Waste heat recovery system and method

Abstract

The present invention provides a waste heat recovery system and method. The system comprises a material waste heat extraction subsystem (200), a flue gas waste heat recovery subsystem (100) and a control subsystem (300); the material waste heat extraction subsystem (200) is in communication with the flue gas waste heat recovery subsystem (100) and is used for extracting, by means of flue gas flowing through the material waste heat extraction subsystem (200), waste heat from a material (7) having waste heat to be recovered; the flue gas waste heat recovery subsystem (100) is used for recovering waste heat of flue gas discharged from an aluminum electrolysis cell (1) and the waste heat extracted from said material (7); and the control subsystem (300) is used for regulating and controlling operation parameters of the material waste heat extraction subsystem (200) and the flue gas waste heat recovery subsystem (100) during waste heat recovery.

Description

Waste heat recovery system and method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 2023106992300 filed on June 13, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of aluminum electrolysis, and in particular to a waste heat recovery system and method thereof. Background Art

[0004] There is a lot of underutilized waste heat in the aluminum electrolysis process. For example, the exhaust gas temperature of the aluminum electrolysis cell is generally 100-140℃, and the flue gas flow rate of a single cell is 3000-10000m 3 / h, and the heat removed by flue gas accounts for approximately 30% of the total heat dissipation in the electrolytic cell. For example, the temperature of hot anode butts removed from the electrolytic cell can reach approximately 900°C, and the temperature of the butt steel claws can exceed 500°C. Currently, much of the waste heat generated in the process is often not fully recovered and utilized, resulting in significant heat waste. For example, a 200,000-ton, 400kA series aluminum electrolytic plant with a daily capacity of 200,000 tons undergoes daily anode replacement, resulting in a daily flue gas output of 27 million cubic meters. This represents a significant amount of waste heat that needs to be utilized. Therefore, efficiently recovering and utilizing the waste heat from the aluminum electrolysis process is a pressing technical challenge.

[0005] Summary of the Invention

[0006] The embodiments of the present disclosure provide a waste heat recovery and utilization system and method thereof. Based on the technical solution provided by the present disclosure, the waste heat of the flue gas discharged from the aluminum electrolysis cell can be efficiently recovered and utilized, and the waste heat of the waste heat materials to be recovered with a large amount of waste heat can be efficiently recovered and utilized. The waste heat of the flue gas can also be used to heat the materials to be heated, thereby achieving energy saving and consumption reduction.

[0007] Other features and advantages of the present disclosure will become apparent from the following detailed description, or may be learned in part by practice of the present disclosure.

[0008] According to a first aspect of the present disclosure, a waste heat recovery and utilization system is provided, which is applied to an aluminum electrolysis process, and the system includes: a material waste heat extraction subsystem, a flue gas waste heat recovery subsystem, and a control subsystem; the material waste heat extraction subsystem is connected to the flue gas waste heat recovery subsystem, and is used to extract waste heat from waste heat materials to be recovered by using the flue gas flowing through it; the flue gas waste heat recovery subsystem is used to recycle waste heat from flue gas discharged from an aluminum electrolysis cell, as well as waste heat extracted from the waste heat materials to be recovered; and the control subsystem is used to regulate the operating parameters of the material waste heat extraction subsystem and the flue gas waste heat recovery subsystem during the waste heat recovery process.

[0009] According to a second aspect of the present disclosure, a waste heat recovery and utilization method is provided, which is executed in a control subsystem, including: when monitoring that the waste heat material to be recovered is placed in the material waste heat extraction subsystem, obtaining the initial flow rate of the flue gas in the flue gas waste heat recovery subsystem, and obtaining the heat exchange rate for the waste heat material to be recovered, the heat exchange rate being the amount of heat extracted by the flue gas flowing through the material waste heat extraction subsystem per unit time; determining the target flow rate of the flue gas flowing through the material waste heat extraction subsystem based on the heat exchange rate, the heat exchange rate being positively correlated with the target flow rate; and regulating the opening of each control valve in the waste heat recovery and utilization system according to the initial flow rate and the target flow rate.

[0010] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0012] FIG1 shows a schematic diagram of the architecture of a waste heat recovery system according to some embodiments of the present disclosure;

[0013] FIG2 shows a detailed schematic diagram of the waste heat recovery system according to some embodiments of the present disclosure;

[0014] FIG3 shows a schematic diagram of the detailed structure of a material waste heat extraction device according to some embodiments of the present disclosure;

[0015] FIG4 shows a schematic diagram of a structure for heating a material to be heated according to some embodiments of the present disclosure; and

[0016] FIG5 shows a schematic flow chart of a waste heat recovery method according to some embodiments of the present disclosure.

