A method and equipment for gas extraction from soft coal seams based on the synergistic effect of CO2 fracturing and permeability enhancement and nanofluids.

Abstract

The present application belongs to the field of coal seam gas extraction, and discloses a soft coal seam gas extraction method and equipment based on CO2 induced fracturing and nano fluid cooperation. During the extraction of soft coal seam gas, the traditional induced fracturing is difficult to achieve uniform fracturing, either local fracturing is insufficient or the coal body is excessively crushed, the coal seam fracture connectivity rate is low, and the gas flow is affected. The method arranges liquid CO2 phase change fracturing holes and gas extraction holes in a net format with a 3-5m interval, after supercritical CO2 (heated to above 31.1℃ or pressure ≥7.38MPa) fracturing and permeation, nano fluid (permeation speed increased by 30%-50% compared with water) is injected, the sealing length is ≥5m (air leakage rate ≤0.5% / d), and then the extraction equipment is connected; the equipment contains a slag removal tank, a swingable air blowing pipe and an automatic slag removal mechanism. It can improve the coal seam fracture connectivity rate, increase the gas displacement efficiency by 25%-35%, prolong the crack stability time, reduce the risk of coal body collapse, the separation rate of the equipment for coarse coal powder with a particle size ≥0.1mm is above 92%, and it is suitable for safe and efficient gas extraction in soft coal seams.

Description

Technical Field

[0001] This invention relates to the field of coal seam gas extraction, and particularly to a method based on... A method and equipment for gas extraction from soft coal seams through the synergistic effect of fracturing and permeability enhancement and nanofluids. Background Technology

[0002] When mining soft coal seams, if the gas accumulated in the coal seam is not dealt with in time, it can easily lead to safety hazards. Therefore, it is necessary to extract the gas to ensure mining safety.

[0003] Currently, the methods used for gas drainage in soft coal seams have several problems. Traditional fracturing methods struggle to achieve uniform fracturing, resulting in either insufficient local fracturing or excessive coal fragmentation, leading to low connectivity of coal seam fractures and hindering gas flow channels. Soft coal seams have low coal strength, and traditional fracturing methods apply high impact pressure, easily triggering coal seam collapse or borehole deformation, increasing construction risks. Furthermore, coal seam fractures close rapidly under the weight of the coal and geostress, typically showing significant closure within a few days. This causes a sharp drop in gas drainage efficiency in a short period, resulting in a short stabilization period and limited cumulative drainage volume.

[0004] Meanwhile, the gas displacement effect is poor. In traditional methods, the coal body has poor hydrophilicity, making it difficult for the aqueous phase to penetrate the coal pores and for the gas to be effectively displaced. Some fracturing processes also produce harmful gases, affecting the underground working environment and the surface ecology.

[0005] Regarding extraction equipment, slag removal often relies on gravity settling or single-screen filtration, resulting in incomplete impurity separation and easy accumulation of clogging in pipelines, requiring frequent shutdowns for cleaning. Furthermore, the filter screen, due to its fixed airflow injection position, is prone to rapid localized clogging, necessitating equipment disassembly for cleaning, increasing maintenance time and costs. To address these issues, this invention proposes a method based on... A method and equipment for gas extraction from soft coal seams through the synergistic effect of fracturing and permeability enhancement and nanofluids. Summary of the Invention

[0006] This invention provides a basis A method and equipment for gas extraction from soft coal seams that combines fracturing and permeability enhancement with nanofluids has been developed, overcoming the shortcomings of existing technologies.

