A method and device for recycling oilfield flare gas

Abstract

The invention discloses a method and device for recycling oilfield flare gas. First, the flare gas is passed into a gas-liquid separator to separate gaseous flare gas and liquid flare gas. The liquid flare gas is pumped to a liquid storage tank for storage. After the gaseous flare gas is pressurized by a first compressor, it enters a membrane separator and an adsorption separator to separate CH4 and C2+ light hydrocarbon components. The separated C2+ light hydrocarbon components are sent to a storage tank for storage. The separated CH4 tail gas enters a gas-fired generator set for power generation, and a waste heat recovery device is used to recover heat in the flue gas of the combustion engine to supply the oilfield heat-using equipment. The oilfield flare gas recovery device utilizes the flare gas discharged from the oilfield as a resource, thereby achieving the purpose of energy saving, emission reduction and efficiency improvement.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas recovery and utilization in petrochemical industry, and more particularly to a method and device for recovering and utilizing oilfield flare gas. Background Art

[0002] During the oilfield exploitation process, there is natural gas that coexists with oil between oil layers and is extracted together with oil, namely oilfield associated gas or light hydrocarbons, whose main components are methane, ethane, propane, butane, and a small amount of pentane and hydrocarbons. Due to the differences in the geographical location of oilfields, the situation of oilfield associated gas is also different, which can be divided into two types: one is that the associated gas volume is relatively large and the distribution is relatively concentrated, and it enters the pipeline network directly after purification; the other is the associated gas that is relatively scattered and in remote well areas. This part of the associated gas has a small output and is far away from the transmission pipeline. It is restricted by many objective conditions and cannot directly enter the pipeline network. The excess associated gas and some low-pressure separation flash gas generated in production, normal exhaust of control valves and sealing gas of process equipment are discharged to the flare device for combustion.

[0003] At present, most of my country's large oil fields have achieved the recycling of associated gas, but scattered and remote well areas do not have advanced recycling technology and have to burn the associated gas into the flare. According to the World Energy Association, about 140 billion cubic meters of associated gas from oil fields around the world are discharged into the atmosphere through flare devices every year, accounting for 25% of the natural gas demand in the European market and can meet Germany's annual electricity demand. Flare gas is rich in light hydrocarbon components, and its long-term combustion leads to a large amount of heat and CO2, NO X The entry of pollutants such as carbon monoxide into the atmosphere not only causes energy waste and atmospheric pollution, but also light hydrocarbons have high economic value. If they are effectively recycled, they will create great economic benefits.

[0004] Therefore, as the world is advocating the development of a green and environmentally friendly economy and responding to climate change, how to provide a method and device for recovering flare gas from scattered and remote well areas with low energy consumption and high efficiency is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method and device for recovering flare gas from scattered and remote well areas with low energy consumption and high efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for recycling oilfield flare gas comprises the following steps:

[0008] S1: transporting the flare gas to a gas-liquid separator for separation to obtain gaseous flare gas and liquid flare gas;

[0009] S2: transporting the liquid flare gas to a liquid storage tank for storage through a pump;

[0010] S3: transporting the gaseous flare gas to a membrane separator for separation, and transporting the flare gas separated by the membrane separator to an adsorption separator;

[0011] S4: The flare gas separated by the membrane separator is separated into CH4 by the adsorption separator, and the CH4 is transported to the gas-fired generator set for power generation and standby;

[0012] S5: The heat generated by the gas generator set is recovered through the waste heat recovery device for standby use.

[0013] Further, the S3 includes:

[0014] S31: pressurizing the gaseous flare gas through a first compressor;

[0015] S32: The pressurized flare gas is transported to a membrane separator for separation, and the flare gas separated by the membrane separator is transported to an adsorption separator.

[0016] Further, the S32 includes:

[0017] S321: The pressurized flare gas is transported to the first membrane separator to separate the permeate gas of C3+ and above components and the retentate gas of C1 and C2 components, and the permeate gas of C3+ and above components is compressed by the second compressor to be converted into liquid and enter the liquid storage tank;

[0018] S322: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second membrane separator, and the light hydrocarbon components attached to the membrane are purged to obtain purge gas;

[0019] S323: The retentate gas of the C1 and C2 components in S321 and the purge gas in S322 are transported together to the adsorption separator.

