Method and apparatus for capturing co2 by partial condensation and / or distillation and / or scrubbing and / or solidification

Abstract

The invention relates to an apparatus for separating a gas mixture containing CO2 and at least one component that is lighter than CO2, which comprises a separation unit (CC) for separation by partial condensation and / or distillation at a temperature lower than 0°C of the gas mixture (MG), generating a CO2-enriched fluid (P) and a first waste gas (PGR) depleted in CO2 which is substantially at the same pressure as the gas mixture and an apparatus for separation by pressure swing adsorption (CO2 PSA) of the first waste gas, producing a first CO2-enriched gas (GE) at a first pressure and a second waste gas (DGR) depleted in CO2 at a second pressure higher than the first pressure, a turbine (T1) and a pipe for sending the first waste gas (PGR) to expand in the turbine (T1) downstream of the separation unit (CC) and upstream of the apparatus for separation by pressure swing adsorption (CO2 PSA).

Description

[0001] Method and apparatus for capturing CO2 by partial condensation and / or distillation and / or washing and / or solidification

[0002] The present invention relates to a method and apparatus for capturing CO2 by partial condensation and / or distillation and / or washing and / or solidification. It relates in particular to a method for separating a gas stream containing CO2 and hydrogen.

[0003] Introduction

[0004] Carbon dioxide (CO2) capture by a partial condensation and / or distillation and / or solidification process on a hydrogen (H2) production unit comprising a pressure swing adsorption hydrogen separation unit (PSA) can be combined with membrane separation. These membranes are intended to separate CO2 and H2 from the rest of the gases. However, this membrane separation can be replaced by at least one pressure swing adsorption separation step.

[0005] State of the art

[0006] US4952223 describes a scheme where the regeneration gas of an H2 PSA is formed by separating the tail gas from the PSA by cryogenic distillation and separating the overhead gas from the distillation by a CO2 PSA.

[0007] WO 2022 / 213053 describes a process flowsheet with pressure-swing adsorption separation for purifying the waste gas from the cryogenic part. It is specifically recommended in paragraphs 099 and 107 of this document to compress the waste gas upstream of the adsorption separation.

[0008] Problem solved by the invention

[0009] Partial condensation of CO2 is optimized at high pressure to increase the partial pressure of CO2 (moderate energy consumption for high CO2 yield).

[0010] Pressure-swing adsorption separation does not necessarily require reaching the same pressure levels as partial condensation to be effective, and even too high a pressure can degrade performance (due to the greater co-adsorption of other molecules). In this case, it is recommended to de-correlate the pressure of partial condensation from that of the PSA by means of an expansion. The pressure energy is dissipated in this expansion if it takes place in a valve.

[0011] Especially since pressure swing adsorption or PSA necessarily produces a low-pressure tail gas, the pressure difference between the inlet gas and the tail gas not being used energetically. For these two reasons, it is advantageous to operate PSA at a lower pressure than cryogenic separation and therefore to carry out an intermediate expansion.

[0012] Since adsorption separation with pressure swing takes place downstream of cryogenic separation, the invention proposes installing a turbine on the residual gas from cryogenic separation to better exploit the energy contained in this gas.

[0013] Description of the invention

[0014] According to an object of the invention, there is provided a method for separating a gas stream containing CO2 and hydrogen as well as possibly at least one other component lighter than CO2 such as helium, methane, carbon monoxide, nitrogen, oxygen or argon comprising the following steps: i) Separation of the gas stream by pressure swing adsorption producing a gas enriched in hydrogen and depleted in CO2 relative to the stream and a gas mixture depleted in hydrogen and enriched in CO2 relative to the stream and at a pressure between 20 and 60 bara, ii) Separation by partial condensation and / or distillation and / or washing and / or solidification at a temperature below 0°C of the gas mixture,generating a fluid enriched in CO2 relative to the gas mixture and a first residual gas depleted in CO2 and enriched in hydrogen relative to the gas mixture which is substantially at the same pressure as the gas mixture and iii) Separation by pressure swing adsorption of the first residual gas producing a first gas enriched in CO2 relative to the first residual gas at a first pressure and a second residual gas depleted in CO2 and enriched in hydrogen relative to the first residual gas at a second pressure higher than the first pressure, characterized in that the gas mixture contains between 25 and 60 mol%, or even between 35 and 50 mol%, of hydrogen on a dry basis and the first residual gas is expanded by means of at least a first turbine downstream of the separation of step ii) and upstream of the pressure swing adsorption of step iii) to a pressure of between 6 and 30 bara.,

