Pre-oxidation furnace based on temperature control air return system and pre-oxidation process for preparing CNFs

Abstract

The invention relates to the technical field of carbon fiber preparation, in particular to a pre-oxidation furnace based on a temperature control air return system and a pre-oxidation process for CNFs preparation. The efficient temperature-control air return device comprises a temperature-control air return channel, a plurality of heat flow filter cartridges, an oxygen filter cartridge, a synchronous cleaning device and a pipeline inner wall cleaning device, the temperature-control air return channel is mounted at the top of the pre-oxidation furnace, the heat flow filter cartridges are mounted on the temperature-control air return channel, the oxygen filter cartridge is mounted beside the heat flow filter cartridges, and the synchronous cleaning device is mounted on the inner wall of the pipeline. The synchronous cleaning device is installed on the heat flow filter cartridge and the oxygen filter cartridge and used for automatically dredging and cleaning the heat flow filter cartridge and the oxygen filter cartridge, and the pipeline inner wall cleaning device is installed in the temperature control air return channel and used for cleaning the inner wall of the temperature control air return channel. The production efficiency and the production quality are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber preparation, in particular to a pre-oxidation furnace based on a temperature-controlled return air system, and in particular to a pre-oxidation process for preparing CNFs. Background Art

[0002] The pre-oxidation furnace is a crucial equipment in the production process of carbon nanofibers (CNFs). It is mainly used to pre-oxidize PAN (polyacrylonitrile) and other raw fibers under high temperature to transform their molecular structure from a linear structure to a heat-resistant ladder structure, laying the foundation for the subsequent carbonization process.

[0003] Chinese patent CN206337341U discloses a return air device and a hot air circulation system for a pre-oxidation furnace, which includes a return air channel arranged inside the furnace body of the pre-oxidation furnace, a circulating fan and a heater arranged in the return air channel, and an air supply port connecting the return air channel with the atmosphere. An air filter is arranged in the return air channel, and the air filter is located between the air supply port and the circulating fan. Impurities such as dust in the air are filtered out by the air filter, which purifies the air, reduces impurities generated during the pre-oxidation treatment of carbon fibers, and improves the quality of the treated products.

[0004] The air filter of the above-mentioned device filters impurities in the air. The existing air filter removes impurities in the air entering the furnace through the filter layer to ensure a pure environment for the pre-oxidation process. However, although the traditional filter layer can block particulate impurities. But after long-term use, the filter layer will gradually become clogged. The foreign matter intercepted by the filter layer cannot be removed by itself. Over time, these foreign matter will accumulate on the filter layer, increasing the filtration resistance. Due to the clogging of the filter layer and the accumulation of foreign matter, the efficiency of the return air system will also be affected, resulting in poor temperature control effect, which will directly affect the product quality. At the same time, by-products such as tar may also be produced during the pre-oxidation process. These substances will not only reduce the air quality in the furnace, but may also adhere to the inside of the return air duct. However, the return air duct is long and inconvenient to clean. Every time the inner wall of the return air duct is cleaned, the return air duct needs to be dismantled, resulting in cumbersome cleaning steps and affecting work efficiency. Summary of the invention

[0005] In view of the above problems, a pre-oxidation furnace based on a temperature-controlled return air system and a pre-oxidation process for preparing CNFs are provided. The production efficiency and production quality can be effectively improved through an efficient temperature-controlled return air device.

[0006] In order to solve the problems of the prior art, the present invention provides a pre-oxidation furnace based on a temperature-controlled return air system, including a high-efficiency temperature-controlled return air device installed on the top of the pre-oxidation furnace, the high-efficiency temperature-controlled return air device including a temperature-controlled return air channel, a heat flow filter cartridge, an oxygen filter cartridge, a synchronous cleaning device and a pipeline inner wall cleaning device, the temperature-controlled return air channel is installed on the top of the pre-oxidation furnace, a circulating air inlet is provided at one end of the temperature-controlled return air channel, a circulating air outlet is provided at the end of the temperature-controlled return air channel away from the circulating air inlet, a low-speed exhaust port is provided at the upper end of the temperature-controlled return air channel, the low-speed exhaust port is connected to the circulating air inlet, a heating device and a suction fan are also installed inside the temperature-controlled return air channel, and a heat A plurality of heat flow filter cartridges are provided and installed on the temperature-controlled return air channel, the air inlet end of the heat flow filter cartridge is connected to the interior of the pre-oxidation furnace, the air outlet end of the heat flow filter cartridge is connected to the interior of the temperature-controlled return air channel, the oxygen filter cartridge is installed beside the heat flow filter cartridge, the air inlet end of the oxygen filter cartridge is connected to the outside of the pre-oxidation furnace, the air outlet end of the oxygen filter cartridge is connected to the interior of the temperature-controlled return air channel, a synchronous cleaning device is installed on the heat flow filter cartridge and the oxygen filter cartridge, the synchronous cleaning device is used to automatically clear and clean the heat flow filter cartridge and the oxygen filter cartridge, the pipeline inner wall cleaning device is installed inside the temperature-controlled return air channel, the pipeline inner wall cleaning device is used to clean the inner wall of the temperature-controlled return air channel.

[0007] Preferably, a first air inlet is provided at one end of the heat flow filter cartridge, a first air outlet is provided at a side of the heat flow filter cartridge, and a first air filter layer is installed on the first air outlet.

