High-efficiency liquid nitrogen pressure injection type fire extinguishing system for goaf

Abstract

The invention discloses a goaf liquid nitrogen efficient pressure injection type fire extinguishing system, and belongs to the technical field of mine fire prevention and extinguishing. The fire extinguishing system comprises a liquid nitrogen storage and supply system, a supercharging device, a tail end flow guide auxiliary device and an intelligent control system. The liquid nitrogen storage and supply system comprises a high-pressure liquid nitrogen storage tank and a pressure control valve system, the high-pressure liquid nitrogen storage tank is connected with the supercharging device through a low-temperature heat insulation pipeline, and the pressure control valve system is connected to the low-temperature heat insulation pipeline in series; the supercharging device comprises a liquid buffer supercharging tank and is used for pressurizing liquid nitrogen and preventing conveying phase change; the tail end flow guide auxiliary device comprises a shell, a vortex atomization head arranged at the front end of the interior of the shell and a negative pressure flow mixer arranged at the rear end of the interior of the shell, and is used for atomizing liquid nitrogen and uniformly diffusing the liquid nitrogen to a target area; the intelligent control system comprises a temperature sensor, a pressure sensor, a distributed optical fiber temperature sensor and a remote control platform which are arranged in a pipeline and a goaf, and is used for monitoring the temperature and pressure of a pressure injection area in real time.

Description

Technical Field

[0001] This invention belongs to the technical field of mine fire prevention and extinguishing, specifically relating to a high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas. Background Technology

[0002] Spontaneous combustion of coal is a common and serious hazard in mine production, especially in areas such as abandoned coal, coal pillars, and old goafs in longwall mining faces. These areas are highly susceptible to spontaneous combustion due to poor ventilation, heat accumulation, and oxygen buildup. These areas often possess complex fracture networks and enclosed space characteristics, making traditional fire extinguishing techniques ineffective. Currently widely used fire extinguishing technologies mainly include nitrogen injection, grouting, and inert gas sealing, but these technologies have significant drawbacks in practical applications. Conventional nitrogen injection technology relies primarily on low-pressure delivery of gaseous nitrogen. Due to nitrogen's low density and high fluidity, it easily dissipates rapidly in complex fractures, making it difficult to form an effective inert gas covering layer. Simultaneously, gaseous nitrogen has a low specific heat capacity, limiting its instantaneous cooling capacity for high-temperature fire sources and failing to quickly interrupt the oxidation chain reaction in coal. While some chemical inhibitors can isolate oxygen, in enclosed or semi-enclosed spaces, heat cannot be dissipated in time, leading to continuous exothermic oxidation of the coal. Furthermore, existing technologies generally have slow response times, often requiring a considerable amount of time from fire detection to system deployment, easily missing the optimal extinguishing opportunity. In deep goaf areas and fractured regions, the permeability and uniform coverage of traditional extinguishing media are difficult to guarantee, frequently resulting in extinguishing blind spots. These technological deficiencies severely restrict the effectiveness of mine fire prevention and control, necessitating the development of a new type of extinguishing system capable of rapid cooling, efficient oxygen isolation, and deep penetration. Existing technologies urgently need improvement to address these issues. Summary of the Invention

[0003] This invention provides a high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas, aiming to solve the problems of slow cooling, insufficient penetration depth, and low coverage efficiency of traditional nitrogen injection technology, and to achieve high efficiency and safety in goaf fire prevention and extinguishing.

