A system and method for auxiliary coal hot co-mining based on heat pipe effect

Abstract

The application discloses a system and method for auxiliary coal and heat co-mining based on heat pipe effect, which comprises an overburden layer, a coal seam and a water-heat type geothermal reservoir from top to bottom, and a water storage pool, a water pumping pump, a buffer tank and a ground heat exchanger are arranged on the overburden layer; a roadway is excavated along a coal mining face in the coal seam, a vertical shaft is arranged in the overburden layer, and a water injection pipeline and a water return pipeline are arranged on two opposite side walls of the vertical shaft and the roadway respectively, the upper end of the water injection pipeline is connected with the ground heat exchanger, the water injection pipeline is connected with a booster through a first power circulation pump after entering the roadway, the underground pipeline output from the booster is continuously laid along the bottom, side and top of the roadway, the tail end of the underground pipeline is connected with the water return pipeline, the upper end of the water return pipeline is connected with the ground heat exchanger, and the underground pipeline, the water injection pipeline and the water return pipeline are provided with heat exchange medium. The application can realize efficient mining of the coal seam and geothermal resources, reduce the environmental temperature of the coal mining shaft roadway and achieve the effect of treating the heat damage in the underground mine.

Description

Technical Field

[0001] This invention relates to the field of coal and coalbed geothermal extraction, and specifically to a system and method for coal-thermal co-extraction based on the heat pipe effect. Background Technology

[0002] In recent years, with the increase in the intensity of coal mining, the mining depth of coal deposits in my country has reached over 1,000 meters, and some typical coal mines, such as Suncun Coal Mine, have reached a mining depth of 1,500 meters. Under the influence of the geothermal gradient, the temperature of underground deposits reaches 60-70℃. The continuous diffusion of this heat to the working face and tunnels leads to a sustained increase in the underground ambient temperature, forming underground heat hazards, which seriously affect the safety and work efficiency of underground workers. On the other hand, the high-temperature heat underground is a valuable renewable geothermal resource. Through effective extraction methods, this geothermal resource can be effectively utilized, while reducing the temperature and humidity of the mining environment, thus achieving the goal of heat hazard control.

[0003] To address the high-temperature challenges encountered during deep coal mining, some scholars and industry researchers have proposed various solutions. For instance, Wan Zhijun et al., in their paper "A Coal-Heat Co-extraction Method Based on High-Geothermal Mines" (CN109057796B), proposed constructing heat exchange stations on the surface and drilling extraction and reinjection wells into the geothermal reservoirs to achieve efficient underground geothermal resource extraction without water extraction. Bai Yanbin et al. proposed a centralized integrated heating and cooling system for coal-heat co-extraction on the surface (CN107461850A). By installing air conditioning terminals and heat extractors at the bottom of the well, and installing integrated cooling / heating units on the ground to form two loops, heat recovery at the bottom of the well is achieved, providing domestic hot water for the mining area while alleviating underground heat hazards; Zeng Yifan et al. proposed a coal-water-heat synergistic mining and water and heat hazard control system (CN114837739A), which realizes the extraction and conversion of geothermal resources by connecting the mine water reinjection unit and the roof aquifer drainage and pressure reduction unit to the heat exchange unit respectively, and finally uses the mine heat energy utilization unit to send the heat energy out of the mine.

[0004] In summary, the coal-thermal co-extraction process is complex and involves multiple energy conversion stages, which is the main reason for the low actual extraction efficiency and high extraction cost of geothermal resources. Summary of the Invention

[0005] To address the problem of high-temperature geothermal influence during deep coal seam mining, the present invention aims to provide a system and method for coal-thermal co-extraction based on the heat pipe effect, which achieves efficient coal seam geothermal extraction while reducing the ambient temperature of coal mine roadways, thereby mitigating underground heat hazards.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A system for coal-heat co-extraction based on the heat pipe effect includes, from top to bottom, overlying strata, coal seam, and hydrothermal geothermal reservoir, wherein:

[0008] A water storage tank is excavated on the overlying stratum. A water pump, a buffer tank, and a ground heat exchanger are installed on the overlying stratum. The suction pipe of the water pump is located below the liquid level of the water storage tank. The discharge pipe of the water pump is connected to the buffer tank. An air vent valve is installed at the upper end of the buffer tank. The outlet of the buffer tank is connected to the cold source inlet of the ground heat exchanger. The hot water outlet of the ground heat exchanger is connected to the heating site through a pipeline. The cold water outlet of the heating site is connected to the water storage tank through a pipeline. A second power circulation pump is installed in this pipeline.

[0009] The coal seam has roadways excavated along the coal mining face. A vertical shaft is set in the overlying strata to connect the roadways and the space above the overlying strata. Water injection pipelines and return water pipelines are arranged on two opposite side walls of the shaft and the roadways, respectively. The upper end of the water injection pipeline is connected to a surface heat exchanger. After entering the roadway, the water injection pipeline is connected to a booster pump via a first power circulation pump. The underground pipeline output from the booster pump is continuously laid along the bottom, sides, and top of the roadway. The tail end of the underground pipeline is connected to a return water pipeline. The upper end of the return water pipeline is connected to the surface heat exchanger. There is a heat exchange medium in the underground pipeline, the water injection pipeline, and the return water pipeline. The bottom surface of the roadway is provided with a hardened road surface, and rail transit is set on the hardened road surface.

[0010] The suction pipe end of the water pump is located inside the water storage tank at a distance of / to / depth from the bottom of the water storage tank.

[0011] The tunnel contains an underground chamber, and the booster pump is located within the chamber.

[0012] There are multiple booster compressors, each located in a separate underground chamber. There are several groups of underground pipelines, and the multiple booster compressors are distributed among these groups of underground pipelines.

[0013] The underground pipelines within the tunnel are arranged in a continuous S-shape.

[0014] The downhole pipeline is made of metal, and the joints of the downhole pipeline at each S-shaped bend use metal braided flexible hoses.

[0015] The downhole pipelines are arranged in the following manner:

[0016] First, before the roadway floor is hardened, a buffer layer without heat insulation is laid. On the buffer layer, the underground pipeline is laid horizontally from one side in an S-shape. After the underground pipeline has laid flat on the ground at the bottom of the underground pipeline, it continues to be laid upward in an S-shape along the side wall of the horizontal roadway.

[0017] The laying sequence of the underground pipeline is as follows: starting from the side where the water injection pipeline reaches the bottom of the shaft, it is laid in an S-shape along the bottom of the tunnel to the other side. After the bottom of the tunnel is laid, it continues to be laid towards the wall of the tunnel, also in an S-shape, until it crosses the top of the tunnel and reaches the bottom of the other side of the tunnel, leaving space for the return water pipeline.

[0018] The downhole pipeline is equipped with a heat insulation layer.

[0019] The heat exchange medium is a medium that easily undergoes sublimation when absorbing heat at room temperature.

[0020] A method for coal-thermal co-extraction includes the following steps:

[0021] Step 1: The first power circulation pump provides operating power for the injected heat exchange medium. The heat exchange medium flows along the water injection pipeline through the booster pump and then flows along the tortuous downhole pipeline after being pressurized.

[0022] Step 2: During the flow of the heat exchange medium, heat exchange occurs with the ground and walls of the roadway, absorbing heat from the geothermal energy of the coal seam. After the temperature of the heat exchange medium rises, it undergoes sublimation and its volume expands rapidly. Driven by the booster and the first power circulation pump, the heat exchange medium flows to the ground heat exchanger.

[0023] Step 3: Water is used as the heat absorption medium and flows in along the cold source inlet of the ground heat exchanger, while the high-temperature heat-carrying medium flowing out from the well is used as the heat source and flows in along the heat source inlet of the ground heat exchanger. The cold source inlet and the heat source inlet are respectively set on both sides of the ground heat exchanger and are distributed diagonally.