[0008] Preferably, a second air outlet is provided at one end of the oxygen filter cartridge, a second air inlet is provided on the side of the oxygen filter cartridge, a second air filter layer is installed on the second air inlet, and a preheating cartridge is installed on the second air outlet, and the preheating cartridge is used to heat the circulating air.

[0009] Preferably, both the front and rear ends of the preheating cylinder are provided with flow ports, a plurality of inclined guide plates are installed inside the preheating cylinder package, a heat-conducting frame is installed outside the preheating cylinder, and a plurality of heat-receiving plates are distributed on the heat-conducting frame.

[0010] Preferably, the synchronous cleaning device includes a plurality of backwash docking sleeves installed on the heat flow filter cartridge and the oxygen filter cartridge, a synchronous connecting plate is installed on the backwash docking sleeve, a linear drive is installed between the synchronous connecting plate and the temperature-controlled return air channel, and the synchronous cleaning device also includes an airflow detector installed inside the temperature-controlled return air channel.

[0011] Preferably, the backwash docking sleeve includes a flushing shaft installed on a synchronous connecting plate, a water spray head is provided on the flushing shaft, a cleaning outer cylinder is installed on the outer side of the flushing shaft, the cleaning outer cylinder is rotatably connected to the flushing shaft, a plurality of spiral cleaning brushes are provided on the inner wall of the cleaning outer cylinder, a sewage outlet is also provided on the cleaning outer cylinder, and the backwash docking sleeve also includes a synchronous driving device for driving the plurality of cleaning outer cylinders to rotate synchronously.

[0012] Preferably, the pipeline inner wall cleaning device includes a chain conveyor installed on the temperature-controlled return air channel, the movable end of the chain conveyor is equipped with a frame mounting rail, the frame mounting rail is detachably connected to the movable end of the chain conveyor, and a detachable inner wall cleaning strip is installed on the frame mounting rail.

[0013] Preferably, a plurality of mounting gears are installed inside the frame mounting rail, a rack mounting belt is sleeved on the outer side of the mounting gear, anti-skid teeth are provided on both the inner and outer sides of the rack mounting belt, the mounting gear is meshed with the anti-skid teeth on the inner wall of the rack mounting belt, a plurality of movable balls are also installed on the outer side of the frame mounting rail, and the frame mounting rail also includes a rotating drive device for driving the mounting gear to rotate.

[0014] Preferably, the front and rear ends of the inner wall cleaning strip are detachably connected, the inner wall of the inner wall cleaning strip is covered with mounting teeth, and the outer wall of the inner wall cleaning strip is provided with a scraping and cleaning surface.

[0015] A pre-oxidation process for preparing CNFs comprises the following steps; S1. Place CNFs into the pre-oxidation furnace, start the pre-oxidation furnace, check whether the heating device and the suction fan in the temperature-controlled return air channel are operating normally, and adjust them to the preset process temperature range; S2. Turn on the heat flow filter cartridge to allow the hot air flow generated inside the pre-oxidation furnace to be sucked in through the air inlet end of the heat flow filter cartridge to remove impurities such as particulate matter and smoke, ensuring that the air flow entering the temperature-controlled return air channel is clean. At the same time, start the oxygen filter cartridge to filter the external fresh air and introduce it into the temperature-controlled return air channel to provide necessary oxygen supplement for the furnace and maintain a suitable oxidation environment.

[0016] S3. The clean hot air flow and fresh oxygen are mixed inside the temperature-controlled return air duct, and are heated or insulated according to the preset process temperature by the heating device to ensure that the return air temperature is accurately controlled within the temperature range that is conducive to the formation of CNFs. The suction fan continues to work to promote the circulation of the air flow in the temperature-controlled return air duct, accelerate the heat exchange process, and improve the utilization rate of thermal energy; S4. The heated and mixed airflow re-enters the pre-oxidation furnace through the circulating air outlet to realize the recycling of heat energy and reduce energy waste. At the same time, the low-speed exhaust port at the upper end of the temperature-controlled return air channel remains open to maintain the airflow balance in the system and prevent excessive pressure.

[0017] S5. The synchronous cleaning device starts automatically to clear and clean the heat flow filter cartridge and the oxygen filter cartridge to prevent blockage and ensure filtration efficiency. This process can be set to be executed regularly to reduce the need for manual maintenance. The inner wall of the pipe inner wall cleaning device is used regularly to clean the inner wall of the temperature-controlled return air duct to remove dust, coke and other attachments to keep the duct unobstructed.

[0018] S6. Under the appropriate temperature, oxygen concentration and air circulation conditions provided by the temperature-controlled return air system, the pre-oxidation reaction is started. According to the specific process requirements, the parameters of the temperature-controlled return air system, such as temperature and air flow velocity, are adjusted to optimize the pre-oxidation reaction process and improve the yield of CNFs.

[0019] S7. When the pre-oxidation reaction reaches a predetermined time or degree, the pre-oxidized material is taken out from the pre-oxidation furnace and subjected to subsequent carbonization, activation and other treatment steps to finally obtain CNFs products.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The device realizes the automatic cleaning function of the heat flow filter cartridge and the oxygen filter cartridge by integrating a synchronous cleaning device. This innovative design not only significantly improves the filtration efficiency and ensures the quality of the air entering the pre-oxidation furnace, but also greatly extends the maintenance cycle of the filter. The problem of traditional filters being blocked due to long-term use has been effectively solved, reducing the downtime and cost caused by frequent replacement or cleaning of filters. At the same time, the automatic cleaning function reduces the need for manual intervention and improves the automation level and operation stability of the production line.

