Separation and recovery method and system for Fischer-Tropsch synthesis tail gas

Abstract

The invention provides a separation and recovery method and system for Fischer-Tropsch synthesis tail gas. The separation and recovery method comprises the following steps: S1, cutting the Fischer-Tropsch synthesis tail gas to obtain a first mixture and a C5 < + > fraction; s2, cutting the first mixture to obtain a second mixture and a C4 fraction; s3, cutting the second mixture to obtain a third mixture and a C3 fraction; s4, cutting the third mixture to obtain a fourth mixture and a C2 fraction; s5, performing dehydrogenation treatment on the fourth mixture to obtain a fifth mixture and hydrogen; s6, separating and purifying the fifth mixture to obtain methane; the method further includes decarburizing and drying the second or third mixture to reduce the content of carbon dioxide and moisture therein. Compared with an existing Fischer-Tropsch synthesis tail gas separation and recovery method, the separation and recovery method can recover methane with high purity and high recovery rate.

Description

Technical Field

[0001] The present invention relates to the field of waste gas recovery and utilization, and in particular to a method and system for separating and recovering Fischer-Tropsch synthesis tail gas. Background Art

[0002] Fischer-Tropsch synthesis is the process of converting synthesis gas into high-carbon hydrocarbons. It is an important way to efficiently convert and utilize non-petroleum carbon-containing resources. Its products mainly include heavy oil, light oil, wax, synthetic water, methane, low-carbon hydrocarbons, unreacted synthesis gas (H2+CO) and nitrogen. Liquid hydrocarbons, solid wax and a large amount of Fischer-Tropsch synthesis tail gas can be obtained by separating and treating the Fischer-Tropsch synthesis products.

[0003] The tail gas of Fischer-Tropsch synthesis mainly includes unreacted hydrogen, carbon monoxide, nitrogen, and carbon dioxide and low-carbon hydrocarbons generated by side reactions. The existing tail gas treatment process of Fischer-Tropsch synthesis usually includes the following steps: first, the C3 component and C4 component with economic value in the synthesis tail gas are removed by low-temperature oil washing physical absorption, and the by-product is liquefied petroleum gas; then, the oil-washed dry gas (oil-washed dry gas refers to the tail gas of Fischer-Tropsch synthesis after low-temperature oil washing) enters the membrane separation device for rough separation of hydrogen to obtain hydrogen-containing permeate gas and methane-rich non-permeate gas, wherein the permeate gas is sent to the pressure swing adsorption device to produce hydrogen, and the non-permeate gas is divided into two parts, one of which is sent to the low-pressure fuel gas pipeline network or boiler for blending, and the other part is increased in hydrogen content through hydrocarbon conversion, transformation, pressure swing adsorption and other sections, and is incorporated into the oil product synthesis device to synthesize oil products.

[0004] However, the above-mentioned Fischer-Tropsch synthesis tail gas treatment process has the problem of low methane recovery rate.

[0005] Therefore, it is particularly important to study and develop a method and system for separating and recovering Fischer-Tropsch synthesis tail gas in order to improve the separation and recovery rate of methane. Summary of the invention

[0006] The main purpose of the present invention is to provide a method and system for separating and recovering Fischer-Tropsch synthesis tail gas, so as to solve the problem of low methane recovery rate in the Fischer-Tropsch synthesis tail gas separation and recovery process in the prior art.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a method for separating and recovering Fischer-Tropsch synthesis tail gas on the one hand, and the separation and recovery method comprises: step S1, using a first distillation device to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture containing a C4- fraction and hydrogen, and a C5+ fraction; step S2, using a second distillation device to cut the first mixture to obtain a second mixture containing a C3- fraction and hydrogen, and a C4 fraction; step S3, using a third distillation device to cut the second mixture to obtain a third mixture containing a C2- fraction and hydrogen, and a C3 fraction; step S4, using a fourth distillation device to cut the third mixture to obtain a third mixture containing a C1 fraction and hydrogen four mixtures, and C2 fractions; the fourth distillation device is the first distillation tower, the top pressure of the first distillation tower is 2.0 to 4.0 MPa, and the top temperature is -141 to -131 ° C; step S5, using a dehydrogenation device to dehydrogenate the fourth mixture to obtain a fifth mixture and hydrogen, wherein the fifth mixture includes methane; step S6, using a fifth distillation device to separate and purify the fifth mixture to obtain methane; the separation and recovery method also includes: before cutting the second mixture or the third mixture, using a decarbonization drying unit to decarbonize and dry the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture.

[0008] Furthermore, the top pressure of the first distillation tower is 2.5 to 3.0 MPa, and the top temperature is -138 to -135°C.

[0009] Furthermore, the Fischer-Tropsch synthesis tail gas includes 30-50 mol% CH4, 20-40 mol% H2, 2-20 mol% N2, 10-20 mol% CO, and the rest includes one or more of CO2, C2 component, C3 component, C4 component, and C5+ component.

[0010] Furthermore, the third distillation device is a second distillation tower, the top pressure of the second distillation tower is 1.5 to 2.0 MPa, and the top temperature is -96 to -92°C.

[0011] Furthermore, the top pressure of the second distillation tower is 1.7 to 1.8 MPa, and the top temperature is -94 to -93°C.

[0012] Furthermore, the dehydrogenation device is a dehydrogenation tower, the top pressure of the dehydrogenation tower is 1.8 to 2.0 MPa, and the top temperature of the tower is -200 to -180°C.

[0013] Furthermore, the fifth distillation device is a third distillation tower, the top pressure of the third distillation tower is 0.5 to 1.8 MPa, and the top temperature is -180 to -160°C.

[0014] Furthermore, the decarbonization process is carried out using an amine method.

[0015] Furthermore, the carbon dioxide content in the decarbonized dried product obtained after the second mixture or the third mixture is decarbonized and dried is ≤20ppm.

[0016] Furthermore, the first distillation device is a fourth distillation tower, the top pressure of the fourth distillation tower is 2.2 to 2.4 MPa, and the top temperature is -52 to -50°C.

[0017] Furthermore, the second distillation device is a fifth distillation tower, the top pressure of the fifth distillation tower is 1.88 to 1.98 MPa, and the top temperature is -75 to -72°C.

