A heat energy extraction and spontaneous combustion prevention system for long-term storage of a fully-enclosed coal storage yard

Abstract

The application discloses a kind of heat energy extraction and spontaneous combustion prevention system of long-term storage of fully enclosed coal storage yard, including industrial water chiller, three-way valve, finned heat exchanger and industrial nitrogen generator.The three-way valve one end is sequentially connected frequency conversion water pump and industrial water chiller by cold water pipe, its other end is connected finned heat exchanger, third end is sequentially connected high-pressure air pump and industrial nitrogen generator by air inlet pipe, automatic exhaust valve is arranged in the finned heat exchanger, its other end is sequentially connected temperature sensor, stop valve and heat pump device, the temperature sensor is sequentially connected fuzzy PID control module and frequency conversion water pump.The application extracts its oxidation heat by pipe burying mode according to fully enclosed coal storage condition, reduces temperature rising range and rate, improves its safe storage time and storage quality, improves heat energy utilization and system efficiency by automatic flow control, when temperature rises out of control, nitrogen injection on air inlet side can also be used to block oxygen, which provides technical support for long-term storage of coal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of efficient coal storage, and particularly relates to a heat energy extraction and spontaneous combustion prevention system for long-term storage of a fully-enclosed coal storage yard. BACKGROUND

[0002] In order to cope with the risk of international energy trade market, the National Development and Reform Commission proposes to accelerate the construction of 200 million tons of government dispatchable coal storage capacity. In order to meet the requirements of long-term storage of government dispatchable coal, fully-enclosed coal storage yards are gradually popularized. Coal will slowly oxidize during storage, resulting in a decrease in its calorific value. The average calorific value of mixed coal will decrease by 2% after six months of storage, and the calorific value loss in the area of the coal pile where oxidation is severe will reach 18%. This cannot meet the requirements of long-term storage of a large amount of coal. The oxidation rate of coal increases exponentially with temperature, so keeping the storage temperature at a low level is beneficial to long-term and efficient storage of the coal pile and can effectively prevent spontaneous combustion. Research shows that when the oxygen concentration is reduced to below 7%, the coal-oxygen reaction is difficult to occur. The oxygen supply inside the coal pile in a fully-enclosed coal storage environment is already insufficient, so controlling the oxygen concentration is a very effective measure. The airflow around the coal pile in a fully-enclosed environment is affected by thermal buoyancy, resulting in the appearance of a "chimney effect" around the coal pile. That is, after the air inside and around the coal pile is heated and warmed, its density decreases, and the airflow moves upward under the action of thermal buoyancy and gradually cools down. At the same time, two low-pressure areas are generated at the bottom of the two wings of the coal pile, and the cooled airflow reenters the coal pile from the bottom of the coal pile. Therefore, the coal pile has sufficient oxygen supply at the bottom, and the high-temperature area is distributed at the bottom of the two wings of the coal pile, approximately 3-4 m from the surface of the coal pile, according to the different spontaneous combustion tendencies of coal.

[0003] At present, the spontaneous combustion prevention technology for fully-enclosed coal storage yards mainly uses the method of spraying water to cool down or reversing the pile to dissipate heat after discovering signs of spontaneous combustion of the coal pile. This method can only interrupt the process of spontaneous combustion of coal, but cannot effectively maintain the calorific value of the coal. At the same time, the coal pile warms up slowly under natural convection and the warming area is large. If the distribution of the high-temperature area of the coal pile under fully-enclosed coal storage conditions is not focused on for cooling and spontaneous combustion risk prevention, it is difficult to resolve the risk of spontaneous combustion of the coal pile in a timely manner, and it will also lead to a large area of loss of the calorific value of the coal, which cannot meet the requirements of long-term and efficient storage of coal. Therefore, it is urgent to propose a system for fully-enclosed coal storage environments that can maintain the calorific value under normal conditions while also responding to the risk of spontaneous combustion of the coal pile in real time, thereby providing strong technical support for long-term and safe and efficient storage of coal and China's energy security strategy and coal storage strategy. SUMMARY

[0004] In view of the above status and deficiencies, the present application proposes a heat energy extraction and spontaneous combustion prevention system for long-term storage of a fully-enclosed coal storage yard.