[0021] 2. The temperature-controlled return air channel and its internal heating device and suction fan together constitute an efficient heat recovery and recycling system. The return air is heated or insulated by the heating device, and combined with the negative pressure effect of the suction fan, the effective circulation of heat energy in the pre-oxidation furnace is achieved. This design not only improves the utilization rate of thermal energy, reduces energy consumption, but also reduces heat loss in the production process. In addition, the design of the temperature-controlled return air channel also takes into account airflow balance and pressure control, ensuring the stability and safety of system operation.

[0022] 3. The device is also equipped with a pipeline inner wall cleaning device, which is used to regularly clean the inner wall of the temperature-controlled return air channel. It effectively prevents the attachment and accumulation of byproducts such as tar on the inner wall of the channel, and maintains the overall cleanliness of the system. The clean inner wall of the channel not only reduces the air flow resistance and improves the operating efficiency of the system, but also avoids the interference of pollutants on the pre-oxidation process, thereby ensuring the stability and consistency of product quality. This comprehensive cleaning and maintenance measure provides a strong guarantee for the long-term stable operation and high-quality production of the pre-oxidation furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A three-dimensional diagram of a pre-oxidation furnace based on a temperature-controlled return air system Figure 1 .

[0024] Figure 2 A three-dimensional diagram of a pre-oxidation furnace based on a temperature-controlled return air system Figure 2 .

[0025] Figure 3 It is a front view of a pre-oxidation furnace based on a temperature-controlled return air system.

[0026] Figure 4 yes Figure 3 Cross-sectional view at section AA.

[0027] Figure 5 yes Figure 3 Cross-sectional view at section BB.

[0028] Figure 6 It is a three-dimensional schematic diagram of a hot flow filter cartridge in a pre-oxidation furnace based on a temperature-controlled return air system.

[0029] Figure 7 It is a three-dimensional schematic diagram of an oxygen filter cartridge in a pre-oxidation furnace based on a temperature-controlled return air system.

[0030] Figure 8 It is a cross-sectional perspective view of an oxygen filter cartridge in a pre-oxidation furnace based on a temperature-controlled return air system.

[0031] Fig. 9 The present invention is a three-dimensional schematic diagram of a backwash docking sleeve in a pre-oxidation furnace based on a temperature-controlled return air system.

[0032] Fig.10 An exploded view of a backwash docking sleeve in a pre-oxidation furnace based on a temperature controlled return air system.

[0033] Fig.11 The present invention is a three-dimensional schematic diagram of a pipe inner wall cleaning device in a pre-oxidation furnace based on a temperature-controlled return air system.

[0034] Fig.12 The diagram is a partial structural exploded view of a pipe inner wall cleaning device in a pre-oxidation furnace based on a temperature-controlled return air system.

[0035] The numbers in the figure are: 1. Pre-oxidation furnace; 2. Temperature-controlled return air channel; 21. Low-speed exhaust port; 22. Circulating air outlet; 23. Circulating air inlet; 24. Heating device; 25. Suction fan; 3. Heat flow filter cartridge; 31. First air inlet; 32. First air outlet; 33. First air filter layer; 4. Oxygen filter cartridge; 41. Second air inlet; 42. Second air outlet; 43. Second air filter layer; 44. Pre-heating cartridge; 441. Flow port; 442. Inclined guide plate; 443. Heat-conducting frame; 444. Heat receiving plate; 5. Same as above. Step cleaning device; 51, backwash docking sleeve; 511, flushing shaft; 5111, water spray head; 512, cleaning outer cylinder; 5121, spiral cleaning brush; 513, synchronous drive device; 52, synchronous connecting plate; 53, linear drive; 6, pipeline inner wall cleaning device; 61, chain conveyor; 62, frame mounting rail; 621, mounting gear; 622, rack mounting belt; 623, anti-skid tooth; 624, rotary drive device; 63, inner wall cleaning strip; 631, mounting clamping tooth; 632, scraping cleaning surface. DETAILED DESCRIPTION

[0036] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0037] See also Figures 1 to 12 As shown, a pre-oxidation furnace based on a temperature-controlled return air system includes a high-efficiency temperature-controlled return air device installed on the top of the pre-oxidation furnace 1, and the high-efficiency temperature-controlled return air device includes a temperature-controlled return air channel 2, a heat flow filter cartridge 3, an oxygen filter cartridge 4, a synchronous cleaning device 5 and a pipeline inner wall cleaning device 6; The temperature-controlled return air channel 2 is installed at the top of the pre-oxidation furnace 1, and a circulating air inlet 23 is provided at one end of the temperature-controlled return air channel 2, and a circulating air outlet 22 is provided at one end of the temperature-controlled return air channel 2 away from the circulating air inlet 23. A low-speed exhaust port 21 is provided at the upper end of the temperature-controlled return air channel 2, and the low-speed exhaust port 21 is connected to the circulating air inlet 23. A heating device 24 and a suction fan 25 are also installed inside the temperature-controlled return air channel 2; A plurality of hot flow filter cartridges 3 are provided and installed on the temperature-controlled return air channel 2. The air inlet end of the hot flow filter cartridge 3 is connected to the interior of the pre-oxidation furnace 1, and the air outlet end of the hot flow filter cartridge 3 is connected to the interior of the temperature-controlled return air channel 2. The oxygen filter cartridge 4 is installed beside the heat flow filter cartridge 3, the air inlet end of the oxygen filter cartridge 4 is connected to the outside of the pre-oxidation furnace 1, and the air outlet end of the oxygen filter cartridge 4 is connected to the inside of the temperature control return air channel 2; The synchronous cleaning device 5 is installed on the heat flow filter cartridge 3 and the oxygen filter cartridge 4, and the synchronous cleaning device 5 is used to automatically clear and clean the heat flow filter cartridge 3 and the oxygen filter cartridge 4; The duct inner wall cleaning device 6 is installed inside the temperature-controlled return air channel 2 , and the duct inner wall cleaning device 6 is used to clean the inner wall of the temperature-controlled return air channel 2 .

