Adsorption-based Claus tail gas treatment.

Abstract

The sulfur recovery method includes converting sulfur-containing compounds in a Claus process tail gas stream to hydrogen sulfide in a hydrotreating reactor to produce a hydrogenated gas stream; feeding the hydrogenated gas stream to a quench tower and condensing liquid water to produce a quench gas stream; feeding the quench gas stream to a first stage adsorber of a first stage adsorption unit to adsorb water from the quench gas stream to produce a first outlet gas stream; feeding the first outlet gas stream to a second stage adsorber of a second stage adsorption unit to adsorb hydrogen sulfide from the first outlet gas stream to produce a second by-product gas stream; separating the second by-product gas stream into a carbon dioxide stream and a nitrogen-enriched stream; and regenerating the second stage adsorber with the nitrogen-enriched stream.

Description

[Technical field]

[0001] Claiming priority (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to Greek Patent Application No. 20210100882, filed December 15, 2021, and U.S. Patent Application No. 17 / 945,809, filed September 15, 2022, the contents of which are incorporated by reference in their entireties herein. [Background technology]

[0002] Sulfur recovery is the conversion of hydrogen sulfide to elemental sulfur. Hydrogen sulfide can be a by-product from the processing of natural gas or the refining of crude oil containing sulfur. A conventional sulfur recovery process is the Claus process. In a conventional Claus process, 95%-98% of the hydrogen sulfide can be recovered. Tail gas from the Claus process can have residual hydrogen sulfide, for example, less than 5% hydrogen sulfide. The Claus process tail gas can be processed to recover this residual hydrogen sulfide. Summary of the Invention

[0003] In one aspect, a method for recovering sulfur comprises: converting sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quench gas stream; supplying the quench gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quench gas stream to produce a first outlet gas stream; supplying the first outlet gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first outlet gas stream to produce a second by-product gas stream; separating at least a portion of the second by-product gas stream into a carbon dioxide stream and a nitrogen-enriched stream; and regenerating the second stage adsorber vessel by feeding a portion of the nitrogen-enriched stream to the second stage adsorber vessel to produce a second outlet gas stream; Includes.

[0004] Implementations may include any combination of one or more of the following features.

[0005] The method includes separating a first portion of the second by-product gas stream into the carbon dioxide stream and the enriched nitrogen stream using cryogenic separation.

[0006] The method includes separating a first portion of the second by-product gas stream into the carbon dioxide stream and the enriched nitrogen stream using a separation membrane. Optionally, the method includes applying a vacuum to the separation membrane.

[0007] The method includes providing the carbon dioxide stream to a thermal oxidizer. Optionally, the method includes providing the carbon dioxide stream to the thermal oxidizer via an ejector.

[0008] The method includes regenerating a first stage adsorber vessel by feeding a first portion of the enriched nitrogen stream to the first stage adsorber vessel and desorbing water to produce a first by-product gas stream. Optionally, the method includes combining the first by-product gas stream with the hydrogenation gas stream to form a combined stream and feeding the combined stream to a quench tower.

[0009] The method includes heating the enriched nitrogen stream in a heat exchanger using heat from the hydrogenation gas stream.

[0010] The method includes compressing the quench gas stream in a compressor and cooling the compressed quench gas stream.

[0011] The method includes providing the quench gas stream to a collection drum and recovering liquid water via a second water condensate stream to generate an adsorption feed that is provided to the first stage adsorption vessel.

[0012] The method includes feeding the water condensate stream to a sour water stripper.

[0013] The method includes supplying a second portion of the second by-product gas stream to a thermal oxidizer.

[0014] The method includes supplying the second outlet gas to a reactor.

[0015] In one aspect, a system for recovering sulfur from a Claus process tail gas comprises: a hydrogenation reactor configured to convert sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide to produce a hydrogenated gas stream; a quench tower fluidly connected to the hydrogenation reactor and configured to receive the hydrogenation gas stream and to produce a quench gas stream by condensing liquid water into a water condensate stream; a first stage adsorption unit including a first stage adsorption vessel fluidly connected to the quench tower during a first stage adsorption cycle and configured to receive the quench gas stream and to produce a first outlet gas stream by adsorbing water from the quench gas stream; a second stage adsorption unit including a second stage adsorption vessel fluidly connected to the first stage adsorption vessel during a second stage adsorption cycle and configured to receive the first outlet gas stream and to produce a second by-product gas stream by adsorbing hydrogen sulfide from the first outlet gas stream; a carbon dioxide separation element configured to receive at least a portion of the second by-product gas stream and separate the portion of the second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream; Including, the second-stage adsorption vessel is configured to receive a portion of the enriched nitrogen stream during a second-stage regeneration cycle. system.

[0016] Implementations may include any combination of one or more of the following features.

[0017] The carbon dioxide separation element includes a separation membrane configured to separate a portion of the second by-product gas stream into the carbon dioxide stream and the enriched nitrogen stream.

[0018] The carbon dioxide separation element includes a cryogenic separation element.

[0019] The system includes a thermal oxidizer configured to receive the carbon dioxide stream. Optionally, the system includes an ejector, and the thermal oxidizer configured to receive the carbon dioxide stream from the ejector.

[0020] The first stage adsorption vessel is configured to receive a first portion of the enriched nitrogen stream during a first stage regeneration cycle and produce a first by-product gas stream by desorbing water.

[0021] The system includes a thermal oxidizer configured to receive a second portion of the second by-product gas stream.

[0022] The system includes a reactor fluidly connected to the second stage adsorption vessel and configured to receive a second outlet gas produced in the second stage adsorption unit during the second stage regeneration cycle.

[0023] The system includes a heat exchanger configured to cool the hydrogenated gas stream with heat from the enriched nitrogen stream.

[0024] The first stage adsorption vessel contains a hydrophilic molecular sieve.

[0025] The second stage adsorption vessel contains a Cu-Y type zeolite.

[0026] The first-stage adsorption unit includes a plurality of first-stage adsorption vessels fluidly connected in parallel, and the second-stage adsorption unit includes a plurality of second-stage adsorption vessels fluidly connected in parallel.

[0027] In one aspect, a method for recovering sulfur comprises: converting sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quench gas stream; supplying the quench gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quench gas stream to produce a first outlet gas stream; supplying the first outlet gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first outlet gas stream to produce a second by-product gas stream; regenerating the second stage adsorber vessel to produce a second outlet gas stream, wherein regenerating the second stage adsorber vessel comprises feeding a portion of the second by-product gas stream and a nitrogen stream to the second stage adsorber vessel to produce a second outlet gas stream; Includes.

[0028] Implementations may include any combination of one or more of the following features.

[0029] Regenerating the second stage adsorber vessel includes providing the nitrogen stream from a cryogenic tank to the second stage adsorber vessel.

[0030] Regenerating the second stage adsorber vessel includes supplying a portion of the second by-product gas stream to the second stage adsorber vessel for a first time period and supplying the nitrogen gas stream to the second stage adsorber vessel for a second time period subsequent to the first time period.

[0031] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a diagram of a Claus process tail gas processing system. [Diagram 2] FIG. 2 is a diagram of a Claus process tail gas processing system. [Diagram 3] FIG. 3 is a diagram of a Claus process tail gas processing system. [Figure 4] FIG. 4 is a diagram of a Claus process tail gas processing system. [Diagram 5] FIG. 5 is a diagram of a Claus process tail gas processing system. [Figure 6] FIG. 6 is a diagram of a Claus process tail gas processing system. [Figure 7A] FIG. 7A is a flow chart. [Figure 7B] FIG. 7B is a flow chart. [Figure 8] FIG. 8 is a plot of a simulated adsorption isotherm of hydrogen sulfide on zeolite Y ion-exchanged with Cu ions ("CuY"). [Figure 9] FIG. 9 is a process flow diagram. [Figure 10] FIG. 10 is a process flow diagram. [Figure 11] FIG. 11 is a plot of a simulated breakthrough curve for water in a water removal adsorption vessel. [Figure 12] FIG. 12 is a process flow diagram. [Figure 13A]FIG. 13A is a plot of simulated breakthrough curves for carbon dioxide and nitrogen in a hydrogen sulfide removal adsorption vessel. [Figure 13B] FIG. 13B is a plot of a simulated breakthrough curve for hydrogen sulfide in a hydrogen sulfide removal adsorber vessel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Described herein are approaches to regenerating hydrogen sulfide adsorber vessels in Claus tail gas processing systems that facilitate high levels of sulfur recovery. In some approaches, a two-stage process is employed for regenerating hydrogen sulfide adsorber vessels. In the first stage, a slip stream of clean gas containing carbon dioxide and nitrogen is fed to the hydrogen sulfide adsorber vessel to desorb hydrogen sulfide from the adsorbent material in the vessel. The clean gas feed is then stopped and a high purity nitrogen stream is fed to the hydrogen sulfide adsorber vessel for further regeneration. In some approaches, the clean gas slip stream is separated into a carbon dioxide stream and a nitrogen stream, for example by a separation membrane, and the nitrogen stream is then directed to the hydrogen sulfide adsorber vessel for regeneration. The carbon dioxide stream may be fed to a thermal oxidizer.

[0034] These approaches to adsorbent regeneration in Claus process tail gas processing systems can help avoid the occurrence of hydrogen sulfide spikes during adsorbent regeneration. In addition, these approaches can facilitate high levels of sulfur recovery, e.g., greater than 99%, greater than 99.5%, greater than 99.9%, or greater than 99.95%, with the recovered hydrogen sulfide being recycled to the Claus process feed gas.

[0035] 1 shows a schematic diagram of a Claus tail gas processing system 100. Further description of the Claus tail gas processing method and system is provided in U.S. Patent No. 10,662,061, the contents of which are incorporated herein by reference in their entirety. System 100 includes a first heat exchanger 102, a hydrogenation reactor 104, a quench tower 106, a second heat exchanger 108, a first stage adsorption unit 110, a second stage adsorption unit 112, a third heat exchanger 114, and a fourth heat exchanger 116.

