Hot fluorine defrosting and decarburization system containing scattered associated gas of carbon dioxide and use method of hot fluorine defrosting and decarburization system

Abstract

The invention relates to the technical field of oil field natural gas recovery, in particular to a hot fluorine defrosting and decarburization system for scattered associated gas containing carbon dioxide and a using method. According to the technical scheme, first-stage cooling is conducted through a pre-cooling radiator, second-stage cooling is conducted through a split type heat exchanger, third-stage cooling is conducted through a fully-closed refrigerating machine, a first shallow cooling evaporator and a second shallow cooling heat exchanger are arranged in the fully-closed refrigerating machine, one is used for refrigerating, the other is used for defrosting or deicing, and the first shallow cooling evaporator and the second shallow cooling heat exchanger alternately operate to remove heavy hydrocarbon components; and four-stage cooling is performed through a shell pass of the carbon dioxide heat exchange tank, and five-stage cooling is performed through the cryogenic evaporator to remove carbon dioxide. The scattered associated natural gas is purified through one-stage filtration, five-stage cooling and physical separation, particulate matter, water, hydrocarbon and carbon dioxide are removed, energy is fully utilized, energy consumption and cost are reduced, the split type heat exchanger and the carbon dioxide heat exchange tank are adopted, and residual cold is fully utilized.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield natural gas recovery, and in particular to a thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide and a use method thereof. Background Art

[0002] CO2 flooding technology is an oil recovery method that increases crude oil recovery by injecting CO2 into the reservoir. It is primarily used in low-permeability reservoirs. Its mechanisms include viscosity reduction, crude oil volume expansion, extraction of light components, and miscibility with crude oil, resulting in a 7-20% increase in oil recovery.

[0003] In the initial stages of CO2-based oil recovery, oil production begins with the release of large amounts of associated gas containing CO2. Furthermore, the CO2 content in this associated gas fluctuates during the recovery period, significantly complicating oilfield operations. When the CO2 content in natural gas exceeds 34%, ignition becomes difficult, rendering it unusable. Installing fixed CO2 removal equipment is costly, and as the CO2 content gradually decreases and even disappears, the equipment becomes ineffective.

[0004] To address these situations, traditionally, chemical / physical methods such as molecular membranes, molecular sieves, chemical reagents, or a combination of the two are used to remove carbon dioxide from associated gas. Such processing equipment is large, contains consumables such as molecular membranes / sieves / reagents, has high energy consumption, and cannot adapt to such situations where there is scattered gas or changes in carbon content. Therefore, temporary pressurized filling and transportation for centralized processing are often adopted, which is very costly.

[0005] Therefore, there is an urgent need to find a new technical route and supporting facilities to meet the needs of high efficiency, emission reduction, energy conservation and production cost in the exploitation of these oil fields. Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned defects of the prior art and provide a thermal fluorination frost decarbonization system and method for using scattered associated gas containing carbon dioxide. The present invention uses only one stage of filtration and five stages of cooling to purify the scattered associated natural gas, and physically separates and removes particulate matter, water, hydrocarbons and carbon dioxide respectively, making full use of energy, reducing energy consumption and costs, and using a split heat exchanger and a carbon dioxide heat exchange tank to fully utilize the residual cooling.

