Waste heat recovery system and method for aluminum electrolysis plant

Abstract

The invention discloses a waste heat recovery system and method for an aluminum electrolysis plant, relates to the technical field of aluminum electrolysis, and can improve the aluminum electrolysis heat recovery utilization rate. According to the waste heat recovery system for the aluminum electrolysis plant, a smoke heat exchanger is arranged on a smoke exhaust pipeline of an aluminum electrolysis cell; the first oil-water heat exchanger is arranged in an air compression station; a gas outlet end of the air compression station is communicated with an aluminum electrolysis cell blanking cylinder; the outlet end of the circulating pump station is respectively communicated with the inlet end of the first oil-water heat exchange waterway channel and the inlet end of the flue gas heat exchanger; the inlet end of the first conveying pipeline is respectively communicated with the waterway outlet end of the first oil-water heat exchanger and the outlet end of the flue gas heat exchanger; the side wall heat exchanger is arranged on the outer side wall of the aluminum electrolysis cell; the water channel inlet end of the second heat exchanger communicates with the outlet end of the first conveying pipeline, the oil channel inlet end of the second oil-water heat exchanger communicates with the oil channel outlet end of the side wall heat exchanger, and the water channel outlet end of the second oil-water heat exchanger communicates with the evaporator inlet end of the power generation device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum electrolysis, and in particular to an aluminum electrolysis plant waste heat recovery system and method. BACKGROUND

[0002] In the aluminum electrolysis production process, the waste heat generated by the electrolytic cell accounts for a large proportion of total fuel consumption, and a large amount of waste heat has a recovery potential. If this waste heat is directly discharged, not only will it cause a huge waste of energy, but also will cause thermal pollution to the environment. At present, waste heat recovery for power generation is an effective way to achieve energy saving and emission reduction. However, in the prior art, the waste heat recovery rate of the waste heat recovery system is low, which leads to insufficient energy recovery rate and easy energy waste. SUMMARY

[0003] The embodiments of the present application provide an aluminum electrolysis plant waste heat recovery system and method, which can improve the aluminum electrolysis waste heat recovery utilization rate and avoid energy waste.

[0004] In a first aspect, the embodiments of the present application provide an aluminum electrolysis plant waste heat recovery system, comprising:

[0005] A flue gas heat exchanger is arranged in the exhaust gas pipeline of the aluminum electrolytic cell.

[0006] A first oil-water heat exchanger is arranged in the air compression station, and a gas outlet end of the air compression station is in communication with a blanking gas cylinder of the aluminum electrolytic cell.

[0007] A circulating pump station, and an outlet end of the circulating pump station is in communication with an inlet end of a water passage of the first oil-water heat exchanger and an inlet end of the flue gas heat exchanger, respectively.

[0008] A first conveying pipeline, and an inlet end of the first conveying pipeline is in communication with an outlet end of the water passage of the first oil-water heat exchanger and an outlet end of the flue gas heat exchanger, respectively.

[0009] A side wall heat exchanger is arranged on the outer side wall of the aluminum electrolytic cell.

[0010] A second oil-water heat exchanger, an inlet end of a water passage of the second heat exchanger is in communication with an outlet end of the first conveying pipeline, an inlet end of an oil passage of the second oil-water heat exchanger is in communication with an outlet end of an oil passage of the side wall heat exchanger, and an outlet end of the water passage of the second oil-water heat exchanger is in communication with an inlet end of an evaporator of a power generation device.

[0011] In some embodiments, the aluminum electrolysis plant waste heat recovery system further comprises:

[0012] A circulating oil pump is arranged between the oil passages of the side wall heat exchanger.

[0013] A side wall heat exchange loop comprising the side wall heat exchanger, the circulating oil pump and the second oil-water heat exchanger in communication with each other.

[0014] In some embodiments, the aluminum electrolysis plant waste heat recovery system further comprises:

[0015] a storage device, an inlet end of a storage pipeline of the storage device being in communication with an outlet end of the second conveying pipeline, and an outlet end of the storage pipeline of the storage device being in communication with an inlet end of the circulating pump station; and / or,

[0016] the outlet end of the storage pipeline of the storage device being in communication with an inlet end of the second oil-water heat exchanger.

[0017] In some embodiments, the aluminum electrolysis plant waste heat recovery system further comprises:

[0018] a first heat exchange loop comprising the circulating pump station, the first oil-water heat exchanger, the second oil-water heat exchanger and the condenser of the power generation device in communication with each other;

[0019] a second heat exchange loop comprising the circulating pump station, the first oil-water heat exchanger and the storage device in communication with each other.