[0036] The tail gas stream 120 is heated in the first heat exchanger 102 to produce a heated tail gas stream 122. The heated tail gas stream 122 is introduced into the hydrogenation reactor 104 to produce a hydrogenated gas stream 124. The hydrogenated gas stream 124 is introduced into the quench tower 106 to produce a quenched quench gas stream 126 and a water condensate stream 128. The quench gas stream 126 is cooled in the second heat exchanger 108 to produce a cooled quench gas stream 130. The cooled quench gas stream 130 is introduced into the first stage adsorption unit 110 to produce a first outlet gas stream 132 and a first by-product stream 136. The first outlet gas stream 132 is cooled in the fourth heat exchanger 116 to produce a cooled first outlet gas stream 134. The cooled first outlet gas stream 134 is introduced into the second stage adsorption unit 112 to produce a second outlet gas stream 140 and a second by-product stream 138 .

[0037] 1, a gas feed 142 is heated in a third heat exchanger 114 to produce a first regeneration gas stream 144 and a second regeneration gas stream 146. The feed 142 may be air (as shown) or a relatively clean gas comprising carbon dioxide and nitrogen. The first regeneration gas stream 144 is introduced into the first stage adsorption unit 110. The second regeneration gas stream 146 is introduced into the second stage adsorption unit 112.

[0038] The tail gas stream 120 comprises sulfur-containing compounds, e.g., Claus process tail gas, including sulfur-containing compounds that were not fully recovered by an upstream Claus unit. The sulfur-containing compounds may exist in forms such as elemental sulfur, hydrogen sulfide, sulfur oxides, and their anionic counterparts. As used herein, the term "elemental sulfur" refers to all phases of sulfur, which may exist in forms such as S, S2, S3, S4, S5, S6, S7, and S8. Non-limiting examples of sulfur oxides include SO, SO2, SO3, SO4, SO, SO2, SO2, SO2, SO2, SO6, SO2, SO6, SO2, SO7, SO2, SO8, SO9, and SO10. 10 O. The Claus process tail gas in tail gas stream 120 may also include carbon dioxide, water, nitrogen, hydrogen, and combinations thereof.

[0039] The first heat exchanger 102 can be any heat exchanger capable of heating a gas stream to a temperature at which the hydrogenation reaction can occur in the hydrogenation reactor 104. The first heat exchanger 102 can heat the tail gas stream 120 such that the heated tail gas stream 122 has a temperature of from about 200° C. to about 300° C., such as from about 220° C. to about 280° C., or from about 240° C. to about 260° C., such as about 250° C. After heating, the heated tail gas stream 122 still contains sulfur-containing compounds, carbon dioxide, water, nitrogen, hydrogen, and combinations thereof, as described above for the tail gas stream 120.

[0040] The hydrogenation reactor 104 may be any reactor, such as a catalytic or non-catalytic reactor, capable of reducing sulfur-containing compounds in the heated tail gas stream 122 other than hydrogen sulfide to hydrogen sulfide. In some examples, hydrogen contained in the heated tail gas stream 122 is used to reduce the sulfur-containing compounds in the heated tail gas stream 122 to hydrogen sulfide. In some examples, a make-up hydrogen gas stream (not shown) is introduced into the hydrogenation reactor 104. In some examples, water is produced as a by-product during the hydrogenation reaction. As a result, the sulfur-containing compounds contained in the hydrogenation gas stream 124 are substantially only hydrogen sulfide. The hydrogenation gas stream 124 may also include carbon dioxide, water, nitrogen, and combinations thereof.

[0041] The quench tower 106 may be any device capable of condensing and recovering water from the hydrogenation gas stream 124. A majority of the water contained in the hydrogenation gas stream 124 is condensed and substantially recovered via a water condensate stream 128. Although a majority of the water contained in the hydrogenation gas stream 124 is removed, the quench gas stream 126 output from the quench tower 106 may still contain a residual amount of gas phase water. For example, the quench gas stream 126 may have a gas phase water content ranging from about 0 mol % to about 20 mol %, e.g., from about 3 mol % to about 15 mol %, or from about 4 mol % to about 10 mol %, e.g., about 8 mol %. The quench gas stream 126 may also contain hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the Claus process tail gas, hydrogen sulfide generated in the hydrogenation reactor 104, or both), carbon dioxide, nitrogen, and combinations thereof. The quench gas stream 126 has a temperature in the range of about 20°C to about 170°C, such as about 30°C to about 100°C, or about 40°C to about 80°C, such as about 43°C.

[0042] The second heat exchanger 108 can be any heat exchanger capable of cooling the gas stream to a temperature at which adsorption occurs in the first stage adsorption unit 110. The second heat exchanger 108 can cool the quench gas stream 126 such that the cooled quench gas stream 130 has a temperature in the range of about 0° C. to about 70° C., e.g., about 10° C. to about 40° C., or about 15° C. to about 30° C., e.g., about 21° C. As the quench gas stream 126 is cooled, the gas phase water content of the cooled quench gas stream 130 is reduced to a range of about 0 mol % to about 10 mol %, e.g., about 0 mol % to about 5 mol %, or about 0 mol % to about 1 mol %, e.g., about 0.46 mol %. The cooled quench gas stream 130 may include hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the Claus process tail gas, hydrogen sulfide produced in the hydrogenation reactor 104, or both), carbon dioxide, water, nitrogen, and combinations thereof.

[0043] First-stage adsorption unit 110 includes one or more first-stage adsorption vessels 150 fluidly connected in series or parallel. Each of the one or more first-stage adsorption vessels 150 is filled with a first adsorbent.

[0044] In some examples, the first adsorbent includes any adsorbent capable of selectively capturing hydrogen sulfide while generally rejecting water from a wet gas stream (such as the cooled quench gas stream 130). Non-limiting exemplary materials used for the first adsorbent include all-silica zeolites having frameworks such as MFI or CHA types. All-silica zeolites are hydrophobic materials and can be used to separate polar molecules such as water from less polar molecules such as hydrogen sulfide, carbon dioxide, and nitrogen. During an adsorption cycle, components of the cooled quench gas stream 130 are introduced through one or more first stage adsorption vessels 150 of the first stage adsorption unit 110. Components of the cooled quench gas stream other than water (e.g., hydrogen sulfide) are captured within the pores of the first adsorbent. Water passes through the first adsorbent and is then collected via the first by-product stream 136. During the regeneration cycle, components of the first regeneration gas stream 144 enter one or more first stage adsorption vessels 150 to regenerate the first adsorbent. Desorption occurs in the one or more first stage adsorption vessels 150 and the first adsorbent releases captured hydrogen sulfide to produce the first outlet gas stream 132 in the substantial absence of water.

[0045] In some examples, the first adsorbent includes any adsorbent capable of selectively capturing water from a wet gas stream (such as the cooled quench gas stream 130) while generally rejecting hydrogen sulfide. Non-limiting exemplary materials for use in the first adsorbent include molecular sieves, such as the hydrophilic 3A molecular sieves described in U.S. Pat. No. 9,701,537, the contents of which are incorporated herein by reference in their entirety. During an adsorption cycle, components of the cooled quench gas stream 130 are introduced through one or more first stage adsorption vessels 150 of the first stage adsorption unit 110. Water (and relatively small amounts of hydrogen sulfide) are captured within the pores of the first adsorbent. Components other than water (e.g., hydrogen sulfide, carbon dioxide, and nitrogen) pass through the first adsorbent to produce the first outlet gas stream 132 in the substantial absence of water. During the regeneration cycle, components of first regeneration gas stream 144 enter one or more first stage adsorber vessels 150 to regenerate the first adsorbent. Desorption occurs in the one or more first stage adsorber vessels 150, where the first adsorbent releases captured water (and relatively small amounts of hydrogen sulfide), which are collected via first by-product stream 136.

[0046] In some examples, the first stage adsorption unit 110 includes at least three first stage adsorption vessels 150 fluidly connected in parallel. At any point during operation, one of the at least three first stage adsorption vessels 150 is undergoing an adsorption cycle, one of the at least three first stage adsorption vessels 150 is undergoing a regeneration cycle, and one of the at least three first stage adsorption vessels 150 is idle. In this manner, components of the cooled quench gas stream 130 can be continuously fed to the first stage adsorption unit 110 to produce a continuous flow of the first outlet gas stream 132 from the first stage adsorption unit 110.

[0047] The fourth heat exchanger 116 can be any heat exchanger capable of cooling the gas stream to a temperature at which adsorption will occur in the second stage adsorption unit 112. The fourth heat exchanger 116 can cool the first outlet gas stream 132 such that the cooled first outlet gas stream 134 has a temperature of from about 0° C. to about 70° C., such as from about 10° C. to about 40° C., or from about 15° C. to about 30° C., such as about 25° C. The first outlet gas stream 132 can include hydrogen sulfide, carbon dioxide, nitrogen, and combinations thereof, all of which are products of the first stage adsorption unit 110.

[0048] The second stage adsorption unit 112 includes one or more second stage adsorption vessels 152 fluidly connected in series or parallel. Each of the one or more second stage adsorption vessels 152 is filled with a second adsorbent. In some examples, the second adsorbent can include any adsorbent that can selectively capture hydrogen sulfide while rejecting carbon dioxide and nitrogen. In some embodiments, the second adsorbent can include any adsorbent that has a breakthrough time difference between hydrogen sulfide and carbon dioxide and a breakthrough time difference between hydrogen sulfide and nitrogen. Non-limiting example materials used for the second adsorbent include molecular sieves (e.g., molecular sieve 4A, etc.), hydrophobic zeolites having frameworks such as MFI, CHA, FAU, MOR, DDR, FER, or MWW types, and hydrophobic zeolites such as MOFs or ZIFs.

[0049] During an adsorption cycle, components of the cooled first outlet gas stream 134 are introduced through one or more second stage adsorption vessels 152 of the second stage adsorption unit 112. Hydrogen sulfide is trapped within the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) pass through the second adsorbent and are then collected via the second by-product stream 138. During a regeneration cycle, components of the second regeneration gas stream 146 enter the one or more second stage adsorption vessels 152 to regenerate the second adsorbent. Desorption occurs in the one or more second stage adsorption vessels 152, and the second adsorbent releases the trapped hydrogen sulfide to produce the second outlet gas stream 140, substantially in the absence of carbon dioxide and nitrogen.

