A kind of underground physical fluidized coal mining system and coal mining method

Abstract

The present invention discloses an underground physical fluidized coal mining system and a coal mining method. The coal mining system includes a fluidized drilling gas-coal mining part and a coal mining cave filling part; the coal mining method includes drilling construction, fluidized gas-coal mining and coal mining cave filling. The present invention adopts an upward hole method to carry out coal mining operations, forms a high-pressure water jet through an injection device and a stretching device, and cooperates with the rotation of a high-pressure sealed drill rod to achieve in-situ crushing and cutting of the coal body, uses an orifice sealing unit and a water-coal separation unit to separate and recover coal and gas from the crushed coal particle-water-gas mixture, and finally fills the coal mining cave to achieve safe, efficient and green mining of coal resources. The present invention can complete the safe and efficient mining operations of difficult-to-mine (legacy) coal resources such as corner coal, chicken nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars, and is particularly suitable for mining inclined soft coal seams.

Description

Technical Field

[0001] The present invention relates to an underground coal mining system and a coal mining method, specifically to an underground physical fluidized coal mining system and a safe and efficient fluidized coal mining method suitable for various types of mines, especially suitable for the mining of difficult-to-mine (legacy) coal resources such as corner coal, chicken nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars, and belongs to the technical field of coal mining. Background Art

[0002] Difficult-to-mine (legacy) coal resources include marginal coal, chicken-nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars.

[0003] At present, the mining methods of the above-mentioned difficult-to-mine (legacy) coal resources are still mainly based on the mining technology of arranging the recovery working face, and they all face unavoidable difficulties. The corner coal itself is a legacy of underground mining. Due to the large changes in its shape and coal thickness, it is impossible to arrange comprehensive mining equipment. There is currently no safe and efficient mining technology, and it is generally abandoned. For thin coal seams and steeply inclined coal seams, due to their own occurrence characteristics, the coal mining space is limited, and it is difficult to arrange conventional comprehensive mining equipment. During the mining process, the safety factor is low, the degree of mechanization is low, the labor intensity is high, and the work efficiency is low, which makes the cost of mining thin coal seams and steeply inclined coal seams too high, and most coal mining companies choose to give up mining them. In summary, for difficult-to-mine (legacy) coal resources such as corner coal, chicken coop coal and geologically complex coal seams, the mining method of arranging recovery working faces faces a series of problems such as high cost, low efficiency, great risk, poor flexibility, and inability to give full play to the technical advantages of mechanized mining. As a result, underground mining technology cannot safely and efficiently mine difficult-to-mine (legacy) coal resources. A new mining model is urgently needed to achieve safe and efficient mining operations of difficult-to-mine (legacy) coal resources. Summary of the invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides an underground physical fluidized coal mining system and a coal mining method, which can realize the safe and efficient mining of difficult-to-mine (legacy) coal resources such as corner coal, chicken nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars, and is particularly suitable for mining inclined soft coal seams with coal seam inclination.

[0005] To achieve the above purpose, the underground physical fluidized coal mining system includes a fluidized drilling gas-coal mining part, which includes a jet coal breaking unit, a hole sealing unit, and a water-coal separation unit;

[0006] The jet coal breaking unit includes a coal breaking drill bit, an injection device, an extension device, a high-pressure sealed drill pipe, a high-pressure water tail, a drilling rig, and a high-pressure water pump; the high-pressure sealed drill pipe is a cylindrical structure with multiple sections of the same outer diameter and sealed and connected, and a hollow water passage is provided inside the high-pressure sealed drill pipe; the front end of the high-pressure sealed drill pipe is sealed and connected to the extension device, and the rear end of the high-pressure sealed drill pipe is sealed and connected to the high-pressure water tail; the front end of the extension device is sealed and installed with a jet device, and the front end of the jet device is threadedly connected to the coal breaking drill bit; the high-pressure water output end of the high-pressure water pump is sealed and connected to the high-pressure water tail through a pipeline; the drilling rig is connected to the high-pressure sealed drill pipe in a transmission manner;

[0007] The orifice sealing unit comprises a front sealing sleeve, a sealing unit body and a rear sealing sleeve which are coaxially butt-jointed and sealed in sequence. The high-pressure sealing drill pipe passes through the orifice sealing unit along the front and rear axial directions of the orifice sealing unit, and a coal-water flow passage is formed between the outer surface of the high-pressure sealing drill pipe and the inner surface of the front sealing sleeve. A supporting sealing ring which is sealed and matched with the outer diameter of the high-pressure sealing drill pipe and is used to seal and support the high-pressure sealing drill pipe is coaxially fixed in the rear sealing sleeve. The sealing unit body is a container structure with a large inner cavity. The top end of the sealing unit body is provided with a gas discharge port which is connected with the inner cavity, and the gas discharge port is sealed and connected with the mine gas extraction pipe through a pipeline. The bottom end of the sealing unit body is provided with a water-coal discharge port which is connected with the inner cavity, and the water-coal discharge port is connected with the input end of a coal-water collecting box through a pipeline. The output end of the coal-water collecting box (6) is connected with the input end of a slurry conveying pump through a pipeline.

