Device and method for preventing and treating coal spontaneous combustion based on phase change of liquid carbon dioxide

Abstract

This invention proposes a device and method for preventing spontaneous combustion of coal in a coal storage silo based on the phase change of liquid carbon dioxide. The device includes a liquid carbon dioxide storage tank, a buffer tank, and a coal storage silo. The inlet of the buffer tank is connected to the outlet of the liquid carbon dioxide storage tank. Several dry ice storage tanks are connected to the inner wall of the coal storage silo. The inlets of the dry ice storage tanks are connected to the outlets of the buffer tanks. A second solenoid valve is connected to the inlet of each dry ice storage tank. Release holes are provided on the side walls of the dry ice storage tanks. The interlayer cavity of the dry ice storage tanks is filled with a phase change heat-conducting material. This invention allows the dry ice to slowly release carbon dioxide through a phase change, eliminating the risk of asphyxiation caused by large-scale carbon dioxide escape. It also reduces the frequency of directly injecting carbon dioxide into the coal storage silo. This invention can automatically control the heat transfer coefficient of the dry ice storage tanks according to the temperature of the coal storage silo, enabling precise prevention and control of spontaneous combustion of coal in the area, effectively improving the utilization rate and efficiency of carbon dioxide extinguishing agents, and reducing the fire prevention and extinguishing costs of the coal storage silo.

Description

Technical Field

[0001] This invention relates to the field of fire protection technology, and in particular to a device and method for preventing spontaneous combustion of coal in coal storage bunkers based on the phase change of liquid carbon dioxide. Background Technology

[0002] Coal storage silos are crucial for coal production and consumption enterprises, serving as vital sites for coal storage and transportation. Currently, cylindrical coal storage silos are the most commonly used in China, offering advantages such as high filling density, good sealing, small footprint, and low environmental pollution. A coal storage silo consists of a cylindrical cylinder and a conical-bottomed discharge opening. After washing and entering the silo, fine-grained coal containing a certain amount of moisture tends to adhere to the walls of the conical-bottomed structure, accumulating and creating a "wall-hanging" effect. If this adhered coal is not cleaned promptly, it will continuously oxidize and heat up, potentially leading to spontaneous combustion. The oxidation and combustion processes produce large amounts of toxic and explosive gases, endangering the occupational health of workers and even causing explosions. Furthermore, spontaneous combustion reduces the calorific value and degrades the coal's quality.

[0003] Common methods for preventing and extinguishing spontaneous combustion of coal in coal storage silos include water injection and inert gas injection. Water injection is a common method after spontaneous combustion in coal storage silos, but due to the large volume of the silos, the location of the fire source is difficult to pinpoint, and large amounts of water injection can affect the structural stability of the silo and the quality of the coal. The water injection process also suffers from a "grooving" effect, making it difficult for the injected water to directly reach the fire source, resulting in unsatisfactory extinguishing effects and a risk of water-gas explosion. Inert gas injection technology utilizes the diffusion and adsorption properties of CO2 / N2 in coal, effectively reducing the oxygen concentration in the coal storage silo during the early stages of coal oxidation. Inert gas injection, as a routine fire prevention technique, does not require production shutdowns and does not affect normal production. Using N2 injection requires adding an air separation unit or nitrogen generator to the production site, resulting in higher construction costs, greater daily maintenance workload, and less frequent on-site use. CO2 is a common industrial waste gas. After capturing, liquefying, and transporting CO2 from industrial exhaust gases, it is directly injected into the coal storage silo and diffuses within the coal to carry out total flooding fire prevention and extinguishing. This method has a triple effect of cooling, oxygen reduction, and inerting, and is currently the most important inerting fire prevention and extinguishing method for coal storage silos. However, liquid CO2 fire prevention and extinguishing has the following problems: (1) The area where spontaneous combustion is likely to occur in the coal storage silo is near the bottom discharge port of the silo. The full flooding fire prevention and extinguishing method of the coal silo can also play a role in fire prevention and extinguishing, but the accuracy of handling spontaneous combustion of coal is not enough. CO2 is easy to escape and lose, the utilization rate is reduced, and the cost of disaster prevention and control is increased; (2) After the liquid CO2 is injected into the coal storage silo, it changes to gaseous state and fills the pores of the coal body. As the bottom discharge port is opened, the "chimney effect" of the coal silo causes CO2 in the pores of the coal body to move upward rapidly and escape from the feed port. CO2 needs to be injected frequently to prevent spontaneous combustion of coal. The labor intensity of workers is high, and a large amount of overflowing CO2 may accumulate at the top of the coal storage silo and the lower production workshop. If the ventilation of the workshop is insufficient, there is a risk of suffocation of the workers. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention provide a device and method for preventing spontaneous combustion of coal in coal storage silos based on liquid carbon dioxide phase change, which can improve the utilization efficiency of carbon dioxide and achieve precise control of spontaneous combustion.

