KR20240124970A - Adsorption-based cloud tail gas treatment - Google Patents

Abstract

A sulfur recovery method comprises the steps of: converting a sulfur-containing compound in a cloud tail gas stream into hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream; supplying the hydrogenated gas stream to a quench tower to condense liquid water to produce a quenched gas stream; supplying the quenched gas stream to a first-stage adsorption vessel of a first-stage adsorption unit to adsorb water from the quenched gas stream to produce a first effluent gas stream; supplying the first effluent gas stream to a second-stage adsorption vessel of a second-stage adsorption unit to adsorb hydrogen sulfide from the first effluent gas stream to produce a second by-product gas stream; separating the second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream; and regenerating the second-stage adsorption vessel using the enriched nitrogen stream.

Description

Adsorption-based cloud tail gas treatment

claim priority

This application claims the benefit of Greek Patent Application No. 20210100882, filed December 15, 2021, and U.S. Patent Application No. 17/945,809, filed September 15, 2022, the entire contents of which are incorporated herein by reference.

Sulfur recovery may refer to the conversion of hydrogen sulfide to elemental sulfur. Hydrogen sulfide may be a byproduct of natural gas processing and sulfur-containing crude oil refining. A conventional method for sulfur recovery is the Claus process. Conventional Claus processes can recover 95% to 98% of hydrogen sulfide. The tail gas from the Claus process may have residual (residual) hydrogen sulfide, such as less than 5% hydrogen sulfide. The Claus tail gas may be processed to recover this residual hydrogen sulfide.

In one aspect, a method for recovering sulfur comprises the steps of: converting, in a hydrogenation reactor, sulfur-containing compounds in a cloud tail gas stream to hydrogen sulfide to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quenched gas stream; feeding the quenched gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quenched gas stream to produce a first effluent gas stream; feeding the first effluent gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first effluent 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 an enriched nitrogen stream; and a step of regenerating the second stage adsorption vessel by supplying a portion of the enriched nitrogen stream to the second stage adsorption vessel to generate a second exhaust gas stream.

Embodiments may include any combination of one or more of the following features:

The method comprises the step of separating a first portion of the second byproduct gas stream into a carbon dioxide stream and an enriched nitrogen stream using cryogenic separation.

The method comprises the step of using a membrane to separate a first portion of the second byproduct gas stream into a carbon dioxide stream and an enriched nitrogen stream. In some cases, the method comprises the step of applying a vacuum to the membrane.

The method comprises the step of supplying a carbon dioxide stream to a thermal oxidizer. In some cases, the method comprises the step of supplying the carbon dioxide stream to the thermal oxidizer through an ejector.

The method comprises the step of regenerating the first stage adsorption vessel by feeding a first portion of the enriched nitrogen stream to the first stage adsorption vessel, thereby desorbing water to produce a first by-product gas stream. In some cases, the method comprises the step of combining the first by-product gas stream with the hydrogenated gas stream to form a combined stream and feeding the combined stream to a quench tower.

The method comprises the step of heating an enriched nitrogen stream in a heat exchanger with heat from a hydrogenated gas stream.

The method comprises the steps of pressurizing a quenched gas stream in a compressor; and cooling the pressurized quenched gas stream.

The method comprises the steps of producing an adsorption feed by feeding a quenched gas stream to a collection drum to recover liquid water via a second water condensate stream, wherein the adsorption feed is fed to a first stage adsorption vessel.

The method comprises the step of feeding a water condensate stream to a sour water stripper.

The method comprises the step of supplying a second portion of the second by-product gas stream to a thermal oxidizer.

The method comprises the step of supplying a second exhaust gas to a reaction furnace.

In one aspect, a system for sulfur recovery from cloud tail gas comprises: a hydrogenation reactor configured to convert sulfur containing compounds in a cloud 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 hydrogenated gas stream and condense liquid water into a water condensate stream to produce a quenched gas stream; a first stage adsorption unit comprising a first stage adsorption vessel, wherein, during a first stage adsorption cycle, the first stage adsorption unit is fluidly connected to the quench tower and configured to receive the quenched gas stream and adsorb water from the quenched gas stream to produce a first effluent gas stream; a second stage adsorption unit comprising a second stage adsorption vessel, wherein, during the second stage adsorption cycle, the second stage adsorption unit is fluidly connected to the first stage adsorption vessel and configured to receive the first effluent gas stream and adsorb hydrogen sulfide from the first effluent gas stream to produce a second byproduct gas stream; A second stage adsorption vessel comprises 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; wherein the second stage adsorption vessel is configured to receive a portion of the enriched nitrogen stream during the second stage regeneration cycle.

Embodiments may include any combination of one or more of the following features:

The carbon dioxide separation member comprises a separation membrane configured to separate a portion of the second byproduct gas stream into a carbon dioxide stream and an enriched nitrogen stream.

The carbon dioxide separation element includes a cryogenic separation element.

The system includes a thermal oxidizer configured to receive a stream of carbon dioxide. In some cases, the system includes an ejector, wherein the thermal oxidizer is configured to receive a stream of carbon dioxide from the ejector.

During the first stage regeneration cycle, the first stage adsorption vessel is configured to receive a first portion of the enriched nitrogen stream and produce a first byproduct gas stream by desorbing water.

The system includes a thermal oxidizer configured to receive a second portion of the second byproduct gas stream.

The system comprises a reactor fluidically connected to the second stage adsorption vessel and configured to receive a second off-gas generated in the second stage adsorption unit during the second stage regeneration cycle.

The system includes a heat exchanger configured to cool a hydrogenated gas stream with heat from an enriched nitrogen stream.

The first stage adsorption vessel contains a hydrophilic molecular sieve.

The second stage adsorption vessel contains Cu-Y type zeolite.

The first stage adsorption unit comprises a plurality of first stage adsorption vessels fluidically connected in parallel, and the second stage adsorption unit comprises a plurality of second stage adsorption vessels fluidically connected in parallel.

In one aspect, a method for recovering sulfur comprises: converting, in a hydrogenation reactor, a sulfur-containing compound in a cloud tail gas stream to hydrogen sulfide to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen; feeding the hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream to produce a quenched gas stream; feeding the quenched gas stream to a first-stage adsorption vessel of a first-stage adsorption unit to adsorb water from the quenched gas stream to produce a first effluent gas stream; feeding the first effluent gas stream to a second-stage adsorption vessel of a second-stage adsorption unit to adsorb hydrogen sulfide from the first effluent gas stream to produce a second by-product gas stream; and regenerating the second-stage adsorption vessel to produce a second effluent gas stream, wherein the step of regenerating the second-stage adsorption vessel comprises feeding a portion of the second by-product gas stream and a nitrogen stream to the second-stage adsorption vessel.

Embodiments may include any combination of one or more of the following features:

The step of regenerating the second stage adsorption vessel comprises the step of supplying a nitrogen stream from a cryogenic tank to the second stage adsorption vessel.

The step of regenerating the second stage adsorption vessel comprises the steps of supplying a portion of the second by-product gas stream to the second stage adsorption vessel for a first period of time; and supplying a nitrogen gas stream to the second stage adsorption vessel for a second period of time after the first period.

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.

Figures 1 to 6 are diagrams of a system for treating cloud tail gas.
Figures 7a and 7b are flow charts.
Figure 8 is a plot of a simulated adsorption isotherm of hydrogen sulfide on Y-zeolite (“CuY”) ion-exchanged with Cu ions.
Figures 9 and 10 are process diagrams.
Figure 11 is a plot of a simulated breakthrough curve of water within a water removal adsorption vessel.
Figure 12 is a process diagram.
Figure 13a is a plot of simulated breakthrough curves of carbon dioxide and nitrogen within a hydrogen sulfide removal adsorption vessel.
Figure 13b is a plot of a simulated breakthrough curve of hydrogen sulfide within a hydrogen sulfide removal adsorption vessel.