[0005] To achieve the above object, the present application provides the following technical solutions: a long-term storage heat energy extraction and spontaneous combustion prevention system for a fully enclosed coal storage yard, comprising an industrial water chiller, a variable frequency water pump, a three-way valve, finned heat exchange pipes, a temperature sensor, a heat pump device, a fuzzy PID control module, a high-pressure air pump and an industrial nitrogen generator. One end of the three-way valve is connected with the variable frequency water pump and the industrial water chiller in sequence through a cold water pipe, the other end is connected with the finned heat exchanger, and the third end is connected with the high-pressure air pump and the industrial nitrogen generator in sequence through an air inlet pipe. The finned heat exchanger is provided with heat exchange fins and an automatic exhaust valve. The other end of the finned heat exchanger is connected with the temperature sensor, a stop valve and the heat pump device in sequence through a water outlet pipe. The temperature sensor is connected with the fuzzy PID control module and the variable frequency water pump in sequence through a cable. When the three-way valve is connected with the cold water pipe and the finned heat exchange pipe, a heat energy extraction system is formed. The finned heat exchanger buried in the easy-to-warm-up area of the coal pile absorbs the heat generated by the oxidation of coal. The heat pump device uses the absorbed heat to automatically regulate the water flow in the pipeline according to the temperature of the water in the water outlet pipe, thereby improving the heat energy extraction efficiency. When the three-way valve is connected with the air inlet pipe and the finned heat exchanger, a spontaneous combustion prevention system is formed. The system injects high-pressure nitrogen into the pipeline to discharge the water remaining in the pipeline, and relies on the automatic exhaust valve in the finned heat exchange pipe to release nitrogen on the upwind side of the coal pile, thereby preventing spontaneous combustion by isolating oxygen.

[0006] As a preferred technical solution of the present application, the plurality of finned heat exchange pipes are arranged at the same angle with the slope of the coal pile, and the vertical distance from the coal pile surface is set to 3-4 m according to the spontaneous combustion tendency of the stored coal. The vertical distance between the plurality of finned heat exchange pipes is 2 m.

[0007] As a preferred technical solution of the present application, an automatic exhaust valve is arranged every 5 meters in each finned heat exchange pipe. The inner diameter of the finned heat exchange pipe is 89.2 mm, the fin thickness is 10.5 mm, and the fin spacing is 25.4 mm.

[0008] As a preferred technical solution of the present application, the cold water pipe and the water outlet pipe are wrapped with thermal insulation materials.

[0009] As a preferred technical solution of the present application, the operating condition of the variable frequency water pump is calculated by the fuzzy PID control module according to the difference between the temperature of the water flow in the water outlet pipe and the set water temperature (26℃).

[0010] As a preferred technical solution of the present application, the use method of the heat energy extraction system comprises the following steps:

[0011] S1. Adjust the three-way valve and open the stop valve to form a passageway for the industrial water chiller, heat pump device, variable frequency water pump and finned tube heat exchanger, thereby forming a heat energy extraction system for maintaining daily heat value;

[0012] S2. Start the industrial water chiller to prepare 5-8℃ cold water, and start the variable frequency water pump to pump the prepared cold water into the finned heat exchange tube buried in the high temperature area to absorb the heat generated by the oxidation of the coal pile;

[0013] S3. Monitor the temperature information in the outlet pipe through the temperature sensor and transmit it to the fuzzy PID control module, and the fuzzy PID control module calculates the optimal water pump operation parameter under the current coal pile temperature state according to the difference between the current water flow temperature and the set temperature (26℃), and controls the variable frequency water pump to adjust the working condition;

[0014] S4. The high temperature water containing the extracted heat energy in the finned heat exchanger enters the heat pump device for heat exchange, and after fully utilizing the heat energy, it enters the industrial water chiller to be prepared into 5-8℃ cold water again;

[0015] S5. Repeat the above steps S2, S3 and S4 to continuously extract the heat generated by the oxidation of the coal pile, so that the easily oxidizable area in the fully enclosed coal pile can always be kept at a lower temperature, effectively delaying the oxidation speed of the coal pile, reducing the heat value loss and prolonging the storage time.

