Coal mine underground liquid nitrogen cooling system

Abstract

The application discloses a coal mine underground liquid nitrogen cooling system and relates to the technical field of coal mine refrigeration. The nitrogen gas is produced by a nitrogen generator, the temperature of the produced nitrogen gas can be reduced by the arrangement of a first cooler and a second cooler, and in the second cooler, the liquid nitrogen is heat-exchanged with the produced nitrogen gas to be vaporized. The vaporized nitrogen gas and the unvaporized liquid nitrogen enter a conveying pipeline and are finally sent to a working face needing cooling together with the cooled produced nitrogen gas, so that the cooling and fire prevention and extinguishing purposes are achieved. The liquid nitrogen is used in cooperation with the nitrogen generator through the second cooler, the nitrogen generator can be arranged on the ground, the heating influence of the nitrogen generator on the underground environment during the production of the nitrogen gas is avoided, the use amount of the liquid nitrogen can be saved, and therefore the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of coal mine refrigeration technology, and in particular to a liquid nitrogen cooling system for underground coal mines. Background Technology

[0002] Commonly used refrigeration methods in coal mine refrigeration technology include: 1. Directly injecting cold air into the mine using air conditioning. The disadvantages of this method are high power consumption, high cost, and the inability to lower the temperature of the air returning to the surface from the return airway below 28°C due to the high outlet temperature at the working face. 2. Pumping liquid carbon dioxide or liquid nitrogen to a vaporizer via a pressure pump. After reaching the set vaporization ratio, it is then transported to the target location for cooling or fire suppression via a long pipeline. However, this method has the disadvantages of high refrigerant consumption and high cost.

[0003] Currently, in order to save refrigerant and reduce production costs, a new technical solution has emerged in coal mine refrigeration technology: nitrogen is produced by a nitrogen generator, cooled, and then transported to the target location in the mining area. However, this technical solution has the following problems in practical application: the nitrogen produced by the nitrogen generator is at a temperature of 70-80℃, so it must be cooled to 0℃ before being transported to the target location. To avoid excessive loss of cooling capacity, the cooling equipment usually needs to be installed underground. As is well known, the cooling equipment continuously releases a large amount of heat into the external environment when it is working, which exacerbates the already high-temperature environment underground. Therefore, its implementation is somewhat restricted and cannot be widely promoted. Summary of the Invention

[0004] The purpose of this invention is to provide a liquid nitrogen cooling system for underground coal mines to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a liquid nitrogen cooling system for underground coal mines, comprising a liquid nitrogen storage tank and a nitrogen generator. The outlet of the liquid nitrogen storage tank is connected to a pressure injection pump. The output end of the nitrogen generator is fixedly connected to a long-distance output pipeline. A first cooler is installed on the long-distance output pipeline, and a delivery pipeline is fixedly connected to the end of the long-distance output pipeline. A second cooler is installed on the delivery pipeline. A flow meter, a shut-off valve, and a check valve are sequentially installed along the gas supply direction on the pipeline between the pressure injection pump and the second cooler, and on the long-distance output pipeline. The second cooler includes a shell. A heat exchanger is installed on the delivery pipeline located within the shell. The outlet end of the pressure injection pump is connected to the shell. A connecting pipe is fixedly connected to the shell and is connected to the delivery pipeline at the outlet end of the shell.

[0006] Preferably, the first cooler is a circulating water cooler, which includes a circulating water tank, a heat dissipation component installed inside the circulating water tank, the heat dissipation component installed on the long-distance output pipeline, a drain outlet fixedly connected to the top of the circulating water tank, a water inlet fixedly connected to the bottom of the circulating water tank, and a cooling tower installed between the drain outlet and the water inlet.

[0007] Preferably, the heat dissipation component includes a distribution pipe, a collection pipe, and several heat dissipation plates disposed in the circulating water tank. The heat dissipation plates have a hollow structure, and both ends of the heat dissipation plates are respectively connected to the distribution pipe and the collection pipe. The several heat dissipation plates are arranged parallel to each other in the horizontal direction. The bottom ends of the distribution pipe and the collection pipe are respectively connected to the long-distance output pipelines on both sides of the circulating water tank.

[0008] Preferably, the thickness of the heat sink is 2cm to 4cm, and the heat sink has several elongated holes.

