Hard and thick coal seam coal caving system based on microwave and liquid nitrogen cold-heat interaction and use method

Abstract

The invention provides a hard and thick coal seam coal caving system based on microwave and liquid nitrogen cold-heat interaction and a using method, and relates to the coal seam fracturing technology, the system comprises a hydraulic support, the hydraulic support comprises a side beam, the side beam is provided with an operation window, the operation window is provided with a sliding opening mechanism, and the sliding opening mechanism is provided with a liquid nitrogen injection opening; the drilling mechanism can penetrate out of the sliding opening mechanism to act on the top coal, and the drilling mechanism comprises a pair of drilling units with variable spacing; the microwave irradiation mechanism can penetrate out of the sliding opening mechanism to act on the top coal, the microwave irradiation mechanism comprises two pairs of orthogonally distributed microwave units, and the distance between the microwave units located on the same straight line is variable; according to the technical scheme, secondary cracking of the top coal occurs, the coal caving efficiency is improved, impact disturbance to an overlying rock stratum is reduced, the stability of the rock stratum can be better maintained, the water consumption is low, and the defect of underground long-distance water delivery is overcome.

Description

Technical Field

[0001] The invention relates to coal seam fracturing technology, and in particular to a hard and thick coal seam caving system based on microwave and liquid nitrogen cold and heat interaction and a use method thereof. Background Art

[0002] When mining hard and thick coal seams, comprehensive mechanized equipment is usually used to mine the lower part of the coal seam first, and then the top coal that has naturally collapsed from the upper layer is released from the tail beam of the hydraulic support through the top coal caving process. However, the coal seams in some mining areas in my country are relatively hard, and the top coal of hard and thick coal seams is not easy to collapse naturally, resulting in a longer hanging time of the top coal, which reduces the efficiency of coal caving and the safety of coal mining operations.

[0003] In order to solve the problem that top coal cannot be naturally discharged, the commonly used auxiliary coal discharge methods are top coal blasting and hydraulic fracturing, which have shown good application effects in some top coal mining areas. However, it is difficult to accurately control the blasting effect during directional blasting in the top coal blasting method, and the explosion shock wave generated by it can easily destroy the stability of the tunnel surrounding rock, thereby causing secondary disasters such as roof collapse, mine earthquake and rock burst. The hydraulic fracturing method is relatively safe and reliable, but the flexibility of high-pressure water delivery over long distances underground is low, and the fracturing range is limited. In addition, when encountering top coal, the two current auxiliary coal discharge methods still have a small part of the top coal attached to the top, which not only has a poor coal discharge effect, but also poses a safety hazard.

[0004] Therefore, the mining engineering field is in urgent need of a safe, convenient, and effective coal caving system and its use method. Summary of the invention

[0005] The present invention provides a hard and thick coal seam caving system and a use method based on microwave and liquid nitrogen hot and cold interaction, the purpose of which is to adopt a coal caving system and method that can reduce secondary disasters and is easy to operate, so as to achieve safe and efficient coal caving.

[0006] In order to achieve the above object, an embodiment of the present invention provides a hard and thick coal seam caving system based on microwave and liquid nitrogen cold and heat interaction, comprising:

[0007] A hydraulic support, wherein the hydraulic support comprises a side beam, an operation window penetrating the thickness of the side beam is provided on the side beam, a sliding opening mechanism for closing the operation window is provided on the operation window, the sliding opening mechanism comprises a bottom plate having an operation opening, a closing plate is slidably provided on the bottom plate, the closing plate is used to close the operation opening, and a liquid nitrogen injection port is provided around the operation opening;

[0008] A drilling mechanism is connected to the lower side beam through a first mechanical arm, and the drilling mechanism can pass through the operation port to act on the top coal, and the drilling mechanism includes a pair of drilling units with variable spacing, and the drilling units are used to drill and infiltrate the top coal;

[0009] A microwave irradiation mechanism is connected to the lower side beam through a second mechanical arm, and the microwave irradiation mechanism can pass through the operation port to act on the top coal. The microwave irradiation mechanism includes two pairs of orthogonally distributed microwave units, and the microwave units are located on the same straight line with a variable spacing. The microwave units are used to heat the top coal in the borehole;

[0010] a liquid nitrogen mechanism, connected to the liquid nitrogen injection port, and used for injecting liquid nitrogen toward the area heated by the microwave unit;

[0011] The control system has signals connected to the sliding opening mechanism, the drilling mechanism, the microwave irradiation mechanism and the liquid nitrogen mechanism.

[0012] Preferably, a disturbance mechanism is also provided on the side beam, and the disturbance mechanism is arranged in front of the operating window. The disturbance mechanism includes a retractable disturbance rod, one end of which is hinged to the side beam, and the other end is extendable. A push rod is also hinged on the disturbance rod, and the other end of the push rod is hinged to the side beam. The disturbance mechanism is connected to the control system signal.