[0018] Furthermore, the separation and recovery method further comprises: using a sixth distillation device to cut the C3 fraction obtained in step S3 to obtain propylene and propane.

[0019] Furthermore, the sixth distillation device is a sixth distillation tower, the top pressure of the sixth distillation tower is 2.00-2.13 MPa, and the top temperature is 50-55°C.

[0020] Furthermore, the separation and recovery method also includes: mixing propane with the C4 fraction to obtain liquefied petroleum gas.

[0021] Furthermore, the separation and recovery method further comprises: using a seventh distillation device to cut the C2 fraction obtained in step S4 to obtain ethylene and ethane.

[0022] Furthermore, the seventh distillation device is a seventh distillation tower, the top pressure of the seventh distillation tower is 1.0 to 2.0 MPa, and the top temperature is -36 to -32°C.

[0023] Furthermore, the separation and recovery method further comprises performing pressure swing adsorption treatment on the hydrogen obtained in step S5 to obtain recovered hydrogen.

[0024] Furthermore, the pressure of the pressure swing adsorption treatment is 3-4 MPa and the temperature is 20-40°C.

[0025] Furthermore, carbon monoxide gas is also obtained in step S6, and the separation and recovery method also includes introducing the carbon monoxide gas into a hydrogen production device to react with water to obtain regenerated hydrogen.

[0026] In order to achieve the above-mentioned purpose, another aspect of the present invention provides a separation and recovery system for implementing the above-mentioned separation and recovery method provided by the present application, and the separation and recovery system includes: a first distillation device, a second distillation device, a third distillation device, a fourth distillation device, a dehydrogenation device, and a fifth distillation device which are connected in sequence, wherein the first distillation device is used to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture and a C5+ fraction; the first distillation device is provided with a Fischer-Tropsch synthesis tail gas inlet, a first mixture outlet and a C5+ fraction outlet; the second distillation device is used to cut the first mixture to obtain a second mixture and a C4 fraction; the second distillation device is provided with a first mixture inlet, a second mixture outlet and a C4 fraction outlet; the third distillation device is used to cut the second mixture to obtain a third mixture and a C3 fraction; the third distillation device is provided with a second mixture inlet, a third mixture outlet and a C3 fraction outlet; the fourth distillation device The distillation device is used to cut the third mixture to obtain a fourth mixture and a C2 fraction; the fourth distillation device is provided with a third mixture inlet, a fourth mixture outlet and a C2 fraction outlet; the fourth distillation device is a first distillation tower; the dehydrogenation device is used to dehydrogenate the fourth mixture to obtain a fifth mixture and hydrogen, wherein the fifth mixture includes methane; the dehydrogenation device is provided with a fourth mixture inlet, a fifth mixture outlet and a hydrogen outlet; the fifth distillation device is used to separate and purify the fifth mixture to obtain methane, the fifth distillation device is provided with a fifth mixture inlet and a methane outlet, and the fifth mixture inlet is connected to the fifth mixture outlet; the separation and recovery system also includes a decarbonization drying unit, which is used to decarbonize and dry the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture; the decarbonization drying unit includes a decarbonization device and a drying device which are connected in sequence.

[0027] Furthermore, the inner cavity of the drying device is filled with molecular sieves.

[0028] Furthermore, the molecular sieve is selected from one or more of type 3A molecular sieve, type 4A molecular sieve and type 5A molecular sieve.

[0029] Furthermore, the filling amount of the molecular sieve is 30-50% based on the total volume of the inner cavity of the drying device.

[0030] Furthermore, the separation and recovery system also includes a sixth distillation device, which is provided with a C3 fraction inlet, a propylene outlet and a propane outlet, and the C3 fraction inlet is connected to the C3 fraction outlet.

[0031] Furthermore, the separation and recovery system also includes a seventh distillation device, which is provided with a C2 fraction inlet, an ethylene outlet and an ethane outlet, and the C2 fraction inlet is connected to the C2 fraction outlet.

[0032] Furthermore, the separation and recovery system also includes a mixing device for mixing propane with the C4 fraction to obtain liquefied petroleum gas. The mixing device is provided with a propane inlet, a C4 fraction inlet and a liquefied petroleum gas outlet. The C4 fraction inlet is connected to the C4 fraction outlet, and the propane inlet is connected to the propane outlet.

[0033] Furthermore, the separation and recovery system also includes a pressure swing adsorption device, which is provided with a hydrogen inlet and a hydrogen recovery outlet, and the hydrogen inlet is connected to the hydrogen outlet.

[0034] Furthermore, the fifth distillation device is also provided with a carbon monoxide outlet; the separation and recovery system also includes a hydrogen production device for reacting carbon monoxide with water to generate regenerated hydrogen, and the hydrogen production device is provided with a carbon monoxide inlet and a regenerated hydrogen outlet; the carbon monoxide inlet is connected to the carbon monoxide outlet.

[0035] By applying the technical scheme of the present invention, the first distillation device is used to cut the Fischer-Tropsch synthesis tail gas, so that the C5+ fraction can be separated from the first mixture of the above-mentioned specific components; the second distillation device is used to cut the first mixture, so that the C4 fraction can be separated from the second mixture of the above-mentioned specific components; the third distillation device is used to cut the second mixture, so that the C3 fraction can be separated from the third mixture of the above-mentioned specific components; the fourth distillation device is used to cut the third mixture, so that the C2 fraction can be separated from the fourth mixture of the above-mentioned specific components, wherein the fourth distillation device is a first distillation tower, which can enrich methane in the fourth mixture, so as to facilitate subsequent processing steps; the fourth mixture is dehydrogenated by a dehydrogenation device, so that the fifth mixture can be separated from hydrogen; the fifth mixture containing methane is separated and purified by a fifth distillation device, so that methane can be separated from CO and N2 in the fifth mixture, so as to obtain the target product methane for forming an LNG product; before the second mixture or the third mixture is cut, the second mixture or the third mixture is decarbonized and dried by a decarbonization drying unit, so as to reduce the content of carbon dioxide and water in the second mixture or the third mixture. The traditional separation and recovery methods do not treat the C 5+ The heavy hydrocarbon components are pretreated (removed) and directly sent to the separation and recovery system, which can easily cause foaming in the decarbonization system and freeze-blocking of the cryogenic separation unit during operation. Compared with traditional methods, the above-mentioned separation and recovery method of the present application can inhibit the generation of bubbles in the decarbonization process, reduce the risk of freezing, improve processing efficiency, and reduce energy consumption, thereby reducing downstream equipment investment.

