Coal in-situ controllable direct combustion power generation, gasification and carbon sequestration system

Abstract

The present application relates to a kind of coal in situ controllable direct combustion energy, gasification and carbon sequestration system;Gas supply station, injection well, horizontal well, gas inlet outer tube, working medium inflow pipe, working medium horizontal pipe, working medium outflow pipe, gas outlet outer tube, ignition heating device, production well, hole hole outer tube, shield equipment, mining unit, gas supply control device, gas separation device, gas chromatograph, external circulation pipe and shield equipment, the injection well extends into middle coal seam, injection well is connected with horizontal well, horizontal well is connected with production well, and all are arranged in casing;The mining unit is composed of two sides airtight wall and upper and lower lining piece and forms a closed lining structure;Shield equipment includes cutterhead and screw conveyor, the cutterhead is stripped after raw coal and is transmitted to mining unit by screw conveyor;Hard coal seam that is not easy to burn is broken in advance, useful gasification products are effectively utilized, waste gas produced after combustion does not escape, and in the case where carbon is still saved in situ after combustion, surface subsidence is avoided.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a system for in-situ controlled direct combustion energy extraction, gasification and carbon sequestration of coal. Background Technology

[0002] Traditional mechanical mining methods, such as blasting and cutting coal, face significant challenges in maintaining the stability of the surrounding rock in mining areas. These methods also involve complex mining systems and enormous energy consumption. Coal chemical mining, on the other hand, involves artificially inducing chemical reactions in coal-bearing strata to extract useful chemical components from raw coal. This unmanned and intelligent mining method fundamentally changes traditional coal mining practices, enabling unmanned underground coal resource extraction, coal-free surface operations, and fluidized product production. This achieves the goals of zero mining failures, zero environmental damage, and clean resource utilization. Traditional coal chemical mining includes three technologies: underground gasification, underground pyrolysis, and biodissolution. With technological advancements, a fourth underground resource extraction method—in-situ combustion energy extraction from coal reservoirs—has been proposed in recent years, distinct from these three methods.

[0003] Chinese patent CN114837648B discloses an integrated system and method for in-situ controlled combustion heat recovery and carbon burial of thermal coal. A horizontal well is located near the bottom of the coal seam where in-situ combustion is to be performed. An auxiliary combustion gas supply pipe is laid along the horizontal well after passing through a vertical well. A heat exchange circulating liquid pipe is laid along the horizontal well after passing through a vertical well and then exits from the vertical well. An electric ignition device is installed at the front end of the auxiliary combustion gas supply pipe. The horizontal section of the auxiliary combustion gas supply pipe adopts a screen pipe structure and is sealed with a high-temperature self-melting material. A sealing structure is provided between the auxiliary combustion gas supply pipe, the heat exchange circulating liquid pipe, and the well wall of the vertical well. The patent is equipped with a pressure sensor, and the heat exchange circulating liquid pipe is connected to the ground heat exchanger for power generation or heating. It also discloses an integrated method for in-situ controlled combustion of thermal coal underground and carbon burial. It can realize in-situ controlled continuous combustion of coal seams underground, fully extract and utilize the combustion heat, and bury carbon underground in-situ. However, the patent has problems such as the difficulty in stable combustion of non-flammable hard coal seams, the large amount of heat loss caused by the contact between the combustion unit and the surrounding rock, the environmental damage and surface subsidence caused by combustion exhaust gas and voids, the escape of gasification products of raw coal from distant places caused by heat radiation and heat conduction, and the poor carbon sequestration effect of carbon generated in the fissures of the combustion voids.

