CN108676579B - Dry gas sequential separation system and separation method based on argon circulation refrigeration - Google Patents
Dry gas sequential separation system and separation method based on argon circulation refrigeration Download PDFInfo
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- CN108676579B CN108676579B CN201810437285.3A CN201810437285A CN108676579B CN 108676579 B CN108676579 B CN 108676579B CN 201810437285 A CN201810437285 A CN 201810437285A CN 108676579 B CN108676579 B CN 108676579B
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- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G70/00—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00
- C10G70/04—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00 by physical processes
- C10G70/041—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00 by physical processes by distillation
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- B01D3/14—Fractional distillation or use of a fractionation or rectification column
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- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G70/00—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00
- C10G70/04—Working-up undefined normally gaseous mixtures obtained by processes covered by groups C10G9/00, C10G11/00, C10G15/00, C10G47/00, C10G51/00 by physical processes
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Abstract
The invention relates to a dry gas sequential separation system and a separation method based on argon circulation refrigeration, wherein the separation system comprises an ethylene-ethane separation module and a methane separation module, and the ethylene-ethane separation module comprises a weight removal separation system, an ethane separation system and an ethylene separation system; the methane separation module comprises a methane separation system and an argon circulation refrigerating system; the dry gas enters a weight removing and separating system to remove propylene, propane and other heavy components by rectification, enters an ethane separating system to separate ethane, enters an ethylene separating system to separate ethylene, enters a methane separating system to separate methane by rectification, and enters an argon circulation refrigerating system after flowing out from the bottom of a methane rectifying tower to transfer the cold energy of the liquid methane to circulation argon, wherein the circulation argon is used for providing cold energy for the methane separating system, so that the recovery and cold energy recycling processes of the four components of hydrogen methane and ethylene ethane in the dry gas are realized.
Description
Technical Field
The invention belongs to the technical field of industrial tail gas product recovery, and relates to a dry gas sequential separation system and a separation method based on argon circulation refrigeration.
Background
The refinery dry gas mainly comes from the processes of heavy oil catalytic cracking, delayed coking, hydrocracking, catalytic reforming and the like in petroleum processing, and the main components of the refinery dry gas comprise hydrogen, nitrogen, methane, ethylene, ethane, propane and the like, wherein the values of the hydrogen, the ethylene, the ethane and the like are higher. Ethylene is a high-value product, hydrogen can be recycled for hydrocracking or sold as a product, and light hydrocarbons such as ethane, propane and the like can be recycled for an ethylene device as high-quality cracking raw materials. However, most refineries use dry gas as fuel gas except for a few refineries with matched ethylene devices, and use valuable products in a low-value manner, so that resource waste is caused.
The separation and recovery of the high-valence products in the dry gas usually adopts one or a combination of adsorption, absorption, membrane and cryogenic separation. The adsorption method utilizes the selective adsorbent to realize the cycle of adsorption and desorption through pressure and temperature changes, and a certain component which is relatively pure is obtained. For example, patent CN201410220850.2, hydrogen and ethylene in dry gas are recovered by light cold adsorption. The yield and purity of the adsorption method are relatively low, and the investment and occupation of the device are large. The absorption rule adopts solvent absorption to carry out selective absorption, and then the high-purity product can be obtained through rectification separation. For example, patent CN201410220882.2 and CN201410359774.3 respectively adopt butane, pentane, aromatic hydrocarbon or acetonitrile and other solvents to make selective absorption, and recover hydrogen and ethylene in the dry gas. Because of the solvent characteristics, the absorption has the defects of low selectivity and low separation yield, and cold energy is still required to be provided for precise separation, so that the application of the method is limited. The membrane separation realizes the separation of the components by utilizing the permeability difference of different components in the dry gas in the special membrane, and is suitable for recycling hydrogen in the dry gas with low pressure and low hydrogen content, but the purity is not high. The cryogenic separation generally uses methane and ethylene propylene propane as refrigerants, and the required low-temperature cold energy is obtained through the compression, condensation, throttling and expansion processes. The cryogenic separation can ensure the purity and high yield of the product, can obtain polymerization-grade ethylene for dry gas separation, and can improve the recovery rate of methane when used for purge gas separation, but the conventional cryogenic method has high operating pressure and high energy consumption, and the expensive refrigeration cost restricts the wide application of the method, so that the method is only suitable for large-scale treatment.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a dry gas sequential separation system and a separation method based on argon circulation refrigeration. According to the dry gas sequential separation method based on argon circulation refrigeration, four components of hydrogen methane and ethylene ethane in the dry gas can be recovered by combining technical methods such as pressure swing adsorption or membrane separation through the ethane-ethylene sequential separation module and the methane separation module.
