly from the dry quenching operation is above its dew point, i.e., is not saturated. Generally, dry quenching operations can facilitate rapid and efficient cooling through direct contact between the high-temperature gasifier effluent and water or other aqueous quench medium.

[0050] Convection Synthetic Gas Cooler (CSC) As described herein, according to preferred embodiments, combining a CSC with a quenching operation characterized by direct contact of syngas (e.g., tar-depleted gasifier effluent from a tar removal operation) with a quenching medium such as water can provide effective cooling for further downstream operations without relying on an RSC for the required removal of ash and formed slag. For example, a CSC can be used to cool the quenched gasifier effluent exiting the quenching operation to provide cooled gasifier effluent, the quenched gasifier effluent optionally having a temperature within the ranges described above and / or the cooled gasifier effluent having a temperature of about 250°C (482°F) to about 600°C (1112°F), and preferably about 275°C (527°F) to about 350°C (662°F), to enable subsequent filtration. The CSC may operate by indirect heat transfer, such as when it has a shell-and-tube configuration, and typically generates steam from a portion of the heat recovered from the gasifier and tar removal operations. According to further specific embodiments, the CSC operates as a boiler (e.g., a fire-tube boiler or a water-tube boiler) for the generation of high- and / or medium-pressure steam.

[0051] Generally, (i) direct cooling, for example, via a quench operation; (ii) indirect cooling, for example, via a CSC or radiant syngas cooler; or (iii) a combination of (i) and (ii) can be used to obtain a cooled gasifier effluent having a temperature within the above representative range.

[0052] Filtration operation Filtration operations using any suitable filter can be used to remove solid particles (particulates) from gasifier effluent, such as cooled gasifier effluent, as described above. In the case of biomass gasification, these solid particles can include charcoal, 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, can also be included in such solid particles. For example, high-temperature filtration using a bundle of metal or ceramic filters can generally be sufficient to reduce the solid particle content in the gasifier effluent, thereby providing a filtered gasifier effluent exiting the filtration operation or obtained directly from the filter and having less than 1 ppm by weight, and in some cases less than 0.1 ppm by weight of solid particles. In an exemplary embodiment, the filtered gasifier effluent can have a temperature within the ranges described above for cooled gasifier effluent.

[0053] In some embodiments, a filtration operation may be performed upstream (before) a tar removal operation, allowing subsequent operations to be performed more efficiently. Removal of solid particles of various 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, removal of coarse solids by centrifugation may be performed immediately downstream of the gasifier and / or may even be performed in situ within the gasifier (e.g., using an internal cyclone to remove solid particles located in the headspace of a fluidized particle bed). The filtration operation may be followed by or integrated with an additional cleaning operation to further purify the gasifier effluent, e.g., further reduce its tar and total hydrocarbon content, by contacting it with a solid "abrasive" material such as a carbon bed. This may provide more thorough removal of benzene, naphthalene, pyrene, toluene, phenol, and other condensable species that may adversely affect downstream operations, such as deposition on equipment.

[0054] The filtration operation generally does not substantially affect the temperature of the process stream being filtered, so that, for example, the filtered effluent may have a temperature within the ranges described above for cooled gasifier effluent.