[0004] Therefore, to ensure the safe and efficient utilization of coal resources and improve carbon sequestration under environmentally friendly conditions, it is necessary to establish a combined system of in-situ controllable direct combustion of coal for energy extraction, gasification, and carbon sequestration to solve the above problems. Summary of the Invention

[0005] This invention provides a coal in-situ controllable direct combustion energy extraction, gasification and carbon sequestration system, which enables the early crushing of non-combustible hard coal seams, realizes full combustion and heat extraction in-situ, and can effectively utilize useful gasification products. The exhaust gas generated after combustion does not escape, reducing the pollution of soil, rock and groundwater environment by waste, and avoiding surface subsidence while ensuring that the carbon after combustion is preserved in situ.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A coal in-situ controllable direct combustion energy extraction, gasification, and carbon sequestration system includes a gas supply station, an injection well, a horizontal well, an inlet gas pipe, a working fluid inflow pipe, a working fluid horizontal pipe, a working fluid outflow pipe, an outlet gas pipe, and an ignition and heating device; it also includes a production well, a perforated outer pipe, a tunnel boring machine, a mining unit, a gas supply control device, a gas separation device, a gas chromatograph, and an external circulation pipe. The injection well extends into the middle of the coal seam, is connected to the horizontal well, and the horizontal well is connected to the production well, all of which are arranged with casing.

[0008] The top of the air intake pipe is sealed, and an air inlet is left at the top side end. The air inlet is connected to the gas supply station through a pipe. The working fluid inflow pipe passes through the top of the air intake pipe and is connected to the working fluid horizontal pipe. The air intake pipe is connected to the perforated outer pipe. The surface of the perforated outer pipe is covered with vent holes, and the working fluid horizontal pipe is arranged concentrically inside. The working fluid inflow pipe is connected to the working fluid horizontal pipe. The ignition heating device is a heating ring sleeved on the outside of the perforated outer pipe. The heating ring is nested at the connection between the perforated outer pipe and the air intake pipe. The exhaust pipe is connected to the perforated outer pipe. The top of the exhaust pipe is sealed, and an air outlet is left at the top side end. The working fluid outflow pipe passes through the top of the exhaust pipe and connects to one end of the external circulation pipe. The other end of the external circulation pipe is connected to the working fluid inflow pipe that passes through the top of the air intake pipe. A working fluid inlet is provided on the external circulation pipe.

[0009] The mining unit is located within the coal seam surrounding the horizontal shaft. The mining unit consists of a closed lining structure consisting of two sealed walls on both sides and upper and lower lining segments.

[0010] The tunnel boring machine is set outside the sealed wall on one side of the mining unit and includes a cutterhead and a screw conveyor. The cutterhead advances before the sealed wall on one side of the mining unit is built. After the cutterhead strips the raw coal, it is transported to the mining unit by the screw conveyor.

[0011] The gas outlet is connected in sequence to a gas chromatograph and a gas separation device via a pipeline. The gas separation device is connected back to the mining unit via a pipeline. The gas chromatograph detects the gas content produced at the gas outlet. The gas chromatograph is electrically connected to the gas supply control equipment, and the gas supply control equipment is electrically connected to the gas supply station.

[0012] Furthermore, the injection well penetrates through the overburden to reach the middle of the coal seam, serving as the starting area of ​​the mining unit, while the production well side serves as the terminal area of ​​the mining unit. The sealed walls and lining segments of the mining unit are composed of concrete and fireproof and heat-insulating materials.

[0013] Furthermore, it also includes working fluid control equipment, centrifugal pump, heat exchanger, turbine, thermometer and flow valve. The external circulation pipe is provided with a parallel pipeline of centrifugal pump, thermometer, turbine and heat exchanger and flow valve from the working fluid outlet pipe end to the working fluid inlet pipe end. The flow valve and thermometer are connected to the working fluid control equipment.

[0014] Furthermore, the lining segments are simultaneously installed by the segment assembly machine during the forward advancement of the tunnel boring machine.

[0015] Furthermore, the arrangement of the horizontal wells, injection wells, and production wells includes the following structures:

[0016] 1) In shallow conditions within 600m: a horizontal well is connected to an injection well and a production well respectively;

[0017] 2) Under deep conditions greater than 600m: multiple horizontal wells are interconnected and then connected to an injection well and a production well respectively;

[0018] 3) When horizontal wells are arranged symmetrically, the symmetrical horizontal wells shall be the same type of injection well or production well;

[0019] 4) When multiple horizontal wells are arranged symmetrically, if the coal seam has no fault zone and is continuous, the multiple horizontal wells arranged symmetrically use the same injection well and different production wells. If the coal seam has a fault fracture zone and loses continuity, the multiple horizontal wells arranged symmetrically use the same production well and different injection wells.