[0013] Preferably, the sliding opening mechanism comprises a pushing unit, and the pushing unit drives the closing plate to slide on the bottom plate to close and open the operating port.

[0014] Preferably, the liquid nitrogen injection port is funnel-shaped, and the end with a larger diameter of the liquid nitrogen injection port is close to the top coal. A hole core is arranged in the liquid nitrogen injection port, and the hole core is funnel-shaped. An axial central flow channel is arranged on the hole core. A circumferential flow channel is formed between the outer wall of the hole core and the hole wall of the liquid nitrogen injection port, and the liquid nitrogen provided by the liquid nitrogen mechanism is sprayed onto the top coal through the central flow channel and the circumferential flow channel.

[0015] Preferably, the drilling mechanism comprises a first base, the drilling unit is arranged on the first base, the first base moves under the drive of the first mechanical arm, the drilling unit comprises a first variable-pitch mechanical arm, a telescopic drill rod arranged on the first variable-pitch mechanical arm, and a water jet drill head arranged on the telescopic drill rod, and the drilling unit is arranged on both sides of the first base;

[0016] The first variable-pitch mechanical arm is a two-axis mechanical arm, and the telescopic drill rod remains in a vertical state during operation.

[0017] Preferably, the microwave irradiation mechanism comprises a second base, the second base moves under the drive of the second mechanical arm, the microwave unit comprises a second variable-pitch mechanical arm, a retractable tubular microwave irradiator arranged on the second variable-pitch mechanical arm, and four microwave units are orthogonally distributed on the second base;

[0018] The second variable-pitch robotic arm is a two-axis robotic arm, and the tubular microwave irradiator remains in a vertical state during operation.

[0019] Preferably, the first robotic arm and the second robotic arm are respectively provided with position sensors, and the position sensors are used to obtain the spatial positions of the drilling mechanism and the microwave irradiation mechanism.

[0020] The present application also provides a method of use, using the aforementioned hard and thick coal seam caving system based on microwave and liquid nitrogen cold and heat interaction, comprising:

[0021] S10. Obtain the area S of the top coal surface above the hydraulic support, and divide the area S of the top coal into a front half top coal surface and a rear half top coal surface, the area of ​​the front half top coal surface is S1 and the area of ​​the rear half top coal surface is S2;

[0022] S20. After adjusting the spacing K1 between the two drilling units, perform the first drilling on the rear half of the top coal surface, and adjust the spacing K2 between the two drilling units to perform the second drilling on the rear half of the top coal surface to obtain a total of four holes, and the connection line of the two drilling units during the first drilling is perpendicular to the connection line of the two drilling units during the second drilling;

[0023] A microwave irradiation mechanism with a radiation radius of R is extended into four boreholes, and the boreholes are subjected to thermal radiation for a duration of t to reach a preset temperature T, and the irradiated area of ​​the rear half of the top coal surface reaches a preset proportion;

[0024] S30. Repeat step S20 on the front half of the top coal surface, and start the liquid nitrogen mechanism to spray liquid nitrogen on the rear half of the top coal surface;

[0025] S40. Perform microwave thermal radiation on the four drill holes in the front half of the top coal surface, and after the thermal radiation, start the liquid nitrogen mechanism to spray liquid nitrogen toward the front half of the top coal surface.

[0026] Preferably, the area S of the top coal is obtained based on the coal placing step distance A of the hydraulic support and the width B of the top beam of the hydraulic support.

[0027] Preferably, when drilling the front half top coal surface and the rear half top coal surface, the affected area of ​​the four holes on the front half top coal surface or the rear half top coal surface is not less than a preset ratio, and the distances K1 and K2 between the two drilling units and the radiation radius R of the microwave are obtained based on the preset ratio.

[0028] The above scheme of the present invention has the following beneficial effects:

[0029] First, the heating by microwave thermal radiation and the rapid cooling by liquid nitrogen cause the crack opening of the top coal to change under the action of heating and cooling, thereby increasing the number of cracks on the top coal and increasing the opening. Specifically, the pores in the top coal contain gases such as methane and carbon dioxide as well as water. When the top coal is heated by microwaves, the water in the pores evaporates, and the gas is desorbed and expanded by heat, both of which generate thermal stress on the top coal. The thermal stress increases the opening of the pores, generating cracks or forming larger cracks. After heating, part of the top coal still has water, while the other part of the top coal loses water due to heating. During the rapid cooling of liquid nitrogen, the top coal containing water will experience a cold expansion effect, while the top coal that has lost water will experience a cold contraction effect, causing the top coal to crack twice. Through the two crackings, larger and / or more cracks are quickly formed on the top coal, thereby causing the top coal to fall off. During the drilling process, the drilling mechanism wets the top coal to make the microwave heating effect better, which also helps to produce a cold expansion effect.

