Light hydrocarbon separation system and method thereof

Abstract

The invention provides a light hydrocarbon separation system and a method thereof. The system comprises a demethanation unit, a decarburized light hydrocarbon unit and an expansion unit, wherein the demethanation unit comprises a first condenser; the demethanation unit, the decarburized light hydrocarbon unit and the expansion unit are sequentially connected through pipelines, and the expansion unit is connected with the first condenser through a pipeline; the demethanization unit is used for separating out methane hydrogen in a material, and the first condenser is used for cooling the methane hydrogen; the decarburized light hydrocarbon unit is used for receiving the residual material conveyed by the demethanation unit and separating out the decarburized light hydrocarbon; the expansion unit is used for receiving the gas-phase carbon disulfide hydrocarbon and conducting expansion treatment on the gas-phase carbon disulfide hydrocarbon, and liquid-phase carbon disulfide hydrocarbon obtained after expansion is conveyed to the first condenser to serve as a refrigerant of the first condenser to provide cooling capacity. According to the system, the carbon disulfide light hydrocarbon in the separation process is conveyed to the condenser to serve as a refrigerant to provide cooling capacity, and energy consumption and cost of light hydrocarbon separation are remarkably reduced.

Description

Technical Field

[0001] This application relates to the field of chemical separation technology, and in particular to a light hydrocarbon separation system and method thereof. Background Technology

[0002] In the existing petrochemical industry, various chemical products and their derivatives prepared from crude oil have become necessities of modern life. With the diversification of light hydrocarbon raw materials and light hydrocarbon production methods, the feed components in light hydrocarbon separation systems also change. In some specific scenarios, these materials are mainly composed of one or more of the following: C2 light hydrocarbons, CO, methane, C3 light hydrocarbons, nitrogen, hydrogen, and argon.

[0003] Traditional light hydrocarbon separation methods typically employ a cold separation process centered around a decarbonization light hydrocarbon tower. This tower is connected to cooling equipment, which uses a C2 refrigeration system with C2 light hydrocarbons at -100°C as the refrigerant. The separation of each light hydrocarbon substance is achieved by controlling the temperature and pressure.

[0004] However, C2 refrigeration systems that use C2 light hydrocarbons as refrigerants need to be set up separately, resulting in high energy consumption and high cost for the light hydrocarbon separation system. Summary of the Invention

[0005] This application provides a light hydrocarbon separation system and method thereof, the system comprising: a demethanizing unit, a decarbonized light hydrocarbon unit, and an expansion unit, wherein the demethanizing unit includes a first condenser;

[0006] The demethanizing unit, the decarbonized light hydrocarbon unit, and the expansion unit are connected in sequence by pipelines, and the expansion unit is connected to the first condenser pipeline;

[0007] The demethanizing unit is used to separate the methane hydrogen from the material, and the first condenser is used to cool the methane hydrogen;

[0008] The decarbonized light hydrocarbon unit is used to receive the remaining material conveyed by the demethanizing unit and separate out the C2 light hydrocarbons, wherein the C2 light hydrocarbons include gaseous C2 light hydrocarbons and liquid C2 light hydrocarbons.

[0009] The expansion unit is used to receive the gaseous C2 light hydrocarbon and expand it, and then transport the expanded liquid C2 light hydrocarbon to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

[0010] In the system described above, the decarbonized light hydrocarbon unit is connected to the first condenser line;

[0011] The decarbonized light hydrocarbon unit is used to transport the liquid-phase C2 light hydrocarbon to the first condenser through a pipeline to provide cooling capacity as a refrigerant for the first condenser.

[0012] The system described above further includes a cryogenic heat exchange unit, a demethanizing unit further includes a demethanizing tower reflux tank, and an expansion unit includes an expander, a compressor, and an expander outlet tank, wherein the expander and the compressor are coaxial devices.

[0013] The low-temperature heat exchange unit is connected to the demethanizer reflux tank, the first condenser, the expander outlet tank, and the compressor pipeline, respectively.

[0014] The low-temperature heat exchange unit is used to cool the material and then deliver it to the demethanizing unit. It also receives the methane hydrogen delivered by the demethanizing tower reflux tank, the C2 light hydrocarbon delivered by the first condenser, and the gaseous C2 light hydrocarbon delivered by the expander outlet tank to recover the cooling energy for its own power supply.

[0015] The demethanizing tower reflux tank is used to receive the methane hydrogen supplied by the first condenser and to supply the methane hydrogen to the low-temperature heat exchange unit;

[0016] The expander is used to receive the gaseous C2 light hydrocarbons conveyed by the decarbonized light hydrocarbon unit and to expand the gaseous C2 light hydrocarbons.

[0017] The expander outlet tank is used to receive the expanded C2 light hydrocarbons conveyed by the expander and to transport the gaseous C2 light hydrocarbons therein to the low-temperature heat exchange unit.

[0018] The compressor is used to receive C2 light hydrocarbons after the subcooling is recovered by the low-temperature heat exchange unit and to pressurize them.

[0019] In the system described above, the compressor is connected to the pretreatment system pipeline to transport the pressurized C2 light hydrocarbons back to the demethanizing unit for recycling;

[0020] The upstream system is connected to the demethanizing unit pipeline and is used to compress the reacted material and transport the compressed material to the demethanizing unit.

[0021] As described above, the decarbonization unit for light hydrocarbons includes an ethylene separation tower and an ethane separation tower. The demethanization unit, the ethylene separation tower, and the ethane separation tower are connected in sequence by pipelines. The ethane separation tower is connected to the expansion unit by pipelines.

[0022] The ethylene separation tower is used to receive the remaining material from the demethanizing unit and separate the ethylene.

[0023] The ethane separation tower is used to receive the remaining material conveyed by the ethylene separation tower and separate out the ethane, wherein the ethane includes gaseous ethane and liquid ethane;

[0024] The expansion unit is used to receive the gaseous ethane and expand it, and then deliver the expanded liquid ethane to the first condenser to provide cooling as a refrigerant for the first condenser.

[0025] In the system described above, the ethane separator is connected to the first condenser pipeline via an ethane separator reflux tank;

[0026] The ethane separation tower reflux tank is used to receive the ethane delivered by the ethane separation tower and to transport the liquid ethane through a pipeline to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

[0027] In the system described above, the cryogenic heat exchange unit is used to receive the methane hydrogen delivered by the demethanizer reflux tank, the ethane delivered by the first condenser, and the gaseous ethane delivered by the expander outlet tank, and recover the cold energy to power itself.

[0028] The expander is used to receive the gaseous ethane conveyed by the ethane separation tower reflux tank and to expand the gaseous ethane.

