System and process for uniformly densifying and drying polyacrylonitrile carbon fiber precursor

Abstract

The invention discloses a system and a process for uniformly densifying and drying polyacrylonitrile carbon fiber precursors, and relates to the technical field of carbon fiber production. Each hot roller is independently driven and independently subjected to steam control, and the hot roller temperature control system, the fiber tension control system, the drying room temperature control system and the drying room humidity control system are additionally arranged; therefore, a uniform and stable drying environment is formed in the drying room, the drying room has proper humidity which gives consideration to moisture evaporation and internal macromolecular chain movement, the roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference requirement, and the roller surface temperature is uniform in the effective length direction of the hot rollers; the fiber tension of each hot roller can be flexibly adjusted according to different required filament bundle tensions, and the deviation of the fiber tension among the rollers is greatly reduced, so that the water-containing polyacrylonitrile carbon fiber precursor filament bundles which enter a drying room and sequentially pass through the hot rollers can be uniformly densified and dried, and the polyacrylonitrile carbon fiber precursor with enhanced mechanical properties is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber production, in particular to a system and process for uniformly densifying and drying polyacrylonitrile carbon fiber precursor. Background Art

[0002] The formation process of polyacrylonitrile carbon fiber precursor is as follows: first, the polyacrylonitrile spinning solution is spun through wet or dry-jet wet spinning to form in a coagulation bath, then it is washed, hot water drawn, oiled, densified and dried, steam drawn, and heat-set to finally form the polyacrylonitrile carbon fiber precursor. The densification and drying process removes moisture from the surface and interior of the fiber, causing the internal pores caused by the diffusion of solvent and coagulant during spinning and coagulation to shrink and close, making the fiber structure more uniform and dense.

[0003] In the traditional production process of polyacrylonitrile carbon fiber precursor, a densification drying method using multiple groups of steam hot rollers is often used. More specifically, in the traditional precursor drying method, the hot rollers are driven by groups and the steam is also controlled by groups. The group drive of the hot rollers means that several hot rollers are grouped together and driven by gears. The speed of the hot rollers in the group is consistent. However, when the fibers shrink during the drying process, the fiber tension deviation between the rollers will be caused, which is not conducive to fiber densification. Similarly, the steam is controlled by groups, which means that several hot rollers are grouped together and controlled by a set of regulating valves. This is not conducive to the precise control of the temperature of a single hot roller. Therefore, in the traditional precursor drying process, the temperature difference between the roller surfaces in the effective length direction is often large (often exceeding 2°C), the temperature and humidity in the drying room are difficult to accurately control, and the resulting polyacrylonitrile precursor has an uneven internal structure, poor density, low dimensional stability, and mechanical properties that do not meet the requirements of high-performance carbon fibers. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned shortcomings and propose a system and process for uniformly densifying and drying polyacrylonitrile carbon fiber precursor. The present invention can accurately control the temperature and humidity of the drying room, provide a uniform and stable drying environment, and provide a suitable humidity that takes into account both water evaporation and the movement of internal macromolecular chains; the present invention can independently control and accurately adjust the temperature of each hot roller, flexibly adjust the roller surface temperature of each hot roller according to the temperature difference required at each stage in the drying process, ensure the uniformity of the roller surface temperature of the hot roller in the effective length direction, and effectively solve the technical problem of large temperature difference of the roller surface of the traditional hot roller in the effective length direction; the present invention can independently drive and accurately adjust the speed of each hot roller, flexibly adjust the fiber tension of each hot roller according to the actual required bundle tension of each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the precursor, enhancing the mechanical properties of the fiber, and thus obtaining uniform, dense, stable, reliable, and high-performance polyacrylonitrile carbon fiber precursor.

