A microwave coal breaking, pressure releasing and permeability improving device and method

Abstract

The present application belongs to the field of coal seam pressure relief and gas control, and specifically relates to a microwave coal breaking, pressure relief and permeability improvement device and method. The device comprises a microwave generating device, a microwave transmission device, a microwave heating antenna, a hole sealing bag and an inert gas device. The microwave generating device generates microwaves which are transmitted to the microwave heating antenna through the microwave transmission device. The microwave heating antenna is arranged in the area to be permeability improved in the borehole, and the borehole opening is sealed by the hole sealing bag. The inert gas device prevents the risk of fire caused by overheating of the coal body. The method arranges the microwave transmission device and the microwave heating antenna in the borehole in the area to be permeability improved, transmits microwaves to the inside of the borehole, causes the internal different minerals of the coal body to heat up through microwave radiation, forms a local temperature difference, generates thermal stress, causes structural damage and crushing of the coal body near the microwave radiation borehole, forms a free surface and provides a deformation space for the coal body, shifts the stress peak to the deep part of the coal seam, thereby improving the permeability of the coal seam through pressure relief and improving the gas extraction efficiency. The present application is energy-saving and environmentally friendly, and has good pressure relief and permeability improvement effect.

Description

Technical Field

[0001] This invention belongs to the field of coal seam depressurization and permeability enhancement gas control, specifically a microwave coal breaking depressurization and permeability enhancement device and method. Background Technology

[0002] For outburst-prone coal seams where protective layers cannot be mined, pre-drainage of coal seam gas is the most effective measure for preventing coal and gas outbursts. Pre-drainage can reduce the gas content of high-gas coal seams, thereby mitigating or eliminating the risk of coal and gas outbursts. As shallow coal mining is nearing depletion and mining depths increase, the immense ground stress reduces the permeability coefficient of the coal seam, necessitating artificial enhancement measures to improve the effectiveness of pre-drainage in preventing coal and gas outbursts. Currently, commonly used measures include hydraulic and mechanical permeability enhancement. Hydraulic permeability enhancement measures include hydraulic fracturing and hydraulic slotting, and engineering practice has proven that these measures significantly increase gas extraction. However, practical applications present some problems. For example, borehole collapse is prone to occur in soft coal seams, while in hard coal seams, ultra-high pressure equipment is required to break the coal body, resulting in high equipment requirements and low economic and safety levels. Mechanical permeability enhancement suffers from difficulties in slag removal and low borehole enlargement efficiency, and mechanical borehole enlargement equipment is expensive and lacks flexibility.

[0003] To address the issues of hydraulic and mechanical permeability enhancement, existing technologies have proposed microwave permeability enhancement. However, existing microwave coal crushing and depressurization permeability enhancement devices suffer from dispersed microwave energy. Even with improvements in concentrated microwave energy, the flue gas generated during microwave coal crushing still affects the microwave generator. Furthermore, existing microwave coal crushing and depressurization permeability enhancement devices are not accurately positioned, with deviations between the actual and set microwave crushing locations. Additionally, existing microwave coal crushing devices lack sufficient safety features. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a microwave coal crushing, depressurization, and permeability enhancement device and a permeability enhancement method based on the device. The microwave coal crushing, depressurization, and permeability enhancement device includes a microwave generator, a microwave transmission device, a microwave heating antenna, and a rail sleeve. The rail sleeve is fixed inside the borehole, and a guide rail is provided on the inner wall of the rail sleeve. The microwave transmission device and the microwave heating antenna are sealed inside the rail sleeve, and the microwave generator emits microwaves that are transmitted to the microwave heating antenna through the microwave transmission device.

[0005] The microwave transmission device includes an aluminum alloy waveguide, a quartz glass plate, and guide wheels. The aluminum alloy waveguide is tubular with flanges at both ends. Multiple aluminum alloy waveguides are fixedly connected by flanges. Guide wheels are provided at the lower part of the flanges and work in conjunction with guide rails. A quartz glass plate is provided inside the aluminum alloy waveguide.