[0029] The expander outlet tank is used to receive the expanded ethane delivered by the expander and to deliver the gaseous ethane therein to the cryogenic heat exchange unit.

[0030] The compressor is used to receive ethane after the subcooling is recovered by the cryogenic heat exchange unit, and then pressurize it before circulating it to the demethanizing unit.

[0031] In the system described above, the ethylene separation tower is connected to the first condenser pipeline via an ethylene separation tower reflux tank;

[0032] The ethylene separation tower reflux tank is used to receive the ethylene delivered by the ethylene separation tower and to transport the ethylene through a pipeline to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

[0033] In the system described above, the low-temperature heat exchange unit is used to receive the methane hydrogen delivered by the demethanizer reflux tank, the ethane and ethylene delivered by the first condenser, and the gaseous ethane delivered by the expander outlet tank to recover the cooling energy for its own power supply.

[0034] The expander is used to receive the gaseous ethane conveyed by the ethane separation tower reflux tank and to expand the gaseous ethane.

[0035] The expander outlet tank is used to receive the expanded ethane delivered by the expander and to deliver the gaseous ethane therein to the cryogenic heat exchange unit.

[0036] The compressor is used to receive ethylene after the subcooling is recovered by the cryogenic heat exchange unit, and then pressurize it before circulating it to the demethanizing unit.

[0037] This application provides a method for separating light hydrocarbons, applied to the above-mentioned light hydrocarbon separation system, the method comprising:

[0038] A demethanizing unit is used to separate the hydrogen methane from the material, and the first condenser in the demethanizing unit is used to cool the hydrogen methane.

[0039] The decarbonyl hydrocarbon unit receives the remaining material from the demethanizing unit and separates out the C2 hydrocarbons, which include gaseous C2 hydrocarbons and liquid C2 hydrocarbons.

[0040] An expansion unit is used to receive gaseous C2 light hydrocarbons and expand them. The resulting liquid C2 light hydrocarbons are then transported to the first condenser to provide cooling as a refrigerant.

[0041] This application provides a light hydrocarbon separation system and method. By connecting an expansion unit to the demethanizing light hydrocarbon unit pipeline, the separated gaseous C2 light hydrocarbons are expanded. The expanded liquid C2 light hydrocarbons are then supplied to a first condenser as a refrigerant to provide cooling, allowing the first condenser to cool the methane. This eliminates the need for a separate C2 refrigeration system for the demethanizing unit, significantly reducing the energy consumption and cost of the light hydrocarbon separation system. The light hydrocarbon separation method uses an expansion unit to expand the gaseous C2 light hydrocarbons separated from the demethanizing unit, and then supplies the expanded liquid C2 light hydrocarbons to the first condenser as a refrigerant. By utilizing the C2 light hydrocarbons from the separation process as a refrigerant, a separate C2 refrigeration system for the demethanizing unit is unnecessary, significantly reducing the energy consumption and cost of the light hydrocarbon separation system. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0043] Figure 1 A schematic diagram (1) of a light hydrocarbon separation system provided in an embodiment of this application;

[0044] Figure 2 A schematic diagram (2) of a light hydrocarbon separation system provided in an embodiment of this application;

[0045] Figure 3A schematic diagram (3) of a light hydrocarbon separation system provided in an embodiment of this application;

[0046] Figure 4 A schematic diagram (4) of a light hydrocarbon separation system provided in an embodiment of this application;

[0047] Figure 5 A schematic diagram (5) of a light hydrocarbon separation system provided in an embodiment of this application;

[0048] Figure 6 A schematic diagram (6) of a light hydrocarbon separation system provided in an embodiment of this application;

[0049] Figure 7 A schematic diagram (7) of a light hydrocarbon separation system provided in an embodiment of this application;

[0050] Figure 8 This is a flowchart of a light hydrocarbon separation method provided in an embodiment of this application.

[0051] Figure Labels

[0052] 101 - Demethanization unit; 102 - Decarbonization unit; 103 - Expansion unit; 101a - First condenser;

[0053] 201b - Demethanizer reflux tank; 201c - Demethanizer; 203a - Expander; 203b - Compressor; 203c - Expander outlet tank; 204 - Cryogenic heat exchange unit; 205 - Pressure reducing valve;

[0054] 302a - Ethylene separation tower; 302b - Ethane separation tower;

[0055] 402c - Ethane separator reflux tank; 402d - Cooler; 404a - First pressure reducing valve; 404b - Second pressure reducing valve;

[0056] 506 - Upstream Unit;

[0057] 602c - Ethylene Separation Tower Reflux Tank;

[0058] 702e - First cooler; 702f - Second cooler.

[0059] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0060] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0061] Figure 1 A schematic diagram (1) of a light hydrocarbon separation system provided in an embodiment of this application is shown below. Figure 1 As shown, the first aspect of this application provides a light hydrocarbon separation system, which includes a demethanizing unit 101, a decarbonylating unit 102, and an expansion unit 103. The demethanizing unit includes a first condenser 101a.

[0062] The demethanizing unit 101, the decarbonized light hydrocarbon unit 102 and the expansion unit 103 are connected in sequence by pipelines, and the expansion unit 103 is connected to the first condenser 101a by pipeline.

[0063] The demethanizing unit 101 is used to separate the methane hydrogen from the material, and the first condenser 101a is used to cool the methane hydrogen.

[0064] The decarbonyl hydrocarbon removal unit 102 is used to receive the remaining material conveyed by the demethanizing unit 101 and separate out the C2 hydrocarbons, wherein the C2 hydrocarbons include gaseous C2 hydrocarbons and liquid C2 hydrocarbons.

[0065] The expansion unit 103 is used to receive gaseous C2 light hydrocarbons and expand them, and then transport the expanded liquid C2 light hydrocarbons to the first condenser 101a to provide cooling capacity as a refrigerant for the first condenser 101a.

[0066] Among them, methane hydrogen is a mixture of at least two of methane, CO, hydrogen, nitrogen, and argon.

[0067] Optionally, the first condenser 101a can be located at the upper end of the demethanizing unit 101 to cool the methane hydrogen, or it can be located at other positions in the demethanizing unit 101, as long as it can cool the methane hydrogen. This embodiment does not limit this.

[0068] The demethanizing unit 101 includes equipment for receiving materials and separating hydrogen methane, such as a demethanizing tower, and a container for holding hydrogen methane condensed by the first condenser 101a, such as a demethanizing tower reflux tank. This embodiment does not limit the scope of the equipment.