[0020] Furthermore, the mining unit includes a coal seam combustion zone, an oxygen-rich combustion zone, an oxygen-poor gasification zone, and a raw coal zone. The gas separation device transmits the separated CO2 through a pipeline to the coal seam combustion zone of the previous mining unit.

[0021] Furthermore, when the gas chromatograph shows that the O2 volume content is less than 21% of the total gas content, the gas supply control equipment automatically increases the oxygen supply.

[0022] Furthermore, the working fluid inlet selects different working fluids to flow in at different stages. When the coal seam is burning and when the coal seam is burning to the boundary, the working fluid is CO2 or supercritical CO2. When the coal seam is burned and the coal seam is completely burned, and the ambient temperature reaches 100°C, the working fluid is water.

[0023] Furthermore, the working fluid inlet pipe and the working fluid outlet pipe are Tesla pipes with opposite directions.

[0024] Furthermore, the working fluid horizontal pipe is spiral-shaped.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1) The shield tunneling mechanism enables the pre-fracture of non-combustible hard coal seams, which greatly increases their ignition and combustion performance, and achieves full combustion of the coal seams in situ.

[0027] 2) The closed mining unit ensures that the fire is controllable throughout the coal combustion process, reduces the pollution of waste gas to the soil, rock and groundwater environment, reduces heat leakage, improves energy utilization, and has a good supporting effect to prevent surface subsidence.

[0028] 3) By making full use of injection wells, horizontal wells and production wells through reasonable pipeline layout, production costs can be reduced and production efficiency and heat utilization can be improved;

[0029] 4) The working fluid inflow rate is automatically adjusted by the working fluid control equipment and thermometer, and the oxidant flow rate is controlled by the gas chromatograph and gas supply control equipment to ensure the full combustion of the in-situ coal seam. The useful gasification products and waste gas are separated by the gas separation device. Attached Figure Description

[0030] Figure 1 This is a system structure diagram of the present invention.

[0031] Figure 2 This is a structural schematic diagram of the 111 arrangement method in the pipeline arrangement method described in this invention.

[0032] Figure 3 This is a structural schematic diagram of the 1N1 arrangement method in the pipeline layout described in this invention.

[0033] Figure 4 This is a structural schematic diagram of the pipeline layout method and the well layout method of the Zhong111 group described in this invention.

[0034] Figure 5 This is a structural schematic diagram of the 1N1 group well arrangement method in the pipeline arrangement method described in this invention.

[0035] Figure 6 This is a schematic diagram of the zoning of the coal seam during combustion in the mining unit described in this invention.

[0036] In the diagram: 1. Gas supply station 2. Injection well 3. Horizontal well 4. Production well 5. Inlet pipe 6. Working fluid inlet pipe 7. Working fluid horizontal pipe 8. Working fluid outlet pipe 9. Outlet pipe 10. Ignition and heating device 11. Perforated pipe 12. Cutter head 13. Screw conveyor 14. Front sealing wall 15. Rear sealing wall 16. Lined segments 17. Gas supply control equipment 18. Gas separation device 19. Gas chromatograph 20. External circulation pipe 21. Centrifugal pump 22. Heat exchanger 23. Turbine 24. Thermometer 25. Flow valve 26. Inlet 27. Outlet 28. Working fluid inlet 29. Surface 30. Overburden 31. Coal seam Detailed Implementation

[0037] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0038] See Figure 1 This is a schematic diagram of the structure of the present invention. The present invention provides a coal in-situ controllable direct combustion energy extraction, gasification and carbon sequestration system, including a gas supply station 1, an injection well 2, a horizontal well 3, an external gas inlet pipe 5, a working fluid inlet pipe 6, a working fluid horizontal pipe 7, a working fluid outlet pipe 8, an external gas outlet pipe 9 and an ignition heating device 10; it also includes a production well 4, a perforated external pipe 11, a tunnel boring machine, a mining unit, a gas supply control device 17, a gas separation device 18, a gas chromatograph 19 and an external circulation pipe 20. The injection well 2 extends into the middle of the coal seam 31, the injection well 2 is connected to the horizontal well 3, the horizontal well 3 is connected to the production well 4, and both are arranged with casing.

