Joint detection experiment device for spontaneous ignition of coal mine goaf and application of joint detection experiment device

Abstract

The invention discloses a coal mine goaf spontaneous ignition joint detection experiment device and application thereof. The device comprises a goaf spontaneous ignition simulation experiment unit, a goaf sinking compaction simulation experiment unit, a fire source positioning unit and a tracer gas goaf air leakage channel analysis unit. All the simulation experiment units achieve information collection and simulation of different purposes, and after all the units are coupled, experimental research on goaf coal spontaneous combustion influence factors is achieved. According to the joint detection experiment device for spontaneous combustion in the coal mine goaf, a coal spontaneous combustion area is positioned according to the characteristic that waves respond sensitively to density change in a coal body: an ultrasonic probe is adopted to capture cracks after coal spontaneous combustion to form sound waves, and the propagation speed and the propagation time are obtained through signal processing and a display; three-dimensionally capturing and positioning a coal spontaneous combustion area; a temperature sensor assists in positioning the position of an ignition area; by injecting tracer gas krypton, an air leakage channel is determined, and the influence of the air leakage channel on coal spontaneous combustion is judged.

Description

Technical Field

[0001] The invention relates to the field of spontaneous combustion detection in coal mine goafs, in particular to a combined detection experimental device for spontaneous combustion in coal mine goafs based on an ultrasonic array and tracer gas and its application. Background Art

[0002] Spontaneous combustion of coal in goaf is a typical disaster that affects mine safety. The prediction and research of spontaneous combustion of coal in goaf is a difficult problem in this field. Due to the poor on-site detection conditions in coal mine goafs, the research and development of laboratory coal spontaneous combustion devices is imperative. At present, experts have developed a series of devices for measuring spontaneous combustion in goafs, which can analyze the temperature and toxic and harmful gases at different ignition stages. However, spontaneous combustion of coal in goafs is a disaster that is bred under complex working conditions and is affected by factors such as tunnel leakage and ground stress. Moreover, since the detection means in the coal body are not easy to arrange, the research progress of high-temperature areas and temperature attenuation laws under complex working conditions is slow. Therefore, it is very necessary to develop a laboratory detection device for spontaneous combustion in goafs that can determine the leakage channel of goafs, study the influence of leakage on coal spontaneous combustion, and accurately locate high-temperature areas.

[0003] Ultrasonic waves are sensitive to changes in density in coal, and during the spontaneous combustion of coal, the density of the coal will change significantly. Therefore, it is feasible to use ultrasonic arrays in conjunction with temperature sensor data to jointly detect the temperature of the goaf. Tracer gas can determine the gas flow channel and further prove the location of the ignition. Therefore, a joint detection experimental device for spontaneous combustion in coal mine goafs was designed. Summary of the invention

[0004] The present invention provides a combined detection experimental device for spontaneous combustion in goaf areas while overcoming the technical background problems. The present invention can realize the judgment of spontaneous combustion air leakage channels in goaf areas of coal mines, high temperature point detection, high temperature area detection and inversion, and analysis of the law of spontaneous combustion of coal, and confirm the ignition location through the collected data.

[0005] In order to achieve the above-mentioned technical effects, the technical solution adopted by the present invention is: a joint detection experimental device for spontaneous combustion in coal mine goafs, including a goaf natural combustion simulation experimental unit, a goaf sinking and compaction simulation experimental unit, a fire source positioning unit, and a tracer gas goaf leakage channel analysis unit; each simulation experimental unit realizes information collection and simulation for different purposes, and after coupling, each unit realizes experimental research on factors affecting spontaneous combustion of coal in goafs.

[0006] As an optimal technical solution: the goaf natural combustion simulation experimental unit includes a coal mine goaf simulated by a cylindrical tank, and an air intake tunnel and a return air tunnel simulated by pipes; the air intake tunnel and the return air tunnel are respectively arranged on both sides of the coal mine goaf, and measuring points for monitoring the air flow in the tunnel are respectively arranged inside the air intake tunnel and the return air tunnel near the mining working face, so as to realize the experimental study on the influence of the mining working face and the tunnel air flow on the natural combustion of the goaf.