[0069] For example, a first condenser 101a is installed at the top of the demethanizer. One end of the first condenser 101a is connected to the top of the demethanizer via a pipeline to receive the separated methane hydrogen. After condensation, the methane hydrogen is transported to the demethanizer reflux tank via a pipeline. At this time, the reflux tank contains two phases of methane hydrogen, gas and liquid. The gas phase is taken out from the top of the demethanizer reflux tank, and the liquid phase is returned to the demethanizer via a pipeline.

[0070] Optionally, a second condenser can be installed in the middle of the demethanizer. The second condenser is used to cool the gas components with higher condensation points in the demethanizer to reduce the mass of the gas components cooled by the first condenser 101a, thereby reducing the energy consumption of the first condenser 101a. The temperature of the second condenser can be provided by a propylene refrigeration system, and the temperature can be set to -35°C, or other temperatures that can be adjusted according to actual conditions. This embodiment does not limit this.

[0071] In a specific implementation, the material enters the demethanizing unit 101 to separate the methane hydrogen from the material. The remaining material is then transported to the decarbonyl hydrocarbon removal unit 102. Upon receiving the remaining material, the decarbonyl hydrocarbon removal unit 102 separates the C2 hydrocarbons. The remaining material is then transported to the downstream device. The separated gaseous C2 hydrocarbons are transported to the expansion unit 103. The expansion unit 103 expands the gaseous C2 hydrocarbons, and a portion of the expanded C2 hydrocarbons becomes liquid. The liquid C2 hydrocarbons are then transported to the first condenser 101a to provide cooling as a refrigerant for the first condenser 101a.

[0072] A pressure reducing valve can be installed on the connecting pipeline between the expansion unit 103 and the first condenser 101a to reduce the pressure of the liquid C2 light hydrocarbons delivered from the expansion unit 103, so that the reduced liquid C2 light hydrocarbons can be cooled to a lower temperature, providing more cooling capacity to the first condenser 101a.

[0073] Optionally, the expanded gaseous C2 light hydrocarbons can be directly extracted, or they can be compressed and recycled to the demethanizing unit 101 to re-enter the separation process as a refrigerant to provide cooling capacity. This embodiment does not limit this.

[0074] Optionally, the liquid C2 hydrocarbons separated from the decarbonized light hydrocarbon unit 102 can also be transported to the first condenser 101a as supplementary refrigerant to provide cooling capacity to the first condenser 101a.

[0075] The decarbonized light hydrocarbon unit 102 includes equipment for receiving the remaining material from the demethanizing unit 101 and separating the light hydrocarbons, such as a decarbonized light hydrocarbon tower, equipment for cooling the separated light hydrocarbons, such as a condenser, and containers for holding the condensed light hydrocarbons, such as a separation tank. This embodiment does not limit these components.

[0076] Optionally, the material can be cooled by a heat exchanger before entering the demethanizing unit 101. The separated methane hydrogen and C2 light hydrocarbons can also enter the heat exchanger before being extracted. Since the methane and C2 light hydrocarbons are cooled after separation and have a low temperature, entering the heat exchanger can provide cooling to the heat exchanger, thereby reducing the energy consumption of the heat exchanger.

[0077] It should be noted that the demethanizing unit 101, the decarbonized light hydrocarbon unit 102, and the expansion unit 103 are connected in sequence via pipelines. The bottom of the demethanizing unit 101 is connected to the pipeline of the decarbonized light hydrocarbon unit 102 so as to transport the remaining material in the demethanizing unit 101 to the decarbonized light hydrocarbon unit 102, or other connection points, as long as it is ensured that the decarbonized light hydrocarbon unit 102 can receive the remaining material. This embodiment does not limit this. The expansion unit 103 can be set downstream of the flow stream of the decarbonized light hydrocarbon unit 102 so as to receive the gaseous C2 light hydrocarbons transported by the decarbonized light hydrocarbon unit 102, or other locations, as long as it is ensured that the expansion unit 103 can receive the gaseous C2 light hydrocarbons. This embodiment does not limit this.

[0078] The light hydrocarbon separation system provided in this embodiment connects the expansion unit 103 to the decarbonized light hydrocarbon unit 102 via pipeline. The expansion unit 103 expands the gaseous C2 light hydrocarbons separated from the decarbonized light hydrocarbon unit, and the expanded liquid C2 light hydrocarbons are then transported to the first condenser 101a as a refrigerant to provide cooling. This eliminates the need to connect a separate C2 refrigeration system to the demethanizing unit 101 to obtain cooling, significantly reducing the energy consumption and cost of the light hydrocarbon separation system.

[0079] In some implementations, the decarbonized light hydrocarbon unit is connected to the first condenser line;

[0080] The decarbonized light hydrocarbon unit is used to transport liquid-phase C2 light hydrocarbons through pipelines to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

[0081] It is understandable that the C2 hydrocarbons separated from the decarbonyl hydrocarbon unit include gaseous C2 hydrocarbons and liquid C2 hydrocarbons.

[0082] Specifically, the liquid C2 hydrocarbons separated in the decarbonized light hydrocarbon unit are transported through pipelines to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

[0083] A pressure reducing valve can be installed on the connecting pipeline between the decarbonized light hydrocarbon unit and the first condenser to reduce the pressure of the liquid-phase light hydrocarbons delivered from the decarbonized light hydrocarbon unit, so that the reduced liquid-phase light hydrocarbons can be cooled to a lower temperature, providing more cooling capacity to the first condenser.

[0084] Optionally, the first condenser can be connected to the bottom pipeline of the decarbonized light hydrocarbon unit to facilitate the delivery of liquid-phase C2 light hydrocarbons to the first condenser, or it can be connected to pipelines at other locations in the decarbonized light hydrocarbon unit, as long as the delivery of liquid-phase C2 light hydrocarbons to the first condenser is ensured. This embodiment does not limit this.

[0085] The light hydrocarbon separation system provided in this embodiment connects the decarbonized light hydrocarbon unit to the first condenser pipeline, so that the separated liquid C2 light hydrocarbons can also enter the first condenser as supplementary refrigerant to provide cooling capacity, ensuring sufficient refrigerant in the condenser and further reducing the energy consumption of the light hydrocarbon separation system.

[0086] Furthermore, a schematic diagram (2) of a light hydrocarbon separation system provided in one embodiment of this application is shown below. Figure 2 As shown, the light hydrocarbon separation system also includes a low-temperature heat exchange unit 204, the demethanizing unit 101 also includes a demethanizing tower reflux tank 201b, and the expansion unit 103 includes an expander 203a, a compressor 203b and an expander outlet tank 203c. The expander 203a and the compressor 203b are coaxial devices.

[0087] The low-temperature heat exchange unit 204 is connected to the demethanizer reflux tank 201b, the first condenser 101a, the expander outlet tank 203c, and the compressor 203b pipeline, respectively.

