A device and method for extracting coal seam gas

Abstract

This invention discloses a coal seam gas extraction device and method for coal seam mining, comprising a carbon dioxide injection pump, a nitrogen injection pump, and a water injection pump. The carbon dioxide injection pump injects hot carbon dioxide into a carbon dioxide mobile device; the nitrogen injection pump and the water injection pump inject liquid nitrogen or water into a nitrogen / water mobile device, respectively; an alternating injection pipe and a gas extraction pipe are installed within the coal seam; the gas extraction pipe is connected to the water injection pump via a return water pipeline; the alternating injection pipe has at least three sets of orifices, each set of orifices being located within a coal seam segment; both the carbon dioxide mobile device and the nitrogen / water mobile device are located within the alternating injection pipe and each has an orifice set, with the carbon dioxide mobile device fitted outside the nitrogen / water mobile device; the outlet of the alternating injection pipe is a closed port. This invention, by dividing the coal seam into several segments, allows for sequential and simultaneous completion of water injection, nitrogen injection, gas injection, and gas extraction, significantly improving gas extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of gas extraction technology, and in particular to a device and method for extracting coal seam gas. Background Technology

[0002] As a highly efficient and clean resource associated with coal, efficient gas extraction is the fundamental method for preventing gas disasters and an important way to obtain clean energy. Coal seams have complex structures and generally low permeability, making their low-permeability characteristics increasingly apparent. However, existing coal seam gas extraction technologies suffer from imperfect extraction processes and low gas extraction efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a coal seam gas extraction device and method to solve the problems existing in the prior art and to address the imperfections in the existing gas extraction technology.

[0004] To achieve the above objectives, the present invention provides the following solution: The present invention provides a coal seam gas extraction device for coal seam mining, comprising a carbon dioxide injection pump, a nitrogen injection pump, and a water injection pump; the carbon dioxide injection pump injects hot carbon dioxide into a carbon dioxide mobile device through a first pipeline; the nitrogen injection pump and the water injection pump inject liquid nitrogen or water into the nitrogen / water mobile device respectively through a second pipeline;

[0005] An alternating injection pipe and a gas extraction pipe are installed within the coal seam; the gas extraction pipe is connected to the water injection pump via a return water pipeline; the alternating injection pipe has at least three sets of orifices, each set of orifices being located within a coal seam segment; the carbon dioxide moving device and the nitrogen / water moving device are both located within the alternating injection pipe and each has an orifice, with the carbon dioxide moving device sleeved outside the nitrogen / water moving device; the port of the alternating injection pipe is a closed port.

[0006] The alternating injection pipe and the gas extraction pipe are fixed inside the coal seam by a sealing device;

[0007] The length of the alternating injection pipe placed in the coal seam is shorter than the thickness of the coal seam; the alternating injection pipe is arranged at intervals at both ends of the working face return air roadway and the working face intake air roadway, and the gas extraction pipe is arranged in a mirror image at both ends of the working face return air roadway and the working face intake air roadway.

[0008] Each of the aforementioned hole groups is provided with three rows of through holes, each row of through holes including a top dense hole, a first side hole, a second side hole and a bottom hole; and each of the three hole groups has a row of through holes on which a first position sensor, a second position sensor and a third position sensor are installed.

[0009] The first pipeline is a carbon dioxide injection pipeline, and valve I and pressure gauge I are installed on the carbon dioxide injection pipeline;

[0010] The second pipeline includes a nitrogen injection pipeline, a water injection pipeline, and a three-way valve; the nitrogen injection pipeline and the water injection pipeline are connected to the nitrogen / water moving device through the three-way valve, and the nitrogen injection pipeline and the water injection pipeline are also connected to a nitrogen injection pump and a water injection pump, respectively; the nitrogen injection pipeline is equipped with valve II, pressure gauge II, and a flow meter; the water injection pipeline is equipped with valve III and pressure gauge III.

[0011] One end of the gas extraction pipe is also connected to the extraction main pipe through a gate valve; the gas extraction pipe includes a pipe body, on which an extraction controller is fixedly installed. The extraction controller controls a double-layer disc through an electric wire; the double-layer disc includes two single-layer discs, one of which is placed at the end of the pipe body, and the other of which is slidably mounted on a fixed rod and electrically connected to the extraction controller; both single-layer discs are wound with insulating resistance wire.

[0012] A settling tank is also fixedly connected to the pipe body; a return water valve is installed at one end of the return water pipe near the settling tank; a bottom hole is provided at the bottom of the settling tank; and a tank valve is also installed on the side wall of the settling tank.

[0013] The carbon dioxide moving device includes an outer cylindrical shell and a first inner cylindrical shell. The outer cylindrical shell has three rows of first corresponding holes with the same position and diameter as those on the outer shell of the gas extraction pipe, next to a hollow circular baffle. Each row of first corresponding holes includes a first top dense hole, a first side dense hole, a second side dense hole, and a first bottom hole. A carbon dioxide controller is provided in the gap between the hollow circular baffle, the outer cylindrical shell, and the first inner cylindrical shell. The carbon dioxide controller controls the extension and retraction of the first telescopic rod.

[0014] The nitrogen / water moving device includes a second inner shell cylinder; the second inner shell cylinder has three rows of second corresponding holes with the same position and diameter as those on the outer shell of the gas extraction pipe next to the closed circular baffle, each row of second corresponding holes includes a second top dense hole, a third side dense hole, a fourth side dense hole, and a second bottom hole; a nitrogen / water controller is also provided inside the first inner shell cylinder; the nitrogen / water controller controls the extension and retraction of the second telescopic rod.

