Device and method for purifying and separating feed gas containing olefin and alkyne

Abstract

The invention discloses a device and a method for purifying and separating feed gas containing olefin and alkyne, and belongs to the technical field of cryogenic separation. The device comprises an MDEA decarburization device, a temperature swing adsorption device, a cryogenic separation cold box, an LPG rectifying tower and a refrigerant compression device, wherein the refrigerant compression device provides cooling capacity for the cryogenic separation cold box. The MDEA decarburization device receives feed gas containing olefin and alkyne, and CO2 in the feed gas is removed. The first temperature swing adsorption device is connected with the MDEA decarbonization device; after water in the raw material gas is removed for the first time, the raw material gas sequentially passes through the heat exchanger I, the washing tower and the LPG rectifying tower through pipelines and then returns to the MDEA decarbonization device; the second temperature swing adsorption device is connected with the MDEA decarburization device, and after water in the raw material gas is removed for the second time, the raw material gas sequentially passes through the first heat exchanger, the LNG rectifying tower, the second heat exchanger and the first heat exchanger through pipelines and then leaves the cryogenic separation cold box. Two times of MDEA decarburization are adopted, the CO2 concentration is reduced, two times of temperature swing adsorption dehydration are coupled at the same time, and then hydrogen-rich gas and LNG co-production is achieved in the cryogenic separation cold box.

Description

Technical Field

[0001] The present invention belongs to the technical field of cryogenic separation, and particularly relates to a purification and separation device and method for raw material gas containing olefins and alkynes. Background Art

[0002] Synthesis tail gas is a product obtained after coal gas conversion or natural gas conversion. At the same time, it is also a raw material gas in various chemical processes, such as in chemical processes like methanol synthesis, ammonia synthesis, ethylene glycol synthesis, acetic acid synthesis, polyglycolic acid, dimethylformamide, etc. Before the synthesis tail gas enters various devices, it needs to be separated and treated. Depending on different situations, the separation means and technologies used are very different. Cryogenic separation is a process that uses low-temperature technology to separate different components in a mixed gas, and is mainly applied in fields such as natural gas treatment, air separation, and purification of chemical products. This technology is based on the boiling point differences of different gas components at low temperatures for rectification separation, and can effectively separate a variety of gas components, and the purity after separation is relatively high. Compared with other chemical separation methods, the cryogenic separation process is relatively clean and has less environmental pollution.

[0003] Special separation processes need to be adopted for raw material gas containing olefins and alkynes. Because the raw material gas of this component cannot be purified by conventional molecular sieve adsorption. While adsorbing CO2 in the raw material gas, olefins and alkynes will also be adsorbed, resulting in the loss of effective components.

[0004] N-Methyldiethanolamine (MDEA) can be used for acid gas purification. Its molecular formula is CH3N(CH2CH2OH)2, molecular weight 119.2, boiling point 246 - 248 °C, flash point 260 °C, freezing point -21 °C, latent heat of vaporization 519.16 kJ / kg, miscible with water and alcohol, slightly soluble in ether. Under certain conditions, it has a strong absorption capacity for acid gases such as carbon dioxide, and has a small reaction heat, a low desorption temperature, stable chemical properties, non-toxic, and is not easily degraded. Pure MDEA solution does not react with CO2, but its aqueous solution can react with CO2 according to the following formula:

[0005] CO2 + H2O + R2NCH3 ≒ R2NCH3H + + HCO3 -

[0006] Therefore, the decarbonization performance of MDEA can be utilized to develop a purification and separation device and method that avoid the adsorption of effective components in the raw material gas. Summary of the Invention

[0007] The purpose of the present invention is to solve the deficiencies in the prior art and provide a purification and separation device and method for raw material gas containing olefins and alkynes.

