Method for recovering flue gas waste heat of electrolytic cell

Abstract

The invention relates to the technical field of exhaust gas collection of electrolysis equipment, in particular to a flue gas waste heat recovery method for an electrolytic bath. The flue gas waste heat recovery method for the electrolytic cell comprises the steps that flue gas discharged from a flue gas outlet in an electrolytic cell covering material enters a high-temperature flue gas channel, flue gas mixed with air in a cavity in the upper portion of the electrolytic cell enters a low-temperature flue gas channel, and the high-temperature flue gas channel and the low-temperature flue gas channel convey the flue gas to a waste heat recovery system; a heat exchange medium in the waste heat recovery system firstly exchanges heat with flue gas in a low-temperature heat exchange section of the low-temperature flue gas channel, then exchanges heat with flue gas in a high-temperature heat exchange section of the high-temperature flue gas channel, and then enters the waste heat utilization equipment to release heat. Low-temperature flue gas can be effectively utilized, heat exchange media are subjected to primary low-temperature heat exchange, then the temperature of the media is increased, preheating is conducted, then secondary high-temperature heat exchange is conducted, the heat utilization rate is high, the flue gas temperature is increased, and the waste heat recovery effect is enhanced.

Description

Technical Field

[0001] This invention relates to the field of electrolysis equipment emission gas collection technology, and specifically to a method for recovering waste heat from electrolytic cell flue gas. Background Technology

[0002] In electrolytic production, the energy utilization rate of the electrolytic cell is less than 50%, with the remainder being lost to the atmosphere as heat. Flue gas heat dissipation accounts for approximately 30%-35% of the lost heat energy. The flue gas generated during aluminum electrolysis reaches temperatures of 900℃-950℃, with a flow rate of approximately 100 standard cubic meters per hour. The flue gas is discharged through exhaust pipes, exchanges heat with the waste heat recovery system, and then enters the purification system.

[0003] Traditional electrolytic cells have gas collection and exhaust structures such as Figure 1 and Figure 2 As shown, the electrolytic cell includes a cell shell 1, an upper outer cover, anode steel claws 9, and a covering material 2. The upper outer cover includes a horizontal cover plate 8 and a gas collecting cover plate 7. The covering material covers the anode carbon blocks. The horizontal cover plate, the gas collecting cover plate, the cell shell, and the covering material form the upper cavity 4 of the electrolytic cell. Flue gas can enter the upper cavity 4 from the flue gas outlet 3 on the covering material. The upper support 6 of the electrolytic cell is fixedly equipped with a flue gas exhaust pipe. The flue gas exhaust pipe includes a main exhaust pipe 101 and multiple exhaust branch pipes 102 arranged along the length of the electrolytic cell on the main exhaust pipe. Each exhaust branch pipe has an exhaust port 103. 3. Facing downwards is a flue gas outlet 3, which is also the feed port or fire port. A shell-breaking feeder 5 is fixedly installed on the upper support of the electrolytic cell. The shell-breaking feeder 5 has a feed pipe that extends out of the exhaust branch pipe 102. The feed channel is isolated from the flue gas channel. The lower end of the feed pipe is located below and close to the exhaust port, used to feed raw materials into the electrolytic cell. The part of the exhaust main pipe extending outside the electrolytic cell connects to the waste heat utilization system and the flue gas purification system. An induced draft fan is installed at the far end of the flue gas purification system. When the induced draft fan is working, it will generate negative pressure in the exhaust pipe and the upper cavity, which serves as the driving force for flue gas discharge. Under the action of negative pressure, the electrolytic flue gas is discharged from the bottom of the anode and enters the upper cavity through the flue gas outlet. A large amount of air also enters the upper cavity through the gaps between the multiple sets of movable gas collecting hoods on both sides and other gaps. The flue gas mixed with a large amount of air enters the exhaust pipe from the exhaust port, and then enters the flue gas purification system after passing through the waste heat utilization system.