[0016] As a preferred technical solution of the present application, the use method of the spontaneous combustion prevention system comprises the following steps:

[0017] s1. Close the variable frequency water pump, industrial water chiller and heat pump device, adjust the three-way valve, connect the high-pressure gas pump and industrial nitrogen generator to the cold water pipe, and form a spontaneous combustion prevention system for emergency disposal of coal pile spontaneous combustion;

[0018] s2. Start the industrial nitrogen generator and high-pressure gas pump, so that the prepared high-pressure nitrogen gas enters the finned heat exchange tube through the cold water pipe, and the original water in the pipeline is discharged under the action of high-pressure gas;

[0019] s3. While discharging the water in the discharge pipeline, the gas in the finned heat exchange tube continuously releases nitrogen gas to the oxidation area of the coal pile on the air inlet side of the coal pile under the action of the automatic exhaust valve;

[0020] s4. After the original water in the finned heat exchange tube is completely discharged, close the stop valve to speed up the nitrogen discharge rate, form a nitrogen barrier on both wings of the coal pile, block the oxygen supply route, and eliminate the risk of coal pile spontaneous combustion.

[0021] Due to the adoption of the above technical solution, the present application has the following beneficial effects:

[0022] 1. The application realizes targeted extraction of heat energy, improves the heat value retention rate of the coal pile and the utilization rate of the extracted heat energy by arranging a plurality of finned heat exchange pipes at the same angle with the coal pile slope, inside the coal pile, at a position with a vertical distance of about 3-4 m from the surface of the coal pile, aiming at the high-temperature area of the coal pile in a fully enclosed coal storage environment.

[0023] 2. The application uses finned heat exchange pipes to improve heat exchange efficiency, which is more conducive to more efficient recovery of heat energy in the case of low storage coal temperature (below 50℃), so as to keep the coal storage in a temperature range with low oxidation rate, thereby improving the heat energy extraction efficiency and heat value retention rate.

[0024] 3. The application recovers the heat generated by the oxidation of coal storage by heat pump technology, thereby improving the utilization rate of coal resources.

[0025] 4. The application controls the working parameters of the variable frequency water pump by a fuzzy PID controller, and improves the heat energy extraction efficiency and the availability of the extracted heat energy by automatic adjustment of the water pump operating conditions in the case of slow temperature rise of the coal pile under natural convection, thereby reducing the system operation cost.

[0026] 5. The application arranges the finned heat exchange pipes at the air inlet of the oxygen supply in the coal storage pile, which not only extracts heat energy from the most serious oxidation area, but also reduces the oxygen concentration in the entire coal storage pile in time by nitrogen injection through the upper air inlet, eliminates the spontaneous combustion danger of the entire coal storage pile, realizes one pipe with multiple uses, reduces the emergency response time of coal pile spontaneous combustion, and improves the emergency disposal capacity of spontaneous combustion. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structure diagram of a heat energy extraction and spontaneous combustion prevention system for long-term storage of a fully enclosed coal storage yard of the application;

[0028] Figure 2 is a sectional view of the arrangement position of the heat energy utilization and nitrogen injection pipeline in the coal storage pile in the application

[0029] Figure 3 is a three-dimensional schematic view of the arrangement position of the heat energy utilization and nitrogen injection pipeline in the coal storage pile in the application

[0030] Figure 4 is a working logic diagram of the fuzzy PID control module in the application

[0031] Fig. 1, industrial water chiller; 2, cold water pipe; 3, variable frequency water pump; 4, three-way valve; 5, finned heat exchanger; 6, automatic exhaust valve; 7, heat exchange fin; 8, water outlet pipe; 9, temperature sensor; 10, stop valve; 11, heat pump device; 12, cable; 13, fuzzy PID control module; 14, air inlet pipe; 15, high-pressure air pump; 16, industrial nitrogen generator. DETAILED DESCRIPTION

[0032] The embodiments of the present application will be described in detail below with reference to the drawings, Figure 2 The arrow in the figure shows the direction of air flow under natural convection in the fully enclosed coal storage yard.