[0036] Compared with the existing separation and recovery methods of Fischer-Tropsch synthesis tail gas, the separation and recovery method provided in the present application can recover methane with high purity and high recovery rate, and can improve the economic value of Fischer-Tropsch synthesis tail gas. The fourth distillation device is a first distillation tower, and the top pressure and top temperature of the first distillation tower include but are not limited to the above ranges. Limiting it to the specific range of the present application can improve the recovery rate of methane, thereby improving the economic value of Fischer-Tropsch synthesis tail gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 A schematic structural diagram of a Fischer-Tropsch synthesis tail gas separation and recovery system in a preferred embodiment is shown.

[0039] The above drawings include the following reference numerals:

[0040] 100, first distillation device; 200, second distillation device; 300, third distillation device; 400, fourth distillation device; 500, dehydrogenation device; 600, fifth distillation device; 700, decarbonization and drying unit; 710, decarbonization device; 720, drying device; 800, sixth distillation device; 900, seventh distillation device; 1000, mixing device; 1100, pressure swing adsorption device; 1200, hydrogen production device. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] As described in the background technology, the existing separation and recovery methods of Fischer-Tropsch synthesis tail gas have the problem of low methane recovery rate. In order to solve the above technical problems, the first aspect of the present application provides a separation and recovery method for Fischer-Tropsch synthesis tail gas, which separation and recovery method includes: step S1, using a first distillation device to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture containing C4-fraction and hydrogen, and a C5+ fraction; step S2, using a second distillation device to cut the first mixture to obtain a second mixture containing C3-fraction and hydrogen, and a C4 fraction; step S3, using a third distillation device to cut the second mixture to obtain a third mixture containing C2-fraction and hydrogen, and a C3 fraction; step S4, using a fourth distillation device to cut the third mixture to obtain a C1-fraction and hydrogen. a fourth mixture, and a C2 fraction; the fourth distillation device is a first distillation tower, the top pressure of the first distillation tower is 2.0 to 4.0 MPa, and the top temperature is -141 to -131°C; step S5, using a dehydrogenation device to dehydrogenate the fourth mixture to obtain a fifth mixture and hydrogen, wherein the fifth mixture includes methane; step S6, using a fifth distillation device to separate and purify the fifth mixture to obtain methane; the separation and recovery method also includes: before cutting the second mixture or the third mixture, using a decarbonization drying unit to decarbonize and dry the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture.

[0043] Cutting the Fischer-Tropsch synthesis tail gas with a first distillation device can separate the C5+ fraction from the first mixture of the above-mentioned specific components; cutting the first mixture with a second distillation device can separate the C4 fraction from the second mixture of the above-mentioned specific components; cutting the second mixture with a third distillation device can separate the C3 fraction from the third mixture of the above-mentioned specific components; cutting the third mixture with a fourth distillation device can separate the C2 fraction from the fourth mixture of the above-mentioned specific components, wherein the fourth distillation device is a first distillation tower, which can enrich methane in the fourth mixture, thereby facilitating subsequent processing steps; dehydrogenating the fourth mixture with a dehydrogenation device can separate the fifth mixture from hydrogen; separating and purifying the fifth mixture containing methane with a fifth distillation device can separate methane from CO and N2 in the fifth mixture, thereby obtaining the target product methane for forming an LNG product; before cutting the second mixture or the third mixture, decarbonizing and drying the second mixture or the third mixture with a decarbonization and drying unit can reduce the content of carbon dioxide and water in the second mixture or the third mixture. The traditional separation and recovery methods do not treat the C 5+The heavy hydrocarbon components are pretreated (removed) and directly sent to the separation and recovery system, which can easily cause foaming in the decarbonization system and freeze-blocking of the cryogenic separation unit during operation. Compared with traditional methods, the above-mentioned separation and recovery method of the present application can inhibit the generation of bubbles in the decarbonization process, reduce the risk of freezing, improve processing efficiency, and reduce energy consumption, thereby reducing downstream equipment investment.

[0044] Compared with the existing separation and recovery methods of Fischer-Tropsch synthesis tail gas, the separation and recovery method provided in the present application can recover methane with high purity and high recovery rate, and can improve the economic value of Fischer-Tropsch synthesis tail gas. The fourth distillation device is a first distillation tower, and the top pressure and top temperature of the first distillation tower include but are not limited to the above ranges. Limiting it to the specific range of the present application can improve the recovery rate of methane, thereby improving the economic value of Fischer-Tropsch synthesis tail gas.

[0045] In order to further improve the recovery rate of methane and thus further improve the economic value of the Fischer-Tropsch synthesis tail gas, in a preferred embodiment, the top pressure of the first distillation tower is 2.5 to 3.0 MPa, and the top temperature is -138 to -135°C.

[0046] In a preferred embodiment, the Fischer-Tropsch synthesis tail gas includes 30-50 mol% CH4, 20-40 mol% H2, 2-20 mol% N2, 10-20 mol% CO, and the rest includes one or more of CO2, C2 component, C3 component, C4 component, and C5+ component. The above method provided in the present application is particularly suitable for Fischer-Tropsch synthesis tail gas containing the above specific components and contents, so as to facilitate the acquisition of methane with higher purity and recovery rate.

[0047] In a preferred embodiment, the third distillation device is a second distillation tower, the tower top pressure of the second distillation tower is 1.5-2.0 MPa, and the tower top temperature is -96--92° C. The various process parameters in step S3 include but are not limited to the above ranges, and limiting them within the above ranges is conducive to improving the separation efficiency of the third mixture and the C3 fraction, thereby facilitating the subsequent recovery rate and purity of propylene, and improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0048] In order to further improve the separation efficiency of the third mixture and the C3 fraction, and further improve the subsequent recovery rate and purity of propylene, preferably, the top pressure of the second distillation tower is 1.7 to 1.8 MPa, and the top temperature is -94 to -93°C.