[0004] This invention provides a high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas, which adopts the following technical solution: including a liquid nitrogen storage and supply system, a pressurization device and an end-of-line diversion auxiliary device; The liquid nitrogen storage and supply system is used to maintain the low temperature and high pressure state of liquid nitrogen during transportation; the liquid nitrogen storage and supply system includes a high-pressure liquid nitrogen storage tank and a pressure control valve system, the high-pressure liquid nitrogen storage tank is connected to the pressurization device through a low temperature insulated pipeline, and the pressure control valve system is connected in series with the low temperature insulated pipeline; The pressurization device includes a liquid buffer pressurization tank for pressurizing liquid nitrogen and preventing phase change during transport; The end-flow guiding auxiliary device includes a housing, a vortex atomizing head disposed at the front end inside the housing, and a negative pressure mixer disposed at the rear end inside the housing. The vortex atomizing head is inserted inside the negative pressure mixer, and the vortex atomizing head and the negative pressure mixer work together to atomize liquid nitrogen and diffuse it evenly to the target area.

[0005] Preferably, an intelligent control system is also included, which includes temperature sensors, pressure sensors, distributed fiber optic temperature sensors arranged in the pipeline and goaf area, and a remote control platform connected to the signal output terminals of each sensor, for real-time monitoring of the temperature and pressure in the injection area.

[0006] Preferably, the liquid buffer pressurization tank is provided with a gas inlet and a liquid inlet at the top, which are connected to the gas phase port and liquid phase port of the high-pressure liquid nitrogen storage tank, respectively, to realize the input of liquid nitrogen and nitrogen gas.

[0007] Preferably, the liquid buffer pressurization tank has a double-layer structure. The interlayer of the double-layer structure is equipped with an electric heating wire, which can increase the nitrogen pressure inside the tank by heating, thereby meeting the pressure requirements of the injection operation. The interlayer is filled with perlite insulation material, and the outer wall of the interlayer is wrapped with an aluminum foil reflective layer to reduce heat radiation loss.

[0008] Preferably, the vortex atomizing head has a conical structure, and the middle of the vortex atomizing head is provided with an axially spirally distributed air guiding channel. The end of the air guiding channel is connected to the jet port. The vortex atomizing head is provided with a spiral liquid guiding groove extending from the outer wall to the middle. The side of the vortex atomizing head is provided with a liquid inlet. One end of the liquid inlet is sealed to the outlet of the liquid buffer pressurization tank, and the other end is connected to the liquid guiding groove. The negative pressure mixer has a mixing chamber inside; The jet inlet of the vortex atomizing head is directly opposite the mixing chamber of the negative pressure mixer.

[0009] Preferably, the number of liquid guiding grooves is 2-6, and the spiral direction is the same. The liquid guiding grooves are recessed into the inner wall of the gas guiding channel, and their cross-section gradually decreases from front to back until they disappear.

[0010] Preferably, the vortex atomizing head is fixed to the shell by a threaded connection or a clamp-type quick connector; the inlet of the shell is sealed to the mine nitrogen pipeline, and the outlet is sealed to the goaf injection hole; the gas guiding channel includes a contraction section, a throat, and an expansion section, and the jet outlet is located at the throat.

[0011] Preferably, after nitrogen enters the shell, a portion of the gas passes through a spiral-shaped gas guide channel, where static pressure is converted into dynamic pressure, forming a high-speed airflow. Simultaneously, liquid nitrogen fluid enters the liquid guide tank through the inlet, where it flows spirally. As the cross-section of the flow channel gradually decreases, the liquid nitrogen fluid gradually overflows into the gas guide channel and enters at a certain angle to the high-speed airflow. At this point, the kinetic energy of the high-speed airflow acts on the liquid nitrogen fluid, causing it to undergo lateral tearing and breakup, forming fine droplets. This forms a gas-liquid two-phase mixed flow that enters the negative pressure mixer. The flow accelerates in the contraction section, and the pressure decreases at the throat, forming a high-speed mixed flow. Furthermore, a side channel is provided between the outer wall of the vortex atomizing head and the shell. Another stream of nitrogen in the side channel is drawn into the mixing chamber under the influence of nitrogen injection pressure and the Venturi effect. This nitrogen further agitates and turbulently with the initially atomized droplets within the negative pressure mixer, ultimately achieving a uniform atomized nitrogen jet output.

