Active cooling method and active cooling device for underground coal gasification

Abstract

The invention relates to the technical field of underground coal gasification, and provides an active cooling method and an active cooling device for underground coal gasification, and the method comprises the following steps: capturing carbon dioxide generated in a gasification process; the captured carbon dioxide is cooled and stored; after gasification is finished, a sealing material is injected into the production well and an annular gap generated in the gasification process, so that the gasification cavity is kept airtight; and the stored carbon dioxide is pressurized and injected into the gas injection well. A carbon dioxide gas injection active cooling mode is adopted, and it is ensured that the inner wall of a combustion space area cannot generate cracks due to drastic temperature change; moreover, carbon dioxide in the gasification process is used as a coolant, so that the collaborative operation of gasification and carbon sealing can be realized, and the target of zero emission is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground coal gasification, and in particular to an active cooling method and an active cooling device for underground coal gasification. Background Art

[0002] Underground coal gasification is a process of controlled combustion of underground coal to produce combustible gas through thermal and chemical reactions on the coal. The coal gasification process generally adopts the CRIP (Controlled Retraction and Injection Point) process. Figure 1 As shown, 10 is a gas injection well, 20 is a gas injection horizontal wellbore, 30 is a production well, 40 is a production well cement sheath, and 50 is a coal seam to be gasified. At the beginning of gasification, ignition is carried out at the toe end of the gas injection horizontal wellbore 20 ( Figure 1 When the combustion zone reaches the preset range, the toe end pipe string is burned out and the gas injection point closer to the heel end of the horizontal well is replaced. Similarly, at the end of gasification, if Figure 2 As shown, a long strip-shaped combustion space 60 is formed inside the coal seam 50 to be gasified, and an annular space 70 is formed around the production well 30 under the action of high temperature.

[0003] The underground coal gasification process can usually be divided into the gasification heating stage, the stable gasification stage and the cooling stage. In the stable gasification stage, the temperature is as high as 1200-1400℃, and the high temperature thermal stress and drastic changes in the mechanical properties of the surrounding rock have great damage to the integrity of the surrounding rock.

[0004] Passive natural cooling is mostly used in the cooling stage. Under the effect of natural cooling, the high temperature field generated during the gasification process will continue to spread to distant strata during the cooling stage, causing deformation and damage to strata in a larger range, which has a great impact on the stability of the surrounding rock, especially the deformation of the overlying rock strata, causing serious ground subsidence problems in shallow coal seams. According to the actual results of on-site settlement, settlement will continue to occur even one year after the end of gasification, that is, the sinking basin during the surface cooling period under natural cooling is still in an unstable state.

[0005] Therefore, in the prior art, in order to accelerate cooling, some adopt a rapid active cooling method, namely, a water injection method. However, rapid cooling will cause a sharp change in the stress field of the surrounding rock in the combustion and air gap area, resulting in a large number of cracks and causing leakage and pollution risks. Summary of the invention

[0006] The present invention provides an active cooling method and an active cooling device for underground coal gasification, which are used to solve the defects in the prior art that rapid active cooling easily leads to a sharp change in the stress field of the surrounding rock in the combustion gap zone, generates a large number of cracks, and causes the risk of leakage, and realizes slow active cooling to ensure that the inner wall of the combustion gap zone will not generate cracks due to drastic temperature changes.

[0007] The present invention provides an active cooling method for underground coal gasification, which is used for cooling a gasification cavity, comprising: Capture of carbon dioxide produced during gasification; Cooling and storing the captured carbon dioxide; After the gasification is completed, the sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification cavity airtight; The stored carbon dioxide is pressurized and injected into the gas injection well.

[0008] According to an active cooling method for underground coal gasification provided by the present invention, the method of capturing carbon dioxide generated during the gasification process comprises: The gasification products are processed.

[0009] According to an active cooling method for underground coal gasification provided by the present invention, the captured carbon dioxide is cooled and stored, comprising: The carbon dioxide is first cooled through a heat exchanger and then stored at high pressure.