[0008] The water-coal separation unit includes a vibrating screen, a scraper conveyor, a sedimentation tank and a filter press; the outlet of the slurry conveying pump output end connecting the pipeline is arranged above the material input end of the vibrating screen, the material output end of the vibrating screen is arranged above the material input end of the scraper conveyor, the sedimentation tank includes a primary sedimentation tank and a secondary filtration tank, the vibration dehydration drain outlet of the vibrating screen is connected to the primary sedimentation tank through a pipeline, the sludge pump at the material input end of the filter press is arranged in the primary sedimentation tank, the filter pressure drain outlet of the filter press is connected to the secondary filtration tank through a pipeline, and the input end of the high-pressure water pump is connected to the secondary filtration tank through a pipeline.

[0009] As a further improvement scheme of the present invention, the underground physical fluidized coal mining system also includes a coal mining cave filling part, the coal mining cave filling part includes a slurry making device and a pump pressure filling device, the slurry making device includes a crusher, a screen, a mixer and a feeder, and the pump pressure filling device includes a filling pump and a filling pipeline.

[0010] As a further improvement of the present invention, the spraying device is provided with 1 to 8 jet nozzles, and the spraying direction of the jet nozzles is at an angle of 45° to 90° to the axial direction of the spraying device.

[0011] As a further improvement of the present invention, the stretching device is provided with a plurality of expansion swing arms symmetrically arranged relative to the center of the base body, the expansion swing arms have a length of 0.5 to 2.5 m, and can be extended radially along the drill pipe through a central rotating shaft, and drainage channels are arranged inside the expansion swing arms and the base body, which cooperate with the jet nozzle of the stretching device arranged in front of the expansion swing arms to generate high-pressure water jets.

[0012] As a further improvement of the present invention, the supporting sealing rings are arranged in at least two groups along the axial direction of the rear sealing sleeve.

[0013] A coal mining method based on an underground physical fluidized coal mining system, specifically comprising the following steps:

[0014] Step 1: Drilling construction: Install the coal-breaking drill bit at the front end of the high-pressure sealed drill pipe, install the high-pressure water tail at the rear end of the high-pressure sealed drill pipe, use the drilling rig to drive the high-pressure sealed drill pipe to drill 2 to 4 meters upward along the coal seam and then stop drilling; withdraw the high-pressure sealed drill pipe and the coal-breaking drill bit, replace the coal-breaking drill bit with the reaming drill bit to reame the hole at the mouth of the borehole, and the inner diameter of the reamed hole is larger than the outer diameter of the front sealing casing; insert the front sealing casing at the reaming position, and inject grout in the annulus between the borehole and the front sealing casing to fix the front sealing Casing, then coaxially and tightly install the sealing unit body and the rear sealing casing on the front sealing casing, and install the gas outlet to be tightly connected with the mine gas extraction pipe through a pipeline, and connect the water-coal outlet to the input end of the coal-water collection box through a pipeline; replace the hole-expanding drill bit with a coal-breaking drill bit, and pass the high-pressure sealed drill rod and the coal-breaking drill bit through the hole sealing unit, use the drilling rig to drive the high-pressure sealed drill rod forward to continue drilling to the set distance, then stop drilling, withdraw the high-pressure sealed drill rod and the coal-breaking drill bit, and complete the coal mining drilling construction;

