A waste heat recovery system for a graphitization furnace

Abstract

The present invention relates to a waste heat recovery and utilization system of a graphitization furnace, comprising a first-level heat extraction module and a second-level heat extraction module arranged along the inner circumference of the furnace wall of the graphitization furnace, wherein the inlet of the first-level heat extraction module is connected to the medium outlet of the evaporator in the first-level waste heat utilization unit, and the outlet of the first-level heat extraction module is connected to the medium inlet of the evaporator; the inlet of the second-level heat extraction module is connected to the medium outlet of the superheater in the second-level waste heat utilization unit, and the outlet of the second-level heat extraction module is connected to the medium inlet of the superheater, and the steam outlet of the superheater is connected to the steam turbine unit; the steam outlet of the steam turbine unit is connected to the condensate unit, and the outlet of the condensate unit is connected to the water inlet of the preheater in the third-level waste heat utilization unit, and the medium inlet of the preheater is connected to the flue gas collecting pipe at the top of the graphitization furnace. The waste heat recovery and utilization system provided by the present invention can not only actively cool the graphitization furnace, but also realize the efficient cascade utilization of waste heat.

Description

Technical Field

[0001] The invention relates to the field of waste heat recovery of a graphitization furnace, and in particular to a waste heat recovery and utilization system of a graphitization furnace. Background Art

[0002] Graphite is a high-quality raw material for producing electrodes, battery negative electrodes, diamonds, and metal smelting recarburizers. The atomic structure of non-graphite carbon changes at high temperatures and turns into graphite carbon with regular and orderly three-dimensional graphite arrangement, which is called graphitization. The graphitization process requires a high temperature environment, generally greater than 2000°C, and is usually achieved by electric heating in industry. At present, the Acheson graphitization furnace, the internal heat series graphitization furnace, and the grid box graphitization furnace have been put into practical use. Among them, the grid box furnace absorbs the characteristics of the traditional Acheson furnace and the internal heat series furnace, and further improves the technology. It has a large furnace load and low power consumption per unit product, and has been widely used in recent years. Currently, after the graphitization furnace completes the graphitization by power-on heating, it uses overall natural cooling to cool down. The finished product is cooled from 3000℃ to 500℃ oxidation critical point in the furnace core, and then to 150℃ before being taken out of the furnace. It usually takes 20 to 30 days, and the cooling time accounts for more than 90% of the entire production time. Natural cooling seriously restricts the production capacity of a single furnace.

[0003] Therefore, how to shorten the cooling time of the graphitization furnace and utilize the waste heat is the current research focus in the industry. For example, CN116336821A discloses a graphitization furnace progressive heat pipe heat extraction device and its intelligent control method. The heat extraction device used in this method is located at the top of the graphitization furnace, which not only affects the feeding, discharging and emergency handling of the graphitization furnace, but also has poor operability.

[0004] CN116242155A discloses an Acheson furnace with the function of extracting waste heat from the furnace core. In the Acheson furnace, cooling and preheating pipes are arranged on the resistor material and the furnace bottom, and cooling or preheating is performed by a trace oxygen gas. However, due to the small specific heat capacity and low heat transfer coefficient of the gas, the cooling and waste heat recovery capabilities are very limited.

[0005] CN115962658A discloses a rapid cooling and waste heat recovery device for a graphitization furnace. A heat exchange device is pre-installed in the insulation material layer, and the graphitization furnace is actively cooled by a heat exchange medium. However, the insulation protection of the heat exchange device when the furnace body is energized in the initial stage of graphitization is not considered, and the waste heat utilization rate is not high.

[0006] Therefore, how to quickly achieve active cooling of the graphitization furnace and realize the cascade recovery and utilization of waste heat is a technical problem that needs to be solved in this field. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a waste heat recovery system for a graphitization furnace. Compared with the prior art, the waste heat recovery system provided by the present invention can not only realize the active and rapid cooling of the graphitization furnace, but also realize the efficient step-by-step utilization of waste heat in different temperature ranges in the graphitization furnace.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a waste heat recovery system for a graphitization furnace, the waste heat recovery system comprising a graphitization furnace production unit, a primary waste heat utilization unit, a secondary waste heat utilization unit, a condensed water unit and a tertiary waste heat utilization unit;

[0010] A furnace wall is arranged around the graphitization furnace in the graphitization furnace production unit, a furnace core is arranged at the inner center of the graphitization furnace, and a primary heat extraction module and a secondary heat extraction module are arranged along the inner circumference of the furnace wall, the primary heat extraction module is arranged on a side close to the inner wall of the furnace wall, and the secondary heat extraction module is arranged on a side close to the furnace core;