[0010] According to an active cooling method for underground coal gasification provided by the present invention, after the gasification is completed, a sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification cavity airtight, comprising: Inject high molecular weight negative carbon filling materials into the production wells and annular gaps generated during the gasification process; The airtightness of the gasification chamber is tested, and after the pressure-bearing requirement is met, the top of the production well is sealed by a casing head.

[0011] According to an active cooling method for underground coal gasification provided by the present invention, before pressurizing the stored carbon dioxide and injecting it into the gas injection well, the method further includes mixing the carbon dioxide and a foaming agent solution.

[0012] The present invention also provides an active cooling device for underground coal gasification, comprising: A carbon dioxide capture device to capture carbon dioxide produced during the gasification process; A carbon dioxide cooling and storage device connected to the carbon dioxide capture device, the carbon dioxide cooling device is used to cool and store the captured carbon dioxide; A gasification chamber sealing device, used to seal the gasification chamber after gasification is completed; The carbon dioxide pressurizing injection device is connected to the carbon dioxide cooling storage device, and the carbon dioxide pressurizing injection device pressurizes and injects the cooled and stored carbon dioxide into the gas injection well.

[0013] An active cooling device for underground coal gasification provided by the present invention further includes: An intermediate mixing container is connected to the carbon dioxide cooling and storage device upstream and to the carbon dioxide pressurizing and injection device downstream. The intermediate mixing container is used to mix the cooled and stored carbon dioxide and the foaming agent.

[0014] According to an active cooling device for underground coal gasification provided by the present invention, the gasification chamber sealing device comprises: High molecular weight negative carbon filler, set in the annular gaps generated during the gasification process; The casing head is arranged at the top end of the gasification chamber.

[0015] An active cooling device for underground coal gasification provided by the present invention also includes a gas processing device for processing gas in the gasification product.

[0016] An active cooling device for underground coal gasification provided by the present invention further includes a foaming agent supply device connected to the intermediate mixing container, and the foaming agent supply device is used to supply the foaming agent.

[0017] The present invention provides an active cooling method for underground coal gasification, which captures carbon dioxide generated during the gasification process, cools and stores the captured carbon dioxide, and after the gasification is completed, injects sealing materials into the production well and the annular gaps generated during the gasification process to keep the gasification cavity airtight; finally, the stored carbon dioxide is pressurized and injected into the gas injection well. The active cooling method of gas injection ensures that the inner wall of the combustion air zone will not produce cracks due to drastic temperature changes; in addition, the carbon dioxide in the gasification process is used as a coolant to achieve the coordinated operation of gasification and carbon sealing, achieving the goal of zero emissions.

[0018] The active cooling device for underground coal gasification provided by the present invention captures the carbon dioxide generated in the gasification process through a carbon dioxide capture device, cools and stores the captured carbon dioxide through a carbon dioxide cooling and storage device, seals the gasification chamber through a gasification chamber sealing device, and pressurized carbon dioxide injection device injects the cooled and stored carbon dioxide into a gas injection well. The active cooling method of injecting carbon dioxide gas can not only achieve slow cooling and ensure that the inner wall of the combustion-air zone will not produce cracks due to drastic temperature changes; moreover, the carbon dioxide in the gasification process is used as a coolant, which can achieve coordinated operation of gasification and carbon sealing and achieve the goal of zero emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a structural schematic diagram of the starting state of underground coal gasification in the prior art.

[0021] Figure 2 It is a structural schematic diagram of the final state of underground coal gasification in the prior art.

[0022] Figure 3 It is a schematic flow diagram of the active cooling method for underground coal gasification provided by the present invention.

[0023] Figure 4 It is a structural principle diagram of the active cooling device for underground coal gasification provided by the present invention during the gasification process.

[0024] Figure 5 This is a structural principle diagram of the active cooling device for underground coal gasification provided by the present invention after the gasification process is completed.