[0050] In some examples, the second stage adsorption unit 112 includes at least three second stage adsorption vessels 152 fluidly connected in parallel. At any point during operation, one of the at least three second stage adsorption vessels 152 is undergoing an adsorption cycle, one of the at least three second stage adsorption vessels 152 is undergoing a regeneration cycle, and one of the at least three second stage adsorption vessels 152 is idle. In this manner, components of the cooled first outlet gas stream 134 can be continuously fed to the second stage adsorption unit 112, which can produce a continuous flow of the second outlet gas stream 140 therefrom.

[0051] The gas feed 142 can be an air feed of any oxygen-containing gas suitable as a regeneration gas for regenerating the adsorbent material. Non-limiting exemplary gases for use as the gas feed 142 include air, oxygen-enriched air, pure oxygen, and combinations thereof. In some examples, the air feed 142 is air. In place of or in addition to the air feed 142, gases can be employed as the regeneration gas. For example, the regeneration gas can include at least one of nitrogen or carbon dioxide.

[0052] The third heat exchanger 114 can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate type heat exchanger, etc.) capable of heating the gas streams to a temperature at which regeneration of the adsorbent occurs in each of the first stage adsorption unit 110 and the second stage adsorption unit 112. The third heat exchanger 114 can heat the air feed 142 so that each of the first regeneration gas stream 144 and the second regeneration gas stream 146 has a temperature of about 150°C to about 350°C, e.g., about 200°C to about 300°C, or about 230°C to about 290°C, e.g., about 260°C.

[0053] The second outlet gas stream 140 comprises hydrogen sulfide. The second outlet gas stream 140 has a hydrogen sulfide content of at least about 95% by weight, e.g., at least about 98% by weight, or at least about 99% by weight. In some examples, the second outlet gas stream 140 is used as a feed gas for a Claus unit.

[0054] 2 is a schematic diagram of a system 200 for Claus process tail gas processing. System 200 includes a hydrogenation reactor 204, a first heat exchanger 205, a quench tower 206, a compressor 207, a second heat exchanger 208, a collection drum 209, a first stage adsorption unit 210, a second stage adsorption unit 212, and a third heat exchanger 214.

[0055] The tail gas stream 220 is introduced into the hydrogenation reactor 204 to produce a hydrogenated gas stream 222. The hydrogenated gas stream 222 is cooled via a first heat exchanger 205 to produce a cooled hydrogenated gas stream 224. The cooled hydrogenated gas stream 224 is introduced into the quench tower 206 to produce a quench gas stream 226 and a first water condensate stream 228. The quench gas stream 226 is compressed by a compressor 207 to produce a compressed quench gas stream 227. The compressed quench gas stream 227 is cooled by a second heat exchanger 208 to produce a cooled quench gas stream 229. The cooled quench gas stream 229 is introduced into a collection drum 209 to produce a second water condensate stream 231 and an adsorption feed stream 230.

[0056] In some examples, the first water condensate stream 228 and the second water condensate stream 231 are introduced to a sour water stripper 260 for further processing. As used herein, the term "sour water stripper" refers to a device or apparatus that removes hydrogen sulfide from water containing hydrogen sulfide (referred to as sour water). For example, liquid water separated by a collection drum may include hydrogen sulfide. The liquid water may be introduced into the sour water stripper, and steam may be injected into the sour water stripper to shift the chemical equilibrium by heating the sour water so that hydrogen sulfide is released.

[0057] Adsorption feed stream 230 is introduced into first stage adsorption vessel 250 of first stage adsorption unit 210 to produce first outlet gas stream 232. First outlet gas stream 232 is introduced into second stage adsorption vessel 255 of second stage adsorption unit 212 to produce second by-product stream 238. Second by-product stream 238 is separated into first portion 239 and second portion 242. In some examples, a conduit joint (e.g., a pipe tee) bifurcates (splits) the flow of second by-product stream 238 into two portions 239 and 242. Flow control valves may be positioned along the conduits carrying portion 239 or portion 242 or both. Other conduit / control devices are also applicable.

[0058] The first portion 239 of the second by-product stream and the first by-product stream 236 are introduced into a thermal oxidizer 262 for further processing. As used herein, the term "thermal oxidizer," sometimes referred to as a thermal incinerator, refers to a device or apparatus that pyrolyzes certain gases at high temperatures and releases them into the atmosphere. For example, the gas stream can be introduced into a thermal oxidizer where any trace amounts of hydrogen sulfide contained in the gas stream are oxidized to sulfur dioxide and then released into the atmosphere. The thermal oxidizer 262 can be, for example, a direct fired thermal oxidizer, a regenerative thermal oxidizer (RTO), a catalytic thermal oxidizer, etc.

[0059] A second portion 242 of the second by-product stream 238 is used as a regeneration gas, as described in the next paragraph. In some examples, a majority of the second by-product stream 238 is diverted to a first portion 239 sent to the thermal oxidizer 262, and the amount of the second by-product stream 238 that constitutes the second portion 242 utilized as a regeneration gas is a slip stream of the second by-product stream 238. As used herein, the term "slip stream" refers to a small amount (e.g., less than 20%) of the main stream.

[0060] The second portion 242 of the second by-product stream 238 is heated via the first heat exchanger 205 to produce a heated second portion 243 of the second by-product stream by heat exchange from the hydrogenation gas stream 222. In some examples (as shown in FIG. 2 ), the second portion 243 of the second by-product stream is further heated via a third heat exchanger 214 to produce a heated second portion 245 of the second by-product stream. The heated second portion 245 of the second by-product stream is separated into a first regeneration gas stream 244 and a second regeneration gas stream 246. The first regeneration gas stream 244 is introduced into a first stage adsorption vessel 251 of the first stage adsorption unit 210 to produce the first by-product stream 236.

[0061] The second regeneration gas stream 246 is introduced into the second stage adsorption vessel 256 of the second stage adsorption unit 212 to produce a second outlet gas stream 240. The second outlet gas stream 240 is introduced into the Claus unit reactor 264 for further processing. As used herein, the term "reactor" refers to a device or apparatus that is typically included in the upstream portion of a Claus unit and that initiates the conversion of hydrogen sulfide and other sulfur-containing compounds to elemental sulfur. The reactor is typically operated at a temperature in excess of 850° C. such that hydrogen sulfide is converted to elemental sulfur.

[0062] The tail gas stream 220 comprises sulfur-containing compounds, e.g., Claus process tail gas that contains sulfur-containing compounds that were not fully recovered by an upstream Claus unit. The sulfur-containing compounds may be present in the form of elemental sulfur, hydrogen sulfide, sulfur oxides, and their anionic counterparts. Non-limiting examples of sulfur oxides include SO, SO2, SO3, SO4, SO, SO2, SO2, SO2, SO6, SO2, SO2, SO2, SO3, SO4, SO, SO2 ... 10 O. The Claus process tail gas in tail gas stream 120 may also include carbon dioxide, water, nitrogen, hydrogen, and combinations thereof.

[0063] In some examples, the tail gas stream 220 is preheated to a temperature at which the hydrogenation reaction can occur in the hydrogenation reactor 204. For example, the tail gas stream 220 is preheated to a temperature of about 200°C to about 300°C, e.g., about 220°C to about 280°C, or about 240°C to about 260°C, e.g., about 250°C.

[0064] The hydrogenation reactor 204 may be any reactor, such as a catalytic or non-catalytic reactor, capable of reducing sulfur-containing compounds in the tail gas stream 220 other than hydrogen sulfide to hydrogen sulfide. In some examples, hydrogen contained in the tail gas stream 220 is used to reduce the sulfur-containing compounds in the tail gas stream 220 to hydrogen sulfide. In some examples, a make-up hydrogen gas stream (not shown) is introduced into the hydrogenation reactor 204. In some examples, water is produced as a by-product during the hydrogenation reaction. As a result, the sulfur-containing compounds contained in the hydrogenated gas stream 222 are substantially only hydrogen sulfide. The hydrogenated gas stream 222 may also include carbon dioxide, water, nitrogen, and combinations thereof.

[0065] The first heat exchanger 205 can be any heat exchanger (e.g., shell-and-tube heat exchanger, plate type heat exchanger, etc.) capable of cooling the gas streams to a temperature suitable for operation of the quench tower 206 instead of heating a separate gas stream. In the example of FIG. 2, the first heat exchanger 205 is a gas-to-gas heat exchanger that allows for cross exchange heat transfer between the hydrogenation gas stream 222 and the second portion 242 of the second by-product stream (described in a later paragraph). The first heat exchanger 205 cools the hydrogenation gas stream 222 such that the cooled hydrogenation gas stream 224 has a temperature of about 20° C. to about 170° C., e.g., about 30° C. to about 100° C., or about 40° C. to about 80° C., e.g., at least about 43° C. The cooled hydrogenation gas stream 224 includes sulfur-containing compounds, carbon dioxide, water, nitrogen, hydrogen, and combinations thereof. In some examples, the first heat exchanger 205 heats the second portion 242 of the by-product stream such that the heated second portion 243 has a temperature of about 150°C to about 350°C, e.g., about 200°C to about 300°C, or about 230°C to about 290°C, e.g., at least about 260°C.

[0066] In some examples, the third heat exchanger 214 can be used to heat the second portion 243 of the second by-product stream to meet the temperature requirements of adsorbent regeneration for each of the first stage adsorption unit 210 and the second stage adsorption unit 212. The third heat exchanger 214 can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate type heat exchanger, etc.) capable of heating the gas stream to a temperature at which adsorbent regeneration occurs in each of the first stage adsorption unit 210 and the second stage adsorption unit 212. In some examples, the third heat exchanger 214 uses steam (e.g., condensing steam), steam condensate, oil, or another heat transfer fluid. The third heat exchanger 214 can heat the second portion 243 of the second by-product stream such that the heated second by-product stream 245 (and thus the first regeneration gas stream 244 and the second regeneration gas stream 246, respectively) has a temperature of about 150° C. to about 350° C., e.g., about 200° C. to about 300° C., or about 230° C. to about 290° C., e.g., about 260° C. In some examples, a controlled temperature ramp is implemented during regeneration, in which the second portion 243 of the second by-product stream is heated to various temperatures over time up to 400° C., e.g., as described in U.S. Patent Application Serial No. 17 / 166,821, the contents of which are incorporated herein by reference in their entirety.

