Method and apparatus for separating a mixture of hydrogen and carbon monoxide at low temperatures
By integrating the pressure swing adsorption (PSA) unit with the cryogenic separation unit, and combining cooling, partial condensation, and gas scrubbing processes, the problems of low separation efficiency and high energy consumption of hydrogen and carbon monoxide mixtures under high pressure are solved, achieving efficient and low-cost hydrogen production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE
- Filing Date
- 2022-04-28
- Publication Date
- 2026-06-23
AI Technical Summary
Existing technologies for separating mixtures of hydrogen and carbon monoxide at low temperatures suffer from low efficiency and high energy consumption, especially under high pressure where multiple pressure adjustments are required, leading to increased equipment costs.
By integrating a pressure swing adsorption (PSA) unit with a cryogenic separation unit, the mixture is cooled to below -180°C in a heat exchanger. Combined with partial condensation, distillation, and gas scrubbing processes, the mixture is further processed in the PSA separation unit. A steam turbine is used to reduce the pressure and provide cooling, thereby achieving efficient separation of hydrogen and carbon monoxide.
This technology enables efficient separation of hydrogen and carbon monoxide mixtures at low temperatures, reducing energy consumption and equipment costs while improving hydrogen yield and purity.
Smart Images
Figure CN115289782B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method and apparatus for separating a mixture of hydrogen and carbon monoxide at low temperatures. Specifically, the invention relates to separation at temperatures below -100°C by distillation and / or scrubbing and / or partial condensation. Background Technology
[0002] The mixture to be separated preferably contains at least 10 mol% hydrogen, or even at least 30 mol% hydrogen.
[0003] The mixture may be a synthesis gas and may contain at least one of the following components in addition to hydrogen and carbon monoxide: carbon dioxide, nitrogen, methane or water.
[0004] The mixture may contain at least one of the following components as additional impurities: sulfides, cyanides, ammonia, or at least one hydrocarbon heavier than methane.
[0005] Partial condensation and scrubbing processes are particularly effective under high pressure; therefore, if separation of a mixture is required at high pressure, it is advantageous to perform the separation by partial condensation or scrubbing under high pressure without reducing the pressure of the mixture. This yields hydrogen gas at a pressure slightly lower than the pressure of the mixture.
[0006] For example, in the case of a pulverized coal gasifier, a mixture of hydrogen and carbon monoxide is obtained at a pressure of 60 bar, so that hydrogen can be obtained at about 56 bar through partial condensation and / or scrubbing.
[0007] Hydrogen produced by separation at low temperature in a pressure swing adsorption (PSA) unit is known from DE4210638 and FR 3 021 044.
[0008] Consider this scenario: the pipeline requires hydrogen at a pressure of 28 bar, while the user requires hydrogen at a pressure of 8 bar. In this case, hydrogen will be produced at the highest pressure to avoid using two PSA units.
[0009] The pressure swing adsorption (PSA) unit is preferably operated at approximately 30 bar for two reasons:
[0010] -30 bar represents the optimal pressure for this technology: operating at higher pressures will reduce hydrogen yields, while operating at lower pressures will prevent the product pressure from being reached.
[0011] -PSA valves must operate at a pressure of about 35 bar to keep the valve within a maximum range of 300 psi; higher pressures require more expensive valves.
[0012] Pressure swing adsorption (PSA) devices operate according to a process used to separate gas mixtures, during which a solid or liquid adsorbs the gas at a given pressure and then desorbs it at a lower pressure, alternating between the two processes.
[0013] This operation involves extracting gases from a gas mixture using chemical affinity and specific properties of the solid material, with the adsorbent exposed to tightly controlled pressure fluctuations. Selective adsorption is achieved through different equilibrium capacities (equilibrium adsorbents) or through differences in adsorption rates (dynamic adsorbents).
[0014] If hydrogen is obtained at 56 bar, in addition to reducing the pressure of the desired product to 8 bar, the hydrogen pressure also needs to be reduced downstream of the adsorption operation. Summary of the Invention
[0015] The purpose of this invention is to integrate a pressure swing adsorption device with a cryogenic separation device, thereby using hydrogen gas at reduced pressure to provide cooling for the cryogenic separation operation.
[0016] US 3,691,779 describes an integration of a device for separation via partial condensation and an adsorption unit operating at -195°C to -162°C. A portion of the hydrogen obtained from adsorption is used to cool the separation unit by reducing its pressure to 2.4 bar in a steam turbine, and subsequently used to regenerate the adsorption unit.