[0004] During normal production, after the flue gas exits from the flue gas outlet, a large amount of air is mixed in the upper cavity before entering the exhaust pipe. The total emission is 8,000-10,000 standard cubic meters per hour, and the temperature drops from 900-950℃ to 110-150℃. When the flue gas mixed with air is used for waste heat utilization, the waste heat utilization rate is low and the utilization value is also low due to the low temperature of the flue gas. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering waste heat from electrolytic cell flue gas, so as to solve the problem of low waste heat utilization rate in current methods for recovering waste heat from electrolytic cell flue gas.

[0006] The technical solution of the waste heat recovery method for electrolytic cell flue gas of the present invention is as follows: A method for recovering waste heat from electrolytic cell flue gas includes: flue gas exiting from the flue gas outlet on the electrolytic cell covering material enters a high-temperature flue gas channel; flue gas mixed with air in the upper cavity of the electrolytic cell enters a low-temperature flue gas channel; the high-temperature flue gas channel and the low-temperature flue gas channel transport the flue gas to a waste heat recovery system; the heat exchange medium in the waste heat recovery system first exchanges heat with the flue gas in the low-temperature heat exchange section of the low-temperature flue gas channel, then exchanges heat with the flue gas in the high-temperature heat exchange section of the high-temperature flue gas channel, and then enters the waste heat utilization equipment to release heat.

[0007] Beneficial Effects: This invention innovatively provides a method for the graded utilization of high-temperature and low-temperature flue gas in electrolytic cell flue gas waste heat recovery. It utilizes a high-temperature flue gas channel to extract high-temperature flue gas directly from the flue gas outlet on the electrolytic cell's covering material, and a low-temperature flue gas channel to extract low-temperature flue gas mixed with air from the upper cavity of the electrolytic cell, ensuring a negative pressure environment within the upper cavity of the electrolytic cell equipment. Simultaneously, it allows the low-temperature flue gas mixed with air and the high-temperature flue gas directly discharged from the flue gas outlet to be transported separately. The heat exchange medium in the waste heat recovery system first exchanges heat with the low-temperature flue gas in the low-temperature heat exchange section of the low-temperature flue gas channel, and then exchanges heat with the high-temperature flue gas in the high-temperature heat exchange section of the high-temperature flue gas channel before entering the waste heat utilization equipment to release heat. This effectively utilizes the low-temperature flue gas. The heat exchange medium undergoes a first low-temperature heat exchange to raise its temperature for preheating, followed by a second high-temperature heat exchange, resulting in high waste heat utilization rate, increased flue gas temperature, and enhanced waste heat recovery effect.

[0008] Furthermore, the flue gas in the high-temperature flue gas channel flows into the low-temperature flue gas channel after passing through the high-temperature heat exchange section.

[0009] Furthermore, the flue gas in the high-temperature flue gas channel flows into the low-temperature flue gas channel from upstream of the low-temperature heat exchange section after passing through the high-temperature heat exchange section.

[0010] Furthermore, the portion of the high-temperature flue gas passage located upstream of the high-temperature heat exchange section independently transports flue gas within the low-temperature flue gas passage, while the high-temperature heat exchange section extends out of the low-temperature flue gas passage to exchange heat with the waste heat recovery system.

[0011] Furthermore, the high-temperature flue gas channel upstream of the high-temperature heat exchange section has a high-temperature main channel and high-temperature branch channels corresponding to each flue gas outlet. The low-temperature flue gas channel upstream of the low-temperature heat exchange section has a low-temperature main channel and low-temperature branch channels corresponding to each high-temperature branch channel. The high-temperature main channel is located inside the low-temperature main channel, the high-temperature branch channels are located inside the low-temperature branch channels, and the low-temperature branch channels and high-temperature branch channels are located in the upper cavity of the electrolytic cell.

[0012] Furthermore, the lower inlet of the high-temperature branch channel is connected to the flue gas outlet, and the lower inlet of the low-temperature branch channel is located above the lower inlet of the high-temperature branch channel.

[0013] Furthermore, the portion of the high-temperature flue gas passage located upstream of the high-temperature heat exchange section independently transports flue gas within the low-temperature flue gas passage. The high-temperature heat exchange section extends out of the low-temperature flue gas passage to exchange heat with the waste heat recovery system. Both the high-temperature flue gas passage and the low-temperature flue gas passage are formed by pipes, with an annular gap between the pipes forming the high-temperature flue gas passage and the pipes forming the low-temperature flue gas passage.