[0015] A method for extracting coal seam gas, comprising a coal seam gas extraction device, including:

[0016] S1. Using the nitrogen / water controller, the nitrogen / water moving device is moved to the designated position. The water injection pump is turned on so that graphite particles and water flow into the first coal seam section through the channel of the nitrogen / water moving device from the first set of holes in the alternating injection pipe, and the coal seam is moistened with water. When a small amount of water is collected in the settling tank, the water injection pump is turned off and the nitrogen injection pump is turned on to inject liquid nitrogen to fracture the first coal seam section.

[0017] S2, When the settling tank can no longer collect water, turn off the nitrogen injection pump and turn on the alternating injection pipe button to energize and heat the alternating injection pipe. After the water collection speed of the settling tank drops from the fastest to a very slow speed, turn off the alternating injection pipe button. Then, when the settling tank can no longer collect water, the effect of liquid nitrogen fracturing the coal seam is evaluated by analyzing the proportion of graphite particles and coal dust flowing into the settling tank, so as to decide whether to introduce liquid nitrogen again.

[0018] S3, after the first coal seam section no longer needs liquid nitrogen injection, use the carbon dioxide controller to move the carbon dioxide moving device to the designated position, turn on the carbon dioxide injection pump to inject hot carbon dioxide gas through the liquid nitrogen / water from the first corresponding hole to displace the first coal seam section. At the same time, use the nitrogen / water controller to move the nitrogen / water moving device to the designated position, turn on the water injection pump containing plasma and water through the channel of the nitrogen / water moving device to inject water into the third coal seam section to moisten the coal seam. When a small amount of water is collected in the settling water tank located at the end of the working face air intake roadway, turn off the water injection pump, turn on the nitrogen injection pump, and inject liquid nitrogen to fracture the third coal seam section. Repeat step S.

[0019] After the carbon dioxide displacement of the first coal seam section is completed, the gate valve of the gas extraction pipe at the end of the return air roadway of the working face is opened to extract the gas from the first coal seam section.

[0020] S4. After nitrogen injection is completed at the third coal seam section, the nitrogen / water moving device is moved to the designated position using the nitrogen / water controller. The water injection pump containing plasma and water is turned on and flows out through the second set of holes in the alternating injection pipe via the channel of the nitrogen / water moving device to inject water into the second coal seam section to moisten the coal seam. The water tank valve is opened and when a small amount of water is collected in the settling water tank, the water injection pump is turned off and the nitrogen injection pump is turned on to inject liquid nitrogen to fracture the third coal seam section. Step S is repeated.

[0021] Subsequently, the carbon dioxide controller is used to move the carbon dioxide mobile device to the designated position, and the carbon dioxide injection pump is turned on to inject hot carbon dioxide into the third coal seam section through the third set of holes opened by the alternating injection pipe. After the gas injection is completed, the gate valve of the gas extraction pipe arranged at the end of the working face air intake roadway is opened to extract gas from the three coal seam sections.

[0022] S5. After the gas injection at the third coal seam section is completed and the nitrogen injection at the second coal seam section is no longer completed, the carbon dioxide controller is used to move the carbon dioxide mobile device to the designated position, and the carbon dioxide injection pump is turned on to inject hot carbon dioxide into the second coal seam section through the second set of holes opened by the alternating injection pipe. After the gas injection is completed, the gas of the second coal seam section is extracted by the gas extraction pipes arranged at the ends of the return air roadway and the intake air roadway of the working face.

[0023] S6. After gas extraction for a period of time, when the extraction rate drops significantly, turn on the alternating injection pipe button to power the alternating injection pipe and generate heat, and adjust the extraction controller to separate the double-layer disc into two single-layer discs and rotate them for cooling.

[0024] S7. After a period of time, close the gate valve on the gas extraction pipe, and repeat steps S1, S2, S3, S4, S5, and S6. By injecting nitrogen, water, and gas in sequence at different locations, gas extraction is achieved, thus realizing repeated extraction of coal seam gas.

[0025] In step 1, when liquid nitrogen is injected into the first coal seam segment, the total amount of liquid nitrogen used for the first coal seam segment is recorded by the flow meter installed on the nitrogen injection pipeline; in steps 3 and 4, the amount of liquid nitrogen injected into the third and second coal seam segments is the total amount of liquid nitrogen used for the first coal seam segment.

[0026] The present invention discloses the following technical effects: 1. The present invention divides the coal seam into several sections, and water injection, nitrogen injection, gas injection and gas extraction can be carried out in sequence and simultaneously, which greatly improves the efficiency of gas mining.

[0027] 2. The presence of graphite particles and coal dust after preliminary fracturing in this invention evaluated the effect of liquid nitrogen fracturing on coal seams. This ensured the fracturing effect while saving liquid nitrogen resources. At the same time, it roughly determined the amount of liquid nitrogen required for fracturing in the second and third coal seam sections, shortened the fracturing evaluation process, and improved work efficiency.

[0028] 3. This invention increases the gas pressure in the coal seam by generating heat through alternating injection pipes and creates a negative pressure space by rotating a double-layer disc for cooling, thereby reducing the gas pressure at the gas extraction pipe inlet and solving the problem of low gas concentration in the later stage of gas extraction.

[0029] 3. This invention collects water injected into the coal seam through a settling tank, processes it secondary, and then returns it to the injection pump for the next injection, thereby realizing water circulation and saving water resources.

