Deep ultra-thick coal seam fluidization filling mining and carbon sealing heat removal integrated method

Abstract

The invention discloses a deep ultra-thick coal seam fluidization filling mining and carbon sealing heat removal integrated method which comprises the following steps: firstly, layering and dividing an ultra-thick coal seam into sections, and arranging a mining main well, a mining horizontal well, a mining branch well, a blanking main well, a blanking horizontal well and a blanking branch well; the method comprises the following steps: performing hydraulic pressure on a coal body in a section, injecting an oxidizing agent to realize oxidative degradation of the coal body, lifting a fluidized product to the ground, laying a heat collection circulating pipeline, preparing spherical solid carbon dioxide and a carbon sequestration filling material on the ground, mixing, heating and stirring the spherical solid carbon dioxide and the carbon sequestration filling material, and conveying the mixture to a goaf for filling and carbon sequestration. And finally, a heat collection circulating pipeline is connected to collect and utilize terrestrial heat. According to the method, the fluidization mining filling and carbon sealing heat removal of the ultra-thick coal seam are completed in the mode that interval mining filling is carried out in the same layer and the layer-by-layer upward mode is carried out. According to the method, integration and cooperation of fluidized mining, solid waste disposal, CO2 storage and geothermal collection of the deep ultra-thick coal seam are achieved.

Description

Technical Field

[0001] This invention belongs to the field of coal mining, specifically relating to an integrated method for fluidized bed filling mining and carbon sealing for heat extraction in deep, thick coal seams, which is particularly suitable for mining deep, thick coal seams with a thickness of more than 50m and abundant geothermal resources. Background Technology

[0003] For deep coal resource mining, my country has established a fluidized bed mining system centered on technologies such as in-situ oxidation degradation, in-situ energy-induced physical fracturing, drilling, and water jet rock breaking. However, these technologies currently cannot solve the challenges of fluidized bed mining of coal seams thicker than 50m. For example, in the technology of in-situ oxidation degradation of coal using oxidant solutions through dual horizontal wells, the mining height (the difference in elevation between the horizontal wells) is usually controlled within 30m. This is because excessive mining height leads to uneven diffusion of the oxidant in the coal seam, forming alternating zones of "local hyperoxidation-weak oxidation," causing localized high-temperature heat accumulation that can trigger spontaneous combustion or even explosions of the coal. Especially under conditions of abundant geothermal resources, high geothermal environments can significantly promote chemical reactions, leading to uncontrolled exothermic oxidation and increased safety risks. In addition, when the mining height is too large, hydraulic fracturing cannot form effective fracture seepage channels in the coal body, thus making in-situ oxidation impossible. Moreover, the greater the mining height, the more prominent the issues of surrounding rock safety and surface subsidence become, increasing the difficulty of fluidized bed mining.

[0004] Therefore, for deep, thick coal seams with abundant geothermal resources, how to carry out reasonable fluidized mining while integrating mine solid waste disposal, CO2 sequestration and geothermal resource extraction has become a major technical challenge for the development of my country's coal industry. Summary of the Invention