[0038] During the operation of the pre-oxidation furnace 1, the hot air flow generated in the furnace is sucked in through the air inlet end of the hot flow filter cartridge 3. These hot air flows may contain impurities such as particulate matter and smoke. At the same time, fresh air from the outside is sucked in through the air inlet end of the oxygen filter cartridge 4, and after filtration, it provides necessary oxygen supplementation, which helps to maintain a suitable oxidation environment in the furnace. The airflows treated by the hot flow filter cartridge 3 and the oxygen filter cartridge 4, that is, the clean hot air flow and fresh oxygen, enter the temperature-controlled return air channel 2 together. The heating device 24 installed inside the temperature-controlled return air channel 2 heats or insulates the airflow entering the channel according to the preset process temperature requirements to ensure that the return air temperature meets the process requirements. The suction fan 25 generates negative pressure to promote the airflow to circulate in the temperature-controlled return air channel 2, accelerate the heat exchange process, and improve the utilization rate of thermal energy. The heated and mixed airflow circulates in the temperature-controlled return air channel 2, and the airflow re-enters the pre-oxidation furnace 1 through the circulation outlet 22, realizing the recycling of thermal energy and reducing energy waste. At the same time, in order to maintain the air flow balance in the system and prevent excessive pressure, the low-speed exhaust port 21 at the upper end of the temperature-controlled return air channel 2 is connected to the circulating air inlet 23, allowing a small amount of airflow to be discharged from the system at a low speed to form a natural convection cycle. The synchronous cleaning device 5 regularly clears and cleans the heat flow filter cartridge 3 and the oxygen filter cartridge 4 to prevent the filter cartridge from being blocked and affecting the air flow, thereby ensuring the filtration efficiency. This automated process reduces the need for manual maintenance and improves the stability and reliability of the system. The pipeline inner wall cleaning device 6 is responsible for cleaning the inner wall of the temperature-controlled return air channel 2, removing dust, coking and other attachments, keeping the channel unobstructed, ensuring smooth airflow, and improving the overall operation efficiency of the system. The comprehensive optimization of the pre-oxidation process effectively improves product quality and production efficiency.

[0039] See also Figures 1 to 5 As shown, a first air inlet 31 is provided at one end of the heat flow filter cartridge 3 , a first air outlet 32 ​​is provided at the side of the heat flow filter cartridge 3 , and a first air filter layer 33 is installed on the first air outlet 32 ​​.

[0040] The hot air flow generated in the pre-oxidation furnace 1 is first sucked in through the first air inlet 31 of the hot flow filter cartridge 3. Impurities such as particulate matter and smoke carried in the hot air flow are effectively intercepted and removed when passing through the first air filter layer 33 inside the hot flow filter cartridge 3. The filtered hot air flow then reaches the first air outlet 32 ​​of the hot flow filter cartridge 3, and the first air outlet 32 ​​transports the air flow to the interior of the temperature-controlled return air channel 2, effectively forming a hot flow circulation filtration.

[0041] See also Figures 1 to 6As shown, a second air outlet 42 is provided at one end of the oxygen filter cartridge 4, a second air inlet 41 is provided at the side of the oxygen filter cartridge 4, a second air filter layer 43 is installed on the second air inlet 41, and a preheating cartridge 44 is installed on the second air outlet 42, and the preheating cartridge 44 is used to heat the circulating air.

[0042] The side of the oxygen filter cartridge 4 is provided with a second air inlet 41, which is connected to the external environment and is used to inhale fresh air. A second air filter layer 43 is installed on the second air inlet 41. This layer of filter material can effectively intercept large particles, dust, pollen and other impurities in the air to ensure the purification of the air entering the oxygen filter cartridge 4. The filtered clean air flows out through one end of the oxygen filter cartridge 4, namely the second air outlet 42, and enters the interior of the preheating cartridge 44, which preheats the clean air entering. Preheating is to make the temperature of the fresh air closer to the process temperature inside the preoxidation furnace 1, thereby reducing the heat loss caused by the excessive temperature difference and improving the thermal energy utilization rate of the entire system. At the same time, the preheated air also helps to maintain the stability of the temperature in the temperature-controlled return air channel 2 and optimize the conditions of the preoxidation process. The preheating cartridge 44 then transports the heated air to the temperature-controlled return air channel 2 and mixes it with the hot air flow output by the hot flow filter cartridge 3.

[0043] See also Figure 6 and Figure 7 As shown, both the front and rear ends of the preheating tube 44 are provided with flow ports 441, a plurality of inclined guide plates 442 are installed inside the preheating tube 44, a heat conducting frame 443 is installed outside the preheating tube 44, and a plurality of heat receiving plates 444 are distributed on the heat conducting frame 443.

