Method and apparatus for membrane separation of a mixture containing hydrogen and carbon dioxide as main components
The method enhances membrane separation efficiency and yield by optimizing energy recovery through heat exchangers, boosters, and turbines, addressing inefficiencies in existing cryogenic separation systems.
Patent Information
- Application Number
- FR2021008056
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-07-26
- Publication Date
- 2025-10-17
- Estimated Expiration
- 2041-07-26
AI Technical Summary
Existing membrane separation processes for hydrogen and carbon dioxide mixtures are inefficient in energy recovery and yield optimization, particularly in cryogenic separation systems where expansion of residual gas for regeneration is costly and energy-intensive.
A method involving heating the mixture in a heat exchanger, permeating it through membrane separation units, and using a booster and turbine to compress and expand residues, optimizing energy recovery by recycling compressed permeate and expanding turbine residues, without additional heating, to enhance separation efficiency and yield.
The method significantly improves energy efficiency and separation yields by reducing pressure ratios and increasing selectivity, allowing for higher CO2 capture and hydrogen production with fewer membrane units and lower operational costs.
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Abstract
Description
Title of the invention: Method and apparatus for membrane separation of a mixture containing hydrogen and carbon dioxide as main components
[0001] The present invention relates to a method and an apparatus for membrane separation of a mixture containing as main components, or even predominantly, hydrogen and carbon dioxide.
[0002] Cryogenic CO2 capture processes treating gases from hydrogen production units comprising a pressure swing adsorption (PSA) hydrogen separation unit are sometimes combined with membrane separation. This allows the hydrogen contained in the treated gas to be recovered and recycled to the PSA producing the hydrogen. The residual gas passes into a second membrane separation unit in order to recover the remaining hydrogen and CO2 which are recycled in the compression upstream of the cryogenic separation.
[0003] The residual gas obtained, still under pressure, is expanded and most often serves as regeneration gas for the dryer upstream of the cryogenic separation. This expansion is carried out in a valve; the installation of a turbine connected to a generator can prove prohibitive when electricity is cheap.
[0004] WO12064938 and WO12064941 mention the passage of waste gas from the se cryogenic separation through a heat exchanger before being sent to a first membrane separation unit. The permeate passes through the heat exchanger again before being sent to the hydrogen production unit. The residue is sent to a second membrane separation unit. Its permeate passes through the heat exchanger before being recycled to the machine upstream of the cryogenic separation. The residue also passes through the heat exchanger and is expanded in a valve before being sent to the dryer, upstream of the cryogenic separation, for regeneration.
[0005] The invention makes it possible to recover the energy lost during the expansion of the residue from the membrane separation units in the form of compression energy which allows the optimization of the membrane separation process. Thus the process is more energy efficient and / or makes it possible to obtain higher CO2 capture and hydrogen production yields.
[0006] According to an object of the invention, there is provided a process for membrane separation of a mixture containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example example chosen from the following group: carbon monoxide, methane, nitrogen comprising the following steps:
[0007] i. Heating the mixture in a heat exchanger to a first temperature ii. Permeation of the mixture heated to the first temperature in a first membrane separation unit making it possible to obtain a first permeate enriched in hydrogen and carbon dioxide compared to the mixture and a first residue depleted in hydrogen and carbon dioxide compared to the mixture iii. Optionally cooling at least part of the first permeate in the heat exchanger iv. Permeation of the first residue in a second membrane separation unit to obtain a second permeate and a second residue depleted in hydrogen and carbon dioxide relative to the second permeate and v. At least a portion of the first permeate, optionally cooled in the heat exchanger, is compressed in a booster, the second residue is expanded in a turbine and the booster is driven by the turbine.
[0008] According to other optional aspects which can be combined with each other in any way compatible with logic and science:
[0009] • at least a portion of the permeate compressed in the booster is sent to a pressure swing adsorption separation unit to extract the hydrogen.
[0010] • the mixture is heated in at least one exchanger only by at least one flow produced by the membrane separation.