[0015] According to other optional characteristics, which can be combined in any way compatible with logic and science:

[0016] • the second residual gas (DGR) is expanded by means of at least one second turbine.

[0017] • the second residual gas provides frigories for separation by partial condensation and / or distillation and / or washing and / or solidification.

[0018] • the second residual gas is separated in a second pressure swing adsorption process generating a gas enriched in CO2 relative to the second residual gas and a third residual gas substantially at the second pressure.

[0019] • the third residual gas is expanded by means of at least one turbine.

[0020] • the third residual gas constitutes a product of the process containing at least 90 mol%, or even at least 95 mol% of hydrogen.

[0021] • the at least one first turbine or the at least one second turbine or the at least one turbine which expands the third residual gas drives a compressor to compress a gas which is the gas mixture upstream of the separation of step i), or a CO2-rich gas resulting from the separation of step ii), or a by-product of the separation by adsorption with pressure swing.

[0022] • the temperature at the outlet of the at least one first turbine and / or the at least one second turbine and / or the at least one turbine which expands the third residual gas is below 0°C, or even below -30°C or even below -50°C.

[0023] • the gas upstream of the at least one first turbine and / or the gas upstream of the at least one second turbine and / or the gas upstream of the at least one turbine which expands the third waste gas is heated in at least one heat exchanger.

[0024] • a heat source sent to the at least one heat exchanger is a source external to the process such as water vapor.

[0025] • a heat source of the at least one heat exchanger is a source internal to the process such as the compression of the gas mixture upstream of the separation by partial condensation and / or distillation and / or solidification or the compression of a gas resulting from the separation by partial condensation and / or distillation and / or solidification.

[0026] • the first residual gas is expanded by means of at least a first turbine downstream of the separation of step ii) and upstream of the pressure swing adsorption of step iii) to a pressure of between 6 and 8 bara, between 8 and 10 bara, between 10 and 12 bara, between 12 and 14 bara, between 14 and 16 bara, between 16 and 18 bara, between 18 and 20 bara, between 20 and 22 bara, between 22 and 24 bara, between 24 and 26 bara, between 26 and 28 bara or between 28 and 30 bara.

[0027] • the first residual gas is expanded from a pressure of between 20 and 60 bara, for example between 20 and 22 bara, between 22 and 24 bara, between 24 and 26 bara, between 26 and 28 bara, between 28 and 30 bara, between 30 and 32 bara, between 32 and 34 bara, between 34 and 36 bara, between 36 and 38 bara, between 38 and 40 bara, between 40 and 42 bara, between 42 and 44 bara, between 44 and 46 bara, between 46 and 48 bara, between 48 and 50 bara, between 50 and 52 bara, between 52 and 54 bara, between 54 and 56 bara, between 56 and 58 bara or between 58 and 60 bara..