[0044] A plurality of inclined guide plates 442 are installed inside the preheating tube 44. These guide plates not only guide the direction of the airflow, but also promote the uniform distribution and full mixing of the airflow in the preheating tube 44 through their special inclination angles. When the air flows through the guide plates, the contact area between the air and the inner wall of the preheating tube 44 and the heat receiving plate 444 is increased, thereby improving the heat exchange efficiency. A heat conducting frame 443 is installed outside the preheating tube 44, and a plurality of heat receiving plates 444 are distributed on the heat conducting frame 443. The heat conducting frame 443 and the heat receiving plate 444 are arranged in the area of ​​the low-speed exhaust port 21. The heat receiving plate 444 contacts the hot air flowing to the low-speed exhaust port 21, and the heat conducting frame 443 and the heat receiving plate 444 absorb the heat of the airflow discharged outward. When the clean air flows through the inside of the preheating tube 44, the heat on the heat receiving plate 444 is transferred to the inner wall of the preheating tube 44 through the heat conducting frame 443, and then transferred to the air flowing through, so as to realize the preheating of the air.

[0045] See also Figure 1 and Figure 2As shown, the synchronous cleaning device 5 includes a plurality of backwash docking sleeves 51 installed on the heat flow filter cartridge 3 and the oxygen filter cartridge 4, a synchronous connecting plate 52 is installed on the backwash docking sleeve 51, a linear drive 53 is installed between the synchronous connecting plate 52 and the temperature-controlled return air channel 2, and the synchronous cleaning device 5 also includes an airflow detector installed inside the temperature-controlled return air channel 2.

[0046] The airflow detector is used to monitor the flow rate of the circulating gas in real time to ensure the balance and stability of the airflow in the system. When the airflow velocity is lower than or higher than the preset threshold, the airflow detector will send a signal to trigger the cleaning process of the synchronous cleaning device 5 to prevent the flow rate from decreasing or the system pressure from being too high due to the blockage of the filter cartridge. When the synchronous cleaning device 5 receives the cleaning instruction, the linear drive 53 starts to push the synchronous connecting plate 52 and the backwashing docking sleeve 51 thereon to move along the axial direction of the filter cartridge. During the movement, the backwashing docking sleeve 51 fits tightly with the inner wall of the filter cartridge, and removes impurities such as particulate matter and smoke attached to the inner wall of the filter cartridge through physical friction and the action of the backwashing fluid. The entire cleaning process is automated and controlled, reducing the need for manual maintenance. Since multiple backwashing docking sleeves 51 work synchronously, the cleaning efficiency is significantly improved, which can ensure that the filter cartridge can restore good filtering performance in a relatively short time. At the same time, the real-time monitoring function of the airflow detector ensures the stability and reliability of the system operation. Regular cleaning and maintenance ensures that the heat flow filter cartridge 3 and the oxygen filter cartridge 4 are unobstructed, so that the hot air flow generated in the furnace and the fresh air outside can smoothly enter the temperature-controlled return air channel 2 for heating and mixing. This helps to maintain a suitable oxidation environment in the furnace, improve product quality and production efficiency. At the same time, it reduces the system downtime caused by filter cartridge blockage and improves the overall operation efficiency of the system.

[0047] See also Figure 2 , Fig. 9 and Fig.10 As shown, the backwash docking sleeve 51 includes a flushing shaft 511 installed on a synchronous connecting plate 52, a water spray head 5111 is provided on the flushing shaft 511, a cleaning outer cylinder 512 is installed on the outer side of the flushing shaft 511, the cleaning outer cylinder 512 is rotatably connected to the flushing shaft 511, a plurality of spiral cleaning brushes 5121 are provided on the inner wall of the cleaning outer cylinder 512, a sewage outlet is also provided on the cleaning outer cylinder 512, and the backwash docking sleeve 51 also includes a synchronous driving device 513 for driving the plurality of cleaning outer cylinders 512 to rotate synchronously.

[0048] The water spray head 5111 of the flushing shaft 511 is connected to the water pipe, and the sewage outlet of the cleaning outer cylinder 512 is connected to the sewage pipe. The synchronous driving device 513 is a prior art and will not be described in detail here.

[0049] When the airflow detector detects that the flow rate of the circulating gas is lower than or higher than the preset threshold, a signal is sent to trigger the start of the synchronous cleaning device 5. After receiving the cleaning instruction, the linear drive 53 pushes the synchronous connecting plate 52 and the backwashing docking sleeve 51 thereon to move to a predetermined position along the axial direction of the filter cartridge. At the same time, the synchronous drive device 513 is started to drive multiple cleaning outer cylinders 512 to rotate at the same speed and direction. The rotating cleaning outer cylinder 512 scrapes and cleans the outer wall of the heat flow filter cartridge 3 or the oxygen filter cartridge 4 through the spiral cleaning brush 5121 on its inner wall to remove attached impurities such as particulate matter and smoke. At the same time, the water spray head 5111 of the flushing shaft 511 starts to work, and the high-pressure water flow is sprayed into the interior of the heat flow filter cartridge 3 or the oxygen filter cartridge 4 through the water spray head 5111, flushing its filtering area from the inside to further remove impurities and blockages. The scraped and flushed impurities, sewage, etc. are discharged into the sewage pipe through the sewage outlet of the cleaning outer cylinder 512, and finally discharged out of the system. After the cleaning process is completed, the linear drive 53 moves the backwash docking sleeve 51 back to its original position and waits for the next cleaning instruction. Since the backwash docking sleeve 51 adopts a combined internal and external cleaning method, namely, the scraping of the external cleaning outer cylinder 512 and the flushing of the internal flushing shaft 511, the filtering area of ​​the heat flow filter cartridge 3 and the oxygen filter cartridge 4 can be fully and thoroughly cleaned, ensuring that they can restore good filtering performance in a relatively short time.

