A device and method for testing the explosion limits of low-concentration methane gas based on combustion and explosion pressure at high temperature regenerative oxidation.

Abstract

A device and method for testing the explosion limits of low-concentration methane gas extracted at high temperatures based on combustion and explosion pressure, belonging to the field of coal mine safety, is described. The device includes a high-temperature heating chamber, a pressure measurement system, a gas supply system, and a vacuum extraction system. The pressure measurement system is installed at the upper opening of the high-temperature heating chamber and uses a cooling component and a heat insulation component in conjunction with a water-cooled pressure sensor to measure the combustion and explosion pressure of low-concentration methane gas extracted at high temperatures through combustion and explosion. The gas supply system uses a solenoid valve to control a high-pressure mixing tank and injects the mixed gas into the high-temperature heating chamber through a multi-channel compressed gas nozzle from the lower opening. The side opening of the high-temperature heating chamber is sequentially connected to the cooling coil, water-cooled jacket, and vacuum pump of the vacuum extraction system. This device solves the problem of vacuum extraction under high-temperature conditions, enabling repeated measurement of the pressure evolution curve of extracted methane gas from oxidation reaction to combustion and explosion under high-temperature conditions, and accurately obtaining the explosion limits of low-concentration methane gas extracted from coal mines within the range of room temperature to 1200℃.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety, specifically a high-temperature regenerative oxidation low-concentration gas explosion limit testing device and method based on combustion and explosion pressure. Background Technology

[0002] Methane gas is a highly efficient and clean fuel widely used in power generation, heating, industrial fuel, and household energy. However, its main component, methane, is also a potent greenhouse gas, with a greenhouse effect 20-25 times that of carbon dioxide and an ozone depletion potential 7 times greater. Therefore, methane gas is crucial for clean energy utilization and reducing greenhouse gas emissions. Low concentrations of methane gas are typically present during ventilation in underground mines such as coal mines. Directly releasing this extracted methane gas into the atmosphere exacerbates the greenhouse effect and negatively impacts the achievement of dual carbon targets. Regenerative thermal oxidation, using a high-temperature environment to oxidize extracted methane gas into water and carbon dioxide, not only avoids environmental pollution but also fully utilizes the oxidation heat energy of the methane gas, making it an effective means of solving the problem of methane gas emissions from coal mines.

[0003] In the oxidation process of coal mine extracted gas, temperature is a crucial factor affecting reaction efficiency. High temperatures provide more energy to overcome the activation energy barrier, making the reaction easier to proceed. Therefore, the higher the regenerative oxidation temperature, the faster the oxidation reaction rate and the higher the oxidation efficiency. However, when handling combustible gases such as methane, special attention must be paid to the operating temperature, as high temperatures may increase the risk of explosion once the lower explosive limit concentration is reached or exceeded. Therefore, blindly changing the methane concentration or the temperature of the regenerative tank to improve its efficiency carries the risk of explosion. To ensure the safe application of regenerative oxidation technology for coal mine extracted gas in industrial production, it is urgent to determine the critical concentration at which methane transitions from oxidation to explosion under different temperature conditions.

[0004] Existing research indicates that increased temperature lowers the lower explosive limit of methane while raising its upper explosive limit. The regenerative oxidation process of extracted methane in coal mines involves a high-temperature range of 500℃ to 1200℃, inevitably resulting in an explosive limit 5%-16% wider than at normal temperature and pressure. Currently, there are few testing devices for the explosive limits of low-concentration methane produced by regenerative oxidation at temperatures above 500℃, and existing devices rely on external scales to determine the occurrence of explosions, failing to provide a direct visual representation of the internal reaction. Recording the evolution of internal pressure can reveal the internal methane oxidation process, allowing for a more precise determination of the explosive limit range of low-concentration methane produced by regenerative oxidation at different temperatures. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure. This device is designed with a high-temperature pressure testing element, which can concretely characterize the pressure evolution process of methane gas oxidation during coal mine extraction, and accurately obtain the explosion limit of methane at temperatures above 500℃.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure, the device includes a high-temperature heating chamber, a pressure measurement system, a gas supply system and a vacuum extraction system.