[0005] One embodiment of the present invention proposes a device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, comprising: a liquid carbon dioxide storage tank, a buffer tank and a coal storage silo, wherein the buffer tank has an inlet and an outlet, the inlet of the buffer tank and the outlet of the liquid carbon dioxide storage tank are connected by a conveying pipeline, and a booster pump and a first solenoid valve are connected to the conveying pipeline, wherein the first solenoid valve is located between the liquid carbon dioxide storage tank and the booster pump.

[0006] The inner wall of the coal storage bunker is connected to several dry ice storage tanks. The inlet of the dry ice storage tank is connected to the outlet of the buffer tank. A second solenoid valve is connected to the inlet of the dry ice storage tank. Several release holes for releasing carbon dioxide are opened on the side wall of the dry ice storage tank. The dry ice storage tank includes an outer shell and an inner shell. A sandwich cavity is set between the outer shell and the inner shell. The sandwich cavity is filled with phase change heat-conducting material.

[0007] In some embodiments, the release hole extends horizontally through the outer shell and the inner shell, and the wall of the release hole is fixedly connected to the cylinder. The two ends of the cylinder along the axial direction are fixedly connected to the outer shell and the inner shell respectively to prevent the phase change heat-conducting material from leaking from the release hole.

[0008] In some embodiments, the lower part of the coal storage bunker is a conical bottom structure, the coal discharge port of the coal storage bunker is located at the center of the conical bottom structure, and all dry ice storage tanks are arranged around the edge of the inner wall of the coal storage bunker and located above the conical bottom structure.

[0009] In some embodiments, the volume of each dry ice storage tank is determined by the following formula:

[0010] Where V is the volume of a single dry ice storage tank; The porosity of the coal in the coal storage bin is obtained based on actual measurements. R is the inner diameter of the coal storage silo; h is the height of the cone-shaped structure; A represents the expansion factor of dry ice phase transition sublimation, which is taken as 750 times. B is the surplus coefficient for the amount of liquid carbon dioxide injected, which is taken as 1.1; n represents the number of dry ice storage tanks located within the coal storage bunker.

[0011] In some embodiments, a flow meter is connected to the delivery pipeline, and the flow meter is located between the liquid carbon dioxide storage tank and the booster pump.

[0012] In some embodiments, a pressure transmitter is connected to the buffer tank, and the pressure transmitter is an anti-icing type pressure transmitter.

[0013] In some embodiments, the coal storage bunker is equipped with temperature and humidity sensors to monitor the temperature and humidity inside the bunker.

[0014] In some embodiments, the device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change further includes a controller, and a flow meter, a first solenoid valve, a booster pump, a pressure transmitter, a second solenoid valve, a temperature sensor, and a humidity sensor are electrically connected to the controller.

[0015] In some embodiments, the phase change thermal conductive material includes a hexadecylamine / aluminum phosphate composite phase change material or a hydrated salt with added CuO nanoparticles.