[0005] The purpose of the present invention can be achieved by the following measures: The present invention provides a system for uniformly densifying and drying polyacrylonitrile carbon fiber precursors, comprising a drying room with symmetrically distributed serpentine heating tubes and uniform air plates on the upper and lower layers, two upper and lower rows of hot rollers arranged in parallel and staggered manner in the middle layer of the drying room with steam as a heat source, for sequentially winding and conveying polyacrylonitrile carbon fiber precursor tows, respectively connected to different positions of the upper and lower serpentine heating tubes, a plurality of drying room temperature control systems for accurately controlling the drying room temperature, and a drying room humidity control system installed on the top of the drying room for accurately controlling the drying room humidity, each of which is independently connected to each hot roller and used to perform a temperature control on each hot roller. Several groups of hot roller temperature control systems are provided for independent and accurate temperature control, and several groups of fiber tension control systems are independently connected to each hot roller for independent driving and accurate speed control of each hot roller; the number of the hot roller temperature control systems and fiber tension control systems is the same as the number of hot rollers, and the fiber tension control system and hot roller temperature control system of the same group are arranged in series at the same end of the corresponding hot roller; the hot roller includes a roller, a hollow shaft installed on the central axis of the roller, and a siphon installed in the inner cavity of the hot roller, with one end close to the wall of the hot roller and the other end connected to the hollow shaft at the input end.

[0006] The drying room temperature control system of the present invention includes a drying room steam inlet pipe and a drying room condensate outlet pipe connected to the serpentine heating pipe, a drying room steam regulating valve installed on the drying room steam inlet pipe, a drying room steam trap installed on the drying room condensate outlet pipe, and a drying room temperature transmitter and a temperature indicating control connected in series on a telecommunication line between the middle layer inner cavity of the drying room and the drying room steam regulating valve; the drying room temperature control system is divided into two rows, upper and lower, and the number of drying room temperature control systems in each row is at least three.

[0007] The drying room humidity control system of the present invention includes an exhaust duct embedded in the top of the drying room, an exhaust branch pipe connected to the exhaust duct, an adjusting air valve and a dehumidifying fan connected in series on the exhaust branch pipe, and a humidity transmitter and a humidity indicating control connected in series on a telecommunication line between the upper inner cavity of the drying room and the adjusting air valve; the number of drying room humidity control systems is at least two.

[0008] The heat roller temperature control system of the present invention includes a rotary joint connected to the hollow shaft at the input end, a heat roller steam inlet pipe and a heat roller condensate outlet pipe respectively connected to the other two interfaces of the rotary joint, a heat roller steam regulating valve installed on the heat roller steam inlet pipe, a heat roller steam trap installed on the heat roller condensate outlet pipe, a pressure transmitter and a pressure indicating control installed in series on the telecommunication line between the outlet end of the heat roller steam inlet pipe and the heat roller steam regulating valve, and a heat roller temperature transmitter and a temperature alarm installed on the telecommunication line led out between the inlet end of the heat roller condensate outlet pipe and the heat roller steam trap.

[0009] The fiber tension control system of the present invention includes a reduction motor connected to a hollow shaft at the input end, and the reduction motor is connected to a rotary encoder for detecting the motor speed and a frequency converter for changing the motor working power frequency to keep the motor speed consistent with the set value.

[0010] In the present invention, the wind uniforming plate is covered with wind uniforming holes that penetrate the thickness of the plate.

