Modularized liquid nitrogen cooling system for deep stope of metal mine and intelligent control method

Abstract

This invention relates to the field of mine heat hazard prevention and safety engineering technology, and particularly to a modular liquid nitrogen cooling system and intelligent control method for deep mining areas in metal mines. The system includes a surface liquid nitrogen supply unit, an insulated and moisture-proof conveying unit, an underground storage and distribution unit, a mining area heat exchange and safety monitoring unit, and an intelligent control unit. Through a three-pipe concentric structure, a vacuum insulation layer is formed, and a slightly positive pressure dry nitrogen gas forms a dry gas barrier, effectively isolating the high-temperature and high-humidity environment in deep mines. An underground vacuum-insulated storage tank and intelligent branch valve group are installed to achieve on-demand distribution of liquid nitrogen to multiple mining areas. The mining area heat exchanger adopts a modular skid-mounted structure, and works with an environmental monitoring box to implement graded safety interlocking logic. The intelligent control unit dynamically adjusts the cooling capacity, calculates liquid nitrogen consumption, and performs cost accounting. This invention has advantages such as low cooling loss, moisture and corrosion resistance, adaptability to dispersed mining areas, and comprehensive safety monitoring, and can significantly improve the heat hazard problem in deep metal mines.

Description

Technical Field

[0001] This invention relates to the field of mine heat hazard prevention and safety engineering technology, and in particular to a modular liquid nitrogen cooling system and intelligent control method for deep mining areas of metal mines. Background Technology

[0002] As metal mineral resources are mined at greater depths, the geothermal gradient effect is exacerbating underground heat hazards. In many deep mining areas, the ambient temperature frequently exceeds 35°C, and relative humidity remains high, severely impacting the health of workers, the lifespan of drilling rigs and other mechanical equipment, and production efficiency. Traditional cooling methods, such as enhanced ventilation and the installation of underground refrigeration units, have limited effectiveness in deep metal mines with high heat loads and dispersed mining areas, and also suffer from drawbacks such as enormous energy consumption and difficulties in equipment maintenance.

[0003] Existing liquid nitrogen cooling technologies are mostly derived from the coal mining industry. For example, patent application CN117052455A discloses a liquid nitrogen cooling system for underground coal mines. This system uses a nitrogen generator to produce nitrogen gas, which is cooled by a first and second cooler before being mixed with liquid nitrogen through heat exchange and transported to the working face. This achieves both cooling and fire prevention, while also saving on liquid nitrogen consumption. However, this technology is primarily designed for coal mining environments and is difficult to directly apply to the special conditions of deep mining areas in metal mines. First, metal mines have multiple mining sections and dispersed working faces, requiring a system with multi-point, multi-line synchronous cooling capabilities. The aforementioned patent uses a single transport pipeline, which cannot achieve on-demand distribution across multiple mining areas. Second, the surrounding rock and groundwater in metal mines are active and often corrosive, resulting in extremely high humidity inside boreholes. Existing technologies do not consider moisture prevention, corrosion prevention, and cold loss control during long-distance vertical transport. Furthermore, although metal mines do not pose a gas risk, the risk of oxygen deficiency and asphyxiation due to nitrogen accumulation is more significant, requiring more intensive environmental monitoring and safety interlocking. Therefore, there is an urgent need to develop a dedicated liquid nitrogen cooling system suitable for deep mining areas in metal mines. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a modular liquid nitrogen cooling system and intelligent control method for deep mining areas in metal mines. It is suitable for deep mining environments in metal mines with high temperature, high humidity, and multiple mining areas, and solves the problem of heat damage.

[0005] To achieve the above objectives, this invention discloses a modular liquid nitrogen cooling system for deep mining areas of metal mines, including interconnected ground liquid nitrogen supply units, heat-insulating and moisture-proof conveying units, underground storage and distribution units, and mining area heat exchange and safety monitoring units, as well as an intelligent control unit; The ground-based liquid nitrogen supply unit includes a mobile liquid nitrogen supply device; The heat-insulating and moisture-proof conveying unit is a casing structure connected to the pipeline of the mobile liquid nitrogen supply equipment. The casing structure extends from the ground to the well through a vertical borehole. The casing structure includes an inner pipe, an outer pipe, and a protective pipe that are sleeved together. The ends of the inner pipe and the outer pipe are sealed together. The inner pipe is used to convey liquid nitrogen. The inner pipe and the outer pipe form a vacuum insulation layer. The outer pipe and the protective pipe form a dry gas barrier layer. The dry gas is slightly positive pressure dry nitrogen gas, and the slightly positive pressure is in the range of 1.05 to 1.2 times the atmospheric pressure. The downhole storage and distribution unit includes a vacuum-insulated storage tank connected to the casing structure, a branch valve group connected to the vacuum-insulated storage tank, and an alarm assembly. The mining area heat exchange and safety monitoring unit includes a heat exchanger, a local fan, and an environmental monitoring box connected to the branch valve group pipeline; The intelligent control unit is communicatively connected to the ground liquid nitrogen supply unit, the heat-insulating and moisture-proof conveying unit, the underground storage and distribution unit, and the mining area heat exchange and safety monitoring unit for overall system control.