[0088] The low-temperature heat exchange unit 204 is used to cool the material and then transport it to the demethanizing unit 101. It also receives the methane hydrogen transported by the demethanizing tower reflux tank 201b, the C2 light hydrocarbons transported by the first condenser 101a, and the gaseous C2 light hydrocarbons transported by the expander outlet tank 203c to recover the cooling capacity for its own energy supply.

[0089] The demethanizer reflux tank 201b is used to receive the methane hydrogen supplied by the first condenser 101a and to transport the methane hydrogen to the cryogenic heat exchange unit 204.

[0090] Expander 203a is used to receive gaseous C2 hydrocarbons conveyed by decarbonized light hydrocarbon unit 102 and to expand the gaseous C2 hydrocarbons.

[0091] Expander outlet tank 203c is used to receive expanded C2 light hydrocarbons conveyed by expander 203a and to transport the gaseous C2 light hydrocarbons therein to low temperature heat exchange unit 204.

[0092] The compressor 203b is used to receive the C2 light hydrocarbons after the subcooling is recovered by the cryogenic heat exchange unit 204 and to pressurize them.

[0093] The demethanizing unit 101 may include equipment for receiving materials and separating methane from them, such as a demethanizing tower, etc., which is not limited in this embodiment.

[0094] Alternatively, the expander 203a can also be coaxial with the motor, and the motor can recover the output energy of the expander 203a as its own driving energy for power generation.

[0095] For example, the material first enters the low-temperature heat exchange unit 204 for cooling, and then is transported through a pipeline to the demethanizer 201c for the separation of methane hydrogen. The upper end of the demethanizer 201c is connected to the first condenser 101a. The methane hydrogen enters the first condenser 101a through the pipeline for cooling. The cooled methane hydrogen enters the demethanizer reflux tank 201b. At this time, the demethanizer reflux tank 201b contains both gas and liquid phases of methane hydrogen. The bottom of the demethanizer reflux tank 201b... The part is connected to the demethanizer 201c pipeline. Liquid methane hydrogen flows back to the demethanizer 201c through the pipeline. The top of the demethanizer reflux tank 201b is connected to the low-temperature heat exchange unit 204 pipeline. Gaseous methane hydrogen enters the low-temperature heat exchange unit 204 through the pipeline. After the low-temperature heat exchange unit 204 recovers the cold energy, it is extracted. The bottom pipeline of the demethanizer 201c is connected to the decarbonyl light hydrocarbon removal unit 102. The remaining material enters the decarbonyl light hydrocarbon removal unit 102 through the pipeline for the separation of C2 light hydrocarbons. The separated gaseous C2 light hydrocarbons are transported to expander 203a for expansion. Expander 203a connects to expander outlet tank 203c. The expanded C2 light hydrocarbons enter expander outlet tank 203c, which now contains both gas and liquid phases of C2 light hydrocarbons. The bottom of expander outlet tank 203c is connected to the first condenser 101a, and a pressure reducing valve 205 is installed on the pipeline to reduce the pressure of the liquid phase C2 light hydrocarbons. The carbon-2 light hydrocarbons are then transported via pipeline to the first condenser 101a as a refrigerant to provide cooling. After the subcooling is recovered in the first condenser 101a, the carbon-2 light hydrocarbons enter the low-temperature heat exchange unit 204 to recover cooling again. The upper end of the expander outlet tank 203c is connected to the pipeline of the low-temperature heat exchange unit 204, and the gaseous carbon-2 light hydrocarbons enter the low-temperature heat exchange unit 204 via pipeline to recover cooling. The carbon-2 light hydrocarbons with subcooling recovered in the low-temperature heat exchange unit 204 are then transported via pipeline to the compressor 203b for pressurization.

[0096] Optionally, the gaseous C2 light hydrocarbons separated from the expander outlet tank 203c can also be directly extracted after the cold energy is recovered by the low-temperature heat exchange unit 204.

[0097] Optionally, compressor 203b can be connected to an upstream system pipeline to circulate the pressurized C2 light hydrocarbons to the demethanizing unit 101 via the upstream system; or it can be connected to an ethylene distillation system pipeline; or the pipeline can be connected to other systems. This embodiment does not limit this. The ethylene distillation system can be an ethylene separation tower, a membrane separation device, etc., and this embodiment does not limit this.

[0098] The pressure in the demethanizer 201c is 1.5~3 MPaA, the temperature of the first condenser 101a is -50~-100℃, the pressure of the decarbonized light hydrocarbon unit 102 is 1.0~2.5 MPaA, the top temperature of the decarbonized light hydrocarbon unit 102 is 0~-39℃, the cooling capacity is supplied by a propylene refrigeration system, the inlet pressure of the expander 203a is 1.0~2.5 MPaA, the outlet pressure is 0.1~0.8 MPaA, the inlet pressure of the compressor 203b is 0.1~0.5 MPaA, and the outlet pressure is 0.1~0.8 MPaA.

[0099] It should be noted that the connection methods between the various units or devices provided in this embodiment are all exemplary, and the specific connection positions are not specifically limited, as long as the implementation of this solution is guaranteed.

[0100] The light hydrocarbon separation system provided in this embodiment includes a low-temperature heat exchange unit 204 for cooling the material, thereby improving the accuracy of subsequent component separation. Methane from the demethanizer reflux tank 201b, C2 light hydrocarbons from the first condenser 101a, and gaseous C2 light hydrocarbons from the expander outlet tank 203c are transported to the low-temperature heat exchange unit 204 for cold energy recovery, reducing the energy consumption of the low-temperature heat exchange unit 204. The expander outlet tank 203c allows for gas-liquid separation of the expanded C2 light hydrocarbons, with the liquid phase C2 light hydrocarbons being transported to the first condenser 101a as a refrigerant. The expander 203a and compressor 203b are coaxial devices; the compressor 203b can recover the output energy of the expander 203a as driving energy, thus saving power consumption. The recovered subcooled C2 light hydrocarbons are then transported to the compressor 203b for pressurization, facilitating subsequent applications of the C2 light hydrocarbons.

[0101] In some implementations, the compressor is connected to the pretreatment system pipeline of the light hydrocarbon separation system to transport the pressurized C2 light hydrocarbons back to the demethanizing unit for recycling;

[0102] The upstream system is used to compress the reacted material and then transport the compressed material to the demethanizing unit.

[0103] The upstream system may include equipment such as product gas compressors, but this embodiment does not limit this.

[0104] It should be noted that before light hydrocarbon separation, the material will first enter the pretreatment system for compression to reduce the material to the target pressure, and then the material will be transported to the demethanizing unit for separation.

