A pretreatment device for efficient pre-oxidation of PAN fibers

Abstract

The utility model discloses a kind of PAN fiber efficient pre-oxidation's pretreatment device, including irradiation room, multiple beam under godet roller and conveying roller are equipped in its inside along the fiber bundle conveying direction. Fiber bundle enters from inlet, is guided by godet roller and conveying roller in turn and then enters pre-oxidation furnace by outlet. It further includes heating unit, for heating fiber bundle in irradiation room. Auxiliary heating is carried out by heating unit during irradiation to improve irradiation effect. Heating mode includes that conveying roller is set as heating roller, and / or hot air is inputted;After irradiation, fiber bundle enters pre-oxidation furnace and completes pre-oxidation. The utility model is by providing the device of irradiation combined with heating treatment, significantly improve PAN fiber aromatization efficiency, shorten pre-oxidation time, reduce production cost, improve production efficiency, meet the yield demand of carbon fiber to each industry.

Description

Technical Field

[0001] This utility model relates to the field of carbon fiber technology, specifically to a pretreatment device for efficient pre-oxidation of PAN fibers. Background Technology

[0002] Carbon fiber, as a novel carbon material, has become an indispensable key material in aerospace, new energy vehicles, high-end sporting goods, and wind power generation due to its superior lightweight, high specific strength, and high specific modulus properties. Its strength can be several times or even tens of times that of steel, while its density is only about one-fifth that of steel. This unique combination of properties gives it unparalleled advantages in lightweight design. However, despite its broad application prospects, the large-scale popularization of carbon fiber, especially the mainstream polyacrylonitrile (PAN)-based carbon fiber, still faces significant challenges.

[0003] The primary constraint lies in its high cost. This stems mainly from two aspects: first, the high cost of raw materials. Each ton of finished carbon fiber requires approximately 2-2.2 tons of precursor fiber, with the precursor fiber alone costing 40,000-60,000 RMB, which is 4-5 times that of steel materials; second, the complex production process and enormous energy consumption, with electricity consumption accounting for approximately 25%-30% of the total production cost. It is worth noting that the cost of precursor fiber accounts for an extremely high proportion of the total cost, reaching 60.26%, which is one of the core reasons for its persistently high price.

[0004] Secondly, the lengthy preparation cycle is also a bottleneck restricting the improvement of production efficiency. The manufacturing of PAN-based carbon fiber requires multiple processes, including precursor production, pre-oxidation, and carbonization. Among them, the pre-oxidation process, as a crucial link between the preceding and following processes, typically needs to be maintained at a temperature range of 180-300℃ for 50 to 90 minutes. This process accounts for approximately 75% to 90% of the total carbon fiber processing time and consumes about 70% of the total electrical energy. Although current mainstream technologies have shortened the pre-oxidation time to 35-40 minutes through process optimization, this process remains the most time- and energy-intensive part of the entire production chain.

[0005] Currently, further optimization of the pre-oxidation process faces technical bottlenecks. Traditional hot air heating methods, in pursuit of shorter processing times, easily lead to uneven heating inside and outside the fiber, resulting in problems such as insufficient or excessive pre-oxidation. Insufficient pre-oxidation causes the fiber to melt and break during subsequent high-temperature carbonization, while excessive oxidation damages the precursor fiber structure, leading to defects such as holes and cracks in the final carbon fiber product, severely reducing its tensile strength and modulus.

[0006] Therefore, how to solve these problems existing in the prior art has become the research topic of this utility model. Utility Model Content

[0007] The purpose of this invention is to provide a pretreatment device for efficient pre-oxidation of PAN fibers.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A pretreatment device for high-efficiency pre-oxidation of PAN fibers is implemented through a pretreatment unit, which is set at the front end corresponding to the inlet side of the pre-oxidation furnace. It includes an irradiation chamber, and multiple fiber guide rollers and conveying rollers are provided in the irradiation chamber corresponding to the fiber bundle conveying direction. The fiber bundle enters through the inlet of the irradiation chamber, passes sequentially through the front guide roller, multiple conveying rollers and the rear guide roller, and then exits through the outlet of the irradiation chamber into the pre-oxidation furnace. It also includes a heating unit, which is provided in relation to the irradiation chamber and is used to heat the fiber bundles in the irradiation chamber.

[0009] A further technical solution is that the irradiation chamber is provided with a hot air circulation area, and the fiber guide roller and the heating roller are provided in the hot air circulation area corresponding to the fiber bundle conveying direction; It also includes a hot air unit, which includes a hot air circulation pipe and a heating element and a fan connected in series in the hot air circulation pipe; the inlet and outlet of the hot air circulation pipe are respectively connected to two different locations in the hot air circulation area for heating the hot air circulation area. The heating unit is the heating roller; Alternatively, the heating unit may be the hot air unit and the hot air circulation area; Alternatively, the heating unit may be a combination of the heating roller, the hot air unit, and the hot air circulation area.