[0020] Furthermore, the specific process of S321 is as follows: valves V1, V2, and V6 on the first membrane separator are opened, valve V5 is closed, and the flare gas enters the first membrane separator through valve V1 to separate the permeate gas of C3+ and above components and the retentate gas of C1 and C2 components. The permeate gas has a pressure of 0.1 to 1.0 MPa, and enters the second compressor through valve V6, where it is compressed to 1.2 to 1.6 MPa and converted into liquid to enter the liquid storage tank; the retentate gas has a pressure of 0.95 to 2.9 MPa.

[0021] The specific process of S322 is as follows: valves V3 and V8 on the second membrane separator are in a closed state, valves V4 and V7 are in an open state, the non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the second membrane separator through valve V7, and the light hydrocarbon components attached to the membrane are purged out to obtain purge gas;

[0022] The specific process of S323 is as follows: the retentate gas is delivered to the adsorption separator through valve V2 and the purge gas is delivered to the adsorption separator through valve V4.

[0023] Further, the step S4 includes:

[0024] S41: The retentate gas of the C1 and C2 components in S323 and the purge gas in S322 are transported to the first adsorption separator, and the adsorbent adsorbs the C2+ light hydrocarbon components to separate CH4, and the CH4 is transported to the gas-fired generator set for power generation standby;

[0025] S42: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second adsorption separator to purge the C2+ light hydrocarbon components adsorbed by the adsorbent. At the same time, the purged C2+ light hydrocarbon components are compressed by the second compressor and converted into liquid to enter the liquid storage tank.

[0026] Furthermore, the specific process of S41 is as follows: valves V10 and V13 on the first adsorption separator are opened, valves V9 and V14 are closed, the retentate gas and the purge gas enter the first adsorption separator through valve V13, C2+ light hydrocarbon components are adsorbed by the adsorbent, the CH4 tail gas separated from the top of the adsorption separator has a pressure of 0.85 to 2.8 MPa, and the CH4 tail gas passes through valve V10 and enters the gas generator set for power generation;

[0027] The specific process of S42 is as follows: valves V11 and V16 on the second adsorption separator are in an open state, and valves V11 and V15 are in a closed state. The non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the adsorption separator through valve V11, and the C2+ light hydrocarbon components adsorbed by the adsorbent are purged out, and the adsorbent is regenerated. The purged C2+ light hydrocarbon components enter the second compressor through valve V16, are compressed to 1.2-1.6 MPa, and are converted into liquid and enter the heat storage tank.

[0028] An oilfield flare gas recovery and utilization device, comprising: a gas-liquid separator, a membrane separator, an adsorption separator, a liquid storage tank, a gas generator set, a waste heat recovery device, and a pump;

[0029] The gas-liquid separator is used to separate the gaseous flare gas from the liquid flare gas in the flare gas, and transport the gaseous flare gas to the membrane separator, and transport the liquid flare gas to the liquid storage tank for storage through a pump;

[0030] The membrane separator is connected to the gas-liquid separator and is used to separate the gaseous flare gas and transport the separated flare gas to the adsorption separator;

[0031] The adsorption separator is connected to the membrane separator, and is used to separate the flare gas after separation by the membrane separator to obtain CH4, and transport the CH4 to the gas generator set for power generation;

[0032] The waste heat recovery device is connected to the gas generator set and is used to recover the heat generated by the gas generator set for standby use.

[0033] Furthermore, it also includes a first compressor, which is arranged between the gas-liquid separator and the membrane separator, and is used to pressurize the gaseous flare gas and transport the pressurized gaseous flare gas to the membrane separator.

[0034] Furthermore, it also includes a second compressor connected to the liquid storage tank, the membrane separator includes a first membrane separator and a second membrane separator, the first compressor is connected to the gas-liquid separator and the first membrane separator, the first membrane separator is also connected to the second membrane separator, and the second membrane separator is connected to the adsorption separator;

[0035] The first membrane separator, the second membrane separator, and the adsorption separator are all connected to the liquid storage tank, and are also connected to the second compressor;

[0036] The first membrane separator is provided with valves V1, V2, V5 and V6, and the second membrane separator is provided with valves V3, V4, V7 and V8.

[0037] Further, the adsorption separator includes a first adsorption separator and a second adsorption separator, and the first membrane separator, the second membrane separator, the first adsorption separator and the second adsorption separator are connected to each other;

[0038] The first adsorption separator and the second adsorption separator are both connected to the liquid storage tank, and are also connected to the second compressor;

[0039] The first adsorption separator is provided with valves V9, V10, V13 and V14, and the second adsorption separator is provided with valves V11, V12, V15 and V16.