[0009] Preferably, the heat exchanger includes a distribution plate, a collection plate, and several branch pipes. The two ends of the branch pipes are respectively connected to the distribution plate and the collection plate. Each branch pipe is divided into an inclined section, a spiral section, and a straight section arranged sequentially. The inclined section is fixedly connected to the distribution plate, and the straight section is fixedly connected to the collection plate. The spiral sections of the branch pipes intertwine to form a hollow frustum structure. The small-diameter end of the frustum structure is located close to the distribution plate. The spiral sections of the branch pipes are sealed together with sealant. A sealing block is fixedly fitted onto the outer side of the large-diameter end of the frustum structure. The sealing block is fixedly connected to the inner wall of the shell. The air inlet of the shell is correspondingly located to the distribution plate. The connecting pipe is located on the side of the collection plate away from the distribution plate.

[0010] Preferably, the gas collecting plate is fixedly installed on the inner wall of the housing, and the gas collecting plate has a honeycomb structure with a honeycomb hole diameter of 5mm to 10mm.

[0011] Preferably, the ratio of the minor diameter to the major diameter of the frustum structure is 1:3 to 1:10.

[0012] Preferably, a support frame is fixedly installed inside the housing, and the smaller diameter end of the frustum structure is fixedly installed on the support frame.

[0013] Preferably, the end of the connecting pipe away from the housing is a constricted end, the constricted end of the connecting pipe extends into the conveying pipeline, and the orientation of the constricted end of the connecting pipe is consistent with the conveying direction of the conveying pipeline.

[0014] Preferably, an insulation layer is fixedly installed on the outer wall of the housing.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects:

[0016] The liquid nitrogen cooling system for underground coal mines provided by this invention produces nitrogen gas through a nitrogen generator. By using a first cooler and a second cooler, the temperature of the produced nitrogen gas can be reduced. In the second cooler, the liquid nitrogen exchanges heat with the produced nitrogen gas and vaporizes. The vaporized nitrogen gas, along with the unvaporized liquid nitrogen, enters the delivery pipeline and is ultimately delivered to the working face requiring cooling, achieving the purpose of cooling and fire prevention. This invention, by using the liquid nitrogen in conjunction with the nitrogen generator through the second cooler, allows the nitrogen generator to be located on the surface, avoiding the heating effect of nitrogen production on the underground environment and saving on liquid nitrogen usage, thereby reducing production costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the underground liquid nitrogen cooling system for coal mines according to the present invention;

[0019] Figure 2 for Figure 1 A magnified view of part A in the image;

[0020] Figure 3 This is a schematic diagram of the structure of the gas collecting plate of the present invention;

[0021] Figure 4 This is a schematic diagram of the heat sink of the present invention;

[0022] The components include: 1. Liquid nitrogen storage tank; 2. Nitrogen generator; 3. Injection pump; 4. Long-distance output pipeline; 5. Delivery pipeline; 6. Flow meter; 7. Shut-off valve; 8. Check valve; 9. Shell; 10. Connecting pipe; 11. Circulating water tank; 12. Drain outlet; 13. Inlet; 14. Cooling tower; 15. Gas distribution pipe; 16. Gas collection pipe; 17. Heat dissipation plate; 18. Long strip hole; 19. Gas distribution plate; 20. Gas collection plate; 21. Branch pipe; 22. Sealing block; 23. Honeycomb hole; 24. Support frame; 25. Insulation layer. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] This invention provides a liquid nitrogen cooling system for underground coal mines, comprising a liquid nitrogen storage tank 1 and a nitrogen generator 2. The outlet of the liquid nitrogen storage tank 1 is connected to a pressure injection pump 3. The output end of the nitrogen generator 2 is fixedly connected to a long-distance output pipeline 4. A first cooler is installed on the long-distance output pipeline 4, and a delivery pipeline 5 is fixedly connected to the end of the long-distance output pipeline 4. A second cooler is installed on the delivery pipeline 5. A flow meter 6, a shut-off valve 7, and a check valve 8 are sequentially installed along the gas supply direction on the pipeline between the pressure injection pump 3 and the second cooler, and on the long-distance output pipeline 4. The second cooler includes a housing 9. A heat exchanger is installed on the delivery pipeline 5 located inside the housing 9. The outlet end of the pressure injection pump 3 is connected to the housing 9. A connecting pipe 10 is fixedly connected to the housing 9, and the connecting pipe 10 is connected to the delivery pipeline 5 at the gas outlet end of the housing 9.