[0039] The top of the air intake pipe 5 is sealed, and an air inlet 26 is left at the top side end. The air inlet 26 is connected to the gas supply station 1 through a pipeline. The working fluid inflow pipe 6 passes through the top of the air intake pipe 5. The working fluid inflow pipe 6 is smoothly connected to the working fluid horizontal pipe 7 in the mining unit. The smooth connection is used to prevent turbulence resistance at the connection. The air intake pipe 5 is smoothly connected to the perforated outer pipe 11 in a rounded arc. The perforated outer pipe 11 in the horizontal well 3 is made of high-temperature alloy steel, which is resistant to high temperature and deformation. It has the function of protecting the hole and allowing the oxidant to pass through. Its surface is covered with vent holes, and the working fluid horizontal pipe 7 is arranged concentrically inside. Both are made of high-temperature alloy steel. The ignition heating device 10 is a heating ring that is sleeved on the outer tube 11 of the flower hole. The heating ring is nested at the connection between the outer tube 11 of the flower hole and the air inlet pipe. The working fluid inlet pipe 6 is connected to the working fluid horizontal pipe 7. The air outlet pipe 9 is smoothly connected to the outer tube 11 of the flower hole in an arc. The top of the air outlet pipe 9 is sealed, and an air outlet 27 is left at the top side end. The working fluid outlet pipe 8 passes through the top of the air outlet pipe 9 and connects to one end of the external circulation pipe 20. The other end of the external circulation pipe 20 is connected to the working fluid inlet pipe 6 that passes through the top of the air inlet pipe 5. A working fluid inlet 28 is provided on the external circulation pipe 20.

[0040] The working fluid inlet pipe 6 and the working fluid outlet pipe 8 are Tesla pipes with opposite directions, so that the working fluid can only flow counterclockwise. This prevents the working fluid from flowing back due to the high internal temperature and pressure after the mining unit is burned. The use of the simplest mechanical structure reduces costs. A heat insulation layer is set between the gas outlet pipe 9 and the coal and rock wall to reduce heat exchange.

[0041] The working fluid horizontal pipe 7 is spiral-shaped. The spiral pipe has a large heating area and a high heat carrying capacity.

[0042] It also includes working fluid control equipment, centrifugal pump 21, heat exchanger 22, turbine 23, thermometer 24 and flow valve 25. The external circulation pipe 20 is provided with a parallel pipeline of centrifugal pump 21, thermometer 24, turbine 23 and heat exchanger 22 and flow valve 25 from the working fluid outlet pipe 8 end to the working fluid inlet pipe 6 end. The flow valve 25 and thermometer 24 are connected to the working fluid control equipment.

[0043] The mining unit is set up in the coal seam 31 surrounding the horizontal well 3. The injection well 2 is constructed downward from the surface 29 of the mining coalfield. The injection well 2 passes through the overburden 30 and reaches the middle of the coal seam 31, serving as the starting area of ​​the mining unit area. The production well 4 is constructed. The production well 4 is completed in one drilling operation, serving as the ending area of ​​the mining unit. The mining unit is a closed lining structure consisting of two sealed walls on both sides and upper and lower lining segments 16.