[0014] Furthermore, the outer wall of the pipe forming the high-temperature flue gas passage and the inner wall of the pipe forming the low-temperature flue gas passage are fixed together by a welded connecting plate.

[0015] Furthermore, after passing through the waste heat recovery system, the flue gas enters the flue gas purification system, and the exhaust fan of the flue gas purification system provides power for extracting the flue gas generated by the electrolytic cell.

[0016] Furthermore, the flue gas from each flue gas outlet on the electrolytic cell covering material enters each high-temperature branch channel of the high-temperature flue gas channel, and the flue gas in each high-temperature branch channel merges into the high-temperature main channel of the high-temperature flue gas channel before being transported out. Attached Figure Description

[0017] Figure 1 This is a front view of the electrolytic cell described in the background section. Figure 2 for Figure 1 A side view of the electrolytic cell in the diagram; Figure 3 This is a schematic diagram of the structure of the electrolytic cell in an embodiment of the waste heat recovery method for flue gas from an electrolytic cell according to the present invention; Figure 4 for Figure 3 A side view of the electrolytic cell in the middle; Figure 5 for Figure 3 A schematic diagram showing the connection between the flue gas pipeline of the electrolytic cell and the waste heat recovery system; Figure 6 for Figure 3A schematic diagram of the flue gas exhaust structure at the flue gas outlet. Figure 7 for Figure 5 A schematic diagram of the waste heat recovery system and heat exchange between the flue gas pipeline.

[0018] In the diagram: 1. Tank shell; 2. Covering material; 3. Flue gas outlet; 4. Upper cavity; 5. Shell-breaking feeder; 6. Upper support; 7. Gas collection hood; 8. Horizontal hood; 9. Anode steel claw; 101. Main exhaust pipe; 102. Branch exhaust pipe; 103. Exhaust port; 201. High-temperature flue gas main pipe; 202. High-temperature flue gas branch pipe; 203. High-temperature flue gas inlet; 211. Low-temperature flue gas main pipe; 212. Low-temperature flue gas branch pipe; 213. Low-temperature flue gas inlet; 300. Waste heat recovery system; 301. Circulating pump set; 302. Primary heat exchanger; 303. Secondary heat exchanger; 304. Waste heat utilization equipment. Detailed Implementation

[0019] The basic concept of the waste heat recovery method for electrolytic cell flue gas of the present invention is to utilize high-temperature flue gas and low-temperature flue gas in stages. The low-temperature flue gas mixed with air and the high-temperature flue gas discharged directly from the flue gas outlet are transported separately. The heat exchange medium in the waste heat recovery system first exchanges heat with the low-temperature flue gas and then with the high-temperature flue gas. This can effectively utilize the low-temperature flue gas, has a high heat utilization rate, increases the flue gas temperature, and enhances the waste heat recovery effect.

[0020] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0021] Embodiments of the waste heat recovery method for electrolytic cell flue gas of the present invention: The waste heat recovery method for electrolytic cell flue gas is used to recover and utilize the heat generated by the flue gas from the electrolytic cell. In this embodiment, the electrolytic cell is an aluminum electrolytic cell. To facilitate understanding of the implementation process of the waste heat recovery method for electrolytic cell flue gas, we will first combine... Figure 3 , Figure 4 , Figure 5The basic structure of the electrolytic cell equipment is described below. The electrolytic cell equipment includes a cell shell 1, an upper outer cover, anode steel claws 9, and a covering material 2. The upper outer cover includes a horizontal cover plate 8 and a gas collecting cover plate 7. The covering material 2 covers the anode carbon blocks. The horizontal cover plate 8, the gas collecting cover plate 7, the cell shell 1, and the covering material 2 form the upper cavity 4 of the electrolytic cell. Flue gas can enter the upper cavity 4 through the flue gas outlet 3 on the covering material 2. An exhaust pipe is fixedly installed on the upper support 6 of the electrolytic cell. The exhaust pipe connects to the waste heat recovery system and the flue gas purification system. An exhaust fan is installed at the far end of the flue gas purification system. When the exhaust fan is working, it generates negative pressure in the exhaust pipe and the upper cavity 4, serving as the driving force for flue gas discharge. The flue gas passes through the waste heat recovery system and then enters the flue gas purification system.