[0028] According to another object of the invention, there is provided an apparatus for separating a gas stream, containing CO2 and hydrogen as well as possibly at least one other component lighter than CO2 such as helium, methane, carbon monoxide, nitrogen, oxygen or argon comprising a pressure swing adsorption separation unit, means for sending the gas stream to separate in the pressure swing adsorption separation unit to produce a gas enriched in hydrogen and depleted in CO2 relative to the gas stream and a gas mixture enriched in CO2 and depleted in CO2 relative to the gas stream, a separation unit for separation by partial condensation and / or distillation and / or washing and / or solidification at a temperature below 0°C of the gas mixture, a pipe for sending the gas mixture to separate in the separation unit,a pipe for outputting a fluid enriched in CO2 relative to the gas mixture from the separation unit, a pipe for outputting a first residual gas depleted in CO2 and enriched in hydrogen relative to the gas mixture which is substantially at the same pressure as the gas mixture and a pressure swing adsorption separation apparatus for the first residual gas producing a first gas enriched in CO2 at a first pressure and a second residual gas depleted in CO2 at a second pressure higher than the first pressure, characterized in that it comprises at least a first turbine,a pipe for sending the first residual gas to expand by means of the at least one first turbine downstream of the partial condensation and / or distillation and / or washing and / or solidification separation unit and upstream of the pressure swing adsorption separation apparatus and a pipe for sending the first expanded residual gas from the at least one first turbine to the adsorption separation apparatus.,

[0029] The use of the term "first turbine" does not imply that there are necessarily other turbines.

[0030] The invention may comprise the following optional steps:

[0031] • the low-pressure, CO2-rich gas from the pressure-shift separation unit can be sent upstream of the separation by partial condensation and / or distillation and / or washing and / or solidification, for example at the inlet of a compressor of the gas mixture C1.

[0032] • the turbine can be connected to an electricity generator.

[0033] • the turbine can be coupled to a booster compressing for example: the inlet gas from the cryogenic separation, the CO2 produced from the capture unit or one of the products from the PSA(s).

[0034] • separate the H2 from the rest of the high-pressure, CO2-depleted gas using adsorption separation with pressure swing to increase H2 production.

[0035] • expand the high-pressure gas, depleted in CO2 and potentially enriched in H2, through a second turbine to a pressure between 1 and 6 bara.

[0036] • as previously, the second turbine can be connected to a generator or a booster.

[0037] • heating upstream of each turbine to recover more energy and regulate their outlet temperatures. This heating can be achieved using an external heat source such as water vapor or by recovering heat within the CO2 capture process (such as the energy from compressing the gas upstream of the separation by partial condensation and / or distillation and / or washing and / or solidification or of the CO2 produced).

[0038] • generate cold temperatures at the outlet of the turbines to produce at least part of the cold consumed by the section by partial condensation and / or distillation and / or washing and / or cryogenic solidification. This invention makes it possible, thanks to the turbine(s) installed around the adsorption separation, to use the pressure energy of the residual gas and possibly to generate cold for the separation section by partial condensation and / or distillation and / or washing and / or solidification.

[0039] The invention will be described in more detail with reference to the figures where: [FIG.1] represents a method according to the invention.

[0040] [FIG.2] represents a method according to the invention.

[0041] [FIG.3] represents a method according to the invention.

[0042] [FIG.1] represents a process according to the invention in which a synthesis gas SG containing hydrogen, carbon monoxide and carbon dioxide and optionally at least one other component lighter than CO2 such as helium, methane, nitrogen, oxygen or argon. This gas is separated by a pressure swing adsorption process H2 PSA producing a flow rich in hydrogen H2 and, at lower pressure and a gas enriched in CO2 and depleted in hydrogen MG compared to the synthesis gas. The gas enriched in CO2 and depleted in hydrogen contains water is compressed by a first compressor C1 and then separated by temperature swing adsorption TSA to remove the water.The dry gas is compressed by two compression stages C2, C3 to a pressure between 20 and 60 bara, cooled and is separated at this pressure by partial condensation and / or distillation and / or washing and / or solidification forming a CO2-rich fluid P (gas or liquid), containing at least 80 mol% of CO2 and a first residual gas substantially at a pressure between 20 and 60 bara enriched in hydrogen and depleted in CO2 relative to the gas mixture MG. This first residual gas may for example come from at least one partial condensation stage possibly upstream of a distillation stage, the distillation stage producing a CO2-rich liquid. The separation apparatus CC may comprise at least one phase separator and / or at least one column, for example a distillation or washing column. A CO2 solidification stage may take place in the apparatus CC.

