Underground return air waste heat collection air supply and inlet preheating system suitable for high and cold mine

Abstract

The invention relates to an inlet air preheating system suitable for underground return air waste heat collection of a high-cold mine, and belongs to the field of underground return air waste heat recovery of the high-cold mine. The inlet air preheating system comprises a return air waste heat collection device, an inlet air preheating device, a water pump, an electric auxiliary heating device, a water inlet pipeline, a first water return pipeline and a second water return pipeline; the return air waste heat recovery device is arranged at the return air inlet of the return air footrill; the air inlet preheating device and the water pump are arranged at an air inlet of the air inlet adit; the water inlet pipeline is connected between the return air waste heat collecting device and the inlet air preheating device; the first water return pipeline is connected between the inlet air preheating device and the water pump; the second water return pipeline is connected between the water pump and the return air waste heat collecting device; the underground return air waste heat recovery is realized by utilizing an environment-friendly refrigerant through pressure-phase change circulation, the recovered heat is transferred to circulating water, and fresh preheated air flow is provided for the underground through the circulating water; and the reserved electric auxiliary heating device ensures the improvement of the working environment and ensures the safety production of the mine.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery technology for underground return air in cold-climate mines. Specifically, it relates to a waste heat collection and preheating system for underground return air in cold-climate mines. Background Technology

[0002] Yunnan Province has a wide distribution of non-ferrous metal mineral resources with a complete range of mineral types. However, the mining areas in northwestern Yunnan are located in high-altitude and cold regions with long winters and outdoor temperatures that are consistently below 0°C. Groundwater seeps into the roof and floor of the main transport tunnels, which remain frozen for extended periods, reducing transportation safety, affecting personnel access, and decreasing equipment operating efficiency. Furthermore, the mining area is located in a nature reserve with high environmental protection requirements. Only clean, low-carbon, and economical technologies can be used to solve the problems of shaft freezing and heating energy consumption in high-altitude and cold regions.

[0003] Mine ventilation systems require a continuous supply of fresh air to dilute toxic and harmful gases and dust. Influenced by geothermal heat, heat dissipation from mechanical equipment, and oxidative heat, the return air temperature in mines remains relatively constant and is significantly higher than the ambient temperature. Traditionally, this low-temperature waste heat is directly discharged into the atmosphere through the return air shaft, resulting in enormous energy waste, while mines themselves require substantial thermal energy to maintain production. Therefore, it is crucial to efficiently extract this high-quality waste heat resource—which, despite its low grade, contains a considerable amount of heat due to its large volume—for shaft antifreeze purposes, ensuring safe hoisting, transportation, and ventilation in winter.

[0004] Traditional waste heat recovery methods for mine return air primarily aim to directly recover the low-temperature heat energy from the return air, reducing exhaust temperature and extracting low-grade heat. These methods typically employ direct contact heat exchange, such as spray towers that atomize cold water through nozzles and spray it into the return airflow. The water mist directly contacts the return air for heat exchange, absorbing heat and raising the water temperature, which is then collected for low-grade heating. Alternatively, indirect surface heat exchange methods can be used, such as finned or tube heat exchangers where the return air passes through metal tube bundles with refrigerant flowing through the tubes, allowing for indirect heat exchange through the tube walls.

[0005] Traditional methods have common drawbacks: First, they cannot improve the heat quality and cannot meet the antifreeze requirement of ≥2℃ for the intake air; second, they have poor adaptability to high cold, and the spray system is prone to freezing and the heat exchanger is prone to cracking; third, they have high maintenance costs and an energy efficiency ratio of less than 1.5.

[0006] In response to the above problems, there is an urgent need for a mine underground return air waste heat collection and preheating system that can solve the problem of improving heat energy quality, has strong antifreeze properties during low-temperature operation on the evaporator side, and is energy-saving and environmentally friendly. Summary of the Invention

[0007] To overcome the problems existing in the background technology, the present invention provides a return air waste heat collection and intake air preheating system suitable for underground mines in cold regions. The system utilizes liquid refrigerant to absorb heat from the return air in the evaporator, and further increases the enthalpy value through a twin-screw compressor, achieving a heating efficiency ratio of 3.2. The heat is then released to cold water through the condenser, and the heated hot water provides fresh preheated airflow to the underground mine through the intake air preheating device. At the same time, an electric auxiliary heating device is reserved to ensure the stability of the entire system.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: The aforementioned system for collecting waste heat from return air and supplying preheated air in cold-climate mines includes a waste heat collection device for return air, a preheating device for air supply, a water pump, an electric auxiliary heating device, an inlet water pipe, a first return water pipe, and a second return water pipe. The return air waste heat recovery device is installed at the return air inlet of the return air adit; the inlet air preheating device and the water pump are installed at the inlet air inlet of the inlet air adit; the water inlet pipe is connected between the return air waste heat collection device and the inlet air preheating device; the first return water pipe is connected between the inlet air preheating device and the water pump; the second return water pipe is connected between the water pump and the return air waste heat collection device.