[0006] Furthermore, the intelligent control unit collects and displays parameters such as pressure, flow rate, temperature, humidity, liquid level, and gas concentration of the entire system, dynamically controls the opening of the branch valve group according to the real-time heat load of each mining area, executes safety interlock logic, and calculates the liquid nitrogen consumption of each mining area for energy consumption analysis and cost accounting.

[0007] Furthermore, multiple guide supports are arranged at intervals between the inner tube and the outer tube along the direction perpendicular to the drilling depth. The guide supports allow the inner tube to slide axially and restrict radial displacement. The inner tube is covered with multiple layers of heat insulation material.

[0008] Furthermore, the mobile liquid nitrogen supply equipment includes mobile liquid nitrogen tank trucks that can operate alternately, the output end of the liquid nitrogen tank truck is connected to a cryogenic liquid pump, and the outlet pipeline of the cryogenic liquid pump is equipped with pressure and flow regulating valves.

[0009] Furthermore, the inner pipe inlet is connected to a mobile liquid nitrogen supply device via a corrugated pipe compensator, and the inner pipe outlet is connected to the vacuum insulated storage tank via a corrugated pipe compensator.

[0010] Furthermore, each outlet of the branch valve group is equipped with an electric regulating valve, a flow meter, and a temperature sensor; the alarm assembly includes an oxygen concentration monitor, an emergency ventilator, and an audible and visual alarm interlocked with the emergency ventilator.

[0011] Furthermore, the heat exchanger is an air-bath vaporization heat exchanger with a skid or wheels at the bottom. The liquid nitrogen inlet of the heat exchanger is equipped with a safety valve, and the gaseous nitrogen outlet is equipped with an explosion-proof diaphragm.

[0012] Furthermore, the environmental monitoring boxes are arranged at least at three monitoring points: the gaseous nitrogen outlet of the heat exchanger, the working point of the mining area, and the return air outlet of the mining area; each environmental monitoring box integrates a temperature sensor, an oxygen concentration sensor, and a carbon monoxide concentration sensor.

[0013] Furthermore, the security interlocking logic includes: When the oxygen concentration at any of the monitoring points is below 19.5%, an early warning is issued to the intelligent control unit. When the oxygen concentration at any of the monitoring points is below 18.0% or the carbon monoxide concentration exceeds the limit, the intelligent control unit sends a shut-off command to the corresponding branch valve group in the mining area to cut off the liquid nitrogen supply and start the backup ventilation system of the mining area and adjacent roadways. The local fan is connected to the liquid nitrogen supply pipeline of the heat exchanger, and the liquid nitrogen supply pipeline must not be opened when the local fan is not started.

[0014] A smart control method for a modular liquid nitrogen cooling system in deep mining areas of metal mines includes the following steps: During the S1 preparation phase, cold nitrogen gas is generated by the ground vaporizer to pre-cool the inner tube, and slightly positive pressure dry nitrogen gas is introduced into the dry gas barrier layer. During the S2 transport phase, the mobile liquid nitrogen supply equipment is activated to transport liquid nitrogen through the inner pipe to the vacuum insulated storage tank. S3 Distribution and Cooling Stage: The intelligent control unit sets the opening degree of the branch valve group according to the real-time heat load of each stope, and distributes liquid nitrogen to the heat exchangers of each stope for heat exchange, so that the high temperature air is significantly cooled into cold air, and finally the cold air is guided to the working face by the local fan; the real-time heat load is obtained by back calculation from the return air temperature of the stope; the intelligent control unit counts the liquid nitrogen consumption of each stope, analyzes energy consumption and performs cost accounting; S4 Monitoring and Adjustment Phase: Data from each sensor is uploaded to the intelligent control unit in real time. The system dynamically adjusts the opening of the branch valve group and executes safety interlock logic when abnormal oxygen or carbon monoxide concentration is detected. S5 shutdown phase: After the operation is completed, gradually close each branch line, stop the ground liquid supply, use residual gas to purge the main pipeline, discharge the residual liquid, and prevent ice blockage after shutdown.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Through the "three-pipe concentric" structure, combined with the vacuum insulation layer and the micro-positive pressure dry nitrogen barrier layer, the high temperature and high humidity environment of deep boreholes is effectively isolated, which greatly reduces the cold loss of liquid nitrogen during long-distance vertical transportation, avoids the problems of inner pipe ice blockage and external corrosion caused by water vapor penetration, and achieves efficient heat insulation and moisture protection.