[0055] Chloride Cleaning Equipment A chloride scrubber can be used to remove chlorides (e.g., HCl) from gasifier effluent, such as filtered gasifier effluent, exiting a filtration operation. This removal can be achieved through contact with a suitable aqueous stream, such as an aqueous chloride scrubber feed. Contacting can be carried out in a countercurrent manner, with the aqueous chloride scrubber feed entering at or near the top of a vertically disposed (e.g., elongated, cylindrical) chloride scrubber vessel and the chloride-depleted syngas exiting at or near the top of the chloride scrubber vessel. Contacting efficiency can be enhanced by the use of suitable high surface area packing material or internal structures such as separate gas-liquid contacting trays. Other types of contacting, such as bubbling the gasifier effluent through the aqueous chloride scrubber feed (e.g., batch mode) or co-current contacting, can be carried out with similar results of obtaining a chloride-depleted syngas with a reduced amount (weight percentage or concentration) of total chloride relative to the gasifier effluent (e.g., filtered gasifier effluent) fed to the chloride scrubber. Generally, chloride scrubbers are selective for removing chlorides over other types of water-soluble contaminants, so that, for example, under the conditions within the chloride scrubber, the chloride removal efficiency exceeds the ammonia removal efficiency. However, the operation may also be effective in removing at least some ammonia and / or other water-soluble contaminants (e.g., HS and / or HCN), as well as some fine solid particles (e.g., char and ash) that may break through upstream filtration operations. The chloride scrubber may be used to provide a chloride-depleted syngas effluent exiting or obtained directly from the operation having a total HCl (or total chloride) content of less than about 10 ppm by weight, less than about 1 ppm by weight, and in some cases less than about 0.1 ppm by weight.

[0056] The chloride scrubber may provide further cooling of the gasifier effluent supplied to the chloride scrubber, for example, cooling of the filtered gasifier effluent beyond that achieved in upstream direct and / or indirect cooling, as described above. In an exemplary embodiment, the chloride-depleted syngas exiting the chloride scrubber may have a temperature in the range of about 100°C (212°F) to about 250°C (482°F), such as 120°C (248°F) to about 200°C (392°F), as described above, which may be related to the operating pressure, as noted above.

[0057] WGS Feed / Waste Heat Exchanger According to some embodiments, as illustrated in Figures 1 and 2, at least a portion of the chloride-depleted syngas exiting the chloride scrubber, i.e., the WGS feed portion, can be heated via indirect heat exchange. This heating can be performed using a WGS feed / effluent exchanger to transfer heat from the H-enriched syngas exiting the WGS operation. According to an alternative embodiment, illustrated by the dashed line in Figure 1, filtered gasifier effluent 26 from filtration operation 70 can provide a heat source for WGS feed portion 28a of chloride-depleted syngas 28 exiting chloride scrubber 801 by feeding it to heat exchanger 75. In this case, because exchanger 75 is not used to cool the H-enriched syngas 34, heat can be recovered from this stream for alternative purposes, such as steam generation (e.g., via WGS effluent cooler 120a) or heat integration in the overall process. In either event, heat transfer from the chloride-depleted syngas to the WGS feed portion can heat this stream from a temperature within the ranges described above to a resulting heated WGS feed portion temperature within the range of about 225°C (437°F) to about 350°C (662°F), such as about 250°C (482°F) to about 300°C (572°F). These higher temperatures are more favorable as inlet conditions for the WGS operation, which can reduce or potentially eliminate the need for heating applied upstream of this operation, such as provided by a supplemental WGS feed heater. Upon exiting the WGS feed / effluent exchanger, the H-enriched syngas can, in turn, be cooled to a temperature in the range of about 175°C (347°F) to about 300°C (572°F), such as about 200°C (392°F) to about 250°C (482°F), as cooled H-enriched syngas. These lower temperatures are more favorable inlet conditions for the ammonia scrubber, which may reduce the load associated with, or possibly eliminate the need for, added cooling upstream of this operation, such as that provided by an auxiliary WGS effluent cooler.However, in some cases, such a cooler may be utilized to provide a more desirable temperature for the gas entering the ammonia scrubber, for example, a temperature within the range of about 100°C (212°F) to about 225°C (437°F), such as about 125°C (257°F) to about 200°C (392°F).