[0015] Step 2: Fluidized gas-coal mining: install the extension device, injection device and coal-breaking drill bit at the front end of the high-pressure sealed drill pipe in sequence, pass the high-pressure sealed drill pipe, extension device, injection device and coal-breaking drill bit through the hole sealing unit, and extend them to the bottom of the coal mining borehole; start the high-pressure water pump, and control the high-pressure sealed drill pipe to rotate at an appropriate speed through the drilling rig to hydraulically break the coal. The broken coal body flows back to the inner cavity of the sealing unit body through the annulus between the borehole and the high-pressure sealed drill pipe with the water, and flows into the coal-water collection box through the water-coal discharge port, and is finally sent to the water-coal separation by the slurry conveying pump The gas released by the broken coal body flows into the inner cavity of the sealing unit body through the annulus between the borehole and the high-pressure sealing drill rod, and enters the gas extraction pipe of the mine through the gas outlet; the step-backward coal mining method is adopted to control the high-pressure sealing drill rod to move forward and backward within the set range until the coal output of the borehole is greatly reduced, and then the high-pressure sealing drill rod is controlled to retreat to the rear by the set step distance, and so on, and the "retreat-coal-break-retreat-coal-break" cycle is carried out until the extension device, the injection device and the coal-breaking drill bit are close to the hole sealing unit, and the mining of the coal body around the borehole is completed;

[0016] Step 3, borehole filling: A borehole coal mining cavern is formed during the retreat of the high-pressure sealed drill rod. After all the coal around the borehole is mined, the borehole coal mining cavern is grouting-filled to form a borehole filling area after grouting of the entire borehole coal mining cavern. After the borehole filling area is formed by grouting, other coal mining boreholes are arranged at set intervals to continue physical fluidization coal mining. After the filling slurry in the borehole filling area solidifies, coal mining boreholes are arranged in the vicinity of the borehole filling area for physical fluidization coal mining.

[0017] As a further improvement scheme of the present invention, the coal mining process within each set backward step is as follows: first, the high-pressure water pump is set to operate within the pressure range of 8 to 15 MPa, so that all the high-pressure water flows out through the jet nozzle of the injection device, and the coal body within this step is cut and crushed; when the coal output under this working state is greatly reduced, the working pressure of the high-pressure water pump is increased to greater than 15 MPa, so that all the high-pressure water flows out through the jet nozzle of the extension device, and the coal body within this step is continued to be cut and crushed, until the coal output from the borehole is greatly reduced again, and the fluidized gas coal mining operation within this step is completed.

[0018] As a further improvement of the present invention, according to the coal seam conditions and tunnel conditions, the fluidized drilling gas coal mining part is set in the lower chute coal tunnel of the coal seam to be mined, or in the bottom rock tunnel of the coal seam to be mined.

[0019] Compared with the prior art, when the underground physical fluidized coal mining system and method are used for coal mining operations, there is no need to arrange the mining face and large-scale mechanical equipment. The operation is simple, safe and reliable, and can achieve safe and efficient mining of difficult-to-mine (legacy) coal resources such as corner coal, chicken nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars. Secondly, the jet crushing of the coal body can make the gas fully desorbed and gushed out. The gas extraction volume and extraction concentration extracted through the gas extraction pipe are high, which can be directly used for gas generators, and can achieve efficient development and utilization of gas resources. Moreover, gas and dust will not be directly discharged into the tunnel or chamber, and the operators are far away from the coal breaking area, which can achieve a better working environment and work safety. In addition, after the mining is completed, the coal mining cave can be filled through the filling pipeline, which can reliably control the deformation of the overburden and the surface subsidence, protect the surface ecological environment, and realize the green mining of the coal seam. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the present invention for mining conventional coal seams, corner coals, and thin coal seams, wherein the arrow indicates a schematic diagram of the arrangement of the fluidized drilling gas-coal mining portion from the back-to-front perspective;

[0021] Figure 2It is a schematic diagram of the arrangement of the filling equipment arrangement area, the goaf area, and the coal mining equipment arrangement area in the mining of conventional coal seams, corner coals, and thin coal seams according to the present invention;

[0022] Figure 3 It is a schematic diagram of the arrangement of the gas-coal simultaneous mining part of the fluidized drilling hole according to the present invention from the rear to the front;

[0023] Figure 4 It is a schematic diagram of the installation structure of the high-pressure sealing drill pipe and the orifice sealing unit of the present invention;

[0024] Figure 5 It is a structural schematic diagram of the water-coal separation unit of the present invention;

[0025] Figure 6 It is a schematic diagram of the present invention for mining high-gas outburst coal seams, steeply inclined coal seams, and coal seams with complex geological conditions, wherein the arrow indicates a schematic layout of the fluidized drilling gas-coal mining part from a back-to-front perspective.