[0017] According to one aspect of the invention, a method is provided for separating a mixture containing hydrogen and carbon monoxide to obtain gaseous hydrogen, wherein:
[0018] i) The mixture is cooled to a temperature below -180°C in a heat exchanger, and then separated at a temperature below -100°C by at least one stage of partial condensation and / or distillation and / or scrubbing, thereby obtaining a hydrogen-rich gas and a carbon monoxide-rich fluid.
[0019] ii) At least a portion of the hydrogen-rich gas is fed into a pressure swing adsorption (PSA) separator operating at a temperature above 0°C, thereby obtaining a hydrogen-rich gas at a pressure of at least 20 bar.
[0020] iii) Cooling at least a portion of the hydrogen-rich gas in a heat exchanger to a temperature below -100°C, reducing the pressure in a steam turbine to at least 8 bar, and reheating it in a heat exchanger to form a hydrogen-rich product at a pressure of at least 8 bar.
[0021] According to other optional aspects:
[0022] - At least a portion of the hydrogen-rich gas is reheated in a heat exchanger located upstream of the adsorption separation unit;
[0023] - The hydrogen-rich gas in stage ii) is at a pressure of at least 51 bar; the hydrogen-rich gas is obtained at a pressure of at least 50 bar by an adsorption separation device, and its pressure is reduced to at least 20 bar by a steam turbine;
[0024] - The hydrogen-rich gas, whose pressure has been reduced to at least 20 bar, is divided into two parts, wherein only a portion of this gas is reheated downstream in a heat exchanger to reduce the pressure to at most 12 bar.
[0025] - The hydrogen-rich gas in stage ii) is at a pressure of 28-32 bar; the hydrogen-rich gas is obtained at a pressure of 27-31 bar by an adsorption separation device, and its pressure is reduced at least partially to a pressure of up to 12 bar by a steam turbine;
[0026] - The gas, whose pressure has been reduced to a maximum of 12 bar, constitutes the hydrogen-rich product of this process;
[0027] - The mixture (1) cooled in the heat exchanger is under a pressure of at least 50 bar;
[0028] - The mixture is separated in the first partial condensation stage, the gas from the first partial condensation stage is cooled and sent to the second partial condensation stage, and the hydrogen-rich gas that has been depressurized in the turbine is reheated by exchanging heat with the cooled gas from the first partial condensation stage.
[0029] - The temperature at the inlet of the second condensation stage is lower than -200°C, and even lower than -203°C;
[0030] - Hydrogen-rich feed streams from external sources are also separated in the pressure swing adsorption separator, which optionally results in a greater amount of gas being depressurized in the turbine than the amount of hydrogen-rich gas being separated at temperatures below -100°C.
[0031] -The temperature of the gas at the turbine outlet is lower than -200°C, and even lower than -203°C;
[0032] According to one aspect of the invention, an apparatus is provided for separating a mixture containing hydrogen and carbon monoxide to obtain gaseous hydrogen, comprising: a separation unit where at least one stage of partial condensation and / or distillation and / or scrubbing is performed; a heat exchanger; a pressure swing adsorption (PSA) separator; a steam turbine; means for feeding the mixture to the heat exchanger, wherein the mixture is cooled to a temperature below -180°C in the heat exchanger; and means for feeding the cooled mixture to the separation unit, wherein separation is performed in the separation unit at a temperature below -100°C by at least one stage of partial condensation and / or distillation and / or scrubbing, thereby obtaining hydrogen-rich gas. The apparatus comprises: a gas and a carbon monoxide-rich fluid; means for feeding at least a portion of the hydrogen-rich gas to a pressure swing adsorption (PSA) separator, the PSA separator operating at a temperature above 0°C to obtain a hydrogen-rich gas at a pressure of at least 20 bar; means for feeding at least a portion of the hydrogen-rich gas to a heat exchanger, in which the gas is cooled to a temperature below -100°C and subsequently depressurized to at least 8 bar in a steam turbine; and means for feeding the depressurized gas to the heat exchanger for a reheating operation, wherein the reheating operation yields a hydrogen-rich product at a pressure of at least 8 bar. Attached Figure Description
[0033] The invention will now be described in more detail with reference to the two accompanying drawings.
[0034] [ Figure 1 The method according to the present invention is shown.
[0035] [ Figure 2 The method according to the present invention is shown. Detailed Implementation
[0036] [ Figure 1 The method is illustrated as follows: A pressure swing adsorption (PSA) unit receives a hydrogen-rich feed stream 11 at approximately 55 bar. The purified hydrogen 13 is at approximately 54 bar, and its pressure can be reduced to provide cooling for the cryogenic separation process. This hydrogen is then returned to the initial isolation chamber, where its pressure is further reduced to aid in cooling and reduce energy consumption. Assuming the gas is very pure hydrogen, its pressure can be reduced to achieve very low temperatures, such as -204°C. This allows hydrogen to be separated at lower temperatures within this chamber, improving the yields of carbon monoxide and, optionally, methane.