[0007] The present invention mentions a thermal fluorination frost decarbonization system containing scattered associated gas containing carbon dioxide, and its technical solution is: including a cyclone separator, a booster, a pre-cooling radiator, a split heat exchanger, a first shallow cooling evaporator, a second shallow cooling heat exchanger, a carbon dioxide heat exchange tank, a liquid carbon dioxide storage tank, a deep cooling evaporator, a liquid storage tank, a sewage pump, and an oil transportation process. The inlet of the cyclone separator is connected to the scattered associated gas pipeline, the outlet of the cyclone separator is connected to the booster, the outlet of the booster is connected to the pre-cooling radiator through a pipeline for primary cooling, the outlet of the pre-cooling radiator is connected to the split heat exchanger through a pipeline for secondary cooling, and the outlet of the split heat exchanger is connected to a fully enclosed refrigerator through a pipeline for tertiary cooling. The fully enclosed refrigerator is provided with a first shallow cooling evaporator. The outlet of the fully enclosed refrigerator is connected to the shell side of the carbon dioxide heat exchange tank through a pipeline for four-stage cooling. The shell side outlet of the carbon dioxide heat exchange tank is connected to the cryogenic evaporator through a pipeline for five-stage cooling to remove carbon dioxide. The outlet of the cryogenic evaporator is connected to the shell side inlet of the split heat exchanger through a pipeline. After fully utilizing the cooling capacity, it is discharged to the natural gas pipeline network through the shell side outlet of the split heat exchanger; the bottom of the shell side of the cryogenic evaporator is connected to the liquid carbon dioxide storage tank through a pipeline; the lower end of the split heat exchanger and the fully enclosed refrigerator are connected to the liquid storage tank through a condensed water pipe, and the outlet of the liquid storage tank is connected to the oil transportation process through a pipeline and a sewage pump.

[0008] Preferably, the above-mentioned fully enclosed refrigeration machine also includes a first control valve, a second control valve, a third control valve, and a fourth control valve. The first control valve is installed on the pipeline at the inlet end of the first shallow cooling evaporator, and the second control valve is installed on the pipeline at the outlet end; the third control valve is installed on the pipeline at the inlet end of the second shallow cooling heat exchanger, and the fourth control valve is installed on the pipeline at the outlet end.

[0009] Preferably, the bottom of the first shallow cooling evaporator is connected to the liquid inlet pipeline of the liquid storage tank through a condensing water pipe, and the bottom of the second shallow cooling heat exchanger is connected to the liquid inlet pipeline of the liquid storage tank through a condensing water pipe.

[0010] Preferably, the split heat exchanger is provided with a carbon dioxide inlet and a cryogenic natural gas inlet at the bottom, and a carbon dioxide outlet and a cryogenic natural gas outlet at the top. The inner cavity of the split heat exchanger is provided with an insulation plate to separate the first heat exchange cavity and the second heat exchange cavity. A scattered gas pipe inlet is provided at the left end of the split heat exchanger, and a scattered gas pipe outlet is provided at the right end of the split heat exchanger.

[0011] Preferably, the shell-side inlet of the precooling radiator is connected to the front-end pipeline at the outlet of the cryogenic natural gas through a pipeline, and the shell-side outlet of the precooling radiator is connected to the rear-end pipeline at the outlet of the cryogenic natural gas through a pipeline.

[0012] Preferably, a control valve is installed between the front-end pipeline and the rear-end pipeline at the above-mentioned cryogenic natural gas outlet.

