Device and method for treating fireflooding tail gas by coupling hydrate method with membrane separation
The hydrate coupling membrane separation technology is used to process the fire-driving exhaust gas and extract CH4 and CO2, which solves the problem of unutilized fire-driving exhaust gas resources, and achieves efficient recycling and utilization of exhaust gas, reducing energy consumption and investment costs.
Patent Information
- Application Number
- CN202510461955.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-06-06
AI Technical Summary
The prior art is difficult to effectively utilize fire-driving exhaust gas, resulting in an intensified greenhouse effect and unused resources.
The hydrate coupled membrane separation technology is used to extract CH4 and CO2 in the fire-driving exhaust gas through the series treatment of the desulfurization unit, the hydration-decomposition unit and the membrane separation unit, and use it for the crude oil dehydration and oil discharging process.
The enrichment of CH4 in the fire-driving exhaust gas is achieved, meeting urban gas standards, and providing a heat source for crude oil dehydration; at the same time, CO2 is separated for return injection and oil discharging, improving oil discharging effect; the remaining N2 mixture is directly discharged, reducing energy consumption and investment costs.
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Figure CN120094370A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of fire drive tail gas treatment in a fire drive oil production process, and in particular to a device and method for treating fire drive tail gas by using a hydrate method coupled with membrane separation. Background Art
[0002] Fire flooding technology is an important method to improve oil recovery. During the production process, a large amount of fire flooding tail gas will be generated. At present, Liaohe Oilfield is the largest oilfield in the application of fire flooding technology, with an annual production of more than 30 million heavy oil. 4 t, annual CO 2 Emissions exceed 42×10 4 t; followed by Xinjiang Oilfield, with an annual heavy oil production of about 10×10 4 t, annual CO 2 Emissions exceed 14×10 4 t. Fire-driven tail gas has typical multi-component characteristics: nitrogen (75%-82mol%), carbon dioxide (10%-15mol%), methane (5%-10mol%), and sulfur compounds (<50ppm). There are currently many ways to treat fire-driven tail gas, including direct venting, underground injection, external discharge after treatment, separation and recovery, etc. Direct venting will lead to an intensification of the greenhouse effect; underground injection and external discharge after treatment will result in the ineffective utilization of tail gas resources, so it is imperative to recycle and utilize fire-driven tail gas.
[0003] Commonly used decarbonization technologies for fire drive tail gas and CH 4 Concentration technologies include chemical absorption, pressure swing adsorption, membrane separation, cryogenic separation and hydrate method. According to the characteristics of different separation technologies, the gas source conditions and separation technologies are optimized and adapted. Compared with the chemical absorption method (the absorbent is often an alcohol amine solution, which is corrosive and has high maintenance costs for chemical equipment), the hydrate method is more environmentally friendly because its main raw material is water, and the decomposition of hydrates does not require huge heating energy consumption. Compared with the pressure swing adsorption method, the hydrate method has the advantages of simple process and low raw material price. Compared with membrane separation, the hydrate method is insensitive to impurities and has a large processing capacity.
[0004] Cryogenic separation is usually used for CO 2 The gas source with high content is not suitable for fire drive tail gas. The hydration separation technology is to use different gases to form hydrates under different temperature and pressure conditions to separate gas CO 2 and CH 4 Capture. When the hydrate formation conditions are met, the gas components with mild formation conditions and easy solubility preferentially form hydrates and are mainly enriched in the hydrate phase; while the gas components with harsh formation conditions form hydrates in small quantities and are mainly enriched in the residual gas phase, thereby achieving CO capture. 2 and CH 4Therefore, the hydrate method has the potential for large-scale application in the field of fire drive tail gas recovery and utilization. By coupling with the membrane separation process, it can further reduce energy consumption and have a positive impact on CH 4 Concentrate. Summary of the invention
[0005] In view of the shortcomings of the prior art, the present invention provides a device and method for treating fire drive tail gas by hydrate method coupled with membrane separation, which can treat CH 4 To concentrate and provide heat source for crude oil dehydration; and to remove CO in tail gas 2 Separate and use for reinjection and oil recovery; the remaining N-rich 2 The mixed gas is discharged directly.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:
[0007] The invention discloses a device for treating fire drive tail gas by hydrate method coupled with membrane separation, comprising a desulfurization unit, a hydration-decomposition unit and a membrane separation unit;
[0008] The desulfurization unit comprises a first air cooler, a first desulfurization tower and a second desulfurization tower which are connected in sequence; the hydration-decomposition unit comprises a venturi jet hydration reactor and a hydrate decomposition kettle connected thereto; the second desulfurization tower is connected to the venturi jet hydration reactor;
[0009] The membrane separation unit comprises a first membrane separation group and a second membrane separation group, wherein the first membrane separation group is connected to a venturi jet hydration reactor, and the second membrane separation group is connected to a hydrate decomposition kettle.