[0026] In the figure: 1, jet coal breaking unit; 1-1, coal breaking drill bit; 1-2, injection device; 1-2-1, jet nozzle; 1-3, extension device; 1-3-1, jet nozzle; 1-4, high-pressure sealing drill pipe; 1-5, high-pressure water tail; 1-6, drilling rig; 1-7, high-pressure water pump; 2, orifice sealing unit; 2-1, front sealing casing; 2-2, sealing unit body; 2-3, rear sealing casing; 2-4, support sealing ring; 2- 5. Gas outlet; 2-6. Water-coal outlet; 3. Water-coal separation unit; 3-1. Vibrating screen; 3-2. Scraper conveyor; 3-3. Sedimentation tank; 3-3-1. Primary sedimentation tank; 3-3-2. Secondary filtration tank; 3-4. Filter press; 4. Borehole filling area; 5. Borehole coal mining cave; 6. Coal-water collection box; 7. Slurry delivery pump; 8. High-pressure water jet; 9. Coal seam to be mined; 10. Lower chute; 11. Gas extraction pipe. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings (hereinafter described with the drilling direction of the high-pressure sealed drill rod 1-4 as the front).

[0028] The underground physical fluidized coal mining system includes fluidized drilling gas-coal mining part, such as Figure 1 , Figure 3 , Figure 6 As shown, the fluidized drilling gas-coal mining part includes a jet coal breaking unit 1, a hole sealing unit 2, and a water-coal separation unit 3;

[0029] like Figure 4As shown, the jet coal breaking unit 1 includes a coal breaking drill bit 1-1, an injection device 1-2, an extension device 1-3, a high-pressure sealed drill pipe 1-4, a high-pressure water tail 1-5, a drilling rig 1-6, and a high-pressure water pump 1-7; the high-pressure sealed drill pipe 1-4 is a cylindrical structure with multiple sections of consistent outer diameter and sealed installation and connection, and a hollow water-passing structure is provided inside the high-pressure sealed drill pipe 1-4, the front end of the high-pressure sealed drill pipe 1-4 is sealed and installed and connected to the extension device 1-3, and the rear end of the high-pressure sealed drill pipe 1-4 is sealed and installed and connected to the high-pressure water tail 1-5; the front end of the extension device 1-3 is sealed and installed with the injection device 1-2, and the front end of the injection device 1-2 is threadedly connected to the coal breaking drill bit; the high-pressure water output end of the high-pressure water pump 1-7 can be sealed and installed with the high-pressure water tail 1-5 through a pipeline; the drilling rig 1-6 is transmission-connected to the high-pressure sealed drill pipe 1-4;

[0030] The orifice sealing unit 2 comprises a front sealing sleeve 2-1, a sealing unit body 2-2 and a rear sealing sleeve 2-3 which are coaxially butt-jointed and sealed in sequence. The high-pressure sealing drill pipe 1-4 can pass through the orifice sealing unit 2 along the front and rear axial direction of the orifice sealing unit 2, and a coal-water flow passage is formed between the outer surface of the high-pressure sealing drill pipe 1-4 and the inner surface of the front sealing sleeve 2-1. A sealing member which is coaxially fixed in the rear sealing sleeve 2-3 and is sealed to match the outer diameter of the high-pressure sealing drill pipe 1-4 and is used to seal and support the high-pressure sealing drill pipe 1-4 The sealing ring 2-4 is supported, and the sealing unit body 2-2 is a container structure with a large inner cavity. The top of the sealing unit body 2-2 is provided with a gas outlet 2-5 which is connected with the inner cavity, and the gas outlet 2-5 is tightly connected with the mine gas extraction pipe 11 through a pipeline. The bottom of the sealing unit body 2-2 is provided with a water-coal outlet 2-6 which is connected with the inner cavity, and the water-coal outlet 2-6 is connected with the input end of the coal-water collecting box 6 through a pipeline, and the output end of the coal-water collecting box 6 is connected with the input end of the slurry delivery pump 7 through a pipeline.

[0031] like Figure 5 As shown, the water-coal separation unit 3 includes a vibrating screen 3-1, a scraper conveyor 3-2, a sedimentation tank 3-3 and a filter press 3-4; the outlet of the slurry delivery pump 7 output end connecting the pipeline is arranged above the material input end of the vibrating screen 3-1, and the material output end of the vibrating screen 3-1 is arranged above the material input end of the scraper conveyor 3-2. The sedimentation tank 3-3 includes a primary sedimentation tank 3-3-1 and a secondary filter tank 3-3-2. The vibration dehydration drain outlet of the vibrating screen 3-1 is connected to the primary sedimentation tank 3-3-1 through a pipeline. The sludge pump at the material input end of the filter press 3-4 is arranged in the primary sedimentation tank 3-3-1. The filter pressure drain outlet of the filter press 3-4 is connected to the secondary filter tank 3-3-2 through a pipeline. The input end of the high-pressure water pump 1-7 is connected to the secondary filter tank 3-3-2 through a pipeline.

