# US 2018/0290100 A1 · Removal of aromatic hydrocarbons from lean acid gas feed for sulfur recovery > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0290100 A1 - Document ID: US20180290100A1 - Status: Published application - Kind: A1 - Application number: 15/570,645 - Filed: 2016-04-28 - Published: 2018-10-11 - Earliest claimed: 2015-04-30 - Assignees: Prosernat - Applicants: Prosernat - Inventors: Emile FILLATRE; Gauthier PERDU; Benoit MARES - Web page: https://patentgrep.com/patent/US20180290100A1 ## CPC - B01D 53/1418: {Recovery of products} - B01D 53/1406: {Multiple stage absorption} - B01D 53/1425: {Regeneration of liquid absorbents} - B01D 53/1468: {Removing hydrogen sulfide} - B01D 53/1487: {Removing organic compounds} - C01B 17/0408: {Pretreatment of the hydrogen sulfide containing gases} - C01B 17/0417: {Combustion reactors} - C01B 17/043: {Catalytic converters} - C10L 3/101: {Removal of contaminants} - C10L 3/103: {Sulfur containing contaminants} - C10L 3/104: {Carbon dioxide} - B01D 2251/30: Alkali metal compounds - B01D 2251/606: Carbonates - B01D 2251/61: Phosphates - B01D 2252/20431: Tertiary amines - B01D 2252/20489: with two or more hydroxyl groups - B01D 2252/2056: Sulfur compounds, e.g. Sulfolane, thiols - B01D 2252/602: Activators, promoting agents, catalytic agents or enzymes - B01D 2256/22: Carbon dioxide - B01D 2256/245: Methane - B01D 2257/7022: Aliphatic hydrocarbons - B01D 2257/7027: Aromatic hydrocarbons - C10L 2290/12: Regeneration of a solvent, catalyst, adsorbent or any other component used to treat or prepare a fuel - C10L 2290/541: Absorption of impurities during preparation or upgrading of a fuel - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - C10L: FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS ## Abstract The present invention is directed to a process for the removal of aromatic hydrocarbons from a lean acid gas containing less than 20 mol. % of H2S, comprising: a) contacting the lean acid gas stream (1) with a H2S-selective liquid absorbent solution (29) in a first absorption zone (2) to produce a gas stream depleted in H2S (3) and an absorbent solution enriched in H2S (4), b) introducing the absorbent solution (4) into a non-thermic stripping zone (8) where it is contacted with a stripping gas stream (7) to obtain an absorbent solution depleted in C4+ aliphatic and aromatic hydrocarbons (9) and a stripping gas stream enriched in aromatic and C4+ aliphatic hydrocarbons (10), c) contacting the stripping gas stream (10) obtained in step b) with a H2S-selective liquid absorbent solution (28) in a second absorption zone (12) to obtain a stripping gas stream depleted in H2S (13), and an absorbent solution enriched in H2S (14) d) introducing the absorbent solution (9) obtained in step b) into a desorption zone (16) wherein the H2S-selective liquid absorbent solution (17) is recovered and a lean acid gas is produced. ## Claims ### Claim 1 A process for the removal of aromatic hydrocarbons, such as benzene, toluene, ethyl benzene and xylene (BTX) and aliphatic hydrocarbons having 4 carbon atoms or more (C4+) from a lean acid gas containing CO2 and less than 20 mol. % of H2S, which process comprises: a) contacting the lean acid gas stream (1) with a H2S-selective liquid absorbent solution (29) in a first absorption zone (2) to produce a gas stream depleted in H2S (3) and containing CO2, aromatic hydrocarbons and C4+ aliphatic hydrocarbons, and an absorbent solution enriched in H2S (4), also containing co-absorbed C4+ aliphatic hydrocarbons, aromatic hydrocarbons and CO2, b) introducing the absorbent solution enriched in H2S (4) into a non-thermic stripping zone (8) where it is contacted with a stripping gas stream (7), preferably fuel gas, to obtain an absorbent solution depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (9) and containing H2S and CO2 and a stripping gas stream enriched in aromatic hydrocarbons and C4+ aliphatic hydrocarbons (10), also containing H2S and CO2, c) contacting the stripping gas stream enriched in aromatic hydrocarbons and C4+ aliphatic hydrocarbons (10), also containing H2S and CO2 obtained in step b) with a H2S-selective liquid absorbent solution (28) in a second absorption zone (12) to obtain a stripping gas stream depleted in H2S and containing aromatic hydrocarbons, C4+ aliphatic hydrocarbons and CO2 (13), and an absorbent solution enriched in H2S (14) also containing co-absorbed aromatic hydrocarbons, C4+ aliphatic hydrocarbons and CO2, said H2S-selective liquid absorbent solution being preferably identical to that used in step a), d) introducing the absorbent solution depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (9) obtained in step b) into a