[0020] In some embodiments, the storage device is provided with a temperature sensor on a side close to the first conveying pipeline, the temperature sensor being used to detect the temperature of the flowing medium in the first conveying pipeline;

[0021] a first valve is provided between the inlet end of the storage pipeline and the temperature sensor;

[0022] a second valve is provided between the outlet end of the storage pipeline and the second oil-water heat exchanger;

[0023] a third valve is provided between the outlet end of the storage pipeline and the circulating pump station;

[0024] wherein, when the temperature sensor detects that the temperature of the flowing medium in the first conveying pipeline is greater than a first preset temperature, the first valve and the third valve are opened, and the second valve is closed;

[0025] when the temperature sensor detects that the temperature of the flowing medium in the first conveying pipeline is less than a second preset temperature, the first valve and the second valve are opened, and the third valve is closed.

[0026] In some embodiments, the power generation device further comprises a turbine, a generator, a condenser and a working medium pump;

[0027] The outlet end of the evaporator is connected with the turbine, and the gas in the evaporator is used to drive the turbine to work to drive the generator to generate electricity.

[0028] The generator is connected with the condenser, the condenser is connected with the working medium pump, the condenser is used to cool the low-pressure working medium generated after the generator generates electricity, and the working medium pump is used to deliver the cooled low-pressure working medium to the condenser.

[0029] In some embodiments, the aluminum electrolysis plant waste heat recovery system further comprises:

[0030] A cooling device in communication with the condenser of the power generation device and the second oil-water heat exchanger of the air compression station, respectively;

[0031] A first cooling circuit comprising the cooling device and the oil circuit of the air compression station in communication with each other;

[0032] A second cooling circuit comprising the cooling device and the condenser in communication with each other.

[0033] In a second aspect, the embodiment of the present application provides an aluminum electrolysis plant waste heat recovery method applied to the aluminum electrolysis plant waste heat recovery system of the first aspect, and the aluminum electrolysis plant waste heat recovery method comprises the following steps:

[0034] Receiving a heat recovery instruction;

[0035] According to the heat recovery instruction, the circulating pump station and the power generation device are started, the flow medium in the circulating pump station is merged into the first transmission pipeline via the first oil-water heat exchanger and the flue gas heat exchanger, respectively, and the flow medium output from the first transmission pipeline flows into the evaporator of the power generation device through the second oil-water heat exchanger;

[0036] The oil circuit passage of the first oil-water heat exchanger is in communication with the oil pipeline of the air compression station, and the oil circuit passage inlet end of the second oil-water heat exchanger is in communication with the oil circuit passage outlet end of the side wall heat exchanger.

[0037] In some embodiments, the aluminum electrolysis plant waste heat recovery method further comprises:

[0038] According to the heat recovery instruction, the evaporator, the turbine, the generator, the condenser and the working medium pump are controlled to start, the evaporator evaporates the liquid input by the second oil-water heat exchanger to form high-pressure working medium, and the turbine works under the action of the high-pressure working medium to drive the generator to output electric energy.

[0039] In some embodiments, the aluminum electrolysis plant waste heat recovery method further comprises:

[0040] According to the heat recovery instruction, the temperature sensor detects the temperature of the flowing medium in the first transmission pipeline, and in the case that the temperature of the flowing medium in the first transmission pipeline is greater than the first preset temperature, the first valve and the third valve are opened, the second valve is closed, and the flowing medium in the first transmission pipeline is controlled to flow into the energy storage device; or,

[0041] In the case that the temperature of the flowing medium in the first transmission pipeline is less than the second preset temperature, the first valve and the second valve are opened, the third valve is closed, and the flowing medium in the first transmission pipeline is controlled to flow into the second oil-water heat exchanger.

[0042] The aluminum electrolysis plant waste heat recovery system and method provided by the embodiment of the present application can preliminarily recover the heat generated by flue gas and the waste heat generated by the air compression station by delivering the flowing medium of the circulating pump station to the flue gas heat exchange device, the first oil-water heat exchanger and the flue gas heat exchanger, and then deliver the preliminarily recovered heat to the second oil-water heat exchanger to exchange heat with the side wall heat exchanger to complete the second heat recovery, and deliver the second recovered heat to the power generation device to provide high-temperature steam for the power generation device to drive the power generation device to generate electricity. Compared with the traditional heat recovery that only recovers the heat of flue gas or side wall, the present application also collects the waste heat generated by the air compression station, and comprehensively recovers the heat of the aluminum electrolysis cell itself and the related equipment of the aluminum electrolysis to generate electricity, thereby improving the heat recovery utilization rate of the aluminum electrolysis plant and avoiding energy waste. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A schematic structural diagram of the aluminum electrolysis plant waste heat recovery system provided by the embodiment of the present application is shown in the figure.