[0007] This invention provides the following technical solution: based on A method for gas extraction from soft coal seams through the synergistic effect of fracturing and permeability enhancement and nanofluids includes the following steps: S1: Construct floor-penetrating boreholes at designed intervals in soft coal seams, while simultaneously arranging liquid... Phase change fracturing holes and gas extraction holes are arranged alternately to form a grid structure. This grid layout ensures that fracturing energy uniformly covers the coal seam. A drilling rig is then used to extract the liquid... The phase change fracturing device is pushed to the target coal seam depth (error ≤ ±0.5m) and connected to the detonator via a detonating wire to ensure synchronous triggering of the fracturing device; S2: Inject high-pressure liquid into the fracturing device It is detonated after being heated (to above 31.1℃) or pressurized (pressure ≥ 7.38MPa) to reach a supercritical state; supercritical It has excellent diffusivity and expansibility. Combined with the grid-like fracturing pore arrangement, it achieves uniform fracturing and permeability enhancement, resulting in a larger fracturing range and avoiding insufficient fracturing or excessive pulverization of the coal body in some areas. S3: Nanofluid is injected into the fractured coal seam using a high-pressure pump. Under high pressure, the nanofluid rapidly penetrates to... Within the micro-fractures formed by fracturing (the permeation rate is 30%-50% higher than that of clean water); utilizing its surface activity (surface tension reduced to 30-40 mN / m), it can peel off coal particles, expand fracture width and connectivity; simultaneously, nanofluids can also enhance coal wettability and hydrophilicity (coal contact angle reduced from 75°-85° to 30°-45°), making it easier for the aqueous phase to penetrate the coal pores during subsequent hydraulic fracturing, resulting in better gas displacement and improved coal seam hydraulic fracturing effect (displacement efficiency increased by 25%-35%), significantly promoting gas flow; in addition, nanofluid particles are also porous media (specific surface area 50-100 m² / g), which can fill the tiny pores at the fracture tip, effectively supporting fractures and pores and delaying fracture closure; S4: Insert a suction pipe into the borehole and seal the borehole with cement slurry or a bag-type sealing device (sealing length ≥ 5m) to ensure airtightness (leakage rate ≤ 0.5% / d); connect the suction pipe to the extraction equipment, connect the gas outlet of the extraction equipment to the extraction main pipe, and finally connect it to the gas extraction pump station (negative pressure -15 to -25kPa) to achieve stable gas extraction.

[0008] The designed spacing in the soft coal seam of S1 is 5-8m, with liquid... The spacing between the phase change fracture pores and the gas extraction pores is 3-5m. The high-pressure liquid in S2... The pressure is 20-25 MPa; the nanofluid in S3 is nano-SiO2 or water-based fluid with a concentration of 0.5%-1.0%; and the water-cement ratio of the cement slurry in S4 is 1:1.2.

[0009] This invention also proposes an extraction device for extracting samples based on... The gas treatment device for soft coal seams using fracturing and permeability enhancement combined with nanofluids includes a housing and a main pipe. A slag removal tank is fixedly connected to one side of the housing. The slag removal tank has a variable diameter, with the upper diameter being larger than the lower diameter. An air inlet pipe connected to an extraction pipe is fixedly connected to one side of the slag removal tank. The air inlet pipe is positioned on one side of the slag removal tank so that air entering the slag removal tank rotates around the inner wall of the slag removal tank. An air outlet pipe is fixedly connected to the center of the top of the slag removal tank. The end of the air outlet pipe extends into the slag removal tank, and a rotary joint is installed at the other end of the air outlet pipe. A rotatable air blowing pipe is installed at one end of the rotary joint. The air blowing pipe rotates through the housing and has an air outlet at its top. A slag discharge pipe is fixedly connected to the bottom of the slag removal tank and penetrates the housing. A partition is fixedly connected between the inner walls of the two sides of the box. A perforation is provided on one side of the top of the partition. A discharge pipe is fixedly connected between the side of the box near the perforation and the main pipe. A slag discharge mechanism is installed inside a slag discharge pipe to discharge impurities.

[0010] Furthermore, a filter screen is fixed between the inner wall of one side of the housing and the partition by bolts, and the filter screen is located above the blower pipe.

[0011] Furthermore, the slag discharge mechanism includes two fixed blocks and an auger. The fixed blocks are all fixed to the open end of the slag discharge pipe. A through slide rod is slidably connected to one side of each fixed block. A pressure plate is fixedly connected between the two slide rods. The pressure plate abuts against the open end of the slag discharge pipe. A spring is fixedly connected between one end of each slide rod and the fixed block. The auger rotates through the end of the slag discharge pipe away from the pressure plate.

[0012] Furthermore, a motor is fixedly installed on the bottom surface of the housing, and one end of the motor output shaft is connected to the auger via a belt and pulley.

[0013] Furthermore, a drive disc is fixedly connected to one end of the auger, and a drive shaft is eccentrically mounted on one side of the drive disc and one end of the blower pipe, with a connecting rod rotatably connected between the two drive shafts.

[0014] Furthermore, the top of the slag discharge pipe is provided with a slag collection port, which is located inside the box. Both sides of the slag collection port and the inner walls of both sides of the box are fixedly connected with inclined baffles to guide dust. A blower box is slidably installed between the inner walls of both sides of the box via guide rails. The bottom of the blower box is provided with an opening and is located above the filter screen. An air pipe is fixedly connected to the top of the blower box. Cylinders are fixedly installed on both outer walls of the box. A T-shaped frame is fixedly connected between the piston rods of the cylinders. The T-shaped frame slides through the partition and is fixed to the blower box.