[0058] Chloride guard beds or guard beds for general contaminant removal A chloride guard bed, comprising a solid bed of material, can be used to supplement chloride removal obtained in a chloride scrubber, thereby providing a WGS feed that enters the WGS operation (e.g., the reactor of the operation) directly and has essentially negligible total chloride content, such as less than about 100 parts per billion by weight (wt-ppb), or even less than about 10 wt-ppb. This overcomes the adverse effects associated with chloride contamination (e.g., poisoning) of the catalyst used in the WGS operation. Suitable solid bed materials include adsorbents that have both the ability to adsorb chloride and the ability to withstand the high temperatures associated with the WGS feed. Materials containing calcium carbonate (CaCO) and / or other minerals containing basic anions, such as carbonates and hydroxides, can be used for this purpose. More generally, and with reference to the drawings, a chloride guard bed can be a guard bed 85 for removing chloride and / or any other contaminants from the WGS feed 32 to improve its quality for processing in the WGS operation 90. For example, guard beds 85 may remove any of chlorides, sulfur, and / or solid particulates, leaving trace amounts or no presence of one or more of these contaminants in WGS feed 32. One or more types of material may be used in guard beds 85 to achieve a given purification objective.

[0059] WGS operation A water-gas shift (WGS) operation reacts CO present in the WGS feed with steam to increase the H concentration (as well as the CO concentration) in the H-rich effluent provided by or exiting the operation, following, for example, heating in a WGS feed / effluent heat exchanger as described above and supplemental chloride removal by a chloride guard bed. This heating and supplemental chloride removal makes the WGS feed more suitable for use in a WGS operation. In view of the fact that the chloride guard bed does not substantially affect the process temperature, the WGS feed entering the WGS operation directly (e.g., the reactor of the operation) can have a temperature within the ranges described above for the heated WGS feed portion.

[0060] In WGS operations, the use of steam in excess of the stoichiometric ratio can be beneficial for many purposes, especially in adiabatic fixed-bed reactors. These include shifting the equilibrium toward hydrogen production, adding heat capacity to limit the increase in exothermic temperature, and minimizing side reactions such as methanation. In this regard, in addition to the steam present in the WGS feed, a supplemental steam source can be incorporated into the feed. The supplemental steam source can be readily available through in-process generation or can be external to the process. In a preferred embodiment, at least a portion of the steam (e.g., high- or medium-pressure steam) generated in the CSC or radiant syngas cooler can be fed or added to the WGS operation (e.g., to one or more reactors used in the operation), thereby improving the overall heat balance / heat integration.

[0061] The reactors used in WGS operations may contain a suitable catalyst, such as one comprising one or more of Co, Ni, Mo, and W on a solid support, specific examples of which are sulfur-tolerant Co / Mo and Ni / Mo catalysts. Other catalysts used in this operation (i.e., contained within one or more WGS reactors) include those based on copper- and / or zinc-containing catalysts, such as Cu-Zn-Al; chromium-containing catalysts; iron oxide; zinc ferrite; magnetite; chromium oxide; and any combination thereof (e.g., Fe2O3-Cr2O3 catalysts).

[0062] In a typical WGS operation, two or more reactors with interstage cooling are used, given the thermodynamic characteristics of the WGS reaction. For example, a high-temperature shift (HTS) reactor may operate at a reactor inlet temperature of about 310°C (590°F) to about 450°C (842°F), with more favorable reaction kinetics and less favorable equilibrium conversion. The effluent from the HTS may then be cooled to a temperature suitable for the reactor inlet of the low-temperature shift (LTS) reactor, such as about 200°C (392°F) to about 250°C (482°F), to provide less favorable reaction kinetics and more favorable equilibrium conversion, so that the combined effect of the HTS and LTS reactors results in high conversion to H2 at favorable residence times. In some cases, it may be desirable to use three or more reactors or catalyst beds to carry out the WGS reaction, again with cooling between successive reactors or catalyst beds.