[0044] Figure 2 A schematic flow chart of the aluminum electrolysis plant waste heat recovery method provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0045] In order to better understand the technical solutions provided by the embodiments of the present application, the technical solutions of the embodiments of the present application will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solutions of the embodiments of the present application, and are not limitations of the technical solutions of the present application. In the case of no conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0046] In this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element. The terms "two or more" and "two or more than two" include both two and more than two entities.

[0047] In the aluminum electrolysis production process, the waste heat generated by the electrolytic cell accounts for a large proportion of the total fuel consumption, and a large amount of waste heat has recovery potential. At the same time, the air compressor station matched therewith also generates waste heat in the form of high-temperature lubricating oil during operation. If these waste heats are directly discharged, not only a great waste of energy will be caused, but also thermal pollution to the environment will be caused. At present, waste heat recovery power generation is an effective way to achieve energy saving and emission reduction. However, in the prior art, the waste heat recovery rate of the waste heat recovery system is low, which leads to insufficient energy recovery rate and easy energy waste.

[0048] Therefore, the embodiments of the present application provide an aluminum electrolysis plant waste heat recovery system for recovering waste heat of an aluminum electrolysis cell and related equipment of the aluminum electrolysis cell. The waste heat of the aluminum electrolysis cell mainly comes from heat generated by flue gas of the aluminum electrolysis cell and heat generated by a side wall of the aluminum electrolysis cell. The waste heat of the related equipment of the aluminum electrolysis cell mainly comes from an air compression station for providing compressed air for a discharging device of the aluminum electrolysis cell. The compressed air generated by the air compression station is transmitted to a discharging cylinder of the aluminum electrolysis cell through an outlet end of the air compression station to drive the discharging cylinder of the aluminum electrolysis cell to lift and complete discharging of the aluminum electrolysis. In the process of generating the compressed air, the oil temperature in an oil circuit of the air compression station is increased, and a large amount of high-temperature waste heat is generated.

[0049] Figure 1 A schematic structural diagram of the aluminum electrolysis plant waste heat recovery system provided by the embodiments of the present application is shown in FIG. 1. As shown in the figure, Figure 1As shown, the waste heat recovery system of the aluminum electrolysis plant comprises a flue gas heat exchanger 1, a first oil-water heat exchanger 5, a circulating pump station 14, a first conveying pipeline 16, a side wall heat exchanger 2 and a second oil-water heat exchanger 3. The flue gas heat exchanger 1 can be installed in the flue gas pipeline of the aluminum electrolysis cell, and the flue gas heat exchanger 1 is provided with a water passage and a flue gas passage, and the water passage is sleeved around the flue gas passage. The side wall heat exchanger 2 is arranged on the outer side wall of the cell shell of the aluminum electrolysis cell, and the side wall heat exchanger 2 is provided with an oil passage. The first oil-water heat exchanger 5 and the second oil-water heat exchanger 3 are both provided with an oil passage and a water passage, which can be two nested cylindrical pipelines, and the oil passage is sleeved outside the water passage. The oil passage and the water passage can be two rectangular cuboid passages arranged in close contact, and heat conduction is carried out through the contact surface in close contact to exchange heat between the oil passage and the water passage.

[0050] For example, referring to Figure 1 The outlet end of the circulating pump station 14 is respectively communicated with the inlet end of the water passage of the first oil-water heat exchanger 5 and the water passage in the flue gas heat exchanger 1. The oil passage of the first oil-water heat exchanger 5 is communicated with the oil passage of the air compression station 4. The outlet end of the water passage of the first oil-water heat exchanger 5 and the outlet end of the water passage of the flue gas heat exchanger 1 are both communicated with the inlet end of the first conveying pipeline 16. The outlet end of the first conveying pipeline 16 is communicated with the inlet end of the water passage of the second oil-water heat exchanger 3, and the oil passage of the second oil-water heat exchanger 3 is communicated with the oil passage of the side wall heat exchanger 2. The outlet end of the water passage of the second oil-water heat exchanger 3 is communicated with the inlet end.