[0016] 2. A vacuum insulated storage tank is installed underground as a "cold energy bank". With the help of intelligent branch valve group, the liquid nitrogen flow rate can be dynamically distributed according to the real-time heat load of each decentralized mining area, realizing multi-point and multi-line synchronous and precise cooling on demand, avoiding the waste of cold energy.

[0017] 3. The stope heat exchanger adopts a modular skid-mounted design with skids or wheels at the bottom, which can be flexibly moved and combined according to the stope space and cooling requirements, perfectly adapting to the changing working conditions of metal mine stopes and narrow roadways.

[0018] 4. The system has deployed environmental monitoring boxes with integrated temperature, oxygen, and CO sensors at multiple key locations such as heat exchanger outlets, work points, and return air inlets. It has also established a graded safety interlock logic of early warning, supply cut-off, and activation of backup ventilation, which effectively prevents the risk of nitrogen asphyxiation and achieves full-coverage intelligent safety monitoring.

[0019] 5. The intelligent control unit not only realizes real-time monitoring and automatic control of all parameters, but also counts the liquid nitrogen consumption of each mining area and performs energy consumption analysis and cost accounting, providing data support for the refined management and production decision-making of mining enterprises. Attached Figure Description

[0020] Figure 1 This is a diagram showing the overall structure of a modular liquid nitrogen cooling system. Figure 2 A schematic diagram of the modular liquid nitrogen cooling system structure and liquid nitrogen flow direction; Figure 3 Cross-sectional view of the casing structure; Figure 4 This is a schematic diagram of the guide support structure.

[0021] In the diagram, 100 is the surface liquid nitrogen supply unit; 101 is the mobile liquid nitrogen tanker; 102 is the cryogenic liquid pump; 103 is the pressure and flow regulating valve; 200 is the insulated and moisture-proof conveying unit; 201 is the inner pipe; 202 is the outer pipe; 203 is the vacuum insulation layer; 204 is the protective pipe; 205 is the dry gas barrier layer; 206 is the guide support; 207 is the vertical borehole; 300 is the underground storage and distribution unit; 301 is the vacuum insulated storage tank; 302 is the branch valve group; 303 is the oxygen concentration monitor; 304 is the audible and visual alarm; 305 is the emergency ventilator; 400 is the stope heat exchange and safety monitoring unit; 401 is the heat exchanger; 402 is the local fan; 403 is the environmental monitoring box; and 500 is the intelligent control unit. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 To be continued Figure 4 The principles and features of the present invention are described, and the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0023] This embodiment provides a modular liquid nitrogen cooling system for deep mining areas in metal mines, including an interconnected surface liquid nitrogen supply unit 100, an insulated and moisture-proof conveying unit 200, an underground storage and distribution unit 300, and a mining area heat exchange and safety monitoring unit 400. It also includes an intelligent control unit 500 that communicates with each system unit. The surface liquid nitrogen supply unit 100 is located on the surface and supplies liquid nitrogen to the entire cooling system. The insulated and moisture-proof conveying unit 200 has a special pipeline structure that utilizes existing vertical boreholes 207 in the metal mine as channels, solving the problems of cold loss and moisture damage during long-distance vertical transport. It delivers liquid nitrogen to the underground storage and distribution unit 300, which temporarily stores the liquid nitrogen and distributes it to each mining area heat exchange and safety monitoring unit 400 as needed. The intelligent control unit 500 is used for the overall management and control of the entire cooling system.