[0010] Preferably, a first compressor, a second air cooler, a second compressor and a first refrigerator are sequentially connected between the second desulfurization tower and the Venturi jet hydration reactor.
[0011] Preferably, the first membrane separation group and the second membrane separation group are connected to a gas mixer, a third compressor and a third air cooler are connected in sequence between the hydrate decomposition kettle and the second membrane separation group, and a second refrigerator and a liquid circulation pump are connected in sequence between the Venturi jet hydration reactor and the hydrate decomposition kettle.
[0012] Preferably, a screen is provided at the bottom of the Venturi jet hydration reactor, and a U-tube heat exchanger with 4-6 tube passes is provided in the hydrate decomposition kettle.
[0013] Accordingly, a method for treating fire drive tail gas using the hydrate method coupled with membrane separation comprises the following steps:
[0014] (1) The fire-driven tail gas is cooled to room temperature by the first air cooler, and the cooled fire-driven tail gas enters the first and second desulfurization towers for desulfurization treatment;
[0015] (2) The fire drive tail gas after desulfurization treatment is compressed to the hydration reaction pressure by the first and second compressors in equal proportions, and then enters the first refrigerator to be cooled to the hydration reaction temperature;
[0016] (3) Entering the Venturi jet hydration reactor for hydration reaction, CO 2 and CH 4 Entering the hydrate phase and being captured, N 2 Discharge to the first membrane separation group for further separation;
[0017] (4) After the hydration reaction, the hydrate slurry enters the hydrate decomposition kettle for decomposition, and the released CO 2 and CH 4 After being cooled to the target temperature and pressure by the third compressor and the third air cooler, it enters the second membrane separation group. 4 The CO2-rich 2 The mixed gas is reinjected to drive oil.
[0018] Preferably, in step (2), the fire drive tail gas is pressurized to 1-4 MPa and the reaction temperature is maintained at 1-10°C.
[0019] Preferably, in step (3), in the hydration reaction, an oil-in-water emulsion system is used, and 5-20wt% tetrabutylammonium bromide is used as a thermodynamic promoter to reduce the temperature and pressure of hydrate formation; in the oil-in-water emulsion system, the oil phase is diesel, the emulsifier is Span80, the water-to-oil volume ratio is 20%-70%, and the gas-liquid ratio is 5:10-9:6.
[0020] The present invention has the following beneficial effects:
[0021] 1. The method for treating fire-driven tail gas disclosed in the present invention does not require the first step of impurity removal and dehydration, which saves a lot of equipment investment costs and energy costs. Since the raw material of the hydration method is water, and the impurity particles have a promoting effect on the growth of hydrates, they can provide more nucleation sites and accelerate the reaction rate. Therefore, when using this method, this part of the cost is saved. At the same time, compared with multi-stage PSA pressure swing adsorption, the hydrate method coupled membrane separation process disclosed in the present invention has the advantages of low pretreatment requirements, low investment scale, and low energy cost, and has good economic indicators for fire-driven tail gas.
[0022] 2. The present invention utilizes two first and second desulfurization towers in series to remove H 2 The S content was reduced to 10 mg / m 3The following meets safety standards. At the same time, the desulfurization unit is connected in series with the hydration-decomposition unit to further reduce H 2 S content, hydration method for H 2 S has a strong capture capacity, providing further guarantee for desulfurization.