[0011] The inlet of the first-level heat extraction module is connected to the medium outlet of the evaporator in the first-level waste heat utilization unit, and the outlet of the first-level heat extraction module is connected to the medium inlet of the evaporator;

[0012] The inlet of the secondary heat extraction module is connected to the medium outlet of the superheater in the secondary waste heat utilization unit, the outlet of the secondary heat extraction module is connected to the medium inlet of the superheater, and the steam outlet of the superheater is connected to the steam turbine unit;

[0013] The steam outlet of the steam turbine unit is connected to the condensate unit, the outlet of the condensate unit is connected to the water inlet of the preheater in the three-stage waste heat utilization unit, and the medium inlet of the preheater is connected to the flue gas collecting pipe on the top of the graphitization furnace.

[0014] On the one hand, the waste heat recovery and utilization system provided by the present invention can realize active rapid cooling of the graphitization furnace, that is, by setting a primary heat extraction module and a secondary heat extraction module to accelerate cooling from the side of the graphitization furnace, and at the same time, by sucking the flue gas at the top of the graphitization furnace, and collecting it through the flue gas collecting pipe as the medium of the preheater, thereby accelerating the heat dissipation of the top of the graphitization furnace, that is, cooling the graphitization furnace from the furnace side and the furnace top at the same time, thereby shortening the production cycle of graphite materials and greatly improving the unit time output of the graphitization furnace. On the other hand, the waste heat recovery and utilization system provided by the present invention can realize efficient cascade utilization of waste heat, that is, the recovered heat mainly includes three parts, namely, the heat absorbed by the primary heat extraction module near the furnace wall side, the heat absorbed by the secondary heat extraction module near the furnace core side, and the heat of the flue gas, respectively, through the evaporator in the primary waste heat utilization unit, the superheater in the secondary waste heat utilization unit, and the preheater in the tertiary waste heat utilization unit, the waste heat in different temperature ranges in the furnace is utilized in turn, thereby achieving cascade utilization of waste heat.

[0015] In the present invention, the furnace core is the part where the raw materials and the product graphite are placed. The operation mode of the graphitization furnace is intermittent operation. The production process is divided into four stages: loading, power-on heating, cooling, and discharging. These four stages are cyclically performed in sequence. In order to complete graphitization, the temperature of the furnace core needs to be raised to 3000°C during the heating stage. The temperature field distribution in the furnace is as follows: the furnace core temperature is the highest, and the temperature decreases linearly from the furnace core to the furnace wall.

[0016] Among them, since the evaporator requires a large amount of heat and the temperature does not need to be too high, the waste heat taken out of the first-level heat extraction module far away from the furnace core is used for evaporation of water in the evaporator, and the first-level heat extraction module is far away from the furnace core, the operating temperature is low, and the service life is long. The equipment and material selection can lower the standards and save costs; the superheater needs to superheat the steam to a higher temperature to improve the efficiency of the steam turbine unit, so the waste heat taken out of the second-level heat extraction module close to the furnace core is used for the superheater, and the second-level heat extraction module uses high-temperature resistant materials for the heat medium and equipment materials; the flue gas temperature at the top of the furnace is not high, and it is generally directly discharged and processed in the existing process, resulting in energy waste. The present invention can use the waste heat of the flue gas to preheat water, so as to achieve the purpose of recovering waste heat and saving energy.

[0017] In the present invention, there is no special limitation on the primary heat extraction module and the secondary heat extraction module, and they can be any structure or device for heat extraction in the art, for example, a serpentine coil structure with a cooling medium running inside, and the cooling medium can be, for example, heat transfer oil or molten salt. As a preferred technical solution, the cooling medium in the primary heat extraction module is preferably heat transfer oil, and the cooling medium in the secondary heat extraction module is preferably molten salt.

[0018] Preferably, the graphitization furnace is filled with a thermal insulation layer, and the furnace core, the primary heat extraction module and the secondary heat extraction module are all buried in the thermal insulation layer.

[0019] Preferably, the primary heat extraction module is arranged in an independent space formed by a furnace wall and an insulating protection module.

[0020] Preferably, the secondary heat extraction module is arranged in an independent space formed by the insulation protection module.

[0021] Preferably, the independent space is filled with a thermally conductive filler.

