A system for recovering and reusing waste heat of graphitization furnace

Abstract

This invention discloses a waste heat recovery and reuse system for a graphitization furnace, comprising a graphitization furnace, a first waste heat utilization unit, a second waste heat utilization unit, and a water supply pipe. The first waste heat utilization unit includes an absorption heat pump system and a flue gas supply pipe, while the second waste heat utilization unit includes a furnace-side heat exchanger and a furnace-side return water supply pipe. This invention utilizes the high-temperature sensible heat released from the flue gas of the graphitization furnace as a driving heat source, based on an absorption heat pump system. Simultaneously, it recovers primary low-temperature waste heat from the furnace-side heat exchanger circuit to heat water in the feedwater system, and recovers secondary high-temperature waste heat from the furnace-side heat exchanger circuit to drive a steam turbine. This significantly reduces production energy consumption and improves the overall energy utilization rate.

Description

Technical Field

[0001] This invention relates to the field of graphitization furnace waste heat utilization technology, specifically a graphitization furnace waste heat recovery and reuse system. Background Technology

[0002] The graphitization furnace is a key high-temperature thermal equipment in the production of carbon materials, lithium battery anode materials, and special graphite products, with operating temperatures typically exceeding 2500℃. During graphitization, a large amount of electrical energy is converted into heat energy to achieve the ordered structure of the carbon material. However, the system inevitably generates a significant amount of waste heat, mainly consisting of two parts: first, the low-temperature radiative and convective heat lost from the furnace body to the environment through the insulation layer; second, the sensible heat carried by the high-temperature flue gas (typically 800–1200℃) directly discharged through the exhaust system; and third, the high-temperature residual heat accumulated in the furnace body and furnace chamber after production. Statistics show that the overall thermal efficiency of the graphitization process is generally low, with waste heat loss accounting for more than 30% of the total energy consumption.

[0003] Currently, the industry's methods for utilizing waste heat from graphitization furnaces are relatively simple and inefficient. Common practices include using flue gas waste heat to preheat combustion air or boiler feedwater, or installing fixed water-cooled coils outside the furnace to recover some heat dissipation. However, these methods have significant limitations: First, although the flue gas waste heat is high in temperature, if it is only used for low-temperature preheating, its high-quality thermal energy value is not fully utilized; second, the furnace body's heat dissipation is medium-low temperature waste heat (usually below 200℃), which is difficult to directly drive conventional thermal cycles and is often directly discarded; third, during the cooling stage of the graphitization furnace, a large amount of high-temperature stored heat (up to 1000℃ or higher) still exists inside the furnace, but due to the lack of an effective dynamic heat extraction mechanism, this high-grade thermal energy is often slowly dissipated through natural cooling, resulting in energy waste.

[0004] Furthermore, existing waste heat recovery systems are mostly statically designed and cannot adapt to the "periodic operation" process characteristics of graphitization furnaces—that is, alternating between high-temperature energized heating stages and natural / forced cooling stages after power outages. During the heating stage, the temperature of the furnace outer wall is relatively controllable, suitable for recovering heat dissipation from the insulation layer; while during the cooling stage, the furnace interior maintains extremely high temperatures, providing high-quality heat source conditions, suitable for power generation or steam production. Traditional stationary heat exchangers struggle to accommodate these two drastically different operating conditions, resulting in either low heat extraction efficiency or equipment susceptible to thermal shock damage.

[0005] In recent years, absorption heat pump technology has attracted attention in the field of industrial waste heat recovery due to its ability to utilize low-grade heat sources to drive and achieve a "temperature boost." However, research on its deep integration with graphitization furnace processes and the tiered utilization of flue gas waste heat, furnace body heat dissipation, and furnace heat storage remains lacking. Furthermore, how to automatically match the optimal waste heat utilization path at different production stages (e.g., using low-temperature heat to produce process hot water and high-temperature heat to drive steam turbine power generation) through intelligent switching mechanisms is also a current technical challenge. Therefore, there is an urgent need to develop a waste heat recovery and reuse system capable of full-cycle coverage, utilization at all temperature levels, and dynamic adaptation to the operating conditions of graphitization furnaces. Summary of the Invention

[0006] The purpose of this invention is to provide a waste heat recovery and reuse system for graphitization furnaces to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this disclosure provides a graphitization furnace waste heat recovery and reuse system, including a graphitization furnace, a first waste heat utilization unit, a second waste heat utilization unit, and a water conveying pipe; The first waste heat utilization unit includes an absorption heat pump system and a flue gas conveying pipe. The absorption heat pump system includes a generator, a condenser, an evaporator, and an absorber. The refrigerant outlet of the generator is connected to the refrigerant inlet of the condenser, the refrigerant outlet of the condenser is connected to the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator is connected to the refrigerant inlet of the absorber, the solution outlet of the generator is connected to the solution inlet of the absorber, and the solution outlet of the absorber is connected to the solution inlet of the generator. The flue gas conveying pipe includes a first flue gas branch pipe and a second flue gas branch pipe. The inlet of the first flue gas branch pipe is used to communicate with the exhaust port of the graphitization furnace, the outlet of the first flue gas branch pipe is connected to the flue gas inlet of the generator, and the inlet of the second flue gas branch pipe is connected to the flue gas outlet of the generator. The second waste heat utilization unit includes a furnace-side heat exchanger and a furnace-side return water conveying pipe. The furnace-side return water conveying pipe includes a primary furnace-side return water pipe and a secondary furnace-side return water pipe. The primary furnace-side return water pipe includes a first primary furnace-side return water branch pipe and a second primary furnace-side return water branch pipe. The inlet of the first primary furnace-side return water branch pipe is connected to the return water pipe of the furnace-side heat exchanger, and the outlet of the first primary furnace-side return water branch pipe is connected to the return water inlet of the evaporator. The inlet of the second primary furnace-side return water branch pipe is connected to the return water outlet of the evaporator, and the outlet of the second primary furnace-side return water branch pipe is used to connect to the return water pipe of the furnace-side heat exchanger. The secondary boiler-side return water pipe includes a first secondary boiler-side return water branch pipe and a second secondary boiler-side return water branch pipe. The inlet of the first secondary boiler-side return water branch pipe is connected to the return water pipe of the boiler-side heat exchanger, and the outlet of the first secondary boiler-side return water branch pipe is used to connect to the return water inlet of the steam turbine generator set. The inlet of the second secondary boiler-side return water branch pipe is connected to the return water outlet of the steam turbine generator set, and the outlet of the second secondary boiler-side return water branch pipe is used to connect to the return water pipe of the boiler-side heat exchanger. The water supply pipe includes a first water supply branch pipe and a second water supply branch pipe. The inlet of the first water supply branch pipe is used to connect with the water supply system, and the outlet of the first water supply branch pipe is connected to the water supply inlet of the condenser. The inlet of the second water supply branch pipe is connected to the water supply outlet of the condenser, and the outlet of the second water supply branch pipe is used to connect with the water outlet system.