[0012] Preferably, the temperature sensor is a K-type thermocouple or a PT100 platinum resistance thermometer, and the temperature sensor is fixed to the outer wall of the low-temperature insulated pipe by a sensor base; the part of the temperature sensor inserted into the pipe is fitted with a low-temperature heat-resistant sleeve, the threaded interface is provided with a polytetrafluoroethylene gasket, and the exposed part is provided with a locking nut and a vibration-damping support clamp. The pressure sensor is a diaphragm pressure transmitter, and its pressure tap is connected to the pipeline / tank body through a welded internal thread seat; the pressure sensor is equipped with a three-valve group and a pulse tube to avoid low-temperature frost and impact stress. The fixed bracket of the distributed optical fiber temperature sensor is a telescopic anchor rod structure, and the end of the bracket is provided with a barbed anti-slip structure; the optical cable of the distributed optical fiber temperature sensor is covered with a protective sleeve at the bend.

[0013] Preferably, a Y-type filter is also included. The Y-type filter is connected in series at one end of the cryogenic insulated pipe near the end flow guide auxiliary device. It can effectively intercept tiny impurities that may exist in the liquid nitrogen fluid and prevent impurities from entering the end flow guide auxiliary device and clogging the nozzle. The lower end of the Y-type filter is provided with a drain port with a manual ball valve.

[0014] The beneficial effects of this invention are: The efficient liquid nitrogen injection fire extinguishing system for goaf areas of this invention effectively solves many pain points of traditional goaf fire extinguishing technologies. First, it has a significant advantage in cooling efficiency. It uses liquid nitrogen with a low boiling point and high specific heat capacity as the extinguishing medium. Compared with traditional gaseous nitrogen, the cooling capacity per unit volume is greatly improved, which can quickly absorb the high temperature heat in the goaf area and instantly suppress the heat release from coal oxidation. At the same time, the terminal flow guiding auxiliary device, through the synergistic effect of the spiral air guiding channel, the spiral liquid guiding groove and the negative pressure mixer, breaks the liquid nitrogen into fine droplets and mixes them violently with the bypass nitrogen gas to form a uniform mist spray. This greatly increases the contact area between the liquid nitrogen and the high temperature coal body, and significantly improves the heat exchange rate. It can reduce the local high temperature area to below the critical temperature for coal auto-ignition in a short time, effectively blocking the chain reaction of coal oxidation.

[0015] The liquid buffer pressurization tank of the pressurization device can flexibly pressurize liquid nitrogen, ensuring that liquid nitrogen is transported in a low-temperature, high-pressure liquid form. This avoids the problem of rapid dispersion of traditional low-pressure gaseous nitrogen due to its low density and high fluidity. As a result, the mist-like liquid nitrogen can penetrate deep into the deep fissures of the goaf, with a significantly improved penetration depth compared to traditional nitrogen injection. It can cover hidden fire sources such as residual coal and coal pillars. Furthermore, the negative pressure mixer, with the turbulent mixing flow formed by the negative pressure effect, has a large jet diffusion angle and uniform droplet size, which can form a three-dimensional coverage layer in the goaf. This completely solves the problem of blind spots in fire extinguishing caused by uneven distribution of media in traditional fire extinguishing technologies.

[0016] The intelligent control system integrates multiple sensors, including temperature sensors for monitoring pipeline temperature, diaphragm pressure transmitters for monitoring pressure, and distributed fiber optic temperature sensors that can cover a wide temperature field in the goaf. These sensors can collect parameters of the entire chain of delivery, injection, and target area in real time, accurately locate high-temperature fire sources, and transmit the data to the remote control platform in real time. After that, the staff can dynamically adjust the liquid nitrogen injection volume and pressure parameters to realize the full automation of the fire detection-system start-up-parameter optimization process, which greatly shortens the response time from several hours in traditional technology and effectively grasps the golden period for fire extinguishing. Attached Figure Description

[0017] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram showing the connection relationship of the system components of the present invention; Figure 2 This is a cross-sectional view of the end-flow guiding auxiliary device of the present invention; Figure 3 for Figure 2 Sectional view at point AA; Figure 4 for Figure 2 Sectional view at point BB.