In order to solve the problems, the invention adopts the following technical scheme:
an argon cycle refrigeration-based dry gas sequential separation system, wherein the ethane-ethylene separation module comprises a weight removal separation system, an ethane separation system and an ethylene separation system; the methane separation module comprises a methane separation system and an argon circulation refrigerating system;
and after the dry gas enters the heavy component discharge system such as propylene propane separated from the bottom of the heavy component removal separation system for rectification separation, the light component separated from the top of the heavy component removal column enters the ethane separation system for rectification separation, the liquid-phase ethane separated from the bottom of the ethane column enters the ethylene separation system for providing cold energy, the top gas separated from the top of the ethane column enters the ethylene separation system for rectification separation, the liquid-phase ethylene discharge system is separated from the bottom of the ethylene column, the top gas separated from the top of the ethylene column enters the methane separation system for rectification separation, the separated liquid methane flows out from the bottom of the methane rectification column and enters the liquid methane-argon heat exchanger in the argon circulation refrigeration system, the cold energy of the liquid methane is transmitted to the circulating argon, and the circulating argon is used for providing cold energy for the methane column top condenser in the methane separation system, so that the dry gas separation process and the cold energy recycling process are realized.
The dry gas raw material enters the feeding heat exchanger through a feeding pipeline to exchange heat, enters the heavy-removal tower bottom reboiler to exchange heat with the bottom liquid of the heavy-removal tower, and then enters the heavy-removal tower to carry out rectification separation; the separated heavy components of the heavy component removal tower enter a heat absorption pipeline of a heavy component cold energy heat exchanger through a heavy component throttling expansion valve to release cold energy, then enter a raw material heat exchanger heat absorption pipeline to release cold energy again, and then are discharged out of the system; the separated gas phase at the top of the heavy-component removal tower enters a heat release pipeline of the heavy-component cold energy heat exchanger. The heavy components such as propylene propane and the like in the liquid phase at the bottom of the heavy component removal tower are circularly fed and heated in a reboiler at the bottom of the tower to generate steam, and the liquid phase heavy components at the bottom of the tower pass through a throttling expansion valve and a heavy component cold energy heat exchanger to release gasification cold energy to enter a raw material heat exchanger to further release cold energy for reheating and then are discharged out of the system; the gas phase at the top of the de-heaving tower is the light component containing ethane, ethylene, methane, nitrogen and hydrogen, and enters an ethane separation system.
Further, the ethane separation system comprises an ethane tower, an ethane tower bottom reboiler and an ethane tower top dephlegmator; the gas phase at the top of the heavy component removal tower leaves the heat release pipeline of the heavy component cold energy heat exchanger, enters the reboiler at the bottom of the ethane tower to exchange heat with the bottom liquid of the ethane tower, and then enters the ethane tower to carry out rectification separation; the separated ethane tower bottom liquid-phase ethane releases cold energy to an ethylene tower top dephlegmator of an ethylene separation system through an ethane throttling expansion valve, then flows into a feeding heat exchanger to further release cold energy and reheat, and is discharged out of the system; the separated ethane column overhead gas enters the ethylene separation system.
Further, the ethylene separation system comprises an ethylene tower, an ethylene tower bottom reboiler and an ethylene tower top dephlegmator; the gas phase at the top of the ethane tower enters an ethylene tower bottom reboiler to exchange heat with the bottom liquid of the ethylene tower, and then enters the ethylene tower to carry out rectification separation; a separated ethylene column bottoms liquid ethylene discharge system; the separated ethylene tower top gas enters the methane separation module. The top of the ethylene tower is light component containing methane, nitrogen, hydrogen and the like, and the bottom of the ethylene tower is liquid-phase ethylene product.
Further, the heavy-removal tower top dephlegmator and the ethane tower top dephlegmator are connected with a refrigerating unit. The purpose of the overhead refrigeration system is to provide refrigeration to the deemphasizing column and the ethane column to form reflux for the separation process. A refrigerating unit using methane or ethylene as refrigerating medium is generally adopted, and belongs to the conventional industrial technology.
Further, the methane separation system comprises a methane rectifying tower, a methane tower bottom reboiler and a methane tower top dephlegmator; and the separated ethylene tower top gas enters a methane tower bottom reboiler to exchange heat with a methane rectifying tower bottom liquid phase and then is conveyed into the methane rectifying tower. The methane separation module is used for separating methane; hydrogen is recovered from hydrogen-containing nitrogen at the top of the methane rectifying tower through pressure swing adsorption or membrane separation, the raw material of gas at the top of the ethylene tower is used as a heat source of a reboiler at the bottom of the methane tower, the raw material transfers heat energy to circulating liquid at the bottom of the methane tower in the reboiler at the bottom of the methane tower, and part of liquid at the bottom of the methane tower is gasified to form gas phase for separation; part of nitrogen in the ascending gas phase in the tower absorbs argon cold energy in the methane tower top dephlegmator and condenses into liquid nitrogen, so that reflux liquid in the tower is formed, and high-efficiency separation of methane and nitrogen is realized. And (3) passing through a methane rectifying tower to obtain hydrogen and nitrogen light components without methane at the top of the tower and liquid methane at the bottom of the tower.