[0008] The high-temperature heating chamber consists of a stainless steel inner liner, an electric heating wire, an insulation layer, and a metal outer shell arranged sequentially from the inside out; the temperature sensor is inserted from the side hole of the stainless steel inner liner to the center of the stainless steel inner liner; glass windows are installed at the front and rear center positions of the high-temperature heating chamber.

[0009] The high-temperature heating cavity has an opening at the top for connecting to a pressure measurement system, an opening at the bottom for connecting to a gas supply system, and an opening at the side for connecting to a vacuum extraction system.

[0010] The pressure measurement system includes a cooling component and a heat insulation component. In the cooling component, the stainless steel cylinder is cylindrical, with heat insulation cotton sandwiched between the stainless steel cylinder and a metal wire mesh. An upper top plate is installed on the upper part of the stainless steel cylinder, and a water-cooled pressure sensor is installed at the center of the upper top plate. The outer flange of the stainless steel cylinder is connected to the inner flange of the stainless steel inner liner by fixing bolts. Below the cooling component, a heat insulation component is installed. One end of the first heat insulation plate and the second heat insulation plate are respectively hinged to the inner wall of the inner flange. The other end of the first heat insulation plate is connected to one end of a first telescopic spring, which is connected to the inner wall of one side of the stainless steel cylinder. The other end of the second heat insulation plate is connected to one end of a second telescopic spring, which is connected to the inner wall of the other side of the stainless steel cylinder. The extension and retraction of the first and second telescopic springs are controlled by external electrical signals.

[0011] The inlet of the cooling coil in the vacuum extraction system is connected to the side opening of the high-temperature heating chamber; the water-cooled jacket is wrapped around the cooling coil; the outlet pipe of the cooling coil is connected to the left end of the vacuum three-way valve, the lower end of the vacuum three-way valve is connected to the vacuum pump, and the upper end is connected to the vent pipe.

[0012] In the gas supply system, high-pressure air cylinders and high-pressure gas cylinders are connected to high-pressure mixing tanks via pipelines. The outlet pipeline of the high-pressure mixing tank is equipped with a flame arrester, a solenoid valve, and a heat insulation valve in sequence. A multi-channel compressed gas nozzle is installed at the end of the pipeline that is inserted into the high-temperature heating chamber.

[0013] A sealing ring is provided between the body flange and the inner liner flange of the stainless steel cylinder.

[0014] The interface between the first heat insulation plate and the second heat insulation plate adopts a stepped structure.

[0015] A temperature control valve and a second pressure gauge are connected to the outlet of the cooling coil.

[0016] A pressure reducing valve and a check valve are installed on the outlet pipe of the high-pressure air cylinder, and a pressure reducing valve and a check valve are installed on the outlet pipe of the high-pressure gas cylinder.

[0017] A first pressure gauge is installed on the high-pressure mixing tank.

[0018] The multi-channel compressed gas nozzle is provided with multiple sets of channels, and the gas forms a 240° injection angle.

[0019] The operating method of the high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure includes the following steps:

[0020] S1. Open the high-pressure air cylinder and introduce air at 1.92~1.98 MPa into the high-pressure mixing tank by adjusting the pressure reducing valve, then close the high-pressure air cylinder; open the high-pressure gas cylinder and introduce gas into the high-pressure mixing tank by adjusting the pressure reducing valve until the pressure gauge reads 2 MPa. At this time, the gas concentration in the high-pressure mixing tank is 1%~4%.

[0021] S2. Open the valve at the inlet of the cooling coil, close the valve on the vent pipe, and turn on the vacuum pump to evacuate the high-temperature heating chamber to a vacuum of less than 3 kPa.

[0022] S3. Use the PLC timing setting device to set the time sequence after pressing the switch as follows: a. Open the first heat insulation plate, b. Open the second heat insulation plate, c. Turn on the data acquisition instrument used by the pressure sensor, d. Open the solenoid valve, e. Close the solenoid valve, f. Close the second heat insulation plate, g. Close the first heat insulation plate;

[0023] The PLC controls the first telescopic spring to open the first heat insulation plate, and then controls the second telescopic spring to open the second heat insulation plate.