[0032] In order to ensure the efficiency of coal-water removal, the multiple high-pressure sealed drill rods 1-4 at the front end can adopt large-diameter triangular drill rods, quadrangular drill rods, hexagonal drill rods and other large-diameter edged drill rods with multiple edges, or high-pressure sealed drill rods with edges and round sealed drill rods are cross-sealed and connected.

[0033] In order to achieve a better hydraulic coal breaking effect, the injection device 1-2 can be set to 1 to 8 jet nozzles 1-2-1, and the injection direction of the jet nozzle 1-2-1 has an axial angle of 45° to 90° with the injection device 1-2. Multiple jet nozzles 1-2-1 are evenly distributed along the circumferential direction of the injection device 1-2, and / or multiple jet nozzles 1-2-1 are evenly distributed along the axial direction of the injection device 1-2.

[0034] In order to increase the range of hydraulic coal breaking, the extension device 1-3 is provided with a plurality of expansion swing arms symmetrically arranged relative to the center of the base body. The expansion swing arms can be 0.5 to 2.5 m long and can be extended radially along the drill pipe through the central rotating shaft. A drainage channel is arranged inside the expansion swing arm and the base body, which cooperates with the jet nozzle 1-3-1 arranged in front of the swing arm to generate a high-pressure water jet.

[0035] When using this underground physical fluidized coal mining system to mine difficult-to-mine (legacy) coal resources, this underground physical fluidized coal mining system is set at the lower end of the coal seam inclination and a retreat-type coal mining method is adopted. The fluidized drilling gas coal mining part can be Figure 1 As shown, it is arranged in the coal lane of the lower drift 10 of the coal seam 9 to be mined, and can also be Figure 6 As shown, it is set in the bottom rock tunnel of the coal seam 9 to be mined and is flexibly arranged according to the coal seam conditions and tunnel conditions.

[0036] When the fluidized drilling gas coal mining part of the underground physical fluidized coal mining system is used for coal mining, the arrangement of the boreholes penetrating the coal seam 12 is an upward hole from bottom to top along the inclined direction of the coal seam, and multiple boreholes can be drilled simultaneously for coal mining. Specifically:

[0037] Step 1, drilling construction: install the coal-breaking drill bit 1-1 at the front end of the high-pressure sealed drill pipe 1-4, install the high-pressure water tail 1-5 at the rear end of the high-pressure sealed drill pipe 1-4, use the drilling rig 1-6 to drive the high-pressure sealed drill pipe 1-4 to drill 2 to 4 meters upward along the coal seam and then stop drilling; withdraw the high-pressure sealed drill pipe 1-4 and the coal-breaking drill bit 1-1, replace the coal-breaking drill bit 1-1 with the reaming drill bit, expand the hole mouth position of the borehole, and the inner diameter of the expanded hole is larger than the outer diameter size of the front sealing casing 2-1; insert the front sealing casing 2-1 at the expanded hole position, and grouting is performed in the annulus between the borehole and the front sealing casing 2-1 to fix the front sealing casing 2 -1, then coaxially and tightly fixedly install the sealing unit body 2-2 and the rear sealing sleeve 2-3 on the front sealing sleeve 2-1, and install the gas outlet 2-5 in tight connection with the mine gas extraction pipe 11 through a pipeline, and connect the water-coal outlet 2-6 to the input end of the coal-water collecting box 6 through a pipeline; replace the hole-expanding drill bit with the coal-breaking drill bit 1-1, and after the high-pressure sealing drill rod 1-4 and the coal-breaking drill bit 1-1 pass through the hole sealing unit 2, use the drilling rig 1-6 to drive the high-pressure sealing drill rod 1-4 to continue drilling forward to the set distance, then stop drilling, withdraw the high-pressure sealing drill rod 1-4 and the coal-breaking drill bit 1-1, and complete the coal mining drilling construction;