[0105] Specifically, the C2 light hydrocarbons, after being pressurized by the compressor, are transported via pipeline to the pretreatment system so that they can re-enter the light hydrocarbon separation system along with the new material to provide cooling as a refrigerant.

[0106] The light hydrocarbon separation system provided in this embodiment uses the output energy of the expander as its own driving energy for the compressor. Therefore, when the C2 light hydrocarbons after being pressurized by the compressor are transported to the pretreatment system, no compression is required or only a small amount of power is consumed, thus reducing the energy consumption of the pretreatment system. Furthermore, the C2 light hydrocarbons are transported to the demethanizing unit through the pretreatment system to achieve circulation. This not only ensures sufficient refrigerant for C2 light hydrocarbons in the light hydrocarbon separation system, but also further reduces the energy consumption of the light hydrocarbon separation system.

[0107] In some embodiments, a schematic diagram (3) of a light hydrocarbon separation system provided in this application is shown, such as... Figure 3 As shown, the decarbonization unit 102 includes an ethylene separation tower 302a and an ethane separation tower 302b. The demethanization unit 101, the ethylene separation tower 302a and the ethane separation tower 302b are connected in sequence by pipelines. The ethane separation tower 302b is connected to the expansion unit 103 by pipelines.

[0108] Ethylene separation tower 302a is used to receive the residual material conveyed by the demethanizing unit 101 and separate out the ethylene;

[0109] Ethane separator 302b is used to receive the remaining material conveyed by ethylene separator 302a and separate out ethane, wherein the ethane includes gaseous ethane and liquid ethane;

[0110] The expansion unit 103 is used to receive gaseous ethane and expand it, and then transport the expanded liquid ethane to the first condenser 101a to provide cooling capacity as a refrigerant for the first condenser 101a.

[0111] Understandably, C2 light hydrocarbons include ethylene and ethane.

[0112] Specifically, after the material is dehydrogenated by the demethanizing unit 101, the remaining material enters the ethylene separation tower 302a to separate and collect the ethylene. The remaining material is then transported to the ethane separation tower 302b, where the ethane is separated out. The gaseous ethane is then transported to the expansion unit 103 for expansion. The expansion unit 103 is connected to the first condenser 101a via pipeline. A pressure reducing valve 205 is installed on the pipeline to reduce the pressure of the liquid ethane before it is transported to the first condenser 101a as a refrigerant to provide cooling.

[0113] Optionally, the liquid ethane separated by the ethane separator 302b can also be sent to the first condenser 101a as a supplementary refrigerant to provide cooling capacity to the first condenser 101a.

[0114] Optionally, the expanded gaseous ethane can be directly extracted, or it can be compressed and recycled to the demethanizing unit 101 to re-enter the separation process as a refrigerant to provide cooling. This embodiment does not limit this.

[0115] The light hydrocarbon separation system provided in this embodiment separates ethylene and ethane by setting up an ethylene separation tower 302a and an ethane separation tower 302b in the decarbonized light hydrocarbon unit 102, which facilitates the subsequent separate use of ethylene or ethane. The expansion unit 103 is connected to the pipeline of the ethane separation tower 302b, and a pressure reducing valve 205 is installed on the pipeline. Liquid ethane can be used as a refrigerant to provide cooling in the first condenser 101a. Moreover, the temperature of the liquid ethane after pressure reduction is lower, and more cooling is provided, thereby reducing the energy consumption of the light hydrocarbon separation system.

[0116] Furthermore, a schematic diagram (4) of a light hydrocarbon separation system provided in one embodiment of this application is shown below. Figure 4 As shown, ethane separator 302b is connected to the first condenser 101a via ethane separator reflux tank 402c.

[0117] The ethane separator reflux tank 402c is used to receive ethane from the ethane separator 302b and to transport the liquid ethane through a pipeline to the first condenser 101a to provide cooling capacity as a refrigerant for the first condenser 101a.

[0118] It should be noted that the ethane entering the reflux tank 402c of the ethane separator includes both liquid ethane and gaseous ethane.

[0119] Specifically, after the material passes through the demethane unit 101 and the ethylene separation tower 302a to remove methane hydrogen and ethylene respectively, it enters the ethane separation tower 302b. The ethane separated in the ethane separation tower 302b is cooled by the cooler 402d and then transported through a pipeline to the ethane separation tower reflux tank 402c. The ethane separation tower reflux tank 402c is connected to the first condenser 101a by a pipeline. A second pressure reducing valve 404b is installed on the pipeline to reduce the pressure of the liquid ethane before it is transported through the pipeline to the first condenser 101a as a refrigerant to provide cooling capacity. The gaseous ethane in the ethane separation tower reflux tank 402c enters the expansion unit 103 through a pipeline. The liquid ethane produced after expansion is then reduced by the first pressure reducing valve 404a and then transported to the first condenser 101a as a refrigerant to provide cooling capacity.

[0120] The first condenser 101a can be connected to the bottom pipeline of the ethane separation tower reflux tank 402c to facilitate the delivery of liquid ethane to the first condenser 101a, or it can be connected to other pipelines in the ethane separation tower reflux tank 402c. It is only necessary to ensure that liquid ethane is delivered to the first condenser 101a. This embodiment does not limit this.

[0121] The light hydrocarbon separation system provided in this embodiment connects the ethane separation tower reflux tank 402c to the first condenser 101a pipeline, which allows the separated liquid ethane to also enter the first condenser 101a as a supplementary refrigerant to provide cooling capacity. Moreover, the temperature of the liquid ethane after depressurization is lower, providing more cooling capacity, ensuring sufficient refrigerant in the first condenser 101a, and further reducing the energy consumption of the light hydrocarbon separation system.

[0122] Furthermore, a schematic diagram (5) of a light hydrocarbon separation system provided in one embodiment of this application is shown below. Figure 5 As shown, the low-temperature heat exchange unit 204 is used to receive the methane hydrogen delivered by the demethanizer reflux tank 201b, the ethane delivered by the first condenser 101a, and the gaseous ethane delivered by the expander outlet tank 203c, and recover the cold energy to power itself.

[0123] Expander 203a is used to receive gaseous ethane from ethane separation tower reflux tank 402c and to expand the gaseous ethane.

[0124] Expander outlet tank 203c is used to receive expanded ethane from expander 203a and transport the gaseous ethane therein to cryogenic heat exchange unit 204.

[0125] The compressor 203b is used to receive ethane after the subcooling is recovered by the cryogenic heat exchange unit 204, and then pressurize it and recycle it to the demethanizing unit 101.

[0126] The demethanizing unit 101 may include equipment for receiving materials and separating the methane hydrogen therein, such as a demethanizing tower, etc., which is not limited in this embodiment.