[0024] Step 4: In the ground heat exchanger, the heat transfer medium and the heat absorption medium undergo heat convection and heat conduction. After the heat exchange is completed, the temperature of the heat transfer medium decreases due to the condensation effect of the heat absorption medium, and it gradually changes from a gaseous state to a liquid state. It is then injected into the well again through the water injection pipeline to complete the next round of heat absorption process.

[0025] Step 5: After absorbing heat, the temperature of the heat-absorbing medium rises. After being output through the ground heat exchanger, it is directly supplied to the heating site. The cold water output from the heating site is then reinjected into the water storage tank.

[0026] Step 6, repeat steps 1 to 5.

[0027] Beneficial effects: The system and method for coal-thermal co-mining based on heat pipe effect provided by this invention can mine underground geothermal resources while mining coal underground, which helps to reduce the impact of underground heat hazards and promote the joint mining of coal and geothermal resources. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the system structure of the present invention based on heat pipe effect-assisted coal heat recovery;

[0029] Figure 2 This is a cross-sectional view showing the layout of underground pipelines and return water pipelines inside the tunnel. Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] like Figure 1 The diagram shows a system for coal-heat co-extraction based on the heat pipe effect, comprising, from top to bottom, an overlying stratum 1, a coal seam 2, and a hydrothermal geothermal reservoir 3, wherein:

[0032] A water storage tank 14 is excavated on the overlying stratum 1. A water pump 13, a buffer tank 12, and a ground heat exchanger 11 are installed on the overlying stratum 1. The suction pipe of the water pump 13 is located below the liquid level of the water storage tank 14. The discharge pipe of the water pump 13 is connected to the buffer tank 12. An air vent valve is installed at the upper end of the buffer tank 12. The outlet of the buffer tank 12 is connected to the cold source inlet of the ground heat exchanger 11. The hot water outlet of the ground heat exchanger 11 is connected to the heating area 15 through a pipeline. The cold water outlet of the heating area 15 is connected to the water storage tank 14 through a pipeline. A second power circulation pump 21 is installed in the pipeline.

[0033] A roadway 20 is excavated along the coal mining face 4 from the coal seam 2. A vertical shaft 19 is set in the overlying stratum 1 to connect the roadway 20 and the space above the overlying stratum 1. Water injection pipeline 7 and return water pipeline 10 are respectively arranged on the two opposite side walls of the vertical shaft 19 and the roadway 20. The upper end of the water injection pipeline 7 is connected to the surface heat exchanger 11. After entering the roadway 20, the water injection pipeline 7 is connected to the booster pump 22 through the first power circulation pump 8. The underground pipeline 23 output from the booster pump 22 is continuously laid along the bottom, side and top of the roadway 20. The tail end of the underground pipeline 23 is connected to the return water pipeline 10. The upper end of the return water pipeline 10 is connected to the surface heat exchanger 11. There is a heat exchange medium in the underground pipeline 23, the water injection pipeline 7 and the return water pipeline 10. The bottom surface of the roadway 20 is provided with a hardened road surface 5, and a rail transit 17 is provided on the hardened road surface 5.

[0034] The specific embodiments of the present invention are as follows:

[0035] (1) At the collapse site or goaf above the coal seam 2, a water storage tank 14 shall be excavated in accordance with the actual site conditions. The size of the water storage tank 14 shall be determined in accordance with the actual water use range.

[0036] (2) After the water storage tank 14 is constructed, the suction pipe of the water pump 13 is lowered. The end of the suction pipe of the water pump 13 is located in the water storage tank 14 at a distance of 1 / 3 to 1 / 2 of the water storage tank depth from the bottom of the water storage tank 14, so as to prevent the mud and sand settled at the bottom of the water storage tank 14 from being pumped out during the operation of the water pump 13.