[0022] Combination Figure 5 , Figure 6 The exhaust piping system includes high-temperature and low-temperature piping. The high-temperature piping includes a high-temperature flue gas main pipe 201 and a high-temperature flue gas branch pipe 202, while the low-temperature piping includes a low-temperature flue gas main pipe 211 and a low-temperature flue gas branch pipe 212. The high-temperature piping directly transports the flue gas exiting from the flue gas outlet 3 on the electrolytic cell covering material 2. The low-temperature piping transports the flue gas mixed with air from the upper cavity 4 of the electrolytic cell. The flue gas enters the high-temperature piping immediately after exiting the flue gas outlet 3, where no air is mixed in, resulting in a very high temperature. The flue gas temperature in the high-temperature piping is higher than that in the low-temperature piping. The high-temperature flue gas main pipe 201 and the high-temperature flue gas branch pipe 202 form a high-temperature flue gas channel, while the low-temperature flue gas main pipe 211 and the low-temperature flue gas branch pipe 212 form a low-temperature flue gas channel.

[0023] The portion of the high-temperature flue gas main pipe 201 located within the upper cavity 4 of the electrolytic cell is its inner section. This inner section extends along the length of the electrolytic cell, with the aluminum outlet end and the flue gas duct end at opposite ends. Figure 3 At both ends of the electrolytic cell, one end of the high-temperature flue gas main pipe 201 is close to the aluminum outlet, and the other end extends from the flue end to the upper outer cover of the electrolytic cell. Multiple high-temperature flue gas branch pipes 202 are located within the upper cavity 4 and are arranged at intervals along the length of the electrolytic cell. The high-temperature flue gas branch pipes 202 are arranged perpendicular to the high-temperature flue gas main pipe 201. The lower end of each high-temperature flue gas branch pipe 202 forms a high-temperature flue gas inlet 203, and the upper end of each high-temperature flue gas branch pipe 202 is fixedly connected to and communicates with the same high-temperature flue gas main pipe 201. Each high-temperature flue gas branch pipe 202 corresponds to a flue gas outlet 3. The lower end of the high-temperature flue gas branch pipe 202 is inserted into a covering material 2 to form a certain seal, allowing the flue gas exiting the flue gas outlet 3 to directly enter the high-temperature flue gas branch pipe 202.

[0024] The portion of the low-temperature flue gas main pipe 211 located within the upper cavity 4 of the electrolytic cell is its in-cell section. This in-cell section extends along the length of the electrolytic cell, with one end near the aluminum outlet and the other end extending from the flue end into the upper outer cover of the electrolytic cell. Multiple low-temperature flue gas branch pipes 212 are located within the upper cavity 4 and are spaced apart along the length of the electrolytic cell. The branch pipes 212 are arranged perpendicular to the high-temperature flue gas main pipe 201. The lower end of each branch pipe 212 has a flared opening to form a bell mouth, constituting a low-temperature flue gas inlet 213. The upper end of each branch pipe 212 is fixedly connected to and communicates with the same low-temperature flue gas main pipe 211.

[0025] The grooved section of the high-temperature flue gas main pipe 201 is located within the inner cavity of the grooved section of the low-temperature flue gas main pipe 211, and they are coaxially arranged. Each low-temperature flue gas branch pipe 212 corresponds to a high-temperature flue gas branch pipe 202, and the high-temperature flue gas branch pipe 202 is located within the corresponding low-temperature flue gas branch pipe 212, and they are coaxially arranged. This forms a sleeve structure, which utilizes the low-temperature pipeline to reduce heat loss from the high-temperature pipeline during flue gas transportation, thus providing insulation.