[0023] 3. Using this hydration method coupled with membrane separation, 5-10% of CH in the fire drive tail gas can be removed. 4 The concentration can be increased to more than 50 mol%, meeting the urban gas standards, and can provide heat for crude oil dehydration on site; at the same time, 10-19% of CO in the fire drive tail gas can be removed. 2 Concentrate to more than 70 mol% for reinjection into oil recovery. 2 The higher the content, the more obvious the improvement of oil recovery effect. 2 The mixed gas with high content has a wider range of practical oil displacement; it can also convert 70-80% of N in the fire drive tail gas into 2 The concentration is increased to more than 98 mol% and discharged directly. Finally, the CO in the fire drive tail gas is realized. 2 and CH 4 recycling.
[0024] 4. The reaction space velocity of the Venturi jet hydration reactor used in the present invention is one order of magnitude higher than that of the conventional mechanical stirring reactor, and the Venturi jet hydration reactor can be applied to the continuous gas separation process.
[0025] 5. The present invention utilizes membrane separation units to carry out CH 4 The invention not only reduces the energy consumption of the device, but also allows the addition of membrane separation groups and replacement of separation membranes according to production needs, which is not only very flexible, but also effectively reduces investment and energy costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a schematic diagram of the structure of the present invention;
[0027] In the figure: 1-first air cooler; 2-first desulfurization tower; 3-second desulfurization tower; 4-first compressor; 5-second air cooler; 6-second compressor; 7-first refrigerator; 8-Venturi jet hydration reactor; 9-hydrate decomposition kettle; 10-second refrigerator; 11-liquid circulation pump; 12-first membrane separation group; 13-N-rich 2 Delivery pipe; 14-gas mixer; 15-third compressor; 16-third air cooler; 17-second membrane separation group; 18-rich CH 4 Transport pipe; 19-rich CO 2 Delivery pipe. DETAILED DESCRIPTION
[0028] 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.
[0029] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.
[0030] The present invention discloses a device for treating fire-driven tail gas by coupling hydrate method with membrane separation, comprising a desulfurization unit, a hydration-decomposition unit and a membrane separation unit, wherein the desulfurization unit and the hydration-decomposition unit are connected in series in sequence;
[0031] Specifically: the desulfurization unit includes a first air cooler 1, a first desulfurization tower 2 and a second desulfurization tower 3 connected in sequence, the first and second desulfurization towers are connected in series, and the adsorbent is iron oxide; the hydration-decomposition unit includes a Venturi jet hydration reactor 8 and a hydrate decomposition kettle 9 connected thereto; the second desulfurization tower 3 is connected to the Venturi jet hydration reactor 8.
[0032] The membrane separation unit comprises a first membrane separation group 12 and a second membrane separation group 17, the first membrane separation group and the second membrane separation group are connected in parallel, the first membrane separation group 12 is connected to the venturi jet hydration reactor 8, and the second membrane separation group 17 is connected to the hydrate decomposition kettle 9. Specifically: the inlet gas of the first membrane separation group is the residual gas of the venturi jet hydration reactor; the inlet gas of the second membrane separation group is the mixed gas decomposed by the hydrate decomposition kettle, and the pipeline between the hydrate decomposition kettle 9 and the second membrane separation group 17 is sequentially connected with a third compressor 15 and a third air cooler 16 for pressurization and cooling; the separation membrane used in the membrane separation device in the first and second membrane separation groups is a polyimide polymer membrane.
[0033] Furthermore, the pipeline between the second desulfurization tower 3 and the Venturi jet hydration reactor 8 is sequentially connected with a first compressor 4, a second air cooler 5, a second compressor 6 and a first refrigerator 7.
[0034] Furthermore, the first membrane separation group 12 and the second membrane separation group 17 are connected to the gas mixer 14, and the pipeline between the venturi jet hydration reactor 8 and the hydrate decomposition kettle 9 is sequentially connected to the second refrigerator 10 and the liquid circulation pump 11.
[0035] Furthermore, a screen is provided at the bottom of the venturi jet hydration reactor 8 to prevent hydrate agglomeration and blockage of the pipeline; two venturi ejectors are provided on both sides of the venturi jet hydration reactor 8, and the venturi ejectors are provided with a liquid inlet, a gas inlet, and a gas-liquid mixture outlet. A U-tube heat exchanger with 4-6 tube passes is provided in the hydrate decomposition kettle 9.
[0036] The present invention discloses a method for treating fire drive tail gas by hydrate method coupled with membrane separation, which can treat CH 4 To concentrate and provide heat source for crude oil dehydration; and to remove CO in tail gas 2 Separate and use for reinjection and oil recovery; the remaining N-rich 2 The mixed gas is discharged directly.