[0025] In use, the nitrogen generator 2 and the first cooler are located on the ground. The nitrogen produced by the nitrogen generator 2 is transported to the second cooler through a long-distance output pipeline 4. During the transport process, the nitrogen produced is cooled by the first cooler, and it also exchanges heat with the air during transport through the long-distance output pipeline 4 to achieve the purpose of cooling. The liquid nitrogen storage tank 1 and the second cooler are located underground. First, the liquid nitrogen exchanges heat with the nitrogen produced by the nitrogen generator 2 through heat exchange elements in the shell 9, thereby cooling the nitrogen in the transport pipeline 5. At the same time, after heat exchange in the shell 9, the liquid nitrogen vaporizes. At this time, the liquid nitrogen inside the shell 9... The liquid nitrogen is in a gas-liquid mixed state, and then mixed with the nitrogen in the delivery pipeline 5 through the connecting pipe 10. On the one hand, the liquid nitrogen can be used to further cool the nitrogen in the delivery pipeline 5, so that the nitrogen in the delivery pipeline 5 meets the usage requirements. On the other hand, by mixing the nitrogen produced by the nitrogen generator 2 with the liquid nitrogen, the nitrogen supply can be increased. While meeting the cooling requirements, the use of liquid nitrogen can be reduced, which can significantly reduce costs. Moreover, by setting the liquid nitrogen storage tank 1 and the second cooler down underground, even if there is a loss of cooling capacity during the transportation process, it will be lost down underground, which has a beneficial effect on reducing the downhole temperature.

[0026] Furthermore, in order to reduce the temperature of the nitrogen produced by the nitrogen generator 2 and thus reduce the amount of liquid nitrogen used, the first cooler is a circulating water cooler. The first cooler includes a circulating water tank 11, and a heat dissipation component is installed inside the circulating water tank 11. The heat dissipation component is installed on the long-distance output pipeline 4. The top of the circulating water tank 11 is fixedly connected to a drain outlet 12, and the bottom of the circulating water tank 11 is fixedly connected to a water inlet 13. A cooling tower 14 is installed between the drain outlet 12 and the water inlet 13.

[0027] The cooling water in the circulating water tank 11 can reduce the temperature of the nitrogen produced by the nitrogen generator 2 to between 25°C and 35°C, which can remove a large amount of heat from the produced nitrogen. After absorbing heat, the water in the circulating water tank 11 can dissipate the absorbed heat into the air through the cooling tower 14, thereby reducing water consumption and conforming to the concept of energy conservation and environmental protection.

[0028] Furthermore, to improve the heat exchange between the nitrogen produced by the nitrogen generator 2 and the circulating water, the heat dissipation components include a gas distribution pipe 15, a gas collection pipe 16, and several heat dissipation plates 17 installed in the circulating water tank 11. The heat dissipation plates 17 have a hollow structure, and both ends of the heat dissipation plates 17 are connected to the gas distribution pipe 15 and the gas collection pipe 16, respectively. The several heat dissipation plates 17 are arranged in parallel along the horizontal direction. The bottom ends of the gas distribution pipe 15 and the bottom ends of the gas collection pipe 16 are connected to the long-distance output pipelines 4 on both sides of the circulating water tank 11, respectively. The thickness of the heat dissipation plates 17 is 2cm to 4cm, and several elongated holes 18 are opened on the heat dissipation plates 17.

[0029] By horizontally setting the heat sink 17 and connecting the bottom ends of the gas distribution pipe 15 and the gas collection pipe 16 to the long-distance output pipes 4 on both sides of the circulating water tank 11, the produced nitrogen gas, when entering each heat sink 17 from the gas distribution pipe 15, undergoes an upward movement. During this process, the nitrogen gas in the gas distribution pipe 15 can be cooled by the cooling water at the bottom of the circulating water tank 11. Similarly, when the nitrogen gas in each heat sink 17 converges into the gas collection pipe 16, it also undergoes a downward movement, and the nitrogen gas in the gas distribution pipe 15 can be cooled by the cooling water at the bottom of the circulating water tank 11. This compensates for the deficiency of insufficient cooling of the nitrogen gas in the upper heat sink 17 caused by the upper layer of water in the circulating water tank 11 being hotter than the lower layer after absorbing heat. The elongated slot 18 increases the contact area between the heat sink 17 and the cooling water in the circulating water tank 11, thereby improving the cooling effect on the nitrogen gas in the heat sink 17.