[0016] Another embodiment of the present invention proposes a method for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change. The method utilizes the aforementioned device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, and includes the following steps: The first solenoid valve and booster pump are turned on, and liquid carbon dioxide is continuously injected into the buffer tank. The pressure in the buffer tank continues to rise. When the pressure in the buffer tank reaches the set value, the second solenoid valve is turned on, and the liquid carbon dioxide enters the dry ice storage tank and is quickly converted into dry ice. The dry ice in the dry ice storage tank sublimates into carbon dioxide gas, which is then slowly and continuously released outward through the release port. When a fire breaks out in the coal storage silo and the temperature rises, the thermal conductivity of the phase change thermal conductive material increases, which in turn increases the rate of dry ice sublimation. The carbon dioxide produced by sublimation is continuously and rapidly released to the outside, thus extinguishing the fire. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings. in: Figure 1 This is a schematic diagram of the structure of a coal storage silo prevention device based on liquid carbon dioxide phase change according to an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the dry ice storage tank in the diagram; Figure 3 for Figure 1 A schematic diagram of the structure of the interlayer cavity in the dry ice storage tank; Figure label: 1. Liquid carbon dioxide storage tank; 2. Controller; 3. First solenoid valve; 4. Flow meter; 5. Booster pump; 6. Buffer tank; 7. Pressure transmitter; 8. Dry ice storage tank; 801. Release port; 802. Interlayer cavity; 803. Outer shell; 804. Inner shell; 9. Coal storage bin; 901. Conical bottom structure; 10. Second solenoid valve. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] The following describes, with reference to the accompanying drawings, an apparatus and method for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, according to embodiments of the present invention.

[0020] like Figures 1-3 As shown, one embodiment of the present invention proposes a device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, comprising: a liquid carbon dioxide storage tank 1, a buffer tank 6, and a coal storage silo 9. The buffer tank 6 has an inlet and an outlet. The inlet of the buffer tank 6 and the outlet of the liquid carbon dioxide storage tank 1 are connected by a conveying pipeline. A booster pump 5 and a first solenoid valve 3 are connected to the conveying pipeline. The first solenoid valve 3 is located between the liquid carbon dioxide storage tank 1 and the booster pump 5.

[0021] The inner wall of the coal storage silo 9 is connected to several dry ice storage tanks 8. The inlet of the dry ice storage tank 8 is connected to the outlet of the buffer tank 6. A second solenoid valve 10 is connected to the inlet of the dry ice storage tank 8. Several release holes 801 for releasing carbon dioxide are opened on the side wall of the dry ice storage tank 8. The dry ice storage tank 8 includes an outer shell 803 and an inner shell 804. A sandwich cavity 802 is provided between the outer shell 803 and the inner shell 804. The sandwich cavity 802 is filled with a phase change heat-conducting material.

[0022] This invention, through the installation of a liquid carbon dioxide storage tank 1, a buffer tank 6, and a dry ice storage tank 8, allows the dry ice to slowly release carbon dioxide through a phase change. This prevents the accumulation of large amounts of carbon dioxide in the production workshop at the top and bottom of the coal storage silo 9, eliminating the risk of asphyxiation caused by the large-scale escape of carbon dioxide. The slow phase change process of a single injection of dry ice can last for several days, reducing the frequency of directly injecting gaseous or liquid carbon dioxide into the coal storage silo 9 and lowering the labor intensity of the workers.

[0023] This invention employs phase change heat-conducting materials to automatically control the heat transfer coefficient of the dry ice storage tank 8 based on the temperature of the coal storage silo 9, and automatically control the sublimation rate of the dry ice. It has the dual functions of phase change heat absorption and cooling, as well as oxygen reduction and inerting, which can achieve precise prevention and control of spontaneous combustion of coal in the area, effectively improve the utilization rate and efficiency of carbon dioxide fire extinguishing agent, and reduce the fire prevention and extinguishing cost of the coal storage silo 9.

[0024] Once the phase change temperature is reached, the thermal conductivity of the dry ice storage tank 8 can be greatly improved, enabling the dry ice storage tank 8 at the high-temperature point of the coal storage bunker 9 to accelerate heat conduction, promote the rapid heating and phase change of the dry ice in the dry ice storage tank 8, release gaseous carbon dioxide, inertate the coal storage bunker 9, and at the same time, the cold energy exported will cool down the coal body and environment around the dry ice storage tank 8, thus achieving comprehensive fire prevention and extinguishing.

[0025] Furthermore, the shell of the liquid carbon dioxide storage tank 1 adopts a double-layer structure, and the space between the two layers is filled with heat-insulating filler, which can withstand a low temperature of -40℃ and a maximum working pressure of 2.5 MPa.

[0026] Furthermore, the booster pump 5 is a reciprocating cryogenic liquid pump with a maximum working pressure of 10 MPa.

[0027] Furthermore, buffer tank 6 is a high-pressure buffer tank, and a spherical tank that can withstand low temperatures of -60℃ and pressures of 15 MPa can be selected.