[0043] The first residual gas is expanded in a turbine T1 to a pressure of between 6 and 30 bara and is sent at this pressure to a pressure swing separation unit. This unit produces a gas GE at a first pressure enriched in CO2 compared to the first residual gas and a second residual gas DGR depleted in CO2 compared to the first residual gas at a second pressure higher than the first pressure. The second residual gas DGR is heated by water vapor and is used to regenerate the temperature swing separation unit TSA which dries the compressed gas in the compressor C1. The regeneration gas thus containing the water can be used as fuel FG. The turbine T1 is coupled to the compression stage C3.

[0044] [FIG.2] represents a process according to the invention in which a synthesis gas SG containing hydrogen, carbon monoxide and carbon dioxide and possibly another component lighter than CO2 such as helium, methane, nitrogen, oxygen or argon. This gas is separated by a pressure swing adsorption process H2 PSA producing a flow rich in hydrogen H2 and, at lower pressure, a gas mixture MG enriched in CO2 and depleted in hydrogen. The gas MG enriched in CO2 and depleted in hydrogen contains water and is compressed by a first compressor C1 and then separated by temperature swing adsorption TSA to remove the water.

[0045] The dry gas is compressed by three compression stages C2, C3, C4 to a pressure between 20 and 60 bara, optionally without cooling between at least two of the stages C2, C3 and C4, cooled in a heat exchanger E and then cooled by a cooler C. Then it is separated at this pressure between 20 and 60 bara by partial condensation and / or distillation and / or washing and / or solidification forming a CO2-rich fluid P, containing at least 80 mol% of CO2 and a first residual gas PGR substantially at the pressure between 20 and 60 bara enriched in hydrogen and depleted in CO2.

[0046] This first residual gas may come, for example, from at least one stage of partial condensation of the MG gas upstream of a distillation stage, the distillation stage producing a liquid rich in CO2 P.

[0047] The CC separation apparatus may comprise at least one phase separator and / or at least one column, for example a distillation or washing column. A CO2 solidification step may take place in the CC apparatus.

[0048] The first PGR waste gas is heated to 80-120°C in heat exchanger E by heat exchange with the MG gas leaving the compression stage C4. It is then expanded in a turbine T1 to a first pressure of between 6 and 30 bara and a temperature of 25-50°C and is sent at this pressure to a CO2 PSA pressure swing separation unit. This unit produces a GE gas at a first pressure enriched in CO2 compared to the first waste gas and a second DGR waste gas depleted in CO2 compared to the first waste gas at a second pressure lower than the first pressure. The second DGR waste gas is heated in exchanger E against the MG gas mixture compressed in stages C2, C3, C4 and then expanded in a second turbine T2 to 3-5 bar for example. The gas expanded in turbine T2 is returned to the CC separation unit by partial condensation and / or distillation and / or solidification.There it can provide cold being at a temperature below 0°C, even below -30°C or below -50°C and / or be separated by partial condensation and / or distillation and / or solidification in the CC unit.

[0049] Turbine T1 is coupled to compression stage C3 and the second turbine T2 is coupled to compression stage C4.

[0050] The temperature swing adsorption unit is regenerated by an OG gas from the CC unit. This gas may consist of at least part of the DGR gas expanded in the T2 turbine.

[0051] [FIG.3] represents a process according to the invention in which a synthesis gas SG containing hydrogen, carbon monoxide and carbon dioxide and possibly another component lighter than CO2 such as helium, methane, nitrogen, oxygen or argon. This gas SG is separated by a pressure swing adsorption process H2 PSA producing a hydrogen-rich stream H2 1 and, at lower pressure, a gas mixture MG enriched in CO2 and depleted in hydrogen compared to the gas SG. The gas enriched in CO2 and depleted in hydrogen MG contains water and is compressed by a first compressor C1 and then separated by temperature swing adsorption TSA to remove the water.The dry gas is compressed by three compression stages C2, C3, C4 to a pressure between 20 and 60 bara, cooled by a cooler C and is separated at this pressure by partial condensation and / or distillation and / or solidification forming a CO2-rich fluid P, containing at least 80 mol% of CO2 and a first residual gas PGR substantially at a pressure between 20 and 60 bara enriched in hydrogen. This first residual gas PGR may for example come from at least one partial condensation stage of the gas mixture MG upstream of a distillation stage, the distillation stage producing a liquid rich in CO2.