[0013] The method for using the thermal fluorination frost decarbonization system containing scattered associated gas containing carbon dioxide mentioned in the present invention includes the following steps: 1. The scattered associated natural gas from oil wells and multi-purpose tanks passes through a cyclone separator to remove particulate matter and liquid substances, and then enters a booster to boost the pressure of the scattered associated natural gas to 0.8MPa. Second, the pressurized scattered associated natural gas is sent to the pre-cooling radiator for the first stage of cooling, reducing the pressurized temperature to room temperature of 30-40°C. It is then sent to the split heat exchanger for the second stage of cooling, where the carbon dioxide at -37°C and the scattered associated natural gas cooled to -50°C are sequentially cooled to 0-5°C to remove most of the moisture. 3. Then, the scattered associated natural gas is sent to a fully enclosed refrigerator, which is equipped with a first shallow cooling evaporator and a second shallow cooling heat exchanger. The compressor and refrigeration system in the fully enclosed refrigerator force the scattered associated natural gas to -25 to -30°C. One of them is used for cooling, and the other is used for hot fluorine defrosting or ice removal. The two operate alternately to achieve the third stage of cooling of the scattered associated natural gas and remove heavy hydrocarbon components. Fourth, it is sent to the carbon dioxide heat exchange tank through a pipeline. The low-temperature scattered associated natural gas exchanges heat with the -50°C low-temperature liquid carbon dioxide from the liquid carbon dioxide storage tank, undergoing the fourth stage of cooling. The scattered associated natural gas continues to cool to -37°C. 5. The scattered associated natural gas at -37℃ then enters the cryogenic evaporator to achieve the fifth level of cooling. The compressor and refrigeration system are used to force the scattered associated natural gas to be cooled to below -50℃, and the carbon dioxide is liquefied and separated. The separated low-temperature carbon dioxide liquid at -50℃ enters the liquid carbon dioxide storage tank to reuse the cold energy. The scattered associated natural gas is pre-cooled by the pre-cooling radiator after heat exchange and heating in the carbon dioxide heat exchange tank. The first heat exchange chamber of the split heat exchanger pre-cools the scattered associated natural gas. The carbon dioxide gas after heat exchange and heating is sent to the original CCUS carbon capture process for treatment; and the dry scattered associated natural gas after dehydration, dehydrocarbonization and decarbonization enters the natural gas pipeline network after heat exchange in the second heat exchange chamber of the split heat exchanger.

[0014] Preferably, the dry scattered associated natural gas passing through the second heat exchange chamber of the split heat exchanger is sent to the shell-side inlet of the pre-cooling radiator through a pipeline to pre-cool the hot scattered associated natural gas from the supercharger, and then discharged into the natural gas pipeline network through the shell-side outlet of the pre-cooling radiator.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Zero emissions: The entire process has no solid or liquid emissions, and no harmful gas emissions; the process is simple, and only one stage of filtration and five stages of cooling are required to purify the associated gas, with physical separation to remove particulate matter, water, hydrocarbons, and carbon dioxide respectively; Second, mature technology: The entire system is fully sealed and does not require disassembly to replace consumables after long-term operation, making it safe and reliable. The present invention adopts a modular, movable skid-mounted design, allowing modules to be added or removed according to operating conditions, making installation and transportation convenient. The refrigeration and decarbonization module, consisting of a split heat exchanger, a first shallow cooling evaporator, a second shallow cooling heat exchanger, a carbon dioxide heat exchange tank, a liquid carbon dioxide storage tank, and a cryogenic evaporator, is added. Once the carbon dioxide in the scattered associated natural gas disappears, the refrigeration and decarbonization module can be removed. 3. Low operating cost: no replacement consumables such as analytical sieves / molecular membranes / chemical reagents; 4. Ingenious process design: 5-stage cooling, alternating refrigeration / defrosting operation without downtime, thus ensuring continuous production and avoiding intermittent emissions from the well site; fully utilizing energy and reducing energy consumption, using split heat exchangers and carbon dioxide heat exchange tanks to fully utilize residual cooling and reduce energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall process flow of the present invention; Figure 2 It is a flow diagram of a split heat exchanger; In the figure: cyclone separator 1, booster 2, pre-cooling radiator 3, split heat exchanger 4, first shallow cooling evaporator 5, second shallow cooling heat exchanger 6, CO2 heat exchange tank 7, liquid CO2 storage tank 8, cryogenic evaporator 9, liquid storage tank 10, sewage pump 11, oil transfer process 12, first control valve 13, second control valve 14, third control valve 15, fourth control valve 16, control valve 17, first heat exchange chamber 4.1, second heat exchange chamber 4.2, insulation board 4.3, CO2 inlet 4.4, cryogenic natural gas inlet 4.5, CO2 outlet 4.6, cryogenic natural gas outlet 4.7, scattered gas pipe inlet 4.8, scattered gas pipe outlet 4.9. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0018] Example 1, reference Figure 1-Figure 2The present invention mentions a thermal fluorination frost decarbonization system containing scattered associated gas containing carbon dioxide, comprising a cyclone separator 1, a booster 2, a pre-cooling radiator 3, a split heat exchanger 4, a first shallow cooling evaporator 5, a second shallow cooling heat exchanger 6, a carbon dioxide heat exchange tank 7, a liquid carbon dioxide storage tank 8, a deep cooling evaporator 9, a liquid storage tank 10, a sewage pump 11, and an oil transportation process 12. The inlet of the cyclone separator 1 is connected to the scattered associated gas pipeline, the outlet of the cyclone separator 1 is connected to the booster 2, the outlet of the booster 2 is connected to the pre-cooling radiator 3 through a pipeline for primary cooling, the outlet of the pre-cooling radiator 3 is connected to the split heat exchanger 4 through a pipeline for secondary cooling, and the outlet of the split heat exchanger 4 is connected to a fully enclosed refrigerator through a pipeline for tertiary cooling. The fully enclosed refrigerator is provided with a first shallow cooling evaporator 5 and a second shallow cooling evaporator 5. The cold heat exchanger 6, one of which is for refrigeration and the other for defrosting or defrosting, operates alternately to remove heavy hydrocarbon components. The outlet of the fully enclosed refrigerator is connected to the shell side of the carbon dioxide heat exchange tank 7 through a pipeline for four-stage cooling. The shell side outlet of the carbon dioxide heat exchange tank 7 is connected to the cryogenic evaporator 9 through a pipeline for five-stage cooling to remove carbon dioxide. The outlet of the cryogenic evaporator 9 is connected to the shell side inlet of the split heat exchanger 4 through a pipeline to fully utilize the cooling capacity and then discharge it to the natural gas pipeline network through the shell side outlet of the split heat exchanger 4; the bottom of the shell side of the cryogenic evaporator 9 is connected to the liquid carbon dioxide storage tank 8 through a pipeline; the lower end of the split heat exchanger 4 and the fully enclosed refrigerator are connected to the liquid storage tank 10 through a condensate pipe, and the outlet of the liquid storage tank 10 is connected to the oil transportation process 12 through a pipeline and a sewage pump 11, which plays a role in viscosity reduction and oil displacement.