[0022] Preferably, the graphitization furnace production unit includes at least one graphitization furnace, for example, 1, 2 or 3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, each of the graphitization furnaces is provided with at least one primary heat extraction module, for example, 1, 2 or 3, but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the primary heat extraction modules are close to the inner wall of the furnace wall and arranged in rows along the length direction.

[0025] Preferably, each of the graphitization furnaces is provided with at least one secondary heat extraction module, for example, 1, 2 or 3, but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the secondary heat extraction modules are close to the furnace core and arranged in rows along the length direction.

[0027] In the present invention, the “arranged in rows along the length direction” refers to arranged in rows along the length direction of the graphitization furnace.

[0028] In the present invention, the graphitization furnace production unit can be provided with a plurality of graphitization furnaces for parallel and alternating operation, and the plurality of graphitization furnaces can share a set of waste heat recovery and utilization system. When a graphitization furnace is stopped for loading and there is no waste heat recovery, the other graphitization furnaces can still be in operation, and the relative stability of the heat extraction of the system can be maintained, thereby maintaining the smooth operation of the steam turbine unit. The parallel and alternating operation of the plurality of graphitization furnaces can be completed by opening and closing the control valve.

[0029] Preferably, the medium outlet of the evaporator is connected to the primary heat extraction module via the primary heat extraction module inlet manifold.

[0030] Preferably, the outlet of the primary heat extraction module is connected to the medium inlet of the evaporator via the primary heat extraction module outlet manifold.

[0031] Preferably, the medium outlet of the superheater is connected to the secondary heat extraction module via the secondary heat extraction module inlet manifold.

[0032] Preferably, the outlet of the secondary heat extraction module is connected to the medium inlet of the superheater via the secondary heat extraction module outlet collecting pipe.

[0033] In the present invention, the "connection" includes direct connection or indirect connection. As a preferred technical solution, when the primary heat extraction module is indirectly connected to the evaporator or the secondary heat extraction module is indirectly connected to the superheater, it is preferred to indirectly connect through the primary heat extraction module inlet manifold, the primary heat extraction module outlet manifold, the secondary heat extraction module inlet manifold and the secondary heat extraction module outlet manifold, etc., which can optimize the structural setting and reduce the material investment cost.

[0034] Preferably, the first-level waste heat utilization unit includes an evaporator and a steam drum; the inlet of the first-level heat extraction module is connected to the tube-side outlet of the evaporator, the outlet of the first-level heat extraction module is connected to the tube-side inlet of the evaporator, the shell-side outlet of the evaporator is connected to the steam drum, and the shell-side inlet of the evaporator is connected to the bottom water outlet of the steam drum.

[0035] In the present invention, the cooling medium flows in the first-level heat extraction module, and the high-temperature heat of the furnace core is transferred from the inside to the outside through the insulation layer, the insulation protection module and the heat-conducting filler in sequence to the cooling medium of the first-level heat extraction module in the form of heat conduction. After the cooling medium is heated, it flows out of the first-level heat extraction module, taking the heat out of the graphitization furnace, thereby accelerating the cooling of the furnace core. After the heated cooling medium enters the evaporator, it exchanges heat with the water in the shell of the evaporator, evaporates part of the water, and at the same time the temperature of the cooling medium is reduced, and then it continues to enter the first-level heat extraction module to extract heat.

[0036] The present invention arranges the shell side inlet of the evaporator to be connected with the bottom water outlet of the steam drum, so that the water in the steam drum can enter the evaporator under the action of gravity, and the water in the evaporator is evaporated by the medium from the primary heat extraction module to form a steam-water mixture; the present invention arranges the shell side outlet of the evaporator to be connected with the steam drum, because the density of the steam-water mixture is smaller than that of pure water, the steam-water mixture returns to the steam drum under the push of the density difference, completes the steam-water separation in the steam drum, and then the steam flows out from the top of the steam drum.

[0037] In the present invention, the cooling medium runs through the tube side in the evaporator, the medium inlet of the evaporator is the tube side inlet, and the medium outlet is the tube side outlet; water and steam run through the shell side in the evaporator.

[0038] Preferably, the secondary waste heat utilization unit includes a superheater and a steam turbine unit; the inlet of the secondary heat extraction module is connected to the tube side outlet of the superheater, the outlet of the secondary heat extraction module is connected to the tube side inlet of the superheater, the shell side inlet of the superheater is connected to the steam outlet of the steam drum, and the shell side outlet of the superheater is connected to the steam turbine unit.