[0038] Step 2, fluidized gas coal mining: install the extension device 1-3, the injection device 1-2 and the coal-breaking drill bit 1-1 at the front end of the high-pressure sealed drill pipe in sequence, and pass the high-pressure sealed drill pipe 1-4, the extension device 1-3, the injection device 1-2 and the coal-breaking drill bit 1-1 through the hole sealing unit 2 and extend them to the bottom of the coal mining borehole; start the high-pressure water pump 1-7, and control the high-pressure sealed drill pipe 1-4 to rotate at an appropriate speed through the drilling rig 1-6 to hydraulically break the coal, and the broken coal body flows back to the inner cavity of the sealing unit body 2-2 with the water through the annulus between the borehole and the high-pressure sealed drill pipe 1-4, and flows into the collection box 6 through the water-coal discharge port 2-6. Finally, it is delivered to the water-coal separation unit 3 by the slurry delivery pump 7, and the gas released by the broken coal body flows into the inner cavity of the sealing unit body 2-2 through the annulus between the borehole and the high-pressure sealing drill rod 1-4, and enters the mine gas extraction pipe 11 through the gas discharge port 2-5; a step-by-step backward coal mining method is adopted to control the high-pressure sealing drill rod 1-4 to move forward and backward within a set range until the coal output of the borehole is greatly reduced, and then the high-pressure sealing drill rod 1-4 is controlled to retreat to the rear by a set step distance, and so on, to carry out the "backward-coal breaking-backward-coal breaking" cycle until the injection device 1-2 approaches the orifice sealing unit 2 to complete the mining of the coal body around the borehole.

[0039] Step 3: Drilling and filling: Figure 2As shown, a borehole coal mining cave 5 is formed during the retreat of the high-pressure sealed drill rod 1-4. After all the coal around the borehole is mined out, the borehole coal mining cave 5 is grouting-filled to form a borehole filling area 4 after grouting of the entire borehole coal mining cave 5. After the borehole filling area 4 is formed by grouting, other coal mining boreholes are arranged at set intervals to continue physical fluidization coal mining. After the filling slurry in the borehole filling area 4 solidifies, coal mining boreholes are arranged in the vicinity of the borehole filling area 4 to carry out physical fluidization coal mining.

[0040] In order to expand the coal mining diameter and increase the coal mining volume of a single borehole, the coal mining process within the single retreat setting step is as follows: first, set the high-pressure water pump 1-7 to work within the pressure range of 8 to 15MPa, so that all the high-pressure water flows out through the jet nozzle 1-2-1 of the injection device 1-2, and the coal body within this step is cut and crushed; when the coal output under this working state is greatly reduced, increase the working pressure of the high-pressure water pump 1-7 to be greater than 15MPa, so that all the high-pressure water flows out through the jet nozzle 1-3-1 of the extension device 1-3, and the coal body within this step is continued to be cut and crushed until the coal output of the borehole is greatly reduced again, and the fluidized gas coal mining operation within this step is completed.

[0041] In order to realize the filling of coal mining caverns, the underground physical fluidized coal mining system also includes a coal mining cave filling part, which includes a slurry making device and a pump pressure filling device. The slurry making device includes a crusher, a screener, a mixer and a feeder. The pump pressure filling device includes a filling pump and a filling pipeline.

[0042] When the underground physical fluidized coal mining system and method are used for coal mining operations, there is no need to arrange the mining face and large-scale mechanical equipment. The operation is simple, safe and reliable, and can achieve safe and efficient mining of difficult-to-mine (legacy) coal resources such as corner coal, chicken nest coal, geologically complex coal seams, thin coal seams, steeply inclined coal seams and legacy coal pillars. Secondly, the jet crushing of the coal body can make the gas fully desorbed and gushed out. The gas extraction volume and extraction concentration extracted through the gas extraction pipe are high, which can be directly used for gas generators, and can achieve efficient development and utilization of gas resources. Moreover, gas and dust will not be directly discharged into the tunnel or chamber, and the operators are far away from the coal breaking area, which can achieve a better working environment and work safety. In addition, after the mining is completed, the coal mining cave can be filled through the filling pipeline, which can control the deformation of the overburden and the surface subsidence, protect the surface ecological environment, and realize the green mining of the coal seam.