[0024] The PLC controls the opening of the solenoid valve, and the gas in the high-pressure mixing tank passes through the flame arrester, solenoid valve, and heat insulation valve in sequence, and is then injected into the high-temperature heating chamber through the orifice on the multi-channel compressed gas nozzle; then, the PLC controls the closing of the solenoid valve.

[0025] After the reaction is complete, the PLC controls the second telescopic spring to close the second heat insulation plate, and then controls the first telescopic spring to close the first heat insulation plate.

[0026] In step S3, timing c is added to activate the high-speed camera system to capture the internal gas combustion and explosion process through the glass window.

[0027] The voltage signal recorded by the pressure sensor is converted into a pressure value. The criterion for determining whether gas changes from an oxidation reaction to an explosion is: the maximum pressure value increases by more than 7%.

[0028] Compared with the prior art, the present invention provides a high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure, which has the following beneficial effects:

[0029] 1. This device and its supporting equipment can be used to conduct repeated experiments to determine the explosion limits of low-concentration methane at temperatures above 500℃ through high-temperature regenerative oxidation. This can guide the design and application of regenerative oxidation utilization of extracted methane in coal mines, reduce investment in the utilization of extracted methane, improve the economic efficiency of utilization, and facilitate its widespread application.

[0030] 2. This device utilizes a cooling component and a switchable heat insulation plate to protect the pressure sensor, which can obtain the pressure evolution process of the high-temperature, low-concentration gas oxidation combustion and explosion process, and determine the explosion limit of high-temperature heat storage oxidation of low-concentration gas based on the pressure evolution curve. This method is more scientific and the results obtained are more accurate.

[0031] 3. The glass window of the device allows for a more direct view of the internal high-temperature, low-concentration gas combustion and explosion reaction process, greatly expanding the scope of research on disasters caused by high-temperature, low-concentration gas combustion and explosion.

[0032] 4. The device uses a cooling coil combined with a water-cooled clamp for vacuum extraction, which protects the safety of the vacuum pump and the high-precision pressure gauge.

[0033] 5. The device pre-mixes gas in a high-pressure mixing tank before injecting it into the chamber. This gas mixing method is more precise and avoids the risk of combustion and explosion when gas is supplied alone, thus improving the safety of the experiment.

[0034] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0035] Figure 1 This is a structural diagram of a high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure.

[0036] Figure 2 This is a structural diagram of the cooling component.

[0037] Figure 3This is an enlarged view of the thermal insulation component.

[0038] Figure 4 This is an enlarged view of a water-cooled pressure sensor.

[0039] Figure 5 This is a cross-sectional view of a multi-channel compressed gas nozzle.

[0040] Attached reference numerals: 1. Stainless steel inner liner; 1a. Inner liner flange; 2. Electric heating wire; 3. Insulation layer; 4. Metal outer shell; 5. Temperature sensor; 6. Glass window; 7. Water-cooled pressure sensor; 8. Stainless steel cylinder; 8a. Cylinder flange; 9. Metal wire mesh; 10. Thermal insulation cotton; 11. Sealing ring; 12. Fixing bolt; 13. Top plate; 14. First thermal insulation plate; 15. Second thermal insulation plate; 16. First telescopic spring; 16a. Second telescopic spring; 17. 18. High-pressure air cylinder; 19. High-pressure gas cylinder; 20. Pressure reducing valve; 21. Check valve; 22. Gas supply three-way valve; 21a. Vacuum three-way valve; 23. High-pressure mixing tank; 24. Flame arrester; 25. First pressure gauge; 26. Solenoid valve; 27. Heat insulation valve; 28. Multi-channel compressed gas nozzle; 29. ​​Channel; 30. Cooling coil; 31. Valve; 32. Water-cooled jacket; 33. Temperature control valve; 34. Second pressure gauge; 35. Vacuum pump; 36. Vent pipe. Detailed Implementation

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples, so that the above-mentioned objects, features and advantages of the present invention will become more apparent and understandable. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0042] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0043] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0044] A high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure includes: a high-temperature heating chamber, a pressure measurement system, a gas supply system, and a vacuum extraction system.

[0045] The high-temperature heating cavity includes: a stainless steel inner liner, an electric heating wire, an insulation layer, a metal outer shell, a temperature sensor, and a glass window.