[0067] The quench tower 206 may be any device capable of condensing and recovering water from the heated hydrogenation gas stream 224. A majority of the water contained in the heated hydrogenation gas stream 224 is condensed and substantially recovered via a first water condensate stream 228. Although a majority of the water contained in the hydrogenation gas stream 224 is removed, the quench gas stream 226 output from the quench tower 206 may still contain a residual amount of vapor phase water. For example, the quench gas stream 226 may have a vapor phase water content ranging from about 0 mol % to about 20 mol %, e.g., from about 3 mol % to about 15 mol %, or from about 4 mol % to about 10 mol %, e.g., about 8 mol %. The quench gas stream 226 may also contain hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the Claus process tail gas, hydrogen sulfide generated in the hydrogenation reactor 204, or both), carbon dioxide, nitrogen, and combinations thereof. The quench gas stream 226 has a temperature in the range of about 20° C. to about 170° C., e.g., about 30° C. to about 100° C., or about 40° C. to about 80° C., e.g., about 43° C. The quench column 206 may be a quench tower, quench vessel, quench column, quench condenser, quench heat exchanger, or the like.

[0068] Compressor 207 may be any type of pressurizing device or apparatus capable of increasing the pressure of quench gas stream 226. Compressor 207 may be a mechanical compressor. For example, compressor 207 may be a diaphragm metering pump. The pressure of quench gas stream 226 is increased through compressor 207 such that pressurized quench gas stream 227 has a pressure in the range of about 1 bar to about 10 bar, e.g., about 1 bar to about 5 bar, or about 2 bar to about 4 bar, e.g., about 3 bar. The unit "bar" as used herein is bar (Gauge) ["bar(g)" or "bar g"].

[0069] The second heat exchanger 208 can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate type heat exchanger, etc.) capable of cooling the gas stream to a temperature at which adsorption will occur in the first stage adsorption unit 210. The second heat exchanger 208 can cool the pressurized quench gas stream 227 such that the cooled quench gas stream 229 has a temperature in the range of about 0° C. to about 50° C., e.g., about 5° C. to about 40° C., or about 10° C. to about 30° C., e.g., about 15° C. As the pressurized quench gas stream 227 is cooled, the gas phase water content of the cooled quench gas stream 229 is reduced to a range of about 0 mol % to about 10 mol %, e.g., about 0 mol % to about 5 mol %, or about 0 mol % to about 1 mol %, e.g., about 0.46 mol %. The cooled quench gas stream 229 may include hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the Claus process tail gas, hydrogen sulfide produced in the hydrogenation reactor 204, or both), carbon dioxide, water, nitrogen, and combinations thereof.

[0070] Collection drum 209 may be any type of separation device (e.g., a separation vessel) capable of separating a fluid stream into a gas phase and a liquid phase. The cooled quench gas stream 229 is separated in collection drum 209 to produce a second water condensate stream 231 (a liquid phase stream) and an adsorption feed stream 230 (a gas phase stream). The adsorption feed stream 230 may include hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the Claus process tail gas, hydrogen sulfide generated in the hydrogenation reactor 204, or both), carbon dioxide, water, nitrogen, and combinations thereof.

[0071] In some examples, the first water condensate stream 228 contains trace amounts of hydrogen sulfide dissolved in the water collected from the quench tower 206. In some examples, the second water condensate stream 231 contains trace amounts of hydrogen sulfide dissolved in the water collected from the collection drum 209. Each of the first water condensate stream 228 and the second water condensate stream 231 may be introduced to a sour water stripper 260 for further processing, such as removing hydrogen sulfide from the water.

[0072] First stage adsorption unit 210 includes first stage adsorption vessels 250, 251, 252 fluidly connected in parallel. At any point during operation, one of the first stage adsorption vessels 250, 251, 252 is undergoing an adsorption cycle, one of the first stage adsorption vessels 250, 251, 252 is undergoing a regeneration cycle, and one of the first stage adsorption vessels 250, 251, 252 is idle. In this manner, components of adsorbed feed stream 230 can be continuously fed to first stage adsorption unit 210, which can produce continuous flows of first outlet gas stream 232 and first by-product stream 236.

[0073] Each of the first stage adsorption vessels 250, 251, 252 is filled (e.g., packed) with a first adsorbent. The first adsorbent may be in a bed of the first adsorbent in the vessels 250, 251, 252. In some examples, the first adsorbent includes any adsorbent that can selectively capture water from a wet gas stream (such as the adsorption feed stream 230) while rejecting hydrogen sulfide, carbon dioxide, and nitrogen. Non-limiting example materials used for the first adsorbent include hydrophilic 3A molecular sieves. During an adsorption cycle, components of the adsorption feed stream 230 are introduced through one of the first stage adsorption vessels 250, 251, 252. Water (and a relatively small amount of hydrogen sulfide) is captured within the pores of the first adsorbent. Components other than water (e.g., hydrogen sulfide, carbon dioxide, and nitrogen) pass through the first adsorbent to produce the first outlet gas stream 232 in the substantial absence of water. During the regeneration cycle, the components of the first regeneration gas stream 244 (e.g., carbon dioxide and nitrogen) enter one of the first stage adsorption vessels 250, 251, 252 to regenerate the first adsorbent. Desorption occurs in one of the first stage adsorption vessels 250, 251, 252, where the first adsorbent releases captured water (and relatively small amounts of hydrogen sulfide) (and possibly trace amounts of carbon dioxide and nitrogen), which are collected via the first by-product stream 236.

[0074] 2, first stage adsorption vessel 250 is undergoing an adsorption cycle, first stage adsorption vessel 251 is undergoing a regeneration cycle, and first stage adsorption vessel 252 is in a standby mode. During an adsorption cycle, the components of adsorption feed stream 230 are introduced through first stage adsorption vessel 250. Water (and relatively small amounts of hydrogen sulfide) are trapped within the pores of the first adsorbent. In some examples, trace amounts of carbon dioxide and nitrogen are trapped within the pores of the first adsorbent. Components other than water (e.g., hydrogen sulfide, carbon dioxide, and nitrogen) pass through the first adsorbent to produce first outlet gas stream 232 in the substantial absence of water.

[0075] During the regeneration cycle, components of first regeneration gas stream 244 (e.g., carbon dioxide and nitrogen) enter first stage adsorber vessel 251 to regenerate the first adsorbent. Desorption occurs in first stage adsorber vessel 251, where the first adsorbent releases trapped water and relatively small amounts of trapped hydrogen sulfide (and possibly trace amounts of carbon dioxide and nitrogen), which are collected via first by-product stream 236.

[0076] The second stage adsorption unit 212 includes second stage adsorption vessels 255, 256, 257 fluidly connected in parallel. At any point during operation, one of the second stage adsorption vessels 255, 256, 257 is undergoing an adsorption cycle, one of the second stage adsorption vessels 255, 256, 257 is undergoing a regeneration cycle, and one of the second stage adsorption vessels 255, 256, 257 is idle. In this manner, components of the first outlet gas stream 232 can be continuously fed to the second stage adsorption unit 212, which can produce a continuous flow of the second outlet gas stream 240 and the second by-product stream 238.

[0077] Each of the second stage adsorption vessels 255, 256, 257 is filled or packed with a second adsorbent. The second adsorbent may be configured as an adsorbent bed within the vessels 255, 256, 257. In some examples, the second adsorbent includes any adsorbent that can selectively capture hydrogen sulfide while rejecting carbon dioxide and nitrogen. In some examples, the second adsorbent includes any adsorbent that has a breakthrough time difference between hydrogen sulfide and carbon dioxide and a breakthrough time difference between hydrogen sulfide and nitrogen. Non-limiting example materials used for the second adsorbent include molecular sieves (e.g., molecular sieve 4A, etc.), hydrophobic zeolites having frameworks such as MFI, CHA, FAU, MOR, DDR, FER, and MWW types, and hydrophobic zeolites such as MOFs and ZIFs. In a specific example, the second adsorbent includes Cu-Y type zeolite, which is a derivative of FAU type zeolite with copper cations as counterions.

[0078] During an adsorption cycle, the components of the first outlet gas stream 232 are introduced through one or more second stage adsorption vessels 255, 256, 257 of the second stage adsorption unit 212. Hydrogen sulfide is trapped within the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) pass through the second adsorbent and are then collected via the second by-product stream 238. During a regeneration cycle, the components of the second regeneration gas stream 246 (e.g., carbon dioxide and nitrogen) enter the one or more second stage adsorption vessels 255, 256, 257 to regenerate the second adsorbent. Desorption occurs in the one or more second stage adsorption vessels 255, 256, 257 where the second adsorbent releases the trapped hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen) to produce the second outlet gas stream 240. The second outlet gas stream 240 comprises hydrogen sulfide, carbon dioxide, and nitrogen.

[0079] In the example of FIG. 2, second stage adsorber vessel 255 is undergoing an adsorption cycle, second stage adsorber vessel 256 is undergoing a regeneration cycle, and second stage adsorber vessel 257 is in standby mode. During an adsorption cycle, components of first outlet gas stream 232 are introduced through second stage adsorber vessel 255. Hydrogen sulfide is trapped within the pores of the second adsorbent. In some examples, trace amounts of carbon dioxide and nitrogen are trapped within the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) pass through the second adsorbent to produce second by-product stream 238 in the substantial absence of hydrogen sulfide. During a regeneration cycle, components of second regeneration gas stream 246 (e.g., carbon dioxide and nitrogen) enter second stage adsorber vessel 256 to regenerate the second adsorbent. Desorption occurs in the second stage adsorption vessel 256, and the second adsorbent releases the captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which are collected via the second outlet gas stream 240.