[0127] Specifically, before entering the demethanizing unit 101, the material is first cooled by the low-temperature heat exchange unit 204, and then enters the demethanizing tower 201c to separate the methane hydrogen. The methane hydrogen is cooled by the first condenser 101a and then enters the demethanizing tower reflux tank 201b. The demethanizing tower reflux tank 201b is connected to the low-temperature heat exchange unit 204 by pipeline. The gaseous methane hydrogen enters the low-temperature heat exchange unit 204 through the pipeline, and is collected after the low-temperature heat exchange unit 204 recovers the cold energy. The liquid methane hydrogen can be refluxed back to the demethanizing tower 201c. After demethanization... The remaining material from tower 201c enters ethylene separation tower 302a to separate ethylene and collect it. The remaining material is then conveyed to ethane separation tower 302b for ethane separation. After being cooled by cooler 402d, the ethane is conveyed to ethane separation tower reflux tank 402c. Ethane separation tower reflux tank 402c conveys the gaseous ethane to expander 203a, where it is expanded. Expander 203a is connected to expander outlet tank 203c. The expanded ethane enters expander outlet tank 203c. At this point, the expander outlet... Tank 203c separates gaseous ethane and liquid ethane. The bottom of the expander outlet tank 203c is connected to the pipeline of the first condenser 101a. A first pressure reducing valve 404a is installed on the pipeline to reduce the pressure of the liquid ethane before it is transported to the first condenser 101a as a refrigerant to provide cooling. After the subcooling is recovered by the first condenser 101a, the ethane enters the low-temperature heat exchange unit 204 to recover cooling again. The upper end of the expander outlet tank 203c is connected to the pipeline of the low-temperature heat exchange unit 204, and the gaseous ethane enters the low-temperature heat exchange unit 204 via the pipeline. The liquid ethane in the ethane separation tower reflux tank 402c is depressurized by the second pressure reducing valve 404b and then transported through pipeline to the first condenser 101a to provide cooling energy as a refrigerant. After the subcooled ethane is recovered by the first condenser 101a, it enters the low-temperature heat exchange unit 204 to recover cooling energy again. The subcooled ethane recovered by the low-temperature heat exchange unit 204 is then transported through pipeline to the compressor 203b for pressurization and then transported to the upstream unit 506 to be recycled with the material to the demethanizing unit 101, realizing the recycling of ethane as a refrigerant.

[0128] Optionally, the ethylene separated by the ethylene separation tower 302a can also be compressed by the low-temperature heat exchange unit 204 after the cold energy is recovered, and then the ethylene is recycled to the demethanizing unit 101 to realize the recycling of ethylene as a refrigerant. The components entering the compressor 203b can be determined according to the actual situation, and this embodiment does not limit this.

[0129] The light hydrocarbon separation system provided in this embodiment transports methane from the demethanizer reflux tank 201b, ethane from the first condenser 101a, and gaseous ethane from the expander outlet tank 203c to the low-temperature heat exchange unit 204 for cold energy recovery. This provides a certain amount of cooling capacity to the low-temperature heat exchange unit 204, thereby reducing its energy consumption. The expander outlet tank 203c is configured to perform gas-liquid separation on the expanded ethane, so that the liquid ethane is transported to the first condenser 101a as a refrigerant to provide cooling capacity. The ethane after recovering the subcooled capacity is transported to the compressor 203b for pressurization and then recycled to the demethanizer unit 101, so as to realize the recycling of ethane as a refrigerant and further save energy consumption of the light hydrocarbon separation system.

[0130] In some embodiments, a schematic diagram (6) of a light hydrocarbon separation system provided in this application is shown; such as Figure 6 As shown, the ethylene separation tower 302a is connected to the first condenser 101a via the ethylene separation tower reflux tank 602c.

[0131] The ethylene separation tower reflux tank 602c is used to receive ethylene from the ethylene separation tower 302a and transport the ethylene through a pipeline to the first condenser 101a to provide cooling capacity as a refrigerant for the first condenser 101a.

[0132] It should be noted that the ethylene entering the ethylene separation tower reflux tank 602c may include liquid ethylene and gaseous ethylene, or it may only include liquid ethylene.

[0133] Specifically, after the material passes through the demethane removal unit 101 to remove methane hydrogen, the remaining material is separated into ethylene by the ethylene separation tower 302a and transported via pipeline to the ethylene separation tower reflux tank 602c. The ethylene separation tower reflux tank 602c is connected to the first condenser 101a via pipeline. A second pressure reducing valve 404b is installed on the pipeline to reduce the pressure of the liquid phase ethylene before it is transported to the first condenser 101a as a refrigerant to provide cooling. The gaseous phase ethylene in the ethylene separation tower reflux tank 602c can be extracted. The ethylene separation tower 302a transports the remaining material to the ethane separation tower 302b. The ethane separated in the ethane separation tower 302b is transported via pipeline to the expansion unit 103. The expanded liquid phase ethane is then reduced in pressure by the first pressure reducing valve 404a and transported to the first condenser 101a as a refrigerant to provide cooling.

[0134] The first condenser 101a can be connected to the bottom pipeline of the ethylene separation tower reflux tank 602c to facilitate the delivery of liquid ethylene to the first condenser 101a, or it can be connected to other pipelines in the ethylene separation tower reflux tank 602c. It is only necessary to ensure that the liquid ethylene is delivered to the first condenser 101a. The output of liquid ethylene can be adjusted, and this embodiment does not limit this.

[0135] Optionally, the ethane separator 302b is connected to the first condenser 101a via pipeline, and liquid ethane is transported to the first condenser 101a via pipeline to provide cooling capacity as a refrigerant for the first condenser 101a. The first condenser 101a can be connected to both the ethane separator 302b and the ethylene separator 302a pipeline at the same time, or it can be connected to either one at will. This can be determined according to the actual production needs, and this embodiment does not limit this.

[0136] The light hydrocarbon separation system provided in this embodiment connects the ethylene separation tower reflux tank 602c to the first condenser 101a via pipeline. The liquid ethylene in the ethylene separation tower reflux tank 602c is transported to the first condenser 101a as a supplementary refrigerant to provide cooling capacity, thereby further ensuring sufficient refrigerant in the first condenser 101a and reducing the energy consumption of the light hydrocarbon separation system.

[0137] In some embodiments, a schematic diagram (7) of a light hydrocarbon separation system provided in an embodiment of this application is shown; such as Figure 7 As shown, the low-temperature heat exchange unit 204 is used to receive the methane hydrogen delivered by the demethanizer reflux tank 201b, the ethane and ethylene delivered by the first condenser 101a, and the gaseous ethane delivered by the expander outlet tank 203c, and recover their cold energy to power itself.