[0049] In a preferred embodiment, the dehydrogenation device is a dehydrogenation tower, the tower top pressure of the dehydrogenation tower is 1.8-2.0 MPa, and the tower top temperature is -200--180° C. The various process parameters in step S5 include but are not limited to the above ranges, and limiting them within the above ranges is conducive to improving the separation efficiency of the fifth mixture and hydrogen, thereby facilitating the recovery rate and purity of hydrogen, and improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0050] In order to improve the separation efficiency of methane and CO and N2 in the mixture, further improve the purity and recovery rate of methane, and further improve the economic value of Fischer-Tropsch synthesis tail gas, in a preferred embodiment, the fifth distillation device is a third distillation tower, the top pressure of the third distillation tower is 0.5 to 1.8 MPa, and the top temperature is -180 to -160°C.

[0051] In a preferred embodiment, the decarbonization process is carried out by the alcohol amine method. In the present application, the alcohol amine method refers to the use of an alkaline amine-based solvent to react chemically with the acidic gas (such as CO2) in the second mixture or the third mixture to absorb CO2, thereby removing CO2. The main process flow of the alcohol amine method is: under the condition of normal temperature and pressure, the alkaline amine liquid is reacted with the acidic gas, and then the process conditions are changed to regenerate under low pressure and temperature conditions. This method has a large acid gas load for the treated gas, a strong selectivity for acidic gases, and the solvent has a very low solubility in hydrocarbons.

[0052] In order to further reduce the risk of freezing and blockage and reduce energy consumption, in a preferred embodiment, the carbon dioxide content in the decarbonized drying product obtained after the second mixture or the third mixture is decarbonized and dried is ≤20ppm.

[0053] In order to increase the load of acid gas in the second mixture or the third mixture, improve the selectivity of acid gas and reduce the solubility of solvent to hydrocarbons, reduce investment and make the operation simple and safe, preferably, the decarbonization process is carried out at 20-40°C and 3-4MPa. In addition, the alkaline amine-based solvent can be regenerated by changing the process conditions. For example, the absorbed CO2 can be easily desorbed under low pressure and temperature conditions, thereby regenerating the alkaline amine-based solvent.

[0054] In a preferred embodiment, the alkaline amine-based solvent includes, but is not limited to, one or more of the group consisting of N-methyldiethanolamine (MDEA), diethanolamine (DEA) and ethanolamine (MEA).

[0055] In a preferred embodiment, the first distillation device is a fourth distillation tower, the top pressure of the fourth distillation tower is 2.2-2.4 MPa, and the top temperature is -52--50° C. The process parameters in step S1 include but are not limited to the above ranges, and limiting them within the above ranges is conducive to improving the separation efficiency of the first mixture and the C5+ fraction, thereby helping to improve the economic value of the Fischer-Tropsch synthesis tail gas.

[0056] In a preferred embodiment, the second distillation device is a fifth distillation tower, the top pressure of the fifth distillation tower is 1.88-1.98 MPa, and the top temperature is -75--72° C. The process parameters in step S2 include but are not limited to the above ranges, and limiting them within the above ranges is conducive to improving the separation efficiency of the second mixture and the C4 fraction, thereby facilitating the subsequent recovery rate and purity of the liquefied petroleum gas and the economic value of the Fischer-Tropsch synthesis tail gas.

[0057] In a preferred embodiment, the separation and recovery method further comprises: using a sixth distillation device to cut the C3 fraction obtained in step S3 to obtain propylene and propane. The above-mentioned cutting process is conducive to separating propylene and propane, thereby obtaining a propylene product, which is conducive to improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0058] In order to facilitate the delivery of the C3 fraction with a lower pressure to the sixth distillation unit, in a preferred embodiment, before the C3 fraction is cut, a boosting device is used to boost the pressure of the C3 fraction and deliver it to the sixth distillation unit for the above-mentioned cutting process. Preferably, the pressure of the boosting device is 2.15-2.3 MPa.

[0059] In order to further improve the separation efficiency of propylene and propane, improve the recovery rate of propylene products, and thus further improve the economic value of Fischer-Tropsch synthesis tail gas, preferably, the sixth distillation device is a sixth distillation tower, the top pressure of the sixth distillation tower is 2.00-2.13 MPa, and the top temperature is 50-55°C.

[0060] In a preferred embodiment, the separation and recovery method further comprises: mixing propane with the C4 fraction to obtain liquefied petroleum gas. Mixing propane with the C4 fraction can obtain liquefied petroleum gas, which is conducive to converting the above components into products and improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0061] In a preferred embodiment, the separation and recovery method further comprises: using the seventh distillation device to cut the C2 fraction obtained in step S4 to obtain ethylene and ethane. The above method can separate ethylene and ethane to obtain ethylene products and ethane products, which is beneficial to improving the economic value of the tail gas from the Fischer-Tropsch synthesis. In addition, the fuel gas pipeline network is an indispensable public engineering system in the production process, which mainly transports fuel gas to the heating furnaces and power boilers of each production unit. The ethane product obtained by the above method can be incorporated into the fuel gas pipeline network, which is beneficial to use ethane as a high-quality fuel by virtue of its high calorific value on the one hand, and on the other hand, it is beneficial to avoid energy waste.

[0062] In order to further improve the separation efficiency of ethylene and ethane, preferably, the seventh distillation device is a seventh distillation tower, the tower top pressure of the seventh distillation tower is 1.0-2.0 MPa, and the tower top temperature is -36--32° C. In the step of separating ethylene and ethane, various process parameters include but are not limited to the above ranges, and limiting them within the above ranges is conducive to further improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0063] In a preferred embodiment, the separation and recovery method further comprises performing pressure swing adsorption treatment on the hydrogen obtained in step S5 to obtain recovered hydrogen. Pressure swing adsorption treatment refers to the process of separating high-purity hydrogen from a hydrogen-containing mixed gas by utilizing the principle that an adsorbent has different adsorption affinities for different gas components.