[0005] To address the aforementioned technical shortcomings, the purpose of this invention is to provide an integrated method for fluidized bed mining and carbon sequestration in deep, thick coal seams, which enables rational fluidized bed mining while simultaneously integrating mine solid waste disposal, CO2 sequestration, and geothermal resource extraction.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides an integrated method for fluidized bed backfilling mining and carbon sealing for heat extraction in deep, thick coal seams, comprising the following steps: Includes the following steps: S1, Coal seam division: Obtain the occurrence characteristics of the target coal seam, and divide the target coal seam into m layers of equal thickness from bottom to top. Each layer has a thickness of h, and each layer is horizontally divided into n segments of equal width. S2, Well Group Layout: Two main mining shafts and a main material discharge shaft with a certain spacing 'a' are drilled in the middle of the dip boundary of the mining area; after drilling to the top of the coal seam, mining horizontal shafts connected to the main mining shafts and material discharge horizontal shafts connected to the main material discharge shafts are drilled on both sides along the dip boundary; on the strike boundary side, mining branch shafts are drilled from the mining horizontal shafts to the bottom of the coal seam, and material discharge branch shafts are drilled from the material discharge horizontal shafts to a position h away from the bottom of the coal seam. S3, Coal body modification: Hydraulic fracturing is performed on the mining section between the feeding branch well and the mining branch well until the coal body in the section forms a fracture seepage channel, and hydraulic cutting is performed on the top surface of the section to the coal body in the boundary areas on both sides to form a planar through-cut groove. S4, fluidized bed mining: Oxidant solution is injected into coal seam fractures and planar through-cut grooves along the main feeding shaft, horizontal feeding shaft and branch feeding shaft, so that the oxidant solution reacts with the coal body to generate fluidized products, and the fluidized products are output to the surface through the main mining shaft, horizontal mining shaft and branch mining shaft; S5, Preparation of backfill material: Grind the crushed gangue and mix it with additives, then add water to make a carbon-fixed backfill material; prepare CO2 into spherical solid carbon dioxide; the additives include fly ash, quicklime and magnesium slag powder; S6, Slurry Mixing: The carbon-fixed filling material is mixed with spherical solid carbon dioxide under heating and stirring conditions to form a mixed filling slurry; the temperature of the mixed filling slurry is kept not lower than 25℃ during the stirring process; S7, Heat extraction system layout: Heat extraction circulation pipelines are laid in the production branch wells, with the inlet extending to the ground and the outlet located at the connection between the production branch well and the production horizontal well. S8, Filling and Carbon Sealing: When the diameter of the spherical solid carbon dioxide in the mixed filling slurry decreases to below the preset value, the mixed filling slurry is pumped to the goaf area for filling by pumping through the main discharge shaft, the horizontal discharge shaft and the branch discharge shaft. Carbon sealing is achieved by chemical reaction between the filling material and the sublimated carbon dioxide. When the height of the mixed filling slurry reaches the bottom plate height of the horizontal section of the branch discharge shaft, grouting is stopped and the grouting pipeline is recovered. S9, Layered Cooperative Operation: Within a layer, fluidized bed mining and backfilling carbon sealing operations are carried out sequentially in the interval sections; after the operation of all sections in the layer is completed, all heat recovery circulation pipelines in this layer are connected in series to form a closed loop, which is then connected to the ground heat exchange system to collect and utilize geothermal energy. S10, Layered Progression: Using the consolidated filling body and its feed branch wells in the already filled layer as the mining guide and structural foundation for the next layer, repeat steps S2 to S9 to complete the mining, filling, carbon sealing and geothermal extraction of all layers from bottom to top.

[0007] Preferably, the specific method for preparing spherical solid carbon dioxide in step S5 is as follows: CO2 gas is dried, filtered, compressed, liquefied, and flash-solidified to prepare snowflake-shaped dry ice, which is then filled into a mold, compacted under high pressure, and demolded and trimmed to prepare spherical solid carbon dioxide, and then placed in an insulated container at -70°C or below for refrigeration.

[0008] Preferably, in step S4, the oxidant solution is preheated using the waste heat of the ground heat exchange system before injection.

[0009] Preferably, the transverse width of the mining section is 10 to 35 m. When the transverse width exceeds 25 m, hydraulic cutting, hydraulic grooving, and hydraulic punching techniques are used in advance to form a fracture space on the top surface of the section, so as to use an oxidant solution to dissolve the coal body in the entire section in a downward manner.

[0010] Preferably, the carbon-fixing backfill material is prepared by mixing gangue crushed slag, fly ash, quicklime and magnesium slag powder in a mass ratio of 10 to 12:1, and then adding 30% to 50% of water by mass of the total carbon-fixing backfill material.

[0011] Preferably, when preparing the carbon-fixing filling material, sodium citrate with a mass fraction of 0.1% to 0.3% is added as a retarder.

[0012] Preferably, the mixing volume ratio of the spherical solid carbon dioxide to the carbon-fixed filling material is less than 1:5, and the spherical solid carbon dioxide injected into the goaf is completely sublimated before the mixed filling slurry initially sets.

[0013] Preferably, during the preparation of solid carbon dioxide, its density is ensured to be more than 95% similar to that of the solid carbon filling material.

[0014] Preferably, for the topmost layer, after its filling and carbon sealing operation is completed, a separate heat extraction circulation pipeline is laid in its discharge branch well and led to the ground to connect to the heat exchange system.

[0015] Preferably, the mixed filling slurry is pumped using a large-channel piston diaphragm pump with an inlet and outlet diameter of 100 mm or more, and the pumping pipeline has anti-corrosion and high-pressure resistance characteristics, with its outlet located on the bottom plate of the goaf.