[0025] Reference numerals: 1. Carbon dioxide capture device; 2. Carbon dioxide cooling and storage device; 21. Carbon dioxide cooling device; 22. Carbon dioxide storage device; 3. Gasification chamber sealing device; 4. Carbon dioxide pressurization injection device; 5. Intermediate mixing container; 31. High molecular negative carbon filler; 32. Casing head; 6. Gasification chamber; 7. Gas processing device; 8. Foaming agent supply device. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0027] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0028] Combine the following Figure 3 The active cooling method for underground coal gasification provided by the first embodiment of the present invention comprises: S1. Capture the carbon dioxide produced during the gasification process.

[0029] During the underground coal gasification process, carbon dioxide capture devices such as chemical absorption towers, membrane separation systems or low-temperature separation technology can be used to efficiently capture carbon dioxide from the mixed gas produced by gasification.

[0030] S2. Cooling and storing the captured carbon dioxide.

[0031] A heat exchanger can be used to cool the captured carbon dioxide gas to a liquid state using cooling water or low-temperature refrigerant to reduce its volume and facilitate storage. Storage facilities can choose pressure-resistant and corrosion-resistant storage tanks to ensure long-term safe storage.

[0032] S3. After the gasification is completed, the sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification cavity airtight.

[0033] According to the geological conditions and the shape of the gasification cavity, select appropriate sealing materials, and ensure that the sealing materials can evenly fill all annular gaps by precisely controlling the grouting pressure and flow rate.

[0034] S4. Pressurize the stored carbon dioxide and inject it into the gas injection well.

[0035] A high pressure pump or compressor may be used to pressurize the liquid carbon dioxide to a pressure suitable for injection into the formation.

[0036] The active cooling method for underground coal gasification provided in the embodiment of the present invention adopts a gas injection cooling method, which can not only achieve slow cooling of the combustion zone and ensure that cracks will not be generated inside the combustion zone due to drastic temperature changes, but also use carbon dioxide in the gasification process as a coolant to achieve coordinated operation of gasification and carbon sealing and achieve the goal of zero emissions.

[0037] In a feasible embodiment of the present invention, in step S1, while capturing the carbon dioxide generated in the gasification process, the gas other than carbon dioxide in the gasification product is also processed.

[0038] During the underground coal gasification process, the gasification products also contain a variety of other gases, such as carbon monoxide, hydrogen, methane, nitrogen, and a small amount of sulfides, nitrogen oxides, etc. Among them, carbon monoxide and hydrogen can be used to synthesize chemicals such as ammonia and methanol, and can be separated from the gasification products by catalytic conversion, separation and purification, and other technologies, and then used later. Methane can be processed into standard natural gas by purification, compression and other technologies, and then stored and used. Nitrogen can be separated from the gasification products by separation and purification, and then used later. Sulfides and nitrogen oxides can be converted into harmless substances by oxidation, absorption, catalytic conversion and other technologies, or removed from the exhaust gas by washing, adsorption and other methods.

[0039] By processing the gases other than carbon dioxide in the gasification products while capturing the carbon dioxide generated in the process, it is possible to effectively process and utilize various gases in the gasification products while reducing environmental pollution and energy waste.

[0040] In a feasible embodiment of the present invention, in step S2, during the process of cooling and storing the captured carbon dioxide, the carbon dioxide is first cooled by a heat exchanger and then stored at a high pressure.

[0041] In the process of cooling carbon dioxide through a heat exchanger, the high-temperature carbon dioxide gas exchanges heat with a low-temperature cooling medium through the heat exchanger, thereby lowering the temperature of the carbon dioxide. The volume of the cooled carbon dioxide gas will be reduced, making it easier to store it later.

[0042] When carbon dioxide is stored under high pressure, the cooled carbon dioxide gas can be transported to a high-pressure storage tank. A pressure control system is provided inside the tank to ensure that the carbon dioxide maintains a stable pressure during the storage process.

[0043] By cooling and capturing carbon dioxide at high pressure, its volume and energy loss can be effectively reduced, and storage efficiency and safety can be improved.