[0019] Among them, the above-mentioned fully enclosed refrigeration machine also includes a first control valve 13, a second control valve 14, a third control valve 15, and a fourth control valve 16. The first control valve 13 is installed on the pipeline at the inlet end of the first shallow cooling evaporator 5, and the second control valve 14 is installed on the pipeline at the outlet end; the third control valve 15 is installed on the pipeline at the inlet end of the second shallow cooling heat exchanger 6, and the fourth control valve 16 is installed on the pipeline at the outlet end.

[0020] The bottom of the first shallow cooling evaporator 5 is connected to the liquid inlet pipeline of the liquid storage tank 10 through a condensing water pipe, and the bottom of the second shallow cooling heat exchanger 6 is connected to the liquid inlet pipeline of the liquid storage tank 10 through a condensing water pipe.

[0021] Reference Figure 2 The split heat exchanger 4 mentioned in the present invention is provided with a carbon dioxide inlet 4.4 and a cryogenic natural gas inlet 4.5 at the bottom, and a carbon dioxide outlet 4.6 and a cryogenic natural gas outlet 4.7 at the top. The inner cavity of the split heat exchanger 4 is provided with a heat insulation plate 4.3, which separates the first heat exchange chamber 4.1 and the second heat exchange chamber 4.2. The split heat exchanger 4 is provided with a scattered gas pipe inlet 4.8 at the left end and a scattered gas pipe outlet 4.9 at the right end.

[0022] The shell side inlet of the precooling radiator 3 is connected to the front end pipeline at the cryogenic natural gas outlet 4.7 through a pipeline, and the shell side outlet of the precooling radiator 3 is connected to the rear end pipeline at the cryogenic natural gas outlet 4.7 through a pipeline.