[0016] The beneficial effects of this invention are as follows: 1. This method divides the thick coal seam into several mining layers, and each layer into several mining sections. Within each mining section, a feeding branch shaft and a mining branch shaft are arranged. The feeding branch shaft is used to oxidize and degrade the coal body with highly oxidizing agents such as hydrogen peroxide and sodium hypochlorite, forming fluidized products. These fluidized products are transported to the surface through the mining branch shaft for separation and refining, yielding high-value-added non-energy chemical products such as carboxylic acids. This method effectively solves key technical problems caused by excessive mining height, such as uneven oxidant diffusion, high-temperature heat accumulation (risk of spontaneous combustion or explosion), surrounding rock instability, and surface subsidence, making fluidized mining of coal seams over 50m thick possible.

[0017] 2. This invention innovatively transforms CO2 gas into a spherical solid and then incorporates it into a carbon-fixed filling material. On the one hand, this achieves complete sealing of carbon dioxide by the carbon-fixed filling material, increasing the contact area. On the other hand, the sublimation rate of solid carbon dioxide can be adjusted by temperature control, thereby regulating the amount of CO2 gas released and ensuring a uniform and complete reaction between the carbon-fixed filling material and CO2.

[0018] 3. During ground mixing and pipeline transportation, spherical carbon dioxide particles can be uniformly distributed throughout the mixed filling slurry and are in dynamic contact at all times. This allows the released CO2 gas to continuously react chemically with the fresh slurry, effectively improving carbon fixation efficiency. This overcomes the shortcomings of traditional gas injection methods, such as easy dispersion and insufficient reaction, and significantly improves storage efficiency and reliability. At the same time, this method also reduces pipeline layout and realizes carbon fixation reaction in the entire process of slurry mixing, transportation, and solidification. Furthermore, the high-temperature environment in deep underground not only facilitates the sublimation of solid CO2 but also avoids the adverse effects of CO2 sublimation endothermic on the carbon fixation slurry.

[0019] 4. A well cluster layout employing vertical shafts, horizontal shafts, and branch shafts integrates coal mining, solid waste disposal, CO2 storage, and thermal energy extraction, achieving fluidized operation throughout all stages. Furthermore, during layered mining, the space reserved for branch shafts through backfilling allows for the secondary utilization of the material feeding branch shafts. That is, the material feeding system of the lower layer (material feeding main shaft, material feeding horizontal shaft, and material feeding branch shaft) is used as the mining system of the upper layer (mining main shaft, mining horizontal shaft, and mining branch shaft), reducing well-making engineering and construction costs. Moreover, the layered mining and backfilling scheme reduces the risk of surrounding rock collapse caused by large single-stage mining heights and solves the problem of surface subsidence caused by mining extremely thick coal seams. This has significant scientific and engineering implications and broad application prospects.

[0020] 5. After the products from fluidized bed mining are brought to the surface, they can be separated and refined into high-value-added non-energy chemical products such as carboxylic acids. This changes the traditional single-mode of coal mining, which only uses coal as fuel, and realizes the added value of coal resources. The entire process design is interconnected, with strong systematicity in well group layout, mining sequence, and pipeline design, and each step is highly coordinated and efficient. The series design of the heating pipeline and the connection to the surface only at the beginning and end simplify the surface system and reduce the complexity and difficulty of the project. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are the front view, side view, and top view of a single-layer, single-section mining well and material unloading well after construction, as provided in the embodiments of the present invention. Figure 2 These are the front view, side view, and top view of the thermal circulation pipeline after the completion of a layered and segmented fluidized mining operation and installation, as provided in the embodiments of the present invention. Figure 3 These are the front view, side view, and top view of a layered, sectioned goaf after being filled and sealed with carbon, as provided in the embodiments of the present invention. Figure 4 These are the front view, side view, and top view of a three-section, layered goaf after being filled and sealed with carbon, as provided in the embodiments of the present invention. Figure 5 These are front, side and top views of a layer of all sections after fluidized mining, filling, carbon sealing and thermal pipeline installation provided in an embodiment of the present invention; Figure 6 These are the front and side views of the completed construction of the two-layer, one-section material unloading well provided in the embodiment of the present invention; Figure 7 These are front and side views of the completed fluidized mining, backfilling, carbon sealing, and thermal pipeline installation in all sections of the two-layer structure provided in this embodiment of the invention.

