A light hydrocarbon recovery system for an offshore floating production storage and offloading unit

Abstract

The utility model relates to a kind of light hydrocarbon recovery system for offshore floating production storage and offloading device.The light hydrocarbon recovery system includes: raw material gas processing module, cooling module, separation module, tower rectification module.Light hydrocarbon recovery method includes the following steps: pressurized cooling raw material gas;Pressurized cooling first remaining part, separation obtains second oil phase part and second gas phase part;Cooling second oil phase part and second gas phase part;Using deethanizer to heat third liquid phase part;Cooling separation fourth gas phase part;Through fifth liquid phase part reflux into deethanizer and fourth gas phase part carry out gas-liquid heat mass exchange;Using debutanizer to heat processing first oil phase part and sixth liquid phase part;Cooling separation seventh gas phase part;Through liquefied petroleum gas into debutanizer and seventh gas phase part carry out gas-liquid heat mass exchange, to obtain light hydrocarbon.The utility model can recover light hydrocarbon on platform, meet environmental protection requirement, while bring remarkable economic benefits.

Description

Technical Field

[0001] This utility model relates to the field of light hydrocarbon recovery, and in particular to a light hydrocarbon recovery system for offshore floating production storage and offloading (FPSO) units. Background Technology

[0002] Associated gas (oilfield gas) in offshore oil fields is an important resource coexisting with seabed oil. It is a mixture of hydrocarbons and non-hydrocarbons extracted during crude oil extraction or separated through oil and gas gathering and transportation. Considering the space limitations of the production platform in Floating Production Storage and Offloading (FPSO) units, the constraints on storage and offloading equipment, and the difficulty in controlling associated gas, a portion of the associated gas becomes fuel for the FPSO, while the surplus gas is directly released and burned as flare gas. Associated gas contains a significant amount of liquefied petroleum gas (LPG) and stable light hydrocarbon components; direct combustion of this resource leads to its waste.

[0003] Furthermore, associated gas containing a high proportion of heavy components has a high calorific value and produces a large amount of polluting gases upon combustion. The establishment of a light hydrocarbon recovery system in the top module of an FPSO is of great significance for reducing the loss of marine oil and gas resources and improving the comprehensive recovery and utilization of associated gas resources.

[0004] Therefore, it is necessary to develop a novel light hydrocarbon recovery system and method for offshore floating production storage and offloading (FPSO) units to address the aforementioned problems in related technologies. Utility Model Content

[0005] The purpose of this invention is to provide a light hydrocarbon recovery system for offshore floating production storage and offloading (FPSO) units, which can recover light hydrocarbons on FPSO platforms and reduce air pollution.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] This utility model provides a light hydrocarbon recovery system for offshore floating production storage and offloading (FPSO) units, comprising:

[0008] The raw gas processing module includes a compressor separator, compressor, cooler, condensate booster pump, and dryer;

[0009] The cooling module includes a first cold box, a second cold box, and a third cold box;

[0010] The separation module includes a cryogenic separator, an ethane removal column top separator, and a butane removal column top separator;

[0011] The tower distillation module includes an ethane stripper and a butane stripper;

[0012] The raw gas processing module, the first cold box, the low-temperature separator, and the de-ethanizer are connected in sequence;

[0013] The gas phase outlet of the deethaner is connected to the top separator of the deethaner via the second cold box;

[0014] The liquid phase outlet of the top separator of the ethane stripper is refluxed to the ethane stripper;

[0015] The ethane removal tower, the butane removal tower, the third cold box, and the butane removal tower top separator are connected in sequence;

[0016] The liquid phase outlet of the top separator of the butane removal tower is refluxed to the butane removal tower.

[0017] Furthermore, the liquid phase outlet of the cryogenic separator is connected to the first cold box via a throttling valve to provide cooling energy to the first cold box; the gas phase outlet of the cryogenic separator is connected to the top separator of the de-ethanizer via an expander to provide cooling energy to the top separator of the de-ethanizer.