[0037] The specific steps include:
[0038] (1) The fire-driven tail gas is cooled to room temperature by the first air cooler 1, and the cooled fire-driven tail gas enters the first and second desulfurization towers 2 and 3 for desulfurization treatment.
[0039] The desulfurization unit adopts dry desulfurization, and the solid adsorbent used is iron oxide with an average pore size of 1 to 3 mm. The dry desulfurization process is simple, easy to operate and maintain, low investment, suitable for low sulfur content conditions, and no pressure requirements. The adsorbent needs to be replaced regularly, and the used adsorbent is recycled and used as raw material for the sulfuric acid plant to meet environmental protection requirements. The working principle is that iron oxide reacts with H 2 S reacts to form iron sulfide and water. The chemical reaction formula is: Fe 2 O 3 ·H 2 O+3H 2 S=Fe 2 S 3 ·H 2 O+3H 2 O. Set up the first and second desulfurization towers, adopt the series desulfurization process, and the hydrogen sulfide content in the tail gas after desulfurization is ≤10mg / m 3 .
[0040] (2) The fire drive tail gas after desulfurization treatment is compressed to the hydration reaction pressure by the first and second compressors 4 and 6 in equal ratios, and then enters the first refrigerator 7 to be cooled to the hydration reaction temperature; the inlet pressure of the fire drive tail gas is 0.05MPa, and after two-stage equal ratio compression (first and second compressors), it is pressurized to 1-4MPa, and then cooled to 1-10°C by the first refrigerator to meet the conditions for hydrate formation.
[0041] (3) The fire-driven tail gas of step (2) is introduced into the venturi jet hydration reactor 8 for hydration reaction, CO 2 and CH 4Entering the hydrate phase and being captured, N 2 The N 2 The concentrated amount is 98 mol% or more and passes through the first membrane separation group 12 to form a nitrogen-rich 2 The delivery pipe 13 is directly discharged to the outside.
[0042] A venturi jet hydration reactor 8 is used. When the emulsion enters the gap inside the venturi jet, a local vacuum is generated in the gap due to the widening of the flow channel. At this time, the gas is sucked into the gap inside the venturi jet hydration reactor from the upper part, and a violent gas-liquid mixing is generated inside the gap. Since the liquid mist is in contact with the gas, the surface area of the gas-liquid contact is effectively increased, and the mass transfer is enhanced. The ejector can significantly shorten the induction time of hydrate formation, so that hydrates are formed in an instant, and can be used for rapid hydrate formation by gas. In addition, the ejection enhancement measures of the ejector can replace the common stirring enhancement mass transfer measures to enhance the hydrate reaction, which is equivalent to "no need" for mechanical energy consumption in the continuous generation process, and can significantly improve the efficiency of the hydrate formation process. At the same time, the ejector has a simple structure, is easy to replace, easy to clean, and is low in cost.
[0043] Furthermore, in the hydration reaction of step (3), an oil-in-water emulsion system is used, and 5-20wt% tetrabutylammonium bromide (TBAB) is used as a thermodynamic promoter to reduce the temperature and pressure of hydrate formation; in the oil-in-water emulsion system, the oil phase is diesel, the emulsifier is Span 80, the water-oil volume ratio is 20%-70% (ratio of water to oil phase), and the gas-liquid ratio is 5:10-9:6 (gas refers to CO 2 and CH 4 , liquid refers to water-in-oil emulsion). The emulsion is added to the venturi jet hydration reactor.
[0044] Specific: With CO 2 and CH 4 The high solubility in the oil phase allows the methane and carbon dioxide in the fire drive tail gas to be selectively absorbed into the oil phase of the water-in-oil emulsion, further improving the separation effect. The emulsion is used to disperse the hydrate particles to prevent the hydrate from clogging the pipeline. Optionally, TBAB, as an organic salt, has low toxicity and can exist stably at room temperature and pressure. At the same time, TBAB does not volatilize after dissolving in water, and captures CO in the hydrate. 2 and CH 4 There will be no loss in the process, and it can be reused without causing environmental problems. Optionally, the water-oil volume ratio is 20%-70%. When the water-oil volume ratio is higher, the water content is higher, N 2 The molecule may react with CO 2 and CH 4 Molecules compete to occupy the small cages in the hemicrystal hydrate, thereby reducing CO 2 and CH4 The occupancy rate of the molecule in the empty cage of the hydrate. Optionally, the gas-liquid ratio is 5:10-9:6. Under the same pressure and temperature conditions, the CO dissolved in the emulsion 2 and CH 4 The number of molecules is proportional to the volume of solution in the system. The smaller the gas-to-liquid ratio, the higher the gas capture rate.
