Waste heat recovery device and method for graphitization furnace

Abstract

The invention discloses a graphitization furnace waste heat recovery device and method.The waste heat recovery device comprises a heat exchange coil and a storage bin, ceramic particles are stored in the storage bin, a jacketed heat exchanger is arranged outside the storage bin, and the heat exchange coil makes contact with a heat preservation layer at the top end of a graphitization furnace; one end of the heat exchange coil pipe is connected with the storage bin, the other end of the heat exchange coil pipe is connected with the cyclone separator through the junction station and the ascending pipe, the cyclone separator is communicated with the storage bin, and the lower end of the storage bin is connected with the fan through the main air supply pipe to introduce inert gas to control the circulation ratio of ceramic particles. According to the graphitization furnace waste heat recovery device and method, sensible heat in the cooling process of heat preservation materials or products can be fully recovered, the discharging time is shortened, and the technological productivity is improved.

Description

Technical Field

[0001] The present invention relates to a waste heat recovery device and method, and particularly to a waste heat recovery device and method for a graphitization furnace. Background Art

[0002] During the production process of a graphitization kiln, electrodes are required to heat the graphitization kiln. The highest temperature of the kiln can reach 3000 °C. After heating, it enters the cooling process. The current process is natural cooling. While cooling, materials are discharged. After the surface layer is cooled to below 500 °C, a suction method is used to discharge the cooled insulating materials or products. This process is repeated until the discharging is completed. According to the current process, it takes about 8 hours for the 15 cm thick surface layer material to be cooled to below 500 °C, and the discharging process for each kiln takes more than 20 days. Natural cooling severely limits the production rate of products. At the same time, the heat of this part is not effectively recovered and utilized, resulting in waste of resources. Due to the high temperature of the graphite kiln, the maximum working temperature of most materials is 1300 °C, which limits the use of many heat exchange methods. At the same time, in order to ensure that the quality of graphite products is not damaged, the implementation of direct contact heat exchange equipment is difficult and has many problems, while non-contact heat exchange methods have better application prospects. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a waste heat recovery device and method for a graphitization furnace, which can fully recover the sensible heat during the cooling process of insulating materials or products, shorten the discharging time, and improve the process productivity.

[0004] The technical solution adopted by the present invention to solve the above technical problem is to provide a waste heat recovery device for a graphitization furnace, including a heat exchange coil and a storage bin. Ceramic particles are stored in the storage bin. A jacketed heat exchanger is arranged outside the storage bin. The heat exchange coil is in contact with the insulation layer at the top of the graphitization furnace. One end of the heat exchange coil is connected to the storage bin, and the other end is connected to a cyclone separator through a confluence device, a riser pipe. The cyclone separator is communicated with the storage bin. The lower end of the storage bin is connected to a blower through a main air supply pipe to introduce inert gas to control the circulation ratio of the ceramic particles.

[0005] Further, the output port diameter of the confluence device is smaller than the input port diameter, and the ratio of the input port diameter to the output port diameter of the confluence device is 2 - 3.

[0006] Further, a gate valve is arranged at the lower end of the storage bin. The gate valve is connected to a J-shaped valve and forms a certain particle accumulation at the J-shaped valve. The J-shaped valve is connected to a diverter. The diverter and the heat exchange coil are flexibly connected through a corrugated hose.

[0007] Further, the heat exchange coil is provided with fins, and the fins of the heat exchange coil are fitted to the insulation layer at the top of the graphitization furnace.

[0008] In order to solve the above technical problems, the present invention also provides a method for recovering waste heat from a graphitization furnace. The waste heat recovery device for a graphitization furnace is used. The waste heat recovery method comprises the following steps: S1) the inert gas is transported into the air supply main pipe, and is divided into three paths in the air supply main pipe, namely the main air, the loosening air and the fluidizing air; S2) after the check valve at the upper end of the cyclone separator is opened, the gate valve at the upper end of the J-shaped valve is closed when the fan is not started, and the ceramic particles enter the silo to form a stacked state. After the silo is filled to a specified height, the gate valve is gradually opened after the feeding is stopped. A certain accumulation height is formed at the J-shaped valve; S3) Turn on the fan, and the inert gas envelops the ceramic particles and gradually forms a fluidized state in the pipeline. In the heat exchange coil area, the ceramic particles absorb the heat of the insulation layer and pass through the riser after being accelerated. After entering the cyclone separator, the inert gas is separated, and the ceramic particles fall into the silo below for accumulation and heat exchange. After continuous circulation, a self-balanced state is gradually formed; S4) The cooling water in the jacketed heat exchanger outside the storage silo adopts a bottom-in and top-out method. After entering, the normal temperature cooling water is heated into hot water / hot steam for secondary energy utilization.