[0063] In this manner, the WGS operation can be used to provide an H-enriched syngas exiting or obtained directly from the operation, and having an increased H:CO molar ratio and an increased H concentration relative to the WGS feed or any syngas otherwise obtained from an upstream operation (e.g., filtered gasifier effluent or chloride-depleted gasifier effluent). For example, the H-enriched syngas can have an H:CO molar ratio of about 0.5 to about 3.5, about 1.0 to about 3.0, or about 1.5 to about 2.5, and / or a hydrogen concentration of at least about 35 mol% (e.g., about 35 mol% to about 80 mol%), at least about 40 mol% (e.g., about 40 mol% to about 70 mol%), or at least about 45 mol% (e.g., about 45 mol% to about 65 mol%). These properties of the H-enriched syngas can be controlled by bypassing the WGS operation more or less (e.g., diverting a smaller or larger amount of the WGS feed to this operation around this operation to provide a portion of the H-enriched syngas). The WGS operation can be further beneficial in terms of converting carbonyl sulfide (COS) to HS, which can be recycled and more easily removed elsewhere in the process, such as in the acid gas removal operation, or possibly, at least to some extent, in a chloride scrubber and / or ammonia scrubber. Due to the exothermic nature of the WGS reaction, the temperature of the H-enriched syngas can be from about 275°C (527°F) to about 500°C (932°F), such as from about 300°C (572°F) to about 475°C (887°F), in exemplary embodiments.

[0064] Ammonia Cleaning Equipment An ammonia scrubber can be used to remove ammonia (NH) from syngas, e.g., a bypass portion of the chloride-depleted syngas that is not subjected to the WGS operation and / or from the cooled H-enriched syngas provided from the WGS operation after being cooled in the WGS feed / effluent exchanger and, optionally, an auxiliary WGS effluent cooler. This removal can be achieved through contact with a suitable aqueous stream, such as aqueous ammonia scrubber feed. Contacting can be carried out in a countercurrent manner, with the aqueous ammonia scrubber feed entering at or near the top of a vertically disposed (e.g., elongated, cylindrical) ammonia scrubber vessel and the chloride-depleted syngas exiting at or near the top of the chloride scrubber vessel. Contacting efficiency can be enhanced by the use of suitable high surface area packing material or internal structures such as separate gas-liquid contact trays. Other types of contacting, such as bubbling gas into an aqueous ammonia scrubber feed (e.g., batch mode), co-current contacting, etc., can be performed with similar results of obtaining a treated syngas having reduced amounts (weight percentages or concentrations) of HCl (or total chlorides) and NH (or total nitrogen) relative to the gasifier effluent (e.g., filtered gasifier effluent) fed to the chloride scrubber. Generally, ammonia scrubbers are selective for the removal of ammonia over other types of water-soluble contaminants, so that, for example, under the conditions present in the ammonia scrubber, the ammonia removal efficiency exceeds the chloride removal efficiency. However, this operation may also be effective in removing at least some water-soluble contaminants other than ammonia (e.g., HS and / or HCN). An ammonia scrubber may be used to provide a treated syngas exiting or obtained directly from the operation, the treated syngas having a total NH (or total nitrogen) content of less than about 10 ppm by weight, less than about 1 ppm by weight, and optionally less than about 0.1 ppm by weight, and a total HCl (or total chloride) content within the ranges set forth above for chloride-depleted syngas.

[0065] The ammonia scrubber can provide additional cooling of the gas fed to the operation, for example, beyond that achieved in the WGS feed / effluent exchanger upstream of the operation and, optionally, in an auxiliary WGS effluent cooler. In an exemplary embodiment, the treated syngas product exiting the ammonia scrubber can have a temperature in the range of about 35°C (95°F) to about 100°C (212°F), such as about 40°C (104°F) to about 60°C (140°F).

[0066] Syngas conversion or separation operations In some embodiments, the processes described herein may also include a syngas conversion or separation operation to produce renewable syngas conversion or separation products, such as liquid hydrocarbons, methanol, or RNG as example conversion products and purified hydrogen as example separation products. Such syngas conversion or separation operations may be directly fed by the syngas stream described herein, e.g., the processed syngas product. In the case of liquid hydrocarbon production, the syngas conversion operation may include a Fischer-Tropsch (FT) reaction stage. One or more reactors in this stage are used to process a syngas mixture of hydrogen (H) and carbon monoxide (CO) by sequential cleavage of C-O bonds and formation of C-C bonds with the incorporation of hydrogen. This mechanism produces hydrocarbons, particularly linear alkanes, whose molecular weight distribution can be controlled to some extent by modifying the FT reaction conditions and catalyst properties. Such properties include pore size and other characteristics of the support material. The selection of the FT catalyst and its active metal (e.g., Fe or Ru) can also affect the yield of FT products in other ways, such as the production of oxygen-containing compounds.