[0017] Reference numerals:

[0018] 100. Flue gas waste heat recovery subsystem; 200. Material waste heat extraction subsystem;

[0019] 300, control subsystem;

[0020] 1. Aluminum electrolytic cell; 2. Flue gas conveying pipe;

[0021] 3. Flue gas inlet pipe; 4. First control valve;

[0022] 5. Flue gas exhaust pipe; 6. Material waste heat extraction device;

[0023] 7. Materials with waste heat to be recovered; 8. First thermometer;

[0024] 9. First flow meter; 10. Second control valve;

[0025] 11. Third control valve; 12. Second flow meter;

[0026] 13. Flue gas heat exchanger; 14. Intermediate heat exchanger;

[0027] 15. Water tank; 16. Heat user;

[0028] 17. Purification unit; 18. First circulation loop;

[0029] 19. Second circulation loop; 20. Second thermometer;

[0030] 603, first filter; 604, second filter;

[0031] 605, guardrail; 606, baffle;

[0032] 607, boss; 608, material tray;

[0033] 609, load-bearing tray; 610, material to be heated;

[0034] 611. Heating box. DETAILED DESCRIPTION

[0035] Some embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure can have various variations in different embodiments without departing from the scope of the present disclosure, and the descriptions and illustrations therein are essentially for illustrative purposes and not for limiting the present disclosure.

[0036] In the description of the present disclosure, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0037] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on specific circumstances.

[0038] The following will describe some embodiments of the present disclosure in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0039] According to a first aspect of the present disclosure, a waste heat recovery system is provided.

[0040] 1 , which shows a schematic diagram of the architecture of a waste heat recovery system according to some embodiments of the present disclosure, including a material waste heat extraction subsystem 200 , a flue gas waste heat recovery subsystem 100 and a control subsystem 300 .

[0041] The material waste heat extraction subsystem 200 is connected to the flue gas waste heat recovery subsystem 100, and is used to extract waste heat from the waste heat material 7 to be recovered by using the flue gas flowing through it.

[0042] It should be noted that the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100 can be connected in parallel or in series, preferably in parallel, which is not limited in this disclosure.

[0043] It should also be noted that the material waste heat extraction subsystem 200 disclosed in the present invention can extract waste heat from the waste heat materials 7 to be recovered, including but not limited to residual electrodes, high-temperature molten aluminum, high-temperature liquid waste, high-temperature solid waste, electrolytes, carbon slag, etc.

[0044] In some embodiments, by setting up a material waste heat extraction subsystem 200 in the waste heat recovery and utilization system of the present disclosure, on the one hand, the heat of materials such as residual poles can be extracted through the subsystem; on the other hand, in the prior art, since materials such as residual poles are generally placed in the workshop for natural cooling, and the residual poles are accompanied by the emission of harmful gases such as fluorides during the cooling process, which will cause serious pollution to the workshop environment, the material waste heat extraction subsystem 200 provided by the present disclosure can effectively recover the harmful gases released by the natural cooling of the residual poles, and the harmful gases are finally processed through the purification unit 17 of the present disclosure, thereby improving the environmental protection effect of the workshop.

[0045] It should also be noted that in the waste heat recovery and utilization system of the present disclosure, there may be one or more parallel material waste heat extraction subsystems 200, so as to improve the waste heat recovery efficiency.

[0046] In some embodiments, the flue gas waste heat recovery subsystem 100 is used to recover and utilize the waste heat of the flue gas discharged from the aluminum electrolysis cell 1 and the waste heat extracted from the waste heat material to be recovered 7.

[0047] It can be understood that the flue gas waste heat recovery subsystem 100 disclosed in the present invention can transport the collected flue gas emitted by the aluminum electrolytic cell 1 to the material waste heat extraction subsystem 200, so that the transported flue gas, when flowing through the material waste heat extraction subsystem 200, performs heat exchange with the waste heat of the waste heat material 7 to be recovered placed in the material waste heat extraction subsystem 200, that is, extracts the waste heat existing in the waste heat material 7 to be recovered, so that the flue gas flowing out of the material waste heat extraction subsystem 200 contains both the waste heat emitted by the aluminum electrolytic cell 1 and the waste heat of the waste heat material 7 to be recovered.

[0048] In some embodiments, the detailed architecture of the waste heat recovery system of the present disclosure is shown in FIG2 . The material waste heat extraction subsystem 200 may include: a flue gas inlet pipe 3 , a flue gas exhaust pipe 5 , and a material waste heat extraction device 6 .

[0049] In some embodiments, the inlet of the flue gas inlet pipe 3 is connected to the flue gas waste heat recovery subsystem 100, and the outlet is connected to the material waste heat extraction device 6; the inlet of the flue gas exhaust pipe 5 is connected to the material waste heat extraction device 6, and the outlet is connected to the flue gas waste heat recovery subsystem 100; the material waste heat extraction device 6 is used to place the waste heat material 7 to be recovered.

[0050] It should be noted that in the present disclosure, the requirements for the material waste heat extraction device 6 are that it can withstand high temperatures, have a heat-insulating structure and a sealed structure, and an automatic sealing function, so as to improve the extraction efficiency of the waste heat of the waste heat material 7 to be recovered.

[0051] As can be seen from FIG. 2 , there are two material waste heat extraction subsystems 200 , which are connected in parallel with the flue gas waste heat recovery subsystem 100 .