[0011] • the heat exchanger has a first end and a second end, the second end being colder than the first and wherein at least a portion of the first permeate is cooled to the second end before being sent to the booster.
[0012] • the inlet temperature of the turbine is substantially equal to the temperature at which the second residue leaves the second membrane separation unit. • the heated mixture enters the first membrane separation unit at a temperature substantially equal to the temperature at which it leaves the heat exchanger. • a variable part of the mixture is not reheated in the heat exchanger and mixes with the mixture reheated upstream of the first membrane separation unit. • at least part of the permeate from the first membrane separation unit is sent directly to the turbine without passing through the heat exchanger and / or without having cooled it. • at least a variable portion of the permeate from the first membrane separation unit is sent directly to the turbine without passing through the heat exchanger.
[0013] • only a part of the first compressed permeate is sent in the booster to the heat exchanger. • the process comprising a separation step operating at a temperature below 0°C by distillation and / or by partial condensation to produce the mixture to be separated and in which the cold produced by the expansion in the turbine is used in the separation unit operating at a temperature below 0°C or in a refrigeration cycle. • the process comprising a separation step operating at a temperature below 0°C by distillation and / or by partial condensation to separate a compressed gas in a booster and to produce the mixture to be separated in which a part of the second permeate is sent to the gas booster, preferably without having been cooled in the heat exchanger. • the mixture comes from a PSA type adsorption unit producing a hydrogen-enriched flow and a flow. • the flow is separated, for example by distillation and / or partial condensation to form the mixture. • at least part of the gas pressurized in the booster is sent to the PSA type adsorption unit, preferably substantially at the outlet pressure of the booster. • there is no first permeate compression machine other than the booster upstream of the adsorption unit • the second permeate is richer in hydrogen and / or carbon dioxide than the first permeate.
[0014] • the second residue is less rich in hydrogen and / or carbon dioxide than the first residue.
[0015] • the second permeate is poorer in hydrogen and / or carbon dioxide than the first permeate. • the second residue is less poor in hydrogen and / or carbon dioxide than the first residue. • at least a portion of the first permeate is cooled at least partially in the heat exchanger before being sent to the booster.
[0016] According to another aspect of the invention, there is provided an apparatus for membrane separation of a mixture containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen comprising:
[0017] a. A heat exchanger and means for sending the mixture to heat in the heat exchanger up to a first temperature b. A first membrane separation unit and means for sending the mixture heated to the first temperature into the first membrane separation unit in order 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 c. Optionally at least one conduit for sending at least a portion of the first permeate to cool in the heat exchanger d. A second membrane separation unit, a pipe for sending the first residue into the second membrane separation unit to obtain a second permeate and a second residue depleted in hydrogen and carbon dioxide compared to the second permeate and e. A booster, means for sending at least a portion of the first permeate, optionally cooled, into the booster to be compressed, optionally means for sending the compressed first permeate to cool in the heat exchanger, a turbine, means for sending the second residue to expand in the turbine and the booster is driven by the turbine.
[0018] According to another object of the invention, there is provided a process for membrane separation of a mixture containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen comprising the following steps:
[0019] • Heating the mixture (1) in a heat exchanger (E) to a first temperature • Permeation of the mixture heated to the first temperature in a first membrane separation unit (Ml) making it possible to obtain a first permeate (7) enriched in hydrogen and carbon dioxide compared to the mixture and a first residue (9) depleted in hydrogen and carbon dioxide compared to the mixture • Optionally cooling at least part of the first permeate in the heat exchanger and • Permeation of the first residue in a second membrane separation unit (M2) making it possible to obtain a second permeate (11) and a second residue (13) depleted in hydrogen and carbon dioxide compared to the second permeate.
[0020] Thus the booster and the turbine are not essential elements, except for a process option.