[0008] Optionally, the first water supply branch pipe includes a first section and a second section. The inlet of the first section is used to communicate with the water supply system, the outlet of the first section is connected to the water supply inlet of the absorber, the inlet of the second section is connected to the water supply outlet of the absorber, and the outlet of the second section is connected to the water supply inlet of the condenser.

[0009] Optionally, the primary furnace side return water pipe further includes a third primary furnace side return water branch pipe, a fifth primary furnace side return water branch pipe, a first switch valve and a second switch valve, and the secondary furnace side return water pipe further includes a third secondary furnace side return water branch pipe, a fifth secondary furnace side return water branch pipe, a third switch valve and a fourth switch valve; The inlet of the third primary boiler-side return water branch pipe is connected to the return water pipe of the boiler-side heat exchanger, the outlet of the third primary boiler-side return water branch pipe is connected to the inlet of the first primary boiler-side return water branch pipe, the outlet of the second primary boiler-side return water branch pipe is connected to the inlet of the fifth primary boiler-side return water branch pipe, and the outlet of the fifth primary boiler-side return water branch pipe is connected to the return water pipe of the boiler-side heat exchanger. The first switch valve is installed on the third primary boiler-side return water branch pipe, and the second switch valve is installed on the fifth primary boiler-side return water branch pipe. The inlet of the third secondary boiler-side return water branch pipe is connected to the return water pipe of the boiler-side heat exchanger, the outlet of the third secondary boiler-side return water branch pipe is connected to the inlet of the first secondary boiler-side return water branch pipe, the outlet of the second secondary boiler-side return water branch pipe is connected to the inlet of the fifth secondary boiler-side return water branch pipe, the outlet of the fifth secondary boiler-side return water branch pipe is connected to the return water pipe of the boiler-side heat exchanger, the third switch valve is installed on the third secondary boiler-side return water branch pipe, and the fourth switch valve is installed on the fifth secondary boiler-side return water branch pipe.

[0010] Optionally, a first through hole is formed on the insulation layer of the graphitization furnace, and a second through hole is formed on the furnace core of the graphitization furnace, which communicates with the first through hole. The first through hole and the second through hole can together form a receiving cavity. The furnace-side heat exchanger includes a housing, a telescopic mechanism, a heat exchange end, and a return water pipe. The receiving cavity is used to accommodate the heat exchange end, and the return water pipe is installed inside the heat exchange end. The housing is installed on the outer wall of the furnace wall of the graphitization furnace. One end of the telescopic mechanism extends out of the furnace wall and is connected to the housing. The other end of the telescopic mechanism is provided with the heat exchange end. The telescopic mechanism can drive the heat exchange end to retract or extend out of the receiving cavity, so that the heat exchange end can switch between a primary heat exchange state and a secondary heat exchange state. In the first-stage heat extraction state, the heat extraction end retracts into the receiving cavity; in the second-stage heat extraction state, the heat extraction end extends out of the receiving cavity and is located inside the furnace.

[0011] Optionally, the waste heat utilization system of the thermal power plant further includes a first heat exchanger; The flue gas conveying pipe further includes a third flue gas branch pipe, a fourth flue gas branch pipe, a fifth flue gas branch pipe, a sixth flue gas branch pipe, and a fifth switching valve. The inlet of the third flue gas branch pipe is used to communicate with the exhaust port of the graphitization furnace. The outlet of the third flue gas branch pipe is connected to the inlet of the first flue gas branch pipe and the inlet of the fourth flue gas branch pipe. The outlet of the fourth flue gas branch pipe and the outlet of the second flue gas branch pipe are both connected to the inlet of the fifth flue gas branch pipe. The inlet of the fifth flue gas branch pipe is connected to the outlet of the second flue gas branch pipe. The outlet of the fifth flue gas branch pipe is connected to the flue gas inlet of the first heat exchanger. The inlet of the sixth flue gas branch pipe is connected to the flue gas outlet of the first heat exchanger. The fifth switching valve is disposed on the fourth flue gas branch pipe. The water delivery pipe also includes a third water delivery branch pipe and a fourth water delivery branch pipe. The inlet of the third water delivery branch pipe is connected to the outlet of the second water delivery branch pipe, and the outlet of the third water delivery branch pipe is connected to the water delivery inlet of the first heat exchanger. The inlet of the fourth water delivery branch pipe is connected to the water delivery outlet of the first heat exchanger, and the outlet of the fourth water delivery branch pipe is used to connect to the water outlet system.

[0012] Optionally, the water delivery pipe further includes a fifth water delivery branch pipe, a sixth water delivery branch pipe, a seventh water delivery branch pipe, a sixth switch valve, an eighth water delivery branch pipe, a ninth water delivery branch pipe, and a seventh switch valve; The inlet of the fifth water supply branch pipe is connected to the outlet of the second water supply branch pipe, the outlet of the fifth water supply branch pipe is connected to the inlet of the third water supply branch pipe and the inlet of the sixth water supply branch pipe, the outlet of the fourth water supply branch pipe and the outlet of the sixth water supply branch pipe are both connected to the inlet of the seventh water supply branch pipe, the outlet of the seventh water supply branch pipe is used to communicate with the water outlet system, and the sixth switch valve is installed on the sixth water supply branch pipe. The inlet of the eighth water supply branch pipe is used to connect with the water supply system. The outlet of the eighth water supply branch pipe is connected to the inlet of the first water supply branch pipe and the inlet of the ninth water supply branch pipe. The outlets of the second water supply branch pipe and the ninth water supply branch pipe are connected to the inlet of the third water supply branch pipe. The seventh switch valve is installed on the ninth water supply branch pipe.