[0050] See also Figure 1 and Fig.11 As shown, the pipeline inner wall cleaning device 6 includes a chain conveyor 61 installed on the temperature-controlled return air channel 2, and a frame mounting rail 62 is installed on the movable end of the chain conveyor 61. The frame mounting rail 62 is detachably connected to the movable end of the chain conveyor 61, and a detachable inner wall cleaning strip 63 is installed on the frame mounting rail 62.

[0051] When dust and tar are attached to the inside of the temperature-controlled return air channel 2 and need to be cleaned regularly, the staff opens the temperature-controlled return air channel 2 and installs the frame mounting rail 62 to the movable end of the chain conveyor 61, and then starts the chain conveyor 61. The chain conveyor 61 moves back and forth in the temperature-controlled return air channel 2 along the preset track. As the chain conveyor 61 moves, the frame mounting rail 62 and the inner wall cleaning strip 63 thereon also move accordingly, closely fitting or approaching the inner wall of the channel. Under the guidance of the frame mounting rail 62, the inner wall cleaning strip 63 scrapes and cleans along the inner wall of the temperature-controlled return air channel 2. The cleaning strip is effective in removing dust, tar and other impurities attached to the inner wall of the channel. After cleaning, the staff will take out the frame mounting rail 62, remove it from the temperature-controlled return air channel 2, check whether the inner wall cleaning strip 63 needs to be replaced, and take out the frame mounting rail 62 at the same time, which can effectively prevent it from blocking the airflow inside the temperature-controlled return air channel 2. The device effectively improves work efficiency.

[0052] See also Fig.11 and Fig.12 As shown, a plurality of mounting gears 621 are installed inside the frame mounting rail 62, a rack mounting belt 622 is sleeved on the outer side of the mounting gear 621, anti-skid teeth 623 are provided on both the inner and outer sides of the rack mounting belt 622, the mounting gear 621 is meshed with the anti-skid teeth 623 on the inner wall of the rack mounting belt 622, a plurality of movable balls are also installed on the outer side of the frame mounting rail 62, and the frame mounting rail 62 also includes a rotating drive device 624 for driving the mounting gear 621 to rotate.

[0053] The movable ball is used to abut against the inner wall of the temperature-controlled return air channel 2. The rotary drive device 624 is a prior art and will not be described in detail herein.

[0054] When dust and tar adhere to the inside of the temperature-controlled return air duct 2 and need to be cleaned regularly, the staff first removably installs the frame mounting rail 62 to the movable end of the chain conveyor 61. Start the chain conveyor 61 and make it move back and forth along the preset track in the temperature-controlled return air duct 2. The multiple movable balls installed on the outside of the frame mounting rail 62 tightly contact the inner wall of the duct during movement, ensuring that the frame mounting rail 62 and the inner wall maintain a stable contact state, reducing friction resistance and protecting the inner wall of the duct from being scratched. The multiple mounting gears 621 installed inside the frame mounting rail 62 work in conjunction with the rack mounting belt 622 mounted on the outside. The anti-skid teeth 623 on the outside of the rack mounting belt 622 are used to install the inner wall cleaning strip 63. When the chain conveyor 61 drives the frame mounting rail 62 to move, the mounting gear 621 rotates under the drive of the rotation drive device 624. The anti-skid teeth 623 are engaged with the rack mounting belt 622 to drive the rack mounting belt 622 to rotate. When the rack mounting belt 622 rotates, the inner wall cleaning strip 63 is driven to rotate synchronously, and the inner wall of the temperature-controlled return air duct 2 is rotated and scraped to clean. As the chain conveyor 61 moves, the inner wall cleaning strip 63 is guided by the frame mounting rail 62 to scrape and clean the dust, tar and other impurities on the inner wall. The inner wall cleaning strip 63 is effectively driven to rotate and clean.

[0055] See also Fig.11 and Fig.12 As shown, the front and rear ends of the inner wall cleaning strip 63 are detachably connected, the inner wall of the inner wall cleaning strip 63 is covered with mounting teeth 631 , and the outer wall of the inner wall cleaning strip 63 is provided with a scraping and cleaning surface 632 .

[0056] The mounting teeth 631 mesh with the anti-skid teeth 623 on the outer wall of the rack mounting belt 622, and the scraping and cleaning surface 632 also has a certain adsorption property. Before the cleaning operation, the staff soaks the inner wall cleaning strip 63 in a detergent so that the scraping and cleaning surface 632 absorbs a certain amount of detergent. These detergents have the function of softening dirt such as tar and dust, which helps to improve the subsequent cleaning effect. The front and rear ends of the inner wall cleaning strip 63 are designed to be detachably connected. During installation, the mounting teeth 631 on the inner wall of the inner wall cleaning strip 63 are meshed with the anti-skid teeth 623 on the outer wall of the rack mounting belt 622 to ensure that the inner wall cleaning strip 63 can be firmly fixed on the rack mounting belt 622 and rotate with it. The scraping and cleaning surface 632 of the inner wall cleaning strip 63 scrapes and cleans the inner wall of the temperature-controlled return air channel 2 during the rotation process. Since the scraping cleaning surface 632 absorbs the cleaning agent, the cleaning agent can soften and decompose the dirt such as tar and dust on the inner wall, so that the scraping cleaning surface 632 can more effectively scrape the dirt off the inner wall. The inner wall cleaning strip 63 can effectively and efficiently clean the inner wall of the temperature control return air channel 2.