[0009] Furthermore, the return air waste heat collection device includes a twin-screw compressor, a water-air heat exchanger, and an evaporator; the evaporator is arranged at the top of the return air inlet of the return air tunnel; the twin-screw compressor, the water-air heat exchanger, and the evaporator are connected to form a circulation loop via a first gas pipe, a second gas pipe, a liquid pipe, and an expansion valve, wherein the second gas pipe connects the evaporator and the twin-screw compressor; the first gas pipe connects the twin-screw compressor and the water-air heat exchanger; an expansion valve is provided on the other side of the evaporator; the liquid pipe connects the expansion valve and the water-air heat exchanger; the circulation loop is filled with refrigerant Ra; and the water inlet pipe is connected to the water-air heat exchanger of the return air waste heat collection device.

[0010] Furthermore, the air inlet preheating device is located at the air inlet of the air inlet tunnel, and has a box structure, which contains a condenser and a centrifugal fan; the centrifugal fan is located on the side of the condenser away from the air inlet; the water inlet pipe is connected to the side of the air inlet preheating device box closest to the condenser.

[0011] Furthermore, the system for collecting waste heat from return air and supplying preheated air to underground mines in cold regions also includes an electric auxiliary heating device; the electric auxiliary heating device is installed at the air inlet of the air intake adit; the electric auxiliary heating device and the air preheating device are connected in parallel, and the two together provide hot air to the underground mine.

[0012] Furthermore, the system for collecting waste heat from return air and supplying preheated air to underground mines in cold and high-altitude mines also includes a first sensor, a second sensor, a third sensor, and a fourth sensor; the first sensor is located at the air inlet of the air intake adit; the second sensor is located at the end of the second return water pipe near the return air waste heat collection device; the third sensor is located at the return air inlet of the return air adit; and the fourth sensor is located at the end of the water inlet pipe near the preheated air device.

[0013] Furthermore, four return air waste heat collection devices are connected in parallel; three inlet air preheating devices are connected in parallel; three water pumps are connected in parallel; the first return water pipe connects the parallel inlet air preheating devices to the parallel water pumps; the inlet water pipe connects the parallel return air waste heat collection devices and the parallel inlet air preheating devices; and the second return water pipe connects the parallel water pumps to the return air waste heat collection devices.

[0014] Furthermore, the water-air heat exchanger is equipped with fins.

[0015] A method for collecting waste heat from return air in underground mines in cold regions and preheating incoming air, using the above-mentioned system for collecting waste heat from return air in underground mines in cold regions and preheating incoming air, includes the following: When the downhole return air temperature detected by the third sensor is > ℃, the twin-screw compressor is started. The evaporator absorbs waste heat, and the gaseous refrigerant heated by the evaporator enters the twin-screw compressor through the second gas pipe. The twin-screw compressor compresses the refrigerant into a high-temperature, high-pressure gas. The high-temperature, high-pressure refrigerant compressed by the twin-screw compressor enters the water-air heat exchanger through the first gas pipe. The water-air heat exchanger absorbs heat from the refrigerant and transfers it to the water, heating the water. Simultaneously, the high-temperature, high-pressure refrigerant releases heat and condenses into a liquid state. The liquid refrigerant flows through the liquid pipe to the expansion valve, where it is throttled and depressurized, becoming a low-temperature, low-pressure liquid refrigerant, which then enters the evaporator to begin the next cycle of waste heat collection from the return air. When the downhole return air temperature detected by the third sensor is ≤ ℃ or the return water temperature detected by the second sensor is > ℃, the twin-screw compressor stops.

[0016] When the inlet air temperature detected by the first sensor is <℃ and the inlet water temperature detected by the fourth sensor is ≥℃, the centrifugal fan is started. The water heated by the water-air heat exchanger enters the inlet air condenser through the inlet water pipe. The centrifugal fan transfers the heat exchanged by the condenser to the inlet air chamber. After the hot water passes through the condenser, the temperature decreases and it is pumped back to the water-air heat exchanger by the water pump through the second return water pipe, completing the circulation of the entire system. When the inlet air temperature detected by the first sensor is less than ℃ and the inlet water temperature detected by the fourth sensor is less than ℃, the electric auxiliary heating devices are turned on one by one; when the inlet water temperature is greater than or equal to ℃ or the inlet air temperature is greater than or equal to ℃, they are turned off one by one in reverse order of turn-on.