[0019] In the picture: 1-Liquid nitrogen storage and supply system; 2-Pressure booster; 3-End flow guide auxiliary device; 301-Shell; 302-Vortex atomizing head; 303-Negative pressure mixer; 304-Gas guide channel; 305-Liquid inlet; 306-Liquid guide groove; 307-Jet outlet; 308-Mixing chamber; 309-Side channel; 4-Intelligent control system. Detailed Implementation

[0020] The following are specific embodiments of the present invention described in conjunction with the accompanying drawings, further illustrating the technical solutions of the present invention. However, the present invention is not limited to these embodiments. Specific details, such as particular configurations and components, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Furthermore, for clarity and brevity, descriptions of known functions and structures have been omitted.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0022] In existing technologies, fire control in mine goaf areas faces challenges such as low efficiency, poor cooling effect, and delayed response of traditional nitrogen injection techniques. Conventional methods rely on low-pressure gas delivery, causing nitrogen to escape in complex fissures and making it difficult to quickly cover high-temperature areas. While chemical inhibitors can isolate oxygen, their instantaneous cooling capacity for high-temperature fire sources is insufficient; heat cannot be dissipated in a timely manner within enclosed spaces, and coal oxidation reactions continue. When a fire occurs, traditional techniques require a long deployment time, missing the optimal opportunity for fire suppression.

[0023] To address the aforementioned technical problems, this application proposes a high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas, such as... Figures 1-4 As shown, the fire extinguishing system includes a liquid nitrogen storage and supply system 1, a pressurization device 2, and an end-of-line flow auxiliary device 3. The liquid nitrogen storage and supply system 1 is used to maintain the liquid nitrogen at a low temperature and high pressure during the transportation process. The liquid nitrogen storage and supply system 1 includes a high-pressure liquid nitrogen storage tank and a pressure control valve system. The high-pressure liquid nitrogen storage tank is connected to the pressurization device 2 through a low-temperature insulated pipeline, and the pressure control valve system is connected in series with the low-temperature insulated pipeline. The pressurization device 2 includes a liquid buffer pressurization tank, which is used to pressurize the liquid nitrogen and prevent phase change during transportation. The end-of-line flow auxiliary device 3 includes a housing 301, a vortex atomizing head 302 disposed at the front end inside the housing 301, and a negative pressure mixer 303 disposed at the rear end inside the housing 301. The vortex atomizing head 302 is inserted inside the negative pressure mixer 303. The vortex atomizing head 302 and the negative pressure mixer 303 cooperate to atomize the liquid nitrogen and diffuse it evenly to the target area.

[0024] Specifically, the liquid nitrogen storage and supply system 1 stores liquid nitrogen in a high-pressure storage tank and regulates the pipeline pressure with a pressure control valve to ensure that the liquid nitrogen remains liquid during transportation; the buffer tank of the pressurization device 2 pressurizes the liquid nitrogen to offset the pressure loss caused by pipeline resistance; in the end flow guiding auxiliary device 3, the vortex atomizing head 302 disperses the liquid nitrogen into fine droplets, and the negative pressure mixer 303 introduces external airflow for secondary mixing to form a uniform mist spray that covers the fire source area.

[0025] Through the above technical solutions, this application solves the problem of vaporization loss during liquid nitrogen transportation, ensuring that liquid nitrogen reaches the fire source area directly; the atomization structure increases the contact area between liquid nitrogen and high-temperature coal, improving heat exchange efficiency; the high-pressure injection method allows liquid nitrogen to penetrate deep into the fracture development area, forming a continuous oxygen-free environment; the system response time is shortened, enabling rapid and precise fire extinguishing in the early stages of a fire.