[0018] Furthermore, the gas phase outlet of the deethaner top separator is connected to the first cold box to provide cooling energy to the first cold box.

[0019] Furthermore, the raw gas processing module includes a first pressurization and separation module and a second pressurization and separation module, wherein the first pressurization and separation module and the second pressurization and separation module are composed of the compressor separator, the compressor and the condensate oil booster pump.

[0020] Furthermore, the first pressurization and separation module is connected to the second pressurization and separation module and the butane removal tower respectively; the second pressurization and separation module is connected to the dryer and the first cold box respectively.

[0021] Furthermore, the liquid phase outlet of the deethaner top separator is connected to the top of the deethaner via pressurized reflux.

[0022] Furthermore, it also includes a circulating refrigeration module, which includes a refrigerant, a throttling valve, a first pressurization separation module, and a second pressurization separation module. The first and second pressurization separation modules are composed of a compressor separator, a compressor, and a cooler. The circulating refrigeration module, the throttling valve, the second cold box, and the third cold box are connected in sequence to provide cooling energy to the second and third cold boxes. The refrigerant is ethane, propane, and butane.

[0023] Furthermore, the cooler and the throttle valve in the second stage of the circulating refrigeration module are connected by a first pipeline, which passes through the second cold box and is used to pre-cool the refrigerant; the throttle valve and the third cold box are connected by a second pipeline, which passes through the second cold box and is used to provide cooling capacity to the second cold box.

[0024] This utility model provides a method for recovering light hydrocarbons in offshore floating production storage and offloading (FPSO) units, comprising the following steps:

[0025] The feed gas is pressurized and cooled to separate the first oil phase and the first remaining phase.

[0026] The first remaining portion is pressurized and cooled to separate the second oil phase portion and the second gas phase portion.

[0027] The second oil phase and the second gas phase are cooled to separate the third liquid phase and the third gas phase.

[0028] The third liquid phase is heated using a deethanizer to obtain the fourth gas phase.

[0029] The fourth gas phase portion is cooled and separated to obtain a fifth gas phase portion and a fifth liquid phase portion;

[0030] The fifth liquid phase is refluxed into the deethanizer and undergoes gas-liquid heat and mass exchange with the fourth gas phase to obtain the sixth liquid phase.

[0031] The first oil phase and the sixth liquid phase are heated using a butanizer to obtain the seventh gas phase.

[0032] The seventh gas phase is cooled and separated to obtain liquefied petroleum gas;

[0033] The liquefied petroleum gas enters the butane removal tower and undergoes gas-liquid heat and mass exchange with the seventh gas phase section to obtain light hydrocarbons.

[0034] Furthermore, in the step of cooling the second oil phase portion and the second gas phase portion to separate and obtain the third liquid phase portion and the third gas phase portion, the method further includes: cooling the second oil phase portion and the second gas phase portion by throttling and depressurizing the third liquid phase portion.

[0035] Furthermore, in the step of cooling and separating the fourth gas phase portion to obtain the fifth gas phase portion and the fifth liquid phase portion, the method further includes cooling the fourth gas phase portion by expanding the third gas phase portion under reduced pressure.

[0036] Furthermore, in the step of cooling the second oil phase portion and the second gas phase portion to separate and obtain the third liquid phase portion and the third gas phase portion, the method further includes: cooling the second oil phase portion and the second gas phase portion through the fifth gas phase portion.

[0037] Further, after step 1: cooling the second oil phase and the second gas phase by the fifth gas phase portion, the method further includes: pressurizing and pre-cooling the fifth gas phase portion; and cooling the seventh gas phase portion by throttling and expanding the fifth gas phase portion.

[0038] Furthermore, it also includes: pressurizing and pre-cooling the refrigerant, wherein the refrigerant is ethane, propane, or butane; and cooling the fourth gas phase portion and the seventh gas phase portion by throttling and depressurizing the refrigerant.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The light hydrocarbon recovery system provided by this utility model can realize the recovery of light hydrocarbons, reduce the pollution of associated gas in oil fields, meet environmental protection requirements, and bring significant economic benefits.