[0040] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method and device for recycling oilfield flare gas, which has the following effective effects:

[0041] 1) The present invention combines the membrane separation and adsorption separation technologies for the recovery of light hydrocarbons from oilfield flare gas, and has the advantage of a high recovery rate.

[0042] 2) The tail gas after light hydrocarbons are recovered by the present invention has high CH4 purity, which is beneficial to the production of gas-fired generator sets.

[0043] 3) The membrane separator and adsorption separator of the present invention both use more than two sets of separation devices, which ensures the continuous operation of the device and improves the separation efficiency and service life of the equipment.

[0044] 4) The present invention uses the non-condensable gas on the upper part of the liquid storage tank to purge and regenerate the membrane and the adsorbent, and does not need to provide regeneration gas from the outside, thus saving energy consumption and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0046] Figure 1 The accompanying drawing is a flow chart of a method for recycling oilfield flare gas provided by the present invention.

[0047] Figure 2 The accompanying drawing is a flowchart of S3 in the present invention.

[0048] Figure 3 The accompanying drawing is a flowchart of S32 in the present invention.

[0049] Figure 4 The accompanying drawing is a flowchart of S4 in the present invention.

[0050] Figure 5 The accompanying drawing is a schematic structural diagram of an oilfield flare gas recovery device provided by the present invention.

[0051] Among them, 1-gas-liquid separator, 2-first compressor, 3-first membrane separator, 4-second membrane separator, 5-first adsorption separator, 6-second adsorption separator, 7-gas generator set, 8-pump, 9-liquid storage tank, 10-second compressor, 11-waste heat recovery device, 12-chimney, 13-heat using equipment. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] See also Figure 1-4 The embodiment of the present invention discloses a method for recycling oilfield flare gas, comprising the following steps:

[0054] S1: transporting the flare gas to a gas-liquid separator for separation to obtain gaseous flare gas and liquid flare gas;

[0055] S2: transporting the liquid flare gas to a liquid storage tank through a pump for storage;

[0056] S3: transporting the gaseous flare gas to a membrane separator for separation, and transporting the flare gas separated by the membrane separator to an adsorption separator;

[0057] S4: The flare gas separated by the membrane separator is separated into CH4 by the adsorption separator, and the CH4 is transported to the gas-fired generator set for power generation and standby;

[0058] S5: The heat generated by the gas generator set is recovered through the waste heat recovery device for standby use.

[0059] Among them, S3 includes:

[0060] S31: pressurizing the gaseous flare gas through a first compressor to 1.0-3.0 MPa, preferably 1.5-2.0 MPa;

[0061] S32: The pressurized flare gas is transported to a membrane separator for separation, and the flare gas separated by the membrane separator is transported to an adsorption separator.

[0062] It should be noted that when the initial pressure of the oilfield flare gas is greater than 1.0 MPa, the flare gas does not pass through the first compressor but directly enters the membrane separator.

[0063] In order to optimize the above technical solution, S32 specifically includes:

[0064] S321: The pressurized flare gas is transported to the first membrane separator to separate the permeate gas of C3+ and above components and the retentate gas of C1 and C2 components, and the permeate gas of C3+ and above components is compressed by the second compressor to be converted into liquid and enter the liquid storage tank;

[0065] S322: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second membrane separator, and the light hydrocarbon components attached to the membrane are purged to obtain purge gas;

[0066] S323: The retentate gas of the C1 and C2 components in S321 and the purge gas in S322 are transported together to the adsorption separator.

[0067] The present invention also provides a specific implementation process of the membrane separator in the above technical solution:

[0068] The specific process of S321 is as follows: valves V1, V2, and V6 on the first membrane separator are opened, and valve V5 is closed. The flare gas enters the first membrane separator through valve V1 to separate the permeate gas of C3+ and above components and the retentate gas of C1 and C2 components. The permeate gas has a pressure of 0.1 to 1.0 MPa, and enters the second compressor through valve V6 to be compressed to 1.2 to 1.6 MPa and converted into liquid to enter the liquid storage tank. The retentate gas has a pressure of 0.95 to 2.9 MPa.