[0026] This application further proposes an intelligent control system 4, which includes temperature sensors, pressure sensors, distributed fiber optic temperature sensors, and a remote control platform connected to the signal output terminals of each sensor, arranged in the pipeline and goaf area, for real-time monitoring of the temperature and pressure in the injection area.

[0027] The temperature sensor is used to collect temperature signals from the liquid nitrogen delivery pipeline and the goaf area. Specifically, a K-type thermocouple or a PT100 platinum resistance thermometer can be used, arranged along key nodes of the delivery pipeline (such as the liquid nitrogen injection port, pressure reducing section, and vaporizer outlet), and fixed by welding a sensor base. The sensor base is made of 316L stainless steel with internal threads for threaded connection with the sensor. During installation, the sensor base is fixed to the outer wall of the pipeline using a seat welding or branch welding method. After welding, an airtightness test is performed to ensure long-term sealing reliability. The portion of the sensor inserted into the pipeline is fitted with a low-temperature resistant heat-resistant sleeve, and a PTFE gasket is installed at the threaded interface. The exposed portion is equipped with a lock nut and vibration-damping support clamp to ensure stable temperature measurement under low-temperature vibration environments. The pressure sensor is used to monitor the internal pressure of the pipeline and tank. Specifically, a diaphragm pressure transmitter can be used, with its pressure tap connected to the pipeline or tank via a welded internal thread seat, and equipped with a three-valve manifold and pulse tube to avoid interference from low-temperature frost and impact stress on signal acquisition. The distributed fiber optic temperature sensor is used for large-scale monitoring of the temperature field in the goaf. Specifically, it can be fixed to the roof or sidewall using a telescopic anchor-type bracket, 50-100 cm in length, with barbs at the end for anti-slip. Protective sleeves are installed at the bends of the fiber optic cable to ensure stable anchoring in soft surrounding rock and prevent stress concentration. The remote control platform is a central processing unit integrating multi-source sensor data. It connects to each sensor via a signal transmission module to analyze temperature and pressure data in real time and generate control commands. This arrangement and installation structure ensures reliable connection between the sensors and pipelines or tunnel spaces, guaranteeing long-term stable acquisition and integration of temperature and pressure signals under low-temperature, high-pressure environments such as liquid nitrogen injection and nitrogen purging. The integrated remote control platform can monitor temperature changes in the injection zone in real time, utilizing gaseous nitrogen for prevention and liquid nitrogen for fire extinguishing.

[0028] This application further proposes that the top of the liquid buffer pressurization tank is equipped with a gas inlet and a liquid inlet, which are connected to the gas phase port and liquid phase port of the high-pressure liquid nitrogen storage tank, respectively, to realize the input of liquid nitrogen and nitrogen gas; the liquid buffer pressurization tank has a double-layer structure, and an electric heating wire is installed in the interlayer of the double-layer structure, which can increase the nitrogen pressure in the tank by heating, thereby meeting the pressure requirements of the injection operation; the interlayer is filled with perlite insulation material, and the outer wall of the interlayer is wrapped with an aluminum foil reflective layer to reduce heat radiation loss.

[0029] The liquid buffer pressurization tank is constructed primarily of Q345 steel, with a volume of 10L and a design pressure resistance of 10MPa. It is equipped with a pressure gauge for real-time internal pressure reading. Radial support ribs with a fixed spacing of approximately 30cm are installed between the inner and outer layers to maintain structural stability during pressure changes. The interlayer has a filling port equipped with a threaded sealing cap, and a low-temperature resistant gasket and compression structure ensure good sealing performance, preventing moisture absorption or leakage of the filling material. When the nitrogen pressure inside the tank is insufficient, an electric heating wire generates heat, which is conducted through the interlayer space to the tank interior, causing the nitrogen to expand and increase pressure. Perlite filler forms a continuous insulation layer within the interlayer, effectively reducing the heat exchange rate between the low-temperature environment inside the tank and the external environment. An aluminum foil reflective layer covers the outer surface of the interlayer, reflecting the thermal radiation energy from the external environment back into the interlayer space, forming a composite insulation system together with the perlite. This technical solution achieves rapid response to pressure regulation and ensures the thermal stability of cryogenic liquid nitrogen during transportation through the synergistic effect of active heating and passive insulation.

