Liquid metal-graphite heat storage device for waste heat recovery of large heat supply unit

Abstract

The invention discloses a liquid metal-graphite heat storage device for waste heat recovery of a large heat supply unit, and belongs to the technical field of waste heat utilization, the device comprises a communicating pipe and a heat storage tank, the heat storage tank comprises a shell, a heat preservation layer and a graphite block layer, the graphite block layer forms a containing cavity, phase change molten metal is contained in the containing cavity, and the communicating pipe is communicated with the shell; the heat storage tank is provided with a first heat exchange pipe used for being inserted into the phase change molten metal. Waste heat of high-temperature waste gas generated in the working process of a large-scale thermal power heat supply unit can be stored, heat is transmitted to the graphite block through liquid metal, the composite structure can improve the rate and performance of the high-temperature heat storage / release process, the economic cost is reduced, the phase-change molten metal has high thermal conductivity and a moderate melting point, and the phase-change molten metal can be recycled. The heat storage tank is compact in structure, large in energy storage density, simple in structure and reliable in operation, the graphite blocks have high specific heat capacity and good heat stability, and the heat storage device sequentially achieves cascade storage of high-grade heat energy, medium-grade heat energy and low-grade heat energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat recovery, and in particular relates to a liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units. Background Art

[0002] In view of the large amount of low-grade waste heat resources in the industrial field, waste heat recovery technology is the development of technology that can convert low-temperature waste heat into electricity or use it in air-conditioning systems, thereby improving the economic utilization value of waste heat. In order to realize the waste heat recovery of thermal power heating units, it is necessary to develop efficient thermal energy storage technology. Waste heat recovery technology has a wide range of applications and an important role. By improving energy utilization efficiency, saving energy costs, reducing environmental pollution, promoting industrial development and sustainability, and realizing the comprehensive utilization of energy, waste heat recovery technology has made important contributions to the efficient utilization of energy and environmental protection. The heat storage performance and efficiency of the existing heat storage devices for waste heat recovery of large-scale heating units need to be improved. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units to meet the waste heat recovery and utilization heat storage needs and reduce economic costs.

[0004] Technical solution: In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] A liquid metal-graphite heat storage device for waste heat recovery of a large-scale heating unit comprises a connecting pipe and a heat storage tank connected to the connecting pipe, wherein one end of the connecting pipe is an inlet end, the inlet end is connected to a first inlet pipe and a second inlet pipe, and the other end of the connecting pipe is an outlet end, the heat storage tank comprises a shell, an insulation layer arranged in the shell, and a graphite block layer arranged inside the insulation layer, the graphite block layer forms a containing cavity, and a phase-change metal liquid is contained in the containing cavity, the heat storage tank is provided with a first heat exchange tube for inserting into the phase-change metal liquid, the inlet and outlet of the first heat exchange tube are both connected to the connecting pipe, and an air valve is provided on the pipe section of the connecting tube located between the inlet and outlet connections of the first heat exchange tube.

[0006] Preferably, the heat storage tank is further provided with a second heat exchange tube for inserting into the phase-change metal liquid, and the inlet and outlet of the second heat exchange tube are both connected to the connecting tube.

[0007] Preferably, the first heat exchange tube is a U-shaped tube, the second heat exchange tube is a spiral tube, the inlet and outlet of the first heat exchange tube are both provided with a first shut-off valve, and the inlet and outlet of the second heat exchange tube are both provided with a second shut-off valve.

[0008] Preferably, the expanded length of the first heat exchange tube is D1, the expanded length of the second heat exchange tube is D2, and D2 is ≥ 1.5D1.

[0009] Preferably, the first inlet pipe is provided with a first regulating valve, the second inlet pipe is provided with a second regulating valve, and the connecting pipe is provided with a flow rate detector.

[0010] Preferably, it also includes a data collection component connected to the heat storage tank, and the data collection component includes a temperature sensor and a pressure sensor.

[0011] Preferably, there are more than two heat storage tanks, and the phase-change metal liquid is a gallium-based alloy, a lead-bismuth alloy or tin.

[0012] Preferably, three heat storage tanks are provided, the phase change metal liquid in the front heat storage tank among the three heat storage tanks is made of gallium-based alloy, the phase change metal liquid in the middle heat storage tank is made of lead-bismuth alloy, and the phase change metal liquid in the rear heat storage tank is made of tin.