[0006] The microwave heating antenna includes a mounting base, a quartz glass cover, and a slit antenna. The mounting base is ring-shaped, with the slit antenna fixed near the inner ring and the quartz glass cover fixed near the outer ring. The quartz glass cover completely encloses the slit antenna inside, and the slit antenna has multiple slits for radiating microwaves outward. The mounting base is detachably connected to the flange at the end of the aluminum alloy waveguide.

[0007] Preferably, the three-phase power supply, continuous wave magnetron, and straight waveguide in the microwave generator are placed inside a protective housing, and the three-phase power supply, straight waveguide, circulator water load, and three-pin tuner are connected in sequence; the continuous wave magnetron is installed on the straight waveguide, the circulator water load is connected to a water chiller, and the power adjustment platform is connected to the three-phase power supply to adjust the operating parameters of the microwave generator.

[0008] Preferably, the rail sleeve is made of polyetheretherketone (PEEK) material, and includes a sleeve wall and a guide rail disposed on the inner wall of the sleeve wall, wherein the outer wall of the sleeve wall is tightly attached to the drill hole.

[0009] Preferably, the guide wheel is located at the lower part of the flange at the outer end of each aluminum alloy waveguide section; the aluminum alloy waveguide end is provided with a stepped opening, and the stepped openings of adjacent aluminum alloy waveguides form an annular groove, and the quartz glass plate is placed in the annular groove, dividing the inner cavity of each aluminum alloy waveguide into an independent space.

[0010] Preferably, the outermost aluminum alloy waveguide end is connected to a three-pin tuner via a flange.

[0011] Preferably, the quartz glass cover is fixed to the outer periphery of the mounting base by a mounting cover plate, and a sealing ring is used to ensure airtightness. The slot antenna is made of aluminum alloy.

[0012] Preferably, it also includes a sealing bag and an inert gas device. The inert gas device is used to inject inert gas into the borehole to prevent the coal seam from overheating and igniting during microwave heating of the coal seam. The sealing bag is fixed between the outer periphery of the microwave transmission device and the inner wall of the rail sleeve to seal the borehole outlet.

[0013] Preferably, the inert gas device includes a nitrogen source and a vacuum pump. The nitrogen source is connected to the rail sleeve via a nitrogen delivery pipe for supplying nitrogen into the borehole, and the vacuum pump is connected to the rail sleeve via a vacuum pipe for extracting the flue gas generated in the borehole during the microwave anti-reflection process.

[0014] Preferably, the sealing bag is a polyurethane sealing bag, which is fixed between the outer periphery of the microwave transmission device and the inner wall of the sleeve, and the nitrogen delivery pipe and the extraction pipe are located between the sealing bag and the inner wall of the sleeve.

[0015] The anti-reflective method includes the following steps:

[0016] a. Design drilling and microwave radiation parameters based on sampling and testing results and actual production conditions at the working face;

[0017] b. Drilling holes into the coal seam;

[0018] c. Install the microwave coal breaking and decompression device, and send the rail sleeve into the borehole and fix it to the borehole wall; connect the microwave generator and the microwave transmission device, connect the microwave transmission device and the microwave heating antenna, and send the microwave transmission device and the microwave heating antenna into the rail sleeve through the cooperation of the guide wheel and the guide rail.

[0019] d. Fix the sealing bag between the outer periphery of the microwave transmission device and the inner wall of the sleeve, and place the nitrogen delivery pipe and the extraction pipe between the sealing bag and the inner wall of the sleeve for sealing;

[0020] e. After setting the microwave power and radiation time to fill the borehole with nitrogen, turn on the microwave generator to perform microwave coal breaking, depressurization, and permeation enhancement, continuously filling the borehole with nitrogen and extracting the flue gas inside the borehole.

[0021] In the preferred step d, the nitrogen delivery pipe is arranged near the microwave heating antenna, and the extraction pipe is arranged near the borehole opening; the leaking parts of the sealing hole are sealed with silicone sealant for secondary sealing to prevent leakage; after sealing the hole, a metal shielding mesh is arranged near the borehole opening.