[0021] The invention comprises at least one of the following steps:
[0022] • Heat the gas to be treated through the heat exchanger • Pass the heated gas through a first membrane separation unit, potentially without additional heating after heating in the heat exchanger, whose permeate is at a lower pressure than that of the PSA inlet • Optionally cool at least part of the permeate through the heat exchanger • Compress the permeate in one or more booster(s) to reach sufficient pressure to recycle it upstream of the PSA • Cool the gas leaving the booster in the heat exchanger before recycling upstream of the PSA • Pass the residue from the first membrane separation unit into a second membrane separation unit, the permeate being recycled in the compression upstream of the cryogenic separation (with or without preliminary cooling in the heat exchanger) • Expand the pressurized and hot residue in one or more turbine(s) which drive the booster.
[0023] Several variants are possible:
[0024] • Absence of an additional heater, the heat to preheat the gas to be treated being entirely supplied by the booster. To do this, means of short-circuiting the heat exchanger may be necessary in order to be able to regulate the temperature and the calories transferred. We will ensure that the temperature at the inlet of the booster is sufficiently high by not cooling all of the permeate from the first membrane separation unit before its compression. We will not necessarily cool all of the compressed permeate in the case where the calories supplied are too high. • Expansion in the turbine to obtain low temperatures to produce cold used in cryogenic separation or in a refrigeration cycle • Recycling to the booster upstream of the cryogenic separation of the second hot permeate without cooling in the heat exchanger.
[0025] This arrangement makes it possible to significantly lower the pressure of the first permeate while still being able to recycle it to the PSA thanks to the booster. The pressure reduction is of the order of a ratio of at most 2, or even at most 1.7. As a result, for an equivalent hydrogen and / or CO2 yield, fewer membrane separation units can be used.
[0026] But even better, due to the lower pressure, the pressure ratio across the membrane separation unit is increased, which allows for better separation efficiency. Thus, the number of membrane separation units can be left constant or even a moderate number can be added in order to obtain much higher yields, particularly in CO2. The pressure ratio in the membrane separation unit is between 2.3 and 3.6. In other words, the increase in yield is achieved at more moderate costs than if it had been necessary to do so with a higher permeate pressure.
[0027] The increase in separation efficiency also makes it possible to obtain better selectivity, thus limiting the recompression energy of the permeates because they are less concentrated in impurities.
[0028] The invention will be described in more detail with reference to the figures:
[0029] [Fig.l] represents a diagram of a comparative process.
[0030] [Fig.2] represents a variant of [Fig.l] according to the invention.
[0031] In [Fig.l], a gas mixture 1 containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen, is heated in a heat exchanger E by indirect heat exchange with three flows separated by the separation process, preferably only with these three flows.
[0032] Mixture 1 preferably comes from a PSA type adsorption unit producing a hydrogen-enriched flow and a flow which is separated to form the mixture.
[0033] The heated flow 3 is heated even further in a heater, heated for example by water vapor S. The flow 5 by the heater is sent to separate in a first membrane separation unit ML. This separation produces a first permeate 7 enriched in hydrogen and carbon dioxide compared to the mixture and depleted in the at least one other component compared to the mixture and a first residue 9 depleted in hydrogen and carbon dioxide compared to the mixture and enriched in the at least one other component compared to the mixture. The first permeate 7 cools in the heat exchanger E to be sent to the PSA. The first residue 9 is sent to a second membrane separation unit M2. to produce a second permeate 11 enriched in hydrogen and carbon dioxide and depleted in the at least one other component and a second residue 13 depleted in hydrogen and carbon dioxide and enriched in the at least one other component. The second permeate 11 is here richer in hydrogen and / or carbon dioxide than the first permeate 7 and the second residue 13 is less rich in hydrogen and / or carbon dioxide than the first residue 9. Otherwise the second permeate 11 may be poorer in hydrogen and / or carbon dioxide than the first permeate 7 and the second residue 13 is richer in hydrogen and / or carbon dioxide than the first residue 9.
[0034] The second permeate 11 is richer in hydrogen and carbon dioxide than the second residue 13.
