Desulfurization of carbon dioxide-containing gases

Abstract

Sulfur-containing compounds are removed from the crude CO2 by conversion to elemental sulfur in the Claus process and subsequent by hydrogenation of the Claus off-gas to convert residual sulfur-containing compounds to H2S, after cooling separation of water and subsequent compression, solid metal sulfides are formed by physical separation or by chemical reaction with solid metal oxides, followed by oxidative regeneration to remove H2S along with any other sulfur-containing impurities, producing purified COz and a recycle gas comprising at least one sulfur-containing compound, which recycle gas is recycled to the Claus process. Some of the H2S in the Claus tail gas may be first removed by selective and / or non-selective amine absorption in a tail gas treatment unit prior to removal of residual H2S and any other residual sulfur-containing impurities by the physical separation or chemical reaction step.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional patent application No. 17 / 856,455, filed on July 1, 2022. Background Art

[0003] The present invention is in the field of recovery and purification of carbon dioxide (CO2). In particular, the present invention relates to a method and apparatus for desulfurizing a CO2-containing stream for carbon capture and storage ("CCS").

[0004] There are many examples in the art of methods for removing sulfur-based compounds such as hydrogen sulfide (H2S), carbonyl sulfide (COS), mercaptans (i.e., mercaptan groups), carbon disulfide (CS2) and / or sulfur oxides (SOx) from crude CO2 or other CO2-containing gases.

[0005] GB871750 relates to a method in which H2S is removed from a CO2-containing gas produced by the combustion of hydrocarbons or in a blast furnace. Such gases typically contain up to 400ppm of H2S. Since CO2 is mainly used for the synthesis of urea, the amount of H2S must be reduced to no more than 2ppm. The reference teaches that the amount of H2S in the CO2 gas is reduced to the necessary level by passing the gas through a zeolite layer that has been activated by heating to remove the water of crystallization. The zeolite is activated by driving out this water to produce lattice gaps of a size that can adsorb H2S. The gas fed to the zeolite can be dried or undried, and the zeolite can be thermally regenerated using heated regeneration gas.

[0006] US5674463A relates to a method for purifying CO2 obtained from natural sources such as natural gas or produced in industry, particularly by the combustion of hydrocarbon products, for use in applications requiring high purity CO2, such as the manufacture of food or medical products. The reference teaches the removal of COS and H2S from CO2 gas by first contacting the CO2 with water vapor in the presence of a hydrolysis catalyst such as activated alumina to convert COS in the gas to H2S, and then converting the H2S in the resulting gas using an oxidation catalyst such as iron oxide to form elemental sulfur and metal sulfides, which are then removed from the gas. Any residual sulfur compounds may be removed by contacting the remaining gas with copper oxide, zinc oxide, or a mixed copper-zinc oxide.

[0007] US2012 / 0012000A is generally concerned with separating a sour (i.e., sulfur-containing) synthesis gas comprising hydrogen (H2) and carbon monoxide (CO) as well as H2S and CO2 obtained from the gasification of a solid or liquid carbonaceous feedstock into at least a CO2 product stream suitable for geological storage, a synthesis gas (H2 / CO) product stream suitable for use in a chemical plant or refinery or as a gas turbine fuel, and an H2S-rich stream that can be further processed in, for example, a Claus unit or other suitable sulfur recovery system. The reference teaches introducing the sour synthesis gas into a pressure swing adsorption (PSA) system that separates the feed gas into a synthesis gas product stream and a stream rich in CO2 and H2S, or separating a H2S-depleted feed gas (produced in a sour-PSA system) into a synthesis gas product stream and a CO2-rich gas stream. The sour-PSA system contains an H2S-selective adsorbent, such as silica gel, activated carbon, or a molecular sieve.

[0008] WO2016 / 075109A discloses a method for removing H2S equivalents such as COS and / or CS2 by adsorption from a Claus tail gas containing CO2. The tail gas containing H2S equivalents and CO2 is fed to an adsorption system in which the tail gas is contacted with an alumina-based adsorbent material to produce a first product gas rich in CO2. The adsorbent material is regenerated using 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 the Claus unit. Optionally, the purged adsorbent material is then dried.

[0009] However, there is still a need for new methods and apparatus for desulfurizing CO2-containing streams, particularly in cases where the CO2 is intended to be used for CCS in view of low maximum limits for sulfur-containing compounds (eg, not more than 100 ppm total). Summary of the invention

[0010] The present invention relates to a method for desulfurizing a gas stream containing CO2. Such streams are typically byproducts of crude oil refining or other industrial processes involving physical and chemical gas treatment units used in refineries, natural gas processing plants and gasification or synthesis gas plants, and may be referred to as "sour" gas streams. These "sour" gases will contain H2S as an impurity, usually (but not always) together with one or more of CS2, COS and mercaptans.

[0011] Such gases are typically treated in the Claus process, which recovers elemental sulfur from gaseous H2S in the presence of O2 according to the following overall reaction:

[0012] 2H2S+3O2→2SO2+2H2O

[0013] 4H2S+2SO2→3S2+4H2O

[0014] The Claus process can involve either a thermal process or a catalytic process, but typically involves a combination of both thermal and catalytic processes to increase the overall sulfur yield. In the thermal process, gaseous H2S reacts in a substoichiometric combustion at temperatures above 850°C to produce elemental sulfur and water. In the catalytic process, gaseous H2S reacts with SO2 over a catalyst such as activated aluminum (III) or titanium (IV) oxide to produce additional elemental sulfur and water.

[0015] Most commercial Claus processes involve a thermal stage followed by one or more catalytic stages, with sulfur removed between stages by condensers. The first stage is typically operated at about 315°C to about 330°C to aid in the hydrolysis of COS and CS2. Although above the dew point of sulfur, subsequent stages are typically operated at lower temperatures to increase catalytic conversion. Thus, the second stage may be operated at about 240°C, while the third stage may be operated at about 200°C. O2 may be provided to the Claus process in the form of air, i.e., an "air-Claus" process, or in the form of pure O2 or O2-enriched air, i.e., an "oxygen-Claus" process.

[0016] The inventors have realised that any sulphur-containing compounds other than H2S (such as COS, CS2 and mercaptans from the raw "sour" gas) can be removed from the tail gas together with the SO2 from the Claus process by hydrogenation to form H2S, which can then be removed together with the residual H2S from the Claus process by physical separation or by chemical reaction with at least one solid metal oxide to form a metal sulphide and subsequent oxidative regeneration to produce purified CO2 and a recycle gas comprising at least one sulphur-containing compound which is recycled to the Claus process.

[0017] Physical separation of H2S and any other sulfur-containing compounds from CO2 can be achieved by:

[0018] (i) the selective adsorption of sulphur-containing compounds on an adsorbent material which is selective for such compounds - the adsorption is purely physical in that the compounds in question are not converted by chemical reaction with the adsorbent material, so that when the adsorbent is regenerated to remove the adsorbed compounds, the spent regeneration gas contains impurities from the impure gas fed to the adsorbent; or

[0019] (ii) Distillation and / or partial condensation with phase separation.

[0020] H2S and any other sulfur-containing compounds can be optionally removed from the impure CO2 gas by reacting with a bed containing at least one solid metal oxide, such as zinc oxide (ZnO), to convert the metal oxide into a metal sulfide, such as zinc sulfide (ZnS). The metal oxide can be regenerated by oxidation using a regeneration gas containing O2, driving the sulfur out of the bed in the form of sulfur dioxide (SO2).

[0021] Thus, according to a first aspect of the present invention, there is provided a method for desulfurizing crude carbon dioxide (CO2) gas comprising hydrogen sulfide (H2S) and optionally at least one other sulfur-containing impurity, the method comprising:

[0022] feeding a crude CO2 gas comprising H2S to a Claus process to convert the H2S into elemental sulfur in the presence of oxygen (O2) gas and produce a Claus tail gas comprising CO2, residual H2S and at least one other sulfur-containing impurity;

[0023] feeding the Claus tail gas to a hydrogenation process to convert the at least one other sulfur-containing impurity into H2S in the presence of hydrogen (H2) and produce a H2S-rich CO2 tail gas;

[0024] Cooling the H2S-rich CO2 tail gas and removing condensed water to produce cooled H2S-rich CO2 tail gas;

[0025] compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom to produce compressed impure CO2 gas containing H2S;

[0026] removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by physical separation or by chemical reaction with at least one solid metal oxide to form a solid metal sulfide followed by oxidative regeneration to produce purified CO2 and a first recycle gas comprising at least one sulfur-containing compound; and

[0027] The first recycle gas is recycled to the Claus process to convert the at least one sulfur-containing compound into elemental sulfur.

[0028] According to a second aspect of the present invention, there is provided an apparatus for desulfurizing a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, the apparatus comprising:

[0029] A Claus unit for removing H2S from a crude CO2 gas, the Claus unit comprising:

[0030] a first inlet for an oxidant gas comprising O2;

[0031] a second inlet for said crude CO2 gas;

[0032] a first outlet for Claus tail gas comprising CO2, residual H2S and at least one other sulfur-containing impurity; and

[0033] a second outlet for elemental sulfur;

[0034] a source of oxidant gas in fluid flow communication with the first inlet of the Claus unit, the source of oxidant gas comprising O2;

[0035] a source of crude CO2 gas in fluid flow communication with a second inlet of the Claus unit;

[0036] A hydrogenation unit for converting the at least one other sulfur-containing impurity in the Claus tail gas into H2S, the hydrogenation unit comprising:

[0037] a first inlet in fluid flow communication with a first outlet of the Claus unit;

[0038] A second inlet for H2; and

[0039] A first outlet for H2S-rich CO2 tail gas;

[0040] a source of H2 in fluid flow communication with a second inlet of the hydrogenation unit;

[0041] A cooling unit for cooling H2S-rich CO2 tail gas, the cooling unit comprising:

[0042] a first inlet in fluid communication with the first outlet of the hydrogenation unit;

[0043] a first outlet for a cooled H2S-rich CO2 tail gas; and

[0044] a second outlet for condensed water;

[0045] A compression unit for compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom, the compression device comprising:

[0046] an inlet in fluid flow communication with a first outlet of the cooling unit; and

[0047] An outlet for compressed impure CO2 gas;

[0048] as well as

[0049] A purification unit for removing H2S and any other sulfur-containing impurities from compressed impure CO2 gas by physical separation or by chemical reaction with at least one metal oxide to form solid metal sulfide and subsequent oxidative regeneration, the purification unit comprising:

[0050] a first inlet in fluid flow communication with an outlet of the compression unit;

[0051] a first outlet for purified CO2; and

[0052] a second outlet for a first recycle gas comprising at least one sulphur-containing compound,

[0053] The second outlet of the purification unit is in fluid communication with the Claus unit.

[0054] The term "crude CO 2 " refers to a gas mixture comprising at least about 50 mol % CO 2 , for example, about 50 mol % to about 80 mol % CO 2. Crude CO 2 is a gaseous mixture comprising H 2 S and typically water, but in some embodiments, other components may be present, such as one or more other sulfur-containing compounds.

[0055] 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 mercaptan groups). H2S is typically present in the crude CO2 feed and is also produced in the hydrogenation step of the present invention. COS and / or CS2 may be present in the crude CO2 feed, but may also be produced in the Claus process. SO2 is not typically present in the crude CO2 feed, but may be produced in the Claus process. Mercaptans are not produced in the process of the present invention, so if present in CO2, they will enter with the crude CO2 feed gas.

[0056] The term "sulfur-containing impurities" refers to individual sulfur-containing compounds present in the gas at impurity levels, for example, not exceeding 5 mole % (or 50,000 ppm), and typically not exceeding 3 mole % (or 30,000 ppm).

[0057] The term "impure CO2" refers to a CO2-containing gas that has a higher proportion (in mole fraction) of CO2 than the crude CO2 from which it is obtained. Such a gas typically contains at least about 80 mole % CO2, for example, 80 mole % to about 95 mole % CO2.

[0058] The term "physical separation" refers to the process of removing at least one sulfur-containing component of a fluid mixture from the other components of the mixture without chemical change, reaction or conversion. In other words, the components are separated from the mixture "as is", i.e., in the form in which they exist in the fluid mixture.

[0059] The term "oxidative regeneration" refers to the process of regenerating solid metal oxides from solid metal sulfides by oxidation, typically using a regeneration gas comprising O2.

[0060] The term "purified CO2" refers to a CO2-containing gas that has a higher proportion (in mole fraction) of CO2 than the impure CO2 from which it is obtained. Such a gas typically contains at least about 95 mole % CO2, e.g., about 95 mole % to 100 mole % CO2, and typically does not contain more than 500 ppm total sulfur-containing compounds, and may not exceed 100 ppm.