[0046] The stainless steel inner liner is wrapped with an electric heating wire, which is then wrapped with an insulation layer, and finally wrapped with a metal outer shell.

[0047] The temperature sensor has a 0.5mm tip and is inserted into the center of the stainless steel inner liner through a small hole on the left side. The contact area between the temperature sensor and the stainless steel inner liner wall is sealed with high-temperature adhesive.

[0048] A circular hole is opened at the center of the front and rear of the stainless steel inner liner, the insulation layer and the metal outer shell for installing a glass window. The window uses No. 4 high temperature resistant glass, which can work for a long time in an environment of 1200℃. A two-component ultra-high temperature adhesive (resistant to 1730℃ high temperature) composed of inorganic ceramic materials and modified curing agent is used to fill the gap between the glass window and the wall to fix and seal it.

[0049] The stainless steel inner liner, insulation layer and metal outer shell have a circular hole at the top for connecting to the pressure measurement system, a hole at the bottom for connecting to the air supply system, and a hole on the side for connecting to the vacuum extraction system.

[0050] The pressure measurement system is connected to the upper opening of the high-temperature heating chamber and includes: a cooling device assembly, a heat insulation assembly, and a water-cooled pressure sensor. The cooling device assembly includes: a stainless steel cylinder, a metal wire mesh, heat insulation cotton, a sealing ring, fixing bolts, and an upper top plate. The heat insulation assembly includes: a first heat insulation plate, a second heat insulation plate, and a telescopic spring.

[0051] The stainless steel cylinder of the cooling component is cylindrical, with heat insulation cotton placed between the stainless steel cylinder and the metal wire mesh; the sealing ring is fixed near the high-temperature heating cavity for sealing; the top plate is fixed to the upper part of the stainless steel cylinder, with a circular hole in the middle for placing a water-cooled pressure sensor; the lower part of the cooling component has a square opening for fixing the heat insulation device.

[0052] The heat insulation device is installed at the lower inlet of the cooling component. The first heat insulation plate and the second heat insulation plate are connected to the lower inner wall of the cooling component by a hinge connection. One end of the telescopic spring is connected to the ends of the first heat insulation plate and the second heat insulation plate, and the other end is connected to the inner wall of the stainless steel cylinder. The telescopic behavior is controlled by an external electrical signal, thereby realizing the opening and closing of the first heat insulation plate and the second heat insulation plate. The interface between the first heat insulation plate and the second heat insulation plate adopts a stepped structure to enhance the heat insulation and sealing performance.

[0053] The heat insulation bolt with internal and external threads is fixed to the circular hole on the top plate of the cooling component, and the water-cooled pressure sensor penetrates into the cooling component through the internal threads of the heat insulation bolt.

[0054] The gas supply system is connected to the lower opening of the high-temperature heating chamber and includes: a high-pressure air cylinder, a high-pressure gas cylinder, a pressure reducing valve, a check valve, a three-way valve, a high-pressure mixing tank, a flame arrester, a first pressure gauge, a solenoid valve, a heat insulation valve, and a multi-channel compressed gas nozzle.

[0055] The outlets of the high-pressure air cylinder and the high-pressure gas cylinder are respectively connected to pipelines through pressure reducing valves, and a check valve is installed between the pressure reducing valve and the three-way valve.

[0056] The inlet of the high-pressure mixing tank is connected to the high-pressure air cylinder and the high-pressure gas cylinder via a three-way valve; a first pressure gauge is installed above the high-pressure mixing tank to detect the internal pressure of the high-pressure mixing tank; a flame arrester is installed between the outlet of the high-pressure mixing tank and the inlet pipe of the solenoid valve.

[0057] The solenoid valve is controlled by an external electrical signal, enabling millisecond-level opening and closing actions; a heat insulation valve is installed between the solenoid valve outlet and the multi-channel compressed gas nozzle.

[0058] The multi-channel compressed gas nozzle ejects uniform gas through multiple holes, forming a 240° spray angle.

[0059] The side opening of the vacuum extraction system connected to the high-temperature heating chamber includes: a cooling coil, a valve, a water-cooled jacket, a temperature control valve, a second pressure gauge, a three-way valve, a vacuum pump, and a vent pipe.