Further, the argon circulation refrigerating system comprises a methane throttling expansion valve, a liquid methane-argon heat exchanger, a liquid argon throttling expansion valve, a cold energy recovery heat exchanger, a circulating argon compressor and a first water-cooling heat exchanger, wherein liquid methane flows into a heat absorption pipeline of the liquid methane-argon heat exchanger from the methane throttling expansion valve to release cold energy to circulating argon, the circulating argon enters a methane tower top condenser through the liquid argon throttling expansion valve to release cold energy, then enters the cold energy recovery heat exchanger through a low-pressure cold argon pipeline to release cold energy again, then enters the circulating argon compressor from a low-pressure reheating argon pipeline to be compressed, further increases the pressure, then enters the first water-cooling heat exchanger to cool and precool, enters the cold energy recovery heat exchanger again through a high-pressure argon pipeline to cool and precool, and then enters the liquid methane-argon heat exchanger to obtain cold energy again to realize an argon circulation refrigerating main loop.
Further, the gas separated in the methane separation system flows out from the top of the methane rectifying tower and enters the cold energy recovery heat exchanger to release cold energy, and then flows into a tower top gas utilization or discharge system from a reheating tower top gas pipeline; the cold energy recovery heat exchanger at the top of the tower releases cold energy to the refrigerating system, so that the cold energy can be further recovered, and the utilization rate of the cold energy is improved. The gas phase at the top of the tower after reheating is discharged out of the system through a pipeline, and the separation of hydrogen and nitrogen can be realized through pressure swing adsorption or membrane separation, so that the utilization rate of dry gas is improved. The pressure swing adsorption or membrane separation of methane gas compression cooling and overhead gas can be performed by adopting a common technical method in industry.
Cold methane gas flowing out of the heat absorption pipeline of the liquid methane-argon heat exchanger enters the cold energy recovery heat exchanger through a cold methane gas pipeline to release cold energy again, and then flows into the methane utilization system from the reheating methane gas pipeline. And the reheated methane gas is discharged out of the system through a pipeline, compressed and cooled according to the pressure requirement of a user, and then is input into a user pipe network.
Further, the argon circulation refrigeration system further comprises an argon circulation refrigeration auxiliary loop, the argon circulation refrigeration auxiliary loop comprises an argon expander, and the argon circulation refrigeration auxiliary loop specifically comprises: one path of circulating argon gas separated from the argon circulation refrigeration main loop enters the cold energy recovery heat exchanger to cool and precool, then directly enters the expander to expand and cool through the expansion end inlet pipeline of the expander, returns to the cold energy recovery heat exchanger through the expansion end outlet pipeline of the expander to release cold energy and reheat, then enters the expander to increase pressure through the compression end inlet pipeline of the expander and enters the second water-cooling heat exchanger to cool through the compression end outlet pipeline of the expander, then enters the first water-cooling heat exchanger to cool after being further increased in pressure through the circulating argon gas compressor, and enters the cold energy recovery heat exchanger to cool and precool through the high-pressure argon gas pipeline to form the argon circulation refrigeration auxiliary loop. The system uses argon as a circulating working medium, methane and nitrogen cold energy is recovered through a heat pump and a cold energy recovery heat exchanger, part of argon is used for supplementing cold energy to an argon circulating refrigeration main loop through the refrigeration of an expander, and then the argon Joule-Thomson effect is utilized for improving the cold energy grade and then is transmitted to a methane separation system.
The invention also provides a separation method of the dry gas sequential separation system based on argon circulation refrigeration, after the dry gas enters the heavy component removal separation system for rectification separation, heavy component separated from the bottom of the heavy component removal column enters the ethane separation system for rectification separation, liquid phase ethane separated from the bottom of the ethane column provides cold energy for the ethane separation system, overhead gas separated from the top of the ethane column enters the ethylene separation system for rectification separation, liquid phase ethylene separated from the bottom of the ethylene column enters the methane separation system for rectification separation, separated liquid methane flows out from the bottom of the methane rectification column and enters the liquid methane-argon heat exchanger in the argon circulation refrigeration system, cold energy of the liquid methane is transmitted to circulation, and the circulation argon is used for providing cold energy for the methane column top condenser in the methane separation system, so that a dry gas separation process and a cold energy recycling process are realized.
Advantageous effects
The invention discloses an ethane-ethylene sequential separation module in a dry gas sequential separation system based on argon circulation refrigeration, which sequentially separates heavy components, ethane and ethylene by adopting three towers. According to the dry gas sequential separation method based on argon circulation refrigeration, four components of hydrogen methane and ethylene ethane in the dry gas can be recovered by combining technical methods such as pressure swing adsorption or membrane separation through the ethane-ethylene sequential separation module and the methane separation module.
According to the ethane-ethylene sequential separation module in the dry gas sequential separation system based on argon circulation refrigeration, the temperature of raw materials fed into the system is generally higher than that of a feeding plate of a tower, heat exchange is carried out between the raw materials and tower bottom liquid before the raw materials are fed into the tower, heat energy of a tower bottom reboiler is provided, and the raw materials are cooled and fed into the tower after the raw materials are cooled, so that the separation efficiency is improved. If the feed heat energy is insufficient, it is necessary to introduce the differential heat energy from outside the system.