[0037] The chamber contains heat exchangers E1 and E2 and phase separators S1 and S2.
[0038] The syngas 1 feed stream at a pressure of 56 bar contains carbon monoxide and hydrogen, preferably at least 10 mol% hydrogen, or even at least 30 mol% hydrogen.
[0039] In addition to hydrogen and carbon monoxide, mixture 1 may also contain at least one of the following components: carbon dioxide, nitrogen, methane or water.
[0040] The mixture may contain at least one of the following components as additional impurities: sulfides, cyanides, ammonia, or at least one hydrocarbon heavier than methane.
[0041] Water and carbon dioxide must be removed before cryogenic treatment.
[0042] Stream 1 is cooled and partially condensed in heat exchanger E1, and then sent to phase separator S1 at -180°C. The resulting liquid 5 can be sent to a cryogenic processing operation, for example, by distillation and / or scrubbing and / or partial condensation at a temperature below -100°C. Cryogenic processing may include, in particular, scrubbing of methane, scrubbing of carbon monoxide, or distillation, thereby separating carbon monoxide and methane, if stream 1 contains them.
[0043] The gas 3 from separator S1 is cooled in heat exchanger E2, thereby partially condensing it at a lower temperature, and then sent to phase separator S2. The resulting liquid 17 can be sent to a cryogenic processing operation, for example, by distillation and / or scrubbing and / or partial condensation at a temperature below -100°C. Cryogenic processing may include, in particular, scrubbing of methane, scrubbing of carbon monoxide, or distillation, thereby separating carbon monoxide and methane if the feed stream 1 contains them.
[0044] The gas 7 from separator S2 is rich in hydrogen and is reheated in heat exchangers E2 and E1, optionally mixed with the hydrogen-rich gas stream 9 from conversion unit at a temperature below 0°C.
[0045] Gas 7 at 55 bar is added to the pressure swing adsorption separation unit, where it is separated into hydrogen-rich gas 13 at 54 bar. Gas 13 is then returned to the chamber containing heat exchangers E1 and E2 and separators S1 and S2, without the need for further purification to remove carbon dioxide and water.
[0046] Gas 13 is cooled in heat exchanger E1 and then depressurized in turbine T, thereby reducing its temperature to -204°C for cooling. The depressurized feed stream 15, at 29 bar, is reheated in heat exchangers E2 and E1 and subsequently used as a product. A portion of the product 15A can be depressurized to up to 12 bar, for example, up to 8 bar, in a valve, thus forming a low-pressure product.
[0047] If hydrogen stream 9 is supplied from another source, the quantities of streams 13 and 15 can be larger than those of stream 7. If stream 9 contains water and / or carbon dioxide, they must be removed from stream 13 upstream of the cryogenic cooling operation.
[0048] Apart from the Joule-Thomson pressure reduction effect in the valves, the pressure reduction operation in the turbine T is the only contribution to providing cooling to the cryogenic separation process.
[0049] [ Figure 2 The method is shown as follows: the pressure swing adsorption (PSA) receiver is in a state of relative [ Figure 1 The lower-pressure feed stream 11 is obtained because the pressure of feed stream 7 has already been reduced to 28-32 bar upstream of the adsorption unit, in this case 29 bar, so that feed stream 7 can operate at a pressure close to the optimal pressure. The adsorption unit obtains hydrogen-rich gas at 27-31 bar, in this case 28 bar. A portion of the product 13B, at a pressure of 28 bar, is directly delivered to the user; the remainder 13A is cooled in heat exchanger E1 and then its pressure is reduced from 28 bar to 8 bar in turbine T, thereby reducing the temperature to -204°C for cooling. The reduced-pressure feed stream 15, at a pressure of 8 bar, is reheated in heat exchangers E2, E1 and subsequently used as the product.
[0050] Therefore, the method of this invention yields two hydrogen streams at two different pressures, one stream at the optimal pressure for adsorption and the other at a lower pressure. The difference between these two pressures corresponds to the pressure reduction in the turbine T.
[0051] The remainder of this method can be found above regarding […]. Figure 1 Description of the operation of processing synthesis gas 1 at 56 bar.