[0030] 4. This invention uses electric wires to heat the insulating resistance wires of both double-layered discs, thereby creating a thermal space to dry the gas and improve the quality of coal seam gas extraction. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0032] Figure 1 This is a schematic diagram illustrating a specific implementation method of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure for controlling carbon dioxide flow according to the present invention;

[0034] Figure 3 This is a schematic diagram of the liquid nitrogen / water flow control structure of the present invention;

[0035] Figure 4 This is a schematic diagram of the arrangement of the electric fuse and resistor structure on the outer shell of the alternating injection tube of the present invention;

[0036] Figure 5 A schematic diagram of the nitrogen and water injection process at the first coal seam location of the alternating injection pipe of this invention;

[0037] Figure 6 A schematic diagram of the nitrogen and water injection process at the third coal seam location of the alternating injection pipe of this invention;

[0038] Figure 7 A schematic diagram of the nitrogen and water injection process for the second coal seam location of the alternating injection pipe of this invention;

[0039] Figure 8 This is a schematic diagram of the carbon dioxide injection process at the second coal seam location using the alternating injection pipe of the present invention;

[0040] Figure 9 This is a schematic diagram of the gas extraction pipe structure of the present invention;

[0041] Figure 10 This is a flowchart illustrating the process of transporting crushed coal in the gas extraction pipe of the present invention.

[0042] Figure 11 This is a schematic diagram of the gas treatment process in the gas extraction pipe of the present invention.

[0043] Figure 12 This is a schematic diagram of the gas cooling process in the gas extraction pipe of the present invention;

[0044] Figure 13 This is a schematic diagram of the drilling arrangement in an embodiment of the present invention;

[0045] Among them, 1-carbon dioxide injection pump, 2-valve I, 3-pressure gauge I, 4-carbon dioxide injection pipeline, 5-nitrogen injection pump, 6-valve II, 7-pressure gauge II, 8-flow meter, 9-nitrogen injection pipeline, 10-water injection pump, 11-valve III, 12-pressure gauge III, 13-water injection pipeline, 14-three-way valve, 15-return water pipeline, 16-extraction main pipe, 17-gate valve, 18-return water pipe valve, 19-sedimentation tank, 20-water tank bottom hole, 21-water tank valve, 22-gas extraction pipe, 23-carbon dioxide moving device, 24-nitrogen / water moving device, 25-alternating injection pipe, 26-sealing device, 27-coal seam, 28-working face cut, 29-working face return airway, 30-working face intake airway, 31-gas, 32-gas extraction borehole radius; 33-alternating injection pipe button;

[0046] 22A - Extraction controller, 22B - Rectangular baffle, 22C - Fixing rod, 22D - Wire, 22E - Double-layer disc, 22F - Insulated resistance wire; 22G - Heating circuit, 22H - Cooling circuit;

[0047] 23A - Top dense holes, 23B - First side dense holes, 23C - Second side dense holes, 23D - First bottom hole, 23E - Carbon dioxide controller, 23F - First telescopic rod, 23G - Outer shell cylinder, 23H - Hollow circular baffle, 23I - First inner shell cylinder;

[0048] 24A - Second top dense hole, 24B - Third side dense hole, 24C - Fourth side dense hole, 24D - Second bottom hole, 24E - Nitrogen / water controller, 24F - Second telescopic rod, 24G - Second inner shell cylinder, 24H - Closed circular baffle;

[0049] 25A - Top dense hole, 25B - First side hole, 25C - Second side hole, 25D - Bottom hole, 25E ​​- First position sensor, 25F - Second position sensor, 25G - Third position sensor, 25H - Closed port; 25I - Circuit; 25J - Fuse; 25K - Resistor. Detailed Implementation

[0050] 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.

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] This invention provides a coal seam gas extraction device for coal seam 27 mining, including a carbon dioxide injection pump 1, a nitrogen injection pump 5, and a water injection pump 10; the carbon dioxide injection pump 1 injects hot carbon dioxide into a carbon dioxide moving device 23 through a first pipeline; the nitrogen injection pump 5 and the water injection pump 10 inject liquid nitrogen or water into a nitrogen / water moving device 24 through a second pipeline, respectively.

[0053] An alternating injection pipe 25 and a gas extraction pipe 22 are installed in the coal seam 27; the gas extraction pipe 22 is connected to the water injection pump 10 through the return water pipe 15; the alternating injection pipe 25 has at least three sets of holes, each set of holes being placed in a coal seam section; the carbon dioxide moving device 23 and the nitrogen / water moving device 24 are both placed in the alternating injection pipe 25 and both have sets of holes, and the carbon dioxide moving device 23 is sleeved on the outside of the nitrogen / water moving device 24; the port of the alternating injection pipe 25 is a closed port 25H.

[0054] The alternating injection pipe 25 and the gas extraction pipe 22 are fixed in the coal seam 27 by the sealing device 26;

[0055] The length of the alternating injection pipe 25 placed in the coal seam 27 is shorter than the thickness of the coal seam 27; the alternating injection pipe 25 is arranged crosswise at both ends of the working face return air roadway 29 and the working face intake air roadway 30, and the gas extraction pipe 22 is arranged mirror-imagely at both ends of the working face return air roadway 29 and the working face intake air roadway 30.

[0056] Furthermore, the length of the alternating injection pipe 25 placed within the coal seam 27 is slightly shorter than the thickness of the coal seam 27, and the length range of the gas extraction pipe 22 placed within the coal seam 27 can be calculated using the following formula:

[0057] Coal seam thickness 27 - gas extraction pipe 22 effective gas extraction diameter / 2

[0058] Furthermore, the spacing between the alternating injection pipe 25 and the gas extraction pipe 22 is the effective radius of the gas extraction pipe 22.

[0059] Furthermore, the length of the alternating injection pipe 25 placed within the coal seam 27 is shorter than the thickness of the coal seam 27, but close to the thickness of the coal seam 27.