[0039] In the present invention, the cooling medium flows in the secondary heat extraction module, and the high temperature heat of the furnace core is transferred from the inside to the outside through the insulation layer, the insulation protection module and the heat conductive filler in sequence to the cooling medium of the secondary heat extraction module in the form of heat conduction. After the cooling medium is heated, it flows out of the secondary heat extraction module, taking the heat out of the graphitization furnace, thereby accelerating the cooling of the furnace core. Since the secondary heat extraction module is closer to the furnace core, the temperature of the cooling medium flowing out of the secondary heat extraction module is higher than that of the cooling medium flowing out of the primary heat extraction module. The cooling medium flowing out of the secondary heat extraction module enters the superheater, superheats the steam in the superheater shell, and reduces the temperature of the cooling medium itself, and continues to enter the secondary heat extraction module for heat extraction.

[0040] In the present invention, the shell side inlet of the superheater is connected to the steam outlet of the steam drum, so that the steam flowing out of the steam drum is superheated by the medium from the secondary heat extraction module in the superheater, and then the superheated steam enters the steam turbine unit to perform work. The steam turbine can drive the generator to generate electricity, and can also drive the operation of machinery such as a compressor or a pump.

[0041] In the present invention, the cooling medium runs through the tube side in the superheater, the medium inlet of the superheater is the tube side inlet, and the medium outlet is the tube side outlet; the steam runs through the shell side in the superheater.

[0042] Preferably, the three-stage waste heat utilization unit includes a filter, an induced draft fan and a preheater; the inlet of the filter is connected to the flue gas collecting pipe; the outlet of the filter is connected to the medium inlet of the preheater via the induced draft fan; the medium outlet of the preheater is connected to the purification and desulfurization pipeline; the water outlet of the preheater is connected to the steam drum.

[0043] In the present invention, the "connection" includes direct connection or indirect connection. As a preferred technical solution, when the medium inlet of the preheater is indirectly connected to the flue gas collecting pipe at the top of the graphitization furnace, it is preferred to connect the flue gas collecting pipe to the medium inlet of the preheater through a filter and an induced draft fan in sequence, that is, the hot flue gas at the top of the graphitization furnace is collected through the flue gas collecting pipe under the suction action of the induced draft fan, filtered out dust through the filter and transported by the induced draft fan, and then enters the shell side of the preheater to preheat the water in the preheater that is about to enter the steam drum, and the preheated water is sent to the steam drum. The flue gas with a lowered temperature after preheating is sent to the purification and desulfurization section and discharged after purification.

[0044] In the present invention, the flue gas flows through the shell side in the preheater, and the water flows through the tube side in the preheater.

[0045] Preferably, the condensate unit comprises a condenser, a condensate pump, a deaerator and a feed water pump which are connected in sequence; the inlet of the condenser is connected to the steam outlet of the steam turbine unit; the outlet of the feed water pump is connected to the water inlet of the preheater.

[0046] In the present invention, the condenser, condensate pump, deaerator, feed water pump, preheater and steam drum are connected in sequence through water pipes. The condensate from the condenser is sent to the deaerator for deoxygenation through the condensate pump. The make-up water of the deaerator is generally room temperature water, which is then sent to the preheater through the feed water pump and preheated by the flue gas.

[0047] Preferably, the medium inlet of the condenser is connected to a cooling tower via a circulating water pump; and the medium outlet of the condenser is connected to a cooling tower.

[0048] In the present invention, the temperature and pressure of the steam that has done work drop significantly, and it is cooled by circulating water in the condenser to become condensed water. The condensed water is sent to the deaerator through the condensate pump. At the same time, the circulating water temperature rises and enters the cooling tower to be cooled by natural air cooling or mechanical fan. Then, it continues to enter the condenser under the action of the circulating water pump to cool the steam.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) In the waste heat recovery system provided by the present invention, the cooling of the graphitization furnace can be accelerated from the side by providing a primary heat extraction module and a secondary heat extraction module, and the heat dissipation of the top of the graphitization furnace can be accelerated by sucking the flue gas from the top of the graphitization furnace. That is, the waste heat recovery system provided by the present invention accelerates the cooling of the graphitization furnace from both the furnace side and the furnace top, thereby effectively shortening the production cycle of graphite materials and greatly improving the unit time output of the graphitization furnace.

[0051] (2) In the waste heat recovery and utilization system provided by the present invention, by setting a primary waste heat utilization unit, a secondary waste heat utilization unit and a tertiary waste heat utilization unit, the waste heat in different temperature ranges can be efficiently utilized in a step-by-step manner through an evaporator, a superheater and a preheater.