[0015] Furthermore, a condenser is fixedly installed on the top of the housing, the condenser includes a condenser tube at its bottom, the condenser tube is inclined and located inside the housing, a water collection box is fixedly connected to one inner wall of the housing, a drain pipe is fixedly connected to the bottom of the water collection box, the other end of the drain pipe passes through the housing and is located below the baffle, a through mounting hole is opened on one side of the housing for connecting pipes and water pumps, and a level gauge is installed inside the housing for monitoring the liquid level.

[0016] Furthermore, a protective cover is fixedly connected to one side of the outer wall of the housing, and the motor is located inside the protective cover.

[0017] Furthermore, protective shells are fixedly connected to both outer walls of the housing, and the cylinders are located inside the protective shells.

[0018] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit the invention.

[0019] In this invention, a mesh-like fracture pore arrangement and supercritical... The fracturing technology achieves uniform fracturing and permeability enhancement, with a larger fracturing range. The radius of influence of single-hole fracturing is increased by 6-9m, and the coal seam fracture connectivity rate is increased by 50%-70%. Combined with the enhanced wettability of nanofluids and the fracture support effect, the hydrophilicity of the coal body is significantly improved, the gas displacement efficiency is increased by 25%-35%, and the fracture stabilization time is extended by 2-3 times, providing sufficient channels for efficient gas extraction.

[0020] In this invention, soft coal seams, due to their low coal strength (uniaxial compressive strength ≤8MPa), are prone to coal seam collapse or borehole deformation under traditional fracturing methods. This process utilizes a mesh-like fracturing pore system (pore spacing 3-5m) to uniformly distribute fracturing energy, achieving supercritical fracturing. The peak impact pressure during fracturing is controlled at 50-80MPa (the impact pressure of traditional explosive fracturing is ≥150MPa), which makes the destructive effect on the coal body more gentle and can effectively avoid the risk of borehole collapse caused by excessive local coal body fracturing (the borehole collapse rate is reduced from 15%-20% in the traditional process to 3%-5%). In addition, after the nanofluid enhances the wettability of the coal body, the shear strength of the coal body is increased by 15%-20%, reducing the coal body spalling phenomenon during the extraction process. At the same time, the improved gas displacement efficiency makes the gas concentration in the coal seam drop rapidly to the safe threshold (≤8%), further reducing the safety hazards such as gas explosion and outburst.

[0021] In this invention, the preferred nanofluid used is a nano-SiO2 / water-based fluid. The nano-SiO2 particles are inorganic non-metallic materials, non-toxic and non-corrosive (pH 6.5-7.5, matching the pH of coal seam water). After injection into the coal seam, no harmful residues such as heavy metals or organic pollutants are produced. Testing shows that the groundwater quality indicators (such as COD and heavy metal content) of the coal seam do not change significantly before and after extraction. Recycling reduces greenhouse gas emissions (annual emission reduction per working face) (500-800t), avoiding NO generated by explosive explosions in traditional fracturing processes. X It can eliminate harmful gases such as SO2 and reduce their impact on the underground working environment and the surface ecology.

[0022] In this invention, traditional processes often result in rapid closure of coal seam fractures due to coal weight and geostress (closure time 3-5 days), leading to a significant decrease in gas extraction efficiency (≥50%) after 10-15 days. In this process, nanofluid particles (porous structure, specific surface area 50-100 m² / g) can embed into the micropores of the fracture walls, forming a "supporting framework" and delaying fracture closure to 7-10 days. Simultaneously, the enhanced coal wettability of the nanofluid makes subsequent hydraulic fracturing more stable. Combined with a grid-like extraction hole layout, the stable gas extraction period can be extended to 45-60 days (compared to 20-30 days in traditional processes), and the gas concentration in the later stages of extraction can still be maintained at 15%-20% (compared to ≤8% in traditional processes), increasing the cumulative gas extraction volume per working face by 50%-70%.

[0023] This invention employs a three-stage impurity removal process (centrifugal slag removal + precision filtration + purging recovery), achieving a separation rate of over 92% for coarse coal powder with a particle size ≥0.1mm and a filtration accuracy of 95% for fine coal powder with a particle size ≥0.05mm. The overall coal powder impurity removal rate remains stable at 88%-93%, effectively preventing impurities from entering the subsequent extraction system. The slag discharge mechanism achieves automatic slag discharge with a discharge efficiency of 0.5-1.0 m³ / h, reducing the frequency of manual cleaning (from 2-3 times / day in traditional equipment to 1 time / 3-5 days), thus lowering maintenance costs.