[0009] Furthermore, the loosening air inlet of the J-shaped valve is located above the bottom of the J-shaped valve, with the side opening at the center of the pipe wall of the vertical pipe. The fluidizing air inlet is at the center of the bottom of the pipe wall of the horizontal pipe at the bottom of the J-shaped valve. The loosening air in the J-shaped valve blows away the ceramic particles accumulated in the pipe horizontally, and the fluidizing air blows away the ceramic particles accumulated in the pipe vertically.

[0010] Furthermore, the loosening air inlet of the J-shaped valve is 70 mm above the bottom of the J-shaped valve, the specified height of the silo added in step S2 is 1.5-2 m, and the stacking height is controlled not to be higher than the loosening air inlet.

[0011] Furthermore, the thermal conductivity of the ceramic particles is greater than 120 W / m·K, the particle size is 18-40 mesh, and the melting point is 2000-2250°C.

[0012] Furthermore, the ceramic particles stay in the storage bin for 1-5 minutes.

[0013] Furthermore, the inert gas is nitrogen, which is produced by a nitrogen generator.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the device and method for recovering waste heat from a graphitization furnace provided by the present invention, the heat exchange coil is in full contact with the insulation layer at the top of the graphitization furnace, the ceramic particles are transported by inert gas, and heat is exchanged with the insulation layer to quickly cool it down, thereby achieving an increase in production capacity, and the subsequent use of hot water or hot steam generated by the water-jacketed heat exchanger also contributes to environmental protection and energy saving, while improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1Schematic structural diagram of the waste heat recovery device for the graphitization furnace of the present invention; Figure 2a Schematic structural diagram of the heat exchange coil of the waste heat recovery device for the graphitization furnace of the present invention; Figure 2b Schematic connection diagram of the heat exchange coil of the waste heat recovery device for the graphitization furnace of the present invention; Figure 3a Schematic side view of the connection between the heat exchange coil and the main pipe in the waste heat recovery device for the graphitization furnace of the present invention; Figure 3b Schematic bottom view of the connection between the heat exchange coil and the main pipe in the waste heat recovery device for the graphitization furnace of the present invention.

[0016] In the figure, the markings are: 1, heat exchange coil; 2, first corrugated hose; 3, manifold; 4, riser pipe; 5, cyclone separator; 6, storage bin; 7, downcomer; 8, J-valve; 9, diverter; 10, second corrugated hose; 11, gate valve; 12, air supply main pipe; 13, fin. Detailed implementation manners

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] Figure 1 Schematic structural diagram of the waste heat recovery device for the graphitization furnace of the present invention.