[0080] The second outlet gas stream 240 comprises hydrogen sulfide, carbon dioxide, and nitrogen. The second outlet gas stream 240 has a hydrogen sulfide content of about 0% to about 99% by weight, e.g., about 5% to about 70% by weight, about 5% to about 50% by weight, about 5% to about 30% by weight, or about 10% to about 20% by weight, e.g., about 13.3% by weight. The second outlet gas stream 240 has a carbon dioxide content of about 0% to about 99% by weight, e.g., about 20% to about 95% by weight, about 30% to about 90% by weight, about 50% to about 80% by weight, or about 60% to about 70% by weight, e.g., about 66.7% by weight. The second outlet gas stream 240 has a nitrogen content of about 0% to about 99% by weight, e.g., about 5% to about 70% by weight, about 5% to about 50% by weight, about 10% to about 30% by weight, or about 15% to about 25% by weight, e.g., about 20.0% by weight. In some examples, the second outlet gas stream 240 is used as a feed gas for a Claus unit. For example, as shown in FIG. 2, the second outlet gas stream 240 is introduced into a reactor 264 of a Claus unit.

[0081] Figure 3 is a schematic diagram of a Claus process tail gas processing system 300. Features of system 300 similar to those described with respect to system 200 are similarly numbered. System 300 of Figure 3 implements an elevated temperature regeneration scheme that utilizes a slip stream of carbon dioxide and nitrogen. Further description of elevated temperature regeneration schemes is provided in U.S. patent application Ser. No. 17 / 166,821, the contents of which are incorporated herein by reference in their entirety.

[0082] The system 300 includes a hydrogenation reactor 204 (e.g., a reaction vessel) for receiving a tail gas stream 320 comprising a Claus process tail gas and hydrogenating sulfur-containing compounds in the Claus process tail gas to hydrogen sulfide to produce a hydrogenated gas stream 322 comprising hydrogen sulfide, water, and at least one of carbon dioxide and water. In some examples, the hydrogenated gas does not include any sulfur-containing compounds other than hydrogen sulfide. In some examples, any sulfur-containing compounds other than hydrogen sulfide in the hydrogenated gas may be present in trace amounts (or may not be easily measurable) in the hydrogenated gas.

[0083] The hydrogenated gas stream 322 is cooled via a first heat exchanger 205 to produce a cooled hydrogenated gas stream 324. The quench tower 206 receives the cooled hydrogenated gas stream 324 and condenses the water in the hydrogenated gas to produce a quench gas stream 326 comprising sulfides, water, and at least one of carbon dioxide and nitrogen. The condensed water (containing some hydrogen sulfide) is recovered in the quench tower 206 as a first water condensate stream 328, which may be sent to a sour water stripper (SWS) tower 260.

[0084] The quench gas stream 326 is pressurized by the compressor 207 to produce a compressed quench gas stream 327. The compressed quench gas stream 327 is cooled by the second heat exchanger 208 to produce a cooled quench gas stream 329. The cooled quench gas stream 329 is introduced into the collection drum 209 to produce a second water condensate stream 331 and an adsorption feed stream 330. The second water condensate stream 331 may be sent to the SWS column 260.

[0085] Adsorption feed stream 330 is introduced into first stage adsorption unit 210. In the illustrated example, first stage adsorption vessel 250 is undergoing an adsorption cycle, first stage adsorption vessel 251 is undergoing a regeneration cycle, and first stage adsorption vessel 252 is in a standby mode. Adsorption feed stream 330 is fed to first stage adsorption vessel 250 operating in an adsorption cycle to adsorb water from adsorption feed stream 330 onto a first adsorbent, thereby producing a first outlet gas stream 332 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. In some examples, a majority (e.g., most or substantially all) of the water in adsorption feed stream 330 is adsorbed onto the first adsorbent in first stage adsorption vessel 250 operating in an adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from adsorption feed stream 330. In some examples, first outlet gas stream 332 contains no water or only trace or unmeasurable amounts of water.

[0086] The first outlet gas stream 332 is introduced into the second stage adsorption unit 212. In the illustrated example, the second stage adsorption vessel 255 is undergoing an adsorption cycle, the second stage adsorption vessel 256 is undergoing a regeneration cycle, and the second stage adsorption vessel 257 is in a standby mode. The first outlet gas stream 332 is fed to the second stage adsorption vessel 255, which operates in an adsorption cycle to adsorb hydrogen sulfide from the first outlet gas stream 332 onto a second adsorbent, thereby producing a second by-product stream 338 comprising at least one of carbon dioxide and nitrogen. In some examples, the second by-product stream 338 contains no hydrogen sulfide or only trace or unmeasurable amounts of hydrogen sulfide.

[0087] The second by-product stream 338 is separated into a first portion 339 and a second portion 342. The first portion 339 of the second by-product stream is introduced into the thermal oxidizer 262 for further processing. The second portion 342 of the second by-product stream, which may be a slip stream of the second by-product stream 338, is used as a regeneration gas.

[0088] The second portion 342 of the second by-product stream 338 is heated via the first heat exchanger 205 to produce a heated second portion 343 of the second by-product stream by heat exchange from the hydrogenation gas stream 322. In some examples (as shown in FIG. 3 ), the second portion 343 of the second by-product stream is further heated via a third heat exchanger 214 to produce a heated second portion 345 of the second by-product stream. The heated second portion 345 of the second by-product stream is separated into a first regeneration gas stream 344 and a second regeneration gas stream 346.

[0089] A first stage adsorber vessel 251 operating in a regeneration cycle receives a first regeneration gas stream 344 as a regeneration gas. The first adsorbent in the first stage adsorber vessel 251 is heated, e.g., through a temperature ramp, to selectively desorb components from the first adsorbent in the first stage adsorber vessel 251 and generate a first by-product stream 336 comprising the desorbed components and at least one of carbon dioxide and nitrogen. During the temperature ramp in the regeneration cycle, hydrogen sulfide is desorbed initially as the temperature is gradually increased, while adsorbed water generally remains initially adsorbed on the first adsorbent. As the temperature is increased, water begins to desorb from the first adsorbent.

[0090] When the temperature of the first adsorbent reaches a level where water begins to desorb into the first by-product stream 336 (breakthrough) and / or the concentration of hydrogen sulfide in the first by-product stream 336 is lower, in some examples, during the second portion of the temperature rise, the components desorbed from the first adsorbent include water, or the concentration of hydrogen sulfide in the first by-product stream 336 is below a threshold value, or both. The second portion of the temperature rise is slower in time and generally is hotter than the first portion of the temperature rise.

[0091] In operation, the first stage adsorption vessel 251 discharges the first by-product stream 336 as first by-product stream 336A to the Claus unit reactor 264 during a first portion of the temperature rise when the components desorbed during the first portion of the temperature rise comprise primarily hydrogen sulfide. During a second portion of the temperature rise, water begins to desorb into the first by-product stream 336 and / or the hydrogen concentration in the first by-product stream 336 falls below a certain value. During this second portion, the first by-product stream 336 is sent to the quench tower 206 as first by-product stream 336B to treat the water and avoid introducing inert components of the regeneration gas into the Claus reactor 264.

[0092] The second regeneration gas stream 346 is introduced into the second stage adsorber vessel 256 of the second stage adsorption unit 212. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent in the second stage adsorber vessel 256 to produce a second outlet gas stream 340 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. The second outlet gas stream 340 is introduced into the Claus unit reactor 264 for further processing.

[0093] 4 is a schematic diagram of a Claus process tail gas processing system 400 implementing a two-stage regeneration cycle for the second stage adsorption vessels. Features of system 400 similar to those described with respect to system 200 are similarly numbered.

[0094] The system 400 includes a hydrogenation reactor 204 (e.g., a reaction vessel) for receiving a tail gas stream 420 comprising a Claus process tail gas and hydrogenating sulfur-containing compounds in the Claus process tail gas to hydrogen sulfide to produce a hydrogenated gas stream 422 comprising hydrogen sulfide, water, and at least one of carbon dioxide and water. In some examples, the hydrogenated gas does not include any sulfur-containing compounds other than hydrogen sulfide. In some examples, any sulfur-containing compounds other than hydrogen sulfide in the hydrogenated gas may be present in trace amounts (or may not be easily measurable) in the hydrogenated gas.

[0095] The hydrogenated gas stream 422 is cooled via a first heat exchanger 205 to produce a cooled hydrogenated gas stream 424. The quench tower 206 receives the cooled hydrogenated gas stream 424 and condenses the water in the hydrogenated gas to produce a quench gas stream 426 comprising sulfides, water, and at least one of carbon dioxide and nitrogen. The condensed water (containing some hydrogen sulfide) is recovered in the quench tower 206 as a first water condensate stream 428, which may be sent to a sour water stripper (SWS) tower 260.

[0096] The quench gas stream 426 is compressed by the compressor 207 to produce a compressed quench gas stream 427. The compressed quench gas stream 427 is cooled by the second heat exchanger 208 to produce a cooled quench gas stream 429. The cooled quench gas stream 429 is introduced into the collection drum 209 to produce a second water condensate stream 431 and an adsorption feed stream 430. The second water condensate stream 431 may be sent to the SWS column 260.

[0097] Adsorption feed stream 430 is introduced into first stage adsorption unit 210. In the illustrated example, first stage adsorption vessel 250 is undergoing an adsorption cycle, first stage adsorption vessel 251 is undergoing a regeneration cycle, and first stage adsorption vessel 252 is in a standby mode. Adsorption feed stream 430 is fed to first stage adsorption vessel 250 operating in an adsorption cycle to adsorb water from adsorption feed stream 430 onto a first adsorbent, thereby producing a first outlet gas stream 432 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. In some examples, a majority (e.g., most or substantially all) of the water in adsorption feed stream 430 is adsorbed onto the first adsorbent in first stage adsorption vessel 250 operating in an adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from adsorption feed stream 430. In some examples, first outlet gas stream 432 contains no water or only trace or unmeasurable amounts of water.