[0069] The specific process of S322 is as follows: valves V3 and V8 on the second membrane separator are in a closed state, valves V4 and V7 are in an open state, the non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the second membrane separator through valve V7, and the light hydrocarbon components attached to the membrane are purged out to obtain purge gas;

[0070] The specific process of S323 is: the retentate gas is transported to the adsorption separator through valve V2 and the purge gas is transported through valve V4.

[0071] In order to optimize the above technical solution, step S4 specifically includes:

[0072] S41: The retentate gas of the C1 and C2 components in S323 and the purge gas in S322 are transported to the first adsorption separator, and the adsorbent adsorbs the C2+ light hydrocarbon components to separate CH4, and the CH4 is transported to the gas-fired generator set for power generation standby;

[0073] S42: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second adsorption separator to purge the C2+ light hydrocarbon components adsorbed by the adsorbent. At the same time, the purged C2+ light hydrocarbon components are compressed by the second compressor and converted into liquid to enter the liquid storage tank.

[0074] The present invention also provides a specific implementation process of the adsorption separator in the above technical solution:

[0075] The specific process of S41 is as follows: valves V10 and V13 on the first adsorption separator are opened, valves V9 and V14 are closed, the retentate gas and the purge gas enter the first adsorption separator through valve V13, C2+ light hydrocarbon components are adsorbed by the adsorbent, the CH4 tail gas separated from the top of the adsorption separator has a pressure of 0.85-2.8 MPa, and the CH4 tail gas passes through valve V10 and enters the gas generator set for power generation;

[0076] The specific process of S42 is as follows: valves V11 and V16 on the second adsorption separator are in the open state, and V11 and V15 are in the closed state. The non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the adsorption separator through valve V11, and the C2+ light hydrocarbon components adsorbed by the adsorbent are purged out, and the adsorbent is regenerated. The purged C2+ light hydrocarbon components enter the second compressor through valve V16, are compressed to 1.2-1.6 MPa, and are converted into liquid and enter the heat storage tank.

[0077] See also Figure 5 The present invention also provides a device for recycling oilfield flare gas, comprising: a gas-liquid separator 1, a membrane separator, an adsorption separator, a liquid storage tank 9, a gas generator set 7, a waste heat recovery device 11, and a pump 8;

[0078] The gas-liquid separator 1 is used to separate the gaseous flare gas from the liquid flare gas in the flare gas, and transport the gaseous flare gas to the membrane separator, and transport the liquid flare gas to the liquid storage tank 9 through the pump 8 for storage;

[0079] The membrane separator is connected to the gas-liquid separator 1 and is used to separate the gaseous flare gas and transport the separated flare gas to the adsorption separator;

[0080] The adsorption separator is connected to the membrane separator, and is used to separate the flare gas after separation by the membrane separator to obtain CH4, and transport the CH4 to the gas generator set 7 for power generation;

[0081] The waste heat recovery device 11 is connected to the gas-fired generator set 7 and is used to recover the heat generated by the gas-fired generator set 7 for standby use.

[0082] The system further comprises a first compressor 2, which is arranged between the gas-liquid separator and the membrane separator and is used for pressurizing the gaseous flare gas and conveying the pressurized gaseous flare gas to the membrane separator.

[0083] It also includes a second compressor 10 connected to the liquid storage tank 9, the membrane separator includes a first membrane separator 3 and a second membrane separator 4, the first compressor 2 is connected to the gas-liquid separator and the first membrane separator 3, the first membrane separator 3 is also connected to the second membrane separator 4, and the second membrane separator 4 is connected to the adsorption separator;

[0084] The first membrane separator 3, the second membrane separator 4, and the adsorption separator are all connected to the liquid storage tank 9, and are also connected to the second compressor 10;

[0085] The first membrane separator 3 is provided with valves V1 , V2 , V5 and V6 , and the second membrane separator 4 is provided with valves V3 , V4 , V7 and V8 .

[0086] The adsorption separator comprises a first adsorption separator 5 and a second adsorption separator 6, and the first membrane separator 3, the second membrane separator 4, the first adsorption separator 5 and the second adsorption separator 6 are connected to each other;

[0087] The first adsorption separator 5 and the second adsorption separator 6 are both connected to the liquid storage tank 9, and are also connected to the second compressor 10;

[0088] The first adsorption separator 5 is provided with valves V9 , V10 , V13 and V14 , and the second adsorption separator 6 is provided with valves V11 , V12 , V15 and V16 .

[0089] The present invention also provides a specific embodiment. In this embodiment, the oilfield flare gas pressure is 0.3 MPa, and the flare gas components are shown in Table 1.