[0008] The specific technical solution adopted by the present invention is as follows:

[0009] In the first aspect, the present invention provides a purification and separation device for raw material gas containing olefins and alkynes, including an MDEA decarbonization device, a first temperature swing adsorption device, a second temperature swing adsorption device, a cryogenic separation cold box, an LPG rectification column, and a refrigerant compression device; wherein a heat exchanger I, a washing tower, a separator, a heat exchanger II, a hydrogen-rich gas flash tank, and an LNG rectification column are provided in the cryogenic separation cold box;

[0010] The inlet of the MDEA decarbonization device receives the raw material gas containing olefins and alkynes from upstream and is used to remove carbon dioxide from the raw material gas; the inlet of the first temperature swing adsorption device is connected to the outlet of the MDEA decarbonization device. After the first dehydration of the raw material gas, the outlet of the first temperature swing adsorption device returns to the MDEA decarbonization device through a pipeline passing through the heat exchanger I, the washing tower, and the LPG rectification column in sequence; the inlet of the second temperature swing adsorption device is connected to the outlet of the MDEA decarbonization device. After the second dehydration of the raw material gas, the outlet of the second temperature swing adsorption device leaves the cryogenic separation cold box through a pipeline passing through the heat exchanger I, the LNG rectification column, the heat exchanger II, and the heat exchanger I in sequence; the cooling capacity in the cryogenic separation cold box is provided by the refrigerant compression device.

[0011] Preferably, the connection modes of each device are specifically as follows:

[0012] The first inlet of the MDEA decarbonization device receives the raw material gas containing olefins and alkynes from upstream, and the first outlet of the MDEA decarbonization device is connected to the inlet of the first temperature swing adsorption device;

[0013] A number of hot-side inlets, cold-side outlets, cold-side inlets, and hot-side outlets are provided on the heat exchanger I and the heat exchanger II in the cryogenic separation cold box; the outlet of the first decarbonization and dehydration raw material gas of the first temperature swing adsorption device is connected to the first hot-side inlet of the heat exchanger I through a pipeline; the first cold-side outlet of the heat exchanger I is connected to the inlet at the bottom of the washing tower through a pipeline, and the liquid-phase outlet at the bottom of the washing tower is connected to the inlet of the LPG rectification column through a pipeline; the methane-rich gas outlet at the top of the LPG rectification column is connected to the second inlet of the MDEA decarbonization device through a pipeline, and the second outlet of the MDEA decarbonization device is connected to the inlet of the second temperature swing adsorption device; the outlet of the second decarbonization and dehydration raw material gas of the second temperature swing adsorption device is connected to the second hot-side inlet of the heat exchanger I through a pipeline; the second cold-side outlet of the heat exchanger I is connected to the inlet of the LNG rectification column through a pipeline;

[0014] The gas-phase outlet at the top of the scrubbing tower is connected to the third heat-side inlet of the first heat exchanger through a pipeline; the third cold-side outlet of the first heat exchanger is connected to the inlet of the separator through a pipeline; the liquid-phase outlet at the bottom of the separator is connected to the scrubbing tower through a pipeline; the gas-phase outlet at the top of the separator is connected to the fourth heat-side inlet of the first heat exchanger through a pipeline; the fourth cold-side outlet of the first heat exchanger is connected to the inlet of the hydrogen-rich gas flash tank through a pipeline after passing through the first heat-side inlet of the second heat exchanger and the first cold-side outlet of the second heat exchanger in sequence;

[0015] The gas-phase outlet at the top of the hydrogen-rich gas flash tank leaves the cryogenic separation cold box through a pipeline after passing through the first cold-side inlet of the second heat exchanger, the first heat-side outlet of the second heat exchanger, the first cold-side inlet of the first heat exchanger, and the first heat-side outlet of the first heat exchanger in sequence; the liquid-phase outlet at the bottom of the hydrogen-rich gas flash tank is connected to the LNG rectification tower through a pipeline;

[0016] The gas-phase outlet at the top of the LNG rectification tower leaves the cryogenic separation cold box through a pipeline after being connected to the second cold-side inlet of the second heat exchanger, the second heat-side outlet of the second heat exchanger, the second cold-side inlet of the first heat exchanger, and the second heat-side outlet of the first heat exchanger in sequence; the liquid-phase outlet at the bottom of the LNG rectification tower is connected to the fifth heat-side inlet of the first heat exchanger through a pipeline; the LNG product gas at the fifth cold-side outlet of the first heat exchanger leaves the cryogenic separation cold box through a pipeline.

[0017] Further, the LPG product outlet at the bottom of the LPG rectification tower is connected to the external LPG product gas recovery tank through a pipeline.

[0018] Further, the first heat-side outlet of the first heat exchanger is connected to the external hydrogen-rich gas recovery tank through a pipeline.

[0019] Further, the second heat-side outlet of the first heat exchanger is connected to the external nitrogen-rich tail gas recovery tank through a pipeline.