[0138] Expander 203a is used to receive gaseous ethane from ethane separation tower reflux tank 402c and to expand the gaseous ethane.

[0139] Expander outlet tank 203c is used to receive expanded ethane from expander 203a and transport the gaseous ethane therein to cryogenic heat exchange unit 204.

[0140] Compressor 203b is used to receive ethylene after the subcooling is recovered by cryogenic heat exchange unit 204, and then pressurize it before circulating it to demethanizing unit 101.

[0141] The demethanizing unit 101 may include equipment for receiving materials and separating the methane hydrogen therein, such as a demethanizing tower, etc., which is not limited in this embodiment.

[0142] Specifically, before entering the demethanizing unit 101, the material is first cooled by the cryogenic heat exchange unit 204, and then enters the demethanizing tower 201c to separate the methane hydrogen. The methane hydrogen is cooled by the first condenser 101a and then enters the demethanizing tower reflux tank 201b. The demethanizing tower reflux tank 201b is connected to the cryogenic heat exchange unit 204 by pipeline. The gaseous methane hydrogen enters the cryogenic heat exchange unit 204 through the pipeline, and is collected after the cryogenic heat exchange unit 204 recovers the cold energy. The liquid methane hydrogen can be refluxed to the demethanizing tower 201c. The remaining material after passing through the demethanizing tower 201c enters the ethylene separation tower 302. Ethylene is separated from condenser 302a. After being cooled by the second cooler 702f, the ethylene is sent to the ethylene separation tower reflux tank 602c. The ethylene separation tower reflux tank 602c is connected to the first condenser 101a by pipeline. A second pressure reducing valve 404b is installed on the pipeline. After the liquid phase ethylene is depressurized by the second pressure reducing valve 404b, it is sent to the first condenser 101a as a refrigerant to provide cooling. After the subcooling is recovered by the first condenser 101a, the ethylene enters the low-temperature heat exchange unit 204 to recover cooling again. The gaseous phase ethylene can be collected. The remaining material in the ethylene separation tower 302a is sent to the ethane separation tower 302b for further processing. Ethane separation: After being cooled by the first cooler 702e, the ethane is fed to the ethane separation tower reflux tank 402c. The ethane separation tower reflux tank 402c conveys the gaseous ethane to the expander 203a, where it is expanded. The expander 203a is connected to the expander outlet tank 203c. The expanded ethane enters the expander outlet tank 203c, which now contains both gas and liquid phases of ethane. The bottom of the expander outlet tank 203c is connected to the first condenser 101a, and a first pressure reducing valve 404a is installed on the pipeline to reduce the pressure of the liquid ethane. Ethane is transported via pipeline to the first condenser 101a as a refrigerant to provide cooling. After the subcooling is recovered in the first condenser 101a, the ethane enters the low-temperature heat exchange unit 204 to recover its cooling again before being extracted. The upper end of the expander outlet tank 203c is connected to the pipeline of the low-temperature heat exchange unit 204. Gas-phase ethane enters the low-temperature heat exchange unit 204 via pipeline to recover its cooling before being extracted. Ethylene, after the subcooling is recovered in the low-temperature heat exchange unit 24, is transported via pipeline to the compressor 203b for pressurization and then transported to the upstream unit 506 to be recycled to the demethanizing unit 101, realizing the recycling of ethylene as a refrigerant.

[0143] Optionally, the ethane separated by the ethane separator 302b can also be compressed by the low-temperature heat exchange unit 204 after recovering its cold energy, and then circulated to the demethanizing unit 101 to realize the cyclic use of ethane as a refrigerant; the components entering the compressor 203b can be determined according to the actual situation, and this embodiment does not limit this.

[0144] The light hydrocarbon separation system provided in this embodiment transports methane from the demethanizer reflux tank 201b, ethane and ethylene from the first condenser 101a, and gaseous ethane from the expander outlet tank 203c to the low-temperature heat exchange unit 204 for cold energy recovery. This provides a certain amount of cooling capacity to the low-temperature heat exchange unit 204, thereby reducing its energy consumption. The expander outlet tank 203c allows for gas-liquid separation of the expanded ethane, with the liquid ethane being transported to the first condenser 101a as a refrigerant to provide cooling capacity. The ethylene, after recovering its subcooled capacity, is transported to the compressor 203b for pressurization and then recycled back to the demethanizer unit 101, thus realizing the recycling of ethylene as a refrigerant and further saving energy consumption in the light hydrocarbon separation system.

[0145] Figure 8 A flowchart of a light hydrocarbon separation method provided in an embodiment of this application is shown below. Figure 8 As shown, the main body for implementing this method is the light hydrocarbon separation system as described in the first aspect, and it specifically includes the following steps:

[0146] S801. A demethanizing unit is used to separate the methane hydrogen from the material, and the first condenser in the demethanizing unit is used to cool the methane hydrogen.

[0147] Specifically, the material is fed into the demethanizing unit, where the methane hydrogen in the material is separated, and the methane hydrogen is cooled by the first condenser in the demethanizing unit before being extracted.

[0148] S802. The decarbonyl hydrocarbon unit receives the remaining material conveyed by the demethanizing unit and separates the C2 hydrocarbons, wherein the C2 hydrocarbons include gaseous C2 hydrocarbons and liquid C2 hydrocarbons.

[0149] Specifically, the remaining material after the methane hydrogen is removed by the demethanizing unit is transported to the decarbonyl hydrocarbon removal unit. After receiving the remaining material, the decarbonyl hydrocarbon removal unit separates the C2 hydrocarbons, which include liquid-phase C2 hydrocarbons and gas-phase C2 hydrocarbons.

[0150] S803. An expansion unit is used to receive gaseous C2 light hydrocarbons and expand them. The resulting liquid C2 light hydrocarbons are then transported to the first condenser to provide cooling as a refrigerant for the first condenser.

[0151] Specifically, the separated gaseous C2 light hydrocarbons are fed to an expander for expansion, and the expanded liquid C2 light hydrocarbons are fed to the first condenser to provide cooling as a refrigerant.

[0152] The expanded C2 light hydrocarbons also include gaseous C2 light hydrocarbons, which can be directly extracted or used for other purposes. This embodiment does not limit this.

[0153] Optionally, the liquid C2 hydrocarbons separated from the decarbonized light hydrocarbon unit can be returned to the decarbonized light hydrocarbon unit, or a portion can be sent to the first condenser as a refrigerant to release cooling capacity, or used for other purposes. This embodiment does not limit this.