[0024] The surface liquid nitrogen supply unit 100 includes a mobile liquid nitrogen supply device, which comprises several mobile liquid nitrogen tank trucks 101 operating alternately to ensure uninterrupted liquid supply. The output end of each mobile liquid nitrogen tank truck 101 is connected to a cryogenic liquid pump 102. The pump's outlet pipeline is equipped with a precision pressure and flow regulating valve 103, allowing for remote adjustment of delivery parameters according to the overall downhole demand. In this embodiment, a vacuum-bath vaporizer and a rewarming pipeline are also provided on the surface for pre-cooling the inner pipe 201 of the insulated and moisture-proof delivery unit 200 before system startup and for draining residual liquid from the pipes after system shutdown to prevent ice blockage. All surface exposed pipelines and valves are wrapped with a high-performance vacuum insulation layer and covered with a rainproof and sunproof protective sleeve.

[0025] The heat-insulating and moisture-proof conveying unit 200 is a "three-pipe concentric" casing structure connected to the pipeline of the mobile liquid nitrogen supply equipment. The casing structure extends from the ground to the well through a vertical borehole 207. The innermost layer of the casing structure is the inner pipe 201, made of austenitic stainless steel, used for conveying liquid nitrogen. The inner wall is polished to reduce flow resistance. An outer pipe 202, made of corrosion-resistant carbon steel, is fitted over the inner pipe 201. The ends of the inner pipe 201 and the outer pipe 202 are sealed together. Multiple layers of heat-insulating material (such as a composite layer of aluminum foil and fiberglass paper) can also be wrapped around the outer wall of the inner pipe 201. A high vacuum is created between the inner pipe 201 and the outer pipe 202, forming a vacuum insulation layer 203, which acts as a highly efficient static heat insulation barrier, significantly reducing radial heat transfer. A protective pipe 204, made of corrosion-resistant carbon steel, is also installed outside the outer pipe 202. The annular space between the protective pipe 204 and the outer pipe 202 forms a dry gas barrier layer 205. During system operation, slightly positive pressure dry nitrogen is continuously introduced into the annular space to form a dynamic drying air curtain, effectively preventing the infiltration and condensation of humid air from the vertical borehole 207 into the inner pipe wall. Dry nitrogen inlets and outlets, as well as humidity sensors, are respectively located at the top and bottom of the annular space. When humidity exceeds the standard, the system automatically increases the flow rate of dry nitrogen for purging. Specifically, the slightly positive pressure is in the range of 1.05 to 1.2 times atmospheric pressure, and can be achieved as follows: A small stream of liquid nitrogen is drawn from the liquid phase outlet of the mobile liquid nitrogen tanker 101, vaporized through a small air-bath vaporizer (vegetable in very small size, similar to a finned coil), and then the pressure is adjusted to 1.05~1.2 times atmospheric pressure (approximately 106~122 kPa absolute pressure, i.e., gauge pressure approximately 5~20 kPa) through a pressure reducing valve before being introduced into the air inlet at the top of the outer protective pipe.

[0026] To compensate for the significant axial expansion and contraction of the inner pipe 201 caused by temperature differences during long-distance vertical transportation, bellows compensators are installed at the top inlet and bottom outlet of the inner pipe 201 to connect the pipeline to the mobile liquid nitrogen supply equipment and the vacuum insulated storage tank 301. The connection between the bellows compensator and the inner pipe 201 is as follows: a flange is welded to the end of the inner pipe 201, which is then connected to the fixed pipeline flange via a large axial bellows compensator. The bellows compensator has mating flanges at both ends, sealed with metal spiral wound gaskets, and secured with high-strength bolts. A guide support is installed near the flange of the inner pipe 201 to constrain radial offset while allowing free axial sliding. The bellows compensator is equipped with a transport limit rod and is pre-deformed according to the calculated displacement during installation. A protective cover is installed on the outside of the compensator at the bottom of the well to prevent rockfall and water erosion. This connection structure effectively absorbs the significant axial expansion and contraction of the inner pipe 201 caused by temperature differences, ensuring the safe operation of the pipeline system. Several guide supports 206 are spaced apart along the depth direction of the vertical borehole 207. These supports only restrict the radial displacement of the inner tube 201, allowing it to slide axially, thus preventing the inner tube 201 from becoming unstable. Specifically, the guide support 206 includes a positioning tube section and several support rods arranged in a radiating pattern on the outer wall of the positioning tube section. The positioning tube section is sleeved on the inner tube 201, and the support rods are supported between the inner and outer tubes.