[0020] Further, the fifth cold-side outlet of the first heat exchanger is connected to the external LNG product gas recovery tank through a pipeline.

[0021] Preferably, the outlet of the refrigerant compression device returns to the inlet of the refrigerant compression device through a pipeline after passing through the sixth heat-side inlet of the first heat exchanger, the sixth cold-side outlet of the first heat exchanger, the second heat-side inlet of the second heat exchanger, the second cold-side outlet of the second heat exchanger, the third cold-side inlet of the second heat exchanger, the third heat-side outlet of the second heat exchanger, the third cold-side inlet of the first heat exchanger, and the third heat-side outlet of the first heat exchanger in sequence, forming a cycle.

[0022] Preferably, a double scrubbing tower is adopted in the MDEA decarbonization device.

[0023] In a second aspect, the present invention provides a method for purifying and separating a raw gas containing olefins and alkynes by using the purification and separation device described in the first aspect, specifically as follows:

[0024] The olefin- and alkyne-containing raw material gas enters the MDEA decarbonization unit. After removing carbon dioxide from the raw material gas, it enters the first temperature swing adsorption unit to obtain the primary decarbonized and dehydrated raw material gas; the primary decarbonized and dehydrated raw material gas is cooled by Heat Exchanger 1 in the cryogenic separation cold box and then enters the washing tower, where heavy components are removed.

[0025] The gas obtained from the gas phase outlet at the top of the washing tower is cooled by Heat Exchanger 1 and then enters the separator. The separated liquid flows back to the washing tower, and the separated gas is cooled by Heat Exchanger 1 and Heat Exchanger 2 in sequence and then enters the hydrogen-rich gas flash tank; the hydrogen-rich gas obtained from the gas phase outlet at the top of the hydrogen-rich gas flash tank is reheated by Heat Exchanger 2 and Heat Exchanger 1 in sequence and then leaves the cryogenic separation cold box; the liquid obtained from the liquid phase outlet at the bottom of the hydrogen-rich gas flash tank flows back to the LNG rectification tower.

[0026] The liquid obtained from the liquid phase outlet at the bottom of the washing tower enters the LPG rectification tower; LPG product gas is obtained at the bottom of the LPG rectification tower, and the methane-rich gas obtained at the top of the LPG rectification tower returns to the MDEA decarbonization unit through a pipeline. After removing carbon dioxide again, it enters the second temperature swing adsorption unit to obtain the secondary decarbonized and dehydrated raw material gas; the secondary decarbonized and dehydrated raw material gas is cooled by Heat Exchanger 1 in the cryogenic separation cold box and then enters the LNG rectification tower.

[0027] The nitrogen-rich tail gas obtained from the gas phase outlet at the top of the LNG rectification tower is reheated by Heat Exchanger 2 and Heat Exchanger 1 in sequence and then leaves the cryogenic separation cold box; the liquid obtained from the liquid phase outlet at the bottom of the LNG rectification tower is cooled by Heat Exchanger 1 to obtain LNG product gas.

[0028] Preferably, the carbon dioxide content in the secondary decarbonized and dehydrated raw material gas is reduced to 20 - 50 ppm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The purification and separation device provided by the present invention can be used to separate the raw material gas containing olefins and alkynes. By adopting the MDEA decarbonization unit and the temperature swing adsorption unit, it avoids the problem of loss of effective gases such as olefins and alkynes caused by adsorbing high-concentration CO2 in the raw material gas while adsorbing the effective components. It also solves the problems of excessive molecular sieve filling amount and excessive consumption of regeneration heat source and cold source caused by the co-adsorption problem when using molecular sieve to adsorb CO2 in the prior art. After being processed by the device provided by the present invention, the CO2 content in the raw material gas can be reduced to 20 - 50 ppm, avoiding the problem of CO2 freezing blockage when entering the low-temperature equipment to separate other product gases subsequently.