[0057] A pre-oxidation process for preparing CNFs comprises the following steps; S1. Put CNFs into the pre-oxidation furnace 1, start the pre-oxidation furnace 1, check whether the heating device 24 and the suction fan 25 in the temperature-controlled return air channel 2 are operating normally, and adjust them to a preset process temperature range.

[0058] S2. Turn on the heat flow filter cartridge 3, so that the hot air flow generated inside the pre-oxidation furnace 1 is sucked in through the air inlet end of the heat flow filter cartridge 3 to remove impurities such as particulate matter and smoke, and ensure that the air flow entering the temperature-controlled return air channel 2 is clean. At the same time, start the oxygen filter cartridge 4 to filter the external fresh air and introduce it into the temperature-controlled return air channel 2 to provide necessary oxygen supplement for the furnace and maintain a suitable oxidation environment.

[0059] S3. The clean hot air flow and fresh oxygen are mixed inside the temperature-controlled return air channel 2, and are heated or insulated according to the preset process temperature by the heating device 24 to ensure that the return air temperature is accurately controlled within a temperature range that is conducive to the formation of CNFs. The suction fan 25 continues to work to promote the circulation of the air flow in the temperature-controlled return air channel 2, accelerate the heat exchange process, and improve the utilization rate of thermal energy.

[0060] S4. The heated and mixed airflow re-enters the pre-oxidation furnace 1 through the circulating air outlet 22, realizing the recycling of heat energy and reducing energy waste. At the same time, the low-speed exhaust port 21 at the upper end of the temperature-controlled return air channel 2 remains open to maintain the airflow balance in the system and prevent excessive pressure.

[0061] S5, the synchronous cleaning device 5 starts automatically to clear and clean the heat flow filter cartridge 3 and the oxygen filter cartridge 4 to prevent blockage and ensure the filtration efficiency. This process can be set to be executed regularly to reduce the need for manual maintenance. The pipeline inner wall cleaning device 6 is used regularly to clean the inner wall of the temperature-controlled return air channel 2 to remove dust, coke and other attachments to keep the channel unobstructed.

[0062] S6. Under the appropriate temperature, oxygen concentration and air circulation conditions provided by the temperature-controlled return air system, the pre-oxidation reaction is started. According to the specific process requirements, the parameters of the temperature-controlled return air system, such as temperature and air flow velocity, are adjusted to optimize the pre-oxidation reaction process and improve the yield of CNFs.

[0063] S7. When the pre-oxidation reaction reaches a predetermined time or degree, the pre-oxidized material is taken out from the pre-oxidation furnace 1 and subjected to subsequent treatment steps such as carbonization and activation to finally obtain CNFs products.

[0064] The above embodiments only express one or several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A pre-oxidation furnace based on a temperature-controlled return air system, characterized in that: It comprises a high-efficiency temperature-controlled return air device installed on the top of a pre-oxidation furnace (1), the high-efficiency temperature-controlled return air device comprising a temperature-controlled return air channel (2), a heat flow filter cartridge (3), an oxygen filter cartridge (4), a synchronous cleaning device (5) and a pipeline inner wall cleaning device (6); A temperature-controlled return air channel (2) is installed at the top of the pre-oxidation furnace (1); a circulating air inlet (23) is provided at one end of the temperature-controlled return air channel (2); a circulating air outlet (22) is provided at one end of the temperature-controlled return air channel (2) away from the circulating air inlet (23); a low-speed exhaust port (21) is provided at the upper end of the temperature-controlled return air channel (2); the low-speed exhaust port (21) is communicated with the circulating air inlet (23); a heating device (24) and a suction fan (25) are also installed inside the temperature-controlled return air channel (2); A plurality of heat flow filter cartridges (3) are provided and installed on the temperature-controlled return air channel (2); an air inlet end of the heat flow filter cartridge (3) is connected to the interior of the pre-oxidation furnace (1); and an air outlet end of the heat flow filter cartridge (3) is connected to the interior of the temperature-controlled return air channel (2); The oxygen filter cartridge (4) is installed beside the heat flow filter cartridge (3), the air inlet end of the oxygen filter cartridge (4) is connected to the outside of the pre-oxidation furnace (1), and the air outlet end of the oxygen filter cartridge (4) is connected to the inside of the temperature-controlled return air channel (2); The synchronous cleaning device (5) is installed on the heat flow filter cartridge (3) and the oxygen filter cartridge (4), and the synchronous cleaning device (5) is used to automatically clear and clean the heat flow filter cartridge (3) and the oxygen filter cartridge (4); The duct inner wall cleaning device (6) is installed inside the temperature-controlled return air duct (2), and the duct inner wall cleaning device (6) is used to clean the inner wall of the temperature-controlled return air duct (2); The synchronous cleaning device (5) comprises a plurality of backwash docking sleeves (51) mounted on the heat flow filter cartridge (3) and the oxygen filter cartridge (4); a synchronous connecting plate (52) is mounted on the backwash docking sleeve (51); a linear drive (53) is mounted between the synchronous connecting plate (52) and the temperature-controlled return air channel (2); and the synchronous cleaning device (5) further comprises an airflow detector mounted inside the temperature-controlled return air channel (2); The backwashing docking sleeve (51) comprises a flushing shaft (511) mounted on a synchronous connecting plate (52); a water spray head (5111) is provided on the flushing shaft (511); a cleaning outer cylinder (512) is mounted on the outer side of the flushing shaft (511); the cleaning outer cylinder (512) is rotatably connected to the flushing shaft (511); a plurality of spiral cleaning brushes (5121) are provided on the inner wall of the cleaning outer cylinder (512); a sewage discharge port is also provided on the cleaning outer cylinder (512); and the backwashing docking sleeve (51) further comprises a synchronous driving device (513) for driving the plurality of cleaning outer cylinders (512) to rotate synchronously.