[0064] In order to improve the recovery rate and purity of the hydrogen obtained in step S5 and reduce the small amount of N2 and CO mixed therein, in a preferred embodiment, a compression device is used to compress the hydrogen obtained in step S5 to obtain compressed hydrogen and a mixture of N2 and CO; the compressed hydrogen is subjected to pressure swing adsorption treatment to obtain recovered hydrogen. The recovered hydrogen can be used for the preparation of Fischer-Tropsch synthetic oil, thereby helping to reduce the production cost of Fischer-Tropsch synthetic oil.

[0065] In order to improve the recovery rate and purity of hydrogen, preferably, the hydrogen obtained in step S5 is pressurized to 3.2-3.4 MPa and then passed into a pressure swing adsorption device for pressure swing adsorption treatment to obtain recovered hydrogen.

[0066] In a preferred embodiment, the pressure of the pressure swing adsorption treatment is 3-4 MPa and the temperature is 20-40° C. The various process parameters in the pressure swing adsorption treatment include but are not limited to the above ranges, and limiting them within the above ranges is conducive to improving the recovery rate and purity of hydrogen, thereby helping to improve the economic value of the Fischer-Tropsch synthesis tail gas.

[0067] In a preferred embodiment, in step S6, carbon monoxide gas is obtained after separation and purification of the fifth mixture, and the above-mentioned separation and recovery method of the present application also includes passing the carbon monoxide gas into a hydrogen production device to react with water to obtain regenerated hydrogen. In the hydrogen production device, under the action of a catalyst, CO and water vapor undergo a series of chemical reactions to generate hydrogen and carbon dioxide. The hydrogen produced by the above method can be used to prepare Fischer-Tropsch synthetic oil, which is beneficial to reduce the production cost of Fischer-Tropsch synthetic oil. In another preferred embodiment, the above-mentioned carbon monoxide-rich gas is used for dryer regeneration after steam heating, and then incorporated into the fuel supply device as a heat exchange medium. Dryer regeneration principle: After the adsorbent is saturated, the adsorbent is regenerated using regeneration gas to restore its adsorption capacity. Carbon monoxide-rich gas (mainly carbon monoxide and nitrogen components) can be used as regeneration gas, which is used for dryer regeneration after steam heating to restore the molecular sieve's ability to adsorb water.

[0068] The second aspect of the present application also provides a separation and recovery system for implementing the above separation and recovery method provided by the present application, such as Figure 1As shown, the separation and recovery system includes a first distillation device 100, a second distillation device 200, a third distillation device 300, a fourth distillation device 400, a dehydrogenation device 500 and a fifth distillation device 600 which are connected in sequence. The first distillation device 100 is used to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture and a C5+ fraction; the first distillation device 100 is provided with a Fischer-Tropsch synthesis tail gas inlet, a first mixture outlet and a C5+ fraction outlet; the second distillation device 200 is used to cut the first mixture to obtain a second mixture and a C4 fraction; the second distillation device 200 is provided with a first mixture inlet, a second mixture outlet and a C4 fraction outlet; the third distillation device 300 is used to cut the second mixture to obtain a third mixture and a C3 fraction; the third distillation device 300 is provided with a second mixture inlet, a third mixture outlet and a C3 fraction outlet; the fourth distillation device 400 is used to cut the third mixture to obtain a fourth mixture and a C2 fraction; the fourth distillation device 400 is provided with a third mixture inlet, a fourth mixture outlet and a C2 fraction. outlet; the fourth distillation device 400 is a first distillation tower; the dehydrogenation device 500 is used to dehydrogenate the fourth mixture to obtain a fifth mixture and hydrogen, wherein the fifth mixture includes methane; the dehydrogenation device 500 is provided with a fourth mixture inlet, a fifth mixture outlet and a hydrogen outlet; the fifth distillation device 600 is used to separate and purify the fifth mixture to obtain methane, and the fifth distillation device 600 is provided with a fifth mixture inlet and a methane outlet, and the fifth mixture inlet is connected to the fifth mixture outlet; the separation and recovery system also includes a decarbonization drying unit 700, which is used to decarbonize and dry the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture; the decarbonization drying unit 700 includes a decarbonization device 710 and a drying device 720 which are connected in sequence.

[0069] The first distillation device 100 is configured to separate the first mixture and the C5+ fraction in the Fischer-Tropsch synthesis tail gas, and obtain corresponding cut products at the first mixture outlet and the C5+ fraction outlet; the first mixture is transported to the second distillation device 200, and is cut in the second distillation device 200 to obtain a second mixture and a C4 fraction, and corresponding cut products are obtained at the second mixture outlet and the C4 fraction outlet; the second mixture is transported to the third distillation device 300, and is cut in the third distillation device 300 to obtain a third mixture and a C3 fraction, and corresponding cut products are obtained at the third mixture outlet and the C3 fraction outlet; the third mixture is transported to the fourth distillation device 400 (specifically, the first distillation tower), and the third mixture is cut in the fourth distillation device 400 (specifically, the first distillation tower). A fourth mixture and a C2 fraction are obtained by cutting, and corresponding cutting products are obtained at the fourth mixture outlet and the C2 fraction outlet; the setting of the dehydrogenation device 500 can separate hydrogen from the fourth mixture to obtain a fifth mixture and hydrogen, and the fifth mixture is transported to the fifth distillation device 600, and is separated and purified in the fifth distillation device 600 to obtain the target product methane, wherein the second mixture or the third mixture is transported to the decarbonization drying unit 700 before being cut, and is decarbonized and dried in the decarbonization drying unit 700 to reduce the content of carbon dioxide and water. The setting of the decarbonization drying unit 700 can suppress the freezing problem of the deep cold separation unit in the separation and recovery process of the Fischer-Tropsch synthesis tail gas, thereby ensuring the smooth progress of the separation and recovery process of the Fischer-Tropsch synthesis tail gas.

[0070] Compared with the existing separation and recovery system for Fischer-Tropsch synthesis tail gas, the separation and recovery system provided in the present application can recover methane with high purity and high recovery rate, and can improve the economic value of the Fischer-Tropsch synthesis tail gas.

[0071] In a preferred embodiment, the inner cavity of the drying device 720 is filled with molecular sieves, which is conducive to the rapid removal of moisture, making the production process more efficient and helping to reduce harm to the environment and human body.