[0051] For example, referring to Figure 1, the circulating pump station 14 is opened, and the flow medium in the circulating pump station 14 enters the water passage of the first oil-water heat exchanger 5 and the water passage of the flue gas heat exchanger 1, respectively. The flue gas duct of the aluminum electrolytic cell is communicated with the flue gas passage of the flue gas heat exchanger 1, and the flue gas passage transmits the heat of the flue gas to the flow medium in the water passage of the flue gas heat exchanger 1 by heat conduction, and the high-temperature flue gas in the flue gas passage exchanges heat with the flow medium in the water passage of the flue gas heat exchanger 1, and the flow medium in the water passage of the flue gas heat exchanger 1 recovers the heat generated by the flue gas of the aluminum electrolytic cell. The oil passage of the first oil-water heat exchanger 5 is communicated with the oil pipeline of the air compression station, and the oil passage in the first oil-water heat exchanger 5 transmits the high-temperature waste heat to the flow medium in the water passage of the first oil-water heat exchanger 5 by heat conduction, and the oil passage in the first oil-water heat exchanger 5 exchanges heat with the water passage in the first oil-water heat exchanger 5, and the flow medium in the water passage of the first oil-water heat exchanger 5 recovers the heat of the high-temperature waste heat of the air compression station. The flow medium can recover the heat in the flue gas duct and the high-temperature waste heat of the air compression station 4 to the first conveying pipeline, complete the preliminary heat recovery treatment, and the temperature of the flow medium after the preliminary heat recovery treatment is about 80-100°C. The flow medium after the preliminary heat recovery treatment is conveyed to the second oil-water heat exchanger 3 through the first conveying pipeline 16, the oil passage in the side wall heat exchanger 2 transmits the heat of the side wall of the aluminum electrolytic cell to the flow medium in the water passage of the second oil-water heat exchanger 3 by heat conduction, the oil passage in the second oil-water heat exchanger 3 exchanges heat with the water passage in the second oil-water heat exchanger 3, and the flow medium in the water passage of the second oil-water heat exchanger 3 recovers the waste heat of the side wall of the aluminum electrolytic cell, and completes the second heat recovery treatment. The temperature of the flow medium after the second heat recovery treatment is greater than 150°C. The high-temperature flow medium after the second heat recovery treatment is conveyed to the evaporator 7 of the power generation device 19, which is used to provide high-temperature steam for the power generation device 19 to drive the power generation device 19 to generate electricity.

[0052] It should be noted that the flow medium of the circulating pump station 14 can include water or oil, and the second oil-water heat exchanger operates independently while the preliminary heat recovery treatment is performed. The two high-temperature water streams flowing out of the flue gas heat exchanger 1 and the first oil-water heat exchanger 5 are combined into the first conveying pipeline 16 before entering the second oil-water heat exchanger 3. The high-temperature flow medium combined into the first conveying pipeline 16 enters the second oil-water heat exchanger 3 and exchanges heat with the high-temperature flow medium of the side wall heat exchange circuit for the second time and at a higher temperature level, and is finally heated into high-temperature and high-pressure steam, which is used as a driving heat source of the power generation device 19.

[0053] The application transports the flow medium of the circulating pump station to the flue gas heat exchange device and the first oil-water heat exchanger and the flue gas heat exchanger to preliminarily recover the heat generated by the flue gas and the waste heat generated by the air compression station, then transmits the preliminarily recovered heat to the second oil-water heat exchanger, exchanges heat with the side wall heat exchanger to complete the second heat recovery, and then delivers the secondary recovered heat to the power generation device to provide high-temperature steam for the power generation device to drive the power generation device to generate electricity. Compared with the traditional heat recovery which only recovers the heat of the flue gas or the side wall, the application also collects the waste heat generated by the air compression station, and comprehensively recovers the heat of the aluminum electrolysis cell itself and the aluminum electrolysis related equipment to improve the aluminum electrolysis heat recovery utilization rate and avoid energy waste.

[0054] In some embodiments, referring to Figure 1 The side wall heat exchanger 2 comprises a circulating oil pump 15, and the aluminum electrolysis plant waste heat recovery system further comprises a side wall heat exchange circuit. The heat of the side wall of the aluminum electrolysis cell tank shell is transmitted to the oil passage channel of the side wall heat exchanger 2 in a heat conduction manner. The circulating oil pump 15 can deliver the high-temperature hot oil in the oil passage channel of the side wall heat exchanger 2 to the oil passage channel of the second oil-water heat exchanger 3. The heat of the high-temperature oil in the oil-water passage channel of the second oil-water heat exchanger 3 is transmitted to the water passage channel of the second oil-water heat exchanger 3 in a heat conduction manner to complete the second heat recovery treatment.

[0055] In some embodiments, the aluminum electrolysis plant waste heat recovery system comprises an energy storage device. The energy storage device can be a phase change energy storage device, and the phase change material can be paraffin or metal alloy. The phase change material is surrounded outside the energy storage pipeline. The inlet end of the energy storage pipeline is in communication with the outlet end of the first delivery pipeline. The flow medium in the first delivery pipeline can transmit the recovered flue gas heat and the high-temperature waste heat of the air compression station to the energy storage pipeline and store the heat in the phase change material to complete the phase change energy storage. The outlet end of the energy storage pipeline can be in communication with the inlet end of the circulating pump station. The outlet end of the energy storage pipeline can be in communication with the inlet end of the second oil-water heat exchanger.