[0024] In this invention, the auger is fixedly connected to the drive plate, and the drive shaft, connecting rod and blower pipe are hinged together. When the auger rotates, it drives the drive plate to rotate synchronously. The drive shaft pulls the blower pipe to swing back and forth around the rotary joint through the connecting rod, so that the gas delivered by the blower pipe is evenly blown to different areas of the filter screen, avoiding premature blockage of the filter screen, ensuring stable filtration effect of the filter screen, and extending its single use time. In this invention, by combining the blower box, air pipe and cylinder, and T-shaped frame, along with the baffle and slag collection port of the slag discharge pipe, high-pressure gas is delivered from the air pipe to the blower box when cleaning the filter screen. The cylinder drives the T-shaped frame to move the blower box, blowing off the clumps of impurities at the bottom of the filter screen. The impurities slide along the baffle into the slag collection port and enter the slag discharge pipe. The filter screen can be cleaned without disassembly, significantly reducing the number of filter screen replacements and lowering equipment maintenance costs. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a three-dimensional structure from a first perspective provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a two-dimensional structure from a second perspective provided in an embodiment of the present invention; Figure 3 This is a cross-sectional structural diagram provided in an embodiment of the present invention; Figure 4 This is a schematic cross-sectional view of the slag removal tank provided in an embodiment of the present invention; Figure 5 Provided by the embodiments of the present invention Figure 4 Enlarged structural diagram of point A in the middle; Figure 6 This is a partial cross-sectional structural schematic diagram provided in an embodiment of the present invention; Figure 7 Provided by the embodiments of the present invention Figure 6 Enlarged structural diagram of point B; Figure 8 This is a schematic diagram of the air blower box installation structure provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the condenser tube installation structure provided in an embodiment of the present invention; Figure 10 This is a flowchart of the sampling method of the present invention.

[0026] Figure label: 1. Housing; 2. Slag removal tank; 3. Air inlet pipe; 4. Air outlet pipe; 5. Discharge pipe; 6. Main pipe; 7. Slag discharge pipe; 8. Protective cover; 9. Protective shell; 10. Partition plate; 11. Perforation; 12. Filter screen; 14. Rotary joint; 15. Air blowing pipe; 16. Screw conveyor; 17. Slag collection port; 18. Pressure plate; 19. Fixing block; 20. Slide rod; 21. Spring; 22. Baffle; 23. Motor; 24. Drive disc; 25. Drive shaft; 26. Connecting rod; 27. Air blowing box; 28. Air pipe; 29. ​​T-shaped frame; 30. Cylinder; 31. Condenser; 32. Condenser pipe; 33. Water collection box; 34. Drain pipe; 35. Mounting hole; 36. Level gauge. Detailed Implementation

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

[0028] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "installation" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, "connection" can be a direct connection or an indirect connection through an intermediate medium. "Fixed" means that the devices are connected to each other and their relative positional relationship remains unchanged after the connection. The directional terms mentioned in the embodiments of the present invention, such as "inner," "outer," "top," and "bottom," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present 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. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0029] References to "one embodiment" or "some embodiments" as used in this specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the invention. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless otherwise specifically emphasized.