[0031] The device provided by the present invention efficiently couples cryogenic separation, MDEA decarbonization, and TSA drying and dehydration, improves the overall benefit, and provides process support for the co-production of hydrogen-rich gas and LNG. Brief Description of the Drawings

[0032] Figure 1 It is a simplified diagram of the purification and separation device for raw material gas containing olefins and alkynes provided in this embodiment;

[0033] Figure 2 It is a specific connection schematic diagram of the purification and separation device for raw material gas containing olefins and alkynes provided in this embodiment;

[0034] In the figure: MDEA decarbonization unit 1, first temperature swing adsorption unit 2, second temperature swing adsorption unit 3, cryogenic separation cold box 4, LPG distillation column 5, refrigerant compression unit 6, heat exchanger 1 7, scrubbing tower 8, separator 9, heat exchanger 2 10, hydrogen-rich gas flash tank 11, LNG distillation column 12, first hot side inlet N1-1 of heat exchanger 1, second hot side inlet N1-2 of heat exchanger 1, third hot side inlet N1-3 of heat exchanger 1, fourth hot side inlet N1-4 of heat exchanger 1, fifth hot side inlet N1-5 of heat exchanger 1, sixth hot side inlet N1-6 of heat exchanger 1, first cold side outlet N2-1 of heat exchanger 1, second cold side outlet N2-2 of heat exchanger 1, third cold side outlet N2-3 of heat exchanger 1, fourth cold side outlet N2-4 of heat exchanger 1, fifth cold side outlet N2-5 of heat exchanger 1, sixth cold side outlet N2-6 of heat exchanger 1, first cold side inlet N3-1 of heat exchanger 1, second cold side inlet N3-2 of heat exchanger 1, third cold side inlet N3-3 of heat exchanger 1, first hot side outlet N4-1 of heat exchanger 1, second hot side outlet N4-2 of heat exchanger 1, third hot side outlet N4-3 of heat exchanger 1, first hot side inlet N5-1 of heat exchanger 2, second hot side inlet N5-2 of heat exchanger 2, first cold side outlet N6-1 of heat exchanger 2, second cold side outlet N6-2 of heat exchanger 2, first cold side inlet N7-1 of heat exchanger 2, second cold side inlet N7-2 of heat exchanger 2, third cold side inlet N7-3 of heat exchanger 2, first hot side outlet N8-1 of heat exchanger 2, second hot side outlet N8-2 of heat exchanger 2, third hot side outlet N8-3 of heat exchanger 2; raw material gas A containing olefins and alkynes; primary decarbonized and dehydrated raw material gas B; LPG product gas C; methane-rich gas D; secondary decarbonized and dehydrated raw material gas E; hydrogen-rich gas F; nitrogen-rich tail gas G; LNG product gas H. Detailed Embodiments

[0035] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined correspondingly without conflict.

[0036] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0037] As Figure 1 shown, as a preferred embodiment of the specific implementation manner, this embodiment provides a purification and separation device for raw material gas containing olefins and alkynes, including an MDEA decarbonization device 1, a first temperature swing adsorption device 2, a second temperature swing adsorption device 3, a cryogenic separation cold box 4, an LPG rectification tower 5, and a refrigerant compression device 6. Among them, a heat exchanger 7, a washing tower 8, a separator 9, a heat exchanger 10, a hydrogen-rich gas flash tank 11, and an LNG rectification tower 12 are provided in the cryogenic separation cold box 4.

[0038] The MDEA decarbonization device is a device for removing carbon dioxide from industrial waste gas. MDEA (N-methyldiethanolamine) is a strong alkaline substance that can react with carbon dioxide to form sodium carbonate and water, thereby achieving the purpose of decarbonization. In this embodiment, the MDEA decarbonization device 1 adopts a double washing tower, and the double washing tower can improve the efficiency and stability of denitrification.

[0039] The temperature swing adsorption device (TSA) is a device used in the cryogenic separation system, and the adsorption and desorption processes are realized by changing the temperature. In the cryogenic separation system, the temperature swing adsorption device is usually used to separate and purify specific gas or liquid mixtures. By adjusting the temperature, the adsorption capacity of the adsorbent can be controlled to achieve the separation purpose.

[0040] As Figure 2 shown, the connection modes of each device in this embodiment are specifically as follows:

[0041] In the device provided in this embodiment, a number of hot side inlets, cold side outlets, cold side inlets, and hot side outlets are opened on the heat exchanger 7 and the heat exchanger 10 in the cryogenic separation cold box 4.