[0067] In the case of methanol production, the synthesis gas conversion operation may include a methanol synthesis reaction stage, in which one or more reactors are used to form methanol according to the following catalytic reaction: CO+2H2→CH3OH(1) A representative catalyst for the synthesis of methanol by this route is characterized as "CZA," referring to copper and zinc on alumina, or Cu / ZnO / Al2O3. Alternatively, or in combination, various other catalytic metals and their oxides can be used, including one or more of W, Zr, In, Pd, Ti, Co, Ga, Ni, Ce, Au, Mn, and combinations thereof.

[0068] In the case of methanation as a synthesis gas conversion operation to provide a renewable natural gas (RNG) product, one or more methanation reactors (e.g., in series or parallel) can react CO and / or CO with hydrogen and thereby provide a high-temperature methanation product having a significantly higher methane concentration relative to the methane concentration initially present (e.g., in the WGS product). Suitable catalysts for use in methanation reactors include ruthenium and / or other noble metals, and supported metals such as molybdenum and tungsten. However, supported nickel catalysts are generally the most cost-effective. Often, methanation reactors are operated using a fixed bed of catalyst.

[0069] In the case of a purified hydrogen product, the syngas separation operation may include a renewable hydrogen separation stage, which may utilize, for example, (i) an adsorbent in the case of PSA separation, or (ii) a membrane. A combination of such stages may be used in a given syngas separation operation. In any such operation, a gaseous separation by-product is also provided, generally enriched in non-hydrogen components of the syngas, such as CO, CO, and / or HO. This by-product may be, for example, a PSA tail gas or otherwise a membrane permeate or retentate, depending on the particular membrane used and whether the renewable hydrogen separation product is subsequently recovered as a membrane retentate or membrane permeate. This hydrogen obtained by 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 greater, such as at least 99.9 mol%, or at least 99.99 mol%).

[0070] Further Exemplary Embodiments of the Gasification Process 1 depicts a flow diagram illustrating one embodiment of a process including the operations described above. According to this embodiment, within a gasifier 50, a carbonaceous feed 10 is combined with an oxygen-containing gasifier feed 14 under gasifying conditions to provide a gasifier effluent, in this case a neat gasifier effluent 16 comprising syngas. The oxygen-containing gasifier feed 14 may comprise HO and O, and optionally CO, alone or in combination with an optional supplemental steam source (not shown), in a total concentration of at least about 90 mol%, at least about 95 mol%, or at least about 99 mol%.

[0071] The raw gasifier effluent 16 is fed to a tar removal operation 55, which provides a tar-depleted gasifier effluent 18 having a reduced amount of tar relative to the raw gasifier effluent 16. As described herein, the extremely high temperature of the tar-depleted gasifier effluent resulting from the tar removal operation generally necessitates the use of one or more direct or indirect cooling operations. For example, according to the specific embodiment illustrated in FIG. 1 , a quenching operation 60 as a direct cooling operation may be used in combination with a convection syngas cooler (CSC) 65 as an indirect cooling operation. The quenching operation 60 may more specifically be a partial dry quench (PDQ) operation for contacting the tar-depleted gasifier effluent 18 with quench water 20 (e.g., by direct contact), thereby providing a quenched gasifier effluent 22 having a temperature that is reduced relative to the temperature of the tar-depleted gasifier effluent 18. The process may additionally include further cooling the quenched gasifier effluent 22 in the CSC 65, such as by indirect heat exchange contact with boiler feedwater 25. This provides cooled gasifier effluent 24 and CSC-generated steam 23. Subjecting the cooled gasifier effluent 24 to a filtration operation 70 provides filtered gasifier effluent 26 having a reduced particulate content. Using a chloride scrubber 801 (FIG. 2) to contact the filtered gasifier effluent 26 or other gasifier effluent with an aqueous chloride scrubber feed 106 provides a chloride-depleted syngas 28 having a reduced total HCl (or total chloride) content relative to the aqueous chloride scrubber feed 106, in addition to an aqueous chloride scrubber product 107 (FIG. 2) having an increased total HCl (or total chloride) content. Generally, prior to contact in the chloride scrubber 801, the gasifier effluent is provided from the gasifier 50 and is followed by one or more intervening operations between the gasifier 50 and the chloride scrubber 801. These intervening operations may include, for example, one or more of a tar removal operation 55, a direct cooling operation such as a quenching operation 60, an indirect cooling operation such as a CSC 65, and a filtration operation 70.