[0026] The length of the low-temperature flue gas branch pipe 212 is shorter than the length of the high-temperature flue gas branch pipe 202, so that the low-temperature flue gas inlet 213 is located above the high-temperature flue gas inlet 203. The low-temperature flue gas inlet 213 is close to the horizontal cover plate 8 to facilitate the extraction of flue gas mixed with a large amount of air from the upper cavity 4. The high-temperature flue gas is transported independently in the slotted section of the high-temperature flue gas main pipe 201 from the slotted section of the low-temperature flue gas main pipe 211. The low-temperature flue gas can be transported using the annulus between the sleeves.

[0027] The upper support 6 of the electrolytic cell is fixedly equipped with a feeder, namely the shell-breaking feeder 5. The shell-breaking feeder 5 has a downward-extending feeder pipe. The feeder pipe passes through the high-temperature flue gas branch pipe 202 and is coaxially arranged. The feeder pipe can avoid the main flue gas pipe so that the feeder channel does not interfere with the flue gas channel. The feeder channel is isolated from the flue gas channel. The feeder port at the lower end of the feeder pipe is located above and directly opposite the flue gas outlet 3. The flue gas outlet 3 serves as the feeder port for feeding raw materials into the electrolytic cell.

[0028] Combination Figure 3 , Figure 7A high-temperature flue gas main pipe 201 extends beyond a low-temperature flue gas main pipe 211 outside the upper outer casing of the electrolytic cell. The portion of the high-temperature flue gas main pipe 201 that deviates from the low-temperature flue gas main pipe 211 constitutes a high-temperature heat exchange section. After extending beyond the low-temperature flue gas main pipe 211, the high-temperature flue gas main pipe 201 connects to the low-temperature flue gas main pipe 211, ensuring that the upstream end of the high-temperature heat exchange section is located inside and isolated from the low-temperature flue gas main pipe 211, while the downstream end connects to and is connected to the low-temperature flue gas main pipe 211. The downstream section of the low-temperature flue gas main pipe 211, located at the connection point with the high-temperature flue gas main pipe 201, constitutes a low-temperature heat exchange section. The flue gas inside the high-temperature flue gas main pipe 201 and the flue gas inside the low-temperature flue gas main pipe 211 converge in the low-temperature heat exchange section. After releasing heat to the waste heat recovery system 300, the flue gas flows to the flue gas purification system connected to the downstream low-temperature flue gas main pipe 211.

[0029] The waste heat recovery system 300 includes a circulating pump set 301, a primary heat exchanger 302, a secondary heat exchanger 303, and a waste heat utilization device 304. All components are installed on the circulating pipeline. The primary heat exchanger 302 is located in the low-temperature heat exchange section of the low-temperature flue gas main pipe 211, and the secondary heat exchanger 303 is located in the high-temperature heat exchange section of the high-temperature flue gas main pipe 201. The heat exchange medium in the pipeline is pressurized by the circulating pump set 301 and then passes sequentially through the primary heat exchanger 302 and the secondary heat exchanger 303 before entering the waste heat utilization device 304, thereby realizing the waste heat recovery method for electrolytic cell flue gas.

[0030] Specific process of waste heat recovery method for electrolytic cell flue gas: The flue gas exiting from the flue gas outlet 3 on the electrolytic cell cover material 2 enters the high-temperature flue gas channel. The flue gas mixed with air in the upper cavity 4 of the electrolytic cell enters the low-temperature flue gas channel. The high-temperature flue gas channel and the low-temperature flue gas channel transport the flue gas to the waste heat recovery system 300. The heat exchange medium in the waste heat recovery system 300 first exchanges heat with the flue gas in the low-temperature heat exchange section of the low-temperature flue gas channel, and then exchanges heat with the flue gas in the high-temperature heat exchange section of the high-temperature flue gas channel, and then enters the waste heat utilization equipment 304 to release heat.