[0030] Example, refer to Figures 1-10 ,based on A method for gas extraction from soft coal seams through the synergistic effect of fracturing and permeability enhancement and nanofluids includes the following steps: S1: Construct floor penetration boreholes in soft coal seams at designed intervals (preferably 5-8m), while simultaneously arranging liquid... Phase change fracturing holes and gas drainage holes are arranged alternately to form a mesh structure (hole spacing 3-5m). This mesh layout ensures that fracturing energy uniformly covers the coal seam. A drilling rig is used to extract liquid... The phase change fracturing device is pushed to the target coal seam depth (error ≤ ±0.5m) and connected to the detonator via a detonating wire to ensure synchronous triggering of the fracturing device; S2: Inject high-pressure liquid into the fracturing device (Pressure 20-25 MPa), it is detonated after reaching a supercritical state through heating (temperature rise to above 31.1℃) or pressurization (pressure ≥ 7.38 MPa); supercritical It has excellent diffusion and expansion properties. Combined with the grid-like fracturing hole arrangement, it achieves uniform fracturing and permeability enhancement, and the fracturing range is larger (the radius of influence of single hole fracturing increases by 6-9m, which is 40%-60% larger than the traditional fracturing range), avoiding insufficient fracturing or excessive crushing of coal body in some areas. S3: Inject nanofluid (preferably nano-SiO2 / water-based fluid, concentration 0.5%-1.0%) into the fractured coal seam using a high-pressure pump (pressure 15-20MPa). The nanofluid rapidly penetrates to the fractured coal seam under high pressure. Within the micro-fractures formed by fracturing (the permeation rate is 30%-50% higher than that of clean water); utilizing its surface activity (surface tension reduced to 30-40 mN / m), it further peels off coal particles, expands fracture width and connectivity; simultaneously, nanofluids can also enhance coal wettability and hydrophilicity (coal contact angle reduced from 75°-85° to 30°-45°), making it easier for the aqueous phase to penetrate the coal pores during subsequent hydraulic fracturing, resulting in better gas displacement and improved coal seam hydraulic fracturing effect (displacement efficiency increased by 25%-35%), significantly promoting gas flow; in addition, nanofluid particles are also porous media (specific surface area 50-100 m² / g), which can fill the tiny pores at the fracture tip, effectively supporting the fractures and pores, and delaying fracture closure (fracture stability time extended to 7-10 days, 2-3 times longer than without nanofluids). S4: Insert a suction pipe (80-100mm in diameter) into the borehole, and seal the borehole with cement slurry (water-cement ratio 1:1.2) or a bag-type sealing device (sealing length ≥5m) to ensure airtightness (leakage rate ≤0.5% / d); connect the suction pipe to the extraction equipment, connect the gas outlet of the extraction equipment to the main extraction pipe (150-200mm in diameter), and finally connect it to the gas extraction pump station (negative pressure -15 to -25kPa) to achieve stable gas extraction.

[0031] The present invention also proposes an extraction device for extracting the material based on claim 1. The gas extraction system for soft coal seams, which combines fracturing and permeability enhancement with nanofluids, comprises a housing 1 and a main pipe 6. The main pipe 6 is connected to a gas extraction pump station, allowing the treated gas to be transported to the pump station for further collection or treatment. A slag removal tank 2 is fixedly connected to one side of the housing 1. The slag removal tank 2 features a variable diameter design, with its upper diameter larger than its lower diameter. This structure better guides gas flow and promotes impurity settling. An air inlet pipe 3 is fixedly connected to one side of the slag removal tank 2, connecting to the extraction pipe. During gas extraction, the gas, along with coal slag, dust, and other foreign matter, enters the slag removal tank 2 through the air inlet pipe 3. Because the air inlet pipe 3 is located on one side of the slag removal tank 2, rather than centrally, the mixed gas and foreign matter entering the slag removal tank 2 can rotate along the inner wall of the slag removal tank 2. Under centrifugal force, denser foreign matter will move towards the tank wall and gradually fall to the bottom of the slag removal tank 2, achieving initial slag removal. A through-hole air outlet pipe 4 is fixedly connected to the center of the top of the slag removal tank 2. The end of the air outlet pipe 4 extends into the interior of the slag removal tank 2 to ensure that the pre-treated gas can smoothly enter the air outlet pipe 4. A rotary joint 14 is installed at the other end of the air outlet pipe 4. A rotatable air blowing pipe 15 is installed at one end of the rotary joint 14. The air blowing pipe 15 rotates through the housing 1 and has an air outlet at the top. The pre-treated gas enters the interior of the housing 1 through the air outlet pipe 4 and the air blowing pipe 15. A slag discharge pipe 7 is fixedly connected to the bottom of the slag removal tank 2. The slag discharge pipe 7 penetrates the housing 1. Impurities falling to the bottom of the slag removal tank 2 will enter the slag discharge pipe 7 and wait for subsequent discharge.

[0032] A partition 10 is fixedly connected between the inner walls of both sides of the housing 1. A perforation 11 is provided on one side of the top of the partition 10. A discharge pipe 5 is fixedly connected between the side of the housing 1 near the perforation 11 and the main pipe 6. After further filtration inside the housing 1, the gas will enter the discharge pipe 5 through the perforation 11 and then be transported to the main pipe 6 by the discharge pipe 5. A filter screen 12 is fixed between the inner wall of one side of the housing 1 and the partition 10 by bolts. The filter screen 12 is located above the blower pipe 15. The gas sent from the blower pipe 15 must first be filtered by the filter screen 12. The filter screen 12 will intercept the fine impurities remaining in the gas. Only after filtration can the gas continue to flow upward into the discharge pipe 5 and the main pipe 6. The bolt connection also facilitates the subsequent disassembly, maintenance or replacement of the filter screen 12.

