H2 recovery and co2 separation using membrane

Abstract

A method of treating a gas stream that includes: performing a first pressure swing adsorption (PSA-1, 202) process generating a first H2-product gas (108) and a first PSA tail gas (204) from a first feed gas (102), the first PSA tail gas (204) including a residual H2 and CO2; separating CO2 from the first PSA tail gas using a CO2 selective membrane (208), generating a CO2-rich permeate gas (210) and a CO2-lean rejected gas (212); performing a second PSA process (PSA-2,216) generating a second H2-product gas and a second PSA tail gas (218) from a second feed gas (104), the second PSA tail gas (218) including another residual H2; mixing (222) the CO2-lean rejected gas (212) and the second PSA tail gas (218) to generate a mixed tail gas (224); and separating the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane (112), generating a recovered H2 permeate gas (114) and a final rejected gas (116).

Description

Attorney Ref.: 38136-2469WO1 H2 RECOVERY AND CO2 SEPARATION USING MEMBRANE Claim of Priority

[0001] This application claims priority to U.S. Patent Application No.18 / 402,277 filed on January 2, 2024, the entire contents of which are hereby incorporated by reference. Technical Field

[0002] This disclosure relates to methods and systems of processing, particularly to hydrogen (H2) recovery and carbon dioxide (CO2) separation using a membrane process. Background

[0003] Hydrogen (H2) is an industrially important feedstock and chemical critical to various chemical and refinery processes such as ammonia production, aromatization, hydrodesulfurization, and the hydrogenation or hydrocracking of hydrocarbons. H2 is commercially produced, for example, through reforming of hydrocarbons in refineries. Hydrogen can also be produced by coal gasification, biomass gasification, water electrolysis, or the reforming or partial oxidation of natural gas or other hydrocarbons.

[0004] The reforming of natural gas is the most prevalent source of hydrogen production. Bulk hydrogen is typically produced by the steam reforming of natural gas, e.g., methane. Conventional steam reforming includes heating the natural gas in the presence of steam and a nickel catalyst. This endothermic reaction generates carbon monoxide and hydrogen. The carbon monoxide gas can be subjected to a water-gas shift reaction to obtain additional hydrogen, generating carbon dioxide (CO2) as a by-product. Accordingly, H2purification and CO2separation from the gas stream is essential steps of a commercial H2 production process. Summary

[0005] An embodiment described herein provides a method of treating a gas stream, where the method includes: performing a first pressure swing adsorption (PSA) process generating a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas including a residual H2and CO2; separating CO2fromAttorney Ref.: 38136-2469WO1 the first PSA tail gas using a CO2 selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas; performing a second PSA process generating a second H2-product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas including another residual H2; mixing the CO2-lean rejected gas and the second PSA tail gas to generate a mixed tail gas; and separating the residual H2 and the another residual H2from the mixed tail gas using an H2selective membrane, generating a recovered H2 permeate gas and a final rejected gas.

[0006] An embodiment described herein provides a gas treatment system that includes: a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas including CO2and a residual H2; a CO2 selective membrane, connected to the first PSA column and configured to separate CO2from the first PSA tail gas, generating a CO2-rich permeate gas and a CO2-lean rejected gas; a second PSA column to generate a second H2- product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas including another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; and an H2 selective membrane to separate the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas.

[0007] An embodiment described herein provides an H2 recovery system that includes: a steam reformer to generate a first feed gas including H2and CO2, where a CO2 concentration of the first feed gas is between 10% and 30%; a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from the first feed gas, the first PSA tail gas including the CO2 and a residual H2; a CO2selective membrane, connected to the first PSA column and configured to separate CO2 from the first PSA tail gas, generating a CO2-rich permeate gas and a CO2-lean rejected gas; an H2production facility to generate a second feed gas including H2, where a CO2 concentration of the second feed gas is less than 0.1%; a second PSA column to generate a second H2-product gas and a second PSA tail gas from the second feed gas, the second PSA tail gas including another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; an H2 selective membrane to separate the residual H2 and the another residual H2from the mixed tail gas using an H2selective membrane, generating aAttorney Ref.: 38136-2469WO1 recovered H2 permeate gas and a final rejected gas; and a feed gas mixer to add the recovered H2permeate gas to the first feed gas. Brief Description of Drawings

[0008] Figure 1 is a block diagram of a tail gas H2 recovery system.