[0072] In order to improve the removal rate of water in the second mixture or the third mixture, preferably, the molecular sieve includes but is not limited to one or more of type 3A molecular sieve, type 4A molecular sieve and type 5A molecular sieve.

[0073] In a preferred embodiment, the molecular sieve is filled in an amount of 30-50% based on the total volume of the inner cavity of the drying device 720. The molecular sieve filling amount includes but is not limited to the above range, and limiting it within the above range is conducive to further improving the water removal rate in the second mixture or the third mixture.

[0074] In a preferred embodiment, the separation and recovery system further comprises a sixth distillation device 800; the sixth distillation device 800 is provided with a C3 fraction inlet, a propylene outlet and a propane outlet, the C3 fraction inlet is connected to the C3 fraction outlet, and the sixth distillation device 800 is used to cut the C3 fraction obtained in step S3 to obtain propane and propylene. The setting of the sixth distillation device 800 is conducive to improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0075] In a preferred embodiment, the separation and recovery system further comprises a seventh distillation device 900, which is provided with a C2 fraction inlet, an ethylene outlet and an ethane outlet, the C2 fraction inlet is connected to the C2 fraction outlet, and the seventh distillation device 900 is used to cut the C2 fraction obtained in step S4 to obtain ethylene and ethane. The setting of the seventh distillation device 900 is conducive to improving the economic value of the Fischer-Tropsch synthesis tail gas.

[0076] In order to further improve the economic value of the Fischer-Tropsch synthesis tail gas, preferably, the separation and recovery system also includes a mixing device 1000 for mixing propane with the C4 fraction to obtain liquefied petroleum gas. The mixing device 1000 is provided with a propane inlet, a C4 fraction inlet and a liquefied petroleum gas outlet. The C4 fraction inlet is connected to the C4 fraction outlet, and the propane inlet is connected to the propane outlet.

[0077] In a preferred embodiment, the separation and recovery system further comprises a pressure swing adsorption device 1100, which is provided with a hydrogen inlet and a recovered hydrogen outlet, and the hydrogen inlet is connected to the hydrogen outlet. The setting of the pressure swing adsorption device is conducive to improving the recovery rate and purity of hydrogen. At the same time, the recovered hydrogen obtained from the recovered hydrogen outlet can be used for the preparation of Fischer-Tropsch synthetic oil, thereby helping to reduce the production cost of Fischer-Tropsch synthetic oil.

[0078] In a preferred embodiment, the fifth distillation device 600 is also provided with a carbon monoxide outlet; the separation and recovery system of the present application further includes a hydrogen production device 1200, which is used to react carbon monoxide with water to generate regenerated hydrogen, and the hydrogen production device is provided with a carbon monoxide inlet and a regenerated hydrogen outlet; the carbon monoxide inlet is connected to the carbon monoxide outlet. The setting of the hydrogen production device is conducive to the recycling of the obtained carbon monoxide, thereby helping to reduce the waste of resources and air pollution. At the same time, the obtained regenerated hydrogen can be used to prepare Fischer-Tropsch synthetic oil, thereby helping to reduce the production cost of Fischer-Tropsch synthetic oil.

[0079] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0080] Example 1

[0081] The Fischer-Tropsch synthesis tail gas in Example 1 is a non-permeate gas after membrane separation treatment. In terms of molar percentage, the Fischer-Tropsch synthesis tail gas includes 40 mol% CH4, 30 mol% H2, 8 mol% N2, 20 mol% CO, and the rest are CO2, C2 components, C3 components, C4 components and C5+ components.

[0082] A method for separating and recovering Fischer-Tropsch synthesis tail gas, the separation and recovery method adopts Figure 1 The separation and recovery system shown is carried out, including:

[0083] (1) using a fourth distillation tower to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture containing a C4- fraction and hydrogen, and a C5+ fraction; wherein the top pressure of the fourth distillation tower is 2.2 MPa, the top temperature is -52°C, and the bottom temperature is 158°C;

[0084] (2) using a fifth distillation tower to cut the first mixture to obtain a second mixture containing a C3- fraction and hydrogen, and a C4 fraction; wherein the top pressure of the fifth distillation tower is 1.98 MPa, the top temperature is -72°C, and the bottom temperature is 100°C;

[0085] (3) using a second distillation tower to cut the second mixture to obtain a third mixture containing a C2-fraction and hydrogen, and a C3 fraction; wherein the top pressure of the second distillation tower is 1.5 MPa, the top temperature is -96°C, and the bottom temperature is 45°C; then, N-methyldiethanolamine (MDEA) is contacted with the third mixture in a decarbonization device at 25°C and 3.4 MPa to react to obtain a decarbonized third mixture having a carbon dioxide content of less than or equal to 20 ppm, and then the decarbonized third mixture is contacted with a 5A zeolite molecular sieve having a filling amount of 45% in a drying device to obtain a decarbonized and dried third mixture having a moisture content of 1 ppm;

[0086] (4) using a first distillation tower to cut the third mixture after decarbonization and drying to obtain a fourth mixture containing a C1 fraction and hydrogen, and a C2 fraction; wherein the top pressure of the first distillation tower is 2.5 MPa, the top temperature is -138° C., and the bottom temperature is 5° C.;

[0087] (5) dehydrogenating the fourth mixture using a dehydrogenation tower to obtain a fifth mixture and hydrogen; wherein the top pressure of the dehydrogenation tower is 1.9 MPa, the top temperature is -190° C., and the bottom temperature is -160° C.;

[0088] (6) Using a third distillation tower to separate and purify the fifth mixture to obtain methane; wherein the top pressure of the third distillation tower is 0.5 MPa, the top temperature is -180°C, and the bottom temperature is -140°C.

[0089] Example 2

[0090] The difference from Example 1 is that the third mixture in step (3) is not subjected to decarbonization and drying treatment, and the second mixture in step (2) is subjected to decarbonization and drying treatment, and then cut by a second distillation tower.

[0091] Example 3

[0092] The difference from Example 1 is that in step (4), the top pressure of the first distillation tower is 2.0 MPa and the top temperature is -141°C.