[0022] The inventive points and beneficial effects of this invention are as follows: 1. This invention uses a fracture antenna as a radiator. During the microwave penetration enhancement process, the fracture antenna focuses microwave energy, rapidly heating the coal near the antenna and causing it to break up, forming a free surface that relieves pressure on the coal near the borehole. The stress peak shifts to the deeper part of the coal seam, significantly increasing the permeability of a large area of ​​the coal seam. 2. This invention uses a multi-section detachable connection form for the aluminum alloy waveguide, which is convenient for different drilling depths. It also allows for the installation of guide wheels and quartz glass. The guide wheels and rails facilitate the installation of the microwave transmission device and the microwave heating antenna. The quartz glass and the external quartz glass cover of the fracture antenna prevent the flue gas generated by microwave coal breaking from entering the microwave generator and affecting the microwave coal breaking process. 3. This invention is the first to use an inert gas device in the microwave coal seam penetration enhancement process, ensuring that the coal near the microwave heating antenna will not ignite during microwave heating, thus improving the safety of the microwave coal breaking, pressure relief, and penetration enhancement technology. 4. This invention offers fast microwave pressure relief and penetration enhancement of the coal seam, with a short working cycle, high efficiency, and energy saving and environmental protection. Components such as the microwave generator, microwave transmission device, and microwave heating antenna can be used repeatedly and for extended periods. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the microwave coal crushing and depressurization device of the present invention;

[0024] Figure 2This is a partial structural diagram of the microwave transmission device of the present invention;

[0025] Figure 3 This is a schematic diagram of the microwave heating antenna structure of the present invention;

[0026] In the diagram: 1-Microwave generator; 101-Protective housing; 102-Three-phase power supply; 103-Continuous wave magnetron; 104-Circulator water load; 105-Three-pin tuner; 106-Power regulation platform; 107-Water chiller; 108-Signal connection port; 109-Straight waveguide; 110-Waveguide connection hole; 2-Microwave transmission device; 201-Flange; 202-Aluminum alloy waveguide; 203-Quartz Glass plate; 204-Guide wheel; 3-Microwave heating antenna; 301-Mounting base; 302-Sealing ring; 303-Cover plate; 304-Quartz glass cover; 305-Crack; 306-Crack antenna; 4-Sealing bag; 5-Rail sleeve; 501-Sleeve wall; 502-Guide rail; 6-Inert gas device; 601-Nitrogen source; 602-Evacuation pump; 603-Nitrogen delivery pipe; 604-Evacuation pipe. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] This invention provides a microwave coal breaking, decompression, and permeability enhancement device and method. By arranging a microwave coal breaking and permeability enhancement device and microwave radiation boreholes in the working face roadway, microwave radiation is applied to low-permeability coal seams. The thermal effect of microwave radiation on different mineral components in the coal body near the borehole leads to strong thermal stress, causing structural damage and breakage of the coal body near the microwave radiation borehole, forming free surfaces and providing deformation space for the coal body. This causes the stress peak to transfer to the deeper part of the coal seam, thereby enhancing the permeability of the coal seam through decompression and achieving the purpose of strengthening gas extraction.

[0029] Based on our research on coal and petrology, we have discovered that: 1. Coal contains various minerals with different dielectric properties. This causes microwaves to create differentiated thermal effects on these minerals, resulting in temperature gradients and strong thermal stress. When the thermal stress in a certain area of ​​the coal exceeds the tensile strength between the coal matrix and the minerals, tensile or shear microcracks appear inside and outside the minerals. These microcracks interconnect to form macrocracks, thereby reducing the strength of the coal and causing it to break. 2. The thermal effect of microwaves on coal is holistic; structural damage and breakage occur in all areas within the influence range, thus increasing the permeability of the coal seam within that range. 3. The thermal effect of microwaves on coal causes it to break, creating free surfaces inside the borehole and providing deformation space for the coal. This allows the stress peak to shift to deeper parts of the coal seam, achieving a pressure relief effect. Based on the above knowledge, we have designed a method for breaking coal, relieving pressure, and increasing permeability using microwave radiation. The technical solution adopted in this invention is as follows:

[0030] like Figure 1 The diagram shows a microwave coal breaking, depressurization, and permeability enhancement device according to the present invention, comprising a microwave generating device 1, a microwave transmitting device 2, a microwave heating antenna 3, a sealing bag 4, a rail sleeve 5, and an inert gas device 6. The rail sleeve 5 is fixed inside the borehole. The microwave transmitting device 2 and the microwave heating antenna 3 are arranged inside the rail sleeve 5 inside the borehole. The microwave generating device 1 emits microwaves, which are transmitted to the microwave heating antenna 3 through the microwave transmitting device 2. The microwave heating creates a huge temperature difference in the coal seam, generating thermal stress, causing the coal body around the borehole to break, providing deformation space for the coal seam, and transferring the stress peak to the interior of the coal seam, thereby improving the permeability of the coal seam. The inert gas device 6 is used to inject inert gas into the borehole to prevent the coal seam from overheating and igniting during the microwave heating process. The sealing bag 4 is fixed between the outer periphery of the microwave transmitting device 2 and the inner wall of the rail sleeve 5 to seal the borehole outlet.

[0031] The microwave generator 1 includes a protective housing 101, a three-phase power supply 102, a continuous wave magnetron 103, a circulator water load 104, a three-pin tuner 105, a power adjustment platform 106, a water chiller 107, a signal connection port 108, a straight waveguide 109, and a waveguide connection hole 110. The three-phase power supply 102, the continuous wave magnetron 103, and the straight waveguide 109 are housed within the protective housing 101, with the outer end of the straight waveguide 109 located at the waveguide connection hole 110 of the protective housing 101. The three-phase power supply 102... A straight waveguide 109, a circulator water load 104, and a three-pin tuner 105 are connected in sequence. A continuous wave magnetron 103 is installed on the straight waveguide 109. The circulator water load 104 is connected to a water chiller 107. The water chiller 107 reduces the temperature of the continuous wave magnetron 103 through water circulation. The power adjustment platform 106 is connected to a three-phase power supply 102 via wiring to adjust the power, operating time, and other operating parameters of the microwave generator 1. The protective housing 101 is provided with a signal connection port 108 for wiring.

[0032] The tracked sleeve 5 is made of polyetheretherketone and includes a sleeve wall 501 and a guide rail 502 disposed on the inner wall of the sleeve wall 501. The outer wall of the sleeve wall 501 is tightly attached to the drill hole.

[0033] like Figure 1-2As shown, the microwave transmission device 2 includes multiple aluminum alloy waveguides 202, quartz glass plates 203, and guide wheels 204. The aluminum alloy waveguides 202 are rectangular tubes with flanges 201 at both ends. Multiple aluminum alloy waveguides 202 are fixedly connected by flanges 201. Guide wheels 204 are provided at the lower part of the flanges and work in conjunction with guide rails 502. Specifically, the guide wheels 204 are located at the lower part of the flanges 201 at the outer end of each section of aluminum alloy waveguide 202. The ends of the aluminum alloy waveguides 202 are provided with stepped openings, and the stepped openings of adjacent aluminum alloy waveguides 202 form annular grooves. The quartz glass plates 203 are placed in the annular grooves, dividing the inner cavity of each aluminum alloy waveguide 202 into an independent space to prevent flue gas from entering the aluminum alloy waveguide 202. The outermost end of the aluminum alloy waveguide 202 is connected to a three-pin tuner 105 through a flange.

[0034] like Figure 1 , 3 As shown, the microwave heating antenna 3 includes a mounting base 301, a quartz glass cover 304, and a slit antenna 306. The mounting base 301 is a rectangular ring. The slit antenna 306 is fixed near the inner ring, and the quartz glass cover 304 is fixed near the outer ring by a mounting cover plate 303. A sealing ring 302 is used to ensure airtightness. The quartz glass cover 304 completely covers the slit antenna 306 inside. The slit antenna 306 is made of aluminum alloy and has multiple slits 305 for radiating microwaves outward. The mounting base 301 is detachably connected to the flange 201 at the end of the aluminum alloy waveguide 202.