[0042] The first inlet of the MDEA decarbonization unit 1 receives the olefin- and alkyne-containing raw gas from upstream for removing carbon dioxide from the raw gas. The first outlet of the MDEA decarbonization unit 1 is connected to the inlet of the first temperature swing adsorption unit 2. In the first temperature swing adsorption unit 2, water in the raw gas is removed for the first time to obtain the primary decarbonized and dehydrated raw gas. The primary decarbonized and dehydrated raw gas outlet of the first temperature swing adsorption unit 2 is connected through a pipeline to the first hot side inlet N1-1 of the first heat exchanger 7, and the primary decarbonized and dehydrated raw gas enters the first heat exchanger 7 for cooling. The first cold side outlet N2-1 of the first heat exchanger is connected through a pipeline to the inlet at the bottom of the scrubbing tower 8, and the liquid phase outlet at the bottom of the scrubbing tower 8 is connected through a pipeline to the inlet of the LPG rectification tower 5. The rich methane gas outlet at the top of the LPG rectification tower 5 is connected through a pipeline to the second inlet of the MDEA decarbonization unit 1. The rich methane gas enters the MDEA decarbonization unit 1 to remove carbon dioxide again. An LPG product outlet is also provided at the bottom of the LPG rectification tower 5, and the LPG product outlet is connected through a pipeline to the external LPG product gas recovery tank for recovering the obtained LPG product gas.

[0043] The gas phase outlet at the top of the scrubbing tower 8 is connected through a pipeline to the third hot side inlet N1-3 of the first heat exchanger, and the gas is cooled in the first heat exchanger 7. The third cold side outlet N2-3 of the first heat exchanger is connected through a pipeline to the inlet of the separator 9. The liquid phase outlet at the bottom of the separator 9 is connected through a pipeline to the scrubbing tower 8. The gas phase outlet at the top of the separator 9 is connected through a pipeline to the fourth hot side inlet N1-4 of the first heat exchanger. The fourth cold side outlet N2-4 of the first heat exchanger is connected through a pipeline to the inlet of the hydrogen-rich gas flash tank 11 after passing through the first hot side inlet N5-1 and the first cold side outlet N6-1 of the second heat exchanger in sequence.

[0044] The second outlet of the MDEA decarbonization unit 1 is connected to the inlet of the second temperature swing adsorption unit 3, and the raw gas with carbon dioxide removed again enters the second temperature swing adsorption unit 3 to remove all water, obtaining the secondary decarbonized and dehydrated raw gas. The secondary decarbonized and dehydrated raw gas outlet of the second temperature swing adsorption unit 3 is connected through a pipeline to the second hot side inlet N1-2 of the first heat exchanger, and the secondary decarbonized and dehydrated raw gas enters the first heat exchanger 7 for cooling. The second cold side outlet N2-2 of the first heat exchanger is connected through a pipeline to the inlet of the LNG rectification tower 12.

[0045] Hydrogen-rich gas is obtained at the top of the hydrogen-rich gas flash tank 11. The gas phase outlet at the top of the hydrogen-rich gas flash tank 11 is connected through a pipeline to the external hydrogen-rich gas recovery tank for recovering the hydrogen-rich gas after passing through the first cold side inlet N7-1, the first hot side outlet N8-1 of the second heat exchanger, the first cold side inlet N3-1 of the first heat exchanger, and the first hot side outlet N4-1 of the first heat exchanger in sequence to leave the cryogenic separation cold box 4. The liquid phase outlet at the bottom of the hydrogen-rich gas flash tank 11 is connected through a pipeline to the LNG rectification tower 12.

[0046] The nitrogen-rich tail gas is obtained at the top of the LNG rectification column 12. The gas-phase outlet at the top of the LNG rectification column 12 is connected to the second cold-side inlet N7-2 of the second heat exchanger, the second hot-side outlet N8-2 of the second heat exchanger, the second cold-side inlet N3-2 of the first heat exchanger, and the second hot-side outlet N4-2 of the first heat exchanger in sequence through pipelines, and then leaves the cryogenic separation cold box 4 and is connected to the external nitrogen-rich tail gas recovery tank for recovering the nitrogen-rich tail gas. The liquid-phase outlet at the bottom of the LNG rectification column 12 is connected to the fifth hot-side inlet N1-5 of the first heat exchanger through a pipeline. The LNG product gas at the fifth cold-side outlet N2-5 of the first heat exchanger leaves the cryogenic separation cold box 4 through a pipeline and is connected to the external LNG product gas recovery tank for recovering the LNG product gas in the boundary.