[0030] Second, in the present application, a drilling mechanism is used to extend into the interior of the top coal, the interior of the top coal is heated up, and then the temperature is quickly cooled down, which not only produces a large number of cracks on the surface of the top coal, but also produces a large number of cracks inside the top coal, ensuring the removal effect of the top coal.

[0031] Third, the drilling mechanism makes four holes in the top coal and determines the interval between the holes drilled at the same time and the expected microwave influence radius to ensure that the front half and the back half of the top coal surface can be fully cracked and fallen off during the cracking process to avoid the top coal being unable to fall off due to adhesion. In addition, the disturbance mechanism can also make the top coal that is difficult to fall off fall off due to vibration, greatly increasing the amount of top coal that falls off.

[0032] Fourthly, the drilling mechanism used in the present application to drill holes in the top coal can guide the top coal to fracture in the direction of the drilling, thereby achieving directional fracture and improving the safety of underground construction.

[0033] Fifth, a sliding opening mechanism is provided on the side beam, which can protect the drilling mechanism and the microwave irradiation mechanism when the top coal is dropped, and avoid damage to them by the falling coal.

[0034] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the drilling mechanism drilling holes in the rear half of the top coal face;

[0036] Figure 2 This is a schematic diagram of the heat radiation of the microwave irradiation mechanism in the rear half of the top coal surface;

[0037] Figure 3It is a schematic diagram of the liquid nitrogen mechanism cooling the rear half of the top coal surface and the drilling mechanism drilling holes in the front half of the top coal surface;

[0038] Figure 4a is a side view of the drilling mechanism;

[0039] Figure 4b It is a top view of the drilling mechanism;

[0040] Figure 5a is a side view of the microwave irradiation mechanism;

[0041] Figure 5b is a top view of the microwave irradiation mechanism;

[0042] Figure 6 is a schematic diagram of a sliding opening mechanism;

[0043] Figure 7 is a cross-sectional schematic diagram of a liquid nitrogen injection port;

[0044] Figure 8 It is a schematic diagram of the disturbance mechanism on the side beam.

[0045] [Description of Reference Numerals]

[0046] 110-side beam, 120-top beam,

[0047] 200-sliding opening mechanism, 210-bottom plate, 220-closing plate, 230-liquid nitrogen injection port, 231-hole core, 232-central flow channel, 233-circumferential flow channel,

[0048] 300-drilling mechanism, 310-drilling unit, 311-first variable pitch mechanical arm, 312-telescopic drill rod, 313-water jet drill head, 320-first base,

[0049] 400-microwave irradiation mechanism, 410-microwave unit, 411-second variable-pitch mechanical arm, 412-tube microwave irradiator, 420-second base,

[0050] 500-Control system,

[0051] 610-disturbance rod, 620-push rod. DETAILED DESCRIPTION

[0052] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0053] like Figures 1 to 8As shown, an embodiment of the present invention provides a hard and thick coal seam coal caving system based on the interaction of microwave and liquid nitrogen heating and cooling, including a hydraulic support, which includes a front beam, a top beam 120, a side beam 110 and a tail beam from front to back, wherein the top beam 120 plays a supporting role, the front beam and the side beam 110 are rotatably arranged at the front end and the rear end of the top beam 120 respectively, the side beam 110 can rotate around the rear end of the top beam 120 under the action of a supporting device, and the tail beam is arranged at the rear end of the side beam 110, and can rotate around the rear end of the side beam 110 under the action of another supporting device.

[0054] An operation window is provided on the side beam 110, and the operation window penetrates the side beam 110 along the thickness direction of the side beam 110, that is, the operation window penetrates the side beam 110 in the up and down direction. A sliding opening mechanism 200 is provided on the operation window, and the sliding opening mechanism 200 is provided on the operation window. Specifically, the sliding opening mechanism 200 includes a bottom plate 210 and a closing plate 220, and the bottom plate 210 has an operation port, and the bottom plate 210 is installed on the operation window. A liquid nitrogen injection port 230 is also provided on the bottom plate 210, and the liquid nitrogen injection port 230 is arranged around the operation port. The aforementioned closing plate 220 is slidably provided on the bottom plate 210, and the purpose of opening or closing the operation port is achieved by sliding the closing plate 220.