[0061] The term "further purified CO2" refers to a CO2-containing gas having a higher proportion (in mole fraction) of CO2 than the purified CO2 from which it was obtained. Such a gas typically contains at least about 99 mole % CO2, e.g., about 99 mole % to 100 mole % CO2, and typically does not contain more than 100 ppm total of sulfur-containing compounds.

[0062] The term "H2S-rich" gas is a gas that contains a higher proportion (in mole fraction) of H2S than the H2S-containing gas from which it was obtained.

[0063] The term "H2S-lean" gas is a gas that contains a lower proportion (in mole fraction) of H2S than the H2S-containing gas from which it was obtained. The term includes (but is not limited to) a gas that does not contain H2S.

[0064] A "sulfur-selective adsorbent material" is a material that adsorbs sulfur-containing compounds in preference to at least one other component in a gas mixture, ie, a material that has a higher affinity for sulfur-containing compounds than for other components of a gas mixture.

[0065] "Selective adsorption" is a process in which sulfur-containing components removed from impure CO2 are selectively adsorbed onto an adsorbent and subsequently recovered (in the same chemical form) by desorption using a regeneration gas.

[0066] A "water-selective adsorbent material" is a material that adsorbs water in preference to at least one other component in a gas mixture, ie, a material that has a higher affinity for water than for the other component.

[0067] The "bed" contains particles of the selective adsorbent material or solid metal oxide, or both types of particles. The bed of particles is usually a packed bed, but can also be a fluidized bed. In a packed bed comprising both types of particles, the particles are usually in separate layers.

[0068] The term "downstream" in the context of a selective adsorption unit or reactor refers to the relative position of the unit or reactor when feeding. The term "upstream" should be interpreted accordingly.

[0069] The term "selective amine absorption" refers to a separation or purification process using an amine that selectively (but not necessarily exclusively) absorbs a particular acid gas component (eg, H 2 S) in a gas mixture (eg, H 2 S-rich CO 2 tail gas).

[0070] The term "non-selective amine absorption" refers to a separation or purification process using an amine to absorb a specific acid gas component (e.g., H2S) in a gas mixture (e.g., H2S-depleted CO2 tail gas) that may be combined with another acid gas component (e.g., CO2).

[0071] The term "non-condensable gas" refers to a gas that is non-condensable under the conditions of the present invention. Examples of non-condensable gases include H2, N2 and O2 and rare gases.

[0072] A "CO2 purification unit" (i.e., "CPU") is a unit that purifies (or further purifies) CO2 by partial condensation with 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 to separate the condensed phase from the gas phase.

[0073] A "distillation unit" is a unit for purifying (or further purifying) CO2 by distillation. Such a unit generally comprises a heat exchanger for cooling and optionally at least partially condensing the gas to be purified and at least one distillation column. The column may contain distillation trays or may be filled with loose and / or structured packing to increase the vapor / liquid contact surface area within the column. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0075] Figure 1 is a simplified flow diagram describing an embodiment of the present invention, wherein the tail gas from the Claus unit is treated in a tail gas treatment unit by hydrogenation and selective amine absorption (to remove H2S), and then the CO2 is recovered and purified by non-selective amine absorption in a selective adsorption unit (or reactor);

[0076] Figure 2 Is a description Figure 1Simplified flow diagram of an alternative embodiment of the invention described in , in which the impure CO2 gas from the tail gas treatment unit is compressed and then first purified in a selective adsorption unit (or reactor) and then purified by distillation or by partial condensation and phase separation;

[0077] Figure 3 Is a description Figure 1 A simplified flow diagram of an improved version of the process described in which there is no selective amine absorption step;

[0078] Figure 4 Is a description Figure 2 A simplified flow diagram of an improved version of the process described in which there is no selective amine absorption step;

[0079] Figure 5 is a simplified flow diagram of an alternative embodiment of the present invention, wherein the purification unit has a first stage comprising a CPU and a second stage comprising a distillation unit;

[0080] Figure 6 Is a description Figure 5 A simplified flow diagram of an improved version of the process described in , wherein sulfur is removed on stream 107 from CPU unit 56 (unit 50); and

[0081] Figure 7 It describes Figures 1 to 5 The tail gas treatment process can be Process and / or A simplified flow chart of an implementation scheme of process integration. DETAILED DESCRIPTION

[0082] A first aspect of the present invention is a method for desulfurizing a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity. The method comprises feeding the crude CO2 gas containing H2S to a Claus process to convert the H2S into elemental sulfur in the presence of O2 gas and produce a Claus tail gas containing CO2, residual H2S and at least one sulfur-containing impurity. The Claus tail gas is fed to a hydrogenation process to convert other sulfur-containing impurities (or multiple impurities) into H2S in the presence of H2 and produce a CO2 tail gas rich in H2S. The CO2 tail gas rich in H2S is cooled to separate water, and the resulting cooled H2S-rich tail gas (or impure CO2 gas containing H2S obtained therefrom) is compressed to produce compressed impure CO2 gas containing H2S. H2S and any other sulfur-containing impurities are removed from the compressed gas by physical separation and / or by chemical reaction with at least one solid metal oxide to form solid metal sulfides to produce purified CO2 and a first recycle gas comprising at least one sulfur-containing compound, which solid metal sulfide is converted back to metal oxide by oxidative regeneration. The first recycle gas is recycled to the Claus process to convert at least one sulfur-containing compound into elemental sulfur.

[0083] Embodiments of the present invention improve the recovery and / or purity of CO 2 in crude CO 2 comprising H 2 S and optionally any other sulfur-containing impurities.

[0084] The Claus process may be a conventional "air-Claus" process or an "oxygen-Claus" process as described above, but in either case typically comprises a thermal stage and at least one (e.g., one to four, preferably two or three) catalytic stage. The recyclable gas may be recycled to the feed provided to the Claus process or to an interstage location, i.e., between two stages or both within the process.

[0085] The Claus process can alternatively be Process or process, or a combination of two Claus processes.

[0086] The process consists of a thermal stage followed by a minimum of three catalytic reaction stages, where sulfur is removed between stages by condensers. The first reactor is filled with a standard Claus catalyst, such as activated alumina, promoted alumina and / or titanium dioxide (TiO2), while 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 combusted with a substoichiometric amount of controlled combustion air (either pure O2 or O2-enriched air) so that the tail gas leaving the last Claus reactor typically contains 0.8 vol% to 1.0 vol% H2S. The selective oxidation catalyst in the final reactor oxidizes H2S to sulfur with an efficiency of over 85%. If sulfur recovery in excess of 99% is desired, a third Claus reactor stage can be installed upstream of the selective oxidation reactor.

[0087] The process consists of three or four catalytic reaction stages followed by a thermal stage, with sulfur being removed between stages by condensers. The final Claus reactor is filled with a layer of 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 substoichiometric amounts of controlled combustion air, and the tail gas leaving the last Claus reaction typically contains 0.8 to 1.0 vol% H2S and 100 to 200 ppmv SO2. This low SO2 content is achieved using a hydrogenation catalyst that converts SO2 to H2S in the last Claus reactor. The selective oxidation catalyst in the final reactor oxidizes H2S to sulfur with an efficiency of over 85%. An overall sulfur recovery efficiency of up to 99.3% can be achieved using three reactor stages, and up to 99.5% using four reactor stages.

[0088] The crude CO2 gas can be fed to the Claus process at a temperature of about 10°C to about 70°C (e.g., about 45°C) and at a pressure in the range of about 0.3 bar g (bar gauge) to about 30 bar g (e.g., about 0.3 bar g to about 1.8 bar g) (e.g., about 0.9 bar g).

[0089] The hydrogenation process requires H2 as a reducing gas. H2 can be generated in a H2 generation process, such as partial oxidation of natural gas with substoichiometric air / oxygen in a reducing gas generator, and then fed to the hydrogenation process. However, by recycling H2 from another point in the process, the need for fresh H2 or "make-up" H2 from the H2 generation process can be reduced or even completely eliminated (see below).

[0090] The Claus tail gas can be fed to the hydrogenation process at a temperature in the range of about 120° C. to about 200° C. (e.g., about 130° C.) and at a pressure in the range of about 0.2 bar g to about 30 bar g (e.g., about 0.2 bar g to about 1.8 bar g) (e.g., about 0.3 bar g). The pressure and / or temperature of the Claus tail gas can be adjusted as desired prior to feeding to the hydrogenation process using conventional methods, although in preferred embodiments, the tail gas is fed to the hydrogenation process without being adjusted in this manner.

[0091] The H2S-rich CO2 tail gas from the hydrogenation process is cooled. Any suitable cooling process may be used, but in a preferred embodiment, the H2S-rich CO2 tail gas is quenched by direct contact with liquid water. After removing the condensed water, the cooled H2S-rich CO2 tail gas is compressed to form a compressed impure CO2 gas containing H2S.

[0092] The cooled H2S-rich CO2 tail gas can be fed to a compression unit at a temperature in the range of about 10°C to about 70°C (e.g., about 45°C) and at a pressure in the range of about 0.3 bar g to about 1.8 bar g (e.g., about 1 bar g). The compression unit compresses the gas to a pressure in the range of about 1 bar g to about 120 bar g (e.g., about 30 bar g).

[0093] The content of H2S and any other sulfur-containing impurities in the compressed impure CO2 gas is significantly reduced in some embodiments to a level below 100 ppm by physical separation or by chemical reaction with at least one solid metal oxide to form a solid metal sulfide and subsequent oxidative regeneration to produce purified CO2 and a first recycle gas containing at least one sulfur-containing compound that is recycled to the Claus process.

[0094] The physical separation can be carried out by selective adsorption or by distillation and / or partial condensation with phase separation.

[0095] In an embodiment using selective adsorption, the method involves removing H2S and any other sulfur-containing compounds from compressed impure CO2 gas by adsorption on a bed of at least one adsorbent material selective for sulfur-containing compounds in a selective adsorption unit to produce purified CO2, and producing a spent regeneration gas as a first recycle gas after desorption, the spent regeneration gas containing H2S and any other sulfur-containing compounds from the compressed impure CO2 gas.

[0096] Such adsorbent materials include silica gel, molecular sieves (e.g., 4A or 5A zeolites), activated alumina, and activated carbon (e.g., Calgon copper material and copper-impregnated carbon). The sulfur-containing compound is reversibly adsorbed on a bed of solid selective adsorbent and then desorbed, preferably once the solid adsorbent is saturated with the sulfur-containing compound. The adsorption process can run any suitable cycle including PSA, vacuum pressure swing adsorption (VSA), or temperature swing adsorption (TSA). Specific examples include TSA using silica gel; PSA or VSA using silica gel; TSA using zeolites (e.g., 4A, 5A); and TSA using copper-impregnated carbon.

[0097] The compressed impure CO 2 gas may be fed to the selective adsorption unit at a temperature in the range of about 10° C. to about 70° C. (eg, about 50° C.).

[0098] The adsorption bed of the selective adsorption unit is appropriately regenerated using the purified (or further purified) CO2 generated in the process. The temperature and / or pressure of the regeneration gas can be adjusted as needed using conventional means, depending on the temperature and / or pressure of the CO2 gas at the location where the CO2 gas is removed from the process and the type of cycle used, such as TSA, VSA or PSA, etc. In an embodiment in which a compressed impure CO2 gas is purified using a solid metal oxide, 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 oxide in the bed into corresponding metal sulfides, thereby removing impurities from the gas and producing purified CO2. The metal oxide in the bed is oxidatively regenerated by passing a regeneration gas containing O2 through the bed, usually in a direction countercurrent to the gas when the bed is "fed", so that sulfur is driven out of the bed in the form of SO2. The spent regeneration gas containing SO2 is then recycled to the Claus process as the first recycle gas.

[0099] 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., a mixed metal oxide) may also be used. In some embodiments, the mixture of solid metal oxides comprises about 40 wt % to about 60 wt % (e.g., about 50 wt %) ZnO.

[0100] Examples of suitable mixed metal oxides are disclosed in US4044114 and comprise 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% aluminum oxide (calculated as Al2O3) and from about 2 wt% to about 45 wt% of a Group II metal oxide, preferably calcium (calculated as oxide) with or without additional elements.

[0101] The compressed impure CO2 gas can 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 (e.g., about 400°C to about 550°C). After compression, the temperature of the compressed gas can be adjusted as desired using conventional means before being fed to the reactor containing the solid metal oxide.

[0102] The mixed metal oxide bed of the reactor is suitably regenerated using an oxygen-containing gas, such as purified (or further purified) CO2 generated during the addition of O2 in an amount in the range of about 1 mol % to about 5 mol % oxygen (e.g., about 2 mol %). The temperature and / or pressure of the regeneration gas can be adjusted as desired using conventional means, depending on the temperature and / or pressure of the CO2 gas at the location where the CO2 gas is removed from the process.