[0060] The inlet of the cooling coil is connected to the side opening of the high-temperature heating chamber, and the opening and closing of the internal space of the chamber and the cooling coil are realized by the valve; the water-cooled jacket is wrapped around the cooling coil to cool it down; the outlet of the cooling coil is connected to a temperature control valve to prevent the outlet temperature from exceeding the working pressure of the pressure gauge and the vacuum pump.

[0061] The three-way valve is connected to the outlet pipe of the cooling coil on the left, the vacuum pump on the lower end, and the vent pipe on the upper end. Its function is to discharge the gas in the chamber in an emergency.

[0062] A method for testing the explosion limits of low-concentration methane gas based on combustion and explosion pressure, using the aforementioned high-temperature regenerative oxidation low-concentration methane gas explosion limit testing device, includes the following steps:

[0063] S1. Open the high-pressure air cylinder and introduce 1.92~1.98 MPa of air into the high-pressure mixing tank by adjusting the pressure reducing valve. Then close the high-pressure air cylinder, open the high-pressure gas cylinder, and introduce gas into the high-pressure mixing tank by adjusting the pressure reducing valve until the pressure gauge reading is 2 MPa. At this time, the gas concentration in the high-pressure mixing tank is 1%~4%.

[0064] S2, open the valve at the inlet of the cooling coil, close the valve on the vent pipe, and turn on the vacuum pump to evacuate the high-temperature chamber to a vacuum of less than 3 kPa.

[0065] S3, set using PLC timing setting device, the time sequence after pressing the switch is as follows: a. Open the first heat insulation plate, b. Open the second heat insulation plate, c. Turn on the data acquisition instrument used by the pressure sensor, d. Open the solenoid valve, e. Close the solenoid valve, f. Close the second heat insulation plate, g. Close the first heat insulation plate.

[0066] S4 converts the voltage signal recorded by the pressure sensor into a pressure value. The method for determining whether gas changes from an oxidation reaction to an explosion is: the maximum pressure value increases by more than 7%.

[0067] Optionally, in step S1, the gas concentration increases at a rate of 0.1% each time.

[0068] Optionally, in step S3, a high-speed camera system can be added to sequence c to capture the internal gas combustion and explosion process through a glass window.

[0069] like Figure 1 As shown, this is a testing device that can accurately determine the explosion limit of low-concentration methane gas in high-temperature regenerative oxidation, comprising: a high-temperature heating chamber, a pressure measurement system, a gas supply system, and a vacuum extraction system.

[0070] See Figure 1The high-temperature heating chamber has a stainless steel inner liner 1 wrapped with an electric heating wire 2, an insulation layer 3 wrapped around the electric heating wire 2, and a metal outer shell 4 wrapped around the insulation layer 3. The temperature sensor 5 has a 0.5mm tip and is inserted into the center of the chamber through a small hole on the left side of the stainless steel inner liner 1. The contact part between the temperature sensor 5 and the wall of the stainless steel inner liner 1 is sealed with high-temperature adhesive. A circular hole is made at the center of the front and rear of the stainless steel inner liner 1, the insulation layer 3, and the metal outer shell 4 for installing a glass window 6. The window is made of No. 4 high-temperature resistant glass and can work for a long time in an environment of 1200℃. A two-component ultra-high temperature adhesive (resistant to 1730℃) composed of inorganic ceramic materials and modified curing agent is used to fill the gap between the glass window and the wall for fixing and sealing. A hole is made at the top of the stainless steel inner liner 1, the insulation layer 3, and the metal outer shell 4 to connect to the pressure measurement system, a hole is made at the bottom to connect to the gas supply system, and a hole is made on the side to connect to the vacuum extraction system.

[0071] See Figure 1 The pressure measurement system is connected to the upper opening of the high-temperature heating chamber and includes: a cooling device assembly, a heat insulation assembly, and a water-cooled pressure sensor 7. The cooling device assembly includes: a stainless steel cylinder 8, a metal wire mesh 9, heat insulation cotton 10, a sealing ring 11, a fixing bolt 12, and an upper top plate 13. The heat insulation assembly includes: a first heat insulation plate 14, a second heat insulation plate 15, and a telescopic spring 16.