[0007] As a preferred technical solution: a hot-bulb wind speed sensor is installed at the measuring point.

[0008] As a preferred technical solution: the goaf sinking and compaction simulation experiment unit includes a hydraulic cylinder simulating the overlying rock pressure of the goaf; the hydraulic cylinder is installed in the upper center area of ​​the cylindrical tank body, and the simulation experiment restores the actual stress conditions on site in the goaf.

[0009] As a preferred technical solution: the fire source locating unit includes a temperature sensor and an ultrasonic probe; temperature sensors are evenly distributed on the side walls and bottom of the cylindrical tank; ultrasonic probes that can actively apply pressure are embedded in the side walls of the cylindrical tank in an array; by actively stimulating ultrasonic signals, temperature signals and other information, the high-temperature points and temperature distribution are comprehensively judged to locate the fire source.

[0010] As a preferred technical solution: multiple ultrasonic probes are embedded in the wall of the tank, arranged in two rows on the inner side of the cylindrical tank, with two ultrasonic probes installed in each row, and the distance between them is 1.2 meters of the bottom circle diameter; each row is 1.6 and 0.7 m away from the bottom of the tank respectively, and two ultrasonic probes are installed on the top of the tank to construct a three-dimensional ultrasonic detection layout to ensure that ultrasonic waves can be excited and received in all directions.

[0011] As a preferred technical solution: the tracer gas goaf area leakage channel analysis unit includes a tracer gas injection port and a tracer gas detection port; the tracer gas injection port is arranged at the upper part of the cylindrical tank body; the tracer gas detection port is arranged at the bottom of the cylindrical tank body, distributed along the circumference to determine the leakage channel.

[0012] An application of a combined detection experimental device is carried out according to the following steps: S1. Construct a device to simulate the environment of the goaf Prepare a cylindrical tank as the goaf, build simulated ventilation tunnels on both sides of the goaf, and place experimental coal in the cylindrical tank; A hydraulic cylinder is arranged above the cylindrical tank; Arrange temperature sensors and ultrasonic probe arrays in the cylindrical tank; S2. Preliminary location of fire source The ultrasonic probe array generates ultrasonic waves through the transmitter and sends them into the cylindrical tank. The receiver receives the reflected waves and determines the propagation speed and attenuation speed of the ultrasonic waves between the two. The externally connected display is used for intuitive observation and the monitoring data is retained. The temperature sensor on the side wall of the cylindrical tank is close to the ultrasonic probe. The position of the coal spontaneous combustion is determined based on the temperature change caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment. S3. Accurately locate the fire source Tracer gas is injected into the tracer gas injection port on the top of the cylindrical tank, and eight detection ports are set within the boundary of the circular area at the bottom of the cylindrical tank. The gas extracted from the detection ports is analyzed for tracer gas content to locate the air leakage channel and further prove the location of the fire.

[0013] As a preferred technical solution: by using a temperature sensor and an ultrasonic probe to monitor the acoustic wave signal generated by the coal during the heating process using acoustic emission technology, the relationship between the speed of sound and the temperature is established based on the acoustic wave characteristics of the tested object to locate the area where the coal spontaneous combustion occurs; During the spontaneous combustion of coal, the generation of coal-rock pores and cracks is one of the main sources of acoustic emission signals. The ultrasonic probes arranged at the six measuring points all received the acoustic emission signals, and the propagation speed, attenuation speed and propagation time of the second to seventh ultrasonic probes were recorded respectively; The temperature rise of this area at that time is determined based on the propagation speed and attenuation speed; The transmission distance d of ultrasonic waves can be calculated by the following formula: d=v i× t i The distance is calculated based on six ultrasonic probes and the coal spontaneous combustion area is preliminarily located.