[0033] The slag discharge pipe 7 is equipped with a slag discharge mechanism for discharging impurities collected in the slag removal tank 2 and the housing 1. The slag discharge mechanism includes two fixed blocks 19 and an auger 16. Both fixed blocks 19 are fixed to the open end of the slag discharge pipe 7. A through-type sliding rod 20 is slidably connected to one side of each fixed block 19. A pressure plate 18 is fixedly connected between the two sliding rods 20, and the pressure plate 18 abuts against the open end of the slag discharge pipe 7. A spring 21 is fixedly connected between one end of the sliding rod 20 and the fixed block 19. The spring 21 provides pressure to the pressure plate 18, keeping it in contact with the open end of the slag discharge pipe 7 and preventing leakage of impurities before they accumulate to a certain amount. The auger 16 rotates through the end of the slag discharge pipe 7 away from the pressure plate 18. A motor 23 is fixedly installed on the bottom surface of the housing 1. One end of the output shaft of the motor 23 is driven by a belt and pulley to the auger 16. During use, motor 23 can be started, and motor 23 drives auger 16 to rotate via belt and pulley. When auger 16 rotates, it pushes impurities in slag discharge pipe 7 toward pressure plate 18. When a large amount of impurities accumulate, as auger 16 continues to rotate, the pushing force of the impurities on pressure plate 18 will exceed the elastic force of spring 21, thus pushing open pressure plate 18 and causing foreign objects to fall from the open end of slag discharge pipe 7. After the impurities are discharged, spring 21 will drive pressure plate 18 to reset and re-engage with the open end of slag discharge pipe 7. A protective cover 8 is fixedly connected to one side of the outer wall of housing 1. Motor 23 is located inside the protective cover 8. The protective cover 8 can prevent external impurities or collisions from damaging motor 23.

[0034] One end of the auger 16 is fixedly connected to a drive disc 24. Drive shafts 25 are eccentrically mounted on one side of the drive disc 24 and one end of the blower pipe 15. A connecting rod 26 rotatably connects the two drive shafts 25. When the auger 16 rotates under the drive of the motor 23, it synchronously drives the drive disc 24 to rotate. During the rotation of the drive disc 24, the eccentrically mounted drive shaft 25 pulls or pushes the drive shaft 25 at one end of the blower pipe 15 through the connecting rod 26, thereby causing the blower pipe 15 to reciprocate around the rotary joint 14. When the blower pipe 15 reciprocates, the air delivered from its top outlet can be blown to different positions on the filter screen 12, preventing the air from being concentrated in one area of ​​the filter screen 12 for a long time, thus avoiding premature clogging of that area and uneven use of the filter screen 12.

[0035] The top of the slag discharge pipe 7 is provided with a slag collection port 17, which is located inside the housing 1. Inclined baffles 22 are fixedly connected to both sides of the slag collection port 17 and the inner walls of both sides of the housing 1. The baffles 22 are used to guide dust and other impurities. A blower box 27 is slidably installed between the inner walls of both sides of the housing 1 via guide rails. The bottom of the blower box 27 has an opening and is located above the filter screen 12. An air pipe 28 is fixedly connected to the top of the blower box 27, which can be connected to an external air source to deliver high-pressure gas into the blower box 27. Cylinders 30 are fixedly installed on both outer walls of the housing 1. A T-shaped frame 29 is fixedly connected between the piston rods of the cylinders 30. The T-shaped frame 29 slides through the partition 10 and is fixed to the blower box 27. Protective shells 9 are fixedly connected to both outer walls of the housing 1, and the cylinders 30 are located inside the protective shells 9. The protective shells 9 prevent the cylinders 30 from being damaged by external forces. When the filter screen 12 needs to be cleaned, air can be supplied to the blower box 27 through the air pipe 28. The high-pressure gas is blown downward from the opening at the bottom of the blower box 27. At the same time, the cylinder 30 is activated. The extension and retraction of the piston rod of the cylinder 30 will drive the T-shaped frame 29 to move horizontally. When the T-shaped frame 29 moves, it will push the blower box 27 to move along the guide rail inside the housing 1, so that the high-pressure gas can be blown all over the top of the filter screen 12, blowing the impurities that have clumped at the bottom of the filter screen 12 downward. These blown-off impurities will fall on the baffle 22, slide along the inclined baffle 22 to the slag collection port 17, and finally enter the slag discharge pipe 7 and be sent out by the screw conveyor 16. This cleaning method can reduce the number of times the filter screen 12 needs to be replaced.