[0017] The beneficial effects of this invention are: This invention offers higher energy efficiency and significant energy savings. By using a reverse Carnot cycle, a compressor is driven with a small amount of electricity, achieving the conversion of "low-grade heat energy to high-grade heat energy," with a measured heating efficiency ratio of 3.2.

[0018] It is adapted to extreme environments in frigid regions below -10 degrees Celsius, with a more stable heat source. Furthermore, the heat source used is mine return air, unaffected by extreme outdoor temperatures, ensuring a stable and sufficient heat source temperature.

[0019] Low-carbon and environmentally friendly, it uses a small amount of electricity as the driving energy source and recovers and utilizes the waste heat from the return air that was originally directly emitted, reducing indirect carbon emissions caused by heat energy waste. Attached Figure Description

[0020] Figure 1 This is a diagram illustrating the application scenario of the present invention; Figure 2 This is a schematic diagram showing the structural connections of the return air waste heat collection device, the inlet air preheating device, the water pump, and the electric auxiliary heating device of the present invention. Figure 3 This is a schematic diagram of the structure of the waste heat collection device for return air according to the present invention; Figure 4 This is a schematic diagram of the air inlet preheating device of the present invention; Figure 5 This is a schematic diagram of the structure of the electric auxiliary heating device of the present invention; Figure 6 This is the electrical schematic diagram of the control system of this invention.

[0021] In the diagram: 1-Return air waste heat collection device, 2-Inlet air preheating device, 3-Water pump, 4-Electric auxiliary heating device, 5-Inlet water pipe, 6-First return water pipe, 7-Second return water pipe, 8-First sensor, 9-Second sensor, 10-Third sensor, 11-Fourth sensor, 101-Twin screw compressor, 102-First gas pipe, 103-Water-air heat exchanger, 104-Liquid pipe, 105-Expansion valve, 106-Evaporator, 107-Second gas pipe, 201-Condenser, 202-Centrifugal fan, 301-Resistance heater, 302-Fan. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, the preferred embodiments of the present invention will be described in detail below to facilitate understanding by those skilled in the art. Example 1

[0023] The present invention discloses a waste heat collection and preheating system for return air in underground mines in cold regions. Its application in a copper mine in Yunnan Province, where the winter temperature is -10℃, is as follows: like Figure 1 and 2As shown, the system of the present invention includes a return air waste heat collection device 1, an inlet air preheating device 2, a water pump 3, an electric auxiliary heating device 4, an inlet water pipe 5, a first return water pipe 6, a second return water pipe 7, a first sensor 8, a second sensor 9, a third sensor 10, and a fourth sensor 11. Four return air waste heat collection devices 1 are arranged in parallel. Each return air waste heat collection device includes a twin-screw compressor 101, a first gas pipe 102, a water-air heat exchanger 103, a liquid pipe 104, an expansion valve 105, an evaporator 106, and a second gas pipe 107. Evaporator 106 is arranged at the top of the return air inlet of the return air tunnel. Evaporator 106 is connected to twin-screw compressor 101 through second gas pipe 107. Twin-screw compressor 101 is connected to water-air heat exchange device 103 through first gas pipe 102. An expansion valve 105 is provided on the other side of evaporator 106 (the side not connected to second gas pipe 107). Expansion valve 105 connects evaporator 106 to water-air heat exchange device 103 through liquid pipe 104. Through the pipe connection, a circulation loop is formed between twin-screw compressor 101, water-air heat exchange device 103 and evaporator 106. The circulation loop of return air waste heat collection device 1 is filled with environmentally friendly refrigerant R134a.

[0024] It should be noted that in the return air waste heat collection device 1, the refrigerant achieves heat transfer through a pressure-phase change cycle. The low-temperature liquid refrigerant has a high latent heat of vaporization and absorbs the waste heat of the mine return air in the evaporator 106, vaporizing into low-pressure steam and capturing low-grade heat energy. The twin-screw compressor 101 consumes electrical energy to pressurize the steam, which jumps to a high-temperature and high-pressure gas of 80-120℃, achieving a jump in heat energy grade. The high-temperature refrigerant releases heat to the cold water in the water-air heat exchanger 103. Its thermal conductivity is moderate. Combined with the enhanced fin design in the water-air heat exchanger 103, it can efficiently complete heat transfer, reduce the heat exchange area requirement, and, in actual use, can output hot water at 35-50℃, with a system heating efficiency ratio of 3.2. The high-pressure liquid is throttled by the expansion valve 105, cooled and depressurized, and then returns to the evaporator 106 to complete the return air waste heat collection cycle.