[0033] It should be clear that the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] Referring to Figure 1 A heat energy extraction and spontaneous combustion prevention system for long-term storage in a fully enclosed coal storage yard, comprising an industrial water chiller 1, a variable frequency water pump 3, a three-way valve 4, a finned heat exchanger pipe 5, a temperature sensor 9, a heat pump device 11, a fuzzy PID control module 13, a high-pressure air pump 15 and an industrial nitrogen generator 16. One end of the three-way valve 4 is connected to the variable frequency water pump 3 and the industrial water chiller 1 in turn through the cold water pipe 2, the other end is connected to the finned heat exchanger 5 through the cold water pipe 2, and the third end is connected to the high-pressure air pump 15 and the industrial nitrogen generator 16 in turn through the air inlet pipe 14. The finned heat exchanger 5 is provided with heat exchange fins 7 and an automatic exhaust valve 6, and the other end of the finned heat exchanger 5 is connected to the temperature sensor 9, the stop valve 10 and the heat pump device 11 in turn through the water outlet pipe 8. The temperature sensor 9 is connected to the fuzzy PID control module 13 and the variable frequency water pump 3 in turn through the cable 12. When the three-way valve 4 connects the cold water pipe 2 and the finned heat exchanger pipe 5, a heat energy extraction system is formed. The finned heat exchanger 5 buried in the easy-to-warm-up area of the coal pile absorbs the heat generated by the oxidation of coal in the form of cold water heat exchange. The heat pump device 11 uses the absorbed heat to improve energy utilization. The water flow in the pipeline is automatically controlled according to the temperature of the water in the water outlet pipe 8 to improve the heat energy extraction efficiency. When the three-way valve 4 connects the air inlet pipe 14 and the finned heat exchanger 5, a spontaneous combustion prevention system is formed. When the coal pile is found to have a too fast heating rate or other signs of spontaneous combustion, high-pressure nitrogen gas is injected into the pipeline to discharge the water remaining in the pipeline, and the automatic exhaust valve 6 arranged in the finned heat exchanger pipe 5 releases nitrogen gas on the upwind side of the coal pile, playing a role in preventing spontaneous combustion by isolating oxygen.

[0035] In the embodiment, the plurality of finned heat exchange pipes are arranged inside the coal pile and maintain the same angle with the slope of the coal pile, the vertical distance from the coal pile surface is set to 3-4m according to the spontaneous combustion tendency of the stored coal, the vertical distance from the ground of the lowermost finned heat exchange pipe is 2m, and the vertical distance between the plurality of finned heat exchange pipes is 2m.

[0036] In the embodiment, an automatic exhaust valve is arranged every 5m in each finned heat exchange pipe, the inner diameter of the finned heat exchange pipe is 89.2mm, the fin thickness is 10.5mm, and the fin spacing is 25.4mm.

[0037] In the embodiment, the cold water pipe and the outlet pipe are both wrapped with thermal insulation materials.

[0038] In the embodiment, the operation condition of the variable frequency water pump is calculated by the fuzzy PID control module according to the difference between the temperature of the water flow in the outlet pipe and the set water temperature (26℃).