According to the ethane-ethylene sequential separation module in the dry gas sequential separation system based on argon circulation refrigeration, the temperature of the bottom liquid of the heavy-removal tower is reduced through throttling expansion of heavy components, heat exchange is performed with the raw materials of the ethane-feeding tower firstly, then heat exchange is performed with the raw materials of the heavy-removal tower, cold energy is fully released and then is recycled out of the system, so that the cold energy can be fully recovered, and energy consumption is saved and separated.
According to the methane separation system in the dry gas sequential separation system based on argon circulation refrigeration, argon is used as a working medium, methane and nitrogen cold energy of the separation system are recovered through the heat pump and the cold energy recovery heat exchanger, part of the argon supplements the cold energy through expansion refrigeration, then the cold energy grade is improved by using the Joule-Thomson effect of the argon and then is transmitted to the methane separation system, high-efficiency separation is realized with lower refrigeration energy consumption, high-efficiency utilization of dry gas resources is realized, and the methane recovery rate can reach more than 99%.
Drawings
FIG. 1 is a schematic diagram of an ethane ethylene sequential separation module in a dry gas sequential separation system of the present invention;
FIG. 2 is a schematic diagram of a methane separation module of the dry gas sequential separation system of the present invention;
FIG. 3 is a schematic diagram of a dry gas sequential separation system based on argon cycle refrigeration in accordance with the present invention;
wherein, the ethane ethylene sequential separation module comprises the following components: s1-feeding heat exchanger, S1-1-dry gas feeding pipeline, S1-2-reheating heavy component discharging pipeline, S1-3-reheating ethane discharging pipeline, S2-deemphasizing tower, S2-1-deemphasizing tower feeding pipeline, S2-2-deemphasizing tower top discharging pipeline, S2-3-deemphasizing tower bottom discharging pipeline, S3-tower bottom reboiler, S4-tower top condenser, S5-heavy component throttling expansion valve, S6-heavy component cold energy heat exchanger, S7-refrigerating unit, S7-1-back refrigerating unit medium pipeline, S7-2-back refrigerating unit medium pipeline, S7-3-out refrigerating unit medium pipeline, S7-4-out refrigerating unit medium pipeline, S8-ethane tower, S8-1-ethane tower feeding pipeline, S8-2-ethylene tower top discharging pipeline, S8-3-ethylene tower bottom pipeline, S9-ethane tower bottom reboiler, S10-ethane tower top condenser, S11-ethane expansion valve, S12-ethylene reboiler, S12-ethylene tower top pipeline S12-1-ethylene tower bottom reboiler, S14-ethylene tower bottom pipeline S14-ethylene tower bottom 14, S14-ethylene tower bottom reboiler, S12-ethylene tower 14-ethylene tower bottom pipeline S14-ethylene tower bottom, S1-ethylene tower 14-ethylene tower bottom pipeline 14-ethylene tower 14.
The methane separation module comprises the following components: the device comprises a reboiler at the bottom of a 1-methane tower, a 1-1-raw gas pipeline, a 2-methane rectifying tower, a 2-1-methane rectifying tower feeding pipeline, a 2-2-tower top gas phase discharging pipeline, a 2-3-tower bottom liquid phase discharging pipeline, a 3-methane tower top segregator, a 3-1-low pressure argon gas pipeline, a 4-cold energy recovery heat exchanger, a 4-1-reheating tower top gas pipeline, a 4-2-reheating methane gas pipeline, a 4-3-low pressure reheating argon gas pipeline, a 5-circulating argon gas compressor, a 6-first water-cooling heat exchanger, a 6-1-high pressure precooling argon gas pipeline, a 7-liquid methane-argon gas heat exchanger, a 7-1-high pressure argon gas pipeline, a 7-2-cold methane gas pipeline, an 8-liquid argon throttling expansion valve, an 8-1-high pressure liquid argon gas pipeline, an 8-2-low pressure argon gas pipeline, a 9-argon gas expander, a 9-1-expander expansion end inlet pipeline, a 9-2-expander expansion end outlet pipeline, a 9-3-expander compressor end inlet pipeline, a 9-4-liquid argon gas inlet pipeline, a 10-liquid methane gas heat exchanger and a second water-cooling heat exchanger.
Detailed Description
The invention is further described below in conjunction with the detailed description. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
Example 1
As shown in fig. 1-3, a dry gas sequential separation system based on argon circulation refrigeration, wherein an ethylene separation module comprises a weight removal separation system, an ethane separation system and an ethylene separation system; the methane separation module comprises a methane separation system and an argon circulation refrigerating system;
after the dry gas enters a rectification separation system in a heavy removal separation system, propylene propane and other heavy components separated from the bottom of the heavy removal column are discharged, light components separated from the top of the heavy removal column enter an ethane separation system for rectification separation, liquid-phase ethane separated from the bottom of the ethane column enters an ethylene separation system for providing cold energy, overhead gas separated from the top of the ethane column enters the ethylene separation system for rectification separation, liquid-phase ethylene separated from the bottom of the ethylene column is discharged, overhead gas separated from the top of the ethylene column enters a methane separation system for rectification separation, separated liquid methane flows out from the bottom of the methane rectification column and enters a liquid methane-argon heat exchanger in an argon circulation refrigerating system, cold energy of the liquid methane is transmitted to circulating argon, and the circulating argon is used for providing cold energy for a methane column top condenser in the methane separation system, so that a dry gas separation process and a cold energy recycling process are realized.