[0037] (3) The drain end of the water pump 13 is connected to the buffer tank 12. The buffer tank 12 plays a role in stabilizing the water flow. In addition, the upper end of the buffer tank 12 is equipped with an exhaust valve to discharge the air entrained by the drain pump 13 during the water pumping process in a timely manner, so as to avoid the formation of unstable flow fields such as local turbulence in the ground heat exchanger 11, which would affect the heat exchange stability and heat exchange efficiency.

[0038] (4) The outlet of the buffer tank 12 is connected to the cold source inlet of the ground heat exchanger 11. The high-temperature hot water flowing out of the ground heat exchanger 11 is transported to the heating site 15 through the pipeline, while the cold water of the heating site 15 is transported to the ground water storage tank 14 through the pipeline. A second power circulation pump 21 is connected in the pipeline between the heating site 15 and the water storage tank 14 to prevent the cold water from flowing back smoothly due to the large resistance along the pipeline process.

[0039] (5) The high-temperature heat transfer medium for extracting geothermal energy from the coal seam flows out from the cold water outlet of the ground heat exchanger 11 after the heat transfer is carried out by the convection of the ground heat exchanger 11 and flows into the water injection pipeline 7 leading to the well.

[0040] (6) The arrangement of the underground equipment is as follows: the water injection pipeline 7 and the return water pipeline 10 are respectively arranged on the two side walls of the vertical shaft 19 and the roadway 20.

[0041] (7) After the water injection pipeline 7 enters the roadway 20, it is connected to the booster pump 22 via the first power circulation pump 8. The underground pipeline 23 output from the booster pump 22 is continuously laid along the bottom, side and top of the roadway 20. The underground booster pump is installed in the underground chamber 9. The chamber 9 is excavated inward along the wall 18 of the horizontal roadway, without occupying the space of large underground machinery and transportation equipment. There are multiple booster pumps 22, each located in an underground chamber 9. There are several groups of underground pipelines 23, with multiple booster pumps 22 distributed among several groups of underground pipelines 23.

[0042] (8) The underground pipeline 23 is arranged in the following manner:

[0043] Before the ground of tunnel 20 is hardened, a buffer layer without heat insulation effect, such as a gravel layer or gangue layer, is laid to prevent underground rock pressure from squeezing and damaging the pipeline.

[0044] The downhole pipeline 23 is arranged laterally from one side in an S-shape above the buffer layer. The material of the downhole pipeline 23 should be a metal material with a small specific heat capacity, good heat absorption and heat conduction, and it should also have certain ductility and corrosion resistance. The wall surface downhole impact pressure and humid environment can cause damage to the pipeline. Materials such as copper pipe and aluminum pipe can be used.

[0045] After the underground pipeline 23 is laid flat on the ground at the bottom, it continues to be laid upward in an S-shape along the side wall 18 of the horizontal tunnel. At each S-shaped bend, a metal braided flexible hose is required, and an extra 20-30cm of length is allowed to flow out at each S-shaped bend to prevent the impact of underground rock pressure.

[0046] The laying sequence of the underground pipeline 23 is as follows: it starts from the side where the water injection pipeline 7 reaches the bottom of the shaft 19, and is laid in an S-shape along the bottom of the tunnel 20 to the other side. After the bottom of the tunnel 20 is laid, it continues to be laid to the wall 18 of the tunnel 20, also in an S-shape, until it crosses the top of the tunnel 20 and reaches the bottom of the other side of the tunnel, leaving space for the return water pipeline 10.

[0047] (9) After the pipeline is laid, a layer of wire mesh is first laid on the surface of the ground and the upper pipeline to reinforce the pipeline. Then, foamed cement is sprayed evenly on all the pipelines with a thickness of 3-5 cm. The main function of foamed cement is to form a heat insulation layer 6, which isolates the high-temperature heat source of the wall surface and the stratum, and at the same time prevents the water injection pipeline 7 from exchanging heat with the underground environment, thus affecting the efficiency of geothermal extraction.