[0090] Table 1 Oilfield flare gas components (V%)

[0091]

[0092] The boiling points of the main components in the flare gas are shown in Table 2.

[0093] Table 2 Boiling points of main components in oilfield flare gas

[0094]

[0095] The flare gas generated during the oil field production process enters the gas-liquid separator 1, the separated liquid is sent to the liquid storage tank 9 by the pump 8, and the separated flare gas enters the first compressor 2 to be pressurized to 1.6 MPa.

[0096] The pressurized 1.6MPa flare gas enters the membrane separator, which includes the first membrane separator 3, the second membrane separator 4 and valves V1 to V8. When the flare gas enters the first membrane separator 3 for separation, the second membrane separator 4 is reversely flushed. Specifically, valves V1, V2, and V6 on the first membrane separator are opened, and valve V5 is closed. The flare gas enters the first membrane separator through valve V1, and permeate gas (C3+ and above components) and retentate gas (C1, C2) are separated. The permeate gas pressure is about 0.2MPa, and enters the second compressor 10 through valve V6, where it is compressed to 1.5MPa, converted into liquid and enters the liquid storage tank 9. The retentate gas pressure is about 1.55MPa and enters the adsorption separator through valve V2. At this time, valves V3 and V8 on the second membrane separator are in a closed state, valves V4 and V7 are in an open state, and the non-condensable gas on the upper part of the liquid storage tank enters the second membrane separator through valve V7 to purge the light hydrocarbon components attached to the membrane, and the purge gas enters the adsorption separation unit together with the retentate gas through valve V4. The first membrane separator 3 and the second membrane separator 4 realize the continuous operation of the recovery device and the purification of the membrane through valve switching, thereby improving the separation efficiency of the membrane separator.

[0097] The components of the permeate gas and the retentate gas of the flare gas after membrane separation in this embodiment are shown in Table 3 and Table 4.

[0098] Table 3 Oilfield flare gas membrane separation permeate gas components (V%)

[0099]

[0100] Table 4 Oilfield flare gas membrane separation retentate gas components (V%)

[0101]

[0102] The adsorption unit includes a first adsorption separator 5, a second adsorption separator 6 and valves V9 to V16. When the first adsorption separator 5 adsorbs, the second adsorption separator 6 desorbs. Specifically, valves V10 and V13 on the first adsorption separator 5 are opened, valves V9 and V14 are closed, and the retentate gas and purge gas of the membrane separator enter the first adsorption separator 5 through valve V13. The C2+ light hydrocarbon components are adsorbed by the adsorbent. The CH4 tail gas separated from the top of the adsorption separator has a pressure of about 1.4 MPa, and the CH4 tail gas enters the gas generator set 7 through valve V10. At this time, valves V11 and V16 on the second adsorption separator are in an open state, and valves V11 and V15 are in a closed state. The non-condensable gas on the top of the liquid storage tank 9 enters the adsorption separator through valve V11, and the C2+ light hydrocarbon components adsorbed by the adsorbent are purged out, and the adsorbent is regenerated. The C2+ light hydrocarbon components enter the second compressor 10 through valve V16, are compressed to 1.5 MPa, and are converted into liquid and enter the heat storage tank 9. The first adsorption separator 5 and the second adsorption separator 6 switch working states through valves to achieve continuous adsorption and desorption.

[0103] The CH4 tail gas components and desorbed gas components after adsorption separation in this embodiment are shown in Tables 5 and 6.

[0104] Table 5 CH4 tail gas components separated by adsorption from oilfield flare gas (V%)

[0105]

[0106] Table 6 Oilfield flare gas adsorption separation desorption gas components (V%)

[0107]

[0108] The CH4 tail gas separated by adsorption enters the gas generator set 7 to generate electricity. Part of the generated electricity is used by the power-consuming equipment of the recovery device, and part is used by the oil field equipment. The high-temperature flue gas generated by the generator set is recovered through the waste heat recovery device 11 to recover the heat in the high-temperature flue gas and supplied to the oil field heat-using equipment 13. The low-temperature flue gas after heat recovery is discharged through the chimney 12.

[0109] The total recovery rate of light hydrocarbons in the embodiment is greater than 98%, and the concentration of CH4 tail gas is greater than 93%, which not only maximizes the recovery rate of light hydrocarbon components in the flare gas, but also ensures the safety of the gas intake of the gas unit. In addition to meeting the power consumption of this system, the combined heat and power (gas generator set and waste heat recovery device) also provides excess electricity and heat energy for the oil field, reducing energy waste and increasing oil field revenue.