Further, the heavy component removal and separation system comprises a feeding heat exchanger S1, a heavy component removal tower S2, a reboiler S3 at the bottom of the heavy component removal tower, a heavy component removal tower top dephlegmator S4, a heavy component throttling expansion valve S5 and a heavy component cold energy heat exchanger S6. The dry gas raw material enters a feeding heat exchanger S1 through a dry gas feeding pipeline S1-1 to exchange heat, enters a heavy-duty removal tower bottom reboiler S3 to exchange heat with tower bottom liquid of a heavy-duty removal tower S2, and then enters the heavy-duty removal tower S2 through a heavy-duty removal tower feeding pipeline S2-1 to carry out rectification separation; the separated bottom liquid of the heavy-duty removal tower flows out through a discharging pipeline S2-3 at the bottom of the heavy-duty removal tower, enters a heat absorption pipeline of a heavy-duty cold energy heat exchanger S6 through a heavy-duty throttling expansion valve S5 to release cold energy, enters a raw material heat exchanger heat absorption pipeline to release cold energy again, and is discharged out of the system through a reheating heavy-duty discharging pipeline S1-2; the separated gas phase at the top of the heavy component removal tower enters a heat release pipeline of the heavy component cold energy heat exchanger S6 through a discharge pipeline S2-2 at the top of the heavy component removal tower. The bottom of the de-heaving tower is a liquid-phase propylene propane and other heavy components, part of the liquid-phase propylene propane is circularly heated in a reboiler at the bottom of the tower to generate steam, the gas phase at the top of the de-heaving tower is a light component containing ethane, ethylene, methane, nitrogen and hydrogen, and the light component enters an ethane separation system.
Further, the ethane separation system comprises an ethane tower S8, an ethane tower bottom reboiler S9 and an ethane tower top dephlegmator S10; the gas phase at the top of the heavy component removal tower leaves the heat release pipeline of the heavy component cold energy heat exchanger S6, enters an ethane tower bottom reboiler S9 to exchange heat with the bottom liquid of the ethane tower S8, and then enters the ethane tower S8 through an ethane tower feeding pipeline S8-1 to carry out rectification separation; after the liquid-phase ethane at the bottom of the separated ethane tower S8 flows out through an ethane tower bottom discharge pipeline S8-3, passes through an ethane throttling expansion valve S11, enters an ethylene tower top dephlegmator through a liquid-phase ethane pipeline S14-1 to release cold energy to the ethylene tower top dephlegmator S14 of the ethylene separation system, flows into a feed heat exchanger S1 through a gas-phase ethane pipeline S14-2 to further release condensation, and is discharged out of the system through a reheat ethane discharge pipeline S1-3; the separated ethane column overhead gas enters the ethylene separation system through ethane column overhead discharge line S8-2. The top of the ethane tower is light component containing ethylene methane, the bottom of the ethane tower is liquid-phase ethane, part of the ethane is circularly heated by feeding in a reboiler at the bottom of the ethane tower to generate steam, and the other ethane is discharged out of the ethane rectifying tower in liquid state.
Further, the ethylene separation system comprises an ethylene tower S12, an ethylene tower bottom reboiler S13 and an ethylene tower top dephlegmator S14; the gas phase at the top of the ethane tower enters an ethylene tower bottom reboiler to exchange heat with the bottom liquid of the ethylene tower, and then enters the ethylene tower through an ethylene tower feeding pipeline S12-1 to carry out gas-liquid separation; the separated ethylene tower bottom liquid-phase ethylene is discharged out of the system through an ethylene tower bottom discharging pipeline S12-2; the separated ethylene tower overhead gas enters a methane separation system. The top of the ethylene tower is light component containing methane, nitrogen, hydrogen and the like, and the bottom of the ethylene tower is liquid-phase ethylene product.
Further, a heavy-duty removal column top dephlegmator S4 and an ethane column top dephlegmator S10 are connected with the refrigerating unit S7. The refrigeration cycle is completed through the medium pipeline S7-1 of the back refrigerating unit, the medium pipeline S7-2 of the back refrigerating unit, the medium pipeline S7-3 of the out refrigerating unit and the medium pipeline S7-4 of the out refrigerating unit, and the purpose of the tower top refrigeration system is to provide cold energy for the heavy-duty removal tower and the ethane tower S8 to form reflux liquid so as to complete the separation process. A refrigerating unit using methane or ethylene as refrigerating medium is generally adopted, and belongs to the conventional industrial technology.