[0014] As a preferred technical solution: in step S2, temperature sensors are evenly arranged near the four ultrasonic probes on the side of the cylindrical tank body, and the temperature sensors are embedded in the side wall of the tank body, with the ends placed inside the tank body; eight temperature sensors are set inside the boundary of the circular area at the bottom of the cylindrical tank body, and the bottom area is divided into eight parts to form a point-surface array of side temperature detection points and bottom surface detection points; the position of the coal spontaneous combustion is judged according to the temperature changes caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention simulates the ventilation environment of the goaf and tunnel in actual work by constructing a cylindrical frame and a pipeline, and sets a hydraulic cylinder above the tank body to simulate the pressure of the overlying rock strata in the goaf, which is closer to the actual situation of the goaf in the coal mine. An ultrasonic probe array is embedded in the wall of the tank body to detect the spontaneous combustion area of ​​the coal, and the spontaneous combustion area of ​​the coal is located by the characteristic that the wave reacts sensitively to the density change in the coal body. The auxiliary temperature sensor captures the temperature data to verify the correctness of the ultrasonic positioning of the spontaneous combustion area of ​​the coal; the tracer gas is used to determine the gas flow channel and its influence on the spontaneous combustion area of ​​the coal, providing basic physical model conditions for the simulation of the natural combustion process and the main influencing factors and laws of the goaf of the coal mine.

[0016] The present invention adopts a combined detection experimental device for spontaneous combustion in coal mine goafs, and locates the coal spontaneous combustion area by using the characteristic that waves react sensitively to density changes in the coal body: an ultrasonic probe is used to capture sound waves formed by cracks after coal spontaneous combustion, and the propagation speed and propagation time are obtained through signal processing and a display, so as to capture and locate the coal spontaneous combustion area in three dimensions; a temperature sensor is used to assist in locating the position of the combustion area; and by injecting tracer gas krypton, the air leakage channel is determined, and the influence of the air leakage channel on the coal spontaneous combustion is judged. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the mining working surface inside the cylindrical tank of the present invention; Figure 3 This is a schematic diagram of the layout of temperature sensors in the mining working face of the present invention; Figure 4 It is a schematic diagram of the bottom of the mining working face in the present invention.

[0018] Wherein: hydraulic cylinder 1, second ultrasonic probe 2, third ultrasonic probe 3, fourth ultrasonic probe 4, fifth ultrasonic probe 5, sixth ultrasonic probe 6, seventh ultrasonic probe 7, bottom of cylindrical tank 8, display 9, tracer gas injection port 10, tracer gas detection port 11, hot ball wind speed sensor 12, return air channel 13, air inlet channel 14, side wall temperature sensor 15, bottom temperature sensor 16. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1-4 The present invention is described in detail with reference to embodiments.

[0020] The combined detection experimental device for spontaneous combustion in coal mine goafs disclosed in the present invention comprises a goaf spontaneous combustion simulation experimental unit, a goaf sinking and compaction simulation experimental unit, a fire source positioning unit, and a tracer gas goaf leakage channel analysis unit; each simulation experimental unit realizes information collection and simulation for different purposes, and after coupling, each unit realizes experimental research on factors affecting spontaneous combustion of coal in goafs.

[0021] The main equipment and device structures used include hydraulic cylinder 1, second ultrasonic probe 2, third ultrasonic probe 3, fourth ultrasonic probe 4, fifth ultrasonic probe 5, sixth ultrasonic probe 6, seventh ultrasonic probe 7, cylindrical tank body 8, display 9, tracer gas injection port 10, tracer gas detection port 11, hot ball wind speed sensor 12, return air roadway 13, air inlet roadway 14, side wall temperature sensor 15, bottom temperature sensor 16. The top of the cylindrical tank is connected to the bottom of the cylindrical tank body to simulate the goaf, and the ultrasonic probe can capture the sound generated during the spontaneous combustion reaction of coal and receive signals.