[0056] For example, referring to Figure 1A temperature sensor 18 is installed on the side of the energy storage device 6 near the first delivery pipeline 16. Temperature sensor 18 is used to detect the temperature of the fluid in the first delivery pipeline 16. A first valve K1 is installed between the inlet of the energy storage device 6 and the temperature sensor 18. A second valve K2 is installed between the outlet of the energy storage device 6 and the second oil-water heat exchanger 3. A third valve K3 is installed between the outlet of the energy storage device 6 and the circulation pump station 14. When the aluminum electrolytic cell is operating normally and there is sufficient flue gas waste heat, and the temperature sensor 18 detects that the temperature of the fluid in the first delivery pipeline 16 is greater than a first preset temperature, the control system opens the first valve K1 and the third valve K3 and closes the second valve K2. At this time, the high-temperature fluid in the flue gas heat exchanger 1 and the first oil-water heat exchanger 5 is transferred through the first delivery pipeline 16 to the energy storage pipeline of the energy storage device 6. The high-temperature fluid entering the energy storage pipeline transfers heat to the phase change material, undergoing phase change heat storage. The low-temperature fluid is then transferred to the circulation pump station 14 through the third valve K3. When the flue gas system is undergoing purification and maintenance, the flue gas volume and temperature drop significantly, the flue gas heat is insufficient, and the temperature sensor 18 detects that the temperature of the flowing medium in the first delivery pipe 16 is lower than the second preset temperature, the control system opens the first valve K1 and the second valve K2, and closes the third valve K3. At this time, the phase change material transfers heat to the flowing medium in the energy storage pipeline, and the flowing medium can enter the second oil-water heat exchanger 3 through the second valve K2 to replenish heat, ensuring that the high-temperature flowing medium can be delivered to the evaporator of the power generation device 19, so that the power generation device 19 can generate electricity stably and avoid shutdown of the power generation device 19.

[0057] Exemplary, reference Figure 1 A fourth valve K4 is installed between the first delivery pipeline 16 and the second oil-water heat exchanger 3. When the aluminum electrolytic cell is operating normally and the flue gas has sufficient waste heat, and the temperature sensor 18 detects that the temperature of the fluid in the first delivery pipeline is greater than a first preset temperature, the control system opens the first valve K1 and the third valve K3, closes the second valve K2, and partially opens the fourth valve K4. The high-temperature fluid in the first delivery pipeline 16 is partially delivered to the energy storage pipeline of the energy storage device 6 for thermal energy storage. Part of the fluid enters the second oil-water heat exchanger 3 for a second heat treatment, and is then delivered to the evaporator 7 of the power generation device 19 via the second delivery pipeline 17. This ensures the stable operation of the power generation device 19 while storing energy.

[0058] Exemplarily, the first preset temperature range is 120°C to 140°C, and may be 120°C, 130°C or 140°C.

[0059] Exemplarily, the second preset temperature range is 70°C to 90°C, and can be 70°C, 80°C or 90°C.

[0060] In some embodiments, the aluminum electrolysis plant waste heat recovery system comprises a first heat exchange circuit and a second heat exchange circuit. The first heat exchange circuit comprises a circulating pump station, a first oil-water heat exchanger, a second oil-water heat exchanger, and a condenser of the power generation device 19, which are connected to each other. The first heat exchange circuit is used for multi-stage heat source recovery of the aluminum electrolysis cell, and recovers flue gas, air compression station, and electrolysis cell sidewall waste heat to the middle, thereby improving the thermoelectric conversion efficiency of the power generation device and the overall energy recovery rate. The second heat exchange circuit comprises a circulating pump station, a first oil-water heat exchanger, and an energy storage device, which are connected to each other. The second heat exchange circuit adds the energy storage device to cut the peak and fill the valley, suppress the fluctuation of the heat source, ensure the uninterrupted and stable operation of the power generation device 19, and avoid the positive loss caused by frequent shutdown and the impact on the equipment of the power generation device 19.

[0061] In some embodiments, referring to Figure 1 The power generation device 19 further comprises a turbine 8, a generator 9, a condenser 10, and a working medium pump 11. The high-temperature flowing medium after the second heat recovery process is transmitted to the evaporator 7 of the power generation device 19. The evaporator 7 vaporizes the high-temperature flowing medium into high-temperature and high-pressure steam. The outlet end of the evaporator 7 is connected to the turbine 8. The high-temperature and high-pressure steam in the evaporator 7 can drive the turbine 8 to work, so as to drive the generator 9 to generate electricity and output electric energy. The generator 9 is connected to the condenser 10. The low-pressure steam after work enters the condenser 10 and is condensed into liquid working medium. The condenser 10 is connected to the working medium pump 11. The liquid working medium is pressurized by the working medium pump 11 and then transmitted to the evaporator, thereby completing the organic Rankine cycle.

[0062] It should be noted that the electric energy output by the generator 9 can be used for the aluminum electrolysis cell itself or for external power generation.