[0009] Figure 2 is a block diagram of a tail gas H2recovery system with single- stage CO2 separation.

[0010] Figure 3 is a block diagram of a tail gas H2recovery system with two-stage CO2 separation.

[0011] Figure 4 is a block diagram of a tail gas H2 recovery system with two-stage CO2separation.

[0012] Figure 5 is an example process flow diagram of a method of tail gas H2 recovery. Detailed Description

[0013] Embodiments described herein provide methods and systems of H2 recovery and CO2separation, particularly for residual H2recovery from multiple pressure swing adsorption (PSA) tail gases. Generally, H2 in refinery is produced from reforming naphtha or hydrocarbon as an off-gas with H2concentration about 70-90%. The rest of gases in the off-gas are mainly hydrocarbons, e.g., un-converted feedstock, with traces of hydrogen sulfide (H2S). H2S in the off-gas is typically removed using H2S selective absorption. The sweet off-gas after the H2S removal can be then sent to a PSA unit to produce pure H2. In the typical PSA unit, hydrocarbons are adsorbed using molecular sieves and other adsorbents while H2are passing through the adsorbent beds and exiting the process at concertation above 99%. Beside producing the pure H2 stream, another stream as a PSA tail gas is produced during the desorption step. The PSA tail gas stream has H2 content about 40-50% and used mostly as a fuel gas. It is therefore desired to recover the residual H2 from the PSA tail gas to improve the overall H2 production efficiency and yield. In many refineries, additional H2 production is needed to meet its H2demand. For example, a steam reforming (SR) can be used in addition to H2 recovery from the refinery off-gas. The SR product gas stream typically contains about 70% H2, about 20% CO2, and about 7% methane or other hydrocarbon, and about 3% carbon monoxide (CO). One common PSA column can be used to purify both the SR outlet and the refinery off-gas by mixing both theAttorney Ref.: 38136-2469WO1 streams. Alternately, two PSA columns can be used to separately treat the two H2- containing streams. This two-PSA process typically achieves about 85% H2recovery.

[0014] Figure 1 is an example of a conventional tail gas H2 recovery system 100. Solid arrows are used in Figure 1 to indicate gas or liquid flows, e.g., inflow and outflow. Generally, to meet the pure H2 demand, most refineries use multiple H2 production routes, e.g., a refinery off-gas and steam reforming (SR). Pressure swing adsorption (PSA) processes may be employed to separate H2 but some residual H2 escapes in the tail gases. The residual H2may be recovered from the tail gases using an H2 selective membrane. In Figure 1, a steam reforming (SR) product gas 102 from a SR process, e.g., steam methane reforming (SMR) and a refinery off-gas 104 are combined and sent to a pressure swing adsorption (PSA) column 106 and separated into an H2product gas 108 and a tail gas 110. The tail gas 110 is then sent to an H2selective membrane 112 to form a recovered H2-rich gas 114 and a final tail gas 116. The recovered H2-rich gas 114 is sent to a recycle gas compressor 118 and then looped back to the PSA column 106 for improving the overall H2 recovery. The final tail gas 116, as a retentate stream can be used as a fuel gas.

[0015] However, the enrichment rate of H2 in the permeate stream of a membrane process in this conventional method can be limited due to the high CO2 concentration in the tail gas 110. Various embodiments described in this disclosure can improve the overall H2 recovery by employing (1) two PSA columns to separately recover H2 from the two streams, and (2) a CO2selective membrane to first recover CO2from the first PSA tail gas, e.g., a CO2-rich gas, before mixing it with the second PSA tail gas, e.g., a CO2-free tail gas.