[0052] The CC separation apparatus may comprise at least one phase separator and / or at least one column, for example a distillation or washing column. A CO2 solidification step may take place in the CC apparatus. The first waste gas PGR is expanded in a turbine T1 to a pressure of between 6 and 30 bara and is sent at this pressure to a CO2 PSA pressure swing separation unit. This CO2 PSA unit produces a GE gas at a first pressure and enriched in CO2 relative to the first waste gas and a second DGR waste gas depleted in CO2 relative to the first waste gas at a second pressure higher than the first pressure.

[0053] The second waste gas is separated in a second H2 PSA 2 pressure swing adsorption unit producing a third hydrogen-enriched TGR waste gas and a hydrogen-depleted R gas compared to the second DGR waste gas. The hydrogen-depleted R gas is used to regenerate the TSA temperature swing adsorption unit. The third TGR waste gas is expanded in a T3 turbine

[0054] Turbine T1 is coupled to compression stage C3 and the third turbine T3 is coupled to compression stage C4.

[0055] The third tail gas TGR contains 90 mol% or at least 95 mol% hydrogen and can be used as a hydrogen-rich product H2 2.

[0056] In the three figures, the at least one first and / or the at least one second and / or the at least one other turbine T1, T2, T3 can be coupled to an electricity generator.

[0057] In the three figures, the at least one first or at least one second or at least one other turbine T1, T2, T3 can be coupled to:

[0058] • A compressor compressing the gas mixture, for example at the inlet of the CC separation.

[0059] • A compressor compressing the CO2 produced P from the CC separation unit.

[0060] • A compressor compressing one of the products of one of the PSAs, for example R, GE, DGR, TGR gas.

[0061] In all three figures, the gas to be expanded can be heated upstream of each turbine T1, T2, T3 to recover more energy and to regulate their outlet temperature. This heating can be achieved using an external heat source such as water vapor or by heat recovery within the CO2 capture process (such as the compression energy of the MG gas upstream of the cryogenic separation or of the CO2 produced P). In figures 1, 2 and 3, temperatures below 0°C, or even below -30°C, can be generated at the outlet of turbines T1, T2, T3 to produce part of the cold consumed by the CC unit.

Claims

Claims 1. A method for separating a gas stream (SG) containing CO2 and hydrogen and possibly at least one other component lighter than CO2 such as helium, methane, carbon monoxide, nitrogen, oxygen or argon comprising the following steps: i) Separation of the gas stream by pressure swing adsorption (H2 PSA) producing a gas enriched in hydrogen and depleted in CO2 relative to the stream and a gas mixture (MG) depleted in hydrogen and enriched in CO2 relative to the stream and at a pressure between 20 and 60 bara ii) Separation (CC) by partial condensation and / or distillation and / or washing and / or solidification at a temperature below 0°C of the gas mixture,generating a fluid enriched in CO2 (P) relative to the gas mixture and a first residual gas (PGR) depleted in CO2 and enriched in hydrogen relative to the gas mixture which is substantially at the same pressure as the gas mixture and iii) Separation (CO2 PSA) by pressure swing adsorption of the first residual gas producing a first gas enriched in CO2 (GE) relative to the first residual gas at a first pressure and a second residual gas (DGR) depleted in CO2 and enriched in hydrogen relative to the first residual gas at a second pressure higher than the first pressure, characterized in that the gas mixture contains between 25 and 60 mol%, or even between 35 and 50 mol%, of hydrogen on a dry basis and in that the first residual gas (PGR) is expanded by means of at least one first turbine (T1) downstream of the separation of step ii) and upstream of the pressure swing adsorption of step iii) up to a pressure between 6 and 30 bara., 2. Method according to claim 1, characterized in that the second residual gas (DGR) is expanded by means of at least one second turbine (T2).