[0013] Optionally, the absorption heat pump system further includes a second heat exchanger and a solution pump; The solution outlet of the generator is connected to the first solution inlet of the second heat exchanger, the first solution outlet of the second heat exchanger is connected to the solution inlet of the absorber, the solution outlet of the absorber is connected to the second solution inlet of the second heat exchanger via the solution pump, and the second solution outlet of the second heat exchanger is connected to the solution inlet of the generator.

[0014] Optionally, the absorption heat pump system further includes a throttling device; The refrigerant outlet of the condenser is connected to the refrigerant inlet of the evaporator via the throttling device.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: The graphitization furnace waste heat recovery and reuse system provided in this disclosure can be based on an absorption heat pump system, utilizing the high-temperature sensible heat released from the flue gas of the graphitization furnace as a driving heat source. Simultaneously, it recovers primary low-temperature waste heat from the furnace-side heat exchanger circuit to heat water in the feedwater system, and recovers secondary high-temperature waste heat from the furnace-side heat exchanger circuit to drive a steam turbine. This significantly reduces production energy consumption and improves the overall energy utilization rate.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of a graphitization furnace waste heat recovery and reuse system provided in an exemplary embodiment of this disclosure; Figure 2 This is a schematic diagram of the connection between a graphitization furnace and a furnace-side heat exchanger provided in an exemplary embodiment of this disclosure.

[0018] In the diagram: 10. Graphitization furnace; 11. Insulation layer; 12. Furnace core; 13. Furnace wall; 14. Receiving cavity; 141. First through hole; 142. Second through hole; 20. Generator; 21. Condenser; 22. Evaporator; 23. Absorber; 30. First flue gas branch pipe; 31. Second flue gas branch pipe; 32. Third flue gas branch pipe; 33. Fourth flue gas branch pipe; 34. Fifth flue gas branch pipe; 35. 36. Sixth flue gas branch pipe; 40. Fifth switch valve; 41. Furnace-side heat exchanger; 42. Casing; 43. Telescopic mechanism; 44. Heat exchange end; 50. Return water pipe; 50. First-stage furnace-side return water pipe; 501. First-stage furnace-side return water branch pipe; 502. Second-stage furnace-side return water branch pipe; 503. Third-stage furnace-side return water branch pipe; 504. Fifth-stage furnace-side return water branch pipe; 505. First switch valve; 506. 51. Second switch valve; 51. Secondary furnace side return water pipe; 511. First and second secondary furnace side return water branch pipe; 512. Second and second secondary furnace side return water branch pipe; 513. Third and second secondary furnace side return water branch pipe; 514. Fifth and second secondary furnace side return water branch pipe; 515. Third switch valve; 516. Fourth switch valve; 60. Steam turbine generator set; 70. First conveying water branch pipe; 701. First section; 702. Second section; 71. Second conveying water branch pipe; 72. Third conveying water branch pipe; 73. Fourth conveying water branch pipe; 74. Fifth conveying water branch pipe; 75. Sixth conveying water branch pipe; 751. Sixth switch valve; 76. Seventh conveying water branch pipe; 77. Eighth conveying water branch pipe; 78. Ninth conveying water branch pipe; 781. Seventh switch valve; 80. First heat exchanger; 81. Second heat exchanger; 82. Solution pump; 83. Throttling device. Detailed Implementation

[0019] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0020] In the description of this disclosure, it should be understood that the terms "upper," "lower," etc., indicate the orientation or positional relationship based on... Figure 1 The orientations shown in the drawings are defined solely for the convenience of describing this disclosure and for simplification, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or a specific orientation construction and operation. Therefore, they should not be construed as limitations on this disclosure. Furthermore, the terms "inner" and "outer" refer to the inner and outer contours of the corresponding structures. In addition, the terms "first," "second," etc., are only used to distinguish one element from another and do not have any sequential or importance.

[0021] In the description of this disclosure, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connect," "link," and "install" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0022] like Figures 1 to 2As shown, this disclosure provides a waste heat recovery and reuse system for a graphitization furnace, including a graphitization furnace 10, a first waste heat utilization unit, a second waste heat utilization unit, and a water delivery pipe. The first waste heat utilization unit includes an absorption heat pump system and a flue gas delivery pipe. The absorption heat pump system includes a generator 20, a condenser 21, an evaporator 22, and an absorber 23. The refrigerant outlet of the generator 20 is connected to the refrigerant inlet of the condenser 21, the refrigerant outlet of the condenser 21 is connected to the refrigerant inlet of the evaporator 22, the refrigerant outlet of the evaporator 22 is connected to the refrigerant inlet of the absorber 23, and the solution outlet of the generator 20 is connected to the solution inlet of the absorber 23. The solution outlet of absorber 23 is connected to the solution inlet of generator 20. The flue gas conveying pipe includes a first flue gas branch pipe 30 and a second flue gas branch pipe 31. The inlet of the first flue gas branch pipe 30 is connected to the exhaust port of graphitization furnace 10, and the outlet of the first flue gas branch pipe 30 is connected to the flue gas inlet of generator 20. The inlet of the second flue gas branch pipe 31 is connected to the flue gas outlet of generator 20. The second waste heat utilization unit includes a furnace-side heat exchanger 40 and a furnace-side return water conveying pipe. The furnace-side return water conveying pipe includes a primary furnace-side return water pipe 50 and a secondary furnace-side return water pipe 51. The primary furnace-side return water pipe 50 includes a first primary furnace-side return water branch pipe 501 and a second primary furnace-side return water branch pipe 502. 02. The inlet of the first-stage boiler-side return water branch pipe 501 is connected to the return water pipe 44 of the boiler-side heat exchanger 40, and the outlet of the first-stage boiler-side return water branch pipe 501 is connected to the return water inlet of the evaporator 22. The inlet of the second-stage boiler-side return water branch pipe 502 is connected to the return water outlet of the evaporator 22, and the outlet of the second-stage boiler-side return water branch pipe 502 is used to connect to the return water pipe 44 of the boiler-side heat exchanger 40. The second-stage boiler-side return water pipe 51 includes a first-stage boiler-side return water branch pipe 511 and a second-stage boiler-side return water branch pipe 512. The inlet of the first-stage boiler-side return water branch pipe 511 is connected to the return water pipe 44 of the boiler-side heat exchanger 40, and the outlet of the second-stage boiler-side return water branch pipe 511 is connected to the return water pipe 44 of the boiler-side heat exchanger 40. The outlet is used to connect to the return water inlet of the turbine generator set 60. The inlet of the second secondary boiler side return water branch pipe 512 is used to connect to the return water outlet of the turbine generator set 60. The outlet of the second secondary boiler side return water branch pipe 512 is used to connect to the return water pipe 44 of the boiler side heat exchanger 40. The water delivery pipe includes a first water delivery branch pipe 70 and a second water delivery branch pipe 71. The inlet of the first water delivery branch pipe 70 is used to connect to the water supply system. The outlet of the first water delivery branch pipe 70 is connected to the water delivery inlet of the condenser 21. The inlet of the second water delivery branch pipe 71 is connected to the water delivery outlet of the condenser 21. The outlet of the second water delivery branch pipe 71 is used to connect to the water outlet system.