[0098] The first outlet gas stream 432 is introduced into the second stage adsorption unit 212. In the illustrated example, the second stage adsorption vessel 255 is undergoing an adsorption cycle, the second stage adsorption vessel 256 is undergoing a regeneration cycle, and the second stage adsorption vessel 257 is in a standby mode. The first outlet gas stream 432 is fed to the second stage adsorption vessel 255, which operates in an adsorption cycle to adsorb hydrogen sulfide from the first outlet gas stream 432 onto a second adsorbent, thereby producing a second by-product stream 438 comprising at least one of carbon dioxide and nitrogen. In some examples, the second by-product stream 438 contains no hydrogen sulfide or a trace or unmeasurable amount of hydrogen sulfide.

[0099] The second by-product stream 438 is separated into a first portion 439 and a second portion 442. The first portion 439 of the second by-product stream is introduced into the thermal oxidizer 262 for further processing. The second portion 442 of the second by-product stream, which may be a slip stream of the second by-product stream 438, is used as a regeneration gas.

[0100] The second portion 442 of the second by-product stream 438 is heated via the first heat exchanger 205 to generate a heated second portion 443 of the second by-product stream by heat exchange from the hydrogenation gas stream 422. In some examples (as shown in FIG. 4), the second portion 443 of the second by-product stream is further heated via the third heat exchanger 214 to generate a heated second portion 445 of the second by-product stream. The heat exchangers 205, 214 heat the second by-product stream to a temperature sufficient to desorb hydrogen sulfide from the adsorber vessel in its regeneration cycle. The heated second portion 445 of the second by-product stream is separated into a first regeneration gas stream 444 and a second regeneration gas stream 446.

[0101] The first regeneration gas stream 444 is fed to the first stage adsorber vessel 251 undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorber vessel 251, where the first adsorbent releases trapped water and relatively small amounts of trapped hydrogen sulfide (and possibly trace amounts of carbon dioxide and nitrogen), which are collected via first by-product stream 436. The first by-product stream 436 is sent to the quench tower 206.

[0102] Regeneration of the second stage adsorber vessel 256 undergoing a regeneration cycle is a two-stage process. In the first stage, a second regeneration gas stream 446, which is a slip stream of a second by-product gas comprising carbon dioxide and nitrogen, is introduced into the second stage adsorber vessel 256. Following the first stage, the flow of the regeneration gas stream 446 is stopped and a second stage of regeneration occurs. In the second stage, a high purity nitrogen gas stream 452 is introduced into the second stage adsorber vessel 256. The high purity nitrogen gas can have a purity of at least 99%, at least 99.5%, at least 99.9%, or at least 99.95%. The high purity nitrogen gas stream 452 is provided from a nitrogen source, such as a nitrogen source available on-site for blanketing or purging, e.g., a cryogenic nitrogen tank. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent in the second stage adsorber vessel 256 to produce a second outlet gas stream 440 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. The second exit gas stream 440 is introduced into the Claus unit reactor 264 for further processing.

[0103] A two-stage regeneration cycle for the second stage adsorption vessel 256, in which regeneration is accomplished first using a slip stream containing carbon dioxide and nitrogen and then using high purity nitrogen, can be advantageous. For example, this two-stage regeneration cycle can facilitate the removal of hydrogen sulfide from the second stage adsorption vessel 256, thereby improving the hydrogen sulfide adsorption capacity during the adsorption cycle.

[0104] 5 is a schematic diagram of a Claus process tail gas processing system 500. Features of system 500 similar to those described with respect to system 200 are similarly numbered.

[0105] The system 500 includes a hydrogenation reactor 204 (e.g., a reaction vessel) for receiving a tail gas stream 520 comprising a Claus process tail gas and hydrogenating sulfur-containing compounds in the Claus process tail gas to hydrogen sulfide to produce a hydrogenated gas stream 522 comprising hydrogen sulfide, water, and at least one of carbon dioxide and water. In some examples, the hydrogenated gas does not include any sulfur-containing compounds other than hydrogen sulfide. In some examples, any sulfur-containing compounds other than hydrogen sulfide in the hydrogenated gas may be present in trace amounts (or may not be easily measurable) in the hydrogenated gas.

[0106] The hydrogenated gas stream 522 is cooled via a first heat exchanger 205 to produce a cooled hydrogenated gas stream 524. The quench tower 206 receives the cooled hydrogenated gas stream 524 and condenses the water in the hydrogenated gas to produce a quench gas stream 526 comprising sulfides, water, and at least one of carbon dioxide and nitrogen. The condensed water (containing some hydrogen sulfide) is recovered in the quench tower 206 as a first water condensate stream 528, which may be sent to a sour water stripper (SWS) tower 260.

[0107] The quench gas stream 526 is compressed by the compressor 207 to produce a compressed quench gas stream 527. The compressed quench gas stream 527 is cooled by the second heat exchanger 208 to produce a cooled quench gas stream 529. The cooled quench gas stream 529 is introduced into the collection drum 209 to produce a second water condensate stream 531 and an adsorption feed stream 530. The second water condensate stream 531 may be sent to the SWS column 260.

[0108] Adsorption feed stream 530 is introduced into first stage adsorption unit 210. In the illustrated example, first stage adsorption vessel 250 is undergoing an adsorption cycle, first stage adsorption vessel 251 is undergoing a regeneration cycle, and first stage adsorption vessel 252 is in a standby mode. Adsorption feed stream 530 is fed to first stage adsorption vessel 250 operating in an adsorption cycle to adsorb water from adsorption feed stream 530 onto a first adsorbent, thereby producing a first outlet gas stream 532 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. In some examples, a majority (e.g., most or substantially all) of the water in adsorption feed stream 530 is adsorbed onto the first adsorbent in first stage adsorption vessel 250 operating in an adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed from adsorption feed stream 530 onto the first adsorbent. In some examples, first outlet gas stream 532 contains no water or only trace or unmeasurable amounts of water.

[0109] First outlet gas stream 532 is introduced into second stage adsorption unit 212. In the illustrated example, second stage adsorption vessel 255 is undergoing an adsorption cycle, second stage adsorption vessel 256 is undergoing a regeneration cycle, and second stage adsorption vessel 257 is in a standby mode. First outlet gas stream 532 is fed to second stage adsorption vessel 255, which operates in an adsorption cycle to adsorb hydrogen sulfide from first outlet gas stream 532 onto a second adsorbent, thereby producing a second by-product stream 538 comprising at least one of carbon dioxide and nitrogen. In some examples, second by-product stream 538 contains no hydrogen sulfide or a trace or unmeasurable amount of hydrogen sulfide.

[0110] The second by-product stream 538 is separated into a first portion 539 and a second portion 542. The first portion 539 of the second by-product stream is introduced into the thermal oxidizer 262 for further processing. The second portion 542 of the second by-product stream, which may be a slip stream of the second by-product stream 538, is used as a regeneration gas.

[0111] The second portion 542 of the second by-product stream 538 is directed through a CO2 separation element 550 that separates carbon dioxide gas (CO2) from the second portion 542 of the stream. In the example of FIG. 5, the CO2 separation element 550 is a CO2 selective membrane that separates the carbon dioxide gas under a vacuum provided by a vacuum pump 554. In some examples, the CO2 separation element 550 is a cryogenic separation element that can separate CO2 from the second portion 542 of the stream at cryogenic temperatures. The output of the CO2 separation element 550 (e.g., from the CO2 selective membrane or the cryogenic separation element) is a carbon dioxide stream 556 and an enriched nitrogen stream 552.

[0112] Carbon dioxide stream 556 is directed to thermal oxidizer 262. Enriched nitrogen stream 552 exiting CO2 separation element 550 is heated via first heat exchanger 205 to produce heated enriched nitrogen stream 543 by heat exchange from hydrogenation gas stream 522. In some examples (as shown in FIG. 5), heated enriched nitrogen stream 543 is further heated via third heat exchanger 214 to produce heated enriched nitrogen stream 545. Heat exchangers 205, 214 heat the enriched nitrogen stream to a temperature sufficient to desorb hydrogen sulfide from the adsorption vessels in their regeneration cycle. Heated enriched nitrogen stream 545 is separated into first regeneration gas stream 544 and second regeneration gas stream 546, both of which are enriched nitrogen streams.

[0113] The first regeneration gas stream 544 (enriched nitrogen stream) is fed to the first stage adsorber vessel 251 undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorber vessel 251, where the first adsorbent releases trapped water and relatively small amounts of trapped hydrogen sulfide (and possibly trace amounts of carbon dioxide and nitrogen), which are collected via first by-product stream 536. First by-product stream 536 is sent to the quench tower 206.

[0114] A second regeneration gas stream 546 (enriched nitrogen stream) is introduced into the second stage adsorber vessel 256 for regeneration for regeneration of the second stage adsorber vessel 256 undergoing a regeneration cycle. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent in the second stage adsorber vessel 256 to produce a second outlet gas stream 540 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. The second outlet gas stream 540 is introduced into the Claus unit reactor 264 for further processing.

[0115] Regeneration of the first stage adsorption vessel 251 and the second stage adsorption vessel 256 with an enriched nitrogen stream can have advantages, for example, in facilitating removal of hydrogen sulfide from the first stage adsorption vessel 251 and the second stage adsorption vessel 256 and increasing hydrogen sulfide adsorption capacity during the adsorption cycle.

[0116] 6 is a schematic diagram of a Claus process tail gas processing system 600. Features of system 600 similar to features described with respect to system 200 are similarly numbered.

[0117] The system 600 includes a hydrogenation reactor 204 (e.g., a reaction vessel) for receiving a tail gas stream 620 comprising a Claus process tail gas and hydrogenating sulfur-containing compounds in the Claus process tail gas to hydrogen sulfide to produce a hydrogenated gas stream 622 comprising hydrogen sulfide, water, and at least one of carbon dioxide and water. In some examples, the hydrogenated gas does not include any sulfur-containing compounds other than hydrogen sulfide. In some examples, any sulfur-containing compounds other than hydrogen sulfide in the hydrogenated gas may be present in trace amounts (or may not be easily measurable) in the hydrogenated gas.

[0118] The hydrogenated gas stream 622 is cooled via a first heat exchanger 205 to produce a cooled hydrogenated gas stream 624. The quench tower 206 receives the cooled hydrogenated gas stream 624 and condenses the water in the hydrogenated gas to produce a quench gas stream 626 comprising sulfides, water, and at least one of carbon dioxide and nitrogen. The condensed water (containing some hydrogen sulfide) is recovered in the quench tower 206 as a first water condensate stream 628, which may be sent to a sour water stripper (SWS) tower 260.

