Desulfurization of carbon dioxide-containing gas

Abstract

Sulfur-containing compounds are converted to elemental sulfur in the Claus process, and subsequently the residual sulfur-containing compounds are converted to H2S by hydrogenation of the Claus tail gas. After cooling, water is removed and compressed, and then removed, either by physical separation or by chemical reaction with a solid metal oxide to form a solid metal sulfide, and then oxidized and regenerated, to produce a recycled gas containing purified CO2 and at least one sulfur-containing compound recycled to the Claus process, along with any other sulfur-containing impurities. Some of the H2S in the Claus tail gas can be first removed by selective and / or non-selective amine absorption in a tail gas treatment unit before the residual H2S and any other residual sulfur-containing impurities are removed in a physical separation or chemical reaction step.

Description

Background Art

[0001] Cross - reference to related applications This application claims the priority of U.S. Non - Provisional Patent Application No. 17 / 856,455, filed on July 1, 2022.

[0002] The present invention is in the field of the recovery and purification of carbon dioxide (CO2). In particular, the present invention relates to methods and apparatuses for the desulfurization of CO2 - containing streams for carbon capture and storage (“CCS”).

[0003] In the art, there are numerous examples of methods for removing sulfur - containing compounds such as hydrogen sulfide (H2S), carbonyl sulfide (COS), mercaptan (i.e., thiol), carbon disulfide (CS2), and / or sulfur oxides (SO x ) from raw CO2 or other CO2 - containing gases.

[0004] GB871750 relates to a method for removing H2S from CO2 - containing gases generated by hydrocarbon combustion or in a blast furnace. Such gases usually contain up to 400 ppm of H2S. Since CO2 is mainly intended to be used in the synthesis of urea, the amount of H2S needs to be reduced to 2 ppm or less. This reference teaches reducing the amount of H2S in the CO2 gas to the required level by passing the gas through a zeolite layer activated by heating and from which the water of crystallization has been removed. The activation of the zeolite by discharging this water creates interstitial voids having dimensions that allow the adsorption of H2S. The gas supply to the zeolite can be dried or undried, and the zeolite can be thermally regenerated using a heated regeneration gas.

[0005] US5674463A relates to a method for purifying CO2 obtained from natural sources such as natural gas or industrially produced, particularly by combustion of hydrocarbon products, for use in applications requiring high-purity CO2, such as the manufacture of food or medical products. This reference first involves contacting CO2 with steam in the presence of a hydrolysis catalyst such as activated alumina to convert COS in the gas to H2S, and then using an oxidation catalyst such as iron oxide to convert the resulting H2S in the gas to form elemental sulfur and metal sulfides, which are then removed from the gas, teaching that COS and H2S are removed from the CO2 gas. Residual sulfur compounds can be removed by contacting the remaining gas with copper oxide, zinc oxide, or a mixed copper-zinc oxide.

[0006] US2012 / 0012000A mainly relates to separating an acidic (i.e., sulfur-containing) synthesis gas containing hydrogen (H2) and carbon monoxide (CO) and H2S and CO2 obtained from the gasification of solid or liquid carbonaceous feedstocks into at least a CO2 product stream suitable for underground storage, a synthesis gas (H2 / CO) product stream suitable for use in chemical plants or refineries or as fuel for gas turbines, and an H2S-enriched stream that can be further processed, for example, in a Claus plant or other suitable sulfur recovery system. This reference teaches introducing the acidic synthesis gas into a pressure swing adsorption (PSA) system that separates the feed gas into a synthesis gas product stream and a stream enriched in CO2 and H2S, or separates a H2S-depleted feed gas (produced in an acidic PSA system) into a synthesis gas product stream and a CO2-enriched gas stream. The acidic PSA system contains an H2S-selective adsorbent such as silica gel, activated carbon, or molecular sieve.

[0007] WO2016 / 075109A discloses a process for removing H2S equivalents such as COS and / or CS2 by adsorbing from Claus tail gas containing CO2. The tail gas containing H2S equivalents and CO2 is fed to an adsorption system where it contacts an alumina-based adsorbent material to produce a CO2-enriched first product gas. The adsorbent material is regenerated with a purge gas containing steam to recover the adsorbed impurities in the form of H2S and obtain a second product gas containing H2S, which is recycled to a Claus unit. Optionally, the purged adsorbent material is then dried.

[0008] However, there is still a need for new methods and apparatus for desulfurizing CO2-containing streams, especially when the CO2 is intended for CCS, taking into account a low maximum limit of sulfur-containing compounds (e.g., 100 ppm or less in total).

SUMMARY OF THE INVENTION

[0009] The present invention relates to a method for desulfurizing a CO2-containing gas stream. Such streams are often by-products of crude oil refining or other industrial processes involving physical and chemical gas treatment units used in refineries, natural gas treatment plants, and gasification or syngas plants and can be referred to as "acid" gas streams. These "acid" gases often (but not always) contain H2S as an impurity, along with one or more of CS2, COS, and mercaptans.

[0010] Such gases are typically treated in a Claus process that recovers elemental sulfur from gaseous H2S in the presence of O2 according to the following overall reactions. 2H2S + 3O2 → 2SO2 + 2H2O 4H2S + 2SO2 → 3S2 + 4H2O

[0011] The Claus process may involve either a thermal process or a catalytic process, but usually involves a combination of both thermal and catalytic processes to increase the overall sulfur yield. In the thermal process, gaseous H2S undergoes a quasi-stoichiometric combustion reaction at a temperature above 850 °C to produce elemental sulfur and water. In the catalytic process, gaseous H2S reacts with SO2 on a catalyst such as activated aluminum(III) or titanium(IV) oxide to produce additional elemental sulfur and water.

[0012] Most commercial Claus processes involve a thermal stage followed by one or more catalytic stages, and sulfur is removed between stages by a condenser. The first stage typically operates at about 315 °C to about 330 °C and helps to hydrolyze COS and CS2. Subsequent stages typically operate at a lower temperature above the sulfur dew point to increase catalytic conversion. Thus, the second stage may operate at about 240 °C and the third stage may operate at about 200 °C. O2 can be provided to the Claus process in the form of air, i.e., the "air-Claus" process, or in the form of pure O2 or O2-enriched air, i.e., the "oxy-Claus" process.

[0013] The inventors have recognized that sulfur-containing compounds other than H2S, such as COS, CS2, and mercaptans, from the original "acid" gas can be removed from the tail gas by forming metal sulfides by hydrogenation, physical separation, or chemical reaction with at least one solid metal oxide to form metal sulfides and then oxidative regeneration, and then producing a recycle gas containing purified CO2 and at least one sulfur-containing compound recycled to the Claus process.

[0014] The physical separation of H2S and any other sulfur-containing compounds from CO2 (i) The selective adsorption - adsorption of sulfur - containing compounds onto an adsorbent material selective for such compounds is purely physical in the sense that the compound in question is not converted by chemical reaction with the adsorbent. As a result, when the adsorbent material is regenerated and the adsorbed compound is removed, the spent regeneration gas will contain impurities from the impure gas feed to the adsorbent, or (ii) may be achieved by either partial condensation by distillation and / or phase separation.

[0015] Alternatively, H2S and any other sulfur - containing compounds can be removed from the impure CO2 gas by reaction with a bed containing at least one solid metal oxide, such as zinc oxide (ZnO), and the metal oxide is converted to a metal sulfide, such as zinc sulfide (ZnS). The metal oxide can be regenerated by oxidation using a regeneration gas containing O2 to discharge sulfur from the bed as sulfur dioxide (SO2).

[0016] Accordingly, according to a first aspect of the present invention, a method for the desulfurization of crude carbon dioxide (CO2) gas containing hydrogen sulfide (H2S) and optionally at least one other sulfur - containing impurity, comprising: feeding the crude CO2 gas containing H2S to a Claus process to convert H2S to elemental sulfur in the presence of oxygen (O2) gas, producing a Claus tail gas containing CO2, residual H2S, and at least one other sulfur - containing impurity; feeding the Claus tail gas to a hydrogenation process to convert the at least one other sulfur - containing impurity to H2S in the presence of hydrogen (H2), producing an H2S - enriched CO2 tail gas; cooling the H2S - enriched CO2 tail gas and removing condensed water to produce a cooled H2S - enriched CO2 tail gas; compressing the cooled H2S - enriched CO2 tail gas or an impure CO2 gas containing H2S derived therefrom to produce a compressed impure CO2 gas containing H2S; Removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by physical separation and / or by forming a solid metal sulfide by chemical reaction with at least one solid metal oxide and then oxidatively regenerating to produce purified CO2 and a first recycle gas containing at least one sulfur-containing compound; There is provided a method comprising recycling the first recycle gas to the Claus process to convert the at least one sulfur-containing compound to elemental sulfur.

[0017] According to a second aspect of the present invention, an apparatus for desulfurizing a raw CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, A Claus unit for removing H2S from the raw CO2 gas, A first inlet for an oxidant gas containing O2, A second inlet for the raw CO2 gas, A first outlet for a Claus tail gas containing CO2, residual H2S, and at least one other sulfur-containing impurity, A second outlet for elemental sulfur, comprising a Claus unit; A source of oxidant gas containing O2 in fluid flow communication with the first inlet of the Claus unit, A source of raw CO2 in fluid flow communication with the second inlet of the Claus unit, A hydrogenation unit for converting the at least one other sulfur-containing impurity in the Claus tail gas to H2S, A first inlet in fluid flow communication with the first inlet of the Claus unit, A second inlet for H2, A first outlet for H2S-enriched CO2 tail gas, comprising a hydrogenation unit; A source of H2 in fluid flow communication with the second inlet of the hydrogenation unit, A cooling unit for cooling the H2S-enriched CO2 tail gas, A first inlet in fluid communication with the first outlet of the hydrogenation unit, a first outlet for the cooled H2S-enriched CO2 tail gas, and a second outlet for the condensed water, and a cooling unit; a compression unit for compressing the cooled H2S-enriched CO2 tail gas or the impure CO2 gas containing H2S derived therefrom, the compression device having an inlet in fluid flow communication with the first outlet of the cooling unit, and an outlet for the compressed impure CO2 gas, and a compression unit; a purification unit for removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by forming solid metal sulfides by physical separation or by chemical reaction with at least one metal oxide and then oxidatively regenerating, a first inlet in fluid flow communication with the first inlet of the Claus unit, and a first outlet for the purified CO2, and a second outlet for the first recycle gas containing at least one sulfur-containing compound, and an apparatus is provided comprising a purification unit in which the second outlet of the purification unit is in fluid communication with the Claus unit.

[0018] The term "raw CO2" refers to a gas mixture containing at least about 50 mol% CO2, e.g., from about 50 mol% to about 80 mol% CO2. Raw CO2 is a gaseous mixture containing H2S and typically water, although in some embodiments other components, e.g., one or more other sulfur-containing compounds, may be present.

[0019] The term "sulfur-containing compound" refers to a compound containing at least one sulfur atom. Examples of sulfur-containing compounds include H2S, COS, CS2, SO2, and mercaptans (or thiols). H2S is typically present in the raw CO2 feed and is also produced in the hydrogenation step of the present invention. COS and / or CS2 may be present in the raw CO2 feed, but can also be produced during the Claus process. SO2 is typically not present in the raw CO2 feed but is produced in the Claus process. Mercaptans are not produced in the process of the present invention and thus, when present in CO2, enter with the raw CO2 feed gas.

[0020] The term "sulfur-containing impurity" refers to individual sulfur-containing compounds that are present in the gas at an impurity level, e.g., 5 mol% (or 50,000 ppm) or less, and typically 3 mol% (or 30,000 ppm) or less.

[0021] The term "impure CO2" refers to a CO2-containing gas that has a higher proportion (in terms of mole fraction) of CO2 than the raw CO2 from which it is derived. Such a gas typically contains at least about 80 mol% CO2, e.g., from about 80 mol% to about 95 mol% CO2.

[0022] The term "physical separation" refers to a process in which at least one sulfur-containing component of a fluid mixture is removed from the other components of the mixture without chemical change, reaction, or conversion. In other words, the components are separated "as is" from the mixture, i.e., in the form in which they exist in the fluid mixture.