[0103] The first recycle gas may be recycled to the Claus process at a temperature in the range of about 10° C. to about 70° C. (e.g., about 50° C.) and a pressure in the range of about 0.3 barg to about 30 bar g (e.g., about 0.3 bar g to about 1.8 bar g) (e.g., about 1 bar g). In embodiments where the temperature and / or pressure of the first recycle gas leaving the purification process is not suitable in view of the operating conditions of the Claus unit, the temperature and / or pressure of the first recycle gas will be adjusted by conventional means as appropriate.

[0104] The impure CO2 gas of the compression that is fed to the selective adsorption unit or the reactor containing solid metal oxide will contain water usually.In such case, water can be removed by adsorbing on at least one adsorbent material that is selective to water in the downstream that is positioned at the adsorbent material or solid metal oxide that is selective to sulfur-containing compounds.Suitable water selective adsorbent material comprises those materials that are identified as sulfur selective adsorbent material above.The water selective adsorbent material can be located in the container identical with sulfur selective adsorbent material or metal oxide, for example, in a separate layer, or in a separate container.

[0105] Alternatively, water may be removed by absorption in a separate vessel (eg, a glycol unit) located downstream of the selective adsorption unit or reactor.

[0106] Whether the sulfur-containing impurities are removed by selective adsorption or by chemical reaction with the solid metal oxide, the regeneration gas may contain a small amount of water. However, if water is present, the amount of water is insufficient to hydrolyze any sulfur-containing compounds driven off from the bed being regenerated. In this regard, the regeneration gas typically contains less than 5 mol%, preferably less than 2 mol%, and more preferably less than 1 mol% water. In the art, such an amount of water would be considered a minute amount.

[0107] The H2S-rich tail gas can be directly fed to a compression unit for compression to produce compressed impure CO2. However, in some embodiments, the method includes recovering H2S from the H2S-rich CO2 tail gas by selective amine absorption to produce H2S-depleted CO2 tail gas and recovered H2S; and, recycling the recovered H2S to the Claus process to convert the recovered H2S into elemental sulfur.

[0108] The H2S-rich CO2 tail gas may be fed to the selective amine absorption unit at a temperature of about 10°C to about 70°C (e.g., about 50°C) and a pressure in the range of about 0.05 bar g to about 30 bar g (e.g., about 0.05 bar g to about 1.8 bar g) (e.g., about 0.1 bar g).

[0109] Conventional selective amine absorption processes using, for example, methyldiethanolamine (MDEA) as the selective amine are suitable for use in these embodiments of the present invention.

[0110] The H2S-rich CO2 tail gas can be fed directly to a compression unit for compression to produce compressed impure CO2. However, in some embodiments, the method includes recovering CO2 and residual H2S from the H2S-depleted CO2 tail gas by non-selective amine absorption to produce an impure CO2 gas comprising H2S and a waste gas comprising CO2 and at least one non-condensable gas.

[0111] The H2S-depleted CO2 tail gas may be fed to the non-selective amine absorption unit at a temperature of about 10°C to about 70°C (e.g., about 50°C) and at a pressure in the range of about 0.01 bar g to about 30 bar g (e.g., about 0.01 bar g to about 1.8 bar g) (e.g., about 0.1 bar g).

[0112] 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.

[0113] Depending on the composition, any waste gas produced in the present invention can be discharged or fed to a thermal oxidizer where it is burned to produce flue gas and optional steam that meets local emission standards. If the waste gas contains a large amount of H2, the waste gas itself can be used as a fuel or H2 can be recovered from the waste gas.

[0114] As described above, the purified CO2 may contain less than 100 ppm of sulfur-containing impurities, in which case CCS generally does not require further purification. However, in embodiments where the amount of impurities exceeds this threshold, further purification is generally required.

[0115] 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 comprising CO2 and H2; and recycling the second recycle gas or the H2-rich gas obtained therefrom to the hydrogenation process. Typically, a portion of the second recycle gas or the H2-rich gas obtained therefrom is purged to prevent the accumulation of H2 (in the case of excess) or N2 and / or Ar non-condensable contaminant gases in the process.

[0116] Further purification processes for further purifying CO2 may include distillation (such as the process disclosed in US10254042) and / or partial condensation with phase separation (such as the process disclosed in US7819951), both of which the inventors have realized may be suitable for combination with the present invention as appropriate.

[0117] Both distillation and partial condensation of CO2 require temperatures in the range of 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, distillation and / or partial condensation with phase separation occurs at "low" (or subambient) temperatures, typically in the range of about +15°C to about 55°C. In other embodiments, distillation and / or partial condensation with phase separation occurs at temperatures in the range of about 0°C to -30°C, particularly for H2S distillation from CO2.

[0118] The purified CO2 is typically at a temperature in the range of about 10°C to about 70°C (e.g., about 50°C) and a pressure of about 10 bar g to about 120 bar g (e.g., about 30 bar g). Therefore, in embodiments where further purification is desired, the purified CO2 is typically cooled, e.g., by heat exchange with a refrigerant to a suitable temperature as described above, prior to further purification. Additionally or alternatively, if the pressure of the gas is insufficient for further purification, the purified CO2 is further compressed.

[0119] Recycling H2 to 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 the required hydrogenation unit, which in turn saves capital and operating costs. In the event that the recycled H2 only partially meets the demand, additional H2 can be generated in the H2 generation process as described above. However, in some embodiments, the amount of H2 recycled to the hydrogenation process is sufficient to meet the demand for H2 in the process, completely eliminating the need for the H2 generation process.

[0120] Recycling CO2 to the hydrogenation process can increase the overall CO2 recovery rate. However, it may be desirable or advantageous to reduce the amount of CO2 in the second recycle gas that is recycled to the hydrogenation unit, for example, to reduce the size of the hydrogenation unit. In such cases, the method may include recovering H2 from the recycle gas that is being fed to the hydrogenation process in the membrane separation process to produce a H2-rich gas that is recycled to the hydrogenation unit and an off-gas comprising CO2 and at least one non-condensable gas.

[0121] Conventional membrane separation units can be used to recover H2 gas from the recycle gas that is recycled to the hydrogenation process. The membrane can be a wound hollow fiber membrane made of a polymer such as polysulfone, polyimide or cellulose acetate. Examples of suitable membrane separation methods are disclosed in US2010 / 126180A, and the inventors have realized that the process can be appropriately combined with the present invention.

[0122] In embodiments where the H2S-rich CO2 tail gas is directly compressed to produce compressed impure CO2 gas containing H2S, the method may include: feeding the purified CO2 to a further purification process as described above to produce further purified CO2 and a second recycle gas containing CO2 and H2; and recycling the second recycle gas or the H2-rich gas obtained therefrom to the hydrogenation process. Typically, a portion of the second recycle gas or the H2-rich gas obtained therefrom is purged to prevent accumulation of H2 (in the case of excess) or N2 and / or Ar in the process.

[0123] As mentioned above, purification by physical separation can be carried out by distillation and / or partial condensation with phase separation.

[0124] In these embodiments, the method generally comprises: removing H2 and any non-condensable gases from the compressed impure CO2 by distillation and / or partial condensation with phase separation to produce a CO2 fluid rich in H2S (which may be liquid, gas or two-phase) and a CO2 gas rich in H2, recycling the CO2 gas rich in H2 or a CO2 gas further rich in H2 obtained therefrom as a second recycle gas to the hydrogenation process; separating the CO2 fluid rich in H2S by distillation and / or partial condensation with phase separation to produce purified CO2 as a tower top gas and a bottom liquid rich in H2S; and evaporating the bottom liquid rich in H2S to produce a H2S gas rich as a first recycle gas. The second recycle gas or a portion of the H2 gas rich therefrom is generally purged to avoid accumulation of H2 (in the case of excess thereof) or N2 and / or Ar in the process.

[0125] As mentioned above, examples of suitable CO2 purification processes in this context are disclosed in US10254042 and US7819951, which the inventors have realised may be suitably combined with the present invention as appropriate.

[0126] In an embodiment in which the purified CO2 includes at least one residual sulfur-containing impurity, the method may include further purifying 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 to produce further purified CO2 and a further recycle gas comprising at least one sulfur-containing compound; and recycling the further recycle gas to the Claus process to convert the sulfur-containing compound into elemental sulfur.

[0127] 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 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 third recycle gas containing at least one sulfur-containing compound. The third recycle gas is recycled to the Claus process to convert the sulfur-containing compounds to elemental sulfur.

[0128] A second aspect of the present invention is an apparatus for desulfurizing a crude CO2 gas comprising H2S and optionally at least one other sulfur-containing impurity, generally according to the method of the first aspect.

[0129] The apparatus comprises a Claus unit for removing H2S from a crude CO2 gas. The Claus unit comprises a first inlet for an oxidant gas comprising O2, a second inlet for a crude CO2 gas, a first outlet for a Claus tail gas comprising 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.

[0130] The apparatus further comprises a source of oxidant gas in fluid flow communication with the first inlet of the Claus unit, the source of oxidant gas comprising O. For a unit operating an "air-Claus" process, the source may simply be a blower with a small filter, while for a unit operating an "oxygen-Claus" process, the source may be a vacuum swing adsorption (VSA) unit or an air separation unit (ASU), optionally in combination with backup systems such as a liquid oxygen tank and a vaporizer.

[0131] In addition, the apparatus includes a source of crude CO2 gas in fluid flow communication with the 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.

[0132] The apparatus further comprises a hydrogenation unit for converting at least one sulfur-containing impurity in the Claus tail gas into H2S. The hydrogenation unit comprises: a first inlet in fluid flow communication with a first outlet of the Claus unit, a second inlet for H2, and a first outlet for H2S-rich CO2 tail gas. An example of a suitable hydrogenation unit is described in US2010 / 0126180A.

[0133] The apparatus also includes a source of H2 in fluid flow communication with the second inlet of the hydrogenation unit. The source may be a unit that generates H2 as described above.

[0134] In addition, the apparatus comprises a cooling unit for cooling the H2S-rich CO2 tail gas, which is separate 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 cooled H2S-rich 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 comprising a second inlet for cooling water. The cooling unit may be a separate unit, or may be integrated with the hydrogenation unit.

[0135] Furthermore, the plant comprises a compression unit for compressing the H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom. The compression unit must therefore be originally adapted to handle "sour" gases.

[0136] 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 compressed impure CO2 gas. The compression unit may comprise one or more centrifugal or reciprocating compressors and / or may be a multi-stage compressor with associated intercoolers and aftercoolers. In particular, the compression unit may be an integrally geared or inline centrifugal compressor.

[0137] In addition, the apparatus includes 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 the solid metal oxide. The purification unit includes: a first inlet in fluid flow communication with the outlet of the compression unit, a first outlet for 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 can be in fluid flow communication with the second outlet of the Claus unit or with a third inlet on the Claus unit that is typically dedicated to the recycle gas.

[0138] Throughout the specification, the term "fluid flow communication" is used to refer to different units (or parts of units, such as inlets / outlets) being connected in a manner that allows fluids (e.g., gases) to flow between units, as appropriate, via conduits, fittings, and / or pipes. The term is intended to include associated flow control devices, such as necessary sensors and / or valves, to ensure operational control of the device. Unless otherwise indicated, the 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) processing units (excluding flow control devices) are provided in the pipeline between the units so connected. "Indirect" fluid (or gas) flow communication should be understood accordingly, that is, one or more other fluid (or gas) processing units are provided in the pipeline between the units so connected.

[0139] In some embodiments, the apparatus includes an H2 generation unit including an outlet for H2 in fluid communication with the second inlet of the hydrogenation unit.

[0140] The purification unit in some embodiments is or includes a selective adsorption unit, the selective adsorption unit including at least one container having an upstream end and a downstream end, and the container or each container includes an adsorbent bed, the adsorbent bed comprising at least one layer of adsorbent material selective for sulfur compounds, a first inlet for compressed impure CO2 gas at the upstream end of the container or each container, a first outlet for purified CO2 at the downstream end of the container or each container, a second inlet for regeneration gas at the downstream end of the container or each container; and a second outlet for spent regeneration gas at the upstream end of the container or each container. The first inlet is fluidly connected to the outlet of the compression unit, and the second outlet is fluidly connected to the Claus unit. In this regard, the second outlet can be fluidly connected to the second outlet of the Claus unit or to the third inlet fluidly connected to the Claus unit, which is usually dedicated to the recycle gas.

