Method and apparatus for membrane separation of a mixture containing predominantly hydrogen and carbon dioxide
The integrated membrane separation process with turbines and compressors optimizes energy use, improving hydrogen and carbon dioxide yields by 14-15% and 6-10% respectively, addressing inefficiencies in existing methods.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE
- Filing Date
- 2022-09-08
- Publication Date
- 2026-06-19
AI Technical Summary
Existing methods for separating hydrogen and carbon dioxide from mixtures containing additional components like carbon monoxide, methane, or nitrogen are inefficient in energy utilization and require additional energy recovery steps.
A membrane separation process integrated with turbines and compressors to optimize energy use, involving heating, permeation through membranes, and expansion of residues to drive compressors, with optional cooling and heating steps to enhance efficiency.
Improves hydrogen and carbon dioxide yields by 14-15% and 6-10% respectively, reducing specific energy costs and enhancing membrane separation efficiency.
Abstract
Description
Title of the invention: Method and apparatus for membrane separation of a mixture containing predominantly hydrogen and carbon dioxide
[0001] The present invention relates to a membrane separation process of a mixture containing predominantly hydrogen and carbon dioxide and in addition at least one other component chosen from carbon monoxide, methane and nitrogen.
[0002] A mixture containing predominantly hydrogen and carbon dioxide has a composition such that at least 50% mol of the mixture is composed of hydrogen and carbon dioxide.
[0003] The capture of carbon dioxide (CO2) by a distillation and / or partial condensation process fed with a waste gas from a hydrogen (H2) production unit comprising a pressure swing adsorption (PSA) hydrogen separation unit is known. The waste gas is depleted in hydrogen compared to the gas feeding this separation unit. The separation unit can be combined with a membrane separation of the carbon dioxide-depleted gas produced by the distillation and / or partial condensation process. These membranes are designed to separate CO2 and H2 from the remaining gases in two stages. The permeate from the first membrane is recycled to the PSA, while the permeate from the second membrane is returned to the compression stage upstream of the distillation and / or partial condensation separation for further compression.The membrane residue is still under pressure; it is released by a valve before regenerating the dryers. This energy could be recovered to improve the efficiency of this CO2 capture process.
[0004] US4639257 describes the passage of the residual gas from cryogenic separation through an economizer before being sent to a first membrane. The permeate from this first membrane is recycled upstream of a compressor of the gas supplying the cryogenic separation.
[0005] The invention proposes an improved process with an integration scheme of at least one turbine coupled with at least one booster to better utilize the energy of the expansion of the second residue of the membranes.
[0006] According to one object of the invention, a membrane separation process is provided for a mixture containing predominantly hydrogen and carbon dioxide and in addition at least one component chosen from the list carbon monoxide, methane or nitrogen, comprising the following steps: i. possibly heating the mixture in a heat exchanger to a temperature between 60 and 100°C ii. permeation of the mixture, possibly heated, through a first membrane to obtain a first permeate enriched in hydrogen and carbon dioxide relative to the mixture and a first residue depleted in hydrogen and carbon dioxide relative to the mixture. iii. possibly cooling of at least part of the first permeate in the heat exchanger. iv. compression of the first permeate, possibly cooled, in a first compressor. v. possibly cooling of at least part of the first permeate compressed in the first blower in the heat exchanger. vi. permeation of the first residue, preferably without having cooled it, in a second membrane allowing to obtain a second permeate enriched in hydrogen and carbon dioxide compared to the first residue and a second residue depleted in hydrogen and carbon dioxide compared to the first residue. vii. possibly cooling of at least part of the second permeate in the heat exchanger. viii. compression of the second permeate, possibly cooled, in a second compressor. ix. possibly cooling of at least part of the second compressed permeate in the heat exchanger and x. expansion of the second residue in at least one turbine driving the first and / or the second compressor.
[0007] According to other optional aspects of the invention: • The mixture is heated in a heat exchanger to a temperature between 60°C and 100°C. • the mixture is heated by indirect heat exchange in the heat exchanger with at least a part of at least one of the following flow rates: first permeate, first residue, second permeate, second residue. • at least part of at least one of the following flow rates: first permeate, first residue, second permeate, second residue is cooled in the heat exchanger. • the second residue is expanded in two turbines in series, each of which drives one of the first and second blowers. • the second residue is expanded in two parallel turbines, each of which drives one of the first and second blowers. • the residue is expanded in the two turbines and after expansion is at a pressure between 3 and 5 bara and / or at a temperature between -30 and -55°C. • The residue relaxed in the two turbines is used to regenerate an adsorption purification unit upstream of a distillation and / or partial condensation process which produces the mixture. • the first residue is not compressed or relaxed between the first and second membranes.