[0060] Both the carbon dioxide moving device 23 and the nitrogen / water moving device 24 have three rows of through holes in their hole groups; each hole group of the alternating injection pipe 25 has three rows of through holes, and each row of through holes includes a top dense hole 25A, a first side hole 25B, a second side hole 25C and a bottom hole 25D; and each of the three hole groups has a row of through holes on which a first position sensor 25E, a second position sensor 25F and a third position sensor 25G are installed.

[0061] The first pipeline is carbon dioxide injection pipeline 4, and valve I2 and pressure gauge I3 are installed on carbon dioxide injection pipeline 4;

[0062] The second pipeline includes a nitrogen injection pipeline 9, a water injection pipeline 13, and a three-way valve 14; the nitrogen injection pipeline 9 and the water injection pipeline 13 are connected to the nitrogen / water moving device 24 through the three-way valve 14, and the nitrogen injection pipeline 9 and the water injection pipeline 13 are also connected to a nitrogen injection pump 5 and a water injection pump 10, respectively; a valve II 6, a pressure gauge II 7, and a flow meter 8 are installed on the nitrogen injection pipeline 9; a valve III 11 and a pressure gauge III 12 are installed on the water injection pipeline 13.

[0063] One end of the gas extraction pipe 22 is also connected to the extraction main pipe 16 through a gate valve 17; the gas extraction pipe 22 includes a pipe body, on which an extraction controller 22A is fixedly installed. The extraction controller 22A controls the double-layer disc 22E through a wire 22D; the double-layer disc 22E includes two single-layer discs, one single-layer disc is placed at the end of the pipe body, and the other single-layer disc is slidably set on a fixed rod 22C and electrically connected to the extraction controller 22A; both single-layer discs are wound with insulating resistance wire 22F.

[0064] In one embodiment of the present invention, the extraction controller 22A is connected to and controls the double-layer disk 22E to separate into two single-layer disks via a fixed rod 22C. One single-layer disk is placed at the end of the tube body, and the other single-layer disk is slidably disposed on the fixed rod 22C. Insulating resistance wires 22F are wound on both single-layer disks. The lower 1 / 4 of the disk is a rectangular baffle 22B. A conductive metal rod is inserted from the center at the upper 3 / 4 of the disk to connect the insulating resistance wires 22F. The fixed rod 22C is provided with wires 22D. Hot wires 22G and cold wires 22H are connected to the double-layer disk 22E.

[0065] Furthermore, after water injection to fracture the coal seam, when a large amount of coal dust remains at the gas extraction pipe 22 opening, the double-layer disc 22E is separated into a single-layer disc by the extraction controller 22A. One disc moves on the fixed rod 22C to transport the coal dust to the settling water tank 19 to prevent the gas extraction pipe 22 opening from becoming blocked. When extracting gas, the double-layer disc 22E is separated into two discs, one disc at the pipe opening and the other disc moves inward and retracts the rectangular baffle 22B. The two discs are separated by a distance. The heating circuit 22G provided in the fixed rod 22C energizes the insulating resistance wire 22F in the disc, thereby generating a thermomagnetic field in the space between the two discs to dry and reduce dust.

[0066] In one embodiment of the present invention, after the two single-layer disks are separated, the two insulating resistance wires 22F are heated by electromagnetic heating to generate a thermal space for drying the gas.

[0067] Furthermore, when the gas concentration around the gas extraction pipe 22 is low after the gas extraction pipe 22 has been extracting for a period of time, the extraction controller 22A is adjusted to make the two discs rotate to draw air into the pipe opening, forming a negative pressure space. The cooling circuit 22G provided in the fixed rod 22C energizes the insulating resistance wire 22F in the disc, thereby generating a cold space in the space between the two discs, thereby reducing the gas pressure at the gas extraction pipe 22 intake.

[0068] In one embodiment of the present invention, after the disc rotates and cools, a negative pressure space and a cold space are generated at the gas extraction pipe 22, thereby solving the problem of low gas concentration and inability to extract gas.

[0069] A settling tank 19 is also fixedly connected to the pipe body; a return water pipe valve 18 is installed at one end of the return water pipe 15 near the settling tank 19; a bottom hole 20 is opened at the bottom of the settling tank 19; a tank valve 21 is also installed on the side wall of the settling tank 19.

[0070] Furthermore, to evaluate the effect of liquid nitrogen fracturing on the coal seam, the extraction controller 22A is used to separate the double-layer disk 22E into a single-layer disk, so that one disk moves on the fixed rod 22C to transport the graphite particles and coal dust trapped in the gas extraction pipe 22 to the settling water tank 19. After the water in the settling water tank 19 is treated to remove impurities by sedimentation, the return water valve 18 is opened and the water is transported to the water injection pump 10 through the return water pipeline 15 for the next coal seam water injection.

[0071] The carbon dioxide moving device 23 includes an outer shell cylinder 23G and a first inner shell cylinder 23I; the outer shell cylinder 23G has three rows of first corresponding holes with the same position and diameter as those on the outer shell of the gas extraction pipe 22 next to the hollow circular baffle 23H; each row of first corresponding holes includes a first top dense hole 23A, a first side dense hole 23B, a second side dense hole 23C, and a first bottom hole 23D; a carbon dioxide controller 23E is provided in the gap between the hollow circular baffle 23H, the outer shell cylinder 23G, and the first inner shell cylinder 23I; the carbon dioxide controller 23E controls the extension and retraction of the first telescopic rod 23F.