[0047] In this embodiment, the cold energy in the cryogenic separation cold box 4 is provided by the refrigerant compression device 6, specifically as follows: The outlet of the refrigerant compression device 6 passes through the sixth hot-side inlet N1-6 of the first heat exchanger, the sixth cold-side outlet N2-6 of the first heat exchanger, the second hot-side inlet N5-2 of the second heat exchanger, the second cold-side outlet N6-2 of the second heat exchanger, the third cold-side inlet N7-3 of the second heat exchanger, the third hot-side outlet N8-3 of the second heat exchanger, the third cold-side inlet N3-3 of the first heat exchanger, and the third hot-side outlet N4-3 of the first heat exchanger in sequence through pipelines, and then returns to the inlet of the refrigerant compression device 6 to form a cycle refrigeration.

[0048] This embodiment provides a method for purifying and separating a raw gas containing olefins and alkynes by using the above purification and separation device, specifically as follows:

[0049] The raw gas A containing olefins and alkynes enters the MDEA decarbonization device 1. After removing carbon dioxide from the raw gas, it enters the first temperature swing adsorption device 2 to obtain a primary decarbonized and dehydrated raw gas B. The primary decarbonized and dehydrated raw gas B is cooled by the heat exchanger 7 in the cryogenic separation cold box 4 and then enters the washing tower 8, where heavy components are removed in the washing tower 8.

[0050] The gas obtained from the gas-phase outlet at the top of the washing tower 8 is cooled by the heat exchanger 7 and then enters the separator 9. The separated liquid flows back to the washing tower 8, and the separated gas is cooled by the heat exchanger 7 and the heat exchanger 10 in sequence and then enters the hydrogen-rich gas flash tank 11. The hydrogen-rich gas F obtained from the gas-phase outlet at the top of the hydrogen-rich gas flash tank 11 passes through the heat exchanger 10 and the heat exchanger 7 in sequence for rewarming and then leaves the cryogenic separation cold box 4. The liquid obtained from the liquid-phase outlet at the bottom of the hydrogen-rich gas flash tank 11 flows back into the LNG rectification column 12.

[0051] The liquid obtained from the bottom liquid phase outlet of the scrubbing tower 8 enters the LPG rectifying column 5. The LPG product gas C is obtained at the bottom of the LPG rectifying column 5, and the methane-rich gas D obtained at the top of the LPG rectifying column 5 is returned to the MDEA decarbonization unit 1 through a pipeline. After removing carbon dioxide again, it enters the second temperature swing adsorption unit 3 to obtain the secondary decarbonized and dehydrated raw gas E. The secondary decarbonized and dehydrated raw gas E enters the LNG rectifying column 12 after being cooled by the heat exchanger 7 in the cryogenic separation cold box 4.

[0052] The nitrogen-rich tail gas G obtained from the top gas phase outlet of the LNG rectifying column 12 is reheated successively through the heat exchanger 10 and the heat exchanger 7 and then leaves the cryogenic separation cold box 4. The liquid obtained from the bottom liquid phase outlet of the LNG rectifying column 12 is cooled by the heat exchanger 7 to obtain the LNG product gas H.

[0053] Through the MDEA decarbonization unit 1 in the device provided in this embodiment, the CO2 content in the secondary decarbonized and dehydrated raw gas can be reduced to 20 ppm, meeting the requirements of subsequent cryogenic separation and avoiding the problem of CO2 freezing blockage when separating other product gases in low-temperature equipment later. The present invention successfully realizes the cryogenic separation cold box system for producing hydrogen-rich gas and co-producing LNG after MDEA purification and TSA purification of the raw gas containing olefins and alkynes, improving the overall device revenue and reducing the production cost and device energy consumption. The above embodiments are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting equivalent replacement or equivalent transformation methods fall within the protection scope of the present invention.

