Device and method for testing explosion limit of high-temperature heat storage oxidation low-concentration gas based on explosion pressure

Abstract

The invention discloses a high-temperature heat storage oxidation low-concentration gas explosion limit testing device and method based on burning explosion pressure, and belongs to the field of coal mine safety. The device comprises a high-temperature heating cavity, a pressure measuring system, an air supply system and a vacuum extraction system. The pressure measuring system is installed at an opening in the upper portion of the high-temperature heating cavity, and a cooling assembly and a heat insulation assembly are matched with a water-cooled pressure sensor to measure the high-temperature low-concentration gas heat storage oxidation explosion pressure. According to the gas supply system, a high-pressure gas mixing tank is controlled by an electromagnetic valve, and mixed gas is pumped into the high-temperature heating cavity from an opening in the lower portion of the high-temperature heating cavity through a multi-hole-channel compressed gas nozzle. And a side opening of the high-temperature heating cavity is sequentially connected with a cooling coil of a vacuum extraction system, a water-cooling clamp sheath and a vacuum pump. The problem of vacuum extraction in a high-temperature environment is solved, repeated measurement of a pressure evolution curve of coal mine extracted gas from an oxidation reaction to a burning explosion process in the high-temperature environment is realized, and the explosion limit of coal mine extracted low-concentration gas in a range of room temperature to 1200 DEG C is accurately obtained.

Description

Technical Field

[0001] The present invention belongs to the field of coal mine safety, and specifically relates to a device and method for testing the explosion limit of low-concentration gas by high-temperature thermal storage oxidation based on explosion pressure. Background Art

[0002] Gas is an efficient and clean fuel widely used in power generation, heating, industrial fuel and household energy. At the same time, methane, the main component of gas, is also a potent greenhouse gas, with a greenhouse effect 20-25 times that of carbon dioxide and an ozone depletion potential 7 times that of carbon dioxide. Therefore, gas is of vital importance in clean energy utilization and greenhouse gas emissions. Low-concentration gas is usually present in the ventilation process of underground mines such as coal mines. Direct discharge of this type of coal mine gas into the atmosphere will aggravate the greenhouse effect. Through thermal storage oxidation, in a high-temperature environment, oxidizing coal mine gas into water and carbon dioxide can not only avoid environmental pollution, but also make full use of the oxidation heat of gas, which is an effective means to solve the problem of coal mine gas emissions.

[0003] In the oxidation process of coal mine gas extraction, temperature is an important factor affecting the reaction efficiency. High temperature can provide more energy to overcome the activation energy barrier of the reaction, making the reaction easier to proceed. Therefore, the higher the thermal storage oxidation temperature, the faster the oxidation reaction rate, and the oxidation efficiency is improved. However, when dealing with combustible gases such as methane, special attention should be paid to the operating temperature, because once the lower explosion limit concentration range is reached or exceeded, high temperature may increase the risk of explosion. Therefore, blindly changing the concentration of gas or the temperature of the thermal storage tank to improve its efficiency will pose a risk of explosion. In order to ensure the safe application of thermal storage oxidation technology for coal mine gas extraction in industrial production, it is urgent to clarify the critical concentration of gas from oxidation to explosion under different temperature conditions.

[0004] Existing studies have shown that rising temperatures will reduce the lower explosion limit of gas and increase the upper explosion limit. During the thermal storage oxidation process of coal mine gas extraction, it will experience a high temperature section of 500°C to 1200°C, and the explosion limit will inevitably be 5%-16% wider than that at normal temperature and pressure. At present, there are few test devices for the explosion limit of low-concentration gas under high-temperature thermal storage oxidation above 500°C, and the existing devices use the observation of external scales as the basis for the occurrence of explosions, and cannot intuitively see the internal reaction situation. By recording the evolution of internal pressure, the internal gas oxidation process can be reflected, and a more accurate range of explosion limits of low-concentration gas under thermal storage oxidation can be obtained at different temperatures. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure. The device is designed with a high-temperature pressure test element, which can concretely characterize the pressure evolution process of coal mine gas oxidation process, and accurately obtain the explosion limit of gas at a high temperature above 500°C.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on 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 cavity is composed of a stainless steel liner, an electric heating wire, a heat-insulating layer and a metal shell arranged in sequence from the inside to the outside; the temperature sensor is inserted from the side hole of the stainless steel liner to the center of the stainless steel liner; a glass window is installed at the front and rear center of the high-temperature heating cavity;

[0009] The high temperature heating chamber has an upper hole connected to a pressure measurement system, a lower hole connected to an air supply system, and a side hole connected to a vacuum extraction system;

[0010] The pressure measurement system includes a cooling component and a heat insulation component. The stainless steel cylinder in the cooling component is cylindrical, and the heat insulation cotton is clamped between the stainless steel cylinder and the metal wire mesh; an upper top plate is arranged on the upper part of the stainless steel cylinder, and a water-cooled pressure sensor is arranged at the center of the upper top plate; the cylinder flange outside the stainless steel cylinder is connected to the inner liner flange fixed on the stainless steel inner liner by fixing bolts; a heat insulation component is arranged below the cooling component, and one end of the first heat insulation plate and the second heat insulation plate are respectively connected to the inner wall surface of the inner liner flange in a hinged manner, and the other end of the first heat insulation plate is connected to one end of the first telescopic spring, and the other end of the first telescopic spring is connected to the inner wall surface of one side of the stainless steel cylinder; the other end of the second heat insulation plate is connected to one end of the second telescopic spring, and the other end of the second telescopic spring is connected to the inner wall surface of the other side of the stainless steel cylinder; the telescopic behavior of the first telescopic spring and the second telescopic spring are respectively 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 cavity; the water-cooling jacket is wrapped around the outer periphery of the cooling coil; the outlet pipeline 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, the high-pressure air bottle and the high-pressure gas bottle are respectively connected to the high-pressure gas mixing tank through pipelines. The outlet pipeline of the high-pressure gas mixing tank is sequentially provided with a flame arrester, a solenoid valve, and a heat insulation valve. The end of the pipeline inserted into the high-temperature heating cavity is provided with a multi-channel compressed gas nozzle.

[0013] A sealing ring is arranged between the cylinder flange and the inner tank flange of the stainless steel cylinder.

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

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

[0016] A pressure reducing valve and a check valve are arranged on the outlet pipeline of the high-pressure air bottle, and a pressure reducing valve and a check valve are arranged on the outlet pipeline of the high-pressure gas bottle.

[0017] The high-pressure gas mixing tank is provided with a first pressure gauge.

[0018] The multi-hole compressed gas nozzle is provided with multiple groups of holes, and the gas forms a spray angle of 240°.

[0019] The working method of the high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on the explosion pressure includes the following steps:

[0020] S1. Open the high-pressure air cylinder, and introduce 1.92~1.98 MPa air into the high-pressure gas mixing tank by adjusting the pressure reducing valve, and then close the high-pressure air cylinder; open the high-pressure gas cylinder, and introduce gas into the high-pressure gas mixing tank by adjusting the pressure reducing valve until the pressure reading is 2 MPa. At this time, the gas concentration in the high-pressure gas 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 below 3 kPa;

[0022] S3, use the PLC timing setting device to set the time sequence after pressing the switch: a. open the first heat insulation board, b. open the second heat insulation board, c. open 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 board, g. close the first heat insulation board;

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

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

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

[0026] In step S3, sequence c is increased to start the high-speed camera system to shoot the internal gas explosion process through the glass window.

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

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

[0029] 1. The device and its supporting equipment can be used to conduct repeated experiments to determine the explosion limit of low-concentration gas in high-temperature thermal storage oxidation above 500°C. This is used to guide the design and application of thermal storage oxidation utilization of gas extracted from coal mines, reduce the investment in utilization of gas extracted from coal mines, improve the economic efficiency of utilization, and promote its application.

[0030] 2. The device uses cooling components and switch-type insulation plates to protect the pressure sensor, which can obtain the pressure evolution process of high-temperature and low-concentration gas oxidation-induced combustion and explosion, and determine the explosion limit of high-temperature heat storage oxidation and 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 intuitive view of the internal high-temperature, low-concentration gas explosion reaction process, greatly expanding the scope of research on high-temperature, low-concentration gas explosion disasters.

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

[0033] 5. The device distributes gas in the high-pressure gas mixing tank in advance and then injects it into the chamber. This gas distribution method is more accurate and avoids explosion accidents when gas is supplied alone, thereby improving the safety of the experiment.

[0034] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and will be apparent to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention to some extent. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural diagram of a high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure.

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

[0037] Figure 3is an enlarged view of the insulation assembly.

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

[0039] Figure 5 It is a parametric diagram of a multi-hole compressed gas nozzle.

[0040] Figure numerals: 1, stainless steel liner, 1a, liner flange, 2, electric heating wire, 3, insulation layer, 4, metal shell, 5, temperature sensor, 6, glass window, 7, water-cooled pressure sensor, 8, stainless steel cylinder, 8a, cylinder flange, 9, metal wire mesh, 10, insulation cotton, 11, sealing ring, 12, fixing bolts, 13, upper top plate, 14, first insulation board, 15, second insulation board, 16, first telescopic spring, 16a, second telescopic spring, 17 , high-pressure air bottle, 18, high-pressure gas bottle, 19, pressure reducing valve, 20, check valve, 21, gas supply three-way valve, 21a, vacuum three-way valve, 22, high-pressure mixing tank, 23, flame arrester, 24, first pressure gauge, 25, solenoid valve, 26, insulation valve, 27, multi-channel compressed gas nozzle, 27a, channel, 28, cooling coil, 29, valve, 30, water-cooled clamp jacket, 31, temperature control valve, 32, second pressure gauge, 33, vacuum pump, 34, vent pipe. DETAILED DESCRIPTION

[0041] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples, so that the above-mentioned objects, features and advantages of the present invention can be more clearly understood. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0042] Among them, the drawings are only used for illustrative explanations, showing only schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention: In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product: For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0043] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] A high-temperature thermal storage oxidation low-concentration gas explosion limit testing device based on explosion pressure comprises: a high-temperature heating cavity, a pressure measurement system, a gas supply system and a vacuum extraction system.

[0045] The high-temperature heating cavity comprises: a stainless steel inner tank, an electric heating wire, a heat-insulating layer, a metal outer shell, a temperature sensor, and a glass window.

[0046] The outer side of the stainless steel inner container is wrapped with an electric heating wire, the outer side of the electric heating wire is wrapped with a heat preservation layer, and the outer side of the heat preservation layer is wrapped with a metal shell.

[0047] The temperature measuring tip of the temperature sensor is 0.5 mm and is inserted from the small hole on the left side of the stainless steel inner liner to the center of the stainless steel inner liner. The contact portion between the temperature sensor and the wall of the stainless steel inner liner is sealed with high-temperature glue.

[0048] A circular hole is opened in the front and rear center of the stainless steel liner, the insulation layer and the metal 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°C. A two-component ultra-high temperature adhesive (resistant to 1730°C) composed of an inorganic ceramic material and a modified curing agent is used to fill the gap between the glass window and the wall to fix and seal it.

[0049] A circular hole is opened on the upper part of the stainless steel liner, the insulation layer and the metal shell to connect the pressure measurement system, a hole is opened on the lower part to connect the air supply system, and a hole is opened on the side to connect the vacuum extraction system.

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

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

[0052] The heat insulation device is installed at the lower inlet of the cooling component, and the first heat insulation plate and the second heat insulation plate are connected to the lower inner wall surface of the cooling component by a hinge connection method; 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 surface of the stainless steel cylinder, and the telescopic behavior is controlled by an external electrical signal to realize 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 properties.

[0053] The heat-insulating bolt with internal and external thread structure is fixed at the circular hole of the top plate of the cooling component, and the water-cooled pressure sensor penetrates into the cooling component through the internal thread of the heat-insulating bolt.

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

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

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

[0057] The solenoid valve is controlled by an external electrical signal and can realize opening and closing actions in milliseconds; a heat insulation valve is installed between the outlet of the solenoid valve and the multi-channel compressed gas nozzle.

[0058] The multi-hole compressed gas nozzle sprays uniform gas through multiple holes to form a spray angle of 240°.

[0059] The vacuum extraction system is connected to the side opening of the high-temperature heating chamber and includes: a cooling coil, a valve, a water-cooling 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 cavity, and the opening and closing between the internal space of the cavity and the cooling coil are realized by a valve; the water-cooling jacket is wrapped around the outer periphery of the cooling coil to play a cooling role; the outlet of the cooling coil is connected to a temperature control valve to prevent the outlet temperature from being higher than the working pressure of the pressure gauge and the vacuum pump.

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

[0062] A method for testing the explosion limit of low-concentration gas by high-temperature thermal storage oxidation based on explosion pressure, using a device for testing the explosion limit of low-concentration gas by high-temperature thermal storage oxidation based on explosion pressure as described above, comprising the following steps:

[0063] S1, open the high-pressure air bottle, and pass 1.92~1.98 MPa air into the high-pressure mixing tank by adjusting the pressure reducing valve. Then close the high-pressure air bottle, open the high-pressure gas bottle, and pass gas into the high-pressure mixing tank by adjusting the pressure reducing valve until the pressure indication reads 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 exhaust pipe, and turn on the vacuum pump to evacuate the high-temperature chamber to a vacuum below 3 kPa.

[0065] S3, use the PLC timing setting device to set, the time sequence after pressing the switch is: a. open the first insulation board, b. open the second insulation board, c. open the data acquisition instrument used by the pressure sensor, d. open the solenoid valve, e. close the solenoid valve, f. close the second insulation board, g. close the first insulation board.

[0066] S4, convert the voltage signal recorded by the pressure sensor into a pressure value. The method for determining whether the gas changes from oxidation reaction to 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, sequence c may be added with a high-speed camera system to capture the internal gas explosion process through a glass window.

[0069] like Figure 1 As shown, a test device that can accurately obtain the explosion limit of low-concentration gas in high-temperature thermal storage oxidation is provided, including: a high-temperature heating chamber, a pressure measurement system, a gas supply system and a vacuum extraction system.

[0070] See also Figure 1The outer side of the stainless steel inner liner 1 of the high-temperature heating cavity is wrapped with an electric heating wire 2, the outer side of the electric heating wire 2 is wrapped with an insulation layer 3, and the outer side of the insulation layer 3 is wrapped with a metal shell 4; the temperature measuring tip of the temperature sensor 5 is 0.5mm, and it is inserted from the small hole on the left side of the stainless steel inner liner 1 to the center of the chamber, and the contact part between the temperature sensor 5 and the wall of the stainless steel inner liner 1 is sealed with high-temperature glue; a circular hole is opened at the front and rear center positions of the stainless steel inner liner 1, the insulation layer 3 and the metal shell 4 for installing a glass window 5, and the window uses No. 4 material high-temperature resistant glass, which can work for a long time in an environment of 1200℃, and a two-component ultra-high temperature adhesive (resistant to 1730℃ high temperature) composed of an inorganic ceramic material and a modified curing agent is filled into the gap between the glass window and the wall to play a fixing and sealing role; a hole is opened at the upper part of the stainless steel inner liner 1, the insulation layer 3 and the metal shell 4 to connect the pressure measurement system, a hole is opened at the lower part to connect the air supply system, and a hole is opened at the side to connect the vacuum extraction system.

[0071] See also Figure 1 The pressure measurement system is connected to the upper opening of the high-temperature heating cavity, 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 board 14, a second heat insulation board 15, and a telescopic spring 16.

[0072] See also Figure 2 The stainless steel cylinder 8 of the cooling component is cylindrical, and the heat insulation cotton 10 is supported between the stainless steel cylinder 8 and the metal wire mesh 9; a sealing ring 11 is set between the cylinder flange 8a and the inner flange 1a, which is fixed near the high-temperature heating cavity and plays a sealing role; the inner flange 1a is welded to the upper opening of the stainless steel inner 1, and the cylinder flange 8a is set on the bottom outside of the stainless steel cylinder 8. The upper top plate 13 is fixed on the upper part of the stainless steel cylinder 8, and a circular hole is opened in the middle for placing the water-cooled pressure sensor 7; the lower part of the cooling component is a square opening for fixing the heat insulation device.

[0073] See also Figure 3 The heat insulation device is installed at the lower inlet of the cooling component, and the first heat insulation board 14 and the second heat insulation board 15 are connected to the inner wall surface of the inner tank flange 1a by a hinge connection method; one end of the first telescopic spring 16 and the second telescopic spring 16a are respectively connected to the end of the first heat insulation board 14 and the second heat insulation board 15, and the other end of the spring is respectively connected to the inner wall surface on both sides of the stainless steel cylinder 8, and the telescopic behavior of the telescopic spring is controlled by an external electrical signal, so as to realize the opening and closing of the first heat insulation board 14 and the second heat insulation board 15; the interface between the first heat insulation board 14 and the second heat insulation board 15 adopts a stepped structure to enhance the heat insulation and sealing properties.

[0074] See also Figure 4The heat-insulating bolts with internal and external thread structures are fixed at 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-insulating bolts.

[0075] See also Figure 1 The gas supply system is connected to the lower opening of the high-temperature heating cavity, and the outlets of the high-pressure air bottle 17 and the high-pressure gas bottle 18 are connected to the pipeline through the pressure reducing valve 19 respectively, and a check valve 20 is installed between the pressure reducing valve 19 and the three-way valve 21; the inlet of the high-pressure mixing tank 22 is connected to the high-pressure air bottle 17 and the high-pressure gas bottle 18 through the three-way valve 21; the 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 realize millisecond-level opening and closing actions; an insulation valve 26 is installed between the outlet of the solenoid valve and the multi-channel compressed gas nozzle.

[0076] See also Figure 5 The multi-hole compressed gas nozzle 27 sprays uniform gas through multiple holes to form a spray angle of 240°.

[0077] See also Figure 1 The vacuum extraction system is connected to the side opening of the high-temperature heating cavity, the inlet of the cooling coil 28 is connected to the side opening of the high-temperature heating cavity, and the opening and closing between the internal space of the cavity and the cooling coil 28 are realized by the valve 29; the water-cooling jacket 30 is wrapped around the outer periphery of the cooling coil 28 to play a cooling role; the outlet of the cooling coil 28 is connected to the temperature control valve 31 to prevent the outlet temperature from being higher than the working pressure of the second pressure gauge 32 and the vacuum pump 33; the left end of the 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, which is used to discharge the gas in the chamber in an emergency.

[0078] A method for testing the explosion limit of low-concentration gas by high-temperature thermal storage oxidation based on explosion pressure, using a device for testing the explosion limit of low-concentration gas by high-temperature thermal storage oxidation based on explosion pressure as described above, comprising the following steps:

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

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

[0081] S3, use the PLC timing setting device to set, the time sequence after pressing the switch is: a. open the first insulation board 14, b. open the second insulation board 15, c. open the data acquisition instrument used by the water-cooled pressure sensor 7 (a high-speed camera system can be added to shoot the internal gas combustion and explosion process through the glass window), d. open the solenoid valve 25, e. close the solenoid valve 25, f. close the second insulation board 15, g. close the first insulation board 14.

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

[0083] Among the currently known public technologies, there are devices that use the method of observing external scales as the basis for explosion occurrence. This method has a single measurement method and cannot intuitively see the internal reaction situation. The method for judging the explosion limit lacks accuracy. The existing pressure sensor can withstand high temperature shock within a few seconds, but cannot achieve long-term measurement work at high temperature. Moreover, most of the current measurement devices for explosion limits are carried out at room temperature and cannot achieve the vacuum extraction function under high temperature conditions. This experiment uses a cooling device in conjunction with a water-cooled pressure sensor to measure the combustion and explosion pressure at high temperature, and designs an open-type insulation device to avoid the pressure sensor from being exposed to a high temperature environment for a long time without affecting the pressure measurement; the cooling method of the cooling coil in the present invention in conjunction with the water-cooled jacket solves the vacuum extraction problem in a high temperature environment; combined with the explosion limit measurement method of the present invention, the pressure evolution curve of the high-temperature thermal storage oxidation low-concentration gas from oxidation reaction to combustion and explosion process can be obtained, and the explosion limit of coal mine gas extraction in the range of 500~1200℃ can be obtained more accurately.

[0084] Finally, it should be noted that the above implementation modes are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the scope of patent protection of the present invention shall be defined by the claims.

Claims

1. A high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure, characterized by: 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 cavity comprises a stainless steel inner liner (1), an electric heating wire (2), a heat-insulating layer (3) and a metal outer shell (4) which are arranged in sequence from the inside to the outside; a temperature sensor (5) is inserted from a side hole of the stainless steel inner liner (1) to the center of the stainless steel inner liner; a glass window (6) is installed at the front and rear center positions of the high-temperature heating cavity; The high temperature heating chamber has an upper hole connected to a pressure measurement system, a lower hole connected to an air supply system, and a side hole connected to a vacuum extraction system; The pressure measurement system comprises a cooling component and a heat insulation component. The stainless steel cylinder (8) in the cooling component is cylindrical, and the heat insulation cotton (10) is clamped between the stainless steel cylinder (8) and the metal wire mesh (9); an upper top plate (13) is arranged on the upper part of the stainless steel cylinder (8), and a water-cooled pressure sensor (7) is arranged at the center of the upper top plate (13); a cylinder flange (8a) outside the stainless steel cylinder (8) is connected to an inner liner flange (1a) fixed on the stainless steel inner liner (1) by fixing bolts (12); a heat insulation component is arranged below the cooling component, and a first heat insulation plate (14) and a second heat insulation plate (1 5) are respectively connected to the inner wall surface of the inner tank flange (1a) in a hinged manner, 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 surface 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 surface of the other side of the stainless steel cylinder (8); the telescopic behavior of the first telescopic spring (16) and the second telescopic spring (16a) are respectively controlled by external electrical signals; 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-cooling jacket (30) is wrapped around the outer periphery of the cooling coil (28); the outlet pipeline 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, a high-pressure air bottle (17) and a high-pressure gas bottle (18) are respectively connected to a high-pressure gas mixing tank (22) through pipelines. The outlet pipeline of the high-pressure gas mixing tank (22) is provided with a flame arrester (23), a solenoid valve (25), and a heat insulation valve (26) in sequence. A multi-hole compressed gas nozzle (27) is provided at the end of the pipeline inserted into the high-temperature heating cavity.

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

3. The high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 1 is characterized in that: The interface between the first heat insulation board (14) and the second heat insulation board (15) adopts a stepped structure.

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

5. The high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 1 is characterized in that: A pressure reducing valve (19) and a check valve (20) are provided on the outlet pipe of the high-pressure air bottle (17), and a pressure reducing valve (19) and a check valve (20) are provided on the outlet pipe of the high-pressure gas bottle (18).

6. The high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 1 is characterized in that: The high-pressure gas mixing tank (22) is provided with a first pressure gauge (24).

7. The high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 1 is characterized in that: The multi-hole compressed gas nozzle (27) is provided with a plurality of groups of holes (27a), and the gas forms a spray angle of 240°.

8. The working method of the high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 1 is characterized in that: The following steps are involved: S1. Open the high-pressure air cylinder (17), and introduce 1.92-1.98 MPa air into the high-pressure gas 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 gas mixing tank (22) by adjusting the pressure reducing valve until the pressure reading is 2 MPa. At this time, the gas concentration in the high-pressure gas 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 below 3 kPa; S3, use the PLC timing setting device to set the time sequence after pressing the switch: a. open the first heat insulation board, b. open the second heat insulation board, c. open 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 board, g. close the first heat insulation board; The PLC controls the first telescopic spring (16) to open the first heat insulation board (14), and then controls the second telescopic spring (16a) to open the second heat insulation board (15); The PLC controls the opening of the solenoid valve (25), and the gas in the high-pressure gas mixing tank (22) passes through the flame arrester (23), the solenoid valve (25), and the heat insulation valve (26) in sequence, and is then sprayed into the high-temperature heating cavity through the hole (27a) on the multi-hole compressed gas nozzle (27); then, the PLC controls the closing of the solenoid valve (25); After the reaction is finished, the PLC controls the second telescopic spring (16a) to close the second heat insulation board (15), and then controls the first telescopic spring (16) to close the first heat insulation board (14).

9. The working method of the high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 8 is characterized in that: In step S3, sequence c is increased to start the high-speed camera system to shoot the internal gas explosion process through the glass window.

10. The working method of the high-temperature thermal storage oxidation low-concentration gas explosion limit test device based on explosion pressure according to claim 8 is characterized in that: The voltage signal recorded by the pressure sensor is converted into a pressure value. The basis for determining whether the gas has transformed from an oxidation reaction to an explosion is when the maximum pressure value increases by more than 7%.

Images