[0044] In a feasible embodiment of the present invention, in step S3, after the gasification is completed, the sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification chamber airtight, including: first injecting high molecular negative carbon filling material into the production well and the annular gap generated during the gasification process; then testing the airtightness of the gasification chamber, the test method includes pressure testing, gas leakage testing, etc., to check whether the gasification chamber achieves the expected airtight effect. When the test result meets the pressure requirement, the top of the production well is sealed by the casing head. The casing head is a special gasification chamber sealing device that can ensure the sealing between the production well and the surface.

[0045] After sealing is completed, the gasification chamber needs to be monitored and maintained for a long time. The monitoring content includes the pressure, temperature, etc. of the gasification chamber. According to the monitoring results, timely measures are taken for maintenance and repair to ensure the long-term stability and safety of the gasification chamber.

[0046] It should be noted that the polymer negative carbon filling material is a prior art and is well known to those skilled in the art, and will not be described in detail here.

[0047] In a feasible embodiment of the present invention, before the stored carbon dioxide is pressurized and injected into the gas injection well in step S5, the carbon dioxide and a foaming agent solution are mixed.

[0048] During the CO2 injection process, the foaming agent can help the CO2 to be better dispersed and dissolved in the underground medium, thereby improving the injection efficiency and storage effect, and ensuring that the CO2 can enter the underground in the best form and dispersion during the injection process. Through the above steps, the CO2 and the foaming agent can be mixed to form CO2 foam, so as to control the mobility of CO2 and slow down gas channeling.

[0049] Therefore, the active cooling method for underground coal gasification provided by the first embodiment of the present invention adopts the method of slow active injection of carbon dioxide for cooling, which not only ensures that the inner wall of the combustion zone will not produce cracks due to drastic temperature changes, but also can use the carbon dioxide in the gasification process as a coolant to achieve the coordinated operation of gasification and carbon sealing, and achieve the goal of zero emissions. In addition, before injecting carbon dioxide, negative carbon filling materials are first filled to ensure that the damage around the production well caused by the gasification process will not affect the quality of the carbon sealing operation.

[0050] like Figure 4 and Figure 5 As shown, the second embodiment of the present invention provides an active cooling device for underground coal gasification, including a carbon dioxide capture device 1, a carbon dioxide cooling storage device 2, a gasification chamber sealing device 3 and a carbon dioxide pressurization injection device 4.

[0051] The carbon dioxide capture device 1 is used to capture carbon dioxide generated during the gasification process. The carbon dioxide capture device can use a chemical absorption tower, a membrane separation system or a low-temperature separation technology to efficiently capture carbon dioxide from the mixed gas generated by gasification, thereby reducing carbon dioxide emissions during underground coal gasification.

[0052] The carbon dioxide cooling and storage device 2 is connected to the carbon dioxide capture device 1, and the carbon dioxide cooling and storage device 2 is used to cool and store the captured carbon dioxide. The carbon dioxide cooling and storage device 2 may include a carbon dioxide cooling device 21 and a carbon dioxide storage device 22. The carbon dioxide cooling device 21 may use a heat exchanger to cool the captured carbon dioxide gas to a liquid state using cooling water or a low-temperature refrigerant to reduce its volume and facilitate storage. The carbon dioxide storage device 22 may select a pressure-resistant and corrosion-resistant storage tank to ensure long-term safe storage. When carbon dioxide is stored under high pressure, the cooled carbon dioxide gas may be transported to a high-pressure storage tank, and a pressure control system is provided inside the storage tank to ensure that the carbon dioxide maintains a stable pressure during storage.

[0053] The carbon dioxide cooling device 21 and the carbon dioxide storage device 22 can effectively reduce the volume and energy loss of carbon dioxide, and improve the storage efficiency and safety.

[0054] The gasification cavity sealing device 3 is used to seal the gasification cavity 6 after the gasification is completed, so that the gasification cavity 6 forms a closed environment, and the injection of carbon dioxide gas can achieve a cooling effect. It should be noted that in the sealing process, suitable sealing materials can be selected according to geological conditions and the shape of the gasification cavity, and the sealing materials can be ensured to evenly fill all annular gaps by accurately controlling the grouting pressure and flow rate.