[0023] The term "oxidative regeneration" refers to a process in which a solid metal oxide is regenerated from a solid metal sulfide by oxidation, typically using a regeneration gas containing O2.

[0024] The term "purified CO2" refers to a CO2-containing gas that has a higher percentage (in terms of mole fraction) of CO2 than the raw CO2 from which it is derived. Such a gas typically contains at least about 95 mol% CO2, for example, from about 95 mol% to about 100 mol% CO2, and typically the total sulfur-containing compounds are 500 ppm or less, and in some cases 100 ppm or less.

[0025] The term "further purified CO2" refers to a CO2-containing gas that has a higher percentage (in terms of mole fraction) of CO2 than the purified CO2 from which it is derived. Such a gas typically contains at least about 99 mol% CO2, for example, from about 99 mol% to 100 mol% CO2, and typically the total sulfur-containing compounds are 100 ppm or less.

[0026] A "H2S-enriched" gas is a gas that contains a higher percentage (in terms of mole fraction) of H2S than the H2S-containing gas from which it is derived.

[0027] A "H2S-depleted" gas is a gas that contains a lower percentage (in terms of mole fraction) of H2S than the H2S-containing gas from which it is derived. This term encompasses (but is not limited to) gases that do not contain H2S.

[0028] A "sulfur-selective adsorbent material" is a material that preferentially adsorbs sulfur-containing compounds over at least one other component in a gas mixture, i.e., has a higher affinity for sulfur-containing compounds than for the other components of the gas mixture.

[0029] "Selective adsorption" is a process in which the sulfur-containing components removed from raw CO2 are selectively adsorbed onto an adsorbent and then recovered (in the same chemical form) by desorption using a regeneration gas.

[0030] A "water-selective adsorbent material" is a material that preferentially adsorbs water over at least one other component in a gas mixture, i.e., has a higher affinity for water than for the other components.

[0031] The "bed" contains particles of either, or both types of, an adsorbent material or a solid metal oxide. The bed of particles is typically a packed bed, but can be a fluidized bed. In a packed bed containing both types of particles, the particles are typically in separate layers.

[0032] The term "downstream" in the context of a selective adsorption unit or reactor refers to the relative location when the unit or reactor is on-feed. The term "upstream" should be interpreted accordingly.

[0033] The term "selective amine absorption" refers to a separation or purification process that uses an amine to selectively (but not necessarily exclusively) absorb a particular acid gas component, such as H2S, in a gas mixture, such as H2S-enriched CO2 tail gas.

[0034] The term "non-selective amine absorption" refers to a separation or purification process that uses an amine to absorb a particular acid gas component, such as H2S, optionally in combination with another acid gas component, such as CO2, in a gas mixture, such as H2S-lean CO2 tail gas.

[0035] The term "non-condensable gas" refers to a gas that cannot be condensed under the conditions of the present invention. Examples of non-condensable gases include H2, N2, and O2, and noble gases.

[0036] A "CO2 purification unit" (i.e., a "CPU") is a unit that purifies (or further purifies) CO2 by partial condensation by phase separation. Such a unit typically comprises a heat exchanger for cooling and partially condensing the gas to be purified, and one or more, e.g., two, phase separators in series for separating the condensed phase from the gas phase.

[0037] The "distillation unit" is a unit for purifying (or further purifying) CO2 by distillation. Such a unit typically comprises a heat exchanger for cooling the gas to be purified and optionally at least partially condensing it, and at least one distillation column. The column may include trays or may be packed with loose and / or structured packing to increase the vapor / liquid contact surface area within the column.

Brief Description of the Drawings

[0038] Preferred embodiments of the present invention will be described with reference to the drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0039] A first aspect of the present invention is a method for desulfurizing a raw CO2 gas containing H2S and optionally at least one other sulfur-containing impurity. The method includes feeding a raw CO2 gas containing H2S to a Claus process to convert H2S to elemental sulfur in the presence of oxygen (O2) gas, producing a Claus tail gas containing CO2, residual H2S, and at least one other sulfur-containing impurity. The Claus tail gas is fed to a hydrogenation process to convert other sulfur-containing impurities (or impurities) to H2S in the presence of H2, producing an H2S-enriched CO2 tail gas. The H2S-enriched CO2 tail gas is cooled to remove water, and the resulting cooled H2S-enriched tail gas (or an impure CO2 gas containing H2S derived therefrom) is compressed to produce a compressed impure CO2 gas containing H2S. By physical separation or by chemical reaction with a solid metal oxide to form a solid metal sulfide, which is returned to the metal oxide by oxidative regeneration, H2S and any other sulfur-containing impurities are removed from the compressed gas, producing purified CO2 and a first recycle gas containing at least one sulfur-containing compound. The first recycle gas is recycled to the Claus process to convert at least one sulfur-containing compound to elemental sulfur.

[0040] Embodiments of the present invention improve the recovery and / or purity of CO2 from raw CO2 containing H2S and optionally any other sulfur-containing impurities.

[0041] The Claus process can be a conventional "Air Claus" process or "Oxy Claus" process as described above. In either case, typically, it includes a thermal stage and at least one, for example, from one to four, preferably two or three catalytic stages. The recycle gas can be recycled to the supply to the Claus process or at a location between stages, that is, between two stages within the process, or to either or both of them.

[0042] Alternatively, the Claus process may be a SUPERCLAUS® process or EUROCLAUS® process, or a combination of two Claus processes.

[0043] The SUPERCLAUS® process is composed of at least three catalytic reaction stages following the thermal stage, and sulfur is removed by a condenser for each stage. The first reactor is filled with a standard Claus catalyst such as activated alumina, promoted alumina and / or titania (TiO2), and the final reactor is filled with a selective oxidation catalyst such as iron oxide and / or chromium oxide (or other metal oxides) on alpha alumina or silica. In the thermal stage, the acid gas is burned with a stoichiometric amount of controlled combustion air (or pure O2 or O2-enriched air), and the tail gas exiting from the last Claus reactor typically contains 0.8 - 1.0% by volume of H2S. The selective oxidation catalyst in the final reactor oxidizes H2S to sulfur with an efficiency of over 85%. If a sulfur recovery rate of over 99% is required, a third Claus reactor stage can be installed upstream of the selective oxidation reactor.

[0044] The EUROCLAUS® process consists of three or four catalytic reaction stages following a thermal stage, and sulfur is removed by condensers at each stage. The final Claus reactor is filled with a layer of a hydrogenation catalyst such as a CoMo catalyst (cobalt and molybdenum oxides on alumina), followed by a reactor filled with a selective oxidation catalyst such as iron oxide and / or chromium oxide (or other metal oxides) on alpha alumina or silica. In the thermal stage, the acid gas is burned with a controlled amount of combustion air at a quasi-stoichiometric ratio, and the tail gas exiting the final Claus reaction typically contains 0.8 - 1.0 volume % H2S and 100 - 200 ppmv SO2. This low SO2 content is obtained with a hydrogenation catalyst that converts SO2 to H2S in the final Claus reactor. The selective oxidation catalyst in the final reactor oxidizes H2S to sulfur with an efficiency of over 85%. A total sulfur recovery efficiency of up to 99.3% can be achieved with a three-stage reactor and up to 99.5% with a four-stage reactor.

[0045] The raw CO2 gas may be fed to the Claus process at a temperature of about 10°C to about 70°C, such as about 45°C, and at a pressure in the range of about 0.3 barg to about 30 barg, such as about 0.3 barg to about 1.8 barg, such as about 0.9 barg.

[0046] The hydrogenation process requires H2 as a reducing gas. H2 can be generated in an H2 generation process such as the partial oxidation of natural gas with quasi-stoichiometric air / oxygen in a reducing gas generator and then fed to the hydrogenation process. However, the need for fresh H2, or "makeup" H2, from the H2 generation process can be reduced or completely eliminated by recycling H2 from another point in the process (see below).

[0047] The Claus tail gas may be supplied to the hydrogenation process at a temperature in the range of about 120°C to about 200°C, for example, about 130°C, and a pressure in the range of about 0.2 barg to about 30 barg, for example, about 0.2 barg to about 1.8 barg, for example, about 0.3 barg. The pressure and / or temperature of the Claus tail gas can be adjusted as necessary using conventional means before being supplied to the hydrogenation process, but in a preferred embodiment, the tail gas is supplied to the hydrogenation process without such adjustment.

[0048] Cool the H2S-enriched CO2 tail gas from the hydrogenation process. Any suitable cooling process may be used, but in a preferred embodiment, the H2S-enriched CO2 tail gas is quenched by direct contact with liquid water. After removing the condensed water, the cooled H2S-enriched CO2 tail gas is compressed to form a compressed impure CO2 gas containing H2S.

[0049] The cooled H2S-enriched CO2 tail gas may be supplied to the compression unit at a temperature in the range of about 10°C to about 70°C, for example, about 45°C, and a pressure in the range of about 0.3 barg to about 1.8 barg, for example, about 1 barg. The compression unit compresses the gas to a pressure in the range of about 1 barg to about 120 barg, for example, about 30 barg.

[0050] The content of H2S and any other sulfur-containing impurities in the compressed impure CO2 gas is purified by physical separation or by chemical reaction with at least one solid metal oxide to form a solid metal sulfide and then oxidative regeneration, producing purified CO2 together with a first recycle gas containing at least one sulfur-containing compound that is recycled to the Claus process, and in some embodiments, is significantly reduced to a level of less than 100 ppm.

[0051] Physical separation can be carried out by selective adsorption or by partial condensation by distillation and / or phase separation.

[0052] In embodiments using selective adsorption, the method removes H2S and any other sulfur-containing compounds in the compressed impure CO2 gas by adsorption on at least one adsorbent material selective for sulfur compounds in the selective adsorption unit to produce purified CO2, and after desorption, produces a spent regeneration gas containing H2S and any other sulfur-containing compounds from the compressed impure CO2 gas as the first recycle gas.

[0053] Such adsorbent materials include silica gel, molecular sieves (e.g., 4A or 5A zeolite), activated alumina, and activated carbon (e.g., Calgon Cu material and Cu-impregnated carbon). The sulfur-containing compounds are reversibly adsorbed onto the bed of the solid selective adsorbent and are then desorbed, preferably when the solid adsorbent is saturated with the sulfur-containing compounds. The adsorption process can operate any suitable cycle including PSA, vacuum swing adsorption (VSA), or temperature swing adsorption (TSA). Specific examples include TSA with silica gel, PSA or VSA with silica gel, TSA with zeolite (e.g., 4A, 5A), and TSA with Cu-impregnated carbon.

[0054] The compressed impure CO2 gas may be supplied to the selective adsorption unit at a temperature in the range of about 10 °C to about 70 °C, for example, at a temperature of about 50 °C.

[0055] The adsorbent bed of the selective adsorption unit is preferably regenerated using the purified (or further purified) CO2 generated in the process. The temperature and / or pressure of the regeneration gas may be adjusted as necessary using conventional means depending on the location where it is removed from the process and the type of cycle used, e.g., the temperature and / or pressure of the CO2 gas in TSA, VSA, or PSA, etc. In embodiments where solid metal oxides are used to purify compressed impure CO2 gas, the method includes passing the compressed gas through a bed containing at least one solid metal oxide in a reactor. H2S and any other sulfur-containing impurities in the gas convert the metal oxides in the bed to the corresponding metal sulfides, thereby removing the impurities from the gas and producing purified CO2. The metal oxides in the bed are typically regenerated oxidatively by passing a regeneration gas containing O2 through the bed in a direction countercurrent to the gas when the bed is "in supply", discharging sulfur from the bed in the form of SO2. The spent regeneration gas containing SO2 is then recycled to the Claus process as a first recycle gas.

[0056] In embodiments where H2S is removed by chemical reaction with at least one solid metal oxide, suitable solid metal oxides include zinc(II) oxide (ZnO), iron(III) oxide (Fe2O3), aluminum(III) oxide (Al2O3), and group II metal oxides such as calcium oxide (CaO), magnesium oxide (MgO), and barium oxide (BaO). A single metal oxide may be used, but in some embodiments, a mixture of metal oxides (i.e., mixed metal oxides) is used. In some embodiments, the mixture of solid metal oxides contains about 40 wt% to about 60 wt%, e.g., about 50 wt% ZnO.

[0057] Examples of suitable mixed metal oxides are disclosed in US4044114 and include from about 20 wt% to about 85 wt%, preferably from about 25 wt% to about 80 wt% zinc oxide (calculated as ZnO), from about 0.9 wt% to about 50 wt% alumina (calculated as Al2O3), and from about 2 wt% to about 45 wt% Group II metal, preferably calcium (calculated as the oxide), with or without additional elements.

[0058] The compressed impure CO2 gas may be fed to the reactor at a temperature in the range of about 300 °C to about 800 °C, or about 300 °C to about 700 °C, for example, about 400 °C to about 550 °C. After compression, the temperature of the compressed gas may be adjusted as necessary using conventional means before it is fed to the reactor containing the solid metal oxide.

[0059] The mixed metal oxide bed of the reactor is suitably regenerated by adding O2 in an amount in the range of about 1 to about 5 mol%, for example about 2 mol% oxygen, to an oxygen-containing gas, for example, purified (or further purified) CO2 generated in the process. The temperature and / or pressure of the regeneration gas can be adjusted as necessary using conventional means depending on the temperature and / or pressure of the CO2 gas at the location where it is removed from the process.

[0060] The first recycle gas can be recycled to the Claus process at a temperature in the range of about 10 °C to about 70 °C, for example, a temperature of about 50 °C, and a pressure in the range of about 0.3 barg to 30 barg, or about 0.3 barg to about 1.8 barg, for example, a pressure of about 1 barg. In embodiments where the temperature and / or pressure of the first recycle gas exiting the purification process is not appropriate considering the operating conditions of the Claus unit, the temperature and / or pressure of the first recycle gas is suitably adjusted by conventional means.

[0061] The compressed impure CO2 gas fed to a selective adsorption unit or a reactor containing a solid metal oxide will typically contain water. In such cases, the water can be removed by adsorbing it onto at least one adsorbent material selective for water, which is disposed downstream of either the adsorbent material selective for sulfur-containing compounds or the solid metal oxide. Suitable water-selective adsorbent materials include those specified above as sulfur-selective adsorbent materials. The water-selective adsorbent material can be disposed in the same container as the sulfur-selective adsorbent material or the metal oxide, for example, in a separate layer or in a separate container.

[0062] Alternatively, the water can be removed by absorption in a separate container, such as a glycol unit, disposed downstream of either the selective adsorption unit or the reactor.

[0063] Regardless of whether sulfur-containing impurities are removed by selective adsorption or by chemical reaction with a solid metal oxide, the regeneration gas can contain a small amount of water. However, when water is present, the amount of water is not sufficient to hydrolyze the sulfur-containing compounds discharged from the regenerated bed. In this regard, the regeneration gas typically contains less than 5 mol%, preferably less than 2 mol%, more preferably less than 1 mol% water. Such an amount of water is considered a minimal amount in the art.

[0064] The H2S-enriched tail gas is fed directly to a compression unit for compression and can produce compressed impure CO2. However, in some embodiments, this method involves recovering H2S from the H2S-enriched CO2 tail gas by selective amine absorption to produce H2S-depleted CO2 tail gas and recovered H2S, and recycling the recovered H2S to a Claus process to convert the recovered H2S to elemental sulfur.

[0065] The H2S-enriched CO2 tail gas can be fed to a selective amine absorption unit at a temperature of about 10 °C to about 70 °C, such as about 50 °C, and a pressure of about 0.05 barg to about 30 barg, such as about 0.05 barg to about 1.8 barg, such as about 0.1 barg.

[0066] For example, conventional selective amine absorption processes using methyldiethanolamine (MDEA) as the selective amine are suitable for use in these embodiments of the present invention.

[0067] The H2S-depleted tail CO2 gas can be fed directly to a compression unit for compression to produce compressed impure CO2. However, in some embodiments, the method involves recovering CO2 and residual H2S from the H2S-depleted CO2 tail gas by non-selective amine absorption to produce an impure CO2 gas containing H2S, along with a waste gas containing CO2 and at least one non-condensable gas.

[0068] The H2S-depleted CO2 tail gas can be fed to a non-selective amine absorption unit at a temperature of about 10 °C to about 70 °C, such as about 50 °C, and a pressure of about 0.01 barg to about 30 barg, such as about 0.01 barg to about 1.8 barg, such as about 0.1 barg.

[0069] Conventional non-selective amine absorption processes using, for example, monoethanolamine (MEA), activated methyldiethanolamine (aMDEA) or diethanolamine (DEA) as the non-selective amine are suitable for use in these embodiments of the present invention.

[0070] Depending on the composition, any waste gas produced in the present invention may be exhausted or fed to a thermal oxidizer, which is combusted to produce flue gas that meets the local emission standards and optionally steam. If the waste gas contains a significant amount of H2, the waste gas itself can be used as fuel or H2 can be recovered from the waste gas.

[0071] As shown above, the purified CO2 may contain sulfur-containing impurities of less than 100 ppm, in which case further purification is typically not required for CCS. However, in embodiments where the amount of impurities exceeds this threshold, typically further purification is required.

[0072] In embodiments where further purification is required, the method may include feeding the purified CO2 to a further purification process to produce further purified CO2 and a second recycle gas containing CO2 and H2, and recycling the second recycle gas, or an H2-enriched gas derived therefrom, to a hydrogenation process. A portion of the second recycle gas, or the H2-enriched gas derived therefrom, is typically purged to prevent the accumulation of H2 (if it is in excess) or non-condensable contaminant gases such as N2 and / or Ar within the process.

[0073] The further purification process for further purifying CO2 may involve distillation such as the process disclosed in US10254042 and / or partial condensation by phase separation such as the process disclosed in US7819951, and the inventors recognize that both of these may be suitably adapted for integration with the present invention.

[0074] Both the distillation and partial condensation of CO2 require temperatures in the range from the critical temperature of CO2 (i.e., about +31 °C) to the triple point temperature of CO2 (i.e., about -57 °C). In some embodiments, the distillation and / or partial condensation by phase separation is carried out at a "low" (or below ambient temperature) temperature, typically in the range of about +15 °C to about -55 °C. In other embodiments, the distillation and / or partial condensation by phase separation is carried out at a temperature in the range of about 0 °C to -30 °C, particularly for the distillation of H2S from CO2.

[0075] The purified CO2 is typically at a temperature of about 10°C to about 70°C, for example, about 50°C, and at a pressure of about 10 barg to about 120 barg, for example, about 30 barg. Thus, in embodiments where further purification is required, the purified CO2 is typically cooled to a suitable temperature as described above, for example, by heat exchange with a refrigerant, before being further purified. Additionally, or alternatively, if the pressure of the gas is not sufficient for further purification, the purified CO2 is further compressed.

[0076] Recycling H2 in the hydrogenation process can reduce the amount of additional H2 that needs to be generated to meet the demand in the process, thereby reducing the size of the required hydrogenation unit or even eliminating it, and thereby saving capital and operating costs. If the demand is only partially met by the recycled H2, additional H2 can be generated in the H2 generation process as discussed above. However, in some embodiments, the amount of H2 recycled to the hydrogenation process is sufficient to meet the H2 demand in the process, completely eliminating the need for the H2 generation process.

[0077] Recycling CO2 to the hydrogenation process increases the overall CO2 recovery. However, for example, it may be desirable or advantageous to reduce the amount of CO2 recycled to the hydrogenation unit in the second recycle gas in order to reduce the size of the hydrogenation unit. In such cases, the method may include recovering H2 gas from the recycle gas fed to the hydrogenation process in a membrane separation process to produce an H2-enriched gas recycled to the hydrogenation unit, along with a waste gas containing CO2 and at least one non-condensable gas.

[0078] Using a conventional membrane separation unit, H2 gas can be recovered from the recycle gas recycled to the hydrogenation process. The membrane can be a spiral type and a hollow fiber membrane made of a polymer such as polysulfone, polyimide, or cellulose acetate. Examples of suitable membrane separation processes are disclosed in US2010 / 126180A, and the inventors recognize that they can be suitably adapted for integration with the present invention.

[0079] In embodiments where the H2S-enriched CO2 tail gas is directly compressed to produce a compressed impure CO2 gas containing H2S, the method comprises feeding the purified CO2 to a further purification process as described above to produce a further purified CO2 and a second recycle gas containing CO2 and H2, and recycling the second recycle gas, or an H2-enriched gas derived therefrom, to the hydrogenation process. A portion of the second recycle gas, or the H2-enriched gas derived therefrom, is typically purged to prevent the accumulation of H2 (if it is in excess), or N2 and / or Ar, within the process.

[0080] As described above, purification by physical separation may be by distillation and / or partial condensation by phase separation.

[0081] In these embodiments, the method typically removes H2 and any non-condensable gas from compressed impure CO2 by distillation and / or partial condensation by phase separation to produce an H2S-enriched CO2 fluid (which may be liquid, gas or two-phase) and an H2-enriched CO2 gas, recycles the H2-enriched CO2 gas, or a further H2-enriched CO2 gas derived therefrom, as a second recycle gas to the hydrogenation process, separates the H2S-enriched CO2 fluid by distillation and / or partial condensation by phase separation to produce purified CO2 as overhead gas and an H2S-enriched bottom liquid, and vaporizes the H2S-enriched bottom liquid to produce an H2S-enriched gas as a first recycle gas. A portion of the second recycle gas, or the H2-enriched gas derived therefrom, is typically purged to avoid accumulation of H2 (if it is in excess), or N2 and / or Ar, within the process.

[0082] As described above, suitable CO2 purification processes in this context are disclosed in US10254042 and US7819951, which the inventors have recognized can be suitably adapted for integration with the present invention.

[0083] In embodiments where the purified CO2 contains at least one residual sulfur-containing impurity, the method further purifies the purified CO2 by selective adsorption or by chemical reaction with at least one solid metal oxide to form a solid metal sulfide, and subsequent oxidative regeneration produces further purified CO2 and a further recycle gas containing at least one sulfur-containing compound, and the further recycle gas may be recycled to the Claus process to convert the sulfur-containing compound to elemental sulfur.

[0084] Alternatively, in embodiments where the purified CO2 overhead gas contains one or more residual sulfur-containing compounds as impurities, the method may include removing H2S and any other sulfur-containing impurities from the purified CO2 overhead gas by selective adsorption or by forming solid metal sulfides by chemical reaction with at least one solid metal oxide and then oxidative regeneration, to produce further purified CO2 and a third recycle gas containing at least one sulfur-containing compound. The third recycle gas may be recycled to a Claus process to convert the sulfur-containing compound to elemental sulfur.

[0085] A second aspect of the invention is an apparatus for desulfurizing a raw CO2 gas typically containing H2S and optionally at least one other sulfur-containing impurity according to the method of the first aspect.

[0086] The apparatus comprises a Claus unit for removing H2S from the raw CO2 gas. The Claus unit comprises a first inlet for an oxidant gas containing O2, a second inlet for the raw CO2 gas, a first outlet for a Claus tail gas containing CO2, residual H2S, and at least one sulfur-containing impurity, and a second outlet for elemental sulfur. An example of a suitable Claus unit is described in US2010 / 0126180A.

[0087] The apparatus also comprises a source of oxidant gas containing O2 in fluid flow communication with the first inlet of the Claus unit. For units operating the "air Claus" process, the source may simply be a blower with a small filter, while for units operating the "oxy Claus" process, the source may be a vacuum swing adsorption (VSA) unit or an air separation unit (ASU), and may optionally be combined with a backup system such as a liquid oxygen tank and vaporizer.

[0088] In addition, the apparatus comprises a source of raw CO2 gas in fluid communication with a second inlet of the Claus unit. Such sources include natural gas "sweetening" units that generate acid gas streams using amine absorption processes / units, membrane separation systems / units and / or cryogenic purification processes / units.

[0089] The apparatus further comprises a hydrogenation unit for converting at least one sulfur-containing impurity in the Claus tail gas to H2S. The hydrogenation unit comprises a first inlet in fluid communication with a first outlet of the Claus unit, a second inlet for H2, and a first outlet for H2S-enriched CO2 tail gas. Examples of suitable hydrogenation units are described in US2010 / 0126180A.

[0090] The apparatus also comprises a source of H2 in fluid communication with the second inlet of the hydrogenation unit. The source may be a unit for generating H2 as described above.

[0091] In addition, the apparatus comprises a cooling unit for cooling the H2S-enriched CO2 tail gas that is separated from or integrated with the hydrogenation unit. The cooling unit comprises a first inlet in fluid communication with the first outlet of the hydrogenation unit, a first outlet for the cooled H2S-enriched CO2 tail gas, and a second outlet for condensed water. The cooling unit may be a heat exchanger using indirect heat exchange with a coolant, but is typically a direct contact cooler including a second inlet for cooling water. The cooling unit may be a separate unit or may be integrated with the hydrogenation unit.

[0092] Furthermore, the apparatus comprises a compression unit for compressing the H2S-enriched CO2 tail gas or impure CO2 gas containing H2S derived therefrom. Thus, the compression unit must be essentially suitable for treating "acid" gases.

[0093] The compression unit comprises an inlet in fluid flow communication with the outlet of the first outlet of the cooling unit, and an outlet for the compressed impure CO2 gas. The compression unit may include one or more centrifugal compressors or reciprocating compressors, and / or may be a multi-stage compressor with associated intercoolers and aftercoolers. In particular, the compression unit may be an integral gear or in-line centrifugal compressor.

[0094] Furthermore, the apparatus comprises a purification unit for removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by physical separation or chemical reaction with a solid metal oxide. The purification unit comprises a first inlet in fluid flow communication with the outlet of the compression unit, a first outlet for the purified CO2, and a second outlet for a first recycle gas containing at least one sulfur-containing compound. The second outlet of the purification unit is in fluid communication with the Claus unit. In this regard, the second outlet may be in fluid flow communication with the second inlet of the Claus unit, or with a third inlet on the Claus unit that is typically dedicated to recycle gas.

[0095] Throughout this specification, the term "in fluid flow communication" is used to appropriately refer to different units (or parts of a unit such as an inlet / outlet) connected by conduits, pipes, and / or ducts in such a way as to allow the flow of fluid, e.g., gas, between the units. This term is intended to include associated flow control devices such as sensors and / or valves necessary to ensure the operational control of the apparatus. Unless otherwise stated, this term is intended to cover both direct and indirect fluid flow communication. "Direct" fluid (or gas) flow communication means that no other fluid (or gas) treatment unit (excluding flow control devices) is provided in the line between the units so connected. "Indirect" fluid (or gas) flow communication should be interpreted accordingly, i.e., one or more other fluid (or gas) treatment units are provided in the line between the units so connected.

[0096] In some embodiments, the apparatus comprises a H2 generation unit including an outlet for H2 in fluid communication with a second inlet of the hydrogenation unit.

[0097] The purification unit in some embodiments is or includes a selective adsorption unit including at least one vessel having an upstream end and a downstream end, said or each vessel including an adsorbent bed including at least one layer of an adsorbent material selective for sulfur-containing compounds, a first inlet for compressed impure CO2 gas at the upstream end of said or each vessel, a first outlet for purified CO2 at the downstream end of said or each vessel, a second inlet for a regeneration gas at the downstream end of said or each vessel, and a second outlet for spent regeneration gas at the upstream end of said or each vessel. The first inlet is in fluid flow communication with the outlet of the compression unit, and the second outlet is in fluid flow communication with the Claus unit. In this regard, the second outlet may be in fluid flow communication with the second inlet of the Claus unit or, typically, a third inlet on the Claus unit dedicated to recycle gas.

[0098] In other embodiments, the purification unit includes a reactor including at least one vessel having an upstream end and a downstream end. Said or each vessel includes a bed including at least one solid metal oxide, a first inlet for compressed impure CO2 gas at the upstream end of said or each vessel, a first outlet for purified CO2 at the downstream end of said or each vessel, a second inlet for a regeneration gas at the downstream end of said or each vessel, and a second outlet for spent regeneration gas at the upstream end of said or each vessel. The first inlet is in fluid flow communication with the outlet of the compression device, and the second outlet is in fluid flow communication with the Claus unit. In this regard, the second outlet may be in fluid flow communication with the second inlet of the Claus unit or, typically, a third inlet on the Claus unit dedicated to recycle gas.

[0099] The inventors recognize that examples of suitable reactors that can be adapted for integration with these embodiments are disclosed in US4797268.

[0100] The bed in the respective or each vessel of the selective adsorption unit or reactor may include at least one layer of an adsorbent material selective for water downstream of at least one layer of an adsorbent material selective for sulfur-containing compounds or solid metal oxides, respectively.

[0101] Alternatively, the purification unit may include a separate dryer unit downstream of any of the selective adsorption units of the reactor. The dryer unit may be an adsorption unit such as a further selective adsorption unit or a glycol unit. In any case, the dryer unit typically and suitably comprises an inlet in fluid communication with the first outlet of the selective adsorption unit or reactor, and an outlet for the dried and purified CO2.

[0102] In some embodiments, the apparatus comprises a selective amine absorption unit for recovering H2S from the H2S-enriched CO2 tail gas. The selective amine absorption unit typically comprises an inlet in fluid flow communication with the first outlet of the cooling unit, a first outlet for the H2S-depleted CO2 tail gas, and a second outlet for the recovered gas containing H2S in fluid flow communication with the Claus unit. In this regard, the second outlet may be in fluid flow communication with the second inlet of the Claus unit or, typically, a third inlet on the Claus unit dedicated to recycle gas. An example of a suitable selective amine absorption unit that the inventors have recognized as being adaptable for use in this context is disclosed in WO93 / 10883A.

[0103] In some embodiments, the first outlet of the selective amine absorption unit is in direct fluid flow communication with the inlet of the compression unit.

[0104] In other embodiments, the apparatus may further include a non-selective amine absorption unit for recovering CO2 and residual H2S from the H2S-deficient CO2 tail gas. The non-selective amine absorption unit typically has an inlet in fluid flow communication with a first outlet of the selective amine absorption unit, a first outlet for the impure CO2 gas, and a second outlet for the waste gas containing CO2 and at least one non-condensable gas. This apparatus usually comprises an exhaust port for the waste gas, and optionally, a thermal oxidizer having an inlet in fluid flow communication with the second outlet of the non-selective amine absorption unit and an outlet for the exhaust gas in fluid communication with the atmosphere via a vent.

[0105] Even after passing through the selective adsorption unit or reactor as described above, in embodiments of the present invention where the content of sulfur-containing impurities in the purified CO2 gas still exceeds a required threshold, for example, 100 ppm, the apparatus may further comprise a further purification unit such as a distillation unit and / or a partial condensation by a phase separation unit (or CPU) for further purifying the purified CO2.

[0106] In these embodiments, the further purification unit comprises an inlet for the purified CO2 in fluid flow communication with a first outlet of the purification unit, a first outlet for the further purified CO2, a second outlet for the second recycle gas containing CO2 and H2 in fluid flow communication with either a hydrogenation unit and / or a Claus unit, and a purge line in fluid flow communication with the second outlet of the further purification unit.

[0107] In these and other embodiments involving the use of additional purification units, the second outlet of the additional purification unit may be in fluid flow communication with the first or second inlet of the hydrogenation unit, or with the third inlet of the hydrogenation unit, which is typically dedicated to recycle gas. The second outlet of the CPU may additionally or alternatively be in fluid communication with the first or second inlet of the Claus unit, or with the third inlet on the Claus unit, which is typically dedicated to recycle gas. Further, the purge line may be in direct fluid communication with an exhaust to the atmosphere or with a thermal oxidizer. Alternatively, the fluid from the purge line may be used as fuel or for H2 recovery.

[0108] The inventors recognize that the CPU described in FIG. 1B of US10254042 can be used (after suitable adaptation) as an additional purification unit of the present invention.

[0109] These embodiments may further include a membrane separation unit for recovering H2 gas from the second recycle gas. The membrane separation unit typically comprises an inlet for the second recycle gas that is in fluid flow communication with the second outlet of the additional purification unit, a first outlet for the H2-enriched gas that is in direct fluid flow communication with the hydrogenation unit and / or the Claus unit, and a second outlet for the waste gas containing CO2 and at least one non-condensable gas.

[0110] These embodiments of the apparatus typically optionally include an exhaust for the waste gas, together with a thermal oxidizer comprising an inlet that is in fluid flow communication with the second outlet of the membrane separation unit and an outlet for the exhaust gas that is in fluid communication with the exhaust.

[0111] In addition, the second outlet of the membrane separation unit may be in fluid flow communication with the second inlet of the hydrogenation unit and / or the Claus unit, or with the third inlet of the hydrogenation unit and / or the Claus unit, which is typically dedicated to recycle gas. In this regard, excess H2 can be supplied to the Claus unit for combustion / disposal if not needed elsewhere.

[0112] In other embodiments, the first outlet of the hydrogenation unit is in direct fluid flow communication with the inlet of the compression unit.

[0113] In these embodiments, the apparatus may further include an additional purification unit for further purifying the purified CO2. The additional purification unit typically has an inlet for the purified CO2 that is in fluid flow communication with the first outlet of the purification unit, a first outlet for the further purified CO2 that is in fluid flow communication with the hydrogenation unit, and a second outlet for a second recycle gas containing CO2 and H2, and a purge line that is in fluid flow communication with the second outlet of the additional purification unit. The second outlet of the additional purification unit may be in fluid flow communication with the inlet of the hydrogenation unit (and / or the Claus unit), or typically with the inlet of the hydrogenation unit (and / or the Claus unit) dedicated to recycle gas.

[0114] These embodiments may further include a membrane separation unit for recovering H2 gas from the second recycle gas. The membrane separation unit typically has an inlet for the second recycle gas that is in fluid flow communication with the second outlet of the additional purification unit, a first outlet for the H2-enriched gas that is in direct fluid flow communication with the hydrogenation unit, and a second outlet for the waste gas containing CO2 and at least one non-condensable gas. The H2-enriched gas is typically taken from the permeate side of the membrane, and the waste gas is typically taken from the residue side of the membrane.

[0115] These embodiments of the apparatus typically, optionally, include an exhaust port for the waste gas, together with a thermal oxidizer having an inlet that is in fluid flow communication with the second outlet of the membrane separation unit and an outlet for the exhaust gas that is in fluid communication with the exhaust port.

[0116] In addition, the second outlet of the membrane separation unit may be in fluid flow communication with the second inlet of the hydrogenation unit and / or the Claus unit, or typically with a third inlet on the hydrogenation unit and / or the Claus unit dedicated to recycle gas.

[0117] In some embodiments, the apparatus comprises a non-selective amine absorption unit for recovering CO2 and H2S from H2S-enriched CO2 tail gas. The non-selective amine absorption unit comprises an inlet in direct fluid flow communication with the outlet of the cooling unit, a first outlet for impure CO2 gas in direct fluid flow communication with the inlet of the compression unit, and a second outlet for waste gas comprising CO2 and at least one non-condensable gas. These embodiments of the apparatus typically, optionally, comprise a thermal oxidizer having an inlet in fluid flow communication with the second outlet of the membrane separation unit and an outlet for exhaust gas in fluid communication with the exhaust port, and an exhaust port for waste residue gas.

[0118] The purification unit can be a single-stage unit. In these embodiments, the purification unit comprises an inlet for compressed impure CO2 in fluid flow communication with the outlet of the compression unit, a first outlet for H2S-enriched CO2 fluid, and a second outlet for H2-enriched CO2 gas in fluid flow communication with the inlet of the hydrogenation unit (and / or the inlet of the Claus unit).

[0119] In these embodiments, the apparatus can further comprise a selective adsorption unit comprising at least one container having an upstream end and a downstream end, wherein the or each container comprises an adsorbent bed, the adsorbent bed comprising at least one layer of an adsorbent material selective for sulfur-containing compounds, a first inlet for H2S-enriched CO2 fluid at the upstream end of the or each container, a first outlet for purified CO2 at the downstream end of the or each container, a second inlet for regeneration gas at the downstream end of the or each container, and a second outlet for used regeneration gas at the upstream end of the or each container. The first inlet of the selective adsorption container is in fluid flow communication with the first outlet of the single-stage purification unit, and the second outlet is in fluid flow communication with the Claus unit.

[0120] Alternatively, the apparatus may comprise a reactor including at least one vessel having an upstream end and a downstream end, said or each vessel comprising a bed including at least one solid metal oxide, a first inlet for a H2S-enriched CO2 fluid at said upstream end of said or each vessel, a first outlet for purified CO2 at said downstream end of said or each vessel, a second inlet for a regeneration gas at said downstream end of said or each vessel, and a second outlet for spent regeneration gas at said upstream end of said or each vessel. The first inlet of the reactor is in fluid flow communication with the first outlet of the single-stage purification unit, and the second outlet is in fluid flow communication with the Claus unit.

[0121] In yet a further embodiment of the apparatus, the purification unit includes a first stage, e.g., a CPU, and a second stage, e.g., a distillation unit.

[0122] The first stage includes an inlet for compressed impure CO2 that is in fluid flow communication with the outlet of the compression unit, a first outlet for a H2S-enriched CO2 fluid, and a second outlet for a H2-enriched CO2 gas that is in fluid flow communication with the inlet of the hydrogenation unit (and / or, the inlet of the Claus unit).

[0123] The second stage includes an inlet for a H2S-enriched CO2 fluid that is in fluid flow communication with the first outlet of the first stage, a first outlet for purified CO2 gas, and a second outlet for a H2S-enriched gas that is in fluid flow communication with the third inlet of the Claus unit. These embodiments of the apparatus further include a purge line that is in fluid flow communication with the second outlet of the first stage of the purification unit.

[0124] The inventors recognize that FIG. 2 of US10254042 depicts an integrated first and second stage configuration that would be suitable for use as a purification unit according to these embodiments of the present invention.

[0125] These embodiments may further include a membrane separation unit for recovering H2 gas from the H2-enriched CO2 gas. The membrane separation unit typically has an inlet for the H2-enriched CO2 gas in fluid flow communication with a second outlet of a first stage of the purification unit, a first outlet for the H2-enriched gas in direct fluid flow communication with an inlet of the hydrogenation unit (and / or an inlet of the Claus unit), and a second outlet for the waste gas containing CO2 and at least one non-condensable gas.

[0126] These embodiments of the apparatus typically optionally include a thermal oxidizer having an inlet in fluid flow communication with the second outlet of the membrane separation unit and an outlet for the exhaust gas in fluid communication with an exhaust port, and include an exhaust port for the waste gas.

[0127] In addition, the second outlet of the membrane separation unit may be in fluid flow communication with a second inlet of the hydrogenation unit and / or the Claus unit, or a third inlet on the hydrogenation unit and / or the Claus unit that is typically dedicated to recycle gas.

[0128] If the amount of sulfur-containing components in the purified CO2 gas still exceeds a required threshold value, such as 100 ppm, these embodiments may further include a further purification unit selected from the selective adsorption unit as described above and a reactor including a bed of solid metal oxides.

[0129] The selective adsorption unit in this context typically comprises at least one container having an upstream end and a downstream end. The said or each container comprises an adsorbent bed including at least one layer of an adsorbent material selective for sulfur-containing compounds, a first inlet for purified CO2 at the upstream end of the said or each container, a first outlet for further purified CO2 at the downstream end of the said or each container, a second inlet for the regeneration gas at the downstream end of the said or each container, and a second outlet for the spent regeneration gas at the upstream end of the said or each container. In these embodiments, the first inlet of the further purification unit is in fluid flow communication with the first outlet of the second stage of the purification unit, and the second outlet is in fluid flow communication with the Claus unit. In this regard, the second outlet of the said or each container may be in fluid flow communication with the second inlet of the Claus unit or a third inlet on the Claus unit which is typically dedicated to recycle gas.

[0130] The reactor unit in this context typically comprises at least one container having an upstream end and a downstream end. The said or each container comprises a bed including at least one solid metal oxide, a first inlet for compressed impure CO2 gas at the upstream end of the said or each container, a first outlet for purified CO2 at the downstream end of the said or each container, a second inlet for the regeneration gas at the downstream end of the said or each container, and a second outlet for the spent regeneration gas at the upstream end of the said or each container. Additionally, the first inlet of the further purification unit is in fluid flow communication with the first outlet of the second stage of the purification unit, and the second outlet is in fluid flow communication with the Claus unit. In this regard, the second outlet of the said or each container may be in fluid flow communication with the second inlet of the Claus unit or a third inlet on the Claus unit which is typically dedicated to recycle gas.

[0131] Referring now to FIG. 1, a stream 100 of raw CO2 gas containing H2S is withdrawn from the acid gas recovery unit 4 and supplied to a Claus unit 6 where the H2S is converted to a stream 102 of elemental sulfur. Using a stoichiometric amount of oxygen from an air stream 101, sufficient H2S in the raw CO2 gas feed is oxidized to produce a mixture of H2S and SO2 in the appropriate ratio for reaction to produce elemental sulfur. The Claus unit 6 typically converts 92 to 99.5 mole % of the H2S in the raw CO2 gas feed to elemental sulfur, depending on the type of Claus process. Residual sulfur compounds exit the Claus unit 6 in a stream 103 of Claus tail gas containing CO2 that is supplied to a tail gas treatment unit 14 that includes a hydrogenation unit 16 and a selective amine absorption unit 20.

[0132] The residual sulfur compounds are converted to H2S in the hydrogenation unit 16 in the presence of H2 gas generated in the reducing gas generation unit 18 to produce a stream 104 of H2S-enriched CO2 tail gas, which is quenched with water in a direct contact cooler (shown as integrated with the hydrogenation unit - see the stream (of water) exiting the hydrogenation unit 16) and then supplied to the selective amine absorption unit 20 where it selectively absorbs H2S to produce a stream 105 of H2S-depleted CO2 tail gas, recovering H2S that is recycled as part of stream 110 to the Claus unit 6. The H2S-depleted CO2 tail gas from the tail gas treatment unit 14 contains primarily CO2, N2, H2 and small amounts of sulfur compounds and is saturated with water.

[0133] In the absence of a CO2 capture unit, stream 105 is typically oxidized in a thermal oxidizer. However, in this case, the CO2 is intended for capture and storage.

[0134] The H2S-deficient CO2 tail gas 105 from the tail gas treatment unit 14 is supplied to the non-selective amine absorption unit 26, where most of the CO2 and sulfur compounds are non-selectively captured and recovered, and depending on its composition, is either directly vented before being exhausted or, together with water supplied to the thermal oxidizer 42, forms a stream 107 of impure CO2 gas together with a stream 115 of waste gas containing CO2 and non-condensable gases, N2 and H2.

[0135] Stream 107 is mainly CO2 but contains sulfur compounds that may not be acceptable for CO2 sequestration or further use. Thus, stream 107 is supplied to a compression device 32 where it is compressed to form a stream 108 of compressed impure CO2 gas, which is then purified using a selective adsorption unit (or reactor) 36 according to the present invention to remove sulfur compounds and produce a stream 111 of purified CO2 for sequestration and a stream 109 of spent regeneration gas (or purge gas) containing desorbed sulfur compounds that is recycled to the Claus unit 6.

[0136] Water can be removed from the compressed impure CO2 gas within the selective adsorption unit (or reactor) 36 by including at least one layer of water adsorbent material downstream of the layer of sulfur-selective adsorbent material or a solid metal oxide such as ZnO. Alternatively, the stream 111 of purified CO2 may be supplied to a dryer unit (not shown) before sequestration.

[0137] The flowsheet depicted in Figure 2 is an alternative to the flowsheet depicted in Figure 1. Unless otherwise indicated, common features between the two flowsheets are given the same reference numerals. The following is a discussion of the features that distinguish Figure 1 from Figure 2.

[0138] Instead of air used in Figure 1, the process of Figure 2 uses a stream 101 of O2 or O2-enriched air as the oxidant to supply the Claus unit 6 and convert the amount of H2S required for the Claus reaction to produce elemental sulfur to SO2.

[0139] In addition, the H2S-deficient CO2 tail gas stream 105 is withdrawn from the tail gas treatment unit 14 and supplied directly to the compression device 46 where it is compressed. Water is removed from the compressed gas with one or more intercoolers and / or aftercoolers (not shown). Next, the compressed impure CO2 gas stream 106 is purified using the selective adsorption unit (or reactor) 50 according to the present invention to remove sulfur-containing compounds, producing a purified CO2 gas stream 107 and a spent regeneration gas (or purge gas) stream 109 containing sulfur-containing compounds that is recycled to the Claus unit 6.

[0140] Water can be removed from the compressed impure CO2 gas within the selective adsorption unit (or reactor) 50 by including at least one layer of a water adsorbent material downstream of a layer of a sulfur-selective adsorbent material or a solid metal oxide, such as ZnO. Alternatively, the purified CO2 stream 111 may be supplied to a dryer unit (not shown) prior to isolation.

[0141] Next, the purified CO2 gas stream 107 is supplied to a further purification unit 56 where the CO2 is further purified by distillation and / or partial condensation and phase separation to produce a further purified CO2 stream 111 for isolation or other use and a waste gas stream 108 containing CO2 and H2.

[0142] The stream 108 can be recycled directly to the hydrogenation unit 16. However, it may be desirable to reduce the amount of CO2 recycled to the hydrogenation unit 16. In such cases, the stream 108 can be supplied to a membrane unit 62 for H2 recovery to produce an H2-enriched gas stream 112 and a waste gas stream 115.

[0143] The stream 112 is recycled to the hydrogenation unit 16. Recycling this stream in this way has the advantage of reducing or even eliminating the need for fresh H2 from a reducing gas generation unit (not shown) for supply to the hydrogenation unit 16.

[0144] Depending on its composition, the waste gas stream 115 may be directly exhausted or supplied to the thermal oxidizer 70 before being exhausted.

[0145] The flow sheet depicted in FIG. 3 is a modified version of the flow sheet depicted in FIG. 1 without the selective amine absorption unit 20. Unless otherwise indicated, common features between the two flow sheets are given the same reference numerals. The following is a discussion of the features that distinguish FIG. 1 from FIG. 3.

[0146] The H2S-enriched CO2 tail gas stream 104 is supplied directly from the hydrogenation unit 16 to the non-selective amine absorption unit 26, in which most of the CO2 and sulfur-containing compounds are non-selectively captured and recovered, and depending on its composition, forms an impure CO2 gas stream 107 either directly exhausted before being exhausted or supplied to the waste gas stream 115 supplied to the thermal oxidizer 42.

[0147] The flow sheet depicted in FIG. 4 is a modified version of the flow sheet depicted in FIG. 2 without the selective amine absorption unit 20. Unless otherwise indicated, common features between the two flow sheets are given the same reference numerals. The following is a discussion of the features that distinguish FIG. 2 from FIG. 4.

[0148] In this configuration, the stream 101 of O2 or O2-enriched air for the Claus unit 6 is generated within the air separation unit 72 by either vacuum swing adsorption (VSA) or cryogenic air separation (air separation unit or ASU).

[0149] The impure CO2 tail gas stream 104 is supplied directly from the hydrogenation unit 16 to the compression device 46, compressed to form a compressed impure CO2 gas stream 106, and then supplied to the selective adsorption unit (or reactor) 50, where H2S (optionally, together with water) is removed from the gas.

[0150] In this configuration, sufficient H2 may be recovered within the membrane separation unit 62 and recycled to the hydrogenator 16 so that a reduction gas generator (not shown) need not provide additional H2.

[0151] The flow sheet depicted in FIG. 5 is a modified version of the flow sheet depicted in FIG. 4, where the purification unit includes a selective adsorption unit (or reactor) for further purifying CO2. Unless otherwise indicated, common features between the two flow sheets are given the same reference numerals. The following is a discussion of the features that distinguish FIG. 4 from FIG. 5.

[0152] The purification unit has a first stage and a second stage. With respect to the first stage, a stream 106 of compressed impure CO2 gas is supplied to the first stage 56, where the CO2 is purified, for example, by partial condensation by phase separation to produce an H2S-enriched CO2 liquid, and a waste gas stream 108 containing CO2 and H2 is optionally passed through the membrane separation unit 62 to recover H2 and then recycled to the hydrogenation unit 16.

[0153] A stream 107 of H2S-enriched CO2 liquid (or gas if vaporized) is supplied to the distillation column system 74, where CO2 and H2S are separated in the second stage to produce purified CO2 as overhead gas and an H2S-enriched bottom liquid that is vaporized before being recycled to the Claus unit 6 in stream 110.

[0154] The stream 111 of purified CO2 may be suitable for sequestration. However, if the total amount of sulfur-containing compounds in the purified CO2 is too high, for example, exceeding 100 ppm, the purified CO2 is further purified in the selective adsorption unit (or reactor) 50 to produce a stream 120 of further purified CO2 for sequestration or further use and a stream 118 of spent regeneration gas (or purge gas) containing desorbed sulfur-containing compounds that is recycled to the Claus unit 6.

[0155] The flow sheets depicted in FIGS. 2, 4, and 5 all involve a membrane separation unit 62 for recovering H2 from the waste gas generated in the purification unit. In these embodiments, a purge stream may be taken from the recycle stream 112 to control the accumulation of H2 (if in excess) or N2 and / or Ar during the process.

[0156] The flow sheet depicted in FIG. 6 is a modified version of the flow sheet depicted in FIG. 5, and the purification unit may include a single stage and use a selective adsorption unit (or reactor) to further purify CO2. Unless otherwise indicated, common features between the two flow sheets are given the same reference numbers. The following is a discussion of the features that distinguish FIG. 5 from FIG. 6.

[0157] The purification unit has a single stage (unit 56). A stream 106 of compressed impure CO2 gas is supplied to unit 56, where CO2 is purified, for example, by partial condensation by phase separation or distillation to produce an H2S-enriched CO2 liquid, and a waste gas stream 108 containing CO2 and H2 is optionally passed through a membrane separation unit 62 to recover H2 and then recycled to a hydrogenation unit 16.

[0158] The level of sulfur-containing compounds in the stream 107 of H2S-enriched CO2 gas typically exceeds 2 mol% and is too high for CCS. However, instead of purifying CO2 by distillation (as in FIG. 5), the stream may be supplied from unit 56 to a selective adsorption unit (or reactor) 50 to produce a stream 111 of purified CO2 for isolation or further use and a stream 110 of spent regeneration gas (or purge gas) containing desorbed sulfur-containing compounds that is recycled to a Claus unit 6.

[0159] The flowchart of FIG. 7 depicts how the SUPERCLAUS process and / or the EUROCLAUS process (unit 6*) can be integrated with the tail gas treatment process depicted in FIGS. 1 to 5. In this regard, unit 26** represents the "CCS block", which comprises a specific combination of a selective amine absorption unit, a non-selective amine absorption unit, a compression unit, a selective adsorption unit, a reactor unit, a membrane separation unit and / or a purification unit, as depicted in one of FIGS. 1 to 5. The H2S-containing recycle stream is fed to the Claus unit 6*, the purified CO2 is removed as stream 111, and the waste gas is sent to the thermal oxidizer unit 42 via stream 115.

[0160] Aspects of the invention Aspect 1: A method for the desulfurization of a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, comprising: feeding the crude CO2 gas containing H2S to a Claus process to convert H2S to elemental sulfur in the presence of oxygen (O2) gas, producing a Claus tail gas containing CO2, residual H2S, and at least one other sulfur-containing impurity; feeding the Claus tail gas to a hydrogenation process to convert the at least one other sulfur-containing impurity to H2S in the presence of H2, producing an H2S-enriched CO2 tail gas; cooling the H2S-enriched CO2 tail gas and removing condensed water to produce a cooled H2S-enriched CO2 tail gas; compressing the cooled H2S-enriched CO2 tail gas or an impure CO2 gas containing H2S derived therefrom to produce a compressed impure CO2 gas containing H2S; removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by physical separation or by forming at least one solid metal sulfide by chemical reaction with at least one solid metal oxide and then oxidatively regenerating to produce purified CO2 and a first recycle gas containing at least one sulfur-containing compound; A method comprising recycling the first recycle gas to the Claus process to convert the at least one sulfur-containing compound into elemental sulfur.

[0161] Aspect 2: Generating H2 in a hydrogen production process, And supplying the H2 to the hydrogenation process, the method according to aspect 1.

[0162] Aspect 3: The method according to aspect 1 or 2, wherein the H2S-enriched CO2 tail gas is cooled by direct contact with water.

[0163] Aspect 4: The method according to any one of #1 to #3, wherein as the physical separation, H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 gas by selective adsorption.

[0164] Aspect 5: The selective adsorption is by adsorption on a bed containing at least one adsorbent material selective for sulfur-containing compounds in a selective adsorption unit to remove H2S and any other sulfur-containing compounds in the compressed impure CO2 gas to produce the purified CO2, and after desorbing with a regeneration gas, a spent regeneration gas containing the H2S and any other sulfur-containing compounds is produced as the first recycle gas from the compressed impure CO2 gas, the method according to aspect 4.

[0165] Aspect 6: The method according to aspect 5, wherein the regeneration gas contains an amount of water insufficient to hydrolyze other sulfur-containing compounds.

[0166] Aspect 7: The compressed impure CO2 gas feed to the selective adsorption unit contains water, and the method includes drying the purified CO2 gas downstream of the adsorbent material selective for sulfur-containing compounds, the method according to aspect 5 or 6.

[0167] Aspect 8: The method according to any one of Aspects 1 to 3, wherein H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 gas by the chemical reaction with at least one solid metal oxide to form a solid metal sulfide, which is then regenerated by oxidation.

[0168] Aspect 9: Passing the compressed impure CO2 gas through a bed containing the at least one solid metal oxide in a reactor to convert the metal oxide to a metal sulfide and produce the purified CO2; Regenerating the bed using a regeneration gas containing O2 to produce a spent regeneration gas containing SO2 as the first recycle gas, the method according to Aspect 8.

[0169] Aspect 10: The method according to Aspect 9, wherein the regeneration gas contains an amount of water insufficient to hydrolyze other sulfur-containing compounds.

[0170] Aspect 11: The method according to Aspect 9 or 10, wherein the compressed impure CO2 gas feed to the reactor contains water, and the method includes drying the purified CO2 gas downstream of the bed containing the solid metal oxide.

[0171] Aspect 12: Recovering H2S from the H2S-enriched CO2 tail gas by selective amine absorption to produce an H2S-depleted CO2 tail gas and the recovered H2S; Recycling the recovered H2S to the Claus process to convert the recovered H2S to elemental sulfur, the method according to any one of Aspects 1 to 11.

[0172] Aspect 13: The method according to Aspect 12, including recovering CO2 and residual H2S from the H2S-depleted CO2 tail gas by non-selective amine absorption to produce the impure CO2 gas for compression together with a waste gas containing CO2 and at least one non-condensable gas.

[0173] Aspect 14: The method according to aspect 12, wherein the H2S-deficient CO2 tail gas is directly compressed to produce the compressed impure CO2 gas.

[0174] Aspect 15: supplying the purified CO2 to a further purification process to produce further purified CO2 and a second recycle gas containing CO2 and H2; recycling the second recycle gas, or the H2-enriched gas derived therefrom, to the hydrogenation process; The method according to aspect 14, wherein a part of the second recycle gas, or a part of the H2-enriched gas derived therefrom, is purged.

[0175] Aspect 16: The method according to aspect 15, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the demand in the process.

[0176] Aspect 17: The method according to aspect 15 or 16, comprising recovering H2 gas from the second recycle gas by a membrane separation process to produce the H2-enriched gas together with a waste gas containing CO2 and at least one non-condensable gas.

[0177] Aspect 18: The method according to any one of aspects 1 to 3, wherein the H2S-enriched CO2 tail gas is directly compressed to produce the compressed impure CO2 gas containing H2S.

[0178] Aspect 19: supplying the purified CO2 to a further purification process to produce further purified CO2 and a second recycle gas containing CO2 and H2; recycling the second recycle gas, or the H2-enriched gas derived therefrom, to the hydrogenation process; The method according to any one of aspects 1 to 18, wherein a part of the second recycle gas, or a part of the H2-enriched gas derived therefrom, is purged.

[0179] Aspect 20: The method according to aspect 19, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the demand in the process.

[0180] Aspect 21: The method according to aspect 19 or 20, comprising recovering H2 gas from the second recycle gas in a membrane separation process to produce the H2-enriched gas for recycling, together with a waste gas containing CO2 and at least one non-condensable gas.

[0181] Aspect 22: The method according to any one of aspects 1 to 3, comprising recovering CO2 and residual H2S from the H2S-enriched CO2 tail gas by non-selective amine absorption to produce the impure CO2 gas for compression, together with a waste gas containing CO2 and at least one non-condensable gas.

[0182] Aspect 23: The method according to aspects 1 to 3, wherein the H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 gas by the aforementioned physical separation, by distillation and / or partial condensation by phase separation.

[0183] Aspect 24: The purified CO2 contains at least one residual sulfur-containing impurity, and the method further purifies the purified CO2 by selective adsorption or chemical reaction with at least one solid metal oxide to form a solid metal sulfide, followed by oxidative regeneration to produce further purified CO2 and a further recycle gas containing at least one sulfur-containing compound; and recycling the further recycle gas to the Claus process to convert the sulfur-containing compound to elemental sulfur. The method according to aspect 23.

[0184] Aspect 25: removing H2 and any other non-condensable gas from the compressed impure CO2 gas by distillation and / or partial condensation by phase separation to produce an H2S-enriched CO2 fluid and an H2-enriched CO2 gas; Recycling the H2-enriched CO2 gas, or a further H2-enriched CO2 gas derived therefrom, as a second recycle gas to the hydrogenation process, and Separating the H2S-enriched CO2 fluid by distillation and / or partial condensation by phase separation to produce the purified CO2 as overhead gas and an H2S-enriched bottom liquid, and Vaporizing the H2S-enriched bottom liquid to produce an H2S-enriched gas as the first recycle gas, comprising The method according to aspect 24, wherein a part of the second recycle gas, or a part of the H2-enriched gas derived therefrom, is purged.

[0185] Aspect 26: The method according to aspect 25, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the demand in the process.

[0186] Aspect 27: The method according to aspect 25 or 26, comprising recovering H2 gas from the second recycle gas in a membrane separation process to produce the further H2-enriched CO2 gas for recycling, together with a waste gas containing CO2 and at least one non-condensable gas.

[0187] Aspect 28: The purified CO2 overhead gas contains one or more residual sulfur-containing compounds, and the method Removing H2S and any other sulfur-containing impurities from the purified CO2 overhead gas by selective adsorption or by chemical reaction with at least one solid metal oxide to form a solid metal sulfide and subsequent oxidative regeneration, and producing a third recycle gas containing further purified CO2 and at least one sulfur-containing compound; and recycling the third recycle gas to the Claus process to convert the sulfur-containing compound to elemental sulfur. The method according to aspects 26 to 28.

[0188] Aspect 29: An apparatus for desulfurization of a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, A Claus unit for removing H2S from crude CO2 gas, a first inlet for an oxidant gas containing O2, a second inlet for the crude CO2 gas, a first outlet for Claus tail gas containing CO2, residual H2S, and at least one other sulfur-containing impurity, a second outlet for elemental sulfur, and a Claus unit comprising the same; a source of oxidant gas containing O2 in fluid flow communication with the first inlet of the Claus unit; a source of crude CO2 in fluid flow communication with the second inlet of the Claus unit; a hydrogenation unit for converting the at least one other sulfur-containing impurity in the Claus tail gas to H2S, a first inlet in fluid flow communication with the first inlet of the Claus unit; a second inlet for H2; a first outlet for H2S-enriched CO2 tail gas, and a hydrogenation unit comprising the same; a source of H2 in fluid flow communication with the second inlet of the hydrogenation unit; a cooling unit for cooling the H2S-enriched CO2 tail gas, a first inlet in fluid communication with the first outlet of the hydrogenation unit; a first outlet for the cooled H2S-enriched CO2 tail gas; a second outlet for condensed water, and a cooling unit comprising the same; a compression unit for compressing the cooled H2S-enriched CO2 tail gas or an impure CO2 gas containing H2S derived therefrom, the compression device having an inlet in fluid flow communication with the first outlet of the cooling unit; an outlet for the compressed impure CO2 gas, and a compression unit comprising the same; A purification unit for removing H2S and any other sulfur-containing impurities from compressed impure CO2 gas by physically separating or forming solid metal sulfides by chemical reaction with at least one metal oxide and then oxidatively regenerating, A first inlet in fluid flow communication with the first inlet of the Claus unit, A first outlet for purified CO2, A second outlet for a first recycle gas containing at least one sulfur-containing compound, and comprising, An apparatus comprising a purification unit, wherein the second outlet of the purification unit is in fluid communication with the Claus unit.

[0189] Aspect 30: The apparatus according to aspect 29, wherein the H2 source is an H2 generation unit comprising an outlet for H2 in fluid communication with the second inlet of the hydrogenation unit.

[0190] Aspect 31: The apparatus according to aspect 29 or 30, wherein the cooling unit is a direct contact cooler further comprising a second inlet for cooling water.

[0191] Aspect 32: The purification unit is a selective adsorption unit, At least one container having an upstream end and a downstream end, wherein the or each container is, An adsorbent bed, the adsorbent bed comprising at least one layer of an adsorbent material selective for sulfur-containing compounds, an adsorbent bed, A first inlet for compressed impure CO2 gas at the upstream end of the or each container, A first outlet for purified CO2 at the downstream end of the or each container, A second inlet for a regeneration gas at the downstream end of the or each container, A second outlet for spent regeneration gas at the upstream end of the or each container, and comprising at least one container, The apparatus according to aspect 29, wherein the first inlet of the selective adsorption unit is in fluid flow communication with the outlet of the compression unit, and the second outlet is in fluid flow communication with the Claus unit.

[0192] Aspect 33: The apparatus according to aspect 32, wherein the adsorbent bed in the or each container comprises at least one layer of an adsorbent material selective for water downstream of at least one layer of an adsorbent material selective for sulfur-containing compounds.

[0193] Aspect 34: A dryer unit downstream of the selective adsorption unit, having an inlet in fluid flow communication with the first outlet of the selective adsorption unit, and an outlet for dried and purified CO2 in fluid flow communication with the inlet of the compression unit, the apparatus according to aspect 33 or 34 comprising a dryer unit.

[0194] Aspect 35: The purification unit is a reactor, comprising at least one container having an upstream end and a downstream end, wherein the or each container comprises a bed containing at least one solid metal oxide, a first inlet for compressed impure CO2 gas at the upstream end of the or each container, a first outlet for purified CO2 at the downstream end of the or each container, a second inlet for regeneration gas at the downstream end of the or each container, and a second outlet for used regeneration gas at the upstream end of the or each container, the apparatus comprising at least one container, wherein the first inlet of the reactor is in fluid flow communication with the outlet of the compression device, and the second outlet is in fluid flow communication with the Claus unit, the apparatus according to aspect 29.

[0195] Aspect 36: The apparatus according to aspect 35, wherein the or each container comprises at least one layer of an adsorbent material selective for water downstream of the bed containing the solid metal oxide.

[0196] Aspect 37: A dryer unit downstream of the reactor, An inlet in fluid communication with the first outlet of the reactor, An outlet for the dried and purified CO2 in fluid flow communication with the compression unit, comprising a dryer unit, the apparatus according to aspect 35 or 36.

[0197] Aspect 38: A selective amine absorption unit for recovering H2S from H2S-enriched CO2 tail gas, An inlet in fluid flow communication with the first outlet of the cooling unit, a first outlet for H2S-depleted CO2 tail gas in fluid flow communication with the inlet of the compression unit, A second outlet for the recovered H2S in fluid flow communication with the Claus unit, comprising a selective amine absorption unit, the apparatus according to any one of aspects 29 to 37.

[0198] Aspect 39: A non-selective amine absorption unit for recovering CO2 and residual H2S from H2S-depleted CO2 tail gas, An inlet in fluid flow communication with the first outlet of the selective amine absorption unit, A first outlet for impure CO2 gas in direct fluid flow communication with the inlet of the compression unit, A second outlet for waste gas containing CO2 and at least one non-condensable gas, comprising a non-selective amine absorption unit, the apparatus according to aspect 38.

[0199] Aspect 40: The apparatus according to aspect 38, wherein the first outlet of the selective amine absorption unit is in direct fluid flow communication with the inlet of the compression unit.

[0200] Aspect 41: The purification unit is a selective adsorption unit or a reactor, and the apparatus is A further purification unit for further purifying the purified CO2, An inlet for purified CO2 that is in fluid flow communication with the selective adsorption unit or the first outlet of the reactor, A first outlet for further purified CO2, A further purification unit comprising a second outlet for a second recycle gas containing CO2 and H2 that is in fluid flow communication with the hydrogenation unit, The apparatus according to aspect 40, further comprising a purge line that is in fluid flow communication with the second outlet of the further purification unit.

[0201] Aspect 42: A membrane separation unit for recovering H2 gas from a second recycle gas, comprising An inlet for a second recycle gas that is in fluid flow communication with the second outlet of the further purification unit, A first outlet for an H2-enriched gas that is in direct fluid flow communication with the hydrogenation unit, A second outlet for waste gas containing CO2 and at least one non-condensable gas, the apparatus according to aspect 41, comprising a membrane separation unit.

[0202] Aspect 43: The apparatus according to any one of aspects 29 to 31, wherein the first outlet of the hydrogenation unit is in direct fluid flow communication with the inlet of the compression unit.

[0203] Aspect 44: The purification unit is a selective adsorption unit or a reactor, and the apparatus Is a further purification unit for further purifying the purified CO2, comprising An inlet for purified CO2 that is in fluid flow communication with the first outlet of the selective adsorption unit or the reactor, A first outlet for further purified CO2, A second outlet for a second recycle gas containing CO2 and H2 that is in fluid flow communication with the hydrogenation unit, a further purification unit The apparatus according to aspect 43, further comprising a purge line in fluid flow communication with a second outlet of the further purification unit.

[0204] Aspect 45: A membrane separation unit for recovering H2 gas from a second recycle gas, comprising: An inlet for a second recycle gas in fluid flow communication with a second outlet of the further purification unit; A first outlet for an H2-enriched permeate gas in direct fluid flow communication with the hydrogenation unit; A second outlet for a waste residue gas containing CO2 and at least one non-condensable gas, the apparatus according to aspect 44, comprising a membrane separation unit.

[0205] Aspect 46: A non-selective amine absorption unit for recovering CO2 and residual H2S from an H2S-enriched CO2 tail gas, comprising: An inlet in direct fluid flow communication with an outlet of the cooling unit; A first outlet for an impure CO2 gas in direct fluid flow communication with an inlet of the compression unit; A second outlet for a waste gas containing CO2 and at least one non-condensable gas, the apparatus according to any one of aspects 29 to 31, comprising a non-selective amine absorption unit.

[0206] Aspect 47: The purification unit is a single-stage purification unit, An inlet for compressed impure CO2 in fluid flow communication with an outlet of the compression unit; A first outlet for an H2S-enriched CO2 fluid; A second outlet for an H2-enriched CO2 gas in fluid flow communication with an inlet of the hydrogenation unit, a single-stage hydrogenation unit, The apparatus is a selective adsorption unit, At least one container having an upstream end and a downstream end, wherein the or each container An adsorbent bed comprising at least one layer of an adsorbent material selective for sulfur-containing compounds, A first inlet for the H2S-enriched CO2 fluid at the upstream end of the or each container, A first outlet for the purified CO2 at the downstream end of the or each container, A second inlet for the regeneration gas at the downstream end of the or each container, A second outlet for the spent regeneration gas at the upstream end of the or each container, comprising at least one container, The apparatus according to any one of aspects 29 to 31, wherein the first inlet of the selective adsorption container is in fluid flow communication with the first outlet of the single-stage purification unit, and the second outlet is in fluid flow communication with the Claus unit.

[0207] Aspect 48: The purification unit is a single-stage purification unit, An inlet for compressed impure CO2 in fluid flow communication with the outlet of the compression unit, A first outlet for the H2S-enriched CO2 fluid, A second outlet for the H2-enriched CO2 gas in fluid flow communication with the inlet of the hydrogenation unit, comprising a single-stage purification unit, The apparatus is a reactor, At least one container having an upstream end and a downstream end, wherein the or each container, A bed comprising at least one solid metal oxide, A first inlet for the H2S-enriched CO2 fluid at the upstream end of the or each container, A first outlet for the purified CO2 at the downstream end of the or each container, A second inlet for the regeneration gas at the downstream end of the or each container, A second outlet for the spent regeneration gas at the upstream end of the or each container, comprising at least one container, The apparatus according to any one of aspects 29 to 31, wherein the first inlet of the reactor is in fluid flow communication with the first outlet of the single-stage purification unit, and the second outlet is in fluid flow communication with the Claus unit.

[0208] Aspect 49: The purification unit is in a first stage, wherein the first stage, has an inlet for compressed impure CO2 that is in fluid flow communication with the outlet of the compression unit, a first outlet for H2S-enriched CO2 fluid, and a second outlet for H2-enriched CO2 gas that is in fluid flow communication with the inlet of the hydrogenation unit, and the first stage; a second stage, wherein the second stage, has an inlet for H2S-enriched CO2 fluid that is in fluid flow communication with the first outlet of the first stage, a first outlet for purified CO2 gas, a second outlet for H2S-enriched gas that is in fluid flow communication with the Claus unit, and a purge line that is in fluid flow communication with the second outlet of the first stage of the purification unit, and the second stage, and a purification unit, and the apparatus according to any one of aspects 29 to 31.

[0209] Aspect 50: A membrane separation unit for recovering H2 gas from H2-enriched CO2 gas, having an inlet for H2-enriched CO2 gas that is in fluid flow communication with the second outlet of the first stage of the purification unit, a first outlet for H2-enriched permeate gas that is in direct fluid flow communication with the hydrogenation unit, and a second outlet for waste residue gas containing CO2 and at least one non-condensable gas, and a membrane separation unit, and the apparatus according to aspect 49.

[0210] Aspect 51: A selective adsorption unit, At least one container having an upstream end and a downstream end, wherein the or each container An adsorbent bed comprising at least one layer of an adsorbent material selective for sulfur-containing compounds, A first outlet for purified CO2 at the downstream end of the or each container, A first outlet for purified CO2 at the downstream end of the or each container, A second inlet for a regeneration gas at the downstream end of the or each container, A second outlet for spent regeneration gas at the upstream end of the or each container, comprising at least one container, The apparatus according to aspect 50, wherein the first inlet of the selective adsorption unit is in fluid flow communication with the first outlet of the second stage of the purification unit, and the second outlet is in fluid flow communication with the Claus unit.

[0211] Aspect 52: A reactor, At least one container having an upstream end and a downstream end, wherein the or each container A bed comprising at least one solid metal oxide, A first outlet for purified CO2 at the downstream end of the or each container, A first outlet for purified CO2 at the downstream end of the or each container, A second inlet for a regeneration gas at the downstream end of the or each container, A second outlet for spent regeneration gas at the upstream end of the or each container, comprising at least one container, The apparatus according to aspect 50, wherein the first inlet of the reactor is in fluid flow communication with the first outlet of the second stage of the purification unit, and the second outlet is in fluid flow communication with the Claus unit.

Examples

[0212] Here, specific embodiments of the present invention are illustrated by computer modeling in the following examples.

[0213] Example 1 The process depicted in the flow sheet of Figure 1, where unit 36 is a reactor containing a bed of mixed metal oxides of the type disclosed in US4797268, was computer modeled using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 1. [Table 1]

[0214] This example illustrates that at 100 mol% purity, the overall CO2 recovery rate is 92.5 mol%, i.e., residual H2S (and water) is completely removed from the impure CO2.

[0215] Example 2 The process depicted in the flow sheet of Figure 2, where unit 50 is a reactor having a bed of mixed metal oxides of the type disclosed in US4797268 and unit 56 is a CPU of the type disclosed in US7819951, was computer modeled using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 2. In the model, the purge stream was zero. [Table 2]

[0216] This example illustrates that at 99.5 mol% purity, the overall CO2 recovery rate is 95.8 mol% and the remainder is H2, i.e., residual H2S (and water) is completely removed from the impure CO2.

[0217] Example 3 The process depicted in the flowsheet of Figure 3, where unit 36 is a reactor containing a bed of mixed metal oxides of the type disclosed in US4797268, was modeled computationally using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 3. [Table 3]

[0218] This example illustrates that at 100 mol% purity, the overall CO2 recovery rate is 91.5 mol%, i.e., residual H2S (and water) is completely removed from the impure CO2.

[0219] Example 4 The process depicted in the flowsheet of Figure 4, where unit 50 is a reactor containing a bed of mixed metal oxides of the type disclosed in US4797268, was modeled computationally using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 4. [Table 4]

[0220] This example illustrates that at 99.5 mol% purity, the overall CO2 recovery rate is 95.8 mol% and the remainder is H2, i.e., residual H2S (and water) is completely removed from the impure CO2.

[0221] Example 5 The process depicted in the flowsheet of Figure 5, where the purification units 56 and 74 are of the type disclosed in Figure 2 of US10254042A, was modeled computationally using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 5. [Table 5]

[0222] This example illustrates that the overall CO2 recovery rate is 95.6 mol% with a purity of 99.5 mol%. The product CO2 also contains approximately 0.5 mol% of H2 and 100 ppm or less of H2S, which meets the specification of H2S required for isolation.

[0223] Example 6 The process depicted in the flow sheet of Figure 1, where unit 36 is a selective adsorption unit of the type disclosed in WO2021130530A, was modeled computationally using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 6. [Table 6]

[0224] This example illustrates that the overall CO2 recovery rate is 91.6 mol% with a purity of 100 mol%, i.e., using the selective adsorption unit 36 (including a layer of water adsorbent material), residual H2S (and water) is completely removed from the impure CO2.

[0225] Example 7 The process depicted in the flow sheet of Figure 6, where the purification unit 56 is of the type disclosed in US10254042A, Figure 1B, was modeled computationally using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 7. [Table 7]

[0226] This example illustrates that the overall CO2 recovery rate is 95.3 mol% with a purity of 99.5 mol%. The product CO2 contains less than 0.5 mol% of H2 and no H2S, thus meeting the specification of H2S required for isolation.

[0227] Example 8 The process depicted in the flowchart of FIG. 7 (where unit 26** represents a specific combination of units 26, 32, and 36 from FIG. 1) was computer modeled using Aspen Plus (version 10), and the heat and mass balance data for the important streams are provided in Table 8.

Table 8

[0228] This example illustrates that the overall CO2 recovery rate is 91.6 mol% at a purity of 100 mol%. Thus, the CO2 recovery is less than in other embodiments, but in this embodiment, the purity of CO2 is high.

[0229] It is understood that the present invention is not limited to the details described above with reference to the preferred embodiments, and that numerous modifications and variations can be made without departing from the spirit and scope of the invention as defined by the following claims.

[0230] As used herein, unless expressly specified otherwise, the word "or" is used in the sense of an operator that returns a true value when either or both of the specified conditions are met, as opposed to an "exclusive or" operator that requires only one of the conditions to be met. The word "comprising" is used in the sense of "including" rather than "consisting of".

[0231] All of the foregoing prior teachings are incorporated herein by reference. The approval of a document previously published in this specification does not admit or represent that the teachings were common general knowledge in Australia or elsewhere as of that date.

Claims

1. Hydrogen sulfide (H 2 S) and optionally at least one other sulfur-containing impurity, for desulfurizing a crude carbon dioxide (CO 2 ) gas, a method comprising H 2 Supply crude CO containing S 2 gas to a Claus process to convert H 2 S to elemental sulfur in the presence of oxygen (O 2 ), and produce Claus tail gas containing CO 2 , residual H 2 S, and at least one other sulfur-containing impurity; Feeding the Claus tail gas to a hydrogenation process to convert the at least one other sulfur-containing impurity in the presence of hydrogen (H 2 ), to H 2 S and generating H 2 S-enriched CO 2 tail gas; Said H 2 S-enriched CO 2 Cool the tail gas, remove the condensed water, and generate cooled H 2 S-enriched CO 2 tail gas; and The cooled H 2 S-enriched CO 2 tail gas, or impure CO containing H 2 S derived therefrom 2 is compressed to produce a compressed impure CO 2 gas containing H 2 S, and forming at least one solid metal sulfide by physical separation or by chemical reaction with at least one solid metal oxide and then oxidatively regenerating to remove H 2 S and any other sulfur-containing impurities from the compressed impure CO 2 gas to produce purified CO 2 and a first recycle gas containing at least one sulfur-containing compound; Recycling the first recycle gas to the Claus process to convert the at least one sulfur-containing compound to elemental sulfur. A method comprising.

2. Generate H in the hydrogen generation process 2 and The aforementioned H 2 is supplied to the hydrogenation process, and The H 2 S-enriched CO 2 CO from tail gas 2 and H 2 S is recovered and the impure CO 2 Gas, CO 2 and producing a waste gas comprising at least one non-condensable gas.

3. The above-mentioned H 2 S-enriched CO 2 directly compresses the tail gas to generate the compressed impure CO 2 containing S, the method according to claim 1. 2 gas.

4. The purified CO 2 is supplied to a further purification unit to produce further purified CO 2 and a second recycle gas containing CO 2 and H 2 and generating the second recycle gas containing CO and H Said second recycle gas, or H derived therefrom 2 Recycling the enriched gas to the hydrogenation process, and Recovering H gas from the second recycle gas in the membrane separation process and recycling the H-enriched gas to the hydrogenation process, and generating the H-enriched gas together with waste gas containing CO and at least one non-condensable gas. 2 gas and recycling it to the hydrogenation process, the H-enriched gas 2 is generated together with waste gas containing CO 2 and at least one non-condensable gas. A part of the second recycle gas or the H derived therefrom 2 The method according to claim 1, wherein a part of the enriched gas is purged.

5. By selective amine absorption, the H 2 S-enriched CO 2 Recover H from the tail gas 2 S to obtain H 2 S-deficient CO 2 Tail gas and the recovered H 2 S are produced, and The recovered H 2 S is recycled to the Claus process to convert the recovered H 2 S into elemental sulfur, and The H by non-selective amine absorption 2 S-deficient CO 2 CO from the tail gas 2 and residual H 2 S are recovered, and the impure CO for compression 2 gas is generated together with the waste gas containing CO 2 and at least one non-condensable gas, The refined CO 2 is supplied to a further purification unit to produce further refined CO 2 and a second recycle gas containing CO 2 and H 2 and to generate the same. Said second recycle gas, or H derived therefrom 2 Recycling the enriched gas to the hydrogenation process, and Recovering H gas from the second recycle gas in the membrane separation process, and generating the H enriched gas together with the waste gas containing CO and at least one non-condensable gas. 2 gas, and 2 the H enriched gas is further generated together with the waste gas containing CO 2 and at least one non-condensable gas. Said H 2 S-deficient CO 2 tail gas is directly compressed to produce said compressed impure CO 2 gas, and a part of said second recycle gas, or said H derived therefrom 2 A method according to claim 1, wherein a part of the enriched gas is purged.

6. forming a solid metal sulfide by said chemical reaction with at least one solid metal oxide and then oxidatively regenerating it, whereby H 2 S and any other sulfur-containing impurities are removed from said compressed impure CO 2 gas, the method according to claim 1.

7. the purified CO downstream of the adsorbent material selective for sulfur-containing compounds 2 further comprising drying The recycled gas contains an insufficient amount of water to hydrolyze other sulfur-containing compounds, and the compressed impure CO to the selective adsorption unit 2 The gas feed contains water, and H 2 S and any other sulfur-containing impurities are removed from the compressed impure CO by selective adsorption as the physical separation 2 gas, and the selective adsorption is by adsorption on a bed containing at least one adsorbent material selective for sulfur-containing compounds in a selective adsorption unit, of the compressed impure CO 2 H in the gas 2 S and any other sulfur-containing compounds are removed to produce the purified CO 2 After desorbing with the recycled gas, the compressed impure CO 2 H from the gas 2 The method according to claim 1, comprising producing the used recycled gas containing S and any other sulfur-containing compounds as the first recycle gas

8. H 2 S and any other sulfur-containing impurities convert the impure CO 2 gas by passing it through a bed containing the at least one solid metal oxide in the reactor to convert the at least one solid metal oxide to at least one metal sulfide and produce the purified CO 2 thereby. O 2 Regenerating the bed using a regeneration gas containing, and producing a spent regeneration gas containing sulfur dioxide (SO 2 ), thereby removing from the compressed impure CO 2 gas, the method according to claim 1.

9. The method according to claim 8, wherein the recycle gas contains an amount of water insufficient to hydrolyze other sulfur-containing compounds.

10. the purified CO downstream of the bed comprising the at least one solid metal oxide 2 further comprising drying the gas, wherein the compressed impure CO gas feed to the reactor 2 contains water, the method according to claim 8.

11. A method comprising Compressed impure CO 2 Remove H and any other non-condensable gas from the gas by distillation and / or partial condensation by phase separation to obtain 2 H 2 S-enriched CO 2 fluid and H 2 enriched CO 2 gas, and Said H 2 Enriched CO 2 gas, or further H 2 enriched CO 2 gas is recycled as a second recycle gas to the hydrogenation process, and By partial condensation by distillation and / or phase separation, the H 2 S-enriched CO 2 fluid is separated to produce purified CO as overhead gas 2 and H 2 S-enriched bottom liquid The above-mentioned H 2 vaporize the H2S-enriched bottom liquid to produce an H2S-enriched gas as the first recycle gas, and 2 include A part of the second recycle gas or the H derived therefrom 2 A method in which a part of the enriched gas is purged.

12. Recovering H from the second recycle gas in a membrane separation process and, together with the waste gas containing CO and at least one non-condensable gas, generating the further H-enriched CO gas for recycling, the method according to claim 11, further comprising. 2 gas and recovering the CO 2 and, together with the waste gas containing at least one non-condensable gas, the further H for recycling 2 enriched CO 2 gas, the method according to claim 11, further comprising.

13. The refined CO 2 The method according to claim 11, wherein the overhead gas contains one or more residual sulfur-containing compounds.

14. By selective adsorption or by forming a solid metal sulfide by chemical reaction with at least one solid metal oxide and then oxidatively regenerating it, H 2 S and any other sulfur-containing impurities are removed from the purified CO 2 overhead gas to produce a further purified CO 2 and a third recycle gas containing at least one sulfur-containing compound; The method according to claim 1138, further comprising recycling the third recycle gas to a Claus process to convert the sulfur-containing compound to elemental sulfur.

15. A system comprising Coarse CO 2 A Claus unit for removing H 2 S from gas, O 2 a first inlet for an oxidizing gas containing said crude CO 2 a second inlet for the gas, CO 2 and residual H 2 S, and a first outlet for Claus tail gas containing at least one other sulfur-containing impurity, A Claus unit comprising a second outlet for elemental sulfur; O that is in fluid flow communication with the first inlet of the Claus unit 2 a source of oxidant gas including, A source of raw CO that is in fluid flow communication with the second inlet of the Claus unit 2 and, A hydrogenation unit for converting the at least one other sulfur-containing impurity in the Claus tail gas to H 2 S, comprising A first inlet in fluid flow communication with the first inlet of the Claus unit; H 2 a second inlet for H 2 S-enriched CO 2 a hydrogenation unit comprising a first outlet for tail gas, and A source of H in fluid flow communication with the second inlet of the hydrogenation unit 2 and, H 2 S-enriched CO 2 A cooling unit for cooling tail gas, A first inlet in fluid communication with the first outlet of the hydrogenation unit; Cooled H 2 S-enriched CO 2 a first outlet for tail gas, and A cooling unit comprising a second outlet for condensed water; Cooled H 2 S-enriched CO 2 Tail gas, or impure CO containing H 2 S derived therefrom 2 A compression unit for compressing the gas, wherein the compression device An inlet in fluid flow communication with the first outlet of the cooling unit; Compressed Impure CO 2 a compression unit comprising an outlet for the gas, and A purification unit for removing H 2 S and any other sulfur-containing impurities from compressed impure CO 2 gas by forming a solid metal sulfide by physical separation or by chemical reaction with at least one metal oxide and then oxidatively regenerating it A first inlet in fluid flow communication with the outlet of the compression unit; Purified CO 2 for a first outlet, and A purification unit comprising a second outlet for a first recycle gas containing at least one sulfur-containing compound; and A system wherein the second outlet of the purification unit is in fluid communication with the Claus unit.

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