[0031] High-temperature flue gas is extracted directly from the flue gas outlet 3 on the electrolytic cell covering material 2 using a high-temperature flue gas channel, while low-temperature flue gas mixed with air is extracted from the upper cavity 4 of the electrolytic cell using a low-temperature flue gas channel. This ensures a negative pressure environment within the upper cavity 4 of the electrolytic cell equipment. Simultaneously, the low-temperature flue gas mixed with air and the high-temperature flue gas discharged directly from the flue gas outlet 3 are transported separately. The high-temperature and low-temperature flue gas are utilized in stages and exchanged heat sequentially. This effectively utilizes the low-temperature flue gas. The heat exchange medium first undergoes a low-temperature heat exchange to raise its temperature for preheating, and then undergoes a second high-temperature heat exchange. This results in high heat utilization, increases the flue gas temperature, and enhances the waste heat recovery effect.

[0032] In this embodiment, the flue gas in the high-temperature flue gas channel merges into the low-temperature flue gas channel after passing through the high-temperature heat exchange section. This allows the flue gas from both channels to enter the flue gas purification system together, facilitating pipeline connection. In other embodiments, the two channels can be connected to the flue gas purification system separately, or the flue gas can be combined within the flue gas purification system.

[0033] The flue gas in the high-temperature flue gas channel exchanges heat in the high-temperature heat exchange section and then flows into the low-temperature flue gas channel upstream of the low-temperature heat exchange section. This allows the flue gas from both channels to converge and exchange heat with the waste heat recovery system 300, making full use of the flue gas temperature in the high-temperature flue gas channel. The secondary heat exchanger 303 allows the heat exchange medium in the pipeline of the waste heat recovery system 300 to exchange heat with the flue gas in the high-temperature heat exchange section of the high-temperature flue gas main pipe 201. After the flue gas temperature decreases, it enters the low-temperature flue gas main pipe 211 and then exchanges heat with the heat exchange medium in the pipeline of the waste heat recovery system 300 through the primary heat exchanger 302, improving heat utilization. In other embodiments, the flue gas in the high-temperature flue gas channel can also exchange heat in the high-temperature heat exchange section and then flow into the low-temperature flue gas channel downstream of the low-temperature heat exchange section, so the primary heat exchanger no longer uses the flue gas after heat exchange in the secondary heat exchanger.

[0034] In this embodiment, a sleeve structure formed by the high-temperature pipeline and the low-temperature pipeline is used to allow the upstream portion of the high-temperature flue gas channel to independently transport flue gas within the low-temperature flue gas channel. This upstream portion of the high-temperature flue gas channel includes its tank section and the high-temperature flue gas branch pipe 202. The high-temperature heat exchange section extends out of the low-temperature flue gas channel to exchange heat with the heat exchange medium of the waste heat recovery system 300. The independent transmission of high-temperature flue gas within the low-temperature pipeline reduces heat loss during transport and saves space. In other embodiments, the high-temperature pipeline and the low-temperature pipeline can be arranged in parallel, spaced apart. In this case, the high-temperature flue gas inlet and outlet face each other, and the low-temperature flue gas inlet is connected to the upper cavity of the electrolytic cell.

[0035] The section inside the high-temperature flue gas main pipe 201 is the high-temperature main channel upstream of the high-temperature heat exchange section of the high-temperature flue gas passage, and the high-temperature flue gas branch pipe 202 constitutes a high-temperature branch channel. The section inside the low-temperature flue gas main pipe 211 is the low-temperature main channel upstream of the low-temperature heat exchange section of the low-temperature flue gas passage, and the low-temperature flue gas branch pipe 212 constitutes a low-temperature branch channel. The high-temperature main channel is located inside the low-temperature main channel, and the high-temperature branch channel is located inside the low-temperature branch channel. The low-temperature branch channel and the high-temperature branch channel are located in the upper cavity 4 of the electrolytic cell. The flue gas from each flue gas outlet 3 on the electrolytic cell covering material 2 enters each high-temperature branch channel of the high-temperature flue gas passage, and the flue gas in each high-temperature branch channel merges into the high-temperature main channel of the high-temperature flue gas passage before being transported out. The low-temperature channel is similar. The flue gas branch pipes are arranged coaxially in a one-to-one correspondence, saving space and facilitating manufacturing. In other embodiments, the low-temperature flue gas branch pipes can also be staggered from the high-temperature flue gas branch pipes, with the high-temperature flue gas branch pipes passing through the low-temperature flue gas main pipe and sealed at the passage.