Claims

1. An underground physical fluidized coal mining system, characterized in that: It includes the fluidized drilling gas-coal mining part and the coal mining cave filling part; The fluidized drilling gas-coal mining part comprises a jet coal breaking unit (1), a hole sealing unit (2), and a water-coal separation unit (3); The jet coal breaking unit (1) comprises a coal breaking drill bit (1-1), an injection device (1-2), an extension device (1-3), a high-pressure sealed drill pipe (1-4), a high-pressure water tail (1-5), a drilling rig (1-6), and a high-pressure water pump (1-7); the high-pressure sealed drill pipe (1-4) is a cylindrical structure with multiple sections of uniform outer diameter and sealed and connected, and a hollow water passage is provided inside the high-pressure sealed drill pipe (1-4); the front end of the high-pressure sealed drill pipe (1-4) is sealed and connected to the extension device (1-3), and the rear end of the high-pressure sealed drill pipe (1-4) is sealed and connected to the high-pressure water tail (1-5); the front end of the extension device (1-3) is sealed and installed with the injection device (1-2), and the front end of the injection device (1-2) is threadedly connected to the coal breaking drill bit (1-1); the high-pressure water output end of the high-pressure water pump (1-7) is sealed and connected to the high-pressure water tail (1-5) through a pipeline; the drilling rig (1-6) is transmission-connected to the high-pressure sealed drill pipe (1-4); The orifice sealing unit (2) comprises a front sealing sleeve (2-1), a sealing unit body (2-2) and a rear sealing sleeve (2-3) which are coaxially butt-jointed and sealed in sequence; a high-pressure sealing drill pipe (1-4) passes through the orifice sealing unit (2) along the axial direction of the orifice sealing unit (2), and a coal-water flow passage is formed between the outer surface of the high-pressure sealing drill pipe (1-4) and the inner surface of the front sealing sleeve (2-1); a support member which is coaxially fixed in the rear sealing sleeve (2-3) and is sealingly matched with the outer diameter of the high-pressure sealing drill pipe (1-4) and is used to seal and support the high-pressure sealing drill pipe (1-4) The sealing ring (2-4) is a container structure with a large inner cavity. The top of the sealing unit body (2-2) is provided with a gas outlet (2-5) penetrating the inner cavity, and the gas outlet (2-5) is in airtight communication with a mine gas extraction pipe (11) through a pipeline. The bottom of the sealing unit body (2-2) is provided with a water-coal outlet (2-6) penetrating the inner cavity, and the water-coal outlet (2-6) is connected to the input end of a coal-water collection box (6) through a pipeline, and the output end of the coal-water collection box (6) is connected to the input end of a slurry delivery pump (7) through a pipeline. The water-coal separation unit (3) comprises a vibrating screen (3-1), a scraper conveyor (3-2), a sedimentation tank (3-3) and a filter press (3-4); the outlet of the slurry delivery pump (7) output end connecting the pipeline is arranged above the material input end of the vibrating screen (3-1), and the material output end of the vibrating screen (3-1) is arranged above the material input end of the scraper conveyor (3-2); the sedimentation tank (3-3) comprises a primary sedimentation tank (3-3-1) and a secondary filtration tank (3-3-2); the vibration dehydration drainage outlet of the vibrating screen (3-1) is connected to the primary sedimentation tank (3-3-1) through a pipeline; the sludge pump at the material input end of the filter press (3-4) is arranged in the primary sedimentation tank (3-3-1); the filter pressure drainage outlet of the filter press (3-4) is connected to the secondary filtration tank (3-3-2) through a pipeline; and the input end of the high-pressure water pump (1-7) is connected to the secondary filtration tank (3-3-2) through a pipeline; The filling part of the coal mining cave includes a pulping device and a pump pressure filling device. The pulping device includes a crusher, a screening machine, a mixer and a batching machine. The pump pressure filling device includes a filling pump and a filling pipeline.

2. The underground physical fluidized coal mining system according to claim 1, characterized in that: The spray device (1-2) is configured as 1 to 8 jet nozzles (1-2-1), and the spray direction of the jet nozzle (1-2-1) and the axial angle of the spray device (1-2) are 45° to 90°.

3. The underground physical fluidized coal mining system according to claim 2, characterized in that: The stretching device (1-3) is provided with a plurality of expansion swing arms symmetrically arranged relative to the center of the base body, the expansion swing arms are 0.5 to 2.5 m long and can be extended radially along the drill pipe through a central rotating shaft, and drainage channels are arranged inside the expansion swing arms and the base body to cooperate with the jet nozzle (1-3-1) of the stretching device (1-3) arranged in front of the expansion swing arms to generate high-pressure water jets.

4. The underground physical fluidized coal mining system according to claim 1, characterized in that: The supporting sealing rings (2-4) are arranged in at least two groups along the axial direction of the rear sealing sleeve (2-3).