[0023] In this system, high-temperature flue gas enters generator 20 through the first flue gas branch pipe 30, heating the binary solution and separating it into a concentrated solution and a vaporized refrigerant. The vaporized refrigerant enters condenser 21, releasing heat and condensing to heat the flowing feedwater into high-temperature process water. The condensed liquid refrigerant enters evaporator 22, absorbing the low-temperature waste heat from the return water in furnace-side heat exchanger 40 and vaporizing, achieving deep recovery of furnace waste heat. The generated vaporized refrigerant enters absorber 23, mixing with the concentrated solution discharged from generator 20 to regenerate a binary solution, which ultimately returns to generator 20, completing the closed-loop system cycle.

[0024] Furthermore, it should be noted that the furnace-side heat exchanger 40 has two operating states: primary heat exchange and secondary heat exchange, to adapt to different production stages of the graphitization furnace 10. When the graphitization furnace 10 is in a production cycle (i.e., the high-temperature energized stage), the heat exchange end 43 of the furnace-side heat exchanger 40 is located inside the insulation layer 11 to extract heat from the insulation layer 11 and recover the heat lost by the furnace body during the heating process. At this time, the primary furnace-side return water pipe 50 is put into operation, and the working fluid (return water) enters the evaporator 22 through the first primary furnace-side return water branch pipe 501 to absorb heat. After being heated, it returns to the furnace-side heat exchanger 40 through the second primary furnace-side return water branch pipe 502, forming a primary heat exchange cycle.

[0025] When the graphitization furnace 10 is in a cooling cycle (power-off and cooling phase), the furnace is powered off, and the furnace temperature gradually decreases. The heat-extracting end 43 of the furnace-side heat exchanger 40 extends into the furnace to directly extract heat from the high-temperature residual heat inside the furnace. At this time, the secondary furnace-side return water pipe 51 is in operation, and the working fluid (return water) flows through the return water inlet of the steam turbine generator set 60, using the residual heat in the furnace to generate steam to drive the steam turbine to do work. The heated working fluid returns to the furnace-side heat exchanger 40 through the second and second-stage furnace-side return water branch pipes 512, completing the secondary heat extraction cycle. In other words, the second waste heat utilization unit can not only recover the heat loss of the insulation layer 11 (primary heat extraction), but also recover the furnace body heat storage after production (secondary heat extraction), thus realizing the full-cycle, full-temperature-level waste heat utilization.

[0026] Through the above technical solution, the graphitization furnace waste heat recovery and reuse system provided in this disclosure can utilize the high-temperature sensible heat released from the flue gas of the graphitization furnace 10 as a driving heat source, based on an absorption heat pump system. Simultaneously, it recovers primary low-temperature waste heat from the furnace-side heat exchanger 40 circuit to heat water in the feedwater system, and recovers secondary high-temperature waste heat from the furnace-side heat exchanger 40 circuit to drive a steam turbine. This significantly reduces production energy consumption and improves the overall energy utilization rate.

[0027] As one implementation method, such as Figures 1 to 2As shown, the first water supply branch pipe 70 includes a first section 701 and a second section 702. The inlet of the first section 701 is used to connect with the water supply system, the outlet of the first section 701 is connected to the water supply inlet of the absorber 23, the inlet of the second section 702 is connected to the water supply outlet of the absorber 23, and the outlet of the second section 702 is connected to the water supply inlet of the condenser 21.

[0028] First stage heating (absorber 23 preheating): Low-temperature water from the water supply system first enters absorber 23 via the first section 701 water delivery branch pipe. Here, the water medium absorbs the heat released by the mixing of the solution in absorber 23, achieving an initial temperature rise, becoming preheated warm water.

[0029] Second stage heating (final heating of condenser 21): The preheated warm water flows out from absorber 23 and enters condenser 21 through the second section 702 water delivery branch pipe. Here, the water medium further absorbs the high-temperature heat released when the refrigerant vapor condenses, and is finally heated into high-temperature process water for use in processes outside the system.

[0030] This design can not only effectively reduce the heat loss of the system to the environment, but also increase the initial temperature of the feed water entering the condenser 21, thereby improving the thermal efficiency and economy of the entire waste heat recovery system.