[0011] The present invention provides a process for densifying and drying polyacrylonitrile carbon fiber precursor using the system according to claim 1, characterized in that the process steps are as follows: A. Tow Winding Roller: The water-containing polyacrylonitrile carbon fiber precursor tow is wound from top to bottom and from front to back in sequence through two rows of hot rollers located in the middle layer of the drying room, which are arranged in parallel and staggered manner; B. Turn on each control system: Turn on each set of drying room temperature control systems connected to the upper and lower serpentine heating tubes for precise control of drying room temperature; turn on the drying room humidity control system installed on the top of the drying room for precise control of drying room humidity; turn on each set of heating roller temperature control systems independently connected to each heating roller for independent and precise temperature control of each heating roller; turn on each set of fiber tension control systems independently connected to each heating roller for independent drive and precise speed control of each heating roller; C. Intelligent temperature adjustment of the drying room: After the drying room steam regulating valve is opened, the steam in the drying room steam inlet pipe enters the serpentine heating tube to heat the air in the upper and lower cavities of the drying room; the steam condenses into condensed water after heat exchange, and the condensed water is discharged through the drying room condensate outlet pipe and the opened drying room drain valve; the hot air is evenly blown to the polyacrylonitrile carbon fiber precursor tow located in the middle layer cavity of the drying room through the uniform air holes on the uniform air plate; at the same time, the temperature in the drying room is achieved by intelligently controlling the opening of the drying room steam regulating valve to adjust the steam flow entering the drying room. That is, when the drying room temperature transmitter detects that the temperature of the middle layer cavity of the drying room deviates from the preset temperature value, the drying room temperature transmitter will promptly transmit the detected temperature signal to the temperature indication control, and the temperature indication control will automatically adjust the opening of the steam regulating valve to ensure that the temperature of the middle layer cavity of the drying room is consistent with the preset temperature value; in this way, with the help of the drying room temperature control system, the temperature of the drying room can be accurately controlled, and a uniform and stable drying environment can be provided for the densification and drying of the tow; D. Intelligent Adjustment of Drying Chamber Humidity: As the tow is dried in the drying chamber, humid air is generated. This humid air is discharged in sequence through the exhaust duct, exhaust branch pipe, regulating damper, and dehumidification fan, all embedded in the top of the drying chamber. At the same time, the humidity in the drying chamber is adjusted by intelligently controlling the opening of the damper to regulate the flow of exhausted humid air. That is, when the humidity transmitter connected to the upper inner cavity of the drying chamber detects a deviation between the humidity in the drying chamber and the preset humidity value, the humidity transmitter promptly transmits the detected humidity signal to the humidity indicator control, which automatically adjusts the opening of the damper to ensure that the humidity in the drying chamber is consistent with the preset humidity value. This humidity control system allows precise control of the humidity in the drying chamber, providing an appropriate humidity for tow densification and drying that balances water evaporation and the movement of internal macromolecular chains. E. Intelligent adjustment of the surface temperature of each hot roller: Steam passes through the opened hot roller steam regulating valve, hot roller steam inlet pipe, and rotary joint in turn into the hollow shaft and roller, heats the roller wall and then dries the polyacrylonitrile carbon fiber precursor tow wound on the roller; the steam condenses into condensed water after heat exchange, and the condensed water is discharged through the siphon, hollow shaft, rotary joint, hot roller condensate outlet pipe and opened hot roller drain valve; at the same time, the surface temperature of the roller is achieved by intelligently controlling the opening of the hot roller steam regulating valve to adjust the steam flow entering the roller - that is, when the surface temperature of the roller deviates from the preset temperature value, the volume of the steam entering the roller cavity will change when it condenses into condensed water, causing the pressure in the roller cavity to change. The pressure transmitter will promptly transmit the detected pressure change detection signal to the pressure indicator The pressure indicator automatically adjusts the opening of the steam regulating valve of the hot roller to ensure that the surface temperature of the roller is consistent with the preset temperature value. In addition, a hot roller temperature transmitter and a temperature alarm are installed on the condensate outlet pipe of the hot roller. When the hot roller temperature transmitter detects that the condensate temperature is lower than the set value, the hot roller temperature transmitter will promptly transmit the detected temperature signal to the temperature alarm, and the temperature alarm will issue a prompt alarm signal. In this way, with the help of each group of hot roller temperature control systems, each hot roller can be independently and accurately controlled. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference required at each stage of the drying process. The roller surface temperature uniformity of the hot roller can be ensured along the effective length direction, which effectively solves the technical problem of large temperature difference along the effective length direction of the traditional hot roller surface. F. Intelligent adjustment of fiber tension: The adjustment of fiber tension is achieved by controlling the speed difference of adjacent rollers - that is, the reduction motor in each group of fiber tension control systems drives the hollow shaft and roller in the corresponding hot roller to rotate, and the frequency converter changes the motor working power frequency to keep the motor speed consistent with the set value, and the motor speed is detected in real time by the rotary encoder. In this way, the fiber tension change in the tow drying process can be maintained and stabilized by controlling the speed difference of adjacent rollers; in this way, with the help of each group of fiber tension control systems, each hot roller can be independently driven and accurately regulated, and the fiber tension of each hot roller can be flexibly adjusted according to the actual tow tension required by each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the precursor, and enhancing the mechanical properties of the fiber, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor; G. Tow densification drying: When each control system runs into normal working state, a uniform and stable drying environment is formed in the drying room, and has the appropriate humidity that takes into account water evaporation and internal macromolecular chain movement. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference, and the uniformity of the roller surface temperature in the effective length direction of the hot roller is guaranteed. The fiber tension of each hot roller can be flexibly adjusted according to the different tow tensions required by actual needs, and the fiber tension deviation between the rollers is greatly reduced. In this way, the water-containing polyacrylonitrile carbon fiber precursor tow entering the drying room and winding around each hot roller in turn can be accurately and uniformly densified and dried - that is, the internal moisture gradually evaporates from the micropores of the polyacrylonitrile carbon fiber and forms a negative pressure. The free movement of the macromolecular chain segments causes the micropores to shrink, fuse and close, making the internal structure of the fiber uniform and dense, and the mechanical properties of the fiber enhanced, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor.