[0072] 1 , a first portion of chloride-depleted syngas 28, i.e., WGS feed portion 28a, is supplied to WGS operation 90 through WGS feed / waste exchanger 75, which provides heated WGS feed portion 30, and through chloride guard bed 85, which provides WGS feed 32. Thus, in various illustrative embodiments, the first portion of chloride-depleted syngas 28 is heated by heat exchange with H-enriched syngas 34 from WGS operation 90 before being supplied to WGS operation 90. If desired, additional heating upstream of the WGS operation can be provided using a supplemental WGS feed heater 110. This first portion of chloride-depleted syngas 28 can alternatively, or in combination, be contacted with chloride guard bed 85 containing, for example, the materials described above, to further remove chlorides beyond the extent of removal provided by chloride scrubber 801.

[0073] From the WGS operation 90, an H-enriched syngas 34 is obtained, which is contacted with aqueous ammonia scrubber feed 101 (FIG. 2) in ammonia scrubber 802 to provide treated syngas product 111. Prior to this contact, the H-enriched syngas 34 is cooled by indirectly exchanging heat with the WGS feed portion in WGS feed / waste exchanger 75 to provide cooled H-enriched syngas 36. If necessary, further cooling upstream of the ammonia scrubber can be provided using an auxiliary WGS scrubber cooler 120 (FIG. 2). At least a second portion, such as bypass portion 28b, of the chloride-depleted syngas 28 can also be fed to ammonia scrubber 802, such as directly from chloride scrubber 801, although in either case, this bypass portion 28b is not subjected to WGS operation 90 to increase its H content. In this manner, the bypass of WGS operation 90 can be used to control the H concentration and / or H:CO molar ratio of the total feed to ammonia scrubber 802 and the treated syngas product 111, which can be used in syngas conversion operation 95. For example, a typical process may include adjusting the flow rates of a first portion (e.g., WGS feed portion 28a) and / or a second portion (e.g., bypass portion 28b) of chloride-depleted syngas 28 to control (e.g., maintain) a set H concentration (e.g., any discrete value within the range of 30% by volume to 70% by volume) and / or a set H:CO molar ratio (e.g., any discrete ratio within the range of 1:2 to 5:1) in the treated syngas product 111. As illustrated in FIG. 1 , bypass portion 28b and cooled H-enriched syngas 36 can be fed separately to ammonia scrubber 802, such as at separate axial elevations. 2, these streams 28b and 36 may be combined upstream of the ammonia scrubber 802. Generally, a representative process may include feeding the H-enriched syngas 34 from the WGS operation 90, in addition to a second portion (e.g., bypass portion 28b) of the chloride-depleted syngas 28, to the ammonia scrubber 802 for contact with the aqueous ammonia scrubber feed 106 to provide the treated syngas product 111.This product may then be fed to a syngas conversion operation or syngas separation operation 95 to provide a renewable gasification product 40, in view of the fact that the treated syngas product 111 has properties more suitable for such operations 95 in terms of low contaminant levels and sufficient hydrogen content.