[0030] This application further proposes that the vortex atomizing head 302 has a conical structure, and the vortex atomizing head 302 has an axially spirally distributed air guide channel 304 in the middle, the end of the air guide channel 304 is connected to the jet port 307, the vortex atomizing head 302 has a spiral liquid guide groove 306 extending from the outer wall to the middle, and a liquid inlet 305 is opened on the side of the vortex atomizing head 302. One end of the liquid inlet 305 is sealed to the outlet of the liquid buffer pressurization tank, and the other end is connected to the liquid guide groove 306; the negative pressure mixer 303 has a mixing chamber 308 inside; the jet port 307 of the vortex atomizing head 302 is directly opposite the mixing chamber 308 of the negative pressure mixer 303. A side channel 309 is formed between the outer side of the vortex atomizing head and the inner wall of the housing 301; there are 2-6 liquid guiding grooves 306, and the spiral direction is the same. The liquid guiding grooves 306 are recessed in the inner wall of the air guiding channel 304, and their cross-section gradually decreases from front to back until they disappear.

[0031] Specifically, after entering the housing 301, the nitrogen gas splits into two streams. One stream enters the spiral-shaped gas guide channel 304 to form a high-speed airflow, while the other stream enters the side channel 309. Liquid nitrogen enters the spiral-shaped liquid guide groove 306 through the liquid inlet 305. As the cross-section of the flow channel gradually decreases, the liquid nitrogen overflows into the gas guide channel 304 under the action of centrifugal force, entering at an angle to the high-speed airflow. The high-speed airflow applies shear force to the liquid nitrogen, breaking it into fine droplets. When the initially atomized gas-liquid mixture enters the negative pressure mixer 303, the nitrogen gas in the side channel is drawn into the mixing chamber 308 under the action of negative pressure, where it undergoes a secondary, intense mixing with the droplets, ultimately forming a uniform mist-like jet.

[0032] Through the above technical solution, this application solves the problems of poor atomization effect and uneven mixing during liquid nitrogen injection, increases the contact area between liquid nitrogen and high-temperature coal, enhances the turbulent mixing effect of gas-liquid two-phase flow, avoids phase change loss caused by local accumulation of liquid nitrogen, and ensures the stability of transportation under low temperature conditions through a sealed connection structure, ultimately achieving a synergistic fire extinguishing effect of rapid cooling and efficient oxygen isolation.

[0033] This application further proposes that the vortex atomizing head 302 and the housing 301 are fixed by threaded connection or clamp-type quick connector, realizing the reliable sealing and quick disassembly and assembly function of the connection structure between the vortex atomizing head 302 and the housing 301; the inlet of the housing 301 is sealed to the mine nitrogen pipeline, and the outlet is sealed to the goaf injection hole; the gas guide channel 304 includes a contraction section, a throat and an expansion section, and the jet port 8 is located at the throat position. When nitrogen enters the housing 301, a portion of the gas is converted from static pressure to dynamic pressure in the spiral gas guide channel 304, forming a high-speed airflow. Simultaneously, liquid nitrogen fluid enters the liquid guide tank 306 through the liquid inlet 305. The liquid nitrogen fluid flows spirally in the liquid guide tank 306. As the cross-section of the flow channel gradually decreases, it gradually overflows into the gas guide channel 304 and enters at a certain angle to the high-speed airflow. At this time, the kinetic energy of the high-speed airflow acts on the liquid nitrogen fluid, causing it to undergo lateral tearing and breakage, forming fine droplets. This forms a gas-liquid two-phase mixed flow and enters the negative pressure mixer 303. The flow accelerates in the contraction section and the pressure decreases at the throat, forming a high-speed mixed flow. Another stream of nitrogen in the side channel 309 is drawn into the mixing chamber 308 under the action of nitrogen injection pressure and the Venturi effect. It further undergoes violent disturbance and turbulence with the initially atomized droplets in the negative pressure mixer 303, ultimately achieving a uniform atomized nitrogen jet output.