[0063] In some embodiments, referring to Figure 1The waste heat recovery system of the aluminum electrolysis plant further comprises a cooling device 12. The cooling device 12 is in communication with the condenser 10 of the power generation device 19 and the first oil-water heat exchanger 5 of the air compression station 4 respectively, and the cooled water is sent out by a cooling water pump 13 in two paths to form two cooling circuits. The first cooling circuit comprises the cooling device 12 and the oil path of the air compression station 4 in communication with each other, and the second cooling circuit comprises the cooling device 12 and the condenser 10 in communication with each other. The cooling device 12 can serve as a central cooling source. The cooling device 12 can divide the cooled flowing medium into two paths for output, one path is used to transport the cooled flowing medium to the condenser 10 of the power generation device 19 to cool the low-pressure steam and condense the working medium into liquid state, and the other path is used to transport the cooled flowing medium to the air compression station 4 to perform secondary deep cooling on the flowing medium cooled by the first oil-water heat exchanger 5, so as to ensure the normal operation of the air compressor in the air compression station 4. The cooled water in the two paths is combined by the cooling water pump 13 and then returned to the cooling device 12 for recycling. One cooling device 12 can provide cooling water for the air compression station 4 and the power generation device 19 at the same time, thereby saving the structure of the water cooling system and reducing the investment cost and the floor area of the cooling equipment. Compared with multiple independent cooling systems, only one cooling device is arranged, the operation and maintenance cost is reduced, and the auxiliary system of the aluminum electrolysis cell is simplified.

[0064] The waste heat recovery system provided by the embodiments of the present application closely combines the three links of waste heat recovery, energy storage and power generation, forms an efficient and recyclable waste heat recovery system, and improves the thermal power conversion efficiency and energy recovery rate of the aluminum electrolysis plant.

[0065] In a second aspect, the embodiments of the present application provide a waste heat recovery method for an aluminum electrolysis plant. Figure 2 A schematic flow chart of the waste heat recovery method for the aluminum electrolysis plant is provided. For example, referring to Figure 1 The waste heat recovery method for the aluminum electrolysis plant comprises the following steps.

[0066] S101: receiving a heat recovery instruction.

[0067] For example, the heat recovery instruction is issued by an upper computer in the control system. A worker edits the control logic according to the actual heat recovery needs, so that the control system issues the heat recovery instruction. The heat recovery instruction can include a preliminary heat recovery processing instruction and a second heat recovery processing instruction.

[0068] S102: according to the heat recovery instruction, the circulating pump station and the power generation device are started, the flowing medium in the circulating pump station is respectively introduced into the first transmission pipeline through the first oil-water heat exchanger and the flue gas heat exchanger, and the flowing medium output by the first transmission pipeline flows into the evaporator of the power generation device through the second oil-water heat exchanger, wherein the oil path channel of the first oil-water heat exchanger is in communication with the oil pipeline of the air compression station, and the inlet end of the oil path channel of the second oil-water heat exchanger is in communication with the outlet end of the oil path channel of the side wall heat exchanger.

[0069] For example, referring to Figures 1 to 2 According to the heat recovery instruction, the control system controls the start of the circulating pump station 14 and the power generation device 19, and the flow medium in the circulating pump station 14 is divided into two paths, the first path flows into the first conveying pipeline 16 through the first oil-water heat exchanger 5, and the second path flows into the first conveying pipeline 16 through the flue gas heat exchanger 1. The flow medium can recover the heat in the exhaust gas pipeline and the high-temperature waste heat of the air compression station to the first conveying pipeline 16, respectively, to complete the preliminary heat recovery process. The flow medium after the preliminary heat recovery process is conveyed to the second oil-water heat exchanger 3 through the first conveying pipeline 16, and the side wall heat exchanger 2 transmits the heat of the aluminum electrolysis cell side wall to the flow medium in the water flow channel of the second oil-water heat exchanger 3 by heat conduction. The oil passage channel in the second oil-water heat exchanger 3 exchanges heat with the water passage channel in the second oil-water heat exchanger 3, and the flow medium in the water passage channel of the second oil-water heat exchanger 3 recovers the waste heat of the aluminum electrolysis cell side wall to complete the second heat recovery process. The flow medium output by the first conveying pipeline 16 flows into the evaporator 7 of the power generation device 19 through the second oil-water heat exchanger 3, which is used to provide high-temperature steam for the power generation device 19 to drive the power generation device 19 to generate electricity.

[0070] In some examples, the aluminum electrolysis plant waste heat recovery method further comprises:

[0071] According to the heat recovery instruction, the control system controls the temperature sensor to detect the temperature of the flow medium in the first transmission pipeline. When it is detected that the temperature of the flow medium in the first transmission pipeline is greater than the first preset temperature, the first valve and the third valve are opened, the second valve is closed, and the flow medium in the first transmission pipeline is controlled to flow into the energy storage device. When it is detected that the temperature of the flow medium in the first transmission pipeline is less than the second preset temperature, the first valve and the second valve are opened, the third valve is closed, and the flow medium in the first transmission pipeline is controlled to flow into the second oil-water heat exchanger.