[0041] 2. This utility model has a flexible process structure design. Based on the specific characteristics of the gas source components, it obtains a suitable refrigerant through raw material gas treatment and adjusts the throttling pressure of the valve, thereby adapting to changes in various gas source conditions and demonstrating the strong adaptability of the raw material gas.

[0042] 3. The feed gas processing capacity of this invention can reach 2×10^4 Sm3 / h, with a C3+ molar content of up to 60%. Through the application of this invention, the recovery rate of liquefied petroleum gas can reach 95%, significantly higher than the 80% recovery rate disclosed by traditional processes. Furthermore, offshore light hydrocarbon recovery does not require excessively high C3 recovery rates; a small amount of C3 flows out along with the C1 and C2 components at the top of the deethaner column as fuel gas, which can improve the calorific value of the fuel gas, fully demonstrating the superiority of this invention.

[0043] 4. After expansion treatment by the expander in this utility model, the generated low-temperature gas directly enters the top separator of the de-ethane tower for separation. This effectively reduces the cold energy supply required in the refrigeration cycle, reduces energy consumption, and improves the overall process efficiency.

[0044] 5. Both the ethane removal tower and the butane removal tower in this utility model adopt a high-efficiency packed tower design, and the bottom reboiler is a kettle heat exchanger. This combination can meet the distillation requirements of different gas sources, ensure separation effect and product quality, and improve the flexibility and adaptability of the process.

[0045] 6. The cold box of the cooling module in this utility model adopts a high-efficiency aluminum plate-fin heat exchanger. This design improves the heat exchange efficiency of the low-temperature heat exchanger, optimizes energy utilization, reduces energy loss, and enhances the overall system performance.

[0046] 7. Both the compressor and expander in this utility model adopt a coupling structure design. The expander efficiently converts internal energy into mechanical energy through an adiabatic expansion process, while the compressor converts mechanical energy into internal energy through the coupling, so that the raw material gas is effectively pressurized. This process significantly saves the energy consumption required for pressurizing the raw material gas and improves the energy efficiency ratio of the system. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the light hydrocarbon recovery system in an embodiment of this utility model.

[0048] Figure label:

[0049] 11. Compressor separator; 12. Compressor; 13. Cooler; 14. Condensate oil booster pump; 15. Dryer; 16. Reflux booster pump;

[0050] 21. First cold box; 22. Second cold box; 23. Third cold box;

[0051] 31. Low-temperature separator; 32. Ethane removal column top separator; 33. Butane removal column top separator;

[0052] 4. Throttling valve;

[0053] 51. First pipeline; 52. Second pipeline;

[0054] 61. Expander compressor; 62. Expander;

[0055] 71. Ethane removal tower; 72. Butane removal tower. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. This embodiment is based on the technical solution of the present invention and provides detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0057] This utility model embodiment provides a light hydrocarbon recovery system for offshore floating production storage and offloading (FPSO) units, comprising:

[0058] The raw gas processing module includes a compressor separator 11, a compressor 12, a cooler 13, a condensate oil booster pump 14, and a dryer 15;

[0059] The cooling module includes a first cold box 21, a second cold box 22, and a third cold box 23;

[0060] The separation module includes a cryogenic separator 31, an ethane removal column top separator 32, and a butane removal column top separator 33;

[0061] The column distillation module includes an ethane stripper 71 and a butane stripper 72;

[0062] The raw gas processing module, the first cold box 21, the cryogenic separator 31 and the ethane stripper 71 are connected in sequence;

[0063] The gas phase outlet of the deethanizer 71 is connected to the top separator 32 of the deethanizer via the second cold box 22;

[0064] The liquid phase outlet of the deethaner top separator 32 is refluxed to the deethaner 71;

[0065] Ethane removal tower 71, butane removal tower 72, third cold box 23 and butane removal tower top separator 33 are connected in sequence;

[0066] The liquid phase outlet of the top separator 33 of the debutanizer is refluxed to the debutanizer 72.