[0013] Preferably, the graphite block layer is formed by pressing and sintering graphite powder.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0015] 1. By setting up connecting pipes and heat storage tanks, the high-temperature exhaust gas generated during the operation of large-scale thermal power heating units can be stored for waste heat, thereby achieving the function of recovering waste heat from the exhaust gas;

[0016] 2. The liquid phase-change metal in the heat storage tank is in close contact with the graphite block, which is made of graphite powder pressed and sintered. Heat is transferred to the graphite block through the liquid metal. This innovative composite structure can improve the rate and performance of high-temperature heat storage / release process and reduce economic costs;

[0017] 3. The phase-change metal liquid has high thermal conductivity and moderate melting point, as well as good fluidity and chemical stability. The heat storage tank has a compact structure, high energy storage density, simple structure and reliable operation. The graphite block has high specific heat capacity and good thermal stability.

[0018] 4. Two types of heat exchange tubes are set up. When storing heat, they can be used according to the flow rate and temperature of the exhaust gas to improve the energy storage efficiency. When releasing heat, the two heating tubes can meet different air heating needs;

[0019] 5. A device for recovering and storing heat energy of different grades based on liquid metal-graphite medium heat storage was constructed. The device has three liquid metal-graphite heat storage systems. According to the law that the energy level gradually decreases during the heat transfer process, the heat storage device realizes the cascade storage of high, medium and low-grade heat energy in turn. The three liquid metal-graphite heat storage systems use liquid gallium-graphite, lead-bismuth alloy-graphite and tin-graphite as heat storage units respectively. The liquid gallium-graphite heat storage unit is used to store high-grade heat energy, the lead-bismuth alloy-graphite heat storage unit is used to store medium-grade heat energy, and the tin-graphite heat storage unit is used to store low-grade heat energy, thereby realizing the full and effective recovery and storage of heat energy of different grades. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the device according to an embodiment of the present invention;

[0021] Figure 2 It is a schematic diagram of the internal structure of the heat storage tank of the embodiment. DETAILED DESCRIPTION

[0022] The present invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0023] like Figure 1 As shown, a liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units includes a connecting pipe 1, three heat storage tanks 2 and a data collection component 3. One end of the connecting pipe 1 is an inlet end, and the inlet end is connected with a first inlet pipe 11 and a second inlet pipe 12. The first inlet pipe 11 is used to connect a normal temperature air pipe. The first inlet pipe 11 is provided with a first regulating valve 111. The second inlet pipe 12 is used to connect a high-temperature exhaust gas pipe when a large thermal power unit is working (when connected to a steam pipe, it can also be used to store high-temperature steam heat energy). The second inlet pipe 12 is provided with a second regulating valve 121. The connecting pipe 1 is made of a material that is resistant to high temperatures and can cope with a high temperature difference (nickel-based alloy, cobalt-based alloy). When it is necessary to utilize the waste heat of the exhaust gas, the second regulating valve 121 is opened, the first regulating valve 111 is closed, and the high-temperature exhaust gas enters the connecting pipe 1 through the second inlet pipe 12. When it is necessary to heat the air, the first regulating valve 111 is opened, the second regulating valve 121 is closed, and the normal temperature air enters the connecting pipe 1 through the first inlet pipe 11. The other end of the connecting pipe 1 is an outlet 13, and the waste gas or air after heat exchange is discharged from the outlet 13. The first inlet pipe 11 and the second inlet pipe 12 are both provided with a flow rate detector 15, which adopts an existing flue gas flow rate detector to monitor the gas flow rate in the pipe.