[0010] In the above solution, the heating roller is existing technology, and its heating method can be electromagnetic induction heating, fluid medium (such as hot oil, steam) heating, resistance heating and other heating methods known to those skilled in the art. Since the heating method of the heating roller is not the point of this utility model, it will not be described in detail here.

[0011] In the above scheme, the heating part of the hot air unit is an electric heating element or heat exchanger that uses the principle of resistance, electromagnetic induction or combustion to heat the air flowing through the hot air circulation pipeline.

[0012] In a further technical solution, there are three heating rollers, which are arranged in parallel along the fiber bundle conveying path; the fiber bundle passes through the lower surface of the front heating roller, then through the upper surface of the middle heating roller, and then through the lower surface of the rear heating roller. The irradiation section of the electron beam accelerator is positioned directly above the central heating roller.

[0013] A further technical solution involves providing several parallel, spaced-apart guide grooves on the surface of the fiber bundle guide roller. These guide grooves are positioned around the roller's axis, and their width corresponds to the width of the fiber bundle. The guide grooves are used to position the fiber bundle, ensuring that the fiber bundle's feeding direction does not deviate.

[0014] A further technical solution is to isolate the hot air circulation area from other areas of the irradiation chamber (which can be achieved through heat insulation panels) to ensure the heating efficiency of the fiber bundle in the hot air circulation area.

[0015] A further technical solution includes a temperature closed-loop control unit, which comprises a temperature sensor located in the hot air circulation area of ​​the irradiation chamber, a valve located in the hot air circulation pipeline, and a controller. The control unit is communicatively connected to the temperature sensor and the valve, respectively. The valve is preferably located at the outlet of the hot air circulation pipeline.

[0016] The temperature sensor is used to detect the temperature within the hot air circulation area; the valve is used to regulate the flow rate of hot air entering the hot air circulation area; the control unit is configured to adjust the opening of the valve according to the detection signal of the temperature sensor, so as to control the hot air volume and achieve real-time adjustment of the temperature within the hot air circulation area.

[0017] In a further technical solution, the hot air unit is also equipped with a hot air bypass, which is connected to the pre-oxidation furnace and used to introduce the hot air from the pre-oxidation furnace into the hot air circulation area of ​​the irradiation chamber. This design enables the reuse of the heat source, thereby significantly reducing the energy consumption of the heater and achieving energy saving and consumption reduction.

[0018] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0019] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the case.

[0020] The working principle and advantages of this utility model are as follows: To address the industry bottleneck of excessively long pre-oxidation stages in carbon fiber manufacturing, this application provides a highly efficient pre-oxidation pretreatment device for polyacrylonitrile (PAN)-based carbon fibers. This process significantly enhances the aromatization reaction rate of the fibers by subjecting PAN fibers to electron beam irradiation before pre-oxidation, combined with environmental or bulk heating techniques during the irradiation process. This synergistic treatment effectively induces crosslinking and cyclization between macromolecular chains, thereby accelerating the formation of stable ladder-like structures at the molecular level.

[0021] In the traditional production process of polyacrylonitrile (PAN)-based carbon fiber, pre-oxidation is a critical and time-consuming step. This process has traditionally been carried out in a multi-temperature zone pre-oxidation furnace (early designs may have required 6 or more independent temperature zones), with traditional pre-oxidation times generally ranging from 60 to 100 minutes (1 hour to 1 hour and 40 minutes).

[0022] Through continuous equipment and process innovation (such as optimizing heating methods, precisely controlling the temperature field and stretching tension), the number of temperature zones in the pre-oxidation furnace has been significantly optimized, and the pre-oxidation time in modern industrial production can now be stably controlled at 45-50 minutes. However, there is a clear technical lower limit to further reducing the pre-oxidation time. The fundamental reason is that it is essential to ensure that the PAN precursor fiber can fully and uniformly complete a series of chemical reactions such as cyclization, dehydrogenation, and oxidation to form a sufficiently stable and dense trapezoidal polymer structure. If the degree of pre-oxidation is insufficient, the fiber will be unable to withstand the stress generated by high-temperature thermal decomposition during the subsequent low-temperature carbonization stage due to insufficient thermal stability of the molecular structure, making it prone to melting or fiber breakage, resulting in a decrease in product qualification rate and production interruption.

[0023] The electron beam irradiation pretreatment technology employed in this invention is an effective solution to the aforementioned technical bottlenecks. This technology utilizes a high-energy electron beam to irradiate PAN precursor fibers under heating conditions, which can pre-initiate cross-linking reactions on their molecular chains and promote the formation of early cyclization structures (e.g., through the generation of free radicals). This is equivalent to "pre-positioning" some of the chemical reactions that would otherwise need to be completed in a high-temperature pre-oxidation furnace, significantly improving the initial structural stability of the precursor fibers and their subsequent thermal oxidation reactivity.