[0072] For example, referring to Figures 1 to 2In the case that the aluminum electrolytic cell is in normal production, the flue gas waste heat is sufficient, and the temperature sensor 18 detects that the temperature of the flowing medium in the first conveying pipeline is greater than the first preset temperature, the control system opens the first valve K1 and the third valve K3, and closes the second valve K2. At this time, part of the high-temperature flowing medium in the flue gas heat exchanger 1 and the first oil-water heat exchanger 5 is divided into the energy storage pipeline of the energy storage device 6 through the first conveying pipeline 16, and the high-temperature flowing medium entering the energy storage pipeline transmits heat to the phase change material to store heat by phase change. The low-temperature flowing medium is conveyed to the circulating pump station 14 through the third valve K3. In the case that the flue gas system is purified and maintained, the flue gas volume and the flue gas temperature decrease greatly, the flue gas heat is insufficient, and the temperature sensor 18 detects that the temperature of the flowing medium in the first conveying pipeline 16 is less than the second preset temperature, the control system opens the first valve K1 and the second valve K2, and closes the third valve K3. At this time, the phase change material transmits heat to the flowing medium in the energy storage pipeline, and the flowing medium can enter the second oil-water heat exchanger 3 through the second valve K2 to supplement heat, so that the power generation device can generate power stably, and the power generation device unit is prevented from being shut down.

[0073] In some embodiments, the electrolytic cell waste heat recovery method further comprises:

[0074] According to the heat recovery instruction, the control system controls the evaporation, the turbine, the generator, the condenser and the working medium pump to start. The evaporation evaporates the liquid input by the second oil-water heat exchanger to form high-pressure working medium. The turbine does work under the action of the high-pressure working medium to drive the generator to output electric energy.

[0075] For example, referring to Figures 1 to 2 The high-temperature flowing medium after the second heat recovery treatment is transmitted to the evaporation 7 of the power generation device 19. The evaporation 7 gasifies the high-temperature flowing medium into high-temperature and high-pressure steam. The outlet end of the evaporation 7 is connected with the turbine 8. The high-temperature and high-pressure steam in the evaporation 7 can drive the turbine 8 to do work to drive the generator 9 to generate power and output electric energy. The generator 9 is connected with the condenser 10. The low-pressure steam after work enters the condenser 10 to condense into liquid working medium. The condenser 10 is connected with the working medium pump 11. The liquid working medium is pressurized by the working medium pump 11 and then conveyed to the condenser 10 to complete the organic Bernoulli cycle. The three links of waste heat recovery, energy storage and power generation are closely combined to improve the heat and power conversion efficiency and the energy recovery rate of the aluminum electrolytic plant.

[0076] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0077] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the system, device and unit described above can refer to the corresponding processes in the foregoing method embodiments, and will not be described here.

[0078] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0079] Although the preferred embodiments of the present specification have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present specification.

[0080] Obviously, those skilled in the art can make various modifications and variations to the present specification without departing from the spirit and scope of the present specification. Thus, if these modifications and variations of the present specification fall within the scope of the claims of the present specification and their equivalent technologies, the present specification also intends to include these modifications and variations.

Claims

1. A waste heat recovery system for an aluminum electrolysis plant, characterized in that: include: A flue gas heat exchanger is provided in the exhaust pipe of the aluminum electrolysis cell; A first oil-water heat exchanger is provided in an air compression station, wherein a gas outlet of the air compression station is connected to the aluminum electrolysis cell unloading cylinder; a circulation pump station, wherein the outlet of the circulation pump station is respectively connected to the inlet of the water channel of the first oil-water heat exchanger and the inlet of the flue gas heat exchanger; a first delivery pipeline, wherein the inlet end of the first delivery pipeline is respectively connected to the outlet end of the water path of the first oil-water heat exchanger and the outlet end of the flue gas heat exchanger; A side wall heat exchanger is provided on the outer side wall of the aluminum electrolysis cell; A second oil-water heat exchanger, wherein the water channel inlet end of the second oil-water heat exchanger is connected to the outlet end of the first delivery pipeline, the oil channel inlet end of the second oil-water heat exchanger is connected to the oil channel outlet end of the sidewall heat exchanger, and the water channel outlet end of the second oil-water heat exchanger is connected to the evaporator inlet end of the power generation device.

2. The waste heat recovery system for an aluminum electrolysis plant according to claim 1, characterized in that: Also includes: A circulating oil pump, the circulating oil pump being arranged between the oil passages of the sidewall heat exchanger; The side wall heat exchange circuit includes the side wall heat exchanger, the circulating oil pump and the second oil-water heat exchanger which are interconnected.