[0074] Additional details are illustrated in Figure 2, which highlights the various aqueous feed and product stream flows to and from the chloride scrubber 801 and ammonia scrubber 802. Also illustrated in the figure is the use of various auxiliary heaters and coolers 110, 120, 130, which may use any suitable heat exchange medium, such as steam at a suitable pressure or cooling water at a suitable temperature. According to Figure 2, optionally, further integration between the chloride scrubber 801 and the ammonia scrubber 802 may be achieved, with the aqueous chloride scrubber feed 106 comprising an aqueous product of the ammonia scrubber 802, such as the first aqueous ammonia scrubber product 105. Alternatively, or in combination, makeup chloride scrubber water 104 may provide all or a portion of the aqueous chloride scrubber feed 106. According to more specific embodiments, the first aqueous ammonia scrubber product 105 is withdrawn from the aqueous recycle loop of the ammonia scrubber 802, which includes all or a portion of the aqueous ammonia scrubber feed 101. Additionally, a second aqueous ammonia scrubber product 103 may be withdrawn from this recycle loop, for example, to limit the accumulation of condensate and / or impurities. At least a portion of the second aqueous ammonia scrubber product 103 may be used for cooling the gasifier effluent, such as directly in the quench operation 60 or indirectly in a CSC 65 or radiant syngas cooler. It is further possible for the first aqueous ammonia scrubber product 105 to be withdrawn from the aqueous recycle loop at a first temperature, i.e., a first ammonia scrubber product temperature, that is higher than the second temperature, i.e., the second ammonia scrubber product temperature, at which the second aqueous ammonia scrubber product 103 is withdrawn. For example, the first aqueous ammonia scrubber product 105 used to provide at least a portion of the aqueous chloride scrubber feed 106 may be withdrawn at a temperature of from about 50°C (122°F) to about 150°C (302°F), while the second aqueous ammonia scrubber product may be withdrawn at a temperature of from about 30°C (86°F) to about 50°C (122°F).The temperature within the aqueous recycle loop is governed by the specific operation of the ammonia scrubber 802 and can be regulated to some extent using the aqueous recycle loop cooler 130 .

[0075] Overall, aspects of the present invention relate to gasification processes that utilize separate scrubbing equipment both upstream and downstream of a WGS operation to efficiently achieve the desired characteristics of the feed to that operation. Additional advantages, such as material and heat consolidation, reduced metal material requirements, and other advantages, are also described herein. Those skilled in the art, armed with knowledge of this disclosure, will recognize that various modifications can be made to these processes to achieve these and other advantages without departing from the scope of the present disclosure. As such, it should be understood that features of the present disclosure are susceptible to modification and / or substitution, and the specific embodiments illustrated and described herein are for purposes of illustration only and do not limit the invention as defined by the appended claims.

Claims

1. 1. A process for gasification of a carbonaceous feed, comprising: The carbonaceous feed is contacted with an oxygen-containing gasifier feed under gasification conditions in a gasifier to produce H ２ providing a gasifier effluent containing CO, and chlorides and ammonia as water-soluble contaminants; contacting the gasifier effluent with an aqueous chloride scrubber feed in a chloride scrubber to provide a chloride-depleted synthesis gas exiting a gas outlet of the chloride scrubber; adjusting the temperature of the chloride-depleted syngas to control a set moisture level (humidity) of the chloride-depleted syngas.

2. 10. The process of claim 1, wherein the set moisture level is from about 30% to about 70% by volume.

3. 3. The process of claim 1 or 2, wherein the temperature of the chloride-depleted syngas is from about 120°C to about 200°C.

4. 4. The process of any one of claims 1 to 3, wherein the temperature of the chloride-depleted synthesis gas is adjusted by varying the flow rate of the aqueous scrubber feed.

5. 1. A process for gasification of a carbonaceous feed, comprising: The carbonaceous feed is contacted with an oxygen-containing gasifier feed under gasification conditions in a gasifier to produce H ２ providing a gasifier effluent containing CO, and chlorides and ammonia as water-soluble contaminants; contacting the gasifier effluent with an aqueous chloride scrubber feed in a chloride scrubber to provide a chloride-depleted synthesis gas exiting a gas outlet of the chloride scrubber; At least a first portion of the chloride-depleted synthesis gas is fed to a water-gas shift (WGS) operation to produce H ２ providing an enriched synthesis gas; In the ammonia scrubber, ２ contacting the enriched syngas with an aqueous ammonia scrubber feed to provide a treated syngas product.