This specification describes approaches to the regeneration of hydrogen sulfide adsorption vessels in a Claus tail gas treatment system that facilitate high levels of sulfur recovery. In some approaches, a two-phase process is used to regenerate the hydrogen sulfide adsorption vessels. In the first phase, a slip stream of clean gas comprising carbon dioxide and nitrogen is fed to the hydrogen sulfide adsorption vessel to desorb hydrogen sulfide from the adsorbent material therein. The clean gas supply is then stopped, and a high purity nitrogen stream is fed to the hydrogen sulfide adsorption vessel for further regeneration. In some approaches, the slip stream of clean gas is separated, for example, by a membrane, into a carbon dioxide stream and a nitrogen stream, and the nitrogen stream is then directed to the hydrogen sulfide adsorption vessel for regeneration. The carbon dioxide stream can be fed to a thermal oxidizer.

These approaches to adsorbent regeneration in a Claus tail gas treatment system may help prevent the occurrence of hydrogen sulfide spikes during adsorbent regeneration. Furthermore, these approaches may 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 feed gas.

FIG. 1 illustrates a schematic diagram of a system (100) for treating cloud tail gas. Additional description of a cloud tail gas treatment process and system may be found in U.S. Pat. No. 10,662,061, the contents of which are incorporated herein by reference in their entirety. The 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).

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

In some examples, for example, as illustrated in FIG. 1, the 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 illustrated) or a relatively clean gas comprising carbon dioxide and nitrogen. The first regeneration gas stream (144) is introduced to the first stage adsorption unit (110). The second regeneration gas stream (146) is introduced to the second stage adsorption unit (112).

The tail gas stream (120) comprises cloud tail gas comprising sulfur containing compounds, for example, sulfur containing compounds that are not completely recovered by the upstream cloud unit. The sulfur containing compounds may be present in forms such as elemental sulfur, hydrogen sulfide, sulfur oxides, and their anion counterparts. As used herein, the term "elemental sulfur" refers to all phases of sulfur which may be present in forms such as S, S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , and S ₈ . Non-limiting exemplary sulfur oxides include SO , SO ₂ , SO ₃ , SO ₄ , S ₂ O , S ₂ O ₂ , S ₆ O , S ₆ O ₂ , S ₇ O , S ₇ O ₂ , S ₈ O , S ₉ O , and S ₁₀ O . The cloud tail gas in the tail gas stream (120) may also contain carbon dioxide, water, nitrogen, hydrogen, and combinations thereof.

The first heat exchanger (102) can be any heat exchanger capable of heating the gas stream to a temperature at which a 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., for example, from about 220° C. to about 280° C., or from about 240° C. to about 260° C., for example, about 250° C. After heating, the heated tail gas stream (122) still comprises sulfur containing compounds, carbon dioxide, water, nitrogen, hydrogen, and combinations thereof as described above with respect to the tail gas stream (120).

The hydrogenation reactor (104) can be any 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 instances, hydrogen contained in the heated tail gas stream (122) is used to reduce sulfur containing compounds in the heated tail gas stream (122) to hydrogen sulfide. In some instances, a make-up hydrogen gas stream (not shown) is introduced to the hydrogenation reactor (104). In some instances, water is produced as a byproduct during the hydrogenation reaction. As a result, the hydrogenated gas stream (124) comprises substantially only hydrogen sulfide as sulfur containing compounds. The hydrogenated gas stream (124) may also comprise carbon dioxide, water, nitrogen, and combinations thereof.

The quench tower (106) can be any device capable of condensing and recovering water from the hydrogenated gas stream (124). A significant portion of the water contained in the hydrogenated gas stream (124) is condensed and substantially recovered via the water condensate stream (128). Although a significant portion of the water contained in the hydrogenated gas stream (124) is removed, the quenched gas stream (126) output from the quench tower (106) can still contain a residual amount of gaseous water. For example, the quenched gas stream (126) can have a gaseous water content in the range of about 0 mol % to about 20 mol %, for example, about 3 mol % to about 15 mol %, or about 4 mol % to about 10 mol %, for example, about 8 mol %. The quenched gas stream (126) may also include hydrogen sulfide (e.g., hydrogen sulfide already present in the cloud tail gas, hydrogen sulfide generated in the hydrogenation reactor (104), or both), carbon dioxide, nitrogen, and combinations thereof. The quenched gas stream (126) has a temperature in the range of about 20° C. to about 170° C., for example, about 30° C. to about 100° C., or about 40° C. to about 80° C., for example, about 43° C.

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 quenched gas stream (126) such that the cooled quenched gas stream (130) has a temperature in the range of about 0° C. to about 70° C., for example, about 10° C. to about 40° C., or about 15° C. to about 30° C., for example, about 21° C. As the quenched gas stream (126) is cooled, the gaseous water content of the cooled quenched gas stream (130) decreases to a range of about 0 mol % to about 10 mol %, for example, about 0 mol % to about 5 mol %, or about 0 mol % to about 1 mol %, for example, about 0.46 mol %. The cooled quenched gas stream (130) may include hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the cloud tail gas, hydrogen sulfide generated in the hydrogenation reactor (104), or both), carbon dioxide, water, nitrogen, and combinations thereof.

The first stage adsorption unit (110) comprises 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.

In some examples, the first adsorbent comprises any adsorbent that is capable of selectively capturing hydrogen sulfide while rejecting water from a wet gas stream (e.g., the cooled quenched gas stream (130)). Non-limiting exemplary materials used for the first adsorbent include all-silica zeolites having a framework such as MFI-type or CHA-type. All-silica zeolites are hydrophobic materials that can be used to separate polar molecules, such as water, from less polar molecules, such as hydrogen sulfide, carbon dioxide, and nitrogen. During the adsorption cycle, components of the cooled quenched 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 quenched gas stream other than water (e.g., hydrogen sulfide) are captured in the pores of the first adsorbent. After passing through the first adsorbent, water is collected via the first byproduct 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) where the first adsorbent removes the captured hydrogen sulfide to produce a first off-gas stream (132) substantially in the absence of water.

In some examples, the first adsorbent comprises any adsorbent capable of selectively capturing water from a wet gas stream (e.g., the cooled quenched gas stream (130)) while generally excluding hydrogen sulfide. Non-limiting exemplary materials used 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 the adsorption cycle, components of the cooled quenched 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 in 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 a first off-gas stream (132) substantially in the absence of water. During the regeneration cycle, components of the first regeneration gas stream (144) enter one or more first adsorption vessels (150) to regenerate the first adsorbent. Desorption occurs in the one or more first stage adsorption vessels (150) where the first adsorbent removes captured water (and relatively small amounts of hydrogen sulfide), which is collected via the first byproduct stream (136).

In some examples, the first stage adsorption unit (110) comprises at least three first stage adsorption vessels (150) fluidly connected in a parallel manner. At any given moment during operation, one of the at least three first stage adsorption vessels (150) is performing an adsorption cycle, one of the at least three first stage adsorption vessels (150) is performing a regeneration cycle, and one of the at least three first stage adsorption vessels (150) is on standby. In this manner, components of the cooled quenched gas stream (130) can be continuously fed to the first stage adsorption unit (110), and a continuous flow of the first effluent gas stream (132) can be produced from the first stage adsorption unit (110).

The fourth heat exchanger (116) can be any heat exchanger capable of cooling the gas stream to a temperature at which adsorption occurs in the second stage adsorption unit (112). The fourth heat exchanger (116) can cool the first off-gas stream (132) such that the cooled first off-gas stream (134) has a temperature in the range of about 0° C. to about 70° C., for example, about 10° C. to about 40° C., or about 15° C. to about 30° C., for example, about 25° C. The first off-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).

The second stage adsorption unit (112) comprises one or more second stage adsorption vessels (152) fluidly connected in series or in 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 comprise any adsorbent capable of selectively capturing hydrogen sulfide while excluding carbon dioxide and nitrogen. In some embodiments, the second adsorbent can comprise any adsorbent having a breakthrough time difference between hydrogen sulfide and carbon dioxide and between hydrogen sulfide and nitrogen. Non-limiting exemplary materials used for the second adsorbent include molecular sieves (e.g., molecular sieve 4A, etc.); hydrophobic zeolites having a framework such as MFI-type, CHA-type, FAU-type, MOR-type, DDR-type, FER-type or MWW-type; and hydrophobic zeolites such as MOF or ZIF.