[0052] As can be seen from Figure 2, the flue gas waste heat recovery subsystem 100 collects the flue gas from the aluminum electrolytic cell 1 and can be transported to the material waste heat extraction device 6 through the flue gas inlet pipe 3, so that the flue gas flows through the material waste heat extraction device 6, and can extract the waste heat of the waste heat material 7 to be recovered. The flue gas after flowing through then flows back into the flue gas waste heat recovery subsystem 100 through the flue gas exhaust pipe 5, so that the flue gas waste heat recovery subsystem 100 can not only recycle the waste heat of the flue gas discharged from the aluminum electrolytic cell 1, but also recycle the waste heat extracted from the waste heat material 7 to be recovered.

[0053] In some embodiments, the specific design of the material waste heat extraction device 6 in the material waste heat extraction subsystem 200 may be as shown in FIG. 3 .

[0054] 3 , which shows a schematic diagram of the detailed architecture of a device for extracting waste heat from materials according to some embodiments of the present disclosure.

[0055] According to some embodiments of the present disclosure, the material waste heat extraction device may include: a load-bearing tray 609, which is arranged in the material waste heat extraction device 6 and is used to carry the waste heat material 7 to be recovered; a telescopic mechanism, which is arranged on the lower side of the load-bearing tray 609 and is used to realize the movement of the waste heat material 7 to be recovered in the material waste heat extraction device 6; a material tray 608, which is arranged on the upper side of the load-bearing tray 609 and is used to place the waste heat material 7 to be recovered; a boss 607, which is arranged on the material tray 608 and is used to isolate the lower surface of the waste heat material 7 to be recovered and the upper surface of the material tray 608; and a protective device, which is arranged in the material waste heat extraction device 6 and is used to protect the waste heat material 7 to be recovered.

[0056] In some embodiments, the telescopic mechanism can adopt conventional technologies such as chain, hydraulic, and cylinder types, and has the function of automatic lifting or horizontal extension, so that the waste heat material 7 to be recovered can be automatically moved from the outside to the material waste heat extraction device 6, or moved from the material waste heat extraction device 6 to the outside.

[0057] In some embodiments, the material tray 608 and the boss 607 can be moved out of or into the material waste heat extraction device 6 along with the waste heat material to be recovered 7. It is understood that the design of the boss 607 in the material waste heat extraction device 6 can ensure sufficient contact between the flue gas and the waste heat material to be recovered 7, thereby facilitating the full extraction of waste heat from the waste heat material to be recovered 7, thereby improving the waste heat recovery efficiency.

[0058] In some embodiments, the protective device includes a guardrail 605 and a baffle 606 as shown in FIG3 , thereby preventing the material to be recovered 7 or the material to be heated 610 from falling into the material waste heat extraction device 6. Of course, the protective device can also be designed according to actual conditions, and this disclosure does not make any specific limitations here.

[0059] In some embodiments, the material waste heat extraction subsystem 200 of the present disclosure is also used to heat the material to be heated 610 using the flue gas flowing through it.

[0060] It should be noted that the material to be heated 610 includes but is not limited to new anodes, fresh alumina, aluminum fluoride, crushed materials and other additives to the aluminum electrolysis cell 1.

[0061] It is understood that in the aluminum electrolysis process, a new anode may need to be preheated before use. Therefore, if preheating is required, placing the new anode in the material waste heat extraction device 6 of the material waste heat extraction subsystem 200 of the disclosed design can allow the flue gas flowing from the flue gas waste heat recovery subsystem 100 to fully and efficiently preheat the new anode, thereby improving the recovery and utilization rate of the flue gas waste heat. In some embodiments, based on an exhaust gas temperature of 120°C from the aluminum electrolysis cell 1, the new anode can be quickly preheated to above 100°C.

[0062] It should also be noted that, in some embodiments, the specific structural design of the material waste heat extraction device 6 for heating the material to be heated 610 can be as shown in FIG. 4 .

[0063] 4 , which shows a schematic diagram of an architecture for heating a material to be heated according to some embodiments of the present disclosure.

[0064] It can be understood that the material waste heat extraction device 6 for heating the material to be heated 610 is basically the same as the material waste heat extraction device 6 for extracting the waste heat of the waste heat material to be recovered 7, except that a heating box 611 is added to the material tray 608 to accommodate the material to be heated 610.

[0065] It should be noted that the heating box 611 is made of a highly thermally conductive metal, such as iron, aluminum, or copper, so that it can hold fresh alumina, aluminum fluoride, crushed material, and other materials added to the aluminum electrolysis cell 1. In some embodiments, the temperature of the flue gas discharged from the aluminum electrolysis cell 1 is generally 120°C, and the material to be heated 610 can be quickly preheated to above 100°C.

[0066] It should also be noted that the material waste heat extraction device 6 may not be provided with the heating box 611 according to actual needs. For example, if a new anode is to be heated, the heating box 611 may not be required.

[0067] In some embodiments, as shown in Figure 3, the material waste heat extraction subsystem 200 of the present disclosure also includes: a first filter 603, which is arranged at the outlet of the flue gas inlet pipe 3, and can also be arranged at the inlet of the flue gas inlet pipe 3; and a second filter 604, which is arranged at the inlet of the flue gas exhaust pipe 5.