[0034] This application further proposes that it also includes a Y-type filter, which is connected in series at one end of the cryogenic insulated pipe near the end flow guide auxiliary device 3. It can effectively intercept tiny impurities that may exist in the liquid nitrogen fluid and prevent impurities from entering the end flow guide auxiliary device 3 and clogging the nozzle. The lower end of the Y-type filter is provided with a drain port with a manual ball valve.

[0035] The Y-type filter housing can be made of 304 stainless steel with a 0.5mm mesh size, effectively intercepting minute impurities that may be present in the liquid nitrogen fluid and preventing them from entering the rear liquid guide tank (306) or the atomizer, thus avoiding nozzle clogging. A drain port is located at the bottom of the filter, featuring a manual ball valve for quick opening to discharge impurities and clean the filter screen under low-temperature conditions, reducing downtime and improving system reliability. The ball valve is made of a low-temperature resistant material and uses a PTFE seal at the valve seat to ensure good sealing performance even at -196℃.

[0036] Through the above technical solution, this application can effectively intercept impurity particles in liquid nitrogen fluid, avoid clogging of the nozzle of the end guide auxiliary device 3, and ensure stable atomization effect; the quick opening and closing design of the drain port significantly shortens maintenance time and reduces system downtime frequency, thereby improving the operational reliability and continuity of the fire extinguishing system.

[0037] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0038] In the description of this application, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas, characterized in that, include: Liquid nitrogen storage and supply system (1), pressurization device (2) and terminal flow guiding auxiliary device (3); The liquid nitrogen storage and supply system (1) is used to maintain the low temperature and high pressure state of liquid nitrogen during the transportation process; the liquid nitrogen storage and supply system (1) includes a high pressure liquid nitrogen storage tank and a pressure control valve system, the high pressure liquid nitrogen storage tank is connected to the pressurization device (2) through a low temperature insulated pipeline, and the pressure control valve system is connected in series on the low temperature insulated pipeline; The pressurization device (2) includes a liquid buffer pressurization tank for pressurizing liquid nitrogen and preventing phase change during transport; The end flow guiding auxiliary device (3) includes a housing (301), a vortex atomizing head (302) disposed at the front end inside the housing (301), and a negative pressure mixer (303) disposed at the rear end inside the housing (301). The vortex atomizing head (302) is inserted inside the negative pressure mixer (303). The vortex atomizing head (302) and the negative pressure mixer (303) work together to atomize liquid nitrogen and diffuse it evenly to the target area.

2. The high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 1, characterized in that, It also includes an intelligent control system (4), which includes temperature sensors, pressure sensors, distributed fiber optic temperature sensors and remote control platforms connected to the signal output terminals of each sensor arranged in the pipeline and goaf area, for real-time monitoring of the temperature and pressure of the injection area.

3. The high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 1, characterized in that, The liquid buffer pressurization tank is equipped with a gas inlet and a liquid inlet at the top, which are connected to the gas phase port and liquid phase port of the high-pressure liquid nitrogen storage tank, respectively, to realize the input of liquid nitrogen and nitrogen gas.

4. The high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 1, characterized in that, The liquid buffer pressurization tank has a double-layer structure. The interlayer of the double-layer structure is equipped with an electric heating wire, which can increase the nitrogen pressure inside the tank by heating, thereby meeting the pressure requirements of the injection operation. The interlayer is filled with perlite insulation material, and the outer wall of the interlayer is wrapped with an aluminum foil reflective layer to reduce heat radiation loss.