[0052] (3) In the waste heat recovery and utilization system provided by the present invention, the first-level heat extraction module is far away from the furnace core, has a lower operating temperature and a longer service life, and the material selection standards for the equipment and the insulation protection module can be appropriately lowered, thereby saving material costs; since the second-level heat extraction module is close to the furnace core, the heat extraction medium and the equipment material are made of materials that are more resistant to high temperatures. In this way, through the stepped configuration, the waste heat is recovered and the process requirements are met, the overall cost of the system is reduced, and the effect of optimizing the system is achieved.

[0053] (4) The waste heat recovery system provided by the present invention can support multiple graphitization furnaces to operate alternately in parallel. Even if the graphitization furnaces are operated intermittently, the heat extraction can still be maintained relatively stable, thereby ensuring the continuous and stable operation of the steam turbine unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic structural diagram of a waste heat recovery system for a graphitization furnace according to Example 1 of the present invention;

[0055] Figure 2 It is a schematic diagram of the top view of the arrangement of the primary heat extraction module and the secondary heat extraction module in the graphitization furnace described in Example 1 of the present invention;

[0056] Figure 3 This is a schematic diagram of the parallel alternating operation of the graphitization furnaces in Example 2 of the present invention;

[0057] Among them, 1-graphitization furnace; 1-1 furnace wall; 1-2 insulation layer; 1-3 furnace core; 1-4 furnace top; 1-5 flue gas collecting pipe;

[0058] 2-insulation protection module; 3-primary heat extraction module; 4-secondary heat extraction module; 5-primary heat extraction module inlet manifold; 6-primary heat extraction module outlet manifold; 7-secondary heat extraction module inlet manifold; 8-secondary heat extraction module outlet manifold; 9-preheater; 10-steam drum; 11-evaporator; 12-superheater; 13-steam turbine unit; 14-condenser; 15-condensate pump; 16-deaerator; 17-feed water pump; 18-circulating water pump; 19-cooling tower; 20-filter; 21-induced draft fan; 22-thermal conductive filler; 23-control valve. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0060] Example 1

[0061] This embodiment provides a waste heat recovery system for a graphitization furnace, such as Figure 1 As shown, the waste heat recovery and utilization system includes a graphitization furnace production unit, a primary waste heat utilization unit, a secondary waste heat utilization unit, a condensed water unit and a tertiary waste heat utilization unit;

[0062] A furnace wall 1-1 is arranged circumferentially of the graphitization furnace 1 in the graphitization furnace production unit, a furnace core 1-3 is arranged at the inner center of the graphitization furnace 1, a primary heat extraction module 3 and a secondary heat extraction module 4 are arranged along the inner circumference of the furnace wall 1-1, the primary heat extraction module 3 is arranged on a side close to the inner wall of the furnace wall 1-1, the secondary heat extraction module 4 is arranged on a side close to the furnace core 1-3, the graphitization furnace 1 is filled with a thermal insulation layer 1-2, the furnace core 1-3, the primary heat extraction module 3 and the secondary heat extraction module 4 are all buried in the thermal insulation layer 1-2, the primary heat extraction module 3 is arranged in an independent space formed by the furnace wall 1-1 and the insulating protection module 2, the secondary heat extraction module 4 is arranged in an independent space formed by the insulating protection module 2, and the independent space is filled with a thermal conductive filler 22; Figure 2As shown, the graphitization furnace 1 is provided with 4 primary heat extraction modules 3 and 4 secondary heat extraction modules 4. The primary heat extraction modules 3 are close to the inner wall of the furnace wall 1-1 and arranged in a row along the length direction of the graphitization furnace 1. The secondary heat extraction modules 4 are close to the furnace core 1-3 and arranged in a row along the length direction of the graphitization furnace 1.

[0063] The primary waste heat utilization unit includes an evaporator 11 and a steam drum 10. The inlet of the primary heat extraction module 3 is connected to the tube side outlet of the evaporator 11 via the primary heat extraction module inlet manifold 5. The outlet of the primary heat extraction module 3 is connected to the tube side inlet of the evaporator 11 via the primary heat extraction module outlet manifold 6. The shell side outlet of the evaporator 11 is connected to the steam drum 10. The shell side inlet of the evaporator 11 is connected to the bottom water outlet of the steam drum 10.