[0048] (10) After the insulation layer 6 is sprayed, sleepers are laid on the hardened road surface 5 again, and rail transit 17 is erected. The distance between the two sleepers should be consistent to prevent stress concentration during transportation, which could cause the water injection pipeline 7 to be damaged.

[0049] (11) The fluid injected into the water injection pipeline 7 is selected to be a medium that is easy to sublimate at room temperature due to heat absorption, such as R134a (tetrafluoroethane) and R600a (isobutane).

[0050] (12) The first power circulation pump 8 provides operating power for the injected heat exchange medium. The heat exchange medium flows along the water injection pipeline 7 through the booster 22 and then flows along the tortuous downhole pipeline 23 after being pressurized.

[0051] (12) During the flow of the heat exchange medium, heat exchange occurs with the ground and walls of the roadway 20, absorbing the heat from the coal seam geothermal energy. After the temperature of the heat exchange medium rises, it undergoes sublimation and its volume rapidly expands. Driven by the booster 22 and the first power circulation pump 8, the heat exchange medium flows to the ground heat exchanger 11.

[0052] (13) Water is used as the heat absorption medium and flows in along the cold source inlet of the ground heat exchanger 11, while the high-temperature heat-carrying heat exchange medium flowing out from the well is used as the heat source and flows in along the heat source inlet of the ground heat exchanger 11. The cold source inlet and the heat source inlet are respectively located on both sides of the ground heat exchanger 11 and are distributed diagonally.

[0053] (14) In the ground heat exchanger 11, the heat transfer medium and the heat absorption medium undergo heat convection and heat conduction. After the heat exchange is completed, the heat transfer medium is affected by the condensation effect of the heat absorption medium. The temperature of the heat transfer medium decreases and gradually changes from gaseous to liquid state. It is then injected into the well through the water injection pipeline 7 to complete the next round of heat absorption process.

[0054] (15) After absorbing heat, the temperature of the heat-absorbing medium rises. After being output through the ground heat exchanger 11, it is directly supplied to the living or ecological breeding, power generation and other heat-using places 15 in the mining area. The cold water output from the heat-using place 15 is then injected back into the water storage tank 14.

[0055] (16) This cycle repeats itself, effectively managing the heat hazards of underground coal mining while extracting geothermal energy, and without consuming underground water resources, achieving the environmentally friendly feature of extracting heat without extracting water.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A system for coal-heat co-extraction based on heat pipe effect, characterized in that: Including, from top to bottom, the overlying strata (1), coal seam (2), and hydrothermal geothermal reservoir (3), of which: A water storage tank (14) is excavated on the overlying stratum (1). A water pump (13), a buffer tank (12), and a ground heat exchanger (11) are installed on the overlying stratum (1). The suction pipe of the water pump (13) is located below the liquid level of the water storage tank (14). The drain pipe of the water pump (13) is connected to the buffer tank (12). An exhaust valve is installed at the upper end of the buffer tank (12). The outlet of the buffer tank (12) is connected to the cold source inlet of the ground heat exchanger (11). The hot water outlet of the ground heat exchanger (11) is connected to the heating site (15) through a pipeline. The cold water outlet of the heating site (15) is connected to the water storage tank (14) through a pipeline. A second power circulation pump (21) is installed in the pipeline. The end of the suction pipe of the water pump (13) is located in the water storage tank (14) at a depth of 1 / 3 to 1 / 2 of the bottom of the water storage tank (14). The coal seam (2) has a roadway (20) excavated along the coal mining face (4). A vertical shaft (19) is set in the overlying stratum (1) to connect the roadway (20) and the space above the overlying stratum (1). Water injection pipeline (7) and return water pipeline (10) are respectively arranged on the two opposite side walls of the vertical shaft (19) and the roadway (20). The upper end of the water injection pipeline (7) is connected to the ground heat exchanger (11). After the water injection pipeline (7) enters the roadway (20), it is connected to the booster pump (22) through the first power circulation pump (8). The underground pipeline (23) output from the booster pump (22) is continuously laid along the bottom, side and top of the roadway (20). 3) The tail end is connected to the return water pipeline (10), the upper end of the return water pipeline (10) is connected to the ground heat exchanger (11), and there is heat exchange medium in the underground pipeline (23), the water injection pipeline (7) and the return water pipeline (10); the bottom surface of the roadway (20) is provided with a hardened road surface (5), and a rail transit (17) is provided on the hardened road surface (5); an underground chamber (9) is provided in the roadway (20), and a booster (22) is provided in the chamber (9); the underground pipeline (23) in the roadway (20) is arranged in a continuous S-shape; the underground pipeline (23) is made of metal, and the joint of the underground pipeline (23) at each S-shaped bend is made of metal braided hose; The downhole pipeline (23) is arranged in the following manner: First, before the ground of the tunnel (20) is hardened, a buffer layer without heat insulation effect is laid. On the buffer layer, the underground pipeline (23) is laid horizontally from one side in an S-shape. After the underground pipeline (23) has laid flat on the ground at the bottom of the underground pipeline (23), it continues to be laid upward in an S-shape along the side wall (18) of the horizontal tunnel. The laying sequence of the underground pipeline (23) is to start from the side where the water injection pipeline (7) reaches the bottom of the shaft (19), and lay it in an S-shape along the bottom of the tunnel (20) to the other side. After the bottom of the tunnel (20) is laid, it continues to be laid to the side wall (18) of the tunnel (20) in the same S-shape until it crosses the top of the tunnel (20) and reaches the bottom of the other side of the tunnel, leaving space for the return water pipeline (10). The downhole pipeline (23) is provided with a heat insulation layer (6).