[0016] In the following, various embodiments of the methods and systems of H2 recovery including separate tail gas treatment are described. Embodiments with one CO2 selective membrane is first described referring to Figure 2, and embodiments with two CO2selective membranes are then described referring to Figure 3-4. Figure 5 is an example process flow diagram. In this disclosure, unless otherwise noted, concentrations of gases components in a fluid are provided based on volumetric concentration in percentile, referred to as %. Single-stage CO2separation

[0017] Figure 2 is an example of a tail gas H2 recovery system 200 with single- stage CO2separation. In Figure 2, unlike the conventional method described referringAttorney Ref.: 38136-2469WO1 to Figure 1, two H2-containig gas streams are separately treated with two PSA columns to recover H2. Each PSA yields a tail gas containing residual H2, which can be recovered by the tail gas H2 recovery system 200. The two tail gas compositions are different at least in the CO2concentration.,

[0018] First, a steam reforming (SR) process, e.g., steam methane reforming (SMR), generates a SR product gas 102 containing H2and CO2. Accordingly, in some embodiments, the tail gas H2 recovery system 200 includes a steam reformer to generate the SR product gas 102. The SR process catalytically convert hydrocarbons such as methane, propane, or butane, to a syn-gas, a mixture of H2 and CO. The SR process can include water-gas shift (WGS) reaction between CO and water (H2O) to produce more H2. CO2 is thus generated as a by-product, making H2 and CO2 the main gas components of the SR product gas 102. In various embodiments, the SR product gas 102 contains about 10% to 30% CO2, for example, about 20%. A first pressure swing adsorption (PSA) column 202 processes the SR product gas 102 and generates an H2 product gas 108 and a first PSA tail gas 204. In some embodiments, the first PSA tail gas 204 contains about 30% to about 70% CO2, for example, about 50%. The CO2 concentration of the first PSA tail gas 204 can be greater than that of the SR product gas 102 as a result of the PSA process. The first PSA tail gas 204 is first processed for CO2recovery prior to mixing with another tail gas.

[0019] In various embodiments, as illustrated in Figure 2, the first PSA tail gas 204 is sent to a first tail gas compressor 206 and then a first CO2selective membrane 208. In some embodiments, the first PSA tail gas 204 is compressed to have a pressure between about 2 bar (200 kPa) and about 20 bar (2,000 kPa), for example, at about 10 bar (1,000 kPa). The first tail gas compressor 206 can compress the first PSA tail gas 204 to optimize its pressure, e.g., about 10 bar, as a feed gas to the first CO2selective membrane 208. The first CO2 selective membrane 208 can separate the first PSA tail gas 204 into a CO2-rich permeate gas 210 and a CO2-lean rejected gas 212. The first CO2 selective membrane 208 can include polymer-based rubbery materials such as polyether-polyamide copolymers, e.g., Pebax®polymer, and polydimethylsiloxane (PDMS). In some embodiments, the tail gas H2 recovery system 200 can include a fluid temperature control system to maintain the temperature of the first PSA tail gas 204, e.g., above its dew point to prevent condensation of a water vapor present in the first PSA tail gas 204. In some embodiments, the process temperature for CO2Attorney Ref.: 38136-2469WO1 separation is between about 25 °C and 60 °C. In one or more embodiments, the tail gas H2recovery system 200 can further include, prior to the first CO2selective membrane 208, an additional pretreatment unit such as heater and carbon bed and particle filter.

[0020] In some embodiments, the CO2concentration in the CO2-rich permeate gas 210 can be about 70-75%, achieving about 95% CO2 recovery from the first PSA tail gas 204. In some embodiments, the CO2-rich permeate gas 210 can be sent to another purification system 214, e.g., a cryogenic distillation system, for further purification to produce a high purity CO2stream, e.g., >99% CO2.

[0021] On the other hand, the residual H2 of the first PSA tail gas 204 is concentrated in the CO2-lean rejected gas 212. Further, other gas components, e.g., methane (CH4), N2, and the like., can also be concentrated in the CO2-lean rejected gas 212.

[0022] Still referring to Figure 2, a second PSA column 216 is used to separate a refinery off-gas 104 into the H2product gas 108 and a second PSA tail gas 218. Although not specifically illustrated in Figure 2, the tail gas H2 recovery system 200 includes an H2 production facility to generate the refinery off-gas 104. Further, the refinery off-gas 104 can be processed in one or more upstream facilities for acid gas removal, e.g., H2S and CO2. For example, an amine-based stripper, e.g., a diglycolamine absorber (DGA) unit, can be used. With the acid removal, the refinery off-gas 104 becomes a so-called “sweetened” product stream. Accordingly, in various embodiments, the second PSA tail gas 218 is a CO2-free gas. In this disclosure, a gas is considered CO2-free if the CO2 concentration is below 0.1%. The second PSA tail gas 218 is then compressed by a second tail gas compressor 220. In some embodiments, the second PSA tail gas 218 is compressed to have a pressure between about 2 bar (200 kPa) and about 20 bar (2,000 kPa), for example, at about 10 bar (1,000 kPa).