[0068] It can be understood that a filter is provided in the material waste heat extraction subsystem 200. On the one hand, it can filter the flue gas flowing into the material waste heat extraction device 6 to prevent residue from entering the material waste heat extraction device 6; on the other hand, it can filter the flue gas flowing out of the material waste heat extraction device 6, thereby preventing the residue of the waste heat material 7 to be recovered from falling into the flue gas waste heat recovery subsystem 100, without affecting the operation of the flue gas waste heat recovery subsystem 100.

[0069] Referring to Figure 2, in some embodiments, the material waste heat extraction subsystem 200 may also include: a first control valve 4, arranged on the flue gas inlet pipe 3, for adjusting the flow rate of the flue gas flowing into the material waste heat extraction device 6; a second control valve 10, arranged on the flue gas exhaust pipe 5, for adjusting the flow rate of the flue gas flowing out of the material waste heat extraction device 6; and a first thermometer 8, arranged on the flue gas exhaust pipe 5, for measuring the temperature of the flue gas flowing out of the material waste heat extraction device 6; and a first flowmeter 9, arranged on the flue gas exhaust pipe 5, for measuring the flow rate of the flue gas flowing out of the material waste heat extraction device 6.

[0070] In some embodiments, the first control valve 4 and the second control valve 10 may be electrically controlled valves or other valves with control functions, which is not limited in the present disclosure.

[0071] In some embodiments, the first thermometer 8 may be a thermocouple or other components with a temperature measurement function, which is not limited in the present disclosure.

[0072] 2 , in some embodiments, the flue gas waste heat recovery subsystem 100 of the present disclosure may include a waste heat treatment unit, a flue gas conveying pipe 2 , a second flow meter 12 , a second thermometer 20 , and a third control valve 11 .

[0073] In some embodiments, the flue gas conveying pipe 2 is used to convey the flue gas discharged from the aluminum electrolysis cell 1 to the waste heat treatment unit; the waste heat treatment unit is used to convert the waste heat of the flue gas discharged from the aluminum electrolysis cell 1 and the waste heat extracted from the waste heat material to be recovered 7 into usable heat; the second flowmeter 12 is arranged near the outlet of the flue gas conveying pipe 2, for measuring the flow rate of the flue gas in the flue gas conveying pipe 2; the second thermometer 20 is arranged on the flue gas conveying pipe 2, for measuring the temperature of the flue gas in the flue gas conveying pipe 2; the third control valve 11 is arranged on the flue gas conveying pipe 2, for adjusting the flow rate of the flue gas flowing through the flue gas conveying pipe 2.

[0074] It should be noted that, in some embodiments, one or more third control valves 11 may be provided on the flue gas conveying pipe 2. The third control valve 11 may be an electrically controlled valve or other valve with a control function, which is not specifically limited in the present disclosure.

[0075] It should also be noted that the second flow meter 12 is capable of monitoring the flow rate of the flue gas flowing into the waste heat treatment unit, and therefore needs to be designed near the outlet of the flue gas conveying pipe 2.

[0076] It should also be noted that, in some embodiments, the positions of the aluminum electrolytic cells 1 are in parallel, and the exhausted flue gas can be discharged into the flue gas conveying pipe 2 of the flue gas waste heat recovery subsystem 100. It can be understood that the inlet of the flue gas conveying pipe 2 can be one or more.

[0077] It should also be noted that the second thermometer 20 can be a thermocouple or other components with a temperature measurement function, which is not limited in the present disclosure.

[0078] In some embodiments, the waste heat treatment unit includes: a flue gas heat exchanger 13, which is connected to the outlet of the flue gas conveying pipe 2 and is used to convert the recovered waste heat into hot water or water vapor; a purification unit 17, which is connected to the flue gas heat exchanger 13 and is used to treat harmful substances input from the flue gas heat exchanger 13; an intermediate heat exchanger 14, which is connected to the flue gas heat exchanger 13 through a first circulation loop 18, and is connected to the heat user 16 through a second circulation loop 19, for regulating and distributing the heat input from the flue gas heat exchanger 13; and a water tank 15, which is arranged on the second circulation loop 19 and is used to stabilize the heat provided to the heat user 16.

[0079] It can be understood that in the present disclosure, by designing the purification unit 17, the flue gas treated by the waste heat recovery and utilization system of the present disclosure can be purified before being discharged into the atmosphere, which is beneficial to improving the production workshop environment and realizing green production process.

[0080] Continuing to refer to Figure 1, the waste heat recovery system of the present disclosure also includes a control subsystem 300, which is respectively connected to the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100, and is used to regulate the operating parameters of the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100 during the waste heat recovery process.

[0081] It can be understood that the control subsystem 300 is capable of performing logical control on the waste heat recovery system, including but not limited to: real-time collection and monitoring of the flow measured by each flow meter; regulating the opening of each control valve; real-time collection and monitoring of the temperature measured by each thermometer; controlling the opening and closing of the material waste heat extraction device 6; controlling the operation of the telescopic mechanism in the material waste heat extraction device 6; and controlling the opening and closing of the waste heat recovery system, etc.

[0082] For the specific execution logic of the control subsystem 300, please refer to the following method embodiment of the second aspect of the present disclosure, which will not be described in detail here.

[0083] According to a second aspect of the present disclosure, a waste heat recovery method is provided, which is executed in the control subsystem 300 .