[0036] In this embodiment, the high-temperature flue gas branch pipe 202 extends onto the covering material 2, connecting the lower inlet of the high-temperature branch channel with the flue gas outlet 3. The lower inlet of the low-temperature branch channel is located above the lower inlet of the high-temperature branch channel, which is the corresponding flue gas inlet. This allows the high-temperature flue gas inlet 203 to directly connect to the flue gas outlet 3, preventing the high-temperature flue gas from being affected by the low-temperature flue gas in the upper cavity 4. In other embodiments, the high-temperature flue gas inlet can also be located above the flue gas outlet, with a closer distance; the closer the distance, the better.

[0037] Both the high-temperature and low-temperature flue gas channels are formed by pipes, with main pipes and branch pipes welded together, and pipes welded together where they pass through each other. An annular gap exists between the pipes forming the high-temperature and low-temperature flue gas channels. The outer wall of the high-temperature flue gas channel and the inner wall of the low-temperature flue gas channel are fixed together by welded connecting plates. The cross-sectional shape of the high-temperature and low-temperature pipelines can be circular or square hollow metal tubular structures. The low-temperature pipeline can be a separate welded steel plate assembly, or it can be a combination of a steel plate and the steel plate of the upper support 6 of the electrolytic cell, welded together. When a separate welded assembly is used, it is fixedly connected to the upper support 6 of the electrolytic cell by connecting steel plates. The high-temperature pipeline is a hollow structure independently welded from steel plates or pipes, located inside the low-temperature pipeline. The high-temperature pipeline is the inner pipe, and the low-temperature pipeline is the outer pipe. The inner pipe is fixed to the outer pipe by connecting steel plates.

[0038] The high-temperature flue gas main pipe 201 extends out of the low-temperature flue gas main pipe 211 from the outside of the upper outer casing and connects to the flue gas pipe joint of the secondary heat exchanger 303 in the high-temperature heat exchange section. The high-temperature flue gas, after heat exchange in the secondary heat exchanger 303, becomes low-temperature flue gas and then enters the low-temperature flue gas main pipe 211. The high-temperature flue gas in the electrolytic cell passes through the high-temperature flue gas main pipe 201, undergoes heat exchange in the secondary heat exchanger 303, and then merges into the low-temperature flue gas main pipe 211 to mix with the low-temperature flue gas from the electrolytic cell. After mixing, all the low-temperature flue gas undergoes further heat exchange in the primary heat exchanger 302. After heat exchange, the flue gas enters the electrolytic cell flue gas purification system. The power driving the flue gas flow is the exhaust fan of the electrolytic cell flue gas purification system.

[0039] For the heat exchange medium in the waste heat recovery system 300, it first exchanges heat with the low-temperature flue gas through the primary heat exchanger 302, and then exchanges heat with the high-temperature flue gas through the secondary heat exchanger 303. For the flue gas, it first exchanges heat with the heat exchange medium through the secondary heat exchanger 303, and then exchanges heat with the heat exchange medium through the primary heat exchanger 302. The flow direction of the heat exchange medium is opposite to the flow direction of the flue gas, forming a secondary counter-current heat exchange. The heat exchange medium first flows through the primary heat exchanger 302 for preheating before flowing into the secondary heat exchanger 303 for high-temperature heat exchange, and the heat exchange medium exchanges heat with the high and low temperature flue gas in a counter-current manner. The waste heat utilization equipment 304 can be a waste heat generator set, a community heating terminal, a refrigeration equipment, etc.

[0040] This method for recovering waste heat from electrolytic cell flue gas effectively utilizes low-temperature flue gas. The heat exchange medium first undergoes a low-temperature heat exchange in a low-temperature heat exchanger to raise its temperature, reaching over 95℃ after preheating. The high-temperature flue gas undergoes a secondary high-temperature heat exchange at 600℃-800℃, and the cold-end heat transfer medium can reach over 200℃ after the heat exchange. The power generation efficiency of the waste heat generator set can reach over 15%. This significantly improves flue gas temperature and waste heat power generation efficiency, enabling high-value recovery of waste heat from aluminum electrolytic cells and facilitating wider promotion and application.