[0023] The CO2-lean rejected gas 212 from the first CO2 selective membrane 208 and the second PSA tail gas 218 from the second PSA column 216 can be mixed using a tail gas mixer 222 to form a mixed tail gas 224. The mixed tail gas 224 is then sent to a heater 226 and an H2selective membrane 112 to form a recovered H2-rich gas 124 and a final tail gas 116. In various embodiments, the mixed tail gas 224 is heated to between about 60 °C and 200 °C, for example, about 150 °C. The H2selective membrane 112 can include a polymer-based membrane in a glassy form, or a denseAttorney Ref.: 38136-2469WO1 protonic ceramic membrane based on a single-phase and mixed-phase perovskite-type oxidic protonic ceramic material.

[0024] In various embodiments, the recovered H2-rich gas 114 is obtained as a permeate gas. The recovered H2-rich gas 114 can be sent to a recycle gas compressor 118 and then looped back to be mixed using a feed gas mixer 228 with the SR product gas 102 for improving the overall H2recovery. In some embodiments, the recovered H2-rich gas 114 is compressed to have a pressure at a same level of the SR product gas 102 that is being fed to the first PSA column 202, e.g., between about 2 bar (200 kPa) and about 40 bar (4,000 kPa), for example, at about 20 bar (2,000 kPa).

[0025] On the other hand, the final tail gas 116 is obtained as a rejected gas. The final tail gas 116 can contain about 30-50% of CH4 or other hydrocarbons and 10-15% H2. The final tail gas 116 can be used, for example, as a fuel gas, mixed with a sale gas stream, or recycled as an additive to a feed to the steam reforming (SR) process. In some embodiments, especially when the heating value is not sufficient for other applications, the final tail gas 116 can be sent to an amine-based CO2 removal facility. By integrating the CO2 separation as a part of H2 recovery, the final tail gas 116 contains less CO2 compared to the conventional methods, thereby improving its heating value.

[0026] In various embodiments, the tail gas H2recovery process with CO2separation can reduce the membrane area required for the H2 selective membrane 112 compared to the conventional methods, thereby also reducing the overall capital expenditure for H2 recovery Two-stage CO2separation

[0027] Figure 3 is an example of a tail gas H2 recovery system 300 with two-stage CO2separation. Like numbered items are as described with respect to Figure 2 and will not be repeated in detail. In Figure 3, the tail gas H2 recovery system 300 uses two CO2selective membranes in series for two-stage CO2separation. The H2production stage can be identical to prior embodiments described referring to Figure 2. An H2 product gas 108 is obtained from each of a SR product gas 102 and a refinery off-gas 104 using a first PSA column 202 and a second PSA column 216, respectively. Further, the first PSA tail gas 204 is separated using a first CO2selective membrane 208 into a CO2-rich permeate gas 210 and a CO2-lean rejected gas 212.Attorney Ref.: 38136-2469WO1

[0028] Unlike the prior embodiments described referring to Figure 2, in Figure 3, the CO2-rich permeate gas 210 is processed for further H2recovery. Using two CO2selective membranes, it is possible to further concentrate the CO2 in the tail gas, e.g., the CO2-rich permeate gas 210 while recovering more H2in the reject sides of both membranes. The CO2-rich permeate gas 210 is sent to a third tail gas compressor 302 for compression and then to a second CO2selective membrane 304 that generates a second CO2-rich permeate gas 306 and a second CO2-lean rejected gas 308. In some embodiments, the second CO2-rich permeate gas 306 contains about 90% CO2. The second CO2-lean rejected gas 308 and the CO2-lean rejected gas 212 can be mixed using a tail gas mixer 222 with the second PSA tail gas 218 to form a mixed tail gas 224. The mixed tail gas 224 can be processed for H2 recovery in the same way as described above referring to Figure 2.