[0141] In other embodiments, the purification unit comprises a reactor comprising at least one container having an upstream end and a downstream end. The container or each container comprises: a bed comprising at least one solid metal oxide; a first inlet for compressed impure CO2 gas at the upstream end of the container or each container; a first outlet for purified CO2 at the downstream end of the container or each container; a second inlet for regeneration gas at the downstream end of the container or each container; and a second outlet for spent regeneration gas at the upstream end of the container or each container. The first inlet is in fluid flow communication with the outlet fluid 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 with a third inlet fluid flow on the Claus unit, which is typically dedicated to recycle gas.

[0142] The inventors have appreciated that examples of suitable reactors that may be adapted for incorporation with these embodiments are disclosed in US 4,797,268.

[0143] The bed in the or each vessel of the selective adsorption unit or reactor may comprise at least one layer of adsorbent material selective for water downstream of the at least one layer of adsorbent material selective for sulphur containing compounds or the solid metal oxide, respectively.

[0144] Alternatively, the purification unit may include a separate dryer unit downstream of any selective adsorption unit of the reactor. The dryer unit may be another selective adsorption unit or an absorption unit, such as an ethylene glycol unit. In either case, the dryer unit typically includes an inlet in fluid communication with the first outlet of the selective adsorption unit or the reactor, as the case may be, and an outlet for the dried and purified CO2.

[0145] In some embodiments, the apparatus includes a selective amine absorption unit for recovering H2S from H2S-rich CO2 tail gas. The selective amine absorption unit typically includes an inlet in fluid flow communication with a first outlet of the cooling unit, a first outlet for H2S-depleted CO2 tail gas, and a second outlet in fluid flow communication with a Claus unit for recycled gas containing H2S. In this regard, the second outlet may be in fluid flow communication with a second inlet of the Claus unit or with a third inlet on the Claus unit typically dedicated to recycle gas. Examples of suitable selective amine absorption units that the inventors have recognized as being applicable herein are disclosed in WO93 / 10883A.

[0146] In some embodiments, the first outlet of the selective amine adsorption unit is in direct fluid flow communication with the inlet of the compression unit.

[0147] In other embodiments, the apparatus may further include a non-selective amine absorption unit for recovering CO2 and residual H2S from the H2S-depleted CO2 tail gas. The non-selective amine absorption unit typically includes an inlet in fluid flow communication with the first outlet of the selective amine absorption unit, a first outlet for impure CO2 gas, and a second outlet for waste gas containing CO2 and at least one non-condensable gas. The apparatus typically includes an exhaust port for the waste gas, optionally with a thermal oxidizer, the thermal oxidizer including an inlet in fluid flow communication with the second outlet of the non-selective amine absorption unit, and an outlet for exhaust gas in fluid communication with the atmosphere through the exhaust port.

[0148] In an embodiment of the present invention, where the content of sulfur-containing impurities in the purified CO2 gas is still higher than the desired threshold, for example, higher than 100 ppm, even after passing through the selective adsorption unit or reactor described above, the equipment may further include further purification units, such as a distillation unit and / or a partial condensation unit (or CPU) with phase separation, for further purifying the purified CO2.

[0149] In these embodiments, the further purification unit comprises an inlet for purified CO2 fluidly connected to a first outlet of the purification unit, a first outlet for further purified CO2, a second outlet for a second recycle gas fluidly connected to either a hydrogenation unit and / or a Claus unit, and a purge line fluidly connected to the second outlet of the further purification unit, the second recycle gas comprising CO2 and H2.

[0150] For these and other embodiments involving the use of a further purification unit, the second outlet of the further purification unit can be in fluid flow communication with the first or second inlet of the hydrogenation unit or with a third inlet on the hydrogenation unit that is typically dedicated to recycle gas. The second outlet of the CPU can additionally or alternatively be in fluid communication with the first or second inlet of the Claus unit or with a third inlet on the Claus unit that is typically dedicated to recycle gas. In addition, the purge line can be in direct fluid communication with an exhaust port to the atmosphere or with a thermal oxidizer. Alternatively, the fluid from the purge line can be used as a fuel or for H2 recovery.

[0151] The inventor has realized that the Figure 1 The CPU described in B can (after appropriate adjustments where appropriate) be used as a further purification unit according to the invention.

[0152] These embodiments may further include a membrane separation unit for recovering H2 gas from the second recycle gas. The membrane separation unit typically includes: an inlet for the second recycle gas in fluid flow communication with a second outlet of the further purification unit, a first outlet for H2-rich gas in direct fluid flow communication with the hydrogenation unit and / or the Claus unit, and a second outlet for waste gas comprising CO2 and at least one non-condensable gas.

[0153] These embodiments of the apparatus generally include an exhaust port for exhaust gas, optionally with a thermal oxidizer including an inlet in fluid flow communication with the second outlet of the membrane separation unit, and an outlet in fluid communication with the exhaust port for exhaust gas.

[0154] Additionally, the second outlet of the membrane separation unit may be in fluid flow communication with a second outlet of the hydrogenation unit and / or Claus unit or with a third inlet on the hydrogenation unit and / or Claus unit typically dedicated for recycle gas. In this regard, additional H2 may be fed to the Claus unit for combustion / processing if not required elsewhere.

[0155] In other embodiments, the first outlet of the hydrogenation unit is in direct fluid flow communication with the inlet of the compression unit.

[0156] In these embodiments, the apparatus may include a further purification unit for further purifying the purified CO2. The further purification unit typically includes an inlet for purified CO2 in fluid flow communication with a first outlet of the purification unit, a first outlet for further purified CO2, and a second outlet for a second recycle gas in fluid flow communication with a hydrogenation unit, and a purge line in fluid flow communication with the second outlet of the further purification unit, the second recycle gas comprising CO2 and H2. The second outlet of the further purification unit may be in fluid flow communication with an inlet of the hydrogenation unit (and / or Claus unit) or with an inlet on the hydrogenation unit (and / or Claus unit) typically dedicated to recycle gas.

[0157] These embodiments may further include a membrane separation unit for recovering H2 from the second recycle gas. The membrane separation unit typically includes an inlet for the second recycle gas in fluid flow communication with the second outlet of the further purification unit, a first outlet for H2-rich gas in direct fluid flow communication with the hydrogenation unit, and a second outlet for waste gas comprising CO2 and at least one non-condensable gas. The H2-rich gas is typically obtained from the permeate side of the membrane, while the waste gas is typically obtained from the retentate side of the membrane.

[0158] These embodiments of the apparatus generally include an exhaust port for exhaust gas, optionally with a thermal oxidizer including an inlet in fluid flow communication with the second outlet of the membrane separation unit, and an outlet in fluid communication with the exhaust port for exhaust gas.

[0159] Furthermore, 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 with a third inlet on the hydrogenation unit and / or the Claus unit typically dedicated for recycle gas.

[0160] In some embodiments, the apparatus includes a non-selective amine absorption unit for recovering CO2 and H2S from an H2S-rich CO2 tail gas. The non-selective amine absorption unit includes: 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 generally include an exhaust port for waste retentate gas, optionally with a thermal oxidizer, the thermal oxidizer including an inlet in fluid flow communication with the second outlet of the membrane separation unit, and an outlet in fluid communication with the exhaust port for exhaust gas.

[0161] The purification unit may 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-rich CO2 fluid; and a second outlet for H2-rich CO2 gas in fluid flow communication with the inlet of the hydrogenation unit (and / or with the inlet of the Claus unit).

[0162] In some embodiments, the apparatus may further include a selective adsorption unit comprising: at least one vessel having an upstream end and a downstream end, wherein the vessel or each vessel includes an adsorbent bed comprising at least one layer of adsorbent material selective for sulfur compounds; a first inlet for H2S-rich CO2 fluid at the upstream end of the vessel or each vessel; a first outlet for purified CO2 at the downstream end of the vessel or each vessel; a second inlet for regeneration gas at the downstream end of the vessel or each vessel; and a second outlet for spent regeneration gas at the upstream end of the vessel or each vessel. The first inlet of the selective adsorption vessel 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.

[0163] Alternatively, the apparatus may comprise a reactor comprising: at least one vessel having an upstream end and a downstream end, wherein the vessel or each vessel comprises a bed comprising at least one solid metal oxide; a first inlet for H2S-rich CO2 fluid at the upstream end of the vessel or each vessel; a first outlet for purified CO2 at the downstream end of the vessel or each vessel; a second inlet for regeneration gas at the downstream end of the vessel or each vessel; and a second outlet for spent regeneration gas at the upstream end of the vessel 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.

[0164] In yet further embodiments of the apparatus, the purification unit comprises a first stage (eg, a CPU) and a second stage (eg, a distillation unit).

[0165] The first stage comprises an inlet for compressed impure CO2 connected to the outlet fluid flow of the compression unit, a first outlet for H2S-rich CO2 fluid and a second outlet for H2-rich CO2 gas connected to the inlet fluid flow of the hydrogenation unit (and / or to the inlet of the Claus unit).

[0166] The second stage includes an inlet for H2S-rich CO2 fluid in fluid flow communication with the first outlet of the first stage, a first outlet for purified CO2 gas, and a second outlet for H2S-rich gas in fluid flow communication with the third inlet of the Claus unit. These embodiments of the apparatus further include a purge line in fluid flow communication with the second outlet of the first stage of the purification unit.

[0167] The inventor has realized that the Figure 2 An integrated first and second stage arrangement is described which would be suitable for use as a purification unit according to these embodiments of the invention.

[0168] These embodiments may further include a membrane separation unit for recovering H2 from the H2-rich CO2 gas. The membrane separation unit typically includes an inlet for the H2-rich CO2 gas in fluid flow communication with the second outlet of the first stage of the purification unit, a first outlet for the H2-rich gas in direct fluid flow communication with the inlet of the hydrogenation unit (and / or with the inlet of the Claus unit), and a second outlet for the waste gas comprising CO2 and at least one non-condensable gas.

[0169] These embodiments of the apparatus generally include an exhaust port for exhaust gas, optionally with a thermal oxidizer including an inlet in fluid flow communication with the second outlet of the membrane separation unit, and an outlet in fluid communication with the exhaust port for exhaust gas.

[0170] Furthermore, 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 with a third inlet on the hydrogenation unit and / or the Claus unit typically dedicated for recycle gas.

[0171] If the amount of sulfur-containing components in the purified CO 2 gas is still above a desired threshold, for example above 100 ppm, these embodiments may further comprise a further purification unit selected from the group consisting of a selective adsorption unit and a reactor comprising a solid metal oxide bed as described above.

[0172] The selective adsorption unit herein typically includes at least one container having an upstream end and a downstream end. The container or each container includes: an adsorbent bed comprising at least one layer of adsorbent material selective for sulfur-containing compounds; a first inlet for purified CO2 at the upstream end of the container or each container; a first outlet for further purified CO2 at the downstream end of the container or each container; a second inlet for regeneration gas at the downstream end of the container or each container; and a second outlet for spent regeneration gas at the upstream end of the container or each container. In these embodiments, the first inlet of the further purification unit is fluidly connected to the first outlet of the second stage of the purification unit, and the second outlet is fluidly connected to the Claus unit. At this point, the second outlet of the container or each container can be fluidly connected to the second inlet of the Claus unit or to the third inlet fluidly connected to the Claus unit, which is usually dedicated to the recycle gas.

[0173] The reactor herein typically includes at least one container having an upstream end and a downstream end. The container or each container includes: at least one solid metal oxide; a first inlet for purified CO2 at the upstream end of the container or each container; a first outlet for further purified CO2 at the downstream end of the container or each container; a second inlet for regeneration gas at the downstream end of the container or each container; and a second outlet for spent regeneration gas at the upstream end of the container or each container. In addition, the first inlet of the further purification unit is fluidly connected to the first outlet of the second stage of the purification unit, and the second outlet is fluidly connected to the Claus unit. At this point, the second outlet of the container or each container can be fluidly connected to the second inlet of the Claus unit or to the third inlet on the Claus unit, which is usually dedicated to the recycle gas.

[0174] Turning now to the accompanying drawings, Figure 1 In the process, a stream 100 of crude CO2 gas containing H2S is taken from the acid gas recovery unit 4 and fed to the Claus unit 6, where the H2S is converted into a stream 102 of elemental sulfur. A substoichiometric amount of oxygen from a stream 101 of air is used to oxidize enough H2S in the crude CO2 gas feed to produce a mixture of H2S and SO2 in the appropriate proportions to react and produce elemental sulfur. Depending on the type of Claus process, the Claus unit 6 typically converts 92 mol% to 99.5 mol% of the H2S in the crude CO2 gas feed into elemental sulfur. The remaining sulfur compounds leave the Claus unit 6 in a stream 103 of Claus tail gas containing CO2, which is fed to a tail gas treatment unit 14 including a hydrogenation unit 16 and a selective amine absorption unit 20.