desorption zone (16) wherein the H2S-selective liquid absorbent solution (17) is recovered and a lean acid gas containing H2S and CO2, depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (21) is produced. ### Claim 2 (depends on 1) Process according to claim 1, wherein the stripping gas (7) used in the stripping zone (8) is a combustible gas meeting standards requirements for a combustible, for example natural gas, hydrogen, and/or synthetic gas containing H2 and CO and is the combustible gas used to run the incinerator (33) and/or utility boilers. ### Claim 3 (depends on 1) Process according to claim 1 wherein, the lean acid gas stream (1) contains: 75 to 99.925 mol. % of CO2, 250 mol. ppm to 20 mol. % of H2S, preferably 500 mol. ppm to 15 mol. % of H2S, more preferably 500 mol. ppm to 10 mol. % of H2S and even more preferably 500 mol. ppm to 5 mol. % H2S, 500 mol. ppm to 5 mol. % of C4+ aliphatic hydrocarbons and aromatic hydrocarbons, the percentages being expressed on a dry basis, in moles, relative to the total moles of the lean acid gas. ### Claim 4 (depends on 1) Process according to claim 1, wherein the H2S-selective liquid absorbent solution contains: a chemical solvent such as alkali metal carbonate and phosphate, or alkanolamines, preferably in the form of aqueous solutions, a physical solvent such as a substituted or unsubstituted tetramethylene sulfone or thioglycols, or mixtures thereof such as a mixture of alkanolamines and thioglycols. ### Claim 5 (depends on 1) Process according to claim 1, wherein the H2S-selective liquid absorbent solution contains an amine, preferably an alkanolamine, more preferably a tertiary alkanolamine or sterically hindered alkanolamine, and even more preferably methyldiethanolamine (MDEA). ### Claim 6 (depends on 1) Process according to claim 1, wherein the H2S-selective liquid absorbent solution contains additives components capable of enhancing the selectivity of H2S adsorption towards CO2 such as acidic components like phosphoric acid (H3PO4). ### Claim 7 (depends on 1) Process according to claim 1, wherein the absorption steps a) and c) are conducted: at a temperature ranging from 10 to 100° C., preferably 30 to 70° C. and more preferably 40 to 60° C., and at a pressure ranging from 1 to 8 barA, preferably 1.5 to 4 barA. ### Claim 8 (depends on 1) Process according to claim 1, wherein the non-thermic stripping in step b) is conducted: at a temperature ranging from 50 to 150° C., preferably 60 to 130° C. and more preferably 70 to 110° C., and at a pressure ranging from 1 to 8 barA, preferably 1.5 to 4 barA. ### Claim 9 (depends on 1) Process according to claim 1, wherein the absorbent solution enriched in H2S (14) exiting the second absorption zone (12) is recycled back to the stripping zone (8) to supplement the absorbent solution enriched in H2S (4) and/or is directly introduced into the desorption zone (16) to supplement the absorbent solution depleted in aromatic hydrocarbons (9) obtained in step b). ### Claim 10 (depends on 1) Process according claim 1, wherein the absorbent solution depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (9) recovered from the stripping zone (8) passes through a heater (15) to increase its temperature before entering the desorption zone. ### Claim 11 (depends on 1) Process according claim 1, wherein the temperature increase in the heater (15) is obtained by recirculating in the heater (15), at least a part of the regenerated liquid absorbent solution (17) recovered from the desorption zone (16). ### Claim 12 (depends on 1) Process according to claim 1, wherein the absorbent solution enriched in H2S (4) passes through a heater (6) to increase its temperature before entering the stripping zone (8). ### Claim 13 (depends on 1) Process according to claim 1, wherein the temperature increase in the heater (6) is obtained by recirculating in the heater (6), at least a part of the H2S-selective liquid absorbent solution (17) recovered from the desorption zone (16), and/or exiting the heat exchanger (15). ### Claim 14 (depends on 1) Process according to claim 1, wherein lean acid gas depleted in aromatic hydrocarbons (21) or (26) is partially recycled to supplement the lean acid gas stream (1) and/or to supplement the stripping gas stream enriched in H2S, CO2 and aromatic hydrocarbons (10). ### Claim 15 (depends on 1) Process according to claim 1, wherein the lean acid gas containing CO2 and less than 20 mol. % of H2S is obtained according to a process comprising: a) contacting natural gas comprising methane (CH4) and ethane (C2H6), CO2, H2S and C4+ aliphatic hydrocarbons and aromatic hydrocarbons, with a liquid absorbent solution in an absorption zone to produce