[0072] The nitrogen / water moving device 24 includes a second inner shell cylinder 24G; the second inner shell cylinder 24G has three rows of second corresponding holes next to the closed circular baffle 24H, which are in the same position and have the same diameter as the outer shell of the gas extraction pipe 22. Each row of second corresponding holes includes a second top dense hole 24A, a third side dense hole 24B, a fourth side dense hole 24C, and a second bottom hole 24D; a nitrogen / water controller 24E is also provided inside the first inner shell cylinder 23I; the nitrogen / water controller 24E controls the extension and retraction of the second telescopic rod 24E.

[0073] A method for extracting coal seam gas, comprising a coal seam gas extraction device, including:

[0074] S1, using the nitrogen / water controller 24E to move the nitrogen / water moving device 24 to the designated position, turn on the water injection pump 10 containing graphite particles and water, and let the water flow out from the first set of holes in the alternating injection pipe 25 through the channel of the nitrogen / water moving device 24 to inject water to wet the coal seam 27 at the first coal seam section. Open the water tank valve 21 and wait for a small amount of water to be collected in the settling water tank 19, then turn off the water injection pump 10 and turn on the nitrogen injection pump 5 to inject liquid nitrogen to fracture the first coal seam section.

[0075] S2, When the settling tank 19 can no longer collect water, turn off the nitrogen injection pump 5, turn on the alternating injection pipe button 33 to make the alternating injection pipe 25 energized and generate heat. After the settling tank 19 collects water from the fastest to a very slow speed, turn off the alternating injection pipe button 33. Then, when the settling tank 19 can no longer collect water, the effect of liquid nitrogen fracturing the coal seam is evaluated by analyzing the proportion of graphite particles and coal dust flowing into the settling tank 19, so as to decide whether to introduce liquid nitrogen again.

[0076] S3, after the first coal seam segment no longer requires liquid nitrogen injection, the carbon dioxide controller 23E is used to move the carbon dioxide moving device 23 to the designated position, and the carbon dioxide injection pump 1 is turned on to inject hot carbon dioxide gas through the liquid nitrogen / water from the first corresponding hole of the carbon dioxide moving device 23 to displace the first coal seam segment. At the same time, the nitrogen / water controller 24E is used to move the nitrogen / water moving device 24 to the designated position, and the water injection pump 10 containing plasma and water is turned on to inject water into the third coal seam segment 27 by injecting water through the third group of holes opened in the alternating injection pipe 25 through the channel of the nitrogen / water moving device 24 to moisten the coal seam 27. When a small amount of water is collected in the settling water tank 19 located at the end of the working face intake airway 30, the water injection pump 10 is turned off, the nitrogen injection pump 5 is turned on, and liquid nitrogen is injected to fracturing the third coal seam segment. Step S2 is repeated.

[0077] After the carbon dioxide displacement of the first coal seam section is completed, the gate valve 17 of the gas extraction pipe at the 29th end of the return air roadway of the working face is opened to extract the gas from the first coal seam section.

[0078] S4, after nitrogen injection is completed at the third coal seam section, the nitrogen / water moving device 24 is moved to the designated position using the nitrogen / water controller 24E. The water injection pump 10, which contains plasma and water, is turned on and flows out through the second set of holes in the alternating injection pipe 25 via the channel of the nitrogen / water moving device 24 to inject water into the second coal seam section to moisten the coal seam 27. The water tank valve 21 is turned on and when a small amount of water is collected in the settling water tank 19, the water injection pump 10 is turned off and the nitrogen injection pump 5 is turned on to inject liquid nitrogen to fracture the third coal seam section. Step S2 is repeated.

[0079] Subsequently, the carbon dioxide controller 23E is used to move the carbon dioxide mobile device 23 to the designated position, and the carbon dioxide injection pump 1 is opened to inject hot carbon dioxide into the third coal seam section through the third set of holes opened by the alternating injection pipe 25. After the gas injection is completed, the gate valve of the gas extraction pipe at the end of the air intake roadway 30 of the working face is opened to extract gas from the three coal seam sections.

[0080] S5, after the gas injection at the third coal seam section is completed and the nitrogen injection at the second coal seam section is no longer completed, the carbon dioxide controller 23E is used to move the carbon dioxide moving device 23 to the designated position, and the carbon dioxide injection pump 1 is opened to inject hot carbon dioxide displacement at the second coal seam section through the second set of holes opened by the alternating injection pipe 25. After the gas injection is completed, the gas extraction pipes arranged at the ends of the working face return air roadway 29 and the working face intake air roadway 30 are used to extract the gas of the second coal seam section.

[0081] S6. After a period of gas extraction, when the extraction rate drops significantly, turn on the alternating injection pipe button 33 to power on the alternating injection pipe 25 to generate heat, and adjust the extraction controller 22A to separate the double-layer disc 22E into two single-layer discs and rotate them for cooling.

[0082] S7. After a period of time, close the gate valve 17 on the gas extraction pipe 22, and repeat steps S1, S2, S3, S4, S5, and S6. By injecting nitrogen, water, and gas in sequence at different locations, gas extraction is achieved, thus realizing repeated extraction of coal seam gas.

[0083] In step 2, the alternating injection tube 25 is made of a material with high thermal and electrical conductivity. The outer shell is embedded with an electric fuse 25J and a resistor 25K, which are connected to the alternating injection tube button 33 through circuit 25I. The heat-generating section of the alternating injection tube 25 is part h placed in the coal seam 27 without the sealing device 26. The maximum heat generation temperature can reach about 100℃. The small hole radius r1 of the alternating injection tube 25 has an area of ​​S=πr1². The tube opening radius r2 of the alternating injection tube 25 has a heat generation surface area expression of 2πr2h-9×4×S.