During the adsorption cycle, components of the cooled first exhaust gas stream (134) are introduced through one or more second stage adsorption vessels (152) of the second stage adsorption unit (112). Hydrogen sulfide is captured in the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) are collected via the second byproduct stream (138) after passing through the second adsorbent. During the regeneration cycle, components of the second regeneration gas stream (146) enter 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) where the second adsorbent rejects the captured hydrogen sulfide to produce a second exhaust gas stream (140) substantially free of carbon dioxide and nitrogen.

In some examples, the second stage adsorption unit (112) comprises at least three second stage adsorption vessels (152) fluidly connected in parallel. At any moment during operation, one of the at least three second stage adsorption vessels (152) is performing an adsorption cycle, one of the at least three second stage adsorption vessels (152) is performing a regeneration cycle, and one of the at least three second stage adsorption vessels (152) is on standby. In this manner, components of the cooled first off-gas stream (134) can be continuously fed to the second stage adsorption unit (112), and a continuous flow of the second off-gas stream (140) can be generated from the second stage adsorption unit (112).

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. Instead of or in addition to the air feed (142), a gas can be used as the regeneration gas. For example, the regeneration gas can comprise at least one of nitrogen or carbon dioxide.

The third heat exchanger (114) can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate heat exchanger, etc.) capable of heating the gas stream to the temperatures at which adsorbent regeneration 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) such 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., for example, about 200° C. to about 300° C., or about 230° C. to about 290° C., for example, about 260° C.

The second exhaust gas stream (140) comprises hydrogen sulfide. The second exhaust gas stream (140) has a hydrogen sulfide content of at least about 95 wt %, for example, at least about 98 wt %, or at least about 99 wt %. In some examples, the second exhaust gas stream (140) is used as a feed gas to the Claus unit.

Figure 2 is a schematic diagram of a system (200) for treating cloud tail gas. The 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).

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

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 for removing hydrogen sulfide from water containing hydrogen sulfide (referred to as sour water). For example, the liquid water separated by the collection drum may contain hydrogen sulfide. The liquid water may be introduced to the sour water stripper, where steam is injected into the sour water stripper to heat the sour water, thereby shifting the chemical equilibrium by releasing the hydrogen sulfide.

An adsorption feed stream (230) is introduced into a first stage adsorption vessel (250) of a first stage adsorption unit (210) to produce a first off-gas stream (232). The first off-gas stream (232) is introduced into a second stage adsorption vessel (255) of a second stage adsorption unit (212) to produce a second by-product stream (238). The second by-product stream (238) is separated into a first portion (239) and a second portion (242). In some examples, a conduit fitting (e.g., a pipe tee) is provided to split (divide) the flow of the second by-product stream (238) into two portions (239) and (242). A flow control valve may be positioned along the conduit conveying portion (239) or portion (242) or both. Other conduit/control arrangements are applicable.

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 also referred to as a thermal incinerator, refers to a device or apparatus that thermally decomposes certain gases at high temperatures and releases them into the atmosphere. For example, a gas stream may be introduced into a thermal oxidizer, wherein any traces of hydrogen sulfide contained in the gas stream are oxidized to sulfur dioxide and then released into the atmosphere. The thermal oxidizer (262) may be, for example, a direct combustion thermal oxidizer, a regenerative thermal oxidizer (RTO), a catalytic oxidizer, or the like.

A second portion (242) of the second by-product stream (238) is used as a regeneration gas, as described in the following paragraph. In some examples, a majority of the second by-product stream (238) is split into a first portion (239) that is sent to a thermal oxidizer (262), and an amount of the second by-product stream (238) that constitutes the second portion (242) that is used as a regeneration gas is a slip stream of the second by-product stream (238). As used herein, the term "slip stream" means a minor (e.g., less than 20%) diversion of a main stream.

A second portion (242) of the second by-product stream (238) is heated through a first heat exchanger (205) to exchange heat with the hydrogenated gas stream (222) to produce a heated second portion (243) of the second by-product stream. In some examples (as shown in FIG. 2 ), the second portion (243) of the second by-product stream is further heated through 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).

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 effluent gas stream (240). The second effluent gas stream (240) is introduced into a reactor (264) of the Claus unit for further processing. As used herein, the term "reactor" refers to a device or apparatus typically included upstream of a Claus unit that initiates the conversion of hydrogen sulfide and other sulfur containing compounds to elemental sulfur. The reactor typically operates at a temperature in excess of 850° C. to convert the hydrogen sulfide to elemental sulfur.

The tail gas stream (220) comprises cloud tail gas comprising sulfur containing compounds, for example, sulfur containing compounds that are not completely recovered by the upstream cloud unit. The sulfur containing compounds may be present in forms such as elemental sulfur, hydrogen sulfide, sulfur oxides, and their anion counterparts. Non-limiting exemplary sulfur oxides include SO, SO ₂ , SO ₃ , SO ₄ , S ₂ O, S ₂ O ₂ , S ₆ O, S ₆ O ₂ , S ₇ O, S ₇ O ₂ , S ₈ O, S ₉ O, and S ₁₀ O. The cloud tail gas in the tail gas stream (220) may also comprise carbon dioxide, water, nitrogen, hydrogen, and combinations thereof.

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., for example, about 220° C. to about 280° C., or about 240° C. to about 260° C., for example, about 250° C.

The hydrogenation reactor (204) can be any catalytic or non-catalytic reactor capable of reducing sulfur containing compounds in the heated tail gas stream (220) other than hydrogen sulfide to hydrogen sulfide. In some instances, hydrogen contained in the tail gas stream (220) is used to reduce sulfur containing compounds in the tail gas stream (220) to hydrogen sulfide. In some instances, a make-up hydrogen gas stream (not shown) is introduced to the hydrogenation reactor (204). In some instances, water is produced as a byproduct during the hydrogenation reaction. As a result, the hydrogenated gas stream (222) comprises substantially only hydrogen sulfide as sulfur containing compounds. The hydrogenated gas stream (222) may also comprise carbon dioxide, water, nitrogen, and combinations thereof.

The first heat exchanger (205) can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate heat exchanger, etc.) that can cool the gas stream to a temperature suitable for operation of the quench tower (206), rather than 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 heat transfer by cross-exchange between the hydrogenated gas stream (222) and a second portion (242) of the second byproduct stream (discussed in a later paragraph). The first heat exchanger (205) cools the hydrogenated gas stream (222) such that the cooled hydrogenated gas stream (224) has a temperature of from about 20° C. to about 170° C., for example, from about 30° C. to about 100° C., or from about 40° C. to about 80° C., for example, about 43° C. The cooled hydrogenated gas stream (224) comprises 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 byproduct stream such that the heated second portion (243) has a temperature of from about 150° C. to about 350° C., for example, from about 200° C. to about 300° C., or from about 230° C. to about 290° C., for example, at least about 260° C.

In some examples, the third heat exchanger (214) may be used to heat a second portion (243) of the second byproduct stream to meet the temperature requirements for adsorbent regeneration in each of the first stage adsorption unit (210) and the second stage adsorption unit (212). The third heat exchanger (214) may be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate 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., condensed 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 each of the first regeneration gas stream (244) and the second regeneration gas stream (246)) has a temperature of from about 150° C. to about 350° C., for example, from about 200° C. to about 300° C., or from about 230° C. to about 290° C., for example, about 260° C. In some examples, a controlled temperature ramp is implemented during regeneration, in which case the second portion (243) of the second by-product stream is heated to different temperatures over time, up to a maximum of 400° C., as described in, for example, U.S. Patent Application No. 17/166,821, the contents of which are incorporated herein by reference in their entirety.

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

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

The second heat exchanger (208) can be any heat exchanger (e.g., a shell-and-tube heat exchanger, a plate heat exchanger, etc.) capable of cooling the gas stream to a temperature at which adsorption occurs in the first stage adsorption unit (210). The second heat exchanger (208) can cool the pressurized quenched gas stream (227) such that the cooled quenched gas stream (229) has a temperature in the range of about 0° C. to about 50° C., for example, about 5° C. to about 40° C., or about 10° C. to about 30° C., for example, about 15° C. As the pressurized quenched gas stream (227) is cooled, the gaseous water content of the cooled quenched gas stream (229) decreases to about 0 mol % to about 10 mol %, for example, about 0 mol % to about 5 mol %, or alternatively about 0 mol % to about 1 mol %, for example, about 0.46 mol %. The cooled quenched gas stream (229) may include hydrogen sulfide (e.g., hydrogen sulfide pre-existing in the cloud tail gas, hydrogen sulfide generated in the hydrogenation reactor (204), or both), carbon dioxide, water, nitrogen, and combinations thereof.