[0036] A condenser 31 is fixedly installed on the top of the housing 1. The condenser 31 includes a condenser tube 32 at its bottom, which is inclined and located inside the housing 1. A water collection box 33 is fixedly connected to the inner wall of one side of the housing 1. A drain pipe 34 is fixedly connected to the bottom of the water collection box 33. The other end of the drain pipe 34 passes through the housing 1 and is located below the baffle 22. A through mounting hole 35 is opened on one side of the housing 1 for connecting pipes and water pumps. A level gauge 36 is installed inside the housing 1 for monitoring the liquid level inside the housing 1. Soft coal seam gas usually contains a certain amount of water vapor. This water vapor may affect the operation of subsequent equipment after entering the housing 1 with the gas. At this time, the condenser 31 can be started. When the condenser 31 is working, the refrigerant will flow in the condenser tube 32 to cool the gas around the condenser tube 32. The water vapor in the gas will condense into water droplets when it encounters the cooler outer wall of the condenser tube 32. These water droplets will flow down along the inclined outer wall of the condenser tube 32 and eventually drip into the water collection box 33. The water in the water collection box 33 will flow into the bottom of the housing 1 through the drain pipe 34 for collection. When the level gauge 36 detects that the liquid level at the bottom of the housing 1 has risen to a certain height, the water collected at the bottom of the housing 1 can be pumped out and discharged through the pipe and water pump connected to the mounting hole 35 to avoid water accumulation affecting the normal operation of the equipment.

[0037] The working principle and usage process of this technical solution are as follows: the main pipe 6 is connected to the gas extraction pump station, the air inlet pipe 3 is connected to the extraction pipe, and when the gas is extracted, the gas and foreign objects enter the slag removal tank 2 together. Since the air inlet pipe 3 is installed on one side of the slag removal tank 2, the mixed gas and foreign objects entering the slag removal tank 2 can rotate along the inner wall of the slag removal tank 2 and then fall to the bottom of the slag removal tank 2. The gas after preliminary treatment enters the box 1 through the air outlet pipe 4 and the air blowing pipe 15, and then enters the discharge pipe 5 and the main pipe 6 after being filtered by the filter screen 12. During use, the motor 23 can be started, and the motor 23 drives the auger 16 to move actively. The auger 16 pushes the falling impurities toward the pressure plate 18. When the impurities accumulate to a large extent, as the auger 16 continues to rotate, it pushes open the pressure plate 18 under pressure, causing the foreign objects to fall. When the auger 16 rotates, it also drives the drive disc 24 to rotate. The drive disc 24 drives the air pipe 15 to swing back and forth through the drive shaft 25 and the connecting rod 26, so that the air pipe 15 can blow air to different positions of the filter screen 12, which is convenient for the uneven use of the filter screen 12. When the filter screen 12 needs to be cleaned, air can be supplied to the air box 27 through the air pipe 28, and then the cylinder 30 drives the T-shaped frame 29 to move. The T-shaped frame 29 pushes the air box 27 to move, thereby blowing the clumps of impurities at the bottom of the filter screen 12 downwards. After being guided by the baffle 22, they are sent out by the auger 16, reducing the number of times the filter screen 12 needs to be replaced. It can also start the condenser 31, and the refrigerant is cooled when it passes through the condenser tube 32, so that the water vapor in the gas can be condensed and enter the water collection box 33 along the condenser tube, and then enter the bottom of the tank 1. When the liquid level rises, it can be pumped out and discharged through the pipeline by a water pump or diaphragm pump.