Claims

1. A purification and separation device for raw gas containing olefins and alkynes, characterized in that: The invention comprises an MDEA decarbonization device (1), a first temperature swing adsorption device (2), a second temperature swing adsorption device (3), a cryogenic separation cold box (4), an LPG distillation tower (5) and a refrigerant compression device (6); wherein the cryogenic separation cold box (4) is provided with a heat exchanger 1 (7), a washing tower (8), a separator (9), a heat exchanger 2 (10), a hydrogen-rich gas flash tank (11) and an LNG distillation tower (12); The inlet of the MDEA decarbonization device (1) receives the raw gas containing olefins and alkynes from the upstream, and is used to remove carbon dioxide in the raw gas; the inlet of the first temperature swing adsorption device (2) is connected to the outlet of the MDEA decarbonization device (1), and after the water in the raw gas is removed for the first time, the outlet of the first temperature swing adsorption device (2) passes through the heat exchanger 1 (7), the washing tower (8) and the LPG distillation tower (5) in sequence through a pipeline and then returns to the MDEA decarbonization device (1); the inlet of the second temperature swing adsorption device (3) is connected to the outlet of the MDEA decarbonization device (1), and after the water in the raw gas is removed for the second time, the outlet of the second temperature swing adsorption device (3) passes through the heat exchanger 1 (7), the LNG distillation tower (12), the heat exchanger 2 (10), and the heat exchanger 1 (7) in sequence through a pipeline and then leaves the deep cold separation cold box (4); the cooling capacity in the deep cold separation cold box (4) is provided by the refrigerant compression device (6).

2. The purification and separation device for raw gas containing olefins and alkynes according to claim 1 is characterized in that: The connection methods of each device are as follows: The first inlet of the MDEA decarbonization device (1) receives the olefin and alkyne-containing raw gas from the upstream, and the first outlet of the MDEA decarbonization device (1) is connected to the inlet of the first temperature swing adsorption device (2); The heat exchanger 1 (7) and the heat exchanger 2 (10) in the deep cold separation cold box (4) are provided with a plurality of hot side inlets, cold side outlets, cold side inlets and hot side outlets; the outlet of the primary decarbonization and dehydration raw gas of the first temperature variable adsorption device (2) is connected to the first hot side inlet (N1-1) of the heat exchanger 1 (7) through a pipeline; the first cold side outlet (N2-1) of the heat exchanger 1 is connected to the inlet at the bottom of the washing tower (8) through a pipeline, and the liquid phase outlet at the bottom of the washing tower (8) is connected to the LPG distillation tower through a pipeline. (5); the methane-rich gas outlet at the top of the LPG distillation tower (5) is connected to the second inlet of the MDEA decarbonization device (1) through a pipeline, and the second outlet of the MDEA decarbonization device (1) is connected to the inlet of the second temperature swing adsorption device (3); the secondary decarbonization and dehydration feed gas outlet of the second temperature swing adsorption device (3) is connected to the second hot side inlet (N1-2) of the heat exchanger through a pipeline; the second cold side outlet (N2-2) of the heat exchanger is connected to the inlet of the LNG distillation tower (12) through a pipeline; The gas phase outlet at the top of the washing tower (8) is connected to the third hot side inlet (N1-3) of the heat exchanger through a pipeline; the third cold side outlet (N2-3) of the heat exchanger is connected to the inlet of the separator (9) through a pipeline; the liquid phase outlet at the bottom of the separator (9) is connected to the washing tower (8) through a pipeline; the gas phase outlet at the top of the separator (9) is connected to the fourth hot side inlet (N1-4) of the heat exchanger through a pipeline; the fourth cold side outlet (N2-4) of the heat exchanger passes through the first hot side inlet (N5-1) of the heat exchanger and the first cold side outlet (N6-1) of the heat exchanger in sequence through a pipeline and is connected to the inlet of the hydrogen-rich gas flash tank (11); The gas phase outlet at the top of the hydrogen-rich gas flash tank (11) passes through the first cold side inlet (N7-1) of the second heat exchanger, the first hot side outlet (N8-1) of the second heat exchanger, the first cold side inlet (N3-1) of the first heat exchanger, and the first hot side outlet (N4-1) of the first heat exchanger in turn through a pipeline, and then leaves the cryogenic separation cold box (4); the liquid phase outlet at the bottom of the hydrogen-rich gas flash tank (11) is connected to the LNG distillation tower (12) through a pipeline; The gas phase outlet at the top of the LNG distillation tower (12) is connected to the second cold side inlet (N7-2) of heat exchanger 2, the second hot side outlet (N8-2) of heat exchanger 2, the second cold side inlet (N3-2) of heat exchanger 1 and the second hot side outlet (N4-2) of heat exchanger 1 in sequence through a pipeline, and then leaves the cryogenic separation cold box (4); the liquid phase outlet at the bottom of the LNG distillation tower (12) is connected to the fifth hot side inlet (N1-5) of heat exchanger 1 through a pipeline; the LNG product gas at the fifth cold side outlet (N2-5) of heat exchanger 1 leaves the cryogenic separation cold box (4) through a pipeline.