[0031] As one implementation method, such as Figures 1 to 2As shown, the primary boiler-side return water pipe 50 also includes a third primary boiler-side return water branch pipe 503, a fifth primary boiler-side return water branch pipe 504, a first switching valve 505, and a second switching valve 506. The secondary boiler-side return water pipe 51 also includes a third secondary boiler-side return water branch pipe 513, a fifth secondary boiler-side return water branch pipe 514, a third switching valve 515, and a fourth switching valve 516. The inlet of the third primary boiler-side return water branch pipe 503 is connected to the return water pipe 44 of the boiler-side heat exchanger 40, and the outlet of the third primary boiler-side return water branch pipe 503 is connected to the inlet of the first primary boiler-side return water branch pipe 501. The outlet of the second primary boiler-side return water branch pipe 502 is connected to the inlet of the fifth primary boiler-side return water branch pipe 504, and the outlet of the fifth primary boiler-side return water branch pipe 504 is connected to the inlet of the boiler-side heat exchanger 40. The return water pipe 44 is connected. The first switch valve 505 is installed on the third primary boiler side return water branch pipe 503. The second switch valve 506 is installed on the fifth primary boiler side return water branch pipe 504. The inlet of the third and second secondary boiler side return water branch pipe 513 is connected to the return water pipe 44 of the boiler side heat exchanger 40. The outlet of the third and second secondary boiler side return water branch pipe 513 is connected to the inlet of the first and second secondary boiler side return water branch pipe 511. The outlet of the second and second secondary boiler side return water branch pipe 512 is connected to the inlet of the fifth and second secondary boiler side return water branch pipe 514. The outlet of the fifth and second secondary boiler side return water branch pipe 514 is connected to the return water pipe 44 of the boiler side heat exchanger 40. The third switch valve 515 is installed on the third and second secondary boiler side return water branch pipe 513. The fourth switch valve 516 is installed on the fifth and second secondary boiler side return water branch pipe 514.

[0032] The primary heat extraction mode (heat pump driven) can be as follows: the first switching valve 505 and the second switching valve 506 are opened simultaneously, while the third switching valve 515 and the fourth switching valve 516 are closed simultaneously. At this time, the primary circuit forms a closed loop. The working fluid flows out from the furnace-side heat exchanger 40, enters the evaporator 22 to absorb heat via the third primary furnace-side return water branch pipe 503 and the first switching valve 505, and then returns via the fifth primary furnace-side return water branch pipe 504 and the second switching valve 506. Simultaneously, because the third switching valve 515 and the fourth switching valve 516 are closed, the passage to the turbine generator set 60 is cut off. This ensures that during the production stage of the graphitization furnace 10, all the low-temperature waste heat emitted by the furnace body is directed to the absorption heat pump for the preparation of high-temperature process water, without any working fluid bypass loss.

[0033] The secondary heat extraction mode (power generation driven) can be as follows: the first switching valve 505 and the second switching valve 506 are closed simultaneously, and the third switching valve 515 and the fourth switching valve 516 are opened simultaneously. At this time, the primary circuit is completely blocked, and the working fluid cannot flow to the evaporator 22. The secondary circuit is open, and the working fluid flows out from the furnace-side heat exchanger 40, enters the turbine generator set 60 through the third secondary furnace-side return water branch pipe 513 and the third switching valve 515 to do work, and then returns through the fifth secondary furnace-side return water branch pipe 514 and the fourth switching valve 516. This state matches the cooling stage of the graphitization furnace 10, which allows the high-temperature heat storage energy in the furnace to be concentrated for driving the turbine to generate electricity, avoiding the diversion of heat by the low-temperature circuit, thereby ensuring power generation efficiency and steam quality.

[0034] As one implementation method, such as Figures 1 to 2 As shown, a first through hole 141 is formed on the insulation layer 11 of the graphitization furnace 10, and a second through hole 142 communicating with the first through hole 141 is formed on the furnace core 12 of the graphitization furnace 10. The first through hole 141 and the second through hole 142 can together form a receiving cavity 14. The furnace-side heat exchanger 40 includes a housing 41, a telescopic mechanism 42, a heat-receiving end 43, and a return water pipe 44. The receiving cavity 14 is used to accommodate the heat-receiving end 43, and the return water pipe 44 is installed inside the heat-receiving end 43. The housing 41 is installed inside the heat-receiving end 43. The outer wall of the furnace wall 13 of the graphitization furnace 10 has a telescopic mechanism 42. One end of the telescopic mechanism 42 extends out of the furnace wall 13 and is connected to the housing 41. The other end of the telescopic mechanism 42 is provided with a heat-receiving end 43. The telescopic mechanism 42 can drive the heat-receiving end 43 to retract or extend out of the receiving cavity 14, so that the heat-receiving end 43 can switch between a primary heat-receiving state and a secondary heat-receiving state. In the primary heat-receiving state, the heat-receiving end 43 retracts into the receiving cavity 14; in the secondary heat-receiving state, the heat-receiving end 43 extends out of the receiving cavity 14 and is located inside the furnace.

[0035] The first-level heat extraction state (retracted into the insulation layer 11) can be as follows: corresponding to the high-temperature energized production stage of the graphitization furnace 10, the telescopic mechanism 42 drives the heat extraction end 43 to completely retract into the receiving cavity 14 formed by the first and second through holes 142. At this time, the heat extraction end 43 is located inside the insulation layer 11, mainly absorbing the heat lost from the furnace body (i.e., the heat dissipation loss of the insulation layer 11). Since the heat extraction end 43 is not directly exposed to the extremely high temperature flame in the furnace, its working environment is relatively mild, which can effectively protect the heat extraction end 43 equipment from the thermal shock and erosion of extreme high temperature, extend its service life, and at the same time realize the recovery of heat dissipation during the production process.

[0036] The secondary heat extraction state (extending into the furnace chamber) can be as follows: corresponding to the cooling cycle (power-off cooling stage) of the graphitization furnace 10, the telescopic mechanism 42 pushes the heat extraction end 43 out of the receiving cavity 14 and directly into the furnace chamber of the graphitization furnace 10. At this time, the graphitization furnace 10 is not powered on, but a large amount of high-temperature stored heat still exists inside the furnace. The heat extraction end 43 extends directly into the furnace chamber, allowing it to come into zero-distance contact with the high-temperature furnace gas and furnace wall, directly extracting the high-temperature residual heat inside the furnace. This direct insertion method greatly improves the heat exchange efficiency and can utilize the high-temperature waste heat to generate high-quality steam, thereby driving a steam turbine to generate electricity.