[0044] The tunnel boring machine (TBM) is installed outside the sealed wall on one side of the mining unit, including a cutterhead 12 and a screw conveyor 13. First, a front-end sealed wall 14 is constructed at the end of the starting area of ​​the mining unit to isolate adjacent mining areas. The TBM is transported from the injection shaft 2 to the coal seam 31. Different types of cutterheads 12 are installed according to the strength and thickness of the coal seam 31. The cutterhead 12 advances according to the pre-designed mining path. After the cutterhead 12 strips the raw coal, it is transported to the mining unit via the screw conveyor 13. During the forward advancement of the TBM, multiple prefabricated lining segments 16 are installed simultaneously. A segment assembly machine assembles the lining segments 16 around the perimeter to form a lining structure, creating a closed environment. After the advancement of a single mining unit is completed, a rear-end sealed wall 15 is set at the tail end, i.e., the final area of ​​the mining unit, so that the front-end sealed wall 14, the lining segments 16, and the rear-end sealed wall 15 form a sealed single mining unit. The sealed wall and lining segments 16 of the mining unit are composed of concrete and fireproof insulation materials, and are pre-marked... The mining unit is divided into several sections. During the development of horizontal well 3, the raw coal is crushed in advance, which significantly increases the ignition and combustion performance of hard coal bodies. The closed mining unit is isolated from the adjacent coal seam 31, with no external combustible gas supplementation, ensuring that the fire is controlled throughout the coal combustion process. The exhaust gas produced after combustion does not escape, reducing the pollution of the soil, rock, and groundwater environment by exhaust gas. In addition, very little heat escapes outward, and the closed mining unit improves energy utilization. When the coal seam 31 is fluidized, surface subsidence 29 is inevitable, especially in shallow and thick coal seams 31, where fracture zones, fissure zones, and bending subsidence zones are more significant. The closed lining structure of the mining unit can adjust its strength according to the stress environment, providing good support and reducing surface disasters 29. The closed space after the coal seam 31 is burned provides storage space for CO2, and the CO2 in the pressurized space can increase its storage capacity, which can provide a reaction force for the strata subsidence and further prevent surface subsidence 29.

[0045] The outlet 27 is connected in sequence to a gas chromatograph 19 and a gas separation device 18 via a pipeline. The gas separation device 18 is connected back to the mining unit via a pipeline. The outlet 27 discharges combustion gas products. After the gas products are detected and analyzed by the gas chromatograph 19, they are separated into gasification products and CO2 by the gas product separation device. The CO2 is then stored in the combustion air zone of the coal seam 31 after combustion in the previous mining unit. The gas chromatograph 19 is electrically connected to the gas supply control device 17, which is electrically connected to the gas supply station 1. The gas supply station 1 contains a gasifying agent and an inert gas. The pipeline of the gas supply station 1 is connected to the inlet 26 of the working fluid inlet pipe 6 to provide the system with an oxygen-rich oxidant or an inert gas to control the intense combustion of coal as a protective gas. After the gas components are analyzed by the gas chromatograph 19, the gas component information is fed back to the gas supply control device 17, which in turn controls the oxidant flow rate of the gas supply station 1.

[0046] The arrangement of the horizontal well 3, injection well 2, and production well 4 varies depending on the burial depth of the coal seam 31, and specifically includes the following:

[0047] 1) In shallow conditions within 600m: Each horizontal pipe "1" is matched with one injection pipe "1" and one outflow pipe "1", which is called the 111 arrangement pattern, see Figure 2 As shown, due to the low stress of the shallow buried bottom layer, the injection well 2 and production well 4 have a short service length and less heat exchange with coal and rock, which improves the heat utilization rate.

[0048] 2) Under conditions of depth greater than 600m: After multiple horizontal pipe "N" wells are interconnected, they are then connected to an injection pipe "1" and a production well "4" respectively, adopting the 1N1 mode, see Figure 3 As shown, due to depths of up to 800 meters and thousands of meters, laying a large number of vertical production wells 4 and injection wells 2 is difficult and costly. The 1N1 model reduces costs, reduces the outflow of thermal working fluid from the surface 29, and reduces the number of vertical production wells 4 and injection wells 2, thus reducing the phenomenon of long-distance heat exchange between the vertical production wells 4 and injection wells 2 and the rock mass.

[0049] 3) When horizontal wells 3 are arranged symmetrically, the symmetrical horizontal wells 3 use the same injection well 2 or production well 4, adopting a 111 well group pattern, see Figure 4 ;

[0050] 4) To fully utilize the vertical production well 4 and injection well 2, multiple horizontal wells 3 can also be symmetrically set up. When the coal seam 31 has no fault structure and is continuous, it is easy to produce, and the same injection well 2 is used. This is because a small amount of oxidant is needed to keep the coal seam 31 burning continuously, resulting in a large heat production, requiring more production wells 4. When the coal seam 31 has fault fracture zones and loses its continuity, it is not conducive to production, and the same production well 4 is used. This is because a large amount of oxidant is needed to keep the coal seam 31 burning continuously, while the heat production is less, requiring fewer production wells 4. A 1N1 group well model is adopted, see [link to relevant documentation]. Figure 5 As shown.