[0035] The second permeate 11 cools in the heat exchanger E and is sent to a compressor. This compressor can, for example, compress a flow intended to be separated by low-temperature separation (distillation and / or partial condensation) to produce the gas 1.
[0036] The second residue 13 is expanded, and can be used to regenerate a dryer and is then optionally sent as fuel to a hydrogen production unit, for example upstream of the adsorption unit.
[0037] In [Fig.2], a gas mixture 1 containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen, is heated in a heat exchanger E by indirect heat exchange with two flows separated by the separation process, preferably only with these three flows.
[0038] Mixture 1 preferably comes from a PSA type adsorption unit producing a hydrogen-enriched flow and a flow which is separated by distillation and / or partial condensation to form mixture 1.
[0039] The heated flow 1 is sent to separate in a first membrane separation unit ML. This separation produces a first permeate 7 enriched in hydrogen and carbon dioxide and depleted in at least one other component and a first residue 9 depleted in hydrogen and carbon dioxide and enriched in the at least one other component. At least a portion of the first permeate 7 (here the entire first permeate) is sent to a booster C. Optionally, at least a portion of the first permeate is cooled in the heat exchanger E upstream of the booster C. The pressurized flow 17 is cooled in the exchanger E.
[0040] The first residue 9 is sent to a second membrane separation unit M2 to produce a second permeate 11 enriched in hydrogen and carbon dioxide and depleted in the at least one other component and a second residue 13 depleted in hydrogen and carbon dioxide and enriched in at least one other component.
[0041] The second permeate 11 may be richer in hydrogen and / or carbon dioxide than the first permeate 7 and the second residue 13 may be less rich in hydrogen and / or carbon dioxide than the first residue 9. Otherwise the second permeate 11 may be poorer in hydrogen and / or carbon dioxide than the first permeate 7 and the second residue 13 may be less poor in hydrogen and / or carbon dioxide than the first residue 9.
[0042] The second permeate 11 is richer in hydrogen and carbon dioxide than the second residue 13.
[0043] The second permeate 11 is sent to a compressor with a flow rate from which the gas 1 is derived by low temperature separation (distillation and / or partial condensation).
[0044] The second residue 13 is sent to a turbine T coupled to the booster C. The flow expanded in the turbine is not cooled here in the exchanger E.
[0045] The second residue 13 expanded in the turbine can be used to regenerate a dryer and / or sent as fuel to a hydrogen production unit, for example a reformer, for example upstream of the adsorption unit.
[0046] Note the absence of any heater between the hot end of the exchanger E and the inlet of the separation unit ML.
[0047] Such a heater may however be present.
[0048] There is a short-circuiting pipe IA making it possible to send part of the flow 1 from the cold end to the hot end of the exchanger E without passing through the heat exchanger E and thus to arrive at the unit 1 without having been reheated.
[0049] This IA pipe is equipped with a valve V3 regulated by the inlet temperature of gas 1 in the ML unit.
[0050] There is also a short-circuiting pipe 7A between the permeate outlet 7 of the unit M1 and the inlet of the booster C, this pipe being provided with a valve V2 regulated by the outlet temperature of the booster C and by the inlet temperature of the gas 1 into the unit.
[0051] Only a portion of the first compressed permeate in the booster C can be sent to the heat exchanger E.
[0052] At least a portion of the first permeate 17 compressed in the booster C may be sent to a pressure swing adsorption unit to be separated and to extract the hydrogen therefrom, preferably at substantially the outlet pressure of the booster C.
[0053] The apparatus may comprise upstream of the membrane separation part a separation unit operating at a temperature below 0°C by distillation and / or by partial condensation to produce the mixture to be separated in the membrane separation part. In this case, the cold produced by the expansion in the turbine T may be used in the separation unit operating at a temperature below 0°C or in a refrigeration cycle.
[0054] A portion of the second permeate 11 may be sent to the compressor of the low-temperature separation unit.
[0055] In both examples, the heat exchanger E can be divided into a plurality of heat exchangers.