[0084] In step 1, the diameter of the graphite particles is less than the width of the coal pores after liquid nitrogen fracturing, and the content of graphite particles in the water injection pump 10 does not exceed 1%. In step 2, after the alternating injection pipe 25 is energized and heat is generated, the graphite particles frozen on the surface of the coal matrix by liquid nitrogen conduct electricity and generate heat. Both of these factors together accelerate the vaporization process after the liquid nitrogen is frozen.

[0085] The method for evaluating the effect of liquid nitrogen fracturing on the coal seam in step 2 is as follows: After the graphite particles and coal dust are transported to the settling water tank 19, the bottom hole 20 of the water tank is opened to collect and separate the graphite particles and coal dust. The effect of liquid nitrogen fracturing on the coal seam is comprehensively considered according to the evaluation methods of graphite particles and coal dust. The evaluation method of coal dust can be expressed as: the longitudinal number of coal dust diameters assesses the degree of porosity development caused by fracturing, and the total amount of coal dust assesses the fracturing intensity. The evaluation method of graphite particles can be expressed as: the proportion Y of the collected graphite particles to the total amount of graphite particles added to the injection water. Then, the effective area of ​​liquid nitrogen fracturing in this case accounts for about Y times the space of the required fracturing coal seam.

[0086] In step 6, the heat generation temperature of the alternating injection pipe 25 after debugging is higher than that of the alternating injection pipe 25 in step 2; the extraction controller 22A is debugged, and the rectangular baffle 22B is retracted and rotated in the single-layer disc inside the pipe opening, thereby generating a section of negative air pressure zone from inside the pipe opening to outside the pipe opening.

[0087] In step 1, when liquid nitrogen is injected into the first coal seam segment and the effect of liquid nitrogen fracturing on the coal seam is evaluated by the device, it is no longer necessary to continue injecting liquid nitrogen. The total amount of liquid nitrogen used for the first coal seam segment is recorded by the flow meter 8 installed on the nitrogen injection pipeline 9. Then, the amount of liquid nitrogen required for fracturing the coal seam at the third and second coal seam segments in steps 3 and 4 is approximately the same as the total amount of liquid nitrogen used for fracturing the first coal seam segment. Then, the evaluation system of the device determines whether the coal seam needs to continue to be injected with liquid nitrogen for fracturing.

[0088] In one embodiment of the present invention, coal seam gas extraction involves many factors: 1. Coal seam occurrence conditions; 2. Enhancing the permeability of the coal seam to create channels for free gas movement; 3. Desorbing the gas adsorbed in the coal matrix; 4. Arrangement of gas extraction boreholes and mining mode; 5. Purity of gas extraction and disaster prevention.

[0089] In one embodiment of the present invention, a rectangular baffle 22B is also provided inside the gas extraction pipe 22, and a single-layer disc slides on the fixing rod 22C to be confined between the rectangular baffle 22B and another single-layer disc.

[0090] In one embodiment of the present invention, in step 2, graphite particles and coal dust are collected and separated by settling tank 19, and the effect of liquid nitrogen fracturing the coal seam is comprehensively considered according to the evaluation method. Then, it is determined whether to continue injecting liquid nitrogen to fracturing the coal seam again. If it is necessary to continue injecting liquid nitrogen, valve 11 is closed to stop water injection, and nitrogen injection pump 5 is turned on to re-inject liquid nitrogen to fracture the coal seam. If it is not necessary to continue injecting liquid nitrogen, proceed to the next step.

[0091] In one embodiment of the present invention, after the liquid nitrogen fracturing effect of the device is evaluated, when enough water is collected in the settling tank 19, the water tank valve 21 is opened. After the coal seam 27 is injected with water, the water flows into the settling tank 19 through the gas extraction pipe 22 to settle. The bottom hole 20 of the water tank is opened to remove impurities in the water. Then the return water pipe valve 18 is opened, and the water returns to the water injection pump 10 through the return water pipe 15 for the next coal seam water injection.

[0092] In one embodiment of the present invention, the portion of the alternating injection pipe 25 within the coal seam 27 includes a shell with nine rows of equally spaced holes. The space between the first and third rows is the location of the first coal seam segment and is the first group of holes. The space between the fourth and sixth rows is the location of the second coal seam segment and is the second group of holes. The space between the seventh and ninth rows is the location of the third coal seam segment and is the third group of holes.

[0093] Furthermore, such as Figures 3-7As shown, the mechanism of directional nitrogen, water, and carbon dioxide injection at different coal seam locations is as follows: The controller 24E of the liquid nitrogen / water nitrogen / water moving device 24 moves the closed circular baffle 24H to the position of the first position sensor 25E on the alternating injection pipe 25. Then, the three rows of holes on the second inner cylinder 24G align with the first, second, and third rows of holes on the outer shell of the alternating injection pipe 25, thus achieving directional nitrogen and water injection at the first coal seam location. Similarly, when the closed circular baffle 24H reaches the position of the third position sensor 25G on the alternating injection pipe 25, the outer shell of the alternating injection pipe 25... The first to sixth rows of holes on the outer shell are blocked by the inner shell cylinder 24G, and the three rows of holes on the inner shell cylinder 24G are aligned with the seventh, eighth, and ninth rows of holes on the outer shell of the alternating injection pipe 25. This allows for nitrogen and water injection into the third coal seam section. Similarly, when the closed circular baffle 24H reaches the position of the second position sensor 25F on the alternating injection pipe 25, the first, second, and third rows of holes on the outer shell of the alternating injection pipe 25 are blocked by the inner shell cylinder 24G, and the three rows of holes on the inner shell cylinder 24G are aligned with the fourth, fifth, and sixth rows of holes on the outer shell of the alternating injection pipe 25. This allows for nitrogen and water injection into the second coal seam section. Nitrogen and water injection are performed directionally at specific coal seam sections. Using the carbon dioxide controller 23E of the carbon dioxide moving device 23, the hollow circular baffle 23H is positioned at the first position sensor 25E of the alternating injection pipe 25. At this point, the three rows of holes on the outer cylinder 23G align with the first, second, and third rows of holes on the outer shell of the alternating injection pipe 25, thus achieving directional carbon dioxide displacement at the first coal seam section. Similarly, the hollow circular baffle 23H is positioned at the third position sensor 25G of the alternating injection pipe 25. At this point, the first to sixth rows of holes on the outer shell of the alternating injection pipe 25 are displaced by the outer cylinder. When the outer shell 23G is blocked and the three rows of holes on the outer shell 23G are aligned with the seventh, eighth, and ninth rows of holes on the outer shell of the alternating injection pipe 25, carbon dioxide can be injected to displace the third coal seam segment. Similarly, when the hollow circular baffle 23H reaches the position of the second position sensor 25F of the alternating injection pipe 25, the first, second, and third rows of holes on the outer shell of the alternating injection pipe 25 are blocked by the outer shell 23G, and the three rows of holes on the outer shell 23G are aligned with the fourth, fifth, and sixth rows of holes on the outer shell of the alternating injection pipe 25, carbon dioxide can be injected to displace the second coal seam segment.