[0055] The hard and thick coal seam caving system based on microwave and liquid nitrogen cold and hot interaction also includes a drilling mechanism 300, a first mechanical arm is arranged below the side beam 110, the first mechanical arm is connected to the drilling mechanism 300, and the first mechanical arm can drive the drilling mechanism 300 to move and rotate in three-dimensional space. In the present application, the drilling mechanism 300, driven by the first mechanical arm, passes through the operating port from the lower end of the operating port, and drills the top coal above the operating port. The drilling mechanism 300 includes a pair of drilling units 310, the spacing between the drilling units 310 can be changed, thereby changing the drilling position, the drilling unit 310 can drill the top coal, and spray water on the borehole during drilling to achieve the effect of infiltrating the borehole, and the infiltration of water can reduce the friction between the drilling unit 310 and the top coal and extend the life of the drilling unit 310. Preferably, a position sensor is arranged on the first mechanical arm, and the position sensor obtains the spatial posture information of the drilling mechanism 300.

[0056] The hard and thick coal seam caving system based on microwave and liquid nitrogen cold and hot interaction also includes a microwave irradiation mechanism 400, a second mechanical arm is arranged below the side beam 110, the second mechanical arm is connected to the microwave irradiation mechanism 400, and the second mechanical arm can drive the microwave irradiation mechanism 400 to move and rotate in three-dimensional space. In the present application, the microwave irradiation mechanism 400 passes through the operation port from the lower end of the operation port under the drive of the second mechanical arm, and performs microwave heating on the top coal above the operation port. The microwave irradiation mechanism 400 includes two pairs of orthogonally distributed microwave units 410, that is, the straight line where a pair of microwave units 410 are located is perpendicular to the straight line where another pair of microwave units 410 are located. The spacing between the microwave units 410 located on the same straight line is variable, so as to ensure that the microwave units 410 can adjust the spacing according to the position of the borehole, insert the microwave units 410 into the borehole, and heat the inside of the top coal. Preferably, another position sensor is arranged on the second mechanical arm, and the position sensor obtains the spatial posture information of the drilling mechanism 300.

[0057] Preferably, the drilling mechanism 300 is disposed at the lower left of the operation port, and the microwave irradiation mechanism 400 is disposed at the lower right of the operation port.

[0058] The hard thick coal seam coal caving system based on the heating and cooling interaction of microwaves and liquid nitrogen also includes a liquid nitrogen mechanism, which is connected to the liquid nitrogen injection port 230. The liquid nitrogen mechanism can provide a large amount of liquid nitrogen to spray the top coal heated by the microwave irradiation mechanism 400 to achieve rapid cooling of the hard coal seam.

[0059] The hard and thick coal seam caving system based on the hot and cold interaction of microwaves and liquid nitrogen also includes a control system 500, and the control system 500 is signal-connected to the sliding opening mechanism 200, the drilling mechanism 300, the microwave irradiation mechanism 400 and the liquid nitrogen mechanism.

[0060] In the present application, by utilizing the heat radiation of microwaves and the rapid cooling of liquid nitrogen, the pores of the top coal contain gases such as methane, carbon dioxide, and water. When the top coal is heated by microwaves, the water in the pores evaporates, and the gas is desorbed and expanded by heat. Both of them generate thermal stress on the top coal, and the thermal stress increases the opening of the pores, generating cracks or forming larger cracks. After heating, part of the top coal still has water, and the other part of the top coal loses water due to heating. During the rapid cooling of liquid nitrogen, the top coal containing water will have a cold expansion effect, while the top coal that loses water will have a cold contraction effect, causing the top coal to crack twice. Through the two cracks, larger and / or more cracks are quickly formed on the top coal, so that the top coal falls off. However, although the solution of rapid temperature change can cause cracks in the top coal, the cracks are mostly concentrated on the surface of the top coal. Although it has a certain degree of falling, the falling effect is not good, and the top coal needs to be peeled off layer by layer from bottom to top. Therefore, in the present application, a hole is drilled inside the top coal by using the drilling mechanism 300, and the microwave unit 410 is extended into the drill hole to heat the inside of the top coal, so that the top coal is quickly heated up inside, and combined with liquid nitrogen cooling, a large number of cracks are generated inside the top coal, thereby causing a large amount of top coal to fall off.

[0061] It can be understood that compared with the lower surface of the top coal, the pores inside the top coal contain more methane, carbon dioxide and other gases. As the drilling depth changes, the opening and number of cracks produced after secondary cracking deep in the top coal are larger and more numerous than the opening and number of cracks on the surface of the top coal, thereby reducing the adhesion of the top coal and making it easier to fall off.

[0062] After drilling, the top coal is subjected to hot and cold treatments in the hole. The top coal will produce a large number of cracks radiating around the hole with the hole as the center. The drilling hole plays a role of directional fracture. On the other hand, the variable spacing between holes can ensure that the cracks are full of top coal during fracturing, thereby preventing part of the top coal from remaining attached after fracturing and unable to fall off by gravity or delayed falling off.