[0067] In some embodiments of this utility model, the liquid phase outlet of the cryogenic separator 31 is connected to the first cold box 21 via a throttling valve 4 to provide cooling energy to the first cold box 21; the gas phase outlet of the cryogenic separator 31 is connected to the de-ethanizer top separator 32 via an expander 62 to provide cooling energy to the de-ethanizer top separator 32.

[0068] In some embodiments of this invention, the gas phase outlet of the deethaner top separator 32 is connected to the first cold box 21 to provide cooling energy to the first cold box 21.

[0069] In some embodiments of this utility model, the raw gas processing module includes a first pressurization and separation module and a second pressurization and separation module, which are composed of a compressor separator 11, a compressor 12 and a condensate oil booster pump 14.

[0070] In some embodiments of this utility model, the first pressurization and separation module is connected to the second pressurization and separation module and the butane removal tower 72, respectively; the second pressurization and separation module is connected to the dryer 15 and the first cold box 21, respectively.

[0071] In some embodiments of this utility model, the liquid phase outlet of the deethaner top separator 32 is connected to the top of the deethaner 71 via pressurized reflux.

[0072] In some specific embodiments, the liquid phase from the top separator 32 of the deethaner and the liquid phase from the top separator 33 of the debutaner are both refluxed via the reflux booster pump 16.

[0073] In some embodiments of this utility model, a circulating refrigeration module is also included. The circulating refrigeration module includes a refrigerant, a throttle valve 4, a first pressurization separation module and a second pressurization separation module. The first pressurization separation module and the second pressurization separation module are composed of a compressor separator 11, a compressor 12 and a cooler 13. The circulating refrigeration module, the throttle valve 4, the second cold box 22 and the third cold box 23 are connected in sequence to provide cooling energy to the second cold box 22 and the third cold box 23. The refrigerant is ethane, propane and butane.

[0074] In some embodiments of this utility model, the circulating refrigeration module and the throttle valve 4 are connected by a first pipeline 51, which passes through the second cold box 22 and is used to pre-cool the refrigerant; the throttle valve 4 and the third cold box 23 are connected by a second pipeline 52, which passes through the second cold box 22 and is used to provide cooling capacity to the second cold box 22.

[0075] This utility model embodiment provides a method for recovering light hydrocarbons in a floating production storage and offloading (FPSO) unit at sea, comprising the following steps:

[0076] S1: Pressurize and cool the feed gas to separate it into a first oil phase and a first residual phase;

[0077] S2: Pressurize and cool the first remaining portion to separate and obtain the second oil phase and the second gas phase;

[0078] S3: Cool the second oil phase and the second gas phase to separate and obtain the third liquid phase and the third gas phase;

[0079] S4: Use deethanizer 71 to heat the third liquid phase section to obtain the fourth gas phase section;

[0080] S5: Cool and separate the fourth gas phase portion to obtain the fifth gas phase portion and the fifth liquid phase portion;

[0081] S6: The fifth liquid phase is refluxed into the deethanizer 71 and undergoes gas-liquid heat and mass exchange with the fourth gas phase to obtain the sixth liquid phase.

[0082] S7: Use debutanizer 72 to heat the first oil phase and the sixth liquid phase to obtain the seventh gas phase;

[0083] S8: Cool and separate the seventh gas phase to obtain liquefied petroleum gas;

[0084] S9: Liquefied petroleum gas enters the butane dehydrogenator 72 and undergoes gas-liquid heat and mass exchange with the seventh gas phase section to obtain light hydrocarbons.

[0085] In some embodiments of this utility model, the step of cooling the second oil phase portion and the second gas phase portion to separate and obtain the third liquid phase portion and the third gas phase portion further includes: cooling the second oil phase portion and the second gas phase portion by throttling and depressurizing the third liquid phase portion.

[0086] In some embodiments of this utility model, the step of cooling and separating the fourth gas phase portion to obtain the fifth gas phase portion and the fifth liquid phase portion further includes: cooling the fourth gas phase portion by expanding the third gas phase portion under reduced pressure.

