Dynamic monitoring method and system for fire prevention and extinguishing of closed goaf

Abstract

The invention relates to the technical field of goaf fire prevention and extinguishment, in particular to a dynamic monitoring method and system for closed goaf fire prevention and extinguishment. According to the dynamic monitoring method, early warning parameters in a closed goaf and the air leakage amount of an air leakage position are monitored, and when the concentration of oxygen in the closed goaf is larger than a safety threshold value, the closed goaf is started; inert gas with the concentration and the flow is dynamically injected into the closed goaf until the concentration of oxygen in the closed goaf is smaller than or equal to a safety threshold value, and monitoring continues; the monitoring system comprises a gas injection system and a monitoring system, wherein the gas injection system is used for injecting inert gas into a plurality of closed goaf areas, and the monitoring system is used for monitoring early warning parameters in the closed goaf areas and the air leakage amount of air leakage positions. And controlling a gas injection system to inject inert gas into the closed goaf according to the oxygen concentration and the air leakage amount in the closed goaf. The purpose of efficient fire prevention and extinguishing through dynamic control over inert gas can be achieved, and spontaneous combustion of residual coal in the goaf is effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of fire prevention and extinguishing in goaf areas, and in particular to a dynamic monitoring method and system for fire prevention and extinguishing in closed goaf areas. Background Art

[0002] For coal seams prone to spontaneous combustion, after the working face is mined, although large areas of goaf are closed, during the excavation or mining of the working face along the goaf in the adjacent area, coal pillars along the goaf side are likely to develop to form air leakage channels, destroying the closed environment of the goaf, resulting in the closed goaf being unable to completely isolate the connection between the inside and outside air. Therefore, changes in external air pressure will inevitably affect the changes in the gas in the goaf, forming a "breathing" phenomenon of the goaf gas. This breathing phenomenon can easily lead to spontaneous combustion of the remaining coal in the goaf, posing a fire hazard. In addition, for large areas of goaf, when there is a high concentration of gas in the goaf, unfavorable control of spontaneous combustion will result in a superimposed disaster of fire and gas explosion, posing a great threat to mine safety production.

[0003] However, to address the problem of air leakage in closed goafs, a fire prevention and extinguishing method can be adopted, which is to inject nitrogen or other inert gases into the closed goafs. However, this nitrogen injection strategy cannot adapt to the dynamic changes of air leakage in goafs, and the nitrogen utilization rate is low and the response is delayed. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a dynamic monitoring method and system for fire prevention and extinguishing in closed goaf areas, wherein the dynamic monitoring method includes the following contents:

[0005] Monitor the warning parameters in the closed goaf and the air leakage Q at the air leakage position in the closed goaf. The warning parameter is the oxygen concentration C in the closed goaf. y ;

[0006] When the oxygen concentration in the closed goaf is C y Greater than the safety threshold C a When the concentration of C is injected into the closed goaf D1 , the flow rate is Q Na of inert gas until the oxygen concentration in the closed goaf reaches C y Less than or equal to the safety threshold C a Stop when the device is running and continue monitoring;

[0007] The concentration is C D1 , the flow rate is Q Na The concentration of inert gas and oxygen in the closed goaf C y and the air leakage Q satisfy the following equation:

[0008]

[0009] Where: Cy1 is the oxygen concentration in the air inside the mine;

[0010] K C is the compensation coefficient of air leakage Q when the air leakage position of the closed goaf is different;

[0011] k is the response coefficient;

[0012] Furthermore, the warning parameters also include: marker gas concentration, temperature in the closed goaf, and pressure difference between the inside and outside of the closed goaf. When any one of the warning parameters is greater than the corresponding safety threshold, a gas with a concentration of C is injected into the closed goaf. D1 , the flow rate is Q Na of inert gas until the oxygen concentration in the closed goaf reaches C y Less than or equal to the safety threshold C a Stop when the device is running and continue monitoring;

[0013] Furthermore, the marker gas is a combination of one or more gases selected from the group consisting of carbon monoxide, gas, ethylene, and carbon dioxide;

[0014] Furthermore, the inert gas is nitrogen;

[0015] Furthermore, the air leakage position of the closed goaf is located on the isolation coal pillar adjacent to the air inlet tunnel of the mining working face, or on the isolation coal pillar between the closed goafs.

[0016] The monitoring system comprises: a gas injection system and a monitoring system, wherein: the gas injection system is used to inject inert gas into multiple closed goafs;

[0017] The monitoring system is used to monitor the warning parameters and air leakage at the leakage location in the closed goaf. When the warning parameters are greater than the safety threshold, the gas injection system is controlled to inject inert gas into the closed goaf according to the oxygen concentration and air leakage in the closed goaf.

[0018] Furthermore, the gas injection system includes a gas source for providing inert gas, the gas outlet end of the gas source is connected to a main gas pipe through a one-way valve, the main gas pipe is connected to a plurality of branch gas pipes, and the plurality of branch gas pipes extend to a plurality of closed goafs respectively;

[0019] Each of the branch airways is equipped with an electric valve, and a flow meter is installed on the side of the branch airway away from the main airway.

[0020] Furthermore, the monitoring system includes: an early warning and control module, multiple data acquisition modules and an information transmission module;

[0021] The number of the plurality of data acquisition modules matches a plurality of closed goafs, and is used to obtain the warning parameter information of each closed goaf and the air leakage amount at the air leakage position, including: a temperature sensor for obtaining temperature information in the closed goaf, a pressure sensor for obtaining pressure difference information inside and outside the closed goaf, a gas concentration sensor for obtaining oxygen and marker gas concentration information in the closed goaf, and a flow sensor for obtaining the air leakage amount at the air leakage position in the closed goaf;

[0022] The information transmission module is used to transmit the data acquired by the multiple data acquisition modules to the early warning and control module;

[0023] The early warning and control module uses the data transmitted by the information transmission module as a signal to control the nitrogen injection action of the gas injection system and the flow rate of the injected inert gas;

[0024] Furthermore, the information transmission module includes a core switch and a ring network switch. The core switch is connected to the early warning and control module for signal transmission, and the core switch is connected to the ring network switch for signal transmission. The ring network switch branches out two optical cables, one of which uses the Modbus protocol to connect the ring network switch to the control end of the electric valve, and the other optical cable connects multiple data acquisition modules.

[0025] The beneficial effects of the present invention are: the dynamic monitoring method provided by the present invention is based on the law of conservation of oxygen mass and gas dilution theory, introduces a correction coefficient to the measured leakage volume for different leakage positions in the closed goaf, and constructs a dynamic mathematical model for calculating the concentration and flow rate of inert gas injected into the closed goaf based on the oxygen concentration and leakage volume in the closed goaf. The size of the response coefficient in the dynamic mathematical model can be adjusted to adapt to environmental changes and external interference, and the response speed of injecting inert gas into the closed goaf to reduce the oxygen concentration can be improved, thereby achieving the purpose of efficient fire prevention and extinguishing of dynamic control of inert gas and effectively preventing spontaneous combustion of coal left in the goaf.

[0026] The monitoring system provided by the present invention utilizes the above-mentioned dynamic monitoring method, and through the cooperation of the gas injection system and the monitoring system, it can grasp the degree of coal spontaneous combustion in the closed goaf in real time, and can automatically inject inert gas into the closed goaf when a closed goaf is in a negative pressure state or the oxygen level increases or the concentration of the marker gas increases, so as to balance the internal and external pressure difference and reduce the oxygen and marker gas concentration in the closed goaf. Different amounts of inert gas can be injected into different closed goafs according to the size of the negative pressure, oxygen concentration and marker gas concentration of different closed goafs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a top view of the structure of the coal seam;

[0028] Figure 2This is a flow chart of a dynamic monitoring method for fire prevention and extinguishing in a closed goaf area according to the present invention;

[0029] Figure 3 This is a structural diagram of a dynamic monitoring system for fire prevention and extinguishing in a closed goaf according to the present invention;

[0030] Among them: 1. Closed goaf; 2. Mining working face; 3. Isolation coal pillar; 4. Sealed wall; 5. Air intake lane; 6. Return air lane; 7. Gas source; 8. One-way valve; 9. Main air pipe; 10. Branch air pipe; 11. Electric valve; 12. Flow meter; 13. Early warning and control module; 14. Data acquisition module; 15. Core switch; 16. Ring network switch; 17. Optical cable. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] First, take a single coal seam in a mining area as an example. Figure 1 The top view of the coal seam structure of the mining area is shown in FIG, wherein the adjacent and mined closed goaf 1 are respectively: Figure 1 Two adjacent and mined closed goafs 1 in the middle and upper parts, and a mining face 2 at the bottom, with the upper and lower ends of the mining face 2 being the intake air lane 5 and the return air lane 6 respectively;

[0033] Isolation coal pillars 3 are provided between the closed goafs 1, and each mined closed goaf 1 is closed by means of closed walls 4 provided at both ends of the closed goafs 1. The air pressure inside the closed goaf 1 is in a stable state after closure, that is, the gas does not flow. When the air intake lane 5 of the adjacent mining working face 2 and the isolation coal pillars 3 or the isolation coal pillars 3 between the closed goaf 1 appear an air leakage channel with the closed goaf 1 under the influence of mining, it will cause the gas in the closed goaf 1 to flow with the outside world, and increase the internal oxygen content, and eventually cause a large amount of residual coal in the closed goaf 1 to spontaneously combust under the influence of the temperature in the closed goaf 1, affecting the safety of the mine.

[0034] In this regard, the present invention provides a dynamic monitoring method for fire prevention and extinguishing in closed goaf areas, such as Figure 2 As shown, the following steps are included:

[0035] S1: monitor the warning parameters in the closed goaf 1;

[0036] From the above content, we can know that the main reason for the spontaneous combustion of coal in the closed goaf 1 is the increase in oxygen concentration in the closed goaf 1 caused by air leakage. Therefore, the warning parameter is the oxygen concentration C in the closed goaf. y ;

[0037] Furthermore, since the spontaneous combustion of the coal is also affected by the temperature in the closed goaf 1 and the pressure difference between the inside and outside of the closed goaf 1, and a large amount of marker gases such as carbon monoxide and ethylene are produced when the coal seam spontaneously combusts, the concentration of the marker gas, the temperature in the closed goaf 1 and the pressure difference between the inside and outside of the closed goaf 1 can also be used as early warning parameters, which has played an early warning role in the closed goaf 1.

[0038] Specifically, in this embodiment, carbon monoxide in the closed goaf 1 is used as the marker gas. Of course, in other embodiments, the marker gas may also be other dangerous gases in the closed goaf 1, such as gas, ethylene, carbon dioxide, etc.;

[0039] S2: monitor the air leakage at the air leakage position of the closed goaf 1;

[0040] The air leakage position of the closed goaf 1 is located on the isolation coal pillar 3 adjacent to the air inlet tunnel 5 of the mining face 2, or on the isolation coal pillar 3 between the closed goaf 1;

[0041] Specifically, in this embodiment, the sulfur hexafluoride (SF6) tracer technology can be used to measure the air leakage position of the closed goaf 1, which is located on the isolation coal pillar 3 adjacent to the air inlet tunnel 5 of the closed goaf 1 and the mining working face 2. At the same time, the air leakage rate Q=86m 3 / min;

[0042] S3: Construct a dynamic mathematical model of the relationship between the flow rate of inert gas injected into the closed goaf 1 (hereinafter referred to as the gas injection rate) and the air leakage rate of the closed goaf 1:

[0043] First, assuming that the air leakage Q of the closed goaf 1 is constant, under steady-state conditions, according to the law of conservation of oxygen mass, we can obtain:

[0044]

[0045] Where: Q N is the flow rate of inert gas injected into the closed goaf 1 (m 3 / min);

[0046] Q is the air leakage volume of closed goaf 1 (m 3 / min), which can be obtained by measurement;

[0047] C y1is the oxygen concentration in the air in the mine, which can be obtained by measurement. In this embodiment, it is 20.9%;

[0048] C D1 is the concentration of the injected inert gas. In this embodiment, the injected inert gas is nitrogen with a concentration of 97%;

[0049] C y The oxygen concentration in the closed goaf 1 can be obtained by measurement;

[0050] Formula (1) can be understood as when the oxygen concentration in the air in the mine is C y1 When the air leakage rate at the air leakage position of the closed goaf 1 is Q, in order to maintain the oxygen concentration in the closed goaf 1 at C y , the injection flow rate into the closed goaf is Q N , concentration is C D1 of inert gas;

[0051] In addition, since the air leakage position of the closed goaf 1 may be located on the isolation coal pillar 3 adjacent to the air inlet roadway 5 of the mining face 2, or on the isolation coal pillar 3 between the closed goaf 1;

[0052] When the air leakage position of the closed goaf 1 is located on the isolation coal pillar 3 between the closed goaf 1, the mining of the close-range coal seam group causes the interlayer cracks to penetrate, forming a "gas corridor". The air leakage volume Q obtained by measurement is affected by the crack permeability K and the pressure difference ΔP, and is usually interlayer crossflow.

[0053] According to Darcy's law:

[0054]

[0055] Where: A is the equivalent crack area (m 2 ), K is the permeability coefficient, ΔP is the pressure difference (Pa);

[0056] When the air leakage position of the closed goaf 1 is located on the isolation coal pillar 3 adjacent to the air intake roadway 5 of the mining face 2, that is, due to the cracks in the isolation coal pillar 3, the closed goaf 1 is connected to the air intake roadway 5; at this time, the air leakage rate Q is determined by the ventilation pressure of the air intake roadway 5 through measurement and needs to be determined through ventilation network solution, which can be obtained:

[0057]

[0058] Where: R is the wind resistance of the air leakage channel (Pa / m); ΔP is the pressure difference (Pa).

[0059] That is, the factors affecting the air leakage Q are different depending on the air leakage position. Therefore, the present invention introduces a correction coefficient K to the air leakage Q obtained by measurement. CGet the corrected air leakage Q t , as shown below:

[0060] Q t =Q·K C (2);

[0061] That is, when the air leakage position is located on the isolation coal pillar 3 between the closed goaf 1 and there is no directly connected tunnel in the closed goaf 1, take K C =0.2~0.4, when there are cracks or abandoned tunnels in the closed goaf 1, take K C =0.5~0.8;

[0062] When the air leakage position is located on the isolation coal pillar 3 adjacent to the air inlet roadway 5 between the closed goaf 1 and the mining working face 2, and there is no directly connected roadway in the closed goaf 1, take K C =0.6~0.8, when there are cracks or abandoned tunnels in the closed goaf 1, take K C =0.2~0.5;

[0063] Specifically, in this embodiment, since the air leakage location is on the isolation coal pillar 3 adjacent to the air inlet roadway 5 of the closed goaf 1 and the mining working face 2, and there is no directly connected roadway in the closed goaf 1, K is taken here. C =0.7, and according to formula (2) the corrected air leakage Q is obtained t =60.2m 3 / min.

[0064] Then, the corrected air leakage Q t Substituting the actual measured air leakage Q into formula (2) into formula (1), the air injection volume Q can be obtained. Nt Corrected air leakage Q of closed goaf 1 t The following equation is satisfied:

[0065]

[0066] In this way, when a safety threshold C of oxygen concentration in the closed goaf 1 is set a , that is, C y =C a When the air leakage Q of the closed goaf 1 is measured, the formula (3) can be used to obtain a value that keeps the oxygen concentration in the closed goaf 1 no greater than the safety threshold C a , the required injection concentration into the closed goaf 1 is C D1 The inert gas, whose flow rate Q Nt The minimum value of

[0067] Therefore, it can be obtained that when the oxygen concentration in the closed goaf 1 is kept at the safety threshold C aWhen the concentration of C is injected into the closed goaf 1, D1 Inert gas flow Q Nt The mathematical relationship between the air leakage Q of the closed goaf 1 is as follows:

[0068]

[0069] Specifically, in this embodiment, by conducting a self-ignition prevention test on the coal seam and combining relevant regulations such as the Coal Mine Safety Regulations and the Coal Mine Fire Prevention and Extinguishing Rules, the safety threshold of the oxygen concentration in the closed goaf 1 is 5%, that is, C a =5%, so when the corrected air leakage Q t =60.2m 3 / min, according to formula (4), it can be obtained that to keep the oxygen concentration in the closed goaf 1 no more than 5%, the nitrogen gas with a concentration of 97% needs to be injected into the closed goaf 1, and its flow rate Q Nt The minimum value of is:

[0070]

[0071] Furthermore, in order to adapt to environmental changes and external interferences and to improve the response speed of injecting inert gas into the closed goaf 1 to reduce the oxygen concentration, the present invention adjusts the gas injection volume Q Nt Perform closed-loop feedback proportional control to obtain dynamically adjusted gas injection volume Q Na , as shown below:

[0072]

[0073] Where: Q Nt is the gas injection volume (m 3 / min);

[0074] C a is the safety threshold of oxygen concentration in the closed goaf 1;

[0075] C y is the oxygen concentration in the closed goaf 1;

[0076] k is the response coefficient, ranging from 0.5 to 1, which can be determined through experiments. In this embodiment, k = 0.8;

[0077] Finally, by substituting formula (4) into formula (5), we can obtain that when the safety threshold of oxygen concentration in the closed goaf 1 is C a , the oxygen concentration in the air in the mine is C y1 When the concentration is C D1 , the flow rate is Q Na The concentration C of inert gas and oxygen in the closed goaf 1 yThe mathematical model of the relationship between Q and air leakage is shown in the following formula:

[0078]

[0079] Specifically, in this embodiment, when C y =7%, Q Nt =10.4m 3 / min, the gas injection volume Q is obtained by formula (6) Nt as follows:

[0080]

[0081] S4: monitor the warning parameters;

[0082] Specifically, when any warning parameter is monitored to exceed the safety threshold, the oxygen concentration C in the closed goaf 1 is y The air leakage Q is injected into the closed goaf 1 using formula (6) as Q Na , concentration is C D1 inert gas until the oxygen concentration in the closed goaf 1 is C y Less than the safety threshold C a Stop when the time comes and continue monitoring.

[0083] Specifically, by conducting a spontaneous combustion prevention test on the coal seam and combining relevant regulations such as the "Coal Mine Safety Regulations" and the "Coal Mine Fire Prevention and Extinguishing Regulations", in this embodiment, the safety threshold of oxygen in the closed goaf 1 is a concentration of no more than 5%, the safety threshold of carbon monoxide is a concentration of less than 24 ppm, the safety threshold of the temperature in the closed goaf 1 is less than 87°C, and the safety threshold of the pressure difference between the inside and outside of the closed goaf 1 is a pressure difference greater than 0;

[0084] That is, when the oxygen concentration C in the closed goaf 1 is monitored y When the pressure difference between the inside and outside of the sealed wall 4 is greater than 5% or the pressure difference between the inside and outside of the sealed wall 4 is less than 0 or the concentration of carbon monoxide is greater than 24ppm or the temperature t in the closed goaf 1 is ≥87℃, nitrogen is injected into the closed goaf 1 according to the flow rate calculated by formula (6) until the oxygen concentration in the closed goaf 1 is less than the safety threshold, and then monitoring is restarted.

[0085] In addition, the present invention also provides a dynamic monitoring system for fire prevention and extinguishing in closed goaf based on the above dynamic monitoring method, such as Figure 3 As shown, it includes: a gas injection system and a monitoring system, wherein:

[0086] The gas injection system is used to inject inert gas into multiple closed goafs 1, including a gas source 7 for providing inert gas. The gas outlet end of the gas source 7 is connected to a main gas pipe 9 through a one-way valve 8. The main gas pipe is connected to multiple branch gas pipes 10, and the multiple branch gas pipes 10 extend into the multiple closed goafs 1 respectively.

[0087] An electric valve 11 is installed in each branch airway 10 , and a flow meter 12 is installed on a side of the branch airway 10 away from the main airway 9 and the electric valve 11 .

[0088] The monitoring system uses the above-mentioned dynamic monitoring method to monitor the warning parameters in the closed goaf 1, and controls the gas injection system to inject inert gas into the closed goaf 1 according to the safety threshold of the set warning parameters;

[0089] It includes an early warning and control module 13, multiple data acquisition modules 14 and an information transmission module, wherein:

[0090] The number of the multiple data acquisition modules 14 matches the number of the multiple closed goafs 1, and is used to obtain warning parameter information of each closed goaf 1, including the concentration of oxygen and marker gas in the closed goaf 1, the temperature in the closed goaf 1, and the pressure difference between the inside and outside of the closed goaf 1;

[0091] In this embodiment, the data acquisition module 14 includes: a temperature sensor for obtaining temperature information in the closed goaf 1, a pressure sensor for obtaining pressure difference information inside and outside the closed goaf 1, a gas concentration sensor for obtaining oxygen and marker gas concentration information in the closed goaf 1, the above sensors can penetrate 30 to 50 meters into the goaf through the pre-buried pipes on the closed wall 4, and a flow sensor for obtaining the amount of air leakage at the leakage position of the closed goaf 1;

[0092] The information transmission module is used to transmit the data acquired by the multiple data acquisition modules 14 to the early warning and control module 13;

[0093] In this embodiment, the information transmission module includes a core switch 15 and a ring network switch 16. The core switch 15 is connected to the early warning and control module 13 for signal transmission, and the core switch 15 is connected to the ring network switch 16 for signal transmission. The ring network switch 16 branches out two optical cables 17, one of which uses the Modbus protocol to connect the ring network switch 16 and the control end of the electric valve 11, and the other optical cable 17 is electrically connected to multiple data acquisition modules 14, that is, the transmission of data obtained by multiple data acquisition modules 14 is realized through this module, and the control of the electric valve 11 by the early warning and control module 13 is realized.

[0094] The early warning and control module 13 uses the data transmitted by the information transmission module as a signal to control the nitrogen injection action of the gas injection system and the flow rate of the injected inert gas.

[0095] When this system is used, the SF6 tracer technology is first used to measure the leakage position of each closed goaf 1, and then multiple data acquisition modules 14 are used to monitor and obtain the warning parameter information and leakage volume in each closed goaf 1 in real time. Then the information transmission module sends the warning parameter information and leakage volume obtained by the data acquisition module 14 to the warning and control module 13. The warning and control module 13 determines whether the warning parameter is within the safety threshold range based on the preset safety threshold of the warning parameter. When any of the warning parameters exceeds the safety threshold, the electric valve 11 in the branch air pipe 10 extending into the closed goaf 1 is controlled to open, and the inert gas provided by the gas source 7 is injected into the closed goaf 1 through the main air pipe 9 and the branch air pipe 10. When the flow meter 12 detects that the actual injected flow is the same as the calculated flow, the electric valve 11 is controlled to close and stop the injection, and re-monitor.

[0096] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A dynamic monitoring method for fire prevention and extinguishing in a closed goaf, comprising the following: Monitor the warning parameters in the closed goaf and the air leakage Q at the air leakage position in the closed goaf. The warning parameter is the oxygen concentration C in the closed goaf. y ; When the oxygen concentration in the closed goaf is C y Greater than the safety threshold C a When the concentration of C is injected into the closed goaf D1 , the flow rate is Q Na of inert gas until the oxygen concentration in the closed goaf reaches C y Less than or equal to the safety threshold C a Stop when the device is running and continue monitoring; It is characterized in that The concentration is C D1 , the flow rate is Q Na The concentration of inert gas and oxygen in the closed goaf C y and the air leakage Q satisfy the following equation: Where: C y1 is the oxygen concentration in the air inside the mine; K C is the compensation coefficient of air leakage Q when the air leakage position of the closed goaf is different; k is the response coefficient.

2. A dynamic monitoring method for fire prevention and extinguishing in a closed goaf according to claim 1, characterized in that: The warning parameters also include: marker gas concentration, temperature in the closed goaf, and pressure difference between the inside and outside of the closed goaf. When any one of the warning parameters is greater than the corresponding safety threshold, a gas with a concentration of C is injected into the closed goaf. D1 , the flow rate is Q Na of inert gas until the oxygen concentration in the closed goaf reaches C y Less than or equal to the safety threshold C a Stop when the time comes and continue monitoring.

3. A dynamic monitoring method for fire prevention and extinguishing in a closed goaf according to claim 2, characterized in that: The marker gas is a combination of one or more gases selected from the group consisting of carbon monoxide, gas, ethylene, and carbon dioxide.

4. A dynamic monitoring method for fire prevention and extinguishing in a closed goaf according to claim 1, characterized in that: The inert gas is nitrogen.

5. A dynamic monitoring method for fire prevention and extinguishing in a closed goaf according to claim 1, characterized in that: The air leakage position of the closed goaf is located on the isolation coal pillar adjacent to the air inlet tunnel of the mining working face, or on the isolation coal pillar between the closed goafs.

6. A monitoring system using the dynamic monitoring method for fire prevention and extinguishing in closed goaf according to claim 1, characterized in that: It includes a gas injection system and a monitoring system, wherein: the gas injection system is used to inject inert gas into multiple closed goafs; The monitoring system is used to monitor the warning parameters and air leakage at the leakage location in the closed goaf. When the warning parameters are greater than the safety threshold, the gas injection system is controlled to inject inert gas into the closed goaf according to the oxygen concentration and air leakage in the closed goaf.

7. A dynamic monitoring system for fire prevention and extinguishing in closed goaf according to claim 6, characterized in that: The gas injection system includes a gas source for providing inert gas, the gas outlet of the gas source is connected to a main gas pipe through a one-way valve, the main gas pipe is connected to a plurality of branch gas pipes, and the plurality of branch gas pipes extend to a plurality of closed goafs respectively; An electric valve is installed in each of the branch airways, and a flow meter is installed on a side of the branch airway that is away from the main airway.

8. A dynamic monitoring system for fire prevention and extinguishing in closed goaf according to claim 7, characterized in that: The monitoring system includes: an early warning and control module, multiple data acquisition modules and an information transmission module; The number of the plurality of data acquisition modules matches a plurality of closed goafs, and is used to obtain the warning parameter information of each closed goaf and the air leakage amount at the air leakage position, including: a temperature sensor for obtaining temperature information in the closed goaf, a pressure sensor for obtaining pressure difference information inside and outside the closed goaf, a gas concentration sensor for obtaining oxygen and marker gas concentration information in the closed goaf, and a flow sensor for obtaining the air leakage amount at the air leakage position in the closed goaf; The information transmission module is used to transmit the data acquired by the multiple data acquisition modules to the early warning and control module; The early warning and control module uses the data transmitted by the information transmission module as a signal to control the nitrogen injection action of the gas injection system and the flow rate of the injected inert gas.

9. A dynamic monitoring system for fire prevention and extinguishing in closed goaf according to claim 8, characterized in that: The information transmission module includes a core switch and a ring network switch. The core switch is connected to the early warning and control module for signal transmission, and the core switch is connected to the ring network switch for signal transmission. The ring network switch branches out two optical cables, one of which uses the Modbus protocol to connect the ring network switch and the control end of the electric valve, and the other optical cable connects multiple data acquisition modules.

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