[0008] According to another aspect of the invention, a method is provided for separating a feed stream containing hydrogen, carbon dioxide and at least one of the components chosen from the list, namely carbon monoxide, methane or nitrogen, comprising the following steps: a. Separation of the feed stream by partial condensation and / or distillation to form a carbon dioxide-rich stream and a mixture containing predominantly hydrogen, carbon dioxide, and at least one of the components chosen from the list: carbon monoxide, methane, or nitrogen and b. Separation of the mixture by the process as described above.
[0009] According to other optional aspects of the invention: • the feed flow is compressed in a compressor upstream of the partial condensation and / or distillation and the second permeate compressed by the second blower is sent to be compressed in the compressor. • The feed flow is compressed in a compressor and then purified into water in an adsorption purification unit upstream of partial condensation and / or distillation, and the second residue is used to regenerate the purification unit. • The feed flow is compressed in a compressor and then cooled in a heat exchange line upstream of the partial condensation and / or distillation, and the second residue is sent to provide cooling to the heat exchange line.
[0010] According to another aspect of the invention, a method is provided for separating a feed stream containing hydrogen, carbon dioxide and at least one of the components chosen from the list, namely carbon monoxide, methane or nitrogen, comprising the following steps: a. Separation of a flow in a PSA to produce a hydrogen-rich gas and a hydrogen-depleted gas containing carbon dioxide and at least one of the components chosen from the list: carbon monoxide, methane or nitrogen, b. Separation of the hydrogen-depleted gas by partial condensation and / or distillation to form a carbon dioxide-rich flow and a mixture containing predominantly hydrogen, carbon dioxide, and at least one of the components selected from the list: carbon monoxide, methane, or nitrogen and c. Separation of the mixture by the process as described above.
[0011] Preferably the first permeate superpressed in the first superpressor is sent to separate in the PSA.
[0012] According to other optional aspects of the invention: • the hydrogen-depleted gas is compressed in a compressor upstream of the partial condensation and / or distillation and the second permeate compressed by the second blower is sent to be compressed in the compressor. • the hydrogen-depleted gas is compressed in a compressor and then purified into water in an adsorption purification unit upstream of partial condensation and / or distillation and the second residue is used to regenerate the purification unit. • The hydrogen-depleted gas is compressed in a compressor and then cooled in a heat exchange line upstream of the partial condensation and / or distillation, and the second residue is sent to provide cooling to the heat exchange line.
[0013] According to another aspect of the invention, a membrane separation apparatus for a mixture containing predominantly hydrogen and carbon dioxide and in addition at least one component chosen from the list, namely carbon monoxide, methane or nitrogen, is provided, comprising a first membrane, a conduit for sending the mixture to separate in the first membrane, allowing a first permeate to be obtained enriched in hydrogen and carbon dioxide relative to the mixture and a first residue depleted in hydrogen and carbon dioxide relative to the mixture, a first blower, a conduit for sending the first permeate to the first blower for compression, a second membrane, a conduit for sending the first residue, preferably without having cooled it,in the second membrane allowing to obtain a second permeate enriched in hydrogen and carbon dioxide compared to the first residue and a second residue depleted in hydrogen and carbon dioxide compared to the first residue, a second blower, a pipe to send the second permeate to the second blower, at least one expansion turbine connected to expand the second residue and to drive the first and / or the second blower.
[0014] Preferably the apparatus comprises two expansion turbines in series connected to drive each one of the first and second blowers.
[0015] The invention will be described in more detail with reference to the figure:
[0016] [Fig-1] represents a separation method according to the invention.
[0017] A hydrogen (H2) production unit comprising a pressure swing adsorption hydrogen separation unit (PSA) produces a hydrogen-rich gas and a hydrogen-depleted residual gas but also containing carbon dioxide as well as nitrogen and / or methane and / or carbon monoxide.
[0018] The waste gas is compressed by a compressor C, dried by dryers in an adsorption purification unit, cooled in a heat exchanger called the exchange line, and then separated by partial condensation and / or distillation to produce a carbon dioxide-rich fluid and a carbon dioxide-depleted gas 1. This fluid and the gas are heated in the exchange line. This low-temperature separation is designated by the acronym CB.
[0019] This gas 1 depleted in carbon dioxide nevertheless contains carbon dioxide, hydrogen as well as nitrogen and / or methane and / or carbon monoxide.
[0020] The gas 1 which is at a pressure between 40 and 70 bara and at a temperature between 0 and 50°C is optionally heated in a heat exchanger E to a temperature between 60 and 100°C and more preferably between 65 and 90°C.