[0030] Furthermore, to improve the cooling effect of liquid nitrogen on the produced nitrogen, the heat exchanger includes a gas distribution plate 19, a gas collecting plate 20, and several branch pipes 21. The two ends of the branch pipes 21 are connected to the gas distribution plate 19 and the gas collecting plate 20, respectively. The branch pipes 21 are divided into inclined sections, spiral sections, and straight sections arranged sequentially. The inclined sections are fixedly connected to the gas distribution plate 19, and the straight sections are fixedly connected to the gas collecting plate 20. The spiral sections of the branch pipes 21 are intertwined to form a hollow frustum structure. The ratio of the minor diameter to the major diameter of the frustum structure is 1:3 to 1:10. The minor diameter end of the frustum structure is located close to the gas distribution plate 19. The spiral sections of the branch pipes 21 are sealed with sealant. A sealing block 22 is fixedly sleeved on the outer side of the major diameter end of the frustum structure. The sealing block 22 is fixedly connected to the inner wall of the shell 9. The air inlet of the shell 9 is correspondingly arranged to the gas distribution plate 19. The connecting pipe 10 is located on the side of the gas collecting plate 20 away from the gas distribution plate 19.

[0031] After entering the shell 9, liquid nitrogen first contacts the gas distribution plate 19, cooling the nitrogen gas in the plate and reducing its pressure, thus slowing the nitrogen gas velocity entering the branch pipe 21. Secondly, the liquid nitrogen and its vaporized portion come into contact with the outer side of the spiral section of the branch pipe 21, further cooling the nitrogen gas and causing it to vaporize. The vaporized liquid nitrogen causes a pressure increase on the side of the sealing block 22 in the shell 9 closest to the gas distribution plate 19, thus rapidly increasing the velocity of the liquid nitrogen along with the vaporized nitrogen gas. The nitrogen gas in branch pipe 21 is cooled again by passing through the hollow frustum structure formed by the spiral section of branch pipe 21. Furthermore, the change in the inner diameter of the frustum structure reduces the velocity and pressure of the liquid nitrogen and its vaporized form, thus enhancing the cooling effect. Finally, the remaining liquid nitrogen and vaporized form mix with the nitrogen in the delivery pipeline 5 through connecting pipe 10, ensuring that the nitrogen temperature in the delivery pipeline 5 remains below 0°C. The second cooler, placed at the working face requiring cooling, not only reduces cooling loss during transport but also allows for the inclusion of a small amount of unvaporized liquid nitrogen in the cooled nitrogen, improving the cooling effect on the environment. This significantly reduces the amount of liquid nitrogen used, lowering production costs while maintaining effective cooling.

[0032] To further improve the cooling effect on the produced nitrogen, the gas collecting plate 20 is fixedly installed on the inner wall of the housing 9. The gas collecting plate 20 has a honeycomb structure, and the diameter of the honeycomb holes 23 on the gas collecting plate 20 is 5mm to 10mm.

[0033] By fixing the gas collecting plate 20 to the housing 9, the liquid nitrogen and the vaporized nitrogen can only enter the connecting pipe 10 through the honeycomb holes 23 on the gas collecting plate 20. This increases the contact area with the gas collecting plate 20, thereby improving the cooling effect on the produced nitrogen.

[0034] Furthermore, to prevent damage to the frustum structure formed by the branch pipe 21, a support frame 24 is fixedly installed inside the housing 9, and the small-diameter end of the frustum structure is fixedly installed on the support frame 24.

[0035] Furthermore, the end of the connecting pipe 10 furthest from the housing 9 is a constricted end, which extends into the conveying pipeline 5, and the orientation of the constricted end of the connecting pipe 10 is consistent with the conveying direction of the conveying pipeline 5.

[0036] By narrowing the connecting pipe 10, the speed of the nitrogen gas after liquid nitrogen vaporization when it enters the delivery pipe 5 can be increased, so that the cooled nitrogen gas can be quickly supplied to the working surface that needs to be cooled, reducing the loss of cooling capacity during the process.

[0037] Furthermore, to reduce the loss of liquid nitrogen cooling capacity, an insulation layer 25 is fixedly installed on the outer wall of the shell 9.

[0038] The liquid nitrogen cooling system for underground coal mines provided by this invention produces nitrogen gas through a nitrogen generator 2. The temperature of the produced nitrogen gas is reduced by the installation of a first cooler and a second cooler. In the second cooler, the liquid nitrogen exchanges heat with the produced nitrogen gas and vaporizes. The vaporized nitrogen gas, along with the unvaporized liquid nitrogen, enters the delivery pipeline 5 and is ultimately delivered to the working face requiring cooling, achieving the purpose of cooling and fire prevention. This invention uses the liquid nitrogen in conjunction with the nitrogen generator 2 through the second cooler, allowing the nitrogen generator 2 to be located on the ground, avoiding the heating effect of nitrogen generator 2 on the underground environment during nitrogen production, and saving on the amount of liquid nitrogen used, thereby reducing production costs.