[0029] In various embodiments, the second CO2 selective membrane 304 can include polymer-based rubbery materials such as polyether-polyamide copolymers, e.g., Pebax®polymer and polydimethylsiloxane (PDMS). In some embodiments, the second CO2 selective membrane 304 can use the same membrane material as the first CO2 selective membrane 208, but it is not necessary. The membrane area can be larger in the first CO2 selective membrane 208 than the second CO2 selective membrane 304. In some embodiments, the CO2-rich permeate gas 210 after the first CO2separation has a pressure of about 1 bar (100 kPa), which can be compressed again using the third tail gas compressor 302 to have a pressure between about 2 bar (200 kPa) and about 20 bar (2,000 kPa), for example, at about 10 bar (1,000 kPa), prior to the second CO2 separation. In one or more embodiments, the tail gas H2recovery system 300 can include one or more additional pretreatment units between the first CO2 selective membrane 208 and the second CO2selective membrane 304.

[0030] Figure 4 is an example of a part of a tail gas H2 recovery system 400 with two-stage CO2separation. Like numbered items are as described with respect to Figures 2-3 and will not be repeated in detail. In Figure 4, some components of the tail gas H2recovery system 400, e.g., PSA columns and H2selective membrane, are omitted for illustration purpose.

[0031] In Figure 4, the second CO2-lean rejected gas 308 is sent back to be added to a feed gas to the first CO2 selective membrane 208. Accordingly, the second CO2-Attorney Ref.: 38136-2469WO1 lean rejected gas 308 is mixed with the first PSA tail gas 204 in Figure 4 instead of mixing with the CO2-lean rejected gas 212 as described in Figure 3.

[0032] In Figure 2-4, the recovered H2-rich gas 114 is sent back to be mixed with the SR product gas 102 for improving the overall H2recovery and CO2capture. By this loop, any residual CO2 in the recovered H2-rich gas 114 can be subject to another cycle of CO2separation after the first PSA column 202. In some embodiments, although not specifically illustrated in Figures 2-4, the recovered H2-rich gas 114 can instead be sent back and mixed with the refinery off-gas 104 to be treated with the second PSA column 216.

[0033] Figure 5 is a process flow diagram of a method 500 of tail gas H2recovery. In Figure 5, the method 500 starts with performing a first pressure swing adsorption (PSA) process 502 generating a first H2-product gas and a first PSA tail gas from a first feed gas, where the first PSA tail gas includes a residual H2 and CO2. Subsequently, CO2is separated 504 from the first PSA tail gas using a CO2selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas. A second PSA process is performed 506 generating a second H2-product gas and a second PSA tail gas from a second feed gas, where the second PSA tail gas includes another residual H2. Next, the CO2-lean rejected gas and the second PSA tail gas are mixed 508 to generate a mixed tail gas, followed by separating 510 H2in the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas. Examples

[0034] The H2recovery and CO2separation was simulated by Aspen HYSYS®V12 to examine its efficiency in an example of two tail gas treatment in accordance with an embodiment. Membrane unit was designed using the Saudi Aramco proprietary Industrial Membrane Process Simulator (IMPS) (External extension within HYSYS). Two feed gasses, a steam reforming (SR) product gas and a refinery off-gas, are first simulated for PSA processes. Table 1 summarizes the two feed gas compositions and the tail gas compositions after the PSA processes. It was confirmed that both tail gases 1 and 2 still contain residual H2 at 26% and 42%, respectively, after the PSA processes. Further, the tail gas 1 contains 47% CO2while the tail gas 2 does not contain any CO2.

[0035] Table 1 Aspen HYSYS®simulation results for PSA process.Attorney Ref.: 38136-2469WO1 SR product Refinery off- Tail gas 1 Tail gas 2 gas gas (from SR) (from off-gas) Temp. (°F) 105.0 105.0 101.4 102.9 Press. (bar) 20.0 20.0 1.5 1.5 Molar flow (lb-mole / h) 1.0 × 1041.0 × 1044341.5 2603.5 Mass flow (ton / day) 1326.0 708.1 1251.1 545.3 H2(%) 70.00 85.00 26.34 42.4 CO (%) 3.00 0.00 7.05 0.00 CO2(%) 20.00 0.00 47.32 0.00 CH4(%) 6.80 5.00 18.65 19.19 C2H6(%) 0.00 5.00 0.13 19.19 C3H8(%) 0.00 3.00 0.04 11.51 C4H10(%) 0.00 2.00 0.01 7.67 H2O (%) 0.20 0.00 0.46 0.00