[0023] In the diagram: 1. Main shaft for single-layer mining; 2. Main shaft for single-layer material feeding; 3. Horizontal shaft for single-layer mining; 4. Horizontal shaft for single-layer material feeding; 5. Branch shaft for single-layer mining in one section; 6. Branch shaft for single-layer material feeding in one section; 7. Heating circulation pipeline; 8. Carbon sequestration filling material; 9. Goaf; 10. Branch shaft for single-layer mining in three sections; 11. Branch shaft for single-layer material feeding in three sections; 12. Main shaft for double-layer material feeding; 13. Horizontal shaft for double-layer material feeding; 14. Branch shaft for double-layer material feeding in one section. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In a mining area in western my country, a coal seam with a thickness of 75m and a burial depth of approximately 1000m has a dip angle of 0-3°. The coal seam is a long-flame coal, and the area is rich in geothermal resources, with geothermal well water temperatures ranging from 70-90℃. To achieve co-extraction of coal and thermal resources, and simultaneously utilize the underground extraction space for CO2 sequestration, this invention discloses an integrated method for fluidized bed backfilling mining and carbon sequestration for deep, thick coal seams. The specific steps are as follows: S1. By acquiring data on the thickness, hardness, dip angle, burial depth, and lithology and thickness of the coal seam in the mining area, and analyzing the physical and mechanical parameters and chemical composition of the coal and rock strata, the thick coal seam is divided into three layers from bottom to top, each layer being 25m thick. Within each layer, the coal body is horizontally divided into 20 mining sections, each 15m wide. S2. Two vertical main shafts are drilled at the middle of the dip boundary of the mining area, with a distance of 10m between the two main shafts. The one closer to the boundary is called the first-level mining main shaft 1, and the one farther from the boundary is called the first-level material feeding main shaft 2. After the main shafts are drilled to the roof strata of the coal seam, horizontal shafts are drilled along the dip boundary of the mining area to both sides to the strike boundary. The one connected to the mining main shaft is called the first-level mining horizontal shaft 3, and the one connected to the material feeding main shaft is called the first-level material feeding horizontal shaft 4. S3. On one side of the strike boundary, a layered mining branch shaft 5 is drilled from a layered mining horizontal shaft 3 towards the coal seam floor, and a layered material unloading branch shaft 6 is drilled from a layered material unloading horizontal shaft 4 towards a position 25m from the coal seam floor; see also Figure 1 ; S4. Perform precise hydraulic fracturing on the coal seam section between the first-layer, first-section feeding branch well 6 and the first-layer, first-section mining branch well 5 until the coal body in the section forms fracture seepage channels. In order to enable the coal body in the lateral boundary area of ​​the section to be fully oxidized and dissolved, hydraulic cuts are made on the top surface of the section to the coal body in the boundary areas on both sides to form a planar through-cut groove; S5. A sodium hypochlorite oxidant solution with a mass concentration of 1% to 6% is injected into the coal seam fractures and planar grooves through a layered main well 2, a layered horizontal well 4, and a layered section branch well 6. The sodium hypochlorite solution reacts with the coal body to form fluidized products. S6. The fluidized products are transported to the surface through a stratified mining main well 1, a stratified mining horizontal well 3, and a stratified single-section mining branch well 5; S7. A heat extraction circulation pipeline 7 is laid within the branch well 5 of the first-level, first-section mining operation. The inlet of the heat extraction circulation pipeline is laid to the surface, and the outlet is located at the connection between the branch well 5 of the first-level, first-section mining operation and the horizontal well 3 of the first-level mining operation; see also Figure 2 ; S8. Grind the gangue slag produced from drilling in the ground material preparation workshop, and mix it with additives such as fly ash, quicklime and magnesium slag powder in a ratio of 10:1. Then add water of 30% of the total mass of the carbon-fixing backfill material and stir to prepare a carbon-fixing backfill material 8 that can chemically react with CO2 gas. S9. In the ground dry ice preparation workshop, the CO2 gas to be treated is prepared into snowflake-shaped dry ice through steps such as drying and filtering, compression and liquefaction, and flash solidification. Then, spherical solid carbon dioxide with a diameter of 3cm is prepared by filling the mold, high pressure compaction and demolding and trimming, and then placed in an insulated container below -70℃ for refrigeration. S10. The carbon-fixed filling material and spherical solid carbon dioxide are transported to an open mixing and heating device for uniform mixing. During the mixing process, the temperature of the mixed filling slurry is kept not lower than 25°C by heating. S11. When the diameter of the spherical solid carbon dioxide in the carbon-fixing filling material decreases to less than 1 cm, the mixed filling slurry is pumped to the goaf 9 via grouting pipelines laid in the main grouting shaft 2, the horizontal grouting shaft 4, and the branch grouting shaft 6. An automatic venting and pressure relief valve is installed every 100 m along the grouting pipelines. When the height of the carbon-fixing filling material 8 reaches the bottom plate height of the horizontal section of the branch grouting shaft 6, grouting is stopped, and the grouting pipelines are retrieved. See also... Figure 3 , Figure 5 ; S12. While laying pipelines and grouting carbon sealing at the lower feeding well, a three-section mining branch well 10 is drilled starting from a level mining horizontal well 3. After the grouting and carbon sealing of the first section is completed, a three-section feeding branch well 11 is drilled starting from a level feeding horizontal well 4. After the three-section mining branch well 10 and the three-section feeding branch well 11 are formed, steps S4~S11 are used to realize the fluidized coal mining, grouting, and carbon sealing operations of the three-section mining. See also Figure 4 ; S13. Following the above steps, the fluidized coal mining, grouting and carbon sealing work is carried out sequentially in sections one, three, five... and sections two, four, six... of the first layer. Only the inlet of the heat circulation pipeline 7 in section one and the outlet of the heat circulation pipeline 7 in section twenty are located on the ground. The other inlets and outlets are located at the connection between each mining branch well and the mining horizontal well. S14. After the first layer of mining, filling and carbon sealing are completed, the inlet and outlet of the heat circulation pipeline 7 laid in the first to twentieth mining branch wells are connected end to end. After the connection, the mining well is grouted and sealed. The geothermal resources are collected and utilized by adding heat transfer medium into the heat circulation pipeline 7 and connecting it to the ground heat energy exchange system. S15. The material distribution branch wells in the first layer and the bottom plate formed after the slurry in the goaf are used as the mining branch wells of the second layer. The second layer material distribution main well 12, the second layer material distribution horizontal well 13 and the second layer first section material distribution branch well 14 are drilled from the ground. The distance between the second layer material distribution main well 12 and the first layer material distribution main well 2 is 10m, and the distance between the second layer material distribution branch well and the second layer mining branch well is 25m. S16. Following steps S4 to S14, complete the mining, backfilling, carbon sealing, and thermal extraction of the two coal seams; see [link / reference]. Figures 6-7 ; S17. Repeat steps S15 and S16 until the mining, filling, carbon sealing, and heat extraction of all three coal seams are completed. For the uppermost coal seam, after the grouting and carbon sealing are completed and the grout has solidified, lay the heat extraction circulation pipeline in the feed branch well according to the aforementioned method and lead it to the surface to connect to the heat exchange system. Finally, grout the feed well and seal it for geothermal extraction.