[0028] Furthermore, both the first solenoid valve 3 and the second solenoid valve 10 are low-temperature, high-pressure normally closed solenoid valves.

[0029] Furthermore, the conveying pipeline is made of stainless steel pipe that is resistant to low temperature and high pressure.

[0030] Furthermore, multiple release holes 801 are provided and are evenly arranged on the dry ice storage tank 8. The number and position of the release holes 801 can also be determined according to actual needs.

[0031] Furthermore, the upper part of the dry ice storage tank 8 is equipped with an anti-impact structure to prevent the dry ice storage tank 8 from being damaged when coal blocks fall.

[0032] In some embodiments, such as Figure 2 As shown, the release hole 801 extends horizontally through the outer shell 803 and the inner shell 804. The wall of the release hole 801 is fixedly connected to the cylinder. The two ends of the cylinder along the axial direction are fixedly connected to the outer shell 803 and the inner shell 804 respectively to prevent the phase change heat-conducting material from leaking from the release hole 801.

[0033] Furthermore, both the outer shell 803 and the inner shell 804 are made of stainless steel, which has good thermal conductivity.

[0034] Furthermore, the outer shell 803 and the inner shell 804 can be manufactured by casting and welding.

[0035] In some embodiments, such as Figure 1 , Figure 2As shown, the lower part of the coal storage bunker 9 is a conical bottom structure 901. The coal discharge port of the coal storage bunker 9 is located at the center of the conical bottom structure 901. All the dry ice storage tanks 8 are arranged around the edge of the inner wall of the coal storage bunker 9 and are located above the conical bottom structure 901. The upper part of the conical bottom structure 901 is a position where spontaneous combustion is more likely to occur. Placing the dry ice storage tanks 8 in this position can minimize the risk of spontaneous combustion of coal powder.

[0036] It should be noted that the dry ice storage tank 8 can be located in any position in the coal storage silo 9 where spontaneous combustion is likely to occur.

[0037] In some embodiments, the volume of each dry ice storage tank 8 is determined by the following formula:

[0038] Where V is the volume of a single dry ice storage tank 8; The porosity of the coal in the coal storage bin is obtained based on actual measurements. R is the inner diameter of coal storage silo 9; h is the height of the cone-shaped structure 901; A represents the expansion factor of dry ice phase transition sublimation, which is taken as 750 times. B is the surplus coefficient for the amount of liquid carbon dioxide injected, which is taken as 1.1; n represents the number of dry ice storage tanks 8 arranged within the coal storage silo 9.

[0039] In some embodiments, such as Figure 1 As shown, a flow meter 4 is connected to the delivery pipeline, and the flow meter 4 is located between the liquid carbon dioxide storage tank 1 and the booster pump 5.

[0040] Furthermore, flow meter 4 is selected as a Coriolis mass flow meter.

[0041] In some embodiments, such as Figure 1 As shown, a pressure transmitter 7 is connected to the buffer tank 6. The pressure transmitter 7 is an anti-icing type pressure transmitter.

[0042] Furthermore, the pressure transmitter 7 has a range of 0-15 MPa.

[0043] In some embodiments, the coal storage silo 9 is equipped with a temperature sensor and a humidity sensor to monitor the temperature and humidity inside the coal storage silo 9.

[0044] In some embodiments, such as Figure 1As shown, the device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change also includes a controller 2. A flow meter 4, a first solenoid valve 3, a booster pump 5, a pressure transmitter 7, a second solenoid valve 10, a temperature sensor, and a humidity sensor are all electrically connected to the controller 2. This allows for automatic control of the entire device. For example, the pressure signal transmitted from the pressure transmitter 7 to the controller 2 controls the opening and closing of the booster pump 5 and the second solenoid valve 10. Similarly, the temperature and humidity signals transmitted from the temperature and humidity sensors to the controller 2 control the opening and closing of the booster pump 5, the first solenoid valve 3, and the second solenoid valve 10. Furthermore, the flow signal transmitted from the flow meter 4 to the controller 2 controls the opening and closing of the first solenoid valve 3.

[0045] In some embodiments, the phase change thermal conductive material includes a hexadecylamine / aluminum phosphate composite phase change material or a hydrated salt with added CuO nanoparticles.