[0022] The cylindrical tank 8 contains coal samples, and a sealed shell is also provided outside the cylindrical tank 8. The cross-section of the cylindrical tank 8 and its shell adopts a "U"-shaped double-layer heat-recovery and heat-insulating structure to minimize the heat dissipated by the cylindrical tank to the environment. The whole is divided into three sections, the tank part is 3 meters high and the bottom circle diameter is 1.3 meters, the internal tank is 2 meters high and the bottom circle diameter is 1.2 meters. The ventilation duct and the tank area are separated by an iron mesh, and the ventilation ducts are set on both sides of the tank, each of which is 5 meters.

[0023] The coal and rock samples are evenly arranged at the bottom of the cylindrical tank 8 so that they are tightly covered without air leakage, ensuring that the placement of the experimental coal sample blocks is consistent with the actual situation of the goaf.

[0024] The goaf spontaneous combustion simulation experimental unit includes a coal mine goaf simulated by a cylindrical tank 8, and an air intake tunnel 14 and a return air tunnel 13 simulated by pipes; the air intake tunnel 14 and the return air tunnel 13 are respectively arranged on both sides of the coal mine goaf, and the positions of the air intake tunnel 14 and the return air tunnel 13 near the mining working face are respectively arranged with measuring points for monitoring the air flow in the tunnel, so as to realize the experimental study on the influence of the mining working face and the tunnel air flow on the spontaneous combustion of the goaf. In this embodiment, the measuring point is installed with a hot ball wind speed sensor 12.

[0025] The goaf sinking and compaction simulation experiment unit includes the pressure of the overburden strata in the goaf simulated by the hydraulic cylinder 1; the hydraulic cylinder 1 is installed in the upper center area of ​​the cylindrical tank 8, and the simulation experiment restores the real stress situation in the goaf. The single-acting hydraulic cylinder set on the upper part of the cylindrical tank 8 relies on the hydraulic pressure to make the cylinder move in one direction, and the reverse direction movement is achieved by external forces such as deadweight. To ensure the uniformity of pressure, the hydraulic cylinder 1 is set at the upper center of the cylindrical tank 8. The hydraulic cylinder converts mechanical energy into pressure, and squeezes the upper part of the cylindrical tank downward to meet the real pressure conditions in the goaf.

[0026] The fire source positioning unit includes a temperature sensor and an ultrasonic probe, wherein the temperature sensor includes a side wall temperature sensor 15 arranged on the side wall of the cylindrical tank body and a bottom temperature sensor 16 arranged on the bottom of the cylindrical tank body; the ultrasonic probe includes six ultrasonic probes, namely, a second ultrasonic probe 2, a third ultrasonic probe 3, a fourth ultrasonic probe 4, a fifth ultrasonic probe 5, a sixth ultrasonic probe 6, and a seventh ultrasonic probe 7. The ultrasonic probes that can actively apply pressure are embedded in the side wall of the cylindrical tank body in an array. By actively exciting ultrasonic signals, temperature signals and other information, the high temperature point and temperature distribution are comprehensively judged to locate the fire source.

[0027] The ultrasonic detection equipment mainly captures sound information, receives signals through the receiver, and completes the task through the signal processor and the display. The ultrasonic sensor is connected to the display 9 to analyze the waveform changes in real time and visually to judge the real-time situation of coal spontaneous combustion. Since the ultrasonic wave is sensitive to the change of density in the coal body, and the density of the coal body will change significantly during the natural combustion of coal, the propagation speed, attenuation speed and propagation time of the reflected ultrasonic wave will be different, which can be directly observed by the display, and the coal spontaneous combustion ignition area can be judged according to the characteristics of the ultrasonic wave after reflection. The second ultrasonic probe 2, the third ultrasonic probe 3, the fourth ultrasonic probe 4, and the fifth ultrasonic probe 5 are embedded in the wall of the tank body in an array, and two rows are arranged on the inner side of the cylindrical tank body. Two ultrasonic probes are installed in each row, and the distance is 1.2 meters of the bottom circle diameter. Each row is 1.6 and 0.7 m away from the bottom of the tank body, respectively. Two ultrasonic probes are installed on the top of the tank body, namely the sixth ultrasonic probe 6 and the seventh ultrasonic probe 7, to construct a three-dimensional ultrasonic detection layout to ensure that ultrasonic waves can be excited and received in all directions.