[0037] As one implementation method, such as Figures 1 to 2 As shown, the waste heat utilization system of the thermal power plant also includes a first heat exchanger 80, and the flue gas conveying pipe includes a third flue gas branch pipe 32, a fourth flue gas branch pipe 33, a fifth flue gas branch pipe 34, a sixth flue gas branch pipe 35, and a fifth switching valve 36. The inlet of the third flue gas branch pipe 32 is connected to the exhaust port of the graphitization furnace 10, and the outlet of the third flue gas branch pipe 32 is connected to the inlet of the first flue gas branch pipe 30 and the inlet of the fourth flue gas branch pipe 33. The outlets of the fourth flue gas branch pipe 33 and the second flue gas branch pipe 31 are both connected to the inlet of the fifth flue gas branch pipe 34, and the inlet of the fifth flue gas branch pipe 34 is connected to the outlet of the second flue gas branch pipe 31. The outlet of the fifth flue gas branch pipe 34 is connected to the flue gas inlet of the first heat exchanger 80, the inlet of the sixth flue gas branch pipe 35 is connected to the flue gas outlet of the first heat exchanger 80, the fifth switch valve 36 is installed on the fourth flue gas branch pipe 33, and the water supply pipe also includes a third water supply branch pipe 72 and a fourth water supply branch pipe 73. The inlet of the third water supply branch pipe 72 is connected to the outlet of the second water supply branch pipe 71, the outlet of the third water supply branch pipe 72 is connected to the water supply inlet of the first heat exchanger 80, the inlet of the fourth water supply branch pipe 73 is connected to the water supply outlet of the first heat exchanger 80, and the outlet of the fourth water supply branch pipe 73 is used to connect to the water outlet system.

[0038] First, since the inlet of the third water delivery branch pipe 72 is connected after the second water delivery branch pipe 71 (typically from the outlet of the preheater or backheater), the water medium has already undergone preliminary heating, but has not yet reached the final temperature required by the process. Then, since the outlet of the third water delivery branch pipe 72 is connected to the water delivery inlet of the first heat exchanger 80, the waste heat released by the flue gas in the fifth flue gas branch pipe 34 can be used to further heat the preheated water (final heating). Finally, the final heated high-temperature water, connected to the water delivery outlet of the first heat exchanger 80, is responsible for delivering it to the outlet water system or directly to the user.

[0039] This design allows for deep coupling of flue gas waste heat recovery and feedwater heating, creating a closed-loop heat cascade utilization chain. This not only improves the overall energy utilization rate but also enhances the system's operational flexibility and controllability.

[0040] The first heat exchanger 80 can be a gas-liquid heat exchanger.

[0041] As one implementation method, such as Figures 1 to 2 As shown, the water delivery pipe also includes a fifth water delivery branch pipe 74, a sixth water delivery branch pipe 75, a seventh water delivery branch pipe 76, a sixth switch valve 751, an eighth water delivery branch pipe 77, a ninth water delivery branch pipe 78, and a seventh switch valve 781. The inlet of the fifth water delivery branch pipe 74 is connected to the outlet of the second water delivery branch pipe 71, and the outlet of the fifth water delivery branch pipe 74 is connected to the inlet of the third water delivery branch pipe 72 and the inlet of the sixth water delivery branch pipe 75. The outlets of the fourth water delivery branch pipe 73 and the sixth water delivery branch pipe 75 are both connected to the seventh water delivery branch pipe 78. The inlet of branch pipe 76 is connected, the outlet of the seventh water supply branch pipe 76 is used to connect with the water outlet system, the sixth switch valve 751 is installed on the sixth water supply branch pipe 75, the inlet of the eighth water supply branch pipe 77 is used to connect with the water supply system, the outlet of the eighth water supply branch pipe 77 is connected to the inlet of the first water supply branch pipe 70 and the inlet of the ninth water supply branch pipe 78, the outlet of the second water supply branch pipe 71 and the outlet of the ninth water supply branch pipe 78 are connected to the inlet of the third water supply branch pipe 72, and the seventh switch valve 781 is installed on the ninth water supply branch pipe 78.

[0042] Specifically, based on the sixth switch valve 751, since the water flow in the sixth water delivery branch pipe 75 has not undergone the heating process corresponding to the fourth water delivery branch pipe 73 (or has undergone a different thermal process), its temperature is usually lower than that of the water flow in the fourth water delivery branch pipe 73. By opening the sixth switch valve 751, the operator can control the flow rate ratio of the low-temperature bypass water. In this way, the low-temperature bypass water is mixed with the high-temperature main water in the seventh water delivery branch pipe 76, thereby regulating the final water temperature entering the outlet system and preventing the outlet water temperature from being too high.

[0043] Specifically, based on the seventh switch valve 781, the low-temperature water (cold source) in the water supply system can be used to regulate the water temperature entering the first heat exchanger 80. Specifically, by opening the seventh switch valve 781, the low-temperature raw water mixes with the high-temperature water from the condenser 21 at the inlet of the third delivery water branch pipe 72. This not only lowers the water temperature entering the first heat exchanger 80, preventing overheating or scaling, but also balances the system's heat load, ensuring the heat exchange process occurs at the optimal temperature difference.

[0044] The high-temperature protection mode allows for the simultaneous opening of the sixth switch valve 751 and the seventh switch valve 781 when the outlet water temperature is too high. A cold source (ninth water supply branch pipe 78) can be introduced at the inlet side to lower the intermediate circulating water temperature and reduce heat absorption. Bypass water (sixth water supply branch pipe 75) can be introduced at the outlet side to dilute the final outlet water temperature.

[0045] The maximum heating mode can be: when maximum heat recovery is required, the sixth switch valve 751 and the seventh switch valve 781 are closed. At this time, all water must be forced to flow through the absorber 23, condenser 21 and subsequent heat exchangers, without bypass diversion, to ensure that the working fluid absorbs as much waste heat as possible and enters the outlet water system at the highest temperature.