Claims
Claims
1. Method for membrane separation of a mixture containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen comprising the following steps: i. Heating the mixture (1) in a heat exchanger (E) up to a first temperature ii. Permeation of the mixture heated to the first temperature in a first membrane separation unit (Ml) making it possible to obtain a first permeate (7) enriched in hydrogen and carbon dioxide compared to the mixture and a first residue (9) depleted in hydrogen and carbon dioxide, compared to the mixture iii. Cooling of at least a part of the first permeate in the heat exchanger iv.Permeation of the first residue in a second membrane separation unit (M2) making it possible to obtain a second permeate (11) and a second residue (13) depleted in hydrogen and carbon dioxide compared to the second permeate and v. At least a portion (7) of the first permeate, cooled in the heat exchanger, is compressed in a booster (C), the second residue (13) is expanded in a turbine (T) and the booster is driven by the turbine.
2. A method according to claim 1 wherein at least a portion (17) of the permeate compressed in the booster (C) is sent to a pressure swing adsorption separation unit to extract hydrogen therefrom.
3. Method according to claim 1 or 2 in which the mixture (1) is heated in the exchanger (E) only by at least one flow (7, 11, 17) produced by the membrane separation.
4. A method according to any preceding claim wherein the heat exchanger (E) has a first end and a second end, the second end being colder than the first and wherein the at least a portion (7) of the first permeate is cooled to the second end before being sent to the booster.
5. Method according to one of the preceding claims in which the inlet temperature of the turbine (T) is substantially equal to the temperature at which the second residue (13) leaves the second membrane separation unit (M2).
6. Method according to one of the preceding claims in which the heated mixture (1) enters the first membrane separation unit (Ml) at a temperature substantially equal to the temperature at which it leaves the heat exchanger (E).
7. Method according to claim 6 in which a variable part (IA) of the mixture is not reheated in the heat exchanger (E) and mixes with the reheated mixture (1) upstream of the first membrane separation unit (Ml).
8. Method according to claim 6 or 7 in which at least a variable part (7 A) of the first permeate from the first membrane separation unit is sent directly to the booster (C) without passing through the heat exchanger.
9. A method according to claim 6, 7 or 8 wherein only a portion of the first compressed permeate (17) is sent in the booster (C) to the heat exchanger.
10. Method according to one of the preceding claims comprising a separation step operating at a temperature below 0°C by distillation and / or by partial condensation to produce the mixture to be separated and in which the cold produced by the expansion in the turbine (T) is used in the separation unit operating at a temperature below 0°C or in a refrigeration cycle.
11. Method according to one of the preceding claims comprising a separation step operating at a temperature below 0°C by distillation and / or by partial condensation to separate a compressed gas in a compressor and to produce the mixture to be separated (1) in which at least a part of the second permeate (11) is sent to the gas compressor, preferably without having been cooled in the heat exchanger (E).
12. Apparatus for membrane separation of a mixture (1) containing as main components, or even predominantly, hydrogen and carbon dioxide as well as at least one other component, for example chosen from the following group: carbon monoxide, methane, nitrogen including: a. A heat exchanger (E) and means for sending the mixture to heat in the heat exchanger up to a first temperature b. A first membrane separation unit (Ml) and means for sending the mixture heated to the first temperature into the first membrane separation unit in order to obtain a first permeate (7) enriched in hydrogen and carbon dioxide and a first residue (9) depleted in hydrogen and carbon dioxide c. At least one conduit for sending at least a portion of the first permeate to cool in the heat exchanger d. A second membrane separation unit (M2), a pipe for sending the first residue into the second membrane separation unit making it possible to obtain a second permeate (11) and a second residue (13) depleted in hydrogen and carbon dioxide compared to the second permeate and e. A booster (C), means connected to the heat exchanger for sending at least one portion (7) of the first permeate, cooled in the heat exchanger, into the booster to be compressed, optionally means for sending the compressed first permeate to cool in the heat exchanger, a turbine (T), means for sending the second residue to expand in the turbine and the booster is coupled to the turbine to be driven by it.