a natural gas stream depleted in H2S and CO2 and comprising methane (CH4) and ethane (C2H6), and an absorbent solution enriched in H2S and CO2, and also containing co-absorbed C4+ aliphatic hydrocarbons and aromatic hydrocarbons and, b) introducing the absorbent solution enriched in H2S and CO2, and also containing co-absorbed C4+ aliphatic hydrocarbons and aromatic hydrocarbons into a desorption zone wherein the liquid absorbent solution is recovered and a lean acid gas containing CO2 and less than 20 mol. % of H2S is produced. ### Claim 16 (depends on 1) A process for sulfur recovery from a lean acid gas containing CO2 and less than 20 mol. % of H2S , which process comprises: i) pretreating the lean acid gas stream (1) for the removal of aromatic hydrocarbons and C4+ aliphatic hydrocarbons in a process according to claim 1 to obtain a lean acid gas depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (21) or (26), ii) mixing at least part of the pretreated lean acid gas depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons (21) or (26) with an oxygen containing gas, for example air, to obtain a gas stream containing both H2S and oxygen, iii) optionally introducing part of the obtained lean acid gas depleted in aromatic hydrocarbons (21) or (26) and oxygen into a furnace to recover elemental sulfur, iv) passing the lean acid gas depleted in C4+ aliphatic hydrocarbons and aromatic hydrocarbons recovered from step ii) and optionally step iii), after having optionally being preheated, into a catalytic reactor containing a catalyst system which catalyzes the direct oxidation of H2S with oxygen and/or the Claus reaction of H2S with sulfur dioxide (SO2) so as to recover a lean acid gas stream depleted in H2S and elemental sulfur. ### Claim 17 (depends on 1) Process according to claim 1, wherein step iv) includes and/or is followed by: iv.1 transferring the lean acid gas stream containing both H2S and oxygen into a first section of a first reactor, after having optionally being preheated, which first section contains a non-cooled adiabatic bed containing a first catalyst which catalyzes the oxidation of H2S with oxygen and the oxidation of H2S with sulfur dioxide, wherein the maximum temperature of the adiabatic bed is T1, iv.2 transferring the lean acid gas stream from the first section of the first reactor to a second section of the first reactor, which second section contains a second catalyst which can be different from the first catalyst and which second section is kept at a temperature T2 wherein T2≤T1 and T2 is higher than the dew point temperature of elemental sulfur, whereby a gas stream depleted in H2S is obtained, iv.3 transferring the gas stream depleted in H2S to a sulfur condenser to obtain a gas stream depleted in sulfur, iv.4 optionally preheating the gas stream depleted in sulfur iv.5 transferring the gas stream depleted in sulfur into the first section of a second reactor, which first section contains a non-cooled adiabatic bed containing the same catalyst as the first section of the first reactor, wherein the first section of the second reactor is operated at a temperature that is above the dew point of the elemental sulfur so that in the first section of the second reactor no elemental sulfur deposits as liquid or solid on the catalyst, iv.6 transferring the gas stream from the first section of the second reactor to the second section of the second reactor which contains the same catalyst as the second section of first reactor and which second section is kept at a temperature that is at or below the dew point of elemental sulfur so that in the second section of the second reactor elemental sulfur deposits as liquid or solid on the catalyst, and desulfurized gas stream meeting standard requirements for air emissions is obtained, iv.7 after a defined time switching the operation conditions of the first reactor and the second reactor and switching the gas flow simultaneously so that the previous second reactor becomes the new first reactor and the previous first reactor becomes the new second reactor. ### Claim 18 (depends on 15) Process according to claim 15, wherein the gas stream depleted in H2S (3), the stripping gas stream depleted in H2S (13) and/or the lean acid gas stream depleted in H2S (32) exiting the sulfur recovery unit in step iv) can then be either transferred to an incinerator (33) where it will be combusted to destruct remaining H2S as well as the aromatic hydrocarbons and C4+ aliphatic hydrocarbons contained therein, thus reaching the standards requirements for air emission or compressed, injected and disposed in an underground storage reservoir rather than being incinerated and released to the atmosphere.