[0063] The aforementioned sliding opening mechanism 200 also includes a pushing unit. The aforementioned bottom plate 210 is arranged at the bottom end of the side beam 110. The bottom plate 210 is located above the operating window. One end of the pushing unit is fixed on the bottom plate 210, and the other end is connected to the closing plate 220. Under the action of the pushing unit, the closing plate 220 can close the operating port located on the bottom plate 210, thereby preventing the hard coal seam from falling and damaging the drilling mechanism 300 and the microwave irradiation mechanism 400.

[0064] In the present application, the push unit adopts a common linear module such as a cylinder, an electric push rod 620, etc. The push unit is connected to the control system 500 by signal, so as to ensure that the closing plate 220 is automatically started or closed.

[0065] In the present application, the operation port has a length of 60 cm and a width of 40 cm. The liquid nitrogen injection ports 230 are arranged around the operation port, and one liquid nitrogen injection port 230 is arranged every 10 cm.

[0066] In the present application, the liquid nitrogen injection port 230 is funnel-shaped, and the end with a larger diameter of the liquid nitrogen injection port 230 is close to the top coal, that is, the diameter of the upper end of the liquid nitrogen injection port 230 is larger than the diameter of the lower end of the liquid nitrogen injection port 230. A hole core 231 is also provided in the liquid nitrogen injection port 230. The hole core 231 is also funnel-shaped, and the hole core 231 has the same shape as the liquid nitrogen injection port 230, and the proportion is smaller than the shape of the liquid nitrogen injection port 230, so as to ensure that the hole core 231 can be provided in the liquid nitrogen injection port 230. The hole core 231 is also provided with a central flow channel 232 along its own axial direction. When the hole core 231 is assembled in the liquid nitrogen injection port 230, a circumferential flow channel 233 is formed between the outer wall of the hole core 231 and the hole wall of the liquid nitrogen injection port 230. Preferably, a connecting rib is also provided between the outer wall of the hole core 231 and the liquid nitrogen injection port 230, and the connecting rib is used to maintain the hole core 231 in the liquid nitrogen injection port 230.

[0067] Preferably, the length of the liquid nitrogen injection port 230 is smaller than the length of the hole core 231, and the two are flush at the end of the liquid nitrogen injection port 230 with a larger diameter, so that when the liquid nitrogen enters the liquid nitrogen injection port 230, the liquid nitrogen is diverted to the central flow channel 232 and the circumferential flow channel 233, ensuring that when the liquid nitrogen is sprayed from the end of the liquid nitrogen injection port 230 with a larger diameter toward the top coal, the injection distance can be guaranteed through the central flow channel 232, and the injection range can be guaranteed through the circumferential flow channel 233, so that the top coal can be quickly cooled over a large range, the cooling effect is improved, and the cooling efficiency is guaranteed.

[0068] Further, the aforementioned drilling mechanism 300 includes a first base 320, a drilling unit 310 is arranged on the first base 320, and the first base 320 is moved and / or rotated under the drive of the first mechanical arm. The aforementioned drilling unit 310 includes a first variable pitch mechanical arm 311, a telescopic drill rod 312 and a water jet drill head 313. One end of the first variable pitch mechanical arm 311 is arranged on the first base 320, and the other end is connected to one end of the telescopic drill rod 312, and the other end of the telescopic drill rod 312 is used to set the water jet drill head 313. Two drilling units 310 are arranged on both sides of the first base 320. The first variable pitch mechanical arm 311 is a two-axis mechanical arm, and the first variable pitch mechanical arm 311 can rotate around the first base 320, and can also drive the telescopic drill rod 312 to rotate around the other end of the first variable pitch mechanical arm 311.

[0069] In the present application, the spacing between the drilling units 310 is adjusted in the following manner: when the spacing between the two drilling units 310 needs to be increased, the first variable pitch mechanical arm 311 rotates clockwise to reduce the angle with the horizontal direction, and at the same time the telescopic drill rod 312 rotates counterclockwise to always maintain a vertical state, and the telescopic drill rod 312 also extends during the rotation process, thereby ensuring that the water jet drill head 313 can drill into the top coal to a certain depth.

[0070] Preferably, the water jet drill bit 313 is a variable diameter drill bit, and a water outlet micro hole is provided on the water jet drill bit 313. The water outlet micro hole is connected to the water supply device.

[0071] The aforementioned microwave irradiation mechanism 400 includes a second base 420, and the second base 420 moves and / or rotates under the drive of the second mechanical arm. The microwave unit 410 includes a second variable pitch mechanical arm 411 and a retractable tubular microwave irradiator 412. The second variable pitch mechanical arm 411 is a two-axis mechanical arm. One end of the second variable pitch mechanical arm 411 is rotatably connected to the second base 420, and the other end is connected to the tubular microwave irradiator 412. The connection line of a pair of tubular microwave irradiators 412 is perpendicular to the connection line of another pair of tubular microwave irradiators 412. The spacing between the tubular microwave irradiators 412 located on the same straight line is variable, and the spacing adjustment method is the same as the spacing adjustment method of the drilling unit 310. The tubular microwave irradiators 412 are also kept in a vertical state when working.