[0035] like Figure 1 As shown, the inert gas device 6 includes a nitrogen source 601 and a vacuum pump 602. The nitrogen source 601 is connected to the rail sleeve 5 through a nitrogen delivery pipe 603 for delivering nitrogen into the borehole. The vacuum pump 602 is connected to the rail sleeve 5 through a vacuum pipe 604 for extracting the flue gas generated in the borehole during the microwave anti-reflection process.

[0036] The sealing bag 4 is a polyurethane sealing bag, which is fixed between the outer periphery of the microwave transmission device 2 and the inner wall of the sleeve wall 501. The nitrogen delivery pipe 603 and the extraction pipe 604 are located between the sealing bag 4 and the inner wall of the sleeve wall 501.

[0037] The present invention also provides a permeability enhancement method based on the aforementioned microwave coal crushing and depressurization device, comprising the following steps:

[0038] a. Based on the underground sampling and testing results and the actual production conditions at the working face, the coal seam in this embodiment is determined to be a near-horizontal coal seam with a mining height of 3m, hard coal quality, and a permeability coefficient of 0.08m. 2 / MPa 2·d, the coal seam has a low permeability coefficient and is a relatively difficult coal seam to pump out; the drilling construction parameters and microwave radiation parameters are designed based on the underground sampling and testing results and the actual production conditions of the working face. Specifically, in this embodiment, the interval between boreholes is 1m, the microwave radiation power is set at 15kW, and the single microwave radiation time is 10min.

[0039] b. Drill holes into the coal seam, with the drilling direction horizontal, using a mechanical drilling rig to drill holes to the required fracturing area, with a 1m interval between holes;

[0040] c. Install the microwave coal breaking and depressurization device, send the rail sleeve 5 to the bottom of the borehole and fix it to the borehole wall; connect the three-pin tuner 105 and the microwave transmission device 2 through the flange 201, connect the microwave transmission device 2 and the microwave heating antenna 3 through the mounting base 301, and send the microwave transmission device 2 and the microwave heating antenna 3 into the rail sleeve 5 through the guide wheel 204 cooperating with the guide rail 502;

[0041] d. Fix the sealing bag 4 between the outer periphery of the microwave transmission device 2 and the inner wall of the sleeve wall 501. Place the nitrogen delivery pipe 603 and the extraction pipe 604 between the sealing bag 4 and the inner wall of the sleeve wall 501. The nitrogen delivery pipe 603 is placed near the microwave heating antenna, and the extraction pipe 604 is placed near the borehole opening. After the sealing bag 4 is fixed, allow the contents to mix and react, causing the polyurethane to expand, thereby achieving the purpose of fixing and sealing the hole. Use silicone sealant to seal any leaks in the sealing area to prevent leakage. After sealing, place a metal shielding mesh near the borehole opening.