2. The system for coal-heat co-extraction based on heat pipe effect according to claim 1, characterized in that: There are multiple booster compressors (22), each booster compressor (22) is located in a downhole chamber (9), and there are several groups of downhole pipelines (23), with multiple booster compressors (22) distributed among several groups of downhole pipelines (23).

3. The system for coal-heat co-extraction based on heat pipe effect according to claim 1, characterized in that: The heat exchange medium is a medium that easily undergoes sublimation when absorbing heat at room temperature.

4. A method for coal-heat co-extraction based on the system described in claim 1, characterized in that: Includes the following steps: Step 1: The first power circulation pump (8) provides operating power for the injected heat exchange medium. The heat exchange medium flows along the water injection pipeline (7) through the booster (22) and then flows along the tortuous downhole pipeline (23) after being pressurized. Step 2: During the flow of the heat exchange medium, heat exchange occurs with the ground and walls of the roadway (20), absorbing the heat from the coal seam geothermal energy. After the temperature of the heat exchange medium rises, sublimation occurs, and the volume expands rapidly. Driven by the booster (22) and the first power circulation pump (8), the heat exchange medium flows to the ground heat exchanger (11). Step 3: Water is used as the heat absorption medium and flows into the cold source inlet of the ground heat exchanger (11), while the high-temperature heat-carrying heat exchange medium flowing out from the well is used as the heat source and flows into the heat source inlet of the ground heat exchanger (11). The cold source inlet and the heat source inlet are respectively set on both sides of the ground heat exchanger (11) and are distributed diagonally. Step 4: In the ground heat exchanger (11), the heat transfer medium and the heat absorption medium undergo heat convection and heat conduction. After the heat exchange is completed, the heat transfer medium is affected by the condensation effect of the heat absorption medium. The temperature of the heat transfer medium decreases and gradually changes from gaseous to liquid state. It is then injected into the well again through the water injection pipeline (7) to complete the next round of heat absorption process. Step 5: After the heat-absorbing medium absorbs heat, its temperature rises and it is directly supplied to the heating site (15) after being output through the ground heat exchanger (11). The cold water output from the heating site (15) is then injected back into the water storage tank (14). Step 6, repeat steps 1 to 5.

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