[0093] Example 4

[0094] The difference from Example 1 is that in step (4), the top pressure of the first distillation tower is 4.0 MPa and the top temperature is -131°C.

[0095] Example 5

[0096] The difference from Example 1 is that in step (5), the top pressure of the dehydrogenation tower is 1.8 MPa, the top temperature is -200°C, and the bottom temperature is -140°C.

[0097] Example 6

[0098] The difference from Example 1 is that in step (5), the top pressure of the dehydrogenation tower is 2.0 MPa, the top temperature is -180°C, and the bottom temperature is -150°C.

[0099] Example 7

[0100] The difference from Example 1 is that in step (5), the top pressure of the dehydrogenation tower is 2.1 MPa and the top temperature is -178°C.

[0101] Example 8

[0102] The difference from Example 1 is that the top pressure of the third distillation tower is 1.8 MPa, the top temperature is -160°C, and the bottom temperature is -140°C.

[0103] Example 9

[0104] The difference from Example 1 is that the top pressure of the third distillation tower is 1.9 MPa and the top temperature is -158°C.

[0105] Example 10

[0106] The difference from Example 1 is that in step (1), the top pressure of the fourth distillation tower is 2.4 MPa, the top temperature is -50°C, and the bottom temperature is 157°C.

[0107] Embodiment 11

[0108] The difference from Example 1 is that in step (2), the top pressure of the fifth distillation tower is 1.88 MPa, the top temperature is -75°C, and the bottom temperature is 106°C.

[0109] Example 12

[0110] The difference from Example 1 is that the C3 fraction obtained in step (3) is pressurized by a booster pump and sent to the sixth distillation tower, the pressure of the booster pump is set to 2.2 MPa, and the C3 fraction obtained in step (3) is cut by the sixth distillation tower to obtain propylene and propane; wherein the top pressure of the sixth distillation tower is 2.0 MPa, the top temperature is 50°C, and the bottom temperature is 53°C.

[0111] Embodiment 13

[0112] The difference from Example 1 is that the C2 fraction obtained in step (4) is cut using a seventh distillation tower to obtain ethylene and ethane; wherein the top pressure of the seventh distillation tower is 1.0 MPa, the top temperature is -36°C, and the bottom temperature is -30°C.

[0113] Comparative Example 1

[0114] The difference from Example 1 is that the top pressure of the first distillation tower is 4.1 MPa and the top temperature is -130°C.

[0115] The methane recovery rate, hydrogen recovery rate and energy consumption of the cryogenic separation unit obtained in all the above examples and comparative examples of the present application are summarized in Table 1, wherein it should be noted that the cryogenic separation unit in the present application refers to the first distillation tower, the dehydrogenation tower and the third distillation tower. The cooling medium of the cryogenic separation unit is liquid nitrogen, which is generally used for low-temperature refrigeration and has a temperature of -196°C.

[0116] Table 1

[0117]

[0118] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: compared with the existing separation and recovery methods of Fischer-Tropsch synthesis tail gas, the above separation and recovery method provided by the present application can recover methane with high purity and high recovery rate, and can improve the economic value of Fischer-Tropsch synthesis tail gas. The fourth distillation device 400 is a first distillation tower, and the top pressure and top temperature of the first distillation tower include but are not limited to the above ranges of the present application. Limiting it to the specific range of the present application is conducive to improving the recovery rate of methane, thereby helping to improve the economic value of Fischer-Tropsch synthesis tail gas.

[0119] Compared with Example 1 in which the third mixture in step (3) is subjected to decarbonization and drying, the energy consumption of the cryogenic separation unit in Example 2 in which the second mixture in step (2) is subjected to decarbonization and drying increases by 36.8%.

[0120] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0121] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for separating and recovering Fischer-Tropsch synthesis tail gas, characterized in that: The separation and recovery method comprises: Step S1, using a first distillation device to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture containing a C4- fraction and hydrogen, and a C5+ fraction; Step S2, cutting the first mixture using a second distillation device to obtain a second mixture containing a C3- fraction and hydrogen, and a C4 fraction; Step S3, using a third distillation device to cut the second mixture to obtain a third mixture containing a C2- fraction and hydrogen, and a C3 fraction; Step S4, cutting the third mixture by a fourth distillation device to obtain a fourth mixture containing a C1 fraction and hydrogen, and a C2 fraction; the fourth distillation device is a first distillation tower, the tower top pressure of the first distillation tower is 2.0 to 4.0 MPa, and the tower top temperature is -141 to -131°C; Step S5, using a dehydrogenation device to dehydrogenate the fourth mixture to obtain a fifth mixture and hydrogen; wherein the fifth mixture includes methane; Step S6, separating and purifying the fifth mixture using a fifth distillation device to obtain methane; The separation and recovery method further includes: before cutting the second mixture or the third mixture, using a decarbonization drying unit to perform decarbonization and drying treatment on the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture.

2. The method for separating and recovering Fischer-Tropsch synthesis tail gas according to claim 1, characterized in that: The tower top pressure of the first distillation tower is 2.5-3.0 MPa, and the tower top temperature is -138--135°C; and / or, Calculated by molar percentage of the Fischer-Tropsch synthesis tail gas, the Fischer-Tropsch synthesis tail gas includes 30-50 mol% CH4, 20-40 mol% H2, 2-20 mol% N2, 10-20 mol% CO, and the rest includes one or more of CO2, C2 components, C3 components, C4 components and C5+ components.

3. The method for separating and recovering Fischer-Tropsch synthesis tail gas according to claim 1 or 2, characterized in that: The third distillation device is a second distillation tower, the tower top pressure of the second distillation tower is 1.5-2.0 MPa, and the tower top temperature is -96--92°C; Preferably, the top pressure of the second distillation tower is 1.7 to 1.8 MPa, and the top temperature is -94 to -93°C; Preferably, the dehydrogenation device is a dehydrogenation tower, the top pressure of the dehydrogenation tower is 1.8 to 2.0 MPa, and the top temperature is -200 to -180°C; Preferably, the fifth distillation device is a third distillation tower, the top pressure of the third distillation tower is 0.5 to 1.8 MPa, and the top temperature is -180 to -160°C; Preferably, the decarbonization process is carried out by an alcoholamine method; Preferably, the carbon dioxide content in the decarbonized and dried product obtained after the decarbonization and drying treatment of the second mixture or the third mixture is ≤20 ppm.