3. The waste heat recovery system for an aluminum electrolysis plant according to claim 1, characterized in that: Also includes: An energy storage device, wherein the inlet end of the energy storage pipeline of the energy storage device is connected to the outlet end of the second delivery pipeline, and the outlet end of the energy storage pipeline of the energy storage device is connected to the inlet end of the circulation pump station; and / or, The outlet end of the energy storage pipeline of the energy storage device is communicated with the inlet end of the second oil-water heat exchanger.

4. The waste heat recovery system for an aluminum electrolysis plant according to claim 3, characterized in that: Also includes: a first heat exchange circuit, the first heat exchange circuit comprising the circulating pump station, the first oil-water heat exchanger, the second oil-water heat exchanger, and the condenser of the power generation device, which are interconnected; The second heat exchange circuit includes the circulating pump station, the first oil-water heat exchanger and the energy storage device which are interconnected.

5. The waste heat recovery system for an aluminum electrolysis plant according to claim 3, characterized in that: A temperature sensor is provided on a side of the energy storage device close to the first delivery pipeline, and the temperature sensor is used to detect the temperature of the flowing medium in the first delivery pipeline; A first valve is provided between the inlet end of the energy storage pipeline and the temperature sensor; A second valve is provided between the outlet end of the energy storage pipeline and the second oil-water heat exchanger; A third valve is provided between the outlet end of the energy storage pipeline and the circulation pump station; Wherein, when the temperature sensor detects that the temperature of the flowing medium in the first delivery pipeline is greater than a first preset temperature, the first valve and the third valve are opened, and the second valve is closed; When the temperature sensor detects that the temperature of the flowing medium in the first delivery pipeline is lower than a second preset temperature, the first valve and the second valve are opened, and the third valve is closed.

6. The waste heat recovery system for an aluminum electrolysis plant according to claim 2, characterized in that: The power generation device also includes a turbine, a generator, a condenser and a working fluid pump; The outlet end of the evaporator is connected to the turbine, and the gas in the evaporator is used to drive the turbine to perform work, thereby driving the generator to generate electricity; The generator is connected to the condenser, and the condenser is connected to the working fluid pump. The condenser is used to cool the low-pressure working fluid generated after the generator generates electricity, and the working fluid pump is used to transport the cooled low-pressure working fluid to the condenser.

7. The waste heat recovery system for an aluminum electrolysis plant according to claim 6, characterized in that: Also includes: a cooling device, the cooling device being in communication with the condenser of the power generation device and the second oil-water heat exchanger of the air compression station; a first cooling circuit, the first cooling circuit comprising the cooling device and the air compressor station oil circuit interconnected; The second cooling circuit includes a cooling device and the condenser that are communicated with each other.

8. A waste heat recovery method for an aluminum electrolysis plant, applied to the waste heat recovery system for an aluminum electrolysis plant according to any one of claims 1 to 7, characterized in that: The waste heat recovery method of an aluminum electrolysis plant comprises: Receive heat recovery instructions; According to the heat recovery instruction, the circulation pump station and the power generation device are started, and the fluid medium in the circulation pump station is respectively fed into the first transmission pipeline through the first oil-water heat exchanger and the flue gas heat exchanger. The fluid medium output from the first transmission pipeline flows into the evaporator of the power generation device through the second oil-water heat exchanger; The oil passage of the first oil-water heat exchanger is connected to the oil pipeline of the air compressor station, and the oil passage inlet of the second oil-water heat exchanger is connected to the oil passage outlet of the sidewall heat exchanger.

9. The method for recovering waste heat from an aluminum electrolysis plant according to claim 8, characterized in that: Also includes: According to the heat recovery instruction, the evaporator, turbine, generator, condenser and working fluid pump are controlled to start. The evaporator evaporates the liquid input from the second oil-water heat exchanger to form a high-pressure working fluid. The turbine performs work under the action of the high-pressure working fluid to drive the generator to output electrical energy.

10. The method for recovering waste heat from an aluminum electrolysis plant according to claim 8, characterized in that: Also includes: controlling the temperature sensor to detect the temperature of the flowing medium in the first transmission pipeline according to the heat recovery instruction, and when detecting that the temperature of the flowing medium in the first transmission pipeline is greater than a first preset temperature, opening the first valve and the third valve, closing the second valve, and controlling the flowing medium in the first transmission pipeline to flow into the energy storage device; or, When it is detected that the temperature of the flowing medium in the first transmission pipeline is lower than the second preset temperature, the first valve and the second valve are opened, and the third valve is closed to control the flowing medium in the first transmission pipeline to flow into the second oil-water heat exchanger.

Images