5. The high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 1, characterized in that, The vortex atomizing head (302) has a conical structure. The vortex atomizing head (302) has an axially spirally distributed air guide channel (304) in the middle. The end of the air guide channel (304) is connected to the jet port (307). The vortex atomizing head (302) has a spiral liquid guide groove (306) extending from the outer wall to the middle. The vortex atomizing head (302) has a liquid inlet (305) on the side. One end of the liquid inlet (305) is sealed to the outlet of the liquid buffer pressurization tank, and the other end is connected to the liquid guide groove (306). The negative pressure mixer (303) has a mixing chamber (308) inside. The jet port (307) of the vortex atomizing head (302) is directly opposite the mixing chamber (308) of the negative pressure mixer (303).

6. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 5, characterized in that, The number of liquid guiding grooves (306) is 2-6, and the spiral direction is the same. The liquid guiding grooves (306) are recessed in the inner wall of the gas guiding channel (304), and their cross-section gradually decreases from front to back until it disappears.

7. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 5, characterized in that, The vortex atomizing head (302) is fixed to the shell (301) by a threaded connection or a clamp-type quick connector; the inlet of the shell (301) is sealed to the mine nitrogen pipeline, and the outlet is sealed to the goaf injection hole. The air passage (304) includes a contraction section, a throat, and an expansion section, and the jet port (8) is located at the throat.

8. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 7, characterized in that, When nitrogen enters the shell (301), a portion of the gas passes through the spiral-shaped gas guiding channel (304), where static pressure is converted into dynamic pressure to form a high-speed airflow. Simultaneously, liquid nitrogen fluid enters the liquid guiding tank (306) through the liquid inlet (305). The liquid nitrogen fluid flows spirally in the liquid guiding tank (306), gradually overflowing into the gas guiding channel (304) as the cross-section of the flow channel gradually decreases, and entering at a certain angle to the high-speed airflow. At this time, the kinetic energy of the high-speed airflow acts on the liquid nitrogen fluid, causing it to undergo lateral tearing and breakage, forming fine liquid... The droplets form a gas-liquid two-phase mixed flow and enter the negative pressure mixer (303). The flow is accelerated in the contraction section and the pressure decreases at the throat, forming a high-speed mixed flow. Furthermore, a side channel (309) is provided between the outer wall of the vortex atomizing head (302) and the shell (301). Another stream of nitrogen in the side channel (309) is drawn into the mixing chamber (308) under the action of nitrogen injection pressure and Venturi effect. It further undergoes violent disturbance and turbulence with the initially atomized droplets in the negative pressure mixer (303), and finally achieves uniform atomized nitrogen jet output.

9. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 2, characterized in that, The temperature sensor is a K-type thermocouple or a PT100 platinum resistance thermometer. The temperature sensor is fixed to the outer wall of the low-temperature insulated pipe by a sensor base. The part of the temperature sensor inserted into the pipe is fitted with a low-temperature heat-resistant sleeve, the threaded interface is provided with a polytetrafluoroethylene gasket, and the exposed part is provided with a lock nut and a vibration-damping support clamp. The pressure sensor is a diaphragm pressure transmitter, and its pressure tap is connected to the pipeline / tank body through a welded internal thread seat; the pressure sensor is equipped with a three-valve group and a pulse tube to avoid low-temperature frost and impact stress. The fixed bracket of the distributed optical fiber temperature sensor is a telescopic anchor rod structure, and the end of the bracket is provided with a barbed anti-slip structure; the optical cable of the distributed optical fiber temperature sensor is covered with a protective sleeve at the bend.

10. A high-efficiency liquid nitrogen injection fire extinguishing system for goaf areas according to claim 1, characterized in that, It also includes a Y-type filter, which is connected in series at one end of the cryogenic insulated pipe near the end flow guide auxiliary device (3). It can effectively intercept small impurities that may exist in the liquid nitrogen fluid and prevent impurities from entering the end flow guide auxiliary device (3) and clogging the nozzle. The lower end of the Y-type filter is provided with a drain port with a manual ball valve.

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