[0025] The air inlet preheating device 2 is a box-shaped structure, inside which is installed a condenser 201 and a centrifugal fan 202. The condenser 201 is connected to the water inlet pipe 5. The centrifugal fan 202 is located on the side of the condenser 201 away from the air inlet. Three air inlet preheating devices 2 are arranged in parallel.

[0026] In actual use, the hot water passing through the water-air heat exchanger 103 enters the condenser 201 of the air inlet preheating device 2. The centrifugal fan 202 drives the airflow through the condenser 201, and transfers the heat released by the condenser 201 to the air inlet chamber, and the air inlet temperature is stabilized at 4℃.

[0027] One end of the inlet pipe 5 near the return air waste heat collection device 1 is connected to the water-air heat exchange device 103. The inlet pipe 5 connects the four parallel return air waste heat collection devices 1 to the three parallel inlet air preheating devices 2. The first return water pipe 6 connects the three parallel inlet air preheating devices 2 to the three parallel water pumps 3.

[0028] The second return water pipe 7 connects the three parallel water pumps 3 to the return air waste heat collection device 1.

[0029] In actual use, the water that has exchanged heat with the air inlet preheating device 2 is pumped back into the water-air heat exchanger 103 by the water pump 3 through the second return water pipe 7, completing the circulation of the entire system.

[0030] like Figure 6 The control method for the waste heat collection and preheating system for return air in high-altitude and cold-climate mines is as follows: When the downhole return air temperature detected by the third sensor 10 is greater than 8°C, the twin-screw compressor 101 is started. The evaporator 106 absorbs residual heat, and the gaseous refrigerant heated by the evaporator 106 enters the twin-screw compressor 101 through the second gas pipe 107. The twin-screw compressor 101 compresses the refrigerant into a high-temperature, high-pressure gas. The high-temperature, high-pressure refrigerant compressed by the twin-screw compressor 101 enters the water-air heat exchanger 103 through the first gas pipe 102. The water-air heat exchanger 103 absorbs heat from the refrigerant and transfers it to the water, heating the water; simultaneously, the high-temperature, high-pressure refrigerant releases heat and condenses into a liquid state. Liquid refrigerant flows through liquid pipe 104 to expansion valve 105. After being throttled and depressurized by expansion valve 105, it becomes low-temperature and low-pressure liquid refrigerant and enters evaporator 106 to start the next cycle of waste heat collection from return air. When the downhole return air temperature detected by the third sensor 10 is ≤8℃ or the return water temperature detected by the second sensor 9 is >50℃, the twin-screw compressor 101 stops.

[0031] When the inlet air temperature detected by the first sensor 8 is <2℃ and the inlet water temperature detected by the fourth sensor 11 is ≥35℃, the centrifugal fan 202 is started. The water heated by the water-air heat exchanger 103 enters the inlet air condenser 201 through the inlet water pipe 5. The centrifugal fan 202 transfers the heat exchanged by the condenser 201 to the inlet air chamber. After the hot water passes through the condenser 201, it becomes cold water and is pumped back to the water-air heat exchanger 103 by the water pump 3 through the second return water pipe 7, completing the circulation of the entire system.

[0032] When the inlet air temperature detected by the first sensor 8 is <2℃ and the inlet water temperature detected by the fourth sensor 11 is <35℃, the electric auxiliary heating devices 4 are turned on one by one; when the inlet water temperature is ≥42℃ or the inlet air temperature is ≥5℃, they are turned off one by one in reverse order of turning on.

[0033] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A system for collecting waste heat from return air and preheating incoming air in cold-climate mines, characterized in that: It includes a return air waste heat collection device (1), an air inlet preheating device (2), a water pump (3), an electric auxiliary heating device (4), an inlet water pipe (5), a first return water pipe (6), and a second return water pipe (7); The return air waste heat recovery device (1) is installed at the return air inlet of the return air tunnel; the inlet air preheating device (2) and the water pump (3) are installed at the inlet air inlet of the inlet air tunnel; the water inlet pipe (5) is connected between the return air waste heat collection device (1) and the inlet air preheating device (2); the first return water pipe (6) is connected between the inlet air preheating device (2) and the water pump (3); the second return water pipe is connected between the water pump (3) and the return air waste heat collection device (1).