[0046] As one implementation method, such as Figures 1 to 2 As shown, the absorption heat pump system also includes a second heat exchanger 81 and a solution pump 82. The solution outlet of the generator 20 is connected to the first solution inlet of the second heat exchanger 81. The first solution outlet of the second heat exchanger 81 is connected to the solution inlet of the absorber 23. The solution outlet of the absorber 23 is connected to the second solution inlet of the second heat exchanger 81 via the solution pump 82. The second solution outlet of the second heat exchanger 81 is connected to the solution inlet of the generator 20.

[0047] The solution pump 82 can transport the dilute absorbent solution from the absorber 23 and the concentrated absorbent solution from the generator 20 to the second heat exchanger 81 for heat exchange. This increases the temperature of the dilute absorbent solution entering the generator 20 and decreases the temperature of the concentrated absorbent solution entering the absorber 23. This configuration is beneficial for improving heat utilization and unit operating efficiency.

[0048] The second heat exchanger 81 can be an internal circulation solution heat exchanger or a tubular solution heat exchanger; this disclosure does not impose any restrictions on this.

[0049] As one implementation method, such as Figures 1 to 2 As shown, the absorption heat pump system also includes a throttling device 83, through which the refrigerant outlet of the condenser 21 is connected to the refrigerant inlet of the evaporator 22.

[0050] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0051] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0052] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A system for recovering and reusing waste heat from a graphitization furnace, characterized in that, Includes a graphitization furnace (10), a first waste heat utilization unit, a second waste heat utilization unit, and a water conveying pipe; The first waste heat utilization unit includes an absorption heat pump system and a flue gas conveying pipe. The absorption heat pump system includes a generator (20), a condenser (21), an evaporator (22), and an absorber (23). The refrigerant outlet of the generator (20) is connected to the refrigerant inlet of the condenser (21), the refrigerant outlet of the condenser (21) is connected to the refrigerant inlet of the evaporator (22), the refrigerant outlet of the evaporator (22) is connected to the refrigerant inlet of the absorber (23), the solution outlet of the generator (20) is connected to the solution inlet of the absorber (23), and the solution outlet of the absorber (23) is connected to the solution inlet of the generator (20). The flue gas conveying pipe includes a first flue gas branch pipe (30) and a second flue gas branch pipe (31). The inlet of the first flue gas branch pipe (30) is used to communicate with the exhaust port of the graphitization furnace (10), the outlet of the first flue gas branch pipe (30) is connected to the flue gas inlet of the generator (20), and the inlet of the second flue gas branch pipe (31) is connected to the flue gas outlet of the generator (20). The second waste heat utilization unit includes a furnace-side heat exchanger (40) and a furnace-side return water conveying pipe. The furnace-side return water conveying pipe includes a primary furnace-side return water pipe (50) and a secondary furnace-side return water pipe (51). The primary furnace-side return water pipe (50) includes a first primary furnace-side return water branch pipe (501) and a second primary furnace-side return water branch pipe (502). The inlet of the first primary furnace-side return water branch pipe (501) is connected to the return water pipe (44) of the furnace-side heat exchanger (40). The outlet of the first primary furnace-side return water branch pipe (501) is connected to the return water inlet of the evaporator (22). The inlet of the second primary furnace-side return water branch pipe (502) is connected to the return water outlet of the evaporator (22). The outlet of the second primary furnace-side return water branch pipe (502) is used to connect to the return water pipe (44) of the furnace-side heat exchanger (40). The secondary furnace-side return water pipe (51) includes a first secondary furnace-side return water branch pipe (511) and a second secondary furnace-side return water branch pipe (512). The inlet of the first secondary furnace-side return water branch pipe (511) is connected to the return water pipe (44) of the furnace-side heat exchanger (40). The outlet of the first secondary furnace-side return water branch pipe (511) is used to connect to the return water inlet of the steam turbine generator set (60). The inlet of the second secondary furnace-side return water branch pipe (512) is connected to the return water outlet of the steam turbine generator set (60). The outlet of the second secondary furnace-side return water branch pipe (512) is used to connect to the return water pipe (44) of the furnace-side heat exchanger (40). The water supply pipe includes a first water supply branch pipe (70) and a second water supply branch pipe (71). The inlet of the first water supply branch pipe (70) is used to connect with the water supply system, the outlet of the first water supply branch pipe (70) is connected to the water supply inlet of the condenser (21), the inlet of the second water supply branch pipe (71) is connected to the water supply outlet of the condenser (21), and the outlet of the second water supply branch pipe (71) is used to connect with the water outlet system.

2. The graphitization furnace waste heat recovery and reuse system according to claim 1, characterized in that, The first water supply branch pipe (70) includes a first section (701) and a second section (702). The inlet of the first section (701) is used to communicate with the water supply system. The outlet of the first section (701) is connected to the water supply inlet of the absorber (23). The inlet of the second section (702) is connected to the water supply outlet of the absorber (23). The outlet of the second section (702) is connected to the water supply inlet of the condenser (21).

3. The graphitization furnace waste heat recovery and reuse system according to claim 2, characterized in that, The primary furnace side return water pipe (50) also includes a third primary furnace side return water branch pipe (503), a fifth primary furnace side return water branch pipe (504), a first switch valve (505), and a second switch valve (506). The secondary furnace side return water pipe (51) also includes a third secondary furnace side return water branch pipe (513), a fifth secondary furnace side return water branch pipe (514), a third switch valve (515), and a fourth switch valve (516). The inlet of the third primary boiler-side return water branch pipe (503) is connected to the return water pipe (44) of the boiler-side heat exchanger (40), the outlet of the third primary boiler-side return water branch pipe (503) is connected to the inlet of the first primary boiler-side return water branch pipe (501), the outlet of the second primary boiler-side return water branch pipe (502) is connected to the inlet of the fifth primary boiler-side return water branch pipe (504), the outlet of the fifth primary boiler-side return water branch pipe (504) is connected to the return water pipe (44) of the boiler-side heat exchanger (40), the first switch valve (505) is installed on the third primary boiler-side return water branch pipe (503), and the second switch valve (506) is installed on the fifth primary boiler-side return water branch pipe (504). The inlet of the third secondary boiler-side return water branch pipe (513) is connected to the return water pipe (44) of the boiler-side heat exchanger (40), the outlet of the third secondary boiler-side return water branch pipe (513) is connected to the inlet of the first secondary boiler-side return water branch pipe (511), the outlet of the second secondary boiler-side return water branch pipe (512) is connected to the inlet of the fifth secondary boiler-side return water branch pipe (514), the outlet of the fifth secondary boiler-side return water branch pipe (514) is connected to the return water pipe (44) of the boiler-side heat exchanger (40), the third switch valve (515) is installed on the third secondary boiler-side return water branch pipe (513), and the fourth switch valve (516) is installed on the fifth secondary boiler-side return water branch pipe (514).