[0042] e. Based on the microwave construction parameters designed in step a, set the microwave power and radiation time on the power adjustment platform 106, turn on the nitrogen source 601 to fill the borehole with nitrogen, turn on the microwave generator 1 to perform microwave coal breaking, depressurization and permeation enhancement, and turn on the air pump 602 to extract the flue gas in the borehole (while continuously filling the borehole with nitrogen). Based on the on-site implementation, monitor the coal seam breaking and depressurization effect in real time during the permeation enhancement process.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microwave coal crushing, pressure relief, and permeability enhancement method, comprising using a microwave coal crushing, pressure relief, and permeability enhancement device for construction, characterized in that... The microwave coal breaking, depressurization and permeability enhancement device includes a microwave generator, a microwave transmission device, a microwave heating antenna and a rail sleeve; the rail sleeve is fixed inside the borehole and a guide rail is provided on the inner wall of the rail sleeve; the microwave transmission device and the microwave heating antenna are sealed inside the rail sleeve, and the microwave generator emits microwaves which are transmitted to the microwave heating antenna through the microwave transmission device. The microwave transmission device includes an aluminum alloy waveguide, a quartz glass plate, and guide wheels. The aluminum alloy waveguide is tubular with flanges at both ends. Multiple aluminum alloy waveguides are fixedly connected by the flanges. Guide wheels are provided at the lower part of the flanges and work in conjunction with guide rails. The ends of the aluminum alloy waveguides are provided with stepped openings. The stepped openings of adjacent aluminum alloy waveguides form annular grooves. The quartz glass plate is placed in the annular grooves, dividing the inner cavity of each aluminum alloy waveguide into an independent space. The microwave heating antenna includes a mounting base, a quartz glass cover, and a slit antenna. The mounting base is ring-shaped, with the slit antenna fixed near the inner ring and the quartz glass cover fixed near the outer ring. The quartz glass cover completely encloses the slit antenna inside, and the slit antenna has multiple slits for radiating microwaves outward. The mounting base is detachably connected to the flange at the end of the aluminum alloy waveguide. It also includes a sealing bag and an inert gas device. The inert gas device is used to inject inert gas into the borehole to prevent the coal seam from overheating and igniting during microwave heating of the coal seam. The sealing bag is fixed between the outer periphery of the microwave transmission device and the inner wall of the rail sleeve to block the borehole outlet. Includes the following steps: a. Design drilling and microwave radiation parameters based on sampling and testing results and actual production conditions at the working face; b. Drilling holes into the coal seam; c. Install the microwave coal breaking and decompression device, send the rail sleeve into the bottom of the borehole and fix it to the borehole wall; connect the microwave generator and the microwave transmission device, connect the microwave transmission device and the microwave heating antenna, and send the microwave transmission device and the microwave heating antenna into the rail sleeve through the cooperation of the guide wheel and the guide rail. d. Fix the sealing bag between the outer periphery of the microwave transmission device and the inner wall of the sleeve, and place the nitrogen delivery pipe and the extraction pipe between the sealing bag and the inner wall of the sleeve for sealing; e. After setting the microwave power and radiation time to fill the borehole with nitrogen, turn on the microwave generator to perform microwave coal breaking, depressurization, and permeation enhancement, and extract the flue gas from the borehole.

2. The method according to claim 1, characterized in that, The three-phase power supply, continuous wave magnetron, and straight waveguide in the microwave generator are housed in a protective enclosure. The three-phase power supply, straight waveguide, circulator water load, and three-pin tuner are connected in sequence. The continuous wave magnetron is installed on the straight waveguide. The circulator water load is connected to a water chiller. The power adjustment platform is connected to the three-phase power supply to adjust the operating parameters of the microwave generator.

3. The method according to claim 1, characterized in that, The tracked sleeve is made of polyetheretherketone and includes a sleeve wall and a guide rail disposed on the inner wall of the sleeve wall. The outer wall of the sleeve wall is tightly attached to the drilled hole.

4. The method according to claim 1, characterized in that, The guide wheel is located at the lower part of the flange at the outer end of each aluminum alloy waveguide section.

5. The method according to claim 2, characterized in that, The outermost aluminum alloy waveguide end is connected to the three-pin tuner via a flange.

6. The method according to claim 1, characterized in that, The quartz glass cover is fixed to the outer periphery of the mounting base by a mounting cover plate, and a sealing ring is used to ensure airtightness. The slot antenna is made of aluminum alloy.

7. The method according to claim 1, characterized in that, The inert gas device includes a nitrogen source and a pump. The nitrogen source is connected to the rail sleeve through a nitrogen delivery pipe to deliver nitrogen into the borehole. The pump is connected to the rail sleeve through a pumping pipe to extract the flue gas generated in the borehole during the microwave anti-reflection process.

8. The method according to claim 7, characterized in that, The sealing bag is a polyurethane sealing bag, which is fixed between the outer periphery of the microwave transmission device and the inner wall of the sleeve. The nitrogen delivery pipe and the extraction pipe are located between the sealing bag and the inner wall of the sleeve.

9. The method according to claim 8, characterized in that, In step d, the nitrogen delivery pipe is positioned near the microwave heating antenna, and the extraction pipe is positioned near the borehole opening.

10. The method according to claim 9, characterized in that, For any leaks in the borehole, a secondary sealant with silicone sealant is used to prevent further leakage. After sealing, a metal shielding mesh is installed near the borehole opening.

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