3. Method according to claim 2 in which the second residual gas (DGR) provides frigories to the separation (CC) by partial condensation and / or distillation and / or washing and / or solidification.

4. Method according to claim 1, characterized in that the second waste gas (DGR) is separated in a second rocking adsorption process. pressure (H2 PSA 2) generating a gas enriched in CO2 compared to the second residual gas and a third residual gas (TGR) substantially at the second pressure.

5. Method according to claim 4, characterized in that the third waste gas is expanded by means of at least one turbine (T3).

6. Method according to claim 4 or 5, characterized in that the third residual gas (TGR) constitutes a product (H2 2) of the process containing at least 90 mol%, or even at least 95 mol% of hydrogen.

7. Method according to one of the preceding claims, characterized in that the at least one first turbine (T1) or the at least second turbine (T2) or the at least one turbine (T3) which expands the third residual gas (TGR) drives a compressor (C1, C2, C3, C4) to compress a gas which is the gas mixture upstream of the separation of step i), or a CO2-rich gas (P) from the separation of step ii), or a by-product (R, GE, DGR, TGR) of the separation by adsorption with pressure swing.

8. Method according to one of the preceding claims, characterized in that the temperature at the outlet of the at least one first turbine (T1) and / or the at least one second turbine (T2) and / or the at least one turbine (T3) which expands the third residual gas (TGR) is below 0°C, or even below -30°C or even below -50°C.

9. Method according to one of the preceding claims, characterized in that the gas (PGR) upstream of the at least one first turbine (T 1 ) and / or the gas (DGR) upstream of the at least one second turbine (T2) and / or the gas upstream of the at least one turbine (T3) which expands the third waste gas (TGR) is heated in at least one heat exchanger (E).

10. Method according to claim 9, characterized in that a heat source sent to the at least one heat exchanger (E) is a source external to the process such as water vapor.

11. Method according to claim 9, characterized in that a heat source of the at least one heat exchanger (E) is a source internal to the process such as the compression (C1, C2, C3, C4) of the gas mixture (MG) upstream of the separation (CC) by partial condensation and / or distillation and / or solidification or the compression of a gas (PGR, DGR) resulting from the separation by partial condensation and / or distillation and / or solidification.

12. Apparatus for separating a gas stream (SG), containing CO2 and hydrogen and possibly at least one other component lighter than CO2 such as helium, methane, carbon monoxide, nitrogen, oxygen or argon comprising a separation unit (H2 PSA) by pressure swing adsorption, means for sending the gas stream to separate in the separation unit by pressure swing adsorption to produce a gas enriched in hydrogen and depleted in CO2 relative to the gas stream and a gas mixture (MG) enriched in CO2 and depleted in hydrogen relative to the gas stream, a separation unit (CC) for separation by partial condensation and / or distillation and / or washing and / or solidification at a temperature below 0°C of the gas mixture (MG), a pipe for sending the gas mixture to separate in the separation unit (CC),a pipe for outputting a fluid (P) enriched in CO2 relative to the gas mixture from the separation unit, a pipe for outputting a first residual gas (PGR) depleted in CO2 and enriched in hydrogen relative to the gas mixture which is substantially at the same pressure as the gas mixture and a pressure swing adsorption separation apparatus (CO2 PSA) of the first residual gas producing a first gas enriched in CO2 (GE) at a first pressure and a second residual gas (DGR) depleted in CO2 at a second pressure higher than the first pressure, characterized in that it comprises at least a first turbine (T1),a pipe for sending the first residual gas (PGR) to expand by means of the at least one first turbine (T1) downstream of the partial condensation and / or distillation and / or washing and / or solidification separation unit and upstream of the pressure swing adsorption separation apparatus and a pipe for sending the first expanded residual gas from the at least one first turbine to the adsorption separation apparatus.,

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