2. The system according to claim 1, characterized in that: The return air waste heat collection device (1) includes a twin-screw compressor (101), a water-air heat exchanger (103), and an evaporator (106); the evaporator (106) is arranged at the top of the return air inlet of the return air tunnel; the twin-screw compressor (101), the water-air heat exchanger (103), and the evaporator (106) are connected to form a circulation loop through a first gas pipe (102), a second gas pipe (107), a liquid pipe (104), and an expansion valve (105), wherein the second gas pipe (107) is connected to the evaporator. Between the evaporator (106) and the twin-screw compressor (101); the first gas pipe (102) is connected between the twin-screw compressor (101) and the water-air heat exchange device (103); an expansion valve (105) is provided on the other side of the evaporator (106); the liquid pipe (104) is connected between the expansion valve (105) and the water-air heat exchange device (103); the circulation loop is filled with refrigerant R134a; the water inlet pipe (5) is connected to the water-air heat exchange device (103) of the return air waste heat collection device (1).

3. The system according to claim 1, characterized in that: The air inlet preheating device (2) is located at the air inlet of the air inlet tunnel. It is a box structure and contains a condenser (201) and a centrifugal fan (202). The centrifugal fan (202) is located on the side of the condenser 201 away from the air inlet. The water inlet pipe (5) is connected to the side of the box of the air inlet preheating device (2) near the condenser (201).

4. The system according to any one of claims 1 to 4, characterized in that: It also includes an electric auxiliary heating device (4); the electric auxiliary heating device (4) is installed at the air inlet of the air intake adit; the electric auxiliary heating device (4) is connected in parallel with the air intake preheating device (2), and the two together provide hot air to the well.

5. The system according to claim 4, characterized in that: It also includes a first sensor (8), a second sensor (9), a third sensor (10), and a fourth sensor (11); the first sensor (8) is located at the air inlet of the air inlet tunnel; the second sensor (9) is located at the end of the second return water pipe (7) near the return air waste heat collection device (1); the third sensor (10) is located at the return air inlet of the return air tunnel; and the fourth sensor (11) is located at the end of the water inlet pipe (5) near the air inlet preheating device (2).

6. The system according to claim 6, characterized in that: Four return air waste heat collection devices (1) are connected in parallel; three inlet air preheating devices (2) are connected in parallel; three water pumps (3) are connected in parallel; the first return water pipe (6) connects the parallel inlet air preheating devices (2) and the parallel water pumps (3); the inlet water pipe (5) connects the parallel return air waste heat collection devices (1) and the parallel inlet air preheating devices (2); the second return water pipe (7) connects the parallel water pumps (3) and the return air waste heat collection devices (1).

7. The system according to claim 1, characterized in that: The water-air heat exchanger (103) is equipped with fins.

8. A method for collecting waste heat from return air in underground mines in cold regions and using it for preheating intake air, characterized in that... Using the system as described in claim 5 includes the following: When the downhole return air temperature detected by the third sensor (10) is >8℃, the twin-screw compressor (101) is started. The residual heat is absorbed through the evaporator (106). The gaseous refrigerant heated by the evaporator (106) enters the twin-screw compressor (101) through the second gas pipe (107). The twin-screw compressor (101) compresses the refrigerant into a high-temperature, high-pressure gas. The high-temperature, high-pressure refrigerant compressed by the twin-screw compressor (101) enters the water-air heat exchanger (103) through the first gas pipe (102). The water-air heat exchanger (103)... 03) Absorb the heat in the refrigerant and transfer it to the water to heat the water; at the same time, the high-temperature and high-pressure refrigerant releases heat and condenses into a liquid state; the liquid refrigerant flows through the liquid pipe (104) to the expansion valve (105), and after being throttled and depressurized by the expansion valve (105), it becomes a low-temperature and low-pressure liquid refrigerant and enters the evaporator (106) to start the next cycle of collecting waste heat from the return air; when the downhole return air temperature detected by the third sensor (10) is ≤8℃ or the return water temperature detected by the second sensor (9) is >50℃, the twin-screw compressor (101) stops; When the inlet air temperature detected by the first sensor (8) is <2℃ and the inlet water temperature detected by the fourth sensor (11) is ≥35℃, the centrifugal fan (202) is started. The water heated by the water-air heat exchanger (103) enters the air inlet condenser (201) through the water inlet pipe (5). The centrifugal fan (202) transports the heat exchanged by the condenser (201) to the air inlet chamber. After the hot water passes through the condenser (201), the temperature decreases and it is pumped back to the water-air heat exchanger (103) by the water pump (3) through the second return water pipe (7) to complete the circulation of the entire system. When the air inlet temperature detected by the first sensor (8) is <2℃ and the water inlet temperature detected by the fourth sensor (11) is <35℃, the electric auxiliary heating devices (4) are turned on one by one; when the water inlet temperature is ≥42℃ or the air inlet temperature is ≥5℃, they are turned off one by one in reverse order of turn-on.

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