[0110] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0111] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling oilfield flare gas, characterized in that: The steps include: S1: transporting the flare gas to a gas-liquid separator for separation to obtain gaseous flare gas and liquid flare gas; S2: transporting the liquid flare gas to a liquid storage tank for storage through a pump; S3: transporting the gaseous flare gas to a membrane separator for separation, and transporting the flare gas separated by the membrane separator to an adsorption separator; S4: The flare gas separated by the membrane separator is separated into CH4 by the adsorption separator, and the CH4 is transported to the gas-fired generator set for power generation and standby; S5: The heat generated by the gas generator set is recovered through a waste heat recovery device for standby use; The S3 includes: S31: pressurizing the gaseous flare gas through a first compressor; S32: transporting the pressurized flare gas to a membrane separator for separation, and transporting the flare gas separated by the membrane separator to an adsorption separator; The S32 includes: S321: The pressurized flare gas is transported to the first membrane separator to separate the permeate gas of C3 and above components and the retentate gas of C1 and C2 components, and the permeate gas of C3 and above components is compressed by the second compressor to be converted into liquid and enter the liquid storage tank; S322: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second membrane separator, and the light hydrocarbon components attached to the membrane are purged to obtain purge gas; S323: transporting the retentate gas of the C1 and C2 components in S321 and the purge gas in S322 to an adsorption separator; The specific process of S321 is as follows: valves V1, V2, and V6 on the first membrane separator are opened, and valve V5 is closed. The flare gas enters the first membrane separator through valve V1 to separate the permeate gas of components C3 and above and the retentate gas of components C1 and C2. The permeate gas has a pressure of 0.1-1.0 MPa, and enters the second compressor through valve V6 to be compressed to 1.2-1.6 MPa and converted into liquid to enter the liquid storage tank. The retentate gas has a pressure of 0.95-2.9 MPa. The specific process of S322 is as follows: valves V3 and V8 on the second membrane separator are in a closed state, valves V4 and V7 are in an open state, the non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the second membrane separator through valve V7, and the light hydrocarbon components attached to the membrane are purged out to obtain purge gas; The specific process of S323 is: the retentate gas is transported to the adsorption separator through valve V2 and the purge gas is transported to the adsorption separator through valve V4; The step S4 comprises: S41: The retentate gas of the C1 and C2 components in S323 and the purge gas in S322 are transported to the first adsorption separator, and the adsorbent adsorbs the C2+ light hydrocarbon components to separate CH4, and the CH4 is transported to the gas-fired generator set for power generation standby; S42: The non-condensable gas and gaseous light hydrocarbons at the top of the liquid storage tank enter the second adsorption separator to purge the C2+ light hydrocarbon components adsorbed by the adsorbent. At the same time, the purged C2+ light hydrocarbon components are compressed by the second compressor and converted into liquid to enter the liquid storage tank; The specific process of S41 is as follows: valves V10 and V13 on the first adsorption separator are opened, valves V9 and V14 are closed, the retentate gas and the purge gas enter the first adsorption separator through valve V13, C2+ light hydrocarbon components are adsorbed by the adsorbent, the CH4 tail gas separated from the top of the adsorption separator has a pressure of 0.85-2.8 MPa, and the CH4 tail gas passes through valve V10 and enters the gas generator set for power generation; The specific process of S42 is as follows: valves V11 and V16 on the second adsorption separator are in an open state, and valves V12 and V15 are in a closed state. The non-condensable gas and gaseous light hydrocarbon components on the upper part of the liquid storage tank enter the adsorption separator through valve V11, and the C2+ light hydrocarbon components adsorbed by the adsorbent are purged out, and the adsorbent is regenerated. The purged C2+ light hydrocarbon components enter the second compressor through valve V16, are compressed to 1.2-1.6 MPa, and are converted into liquid and enter the heat storage tank. The membrane separator includes a first membrane separator, a second membrane separator and valves V1 to V8. The first membrane separator and the second membrane separator realize continuous operation and membrane purification through valve switching. The adsorption unit includes a first adsorption separator, a second adsorption separator and valves V9 to V16. The first adsorption separator and the second adsorption separator switch working states through valves to achieve continuous adsorption and desorption.

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