[0021] At this temperature and pressure or otherwise without having been heated, it is separated by permeation in a first membrane Ml to produce a first permeate PI enriched in hydrogen and carbon dioxide compared to the mixture and depleted in nitrogen and / or carbon monoxide and / or methane compared to the mixture at between 15 and 30 bara and more specifically between 17 and 25 bara, which is lower than the inlet pressure of the hydrogen separation unit by adsorption with pressure switch.
[0022] The first permeate PI is therefore compressed in a blower Cl to reach a pressure sufficient for recycling it upstream of the PSA, between 20 and 40 bara, and more specifically between 20 and 30 bara. Then all or part of the permeate can be cooled in the heat exchanger E and is sent to separate in the hydrogen separation unit by pressure-switching adsorption.
[0023] The first residue RI depleted in hydrogen and carbon dioxide and enriched in nitrogen and / or carbon monoxide and / or methane from the first membrane is sent to a second membrane M2.
[0024] The pressure of the second permeate P2, enriched in hydrogen and carbon dioxide and depleted in nitrogen and / or carbon monoxide and / or methane, produced by the second membrane M2 is lower than the pressure of the compressor stage C to which it is recycled, this pressure is between 4 and 11 bara and more specifically between 5 and 9 bara.
[0025] The second permeate P2 is therefore compressed in a second compressor C2 to reach a pressure sufficient for recycling to a stage of compressor C upstream of the cryogenic separation to obtain a pressure between 5 and 15 bara, and more specifically between 8 and 11 bara. All or part of the second permeate P2 can be cooled in the heat exchanger E and is preferably sent to the inlet of compressor C.
[0026] The second residue depleted in hydrogen and carbon dioxide and enriched in nitrogen and / or carbon monoxide and / or methane produced by the second membrane M2 is expanded in at least one turbine, here two turbines in series T1 and T2 which drive the two blowers Cl, C2 to obtain a gas at low pressure (3-5 bara) and with a low temperature of between -30 and -55°C.
[0027] This R2 gas expanded in the two turbines T1, T2 can be used to regenerate the dryers upstream of the cold separation.
[0028] The following steps of the process, described above, are in fact optional: • Heating of the residual gas 1 from the separation by distillation and / or partial condensation through an exchanger E before the first membrane separation to reach a temperature between 60 and 100°C and more preferably between 65 and 90°C. • Cooling of the first permeate PI through the heat exchanger E to reach a temperature between 15 and 80°C before compression. This step can be carried out as illustrated by cooling only a portion 7 of the permeate PI to a lower temperature (between 15 and 30°C for example) which is then combined with the rest of the permeate. • Cooling of all or part of the gas exiting the first booster Cl in the heat exchanger E before recycling upstream of the PSA to reach a temperature range between 10 and 50°C and more specifically between 20 and 40°C. • Cooling of the second permeate P2 through the heat exchanger E to reach a temperature between 10 and 50°C. This step can be carried out by cooling only a part 17 of the permeate to a colder temperature (between 15 and 30°C for example) which is then combined with the rest of the hot permeate. • Cooling of all or part of the gas exiting the second blower in the exchanger E before recycling upstream of the cryogenic separation to reach a temperature between 20 and 80°C and more specifically between 30 and 70°C. • Sending the cold gas from the outlet of the second turbine T2 into the main exchanger of the cryogenic separation where the feed gas from a hydrogen (H2) production unit is cooled, including a hydrogen separation unit by adsorption with pressure switching.
[0029] A variant is possible: • Add a heater downstream of turbines T1, T2 to obtain a hotter gas at the turbine inlet. In this case, the gas exiting the second turbine is not sent to the cryogenic section.
[0030] This arrangement makes it possible to lower the pressure of the two permeates, for example, by recycling the first permeate to the PSA and the second to the same stage of the machine upstream of the cryogenic separation, using the boosters. The reduction in permeate pressure generates higher pressure ratios across the two membranes, which increases the membrane separation efficiency.
[0031] This invention can be used in two different ways: either by keeping the number of membranes constant (which allows for better CO2 and H2 yields (at marginal specific energy cost), or by decreasing the number of membranes to obtain yields similar to the configuration without turbomachine (in this case the specific energy of CO2 capture is reduced).
[0032] The following table illustrates the differences in membrane efficiency according to the invention and without the turbine driving the blower with the same membrane surface area and the same inlet composition of the membranes.
[0033] On the first stage Ml, the yields are improved between 14 and 15% respectively for H2 and CO2.
[0034] On the second stage M2, the yields are improved between 6 and 10% respectively for H2 and CO2.