[0064] The secondary waste heat utilization unit includes a superheater 12 and a steam turbine unit 13. The inlet of the secondary heat extraction module 4 is connected to the tube side outlet of the superheater 12 via the secondary heat extraction module inlet manifold 7, the outlet of the secondary heat extraction module 4 is connected to the tube side inlet of the superheater 12 via the secondary heat extraction module outlet manifold 8, the shell side inlet of the superheater 12 is connected to the steam outlet of the steam drum 10, and the shell side outlet of the superheater 12 is connected to the steam turbine unit 13;

[0065] The three-stage waste heat utilization unit includes a filter 20, an induced draft fan 21 and a preheater 9, the inlet of the filter 20 is connected to the flue gas manifold 1-5, the outlet of the filter 20 is connected to the medium inlet of the preheater 9 through the induced draft fan 21, the medium outlet of the preheater 9 is connected to the purification and desulfurization pipeline, and the water outlet of the preheater 9 is connected to the steam drum 10;

[0066] The condensate unit includes a condenser 14, a condensate pump 15, a deaerator 16 and a feed pump 17 which are connected in sequence. The inlet of the condenser 14 is connected to the steam outlet of the steam turbine unit 13, the outlet of the feed pump 17 is connected to the water inlet of the preheater 9, the medium inlet of the condenser 14 is connected to the cooling tower 19 via a circulating water pump 18, and the medium outlet of the condenser 14 is connected to the cooling tower 19.

[0067] The operation process of the waste heat recovery system provided in this embodiment is as follows:

[0068] The operation mode of the graphitization furnace 1 is intermittent operation, and the production process is divided into four stages: loading, power-on heating, cooling, and discharging. When the graphitization furnace 1 needs to cool down, the high-temperature heat of the furnace core 1-3 is transferred from the inside to the outside through the insulation layer 1-2, the insulation protection module 2, and the heat-conducting filler 22 in turn to the cooling medium of the primary heat extraction module 3 and the secondary heat extraction module 4 in the form of heat conduction;

[0069] After the cooling medium is heated up, the cooling medium in the primary heat extraction module 3 flows into the tube side of the evaporator 11 through the primary heat extraction module outlet manifold 6, exchanges heat with the water in the shell side of the evaporator 11, partially evaporates the water and reduces the temperature of the cooling medium, and the cooling medium continues to enter the primary heat extraction module 3 through the primary heat extraction module inlet manifold 5 to extract heat, and the water in the evaporator 11 is partially evaporated to form a steam-water mixture, which returns to the steam drum 10 driven by the density difference and completes the steam-water separation in the steam drum 10, and then flows from the steam drum 10 into the superheater 12;

[0070] The cooling medium in the secondary heat extraction module 4 flows into the superheater 12 through the secondary heat extraction module outlet manifold 8, superheating the steam in the shell of the superheater 12 while reducing the temperature of the cooling medium itself, and then continues to enter the secondary heat extraction module 4 through the secondary heat extraction module inlet manifold 7 to extract heat. The superheated steam in the superheater 12 enters the steam turbine unit 13 to perform work. The steam turbine can drive the generator to generate electricity, and can also drive the running machinery such as a compressor or a pump.

[0071] After doing work, the temperature and pressure of the steam drop significantly, and it is cooled by circulating water in the condenser 14 to become condensed water. The condensed water is sent to the deaerator 16 through the condensate pump 15. At the same time, the circulating water temperature rises and enters the cooling tower 19 to be cooled by natural wind cooling or mechanical fan. Then, it continues to enter the condenser 14 to cool the steam under the action of the circulating water pump 18. The condensed water and the deaerator 16 make-up water are deoxygenated in the deaerator 16, and then sent to the preheater 9 through the feed water pump 17;

[0072] The hot flue gas at the furnace top 1-4 of the graphitization furnace 1 is collected through the flue gas collecting pipe 1-5 under the suction action of the induced draft fan 21, filtered out dust through the filter 20 and transported into the shell side of the preheater 9 by the induced draft fan 21, and the water in the preheater 9 that is about to enter the steam drum 10 is preheated, and the preheated water is sent to the steam drum 10. The flue gas with a lowered temperature after preheating is sent to the purification and desulfurization section and discharged after purification.