[0012] The temperature difference of the surface temperature of the hot roller in the effective length direction is not greater than 1 o C.

[0013] The design principles of the present invention are as follows: The present invention changes the process mode of group-driven hot rollers and group-controlled steam in the traditional precursor drying method. The present invention improves this mode to individually drive and individually control the steam for each hot roller. That is, the present invention adds a number of hot roller temperature control systems equal to the number of hot rollers. With the help of each group of hot roller temperature control systems, each hot roller can be independently and accurately controlled. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference required at each stage of the drying process, ensuring the uniformity of the roller surface temperature along the effective length of the hot roller, effectively solving the technical problem of large temperature differences along the effective length of the traditional hot roller surface. The present invention also adds a number of fiber tension control systems equal to the number of hot rollers. With the help of each group of fiber tension control systems, each hot roller can be independently driven and accurately controlled. The fiber tension of each hot roller can be flexibly adjusted according to the actual tow tension required by each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the precursor, and enhancing the mechanical properties of the fiber, thereby obtaining uniform, dense, stable, reliable, and high-performance polyacrylonitrile carbon fiber precursor. At the same time, the present invention also adds a drying room temperature control system and a drying room humidity control system in the drying room - with the help of the drying room temperature control system, the temperature of the drying room can be accurately controlled, and a uniform and stable drying environment can be provided for the densification drying of the yarn bundle; with the help of the drying room humidity control system, the humidity of the drying room can be accurately controlled, and a suitable humidity that takes into account both water evaporation and the movement of internal macromolecular chains can be provided for the densification drying of the yarn bundle. Since the present invention is additionally provided with a hot roller temperature control system, a fiber tension control system, a drying room temperature control system and a drying room humidity control system, when each control system operates to a normal working state, a uniform and stable drying environment is formed in the drying room, and has an appropriate humidity that takes into account both water evaporation and the movement of internal macromolecular chains. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference requirements, and the uniformity of the roller surface temperature in the effective length direction of the hot roller is ensured. The fiber tension of each hot roller can be flexibly adjusted according to the different tow tensions required by actual needs, and the fiber tension deviation between the rollers is greatly reduced. In this way, the water-containing polyacrylonitrile carbon fiber precursor tow entering the drying room and passing through each hot roller in turn can be accurately and uniformly densified and dried - that is, the internal moisture gradually evaporates from the micropores of the polyacrylonitrile carbon fiber and forms a negative pressure, and the free movement of the macromolecular chain segments causes the micropores to shrink, fuse and close, so that the internal structure of the fiber is uniform and dense, and the mechanical properties of the fiber are enhanced, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor.

[0014] The beneficial technical effects of the present invention are as follows: The present invention can accurately control the temperature and humidity of the drying room, provide a uniform and stable drying environment, and provide an appropriate humidity that takes into account both water evaporation and the movement of internal macromolecular chains; the present invention can independently and accurately control the temperature of each hot roller, flexibly adjust the roller surface temperature of each hot roller according to the temperature difference required in each stage of the drying process, ensure the uniformity of the roller surface temperature of the hot roller in the effective length direction, and effectively solve the technical problem of large temperature difference of the roller surface of the traditional hot roller in the effective length direction; the present invention can independently drive and accurately adjust the speed of each hot roller, flexibly adjust the fiber tension of each hot roller according to the actual required tow tension of each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the raw silk, enhancing the mechanical properties of the fiber, and thus obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber raw silk. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the arrangement of the hot rollers and the orientation of the filament bundles in the drying room of the present invention.