[0119] The quench gas stream 626 is pressurized by the compressor 207 to produce a compressed quench gas stream 627. The compressed quench gas stream 627 is cooled by the second heat exchanger 208 to produce a cooled quench gas stream 629. The cooled quench gas stream 629 is introduced into the collection drum 209 to produce a second water condensate stream 631 and an adsorption feed stream 630. The second water condensate stream 631 may be sent to the SWS column 260.

[0120] Adsorption feed stream 630 is introduced into first stage adsorption unit 210. In the illustrated example, first stage adsorption vessel 250 is undergoing an adsorption cycle, first stage adsorption vessel 251 is undergoing a regeneration cycle, and first stage adsorption vessel 252 is in a standby mode. Adsorption feed stream 630 is fed to first stage adsorption vessel 250 operating in an adsorption cycle to adsorb water from adsorption feed stream 630 onto a first adsorbent, thereby producing a first outlet gas stream 632 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. In some examples, a majority (e.g., most or substantially all) of the water in adsorption feed stream 630 is adsorbed onto the first adsorbent in first stage adsorption vessel 250 operating in an adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed from adsorption feed stream 630 onto the first adsorbent. In some examples, first outlet gas stream 632 contains no water or only trace or unmeasurable amounts of water.

[0121] The first outlet gas stream 632 is introduced into the second stage adsorption unit 212. In the illustrated example, the second stage adsorption vessel 255 is undergoing an adsorption cycle, the second stage adsorption vessel 256 is undergoing a regeneration cycle, and the second stage adsorption vessel 257 is in a standby mode. The first outlet gas stream 632 is fed to the second stage adsorption vessel 255, which operates in an adsorption cycle to adsorb hydrogen sulfide from the first outlet gas stream 632 onto a second adsorbent, thereby producing a second by-product stream 638 comprising at least one of carbon dioxide and nitrogen. In some examples, the second by-product stream 638 contains no hydrogen sulfide or a trace or unmeasurable amount of hydrogen sulfide.

[0122] The second by-product stream 638 is separated into a first portion 639 and a second portion 642. The first portion 639 of the second by-product stream is introduced into the thermal oxidizer 262 for further processing. The second portion 642 of the second by-product stream, which may be a slip stream of the second by-product stream 638, is used as a regeneration gas.

[0123] The second portion 642 of the second by-product stream 638 is directed through a CO2 separation element 650 that separates carbon dioxide gas (CO2) from the second portion 642 of the stream. In the example of Figure 6, the CO2 separation element 650 is a CO2 selective membrane that separates the carbon dioxide gas from the stream 642. In some examples, the CO2 separation element 650 is a cryogenic separation element that can separate CO2 from the second portion 642 of the stream at cryogenic temperatures. The output of the CO2 separation element 650 (e.g., from the CO2 selective membrane or the cryogenic separation element) is a carbon dioxide stream 656 and an enriched nitrogen stream 652.

[0124] Carbon dioxide stream 656 is directed to thermal oxidizer 262 via ejector 650. Enriched nitrogen stream 652 exiting CO2 separation element 650 is heated via first heat exchanger 205 to produce heated enriched nitrogen stream 643 by heat exchange from hydrogenation gas stream 622. In some examples (as shown in FIG. 6), heated enriched nitrogen stream 643 is further heated via third heat exchanger 214 to produce heated enriched nitrogen stream 645. Heat exchangers 205, 214 heat the enriched nitrogen to a temperature sufficient to desorb hydrogen sulfide from the adsorption vessels in their regeneration cycle. The heated second portion 645 of the second by-product stream is separated into first regeneration gas stream 644 and second regeneration gas stream 646, both of which are enriched nitrogen streams.

[0125] The first regeneration gas stream 644 (enriched nitrogen stream) is fed to the first stage adsorber vessel 251 undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorber vessel 251, where the first adsorbent releases trapped water and relatively small amounts of trapped hydrogen sulfide (and possibly trace amounts of carbon dioxide and nitrogen), which are collected via first by-product stream 636. First by-product stream 636 is sent to the quench tower 206.

[0126] A second regeneration gas stream 646 (enriched nitrogen stream) is introduced into the second stage adsorber vessel 256 for regeneration for regeneration of the second stage adsorber vessel 256 undergoing a regeneration cycle. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent in the second stage adsorber vessel 256 to produce a second outlet gas stream 640 comprising hydrogen sulfide and at least one of carbon dioxide and nitrogen. The second outlet gas stream 640 is introduced into the Claus unit reactor 264 for further processing.

[0127] Regeneration of the first stage adsorption vessel 251 and the second stage adsorption vessel 256 with an enriched nitrogen stream can have advantages, for example, in facilitating removal of hydrogen sulfide from the first stage adsorption vessel 251 and the second stage adsorption vessel 256 and increasing hydrogen sulfide adsorption capacity during the adsorption cycle.

[0128] 7A, in an exemplary process for removing hydrogen sulfide from a Claus tail gas, sulfur-containing compounds in a Claus tail gas stream are converted to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream (700). The hydrogenated gas stream comprises hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen. The hydrogenated gas stream is fed to a quench tower to produce a quenched gas stream by condensing liquid water into a water condensate stream (702). The quench gas stream comprises hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen.

[0129] The quench gas stream is compressed in a compressor, cooled, and fed to a first stage adsorber vessel of a first stage adsorption unit to adsorb water from the quench gas stream onto the adsorbent of the first stage adsorber vessel to produce a first outlet gas stream (704). In some examples, the cooled, pressurized, quenched gas stream is fed to a collection drum to recover liquid water to produce an adsorption feed, which is fed to the first stage adsorber vessel. The first outlet gas stream comprises hydrogen sulfide and at least one of carbon dioxide and nitrogen. The first outlet gas stream is fed to a second stage adsorber vessel of a second stage adsorption unit to adsorb hydrogen sulfide onto the adsorbent of the second stage adsorber vessel to produce a second by-product gas stream (706). The second by-product gas stream comprises at least one of carbon dioxide and nitrogen.

[0130] The first portion of the second by-product gas stream is separated into a carbon dioxide stream and an enriched nitrogen stream (708). In some examples, separating the second portion of the second by-product gas stream into a nitrogen stream and a carbon dioxide stream is accomplished by applying a vacuum to a carbon dioxide separation membrane. In some examples, the separation is accomplished by flowing the carbon dioxide stream through an ejector to a thermal oxidizer. In some examples, the separation is a cryogenic separation process.

[0131] The carbon dioxide stream is directed to a thermal oxidizer (710). The enriched nitrogen stream can be heated upstream, for example, using heat from the hydrogenation gas stream. A first portion of the enriched nitrogen stream is fed to a first stage adsorber vessel for regenerating the adsorbent in the first stage adsorber vessel by desorbing water from the adsorbent in the first stage adsorber vessel, thereby producing a first by-product gas stream (712). The first by-product gas stream comprises at least one of carbon dioxide and nitrogen. In some examples, the first by-product gas stream is combined with the hydrogenation gas stream fed to the quench tower.

[0132] A second portion of the enriched nitrogen stream is fed to a second stage adsorber vessel for regeneration of the adsorbent therein (714). A second portion of the second by-product gas stream output from the second stage adsorber vessel during the regeneration cycle is a second outlet gas comprising hydrogen sulfide. The second outlet gas may be fed to a reactor, such as the reactor of the Claus unit that produced the Claus process tail gas.

[0133] A third portion of the second by-product gas stream is provided to the thermal oxidizer. In some examples, the first and second portions of the second by-product gas stream combine to provide a slip stream of the second by-product gas stream.

[0134] 7B, in an exemplary process for removing hydrogen sulfide from a Claus tail gas, sulfur-containing compounds in a Claus tail gas stream are converted to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream (750). The hydrogenated gas stream comprises hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen. The hydrogenated gas stream is fed to a quench tower to produce a quench gas stream by condensing the water into a water condensate stream (752). The quench gas stream comprises hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen.

[0135] The quench gas stream is compressed in a compressor, cooled, and fed to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quench gas stream onto the adsorbent of the first stage adsorption vessel to produce a first outlet gas stream (754). In some examples, the cooled, pressurized, quenched gas stream is fed to a collection drum to recover liquid water to produce an adsorption feed, which is fed to the first stage adsorption vessel. The first outlet gas stream comprises hydrogen sulfide and at least one of carbon dioxide and nitrogen. The first outlet gas stream is fed to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide onto the adsorbent of the second stage adsorption vessel to produce a second by-product gas stream (756). The second by-product gas stream comprises at least one of carbon dioxide and nitrogen. The second by-product gas stream is heated, for example, with heat from the hydrogenation gas stream.

[0136] A first portion of the second by-product gas stream is fed to a first stage adsorber vessel for regenerating the adsorbent in the first stage adsorber vessel by desorbing water from the adsorbent in the first stage adsorber vessel to produce a first by-product gas stream (758). The first by-product gas stream comprises at least one of carbon dioxide and nitrogen. In some examples, the first by-product gas stream is combined with the hydrogenation gas stream fed to the quench tower.

[0137] A second portion of the second by-product gas stream is fed to the second stage adsorber vessel for regeneration of the adsorbent therein (760). After a period of time, the feeding of the second portion of the second by-product stream to the second stage adsorber vessel is stopped (762) and a high purity nitrogen stream is fed to the second stage adsorber vessel, for example, from a cryogenic tank (764). The output from the second stage adsorber vessel during the regeneration cycle is a second outlet gas comprising hydrogen sulfide. The second outlet gas may be fed to a reactor, such as the reactor of the Claus unit that produced the Claus process tail gas. EXAMPLES

[0138] Example 1: CuY zeolite as the second stage adsorbent material

[0139] In this example, Y-type zeolite ion-exchanged with Cu ions (referred to as "CuY zeolite" or "CuY") was used as the adsorbent material for the second stage adsorption cycle to separate hydrogen sulfide from carbon dioxide. The high polarity of CuY results in a high affinity between the adsorbent material and hydrogen sulfide.