[0073] Example 2

[0074] This embodiment provides a waste heat recovery system for a graphitization furnace, which is different from Embodiment 1 only in that the graphitization furnace production unit includes three graphitization furnaces;

[0075] The schematic diagram of the parallel alternating operation of the three graphitization furnaces is as follows: Figure 3 As shown, control valves 23 are respectively provided between the medium outlet of the evaporator 11 and the first-stage heat extraction module inlet manifold, between the first-stage heat extraction module inlet manifold and the first-stage heat extraction module, between the medium inlet of the evaporator 11 and the first-stage heat extraction module outlet manifold, and between the first-stage heat extraction module outlet manifold and the first-stage heat extraction module;

[0076] Control valves 23 are respectively provided between the medium outlet of the superheater 12 and the secondary heat extraction module inlet manifold, between the secondary heat extraction module inlet manifold and the secondary heat extraction module, between the medium inlet of the superheater 12 and the secondary heat extraction module outlet manifold, and between the secondary heat extraction module outlet manifold and the secondary heat extraction module;

[0077] The flue gas collecting pipe of each graphitization furnace 1 is connected to the filter 20 through a control valve 23 , the outlet of the filter 20 is connected to the induced draft fan 21 , and the outlet of the induced draft fan 21 is connected to the medium inlet of the preheater 9 .

[0078] The waste heat recovery system provided in this embodiment can support the parallel alternating operation of multiple graphitization furnaces. Even if the graphitization furnaces are operated intermittently, the heat extraction can still be maintained relatively stable, thereby ensuring the continuous and stable operation of the steam turbine unit.

[0079] Comparative Example 1

[0080] This comparative example provides a waste heat recovery system for a graphitization furnace, which is different from Example 2 in that no primary heat extraction module is provided, and the internal heat medium of the evaporator is heated externally.

[0081] Comparative Example 2

[0082] This comparative example provides a waste heat recovery system for a graphitization furnace, which is different from Example 2 in that no secondary heat extraction module is provided, and the internal heat medium of the superheater is supplied with external heat.

[0083] Comparative Example 3

[0084] This comparative example provides a waste heat recovery system for a graphitization furnace, which is different from Example 2 in that the preheater does not use the flue gas from the flue gas collecting pipe as the heat medium, the heat medium of the preheater uses external heating, and the flue gas collecting pipe is emptied.

[0085] The cooling effect and waste heat utilization effect of the graphitization furnace in the waste heat recovery and utilization system described in Examples 1-2 and Comparative Examples 1-3 were evaluated, and the results are shown in Table 1.

[0086] Table 1

[0087] Waste heat utilization / (MW) Cooling time reduction ratio / (%) Example 1 1.2～1.8 25～40 Embodiment 2 (three furnaces in parallel) 3.6～4.8 25～40 Comparative Example 1 (three furnaces in parallel) 1.0～1.3 7～11 Comparative Example 2 (three furnaces in parallel) 3.0～4.0 21～33 Comparative Example 3 (three furnaces in parallel) 3.2～4.3 23～35

[0088] From the data in Table 1, we can see the following points:

[0089] (1) It can be seen from the data of Examples 1-2 that the waste heat recovery system provided by the present invention can effectively shorten the cooling time by 25-40% compared with the cooling time of a conventional graphitization furnace of 28-50 days, that is, accelerate the cooling of the graphitization furnace; at the same time, it has a higher waste heat utilization amount. When the graphitization furnace production unit adopts one graphitization furnace to operate, the waste heat utilization amount can reach 1.2-1.8 MW. When three graphitization furnaces are operated alternately in parallel, the waste heat utilization amount can reach 3.6-4.8 MW, that is, it can effectively realize the waste heat utilization.

[0090] (2) Comprehensively comparing the data of Example 2 and Comparative Examples 1-3, it can be seen that the amount of waste heat utilization and the ratio of cooling time reduction in Example 2 are both higher than those in Comparative Examples 1-3. It can be seen that, on the one hand, the present invention can accelerate the cooling of the graphitization furnace by synergistically cooling the furnace side and the furnace top of the graphitization furnace; on the other hand, by setting up three-stage waste heat utilization, it can effectively realize the cascade utilization of waste heat while accelerating cooling.

[0091] In summary, the waste heat recovery system provided by the present invention can not only realize the active rapid cooling of the graphitization furnace, but also realize the efficient step-by-step utilization of waste heat in different temperature ranges in the graphitization furnace.

[0092] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A waste heat recovery system for a graphitization furnace, characterized in that: The waste heat recovery and utilization system includes a graphitization furnace production unit, a primary waste heat utilization unit, a secondary waste heat utilization unit, a condensed water unit and a tertiary waste heat utilization unit; A furnace wall is arranged around the graphitization furnace in the graphitization furnace production unit, a furnace core is arranged at the inner center of the graphitization furnace, and a primary heat extraction module and a secondary heat extraction module are arranged along the inner circumference of the furnace wall, the primary heat extraction module is arranged on a side close to the inner wall of the furnace wall, and the secondary heat extraction module is arranged on a side close to the furnace core; The inlet of the first-level heat extraction module is connected to the medium outlet of the evaporator in the first-level waste heat utilization unit, and the outlet of the first-level heat extraction module is connected to the medium inlet of the evaporator; The inlet of the secondary heat extraction module is connected to the medium outlet of the superheater in the secondary waste heat utilization unit, the outlet of the secondary heat extraction module is connected to the medium inlet of the superheater, and the steam outlet of the superheater is connected to the steam turbine unit; The steam outlet of the steam turbine unit is connected to the condensate unit, the outlet of the condensate unit is connected to the water inlet of the preheater in the three-stage waste heat utilization unit, and the medium inlet of the preheater is connected to the flue gas collecting pipe on the top of the graphitization furnace.