The collection drum (209) can be any type of separation device (e.g., a separation vessel) capable of separating a fluid stream into a gaseous stream and a liquid stream. The cooled quenched gas stream (229) is separated in the collection drum (209) to produce a second water condensate stream (231) (a liquid stream) and an adsorption feed stream (230) (a gaseous stream). The adsorption feed stream (230) can include hydrogen sulfide (e.g., hydrogen sulfide already present in the cloud tail gas, hydrogen sulfide generated in the hydrogenation reactor (204), or both), carbon dioxide, water, nitrogen, and combinations thereof.

In some examples, the first water condensate stream (228) comprises trace amounts of hydrogen sulfide dissolved in water collected from the quench tower (206). In some examples, the second water condensate stream (231) comprises trace amounts of hydrogen sulfide dissolved in 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 treatment, such as stripping hydrogen sulfide from the water.

The first stage adsorption unit (210) comprises first stage adsorption vessels (250, 251, 252) fluidly connected in a parallel manner. At any given moment 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 on standby. In this manner, components of the adsorption feed stream (230) can be continuously fed to the first stage adsorption unit (210), and a continuous flow of a first off-gas stream (232) and a first by-product stream (236) can be produced from the first stage adsorption unit (210).

Each of the first stage adsorption vessels (250, 251, 252) is filled with a first adsorbent, for example, packed. The first adsorbent can be in a first adsorbent bed within the vessel (250, 251, 252). In some examples, the first adsorbent comprises any adsorbent capable of selectively capturing water from a wet gas stream (e.g., adsorption feed stream (230)) while excluding hydrogen sulfide, carbon dioxide and nitrogen. A non-limiting exemplary material used in the first adsorbent includes a hydrophilic 3A molecular sieve. During the adsorption cycle, components of the adsorption feed stream (230) are introduced through one of the first stage adsorption vessels (250, 251, 252). Water (and relatively small amounts of hydrogen sulfide) are captured in 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 a first off-gas stream (232) substantially in the absence of water. During the regeneration cycle, 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 optionally trace amounts of carbon dioxide and nitrogen), which are collected via the first byproduct stream (236).

In the example of FIG. 2, the first stage adsorption vessel (250) is undergoing an adsorption cycle, the first stage adsorption vessel (251) is undergoing a regeneration cycle, and the first stage adsorption vessel (252) is in standby mode. During the adsorption cycle, components of the adsorption feed stream (230) are introduced through the first stage adsorption vessel (250). Water (and relatively small amounts of hydrogen sulfide) are captured in the pores of the first adsorbent. In some examples, trace amounts of carbon dioxide and nitrogen are captured in 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 a first off-gas stream (232) substantially in the absence of water.

During the regeneration cycle, components of the first regeneration gas stream (244) (e.g., carbon dioxide and nitrogen) enter the first stage adsorption vessel (251) to regenerate the first adsorbent. Desorption occurs in the first stage adsorption vessel (251), where the first adsorbent releases captured water and a relatively small amount of captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which are collected via the first byproduct stream (236).

The second stage adsorption unit (212) comprises second stage adsorption vessels (255, 256, 257) fluidly connected in a parallel manner. At any given moment 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 in standby. In this manner, components of the first off-gas stream (232) can be continuously fed to the second stage adsorption unit (212), and a continuous flow of the second off-gas stream (240) and the second by-product stream (238) can be produced from the second stage adsorption unit (212).

Each of the second stage adsorption vessels (255, 256, 257) is filled or packed with a second adsorbent. The second adsorbent can be comprised of an adsorbent bed in the vessels (255, 256, 257). In some examples, the second adsorbent comprises any adsorbent that is capable of selectively capturing hydrogen sulfide while excluding carbon dioxide and nitrogen. In some examples, the second adsorbent comprises any adsorbent having a difference in breakthrough time between hydrogen sulfide and carbon dioxide and between hydrogen sulfide and nitrogen. Non-limiting exemplary materials used in the second adsorbent include molecular sieves (e.g., molecular sieve 4A, etc.); hydrophobic zeolites having frameworks such as MFI type, CHA type, FAU type, MOR type, DDR type, FER type and MWW type; and hydrophobic zeolites such as MOF and ZIF. In a specific example, the second adsorbent comprises a Cu-Y type zeolite, which is a derivative of a FAU type zeolite containing copper cations as counter ions.

During the adsorption cycle, components of the first off-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 captured in the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) pass through the second adsorbent and are collected via the second byproduct stream (238). During the regeneration cycle, components of the second regeneration gas stream (246) (e.g., carbon dioxide and nitrogen) enter 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 captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen) to produce the second off-gas stream (240). The second exhaust gas stream (240) contains hydrogen sulfide, carbon dioxide and nitrogen.

In the example of FIG. 2, 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 standby mode. During the adsorption cycle, components of the first off-gas stream (232) are introduced through the second stage adsorption vessel (255). Hydrogen sulfide is captured in the pores of the second adsorbent. In some instances, trace amounts of carbon dioxide and nitrogen are captured in the pores of the second adsorbent. Components other than hydrogen sulfide (e.g., carbon dioxide and nitrogen) pass through the second adsorbent to produce a second byproduct stream (238) substantially in the absence of hydrogen sulfide. During the regeneration cycle, components of the second regeneration gas stream (246) (e.g., carbon dioxide and nitrogen) enter the second stage adsorption vessel (256) to regenerate the second adsorbent. Desorption occurs in the second stage adsorption vessel (256), where the second adsorbent releases the captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which is collected via the second off-gas stream (240).

The second exhaust gas stream (240) comprises hydrogen sulfide, carbon dioxide and nitrogen. The second exhaust gas stream (240) has a hydrogen sulfide content in the range of about 0 wt % to about 99 wt %, for example, about 5 wt % to about 70 wt %, about 5 wt % to about 50 wt %, about 5 wt % to about 30 wt %, or about 10 wt % to about 20 wt %, for example, about 13.3 wt %. The second exhaust gas stream (240) has a carbon dioxide content in the range of about 0 wt % to about 99 wt %, for example, about 20 wt % to about 95 wt %, about 30 wt % to about 90 wt %, about 50 wt % to about 80 wt %, or about 60 wt % to about 70 wt %, for example, about 66.7 wt %. The second exhaust gas stream (240) has a nitrogen content in the range of about 0 wt % to about 99 wt %, for example, about 5 wt % to about 70 wt %, about 5 wt % to about 50 wt %, about 10 wt % to about 30 wt %, or about 15 wt % to about 25 wt %, for example, about 20.0 wt %. In some examples, the second exhaust gas stream (240) is used as a feed gas to the Claus unit. For example, as illustrated in FIG. 2, the second exhaust gas stream (240) is introduced into the reactor (264) of the Claus unit.

FIG. 3 is a schematic diagram of a Claus tail gas treatment system (300). Features of the system (300) that are similar to those described with respect to the system (200) are given similar reference numerals. The system (300) of FIG. 3 implements a temperature ramping regeneration system utilizing a slip stream of carbon dioxide and nitrogen. Additional description of the temperature ramping regeneration system can be found in U.S. patent application Ser. No. 17/166,821, the contents of which are incorporated herein by reference in their entirety.

The system (300) receives a tail gas stream (320) comprising a cloud tail gas and includes a hydrogenation reactor (204) (e.g., a reactor vessel) that hydrogenates sulfur-containing compounds in the cloud 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 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 only in trace amounts (or not readily measurable) in the hydrogenated gas.

The hydrogenated gas stream (322) is cooled through a first heat exchanger (205) to produce a cooled hydrogenated gas stream (324). A quench tower (206) receives the cooled hydrogenated gas stream (324) and condenses water in the hydrogenated gas to produce a quenched gas stream (326) containing sulfide, water, and at least one of carbon dioxide or nitrogen. The condensed water (having some hydrogen sulfide) is recovered from the quench tower (206) as a first water condensate stream (328), which can be sent to a sour water stripper (SWS) column (260).