Claims
1. A method for separating a mixture (1) containing hydrogen and carbon monoxide to obtain gaseous hydrogen, wherein: i) The mixture is cooled to a temperature below -180°C in a heat exchanger (E1), and then separated at a temperature below -100°C by at least one stage of partial condensation and / or distillation and / or scrubbing, thereby obtaining a hydrogen-rich gas (7) and a carbon monoxide-rich fluid (17). ii) At least a portion of the hydrogen-rich gas is fed to a pressure swing adsorption (PSA) separator operating at a temperature above 0°C, thereby obtaining a hydrogen-rich gas (13) at a pressure of at least 20 bar, and iii) A hydrogen-rich gas (13) or a portion thereof (13A) at a pressure of at least 20 bar is cooled to a temperature below -100°C in a heat exchanger, its pressure is reduced to at least 8 bar in a steam turbine (T), and it is reheated in a heat exchanger to form a hydrogen-rich product (15, 15A) at a pressure of at least 8 bar.
2. The method according to claim 1, wherein at least a portion of the hydrogen-rich gas (7) is reheated in a heat exchanger (E1) located upstream of the adsorption separation unit (PSA).
3. The method according to claim 1 or 2, wherein the hydrogen-rich gas (7) in stage ii) is at a pressure of at least 51 bar; the hydrogen-rich gas (13) is obtained at a pressure of at least 50 bar by an adsorption separation device (PSA), and its pressure is reduced to at least 20 bar by a steam turbine.
4. The method of claim 1, wherein the hydrogen-rich gas (13) at a pressure of at least 20 bar is split into two portions, and only a portion (13A) of this gas is reduced to a pressure of at most 12 bar downstream of the reheating operation in the heat exchanger.
5. The method according to claim 1 or 2, wherein the hydrogen-rich gas (7) in stage ii) is at a pressure of 28-32 bar; the hydrogen-rich gas (13) is obtained at a pressure of 27-31 bar by an adsorption separation device (PSA), and its pressure is reduced at least partially to a pressure of up to 12 bar by a steam turbine (T).
6. The method of claim 5, wherein the gas whose pressure has been reduced to at most 12 bar constitutes the hydrogen-rich product (15) of this process.
7. The method according to claim 1 or 2, wherein the mixture (1) cooled in the heat exchanger (E1) is at a pressure of at least 50 bar.
8. The method according to claim 1 or 2, wherein the mixture (1) is separated in a first partial condensation stage, the gas (3) from the first partial condensation stage is cooled and sent to a second partial condensation stage, and the hydrogen-rich gas, which has been depressurized in the turbine (T), is reheated by exchanging heat with the cooled gas from the first partial condensation stage.
9. The method of claim 8, wherein the temperature at the inlet of the second partial condensation stage is lower than -200°C.
10. The method of claim 9, wherein the temperature at the inlet of the second partial condensation stage is lower than -203°C.
11. The method according to claim 1 or 2, wherein the hydrogen-rich feed stream (9) from an external source is also separated in a pressure swing adsorption (PSA) separator.
12. The method according to claim 1 or 2, wherein the hydrogen-rich feed stream (9) from an external source is also separated in a pressure swing adsorption separator (PSA), such that the amount of gas that has been depressurized in the turbine (T) is greater than the amount of hydrogen-rich gas (7) separated at a temperature below -100°C.
13. The method according to claim 1 or 2, wherein the temperature of the gas at the turbine (T) outlet is lower than -200°C.
14. The method of claim 13, wherein the temperature of the gas at the turbine (T) outlet is lower than -203°C.
15. An apparatus for separating a mixture (1) containing hydrogen and carbon monoxide to obtain gaseous hydrogen, comprising: The separation unit is where at least one stage of partial condensation and / or distillation and / or gas scrubbing (S1, S2) is carried out; A heat exchanger (E1); a pressure swing adsorption (PSA) separator; a steam turbine (T); means for feeding the mixture to the heat exchanger (E1), wherein the mixture is cooled to a temperature below -180°C in the heat exchanger (E1); means for feeding the cooled mixture to a separation unit, wherein separation is carried out in the separation unit at a temperature below -100°C by at least one stage of partial condensation and / or distillation and / or scrubbing, thereby obtaining a hydrogen-rich gas (7) and a carbon monoxide-rich fluid (17); means for feeding at least a portion of the hydrogen-rich gas to the pressure swing adsorption (PSA) separator, the pressure swing adsorption separator... The apparatus comprises: a device for operating at a temperature above 0°C to obtain a hydrogen-rich gas (13) at a pressure of at least 20 bar; means for feeding the hydrogen-rich gas (13) or a portion thereof (13A) at a pressure of at least 20 bar to a heat exchanger, wherein the hydrogen-rich gas (13) or a portion thereof (13A) at a pressure of at least 20 bar is cooled to a temperature below -100°C in the heat exchanger and subsequently its pressure is reduced to at least 8 bar in a steam turbine (T); and means for feeding the reduced-pressure gas to the heat exchanger for a reheating operation, wherein the reheating operation yields a hydrogen-rich product (15, 15A) at a pressure of at least 8 bar.