[0154] The light hydrocarbon separation method provided in this embodiment uses an expansion unit to expand the gaseous C2 light hydrocarbons separated from the decarbonization unit, and then transports the expanded liquid C2 light hydrocarbons to the first condenser as a refrigerant to provide cooling. By using the C2 light hydrocarbons in the separation process as a refrigerant, there is no need to set up a separate C2 refrigeration system for the demethanization unit, which significantly reduces the energy consumption and cost of the light hydrocarbon separation system.

[0155] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A light hydrocarbon separation system, characterized in that, The system includes: a demethanizing unit, a decarbonized light hydrocarbon unit, and an expansion unit, wherein the demethanizing unit includes a first condenser; The demethanizing unit, the decarbonized light hydrocarbon unit, and the expansion unit are connected in sequence by pipelines, and the expansion unit is connected to the first condenser pipeline; The demethanizing unit is used to separate the methane hydrogen from the material, and the first condenser is used to cool the methane hydrogen; The decarbonized light hydrocarbon unit is used to receive the remaining material conveyed by the demethanizing unit and separate out the C2 light hydrocarbons, wherein the C2 light hydrocarbons include gaseous C2 light hydrocarbons and liquid C2 light hydrocarbons. The expansion unit is used to receive the gaseous C2 light hydrocarbon and expand it, and then transport the expanded liquid C2 light hydrocarbon to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

2. The system according to claim 1, characterized in that, The decarbonized light hydrocarbon unit is connected to the first condenser pipeline; The decarbonized light hydrocarbon unit is used to transport the liquid-phase C2 light hydrocarbon to the first condenser through a pipeline to provide cooling capacity as a refrigerant for the first condenser.

3. The system according to claim 1 or 2, characterized in that, The system also includes a cryogenic heat exchange unit, the demethanizing unit includes a demethanizing tower reflux tank, and the expansion unit includes an expander, a compressor, and an expander outlet tank, wherein the expander and the compressor are coaxial devices. The low-temperature heat exchange unit is connected to the demethanizer reflux tank, the first condenser, the expander outlet tank, and the compressor pipeline, respectively. The low-temperature heat exchange unit is used to cool the material and then deliver it to the demethanizing unit. It also receives the methane hydrogen delivered by the demethanizing tower reflux tank, the C2 light hydrocarbon delivered by the first condenser, and the gaseous C2 light hydrocarbon delivered by the expander outlet tank to recover the cooling energy for its own power supply. The demethanizing tower reflux tank is used to receive the methane hydrogen supplied by the first condenser and to supply the methane hydrogen to the low-temperature heat exchange unit; The expander is used to receive the gaseous C2 light hydrocarbons conveyed by the decarbonized light hydrocarbon unit and to expand the gaseous C2 light hydrocarbons. The expander outlet tank is used to receive the expanded C2 light hydrocarbons conveyed by the expander and to transport the gaseous C2 light hydrocarbons therein to the low-temperature heat exchange unit. The compressor is used to receive C2 light hydrocarbons after the subcooling is recovered by the low-temperature heat exchange unit and to pressurize them.

4. The system according to claim 3, characterized in that, The compressor is connected to the pretreatment system pipeline to transport the pressurized C2 light hydrocarbons back to the demethanizing unit for recycling; The upstream system is connected to the demethanizing unit pipeline and is used to compress the reacted material and transport the compressed material to the demethanizing unit.

5. The system according to claim 3, characterized in that, The decarbonization unit for light hydrocarbons includes an ethylene separation tower and an ethane separation tower. The demethanization unit, the ethylene separation tower, and the ethane separation tower are connected in sequence by pipelines. The ethane separation tower is connected to the expansion unit by pipelines. The ethylene separation tower is used to receive the remaining material from the demethanizing unit and separate the ethylene. The ethane separation tower is used to receive the remaining material conveyed by the ethylene separation tower and separate out the ethane, wherein the ethane includes gaseous ethane and liquid ethane; The expansion unit is used to receive the gaseous ethane and expand it, and then deliver the expanded liquid ethane to the first condenser to provide cooling as a refrigerant for the first condenser.

6. The system according to claim 5, characterized in that, The ethane separator is connected to the first condenser pipeline via an ethane separator reflux tank. The ethane separation tower reflux tank is used to receive the ethane delivered by the ethane separation tower and to transport the liquid ethane through a pipeline to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

7. The system according to claim 5 or 6, characterized in that, The low-temperature heat exchange unit is used to receive the methane hydrogen delivered by the demethanizer reflux tank, the ethane delivered by the first condenser, and the gaseous ethane delivered by the expander outlet tank, and recover the cold energy to power itself. The expander is used to receive the gaseous ethane conveyed by the ethane separation tower reflux tank and to expand the gaseous ethane. The expander outlet tank is used to receive the expanded ethane delivered by the expander and to deliver the gaseous ethane therein to the cryogenic heat exchange unit. The compressor is used to receive ethane after the subcooling is recovered by the cryogenic heat exchange unit, and then pressurize it before circulating it to the demethanizing unit.

8. The system according to claim 5, characterized in that, The ethylene separation tower is connected to the first condenser pipeline via an ethylene separation tower reflux tank. The ethylene separation tower reflux tank is used to receive the ethylene delivered by the ethylene separation tower and to transport the ethylene through a pipeline to the first condenser to provide cooling capacity as a refrigerant for the first condenser.

9. The system according to claim 8, characterized in that, The low-temperature heat exchange unit is used to receive the methane hydrogen delivered by the demethanizer reflux tank, the ethane and ethylene delivered by the first condenser, and the gaseous ethane delivered by the expander outlet tank to recover the cooling capacity for its own power supply. The expander is used to receive the gaseous ethane conveyed by the ethane separation tower reflux tank and to expand the gaseous ethane. The expander outlet tank is used to receive the expanded ethane delivered by the expander and to deliver the gaseous ethane therein to the cryogenic heat exchange unit. The compressor is used to receive ethylene after the subcooling is recovered by the cryogenic heat exchange unit, and then pressurize it before circulating it to the demethanizing unit.

10. A method for separating light hydrocarbons, characterized in that, The method is applied to the light hydrocarbon separation system according to any one of claims 1 to 9, the method comprising: A demethanizing unit is used to separate the hydrogen methane from the material, and the first condenser in the demethanizing unit is used to cool the hydrogen methane. A decarbonyl hydrocarbon removal unit receives the remaining material conveyed by the demethanizing unit and separates out the C2 hydrocarbons, wherein the C2 hydrocarbons include gaseous C2 hydrocarbons and liquid C2 hydrocarbons; An expansion unit is used to receive the gaseous C2 light hydrocarbon and expand it. The resulting liquid C2 light hydrocarbon is then transported to the first condenser to provide cooling as a refrigerant for the first condenser.

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