[0039] In the embodiment, the use method of the heat energy extraction system includes the following steps:

[0040] S1. Adjust the three-way valve and open the stop valve to form a path for the industrial water chiller unit, the heat pump device, the variable frequency water pump and the finned tube heat exchanger, and form a heat energy extraction system for daily heat value maintenance;

[0041] S2. Start the industrial water chiller unit to prepare 5-8℃ cold water, and start the variable frequency water pump to pump the prepared cold water into the finned heat exchange pipe buried in the high temperature area for heat exchange to absorb the heat generated by the oxidation of the coal pile;

[0042] S3. Monitor the temperature information through the temperature sensor in the outlet pipe and transmit it to the fuzzy PID control module, and the fuzzy PID control module calculates the optimal water pump operation parameters under the current coal pile temperature rising state according to the difference between the current water flow temperature and the set temperature (26℃), and controls the variable frequency water pump to adjust the working condition;

[0043] S4. The high temperature water containing the extracted heat energy of the finned heat exchanger enters the heat pump device for heat exchange, and after fully utilizing the heat energy, it enters the industrial water chiller unit to be prepared into 5-8℃ cold water again;

[0044] S5. Repeat the above steps S2, S3 and S4 to continuously extract the heat generated by the oxidation of the stored coal pile, so that the easily oxidizable area in the fully enclosed coal pile is always maintained at a lower temperature, effectively delaying the oxidation speed of the stored coal, reducing the heat value loss, and prolonging the storage time.

[0045] In the embodiment, the use method of the spontaneous combustion prevention and control system includes the following steps:

[0046] s1. Turn off the frequency conversion water pump, industrial water chiller and heat pump device, adjust the three-way valve, connect the high-pressure air pump and industrial nitrogen generator to the cold water pipe to form a spontaneous combustion prevention system for emergency disposal of coal pile spontaneous combustion;

[0047] s2. Turn on the industrial nitrogen generator and high-pressure air pump, and make the prepared high-pressure nitrogen gas enter the finned heat exchange pipe through the cold water pipe, so that the original water in the pipeline is discharged under the action of high-pressure gas;

[0048] s3. While discharging the water in the pipeline, the gas in the finned heat exchange pipe continuously releases nitrogen gas to the oxidation area of the coal storage pile under the action of the automatic exhaust valve;

[0049] s4. After the original water in the finned heat exchange pipe is completely discharged, close the stop valve, speed up the nitrogen discharge rate, form a nitrogen barrier on both wings of the coal pile, block the oxygen supply route, and eliminate the risk of coal pile spontaneous combustion.

[0050] The above is only a preferred specific embodiment of the application, but the protection scope of the application is not limited thereto, any person skilled in the art within the technical range disclosed by the application, according to the technical scheme and the inventive concept of the application, makes equivalent replacement or change, which should be covered in the protection scope of the application.

Claims

1. A system for extracting heat energy and preventing spontaneous combustion during long-term storage in a fully enclosed coal storage yard, characterized in that: This includes industrial chillers, variable frequency water pumps, three-way valves, finned heat exchange tubes, temperature sensors, heat pump devices, fuzzy PID control modules, high-pressure air pumps, and industrial nitrogen generators. One end of the three-way valve is connected to a variable frequency water pump and an industrial chiller unit in sequence via a cold water pipe, the other end is connected to a finned heat exchange tube, and the third end is connected to a high-pressure air pump and an industrial nitrogen generator in sequence via an air inlet pipe. The finned heat exchange tube is equipped with heat exchange fins and an automatic exhaust valve. The finned heat exchange tubes are arranged inside the coal pile in the fully enclosed coal storage yard, maintaining the same angle as the coal pile slope; the vertical distance from the coal pile surface is set to 3-4m according to the spontaneous combustion tendency of the stored coal, the vertical distance between the lowest finned heat exchange tube and the ground is 2m, and the vertical distance between multiple finned heat exchange tubes is 2m; an automatic exhaust valve is installed every 5 meters in each finned heat exchange tube, the inner diameter of the finned heat exchange tube is 89.2mm, the fin thickness is 10.5mm, and the fin spacing is 25.4mm; The other end of the finned heat exchange tube is connected in sequence to a temperature sensor, a shut-off valve, and a heat pump device via a water outlet pipe; the temperature sensor is connected in sequence to a fuzzy PID control module and a variable frequency water pump via a cable; the fuzzy PID control module calculates and controls the optimal operating conditions of the variable frequency water pump based on the difference between the temperature of the water flow in the water outlet pipe and the set water temperature of 26℃. When the three-way valve is connected to the cold water pipe and the finned heat exchange tube, a heat extraction system is formed. The heat generated by coal oxidation is absorbed through the finned heat exchange tube buried in the easily heated area of ​​the coal pile, and the absorbed heat is utilized by a heat pump device. When the three-way valve is connected to the air inlet pipe and the finned heat exchange tube, a spontaneous combustion prevention system is formed. High-pressure nitrogen gas prepared by an industrial nitrogen generator is injected into the pipeline through a high-pressure air pump to expel the water remaining in the pipeline. Nitrogen gas is released into the oxidation area of ​​the coal pile on the air inlet side of the coal pile by the automatic exhaust valve in the finned heat exchange tube, forming a nitrogen barrier to isolate oxygen and prevent spontaneous combustion.