5. An underground physical fluidized coal mining method based on the underground physical fluidized coal mining system according to claim 1, characterized in that: The specific steps include: Step 1, drilling construction: install the coal-breaking drill bit (1-1) at the front end of the high-pressure sealed drill pipe (1-4), install the high-pressure water tail (1-5) at the rear end of the high-pressure sealed drill pipe (1-4), use the drilling rig (1-6) to drive the high-pressure sealed drill pipe (1-4) to drill 2 to 4 meters upward along the coal seam and then stop drilling; withdraw the high-pressure sealed drill pipe (1-4) and the coal-breaking drill bit (1-1), replace the coal-breaking drill bit (1-1) with an expansion drill bit, expand the borehole, and the expanded hole inner diameter is larger than the outer diameter of the front sealing casing (2-1); insert the front sealing casing (2-1) into the expanded borehole, and inject grout into the annulus between the borehole and the front sealing casing (2-1) to fix the front sealing casing (2-1), Then, the sealing unit body (2-2) and the rear sealing sleeve (2-3) are coaxially and hermetically fixedly installed on the front sealing sleeve (2-1), and the gas outlet (2-5) is connected to the mine gas extraction pipe (11) through a pipeline, and the water-coal outlet (2-6) is connected to the input end of the coal-water collection box (6) through a pipeline; the hole expansion drill bit is replaced with a coal-breaking drill bit (1-1), and the high-pressure sealing drill rod (1-4) and the coal-breaking drill bit (1-1) are passed through the hole sealing unit (2), and the high-pressure sealing drill rod (1-4) is driven by the drilling rig (1-6) to continue drilling forward to a set distance, and then the drilling is stopped, and the high-pressure sealing drill rod (1-4) and the coal-breaking drill bit (1-1) are withdrawn, and the coal mining drilling construction is completed; Step 2: fluidized gas coal mining: the extension device (1-3), the injection device (1-2) and the coal-breaking drill bit (1-1) are sequentially installed at the front end of the high-pressure sealed drill pipe (1-4), and the high-pressure sealed drill pipe (1-4), the extension device (1-3), the injection device (1-2) and the coal-breaking drill bit (1-1) are passed through the hole sealing unit (2) and extended to the bottom of the coal mining borehole; after starting the high-pressure water pump (1-7), the high-pressure sealed drill pipe (1-4) is controlled by the drilling rig (1-6) to rotate at an appropriate speed to hydraulically break the coal, and the broken coal body flows back to the inner cavity of the sealing unit body (2-2) along with the water flow through the annulus between the borehole and the high-pressure sealed drill pipe (1-4), and flows into the coal-water collection box (6) through the water-coal discharge port (2-6). Finally, the coal is delivered to the water-coal separation unit (3) by the slurry delivery pump (7); the gas released by the broken coal body flows into the inner cavity of the sealing unit body (2-2) through the annular space between the borehole and the high-pressure sealing drill rod (1-4), and enters the mine gas extraction pipe (11) through the gas outlet (2-5); a step-by-step backward coal mining method is adopted to control the high-pressure sealing drill rod (1-4) to move forward and backward within a set range until the coal output of the borehole is greatly reduced, and then the high-pressure sealing drill rod (1-4) is controlled to retreat by a set step distance, and so on, and the "retreat-coal-break-backward-coal-break" cycle is carried out until the extension device (1-3), the injection device (1-2) and the coal-breaking drill bit (1-1) are close to the hole mouth sealing unit (2), and the mining of the coal body around the borehole is completed; Step 3, borehole filling: A borehole coal mining cave (5) is formed during the retreat of the high-pressure sealed drill rod (1-4). After all the coal around the borehole is mined out, the borehole coal mining cave (5) is grouting filled, so that the entire borehole coal mining cave (5) forms a borehole filling area (4) after grouting. After the borehole filling area (4) is formed by grouting, other coal mining boreholes are arranged at set intervals to continue physical fluidized coal mining. After the filling slurry in the borehole filling area (4) solidifies, coal mining boreholes are arranged in the vicinity of the borehole filling area (4) to carry out physical fluidized coal mining.

6. The underground physical fluidized coal mining method according to claim 5, characterized in that: The coal mining process within each set backward step is as follows: first, the high-pressure water pump (1-7) is set to work within the pressure range of 8 to 15 MPa, so that all the high-pressure water flows out through the jet nozzle (1-2-1) of the injection device (1-2), and the coal body within this step is cut and crushed; when the coal output under this working state is greatly reduced, the working pressure of the high-pressure water pump (1-7) is increased to greater than 15 MPa, so that all the high-pressure water flows out through the jet nozzle (1-3-1) of the extension device (1-3), and the coal body within this step is continued to be cut and crushed until the coal output of the borehole is greatly reduced again, and the fluidized gas coal mining operation within this step is completed.

7. The underground physical fluidized coal mining method according to claim 5, characterized in that: According to the coal seam conditions and tunnel conditions, the fluidized drilling gas coal mining part is set in the coal tunnel of the lower drift (10) of the coal seam to be mined (9), or in the bottom rock tunnel of the coal seam to be mined (9).

Images