The methane separation system comprises a methane rectifying tower 2, a methane tower bottom reboiler 1 and a methane tower top dephlegmator 3; one end of the methane tower bottom reboiler 1 is connected with a raw material gas pipeline 1-1 for conveying the top gas of the ethylene tower, and the other end of the methane tower bottom reboiler is used for conveying the top gas of the ethylene tower into the methane rectifying tower 2 through a methane rectifying tower feeding pipeline 2-1. The top gas of the ethylene tower is used as a heat source of a reboiler 1 at the bottom of the methane tower, heat energy is transferred to circulating liquid at the bottom of the methane tower in the reboiler 1 at the bottom of the methane tower, and part of the liquid at the bottom of the methane tower is gasified to form gas phase for separation; part of nitrogen in the ascending gas phase in the tower absorbs argon cold energy in the methane tower top dephlegmator 3 to be condensed into liquid nitrogen, so that reflux liquid in the tower is formed, and the methane and the nitrogen are efficiently separated. And (3) passing through a methane rectifying tower 3, obtaining light components without methane at the top of the tower through a tower top gas phase discharge pipeline 2-2, including nitrogen and hydrogen, and obtaining liquid methane at the bottom of the tower through a tower bottom liquid phase discharge pipeline 2-3.
Further, the argon circulation refrigerating system comprises a methane throttling expansion valve 11, a liquid methane-argon heat exchanger 7, a liquid argon throttling expansion valve 8, a cold energy recovery heat exchanger 4, a circulating argon compressor 5 and a first water-cooling heat exchanger 6. The liquid methane flows into the circulating argon which is released by cold energy from the heat absorption pipeline of the liquid methane-argon heat exchanger 7 through the methane throttling expansion valve 11, the pipeline of the circulating argon before passing through the liquid argon throttling expansion valve 8 is a high-pressure liquid argon pipeline 8-1, and the pipeline after passing through the liquid argon throttling expansion valve 8 is a low-pressure liquid argon pipeline 8-2; after the circulating argon enters the methane tower top condenser 3 through the liquid argon throttling expansion valve 8 to release cold energy, the circulating argon enters the cold energy recovery heat exchanger 4 through the low-pressure cold argon pipeline 3-1 to release cold energy again, then enters the circulating argon compressor 5 from the low-pressure reheating argon pipeline 4-3 to be compressed, enters the first water cooling heat exchanger 6 to be cooled and precooled, enters the cold energy recovery heat exchanger 4 again through the high-pressure argon pipeline to be cooled and precooled, and then enters the liquid methane-argon heat exchanger 7 through the high-pressure cold argon pipeline 7-1 to obtain cold energy again, so that an argon circulating refrigeration main loop is realized.
Further, the gas separated in the methane separation system flows out from the top of the methane rectifying tower 2, enters the cold energy recovery heat exchanger 4 to release cold energy, and then flows into the top gas utilization or discharge system from the reheating top gas pipeline 4-1. The cold energy recovery heat exchanger 4 is used for releasing cold energy to the refrigerating system, so that the cold energy can be further recovered, and the utilization rate of the cold energy is improved. The gas phase at the top of the tower after reheating is discharged out of the system through a pipeline, and the separation of hydrogen, carbon monoxide, nitrogen and hydrogen can be realized through pressure swing adsorption or membrane separation, and the hydrogen is used as a raw material for synthesizing methanol or a hydrogenation raw material, so that the utilization rate of dry gas is improved. The pressure swing adsorption or membrane separation of methane gas compression cooling and overhead gas can be performed by adopting a common technical method in industry.
Further, cold methane gas flowing out of the heat absorption pipeline of the liquid methane-argon heat exchanger 7 enters the cold energy recovery heat exchanger 4 through the cold methane gas pipeline 7-2 to release cold energy again, and then flows into the methane utilization system from the reheating methane gas pipeline 4-2. And the reheated methane gas is discharged out of the system through a pipeline, compressed and cooled according to the pressure requirement of a user, and then is input into a user pipe network.
Further, the argon circulation refrigeration system also comprises an argon circulation refrigeration auxiliary loop, wherein the argon circulation refrigeration auxiliary loop comprises an argon expander 9, and specifically: one path of circulating argon gas separated from the argon circulating refrigeration main loop enters the cold energy recovery heat exchanger 4 for cooling and precooling, then enters the expander 9 for expansion and cooling through the expander expansion end inlet pipeline 9-1, returns to the cold energy recovery heat exchanger 4 through the expander expansion end outlet pipeline 9-2 for releasing cold energy and reheating, enters the expander compression end through the expander compression end inlet pipeline 9-3 for increasing pressure, enters the second water-cooling heat exchanger 10 for cooling through the expander compression end outlet pipeline 9-4, enters the first water-cooling heat exchanger 6 for cooling after further increasing pressure through the circulating argon gas compressor 5, and enters the cold energy recovery heat exchanger 4 for cooling and precooling through the high-pressure precooled argon gas pipeline 6-1 to form the argon circulating refrigeration auxiliary loop. The system takes circulating argon as working medium, recovers methane and nitrogen cold energy through a heat pump and cold energy recovery heat exchanger 4, supplements cold energy of a main argon circulation refrigeration loop through the refrigeration of an expander 9-1, and then utilizes argon Joule-Thomson effect to improve the grade of the cold energy and then transmits the grade to a methane separation system.