[0023] A control valve 17 is installed between the front-end pipeline and the rear-end pipeline at the above-mentioned cryogenic natural gas outlet 4.7.

[0024] The method for using the thermal fluorination frost decarbonization system containing scattered associated gas containing carbon dioxide mentioned in the present invention includes the following steps: 1. The scattered associated natural gas from oil wells and multi-purpose tanks passes through the cyclone separator 1 to remove particulate matter and liquid water, and then enters the booster 2 to boost the pressure of the scattered associated natural gas to 0.8MPa. Second, the pressurized scattered associated natural gas is sent to the pre-cooling radiator 3 for the first stage of cooling, reducing the pressurized temperature to room temperature of 30-40°C. It is then sent to the split heat exchanger 4 for the second stage of cooling, where the carbon dioxide at -37°C and the scattered associated natural gas cooled to -50°C are sequentially cooled to 0-5°C to remove most of the moisture. 3. Then, the scattered associated natural gas is sent to the fully enclosed refrigerator, which is equipped with a first shallow cooling evaporator 5 and a second shallow cooling heat exchanger 6. The compressor and refrigeration system in the fully enclosed refrigerator are used to force the scattered associated natural gas to be cooled to -25 to -30°C. One of them is used for cooling and the other is used for thermal fluorination defrosting or deicing. The two are operated alternately to achieve the third stage cooling of the scattered associated natural gas and remove heavy hydrocarbon components. If frost or ice appears on the first shallow cooling evaporator 5 and / or the second shallow cooling heat exchanger 6, its cooling efficiency will be greatly reduced. On the one hand, it cannot meet the cooling and refrigeration requirements, and on the other hand, energy consumption will increase significantly. Specifically, when frost or ice appears on the first shallow cooling evaporator 5, it is subjected to thermal fluorination defrosting or deicing, and the second shallow cooling heat exchanger 6 is in normal cooling condition. Conversely, when frost or ice appears on the second shallow cooling heat exchanger 6, it is subjected to thermal fluorination defrosting or deicing, and the first shallow cooling evaporator 5 is in normal cooling condition, thereby achieving the third stage cooling of the scattered associated natural gas in the fully enclosed refrigerator. Fourth, it is sent to the carbon dioxide heat exchange tank 7 through a pipeline. The low-temperature scattered associated natural gas exchanges heat with the -50°C low-temperature liquid carbon dioxide from the liquid carbon dioxide storage tank 8, and undergoes the fourth stage of cooling. The scattered associated natural gas continues to cool to -37°C. 5. The -37°C scattered associated natural gas then enters the cryogenic evaporator 9 to achieve the fifth stage of cooling. The compressor and refrigeration system are used to force the scattered associated natural gas to be cooled to below -50°C, and the carbon dioxide is liquefied and separated. The separated -50°C low-temperature carbon dioxide liquid enters the liquid carbon dioxide storage tank 8 to reuse the cold energy. The scattered associated natural gas pre-cooled by the pre-cooling radiator 3 is pre-cooled by heat exchange in the carbon dioxide heat exchange tank 7 and the first heat exchange chamber 4.1 of the split heat exchanger 4. The carbon dioxide gas after heat exchange and heating is sent to the existing CCUS carbon capture process for treatment; and the dry scattered associated natural gas after dehydration, dehydrocarbonization and decarbonization passes through the second heat exchange chamber 4.2 of the split heat exchanger 4 and enters the natural gas pipeline network for use.

[0025] In addition, the lower ends of the split heat exchanger 4 and the fully enclosed refrigerator are respectively connected to the liquid storage tank 10 through the condensate pipe. The outlet of the liquid storage tank 10 is connected to the oil transfer process 12 through the pipeline and the sewage pump 11, which plays the role of viscosity reduction and oil displacement.