[0036] Further, the H2 recovery and CO2 separation from these tail gases using two-stage CO2separation were simulated. Membrane permeance used in the simulation and the result of the simulation are summarized in Tables 2 and 3, respectively. The CO2separation from the tail 1 using two CO2selective membranes was simulated at following process conditions: temperature at 105 °F (40.6 °C) and pressure at 10.0 bar. The first permeated gas (permeate CO2-1) is sent to the second CO2 selective membrane. The rejected gases from the two CO2 selective membranes (rejected CO2-1 and rejected CO2-2) are combined for the subsequent H2separation using an H2 selective membrane simulated at a temperature of 300 °F (148.9 °C) and a pressure of 10 bar. The residual H2 present in the two tail gases is recovered as the permeate gas. The unrecovered H2is 6.8% H2in the final CO2permeate (permeate CO2-2 in Table 3) and 10.7% H2 in the rejected gas after the H2 separation. Based on the initial volume of H2in the two feed gases, the PSA processes followed by the tail gas H2 recovery yielded about 97% H2 recovery. The use of this tail gas H2 recovery process improved the H2recovery from about 85%. On the other hand, the CO2in the tail gas 1 is recovered as the final CO2 permeate (permeate CO2-2 in Table 3). A high concentration of about 90% CO2is obtained, and more than 85% of CO2is recovered. Consequently, the final tail gas contains about 38% methane and only about 8% CO2, this tail gas has a heating value greater than a tail gas from a conventional process.Attorney Ref.: 38136-2469WO1

[0037] Table 2 Membrane permeance used in Aspen HYSYS®simulation. CO2selective membrane H2selective membrane (GPU) (GPU) H237.5 300 N210 10 CO 20 2 CO2300 30 CH4 20 10 C2H650 1

[0038] Table 3 Aspen HYSYS®simulation results for tail gas H2recovery using two-stage CO2 separation. Rejected Permeate Rejected Permeate Rejected Permeate CO2-1 CO2-1 CO2-2 CO2-2  H2  H2105.0 105.0 105.0 105.0 300.0 300.0Molar flow 1860.6 2480.9 521.7 1959.2 2991.3 1994.4 (lb-mole / h) Mass flow (ton / day) 299.5 951.5 92.0 859.5 842.9 93.3 H2(%) 41.20 15.18 46.65 6.81 10.74 89.94 CO (%) 13.21 2.43 9.10 0.65 9.59 0.32 CO2(%) 10.41 75.01 19.85 89.69 8.06 2.82 CH4(%) 34.96 6.42 24.08 1.71 38.29 6.52 C2H6(%) 0.18 0.09 0.24 0.05 16.66 0.28 C3H8(%) 0.03 0.05 0.06 0.04 9.99 0.08 C4H10(%) 0.00 0.02 0.00 0.02 6.66 0.03 H2O (%) 0.01 0.81 0.01 1.02 0.00 0.01 Embodiments

[0039] An embodiment described herein provides a method of treating a gas stream, where the method includes: performing a first pressure swing adsorption (PSA) process generating a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas including a residual H2 and CO2; separating CO2 from the first PSA tail gas using a CO2selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas; performing a second PSA process generating aAttorney Ref.: 38136-2469WO1 second H2-product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas including another residual H2; mixing the CO2-lean rejected gas and the second PSA tail gas to generate a mixed tail gas; and separating the residual H2 and the another residual H2from the mixed tail gas using an H2selective membrane, generating a recovered H2 permeate gas and a final rejected gas.

[0040] In an aspect, combinable with any other aspect, the method further includes mixing the recovered H2 permeate gas with the first feed gas.

[0041] In an aspect, combinable with any other aspect, the method further includes compressing the first PSA tail gas prior to separating the CO2 from the first PSA tail gas.

[0042] In an aspect, combinable with any other aspect, the method further includes passing the CO2-rich permeate gas through another CO2selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas.

[0043] In an aspect, combinable with any other aspect, the method further includes compressing the CO2-rich permeate gas prior to passing the CO2-rich permeate gas through the another CO2 selective membrane.