[0087] In some embodiments of this utility model, the step of cooling the second oil phase portion and the second gas phase portion to separate and obtain the third liquid phase portion and the third gas phase portion further includes: cooling the second oil phase portion and the second gas phase portion through the fifth gas phase portion.

[0088] In some embodiments of this utility model, after the step of cooling the second oil phase and the second gas phase by the fifth gas phase portion, the method further includes: pressurizing and pre-cooling the fifth gas phase portion; and cooling the seventh gas phase portion by throttling and expanding the fifth gas phase portion.

[0089] In some embodiments of this invention, the method further includes: pressurizing and pre-cooling the refrigerant, wherein the refrigerant is ethane, propane, or butane; and cooling the fourth and seventh gas phase portions by throttling and depressurizing the refrigerant.

[0090] In some specific embodiments, the raw gas is processed by a pressurization and separation module, specifically by sequentially passing through a compressor separator 11, a compressor 12, and a cooler 13 to achieve pressurization and cooling. The raw gas passes through a first pressurization and separation module and a second pressurization and separation module arranged in two stages, and is finally pressurized to 2500 kPa to 2600 kPa and cooled to 35°C before entering the dryer 15. The dryer 15 is a molecular sieve dehydrator, and the compressor separator 11 is a vertical three-phase separator. The aqueous phase is sent to the water treatment unit. The first oil phase and the first residual phase obtained by the first pressurization and separation module are separated. The first oil phase is sent to the butane removal tower 72. The second oil phase obtained by the second pressurization and separation module and the dried second gas phase are sent together to the first cold box 21. After being cooled to -45°C to -41°C by the first cold box 21, the gas enters the low-temperature separator 31 for separation.

[0091] In some specific embodiments, the cryogenic separator 31 separates a third liquid phase and a third gas phase; the third liquid phase is first transported to the first cold box 21 via the throttle valve 4 to provide cold energy to the first cold box 21 to cool the second oil phase and the second gas phase, and then transported to the deethanizer 71; the third gas phase is depressurized and expanded by the expander 62 and transported to the deethanizer top separator 32 to provide cold energy to the deethanizer top separator 32 to cool the fourth gas phase.

[0092] In some specific embodiments, a reboiler is installed at the bottom of the deethanizer 71. The third liquid phase is heated by heat transfer oil, electricity, or steam to obtain the fourth gas phase. The fourth gas phase is cooled to -45°C to -40°C by the second cold box 22 and then sent to the top separator 32 of the deethanizer for cooling and separation.

[0093] In some specific embodiments, the top separator 32 of the deethanizer separates a fifth gas phase and a fifth liquid phase; the fifth gas phase mainly consists of C1 and C2, with small amounts of C3 and C4. The fifth gas phase is fed as a cold stream to the first cold box 21 to cool the second oil phase and the second gas phase; the fifth liquid phase is refluxed to the top of the deethanizer 71 via a booster pump, forming a sixth liquid phase at the bottom of the deethanizer 71, wherein the sixth liquid phase is composed of C1 and C2. 3+ After the sixth liquid phase is depressurized, it is sent to the butane removal tower 72.

[0094] In some specific embodiments, the butane desane tower 72 processes the first oil phase and the sixth liquid phase through a reboiler to obtain the seventh gas phase at the top of the tower. The seventh gas phase is cooled to 24°C to 26°C by the third cold box 23. After the gas is completely condensed, it enters the butane desane tower top separator 33 for separation to obtain liquefied petroleum gas (LPG). Part of the LPG is exported, and the other part is refluxed back to the top of the butane desane tower 72, where light hydrocarbons are formed at the bottom of the butane desane tower 72, thus obtaining C2O4. 5+ .

[0095] In some specific embodiments, the gaseous natural gas flowing out of the deethaner top separator 32 enters the first cold box 21 as a cold source for heat exchange, and then is pressurized by the expansion compressor 61 and enters the second cold box 22 for pre-cooling. After pre-cooling, it is expanded again through the throttle valve 4 and enters the third cold box 23 to cool the seventh gas phase. After heat exchange, it is exported.