[0084] 5 , which shows a schematic flow chart of a waste heat recovery method according to some embodiments of the present disclosure. The waste heat recovery method according to some embodiments of the present disclosure may include steps S110 to S130 .

[0085] In step S110, when it is monitored that the waste heat material to be recovered is placed in the material waste heat extraction subsystem, the initial flow rate of the flue gas in the flue gas waste heat recovery subsystem is obtained, and the heat exchange rate for the waste heat material to be recovered is obtained. The heat exchange rate is the amount of heat extracted per unit time from the flue gas flowing through the material waste heat extraction subsystem.

[0086] In some embodiments, the initial flow rate can be obtained by the second flow meter 12 designed as described above.

[0087] It should be noted that when the waste heat recovery system does not need to recover the waste heat of the waste heat material 7 to be recovered, the material waste heat extraction subsystem 200 is in a closed state. This closed state means that no flue gas is exchanged between the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100. In some embodiments, for example, by closing the first control valve 4 on the flue gas inlet pipe 3 and the second control valve 10 on the flue gas exhaust pipe 5, the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100 are prevented from exchanging flue gas.

[0088] It should also be noted that as long as the aluminum electrolysis cell 1 is in operation, the flue gas waste heat recovery subsystem 100 of the present disclosure can be in an open state, thereby efficiently recovering and utilizing the waste heat of the flue gas. Therefore, it can be understood that when the material waste heat extraction subsystem 200 is not loaded with the waste heat recovery material 7, the corresponding first control valve 4 and second control valve 10 are in a closed state.

[0089] It should also be noted that in the present disclosure, in order to ensure that the waste heat treatment unit in the flue gas waste heat recovery subsystem 100 can continuously and stably process the recovered waste heat, it is necessary to ensure that the flow rate of the flue gas input to the flue gas exchanger of the waste heat treatment unit is stable.

[0090] Therefore, if the flue gas waste heat recovery subsystem 100 is in operation, it is necessary to use the material waste heat extraction subsystem 200 to recover the waste heat in the waste heat material 7 to be recovered, then it is necessary to ensure that after the material waste heat extraction subsystem 200 is turned on, the flow rate of the flue gas flowing into the flue gas exchanger of the waste heat treatment unit remains unchanged, that is, after the material waste heat extraction subsystem 200 is turned on, the flow rate of the flue gas flowing into the flue gas exchanger of the waste heat treatment unit still needs to be maintained at the initial flow rate.

[0091] In some embodiments, the specific implementation method of obtaining the heat exchange rate for the waste heat material to be recovered 7 can be manually set according to the material properties of the waste heat material to be recovered 7, the process requirements of the workshop, etc. For example, it is set to 6kWh / min, which means that 6kWh of heat needs to be extracted from the waste heat material to be recovered 7 within 1 minute.

[0092] In some embodiments, the specific implementation of obtaining the heat exchange rate for the waste heat material to be recovered 7 can be performed according to the following steps S111 to S113.

[0093] In step S111, the initial temperature of the flue gas in the flue gas waste heat recovery subsystem, the initial residual heat of the waste heat material to be recovered, and the preset time for waste heat extraction from the waste heat material to be recovered are obtained.

[0094] In some embodiments, the initial temperature can be obtained by the second thermometer 20 of the above design. It is understood that before the material waste heat extraction subsystem 200 starts operating, the initial temperature detected represents the temperature of the flue gas in the flue gas conveying pipe 2.

[0095] It should be noted that the initial residual heat of the waste heat material 7 to be recovered is related to the aluminum electrolysis process and the properties of the waste heat material 7 itself. Generally, the initial residual heat of the waste heat material 7 to be recovered can be determined based on empirical values. In some embodiments, the temperature of the hot anode butts removed from the aluminum electrolysis cell 1 is generally as high as approximately 900°C, and the temperature of the butt steel claws is above 500°C. Therefore, the initial residual heat of the hot anode butts and butt steel claws from which waste heat is to be extracted can be determined based on the temperatures.

[0096] It should also be noted that the preset duration for waste heat extraction can be determined based on the aluminum electrolysis production process. In some embodiments, a single cell is equipped with 48 anodes, the anode replacement cycle is 30 days, the total number of anode replacements per day for the entire plant is 288, and the number of anode replacements per hour is 12. If the material waste heat extraction subsystem 200 can accommodate 6 spent anodes at a time, the preset duration can be set to 0.5 hours.

[0097] In step S112, the residual heat corresponding to the waste heat material to be recovered when the temperature is the initial temperature is determined as the target residual heat.

[0098] It should be noted that only when the temperature of the flue gas discharged from the aluminum electrolysis cell 1 is lower than the temperature of the waste heat material 7 to be recovered can the waste heat of the waste heat material 7 to be recovered be extracted by the flue gas flowing through it. Therefore, when the waste heat material 7 to be recovered is placed in the material waste heat extraction subsystem 200 for waste heat extraction, the temperature of the waste heat material 7 to be recovered will gradually decrease as the heat is gradually transferred to the flue gas flowing through it.