[0028] The tracer gas goaf leakage channel analysis unit includes a tracer gas injection port 10 and a tracer gas detection port 11. The tracer gas injection port 10 is arranged at the upper part of the cylindrical tank; the tracer gas detection port 11 is arranged at the bottom of the cylindrical tank, distributed along the circumference, to determine the leakage channel.

[0029] As a preferred embodiment, taking into account the time cost, economic cost, applicability, safety and other issues required for disaster identification, a method of quickly identifying air leakage channels in goafs using a tracer gas method, which is easy to operate, fast and safe to use, is designed.

[0030] In this embodiment, krypton is used as the tracer gas. Krypton is a colorless and odorless gas at room temperature and pressure. Krypton has high chemical inertness and is not easy to react with other elements or compounds. It is three times denser than air. Krypton is injected from the top of the cylindrical tank body, and the gas can flow into the bottom of the tank body so that it can be extracted at the next sampling port. Krypton is introduced into the tracer gas injection port 10 at the top of the cylindrical tank body, and eight tracer gas detection ports 11 are respectively set in the centers of the eight circular areas at the bottom to analyze the extracted gas, determine the krypton content, and locate the air leakage channel.

[0031] As a preferred solution: accurately control ventilation conditions, simulate tunnel wind flow, and set measurement points in the pipeline entering the tank. The wind speed entering the tank pipeline uses a hot bulb wind speed sensor 12; the air volume is measured in the main air duct using a pitot tube and a pressure difference sensor for calibration.

[0032] The application process of the above-mentioned joint detection experimental device is carried out according to the following steps: S1. Construct a device to simulate the environment of the goaf A cylindrical tank body is prepared as the goaf, simulated ventilation tunnels are constructed on both sides of the goaf, and experimental coal is placed in the cylindrical tank body; a hydraulic cylinder is set above the cylindrical tank body; a temperature sensor and an ultrasonic probe array are arranged in the cylindrical tank body, and an ultrasonic probe array that can actively apply pressure is embedded in the tank body wall, which is coupled with the spontaneous combustion environment of the goaf and forms a blocked monitoring path with the temperature sensors in the area.

[0033] S2. Preliminary location of fire source The ultrasonic probes are arranged in two rows around the cylindrical tank, evenly distributed, and two ultrasonic probes are placed above the coal body to fully cover the detection position. Figure 1 As shown. The ultrasonic probe array generates ultrasonic waves through the transmitter and sends them into the cylindrical tank. The receiver receives the reflected wave and determines the propagation speed and attenuation speed of the ultrasonic wave between the two. The display is connected for intuitive observation and the monitoring data is retained. The temperature sensor is close to the ultrasonic probe and is installed inside the tank. The position of the coal spontaneous combustion is determined according to the temperature change caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment.

[0034] S3. Accurately locate the fire source Tracer gas is injected into the tracer gas injection port above the cylindrical tank, and eight detection ports are set inside the boundaries of the eight circular areas at the bottom of the cylindrical tank, dividing the bottom area into eight parts. The gas flow channel is determined by the extraction of tracer gas from the middle injection port and the bottom boundary detection port, which can also further prove the location of the fire. The tracer gas content of the gas extracted from the detection port is analyzed to locate the air leakage tunnel, further proving the location of the fire.

[0035] In step S2, the acoustic emission technology is used to monitor the acoustic wave signal generated by the coal during the heating process by cooperating with the temperature sensor and the ultrasonic probe, and the relationship between the sound velocity and the temperature is established based on the acoustic wave characteristics of the tested object to locate the area where the coal spontaneous combustion occurs; Before the test measurement begins, multiple groups of measurement experiments are carried out to determine the influence of different pressures and ventilation speeds on the speed of sound wave propagation, as well as the influence on the amplitude of sound waves, and the threshold value is adjusted to filter out environmental noise.