[0026] In the process, the control valve 17 is closed, and the dry scattered associated natural gas passing through the second heat exchange chamber 4.2 of the split heat exchanger 4 is then sent to the shell-side inlet of the pre-cooling radiator 3 through a pipeline to pre-cool the hot scattered associated natural gas from the supercharger 2. The natural gas is then discharged into the natural gas pipeline network through the shell-side outlet of the pre-cooling radiator 3.

[0027] The above descriptions are merely some preferred embodiments of the present invention. Anyone skilled in the art may be able to modify the above-described technical solutions or convert them into equivalent technical solutions. Therefore, any corresponding simple modifications or equivalent transformations based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A thermal fluorination frost decarbonization system containing scattered associated gas containing carbon dioxide, comprising a cyclone separator (1) and a booster (2), characterized in that: It also includes a pre-cooling radiator (3), a split heat exchanger (4), a first shallow cooling evaporator (5), a second shallow cooling heat exchanger (6), a carbon dioxide heat exchange tank (7), a liquid carbon dioxide storage tank (8), a deep cooling evaporator (9), a liquid storage tank (10), a sewage pump (11), and an oil transportation process (12). The inlet of the cyclone separator (1) is connected to the scattered associated gas pipeline, the outlet of the cyclone separator (1) is connected to the booster (2), the outlet of the booster (2) is connected to the pre-cooling radiator (3) through a pipeline for primary cooling, the outlet of the pre-cooling radiator (3) is connected to the split heat exchanger (4) through a pipeline for secondary cooling, and the outlet of the split heat exchanger (4) is connected to the fully enclosed refrigerator through a pipeline for tertiary cooling. The fully enclosed refrigerator is provided with a first shallow cooling evaporator (5) and a second shallow cooling heat exchanger (6), wherein One is for refrigeration and the other is for defrosting or defrosting, and the two are operated alternately to remove heavy hydrocarbon components. The outlet of the fully enclosed refrigerator is connected to the shell side of the carbon dioxide heat exchange tank (7) through a pipeline for four-stage cooling. The shell side outlet of the carbon dioxide heat exchange tank (7) is connected to the deep cooling evaporator (9) through a pipeline for five-stage cooling to remove carbon dioxide. The outlet of the deep cooling evaporator (9) is connected to the shell side inlet of the split heat exchanger (4) through a pipeline to fully utilize the cooling capacity and then discharge it to the natural gas pipeline network through the shell side outlet of the split heat exchanger (4); the shell side bottom of the deep cooling evaporator (9) is connected to the liquid carbon dioxide storage tank (8) through a pipeline; the lower end of the split heat exchanger (4) and the fully enclosed refrigerator are connected to the liquid storage tank (10) through a condensate pipe, and the outlet of the liquid storage tank (10) is connected to the oil transportation process (12) through a pipeline and a sewage pump (11).

2. The thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide according to claim 1, characterized in that: The fully enclosed refrigerator further comprises a first control valve (13), a second control valve (14), a third control valve (15), and a fourth control valve (16). The first control valve (13) is installed on the pipeline at the inlet end of the first shallow cooling evaporator (5), and the second control valve (14) is installed on the pipeline at the outlet end; the third control valve (15) is installed on the pipeline at the inlet end of the second shallow cooling heat exchanger (6), and the fourth control valve (16) is installed on the pipeline at the outlet end.

3. The thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide according to claim 2, characterized in that: The bottom of the first shallow cooling evaporator (5) is connected to the liquid inlet pipeline of the liquid storage tank (10) through a condensing water pipe, and the bottom of the second shallow cooling heat exchanger (6) is connected to the liquid inlet pipeline of the liquid storage tank (10) through a condensing water pipe.

4. The thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide according to claim 3, characterized in that: The split heat exchanger (4) is provided with a carbon dioxide inlet (4.4) and a cryogenic natural gas inlet (4.5) at the bottom, and a carbon dioxide outlet (4.6) and a cryogenic natural gas outlet (4.7) at the top. The inner cavity of the split heat exchanger (4) is provided with a heat insulation plate (4.3) to separate a first heat exchange cavity (4.1) and a second heat exchange cavity (4.2). A scattered gas pipe inlet (4.8) is provided at the left end of the split heat exchanger (4), and a scattered gas pipe outlet (4.9) is provided at the right end of the split heat exchanger (4).