[0016] Figure 2 It is a schematic structural diagram of the drying system of the present invention. Figure 3 This is a schematic diagram of the structure of the drying room temperature control system (i.e., component 7) in the present invention.

[0017] Figure 4 It is a structural principle diagram of the drying room humidity control system (i.e., component 8) in the present invention.

[0018] Figure 5 It is a structural principle diagram of the hot roller temperature control system (i.e., component 5) and the fiber tension control system (i.e., component 6) in the present invention.

[0019] Parts number description in the figure: 1. Drying room; 2. Hot roller, 2-1. Roller, 2-2. Siphon, 2-3. Hollow shaft; 3. Serpentine heating tube; 4. Air uniformity plate; 5. Hot roller temperature control system, 5-1. Hot roller steam regulating valve, 5-2. Rotary joint, 5-3. Hot roller drain valve, 5-4. Hot roller steam inlet pipe, 5-5. Hot roller condensate outlet pipe, PT, pressure transmitter, PIC, pressure indication control, TT-2, hot roller temperature transmitter, TA, temperature alarm; 6. Fiber tension control system, 6-1. Speed ​​reducer Motor, EC, rotary encoder, VFD, inverter; 7. Drying room temperature control system, 7-1. Drying room steam regulating valve, 7-2. Drying room steam trap, 7-3. Drying room steam inlet pipe, 7-4. Drying room condensate outlet pipe, TT-1. Drying room temperature transmitter, TIC, temperature indicating control; 8. Drying room humidity control system, 8-1. Exhaust duct, 8-2. Regulating air valve, 8-3. Dehumidification fan, 8-4. Exhaust branch pipe, WT, humidity transmitter, WIC, humidity indicating control; 9. Polyacrylonitrile carbon fiber precursor tow. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings: like Figures 1 to 5 As shown, a system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor of the present invention includes a drying room 1 with symmetrically distributed serpentine heating tubes 3 and uniform air plates 4 on the upper and lower layers, two upper and lower rows of hot rollers 2 using steam as a heat source, arranged in parallel and staggered manner in the middle layer of the drying room 1 for sequentially winding and conveying polyacrylonitrile carbon fiber precursor tows 9, respectively connected to different positions of the upper and lower serpentine heating tubes 3, a plurality of groups of drying room temperature control systems 7 for accurately controlling the drying room temperature, a drying room humidity control system 8 installed on the top of the drying room for accurately controlling the drying room humidity, each of which is independently connected to each hot roller for independently controlling each hot roller. Several groups of hot roller temperature control systems 5 for controlling and accurately adjusting the temperature, and several groups of fiber tension control systems 6 independently connected to each hot roller for independently driving and accurately adjusting the speed of each hot roller; the number of the hot roller temperature control systems 5 and the fiber tension control systems 6 are the same as the number of hot rollers 2, and the fiber tension control systems 6 and hot roller temperature control systems 5 of the same group are arranged in series at the same end of the corresponding hot roller 2; the hot roller 2 includes a roller 2-1, a hollow shaft 2-3 installed on the central axis of the roller, and a siphon tube 2-2 installed in the inner cavity of the hot roller, with one end close to the wall of the hot roller and the other end connected to the hollow shaft at the input end.

[0021] The drying room temperature control system 7 described in the present invention includes a drying room steam inlet pipe 7-3 and a drying room condensate outlet pipe 7-4 connected to the serpentine heating pipe 3, a drying room steam regulating valve 7-1 installed on the drying room steam inlet pipe 7-3, a drying room steam trap 7-2 installed on the drying room condensate outlet pipe, and a drying room temperature transmitter TT-1 and a temperature indicating control TIC connected in series on a telecommunication line between the middle layer inner cavity of the drying room 1 and the drying room steam regulating valve 7-1; the drying room temperature control system 7 is divided into two rows, upper and lower, and the number of drying room temperature control systems 7 in each row is at least three.