[0038] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. In the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A gas extraction device that utilizes a gas extraction method for soft coal seams based on CO2 fracturing and permeability enhancement combined with nanofluid synergy, characterized in that, Includes the following steps: S1: Drill through the bottom plate in the soft coal seam at the designed interval, and simultaneously arrange liquid CO2 phase change fracturing holes and gas extraction holes, which are arranged alternately to form a grid structure. The grid layout ensures that the fracturing energy is evenly covered in the coal seam. The drilling rig pushes the liquid CO2 phase change fracturing device to the target coal seam depth, and the detonator is connected to the detonator through the detonation wire to ensure that the fracturing device is triggered synchronously. S2: High-pressure liquid CO2 is injected into the fracturing device, and it is detonated after reaching a supercritical state through heating or pressurization. Supercritical CO2 has excellent diffusivity and expansion properties. Combined with the grid-like fracturing hole arrangement, it achieves uniform fracturing and permeability enhancement, resulting in a larger fracturing range and avoiding insufficient fracturing or excessive crushing of the coal body in some areas. S3: The nanofluid is injected into the fractured coal seam through a high-pressure pump. Under high pressure, the nanofluid rapidly penetrates into the micro-fractures formed by CO2 fracturing. Utilizing its surface activity, it can peel off coal particles, expand fracture width and connectivity; at the same time, nanofluids can also enhance the wettability of coal, making it more hydrophilic, so that the water phase can more easily penetrate the pores of the coal body during subsequent hydraulic fracturing, resulting in better gas displacement and better hydraulic fracturing effect in coal seams, significantly promoting gas flow; in addition, nanofluid particles are also porous media that can fill the tiny pores at the fracture tip, effectively supporting the fractures and pores and delaying fracture closure. S4: Insert a suction pipe into the borehole and seal the borehole with cement slurry or a bag-type sealing device to ensure airtightness; connect the suction pipe to the extraction equipment, connect the gas outlet of the extraction equipment to the extraction main pipe, and finally connect it to the gas extraction pump station to achieve stable gas extraction. It also includes a box body (1) and a main pipe (6). A slag removal tank (2) is fixedly connected to one side of the box body (1). The slag removal tank (2) is configured with a variable diameter and the upper diameter is larger than the bottom diameter. An air inlet pipe (3) connected to the extraction pipe is fixedly connected to one side of the slag removal tank (2). The air inlet pipe (3) is set on one side of the slag removal tank (2) so that when air enters the slag removal tank (2), it rotates around the inner wall of the slag removal tank (2). A through air outlet pipe (4) is fixedly connected to the center of the top of the slag removal tank (2). The end of the air outlet pipe (4) extends into the slag removal tank (2). A rotary joint (14) is installed at the other end of the air outlet pipe (4). A rotatable air blowing pipe (15) is installed at one end of the rotary joint (14). The air blowing pipe (15) rotates through the box body (1) and has an air outlet at its top. A slag discharge pipe (7) is fixedly connected to the bottom of the slag removal tank (2). The slag discharge pipe (7) passes through the box body (1). A partition (10) is fixedly connected between the inner walls of the two sides of the box (1). A perforation (11) is provided on one side of the top of the partition (10). A discharge pipe (5) is fixedly connected between the side of the box (1) near the perforation (11) and the main pipe (6). The slag discharge mechanism is installed inside the slag discharge pipe (7) to discharge impurities. A filter screen (12) is fixed between the inner wall of one side of the box (1) and the partition (10) by bolts. The filter screen (12) is located above the blower pipe (15). The slag discharge mechanism includes two fixing blocks (19) and an auger (16). The fixing blocks (19) are all fixed to the open end of the slag discharge pipe (7). A through sliding rod (20) is slidably connected to one side of each fixing block (19). A pressure plate (18) is fixedly connected between the rods (20). The pressure plate (18) abuts against the open end of the slag discharge pipe (7). A spring (21) is fixedly connected between one end of the sliding rod (20) and the fixing block (19). The auger (16) rotates through the end of the slag discharge pipe (7) away from the pressure plate (18). A motor (23) is fixedly installed on the bottom surface of the box (1). One end of the output shaft of the motor (23) is driven by the auger (16) through a belt and a pulley. One end of the auger (16) is fixedly connected to a drive disc (24). A drive shaft (25) is eccentrically mounted on one side of the drive disc (24) and one end of the blower pipe (15). A connecting rod (26) is rotatably connected between the two drive shafts (25). A slag collection port (17) is opened at the top of the slag discharge pipe (7). The slag collection port (17) is located inside the box (1). Inclined baffles (22) are fixedly connected to both sides of the slag collection port (17) and the inner walls of both sides of the box (1) for guiding ash. Dust, a blower box (27) is slidably installed between the inner walls of the two sides of the box (1) via a guide rail. The bottom of the blower box (27) has an opening and is located above the filter screen (12). An air pipe (28) is fixedly connected to the top of the blower box (27). Cylinders (30) are fixedly installed on the outer walls of both sides of the box (1). A T-shaped frame (29) is fixedly connected between the piston rods of the cylinders (30). The T-shaped frame (29) slides through the partition (10) and is fixed to the blower box (27).

2. The extraction equipment according to claim 1, characterized in that, A condenser (31) is fixedly installed on the top of the box (1). The condenser (31) includes a condenser pipe (32) at its bottom. The condenser pipe (32) is inclined and located inside the box (1). A water collection box (33) is fixedly connected to the inner wall of one side of the box (1). A drain pipe (34) is fixedly connected to the bottom of the water collection box (33). The other end of the drain pipe (34) passes through the box (1) and is located below the baffle (22). A through mounting hole (35) is opened on one side of the box (1) for connecting the pipe and the water pump. A level gauge (36) is installed inside the box (1) for monitoring the liquid level.

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