[0055] The carbon dioxide pressurizing injection device 4 is connected to the carbon dioxide cooling storage device 2, and the carbon dioxide pressurizing injection device 4 pressurizes and injects the carbon dioxide in the cooling storage into the gas injection well. A high-pressure pump or compressor can be used to pressurize the liquid carbon dioxide to a pressure suitable for injection into the formation.

[0056] The active cooling device for underground coal gasification provided in the embodiment of the present invention adopts a gas injection cooling method, which can not only achieve slow cooling of the combustion zone and ensure that cracks will not be generated inside the combustion zone due to drastic temperature changes, but also use the carbon dioxide in the gasification process as a coolant to achieve coordinated operation of gasification and carbon sealing and achieve the goal of zero emissions.

[0057] In a feasible embodiment of the present invention, it also includes: an intermediate mixing container 5, the upstream of the intermediate mixing container 5 is connected to the carbon dioxide cooling and storage device 2, and the downstream of the intermediate mixing container 5 is connected to the carbon dioxide pressurization injection device 4, and the intermediate mixing container 5 is used to mix the cooled and stored carbon dioxide and the foaming agent.

[0058] During the CO2 injection process, the foaming agent can help the CO2 to be better dispersed and dissolved in the underground medium, thereby improving the injection efficiency and storage effect, and ensuring that the CO2 can enter the underground in the best form and dispersion during the injection process. Through the above steps, the CO2 and the foaming agent can be mixed to form CO2 foam, so as to control the mobility of CO2 and slow down gas channeling.

[0059] In a feasible embodiment of the present invention, the gasification chamber sealing device 3 specifically includes a polymer negative carbon filler 31 and a casing head 32. The polymer negative carbon filler 31 is arranged in the annular gap generated during the gasification process; the casing head 32 is arranged at the top of the gasification chamber 6. After the gasification is completed, the polymer negative carbon filler 31 is injected into the production well and the annular gap generated during the gasification process to keep the gasification chamber 6 airtight. More specifically, the polymer negative carbon filling material is first injected into the production well and the annular gap generated during the gasification process; then the airtightness of the gasification chamber is tested, and the test method includes pressure testing, gas leakage testing, etc., to check whether the gasification chamber 6 achieves the expected airtight effect. When the test result meets the pressure requirement, the casing head is sealed at the top of the production well. The casing head 32 is a special sealing device that can ensure the sealing between the production well and the surface.

[0060] It should be noted that the polymer negative carbon filling material is a prior art and is well known to those skilled in the art, and will not be described in detail here.

[0061] In a feasible embodiment of the present invention, a gas processing device 7 is further included for processing the gas in the gasification product. The gas processing device 7 can be connected to the carbon dioxide capture device 1 to process the gas other than carbon dioxide in the gasification product.

[0062] During the underground coal gasification process, the gasification products also contain a variety of other gases, such as carbon monoxide, hydrogen, methane, nitrogen, and a small amount of sulfides, nitrogen oxides, etc. Among them, carbon monoxide and hydrogen can be used to synthesize chemicals such as ammonia and methanol, and can be separated from the gasification products by catalytic conversion, separation and purification, and other technologies, and then used later. Methane can be processed into standard natural gas by purification, compression and other technologies, and then stored and used. Nitrogen can be separated from the gasification products by separation and purification, and then used later. Sulfides and nitrogen oxides can be converted into harmless substances by oxidation, absorption, catalytic conversion and other technologies, or removed from the exhaust gas by washing, adsorption and other methods.

[0063] By processing the gases other than carbon dioxide in the gasification products while capturing the carbon dioxide generated in the process, it is possible to effectively process and utilize various gases in the gasification products while reducing environmental pollution and energy waste.

[0064] In a feasible embodiment of the present invention, a foaming agent supply device 8 is also included, which is connected to the intermediate mixing container 5. The foaming agent supply device 8 is used to supply the foaming agent. In the intermediate mixing container 5, the carbon dioxide and the foaming agent are mixed. During the carbon dioxide injection process, the foaming agent can help the carbon dioxide to be better dispersed and dissolved in the underground medium, thereby improving the injection efficiency and storage effect, and ensuring that the carbon dioxide can enter the underground in the best form and dispersion during the injection process. Through the above steps, the carbon dioxide and the foaming agent can be mixed to form carbon dioxide foam to control the fluidity of the carbon dioxide and slow down gas channeling.