[0026] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A deep thick coal seam fluidized filling mining and carbon sealing heat extraction integrated method, characterized in that, The method comprises the following steps: S1, coal seam division: obtaining the occurrence characteristics of the target coal seam, and dividing the target coal seam into m equal-thickness sub-layers from bottom to top according to the occurrence characteristics, wherein each sub-layer is divided into n equal-width sections horizontally; S2, well group arrangement: drilling two mining main wells and unloading main wells with a certain interval a in the middle of the dip boundary of the mining area; after drilling to the coal seam roof, drilling mining horizontal wells connected with the mining main wells and unloading horizontal wells connected with the unloading main wells to the two sides along the dip boundary; on one side of the strike boundary, drilling mining branch wells from the mining horizontal wells to the coal seam floor and drilling unloading branch wells from the unloading horizontal wells to the coal seam at a position h away from the floor; S3, coal body reconstruction: performing hydraulic fracturing on the mining sections between the unloading branch wells and the mining branch wells until the coal body in the sections forms a fissure seepage channel, and performing hydraulic slotting on the coal body in the boundary area on both sides of the section top surface to form a plane through slot; S4, fluidized mining: injecting an oxidizing agent solution into the coal seam fissures and the plane through slot along the unloading main wells, the unloading horizontal wells and the unloading branch wells, so that the oxidizing agent solution reacts with the coal body to generate fluidized products, and the fluidized products are output to the ground through the mining main wells, the mining horizontal wells and the mining branch wells; S5, preparation of filling material: grinding gangue slag and mixing with additives to prepare carbon fixation filling material; preparing CO2 into spherical solid carbon dioxide; the additives include fly ash, quicklime and magnesium slag powder; S6, slurry mixing: mixing the carbon fixation filling material and the spherical solid carbon dioxide under heating and stirring to form mixed filling slurry; the temperature of the mixed filling slurry is ensured to be not lower than 25 DEG C during stirring; S7, arrangement of heat extraction system: arranging a heat extraction circulation pipeline in the mining branch well, with the liquid inlet extending to the ground and the liquid outlet located at the connection between the mining branch well and the mining horizontal well; S8, carbon filling and sealing: when the diameter of the spherical solid carbon dioxide in the mixed filling slurry is reduced to a preset value, the mixed filling slurry is pumped along the unloading main wells, the unloading horizontal wells and the unloading branch wells to the goaf for filling, and carbon sealing is realized by the chemical reaction between the filling material and the sublimated carbon dioxide; when the height of the mixed filling slurry reaches the floor height of the horizontal section of the unloading branch well, the grouting is stopped, and the grouting pipeline is recovered; S9, sub-layer coordinated operation: in one sub-layer, the fluidized mining and carbon filling and sealing operations are sequentially performed on the interval sections; after the operation of all the sections in the sub-layer is completed, all the heat extraction circulation pipelines in the sub-layer are connected in series to form a closed loop, and are connected to a ground heat exchange system to collect and utilize geothermal heat; S10, sub-layer progression: taking the consolidated filling body in the filled sub-layer and the unloading branch well as the mining guide and structural foundation of the previous sub-layer, repeating steps S2 to S9, and completing the mining, filling, carbon sealing and geothermal heat collection of all the sub-layers from bottom to top.