[0045] (4) After the hydration reaction, the hydrate slurry enters the hydrate decomposition reactor 9 for decomposition. 2 and CH 4 released; released CO 2 and CH 4 After being cooled to the target temperature and pressure by the third compressor 15 and the third air cooler 16, the air enters the second membrane separation group 17. 4 The gas is concentrated to a specified concentration, which meets the urban gas standard, and passes through the CH4-rich gas on the second membrane separation group 17. 4 The separated rich CO 2 The mixed gas is reinjected for oil recovery, that is, the separated CO2-rich 2 The CO separated by the first membrane separation group 12 in step (3) 2 The gas is transported to the gas mixer 14, and the CO2-rich 2 The delivery pipe 19 is used for oil recovery or collection.
[0046] The present invention will be further described below in conjunction with specific embodiments.
[0047] Example 1
[0048] The process of treating fire drive tail gas by hydrate method coupled with membrane separation is as follows:
[0049] The composition of the fire drive tail gas is 77 mol% N 2 +15mol%CO 2 +8 mol% CH 4 +72.1mg / m 3 H 2 S. The temperature of the fire drive tail gas is 50°C and the pressure is 0.5MPa.
[0050] (1) The tail gas discharged from the fire drive oil production outlet first enters the first air cooler 1 to be cooled to room temperature (25°C); then it is transported to the bottom of the first desulfurization tower 2 and enters the first desulfurization tower 2. 2 S and Fe 2 O 3 Reaction; the gas is transported from the top of the first desulfurization tower 2 to the bottom of the second desulfurization tower 3 and enters the second desulfurization tower for further desulfurization. After desulfurization, the hydrogen sulfide content of the fire drive tail gas is ≤10mg / m 3The desulfurized tail gas is transported to the first compressor 4 for primary compression, and the tail gas temperature and pressure increase significantly; in order to reduce the energy consumption of secondary compression, the gas is transported to the second air cooler 5 to be cooled to room temperature; after cooling, it is transported to the second compressor 6 for secondary compression, and the pressure reaches the hydration target pressure; finally, it is transported to the first refrigerator 7 to be cooled to the hydration target temperature.
[0051] (2) Subsequently, the tail gas is transported to the venturi jet hydration reactor 8 to undergo hydration reaction with the emulsion. Two venturi ejectors are provided on both sides of the venturi jet hydration reactor 8. The interior of the venturi ejector is hollow and includes a liquid inlet, a gas inlet, and a gas-liquid mixture outlet. During the reaction, the emulsion temperature is maintained at 2-10°C. A screen is provided at the bottom of the venturi jet hydration reactor 8 to prevent hydrate agglomeration and cause pipeline blockage.
[0052] (3) After the hydration reaction is completed, CO 2 and CH 4 It is captured in the hydrate phase and flows into the hydrate decomposition reactor 9 in the form of hydrate slurry. The hydrate decomposition reactor is equipped with a U-tube heat exchanger to decompose the hydrate slurry by reducing pressure and heating. At the same time, after the hydration is completed, the remaining gas in the Venturi injection hydration reactor 8 enters the first membrane separation group 12 for N 2 Concentration, when the retentate side N 2 After the concentration reaches 98 mol%, it is directly discharged, and the permeate side is sent to the gas mixer 14.
[0053] After decomposition in hydrate decomposition reactor 9, CO 2 and CH 4 The released CO enters the third compressor 15 to be pressurized to 0.2-0.4 MPa, and then enters the third air cooler 16 to be cooled to room temperature. 2 and CH 4 The mixed gas enters the second membrane separation group 17 for CH 4 Concentration, retentate side CH 4 When the concentration reaches 50 mol % or more, the permeate gas and the permeate gas of the first membrane separation group enter the gas mixer 14. The side where the mixed gas passes through the membrane is called the permeate side, and the side where the gas cannot pass through the membrane is called the retentate side.