[0094] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0095] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A coal seam gas extraction device, characterized in that, A coal seam (27) mining device comprises: a carbon dioxide injection pump (1), a nitrogen injection pump (5) and a water injection pump (10); the carbon dioxide injection pump (1) injects hot carbon dioxide into a carbon dioxide moving device (23) through a first pipeline; the nitrogen injection pump (5) and the water injection pump (10) inject liquid nitrogen or water into a nitrogen / water moving device (24) through a second pipeline; the coal seam (27) is provided with an alternating injection pipe (25) and a gas extraction pipe (22); the gas extraction pipe (22) is communicated with the water injection pump (10) through a water return pipeline (15); the alternating injection pipe (25) is provided with at least three groups of holes, and each group of holes is arranged in a coal seam section; the carbon dioxide moving device (23) and the nitrogen / water moving device (24) are arranged in the alternating injection pipe (25) and are provided with a group of holes, and the carbon dioxide moving device (23) is arranged outside the nitrogen / water moving device (24); the pipe opening of the alternating injection pipe (25) is a closed port (25H); each group of holes of the carbon dioxide moving device (23) and the nitrogen / water moving device (24) is provided with three rows of through holes; each group of holes of the alternating injection pipe (25) is provided with three rows of through holes, and each row of through holes comprises a top dense hole (25A), a first side hole (25B), a second side hole (25C) and a bottom hole (25D); and a first position sensor (25E), a second position sensor (25F) and a third position sensor (25G) are arranged on one row of through holes of the three groups of holes respectively; the carbon dioxide moving device (23) comprises an outer shell cylinder (23G) and a first inner shell cylinder (23I); the outer shell cylinder (23G) is provided with three rows of first corresponding holes with the same interval and the same aperture as the outer shell of the gas extraction pipe (22) beside a hollow circular baffle (23H); each row of first corresponding holes comprises a first top dense hole (23A), a first side dense hole (23B), a second side dense hole (23C) and a first bottom hole (23D); a gap between the hollow circular baffle (23H), the outer shell cylinder (23G) and the first inner shell cylinder (23I) is provided with a carbon dioxide controller (23E); the carbon dioxide controller (23E) controls a first telescopic rod (23F) to extend and retract; the second pipeline comprises a nitrogen injection pipeline (9), a water injection pipeline (13) and a three-way valve (14); the nitrogen injection pipeline (9) and the water injection pipeline (13) are communicated with the nitrogen / water moving device (24) through the three-way valve (14); the nitrogen injection pipeline (9) is provided with a valve II (6), a pressure gauge II (7) and a flowmeter (8); The nitrogen / water moving device (24) comprises a second inner shell cylinder (24G); the second inner shell cylinder (24G) is provided with three rows of second corresponding holes with the same spacing and aperture on the outer shell of the gas extraction pipe (22) beside the closed circular baffle (24H), each row of the second corresponding holes comprises a second top dense hole (24A), a third side dense hole (24B), a fourth side dense hole (24C) and a second bottom hole (24D); the first inner shell cylinder (23I) is further provided with a nitrogen / water controller (24E); and the nitrogen / water controller (24E) controls the extension and retraction of the second telescopic rod (24F).

2. The coal seam gas extraction device according to claim 1, characterized in that: The alternating injection pipe (25) and the gas extraction pipe (22) are fixed in the coal seam (27) through the hole sealing device (26); The length of the alternating injection pipe (25) in the coal seam (27) is shorter than the thickness of the coal seam (27); the alternating injection pipe (25) is arranged at intervals between the working face return airway (29) and the working face air inlet roadway (30), and the gas extraction pipe (22) is arranged in mirror image at both ends of the working face return airway (29) and the working face air inlet roadway (30).

3. The coal seam gas extraction device according to claim 1, characterized in that: The first pipeline is a carbon dioxide injection pipeline (4), and the carbon dioxide injection pipeline (4) is provided with a valve I (2) and a pressure gauge I (3); The nitrogen injection pipeline (9) and the water injection pipeline (13) are further respectively communicated with a nitrogen injection pump (5) and a water injection pump (10); and the water injection pipeline (13) is provided with a valve III (11) and a pressure gauge III (12).