[0024] like Figure 1 and Figure 2As shown, the heat storage tank 2 includes a shell 21, a heat-insulating layer 22 and a graphite block layer 23. The shell 21 is a hollow cylindrical shell. The heat-insulating layer 22 is arranged on the inner wall of the shell 21. The heat-insulating layer 22 uses glass wool or rock wool board for heat preservation. The graphite block layer 23 is arranged on the inner side of the heat-insulating layer 22. The graphite block layer 23 uses graphite blocks that have been subjected to powder pressing and sintering treatment (powder pressing: putting the pre-treated graphite powder into a press for pressing, the pressing pressure is 100-200MPa, and the powder is compressed into a block or a desired shape by high pressure. In this embodiment, it is pressed into a barrel shape; sintering treatment :Put the pressed graphite block into a high temperature furnace, sinter at a temperature between 1400℃ and 2300℃, and process for 10 hours to transform it into a highly crystallized form and enhance its physical and chemical properties). The porous graphite matrix can increase the contact area between the liquid metal and the graphite, and improve the heat transfer efficiency. The inner side of the graphite block layer 23 forms a receiving cavity. The end cover at the top of the heat storage tank 2 is composed of the top shell 21 and the top insulation layer 22. The receiving cavity contains the phase change metal liquid 24. The phase change metal liquid 24 selects liquid metal with high thermal conductivity and moderate melting point as the heat conduction medium. The liquid metal is in close contact with the inner wall of the graphite block layer 23, which can improve the rate and performance of the high-temperature heat storage / release process and reduce the economic cost. The heat storage tank 2 is provided with a first heat exchange tube 25 for inserting into the phase-change metal liquid 24. The first heat exchange tube 25 is a U-shaped tube. The first heat exchange tube 25 includes two straight tube sections and one curved tube section. Most of the tube sections of the first heat exchange tube 25 are located in the phase-change metal liquid 24. One of the upper ends of the two straight tube sections is connected to the connecting tube 1 as an inlet, and the upper end of the other straight tube section is connected to the connecting tube 1 as an outlet. The connecting tube 1 is provided with an air valve 14 on the tube section between the inlet connection of the first heat exchange tube 25 and the outlet connection of the first heat exchange tube 25. Under the obstruction of the air valve 14, the gas entering the inlet end of the connecting tube 1 passes through the first heat exchange tube 25, exchanges heat with the phase-change metal liquid 24 in the heat storage tank 2, and returns to the connecting tube 1 after heat exchange to be discharged from the outlet end 13.

[0025] like Figure 1 and Figure 2As shown, the heat storage tank 2 is also provided with a second heat exchange tube 26 for inserting into the phase-change metal liquid 24. The second heat exchange tube 26 is a spiral tube. Most of the pipe section of the second heat exchange tube 26 is located in the phase-change metal liquid 24. The inlet and outlet of the second heat exchange tube 26 are also connected to the connecting tube 1, and the inlet of the second heat exchange tube 26 is connected to the pipe section before the air valve 14, and the outlet of the second heat exchange tube 26 is connected to the pipe section after the air valve 14. The first heat exchange tube 25 is deployed for a length of D1, and the second heat exchange tube 26 is deployed for a length of D2, and D2 ≥ 1.5D1, so that the heat exchange path of the gas passing through the second heat exchange tube 26 is longer. The inlet and outlet of the first heat exchange tube 25 are both provided with a first shut-off valve 251, and the inlet and outlet of the second heat exchange tube 26 are both provided with a second shut-off valve 261. By controlling the switches of the first shut-off valve 251 and the second shut-off valve 261, it is possible to control whether the gas at the inlet end of the connecting tube 1 passes through the first heat exchange tube 25 or the second heat exchange tube 26. During heat storage, when the exhaust gas temperature is too high and the flow rate is fast, the second heat exchange tube 26 is selected to increase the heat exchange time between the exhaust gas and the phase-change metal liquid 24 to achieve the goal, and when the exhaust gas temperature is not high and the flow rate is slow, the first heat exchange tube 25 is selected to reduce the heat exchange time between the exhaust gas and the liquid metal 23 in order to save time as soon as possible. During heat release, when the air temperature requirement is high, by controlling the switch of the corresponding shut-off valve, the air goes through the second heat exchange tube 26, and the heat exchange time between the air and the phase-change metal liquid 24 is increased to reach the target temperature; when the air temperature requirement is not high, the air goes through the first heat exchange tube 25, and the air after heat exchange is discharged from the outlet 13 into the required workplace. The two heating tubes meet different air heating needs.

[0026] like Figure 1 As shown, three heat storage tanks 2 are connected to the connecting pipe 1 in sequence, one of the three heat storage tanks 2 is connected to the front end of the connecting pipe 1, the second heat storage tank 2 is connected to the middle part of the connecting pipe 1, and the last heat storage tank 2 is connected to the rear end of the connecting pipe 1, so that the first heat exchange tubes 25 or the second heat exchange tubes 26 of the three heat storage tanks 2 form a series pipeline, and the exhaust gas or air passes through the three heat storage tanks 2 in sequence. In this embodiment, the phase-change metal liquid 24 in the front heat storage tank 2 of the three heat storage tanks 2 is a gallium-based alloy, the phase-change metal liquid 24 in the middle heat storage tank 2 is a lead-bismuth alloy, and the phase-change metal liquid 24 in the rear heat storage tank 2 is tin. Thus, the whole device includes three heat energy recovery and storage systems of different grades formed by different liquid metal-graphite medium heat storage units, gallium-based alloy, lead-bismuth alloy and tin three liquid metals, by using different thermal conductivity and different heat storage density of liquid metals to respectively recover high, medium and low grades of heat energy economically. When in use, the air valve 14, the first shut-off valve 251 and the second shut-off valve 261 corresponding to the three heat storage tanks 2 are opened respectively according to the grade of recovered heat energy, so that the exhaust gas or air can be controlled to enter the corresponding heat storage tank 2 for heat exchange. One, two or three heat storage tanks 2 can be selected for use.