[0054] After the above steps, the discharged N-rich 2 It meets the emission requirements of GB 16297-1996 Comprehensive Emission Standard of Air Pollutants and GB 14554-1993 Emission Standard of Malodorous Pollutants in Class II areas. 4 It meets the 6T standard for urban gas. The composition and proportion are shown in Table 1.
[0055] Table 1 Exhaust gas components and proportions
[0056]
[0057] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.
Claims
1. A device for treating fire drive tail gas by hydrate method coupled with membrane separation, characterized in that: It includes a desulfurization unit, a hydration-decomposition unit and a membrane separation unit; The desulfurization unit comprises a first air cooler (1), a first desulfurization tower (2) and a second desulfurization tower (3) which are connected in sequence; the hydration-decomposition unit comprises a Venturi jet hydration reactor (8) and a hydrate decomposition kettle (9) connected thereto; the second desulfurization tower (3) is connected to the Venturi jet hydration reactor (8); The membrane separation unit comprises a first membrane separation group (12) and a second membrane separation group (17), wherein the first membrane separation group (12) is connected to a Venturi jet hydration reactor (8), and the second membrane separation group (17) is connected to a hydrate decomposition kettle (9).
2. The device for treating fire drive tail gas by hydrate method coupled with membrane separation according to claim 1, characterized in that: A first compressor (4), a second air cooler (5), a second compressor (6) and a first refrigerator (7) are sequentially connected between the second desulfurization tower (3) and the Venturi jet hydration reactor (8).
3. The device for treating fire drive tail gas by hydrate method coupled with membrane separation according to claim 1, characterized in that: The first membrane separation group (12) and the second membrane separation group (17) are connected to a gas mixer (14); a third compressor (15) and a third air cooler (16) are connected in sequence between the hydrate decomposition kettle (9) and the second membrane separation group (17); and a second refrigerator (10) and a liquid circulation pump (11) are connected in sequence between the Venturi jet hydration reactor (8) and the hydrate decomposition kettle (9).
4. The device for treating fire drive tail gas by hydrate method coupled with membrane separation according to claim 1, characterized in that: The bottom of the Venturi jet hydration reactor (8) is provided with a screen, and the hydrate decomposition kettle (9) is provided with a U-tube heat exchanger with 4 to 6 tube passes.
5. A method for treating fire drive tail gas using the device for hydrate method coupled with membrane separation as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: (1) The fire-driven tail gas is cooled to room temperature by a first air cooler (1), and the cooled fire-driven tail gas enters a first desulfurization tower (2) and a second desulfurization tower (3) for desulfurization treatment; (2) the fire drive tail gas after desulfurization treatment is compressed to a hydration reaction pressure by the first and second compressors (4, 6) in equal proportions, and then enters the first refrigerator (7) to be cooled to a hydration reaction temperature; (3) entering the Venturi jet hydration reactor (8) for hydration reaction, CO2 and CH4 enter the hydrate phase and are captured, and N2 is discharged to the first membrane separation group (12) for further separation; (4) After the hydration reaction, the hydrate slurry enters the hydrate decomposition kettle (9) for decomposition. The released CO2 and CH4 are cooled to the target temperature and pressure through the third compressor (15) and the third air cooler (16) in turn and then enter the second membrane separation group (17). CH4 is concentrated to a specified concentration and the separated CO2-rich mixed gas is reinjected for oil recovery.
6. The method for treating fire drive tail gas by hydrate method coupled with membrane separation according to claim 5, characterized in that: In step (2), the fire drive tail gas is pressurized to 1-4 MPa and the reaction temperature is maintained at 1-10°C.
7. The method for treating fire drive tail gas by hydrate method coupled with membrane separation according to claim 5, characterized in that: Step (3), in the hydration reaction, a water-in-oil emulsion system is used, and 5-20wt% tetrabutylammonium bromide is used as a thermodynamic promoter to reduce the temperature and pressure of hydrate formation; in the water-in-oil emulsion system, the oil phase is diesel, the emulsifier is Span 80, the water-to-oil volume ratio is 20%-70%, and the gas-liquid ratio is 5:10-9:6.