[0035] [T AB 1] Yields for the PI permeate, P2 Anterior Art Invention % Ml CO2 Yield % 64 74 15% H2 Yield % 75 86 14% M2 CO2 Yield % 76 84 10% H2 Yield % 88 94 6%
Claims
1. Demands A process for separating a feed stream containing hydrogen, carbon dioxide and at least one of the components selected from the list (carbon monoxide, methane or nitrogen) comprising the following steps: a) Compression of the feed flow in a compressor (C), water purification of the feed flow in an adsorption purification unit, and / or cooling of the water-purified flow in a heat exchanger line, separation of the purified and / or cooled feed flow by partial condensation and / or distillation (CB) to form a carbon dioxide-rich flow and a mixture (1) containing predominantly hydrogen, carbon dioxide and at least one of the components selected from the list: carbon monoxide, methane or nitrogen and b) Separation of the mixture by a membrane separation process comprising the following steps: i) optionally heating of the mixture (1) in a heat exchanger (E) up to a temperature between 60 and 100°C. ii) permeation of the mixture (3), possibly heated, in a first membrane (Ml) allowing to obtain a first permeate (PI) enriched in hydrogen and carbon dioxide compared to the mixture and a first residue (RI) depleted in hydrogen and carbon dioxide compared to the mixture. iii) possibly cooling of at least part of the first permeate in the heat exchanger. iv) compression of the first permeate, possibly cooled, in a first supercharger (Cl). (v) possibly cooling of at least part of the first permeate compressed in the first blower in the heat exchanger. vi) permeation of the first residue, preferably without having cooled it, in a second membrane (M2) allowing to obtain a second permeate (P2) enriched in hydrogen and carbon dioxide compared to the first residue and a second residue (R2) depleted in hydrogen and carbon dioxide compared to the first residue. vii) possibly cooling of at least part of the second permeate in the heat exchanger. viii) compression of the second permeate, possibly cooled, in a second blower (C2). ix) optionally cooling of at least part of the second compressed permeate in the heat exchanger, x) expansion of the second residue in at least one turbine (T1,T2) driving the first and / or the second blower and sending the expanded second residue to the purification unit as regeneration gas and / or sending the expanded second residue to provide cooling to the heat exchange line.
2. A method according to claim 1 in which the mixture (3) is heated in the heat exchanger (E) to a temperature between 60 and 100°C.
3. A method according to claim 2 wherein the mixture (1) is heated by indirect heat exchange in the heat exchanger with at least a part of at least one of the following flow rates: first permeate (PI), first residue (RI), second permeate (P2), second residue (R2).
4. A method according to any one of the preceding claims wherein the second residue is expanded in two turbines (T1, T2) in series, each of which drives one of the first and second blowers (Cl, C2).
5. A method according to claim 4 wherein the residue (R2) expanded in the two turbines (T1, T2) is after expansion at a pressure between 3 and 5 bara and / or at a temperature between -30 and -55°C.
6. A method according to any one of claims 1 to 5 wherein the feed flow is compressed in a compressor (C) upstream of the partial condensation and / or distillation (CB) and the second permeate (P2) compressed by the second blower (C2) is sent to be compressed in the compressor.
7. Apparatus for separating a feed stream containing hydrogen, carbon dioxide, and at least one of the components selected from the list, carbon monoxide, methane, or nitrogen, comprising a compressor (C), a purification unit and / or a heat exchanger line, means for sending the compressed feed stream from the compressor to the purification unit and / or the heat exchanger line, and a unit for separating the purified and / or cooled feed stream by partial condensation and / or distillation (CB) to form a carbon dioxide-rich flow and a mixture (1) containing predominantly hydrogen, carbon dioxide and at least one of the components selected from the list: carbon monoxide, methane or nitrogen, means for sending the feed flow from the purification unit and / or the exchange line to the separation unit, a membrane separation apparatus comprising a first membrane (M1), a conduit for sending the mixture to separate in the first membrane, allowing a first permeate (PI) enriched in hydrogen and carbon dioxide relative to the mixture and a first residue (RI) depleted in hydrogen and carbon dioxide relative to the mixture, a first blower (Cl), a conduit for sending the first permeate to the first blower for compression, a second membrane (M2), a conduit for sending the first residue, preferably without having cooled it,in the second membrane allowing to obtain a second permeate (P2) enriched in hydrogen and carbon dioxide compared to the first residue and a second residue (R2) depleted in hydrogen and carbon dioxide compared to the first residue, a second blower (C2), a line to send the second permeate to the second blower, at least one expansion turbine (T1, T2) connected to expand the second residue and to drive the first and / or the second blower and means to send the second residue from the at least one expansion turbine to the purification unit as regeneration gas and / or to the heat exchange line to provide cooling.