2. The thermal energy extraction and spontaneous combustion prevention system for long-term storage of fully enclosed coal in a coal storage yard according to claim 1, characterized in that: Both the cold water pipe and the outlet pipe are wrapped with insulation material.

3. The thermal energy extraction and spontaneous combustion prevention system for long-term storage of fully enclosed coal in a coal storage yard according to claim 1, characterized in that: The method of using the thermal energy extraction system includes the following steps: S1. Adjust the three-way valve and open the shut-off valve to make the industrial chiller, heat pump unit, variable frequency water pump and finned heat exchange tube form a passage to form a heat energy extraction system for maintaining daily calorific value; S2. Start the industrial chiller unit to prepare chilled water at 5-8℃, and at the same time start the variable frequency water pump to pump the prepared chilled water into the finned heat exchange tubes buried in the high temperature area for heat exchange and to absorb the heat generated by the oxidation of the coal pile. S3. The temperature information is monitored by the temperature sensor in the water outlet pipe and transmitted to the fuzzy PID control module. The fuzzy PID control module calculates the optimal water pump operating parameters under the current coal pile heating state based on the difference between the current water flow temperature and the set temperature (26℃), and controls the variable frequency water pump to adjust the operating conditions. S4. The high-temperature water containing the heat energy extracted from the finned heat exchange tubes enters the heat pump device for heat exchange. After making full use of the heat energy, it enters the industrial chiller unit to be reprocessed into chilled water at 5-8°C. S5. Repeat steps S2, S3 and S4 above to continuously extract the heat generated by oxidation in the coal storage pile, so that the easily oxidized areas in the coal storage pile under fully enclosed conditions are always kept at a low temperature, effectively slowing down the oxidation rate of the coal, reducing calorific value loss and extending the storage time.

4. The thermal energy extraction and spontaneous combustion prevention system for long-term storage of fully enclosed coal in a coal storage yard according to claim 1, characterized in that: The method of using the spontaneous combustion prevention system includes the following steps: s1. Turn off the variable frequency water pump, industrial chiller and heat pump, adjust the three-way valve to connect the high pressure air pump and industrial nitrogen generator to the chilled water pipe to form a spontaneous combustion prevention system for emergency response to coal pile spontaneous combustion; s2. Turn on the industrial nitrogen generator and high-pressure gas pump, so that the prepared high-pressure nitrogen gas enters the finned heat exchange tube through the cold water pipe, and the water in the pipe is discharged under the action of the high-pressure gas. s3. While draining water from the pipeline, the gas in the finned heat exchange tubes continuously releases nitrogen into the oxidation zone of the coal storage pile on the air intake side of the coal storage pile under the action of the automatic exhaust valve; s4. After the water in the finned heat exchange tubes is completely drained, close the shut-off valve to accelerate the nitrogen emission rate, form a nitrogen barrier on both sides of the coal pile, block the oxygen supply route, and eliminate the risk of spontaneous combustion of the coal pile.

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