4. The method for separating and recovering Fischer-Tropsch synthesis tail gas according to any one of claims 1 to 3, characterized in that: The first distillation device is a fourth distillation tower, the top pressure of the fourth distillation tower is 2.2 to 2.4 MPa, and the top temperature is -52 to -50°C; Preferably, the second distillation device is a fifth distillation tower, the top pressure of the fifth distillation tower is 1.88 to 1.98 MPa, and the top temperature is -75 to -72°C; Preferably, the separation and recovery method further comprises: using a sixth distillation device to cut the C3 fraction obtained in step S3 to obtain propylene and propane; Preferably, the sixth distillation device is a sixth distillation tower, the tower top pressure of the sixth distillation tower is 2.00-2.13 MPa, and the tower top temperature is 50-55° C.; Preferably, the separation and recovery method further comprises: mixing the propane with the C4 fraction to obtain liquefied petroleum gas.

5. The method for separating and recovering Fischer-Tropsch synthesis tail gas according to any one of claims 1 to 4, characterized in that: The separation and recovery method further comprises: using a seventh distillation device to cut the C2 fraction obtained in step S4 to obtain ethylene and ethane; Preferably, the seventh distillation device is a seventh distillation tower, the tower top pressure of the seventh distillation tower is 1.0 to 2.0 MPa, and the tower top temperature is -36 to -32°C; Preferably, the separation and recovery method further comprises performing pressure swing adsorption treatment on the hydrogen obtained in step S5 to obtain recovered hydrogen; Preferably, the pressure of the pressure swing adsorption treatment is 3-4 MPa and the temperature is 20-40°C; Preferably, carbon monoxide gas is also obtained in step S6, and the separation and recovery method further comprises passing the carbon monoxide gas into a hydrogen production device to react with water to obtain regenerated hydrogen.

6. A separation and recovery system for implementing the separation and recovery method according to any one of claims 1 to 5, characterized in that: The separation and recovery system comprises: A first distillation device (100) is used to cut the Fischer-Tropsch synthesis tail gas to obtain a first mixture and a C5+ fraction; the first distillation device (100) is provided with a Fischer-Tropsch synthesis tail gas inlet, a first mixture outlet and a C5+ fraction outlet; A second distillation device (200) is used to cut the first mixture to obtain a second mixture and a C4 fraction; the second distillation device (200) is provided with a first mixture inlet, a second mixture outlet and a C4 fraction outlet; A third distillation device (300) is used to cut the second mixture to obtain a third mixture and a C3 fraction; the third distillation device (300) is provided with a second mixture inlet, a third mixture outlet and a C3 fraction outlet; a fourth distillation device (400), used for cutting the third mixture to obtain a fourth mixture and a C2 fraction; the fourth distillation device (400) is provided with a third mixture inlet, a fourth mixture outlet and a C2 fraction outlet; the fourth distillation device is a first distillation tower; A dehydrogenation device (500) is used to perform a dehydrogenation treatment on the fourth mixture to obtain a fifth mixture and hydrogen, wherein the fifth mixture includes methane; the dehydrogenation device (500) is provided with a fourth mixture inlet, a fifth mixture outlet and a hydrogen outlet; a fifth distillation device (600), used for separating and purifying the fifth mixture to obtain methane, the fifth distillation device (600) being provided with a fifth mixture inlet and a methane outlet, the fifth mixture inlet being in communication with the fifth mixture outlet; The separation and recovery system also includes a decarbonization and drying unit (700) for performing a decarbonization and drying treatment on the second mixture or the third mixture to reduce the content of carbon dioxide and water in the second mixture or the third mixture; the decarbonization and drying unit (700) includes a decarbonization device (710) and a drying device (720) which are connected in sequence.

7. The Fischer-Tropsch synthesis tail gas separation and recovery system according to claim 6, characterized in that: The inner cavity of the drying device (720) is filled with a molecular sieve; Preferably, the molecular sieve is selected from one or more of type 3A molecular sieve, type 4A molecular sieve and type 5A molecular sieve; More preferably, the filling amount of the molecular sieve is 30-50% based on the total volume of the inner cavity of the drying device (720).

8. The Fischer-Tropsch synthesis tail gas separation and recovery system according to claim 6 or 7, characterized in that: The separation and recovery system further comprises a sixth distillation device (800), wherein the sixth distillation device (800) is provided with a C3 fraction inlet, a propylene outlet and a propane outlet, wherein the C3 fraction inlet is connected to the C3 fraction outlet; and / or, The separation and recovery system further comprises a seventh distillation device (900), wherein the seventh distillation device (900) is provided with a C2 fraction inlet, an ethylene outlet and an ethane outlet, wherein the C2 fraction inlet is connected to the C2 fraction outlet; Preferably, the separation and recovery system further comprises a mixing device (1000) for mixing the propane with the C4 fraction to obtain liquefied petroleum gas, the mixing device (1000) being provided with a propane inlet, a C4 fraction inlet and a liquefied petroleum gas outlet, the C4 fraction inlet being connected to the C4 fraction outlet, and the propane inlet being connected to the propane outlet.

9. The separation and recovery system of Fischer-Tropsch synthesis tail gas according to any one of claims 6 to 8, characterized in that: The separation and recovery system further comprises a pressure swing adsorption device (1100), wherein the pressure swing adsorption device (1100) is provided with a hydrogen inlet and a hydrogen recovery outlet, wherein the hydrogen inlet is in communication with the hydrogen outlet.

10. The Fischer-Tropsch synthesis tail gas separation and recovery system according to claim 7, characterized in that: The fifth distillation device (600) is also provided with a carbon monoxide outlet; the separation and recovery system also includes a hydrogen production device (1200) for reacting carbon monoxide with water to generate regenerated hydrogen, and the hydrogen production device (1200) is provided with a carbon monoxide inlet and a regenerated hydrogen outlet; the carbon monoxide inlet is connected to the carbon monoxide outlet.

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