[0044] In an aspect, combinable with any other aspect, the method further includes adding the another CO2-lean rejected gas to the mixed tail gas prior to separating the H2from the mixed tail gas.

[0045] In an aspect, combinable with any other aspect, the method further includes adding the another CO2-lean rejected gas to the first PSA tail gas or the second PSA tail gas.

[0046] In an aspect, combinable with any other aspect, the method further includes performing a steam reforming, generating the first feed gas.

[0047] In an aspect, combinable with any other aspect, a CO2concentration of the first feed gas is between 10% and 30%.

[0048] In an aspect, combinable with any other aspect, a CO2concentration of the second feed gas is 0.1% or less.

[0049] An embodiment described herein provides a gas treatment system that includes: a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas including CO2and a residual H2; a CO2 selective membrane, connected to the first PSA column and configured to separate CO2from the first PSA tail gas, generating a CO2-rich permeateAttorney Ref.: 38136-2469WO1 gas and a CO2-lean rejected gas; a second PSA column to generate a second H2- product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas including another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; and an H2selective membrane to separate the residual H2 and the another residual H2 from the mixed tail gas using an H2selective membrane, generating a recovered H2permeate gas and a final rejected gas.

[0050] In an aspect, combinable with any other aspect, the gas treatment system further includes: a first compressor between the first PSA column and the CO2 selective membrane; and a second compressor between the second PSA column and the H2 selective membrane.

[0051] In an aspect, combinable with any other aspect, the gas treatment system further includes: another CO2 selective membrane to receive the CO2-rich permeate gas from the CO2selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas; and a third compressor between the CO2 selective membrane and the another CO2 selective membrane.

[0052] In an aspect, combinable with any other aspect, the tail gas mixer is configured to add the another CO2-lean rejected gas to the mixed tail gas.

[0053] In an aspect, combinable with any other aspect, the gas treatment system further includes a CO2 mixer between the first PSA column and the CO2 selective membrane, where the CO2mixer is configured to add the another CO2-lean rejected gas to the first PSA tail gas.

[0054] In an aspect, combinable with any other aspect, the gas treatment system further includes a heater to heat the mixed tail gas, where the heater is between the mixer and the H2selective membrane.

[0055] In an aspect, combinable with any other aspect, the gas treatment system further includes a feed mixer to add the recovered H2permeate gas to the first feed gas.

[0056] An embodiment described herein provides an H2 recovery system that includes: a steam reformer to generate a first feed gas including H2and CO2, where a CO2 concentration of the first feed gas is between 10% and 30%; a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from the first feed gas, the first PSA tail gas including the CO2 and a residual H2; a CO2selective membrane, connected to the first PSA column and configured toAttorney Ref.: 38136-2469WO1 separate CO2 from the first PSA tail gas, generating a CO2-rich permeate gas and a CO2-lean rejected gas; an H2production facility to generate a second feed gas including H2, where a CO2 concentration of the second feed gas is less than 0.1%; a second PSA column to generate a second H2-product gas and a second PSA tail gas from the second feed gas, the second PSA tail gas including another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; an H2 selective membrane to separate the residual H2 and the another residual H2from the mixed tail gas using an H2selective membrane, generating a recovered H2 permeate gas and a final rejected gas; and a feed gas mixer to add the recovered H2permeate gas to the first feed gas.

[0057] In an aspect, combinable with any other aspect, the H2 recovery system further includes another CO2selective membrane to receive the CO2-rich permeate gas from the CO2 selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas.

[0058] In an aspect, combinable with any other aspect, the H2 recovery system further includes a cryogenic distillation system to purify the another CO2-rich permeate gas from the another CO2 selective membrane.

[0059] While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.

Claims

Attorney Ref.: 38136-2469WO1 Claims What is claimed is:

1. A method of treating a gas stream, the method comprising: performing a first pressure swing adsorption (PSA) process generating a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas comprising a residual H2and CO2; separating CO2from the first PSA tail gas using a CO2selective membrane, generating a CO2-rich permeate gas and a CO2-lean rejected gas; performing a second PSA process generating a second H2-product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas comprising another residual H2; mixing the CO2-lean rejected gas and the second PSA tail gas to generate a mixed tail gas; and separating the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas.