The quenched gas stream (326) is pressurized by the compressor (207) to produce a pressurized quenched gas stream (327). The pressurized quenched gas stream (327) is cooled by the second heat exchanger (208) to produce a cooled quenched gas stream (329). The cooled quenched 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) can be sent to the SWS column (260).

An adsorption feed stream (330) is introduced into a first stage adsorption unit (210). In the illustrated example, the first stage adsorption vessel (250) is undergoing an adsorption cycle, the first stage adsorption vessel (251) is undergoing a regeneration cycle, and the first stage adsorption vessel (252) is in standby mode. The adsorption feed stream (330) is provided to the first stage adsorption vessel (250) operating in the adsorption cycle, and water from the adsorption feed stream (330) is adsorbed onto a first adsorbent to produce a first off-gas stream (332) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. In some examples, a significant portion (e.g., most or substantially all) of the water in the adsorption feed stream (330) is adsorbed onto the first adsorbent in the first stage adsorption vessel (250) operating in the adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from the adsorption feed stream (330). In some examples, the first exhaust gas stream (332) contains no water, or contains only trace or unmeasurable amounts of water.

A first off-gas stream (332) is introduced into a 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 standby mode. The first off-gas stream (332) is provided to the second stage adsorption vessel (255), which operates in the adsorption cycle to adsorb hydrogen sulfide from the first off-gas stream (332) to a second adsorbent to produce a second byproduct stream (338) comprising at least one of carbon dioxide or nitrogen. In some examples, the second byproduct stream (338) includes no hydrogen sulfide, or includes trace or unmeasurable amounts of hydrogen sulfide.

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 a 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.

A second portion (342) of the second by-product stream (338) is heated through the first heat exchanger (205) to exchange heat with the hydrogenated gas stream (322) to produce a heated second portion (343) of the second by-product stream. In some examples (as shown in FIG. 3), the second portion (343) of the second by-product stream is further heated through the 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).

A first stage adsorption vessel (251) operating in a regeneration cycle receives a first regeneration gas stream (344) as a regeneration gas. The first adsorbent of the first stage adsorption vessel (251) is heated, for example, according to a temperature ramp, to selectively desorb components from the first adsorbent of the first stage adsorption vessel (251) to produce a first byproduct stream (336) comprising the desorbed components and at least one of carbon dioxide or nitrogen. As the temperature gradually increases during the temperature ramp in the regeneration cycle, hydrogen sulfide is initially desorbed while the adsorbed water initially remains generally adsorbed on the first adsorbent. As the temperature increases, water begins to desorb from the first adsorbent.

In some instances, during the second part of the temperature ramp, when the temperature of the first adsorbent reaches a level at which water begins to desorb (break through) into the first byproduct stream (336) and/or the concentration of hydrogen sulfide in the first byproduct stream (336) is lower, the component desorbed from the first adsorbent comprises water, or the concentration of hydrogen sulfide in the first byproduct stream (336) is below a threshold, or both. The second part of the temperature ramp is later in time and is generally at a higher temperature than the first part of the temperature ramp.

In operation, the first stage adsorption vessel (251) discharges a first by-product stream (336) as a first by-product stream (336A) to the Claus unit reactor (264) during a first part of the temperature ramp, wherein the components desorbed during the first part of the temperature ramp primarily comprise hydrogen sulfide. During a second part of the temperature ramp, water begins to desorb into the first by-product stream (336) and/or the hydrogen concentration in the first by-product stream (336) drops below a specified value. During this second part, the first by-product stream (336) is routed to the quench tower (206) as a first by-product stream (336B) to handle the water and prevent inert components of the regeneration gas from being introduced into the Claus unit reactor (264).

The second regeneration gas stream (346) is introduced into the second stage adsorption 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 adsorption vessel (256) to produce a second off-gas stream (340) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. The second off-gas stream (340) is introduced into the reactor (264) of the Claus unit for further processing.

Figure 4 is a schematic diagram of a Claus tail gas treatment system (400) implementing a two-phase regeneration cycle for a second stage adsorption vessel. Features of the system (400) similar to those described with respect to the system (200) are given similar reference numerals.

The system (400) receives a tail gas stream (420) comprising cloud tail gas and includes a hydrogenation reactor (204) (e.g., a reactor vessel) that hydrogenates sulfur-containing compounds in the cloud 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 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 only in trace amounts (or not readily measurable) in the hydrogenated gas.

The hydrogenated gas stream (422) is cooled through a first heat exchanger (205) to produce a cooled hydrogenated gas stream (424). A quench tower (206) receives the cooled hydrogenated gas stream (424) and condenses water in the hydrogenated gas to produce a quenched gas stream (426) containing sulfide, water, and at least one of carbon dioxide or nitrogen. The condensed water (having some hydrogen sulfide) is recovered from the quench tower (206) as a first water condensate stream (428), which can be sent to a sour water stripper (SWS) column (260).

The quenched gas stream (426) is pressurized by the compressor (207) to produce a pressurized quenched gas stream (427). The pressurized quenched gas stream (427) is cooled by the second heat exchanger (208) to produce a cooled quenched gas stream (429). The cooled quenched 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) can be sent to the SWS column (260).

An adsorption feed stream (430) is introduced into a first stage adsorption unit (210). In the illustrated example, the first stage adsorption vessel (250) is undergoing an adsorption cycle, the first stage adsorption vessel (251) is undergoing a regeneration cycle, and the first stage adsorption vessel (252) is in standby mode. The adsorption feed stream (430) is provided to the first stage adsorption vessel (250) operating in the adsorption cycle, which adsorbs water from the adsorption feed stream (430) onto a first adsorbent to produce a first off-gas stream (432) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. In some examples, a significant portion (e.g., most or substantially all) of the water in the adsorption feed stream (430) is adsorbed onto the first adsorbent in the first stage adsorption vessel (250) operating in the adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from the adsorption feed stream (430). In some examples, the first exhaust gas stream (432) contains no water, or contains only trace or unmeasurable amounts of water.

A first off-gas stream (432) is introduced into a 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 standby mode. The first off-gas stream (432) is provided to the second stage adsorption vessel (255), which operates in the adsorption cycle to adsorb hydrogen sulfide from the first off-gas stream (432) to a second adsorbent, thereby producing a second byproduct stream (438) comprising at least one of carbon dioxide or nitrogen. In some examples, the second byproduct stream (438) includes no hydrogen sulfide, or includes trace or unmeasurable amounts of hydrogen sulfide.

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 a 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.

A second portion (442) of the second byproduct stream (438) is heated through the first heat exchanger (205) to exchange heat with the hydrogenated gas stream (422) to produce a heated second portion (443) of the second byproduct stream. In some examples (as shown in FIG. 4), the second portion (443) of the second byproduct stream is further heated through the third heat exchanger (214) to produce a heated second portion (445) of the second byproduct stream. The heat exchangers (205, 214) heat the second byproduct stream to a temperature sufficient to desorb hydrogen sulfide from the adsorption vessel in the regeneration cycle. The heated second portion (445) of the second byproduct stream is separated into a second regeneration gas stream (444) and a second regeneration gas stream (446).

The first regeneration gas stream (444) is fed to the first stage adsorption vessel (251) undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorption vessel (251) where the first adsorbent releases captured water and a relatively small amount of captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which are collected via the first byproduct stream (436). The first byproduct stream (436) is routed to the quench tower (206).

The regeneration of the second stage adsorption vessel (256) undergoing a regeneration cycle is a two-phase process. In the first phase, a second regeneration gas stream (446), which is a slip stream of the second by-product gas and comprises carbon dioxide and nitrogen, is introduced into the second stage adsorption vessel (256). Following the first phase, the flow of the regeneration gas stream (446) is stopped and a second regeneration step occurs, wherein a high purity nitrogen gas stream (452) is introduced into the second stage adsorption 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 from a cryogenic nitrogen tank, such as a nitrogen source available on-site for blanketing or purging. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent in the second stage adsorption vessel (256) to produce a second off-gas stream (440) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. The second off-gas stream (440) is introduced into the reactor (264) of the Claus unit for further processing.