[0046] Both materials have low thermal conductivity at room temperature, and the rate at which dry ice in the dry ice storage tank 8 sublimates into gas is slow. After reaching the phase change temperature, the thermal conductivity increases significantly. The phase change temperature of the material is 50℃, which is lower than the critical temperature of coal self-ignition of 60℃. When the phase change heat-conducting material reaches the phase change temperature, the heat conduction capacity of the dry ice storage tank 8 is greatly improved, enabling the dry ice storage tank 8 at the high temperature point of the coal storage bunker 9 to accelerate heat conduction, promote the rapid heating and phase change of the dry ice in the dry ice storage tank 8, release gaseous carbon dioxide, inertate the coal storage bunker 9, and at the same time, the cold energy discharged cools the coal body and environment around the dry ice storage tank 8, achieving comprehensive fire prevention and extinguishing.

[0047] Both materials are active phase change materials, requiring no manual control. When there is no heat source, they automatically convert to a low thermal conductivity state, achieving a slow phase change of dry ice; when the phase change temperature is reached, the dry ice undergoes a rapid phase change, causing the coal storage bin 9 to cool down and inertize quickly, thus inhibiting spontaneous combustion of coal.

[0048] The arrangement method of the coal storage bunker spontaneous combustion prevention device based on liquid carbon dioxide phase change according to an embodiment of the present invention includes the following steps: (1) Install a liquid carbon dioxide storage tank 1, a booster pump 5 and a buffer tank 6 on the ground near the coal storage bunker 9, and connect them in sequence by means of a conveying pipeline; install a pressure transmitter 7 on the top of the buffer tank 6; connect the pressure transmitter 7, the flow meter 4, the second solenoid valve 10, the booster pump 5 and the controller 2 by means of a communication cable.

[0049] (2) A first solenoid valve 3 and a flow meter 4 are installed in the middle of the conveying pipeline connecting the liquid carbon dioxide storage tank 1 and the booster pump 5. A second solenoid valve 10 is installed at the liquid inlet of the dry ice storage tank 8. The conveying pipeline is extended to the outer wall of the coal storage bunker 9, 0.5m above the cone bottom structure 901 area. At this position, a ring conveying pipeline is arranged horizontally along the circumference of the outer wall. Multiple tee fittings are arranged at equal intervals at different positions on the ring conveying pipeline.

[0050] (3) At the tee joint, drill multiple equally spaced holes perpendicular to the wall, connect the conveying pipeline to the tee and extend it into the coal bunker, and connect the end of the conveying pipeline to the dry ice storage tank 8. Set the number of dry ice storage tanks 8 to n according to the actual situation. According to the diffusion radius of gaseous carbon dioxide, the distance between two adjacent dry ice storage tanks 8 should be selected as 10-20m.

[0051] like Figure 1 As shown, another embodiment of the present invention proposes a method for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change. The method utilizes the aforementioned device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, and includes the following steps: Step S1: Open the first solenoid valve 3 and the booster pump 5. Liquid carbon dioxide is continuously injected into the buffer tank 6. The pressure in the buffer tank 6 continues to rise. When the pressure transmitter 7 detects that the pressure in the buffer tank 6 reaches 7MPa, the signal is fed back to the controller 2 and the second solenoid valve 10 is opened. Liquid carbon dioxide enters the dry ice storage tank 8 and is quickly converted into dry ice. Step S2: The dry ice in the dry ice storage tank 8 sublimates into carbon dioxide gas and is continuously and slowly released outward through the release hole 801; Step S3: When a fire breaks out in the coal storage silo 9, causing the temperature to rise, the thermal conductivity of the phase change heat-conducting material increases, thereby increasing the sublimation rate of the dry ice. The carbon dioxide produced by sublimation is continuously and rapidly released outwards to extinguish the fire. When all the dry ice has sublimated, steps S1-S3 are repeated to achieve multiple fillings of dry ice.

[0052] Furthermore, when the pressure transmitter 7 detects that the pressure in the buffer tank 6 exceeds 10 MPa, the controller 2 shuts down the booster pump 5, and the liquid carbon dioxide in the buffer tank 6 is continuously transported to the dry ice storage tank 8; when the pressure transmitter 7 detects that the pressure in the buffer tank 6 is lower than 7 MPa, the controller 2 restarts the booster pump 5.