[0072] Preferably, both the first base 320 and the second base 420 are provided with a receiving groove, and the receiving groove is used to receive the drilling unit or the microwave unit 410 .

[0073] In order to solve the problem that part of the top coal still cannot fall off after the liquid nitrogen is sprayed, a disturbance mechanism is further provided on the side beam 110, and the disturbance mechanism is arranged in front of the operating window. The disturbance mechanism includes a disturbance rod 610 and a push rod 620, wherein one end of the disturbance rod 610 is hinged to the side beam 110, and the other end is a free end, and the free end can be extended and retracted. One end of the push rod 620 is also hinged to the side beam 110, and the other end of the push rod 620 is hinged to the disturbance rod 610. Under the action of the push rod 620, the disturbance rod 610 can rotate relative to the side beam 110, so that the disturbance rod 610 can act on the front end of the front top coal surface, and the free end hammers the top coal through high-frequency extension and retraction, so as to shake off the top coal with cracks on the front and rear top coal surfaces.

[0074] The present application also provides a method for using the aforementioned hard and thick coal seam caving system based on microwave and liquid nitrogen cold and heat interaction, comprising the following steps:

[0075] S10. Obtain the area S of the top coal surface above the hydraulic support, and divide the top coal surface into a front half top coal surface and a rear half top coal surface, where the area of ​​the front half top coal surface is S1 and the area of ​​the rear half top coal surface is S2.

[0076] In this step, the area S of the top coal is obtained according to the coal placing step A of the hydraulic support and the width B of the top beam 120 of the hydraulic support, where S=A*B. The control system 500 divides the area S of the top coal surface into the front half top coal surface and the rear half top coal surface, the area of ​​the front half top coal surface is S1, and the area of ​​the rear half top coal surface is S2. The control system 500 can divide the area of ​​the top coal by using an existing algorithm. Preferably, the area S1 of the front half top coal surface is equal to the area S2 of the rear half top coal surface.

[0077] S20. Adjust the distance K1 between the two drilling units 310, and perform the first drilling on the rear half of the top coal surface, adjust the distance K2 between the two drilling units 310, and perform the second drilling on the rear half of the top coal surface. The line connecting the two drilling units 310 during the first drilling is perpendicular to the line connecting the two drilling units 310 during the second drilling.

[0078] Specifically, the drilling mechanism 300 extends from the operation port to the top of the operation port, and before the first drilling, the distance K1 between the two drilling units 310 is adjusted by adjusting the first variable-pitch mechanical arm 311. After the distance K1 is determined, the drilling mechanism 300 drills the rear half of the top coal face to obtain the first pair of holes.

[0079] The drilling mechanism 300 exits the first pair of boreholes, and the first base 320 rotates 90 degrees under the drive of the first mechanical arm, and the spacing K2 of the drilling unit 310 is adjusted. After the spacing K2 is determined, the drilling mechanism 300 drills the rear half of the top coal surface to obtain the second pair of boreholes. In the two drillings, the drilling depth H is 2 / 3 of the top coal thickness. During the drilling process, the water jet drill 313 sprays water.

[0080] When drilling holes in the rear half of the top coal surface, the influence area of ​​the four holes on the rear half of the top coal surface is required to be no less than a preset ratio, based on which the distances K1 and K2 between the two drilling units 310 and the expected influence radius R of the microwave can be obtained.

[0081] In this embodiment, the influence area of ​​the four boreholes on the rear half of the top coal surface is not less than 70%, thereby determining the radiation radius R of the microwave and the distances K1 and K2 between the two drilling units 310 .

[0082] Specifically, input the initial values ​​for the radiation radius R and the spacing K1 and K2, and calculate the current total radiation area A total , if A total If the area of ​​the rear half of the top coal is less than 70%, increase the radiation radius or adjust K1 and K2 to reduce the overlapping area of ​​microwave radiation in the four boreholes. Repeat the above steps until A totalGreater than or equal to 70% of the rear half of the top coal surface. It should be noted that the radiation radius of the microwave is positively correlated with its power, so the radiation radius R of the microwave can be adjusted by the power of the microwave unit 410.

[0083] In the above content, A total =4πR 2 -A overlap， Among them A overlap is the radiation overlapping area of ​​the microwave irradiation mechanism 400.

[0084] After the drilling mechanism 300 finishes drilling, the position sensor located on the first robot arm obtains the positions of the four drilled holes and transmits the position information to the control system 500 .