[0140] Grand Canonical Monte Carlo (GCMC) simulations were performed to determine the adsorption of hydrogen sulfide on CuY under the assumption that no chemical processes occur. In the GCMC simulations, the total solid and gas system was subjected to a 6×10 6 , and then perform an additional 6 × 10 Monte Carlo step to obtain the statistical average. 6 Steps were performed. The simulation was performed under the assumption that there were no other competing gases in the mixture.

[0141] The adsorption capacity (mmol / g: millimoles per gram) of the adsorbed gas molecules on the system at each thermodynamic point was calculated. The results are shown in Figure 8. These results show that the adsorption capacity of 1% H2S on CuY approaches 0.8 mmol / g at 1 bar g and 298 Kelvin (K).

[0142] Example 2: Simulation of an adsorption-based tail gas treatment process

[0143] Aspen simulations were performed to determine the Claus tail gas composition of an ultra-lean gas plant (20% H2S acid gas stream) with co-firing and a 3-stage Claus configuration. The acid gas stream was defined as 50 million standard cubic feet per day (MMSCFD). The simulations covered an adsorption-based tail gas treatment process from the hydrotreatment reactor to the water removal stage.

[0144] Figure 9 shows the process flow diagram 900 for this simulation. A sulfur recovery unit (SRU) feed stream 910 from the hydrotreating reactor enters a compressor 902 and the compressed gas output from the compressor is fed to a chiller 904. The cooled gas output from the chiller is separated by a separator 905 into a first stream 906 that is directed to a water adsorption vessel and a second stream 908 that is directed to a sour water stripper. Table 1 shows the simulated gas composition flows from the SRU feed stream to the water adsorption vessel. Note that "lbmol / h" stands for "pound moles per hour."

[0145] [Table 1]

[0146] Example 3: Simulation of an adsorption-based tail gas treatment process

[0147] An Aspen simulation of the water removal stage of the tail gas treatment process was performed to determine the specific gas flows and adsorption vessel sizes for a 24-hour adsorption cycle.

[0148] Figure 10 shows the process flow diagram 950 for this simulation. The first stream 906 from separator 905 (see Figure 9) is directed to a water adsorption vessel 952 having molecular sieve 3A as the adsorbent material. The adsorption vessel 952 has a diameter of 3.3 meters (m) and a height of 8.6 m. The adsorption cycle was 24 hours (86,400 seconds).

[0149] 11 shows the breakthrough curve for water in the water removal adsorber vessel 952 for an 86,400 second adsorption cycle. The y-axis label is mol HO / mol tot (moles of water divided by total moles of gas mixture). Table 2 shows the simulated gas composition flow from separator 905 to the water adsorber vessel 952 (Stream S1) and from the water adsorber vessel 952 to the hydrogen sulfide adsorber vessel (Stream S2).

[0150] [Table 2]

[0151] Example 4: Simulation of an adsorption-based tail gas treatment process

[0152] An Aspen simulation of the hydrogen sulfide removal stage of the tail gas treatment process was performed to determine the specific gas flows and adsorption vessel sizes for a 24-hour adsorption cycle.

[0153] Figure 12 shows the process flow diagram 50 for this simulation. Stream S1 from water adsorption vessel 952 (Figure 10) is directed to hydrogen sulfide adsorption vessel 52 having CuY zeolite as the adsorbent material. Adsorption vessel 52 has a diameter of 4.63 meters (m) and a height of 12.1 m. The adsorption cycle was 24 hours (86400 seconds).

[0154] Figure 13A shows the breakthrough curves for nitrogen (curve 54) and carbon dioxide (curve 56) in hydrogen sulfide adsorption vessel 52 for an 86,400 second adsorption cycle. Figure 13B shows the breakthrough curve for hydrogen sulfide in hydrogen sulfide adsorption vessel 52. The y-axis labels in Figures 13A and 13B are mol HO / mol tot (moles of water divided by total moles of gas mixture).

[0155] Table 3 shows the simulated gas composition flow from the water adsorption vessel 952 to the hydrogen sulfide adsorption vessel 52 (stream S3) and the simulated gas composition flow from the hydrogen sulfide adsorption vessel 52 to the thermal oxidant and / or as a regenerative slipstream (stream S4).

[0156] [Table 3]

[0157] While specific embodiments of the present subject matter have been described, other embodiments are within the scope of the following claims.

Claims

1. 1. A method for recovering sulfur, comprising: converting sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quench gas stream; supplying the quench gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quench gas stream to produce a first outlet gas stream; supplying the first outlet gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first outlet gas stream to produce a second by-product gas stream; separating at least a portion of the second by-product gas stream into a carbon dioxide stream and a nitrogen-enriched stream; regenerating the second stage adsorption vessel by feeding a portion of the enriched nitrogen stream to the second stage adsorption vessel to produce a second outlet gas stream; The method includes:

2. 2. The method of claim 1, comprising separating a first portion of the second by-product gas stream into the carbon dioxide stream and the enriched nitrogen stream using cryogenic separation.

3. 2. The method of claim 1, comprising separating a first portion of said second by-product gas stream into said carbon dioxide stream and said enriched nitrogen stream using a separation membrane.

4. The method of claim 3 comprising applying a vacuum to the separation membrane.

5. The method of claim 1 comprising feeding the carbon dioxide stream to a thermal oxidizer.

6. The method of claim 5 comprising providing the carbon dioxide stream to the thermal oxidizer through an ejector.

7. 2. The method of claim 1, comprising regenerating said first stage adsorption vessel by supplying a first portion of said enriched nitrogen stream to said first stage adsorption vessel to desorb water thereby producing a first by-product gas stream.

8. 8. The method of claim 7, comprising combining said first by-product gas stream with said hydrogenated gas stream to form a combined stream and feeding said combined stream to said quench tower.

9. 2. The method of claim 1 comprising heating the enriched nitrogen stream in a heat exchanger using heat from the hydrogenation gas stream.

10. 2. The method of claim 1 comprising compressing the quench gas stream in a compressor and cooling the compressed quench gas stream.

11. 2. The method of claim 1, comprising: feeding the quench gas stream to a collection drum and recovering liquid water via a second water condensate stream to generate an adsorption feed that is fed to the first stage adsorption vessel.

12. 10. The method of claim 1 comprising feeding the water condensate stream to a sour water stripper.

13. The method of claim 1 comprising supplying a second portion of the second by-product gas stream to a thermal oxidizer.

14. The method of claim 1 comprising feeding the second outlet gas stream to a reactor.

15. 1. A system for recovering sulfur from a Claus process tail gas, comprising: a hydrogenation reactor configured to convert sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide to produce a hydrogenated gas stream; a quench tower fluidly connected to the hydrogenation reactor and configured to receive the hydrogenation gas stream and to produce a quench gas stream by condensing liquid water into a water condensate stream; a first stage adsorption unit including a first stage adsorption vessel fluidly connected to the quench tower during a first stage adsorption cycle and configured to receive the quench gas stream and to produce a first outlet gas stream by adsorbing water from the quench gas stream; a second stage adsorption unit including a second stage adsorption vessel fluidly connected to the first stage adsorption vessel during a second stage adsorption cycle and configured to receive the first outlet gas stream and to produce a second by-product gas stream by adsorbing hydrogen sulfide from the first outlet gas stream; a carbon dioxide separation element configured to receive at least a portion of the second by-product gas stream and separate the portion of the second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream; Including, the second stage adsorption vessel is configured to receive a portion of the enriched nitrogen stream during a second stage regeneration cycle. system.

16. 16. The system of claim 15, wherein the carbon dioxide separation element comprises a separation membrane configured to separate a portion of the second by-product gas stream into the carbon dioxide stream and the enriched nitrogen stream.

17. The system of claim 15 , wherein the carbon dioxide separation element comprises a cryogenic separation element.

18. The system of claim 15 comprising a thermal oxidizer configured to receive the carbon dioxide stream.

19. 20. The system of claim 18, further comprising an ejector, the thermal oxidizer configured to receive the carbon dioxide stream from the ejector.

20. 16. The system of claim 15, wherein the first stage adsorption vessel is configured to receive a first portion of the enriched nitrogen stream during a first stage regeneration cycle and produce a first by-product gas stream by desorbing water.

21. The system of claim 15 comprising a thermal oxidizer configured to receive a second portion of the second by-product gas stream.

22. 16. The system of claim 15, comprising a reactor fluidly connected to the second stage adsorption vessel and configured to receive a second outlet gas produced in the second stage adsorption unit during the second stage regeneration cycle.

23. 16. The system of claim 15, comprising a heat exchanger configured to cool the hydrogenated gas stream with heat from the enriched nitrogen stream.

24. 16. The system of claim 15, wherein the first stage adsorption vessel comprises a hydrophilic molecular sieve.

25. 16. The system of claim 15, wherein the second stage adsorption vessel comprises a Cu-Y type zeolite.

26. 16. The system of claim 15, wherein the first-stage adsorption unit comprises a plurality of first-stage adsorption vessels fluidly connected in parallel and the second-stage adsorption unit comprises a plurality of second-stage adsorption vessels fluidly connected in parallel.

27. 1. A method for recovering sulfur, comprising: converting sulfur-containing compounds in the Claus process tail gas stream to hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quench gas stream; supplying the quench gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quench gas stream to produce a first outlet gas stream; supplying the first outlet gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first outlet gas stream to produce a second by-product gas stream; regenerating the second stage adsorber vessel to produce a second outlet gas stream, wherein regenerating the second stage adsorber vessel comprises feeding a portion of the second by-product gas stream and a nitrogen stream to the second stage adsorber vessel to produce a second outlet gas stream; The method includes:

28. 30. The method of claim 27, wherein regenerating the second stage adsorption vessel comprises supplying the nitrogen stream to the second stage adsorption vessel from a cryogenic tank.

29. regenerating the second stage adsorption vessel; supplying a portion of the second by-product gas stream to the second stage adsorption vessel for a first time period; supplying the nitrogen gas stream to the second-stage adsorption vessel for a second time period subsequent to the first time period; 28. The method of claim 27, comprising:

Images