[0053] Furthermore, the density ratio of dry ice to liquid carbon dioxide is 1.42. The dry ice storage tank 8 is determined to be full based on the injection volume monitored by the flow meter 4. When the dry ice storage tank 8 is full, the first solenoid valve 3 is closed, and the controller 2 closes the booster pump 5 and the second solenoid valve 10, thus completing a single filling of dry ice.

[0054] Furthermore, based on the temperature and humidity of the coal storage silo 9 and the heat transfer performance of the phase change heat-conducting material, the sublimation rate of dry ice in the dry ice storage tank 8 is determined.

[0055] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0059] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change, characterized in that, include: Liquid carbon dioxide storage tank; A buffer tank has an inlet and an outlet. The inlet of the buffer tank is connected to the outlet of the liquid carbon dioxide storage tank through a delivery pipeline. A booster pump and a first solenoid valve are connected to the delivery pipeline. The first solenoid valve is located between the liquid carbon dioxide storage tank and the booster pump. The coal storage silo has several dry ice storage tanks connected to its inner wall. The inlet of each dry ice storage tank is connected to the outlet of a buffer tank. A second solenoid valve is connected to the inlet of each dry ice storage tank. Several release holes for releasing carbon dioxide are provided on the side wall of each dry ice storage tank. Each dry ice storage tank includes an outer shell and an inner shell. A sandwich cavity is provided between the outer shell and the inner shell, and the sandwich cavity is filled with a phase change thermally conductive material.

2. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 1, characterized in that, The release hole extends horizontally through the outer shell and the inner shell. The wall of the release hole is fixedly connected to a cylinder. The two ends of the cylinder along the axial direction are fixedly connected to the outer shell and the inner shell, respectively, to prevent the phase change heat-conducting material from leaking from the release hole.

3. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 1, characterized in that, The lower part of the coal storage bunker has a conical bottom structure, and the coal discharge port of the coal storage bunker is located at the center of the conical bottom structure. All the dry ice storage tanks are arranged around the edge of the inner wall of the coal storage bunker and are located above the conical bottom structure.

4. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 3, characterized in that, The volume of each of the dry ice storage tanks is determined by the following formula: Where V is the volume of a single dry ice storage tank; The porosity of the coal in the coal storage bin is obtained from actual measurements; R is the inner diameter of the coal storage bin; h is the height of the cone-shaped base structure; A represents the expansion factor of dry ice phase transition sublimation, which is taken as 750 times. B is the surplus coefficient for the amount of liquid carbon dioxide injected, which is taken as 1.1; n is the number of dry ice storage tanks arranged in the coal storage bunker.

5. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 1, characterized in that, A flow meter is connected to the delivery pipeline, and the flow meter is located between the liquid carbon dioxide storage tank and the booster pump.

6. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 5, characterized in that, The buffer tank is connected to a pressure transmitter, which is an anti-icing type pressure transmitter.

7. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 6, characterized in that, The coal storage silo is equipped with temperature and humidity sensors to monitor the temperature and humidity inside the silo.

8. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 7, characterized in that, It also includes a controller, and the flow meter, the first solenoid valve, the booster pump, the pressure transmitter, the second solenoid valve, the temperature sensor, and the humidity sensor are all electrically connected to the controller.

9. The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change according to claim 1, characterized in that, The phase change thermal conductive material includes hexadecylamine / aluminum phosphate composite phase change material or hydrated salt with added CuO nanoparticles.

10. A method for preventing spontaneous combustion of coal in coal storage bunkers based on liquid carbon dioxide phase change, characterized in that, The device for preventing spontaneous combustion of coal in a coal storage silo based on liquid carbon dioxide phase change as described in any one of claims 1-9 includes the following steps: The first solenoid valve and booster pump are turned on, and liquid carbon dioxide is continuously injected into the buffer tank. The pressure in the buffer tank continues to rise. When the pressure in the buffer tank reaches the set value, the second solenoid valve is turned on, and the liquid carbon dioxide enters the dry ice storage tank and is quickly converted into dry ice. The dry ice in the dry ice storage tank sublimates into carbon dioxide gas, which is continuously and slowly released outward through the release hole. When a fire breaks out in the coal storage silo and the temperature rises, the thermal conductivity of the phase change thermal conductive material increases, which in turn increases the rate of dry ice sublimation. The carbon dioxide produced by sublimation is continuously and rapidly released to the outside, thus extinguishing the fire.

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