[0027] The underground storage and distribution unit 300 is located in a safety chamber near the underground central substation. It includes a vacuum-insulated storage tank 301, which acts as a "cold energy bank" for temporary storage of liquid nitrogen, buffering the intermittent delivery from the surface and providing a stable liquid supply pressure to each stope. The outlet of the vacuum-insulated storage tank 301 is connected to an intelligent branch valve assembly 302, which has multiple outputs, each equipped with an electric regulating valve, a high-precision flow meter, and a temperature sensor. The branch valve assembly 302 receives instructions from the intelligent control unit 500 and dynamically distributes the liquid nitrogen flow according to the real-time heat load of each stope, achieving "on-demand cooling." An alarm system is installed in the area where the vacuum-insulated storage tank 301 is located to monitor and alarm on the working environment of the area. The alarm system includes two high-sensitivity oxygen concentration monitors 303 and interlocked audible and visual alarms 304 and emergency ventilation fans 305. Set oxygen concentration monitoring thresholds, for example, trigger an alarm when the oxygen concentration is below 19.5%, and automatically interlock to start the emergency ventilator 305 when it is below 18%.

[0028] To address the issue of insufficient liquid supply pressure caused by some mining areas being too far from the vacuum insulated storage tank 301, a secondary circulation booster pump was added to the long-distance main delivery pipeline downstream of the branch valve group 302 to ensure that the remote heat exchanger 401 has sufficient liquid nitrogen supply pressure.

[0029] A heat exchange and safety monitoring unit 400 is installed in each stope requiring cooling, including a heat exchanger 401, a local fan 402, and an environmental monitoring box 403. The heat exchanger 401 can be an air-bath vaporization heat exchanger, designed as a compact skid-mounted structure with skids or wheels at the bottom for flexible movement according to the stope space. The heat exchange core of the heat exchanger 401 adopts a finned tube structure; liquid nitrogen vaporizes and absorbs heat inside the tubes, while underground air is cooled by sweeping across the outer wall of the finned tubes driven by the explosion-proof local fan 402. For large stopes, two heat exchange modules can be used in parallel. A safety valve is installed at the liquid nitrogen inlet of the heat exchanger 401, and an explosion-proof diaphragm is installed at the gaseous nitrogen outlet, achieving dual safety venting.

[0030] The environmental monitoring box 403 is installed at at least three monitoring points: the gaseous nitrogen outlet of the heat exchanger 401, the working point in the stope, and the return air vent in the stope. Each environmental monitoring box 403 integrates a temperature sensor, an oxygen concentration sensor, and a carbon monoxide concentration sensor.

[0031] The liquid nitrogen supply pipeline between the monitoring point and heat exchanger 401 is interlocked and controlled by the intelligent control unit 500. The safety interlock logic is as follows: When the oxygen concentration at any monitoring point is lower than 19.5%, an early warning is sent to the intelligent control unit 500. When the oxygen concentration at any monitoring point is below 18.0% or the carbon monoxide concentration exceeds 24 ppm (0.0024%), the intelligent control unit 500 sends a closing command to the branch valve group 302 of the corresponding mining area to cut off the liquid nitrogen supply and start the original backup ventilation system of the mining area and adjacent roadways. When the local fan 402 is not started, the liquid nitrogen supply line cannot be opened to prevent cold air from accumulating and causing local oxygen deficiency.

[0032] The intelligent control unit 500 includes a ground control center, an underground data acquisition substation, and a fiber optic communication network. The intelligent control unit 500 collects and displays all parameters of the entire system in real time, including pressure, flow rate, temperature, humidity, liquid level, and gas concentration. The control center has a built-in control algorithm based on a heat load model. Based on preset target temperatures for each stope (e.g., 28°C), it automatically calculates the required cooling capacity and sends adjustment commands to the underground branch valve group 302. The system automatically executes safety interlock logic and records all alarm events. Simultaneously, the system can statistically analyze the liquid nitrogen consumption per shift in each stope, generating energy consumption reports for cost accounting and system optimization.

[0033] This invention also provides a modular liquid nitrogen cooling intelligent control method for deep mining areas in metal mines, comprising: S1 Preparation Phase: Before operation, start the ground vaporizer to generate room temperature nitrogen gas to pre-cool the inner pipe 201, gradually reducing the pipe wall temperature to near the liquid nitrogen temperature to prevent violent vaporization after liquid nitrogen enters. At the same time, introduce slightly positive pressure dry nitrogen gas into the dry gas barrier layer 205 and monitor the exhaust humidity until the humidity drops to the qualified range.