[0072] See Figure 2 The stainless steel cylinder 8 of the cooling component is cylindrical, with insulation cotton 10 placed between the stainless steel cylinder 8 and the metal wire mesh 9. A sealing ring 11 is installed between the cylinder flange 8a and the inner liner flange 1a, fixed near the high-temperature heating chamber for sealing. The inner liner flange 1a is welded to the upper opening of the stainless steel inner liner 1, and the cylinder flange 8a is located on the bottom outer side of the stainless steel cylinder 8. The top plate 13 is fixed to the upper part of the stainless steel cylinder 8, with a circular hole in the middle for placing the water-cooled pressure sensor 7. The lower part of the cooling component has a square opening for fixing the heat insulation device.

[0073] See Figure 3 The heat insulation device is installed at the lower inlet of the cooling component. The first heat insulation plate 14 and the second heat insulation plate 15 are connected to the inner wall of the inner flange 1a by a hinge connection. One end of the first telescopic spring 16 and the second telescopic spring 16a are respectively connected to the ends of the first heat insulation plate 14 and the second heat insulation plate 15, and the other end of the spring is respectively connected to the inner wall of both sides of the stainless steel cylinder 8. The extension and retraction behavior of the telescopic springs is controlled by an external electrical signal, thereby realizing the opening and closing of the first heat insulation plate 14 and the second heat insulation plate 15. The interface between the first heat insulation plate 14 and the second heat insulation plate 15 adopts a stepped structure to enhance the heat insulation and sealing performance.

[0074] See Figure 4The heat insulation bolts with internal and external threads are fixed to the circular holes on the top plate of the cooling component, and the water-cooled pressure sensor penetrates into the cooling component through the internal threads of the heat insulation bolts.

[0075] See Figure 1 The gas supply system is connected to the lower opening of the high-temperature heating chamber. The outlets of the high-pressure air cylinder 17 and the high-pressure gas cylinder 18 are respectively connected to pipelines through pressure reducing valves 19. A check valve 20 is installed between the pressure reducing valve 19 and the gas supply three-way valve 21. The inlet of the high-pressure mixing tank 22 is connected to the high-pressure air cylinder 17 and the high-pressure gas cylinder 18 through the gas supply three-way valve 21. A first pressure gauge 24 is installed above the high-pressure mixing tank 22 to detect the internal pressure of the tank. A flame arrester 23 is installed between the outlet of the high-pressure mixing tank 22 and the inlet pipeline of the solenoid valve 25. The solenoid valve 25 is controlled by an external electrical signal and can achieve millisecond-level opening and closing actions. A heat insulation valve 26 is installed between the outlet of the solenoid valve and the multi-channel compressed gas nozzle.

[0076] See Figure 5 The multi-channel compressed gas nozzle 27 sprays uniform gas through multiple holes, forming a 240° spray angle.

[0077] See Figure 1 The vacuum extraction system is connected to the side opening of the high-temperature heating chamber. The inlet of the cooling coil 28 is connected to the side opening of the high-temperature heating chamber. The valve 29 is used to open and close the space inside the chamber and the cooling coil 28. The water-cooled jacket 30 is wrapped around the cooling coil 28 to cool it down. The outlet of the cooling coil 28 is connected to a temperature control valve 31 to prevent the outlet temperature from exceeding the working pressure of the second pressure gauge 32 and the vacuum pump 33. The left end of the vacuum three-way valve 21a is connected to the outlet pipe of the cooling coil 28, the lower end is connected to the vacuum pump 33, and the upper end is connected to the vent pipe 34. Its function is to discharge the gas in the chamber in an emergency.

[0078] A method for testing the explosion limits of low-concentration methane gas based on combustion and explosion pressure, using the aforementioned high-temperature regenerative oxidation low-concentration methane gas explosion limit testing device, includes the following steps:

[0079] S1. Open the high-pressure air cylinder 17 and introduce 1.92~1.98 MPa of air into the high-pressure mixing tank 22 by adjusting the pressure reducing valve 19. Then close the high-pressure air cylinder 17, open the high-pressure gas cylinder 18, and introduce gas into the high-pressure mixing tank until the pressure gauge reading is 2 MPa. At this time, the gas concentration in the high-pressure mixing tank 22 is 1%~4% (increasing the gas concentration at a rate of 0.1% each time).

[0080] S2, open valve 29 at the inlet of cooling coil 28, close valve on vent pipe, and turn on vacuum pump 33 to evacuate the high-temperature chamber to a vacuum below 3 kPa.

[0081] S3, using the PLC timing setting device, the sequence of time after pressing the switch is as follows: a. Open the first heat insulation plate 14, b. Open the second heat insulation plate 15, c. Open the data acquisition instrument used by the water-cooled pressure sensor 7 (a high-speed camera system can be added to capture the internal gas combustion process through the glass window), d. Open the solenoid valve 25, e. Close the solenoid valve 25, f. Close the second heat insulation plate 15, g. Close the first heat insulation plate 14.

[0082] S4 converts the voltage signal recorded by the pressure sensor into a pressure value. The method for determining whether gas changes from an oxidation reaction to an explosion is: the maximum pressure value increases by 7%.

[0083] Currently known publicly available technologies use external scales as the basis for determining the occurrence of an explosion. However, this method is simplistic and cannot visually reveal the internal reaction. The method for determining the explosion limit lacks precision. Existing pressure sensors can withstand high-temperature shocks for a few seconds, but cannot perform long-term measurements at high temperatures. Furthermore, most current explosion limit measurement devices operate at room temperature, failing to provide vacuum extraction capabilities at high temperatures. This experiment utilizes a cooling device in conjunction with a water-cooled pressure sensor to measure the combustion and explosion pressure at high temperatures. An openable heat insulation device is designed to prevent the pressure sensor from being exposed to high temperatures for extended periods without affecting pressure measurement. The cooling coil combined with a water-cooled jacket in this invention solves the vacuum extraction problem at high temperatures. Combined with the explosion limit measurement method in this invention, the pressure evolution curve of low-concentration methane gas undergoing oxidation from oxidation to combustion and explosion can be obtained, providing a more accurate assessment of the explosion limit of coal mine extracted methane gas within the range of 500–1200°C.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure, characterized in that: The device includes a high-temperature heating chamber, a pressure measurement system, a gas supply system, and a vacuum extraction system; The high-temperature heating chamber is composed of a stainless steel inner liner (1), an electric heating wire (2), a heat insulation layer (3), and a metal outer shell (4) arranged sequentially from the inside to the outside; the temperature sensor (5) is inserted into the center of the stainless steel inner liner through the side hole of the stainless steel inner liner (1); a glass window (6) is installed at the front and rear center positions of the high-temperature heating chamber. The high-temperature heating cavity has an opening at the top for connecting to a pressure measurement system, an opening at the bottom for connecting to a gas supply system, and an opening at the side for connecting to a vacuum extraction system. The pressure measurement system includes a cooling component and a heat insulation component. In the cooling component, the stainless steel cylinder (8) is cylindrical, and the heat insulation cotton (10) is sandwiched between the stainless steel cylinder (8) and the metal wire mesh (9). An upper top plate (13) is provided on the upper part of the stainless steel cylinder (8), and a water-cooled pressure sensor (7) is provided at the center of the upper top plate (13). The cylinder flange (8a) outside the stainless steel cylinder (8) is connected to the inner liner flange (1a) fixed on the stainless steel inner liner (1) by fixing bolts (12). A heat insulation component is provided below the cooling component. The interface between the first heat insulation plate (14) and the second heat insulation plate (15) used to enhance the heat insulation and sealing is stepped. The structure is trapezoidal; one end of the first heat insulation plate (14) and the second heat insulation plate (15) are respectively connected to the inner wall of the inner flange (1a) by hinge; the other end of the first heat insulation plate (14) is connected to one end of the first telescopic spring (16), and the other end of the first telescopic spring (16) is connected to the inner wall of one side of the stainless steel cylinder (8); the other end of the second heat insulation plate (15) is connected to one end of the second telescopic spring (16a), and the other end of the second telescopic spring (16a) is connected to the inner wall of the other side of the stainless steel cylinder (8); the extension and retraction behavior of the first telescopic spring (16) and the second telescopic spring (16a) are controlled by external electrical signals respectively. The inlet of the cooling coil (28) in the vacuum extraction system is connected to the side opening of the high-temperature heating chamber; the water-cooled jacket (30) is wrapped around the cooling coil (28); the outlet pipe of the cooling coil (28) is connected to the left end of the vacuum three-way valve (21a), the lower end of the vacuum three-way valve (21a) is connected to the vacuum pump (33), and the upper end is connected to the vent pipe (34). In the gas supply system, the high-pressure air cylinder (17) and the high-pressure gas cylinder (18) are respectively connected to the high-pressure mixing tank (22) through pipelines. The outlet pipeline of the high-pressure mixing tank (22) is equipped with a flame arrester (23), a solenoid valve (25), and a heat insulation valve (26) in sequence. The end of the pipeline inserted into the high-temperature heating chamber is equipped with a multi-hole compressed gas nozzle (27).