5. The thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide according to claim 4, characterized in that: The shell-side inlet of the precooling radiator (3) is connected to the front-end pipeline at the deep-cold natural gas outlet (4.7) through a pipeline, and the shell-side outlet of the precooling radiator (3) is connected to the rear-end pipeline at the deep-cold natural gas outlet (4.7) through a pipeline.

6. The thermal fluorination frost decarbonization system for scattered associated gas containing carbon dioxide according to claim 5, characterized in that: A control valve (17) is installed between the front pipeline and the rear pipeline at the cryogenic natural gas outlet (4.7).

7. The method for using the thermal fluorination frost decarburization system for scattered associated gas containing carbon dioxide according to claim 6, characterized in that: The following processes are included:

1. The scattered associated natural gas from the oil well and the multi-purpose tank passes through the cyclone separator (1) to remove particulate matter and liquid matter, and then enters the booster (2) to boost the pressure of the scattered associated natural gas to 0.8MPa. Second, the pressurized scattered associated natural gas is sent to the pre-cooling radiator (3) for the first stage of cooling, reducing the pressurized temperature to room temperature of 30-40°C, and then sent to the split heat exchanger (4) for the second stage of cooling, where the carbon dioxide at -37°C and the scattered associated natural gas cooled to -50°C are used to cool the natural gas to 0-5°C in sequence, in order to remove most of the moisture; 3. Then, the scattered associated natural gas is sent to a fully enclosed refrigerator, which is provided with a first shallow cooling evaporator (5) and a second shallow cooling heat exchanger (6). The compressor and refrigeration system in the fully enclosed refrigerator are used to force cool the scattered associated natural gas to -25 to -30°C. One of the refrigerators is used for cooling, while the other is used for hot fluorine defrosting or ice-melting. The two are operated alternately, thereby achieving the third stage of cooling of the scattered associated natural gas and removing heavy hydrocarbon components. Fourth, the gas is sent to the carbon dioxide heat exchange tank (7) through a pipeline, and the low-temperature scattered associated natural gas is heat-exchanged with the -50°C low-temperature liquid carbon dioxide from the liquid carbon dioxide storage tank (8), and the fourth stage of cooling is performed, and the scattered associated natural gas is further cooled to -37°C; 5. The scattered associated natural gas at -37°C then enters the cryogenic evaporator (9) to achieve the fifth stage of cooling. The compressor and refrigeration system are used to force the scattered associated natural gas to be cooled to below -50°C, and the carbon dioxide is liquefied and separated. The separated low-temperature carbon dioxide liquid at -50°C enters the liquid carbon dioxide storage tank (8) to reuse the cold energy. After heat exchange and heating in the carbon dioxide heat exchange tank (7) and the first heat exchange chamber (4.1) of the split heat exchanger (4), the scattered associated natural gas pre-cooled by the pre-cooling radiator (3) is pre-cooled. The carbon dioxide gas after heat exchange and heating is sent to the original CCUS carbon capture process for treatment; and the dry scattered associated natural gas after dehydration, dehydrogenation and decarbonization enters the natural gas pipeline network after heat exchange in the second heat exchange chamber (4.2) of the split heat exchanger (4).

8. The method for using the thermal fluorination frost decarburization system for scattered associated gas containing carbon dioxide according to claim 7, characterized in that: The dry scattered associated natural gas that has passed through the second heat exchange chamber (4.2) of the split heat exchanger (4) is sent to the shell-side inlet of the pre-cooling radiator (3) through a pipeline to pre-cool the hot scattered associated natural gas from the supercharger (2), and then discharged into the natural gas pipeline network through the shell-side outlet of the pre-cooling radiator (3).

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