[0019] Please refer to Figure 1, the waste heat recovery device for the graphitization furnace provided by the present invention includes a heat exchange coil 1, a confluent 3, a riser 4, a cyclone separator 5, a water jacket type storage bin 6, a downcomer 7, a J-valve 8, a diverter 9, a gate valve 11 and a main air supply pipe 12. One side of the heat exchange coil 1 is in full contact with the insulation layer at the top of the graphitization furnace. The other end of the heat exchange coil 1 is connected to the confluent 3 through a corrugated hose. The confluent 3 also serves the function of reducing the diameter. After the inert gas accelerates, it enters the riser 4. The riser 4 is connected to the cyclone separator 5. The cyclone separator 5 is communicated with the storage bin 6. A jacket type heat exchanger is arranged outside the storage bin 6. A gate valve 11 is arranged at the lower end of the storage bin 6. The gate valve 11 is connected to the J-valve 8. A certain amount of particle accumulation is formed at the J-valve 8. The circulation ratio of the particles is controlled by the loosening air and the fluidizing air. The J-valve 8 is connected to the diverter 9. The diverter 9 is then flexibly connected to the heat exchange coil 1 through a corrugated hose. The heat of the graphitization furnace is transferred to the ceramic particles through the heat exchange coil 1. After the heat replacement, the cooling rate of the upper insulation material layer of the graphitization furnace is accelerated. The inert gas carries the ceramic particles and converges into the confluent 3. After accelerating, it flows through the riser 4 and enters the cyclone separator 5 for solid-gas separation. The relatively high-temperature ceramic particles fall into the lower water jacket type storage bin 6 to form a particle accumulation layer with a certain height. The cooling water enters from the lower part of the jacket and exits from the upper part. After exchanging heat with the ceramic particles, hot water / thermal steam is produced. The cooled ceramic particles circulate in the pipe. The hot water or thermal steam recovers part of the heat. The present invention not only improves the product production capacity but also contributes to the energy conservation and environmental protection of the process flow.

[0020] To ensure that the confluent 3 plays a better role in reducing the diameter, the output port diameter of the confluent 3 is smaller than the input port diameter. Preferably, the diameter ratio ranges from 2 to 3, so that the inert gas accelerates and enters the riser 4. If the diameter ratio is too large, the lifting speed is too fast, which will cause serious wear at the elbow and reduce the service life of the pipeline. If the diameter ratio is small, the speed will be low, and the material cannot be fully lifted, resulting in material accumulation and pipeline blockage.

[0021] Refer to Figure 2a and Figure 2b , the heat exchange coil 1 is uniformly welded and arranged with fins 13. The confluent 3 and the heat exchange coil 1 are connected through a first corrugated hose 2, and the diverter 9 and the heat exchange coil 1 are connected through a second corrugated hose 10. Hoisting lock holes are arranged on the fins 13.

[0022] The heat exchange coil 1 with fins can be divided into several groups and selected according to the area. The preferred area of the top of the graphitization furnace in the embodiment of the present invention is 4×4 meters, and four groups of coils are arranged. At the same time, the hoisting moves the coils to other high-temperature positions, and subsequent processes such as material suction can be carried out in the cooled area.

[0023] Refer to Figure 3a and Figure 3bThere are many ways to connect the heat exchange coil 1 to the main pipe. This implementation case adopts a lotus-shaped arrangement. The pipe section gradually widens and narrows at the confluence outlet, and several inlets and outlets of the pipeline are arranged on the side with a larger area. On the one hand, the arrangement of the flow divergence and confluence plays a role in controlling the flow rate. The ceramic particles can be accelerated by 400% after flowing through the tapered pipe so that they have enough kinetic energy to enter the riser 4; on the other hand, the lotus-shaped arrangement can reduce local pressure loss and avoid the problem of particle accumulation at the bend and uneven distribution of particles in each branch pipe.

[0024] The present invention also provides a method for recovering waste heat from a graphitization furnace, comprising the following steps: S1) Inert gas nitrogen is generated by a nitrogen generator and transported into the air supply main pipe by a blower (not shown in the figure), where it is divided into three routes, namely main air, loose air and fluidizing air; S2) After the check valve at the upper end of the cyclone separator 5 is opened, and the fan is not started, close the upper gate valve of the J-shaped valve 8, and the ceramic particles enter the silo to form a pile state. After the silo is filled to the specified height, the height is determined by the physical properties of the material and the volume parameters of the silo. Preferably, the height range is 1.5-2m. If it is lower than the height, the silo pile pressure will be insufficient, causing gas blowby. The gas will not participate in the circulation and directly escape from the cyclone separator. After stopping the feeding, gradually open the gate valve 11. After a certain pile height is formed at the J-shaped valve 8, the pile height should not be higher than the loose air inlet, otherwise it will easily cause blockage. Turn on the fan, and the inert gas will gradually form a fluidized state in the pipeline with the ceramic particles. In the heat exchange coil area, the ceramic particles with good thermal conductivity absorb heat, cool the ten-centimeter insulation layer below the coil, and then pass through the riser 4 after speeding up. After entering the cyclone separator 5, the inert gas is separated, and the ceramic particles fall into the storage silo 6 below for piled heat exchange. After continuous circulation, a self-balanced state is gradually formed; S3) The cooling water of the jacketed heat exchanger outside the storage bin 6 enters from the bottom and exits from the top. After entering, the normal temperature cooling water is heated into hot water / hot steam, which improves the quality and is suitable for secondary energy utilization or steam power generation at the back end.