Furthermore, the invention also provides a separation method of the dry gas sequential separation system based on argon circulation refrigeration, liquid methane separated by the methane separation system enters the liquid methane-argon heat exchanger 7, cold energy of the liquid methane is transferred to circulating argon, and the circulating argon is used for providing cold energy for the methane tower top dephlegmator 3 in the methane separation system, so that the separation of ethylene tower top gas is realized.
The argon circulation refrigerating system uses argon as a circulation working medium, the methane and nitrogen cold energy of the separating system is recovered through the heat pump and the cold energy recovery heat exchanger, part of the argon supplements the cold energy through expansion refrigeration, and then the argon Joule-Thomson effect is utilized to improve the cold energy grade and then is transmitted to the methane tower top gas separating system, so that the high-efficiency separation is realized with lower refrigeration energy consumption, the high-price utilization of dry gas resources is realized, and the methane recovery rate can reach more than 99%.
According to the argon circulation refrigerating system, the liquid methane-argon heat exchanger is adopted, argon is used as a working medium to recycle liquid methane cold energy through the heat pump, the cold energy grade is improved by utilizing the Joule-Thomson effect of the argon and then is transmitted to a cooled medium, so that the liquid methane cold energy utilization rate can be effectively improved, the liquid methane cold energy utilization rate is improved to be more than 90%, the environment-friendly concept is better realized, and the energy-saving effect is clearly recorded in patent texts of application numbers 2018100218512 or 2018200373138 of the applicant.
While the methods and techniques of the present invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the art from this disclosure that variations and rearrangements of the methods and techniques can be made by those skilled in the art to arrive at a final preparation technique without departing from the spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be included within the spirit, scope and content of the invention.
Claims (6)
1. A dry gas sequential separation system based on argon circulation refrigeration is characterized in that: the system comprises an ethane-ethylene separation module and a methane separation module, wherein the ethane-ethylene separation module comprises a weight removal separation system, an ethane separation system and an ethylene separation system; the methane separation module comprises a methane separation system and an argon circulation refrigerating system;
the dry gas enters the heavy removal separation system for rectification separation, then a heavy component discharge system containing liquid-phase propylene and propane is separated from the bottom of the heavy removal column, the gas-phase light component separated from the top of the heavy removal column enters the ethane separation system for rectification separation, then the liquid-phase ethane separated from the bottom of the ethane column enters the ethylene separation system for providing cold energy, the top gas separated from the top of the ethane column enters the ethylene separation system for rectification separation, the liquid-phase ethylene discharge system is separated from the bottom of the ethylene column, the top gas separated from the top of the ethylene column enters the methane separation system for rectification separation, the separated liquid methane flows out from the bottom of the methane rectification column and enters a liquid methane-argon heat exchanger in the argon circulation refrigeration system, the cold energy of the liquid methane is transferred to circulation argon, and the circulation argon is used for providing cold energy for a methane top condenser in the methane separation system, so that a dry gas separation process and a cold energy recycling process are realized;
the methane separation system comprises a methane rectifying tower, a methane tower bottom reboiler and a methane tower top dephlegmator; the separated ethylene tower top gas enters a methane tower bottom reboiler to exchange heat with a methane rectifying tower bottom liquid phase and then is conveyed into the methane rectifying tower;
the argon circulation refrigerating system comprises a methane throttling expansion valve, a liquid methane-argon heat exchanger, a liquid argon throttling expansion valve, a cold energy recovery heat exchanger, a circulating argon compressor and a first water-cooling heat exchanger, wherein cold energy is released to circulating argon through a heat absorption pipeline of the liquid methane-argon heat exchanger, the circulating argon enters a methane tower top condenser through the liquid argon throttling expansion valve to release cold energy, enters the cold energy recovery heat exchanger through a low-pressure cold argon pipeline to release cold energy again, then enters the circulating argon compressor from a low-pressure reheating argon pipeline to be compressed, further increases the pressure, then enters the first water-cooling heat exchanger to be cooled and precooled, enters the cold energy recovery heat exchanger again through a high-pressure argon pipeline to be cooled and precooled, and then enters the liquid methane-argon heat exchanger to obtain cold energy again, so that a main argon circulation refrigerating loop is realized;
the gas separated in the methane separation system flows out from the top of the methane rectifying tower, enters the cold energy recovery heat exchanger to release cold energy, and flows into a tower top gas utilization or discharge system from a reheating tower top gas pipeline;
cold methane gas flowing out of a heat absorption pipeline of the liquid methane-argon heat exchanger enters the cold energy recovery heat exchanger through a cold methane gas pipeline to release cold energy again, and then flows into a methane utilization system from a reheating methane gas pipeline;
the argon circulation refrigerating system also comprises an argon circulation refrigerating auxiliary loop, wherein the argon circulation refrigerating auxiliary loop comprises an argon expander, and the argon circulation refrigerating auxiliary loop comprises the following components: one path of circulating argon gas separated from the argon circulation refrigeration main loop enters the cold energy recovery heat exchanger to cool and precool, then directly enters the expander to expand and cool through the expansion end inlet pipeline of the expander, returns to the cold energy recovery heat exchanger through the expansion end outlet pipeline of the expander to release cold energy and reheat, then enters the expander to increase pressure through the compression end inlet pipeline of the expander and enters the second water-cooling heat exchanger to cool through the compression end outlet pipeline of the expander, then enters the first water-cooling heat exchanger to cool after being further increased in pressure through the circulating argon gas compressor, and enters the cold energy recovery heat exchanger to cool and precool through the high-pressure argon gas pipeline to form the argon circulation refrigeration auxiliary loop.