[0036] During the spontaneous combustion of coal, the generation of coal-rock pores and cracks is one of the main sources of acoustic emission signals. The ultrasonic probes arranged at the six measuring points all receive acoustic emission signals, and the propagation speed v20, attenuation speed v'20 and propagation time t20 of the second ultrasonic probe 2 are recorded; the propagation speed v30, attenuation speed v'30 and propagation time t30 of the third ultrasonic probe 3; the propagation speed v40, attenuation speed v'40 and propagation time t40 of the fourth ultrasonic probe 4; the propagation speed v50, attenuation speed v'50 and propagation time t50 of the fifth ultrasonic probe 5; the propagation speed v60, attenuation speed v'60 and propagation time t60 of the sixth ultrasonic probe 6; the propagation speed v70, attenuation speed v'70 and propagation time t70 of the seventh ultrasonic probe 7; As the temperature increases, the acoustic emission signal shows a trend of gradual increase. The propagation velocity vhi, attenuation velocity v'hi and propagation time thi of the ultrasonic probe point can be recorded again; record multiple times and select the stable data value as the final data result.

[0037] The temperature rise of this area at that time can be determined based on the propagation speed and attenuation speed.

[0038] The transmission distance d of ultrasonic waves can be calculated by the following formula: d=v i× t i The distance is calculated based on six ultrasonic probes and the coal spontaneous combustion area is preliminarily located.

[0039] As another preferred embodiment, in step S2, temperature sensors are evenly arranged near the four ultrasonic probes on the side of the cylindrical tank body, and the temperature sensors are embedded in the side wall of the tank body, with the ends placed inside the tank body; eight temperature sensors are set inside the boundary of the circular area at the bottom of the cylindrical tank body, and the bottom area is divided into eight parts to form a point-surface array of side temperature detection points and bottom surface detection points; the position of the coal spontaneous combustion is judged according to the temperature changes caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment.

Claims

1. A combined detection experimental device for spontaneous combustion in coal mine goaf, characterized in that: It includes the goaf spontaneous combustion simulation experiment unit, goaf sinking and compaction simulation experiment unit, fire source location unit, and tracer gas goaf leakage channel analysis unit; after coupling each unit, the experimental study on the factors affecting spontaneous combustion of coal in the goaf can be realized; The goaf spontaneous combustion simulation experimental unit includes a coal mine goaf simulated by a cylindrical tank, and an air intake tunnel and a return air tunnel simulated by pipes; the air intake tunnel and the return air tunnel are respectively arranged on both sides of the coal mine goaf, and measuring points for monitoring the air flow in the tunnel are respectively arranged near the mining working face inside the air intake tunnel and the return air tunnel, so as to realize the experimental study on the influence of the mining working face and the tunnel air flow on the spontaneous combustion of the goaf.

2. The combined detection experimental device for spontaneous combustion in coal mine goaf according to claim 1 is characterized in that: A thermal bulb wind speed sensor is installed at the measuring point.

3. The combined detection experimental device for spontaneous combustion in coal mine goaf according to claim 1 is characterized in that: The goaf sinking and compaction simulation experiment unit includes a hydraulic cylinder simulating the overburden stratum pressure of the goaf; the hydraulic cylinder is installed in the upper center area of ​​the cylindrical tank, and the simulation experiment restores the real stress condition of the goaf on site.

4. The combined detection experimental device for spontaneous combustion in coal mine goaf according to claim 1 is characterized in that: The fire source locating unit includes a temperature sensor and an ultrasonic probe; temperature sensors are evenly distributed on the side walls and bottom of the cylindrical tank; ultrasonic probes that can actively apply pressure are embedded in the side walls of the cylindrical tank in an array; by actively stimulating ultrasonic signals, temperature signals and other information, the high-temperature points and temperature distribution are comprehensively judged to locate the fire source.