[0025] In step S1, the ceramic particles in the tube are transported by an inert gas (nitrogen). The inert gas is stable in nature, and even if a pipeline leak occurs in a high-temperature working environment, no safety accident will occur.

[0026] The inlet of the J-shaped valve's loosening air is 70 mm above the bottom of the J-shaped valve. This height is preferably the center position of the horizontal pipe section. If it is too high, the loosening air cannot blow the particles deposited at the bottom; if it is too low, it is easy to cause blockage of the air supply port. The side opening is at the center position of the wall of the vertical pipe. The inlet of the fluidizing air is at the center position of the bottom of the wall of the horizontal pipe at the bottom of the J-shaped valve. The loosening air and the fluidizing air in the J-shaped valve 8 blow the ceramic particles accumulated in the pipe from the horizontal and vertical directions respectively. The flow state of the ceramic particles is similar to the fluidization state of the particles in a fluidized bed, which is used to control the circulation ratio of the particles in the system. Using this method can improve the control accuracy by 10-20% compared with the conventional method. At the same time, compared with the gate valve, the J-shaped valve 8 has stronger pressure-bearing and load-bearing capabilities, which extends the service life of the front-end gate valve.

[0027] In step S2, the ceramic particles in the pipe are a non-metallic non-mineral product with high temperature resistance (1600 °C), high thermal conductivity (>120 W / m·K), and good wear resistance, such as silicon carbide material. The particle size is preferably 18-40 mesh. If the particle size is too small, the efficiency of the cyclone separator will decrease and the material loss will be serious. If it is too large, it is easy to cause the accumulation of materials in the coil due to the lack of power in gas conveying of the materials. The melting point is 2000-2250 °C, and it is a product with good thermal conductivity and appropriate market price.

[0028] When the temperature of the ceramic particles rises by 40 °C, the cooling rate of the insulating material with a thickness of 10 cm at the top of the insulation layer increases by 50%, effectively saving the product production cycle.

[0029] In step S3, the temperature rise on the water side of the jacketed heat exchange tube is determined by the water side flow rate and the residence time of the ceramic particles in the bin. It can be either domestic water or high-temperature medium-pressure steam for steam turbine power generation.

[0030] The present invention adopts a set of recyclable and highly efficient heat recovery method for the graphitization furnace. The surface insulation layer is cooled by the ceramic particles transported by pneumatic conveying, which speeds up the graphite feeding speed and realizes the improvement of the production capacity of graphite products. The ceramic particles heated up after heat absorption are heat-exchanged through a water-cooled jacket. The cooling water can be used as domestic hot water or hot steam after heat exchange, realizing the secondary utilization of heat.

[0031] Compared with the traditional graphitization furnace cooling method, the present invention has the following advantages: (1) The present invention transfers the heat of the graphitization furnace to the ceramic particles through the heat exchange coil. After the heat replacement, the cooling rate of the upper insulation layer of the graphitization furnace is accelerated, the product production capacity is improved, and the product production cycle is shortened.

[0032] (2) After the ceramic particles are transported by pneumatic conveying, they are separated by a cyclone separator and then heat-exchanged with a jacketed storage bin. The water in the water jacket can be heated to produce hot water or hot steam, and this part of the heat is effectively recovered and utilized, reducing resource waste and strengthening the green environmental protection concept of the process flow.

[0033] (3) During the cooling process of the traditional graphitization furnace, only natural convection heat dissipation is relied on, resulting in a slow cooling rate, which restricts the improvement of production capacity. Moreover, a large amount of heat is dissipated into the air and not effectively utilized, causing serious energy losses. In the present invention, however, ceramic particles with high temperature resistance, high thermal conductivity, and good wear resistance are circulated to carry away the heat of the insulation layer, providing a new solution for the traditional graphite material production and manufacturing industry in the field of energy conservation and emission reduction.