[0039] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A liquid nitrogen cooling system for underground coal mines, comprising a liquid nitrogen storage tank (1) and a nitrogen generator (2), characterized in that, The liquid nitrogen storage tank (1) is connected to a pressure injection pump (3) at its outlet. The output end of the nitrogen generator (2) is fixedly connected to a long-distance output pipeline (4). A first cooler is installed on the long-distance output pipeline (4). A delivery pipeline (5) is fixedly connected to the end of the long-distance output pipeline (4). A second cooler is installed on the delivery pipeline (5). A flow meter (6), a shut-off valve (7), and a check valve (8) are installed sequentially on the pipeline between the pressure injection pump (3) and the second cooler, and on the long-distance output pipeline (4) along the gas supply direction. The second cooler includes a shell (9). A heat exchanger is installed on the delivery pipeline (5) located inside the shell (9). The liquid outlet of the pressure injection pump (3) is connected to the shell (9). A connecting pipe (10) is fixedly connected to the shell (9). The connecting pipe (10) is connected to the delivery pipeline (5) at the gas outlet of the shell (9). The heat exchanger includes a gas distribution plate (19), a gas collecting plate (20), and several branch pipes (21). The two ends of the several branch pipes (21) are respectively connected to the gas distribution plate (19) and the gas collecting plate (20). The branch pipes (21) are divided into inclined sections, spiral sections, and straight sections arranged in sequence. The inclined sections are fixedly connected to the gas distribution plate (19), and the straight sections are fixedly connected to the gas collecting plate (20). The spiral sections of the several branch pipes (21) are intertwined to form a hollow circle. The truncated cone structure has a small diameter end near the air distribution plate (19), and the spiral segments of several branch pipes (21) are sealed with sealant; a sealing block (22) is fixedly sleeved on the outer side of the large diameter end of the truncated cone structure, and the sealing block (22) is fixedly connected to the inner wall of the housing (9). The air inlet of the housing (9) is correspondingly set to the air distribution plate (19), and the connecting pipe (10) is set on the side of the air collection plate (20) away from the air distribution plate (19).

2. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, The first cooler is a circulating water cooler. The first cooler includes a circulating water tank (11). A heat dissipation component is provided inside the circulating water tank (11). The heat dissipation component is installed on the long-distance output pipeline (4). A drain outlet (12) is fixedly connected to the top of the circulating water tank (11). A water inlet (13) is fixedly connected to the bottom of the circulating water tank (11). A cooling tower (14) is provided between the drain outlet (12) and the water inlet (13).

3. The underground liquid nitrogen cooling system for coal mines according to claim 2, characterized in that, The heat dissipation component includes a gas distribution pipe (15), a gas collection pipe (16), and several heat dissipation plates (17) disposed in the circulating water tank (11). The heat dissipation plate (17) has a hollow structure. Both ends of the heat dissipation plate (17) are connected to the gas distribution pipe (15) and the gas collection pipe (16) respectively. Several heat dissipation plates (17) are arranged in parallel along the horizontal direction. The bottom end of the gas distribution pipe (15) and the bottom end of the gas collection pipe (16) are connected to the long-distance output pipeline (4) on both sides of the circulating water tank (11) respectively.

4. The underground liquid nitrogen cooling system for coal mines according to claim 3, characterized in that, The thickness of the heat sink (17) is 2cm to 4cm, and the heat sink (17) has several elongated holes (18).

5. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, The gas collecting plate (20) is fixedly installed on the inner wall of the housing (9). The gas collecting plate (20) has a honeycomb structure and the diameter of the honeycomb holes (23) on the gas collecting plate (20) is 5mm to 10mm.

6. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, The ratio of the minor diameter to the major diameter of the frustum structure is 1:3 to 1:

10.

7. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, A support frame (24) is fixedly installed inside the housing (9), and the small-diameter end of the frustum structure is fixedly installed on the support frame (24).

8. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, The end of the connecting pipe (10) away from the housing (9) is a constricted end. The constricted end of the connecting pipe (10) extends into the conveying pipeline (5), and the orientation of the constricted end of the connecting pipe (10) is consistent with the conveying direction of the conveying pipeline (5).

9. The underground liquid nitrogen cooling system for coal mines according to claim 1, characterized in that, An insulation layer (25) is fixedly installed on the outer wall of the shell (9).

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