A two-phase regeneration cycle using a slip stream containing carbon dioxide and nitrogen to first complete regeneration and then a second stage adsorption vessel (256) using high purity nitrogen may have advantages. For example, this two-phase regeneration cycle may facilitate the removal of hydrogen sulfide in the second stage adsorption vessel (256), which may improve the hydrogen sulfide adsorption capacity during the adsorption cycle.

Figure 5 is a schematic diagram of a Claus tail gas treatment system (500). Features of the system (500) similar to those described with respect to the system (200) are given similar reference numerals.

The system (500) receives a tail gas stream (520) comprising cloud tail gas and includes a hydrogenation reactor (204) (e.g., a reactor vessel) that hydrogenates sulfur-containing compounds in the cloud 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 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 only in trace amounts (or not readily measurable) in the hydrogenated gas.

The hydrogenated gas stream (522) is cooled through a first heat exchanger (205) to produce a cooled hydrogenated gas stream (524). A quench tower (206) receives the cooled hydrogenated gas stream (524) and condenses water in the hydrogenated gas to produce a quenched gas stream (526) containing sulfide, water, and at least one of carbon dioxide or nitrogen. The condensed water (having some hydrogen sulfide) is recovered from the quench tower (206) as a first water condensate stream (528), which can be sent to a sour water stripper (SWS) column (260).

The quenched gas stream (526) is pressurized by the compressor (207) to produce a pressurized quenched gas stream (527). The pressurized quenched gas stream (527) is cooled by the second heat exchanger (208) to produce a cooled quenched gas stream (529). The cooled quenched 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) can be sent to the SWS column (260).

An adsorption feed stream (530) is introduced into a first stage adsorption unit (210). In the illustrated example, the first stage adsorption vessel (250) is undergoing an adsorption cycle, the first stage adsorption vessel (251) is undergoing a regeneration cycle, and the first stage adsorption vessel (252) is in standby mode. The adsorption feed stream (530) is provided to the first stage adsorption vessel (250) operating in the adsorption cycle, and water from the adsorption feed stream (530) is adsorbed onto a first adsorbent to produce a first off-gas stream (532) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. In some examples, a significant portion (e.g., most or substantially all) of the water in the adsorption feed stream (530) is adsorbed onto the first adsorbent in the first stage adsorption vessel (250) operating in the adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from the adsorption feed stream (530). In some examples, the first exhaust gas stream (532) contains no water, or contains only trace or unmeasurable amounts of water.

A first off-gas stream (532) is introduced into a 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 standby mode. The first off-gas stream (532) is provided to the second stage adsorption vessel (255), which operates in the adsorption cycle to adsorb hydrogen sulfide from the first off-gas stream (532) to a second adsorbent, thereby producing a second byproduct stream (538) comprising at least one of carbon dioxide or nitrogen. In some examples, the second byproduct stream (538) includes no hydrogen sulfide, or includes trace or unmeasurable amounts of hydrogen sulfide.

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 a 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.

A second portion (542) of the second byproduct 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 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 capable of separating CO2 from the second portion (542) of the stream at a cryogenic temperature. The output of the CO2 separation element (550) (e.g., from the CO2 selective membrane or the cryogenic separation element) is a stream of carbon dioxide (556) and a stream of enriched nitrogen (552).

A stream of carbon dioxide (556) is directed to a thermal oxidizer (262). A stream of enriched nitrogen (552) from the CO2 separation element (550) is heated through a first heat exchanger (205) to exchange heat with the hydrogenated gas stream (522) to produce a heated stream of enriched nitrogen (543). In some examples (as shown in FIG. 5 ), the heated stream of enriched nitrogen (543) is further heated through a third heat exchanger (214) to produce a heated stream (545). The heat exchangers (205, 214) heat the enriched nitrogen stream to a temperature sufficient to desorb hydrogen sulfide from the adsorption vessel in the regeneration cycle. The heated stream of enriched nitrogen (545) is separated into a first regeneration gas stream (544) and a second regeneration gas stream (546), both of which are enriched nitrogen streams.

The first regeneration gas stream (544) (enriched nitrogen stream) is fed to the first stage adsorption vessel (251) undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorption vessel (251) where the first adsorbent releases captured water and a relatively small amount of captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which are collected via the first byproduct stream (536). The first byproduct stream (536) is routed to the quench tower (206).

For regeneration of the second stage adsorption vessel (256) undergoing a regeneration cycle, a second regeneration gas stream (546) (enriched nitrogen stream) is introduced into the second stage adsorption vessel (256) for regeneration. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent of the second stage adsorption vessel (256) to produce a second off-gas stream (540) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. The second off-gas stream (540) is introduced into a reactor (264) of the Claus unit for further processing.

Regenerating the first stage adsorption vessel (251) and the second stage adsorption vessel (256) using an enriched nitrogen stream may have the advantage of, for example, facilitating the removal of hydrogen sulfide from the first and second stage adsorption vessels (251, 256), thereby improving the hydrogen sulfide adsorption capacity during the adsorption cycle.

Figure 6 is a schematic diagram of a Claus tail gas treatment system (600). Features of the system (600) similar to those described with respect to the system (200) are given similar reference numerals.

The system (600) receives a tail gas stream (620) comprising cloud tail gas and includes a hydrogenation reactor (204) (e.g., a reactor vessel) that hydrogenates sulfur-containing compounds in the cloud 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 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 only in trace amounts (or not readily measurable) in the hydrogenated gas.

The hydrogenated gas stream (622) is cooled through a first heat exchanger (205) to produce a cooled hydrogenated gas stream (624). A quench tower (206) receives the cooled hydrogenated gas stream (624) and condenses water in the hydrogenated gas to produce a quenched gas stream (626) containing sulfide, water, and at least one of carbon dioxide or nitrogen. The condensed water (having some hydrogen sulfide) is recovered from the quench tower (206) as a first water condensate stream (628), which can be sent to a sour water stripper (SWS) column (260).

The quenched gas stream (626) is pressurized by the compressor (207) to produce a pressurized quenched gas stream (627). The pressurized quenched gas stream (627) is cooled by the second heat exchanger (208) to produce a cooled quenched gas stream (629). The cooled quenched 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) can be sent to the SWS column (260).

An adsorption feed stream (530) is introduced into a first stage adsorption unit (210). In the illustrated example, the first stage adsorption vessel (250) is undergoing an adsorption cycle, the first stage adsorption vessel (251) is undergoing a regeneration cycle, and the first stage adsorption vessel (252) is in standby mode. An adsorption feed stream (630) is provided to the first stage adsorption vessel (250) operating in the adsorption cycle, which adsorbs water from the adsorption feed stream (630) onto a first adsorbent to produce a first off-gas stream (632) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. In some examples, a significant portion (e.g., most or substantially all) of the water in the adsorption feed stream (630) is adsorbed onto the first adsorbent in the first stage adsorption vessel (250) operating in the adsorption cycle. A relatively small amount of hydrogen sulfide may be adsorbed onto the first adsorbent from the adsorption feed stream (630). In some examples, the first exhaust gas stream (632) contains no water, or contains only trace or unmeasurable amounts of water.

A first off-gas stream (632) is introduced into a 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 standby mode. The first off-gas stream (632) is provided to the second stage adsorption vessel (255), which operates in the adsorption cycle to adsorb hydrogen sulfide from the first off-gas stream (632) to a second adsorbent to produce a second byproduct stream (638) comprising at least one of carbon dioxide or nitrogen. In some examples, the second byproduct stream (638) includes no hydrogen sulfide, or includes trace or unmeasurable amounts of hydrogen sulfide.

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 a 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.

A second portion (642) of the second byproduct 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 FIG. 6, the CO2 separation element (650) is a CO2 selective membrane that separates carbon dioxide gas from the stream (642). In some examples, the CO2 separation element (650) is a cryogenic separation element capable of separating 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 stream of carbon dioxide (656) and a stream of enriched nitrogen (652).

A stream of carbon dioxide (656) is directed to a thermal oxidizer (262) through an ejector (650). A stream of enriched nitrogen (652) from the CO2 separation element (650) is heated through a first heat exchanger (205) to exchange heat with the hydrogenated gas stream (622) to produce a heated stream of enriched nitrogen (643). In some examples (as illustrated in FIG. 6), the heated stream of enriched nitrogen (643) is further heated through a third heat exchanger (214) to produce a heated stream of enriched nitrogen (645). The heat exchangers (205, 214) heat the enriched nitrogen stream to a temperature sufficient to desorb hydrogen sulfide from the adsorption vessel in the regeneration cycle. The heated stream of enriched nitrogen (645) is separated into a first regeneration gas stream (644) and a second regeneration gas stream (646), both of which are enriched nitrogen streams.