[0034] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the claims.

Claims

1. A waste heat recovery device for a graphitization furnace, characterized in that, It includes a heat exchange coil and a storage bin, wherein ceramic particles are stored in the storage bin, a jacketed heat exchanger is arranged outside the storage bin, the heat exchange coil is in contact with the insulation layer at the top of the graphitization furnace, one end of the heat exchange coil is connected to the storage bin, and the other end is connected to a cyclone separator via a confluence and a riser, the cyclone separator is communicated with the storage bin, and the lower end of the storage bin is connected to a fan via an air supply main pipe to introduce inert gas to control the circulation rate of the ceramic particles.

2. The waste heat recovery device of the graphitization furnace according to claim 1, wherein The diameter of the output port of the flow combiner is smaller than the diameter of the input port, and the ratio of the diameter of the input port to the diameter of the output port of the flow combiner is 2-3.

3. The waste heat recovery device of the graphitization furnace according to claim 1, characterized in that, A gate valve is arranged at the lower end of the storage bin, the gate valve is connected to the J-shaped valve and forms a certain amount of particle accumulation at the J-shaped valve, the J-shaped valve is connected to the diverter, and the diverter is flexibly connected to the heat exchange coil through a corrugated hose.

4. The waste heat recovery device of the graphitization furnace according to claim 1, characterized in that, The heat exchange coil is provided with fins, and the fins of the heat exchange coil are in contact with the thermal insulation layer at the top of the graphitization furnace.

5. A method for recovering waste heat from a graphitization furnace, which uses the waste heat recovery device for a graphitization furnace as described in claim 3, characterized in that, The waste heat recovery method comprises the following steps: S1) The inert gas is transported into the air supply main pipe and divided into three routes in the air supply main pipe, namely main air, loosening air and fluidizing air; S2) After the check valve at the upper end of the cyclone separator is opened, the gate valve at the upper end of the J-shaped valve is closed without starting the fan, and the ceramic particles enter the silo to form a pile state. After the silo is filled to a specified height, the feeding is stopped and the gate valve is gradually opened to form a certain pile height at the J-shaped valve; S3) Turn on the fan, and the inert gas envelops the ceramic particles and gradually forms a fluidized state in the pipeline. In the heat exchange coil area, the ceramic particles absorb the heat of the insulation layer and pass through the riser at an accelerated speed. After entering the cyclone separator, the inert gas is separated and the ceramic particles fall into the silo below for accumulation and heat exchange. After continuous circulation, a self-balanced state is gradually formed; S4) The cooling water in the jacketed heat exchanger outside the storage silo adopts a bottom-in and top-out method. After entering, the room temperature cooling water is heated into hot water / hot steam for secondary energy utilization.

6. The method for recovering waste heat of a graphitization furnace according to claim 5, wherein, The loosening air inlet of the J-shaped valve is located above the bottom of the J-shaped valve, and the side opening is at the center of the pipe wall of the vertical pipe. The fluidizing air inlet is at the center of the bottom of the pipe wall of the horizontal pipe at the bottom of the J-shaped valve. The loosening air in the J-shaped valve blows away the ceramic particles accumulated in the pipe horizontally, and the fluidizing air blows away the ceramic particles accumulated in the pipe vertically.

7. The method for recovering waste heat of a graphitization furnace according to claim 5, wherein, The loosening air inlet of the J-shaped valve is 70 mm above the bottom of the J-shaped valve. The specified height of the silo added in step S2 is 1.5-2 m, and the stacking height is controlled not to be higher than the loosening air inlet.

8. The method for recovering waste heat of a graphitization furnace according to claim 5, wherein, The thermal conductivity of the ceramic particles is greater than 120 W / m·K, the particle size is 18-40 meshes, and the melting point is 2000-2250°C.

9. The method for recovering waste heat from a graphitization furnace according to claim 5, characterized in that, The ceramic particles stay in the storage bin for 1 to 5 minutes.

10. The method for recovering waste heat of a graphitization furnace according to claim 5, wherein, The inert gas is nitrogen, which is produced by a nitrogen generator.

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