4. The graphitization furnace waste heat recovery and reuse system according to claim 3, characterized in that, A first through hole (141) is formed on the insulation layer (11) of the graphitization furnace (10), and a second through hole (142) communicating with the first through hole (141) is formed on the furnace core (12) of the graphitization furnace (10). The first through hole (141) and the second through hole (142) can together form a receiving cavity (14). The furnace-side heat exchanger (40) includes a housing (41), a telescopic mechanism (42), a heat exchange end (43), and a return water pipe (44). The receiving cavity (14) is used to accommodate the heat exchange end (43). The return water pipe (44) is installed inside the heat exchange end (43). The housing (41) is installed on the outer wall of the furnace wall (13) of the graphitization furnace (10). One end of the telescopic mechanism (42) extends out of the furnace wall (13) and is connected to the housing (41). The other end of the telescopic mechanism (42) is provided with the heat exchange end (43). The telescopic mechanism (42) can drive the heat exchange end (43) to retract or extend from the receiving cavity (14) so ​​that the heat exchange end (43) can switch between a primary heat exchange state and a secondary heat exchange state. In the first-stage heat extraction state, the heat extraction end (43) retracts into the receiving cavity (14); in the second-stage heat extraction state, the heat extraction end (43) extends out of the receiving cavity (14) and is located inside the furnace.

5. The graphitization furnace waste heat recovery and reuse system according to claim 2, characterized in that, The waste heat utilization system of the thermal power plant also includes a first heat exchanger (80). The flue gas conveying pipe also includes a third flue gas branch pipe (32), a fourth flue gas branch pipe (33), a fifth flue gas branch pipe (34), a sixth flue gas branch pipe (35), and a fifth switching valve (36). The inlet of the third flue gas branch pipe (32) is connected to the exhaust port of the graphitization furnace (10), and the outlet of the third flue gas branch pipe (32) is connected to the inlet of the first flue gas branch pipe (30) and the inlet of the fourth flue gas branch pipe (33). The outlet of the fourth flue gas branch pipe (33) and the fifth switching valve (36) are connected to the exhaust port of the graphitization furnace (10). The outlet of the second flue gas branch pipe (31) is connected to the inlet of the fifth flue gas branch pipe (34), the inlet of the fifth flue gas branch pipe (34) is connected to the outlet of the second flue gas branch pipe (31), the outlet of the fifth flue gas branch pipe (34) is connected to the flue gas inlet of the first heat exchanger (80), the inlet of the sixth flue gas branch pipe (35) is connected to the flue gas outlet of the first heat exchanger (80), and the fifth switch valve (36) is installed on the fourth flue gas branch pipe (33). The water delivery pipe also includes a third water delivery branch pipe (72) and a fourth water delivery branch pipe (73). The inlet of the third water delivery branch pipe (72) is connected to the outlet of the second water delivery branch pipe (71), the outlet of the third water delivery branch pipe (72) is connected to the water delivery inlet of the first heat exchanger (80), the inlet of the fourth water delivery branch pipe (73) is connected to the water delivery outlet of the first heat exchanger (80), and the outlet of the fourth water delivery branch pipe (73) is used to communicate with the water outlet system.

6. The graphitization furnace waste heat recovery and reuse system according to claim 2, characterized in that, The water delivery pipe also includes a fifth water delivery branch pipe (74), a sixth water delivery branch pipe (75), a seventh water delivery branch pipe (76), a sixth switch valve (751), an eighth water delivery branch pipe (77), a ninth water delivery branch pipe (78), and a seventh switch valve (781). The inlet of the fifth water supply branch pipe (74) is connected to the outlet of the second water supply branch pipe (71), the outlet of the fifth water supply branch pipe (74) is connected to the inlet of the third water supply branch pipe (72) and the inlet of the sixth water supply branch pipe (75), the outlet of the fourth water supply branch pipe (73) and the outlet of the sixth water supply branch pipe (75) are both connected to the inlet of the seventh water supply branch pipe (76), the outlet of the seventh water supply branch pipe (76) is used to communicate with the water outlet system, and the sixth switch valve (751) is installed on the sixth water supply branch pipe (75); The inlet of the eighth water supply branch pipe (77) is used to connect with the water supply system. The outlet of the eighth water supply branch pipe (77) is connected to the inlet of the first water supply branch pipe (70) and the inlet of the ninth water supply branch pipe (78). The outlet of the second water supply branch pipe (71) and the outlet of the ninth water supply branch pipe (78) are connected to the inlet of the third water supply branch pipe (72). The seventh switch valve (781) is installed on the ninth water supply branch pipe (78).

7. The graphitization furnace waste heat recovery and reuse system according to claim 2, characterized in that, The absorption heat pump system also includes a second heat exchanger (81) and a solution pump (82). The solution outlet of the generator (20) is connected to the first solution inlet of the second heat exchanger (81), the first solution outlet of the second heat exchanger (81) is connected to the solution inlet of the absorber (23), the solution outlet of the absorber (23) is connected to the second solution inlet of the second heat exchanger (81) via the solution pump (82), and the second solution outlet of the second heat exchanger (81) is connected to the solution inlet of the generator (20).

8. The graphitization furnace waste heat recovery and reuse system according to claim 2, characterized in that, The absorption heat pump system also includes a throttling device (83). The refrigerant outlet of the condenser (21) is connected to the refrigerant inlet of the evaporator (22) via the throttling device (83).

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