3. The purification and separation device for raw gas containing olefins and alkynes according to claim 2 is characterized in that: The LPG product outlet at the bottom of the LPG distillation tower (5) is connected to an external LPG product gas recovery tank through a pipeline.

4. The purification and separation device for raw gas containing olefins and alkynes according to claim 2 is characterized in that: The first hot side outlet (N4-1) of the heat exchanger 1 (7) is connected to an external hydrogen-rich gas recovery tank through a pipeline.

5. The purification and separation device for raw gas containing olefins and alkynes according to claim 2 is characterized in that: The second hot side outlet (N4-2) of the heat exchanger 1 (7) is connected to an external nitrogen-rich tail gas recovery tank through a pipeline.

6. The purification and separation device for raw gas containing olefins and alkynes according to claim 2 is characterized in that: The fifth cold side outlet (N2-5) of the heat exchanger 1 (7) is connected to the external LNG product gas recovery tank through a pipeline.

7. The purification and separation device for raw gas containing olefins and alkynes according to claim 1 is characterized in that: The outlet of the refrigerant compression device (6) passes through the sixth hot side inlet (N1-6) of heat exchanger 1, the sixth cold side outlet (N2-6) of heat exchanger 1, the second hot side inlet (N5-2) of heat exchanger 2, the second cold side outlet (N6-2) of heat exchanger 2, the third cold side inlet (N7-3) of heat exchanger 2, the third hot side outlet (N8-3) of heat exchanger 2, the third cold side inlet (N3-3) of heat exchanger 1 and the third hot side outlet (N4-3) of heat exchanger 1 in sequence through a pipeline, and then returns to the inlet of the refrigerant compression device (6), forming a cycle.

8. The purification and separation device for raw gas containing olefins and alkynes according to claim 1 is characterized in that: The MDEA decarbonization device (1) uses double scrubbing towers.

9. A method for purifying and separating a raw gas containing olefins and alkynes using the purification and separation device according to any one of claims 2 to 8, characterized in that: The details are as follows: The raw gas containing olefins and alkynes enters the MDEA decarbonization device (1), and after the carbon dioxide in the raw gas is removed, it enters the first temperature swing adsorption device (2) to obtain a primary decarbonized and dehydrated raw gas; the primary decarbonized and dehydrated raw gas is cooled by the heat exchanger 1 (7) in the deep cold separation cold box (4), and then enters the washing tower (8), and the heavy components are removed in the washing tower (8); The gas obtained at the gas phase outlet at the top of the washing tower (8) passes through the heat exchanger 1 (7) for cooling and then enters the separator (9); the separated liquid flows back to the washing tower (8); the separated gas passes through the heat exchanger 1 (7) and the heat exchanger 2 (10) for cooling and then enters the hydrogen-rich gas flash tank (11); the hydrogen-rich gas obtained at the gas phase outlet at the top of the hydrogen-rich gas flash tank (11) passes through the heat exchanger 2 (10) and the heat exchanger 1 (7) for reheating and then leaves the cryogenic separation cold box (4); the liquid obtained at the liquid phase outlet at the bottom of the hydrogen-rich gas flash tank (11) flows back to the LNG distillation tower (12); The liquid obtained at the bottom liquid phase outlet of the washing tower (8) enters the LPG distillation tower (5); the LPG product gas is obtained at the bottom of the LPG distillation tower (5), and the methane-rich gas obtained at the top of the LPG distillation tower (5) is returned to the MDEA decarbonization device (1) through a pipeline, and after the carbon dioxide is removed again, it enters the second temperature swing adsorption device (3) to obtain a secondary decarbonization and dehydration raw gas; the secondary decarbonization and dehydration raw gas is cooled by the heat exchanger 1 (7) in the deep cold separation cold box (4) and then enters the LNG distillation tower (12); The nitrogen-rich tail gas obtained at the gas phase outlet at the top of the LNG distillation tower (12) passes through heat exchanger 2 (10) and heat exchanger 1 (7) in sequence to be reheated before leaving the deep-cold separation cold box (4); the liquid obtained at the liquid phase outlet at the bottom of the LNG distillation tower (12) is cooled by heat exchanger 1 (7) to obtain LNG product gas.

10. The method for purifying and separating a raw gas containing olefins and alkynes according to claim 9, characterized in that: The carbon dioxide content in the secondary decarbonization and dehydration raw gas is reduced to 20-50 ppm.

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