The first regeneration gas stream (644) (enriched nitrogen stream) is fed to the first stage adsorption vessel (251) undergoing a regeneration cycle to regenerate the first adsorbent. Desorption occurs in the first stage adsorption vessel (251) where the first adsorbent releases captured water and a relatively small amount of captured hydrogen sulfide (and optionally trace amounts of carbon dioxide and nitrogen), which are collected via the first byproduct stream (636). The first byproduct stream (636) is routed to the quench tower (206).

For regeneration of the second stage adsorption vessel (256) undergoing a regeneration cycle, a second regeneration gas stream (646) (enriched nitrogen stream) is introduced into the second stage adsorption vessel (256) for regeneration. In the regeneration cycle, hydrogen sulfide is desorbed from the second adsorbent of the second stage adsorption vessel (256) to produce a second off-gas stream (640) containing hydrogen sulfide and at least one of carbon dioxide or nitrogen. The second off-gas stream (640) is introduced into a reactor (264) of the Claus unit for further processing.

Regenerating the first stage adsorption vessel (251) and the second stage adsorption vessel (256) using an enriched nitrogen stream may have the advantage of, for example, facilitating the removal of hydrogen sulfide from the first and second stage adsorption vessels (251, 256), thereby improving the hydrogen sulfide adsorption capacity during the adsorption cycle.

Referring to FIG. 7a, in an exemplary process for removing hydrogen sulfide from a cloud tail gas, sulfur-containing compounds in a cloud tail gas stream are converted into hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream (700). The hydrogenated gas stream contains hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen. The hydrogenated gas stream is fed to a quench tower to condense liquid water into a water condensate stream, thereby producing a quenched gas stream (702). The quenched gas stream contains hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen.

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

A first portion of the second by-product gas stream is separated into a carbon dioxide stream and an enriched nitrogen stream (708). In some instances, 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 the carbon dioxide separation membrane. In some instances, the separation is accomplished by flowing the carbon dioxide stream through an ejector into a thermal oxidizer. In some instances, the separation is a cryogenic separation process.

A carbon dioxide stream is directed to a thermal oxidizer (710). The enriched nitrogen stream can be heated upstream, for example, with heat from the hydrogenated gas stream. A first portion of the enriched nitrogen stream is fed to a first stage adsorption vessel for regeneration of the adsorbent in the first stage adsorption vessel by desorption of water from the adsorbent in the first stage adsorption vessel, thereby producing a first by-product gas stream by desorption of water from the adsorbent in the first stage adsorption vessel (712). The first by-product gas stream contains at least one of carbon dioxide or nitrogen. In some examples, the first by-product gas stream is combined with a hydrogenated gas stream fed to a quench tower.

A second portion of the enriched nitrogen stream is fed to the second stage adsorption vessel for regeneration of the adsorbent in the second stage adsorption vessel (714). The output from the second stage adsorption vessel during the second portion regeneration cycle of the second byproduct gas stream is a second off-gas containing hydrogen sulfide. The second off-gas can be fed to a reactor, such as a reactor of the Claus unit that produced the Claus tail gas.

A third portion of the second by-product gas stream is fed to a thermal oxidizer. In some instances, the first and second portions of the second by-product gas stream together are a slip stream of the second by-product gas stream.

Referring to FIG. 7b, in an exemplary process for removing hydrogen sulfide from a cloud tail gas, sulfur-containing compounds in a cloud tail gas stream are converted into hydrogen sulfide in a hydrogenation reactor to produce a hydrogenated gas stream (750). The hydrogenated gas stream contains hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen. The hydrogenated gas stream is fed to a quench tower to condense liquid water into a water condensate stream, thereby producing a quenched gas stream (752). The quenched gas stream contains hydrogen sulfide, water, and at least one of carbon dioxide or nitrogen.

The quenched gas stream is pressurized in a compressor, cooled, and fed to a first stage adsorption vessel of a first adsorption unit to adsorb water from the quenched gas stream onto the adsorbent in the first stage adsorption vessel, thereby producing a first off-gas stream (754). In some examples, the cooled, pressurized, and 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 off-gas stream comprises hydrogen sulfide and at least one of carbon dioxide or nitrogen. The first off-gas stream is fed to a second stage adsorption vessel of a second adsorption unit to adsorb hydrogen sulfide onto the adsorbent in the second stage adsorption vessel, thereby producing a second by-product gas stream (756). The second by-product gas stream comprises at least one of carbon dioxide or nitrogen. The second by-product gas stream is heated, for example, with the heat of the hydrogenated gas stream.

A first portion of the second by-product gas stream is fed to the first stage adsorption vessel for regeneration of the adsorbent in the first stage adsorption vessel by desorption of water from the adsorbent in the first stage adsorption vessel, thereby generating a first by-product gas stream by desorption of water from the adsorbent in the first stage adsorption vessel (758). The first by-product gas stream comprises at least one of carbon dioxide or nitrogen. In some examples, the first by-product gas stream is combined with a hydrogenated gas stream fed to the quench tower.

A second portion of the second by-product gas stream is fed to the second stage adsorption vessel for regeneration of the adsorbent in the second stage adsorption vessel (760). After a predetermined amount of time, the feeding of the second portion of the second by-product stream to the second stage adsorption vessel is stopped (762) and a high purity nitrogen stream, for example from a cryogenic tank, is fed to the second stage adsorption vessel (764). The output of the second stage adsorption vessel during the regeneration cycle is a second exhaust gas containing hydrogen sulfide. The second exhaust gas can be fed to a reactor, such as a reactor of a Claus unit that produced the Claus tail gas.

Example

Example 1: CuY zeolite as a second stage adsorbent material

In this example, Y-zeolite ion-exchanged with Cu ions (hereinafter referred to as “CuY zeolite” or “CuY”) is used as an adsorbent material for a 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.

The adsorption of hydrogen sulfide on CuY was determined by performing the Grand Canonical Monte Carlo (GCMC) simulation technique assuming that no chemical process occurs. For the GCMC simulation of the entire system of solid and gas, 6x10 ⁶ Monte Carlo steps were performed to allow the system to reach equilibrium and then an additional 6x10 ⁶ steps were performed to obtain a statistical average. The simulations were performed under the assumption that no other competing gases were present in the mixture.

At each thermodynamic point, the adsorption capacity (in millimoles (mmol) per gram (g), mmol/g) of gas molecules adsorbed on the system was calculated. The results are shown in Fig. 8. These results indicate that the adsorption capacity of 1% H ₂ S on CuY approaches 0.8 mmol/g at 1 barg and 298 Kelvin (K).

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

An Aspen simulation was performed to determine the cloud tail gas composition of an ultra-lean gas plant (20% H2S acid gas stream) with co-firing and a three-stage cloud configuration. The acid gas flow rate was defined as 50 million standard cubic feet per day (MMSCFD). The simulation covered the adsorption-based tail gas treatment process from the hydrogenation reactor to the water removal stage.

Figure 9 shows a process flow diagram (900) for this simulation. A sulfur recovery unit (SRU) feed stream (910) from a hydrogenation reactor enters a compressor (902) and the compressed gas output from the compressor is fed to a cooler (904). The cooled gas output from the cooler is separated by a separator (905) into a first stream (906) directed to a water adsorption vessel and a second stream (908) directed to a sour water stripper. Table 1 shows the simulated gas composition flow rates from the feed stream to the water adsorption vessel.

[Table 1]

Simulated gas flow composition

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

Aspen simulations were performed for the water removal step of the tail gas treatment process to determine the size of the adsorption vessel for a given gas flow rate and 24-hour adsorption cycle.

Figure 10 shows a process flow diagram (950) for this simulation. A first stream (906) (see Figure 9) from a separator (905) is directed to a water adsorption vessel (952) having molecular sieve 3A as an 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 (86400 s).