[0065] Therefore, the active cooling device for underground coal gasification provided by the second embodiment of the present invention adopts the method of slow active injection of carbon dioxide for cooling, which not only ensures that the inner wall of the combustion zone will not produce cracks due to drastic temperature changes, but also can use the carbon dioxide in the gasification process as a coolant to achieve the coordinated operation of gasification and carbon sealing, and achieve the goal of zero emissions. In addition, before injecting carbon dioxide, negative carbon filling materials are first filled to ensure that the damage around the production well caused by the gasification process will not affect the quality of the carbon sealing operation.

[0066] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "mode", "specific mode", or "some modes" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or mode are included in at least one embodiment or mode of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or mode. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or modes in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or modes described in this specification and the features of the different embodiments or modes, without contradiction.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An active cooling method for underground coal gasification, characterized in that: For cooling the gasification chamber, including: Capture of carbon dioxide produced during gasification; Cooling and storing the captured carbon dioxide; After the gasification is completed, the sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification cavity airtight; The stored carbon dioxide is pressurized and injected into the gas injection well.

2. The active cooling method for underground coal gasification according to claim 1, characterized in that: The method of capturing carbon dioxide generated during the gasification process comprises: The gasification products produced during the gasification process are treated.

3. The active cooling method for underground coal gasification according to claim 1, characterized in that: The method of cooling and storing the captured carbon dioxide comprises: The carbon dioxide is first cooled through a heat exchanger and then stored at high pressure.

4. The active cooling method for underground coal gasification according to claim 1, characterized in that: After the gasification is completed, a sealing material is injected into the production well and the annular gap generated during the gasification process to keep the gasification cavity airtight, including: After the gasification is completed, a gasification cavity is formed underground; Inject high molecular weight negative carbon filling materials into the production wells and annular gaps generated during the gasification process; The airtightness of the gasification chamber is tested, and after the pressure-bearing requirement is met, the top of the production well is sealed by a casing head.

5. The active cooling method for underground coal gasification according to claim 1, characterized in that: Before the stored carbon dioxide is pressurized and injected into the gas injection well, the method further includes mixing the carbon dioxide with a foaming agent solution.

6. An active cooling device for underground coal gasification, characterized in that: include: A carbon dioxide capture device (1) for capturing carbon dioxide generated during the gasification process; A carbon dioxide cooling and storage device (2) connected to the carbon dioxide capture device (1), the carbon dioxide cooling and storage device (2) being used to cool and store captured carbon dioxide; A gasification chamber sealing device (3), used to seal the gasification chamber after gasification is completed; The carbon dioxide pressurizing injection device (4) is connected to the carbon dioxide cooling storage device (2), and the carbon dioxide pressurizing injection device (4) pressurizes and injects the cooled and stored carbon dioxide into the gas injection well.

7. The active cooling device for underground coal gasification according to claim 6, characterized in that: Also includes: An intermediate mixing container (5) is connected to the carbon dioxide cooling and storage device (2) upstream and to the carbon dioxide pressurizing and injection device (4) downstream. The intermediate mixing container (5) is used to mix the cooled and stored carbon dioxide and the foaming agent.

8. The active cooling device for underground coal gasification according to claim 6, characterized in that: The gasification chamber sealing device (3) comprises: A high molecular weight negative carbon filler (31) is arranged in the annular gap generated during the gasification process; The sleeve head (32) is arranged at the top end of the gasification chamber (6).

9. The active cooling device for underground coal gasification according to claim 6, characterized in that: It also includes a gas processing device (7) for processing the gas in the gasification product.

10. The active cooling device for underground coal gasification according to claim 7, characterized in that: It also comprises a foaming agent supply device (8) connected to the intermediate mixing container (5), and the foaming agent supply device (8) is used to supply the foaming agent.

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