[0041] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering waste heat from flue gas in an electrolytic cell, characterized in that, The flue gas exiting from the flue gas outlet on the electrolytic cell cover material enters the high-temperature flue gas channel. The flue gas mixed with air in the upper cavity of the electrolytic cell enters the low-temperature flue gas channel. The high-temperature flue gas channel and the low-temperature flue gas channel transport the flue gas to the waste heat recovery system. The heat exchange medium in the waste heat recovery system first exchanges heat with the flue gas in the low-temperature heat exchange section of the low-temperature flue gas channel, and then exchanges heat with the flue gas in the high-temperature heat exchange section of the high-temperature flue gas channel, before entering the waste heat utilization equipment to release heat.

2. The method for recovering waste heat from electrolytic cell flue gas according to claim 1, characterized in that, The flue gas in the high-temperature flue gas channel flows into the low-temperature flue gas channel after passing through the high-temperature heat exchange section.

3. The method for recovering waste heat from electrolytic cell flue gas according to claim 2, characterized in that, After passing through the high-temperature heat exchange section, the flue gas in the high-temperature flue gas channel merges into the low-temperature flue gas channel from upstream of the low-temperature heat exchange section.

4. The method for recovering waste heat from electrolytic cell flue gas according to claim 1, 2, or 3, characterized in that, at high temperature... The section of the flue gas passage located upstream of the high-temperature heat exchange section independently transports flue gas inside the low-temperature flue gas passage, while the high-temperature heat exchange section extends out of the low-temperature flue gas passage to exchange heat with the waste heat recovery system.

5. The method for recovering waste heat from electrolytic cell flue gas according to claim 4, characterized in that, at high temperature... The portion of the flue gas passage upstream of the high-temperature heat exchange section has a high-temperature main passage and high-temperature branch passages corresponding to each flue gas outlet. The portion of the low-temperature flue gas passage upstream of the low-temperature heat exchange section has a low-temperature main passage and low-temperature branch passages corresponding to each high-temperature branch passage. The high-temperature main passage is located inside the low-temperature main passage, and the high-temperature branch passages are located inside the low-temperature branch passages. The low-temperature branch passages and the high-temperature branch passages are located in the upper cavity of the electrolytic cell.

6. The method for recovering waste heat from electrolytic cell flue gas according to claim 5, characterized in that, The lower inlet of the high-temperature branch channel is connected to the flue gas outlet, and the lower inlet of the low-temperature branch channel is located above the lower inlet of the high-temperature branch channel.

7. The method for recovering waste heat from electrolytic cell flue gas according to claim 1, 2, or 3, characterized in that, at high temperature... The section of the flue gas passage located upstream of the high-temperature heat exchange section independently transports flue gas inside the low-temperature flue gas passage. The high-temperature heat exchange section extends out of the low-temperature flue gas passage to exchange heat with the waste heat recovery system. Both the high-temperature flue gas passage and the low-temperature flue gas passage are formed by pipes, and there is an annular gap between the pipes forming the high-temperature flue gas passage and the pipes forming the low-temperature flue gas passage.

8. The method for recovering waste heat from electrolytic cell flue gas according to claim 7, characterized in that, The outer wall of the pipe forming the high-temperature flue gas passage and the inner wall of the pipe forming the low-temperature flue gas passage are fixed together by a welded connecting plate.

9. The method for recovering waste heat from electrolytic cell flue gas according to claim 1, 2, or 3, characterized in that, After passing through the waste heat recovery system, the flue gas enters the flue gas purification system, and the exhaust fan of the flue gas purification system provides power for the extraction of flue gas generated by the electrolytic cell.

10. The method for recovering waste heat from electrolytic cell flue gas according to claim 1, 2, or 3, characterized in that, The flue gas from each outlet on the electrolytic cell cover material enters the respective high-temperature branch channels of the high-temperature flue gas channel. The flue gas in each high-temperature branch channel merges into the high-temperature main channel of the high-temperature flue gas channel before being transported out.

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