2. The dry gas sequential separation system based on argon cycle refrigeration of claim 1, wherein: the heavy-removal separation system comprises a feeding heat exchanger, a heavy-removal tower, a reboiler at the bottom of the heavy-removal tower, a heavy-removal tower top segregator, a heavy component throttling expansion valve and a heavy component cold energy heat exchanger, wherein the dry gas raw material enters the feeding heat exchanger through a feeding pipeline to exchange heat, enters the reboiler at the bottom of the heavy-removal tower to exchange heat with the bottom liquid of the heavy-removal tower, and then enters the heavy-removal tower to carry out rectification separation; the separated heavy component of the liquid-phase propane propylene of the heavy component removal tower enters a heat absorption pipeline of a heavy component cold energy heat exchanger through a heavy component throttling expansion valve to release cold energy, then enters a heat absorption pipeline of a raw material heat exchanger to release cold energy again to reheat, and then is discharged out of the system; the separated gas phase at the top of the heavy-component removal tower enters a heat release pipeline of the heavy-component cold energy heat exchanger.
3. The dry gas sequential separation system based on argon cycle refrigeration of claim 2, wherein: the ethane separation system comprises an ethane tower, an ethane tower bottom reboiler and an ethane tower top dephlegmator; the gas phase at the top of the heavy component removal tower leaves the heat release pipeline of the heavy component cold energy heat exchanger, enters the reboiler at the bottom of the ethane tower to exchange heat with the bottom liquid of the ethane tower, and then enters the ethane tower to carry out rectification separation; the separated ethane tower bottom liquid-phase ethane passes through an ethane throttling expansion valve to release cold energy to an ethylene tower top dephlegmator of an ethylene separation system, and then flows into a feeding heat exchanger to be further released and condensed, and is discharged out of the system; the separated ethane column overhead gas enters the ethylene separation system.
4. The dry gas sequential separation system based on argon cycle refrigeration of claim 2, wherein: the ethylene separation system comprises an ethylene tower, an ethylene tower bottom reboiler and an ethylene tower top dephlegmator; the gas phase at the top of the ethane tower enters an ethylene tower bottom reboiler to exchange heat with the bottom liquid of the ethylene tower, and then enters the ethylene tower to carry out rectification separation; the separated liquid-phase ethylene is discharged from the bottom of the ethylene tower to the system; the separated ethylene tower top gas enters the methane separation module.
5. A dry gas sequential separation system based on argon cycle refrigeration as claimed in claim 3 wherein: the heavy-removal tower top dephlegmator and the ethane tower top dephlegmator are connected with a refrigerating unit.
6. The separation method of the dry gas sequential separation system based on argon circulation refrigeration according to any one of claims 1 to 5, characterized by: and after the dry gas enters the heavy component containing propylene and propane and is rectified and removed by the heavy component removing separation system, heavy component discharging system is used for separating heavy component from the bottom of the heavy component removing tower, the top gas separated from the top of the heavy component removing tower enters the ethane separation system for rectification and separation, the liquid-phase ethane separated from the bottom of the ethane tower provides cold energy for the ethylene separation system, the top gas separated from the top of the ethane tower enters the ethylene separation system for rectification and separation, the liquid-phase ethylene discharged from the bottom of the ethylene tower enters the methane separation system for rectification and separation, the separated liquid methane flows out from the bottom of the methane rectification tower and enters the liquid methane-argon heat exchanger in the argon circulation refrigerating system, the cold energy of the liquid methane is transmitted to the circulating argon, and the circulating argon is used for providing cold energy for the methane tower top condenser in the methane separation system, so that a dry gas separation process and a cold energy recycling process are realized.
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| CN102115355B (en) * | 2010-12-27 | 2013-07-31 | 东华工程科技股份有限公司 | Method for separating low-carbon olefins |
| JP5500240B2 (en) * | 2012-05-23 | 2014-05-21 | ダイキン工業株式会社 | Refrigeration equipment |
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| JP2005221199A (en) * | 2004-02-09 | 2005-08-18 | Kobe Steel Ltd | Air separation device |
| CN102419071A (en) * | 2011-12-12 | 2012-04-18 | 杭州中泰深冷技术股份有限公司 | Separation and recycling device and recycling method for methane and argon in synthetic ammonia relief gas |
| CN106256813A (en) * | 2015-06-16 | 2016-12-28 | 中国石化工程建设有限公司 | A kind of separation and recovery method of Fischer-Tropsch process exhaust |
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