[0051] In-situ combustion of coal seam 31 is used for heat extraction to ensure complete combustion. This requires the introduction of a large amount of oxygen for a controlled and vigorous oxidation reaction. Therefore, during combustion, the coal seam 31 mining unit includes: I. Coal seam combustion goaf zone, II. Oxygen-rich combustion zone, III. Oxygen-lean oxidation zone, and IV. Raw coal zone. (See...) Figure 6 As shown,

[0052] I. The scavenging zone of the coal seam mainly consists of coal ash, with a small amount of coal coke;

[0053] II. The main reactions occurring in the oxygen-rich combustion zone are: C + O2 = CO2; CO + O2 = O2; CH4 + O2 = CO2 + H2O;

[0054] The main reactions occurring in the oxygen-deficient oxidation zone (III) are: C + O₂ = CO; C + H₂O = H₂ + CO + CO₂; C - CO + CO₂ + H₂ + CH₄ + H₂O

[0055] IV. The raw coal zone represents the original form of coal occurrence;

[0056] The entire process mainly utilizes the oxygen-enriched combustion zone II for combustion and heat extraction. The oxygen-enriched atmosphere generates a large amount of CO2 and heat. After drying the raw coal, the heat undergoes a coal gasification reaction. Therefore, the gas produced at the outlet 27 is mostly CO2 with a small portion of CO, CxHy and other gases. The oxygen supply is regulated by the gas supply control device 17. When the gas chromatograph 19 shows that the O2 volume content is less than 21%, the gas supply control device 17 automatically increases the oxygen supply.

[0057] The working fluid outlet pipe 8 is connected to the external circulation pipe 20. The external circulation pipe 20 generates electricity through the turbine 23 or extracts heat from the heat exchanger 22. The turbine 23 and the heat exchanger 22 are connected in parallel. Two valves are set on the branches of the parallel pipe to control the passage and disconnection of the pipe. After the parallel pipes converge into the external circulation pipe 20, they are connected to the working fluid inlet pipe 6. The flow valve 25 set at the output end of the turbine 23 and the heat exchanger 22 is connected to the working fluid control device. The working fluid inlet 28 is set on the air inlet 26 side of the external circulation pipe 20 for adding working fluid and compensating for the loss of working fluid circulation. The thermometer 24 adjusts the flow valve 25 through the working fluid control device. When the thermometer 24 detects that the working fluid temperature exceeds the set high limit temperature, it indicates that the power generation and heat exchange equipment is not being used sufficiently. At this time, the working fluid control device increases the working fluid inflow. When the working fluid temperature is lower than the set low limit temperature, the power generation and heat exchange equipment is not being used sufficiently. At this time, the working fluid control device reduces the working fluid inflow.

[0058] The working fluid used in different stages of combustion is different. When the coal seam 31 is burning and when the coal seam 31 is burning to the boundary, CO2 or supercritical CO2 is selected as the working fluid. CO2 has good heat carrying capacity. At the same time, the density of CO2 decreases when heated in the working fluid horizontal pipe 7. The pressure difference between the working fluid inlet pipe 6 and the working fluid outlet pipe 8 accelerates the flow of CO2 in the working fluid pipe and quickly carries the heat generated by coal combustion to the external circulation pipe 20. At this time, a turbine generator is selected to generate electricity. When the coal seam 31 is burned and the coal seam 31 is completely burned, when the ambient temperature reaches 100℃, water is used as the working fluid and enters the heat exchanger 22 for heat exchange.

[0059] The above embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the above embodiments. Unless otherwise specified, the methods used in the above embodiments are conventional methods.