[0096] In some specific embodiments, the refrigerant components of the circulating refrigeration module are mainly ethane, propane and butane. After being pressurized by two-stage compression, the refrigerant enters the second cold box 22 for pre-cooling and then returns to the second cold box 22 for heat exchange through the throttling valve 4. The refrigeration temperature range is -55℃ to -50℃. After that, it continues to enter the third cold box 23 to provide cooling capacity. After heat exchange, it returns to the compression process to complete the refrigeration cycle.

[0097] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0098] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0099] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0100] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0101] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0102] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A light hydrocarbon recovery system for offshore floating production storage and offloading (FPSO) units, characterized in that, include: The raw gas processing module includes a compressor separator (11), a compressor (12), a cooler (13), a condensate oil booster pump (14), and a dryer (15); The cooling module includes a first cold box (21), a second cold box (22), and a third cold box (23); The separation module includes a cryogenic separator (31), an ethane stripper top separator (32), and a butane stripper top separator (33); The column distillation module includes an ethane stripper (71) and a butane stripper (72); The raw gas processing module, the first cold box (21), the low-temperature separator (31) and the de-ethanizer (71) are connected in sequence; The gas phase outlet of the deethanizer (71) is connected to the top separator (32) of the deethanizer via the second cold box (22); The liquid phase outlet of the top separator (32) of the deethaner is refluxed to the deethaner (71); The ethane removal tower, the butane removal tower (72), the third cold box (23), and the butane removal tower top separator (33) are connected in sequence; The liquid phase outlet of the top separator (33) of the debutanizer is refluxed to the debutanizer (72).

2. The light hydrocarbon recovery system according to claim 1, characterized in that, The liquid phase outlet of the cryogenic separator (31) is connected to the first cold box (21) via a throttle valve (4) to provide cooling energy to the first cold box (21); the gas phase outlet of the cryogenic separator (31) is connected to the de-ethanizer top separator (32) via an expander (62) to provide cooling energy to the de-ethanizer top separator (32).

3. The light hydrocarbon recovery system according to claim 1, characterized in that, The gas phase outlet of the de-ethane separator (32) is connected to the first cold box (21) to provide cooling energy to the first cold box (21).

4. The light hydrocarbon recovery system according to claim 1, characterized in that, The raw gas processing module includes a first booster separation module and a second booster separation module. The first booster separation module and the second booster separation module are composed of the compressor separator (11), the compressor (12) and the condensate booster pump (14).

5. The light hydrocarbon recovery system according to claim 4, characterized in that, The first pressurization and separation module is connected to the second pressurization and separation module and the butane removal tower (72); the second pressurization and separation module is connected to the dryer (15) and the first cold box (21).

6. The light hydrocarbon recovery system according to claim 1, characterized in that, The liquid phase outlet of the deethaner top separator (32) is connected to the top of the deethaner (71) via pressurized reflux.

7. The light hydrocarbon recovery system according to claim 1, characterized in that, It also includes a circulating refrigeration module, which includes a refrigerant, a throttle valve (4), a first pressurization separation module and a second pressurization separation module. The first pressurization separation module and the second pressurization separation module are composed of a compressor separator (11), a compressor (12) and a cooler (13). The circulating refrigeration module, the throttle valve (4), the second cold box (22) and the third cold box (23) are connected in sequence to provide cooling energy to the second cold box (22) and the third cold box (23). The refrigerant is ethane, propane and butane.

8. The light hydrocarbon recovery system according to claim 7, characterized in that, The circulating refrigeration module and the throttle valve (4) are connected by a first pipeline (51), which passes through the second cold box (22) and is used to pre-cool the refrigerant; the throttle valve (4) and the third cold box (23) are connected by a second pipeline (52), which passes through the second cold box (22) and is used to provide cooling capacity to the second cold box (22).

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