[0099] Therefore, during the waste heat extraction process, when the temperature of the waste heat material 7 to be recovered gradually decreases to reach the initial temperature, it means that the waste heat extraction process of the waste heat material 7 to be recovered has been completed. Therefore, based on the initial temperature of the flue gas, it can be determined that the heat remaining in the waste heat material 7 to be recovered when the waste heat extraction is completed is the target residual heat.

[0100] In step S113 , the heat exchange rate is determined based on the initial residual heat, the target residual heat, and the preset time.

[0101] In some embodiments, the heat transfer rate can be calculated according to the following formula:

[0102] Heat exchange rate = (initial residual heat - target residual heat) / preset time

[0103] Continuing to refer to FIG. 5 , in step S120 , a target flow rate of the flue gas flowing through the material waste heat extraction subsystem is determined based on the heat exchange rate, and the heat exchange rate is positively correlated with the target flow rate.

[0104] It can be understood that if the heat exchange rate required to extract the waste heat of the waste heat material 7 to be recovered is higher, then the flow rate of the flue gas flowing through the material waste heat extraction device 6 needs to be larger, so that more waste heat can be extracted per unit time.

[0105] In some embodiments, the relationship between the heat exchange rate and the target flow rate can be determined experimentally. The relationship obtained is: target flow rate = A × heat exchange rate, where A is a conversion coefficient determined experimentally. Based on the obtained heat exchange rate, the target flow rate for the waste heat material 7 to be recovered can be determined.

[0106] 5 , in step S130 , the opening of each control valve in the waste heat recovery system is regulated according to the initial flow rate and the target flow rate.

[0107] It should be noted that, because during the operation of the material waste heat extraction subsystem 200, it is necessary to ensure that the flow rate of the flue gas at the position of the second flow meter 12 as shown in Figure 2 is stable, then when the material waste heat extraction subsystem 200 is turned on and operated, it is necessary to adjust the opening of the first control valve 4, the second control valve 10 in the material waste heat extraction subsystem 200 and the third control valve 11 in the flue gas waste heat recovery subsystem 100 so that the flow rate of the flue gas at the position of the second flow meter 12 remains at the initial flow rate.

[0108] It should also be noted that once the target flow rate through the material waste heat extraction device 6 is determined, the openings of the first control valve 4 and the second control valve 10 can be determined. The flow rate of the flue gas flowing through the third control valve 11 can also be determined based on the target flow rate and the initial flow rate, thereby determining the opening of the third control valve 11.

[0109] In some embodiments, the corresponding relationship between the opening of each control valve and the flue gas flow rate can be determined through experiments, thereby achieving precise regulation of the opening of each control valve.

[0110] It can be understood that according to the technical solutions of some embodiments of the present disclosure, the waste heat recovery and utilization system can maintain stable operation during the process of recovering waste heat from the waste heat material 7 to be recovered, the recovery efficiency can be improved, and the waste heat of the waste heat material 7 to be recovered can be accurately recovered.

[0111] In some embodiments, there are two implementations for determining whether the waste heat extraction of the waste heat material 7 to be recovered is completed.

[0112] In a first embodiment, the waste heat extraction of the waste heat material 7 to be recovered may be stopped by monitoring the time and when the preset time is reached.

[0113] According to other embodiments of the present disclosure, the waste heat recovery method may include the following steps S100 to S200.

[0114] In step S100, during the process of extracting waste heat from the waste heat material to be recovered, the flue gas temperature flowing out of the material waste heat extraction subsystem is monitored in real time.

[0115] In some embodiments, the temperature of the flue gas flowing out of the material waste heat extraction subsystem 200 can be measured by a first thermometer 8 disposed on the flue gas exhaust pipe 5 to achieve real-time monitoring of the flue gas temperature. It is understood that the flue gas temperature flowing out of the material waste heat extraction subsystem 200 is equal to the temperature of the flue gas flowing out of the material waste heat extraction device 6.

[0116] In step S200, when it is monitored that the flue gas temperature is less than or equal to the initial temperature, the waste heat extraction of the waste heat material to be recovered is stopped.

[0117] It can be understood that when the flue gas temperature is monitored to be less than or equal to the initial temperature, it means that the temperature of the waste heat material 7 to be recovered placed in the material waste heat extraction subsystem 200 is less than or equal to the initial temperature, which means that the waste heat extraction of the waste heat material 7 to be recovered has been completed and needs to be stopped.

[0118] In some embodiments, stopping the waste heat extraction of the waste heat material to be recovered 7 can be performed according to the following steps S210 to S220.

[0119] In step S210 , the first control valve and the second control valve are closed, and the third control valve is fully opened.

[0120] In step S220, when it is monitored that the flow rate measured by the first flow meter is zero, the telescopic mechanism is controlled to move the waste heat material to be recovered out of the material waste heat extraction device.

[0121] In some embodiments, stopping the waste heat extraction of the waste heat material to be recovered 7 can be designed according to actual conditions, and the present disclosure does not limit this.

[0122] In order to enable those skilled in the art to better understand the beneficial effects brought about by the technical solution of the present disclosure, the waste heat recovery and utilization system and method of the present disclosure will be illustrated with reference to the following Example 1.