[0024] Electron beam irradiation modified precursor fibers exhibit reduced activation energy, accelerated cyclization reaction rate, and a more gradual exothermic peak during subsequent thermal oxidation. This significantly shortens the total pre-oxidation time and reduces stringent requirements on the number, length, or energy consumption of pre-oxidation furnace temperature zones, providing a reliable technical approach to reduce equipment investment, system energy consumption, and production costs.

[0025] In summary, the introduction of irradiation technology can effectively stimulate the activity of PAN molecular chains, enhance their cross-linking ability, and promote the faster formation of stable aromatized structures in fibers, thereby significantly shortening the pre-oxidation time. This invention, through the innovative design of a heated irradiation pretreatment device, not only significantly improves pre-oxidation efficiency but also helps reduce overall production energy consumption and costs, while simultaneously improving the yield and quality consistency of carbon fibers, better meeting the growing demand for high-performance carbon fibers from various downstream applications. Attached Figure Description

[0026] Appendix Figure 1This is a schematic diagram of the pre-processing unit in an embodiment of the present invention; Appendix Figure 2 This is a top view of the lower wire guide roller in an embodiment of the present invention; Appendix Figure 3 This is a schematic diagram of the system structure of an embodiment of the present utility model.

[0027] In the above figures: 1. Fiber bundle; 2. Irradiation chamber; 3. Pre-oxidation furnace; 4. Hot air circulation area; 5. Guide roller below the bundle; 6. Heating roller; 6a. Front heating roller; 6b. Middle heating roller; 6c. Rear heating roller; 7. Hot air circulation pipeline; 8. Heating section; 9. Irradiation section of electron beam accelerator; 10. Guide groove; 11. Unwinding frame; 12. Guide wheel; 13. Low-temperature carbonization furnace; 14. High-temperature carbonization furnace; 15. Drawing machine; 16. Winding machine; 17. Surface treatment tank; 18. Sizing tank; 19. Drying equipment; 20. Hot air bypass; 21. Fan; 22. Valve. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments: The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the embodiments of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0029] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms.

[0030] This utility model discloses a pretreatment device for high-efficiency pre-oxidation of PAN fibers, such as... Figure 1 As shown, this is achieved through a pre-treatment unit, which is located at the front end of the inlet side of the pre-oxidation furnace 3. It includes an irradiation chamber 2, and a hot air circulation area 4 is provided in the irradiation chamber 2. In the hot air circulation area 4, a plurality of fiber guide rollers 5 and heating rollers 6 are provided in the direction of fiber bundle 1.

[0031] The fiber bundle 1 enters through the inlet of the irradiation chamber 2, passes sequentially through the front end guide roller 5, multiple heating rollers 6 and the rear end guide roller 5, and then exits through the outlet of the irradiation chamber 2 and enters the pre-oxidation furnace 3.

[0032] It also includes a hot air unit, which includes a hot air circulation pipe 7 and a heating part 8 and a fan 21 connected in series in the hot air circulation pipe 7; the inlet and outlet of the hot air circulation pipe 7 are respectively connected to two different positions of the hot air circulation area 4 for heating the hot air circulation area 4.

[0033] Preferably, there are three heating rollers 6, which are arranged in parallel along the conveying path of the fiber bundle 1; the fiber bundle 1 passes through the lower surface of the front heating roller 6a, then through the upper surface of the middle heating roller 6b, and then through the lower surface of the rear heating roller 6c.

[0034] The irradiation section 9 of the electron beam accelerator is positioned directly above the central heating roller 6b.

[0035] Preferred, such as Figure 2 As shown, the surface of the fiber guide roller 5 is provided with several parallel and spaced guide grooves 10. The guide grooves 10 are arranged around the axis of the roller, and the width of the grooves corresponds to the width of the fiber bundle 1.

[0036] Preferably, the hot air circulation area 4 is relatively isolated from other areas of the irradiation chamber 2 (this can be achieved through a heat insulation plate, which is not shown in the figure).

[0037] Preferably, it also includes a temperature closed-loop control unit, which includes a temperature sensor disposed in the hot air circulation area 4 of the irradiation chamber 2, a valve 22 disposed in the hot air circulation pipeline 7, and a control unit. The control unit is communicatively connected to the temperature sensor and the valve 22, respectively. The valve 22 is preferably disposed at the outlet of the hot air circulation pipeline 7.

[0038] The temperature sensor is used to detect the temperature within the hot air circulation zone 4; the valve is used to regulate the flow rate of hot air entering the hot air circulation zone 4; the control unit is configured to adjust the opening of the valve according to the detection signal of the temperature sensor, so as to control the hot air volume and achieve real-time adjustment of the temperature within the hot air circulation zone 4.