6. The H ２ 6. The process of claim 5, wherein enriched syngas is cooled by heat exchange with the first portion of the chloride-depleted syngas prior to contacting the aqueous ammonia scrubber feed in the ammonia scrubber.

7. The H ２ 7. The process of claim 6, wherein enriched syngas is cooled by said heat exchange with said first portion of said chloride-depleted syngas in combination with an auxiliary WGS effluent cooler prior to contacting said aqueous ammonia scrubber feed in said ammonia scrubber.

8. The process of any one of claims 5 to 7, further comprising feeding at least a second portion of the chloride-depleted synthesis gas to the ammonia scrubber.

9. The process of any one of claims 5 to 8, wherein the aqueous chloride scrubber feed comprises the aqueous product of the ammonia scrubber.

10. 10. The process of claim 9, wherein the aqueous product of the ammonia scrubber is a first aqueous ammonia scrubber product withdrawn from an aqueous recycle loop of the ammonia scrubber, the process further comprising withdrawing a second aqueous ammonia scrubber product from the aqueous recycle loop.

11. 11. The process of claim 10, wherein at least a portion of the second aqueous ammonia scrubber product is used for direct or indirect cooling of the gasifier effluent.

12. 12. The process of claim 10 or 11, wherein the first aqueous ammonia scrubber product is withdrawn from the aqueous recycle loop at a first ammonia scrubber product temperature that is higher than a second ammonia scrubber product temperature at which the second aqueous ammonia scrubber product is withdrawn.

13. 13. The process of any one of claims 5 to 12, wherein the gasifier effluent is provided from the gasifier after one or more intervening operations selected from a tar removal operation, a direct cooling operation, an indirect cooling operation, and a filtration operation prior to contacting in the chloride scrubber.

14. 1. A process for gasification of a carbonaceous feed, comprising: The carbonaceous feed is contacted with an oxygen-containing gasifier feed under gasification conditions in a gasifier to produce H ２ providing a gasifier effluent containing CO, and chlorides and ammonia as water-soluble contaminants; contacting the gasifier effluent with an aqueous chloride scrubber feed in a chloride scrubber to provide a chloride-depleted synthesis gas exiting a gas outlet of the chloride scrubber; At least a first portion of the chloride-depleted synthesis gas is fed to a water-gas shift (WGS) operation to produce H ２ providing an enriched synthesis gas; and feeding at least a second portion of said chloride-depleted synthesis gas to an ammonia scrubber without subjecting said second portion to said WGS operation.

15. Before the first portion of the chloride-depleted synthesis gas is supplied to the WGS operation, ２ 15. The process of claim 14 wherein the process is heated by heat exchange with enriched syngas.

16. The first portion of the chloride-depleted synthesis gas is combined with an auxiliary WGS feed heater to generate the H ２ 16. The process of claim 15, wherein heating is achieved by said heat exchange with enriched syngas.

17. 17. The process of any one of claims 14 to 16, wherein the first portion of the chloride-depleted synthesis gas is contacted with a chloride guard bed to further remove chlorides before being fed to the WGS operation.

18. In addition to the second portion of the chloride-depleted synthesis gas, ２ 18. The process of any one of claims 14 to 17, further comprising contacting the enriched syngas with an aqueous ammonia scrubber feed and feeding the enriched syngas to an ammonia scrubber to provide a treated syngas product.

19. adjusting the flow rate of the first portion and / or the second portion of the chloride-depleted syngas to produce a set H ２ Density or setting H ２ 20. The process of claim 18, further comprising controlling the :CO molar ratio.

20. 20. The process of claim 18 or 19, further comprising feeding the treated syngas product to a syngas conversion operation or a syngas separation operation to provide a renewable gasification product.

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