[0123] Example 1:

[0124] An aluminum plant operates 180 400kA electrolytic cells, with a flue gas temperature of 120°C and an initial flow rate of 6000m 3 / h; a single cell is equipped with 48 anodes, with a 30-day pole-changing cycle. The plant-wide pole-changing frequency is 288 per day, or 12 per hour. The waste heat recovery system's operating parameters are set based on the initial flue gas conditions, controlling the material waste heat extraction subsystem 200 to operate for a 0.5-hour heat extraction cycle. Six anode scraps are installed each time, and the steel claws recover approximately 30 kWh of waste heat, resulting in an hourly heat recovery of 360 kWh. Based on an electricity price of 0.45 yuan, the technology generates an annual economic benefit of 1.42 million yuan.

[0125] In the technical solutions provided in some embodiments of the present disclosure, a waste heat recovery system designed for use in an aluminum electrolysis process includes: a material waste heat extraction subsystem 200, which is connected to the flue gas waste heat recovery subsystem 100 and is used to extract waste heat from the waste heat material 7 to be recovered by utilizing the flue gas flowing through it; a flue gas waste heat recovery subsystem 100, which is used to recycle the waste heat of the flue gas discharged from the aluminum electrolysis cell 1, as well as the waste heat extracted from the waste heat material 7 to be recovered; a control subsystem 300, which is used to regulate the operating parameters of the material waste heat extraction subsystem 200 and the flue gas waste heat recovery subsystem 100 during the waste heat recovery process.

[0126] According to the technical solutions of some embodiments of the present disclosure, at least the following technical effects can be achieved.

[0127] 1. By designing the flue gas waste heat recovery subsystem 100, the waste heat of the flue gas generated during the operation of the aluminum electrolysis cell 1 can be fully and efficiently recovered and utilized, thereby achieving energy conservation and emission reduction;

[0128] 2. The material waste heat extraction subsystem 200 is designed to efficiently recover and utilize the waste heat from waste heat materials 7 that contain a large amount of waste heat, such as butted anodes, high-temperature aluminum liquid, and high-temperature solid waste, thereby efficiently recovering a large amount of untapped waste heat in the aluminum electrolysis process.

[0129] 3. The provided material waste heat extraction subsystem 200 can efficiently recover and utilize the waste heat of the flue gas emitted by the heated material 610, thereby realizing multi-dimensional utilization of the waste heat of the flue gas;

[0130] 4. By providing a telescopic mechanism in the material waste heat extraction subsystem 200 and a control subsystem 300, the waste heat extraction process of the waste heat material 7 to be recovered is fully automated, thereby improving operational safety;

[0131] 5. The technical solution of the waste heat recovery method disclosed in this disclosure can ensure stable operation during the waste heat recovery process, thereby improving recovery efficiency;

[0132] 6. Designing a purification unit 17 in the system can improve environmental protection effects.

[0133] According to the technical solutions of some embodiments of the present disclosure, it can be applied to the aluminum electrolysis process. The designed waste heat recovery and utilization system includes a material waste heat extraction subsystem that is connected to the flue gas waste heat recovery subsystem and is used to extract the waste heat of the waste heat material to be recovered by using the flue gas flowing through it; it also includes a flue gas waste heat recovery subsystem for recycling the waste heat of the flue gas discharged from the aluminum electrolysis cell and the waste heat extracted from the waste heat material to be recovered; it also includes a control subsystem for regulating the operating parameters of the material waste heat extraction subsystem and the flue gas waste heat recovery subsystem during the waste heat recovery and utilization process. It can be seen that in the present disclosure, the waste heat of the flue gas discharged from the aluminum electrolysis cell can be efficiently recovered and utilized by designing the flue gas waste heat recovery subsystem, and the waste heat of the waste heat material to be recovered with a large amount of waste heat can be efficiently recovered and utilized by designing the material waste heat extraction subsystem. Therefore, the technical solution disclosed in the present invention can be used to recycle the waste heat of materials with a large amount of waste heat, such as residual electrodes, high-temperature aluminum liquid, high-temperature solid waste, etc. Compared with the current technological status, it can achieve efficient recycling of a large amount of untapped waste heat, thereby achieving energy conservation and emission reduction, and improving environmental protection effects.

[0134] The foregoing description is merely an embodiment of the present disclosure and is not intended to limit the present disclosure. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure are intended to be within the scope of the claims of the present disclosure.

Claims

1. A waste heat recovery system, applied to aluminum electrolysis process, comprising: Material waste heat extraction subsystem, flue gas waste heat recovery subsystem and control subsystem; The material waste heat extraction subsystem is connected to the flue gas waste heat recovery subsystem, and is used to extract waste heat of the waste heat material to be recovered by using the flue gas flowing through it; The flue gas waste heat recovery subsystem is used to recover and utilize the waste heat of the flue gas discharged from the aluminum electrolysis cell, as well as the waste heat extracted from the waste heat material to be recovered; as well as The control subsystem is used to regulate the operating parameters of the material waste heat extraction subsystem and the flue gas waste heat recovery subsystem during the waste heat recovery and utilization process.

2. The system according to claim 1, wherein: The material waste heat extraction subsystem is also used to heat the material to be heated by utilizing the flue gas flowing through it.