Figure 11 shows the breakthrough curve of water in the water removal adsorption vessel (952) during the 86400 s adsorption cycle. The y-axis labels are mol _H2O /mol _tot (mol of water divided by total mol of gas mixture). Table 2 shows the simulated gas composition flow rates from the separator (905) to the water adsorption vessel (952) (stream S1) and the simulated gas composition flow rates from the water adsorption vessel (952) to the hydrogen sulfide adsorption vessel (stream S2).

[Table 2]

Simulated gas flow composition

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

Aspen simulations were performed for the hydrogen sulfide removal step of a tail gas treatment process to determine the size of the adsorption vessel for a given gas flow rate and 24-hour adsorption cycle.

Figure 12 shows a process flow diagram (50) for this simulation. Stream S1 from a water adsorption vessel (952) (Figure 10) is directed to a hydrogen sulfide adsorption vessel (52) having CuY zeolite as an adsorbent material. The adsorption vessel (52) has a diameter of 4.63 meters (m) and a height of 12.1 m. The adsorption cycle was 24 hours (86,400 s).

Figure 13a shows breakthrough curves for nitrogen (curve 54) and carbon dioxide (curve 56) in the hydrogen sulfide adsorption vessel (52) over an 86,400 second adsorption cycle. Figure 13b shows breakthrough curves for hydrogen sulfide in the hydrogen sulfide adsorption vessel (52). For Figures 13a and 13b, the y-axis labels are mol _H2O /mol _tot (mol of water divided by total mol of gas mixture). Table 3 shows the simulated gas composition flow rates from the water adsorption vessel (952) to the hydrogen sulfide adsorption vessel (52) (stream S3) and the simulated gas composition flow rates from the hydrogen sulfide adsorption vessel (952) to the thermal oxidizer and/or as a regeneration slip stream (stream S4).

[Table 3]

Simulated gas flow composition

Specific embodiments of the subject matter are described. Other embodiments are within the scope of the following claims.

Claims (29)

As a method of recovering sulfur,
In a hydrogenation reactor, a step of converting sulfur-containing compounds in a Claus tail gas stream into hydrogen sulfide to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen;
A step of supplying a hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream, thereby producing a quenched gas stream;
A step of supplying the quenched gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quenched gas stream, thereby generating a first exhaust gas stream;
A step of supplying a first exhaust gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first exhaust gas stream, thereby generating a second by-product gas stream;
separating at least a portion of the second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream; and
A step of regenerating the second stage adsorption vessel by supplying a portion of the enriched nitrogen stream to the second stage adsorption vessel to produce a second exhaust gas stream.
A method for recovering sulfur, comprising: A method according to claim 1, comprising the step of separating a first portion of the second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream using cryogenic separation. A method according to claim 1, comprising the step of separating a first portion of a second by-product gas stream into a carbon dioxide stream and an enriched nitrogen stream using a separation membrane. A method comprising the step of applying a vacuum to a membrane in the third paragraph. A method according to claim 1, comprising the step of supplying a carbon dioxide stream to a thermal oxidation device. A method comprising the step of supplying a carbon dioxide stream to a thermal oxidizer through an ejector in claim 5. A method comprising the step of regenerating the first stage adsorption vessel by supplying a first portion of the enriched nitrogen stream to the first stage adsorption vessel, thereby desorbing water to produce a first by-product gas stream. A method in accordance with claim 7, comprising the steps of combining a first by-product gas stream with a hydrogenated gas stream to form a combined stream and supplying the combined stream to a quench tower. A method according to claim 1, comprising the step of heating the enriched nitrogen stream in a heat exchanger with heat from a hydrogenated gas stream. A method comprising the steps of: pressurizing a quenched gas stream in a compressor; and cooling the pressurized quenched gas stream. A method comprising the step of producing an adsorption feed by supplying a quenched gas stream to a collection drum and recovering liquid water through a second water condensate stream in the first stage, wherein the adsorption feed is supplied to a first stage adsorption vessel. A method according to claim 1, comprising the step of supplying a water condensate stream to a sour water stripper. A method according to claim 1, comprising the step of supplying a second portion of the second by-product gas stream to a thermal oxidizer. A method according to claim 1, comprising the step of supplying a second exhaust gas to a reaction furnace. As a system for recovering sulfur from Claus tail gas,
A hydrogenation reactor configured to convert sulfur-containing compounds in a cloud tail gas stream into hydrogen sulfide to produce a hydrogenated gas stream;
A quench tower fluidically connected to the hydrogenation reactor and configured to receive a hydrogenated gas stream and condense liquid water into a water condensate stream to produce a quenched gas stream;
A first stage adsorption unit comprising a first stage adsorption vessel, wherein the first stage adsorption unit is fluidically connected to the quench tower and configured to receive a quenched gas stream and adsorb water from the quenched gas stream during a first stage adsorption cycle, thereby producing a first effluent gas stream;
A second stage adsorption unit comprising a second stage adsorption vessel, wherein the second stage adsorption unit is fluidically connected to the first stage adsorption vessel and configured to receive a first effluent gas stream and adsorb hydrogen sulfide from the first effluent gas stream during a second stage adsorption cycle, thereby producing a second by-product 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;
A system for sulfur recovery from cloud tail gas, wherein the second stage adsorption vessel is configured to receive a portion of the enriched nitrogen stream during the second stage regeneration cycle. A system in accordance with claim 15, wherein the carbon dioxide separation member comprises a separation membrane configured to separate a portion of the second byproduct gas stream into a carbon dioxide stream and an enriched nitrogen stream. A system in claim 15, wherein the carbon dioxide separation member includes a cryogenic separation member. A system comprising a thermal oxidizer configured to receive a carbon dioxide stream in accordance with claim 15. A system in accordance with claim 18, comprising an ejector, wherein the thermal oxidizer is configured to receive a carbon dioxide stream from the ejector. A system in accordance with claim 15, wherein the first stage adsorption vessel is configured to receive a first portion of the enriched nitrogen stream and desorb water during the first stage regeneration cycle to produce a first by-product gas stream. A system comprising a thermal oxidizer configured to receive a second portion of the second by-product gas stream in claim 15. A system in accordance with claim 15, comprising a reactor fluidically connected to the second stage adsorption vessel and configured to receive a second exhaust gas generated in the second stage adsorption unit during the second stage regeneration cycle. A system comprising a heat exchanger configured to cool a hydrogenated gas stream with heat from an enriched nitrogen stream in accordance with claim 15. A system in claim 15, wherein the first stage adsorption vessel comprises a hydrophilic molecular sieve. A system in claim 15, wherein the second stage adsorption vessel comprises Cu-Y type zeolite. A system in accordance with claim 15, wherein the first stage adsorption unit comprises a plurality of first stage adsorption vessels fluidically connected in parallel, and the second stage adsorption unit comprises a plurality of second stage adsorption vessels fluidically connected in parallel. As a method of recovering sulfur,
In a hydrogenation reactor, a step of converting sulfur-containing compounds in a cloud tail gas stream into hydrogen sulfide to produce a hydrogenated gas stream comprising hydrogen sulfide, water, and at least one of carbon dioxide and nitrogen;
A step of supplying a hydrogenated gas stream to a quench tower to condense liquid water into a water condensate stream, thereby producing a quenched gas stream;
A step of supplying the quenched gas stream to a first stage adsorption vessel of a first stage adsorption unit to adsorb water from the quenched gas stream, thereby generating a first exhaust gas stream;
A step of supplying a first exhaust gas stream to a second stage adsorption vessel of a second stage adsorption unit to adsorb hydrogen sulfide from the first exhaust gas stream, thereby generating a second by-product gas stream; and
A step of regenerating the second stage adsorption vessel to produce a second off-gas stream, wherein the step of regenerating the second stage adsorption vessel comprises the step of supplying a portion of the second by-product gas stream and a nitrogen stream to the second stage adsorption vessel.
A method for recovering sulfur, comprising: A method according to claim 27, wherein the step of regenerating the second stage adsorption vessel comprises the step of supplying a nitrogen stream from a cryogenic tank to the second stage adsorption vessel. In the 27th paragraph, the step of regenerating the second stage adsorption vessel is
The step of supplying a portion of the second by-product gas stream to the second stage adsorption vessel during the first period; and
A step of supplying a nitrogen gas stream to a second stage adsorption vessel for a second period after a first period.
A method comprising: