Coal mine goaf low-temperature nitrogen fire preventing and extinguishing process integrating intelligent monitoring and control

Abstract

The invention discloses a coal mine goaf low-temperature nitrogen fire preventing and extinguishing technology integrating intelligent monitoring and control, and belongs to the technical field of coal mine goaf fire preventing and extinguishing. The system comprises a ground nitrogen making machine, a ground monitoring center, an underground nitrogen cooling device, an intelligent monitoring module and a PLC intelligent control module. The nitrogen cooling device comprises a plate heat exchanger, a variable-frequency single-screw compressor, an air-cooled condenser, a liquid storage tank and an electromagnetic control valve which are connected in sequence; the intelligent monitoring module comprises a sensor unit and a communication transmission module; the PLC intelligent control module comprises a core controller, a man-machine interaction unit and a remote transmission unit; and the PLC intelligent control module automatically controls the start and stop of the system according to a preset three-level fire prevention and extinguishing threshold value, and dynamically adjusts the cooling temperature and the refrigerating capacity. According to the invention, 'monitoring-regulation-feedback 'closed-loop intelligent control is realized, an efficient and safe fire prevention and extinguishing technical support is provided for a special mining period of a mine easy to spontaneously ignite, and the system adapts to an underground complex environment.

Description

Technical Field

[0001] This invention relates to the field of fire prevention and extinguishing technology in coal mine goaf areas, specifically to a low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas that integrates intelligent monitoring and control. Background Technology

[0002] Spontaneous combustion of coal is one of the major hazards in coal production. Goaf areas are key areas prone to spontaneous combustion of residual coal, easily triggering secondary disasters such as gas explosions. Currently, nitrogen injection into goaf areas is a widely used fire prevention and extinguishing method in coal mines. However, during special stages such as fault crossings, final mining phases, and retreat, the pressure for fire prevention and extinguishing increases, and conventional room-temperature nitrogen cannot achieve rapid fire prevention and extinguishing effects. Furthermore, liquid nitrogen injection into goaf areas has drawbacks such as high cost and complex processes. Therefore, low-temperature nitrogen, which has lower cost and simpler preparation and transportation processes, is gradually being applied to fire prevention and extinguishing work during special mining periods.

[0003] Currently, domestic and international researchers have conducted extensive studies on nitrogen injection, liquid nitrogen injection, and liquid CO2 injection processes in goaf areas. However, research on rapid fire prevention and extinguishing processes using cryogenic nitrogen injection in goaf areas during special mining periods in easily ignited working faces is limited. Cryogenic nitrogen can be prepared in two ways: liquid nitrogen vaporization and nitrogen cooling. However, research on how to conveniently and rapidly prepare cryogenic nitrogen underground is lacking. Considering the cost and complex transportation process of liquid nitrogen vaporization, it is unsuitable for underground cryogenic nitrogen preparation. Therefore, existing technologies propose designing underground cryogenic nitrogen preparation devices using nitrogen cooling principles, but the following key technical shortcomings still exist:

[0004] (1) Fixed cooling temperature and poor adaptability: Existing cooling devices can only cool nitrogen to a fixed temperature (e.g., -20℃) and cannot adjust the cooling intensity according to the real-time temperature, oxygen concentration, and CO concentration of the goaf. When the goaf is only in the "spontaneous combustion warning" state (temperature 40~60℃), the fixed -20℃ cooling leads to energy waste; when the goaf has already experienced "local high temperature" (temperature >70℃), the fixed temperature cannot meet the demand for rapid cooling.

[0005] (2) Start-up and shutdown depend on manual operation and response is delayed: the start-up and shutdown of the system requires manual judgment of the goaf status and operation. From the discovery of the fire to the start-up of the device, it takes an average of 30 to 60 minutes, missing the best opportunity for "initial suppression", which can easily lead to the spread of the fire.

[0006] (3) Lack of real-time monitoring and blind operation: The existing system has no feedback mechanism for environmental parameters in the goaf area, and cannot keep track of the fire prevention and extinguishing effect after nitrogen injection in real time (such as whether the oxygen concentration drops below 5% or whether the temperature is stable). This may result in "over-injection of nitrogen" or "under-injection of nitrogen", which wastes resources and poses safety risks.

[0007] This shows that the existing technology needs further improvement. Summary of the Invention

[0008] The purpose of this invention is to provide a low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas that integrates intelligent monitoring and control. It can dynamically adjust the cooling temperature of nitrogen according to needs, and adopts intelligent monitoring and PLC intelligent control module adjustment technology to meet the needs of rapid and efficient fire prevention and extinguishing during special mining periods in flammable working faces.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A low-temperature nitrogen fire extinguishing process for coal mine goaf areas, integrating intelligent monitoring and control, comprises a ground-based nitrogen generator, a ground-based monitoring center, and an underground nitrogen cooling device, an intelligent monitoring module, and a PLC intelligent control module. The nitrogen cooling device includes a plate heat exchanger, a variable-frequency single-screw compressor, an air-cooled condenser, a liquid storage tank, and an electromagnetic control valve connected in sequence. The intelligent monitoring module includes a sensor unit and a communication transmission module. The PLC intelligent control module includes a core controller, a human-machine interface unit, and a remote transmission unit.

[0011] The process includes the following steps:

[0012] a. Install and debug the required system. The ground nitrogen generator is connected to the inlet of the plate heat exchanger via a nitrogen inlet pipe. Refrigerant R22 is installed inside the plate heat exchanger to cool the nitrogen supplied by the ground nitrogen generator. The cooled nitrogen is then transported to the coal mine goaf via a nitrogen exhaust pipe connected to the outlet of the plate heat exchanger. An intelligent monitoring module is installed in the coal mine goaf. The PLC intelligent control module is connected to the ground nitrogen generator, the intelligent monitoring module, and the nitrogen cooling device via explosion-proof cables. After being discharged from the plate heat exchanger, the refrigerant R22 flows sequentially through a variable frequency single-screw compressor, an air-cooled condenser, a liquid storage tank, and an electromagnetic control valve before returning to the plate heat exchanger for recycling.

[0013] b. The temperature and carbon monoxide concentration of the goaf are acquired through the sensor unit. The three-level fire prevention and extinguishing parameter thresholds are set through the human-machine interaction unit, namely normal state, early warning state, and emergency state. When the fire prevention and extinguishing level is normal state, the goaf temperature T < 40℃ and the CO concentration < 20ppm, at which time the nitrogen cooling device stops operating; when the fire prevention and extinguishing level is early warning state, the goaf temperature 40℃≤T≤60℃ and the CO concentration 20ppm≤CO <50ppm, at which time the cooling temperature of the nitrogen cooling device is set to -20℃~-15℃; when the fire prevention and extinguishing level is emergency state, the goaf temperature T > 60℃ and the CO concentration ≥ 50ppm, at which time the cooling temperature of the nitrogen cooling device is set to -50℃~-21℃.

[0014] c. When the system is started and running, if the PLC intelligent control module displays an early warning state, the opening of the solenoid control valve is adjusted through the PLC control system to stabilize the cooling temperature at -20℃ to -15℃; if the PLC intelligent control module displays an emergency state, the opening of the solenoid control valve is adjusted through the PLC control system to stabilize the cooling temperature at -50℃ to -21℃, while increasing the nitrogen supply of the ground nitrogen generator.

[0015] d. If the PLC intelligent control module displays a normal state for 10 minutes, the nitrogen cooling device and the ground nitrogen generator will be shut down via the PLC intelligent control module.

[0016] The aforementioned integrated intelligent monitoring and control system for low-temperature nitrogen fire prevention and extinguishing in coal mine goaf areas includes a PLC intelligent control module integrated into an explosion-proof control cabinet, which is located in a safe area of ​​the roadway. The sensor unit is also used to collect oxygen and gas concentration data in the goaf area.

[0017] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf includes a dust filter, a gas-water separator, and a flow sensor sequentially installed on the nitrogen inlet pipeline, starting from the side closest to the ground nitrogen generator. The flow sensor monitors the nitrogen flow rate in the nitrogen inlet pipeline and transmits the data to the PLC intelligent control module in real time. When the flow sensor displays a flow rate below 5 m³ / h, it indicates that the nitrogen inlet pipeline is blocked.

[0018] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf areas includes a nitrogen cooling device in which the air outlet direction of the air-cooled condenser is consistent with the ventilation direction of the roadway; the variable frequency single screw compressor has a speed of 500~1500 r / min, realizing dynamic adjustment of cooling capacity; the variable frequency single screw compressor consists of a rotor base, a rotor, and two star wheels.

[0019] In the above-mentioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf, in step c, when the opening degree of the electromagnetic control valve is adjusted, when the cooling temperature is stable at -20℃ to -15℃, the opening degree of the electromagnetic control valve is adjusted to 50 to 70%; when the cooling temperature is stable at -50℃ to -21℃, the opening degree of the electromagnetic control valve is adjusted to 90 to 100%.

[0020] The above-mentioned integrated intelligent monitoring and control low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas includes the following cooling process of the nitrogen cooling device: nitrogen provided by the ground nitrogen generator is cooled by a plate heat exchanger and then transported to the coal mine goaf area through a nitrogen exhaust pipeline; refrigerant R22 in the plate heat exchanger is discharged from the plate heat exchanger and then flows back to the plate heat exchanger to participate in cooling again after being evaporated and absorbed, compressed, condensed and released, and expanded.

[0021] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf areas includes a heat insulation layer on the nitrogen exhaust pipe and a temperature sensor at the outlet end.

[0022] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf includes a sensor unit comprising a temperature sensor, an oxygen sensor, a carbon monoxide sensor, and a gas sensor. The temperature sensor has a monitoring range of -20℃ to 150℃, the oxygen sensor has a monitoring range of 0 to 25% VOL, the carbon monoxide sensor has a monitoring range of 0 to 1000ppm, and the gas sensor has a monitoring range of 0 to 5%.

[0023] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire extinguishing process for coal mine goaf areas, when the opening degree of the electromagnetic control valve is adjusted to 50-70%, the speed of the variable frequency single screw compressor is controlled to be 800-1000 r / min through the PLC intelligent control module; when the opening degree of the electromagnetic control valve is adjusted to 90-100%, the speed of the variable frequency single screw compressor is controlled to be 1500 r / min through the PLC intelligent control module.

[0024] The aforementioned integrated intelligent monitoring and control low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas uses an S7-1200 explosion-proof version as the core controller of the PLC intelligent control module, a KT158 explosion-proof touch screen as the human-machine interaction unit, and an MGTSV-8B1 mining fiber optic cable as the remote transmission unit, which supports historical data storage of ≥3 months and remote ground monitoring.

[0025] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0026] (1) Achieve intelligent dynamic control and significantly improve fire prevention and extinguishing accuracy: Through the linkage of PLC intelligent control module with variable frequency single screw compressor and electromagnetic control valve, the cooling temperature can be accurately controlled within the range of -50℃ to 10℃ (accuracy ±2℃), which is suitable for different fire situations in the goaf area from "early warning" to "emergency". Compared with fixed temperature cooling, the fire prevention and extinguishing efficiency is effectively improved.

[0027] (2) Automatic response to fire, significantly shortening emergency response time: The "automatic start and stop" function based on real-time parameters of the goaf ensures that the response time from the fire trigger to the system startup is ≤1 minute, which is much shorter than manual operation and effectively prevents the fire from spreading.

[0028] (3) Energy saving and consumption reduction, and significantly reduced operating costs: Through the "on-demand control" logic, the system operates at low load in the "early warning state". Compared with the original fixed temperature system, energy consumption is reduced by 35%~45%, and the annual electricity cost per working face is saved.

[0029] (4) Multiple safety protections to adapt to complex underground environment: The addition of gas and CO interlocking protection in the goaf area, combined with the original equipment fault protection, forms a dual safety barrier of "equipment-environment" to meet the requirements of explosion prevention and inherent safety in coal mines.

[0030] (5) Data visualization and remote control improve management efficiency: Real-time visualization of the environment and equipment status of the goaf area is achieved through PLC human-machine interaction unit and ground remote monitoring. Historical data storage (≥3 months) supports subsequent fire analysis and process optimization, reducing the frequency of manual inspections underground.

[0031] (6) The low-temperature nitrogen fire prevention and extinguishing process with integrated intelligent monitoring and control adopted in this invention has good applicability. The low-temperature nitrogen preparation conditions are easy to achieve, and the production and transportation costs are low. The method of this invention can inject low-temperature nitrogen into the goaf more efficiently under good heat preservation conditions, providing technical support for fire prevention and extinguishing work during special mining periods of easily spontaneously combustible working faces. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] Figure 1 This is a simplified diagram of the system structure of the present invention;

[0034] In the picture:

[0035] 1. Ground-based nitrogen generator; 2. Nitrogen inlet pipeline; 2a. Dust filter; 2b. Gas-liquid separator; 2c. Flow sensor; 3. Nitrogen cooling device; 3a. Variable frequency single-screw compressor; 3b. Air-cooled condenser; 3c. Electromagnetic control valve; 3d. Enhanced explosion-proof electrical protection circuit; 3e. Liquid storage tank; 3f. Plate heat exchanger; 3g. Intake filter; 4. Intelligent monitoring module; 4a. Sensor unit; 4b. Communication transmission module; 5. PLC intelligent control module; 5a. Core controller; 5b. Human-machine interaction unit; 5c. Remote transmission unit; 6. Nitrogen exhaust pipeline; 6a. Temperature sensor; 6b. Insulation layer; 7. Goaf area; 8. Ground monitoring center. Detailed Implementation

[0036] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, the system of this invention includes a surface nitrogen generator 1, a surface monitoring center 8, a nitrogen cooling device 3 located underground, an intelligent monitoring module 4, and a PLC intelligent control module 5; wherein the surface nitrogen generator 1 and the surface monitoring center 8 are located on the surface, while the nitrogen cooling device 3, the intelligent monitoring module 4, and the PLC intelligent control module 5 are located underground. The surface nitrogen generator 1 adopts a nitrogen generator of existing technology, which provides nitrogen at a temperature generally between 20℃ and 40℃. However, nitrogen in this temperature range is not suitable for use in underground coal mines. Therefore, this invention, by combining the nitrogen cooling device, the intelligent monitoring module, the PLC intelligent control module, and the surface monitoring center, can achieve intelligent dynamic adjustment of the cooling temperature.

[0038] Specifically, the nitrogen cooling device includes a plate heat exchanger 3f, a variable frequency single-screw compressor 3a, an air-cooled condenser 3b, a liquid storage tank 3e, an electromagnetic control valve 3c, an enhanced explosion-proof electrical protection circuit 3d, and an intake filter 3g, connected in sequence. The intake filter is connected between the plate heat exchanger and the variable frequency single-screw compressor. The ground nitrogen generator 1 is connected to the plate heat exchanger via a nitrogen inlet pipe 2. Room temperature nitrogen exchanges heat with R22 to form low-temperature nitrogen. A dust filter 2a, a gas-liquid separator 2b, and a flow sensor 2c are installed on the nitrogen inlet pipe near the nitrogen cooling device 3. The dust filter and gas-liquid separator pre-treat the nitrogen supplied by the ground nitrogen generator 1. The flow sensor monitors the nitrogen flow rate and can also determine if the nitrogen inlet pipe is blocked. The flow sensor has a measurement range of 0~50 m³ / h and an accuracy of ±1%. When the flow rate is below 5 m³ / h, the PLC intelligent control module will automatically indicate a blockage in the nitrogen inlet pipe. The air outlet direction of the fan in the air-cooled condenser should be consistent with the ventilation direction of the roadway to ensure sufficient heat dissipation; the variable frequency single screw compressor and the electromagnetic control valve are connected to the PLC intelligent control module.

[0039] The cooling mechanism of the nitrogen cooling device is as follows: After the electromagnetic starter is activated, the compressor operates, and the refrigerant is compressed and enters the condenser to supply liquid to the system. The system will stop operating if the high-pressure switch, low-pressure switch, or temperature switch in the protection circuit malfunctions. A new "goaf parameter interlocking protection unit" has been added to the electrical protection circuit. When the intelligent monitoring module detects that the goaf gas concentration is ≥1.0% or the CO concentration is ≥100ppm, the system will automatically shut down and issue an audible and visual warning.

[0040] The cooling medium of the plate heat exchanger is refrigerant R22. The cooling temperature of nitrogen by R22 can be controlled by the circulation of R22. After cooling nitrogen, R22 passes through a variable frequency single-screw compressor, an air-cooled condenser, a liquid receiver, and a solenoid control valve before returning to the plate heat exchanger, sequentially completing the evaporation (heat absorption), compression, condensation (heat release), and expansion processes. The amount of R22 entering the plate heat exchanger is adjusted by controlling the opening of the solenoid control valve. For example, when the cooling temperature is stable at -20℃ to -15℃, the opening of the solenoid control valve is adjusted to 50% to 70%; when the cooling temperature is stable at -50℃ to -21℃, the opening of the solenoid control valve is adjusted to 90% to 100%.

[0041] The compression process described above involves the heat-absorbing refrigerant R22 heating up and being compressed into a high-temperature, high-pressure gas by a compressor driven by an explosion-proof motor. If a variable-frequency single-screw compressor is used, the pressure and displacement during compression can be dynamically adjusted by the motor speed to adapt to different cooling requirements. The condensation (heat release) process involves the high-temperature, high-pressure gaseous refrigerant exchanging heat with a condenser and cooling fan to cool down. The expansion process involves the liquid working fluid being filtered and throttled through an expansion valve to become a low-temperature, low-pressure saturated gas, which then enters the next refrigeration cycle. If an electromagnetic control valve is used, the degree of throttling can be precisely controlled by the valve opening, further optimizing the refrigeration cycle efficiency.

[0042] After being cooled by the plate heat exchanger, the nitrogen gas is discharged from the nitrogen exhaust pipe 6. The nitrogen exhaust pipe is equipped with a temperature sensor 6a and an insulation layer 6b. The insulation layer provides insulation for the nitrogen exhaust pipe, while ensuring it is sealed and waterproof. The nitrogen exhaust pipe must be suspended and must not be laid on the ground or buried. Temperature measurement ports must be installed. When the length of the nitrogen exhaust pipe is ≤30 meters, a 3cm thick flexible rubber-plastic insulation layer can be applied to the outside of the nitrogen exhaust pipe; when the length of the nitrogen exhaust pipe is ≥30 meters, at least a 10cm thick polyurethane insulation layer should be applied to the outside of the nitrogen exhaust pipe. The maximum distance for laying the nitrogen exhaust pipe should not exceed 300 meters. The temperature sensor monitors the output nitrogen temperature in real time and feeds it back to the PLC intelligent control module, forming a closed loop for cooling temperature control.

[0043] The intelligent monitoring module 4 includes a sensor unit 4a and a communication transmission module 4b. The sensor unit includes a temperature sensor, an oxygen sensor, a carbon monoxide sensor, and a gas sensor. The temperature sensor has a monitoring range of -20℃ to 150℃, the oxygen sensor has a monitoring range of 0 to 25% VOL, the carbon monoxide sensor has a monitoring range of 0 to 1000 ppm, and the gas sensor has a monitoring range of 0 to 5%. The sensor units are installed within 10 to 15 meters around the residual coal concentration area and nitrogen injection point in the goaf 7 area. The sensor groups are fixed with anchor bolts, and the sensor probes are ≤0.5 meters away from the surface of the residual coal. The communication transmission module is installed on the sidewall of the roadway and connected to the PLC intelligent control module.

[0044] The PLC intelligent control module includes a core controller 5a, a human-machine interface unit 5b, and a remote transmission unit 5c. The core controller, human-machine interface unit, and remote transmission unit are integrated and installed in an explosion-proof control cabinet. The control cabinet is fixed in a safe area of ​​the tunnel (away from areas with water accumulation or dust buildup). Explosion-proof cables connect the intelligent monitoring module, the ground nitrogen generator, and the nitrogen cooling device. PLC parameter initialization and system debugging: The threshold values ​​for three levels of fire prevention and extinguishing parameters are set through the human-machine interface unit, as shown in Table 1. The sensor accuracy of the intelligent monitoring module is calibrated (temperature measurement accuracy ≤ ±0.5℃, gas concentration measurement accuracy ≤ ±1%).

[0045] Debugging data transmission function: Ensure that data from the intelligent monitoring module, the operating status of the nitrogen cooling device, and parameters of the intake and exhaust pipelines can be uploaded to the ground monitoring center in real time; Test interlocking protection function: Simulate scenarios such as goaf gas concentration ≥1.0% and sensor failure to verify whether the system can automatically shut down and issue audible and visual warnings. Set three levels of fire prevention and extinguishing parameter thresholds through the human-machine interaction unit, namely normal state, warning state, and emergency state. When the fire prevention and extinguishing level is normal state, the goaf temperature T < 40℃ and CO concentration < 20ppm, at which time the nitrogen cooling device stops operating; when the fire prevention and extinguishing level is warning state, the goaf temperature 40℃≤T≤60℃ and 20ppm≤CO concentration<50ppm, at which time the nitrogen cooling device cooling temperature is set to -20℃~-15℃; when the fire prevention and extinguishing level is emergency state, the goaf temperature T > 60℃ and CO concentration ≥ 50ppm, at which time the nitrogen cooling device cooling temperature is set to -50℃~-21℃.

[0046] Table 1

[0047] Fire protection rating Temperature T in goaf carbon monoxide concentration (CO) Cooling temperature setting System status Normal state T＜40℃ CO < 20 ppm shutdown standby Alert status 40℃≤T≤60℃ 20ppm≤CO<50ppm -20℃~-15℃ Low load operation State of emergency T＞60℃ CO ≥ 50 ppm -50℃~-21℃ Full load operation

[0048] Furthermore, the variable frequency single-screw compressor consists of a rotor housing, a rotor, and two star wheels. The single-screw compressor uses an integral rotor housing. It has circular holes at the front and rear ends, with the rear hole being larger, through which the assembled screw assembly is inserted; it also has circular windows on the left and right sides, through which the assembled star wheel assemblies are inserted. The variable frequency single-screw compressor can adjust its speed (500~1500 r / min) via a PLC intelligent control module, achieving dynamic adjustment of the cooling capacity (5~15 kW).

[0049] The specific process of this invention is as follows: A surface nitrogen generator produces ambient and high-temperature nitrogen gas, which is then transported through an external inlet pipeline to a plate heat exchanger in the underground nitrogen cooling device. After exchanging heat with refrigerant R22 in the plate heat exchanger, low-temperature nitrogen gas is formed and transported to the goaf through a nitrogen exhaust pipeline. The sensor unit of the intelligent monitoring module collects real-time data on the goaf temperature, oxygen concentration, CO concentration, and methane concentration, transmitting this data to the PLC intelligent control module via a communication transmission module. The core controller 5 of the PLC intelligent control module controls the speed of the variable frequency single-screw compressor and the opening of the electromagnetic control valve based on the collected data, achieving dynamic regulation of the cooling temperature. Simultaneously, the data is uploaded to the ground monitoring center via a remote transmission unit. The refrigerant R22, which absorbs heat, enters the variable frequency single screw compressor through the suction filter. After compression, it forms a high-temperature and high-pressure gas and is sent to the air-cooled condenser. The air-cooled condenser exchanges heat with the cooling fan and cools down to form a liquid working fluid, which is then sent to the liquid storage tank. Finally, the liquid working fluid is filtered and throttled by the expansion valve to become a low-temperature and low-pressure saturated gas, which is then sent to the plate heat exchanger to enter the next cycle.

[0050] The method of the present invention will be further described below with reference to specific embodiments.

[0051] Example 1:

[0052] A low-temperature nitrogen fire extinguishing process integrating intelligent monitoring and control specifically includes the following steps:

[0053] Step 1: Installation of nitrogen cooling device and intelligent module.

[0054] Nitrogen cooling device installation: After assembling the variable frequency single screw compressor, electromagnetic control valve, air-cooled condenser and other components on the ground, transport them to the mine. The air outlet direction of the fan is consistent with the ventilation direction of the roadway to ensure sufficient heat dissipation. Connect the variable frequency single screw compressor, electromagnetic control valve and PLC intelligent control module through explosion-proof cables.

[0055] Intelligent monitoring module installation: Within a 12m radius of the concentrated coal residue area and nitrogen injection point in the goaf, the sensor group (temperature sensor, oxygen sensor, CO sensor, and gas sensor) is fixed with anchor bolts, with the sensor probes 0.4m from the surface of the coal residue; the explosion-proof communication module is installed on the side wall of the roadway (1.6m from the ground), and the sensor group is connected to the PLC intelligent control module through an explosion-proof cable;

[0056] PLC intelligent control module installation: The core controller, human-machine interaction unit and remote transmission unit are integrated and installed in an explosion-proof control cabinet. The control cabinet is fixed in a safe area of ​​the roadway and connected to the intelligent monitoring module, ground nitrogen generator and nitrogen cooling device through explosion-proof cables.

[0057] Step 2: Installation of the external nitrogen inlet pipeline. The nitrogen inlet pipeline should be cleaned to remove oil, water, dust, impurities, etc., to prevent evaporator blockage. Install a dust filter, a gas-liquid separator, and an LWGY-25 flow sensor before the nitrogen cooling device inlet. The connection sequence is: dust filter → gas-liquid separator → flow sensor → nitrogen inlet of the nitrogen cooling device. The flow sensor monitors the inlet flow rate in real time and transmits the data to the PLC intelligent control module. When the flow rate is below 5 m³ / h, it automatically alerts the system to pipeline blockage.

[0058] Step 3: Installation of the external nitrogen exhaust pipeline. The external nitrogen exhaust pipeline is DN65, using a double-layer steel wire braided hydraulic hose RB2-76 as the base pipe, 70kg / m³ density polyurethane foam as the insulation layer (10cm thick polyurethane insulation for a pipeline length of 45m), and polyethylene tape as the outer sheath layer. It is suspended by a bracket (approximately 0.4m above the ground) and must not be laid on the ground or buried. An outlet temperature sensor is installed at the outlet end of the nitrogen exhaust pipeline to monitor the output nitrogen temperature in real time and feed it back to the PLC intelligent control module. The pipeline is equipped with a temperature measuring port, and proper sealing and waterproofing treatment are ensured. The pipeline length is ≤300m.

[0059] Step 4: PLC parameter initialization and system debugging.

[0060] The KT158 touchscreen allows you to set three levels of fire prevention and extinguishing parameter thresholds: normal state (T < 40℃, CO < 20ppm), warning state (40℃ ≤ T ≤ 60℃, 20ppm ≤ CO < 50ppm), and emergency state (T > 60℃, CO ≥ 50ppm).

[0061] Calibrate sensor accuracy: temperature measurement accuracy ±0.4℃, gas concentration measurement accuracy ±0.8%; debug data transmission function to ensure that all types of data can be uploaded to the ground monitoring center in real time;

[0062] Test the interlocking protection: Simulate a gas concentration of 1.2% in the goaf area. The system automatically shuts down and issues an audible and visual warning, verifying the effectiveness of the protection function.

[0063] Step 5: Start the ground nitrogen generator. Send a "start command" to the ground nitrogen generator via the PLC intelligent control module to start the nitrogen delivery. The flow sensor monitors the flow rate, and the pipeline is purged of moisture and impurities. After confirming that there is no risk of blockage, prepare to start the nitrogen cooling device.

[0064] Step 6: Start the nitrogen cooling device and intelligent control.

[0065] The PLC intelligent control module receives data from the intelligent monitoring module in real time. If it determines that the state is "early warning", it automatically sends a "start command" to the nitrogen cooling device.

[0066] The PLC intelligent control module controls the variable frequency single screw compressor to a speed of 900 r / min and the electromagnetic control valve to open at 60%, stabilizing the cooling temperature at -18℃. The outlet temperature sensor provides real-time feedback of temperature data. When the temperature deviates, the PLC automatically fine-tunes the compressor speed and the expansion valve opening.

[0067] After startup, check the system operation status via the touch screen: there is stable liquid flow in the sight glass, the gauge pressure is within the normal range, and the temperature display is normal.

[0068] Step 7: Stop running.

[0069] 1. When the system is running, if the intelligent monitoring module detects that the temperature in the goaf has returned to "normal" and remains so for 10 minutes, the PLC intelligent control module will automatically send a "stop command".

[0070] 2. First, shut down the nitrogen cooling device. After there is no nitrogen output from the exhaust pipe, shut down the ground nitrogen generator.

[0071] 3. Record operational data to ensure fire prevention and extinguishing effectiveness meets standards.

[0072] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0073] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application should fall within the scope of protection of the claims of this application.

Claims

1. A low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control, the system of which includes a ground nitrogen generator and a ground monitoring center, characterized in that: It also includes a nitrogen cooling device, an intelligent monitoring module, and a PLC intelligent control module located downhole; the nitrogen cooling device includes a plate heat exchanger, a variable frequency single screw compressor, an air-cooled condenser, a liquid storage tank, and an electromagnetic control valve connected in sequence; the intelligent monitoring module includes a sensor unit and a communication transmission module; the PLC intelligent control module includes a core controller, a human-machine interaction unit, and a remote transmission unit. The process includes the following steps: a. Install and debug the required system. The ground nitrogen generator is connected to the inlet of the plate heat exchanger via a nitrogen inlet pipe. Refrigerant R22 is installed inside the plate heat exchanger to cool the nitrogen supplied by the ground nitrogen generator. The cooled nitrogen is then transported to the coal mine goaf via a nitrogen exhaust pipe connected to the outlet of the plate heat exchanger. An intelligent monitoring module is installed in the coal mine goaf. The PLC intelligent control module is connected to the ground nitrogen generator, the intelligent monitoring module, and the nitrogen cooling device via explosion-proof cables. After being discharged from the plate heat exchanger, the refrigerant R22 flows sequentially through a variable frequency single-screw compressor, an air-cooled condenser, a liquid storage tank, and an electromagnetic control valve before returning to the plate heat exchanger for recycling. b. The temperature and carbon monoxide concentration of the goaf are acquired through the sensor unit. The three-level fire prevention and extinguishing parameter thresholds are set through the human-machine interaction unit, namely normal state, early warning state, and emergency state. When the fire prevention and extinguishing level is normal state, the goaf temperature T < 40℃ and the CO concentration < 20ppm, at which time the nitrogen cooling device stops operating; when the fire prevention and extinguishing level is early warning state, the goaf temperature 40℃≤T≤60℃ and the CO concentration 20ppm≤CO <50ppm, at which time the cooling temperature of the nitrogen cooling device is set to -20℃~-15℃; when the fire prevention and extinguishing level is emergency state, the goaf temperature T > 60℃ and the CO concentration ≥ 50ppm, at which time the cooling temperature of the nitrogen cooling device is set to -50℃~-21℃. c. When the system is started and running, if the PLC intelligent control module displays an early warning state, the opening of the solenoid control valve is adjusted through the PLC control system to stabilize the cooling temperature at -20℃ to -15℃; if the PLC intelligent control module displays an emergency state, the opening of the solenoid control valve is adjusted through the PLC control system to stabilize the cooling temperature at -50℃ to -21℃, while increasing the nitrogen supply of the ground nitrogen generator. d. If the PLC intelligent control module displays a normal state for 10 minutes, the nitrogen cooling device and the ground nitrogen generator will be shut down via the PLC intelligent control module.

2. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: The PLC intelligent control module is integrated and installed in the explosion-proof control cabinet, which is set in a safe area of ​​the roadway; the sensor unit is also used to collect oxygen concentration and gas concentration data in the goaf.

3. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: On the nitrogen inlet pipeline, a dust filter, a gas-liquid separator, and a flow sensor are sequentially installed on the side closest to the ground nitrogen generator. The flow sensor is used to monitor the nitrogen flow rate in the nitrogen inlet pipeline and transmit the data to the PLC intelligent control module in real time. When the flow sensor shows that the flow rate is lower than 5 m³ / h, it indicates that the nitrogen inlet pipeline is blocked.

4. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: In the nitrogen cooling device, the air outlet direction of the air-cooled condenser is consistent with the ventilation direction of the roadway; the speed of the variable frequency single screw compressor is 500~1500 r / min, realizing dynamic adjustment of the cooling capacity; the variable frequency single screw compressor consists of a rotor base, a rotor, and two star wheels.

5. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: In step c, when adjusting the opening of the solenoid control valve, when the cooling temperature is stable at -20℃ to -15℃, the opening of the solenoid control valve is adjusted to 50 to 70%; when the cooling temperature is stable at -50℃ to -21℃, the opening of the solenoid control valve is adjusted to 90 to 100%.

6. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: The cooling process of the nitrogen cooling device is as follows: the nitrogen provided by the ground nitrogen generator is cooled by the plate heat exchanger and then transported to the coal mine goaf through the nitrogen exhaust pipeline; the refrigerant R22 in the plate heat exchanger is discharged from the plate heat exchanger and then flows back to the plate heat exchanger to participate in the cooling again after evaporation heat absorption, compression, condensation heat release, expansion.

7. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: The nitrogen exhaust pipe is equipped with an insulation layer and a temperature sensor is installed at the outlet end.

8. The low-temperature nitrogen fire prevention and extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: The sensor unit includes a temperature sensor, an oxygen sensor, a carbon monoxide sensor, and a gas sensor. The temperature sensor has a monitoring range of -20℃ to 150℃, the oxygen sensor has a monitoring range of 0 to 25% VOL, the carbon monoxide sensor has a monitoring range of 0 to 1000 ppm, and the gas sensor has a monitoring range of 0 to 5%.

9. A low-temperature nitrogen fire extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 5, characterized in that: When the opening of the solenoid control valve is adjusted to 50-70%, the speed of the variable frequency single screw compressor is controlled to be 800-1000 r / min by the PLC intelligent control module. When the opening of the solenoid control valve is adjusted to 90-100%, the speed of the variable frequency single screw compressor is controlled to be 1500 r / min by the PLC intelligent control module.

10. A low-temperature nitrogen fire extinguishing process for coal mine goaf areas integrating intelligent monitoring and control according to claim 1, characterized in that: The core controller of the PLC intelligent control module is the S7-1200 explosion-proof version, the human-machine interaction unit is the KT158 explosion-proof touch screen, and the remote transmission unit adopts the MGTSV-8B1 mining fiber optic cable, which supports the storage of historical data for ≥3 months and remote monitoring from the ground.

Images