[0085] The microwave irradiation mechanism 400 extends into the four boreholes and radiates heat to the entire borehole for a duration of t to reach a preset temperature T.

[0086] Based on the position information of the four boreholes obtained by the control system 500, the microwave irradiation mechanism 400 is controlled to extend into the four boreholes to perform thermal radiation heating on the rear half of the top coal surface. The tubular microwave irradiator 412 reaches a preset temperature T at a heating time t with a power W. The preset temperature T can be stored in the control system 500.

[0087] The heating time t can be obtained by setting a temperature sensor on the side beam 110 to measure the rear half of the top coal surface and obtain it in real time; it can also be obtained by calculation and stored in the control system 500. The heating time t satisfies:

[0088] t=(mcΔT) / (ηW)

[0089] ΔT=T-T0

[0090] Wherein, m is the mass of top coal, c is the specific heat capacity of top coal, ΔT is the temperature change, η is the microwave absorption efficiency, W is the microwave power, and T0 is the initial temperature of top coal.

[0091] S30. Repeat step S20 on the front half of the top coal surface, and start the liquid nitrogen mechanism to spray liquid nitrogen on the rear half of the top coal surface.

[0092] In this step, the drilling mechanism 300 moves to the front half of the top coal surface, and adjusts the spacing K3 between the drilling units 310 of the chain by adjusting the first variable-pitch mechanical arm 311. After the spacing K3 is determined, the drilling mechanism 300 drills the front half of the top coal surface to obtain the first pair of holes.

[0093] The drilling mechanism 300 exits the first pair of boreholes, and the first base 320 rotates 90 degrees under the drive of the first mechanical arm, and the spacing K4 of the drilling unit 310 is adjusted. After the spacing K4 is determined, the drilling mechanism 300 drills the front half of the top coal surface to obtain the second pair of boreholes. In the two drillings, the drilling depth H is 2 / 3 of the thickness of the top coal. During the drilling process, the water jet drill 313 sprays water.

[0094] While the drilling mechanism 300 is drilling a hole in the front half of the top coal face, the liquid nitrogen mechanism sprays liquid nitrogen to the rear half of the top coal face through the liquid nitrogen spray port 230. The liquid nitrogen spray pressure P and the liquid nitrogen spray time t1 are pre-set in the central control system. In this embodiment, t1 = 3 min, P = 25 MPa.

[0095] S40. Referring to step S30, the four drill holes on the front half of the top coal surface are subjected to microwave thermal radiation, and after the thermal radiation is completed, the liquid nitrogen mechanism is turned on to spray liquid nitrogen onto the front half of the top coal surface.

[0096] The method for using the aforementioned hard and thick coal seam coal caving system based on microwave and liquid nitrogen hot and cold interaction also includes step S50. After liquid nitrogen is sprayed on the front half of the top coal surface or during the spraying process, the top coal in front of the front half of the top coal surface can be hammered by controlling the disturbance mechanism, so that the top coal on the front half of the top coal surface and the rear half of the top coal surface can fall off through vibration.

[0097] The technical solution provided by this application uses microwaves and liquid nitrogen to produce secondary cracking of the coal seam, thereby improving the efficiency of coal placement. Compared with the conventional directional blasting coal placement method, it reduces the impact disturbance on the overlying rock formation, is more conducive to maintaining the stability of the rock formation, and uses less water, overcoming the disadvantage of long-distance water transportation underground.

[0098] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A hard and thick coal seam caving system based on microwave and liquid nitrogen hot and cold interaction, characterized in that: include: A hydraulic support, the hydraulic support comprising a side beam (110), the side beam (110) being provided with an operation window penetrating the thickness of the side beam (110), the operation window being provided with a sliding opening mechanism (200) for closing the operation window, the sliding opening mechanism (200) comprising a bottom plate (210) having an operation opening, a closing plate (220) being slidably provided on the bottom plate (210), the closing plate (220) being used for closing the operation opening, and a liquid nitrogen injection port (230) being provided around the operation opening; A drilling mechanism (300) is connected to the lower side beam (110) through a first mechanical arm, and the drilling mechanism (300) can pass through the operation port to act on the top coal, and the drilling mechanism (300) includes a pair of drilling units (310) with variable spacing, and the drilling units (310) are used to drill and infiltrate the top coal; A microwave irradiation mechanism (400) is connected to the lower side beam (110) through a second mechanical arm, and the microwave irradiation mechanism (400) can pass through the operation port to act on the top coal. The microwave irradiation mechanism (400) includes two pairs of orthogonally distributed microwave units (410), and the microwave units (410) located on the same straight line have a variable spacing. The microwave units (410) are used to heat the top coal in the borehole; a liquid nitrogen mechanism, connected to the liquid nitrogen injection port (230), the liquid nitrogen mechanism being used to inject liquid nitrogen toward the area heated by the microwave unit (410); The control system (500) is signal-connected to the sliding opening mechanism (200), the drilling mechanism (300), the microwave irradiation mechanism (400) and the liquid nitrogen mechanism.

2. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized in that: The side beam (110) is also provided with a disturbance mechanism, which is arranged in front of the operating window. The disturbance mechanism includes a retractable disturbance rod (610), one end of which is hinged to the side beam (110) and the other end of which is extendable. A push rod (620) is also hinged to the disturbance rod (610), and the other end of which is hinged to the side beam (110). The disturbance mechanism is connected to the control system (500) by signal.

3. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized by: The sliding opening mechanism (200) comprises a pushing unit, and the pushing unit drives the closing plate (220) to slide on the bottom plate (210) to close and open the operating port.

4. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized by: The liquid nitrogen injection port (230) is funnel-shaped, and the end of the liquid nitrogen injection port (230) with a larger diameter is close to the top coal. A hole core (231) is arranged in the liquid nitrogen injection port (230), and the hole core (231) is funnel-shaped. An axial central flow channel (232) is arranged on the hole core (231). A circumferential flow channel (233) is formed between the outer wall of the hole core (231) and the hole wall of the liquid nitrogen injection port (230). The liquid nitrogen provided by the liquid nitrogen mechanism is sprayed onto the top coal through the central flow channel (232) and the circumferential flow channel (233).

5. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized in that: The drilling mechanism (300) comprises a first base (320), the drilling unit (310) is arranged on the first base (320), the first base (320) moves under the drive of the first mechanical arm, the drilling unit (310) comprises a first variable-pitch mechanical arm (311), a telescopic drill rod (312) arranged on the first variable-pitch mechanical arm (311), and a water jet drill head (313) arranged on the telescopic drill rod (312), and the drilling unit (310) is arranged on both sides of the first base (320); The first variable-pitch mechanical arm (311) is a two-axis mechanical arm, and the telescopic drill rod (312) remains in a vertical state during operation.

6. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized in that: The microwave irradiation mechanism (400) comprises a second base (420), the second base (420) moves under the drive of the second mechanical arm, the microwave unit (410) comprises a second variable-pitch mechanical arm (411), and a retractable tubular microwave irradiator (412) arranged on the second variable-pitch mechanical arm (411), and four microwave units (410) are orthogonally distributed on the second base (420); The second variable-pitch mechanical arm (411) is a two-axis mechanical arm, and the tubular microwave irradiator (412) remains in a vertical state during operation.

7. The hard and thick coal seam caving system based on microwave and liquid nitrogen heating and cooling interaction according to claim 1 is characterized by: Position sensors are respectively provided on the first mechanical arm and the second mechanical arm, and the position sensors are used to obtain the spatial positions of the drilling mechanism (300) and the microwave irradiation mechanism (400).

8. A method of use, using the hard and thick coal seam caving system based on microwave and liquid nitrogen cold and heat interaction as described in any one of claims 2 to 7, characterized in that: include: S10. Obtain the area S of the top coal surface above the hydraulic support, and divide the area S of the top coal into a front half top coal surface and a rear half top coal surface, the area of ​​the front half top coal surface is S1 and the area of ​​the rear half top coal surface is S2; S20. After adjusting the spacing K1 between the two drilling units (310), the first drilling is performed on the rear half of the top coal surface, and the spacing K2 between the two drilling units (310) is adjusted to perform the second drilling on the rear half of the top coal surface to obtain a total of four holes, wherein the connecting line of the two drilling units (310) during the first drilling is perpendicular to the connecting line of the two drilling units (310) during the second drilling; A microwave irradiation mechanism (400) with a radiation radius of R is extended into four boreholes, and the boreholes are subjected to thermal radiation for a duration of t to reach a preset temperature T, and the irradiated area of ​​the rear half of the top coal surface reaches a preset ratio; S30. Repeat step S20 on the front half of the top coal surface, and start the liquid nitrogen mechanism to spray liquid nitrogen on the rear half of the top coal surface; S40. Perform microwave thermal radiation on the four drill holes in the front half of the top coal surface, and after the thermal radiation, start the liquid nitrogen mechanism to spray liquid nitrogen toward the front half of the top coal surface.

9. The method of use according to claim 7, characterized in that: Based on the coal placing step distance A of the hydraulic support and the width B of the hydraulic support top beam (120), the area S of the top coal is obtained.

10. The method of use according to claim 8, characterized in that: When drilling holes on the front half of the top coal surface and the rear half of the top coal surface, the impact area of ​​the four holes on the front half of the top coal surface or the rear half of the top coal surface is not less than a preset ratio, and the distances K1 and K2 between the two drilling units (310) and the radiation radius R of the microwave are obtained based on the preset ratio.

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