2. The integrated method for fluidized filling mining and carbon sealing and heat extraction of deep thick coal seam according to claim 1, characterized in that: The specific method for preparing spherical solid carbon dioxide in step S5 is as follows: CO2 gas is dried, filtered, compressed, liquefied, and flash-solidified to prepare snowflake-shaped dry ice. Then, spherical solid carbon dioxide is prepared by filling a mold, high-pressure compaction, and demolding and trimming. The spherical solid carbon dioxide is then placed in an insulated container at a temperature below -70°C for refrigeration.

3. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep and thick coal seam according to claim 1, characterized in that: In step S4, the oxidant solution is preheated using the waste heat of the ground heat exchange system before injection.

4. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: The transverse width of the mining section is 10-35m. When the transverse width exceeds 25m, hydraulic cutting, hydraulic grooving and hydraulic punching techniques are used in advance to form a fracture space on the top surface of the section, so as to use oxidant solution to dissolve the coal body of the entire section in a downward manner.

5. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: The carbon-fixing backfill material is made by mixing gangue crushed slag, fly ash, quicklime and magnesium slag powder in a mass ratio of 10 to 12:1, and then adding 30% to 50% water of the total mass of the carbon-fixing backfill material and stirring.

6. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that, In the preparation of carbon-fixing filling materials, sodium citrate with a mass fraction of 0.1% to 0.3% is also added as a retarder.

7. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: The volume ratio of the spherical solid carbon dioxide to the carbon-fixed filling material is less than 1:5, and the spherical solid carbon dioxide injected into the goaf is guaranteed to completely sublimate before the mixed filling slurry initially sets.

8. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: During the preparation of solid carbon dioxide, its density is ensured to be more than 95% similar to that of the solid carbon filling material.

9. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: For the topmost layer, after its filling and carbon sealing operation is completed, a separate heat extraction circulation pipeline is laid in its discharge branch well and led to the ground to connect to the heat exchange system.

10. The integrated method of fluidized filling mining and carbon sealing and heat extraction in deep thick coal seam according to claim 1, characterized in that: The mixed filling slurry is pumped using a large-channel piston diaphragm pump with an inlet and outlet diameter of 100mm or more, and the pumping pipeline has corrosion resistance and high pressure resistance characteristics, with its outlet located on the bottom plate of the goaf.

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