2. The method of claim 1, further comprising mixing the recovered H2permeate gas with the first feed gas.

3. The method of claim 1, further comprising compressing the first PSA tail gas prior to separating the CO2from the first PSA tail gas.

4. The method of claim 1, further comprising passing the CO2-rich permeate gas through another CO2 selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas.

5. The method of claim 4, further comprising compressing the CO2-rich permeate gas prior to passing the CO2-rich permeate gas through the another CO2 selective membrane.

6. The method of claim 4, further comprising adding the another CO2-lean rejected gas to the mixed tail gas prior to separating the H2from the mixed tail gas.

7. The method of claim 4, further comprising adding the another CO2-lean rejected gas to the first PSA tail gas or the second PSA tail gas.Attorney Ref.: 38136-2469WO1 8. The method of claim 1, further comprising performing a steam reforming, generating the first feed gas.

9. The method of claim 1, wherein a CO2 concentration of the first feed gas is between 10% and 30%.

10. The method of claim 1, wherein a CO2concentration of the second feed gas is 0.1% or less.

11. A gas treatment system comprising: a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from a first feed gas, the first PSA tail gas comprising CO2and a residual H2; a CO2 selective membrane, connected to the first PSA column and configured to separate CO2 from the first PSA tail gas, generating a CO2-rich permeate gas and a CO2-lean rejected gas; a second PSA column to generate a second H2-product gas and a second PSA tail gas from a second feed gas, the second PSA tail gas comprising another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; and an H2selective membrane to separate the residual H2and the another residual H2from the mixed tail gas using an H2selective membrane, generating a recovered H2permeate gas and a final rejected gas.

12. The gas treatment system of claim 11, further comprising: a first compressor between the first PSA column and the CO2selective membrane; and a second compressor between the second PSA column and the H2selective membrane.

13. The gas treatment system of claim 11, further comprising: another CO2 selective membrane to receive the CO2-rich permeate gas from the CO2 selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas; andAttorney Ref.: 38136-2469WO1 a third compressor between the CO2 selective membrane and the another CO2 selective membrane.

14. The gas treatment system of claim 13, wherein the tail gas mixer is configured to add the another CO2-lean rejected gas to the mixed tail gas.

15. The gas treatment system of claim 13, further comprising a CO2 mixer between the first PSA column and the CO2selective membrane, the CO2mixer configured to add the another CO2-lean rejected gas to the first PSA tail gas.

16. The gas treatment system of claim 11, further comprising a heater to heat the mixed tail gas, the heater being between the mixer and the H2selective membrane.

17. The gas treatment system of claim 11, further comprising a feed mixer to add the recovered H2 permeate gas to the first feed gas.

18. An H2 recovery system comprising: a steam reformer to generate a first feed gas comprising H2 and CO2, wherein a CO2 concentration of the first feed gas is between 10% and 30%; a first pressure swing adsorption (PSA) column to generate a first H2-product gas and a first PSA tail gas from the first feed gas, the first PSA tail gas comprising the CO2 and a residual H2; a CO2selective membrane, connected to the first PSA column and configured to separate CO2from the first PSA tail gas, generating a CO2-rich permeate gas and a CO2-lean rejected gas; an H2production facility to generate a second feed gas comprising H2, wherein a CO2concentration of the second feed gas is less than 0.1%; a second PSA column to generate a second H2-product gas and a second PSA tail gas from the second feed gas, the second PSA tail gas comprising another residual H2; a tail gas mixer to mix the CO2-lean rejected gas and the second PSA tail gas, generating a mixed tail gas; an H2 selective membrane to separate the residual H2 and the another residual H2 from the mixed tail gas using an H2 selective membrane, generating a recovered H2 permeate gas and a final rejected gas; and a feed gas mixer to add the recovered H2 permeate gas to the first feed gas.Attorney Ref.: 38136-2469WO1 19. The H2 recovery system of claim 18, further comprising another CO2 selective membrane to receive the CO2-rich permeate gas from the CO2 selective membrane, generating another CO2-rich permeate gas and another CO2-lean rejected gas.

20. The H2 recovery system of claim 19, further comprising a cryogenic distillation system to purify the another CO2-rich permeate gas from the another CO2 selective membrane.

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