[0175] In the hydrogenation unit 16, the residual sulfur compounds are converted to H2S in the presence of H2 gas produced in the reducing gas generation unit 18 to produce a stream 104 of H2S-rich CO2 tail gas, which, after being quenched with water in a direct contact cooler (shown as integral to the hydrogenation unit - see the (water) stream leaving the hydrogenation unit 16), is then fed to the selective amine absorption unit 20, which selectively absorbs H2S to produce a stream 105 of H2S-depleted CO2 tail gas and recovered H2S, which is recycled back to the Claus unit 6 as part of stream 110. The H2S-depleted CO2 tail gas from the tail gas treatment unit 14 contains mainly CO2, N2, H2 and small amounts of sulfur compounds, and is saturated with water.

[0176] In the absence of a CO2 capture unit, stream 105 is typically oxidized in a thermal oxidizer. In this case, however, the CO2 is intended for capture and storage.

[0177] The H2S-depleted CO2 tail gas 105 from the tail gas treatment unit 14 is fed to a non-selective amine absorption unit 26, in which most of the CO2 and sulfur compounds are non-selectively captured and recovered to produce a stream 107 of impure CO2 gas, and a stream 115 of waste gas containing CO2 and non-condensable gases (N2 and H2) and water, which is directly discharged or fed to a thermal oxidizer 42 before discharge, depending on its composition.

[0178] Stream 107 is primarily CO2, but contains sulfur compounds that may be undesirable for CO2 sequestration or further use. Stream 107 is therefore fed to compression unit 32 where it is compressed to form stream 108 of compressed impure CO2 gas, which is then purified according to the invention using selective adsorption unit (or reactor) 36 to remove sulfur compounds and produce stream 111 of purified CO2 for sequestration and stream 109 of spent regeneration gas (or purge gas) containing desorbed sulfur compounds that is recycled to Claus unit 6.

[0179] Water may be removed from the compressed impure CO2 gas by including at least one layer of water adsorbent material downstream of the layer of sulfur selective adsorbent material or the layer of solid metal oxide (e.g., ZnO) in the selective adsorption unit (or reactor) 36. Optionally, the stream 111 of purified CO2 may be fed to a dryer unit (not shown) prior to sequestration.

[0180] Figure 2 The flowchart described in is Figure 1 Unless otherwise stated, common features between the two flowcharts are indicated by the same reference numerals. Figure 2 and Figure 1 Discussion of distinguishing features.

[0181] and Figure 1 The air used is different. Figure 2 The process uses a stream 101 of O 2 or O 2 enriched air as an oxidant to feed the Claus unit 6 for converting the required amount of H 2 S into SO 2 in order to carry out the Claus reaction to produce elemental sulfur.

[0182] In addition, a stream 105 of H2S-depleted CO2 tail gas is taken from the tail gas treatment unit 14 and fed directly to the compression device 46 where it is compressed. Water is separated from the compressed gas in one or more intercoolers and / or aftercoolers (not shown). The compressed impure CO2 gas stream 106 is then purified according to the present invention using a selective adsorption unit (or reactor) 50 to remove sulfur compounds and produce a stream 107 of purified CO2 and a stream 109 of spent regeneration gas (or purge gas) including sulfur compounds that is recycled to the Claus unit 6.

[0183] Water may be removed from the compressed impure CO2 gas by including at least one layer of water adsorbent material downstream of the layer of sulfur selective adsorbent material or the layer of solid metal oxide (e.g., ZnO) in the selective adsorption unit (or reactor) 50. Optionally, the stream 111 of purified CO2 may be fed to a dryer unit (not shown) prior to sequestration.

[0184] The purified CO2 stream 107 is then fed to a further purification unit 56 where the CO2 is further purified by distillation and / or by partial condensation and phase separation to produce a stream 111 of further purified CO2 for sequestration or other uses and a stream 108 of waste gas comprising CO2 and H2.

[0185] Stream 108 may be recycled directly to hydrogenation unit 16. However, it may be desirable to reduce the amount of CO2 recycled to hydrogenation unit 16. In such cases, stream 108 may be fed to membrane unit 62 for H2 recovery to produce stream 112 of H2-rich gas and stream 115 of waste gas.

[0186] Stream 112 is recycled to the hydrogenation unit 16. Recycling this stream in this way has the benefit of reducing or even eliminating the need for fresh H2 from a reducing gas generation unit (not shown) to feed the hydrogenation unit 16.

[0187] Stream 115 of exhaust gas may be discharged directly or fed to thermal oxidizer 70 prior to discharge, depending on its composition.

[0188] Figure 3The flowchart described in is Figure 1 , without the selective amine adsorption unit 20. Unless otherwise stated, common features between the two flow diagrams are indicated by the same reference numerals. Figure 3 and Figure 1 Discussion of distinguishing features.

[0189] A stream 104 of H2S-rich CO2 tail gas is fed directly from the hydrogenation unit 16 to a non-selective amine absorption unit 26, in which a majority of the CO2 and sulfur compounds are non-selectively captured and recovered to produce a stream 107 of impure CO2 gas, and a stream 115 of waste gas which is either discharged directly or fed to a thermal oxidizer 42 before discharge, depending on its composition.

[0190] Figure 4 The flowchart described in is Figure 2 , without the selective amine adsorption unit 20. Unless otherwise stated, common features between the two flow diagrams are indicated by the same reference numerals. Figure 4 and Figure 2 Discussion of distinguishing features.

[0191] In this arrangement, a stream 101 of O2 or O2-rich air for the Claus unit 6 is produced in the air separation unit 72 by vacuum swing adsorption (VSA) or cryogenic air separation (in an air separation unit or ASU).

[0192] A stream 104 of impure CO tail gas is fed directly from the hydrogenation unit 16 to a compression device 46 where it is compressed to form a stream 106 of compressed impure CO gas, which is then fed to a selective adsorption unit (or reactor) 50 where H2S (optionally together with water) is removed from the gas.

[0193] In this arrangement, sufficient H 2 can be recovered in the membrane separation unit 62 and recycled to the hydrogenator 16 so that a reducing gas generator (not shown) is not required to provide additional H 2 .

[0194] Figure 5 The flowchart described in is Figure 4 The present invention is a modified version of the flow chart described in , wherein the purification unit includes a selective adsorption unit (or reactor) to further purify the CO2. Unless otherwise stated, common features between the two flow charts are indicated by the same reference numerals. Figure 5 and Figure 4 Discussion of distinguishing features.

[0195] 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 fed to the first stage 56 where the CO2 is purified, for example by partial condensation with phase separation, to produce H2S-rich CO2 liquid and a stream 108 of off-gas comprising CO2 and H2 for recycling to the hydrogenation unit 16, optionally after passing through a membrane separation unit 62 to recover H2.

[0196] A stream 107 of H2S-rich CO2 liquid (or gas in the case of vaporization) is fed to a distillation column system 74 where the CO2 and H2S are separated in a second stage to produce purified CO2 as overhead gas and H2S-rich bottoms liquid which vaporizes before being recycled as stream 110 to the Claus unit 6.

[0197] The purified CO2 stream 111 may be suitable for sequestration. However, if the total amount of sulfur compounds in the purified CO2 is too high, for example, more than 100 ppm, the purified CO2 may be further purified in a 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 compounds that is recycled to the Claus unit 6.

[0198] Figure 2 , Figure 4 and Figure 5 The described flow charts all involve a membrane separation unit 62 for recovering H2 from the exhaust gas generated in the purification unit. In these embodiments, a purge stream can be obtained from the recycle stream 112 to control the accumulation of H2 (if it is excessive) or N2 and / or Ar.

[0199] Figure 6 The flowchart described in is Figure 5 A modified version of the flow diagram described in , wherein the purification unit comprises a single stage and a selective adsorption unit (or reactor) can be used to further purify the CO2. Unless otherwise stated, common features between the two flow diagrams are indicated by the same reference numerals. Figure 6 and Figure 5 Discussion of distinguishing features.

[0200] The purification unit has a single stage (unit 56). A stream 106 of compressed impure CO2 gas is fed to unit 56 where the CO2 is purified, for example by partial condensation with phase separation, to produce a CO2 liquid rich in H2S and a stream 108 of off-gas comprising CO2 and H2 for recycling to the hydrogenation unit 16, optionally after passing through a membrane separation unit 62 to recover H2.

[0201] The level of sulfur compounds in the H2S-rich CO2 gas stream 107 is generally in excess of 2 mol%, which is too high for CCS. Figure 5 In the embodiment of the present invention, the CO2 can be purified as in the embodiment of the present invention, the feed stream from unit 56 can be fed to a selective adsorption unit (or reactor) 50 to produce a feed stream 111 of further purified CO2 for storage or further use and a feed stream 110 of spent regeneration gas (or purge gas) containing desorbed sulfur-containing compounds for recycling to the Claus unit 6.

[0202] Figure 7 The flowchart in describes how the SUPERCLAUS process and / or the EUROCLAUS process (unit 6*) can be combined with Figures 1 to 5 In this regard, unit 26** represents a "CCS block" which includes Figures 1 to 5 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 described in one of the above. The recycle stream containing H2S is fed to the Claus unit 6*, the purified CO2 is removed as stream 111, and the off-gas is sent to the thermal oxidizer unit 42 via stream 115.

[0203] Aspects of the Invention

[0204] Aspect 1: A method for desulfurizing a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, the method comprising:

[0205] feeding a crude CO2 gas comprising H2S to a Claus process to convert the H2S into elemental sulfur in the presence of O2 gas and produce a Claus tail gas comprising CO2, residual H2S and at least one other sulfur-containing impurity;

[0206] feeding the Claus tail gas to a hydrogenation process to convert the at least one other sulfur-containing impurity into H2S in the presence of H2 and produce a H2S-rich CO2 tail gas;

[0207] Cooling the H2S-rich CO2 tail gas and removing condensed water to produce cooled H2S-rich CO2 tail gas;

[0208] compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom to produce compressed impure CO2 gas containing H2S;

[0209] removing H2S and any other sulfur-containing impurities from the compressed impure CO2 gas by physical separation or by chemical reaction with at least one solid metal oxide to form at least one solid metal sulfide followed by oxidative regeneration to produce purified CO2 and a first recycle gas comprising at least one sulfur-containing compound; and

[0210] The first recycle gas is recycled to the Claus process to convert the at least one sulfur-containing compound into elemental sulfur.

[0211] Aspect 2: The method according to aspect 1, comprising:

[0212] generating H2 in a hydrogen generation process; and

[0213] The H2 is fed to the hydrogenation process.

[0214] Aspect 3: The method according to aspect 1 or 2, wherein the H2S-rich CO2 tail gas is cooled by direct contact with water.

[0215] Aspect 4: A method according to any one of #1 to #3, wherein H 2 S and any other sulfur-containing impurities are removed from the compressed impure CO 2 gas by selective adsorption as the physical separation.

[0216] Aspect 5: A method according to Aspect 4, wherein the selective adsorption involves removing H2S and any other sulfur-containing compounds in the compressed impure CO2 gas by adsorption on a bed of at least one adsorbent material selective for sulfur-containing compounds in a selective adsorption unit to produce the purified CO2 and a spent regeneration gas as a first recycled gas after desorption using a regeneration gas, wherein the spent regeneration gas contains the H2S and any other sulfur-containing compounds from the compressed impure CO2 gas.

[0217] Aspect 6: The method according to Aspect 5, wherein the regeneration gas contains water in an amount insufficient to hydrolyze other sulfur-containing compounds.

[0218] Aspect 7: The method according to aspect 5 or 6, wherein the compressed impure CO2 gas fed 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.

[0219] Aspect 8: The method according to aspects 1 to 3, wherein H 2 S and any other sulfur-containing impurities are removed from the compressed impure CO 2 gas by chemically reacting with at least one metal oxide to form solid metal sulfide and then performing oxidative regeneration.

[0220] Aspect 9: The method according to aspect 8, the method comprising:

[0221] passing said compressed impure CO2 gas through a bed comprising said at least one solid metal oxide in a reactor to convert the metal oxide into a metal sulfide and produce said purified CO2; and

[0222] The bed is regenerated using a regeneration gas comprising O 2 to produce a spent regeneration gas comprising SO 2 as the first recycle gas.

[0223] Aspect 10: The method according to Aspect 9, wherein the regeneration gas contains water in an amount insufficient to hydrolyze other sulfur-containing compounds.

[0224] Aspect 11: A method according to aspect 9 or 10, wherein the compressed impure CO2 gas fed to the reactor contains water, and the method includes drying the purified CO2 gas downstream of the bed containing the solid metal oxide.

[0225] Aspect 12: The method according to any one of aspects 1 to 11, comprising:

[0226] recovering H2S from the H2S-rich CO2 tail gas by selective amine absorption to produce H2S-depleted CO2 tail gas and recovered H2S; and

[0227] The recovered H 2 S is recycled to the Claus process to convert the recovered H 2 S into elemental sulfur.

[0228] Aspect 13: The method according to Aspect 12 includes 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 and a waste gas comprising CO2 and at least one non-condensable gas.

[0229] Aspect 14: The method according to Aspect 12, wherein the H 2 S-depleted CO 2 tail gas is directly compressed to produce the compressed impure CO 2 gas.

[0230] Aspect 15: The method according to aspect 14, the method comprising:

[0231] feeding the purified CO2 to a further purification process to produce further purified CO2 and a second recycle gas comprising CO2 and H2; and

[0232] The second recycle gas or the H 2 rich gas derived therefrom is recycled to the hydrogenation process, wherein a portion of the second recycle gas or the H 2 rich gas derived therefrom is purged.

[0233] Aspect 16: A method according to aspect 15, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the needs of the process.

[0234] Aspect 17: The method according to aspect 15 or 16, comprising recovering H2 gas from the second recycle gas in a membrane separation process to produce the H2-rich gas and a waste gas comprising CO2 and at least one non-condensable gas.

[0235] Aspect 18: The method according to any one of aspects 1 to 3, wherein the H 2 S-rich CO 2 tail gas is directly compressed to produce the compressed impure CO 2 gas containing H 2 S.

[0236] Aspect 19: The method according to any one of aspects 1 to 18, comprising:

[0237] feeding the purified CO2 to a further purification process to produce further purified CO2 and a second recycle gas comprising CO2 and H2; and

[0238] The second recycle gas or the H 2 rich gas derived therefrom is recycled to the hydrogenation process, wherein a portion of the second recycle gas or the H 2 rich gas derived therefrom is purged.

[0239] Aspect 20: The method according to Aspect 19, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the needs of the process.

[0240] 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-rich gas for recycling and a waste gas comprising CO2 and at least one non-condensable gas.

[0241] Aspect 22: A method according to any one of Aspects 1 to 3, comprising recovering CO2 and H2S from the H2S-rich CO2 tail gas by non-selective amine absorption to produce the impure CO2 gas for compression and a waste gas comprising CO2 and at least one non-condensable gas.

[0242] Aspect 23: The method according to aspects 1 to 3, wherein the H 2 S and any other sulfur-containing impurities are removed from the compressed impure CO 2 gas by distillation and / or partial condensation with phase separation as the physical separation.

[0243] Aspect 24: The method according to aspect 23, wherein the purified CO2 contains at least one residual sulfur-containing impurity, the method comprising:

[0244] further purifying the purified CO2 by selective adsorption or by 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 comprising at least one sulfur-containing compound; and

[0245] The further recycle gas is recycled to the Claus process to convert the sulphur-containing compounds into elemental sulphur.

[0246] Aspect 25: The method according to Aspect 24, comprising:

[0247] removing H2 and any other non-condensable gases from the compressed impure CO2 gas by distillation and / or partial condensation with phase separation to produce H2S-rich CO2 fluid and H2-rich CO2 gas;

[0248] recycling the H2-enriched CO2 gas or the further H2-enriched CO2 gas obtained therefrom to the hydrogenation process as a second recycle gas; and

[0249] separating the H2S-rich CO2 stream by distillation and / or partial condensation with phase separation to produce the purified CO2 as overhead gas and a H2S-rich bottoms liquid;

[0250] evaporating the H2S-rich bottom liquid to generate H2S-rich gas as the first recycle gas;

[0251] The second recycle gas or a portion of the H2-rich gas obtained therefrom is purged.

[0252] Aspect 26: A method according to aspect 25, wherein the amount of H2 recycled to the hydrogenation process is sufficient to meet the needs of the process.

[0253] Aspect 27: The method according to Aspect 25 or 26 includes recovering H2 gas from the second recycled gas in a membrane separation process to produce the further H2-enriched CO2 gas for recycling and a waste gas comprising CO2 and at least one non-condensable gas.

[0254] Aspect 28: The method according to aspects 26 to 28, wherein the purified CO2 overhead gas contains one or more residual sulfur-containing compounds, the method comprising:

[0255] 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 followed by oxidative regeneration to produce further purified CO2 and a third recycle gas comprising at least one sulfur-containing compound; and

[0256] The third recycle gas is recycled to the Claus process to convert the sulfur-containing compounds into elemental sulfur.

[0257] Aspect 29: An apparatus for desulfurizing a crude CO2 gas containing H2S and optionally at least one other sulfur-containing impurity, the apparatus comprising:

[0258] A Claus unit for removing H2S from a crude CO2 gas, the Claus unit comprising:

[0259] a first inlet for an oxidant gas, the oxidant gas comprising O2;

[0260] a second inlet for said crude CO2 gas;

[0261] a first outlet for Claus tail gas comprising CO2, residual H2S and at least one other sulfur-containing impurity; and

[0262] a second outlet for elemental sulfur;

[0263] a source of oxidant gas in fluid flow communication with the first inlet of the Claus unit, the source of oxidant gas comprising O2;

[0264] a source of crude CO2 gas in fluid flow communication with the second inlet of the Claus unit;

[0265] A hydrogenation unit for converting the at least one other sulfur-containing impurity in the Claus tail gas into H2S, the hydrogenation unit comprising:

[0266] a first inlet in fluid flow communication with the first outlet of the Claus unit;

[0267] A second inlet for H2; and

[0268] A first outlet for H2S-rich CO2 tail gas;

[0269] a source of H2 in fluid flow communication with the second inlet of the hydrogenation unit;

[0270] A cooling unit for cooling H2S-rich CO2 tail gas, the cooling unit comprising:

[0271] a first inlet in fluid communication with the first outlet of the hydrogenation unit;

[0272] a first outlet for a cooled H2S-rich CO2 tail gas; and

[0273] a second outlet for condensed water;

[0274] A compression unit for compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom, the compression device comprising:

[0275] an inlet in fluid flow communication with the first outlet of the cooling unit; and

[0276] An outlet for compressed impure CO2 gas;

[0277] as well as

[0278] A purification unit for removing H2S and any other sulfur-containing impurities from compressed impure CO2 gas by physical separation or by chemical reaction with at least one metal oxide to form solid metal sulfide and subsequent oxidative regeneration, the purification unit comprising:

[0279] a first inlet in fluid flow communication with the outlet of the compression unit;

[0280] a first outlet for purified CO2; and

[0281] a second outlet for a first recycle gas comprising at least one sulphur-containing compound,

[0282] The second outlet of the purification unit is in fluid communication with the Claus unit.

[0283] Aspect 30: The apparatus according to aspect 29, wherein the H2 source is an H2 generation unit, the H2 generation unit comprising an outlet for H2 in fluid communication with the second inlet of the hydrogenation unit.

[0284] Aspect 31: The apparatus of aspect 29 or 30, wherein the cooling unit is a direct contact cooler, the direct contact cooler further comprising a second inlet for cooling water.

[0285] Aspect 32: The apparatus according to aspect 29, wherein the purification unit comprises a selective adsorption unit, the selective adsorption unit comprising:

[0286] at least one container having an upstream end and a downstream end, the or each container comprising:

[0287] an adsorbent bed comprising at least one layer of adsorbent material selective for sulfur-containing compounds;

[0288] a first inlet for compressed impure CO2 gas at the upstream end of the or each vessel;

[0289] a first outlet for purified CO2 at the downstream end of the or each vessel;

[0290] a second inlet for regeneration gas at the downstream end of the or each vessel; and

[0291] a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0292] Wherein the first inlet of the selective adsorption unit is in fluid flow communication with the outlet of the compression unit, and wherein the second outlet is in fluid flow communication with the Claus unit.

[0293] Aspect 33: Apparatus according to aspect 32, wherein the adsorbent bed in the or each vessel comprises at least one layer of adsorbent material selective for water downstream of the at least one layer of adsorbent material selective for sulphur-containing compounds.

[0294] Aspect 34: The apparatus according to aspect 33 or 34, comprising a dryer unit downstream of the selective adsorption unit, the dryer unit comprising:

[0295] an inlet in fluid flow communication with the first outlet of the selective adsorption unit; and

[0296] An outlet for dry purified CO2 is in fluid flow communication with the inlet of the compression unit.

[0297] Aspect 35: The apparatus according to aspect 29, wherein the purification unit comprises a reactor, the reactor comprising:

[0298] at least one container having an upstream end and a downstream end, the or each container comprising:

[0299] a bed comprising at least one solid metal oxide;

[0300] a first inlet for compressed impure CO2 gas at the upstream end of the or each vessel;

[0301] a first outlet for purified CO2 at the downstream end of the or each vessel;

[0302] a second inlet for regeneration gas at the downstream end of the or each vessel; and

[0303] a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0304] Wherein the first inlet of the reactor is in fluid flow communication with the outlet of the compression unit, and wherein the second outlet is in fluid flow communication with the Claus unit.

[0305] Aspect 36: Apparatus according to aspect 35, wherein the or each vessel comprises at least one layer of adsorbent material selective for water downstream of the bed comprising the solid metal oxide.

[0306] Aspect 37: The apparatus according to aspect 35 or 36, comprising a dryer unit downstream of the reactor, the dryer unit comprising:

[0307] an inlet in fluid communication with a first outlet of the reactor; and

[0308] An outlet for dry purified CO2 is in fluid flow communication with the compression unit.

[0309] Aspect 38: The apparatus according to any one of aspects 29 to 37, comprising:

[0310] A selective amine absorption unit for recovering H2S from H2S-rich CO2 tail gas, the selective amine absorption unit comprising:

[0311] an inlet in fluid flow communication with the first outlet of the cooling unit; and

[0312] a first outlet for H2S-lean CO2 tail gas in fluid flow communication with the inlet of the compression unit; and

[0313] A second outlet for recovered H2S is in fluid flow communication with the Claus unit.

[0314] Aspect 39: The device according to aspect 38, the device comprising:

[0315] A non-selective amine absorption unit for recovering CO2 and residual H2S from H2S-depleted CO2 tail gas, the non-selective amine absorption unit comprising:

[0316] an inlet in fluid flow communication with the first outlet of the selective amine absorber unit;

[0317] a first outlet for impure CO2 gas in direct fluid flow communication with the inlet of the compression unit; and

[0318] A second outlet for waste gas comprising CO2 and at least one non-condensable gas.

[0319] Aspect 40: The apparatus of aspect 38, wherein the first outlet of the selective amine adsorption unit is in direct fluid flow communication with the inlet of the compression unit.

[0320] Aspect 41: The apparatus according to aspect 40, wherein the purification unit is a selective adsorption unit or a reactor, and the apparatus further comprises:

[0321] A further purification unit for further purifying the purified CO2, the further purification unit comprising:

[0322] an inlet for purified CO2 in fluid flow communication with the first outlet of the selective adsorption unit or the reactor;

[0323] a first outlet for further purified CO2; and

[0324] a second outlet for a second recycle gas comprising CO2 and H2 in fluid flow communication with the hydrogenation unit,

[0325] as well as

[0326] A purge line is in fluid flow communication with the second outlet of the further purification unit.

[0327] Aspect 42: The device according to aspect 41, the device comprising:

[0328] A membrane separation unit for recovering H2 gas from the second recycle gas, the membrane separation unit comprising:

[0329] an inlet for a second recycle gas in fluid flow communication with the second outlet of the further purification unit;

[0330] a first outlet for H2-rich gas in direct fluid flow communication with the hydrogenation unit; and

[0331] A second outlet for waste gas comprising CO2 and at least one non-condensable gas.

[0332] 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.

[0333] Aspect 44: The apparatus according to aspect 43, wherein the purification unit is a selective adsorption unit or a reactor, and the apparatus further comprises:

[0334] A further purification unit for further purifying the purified CO2, the further purification comprising:

[0335] an inlet for purified CO2 in fluid flow communication with the first outlet of the selective adsorption unit or the reactor;

[0336] a first outlet for further purified CO2; and

[0337] a second outlet for a second recycle gas comprising CO2 and H2 in fluid flow communication with the hydrogenation unit,

[0338] as well as

[0339] A purge line is in fluid flow communication with the second outlet of the further purification unit.

[0340] Aspect 45: The device according to aspect 44, the device comprising:

[0341] A membrane separation unit for recovering H2 gas from the second recycle gas, the membrane separation unit comprising:

[0342] an inlet for a second recycle gas in fluid flow communication with the second outlet of the further purification unit;

[0343] a first outlet for H2-rich permeate gas in direct fluid flow communication with an inlet of said hydrogenation unit; and

[0344] A second outlet for spent retentate gas comprising CO2 and at least one non-condensable gas.