5. The combined detection experimental device for spontaneous combustion in coal mine goaf according to claim 1 is characterized in that: Multiple ultrasonic probes are embedded in the wall of the tank and arranged in two rows on the inner side of the cylindrical tank. Two ultrasonic probes are installed in each row, and the distance between them is 1.2 meters of the bottom circle diameter. Each row is 1.6 and 0.7 m away from the bottom of the tank respectively. Two ultrasonic probes are installed on the top of the tank to construct a three-dimensional ultrasonic detection layout to ensure that ultrasonic waves can be excited and received in all directions.

6. The combined detection experimental device for spontaneous combustion in coal mine goaf according to claim 1 is characterized in that: The tracer gas goaf leakage channel analysis unit comprises a tracer gas injection port and a tracer gas detection port; the tracer gas injection port is arranged at the upper part of the cylindrical tank body; the tracer gas detection port is arranged at the bottom of the cylindrical tank body and distributed along the circumference to determine the leakage channel.

7. An application of the combined detection experimental device according to any one of claims 1 to 6, characterized in that: Follow these steps: S1. Construct a device to simulate the environment of the goaf Prepare a cylindrical tank as the goaf, build simulated ventilation tunnels on both sides of the goaf, and place experimental coal in the cylindrical tank; A hydraulic cylinder is arranged above the cylindrical tank; Arrange temperature sensors and ultrasonic probe arrays in the cylindrical tank; S2. Preliminary location of fire source The ultrasonic probe array generates ultrasonic waves through the transmitter and sends them into the cylindrical tank. The receiver receives the reflected waves and determines the propagation speed and attenuation speed of the ultrasonic waves between the two. The externally connected display is used for intuitive observation and the monitoring data is retained. The temperature sensor on the side wall of the cylindrical tank is close to the ultrasonic probe. The position of the coal spontaneous combustion is determined based on the temperature change caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment. S3. Accurately locate the fire source Tracer gas is injected into the tracer gas injection port on the top of the cylindrical tank, and eight detection ports are set within the boundary of the circular area at the bottom of the cylindrical tank. The gas extracted from the detection ports is analyzed for tracer gas content to locate the air leakage channel and further prove the location of the fire.

8. The application of the combined detection experimental device according to claim 7 is characterized in that: In step S2, the acoustic emission technology is used to monitor the acoustic wave signal generated by the coal during the heating process by cooperating with the temperature sensor and the ultrasonic probe, and the relationship between the sound velocity and the temperature is established based on the acoustic wave characteristics of the tested object to locate the area where the coal spontaneous combustion occurs; During the spontaneous combustion of coal, the generation of coal-rock pores and cracks is one of the main sources of acoustic emission signals. The ultrasonic probes arranged at the six measuring points all received the acoustic emission signals, and the propagation speed, attenuation speed and propagation time of the second to seventh ultrasonic probes were recorded respectively; The temperature rise of this area at that time is determined based on the propagation speed and attenuation speed; The transmission distance d of ultrasonic waves can be calculated by the following formula: d=v i× t i The distance is calculated based on six ultrasonic probes and the coal spontaneous combustion area is preliminarily located.

9. The application of the combined detection experimental device according to claim 7, characterized in that: In step S2, temperature sensors are evenly arranged near the four ultrasonic probes on the side of the cylindrical tank body, and the temperature sensors are embedded on the side wall of the tank body, with the ends placed inside the tank body; eight temperature sensors are set inside the boundary of the circular area at the bottom of the cylindrical tank body, and the bottom area is divided into eight parts to form a point-surface array of side temperature detection points and bottom detection points; the position of the coal spontaneous combustion is judged according to the temperature changes caused by the spontaneous combustion of the coal, and the ultrasonic signal is used to assist in improving the accuracy of the experimental result judgment.

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