2. A pre-oxidation furnace based on a temperature-controlled return air system according to claim 1, characterized in that: A first air inlet (31) is provided at one end of the heat flow filter cartridge (3), a first air outlet (32) is provided at the side of the heat flow filter cartridge (3), and a first air filter layer (33) is installed on the first air outlet (32).

3. The pre-oxidation furnace based on the temperature control return air system according to claim 1 is characterized in that: A second air outlet (42) is provided at one end of the oxygen filter cartridge (4), a second air inlet (41) is provided at the side of the oxygen filter cartridge (4), a second air filter layer (43) is installed on the second air inlet (41), and a preheating cartridge (44) is installed on the second air outlet (42), and the preheating cartridge (44) is used to heat the circulating air.

4. A pre-oxidation furnace based on a temperature-controlled return air system according to claim 3, characterized in that: The front and rear ends of the preheating tube (44) are both provided with flow ports (441), a plurality of inclined guide plates (442) are installed inside the preheating tube (44), a heat conducting frame (443) is installed outside the preheating tube (44), and a plurality of heat receiving plates (444) are distributed on the heat conducting frame (443).

5. The pre-oxidation furnace based on the temperature control return air system according to claim 1, characterized in that: The duct inner wall cleaning device (6) comprises a chain conveyor (61) mounted on the temperature-controlled return air duct (2); a frame mounting rail (62) is mounted on the movable end of the chain conveyor (61); the frame mounting rail (62) is detachably connected to the movable end of the chain conveyor (61); and a detachable inner wall cleaning strip (63) is mounted on the frame mounting rail (62).

6. A pre-oxidation furnace based on a temperature-controlled return air system according to claim 5, characterized in that: A plurality of mounting gears (621) are installed inside the frame mounting rail (62), a rack mounting belt (622) is sleeved on the outer side of the mounting gear (621), anti-skid teeth (623) are provided on both the inner and outer sides of the rack mounting belt (622), the mounting gear (621) is meshed with the anti-skid teeth (623) on the inner wall of the rack mounting belt (622), a plurality of movable balls are also installed on the outer side of the frame mounting rail (62), and the frame mounting rail (62) further comprises a rotation driving device (624) for driving the mounting gear (621) to rotate.

7. A pre-oxidation furnace based on a temperature-controlled return air system according to claim 6, characterized in that: The front and rear ends of the inner wall cleaning strip (63) are detachably connected, the inner wall of the inner wall cleaning strip (63) is covered with mounting teeth (631), and the outer wall of the inner wall cleaning strip (63) is provided with a scraping and cleaning surface (632).

8. A pre-oxidation process for preparing CNFs, using a pre-oxidation furnace based on a temperature-controlled return air system as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1, placing CNFs into a pre-oxidation furnace (1), starting the pre-oxidation furnace (1), checking whether the heating device (24) and the suction fan (25) in the temperature-controlled return air channel (2) are operating normally, and adjusting them to a preset process temperature range; S2, start the heat flow filter cartridge (3), so that the hot air flow generated inside the pre-oxidation furnace (1) is sucked in through the air inlet end of the heat flow filter cartridge (3), and the particulate impurities therein are removed, so as to ensure that the air flow entering the temperature-controlled return air channel (2) is clean; at the same time, start the oxygen filter cartridge (4), and introduce the external fresh air into the temperature-controlled return air channel (2) after filtering, so as to provide necessary oxygen supplement for the furnace and maintain a suitable oxidation environment; S3, the clean hot air flow and the fresh oxygen are mixed inside the temperature-controlled return air channel (2), and are heated or insulated according to the preset process temperature by the heating device (24), so as to ensure that the return air temperature is accurately controlled within the temperature range that is conducive to the formation of CNFs, and the suction fan (25) is continuously operated to promote the circulation of the air flow in the temperature-controlled return air channel (2), accelerate the heat exchange process, and improve the utilization rate of thermal energy; S4, the heated and mixed airflow re-enters the pre-oxidation furnace (1) through the circulating air outlet (22), realizing the recycling of heat energy and reducing energy waste. At the same time, the low-speed exhaust port (21) at the upper end of the temperature-controlled return air channel (2) remains open to maintain the airflow balance in the system and prevent excessive pressure. S5, the synchronous cleaning device (5) automatically starts to clear and clean the heat flow filter cartridge (3) and the oxygen filter cartridge (4) to prevent blockage and ensure filtering efficiency. This process can be set to be performed regularly to reduce the need for manual maintenance. The pipeline inner wall cleaning device (6) is regularly used to clean the inner wall of the temperature control return air channel (2) to remove dust and coking attachments to keep the channel unobstructed; S6. Under the appropriate temperature, oxygen concentration and airflow circulation conditions provided by the temperature control return air system, the pre-oxidation reaction is started. According to the specific process requirements, the parameters of the temperature control return air system, such as temperature and airflow velocity, are adjusted to optimize the pre-oxidation reaction process and improve the yield of CNFs. S7. When the pre-oxidation reaction reaches a predetermined time or degree, the pre-oxidized material is taken out from the pre-oxidation furnace (1) and subjected to subsequent carbonization and activation treatment steps to finally obtain a CNFs product.

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