2. The high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 1, characterized in that: A sealing ring (11) is provided between the cylinder flange (8a) and the inner liner flange (1a) of the stainless steel cylinder (8).

3. The high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 1, characterized in that: The outlet of the cooling coil (28) is connected to a temperature control valve (31) and a second pressure gauge (32).

4. The high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 1, characterized in that: A pressure reducing valve (19) and a check valve (20) are installed on the outlet pipe of the high-pressure air cylinder (17), and a pressure reducing valve (19) and a check valve (20) are installed on the outlet pipe of the high-pressure gas cylinder (18).

5. The high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 1, characterized in that: A first pressure gauge (24) is installed on the high-pressure mixing tank (22).

6. The high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 1, characterized in that: The multi-channel compressed gas nozzle (27) is provided with multiple sets of channels (27a), and the gas forms a 240° injection angle.

7. The operating method of the high-temperature regenerative oxidation low-concentration methane explosion limit testing device based on combustion and explosion pressure as described in claim 1, characterized in that, Includes the following steps: S1. Open the high-pressure air cylinder (17) and introduce 1.92-1.98 MPa of air into the high-pressure mixing tank (22) by adjusting the pressure reducing valve, and then close the high-pressure air cylinder (17); open the high-pressure gas cylinder (18) and introduce gas into the high-pressure mixing tank (22) by adjusting the pressure reducing valve until the pressure gauge reading is 2 MPa. At this time, the gas concentration in the high-pressure mixing tank (22) is 1%-4%. S2. Open the valve (29) at the inlet of the cooling coil (28), close the valve on the vent pipe (34), and turn on the vacuum pump (33) to evacuate the high-temperature heating chamber to a vacuum of less than 3 kPa. S3. Use the PLC timing setting device to set the time sequence after pressing the switch as follows: a. Open the first heat insulation plate, b. Open the second heat insulation plate, c. Turn on the data acquisition instrument used by the pressure sensor, d. Open the solenoid valve, e. Close the solenoid valve, f. Close the second heat insulation plate, g. Close the first heat insulation plate; The PLC controls the first telescopic spring (16) to open the first heat insulation plate (14), and then controls the second telescopic spring (16a) to open the second heat insulation plate (15). The PLC controls the opening of the solenoid valve (25), and the gas in the high-pressure mixing tank (22) passes through the flame arrester (23), the solenoid valve (25), and the heat insulation valve (26) in sequence, and is then injected into the high-temperature heating chamber through the channel (27a) on the multi-channel compressed gas nozzle (27); then, the PLC controls the closing of the solenoid valve (25). After the reaction is completed, the PLC controls the second telescopic spring (16a) to close the second heat insulation plate (15), and then controls the first telescopic spring (16) to close the first heat insulation plate (14).

8. The working method of the high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 7, characterized in that, In step S3, timing c is added to activate the high-speed camera system to capture the internal gas combustion and explosion process through the glass window.

9. The working method of the high-temperature regenerative oxidation low-concentration gas explosion limit testing device based on combustion and explosion pressure according to claim 7, characterized in that, The voltage signal recorded by the pressure sensor is converted into a pressure value. The criterion for determining whether gas changes from an oxidation reaction to an explosion is: the maximum pressure value increases by more than 7%.

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