[0345] Aspect 46: The apparatus according to any one of aspects 29 to 31, comprising:

[0346] A non-selective amine absorption unit for recovering CO2 and H2S from H2S-rich CO2 tail gas, the non-selective amine absorption unit comprising:

[0347] an inlet in direct fluid flow communication with the outlet of the cooling unit;

[0348] a first outlet for impure CO2 gas in direct fluid flow communication with the inlet of the compression unit; and

[0349] A second outlet for waste gas comprising CO2 and at least one non-condensable gas.

[0350] Aspect 47: The apparatus according to any one of aspects 29 to 31, wherein the purification unit is a single-stage purification unit, the single-stage purification unit comprising:

[0351] an inlet for compressed impure CO2 in fluid flow communication with the outlet of the compression unit;

[0352] a first outlet for a H2S-rich CO2 fluid;

[0353] a second outlet for H2-rich CO2 gas in fluid flow communication with the inlet of the hydrogenation unit;

[0354] The apparatus comprises a selective adsorption unit, the selective adsorption unit comprising:

[0355] at least one container having an upstream end and a downstream end, the or each container comprising:

[0356] an adsorbent bed comprising at least one layer of adsorbent material selective for sulfur-containing compounds;

[0357] a first inlet for H2S-rich CO2 fluid at the upstream end of the or each vessel;

[0358] a first outlet for purified CO2 at the downstream end of the or each vessel;

[0359] a second inlet for regeneration gas at the downstream end of the or each vessel; and a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0360] Wherein the first inlet of the selective adsorption vessel is in fluid flow communication with the first outlet of the single-stage purification unit, and wherein the second outlet is in fluid flow communication with the Claus unit.

[0361] Aspect 48: The apparatus according to any one of aspects 29 to 31, wherein the purification unit is a single-stage purification unit, the single-stage purification unit comprising:

[0362] an inlet for compressed impure CO2 in fluid flow communication with the outlet of the compression unit;

[0363] a first outlet for a H2S-rich CO2 fluid;

[0364] a second outlet for H2-rich CO2 gas in fluid flow communication with the inlet of the hydrogenation unit;

[0365] The apparatus comprises a reactor comprising:

[0366] at least one container having an upstream end and a downstream end, the or each container comprising:

[0367] a bed comprising at least one solid metal oxide;

[0368] a first inlet for H2S-rich CO2 fluid at the upstream end of the or each vessel;

[0369] a first outlet for purified CO2 at the downstream end of the or each vessel;

[0370] a second inlet for regeneration gas at the downstream end of the or each vessel; and

[0371] a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0372] Wherein the first inlet of the reactor is in fluid flow communication with the first outlet of the single-stage purification unit, and wherein the second outlet is in fluid flow communication with the Claus unit.

[0373] Aspect 49: The apparatus according to any one of aspects 29 to 31, wherein the purification unit comprises a purification unit including a first stage and a second stage;

[0374] The first level includes:

[0375] an inlet for compressed impure CO2 in fluid flow communication with the outlet of the compression unit;

[0376] a first outlet for a H2S-rich CO2 fluid;

[0377] a second outlet for H2-rich CO2 gas in fluid flow communication with the inlet of the hydrogenation unit;

[0378] The second level includes:

[0379] an inlet for H2S-rich CO2 fluid in fluid flow communication with said first outlet of said first stage;

[0380] a first outlet for purified CO2 gas;

[0381] A second outlet for H2S-rich gas in fluid flow communication with the Claus unit

[0382] as well as

[0383] A purge line is in fluid flow communication with the second outlet of the first stage of the purification unit.

[0384] Aspect 50: The apparatus according to aspect 49, the apparatus comprising:

[0385] A membrane separation unit for recovering H2 gas from H2-rich CO2 gas, the membrane separation unit comprising:

[0386] an inlet for H2-rich CO2 gas in fluid flow communication with the second outlet of the first stage of the purification unit;

[0387] a first outlet for H2-rich permeate gas in direct fluid flow communication with an inlet of said hydrogenation unit; and

[0388] A second outlet for spent retentate gas comprising CO2 and at least one non-condensable gas.

[0389] Aspect 51: The device according to Aspect 50, comprising: a selective adsorption unit, wherein the selective adsorption unit comprises:

[0390] at least one container having an upstream end and a downstream end, the or each container comprising:

[0391] an adsorbent bed comprising at least one layer of adsorbent material selective for sulfur-containing compounds;

[0392] a first inlet for purified CO2 at the upstream end of the or each vessel;

[0393] a first outlet for further purified CO2 at the downstream end of the or each vessel;

[0394] a second inlet for regeneration gas at the downstream end of the or each vessel; and

[0395] a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0396] 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 wherein the second outlet is in fluid flow communication with the Claus unit.

[0397] Aspect 52: The apparatus according to aspect 50, comprising a reactor, wherein the reactor comprises:

[0398] at least one container having an upstream end and a downstream end, the or each container comprising:

[0399] a bed comprising at least one solid metal oxide;

[0400] a first inlet for purified CO2 at the upstream end of the or each vessel;

[0401] a first outlet for further purified CO2 at the downstream end of the or each vessel;

[0402] a second inlet for regeneration gas at the downstream end of the or each vessel; and

[0403] a second outlet for spent regeneration gas at the upstream end of the or each vessel,

[0404] 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 wherein the second outlet is in fluid flow communication with the Claus unit.

[0405] Example

[0406] Specific embodiments of the invention will now be illustrated by computer modeling in the following examples.

[0407] Example 1

[0408] Aspen Plus (version 10) was used to Figure 1 The process described in the flow diagram of FIG. 3 (in which unit 36 ​​is a reactor containing a mixed metal oxide bed of the type disclosed in US Pat. No. 4,797,268) was modeled and heat and mass balance data for the key streams are provided in Table 1.

[0409] 100 101 102 103 104 105 107 108 109 110 111 115 Mutually Vapor Phase Vapor Phase Liquid Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase temperature C 45.0 28.0 135.0 130.0 50.0 50.0 45.0 500 500 52.1 50.0 50.0 pressure barg 0.9 0.8 0.5 0.3 0.1 0.1 1.0 30.0 30.0 10 30.0 0.0 Molar flow rate kmol / hr 1000.0 879.5 400.0 1786.3 1701.1 1624.7 541.8 518.2 9.6 85.9 508.7 1083.0 Mole fraction <![CDATA[CO2]]> 0.5500 0.0000 0.0000 0.3386 0.3649 0.3515 0.9487 0.9918 0.5386 0.6378 1.0000 0.0527 <![CDATA[H2S]]> 0.4000 0.0000 0.0000 0.0086 0.0124 0.0001 0.0002 0.0002 0.0000 0.2442 0.0000 0.0000 <![CDATA[SO2]]> 0.0000 0.0000 0.0000 0.0017 0.0000 0.0000 0.0000 0.0000 0.0110 0.0012 0.0000 0.0000 <![CDATA[H2O]]> 0.0500 0.0000 0.0000 0.2371 0.1118 0.1135 0.0511 0.0082 0.4525 0.1168 0.0000 0.1447 sulfur 0.0000 0.0000 1.0000 0.0014 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[H2]]> 0.0000 0.0000 0.0000 0.0236 0.0272 0.0285 0.0000 0.0000 0.0000 0.0000 0.0000 0.0427 <![CDATA[N2]]> 0.0000 0.7900 0.0000 0.3890 0.4837 0.5064 0.0000 0.0000 0.0000 0.0000 0.0000 0.7598 <![CDATA[O2]]> 0.0000 0.2100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0410] Table 1

[0411] This example illustrates an overall CO2 recovery of 92.5 mol% at 100 mol% purity, ie, complete removal of residual H2S (and water) from the impure CO2.

[0412] Example 2

[0413] Aspen Plus (version 10) was used to Figure 2 The process described in the flow diagram of (where unit 50 is a reactor containing a mixed metal oxide bed of the type disclosed in US4797268 and unit 56 is a CPU of the type disclosed in US7819951) was modeled and the heat and mass balance data for the key streams are provided in Table 2. In the model, the flow rate of the purge stream is zero.

[0414]

[0415] Table 2

[0416] This example illustrates that the total CO2 recovery at 99.5 mol% purity is 95.8 mol%, the remainder being H2, i.e., the residual H2S (and water) is completely removed from the impure CO2.

[0417] Example 3

[0418] Aspen Plus (version 10) was used to Figure 3 The process described in the flow diagram of (where unit 36 ​​is a reactor having a mixed metal oxide bed of the type disclosed in US4797268) was modeled and heat and mass balance data for the key streams are provided in Table 3.

[0419] 100 101 102 103 104 107 108 110 111 115 Mutually Vapor Phase Vapor Phase Vapor Phase Liquid Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase temperature C 45.0 28.0 135.0 130.0 50.0 45.0 50.0 27.1 50.0 50.0 pressure barg 0.9 0.8 0.5 0.3 0.1 1.0 30.0 1.0 30.0 0.0 Molar flow rate kmol / hr 1000.0 734.3 400.0 1667.7 1570.8 607.2 585.6 103.1 503.7 963.6 Mole fraction <![CDATA[CO2]]> 0.5500 0.0000 0.0000 0.3634 0.3959 0.9218 0.9556 0.5428 1.0000 0.0645 <![CDATA[H2S]]> 0.4000 0.0000 0.0000 0.0093 0.0135 0.0349 0.0361 0.0000 0.0000 0.0000 <![CDATA[SO2]]> 0.0000 0.0000 0.0000 0.0019 0.0000 0.0000 0.0000 0.2052 0.0000 0.0000 <![CDATA[H2O]]> 0.0500 0.0000 0.0000 0.2521 0.1118 0.0434 0.0082 0.2520 0.0000 0.1549 sulfur 0.0000 0.0000 1.0000 0.0015 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[H2]]> 0.0000 0.0000 0.0000 0.0240 0.0281 0.0000 0.0000 0.0000 0.0000 0.0458 <![CDATA[N2]]> 0.0000 0.7900 0.0000 0.3478 0.4508 0.0000 0.0000 0.0000 0.0000 0.7348 <![CDATA[O2]]> 0.0000 0.2100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0420] Table 3

[0421] This example illustrates an overall CO2 recovery of 91.5 mol% at 100 mol% purity, ie, complete removal of residual H2S (and water) from the impure CO2.

[0422] Example 4

[0423] Aspen Plus (version 10) was used to Figure 4 The process described in the flow diagram of (where unit 50 is a reactor having a mixed metal oxide bed of the type disclosed in US4797268) was modeled and heat and mass balance data for the key streams are provided in Table 4.

[0424] 100 101 102 103 104 106 107 108 110 111 112 115 Mutually Vapor Phase Vapor Phase Vapor Phase Liquid Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase temperature C 45.0 28.0 135.0 130.0 50.0 50.0 50.0 30.0 27.8 20.0 30.0 29.6 pressure barg 0.9 0.8 0.5 0.3 0.1 30.0 30.0 30.0 1.0 14.0 25.0 29.5 Molar flow rate kmolhr 1000.0 163.7 400.0 1085.1 754.8 675.8 595.0 65.7 94.3 529.3 13.4 52.3 Mole fraction <![CDATA[CO2]]> 0.5500 0.0000 0.0000 0.5636 0.8168 0.9120 0.9321 0.4221 0.6535 0.9954 0.3677 0.4360 <![CDATA[H2S]]> 0.4000 0.0000 0.0000 0.0085 0.0180 0.0201 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[SO2]]> 0.0000 0.0000 0.0000 0.0017 0.0000 0.0000 0.0000 0.0000 0.1440 0.0000 0.0000 0.0000 <![CDATA[H2O]]> 0.0500 0.0000 0.0000 0.3870 0.1117 0.0082 0.0000 0.0000 0.2025 0.0000 0.0000 0.0000 sulfur 0.0000 0.0000 1.0000 0.0024 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[H2]]> 0.0000 0.0000 0.0000 0.0369 0.0535 0.0598 0.0679 0.5779 0.0000 0.0046 0.6323 0.5640 <![CDATA[N2]]> 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[O2]]> 0.0000 1.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0425] Table 4

[0426] This example illustrates that the total CO2 recovery at 99.5 mol% purity is 95.8 mol%, the remainder being H2, i.e., the residual H2S (and water) is completely removed from the impure CO2.

[0427] Example 5

[0428] Aspen Plus (version 10) was used to Figure 5 The process described in the flow chart of Figure 2 ) were modeled and heat and mass balance data for key streams are provided in Table 5.