4. The coal seam gas extraction device according to claim 1, characterized in that: One end of the gas extraction pipe (22) is further communicated with the extraction main pipe (16) through a gate valve (17); the gas extraction pipe (22) comprises a pipe body, the pipe body is fixedly provided with an extraction controller (22A), the extraction controller (22A) controls a double-layer disc (22E) through an electric wire (22D); the double-layer disc (22E) comprises two single-layer discs, one single-layer disc is arranged at the end of the pipe body, and the other single-layer disc is slidably arranged on a fixed rod (22C) and electrically connected with the extraction controller (22A); the two single-layer discs are both wound with an insulating resistance wire (22F).

5. The coalbed gas extraction device of claim 4, wherein: The pipe body is further fixedly connected with a precipitation water tank (19); a return water pipe valve (18) is arranged at one end of the return water pipeline (15) close to the precipitation water tank (19); a water tank pull-out hole (20) is arranged at the bottom of the precipitation water tank (19); and a water tank valve (21) is further arranged on the side wall of the precipitation water tank (19).

6. A coal seam gas extraction method comprising the coal seam gas extraction device according to any one of claims 1-5, characterized in that, It comprises: S1, using the nitrogen / water controller (24E) to operate the nitrogen / water moving device (24) to the designated position, opening the water injection pump (10) to make the graphite particles and water flow into the first coal seam section position from the first group of holes of the alternating injection pipe (25) through the channel of the nitrogen / water moving device (24), and injecting water to wet the coal seam (27); when a small amount of water is collected in the precipitation water tank (19), the water tank valve (21) is opened, the water injection pump (10) is closed, the nitrogen injection pump (5) is opened, and liquid nitrogen is injected to crack the first coal seam section position; S2, when the settling tank (19) does not collect water, the nitrogen filling pump (5) is closed, the alternating injection pipe button (33) is opened to make the alternating injection pipe (25) generate heat, and when the speed of water collected in the settling tank (19) changes from the fastest to very slow, the alternating injection pipe button (33) is closed, and then when the settling tank (19) does not collect water, the effect of liquid nitrogen induced cracking of the coal seam is evaluated by analyzing the proportion of graphite particles and coal dust flowing into the settling tank (19), so as to determine whether to inject liquid nitrogen again; S3, after the first coal seam section position does not need to inject liquid nitrogen, the carbon dioxide moving device (23) is operated to the specified position by using the carbon dioxide controller (23E), the hot carbon dioxide gas is flowed out from the first corresponding hole through the carbon dioxide moving device (23) by opening the carbon dioxide filling pump (1) to inject hot carbon dioxide displacement to the first coal seam section position, at the same time, the nitrogen / water moving device (24) is operated to the specified position by using the nitrogen / water controller (24E), the water injection pump (10) filled with plasma and water is opened to flow out from the third group of holes of the alternating injection pipe (25) through the channel of the nitrogen / water moving device (24) to inject water to wet the coal seam (27) of the third coal seam section position, when a small amount of water is collected in the settling tank (19) arranged at the end of the working face air inlet roadway (30), the water injection pump (10) is closed, the nitrogen filling pump (5) is opened, and liquid nitrogen is injected to crack the third coal seam section position, and the step S2 is repeated; When the first coal seam section position injects carbon dioxide displacement, the gate valve (17) arranged in the gas extraction pipe of the working face return air roadway (29) is opened to extract the gas of the first coal seam section position; S4, after the nitrogen injection of the third coal seam section position is completed, the nitrogen / water moving device (24) is operated to the specified position by using the nitrogen / water controller (24E), the water injection pump (10) filled with plasma and water is opened to flow out from the second group of holes of the alternating injection pipe (25) through the channel of the nitrogen / water moving device (24) to inject water to wet the coal seam (27) of the second coal seam section position, the water tank valve (21) is opened, and when a small amount of water is collected in the settling tank (19), the water injection pump (10) is closed, the nitrogen filling pump (5) is opened, and liquid nitrogen is injected to crack the third coal seam section position, and the step S2 is repeated; Then, the carbon dioxide moving device (23) is operated to the specified position by using the carbon dioxide controller (23E), the hot carbon dioxide gas is injected to the third coal seam section position through the third group of holes of the alternating injection pipe (25) by opening the carbon dioxide filling pump (1), and after the gas injection is completed, the gate valve arranged in the gas extraction pipe of the working face air inlet roadway (30) is opened to extract the gas of the three coal seam section positions; S5, after the third coal seam section position injection gas end and the second coal seam section position no longer injection of nitrogen, using carbon dioxide controller (23E) carbon dioxide mobile device (23) to run to the designated position, open carbon dioxide injection pump (1) through the alternate injection pipe (25) open the second group of holes set to the second coal seam section position injection of hot carbon dioxide displacement, after the injection end by the arrangement in the working face return air roadway (29) and working face air entry roadway (30) roadway end of the gas extraction pipe together extraction of the second coal seam gas; S6, after a period of time of gas extraction, when the extraction rate is greatly reduced, open the alternate injection pipe button (33) to make the alternate injection pipe (25) power heating, and debug the extraction controller (22A) to make the double-layer disc (22E) separate into two single-layer discs and rotate to refrigerate; S7, after a period of time, close the gate valve (17) on the gas extraction pipe (22), and then repeat steps S1, S2, S3, S4, S5, S6, by injecting nitrogen, water and gas in different positions in sequence, the repeated extraction of coal seam gas is realized.

7. The method of claim 6, wherein: In the step S1, after the first coal seam section position is started to inject liquid nitrogen to evaluate the effect of liquid nitrogen on the coal seam, the total amount of liquid nitrogen injected in the first coal seam section position is recorded by the flow meter (8) installed on the nitrogen injection pipeline (9). In the steps S3 and S4, the initial liquid nitrogen injection amount of the third coal seam section position and the second coal seam section position is the total amount of liquid nitrogen injected in the first coal seam section position.

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