Claims

1. A coal in-situ controllable direct combustion energy extraction, gasification, and carbon sequestration system, comprising a gas supply station, an injection well, a horizontal well inlet pipe, a working fluid inlet pipe, a working fluid horizontal pipe, a working fluid outlet pipe, an outlet pipe, and an ignition and heating device; characterized in that, It also includes production wells, perforated outer pipes, tunnel boring machines, mining units, gas supply control equipment, gas separation devices, gas chromatographs, and external circulation pipes. The injection well extends into the middle of the coal seam, and the injection well is connected to the horizontal well. The horizontal well is connected to the production well, and all of them are arranged with casing. The top of the air intake pipe is sealed, and an air inlet is left at the top side end. The air inlet is connected to the gas supply station through a pipe. The working fluid inflow pipe passes through the top of the air intake pipe and is connected to the working fluid horizontal pipe. The air intake pipe is connected to the perforated outer pipe. The surface of the perforated outer pipe is covered with vent holes, and the working fluid horizontal pipe is arranged concentrically inside. The working fluid inflow pipe is connected to the working fluid horizontal pipe. The ignition heating device is a heating ring sleeved on the outside of the perforated outer pipe. The heating ring is nested at the connection between the perforated outer pipe and the air intake pipe. The exhaust pipe is connected to the perforated outer pipe. The top of the exhaust pipe is sealed, and an air outlet is left at the top side end. The working fluid outflow pipe passes through the top of the exhaust pipe and connects to one end of the external circulation pipe. The other end of the external circulation pipe is connected to the working fluid inflow pipe that passes through the top of the air intake pipe. A working fluid inlet is provided on the external circulation pipe. The mining unit is located within the coal seam surrounding the horizontal shaft. The mining unit consists of a closed lining structure consisting of two sealed walls on both sides and upper and lower lining segments. The tunnel boring machine is set outside the sealed wall on one side of the mining unit and includes a cutterhead and a screw conveyor. The cutterhead advances before the sealed wall on one side of the mining unit is built. After the cutterhead strips the raw coal, it is transported to the mining unit by the screw conveyor. The gas outlet is connected in sequence to a gas chromatograph and a gas separation device via pipelines. The gas separation device is connected back to the production unit via pipelines. The gas chromatograph detects the gas content produced at the outlet. The gas chromatograph is electrically connected to the gas supply control equipment, which is electrically connected to the gas supply station. The horizontal wells, injection wells, and production wells can be arranged in the following structures: 1) In shallow conditions within 600m: a horizontal well is connected to an injection well and a production well respectively; 2) Under conditions of depth greater than 600m: multiple horizontal wells are interconnected and then connected to an injection well and a production well respectively; 3) When horizontal wells are arranged symmetrically, the symmetrical horizontal wells shall be the same type of injection well or production well; 4) When multiple horizontal wells are arranged symmetrically, if the coal seam has no fault structure zone and is continuous, the multiple horizontal wells arranged symmetrically use the same injection well and different production wells. If the coal seam has a fault fracture zone and loses continuity, the multiple horizontal wells arranged symmetrically use the same production well and different injection wells.

2. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The injection well penetrates through the overburden to the middle of the coal seam, serving as the starting area of ​​the mining unit. The production well side serves as the terminal area of ​​the mining unit. The sealed walls and lining segments of the mining unit are composed of concrete and fireproof and heat-insulating materials.

3. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, It also includes working fluid control equipment, centrifugal pump, heat exchanger, turbine, thermometer and flow valve. The external circulation pipe is provided with a parallel pipeline of centrifugal pump, thermometer, turbine and heat exchanger and flow valve from the working fluid outlet pipe end to the working fluid inlet pipe end. The flow valve and thermometer are connected to the working fluid control equipment.

4. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The lining segments are installed simultaneously by the segment assembly machine as the tunnel boring machine advances.

5. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The coal seam combustion zones in the mining unit include a coal seam combustion zone, an oxygen-rich combustion zone, an oxygen-poor combustion zone, and a raw coal zone. The gas separation device transmits the separated CO2 through pipelines to the coal seam combustion zone of the previous mining unit.

6. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, When the gas chromatograph shows that the O2 volume content is less than 50% of the total gas content, the gas supply control equipment automatically increases the oxygen supply.

7. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The working fluid inlet selects different working fluids to flow in at different stages. When the coal seam is burning and when the coal seam is burning to the boundary, the working fluid is CO2 or supercritical CO2. When the coal seam is burned and the coal seam is completely burned, and the ambient temperature reaches 100°C, the working fluid is water.

8. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The working fluid inlet pipe and the working fluid outlet pipe are Tesla pipes with opposite directions.

9. The coal in situ controllable direct combustion power generation, gasification and carbon sequestration system of claim 1, wherein, The working fluid horizontal pipe is spiral-shaped.

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