3. The system according to claim 1, wherein: The material waste heat extraction subsystem comprises: a smoke inlet pipe, a smoke exhaust pipe and a material waste heat extraction device; The inlet of the flue gas inlet pipe is connected to the flue gas waste heat recovery subsystem, and the outlet of the flue gas inlet pipe is connected to the material waste heat extraction device; The inlet of the flue gas exhaust pipe is connected to the material waste heat extraction device, and the outlet of the flue gas exhaust pipe is connected to the flue gas waste heat recovery subsystem; and The material waste heat extraction device is used for placing materials whose waste heat is to be recovered.

4. The system according to claim 3, wherein: The material waste heat extraction subsystem also includes: A first filter screen is arranged at the inlet or outlet of the smoke inlet pipe; A second filter screen is arranged at the inlet of the smoke exhaust pipe; A first control valve, disposed on the flue gas inlet pipe, for adjusting the flow rate of flue gas flowing into the material waste heat extraction device; A second control valve is provided on the flue gas exhaust pipe and is used to adjust the flow rate of the flue gas flowing out of the material waste heat extraction device; A first thermometer, disposed on the flue gas exhaust pipe, for measuring the temperature of the flue gas flowing out of the material waste heat extraction device; and The first flow meter is arranged on the flue gas exhaust pipe and is used to measure the flow rate of the flue gas flowing out of the material waste heat extraction device.

5. The system according to claim 3, wherein: The material waste heat extraction device is a closed structure, and the material waste heat extraction device comprises: A load-bearing tray, arranged in the material waste heat extraction device, for carrying the waste heat material to be recovered; A telescopic mechanism, arranged at the lower side of the load-bearing tray, for realizing the moving in and out of the waste heat material to be recovered in the waste heat extraction device; A material tray, disposed on the upper side of the load-bearing tray, for placing the waste heat material to be recovered; A boss, disposed on the material tray, for isolating a lower surface of the waste heat material to be recovered from an upper surface of the material tray; and The protective device is arranged in the material waste heat extraction device and is used to protect the waste heat material to be recovered.

6. The system according to claim 1, wherein: The flue gas waste heat recovery subsystem includes a waste heat treatment unit, a flue gas delivery pipe, a second flow meter, a second temperature meter, and a third control valve; The fume conveying pipe is used to convey the fume discharged from the aluminum electrolysis cell to the waste heat treatment unit; The waste heat treatment unit is used to recover the waste heat of the flue gas discharged from the aluminum electrolysis cell and to obtain The waste heat is converted into usable heat; The second flow meter is arranged near the outlet of the smoke conveying pipe and is used to measure the flow rate of smoke in the smoke conveying pipe; The second thermometer is arranged on the smoke conveying pipe and is used to measure the temperature of the smoke in the smoke conveying pipe; as well as The third control valve is arranged on the smoke conveying pipe, and is used to adjust the flow rate of the smoke flowing through the smoke conveying pipe.

7. The system according to claim 6, wherein: The waste heat treatment unit comprises: a flue gas heat exchanger, connected to the outlet of the flue gas conveying pipe, for converting the recovered waste heat into hot water or water vapor; a purification unit connected to the flue gas heat exchanger and used for treating harmful substances input from the flue gas heat exchanger; an intermediate heat exchanger, connected to the flue gas heat exchanger via a first circulation loop and connected to a heat user via a second circulation loop, for regulating and distributing heat input from the flue gas heat exchanger; and A water tank is arranged on the second circulation loop and is used for stabilizing the heat provided to the heat user.

8. A waste heat recovery method, executed in the control subsystem of the waste heat recovery system according to any one of claims 1 to 7, the method comprising: When it is monitored that the waste heat material to be recovered is placed in the material waste heat extraction subsystem, the initial flow rate of the flue gas in the flue gas waste heat recovery subsystem is obtained, and the heat exchange rate for the waste heat material to be recovered is obtained, and the heat exchange rate is the heat extracted by the flue gas flowing through the material waste heat extraction subsystem per unit time; Determining a target flow rate of flue gas flowing through the material waste heat extraction subsystem based on the heat exchange rate, wherein the heat exchange rate is positively correlated with the target flow rate; as well as The opening degree of each control valve in the waste heat recovery system is regulated according to the initial flow rate and the target flow rate.

9. The method according to claim 8, wherein: The obtaining of the heat exchange rate for the waste heat material to be recovered comprises: Obtaining the initial temperature of the flue gas in the flue gas waste heat recovery subsystem, the initial residual heat of the waste heat material to be recovered, and the preset time for extracting waste heat from the waste heat material to be recovered; Determine the residual heat corresponding to the waste heat material to be recovered when the temperature is the initial temperature as the target residual heat; and The heat exchange rate is determined based on the initial residual heat, the target residual heat, and the preset time.

10. The method according to claim 9, further comprising: During the process of extracting waste heat from the waste heat material to be recovered, real-time monitoring of the flue gas temperature of the flue gas flowing out of the material waste heat extraction subsystem; as well as When it is monitored that the flue gas temperature is less than or equal to the initial temperature, the waste heat extraction of the waste heat material to be recovered is stopped.

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