[0034] S2 Transport Phase: The surface cryogenic liquid pump 102 is activated to pressurize the liquid nitrogen in the mobile liquid nitrogen tanker 101 and send it into the inner pipe 201. The liquid nitrogen descends using a combination of gravity and pump pressure, eventually entering the downhole vacuum insulated storage tank 301. During the transport process, the intelligent control unit 500 monitors the pressure and temperature of the transport pipeline and the liquid level in the vacuum insulated storage tank 301.

[0035] S3 Distribution and Cooling Stage: The intelligent control unit 500 automatically sets the opening degree of each outlet electric regulating valve of the branch valve group 302 based on the real-time heat load calculated from the return air temperature of each stope. Liquid nitrogen is distributed to the heat exchangers 401 in each stope. The liquid nitrogen flows through the tube side of the heat exchanger 401 and undergoes indirect heat exchange with the high-temperature air flowing in the shell side (or outside the tubes). The liquid nitrogen vaporizes and absorbs a large amount of latent heat from the air outside the tubes, significantly cooling the high-temperature air into cold air. Finally, the cold air is guided to the working face by the local fan 402. The system synchronously counts the instantaneous and cumulative liquid nitrogen consumption of each stope.

[0036] S4 Monitoring and Adjustment Phase: Sensor data from each environmental monitoring box 403 is uploaded to the intelligent control unit 500 in real time. The system dynamically adjusts the opening of the branch valve group 302 to ensure that the temperature of each stope remains stable within the set range. If the oxygen concentration at a monitoring point in a stope drops to 19.5%, the system issues an early warning; if it drops to 18.0% or the CO concentration exceeds the limit, the system immediately closes the branch of the branch valve group 302 corresponding to that stope, cuts off the liquid nitrogen supply, and remotely starts the backup ventilation system of that stope and adjacent roadways.

[0037] S5 Shutdown Phase: After the mining operations are completed, the electric regulating valves of each branch are gradually closed through the intelligent control unit 500, and the ground cryogenic liquid pump 102 is stopped. The main pipeline is purged using residual nitrogen and a small amount of room temperature nitrogen in the pipeline to remove residual liquid nitrogen or cryogenic gas and prevent ice blockage after shutdown.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modular liquid nitrogen cooling system for deep mining areas in metal mines, comprising interconnected ground liquid nitrogen supply units (100), heat-insulating and moisture-proof conveying units (200), underground storage and distribution units (300), and mining area heat exchange and safety monitoring units (400), characterized in that, It also includes an intelligent control unit (500); The ground-based liquid nitrogen supply unit (100) includes a mobile liquid nitrogen supply device; The heat-insulating and moisture-proof conveying unit (200) is a casing structure connected to the pipeline of the mobile liquid nitrogen supply equipment. The casing structure extends from the ground to the well through a vertical borehole (207). The casing structure includes an inner pipe (201), an outer pipe (202), and a protective pipe (204) that are sleeved and connected. The ends of the inner pipe (201) and the outer pipe (202) are sealed and connected. The inner pipe (201) is used to convey liquid nitrogen. The inner pipe (201) and the outer pipe (202) form a vacuum insulation layer (203). The outer pipe (202) and the protective pipe (204) form a dry gas barrier layer (205). The dry gas is slightly positive pressure dry nitrogen. The slightly positive pressure is in the range of 1.05 to 1.2 times the normal pressure. The downhole storage and distribution unit (300) includes a vacuum insulated storage tank (301) connected to the casing structure, a branch valve group (302) connected to the vacuum insulated storage tank (301), and an alarm assembly. The mining area heat exchange and safety monitoring unit (400) includes a heat exchanger (401), a local fan (402), and an environmental monitoring box (403) connected to the branch valve group (302) via pipeline. The intelligent control unit (500) is communicatively connected to the ground liquid nitrogen supply unit (100), the heat preservation and moisture-proof conveying unit (200), the underground storage and distribution unit (300), and the mining area heat exchange and safety monitoring unit (400) for overall system control.

2. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 1, characterized in that, The intelligent control unit (500) collects and displays the system's pressure, flow rate, temperature, humidity, liquid level, and gas concentration parameters. It dynamically controls the opening of the branch valve group (302) based on the real-time heat load of each mining area, executes safety interlock logic, and calculates the liquid nitrogen consumption of each mining area for energy consumption analysis and cost accounting.

3. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 1, characterized in that, Multiple guide supports (206) are arranged at intervals between the inner tube (201) and the outer tube (202) along the depth direction of the vertical borehole (207). The guide supports (206) allow the inner tube (201) to slide axially and restrict radial displacement. The inner tube (201) is covered with multiple layers of heat insulation material.

4. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 3, characterized in that, The mobile liquid nitrogen supply equipment includes a mobile liquid nitrogen tanker (101) that can operate alternately. The output end of the mobile liquid nitrogen tanker (101) is connected to a cryogenic liquid pump (102). The outlet pipeline of the cryogenic liquid pump (102) is equipped with a pressure and flow regulating valve (103).

5. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 3, characterized in that, The inlet of the inner pipe (201) is connected to the mobile liquid nitrogen supply equipment through a corrugated pipe compensator pipeline, and the outlet of the inner pipe (201) is connected to the vacuum insulated storage tank (301) through a corrugated pipe compensator pipeline.

6. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 1, characterized in that, Each outlet of the branch valve group (302) is equipped with an electric regulating valve, a flow meter and a temperature sensor; the alarm assembly includes an oxygen concentration monitor (303), an emergency ventilator (305) and an audible and visual alarm (304) interlocked with the emergency ventilator (305).

7. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 1, characterized in that, The heat exchanger (401) is an air-bath vaporization heat exchanger with a skid or wheels at the bottom. The liquid nitrogen inlet of the heat exchanger (401) is equipped with a safety valve, and the gaseous nitrogen outlet is equipped with an explosion-proof diaphragm.

8. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 2, characterized in that, The environmental monitoring box (403) is arranged at least at three monitoring points: the gaseous nitrogen outlet of the heat exchanger (401), the working point of the mining area, and the return air outlet of the mining area; each environmental monitoring box (403) integrates a temperature sensor, an oxygen concentration sensor, and a carbon monoxide concentration sensor.

9. The modular liquid nitrogen cooling system for deep mining areas in metal mines according to claim 8, characterized in that, The safety interlock logic includes: When the oxygen concentration at any of the monitoring points is below 19.5%, an early warning is issued to the intelligent control unit (500); When the oxygen concentration at any of the monitoring points is below 18.0% or the carbon monoxide concentration exceeds the limit, the intelligent control unit (500) sends a shutdown command to the corresponding branch valve group (302) of the mining area to cut off the liquid nitrogen supply and start the original backup ventilation system of the mining area and adjacent roadways. The local fan (402) is connected to the liquid nitrogen supply pipeline of the heat exchanger (401) and the liquid nitrogen supply pipeline is prohibited from being opened when the local fan (402) is not started.

10. An intelligent control method for the modular liquid nitrogen cooling system in deep mining areas of metal mines according to any one of claims 1 to 9, characterized in that, Includes the following steps: During the S1 preparation stage, cold nitrogen gas is generated by the ground vaporizer to pre-cool the inner tube (201), and slightly positive pressure dry nitrogen gas is introduced into the dry gas barrier layer (205). During the S2 transport phase, the mobile liquid nitrogen supply equipment is activated to transport liquid nitrogen through the inner pipe (201) to the vacuum insulated storage tank (301); S3 Distribution and Cooling Stage: The intelligent control unit (500) sets the opening degree of the branch valve group (302) according to the real-time heat load of each mining area, and distributes liquid nitrogen to the heat exchangers (401) of each mining area for heat exchange, so that the high temperature air is significantly cooled into cold air, and finally the cold air is guided to the working face by the local fan (402); the real-time heat load is obtained by back calculation through the return air temperature of the mining area; the intelligent control unit (500) counts the liquid nitrogen consumption of each mining area, analyzes the energy consumption and performs cost accounting; S4 Monitoring and Adjustment Phase: Data from each sensor is uploaded to the intelligent control unit (500) in real time. The system dynamically adjusts the opening of the branch valve group (302) and executes safety interlock logic when abnormal oxygen or carbon monoxide concentration is detected. S5 shutdown phase: After the operation is completed, gradually close each branch line, stop the ground liquid supply, use residual gas to purge the main pipeline, discharge the residual liquid, and prevent ice blockage after shutdown.

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