[0429]

[0430] Table 5

[0431] This example illustrates a total CO2 recovery of 95.6 mol% at 99.5 mol% purity. The product CO2 also contains about 0.5 mol% H2 and no more than 100 ppm H2S, which meets the specifications for H2S required for sequestration.

[0432] Example 6

[0433] Aspen Plus (version 10) was used to Figure 1 The process described in the flow chart of (wherein unit 36 ​​is a selective adsorption unit of the type disclosed in WO2021130530A) was modeled and

[0434] Heat and mass balance data for key streams are provided in Table 6.

[0435]

[0436] Table 6

[0437] This example illustrates a total CO2 recovery of 91.6 mol% at 100 mol% purity, ie, complete removal of residual H2S (and water) from the impure CO2 using the selective adsorption unit 36 ​​(including a layer of water adsorbent material).

[0438] Example 7

[0439] Aspen Plus (version 10) was used to Figure 6 The process described in the flow chart of US10254042A (wherein the purification unit 56 has the same Figure 1 B) was modeled and the heat and mass balance data for the key streams are provided in Table 7.

[0440] 100 101 102 103 104 106 107 108 110 111 112 115 Mutually Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase temperature C 45.0 28.0 135.0 130.0 50.0 60.0 60.0 30.0 26.3 60.0 30.0 29.6 pressure barg 0.9 0.8 0.5 0.3 0.1 29.5 29.5 30.0 1.0 29.5 25.0 29.5 Molar flow rate kmol / hr 1000.0 163.6 400.0 1076.3 750.3 666.3 598.4 67.9 85.4 526.5 12.9 55.1 Mole fraction <![CDATA[CO2]]> 0.5500 0.0000 0.0000 0.5651 0.8173 0.9201 0.9733 0.4512 0.6816 0.9955 0.3973 0.4638 <![CDATA[H2S]]> 0.4000 0.0000 0.0000 0.0085 0.0181 0.0204 0.0227 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[SO2]]> 0.0000 0.0000 0.0000 0.0017 0.0000 0.0000 0.0000 0.0000 0.1592 0.0000 0.0000 0.0000 <![CDATA[H2O]]> 0.0500 0.0000 0.0000 0.3850 0.1117 0.0000 0.0000 0.0000 0.1592 0.0000 0.0000 0.0000 SULFU-01 0.0000 0.0000 1.0000 0.0024 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[H2]]> 0.0000 0.0000 0.0000 0.0372 0.0529 0.0595 0.0040 0.5488 0.0000 0.0045 0.6027 0.5362 <![CDATA[N2]]> 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 <![CDATA[O2]]> 0.0000 1.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0441] Table 7

[0442] This example illustrates a total CO2 recovery of 95.3 mol% at 99.5 mol% purity. The product CO2 also contains less than 0.5 mol% H2 and no H2S, which meets the specifications for H2S required for sequestration.

[0443] Example 8

[0444] Aspen Plus (version 10) was used to Figure 7 The process described in the flowchart (where unit 26** represents Figure 1The specific combination of units 26, 32 and 36 in the flow cell was modeled and the heat and mass balance data for the key streams are provided in Table 8.

[0445] 100 101 102 103 104 110 111 115 Mutually Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase Vapor Phase temperature C 45.0 28.0 135.0 130.0 50.0 27.4 60.0 50.0 pressure barg 0.9 0.8 0.5 0.3 0.1 1.0 30.0 0.0 Molar flow rate kmol / hr 1000.0 838.0 400.0 1729.7 1652.6 68.7 503.7 1061.1 Mole fraction <![CDATA[CO2]]> 0.5500 0.0000 0.0000 0.3503 0.3763 0.8149 1.0000 0.0586 <![CDATA[H2S]]> 0.4000 0.0000 0.0000 0.0006 0.0024 0.0001 0.0000 0.0000 <![CDATA[SO2]]> 0.0000 0.0000 0.0000 0.0003 0.0000 0.0587 0.0000 0.0000 <![CDATA[H2O]]> 0.0500 0.0000 0.0000 0.2415 0.1118 0.1263 0.0000 0.1479 SULFU-01 0.0000 0.0000 1.0000 0.0015 0.0000 0.0000 0.0000 0.0000 <![CDATA[H2]]> 0.0000 0.0000 0.0000 0.0231 0.0314 0.0000 0.0000 0.0490 <![CDATA[N2]]> 0.0000 0.7900 0.0000 0.3827 0.4780 0.0000 0.0000 0.7445 <![CDATA[O2]]> 0.0000 0.2100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0446] Table 8

[0447] This example illustrates a total CO2 recovery of 91.6 mole percent at 100 mole percent purity. Thus, although the CO2 recovery is less than the other embodiments, the purity of the CO2 is higher in this embodiment.

[0448] It will be understood that the present invention is not limited to the details described above with reference to the preferred embodiments, but that numerous modifications and variations are possible without departing from the spirit and scope of the present invention as defined in the appended claims.

[0449] In this specification, unless expressly stated otherwise, the word "or" is used in the sense of an operator that returns a true value when one or both of the conditions are met, as opposed to the operator "exclusive or" which requires only one of the conditions to be met. The word "comprising" is used to mean "including", rather than to mean "consisting of".

[0450] All of the prior art teachings above are incorporated herein by reference. Acknowledgment of any prior-published document herein is not to be taken as an acknowledgment or representation that its teachings were common general knowledge in Australia or elsewhere as at the date of its publication.

Claims

1. A method for desulfurizing crude carbon dioxide (CO ) gas containing hydrogen sulfide (H 2 S) and optionally at least one other sulfur-containing impurity, the method comprising: feeding a crude CO2 gas comprising H2S to a Claus process to convert the H2S into elemental sulfur in the presence of oxygen (O2) gas and produce a Claus tail gas comprising 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 into H2S in the presence of hydrogen (H2) and produce a H2S-rich CO2 tail gas; Cooling the H2S-rich CO2 tail gas and removing condensed water to produce cooled H2S-rich CO2 tail gas; compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom to produce 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 chemical reaction with at least one solid metal oxide to form at least one solid metal sulfide followed by oxidative regeneration to produce purified CO2 and a first recycle gas comprising at least one sulfur-containing compound; as well as The first recycle gas is recycled to the Claus process to convert the at least one sulfur-containing compound into elemental sulfur.

2. The method according to claim 1, further comprising: H2 is generated during hydrogen generation; feeding the H2 to the hydrogenation process; as well as CO2 and H2S are recovered from the H2S-rich CO2 tail gas by non-selective amine absorption to produce the impure CO2 gas for compression and a waste gas comprising CO2 and at least one non-condensable gas.

3. The method of claim 1, wherein the H2S-rich CO2 tail gas is directly compressed to produce the compressed impure CO2 gas containing H2S.

4. The method according to claim 1, further comprising: feeding the purified CO2 to a further purification unit to produce further purified CO2 and a second recycle gas comprising CO2 and H2; recycling the second recycle gas or the H2-rich gas obtained therefrom to the hydrogenation process; as well as recovering H2 gas from the second recycle gas in a membrane separation process to produce the H2-rich gas for recycling to the hydrogenation process and an off-gas comprising CO2 and at least one non-condensable gas, The second recycle gas or a portion of the H2-rich gas obtained therefrom is purged.

5. The method according to claim 1, further comprising: recovering H2S from the H2S-rich CO2 tail gas by selective amine absorption to produce H2S-depleted CO2 tail gas and recovered H2S; recycling the recovered H 2 S to the Claus process to convert the recovered H 2 S into elemental sulfur; and recovering CO2 and residual H2S from said H2S-depleted CO2 tail gas by non-selective amine absorption to produce said impure CO2 gas for compression and a waste gas comprising CO2 and at least one non-condensable gas; feeding the purified CO2 to a further purification unit to produce further purified CO2 and a second recycle gas comprising CO2 and H2; recycling the second recycle gas or the H2-rich gas obtained therefrom to the hydrogenation process; as well as recovering H2 gas from the second recycle gas in a membrane separation process to produce the H2-rich gas and an off-gas comprising CO2 and at least one non-condensable gas, wherein the H 2 S-depleted CO 2 tail gas is directly compressed to produce the compressed impure CO 2 gas, and wherein the second recycle gas or a portion of the H 2 -rich gas obtained therefrom is purged.

6. The method of claim 1, wherein H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 gas by the chemical reaction with at least one metal oxide to form solid metal sulfide and subsequent oxidative regeneration.

7. The method according to claim 1, further comprising drying the purified CO2 gas downstream of the adsorbent material having selectivity for sulfur-containing compounds, wherein the regeneration gas contains water in an amount insufficient to hydrolyze the other sulfur-containing compounds, and wherein the compressed impure CO2 gas fed to the selective adsorption unit contains water; and wherein H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 gas by selective adsorption as the physical separation, wherein the selective adsorption involves removing H2S and any other sulfur-containing compounds in the compressed impure CO2 gas by adsorption on a bed of at least one adsorbent material selective for sulfur-containing compounds in the selective adsorption unit to produce the purified CO2 and a spent regeneration gas as the first recycle gas after desorption using the regeneration gas, the spent regeneration gas containing the H2S and any other sulfur-containing compounds from the compressed impure CO2 gas.

8. The process of claim 1, wherein H2S and any other sulfur-containing impurities are removed from the compressed impure CO2 by passing the impure CO2 gas through a bed comprising at least one solid metal oxide in a reactor to convert the at least one solid metal oxide into at least one metal sulfide and produce the purified CO2; and The bed is regenerated using a regeneration gas comprising O2 to produce a spent regeneration gas comprising sulfur dioxide (SO2) as the first recycle gas.

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

10. The method of claim 8, further comprising drying the purified CO2 gas downstream of the bed comprising the at least one solid metal oxide; wherein the compressed impure CO2 gas fed to the reactor comprises water.

11. A method comprising: removing H2 and any other non-condensable gases from the compressed impure CO2 gas by distillation and / or partial condensation with phase separation to produce an H2S-rich CO2 fluid and an H2-rich CO2 gas; recycling the H2-enriched CO2 gas or the further H2-enriched CO2 gas obtained therefrom to the hydrogenation process as a second recycle gas; and separating the H2S-rich CO2 stream by distillation and / or partial condensation with phase separation to produce purified CO2 as overhead gas and H2S-rich bottoms liquid; evaporating the H2S-rich bottom liquid to generate H2S-rich gas as the first recycle gas; The second recycle gas or a portion of the H2-rich gas obtained therefrom is purged.

12. The method according to claim 11, further comprising recovering H2 gas from the second recycle gas in a membrane separation process to produce the further H2-enriched CO2 gas for recycling and a waste gas comprising CO2 and at least one non-condensable gas.

13. The method of claim 11, wherein the purified CO2 overhead gas contains one or more residual sulfur-containing compounds.

14. The method of claim 1138, further comprising: 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 followed by oxidative regeneration to produce further purified CO2 and a third recycle gas comprising at least one sulfur-containing compound; and The third recycle gas is recycled to the Claus process to convert the sulfur-containing compounds into elemental sulfur.

15. A system, comprising: A Claus unit for removing H2S from a crude CO2 gas, the Claus unit comprising: a first inlet for an oxidant gas, the oxidant gas comprising O2; a second inlet for said crude CO2 gas; a first outlet for Claus tail gas comprising CO2, residual H2S and at least one other sulfur-containing impurity; and a second outlet for elemental sulfur; a source of oxidant gas in fluid flow communication with the first inlet of the Claus unit, the source of oxidant gas comprising O2; a source of crude CO2 gas 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 into H2S, the hydrogenation unit comprising: a first inlet in fluid flow communication with the first outlet of the Claus unit; A second inlet for H2; and A first outlet for H2S-rich CO2 tail gas; a source of H2 in fluid flow communication with the second inlet of the hydrogenation unit; A cooling unit for cooling H2S-rich CO2 tail gas, the cooling unit comprising: a first inlet in fluid communication with the first outlet of the hydrogenation unit; a first outlet for cooled H2S-rich CO2 tail gas; and a second outlet for condensed water; A compression unit for compressing the cooled H2S-rich CO2 tail gas or the impure CO2 gas containing H2S obtained therefrom, the compression device comprising: an inlet in fluid flow communication with the first outlet of the cooling unit; and An outlet for compressed impure CO2 gas; as well as A purification unit for removing H2S and any other sulfur-containing impurities from compressed impure CO2 gas by physical separation or by chemical reaction with at least one metal oxide to form solid metal sulfide and subsequent oxidative regeneration, the purification unit comprising: a first inlet in fluid flow communication with the outlet of the compression unit; a first outlet for purified CO2; and a second outlet for a first recycle gas comprising at least one sulphur-containing compound, The second outlet of the purification unit is in fluid communication with the Claus unit.

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