[0039] Preferably, the hot air unit is further provided with a hot air bypass 20, which is connected to the pre-oxidation furnace 3 and is used to introduce the hot air in the pre-oxidation furnace 3 into the hot air circulation area 4 of the irradiation chamber 2.

[0040] like Figure 3 As shown, the pretreatment process includes: The fiber bundle 1 is placed on the unwinding frame 11 and unwinding is performed; The fiber bundle 1 enters the irradiation chamber through the guide wheel 12, and is then guided by the lower guide roller 5 before being irradiated in the irradiation chamber 2. During irradiation, the irradiation dose is 200 kJ and the irradiation time is 5-7 seconds.

[0041] During the irradiation process, heating roller 6 and hot air circulation are used for simultaneous heating to improve the irradiation effect; the working temperature of heating roller 6 is set to 160~200℃, and the temperature range of the hot air output by the hot air unit is 120~180℃.

[0042] The irradiated fiber bundle 1 enters the pre-oxidation furnace 3 for pre-oxidation to obtain pre-oxidized fibers.

[0043] like Figure 3 As shown, the system includes a low-temperature carbonization furnace 13 and a high-temperature carbonization furnace 14 located behind the pre-oxidation furnace 3, and the three are arranged in sequence from front to back according to the fiber bundle 1 feeding direction.

[0044] During the modification process, the fiber bundle 1 is given traction force by the drawing machine 15 in the production line, and the fiber is fed and wound up by the unwinding frame 11 and the winding machine 16 at both ends.

[0045] After being irradiated in irradiation chamber 2, fiber bundle 1 is sequentially processed in pre-oxidation furnace 3, low-temperature carbonization furnace 13, high-temperature carbonization furnace 14, surface treatment tank 17, and sizing tank 18. Finally, it is dried in drying equipment 19 to complete the modification process and then the fibers are collected.

[0046] The pre-oxidation time can be reduced to 20 minutes, and the subsequent processes can adopt the requirements of conventional carbon fiber processing technology, which will not be elaborated in this case.

[0047] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be included within the scope of protection of this utility model.

Claims

1. A pretreatment device for high-efficiency pre-oxidation of PAN fibers, characterized in that: The front end of the pre-oxidation furnace is provided at the inlet side. It includes an irradiation chamber, and multiple fiber guide rollers and conveying rollers are provided in the irradiation chamber in the direction of fiber bundle conveying. The fiber bundle enters through the inlet of the irradiation chamber, passes sequentially through the front guide roller, multiple conveying rollers and the rear guide roller, and then exits through the outlet of the irradiation chamber into the pre-oxidation furnace. It also includes a heating unit, which is provided in relation to the irradiation chamber and is used to heat the fiber bundles in the irradiation chamber.

2. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 1, characterized in that: The irradiation chamber is provided with a hot air circulation area, and the fiber guide roller and heating roller are provided in the hot air circulation area corresponding to the fiber bundle conveying direction. It also includes a hot air unit, which includes a hot air circulation pipe and a heating element and a fan connected in series in the hot air circulation pipe; the inlet and outlet of the hot air circulation pipe are respectively connected to two different locations in the hot air circulation area for heating the hot air circulation area. The heating unit is the heating roller; Alternatively, the heating unit may be the hot air unit and the hot air circulation area; Alternatively, the heating unit may be a combination of the heating roller, the hot air unit, and the hot air circulation area.

3. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 2, characterized in that: There are three heating rollers, which are arranged in parallel along the fiber bundle conveying path; the fiber bundle passes through the lower surface of the front heating roller, then through the upper surface of the middle heating roller, and then through the lower surface of the rear heating roller. The irradiation section of the electron beam accelerator is positioned directly above the central heating roller.

4. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 1, characterized in that: The surface of the fiber guide roller is provided with several parallel and spaced guide grooves, which are arranged around the axis of the fiber guide roller, and the width of the grooves corresponds to the width of the fiber bundle.

5. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 2, characterized in that: The hot air circulation area is relatively isolated from other areas of the irradiation chamber.

6. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 2, characterized in that: It also includes a temperature closed-loop control unit, which includes a temperature sensor located in the hot air circulation area of ​​the irradiation chamber, a valve located in the hot air circulation pipeline, and a control unit, the control unit being communicatively connected to the temperature sensor and the valve respectively.

7. The pretreatment device for high-efficiency pre-oxidation of PAN fibers according to claim 2, characterized in that: The hot air unit is also provided with a hot air bypass, which is connected to the pre-oxidation furnace and is used to introduce the hot air in the pre-oxidation furnace into the hot air circulation area of ​​the irradiation chamber.

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