[0027] like Figure 1 As shown, the data collection component 5 includes a temperature sensor 51, a pressure sensor 52 and a recorder. The temperature sensor 51 is arranged in the insulation layer 22 and abuts on the graphite block layer 23. The temperature sensor 51 adopts an existing thermocouple, and the recorder adopts an existing temperature data recorder. The temperature sensor 51 monitors the temperature in the heat storage tank 2 and sends the temperature data to the recorder for storage. The pressure sensor 52 adopts an existing PT series high-temperature melt pressure sensor. The sensor end can withstand a temperature of 80°C; the probe end can withstand a temperature of 400°C (the melting point of tin is 231°C, and the sensor meets the use requirements). The probe end of the pressure sensor 52 enters the phase-change metal liquid 24 to monitor the pressure state in the heat storage tank 2 in real time. When the pressure exceeds the set value, the external alarm device is automatically triggered and corresponding protection measures are taken, such as discharging pressure, starting the safety valve, etc., to prevent the system from overpressure and causing safety accidents, so as to achieve stable operation of the equipment.

[0028] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units, characterized in that: The invention comprises a connecting pipe (1) and a heat storage tank (2) connected to the connecting pipe (1), wherein one end of the connecting pipe (1) is an inlet end, the inlet end is connected to a first inlet pipe (11) and a second inlet pipe (12), and the other end of the connecting pipe (1) is an outlet end (13). The heat storage tank (2) comprises a shell (21), a heat-insulating layer (22) arranged in the shell (21), and a graphite block layer (23) arranged inside the heat-insulating layer (22), the graphite block layer (23) forming a receiving cavity, the receiving cavity receiving a phase-change metal liquid (24), the heat storage tank (2) being provided with a first heat exchange tube (25) for inserting into the phase-change metal liquid (24), the inlet and outlet of the first heat exchange tube (25) being both connected to the connecting pipe (1), and an air valve (14) being provided on the pipe section of the connecting pipe (1) between the inlet and outlet connection points of the first heat exchange tube (25).

2. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: The heat storage tank (2) is also provided with a second heat exchange tube (26) for inserting into the phase-change metal liquid (24), and the inlet and outlet of the second heat exchange tube (26) are both connected to the connecting tube (1).

3. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 2 is characterized in that: The first heat exchange tube (25) is a U-shaped tube, the second heat exchange tube (26) is a spiral tube, the inlet and outlet of the first heat exchange tube (25) are both provided with a first shut-off valve (251), and the inlet and outlet of the second heat exchange tube (26) are both provided with a second shut-off valve (261).

4. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 3 is characterized in that: The first heat exchange tube (25) has an expanded length of D1, the second heat exchange tube (26) has an expanded length of D2, and D2 is ≥ 1.5D1.

5. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: The first inlet pipe (11) is provided with a first regulating valve (111), the second inlet pipe (12) is provided with a second regulating valve (121), and the connecting pipe (1) is provided with a flow rate detector (15).

6. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: It also comprises a data collection component (5) connected to the heat storage tank (2), wherein the data collection component (5) comprises a temperature sensor (51) and a pressure sensor (52).

7. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: The heat storage tanks (2) are provided with more than two, and the phase-change metal liquid (24) is a gallium-based alloy, a lead-bismuth alloy or tin.

8. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: The heat storage tanks (2) are provided with three heat storage tanks (2); the phase change metal liquid (24) in the front heat storage tank (2) of the three heat storage tanks (2) is made of a gallium-based alloy, the phase change metal liquid (24) in the middle heat storage tank (2) is made of a lead-bismuth alloy, and the phase change metal liquid (24) in the rear heat storage tank (2) is made of tin.

9. The liquid metal-graphite heat storage device for waste heat recovery of large-scale heating units according to claim 1 is characterized in that: The graphite block layer (23) is formed by pressing and sintering graphite powder.

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