2. The waste heat recovery system according to claim 1, characterized in that: The graphitization furnace is filled with a heat-insulating layer, and the furnace core, the primary heat-extracting module and the secondary heat-extracting module are all buried in the heat-insulating layer.

3. The waste heat recovery system according to claim 1, characterized in that: The primary heat extraction module is arranged in an independent space formed by the furnace wall and the insulation protection module.

4. The waste heat recovery system according to claim 1, characterized in that: The secondary heat extraction module is arranged in an independent space formed by the insulation protection module.

5. The waste heat recovery system according to claim 3 or 4, characterized in that: The independent space is filled with a thermally conductive filler.

6. The waste heat recovery system according to claim 1, characterized in that: The graphitization furnace production unit includes at least one graphitization furnace.

7. The waste heat recovery system according to claim 1, characterized in that: At least one primary heat extraction module is arranged in each graphitization furnace.

8. The waste heat recovery system according to claim 1, characterized in that: The primary heat extraction modules are close to the inner wall of the furnace wall and are arranged in rows along the length direction.

9. The waste heat recovery system according to claim 1, characterized in that: At least one secondary heat extraction module is arranged in each graphitization furnace.

10. The waste heat recovery system according to claim 1, characterized in that: The secondary heat extraction modules are close to the furnace core and arranged in rows along the length direction.

11. The waste heat recovery system according to claim 1, characterized in that: The medium outlet of the evaporator is connected to the primary heat extraction module via the primary heat extraction module inlet manifold.

12. The waste heat recovery system according to claim 1, characterized in that: The outlet of the first-stage heat extraction module is connected to the medium inlet of the evaporator through the first-stage heat extraction module outlet collecting pipe.

13. The waste heat recovery system according to claim 1, characterized in that: The medium outlet of the superheater is connected to the secondary heat extraction module via the secondary heat extraction module inlet manifold.

14. The waste heat recovery system according to claim 1, characterized in that: The outlet of the secondary heat extraction module is connected to the medium inlet of the superheater via the secondary heat extraction module outlet collecting pipe.

15. The waste heat recovery system according to claim 1, characterized in that: The primary waste heat utilization unit includes an evaporator and a steam drum; The inlet of the first-level heat extraction module is connected to the tube-side outlet of the evaporator, the outlet of the first-level heat extraction module is connected to the tube-side inlet of the evaporator, the shell-side outlet of the evaporator is connected to the steam drum, and the shell-side inlet of the evaporator is connected to the bottom water outlet of the steam drum.

16. The waste heat recovery system according to claim 1, characterized in that: The secondary waste heat utilization unit includes a superheater and a steam turbine unit; The inlet of the secondary heat extraction module is connected to the tube side outlet of the superheater, the outlet of the secondary heat extraction module is connected to the tube side inlet of the superheater, the shell side inlet of the superheater is connected to the steam outlet of the steam drum, and the shell side outlet of the superheater is connected to the steam turbine unit.

17. The waste heat recovery system according to claim 1, characterized in that: The three-stage waste heat utilization unit includes a filter, an induced draft fan and a preheater; The inlet of the filter is connected to the smoke collecting pipe; The outlet of the filter is connected to the medium inlet of the preheater via an induced draft fan; The medium outlet of the preheater is connected to the purification and desulfurization pipeline; The water outlet of the preheater is connected to the steam drum.

18. The waste heat recovery system according to claim 1, characterized in that: The condensate unit comprises a condenser, a condensate pump, a deaerator and a feed water pump which are connected in sequence; The inlet of the condenser is connected to the steam outlet of the steam turbine unit; The outlet of the water feed pump is connected to the water inlet of the preheater.

19. The waste heat recovery system according to claim 18, characterized in that: The medium inlet of the condenser is connected to the cooling tower via a circulating water pump; The medium outlet of the condenser is connected to a cooling tower.

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