[0022] The drying room humidity control system 8 of the present invention includes an exhaust duct 8-1 embedded in the top of the drying room, an exhaust branch duct 8-4 connected to the exhaust duct 8-1, an adjusting air valve 8-2 and a dehumidifying fan 8-3 connected in series on the exhaust branch duct 8-4, and a humidity transmitter WT and a humidity indicating control WIC connected in series on a telecommunication line between the upper inner cavity of the drying room 1 and the adjusting air valve 8-2. The number of drying room humidity control systems 8 is at least two.

[0023] The hot roller temperature control system 5 described in the present invention includes a rotary joint 5-2 connected to the hollow shaft 2-3 at the input end, a hot roller steam inlet pipe 5-4 and a hot roller condensate outlet pipe 5-5 respectively connected to the other two interfaces of the rotary joint 5-2, a hot roller steam regulating valve 5-1 installed on the hot roller steam inlet pipe 5-4, a hot roller steam trap 5-3 installed on the hot roller condensate outlet pipe 5-5, and a pressure transmitter PT and a pressure indicating control PIC installed in series on the telecommunication line between the outlet end of the hot roller steam inlet pipe 5-4 and the hot roller steam regulating valve 5-1, and a hot roller temperature transmitter TT-2 and a temperature alarm TA installed on the telecommunication line led out between the inlet end of the hot roller condensate outlet pipe 5-5 and the hot roller steam trap 5-3.

[0024] The fiber tension control system 6 in the present invention includes a reduction motor 6-1 connected to the hollow shaft 2-3 at the input end, and the reduction motor 6-1 is connected to a rotary encoder EC for detecting the motor speed and a frequency converter VFD for changing the motor working power frequency to keep the motor speed consistent with the set value.

[0025] In the present invention, the wind uniforming plate 4 is covered with wind uniforming holes that penetrate the thickness of the plate.

[0026] The process steps for uniformly densifying and drying polyacrylonitrile carbon fiber precursor using the system of the present invention are as follows: A. Tow Winding: The water-containing polyacrylonitrile carbon fiber precursor tow is wound from top to bottom and from front to back in sequence through two rows of hot rollers 2 located in the middle layer of the drying room 1, which are arranged in parallel and staggered manner; B. Start each control system: Start each set of drying room temperature control systems 7 connected to the upper and lower serpentine heating tubes 3 for precise control of drying room temperature; start each set of drying room humidity control systems 8 installed on the top of the drying room for precise control of drying room humidity; start each set of heating roller temperature control systems 5 independently connected to each heating roller for independent and precise temperature control of each heating roller; start each set of fiber tension control systems 6 independently connected to each heating roller for independent drive and precise speed control of each heating roller; C. Intelligent regulation of drying room temperature: After the drying room steam regulating valve 7-1 is opened, the steam in the drying room steam inlet pipe 7-3 enters the serpentine heating pipe 3 to heat the air in the upper and lower layers of the drying room 1; the steam condenses into condensed water after heat exchange, and the condensed water is discharged through the drying room condensate outlet pipe 7-4 and the opened drying room steam trap 7-2; the hot air is evenly blown to the polyacrylonitrile carbon fiber precursor tow located in the middle layer of the drying room 1 through the uniform air holes on the uniform air plate 4; at the same time, the temperature in the drying room 1 is regulated by intelligently controlling the opening of the drying room steam regulating valve 7-1 The steam flow entering the drying room 1 is realized - that is, when the drying room temperature transmitter TT-1 detects that the temperature of the middle layer cavity of the drying room 1 deviates from the preset temperature value, the drying room temperature transmitter TT-1 promptly transmits the detected temperature signal to the temperature indicating control TIC, and the temperature indicating control TIC automatically adjusts the opening of the steam regulating valve 7-1, thereby ensuring that the temperature of the middle layer cavity of the drying room 1 is consistent with the preset temperature value; in this way, the drying room temperature control system 7 can accurately control the temperature of the drying room, and provide a uniform and stable drying environment for the densification and drying of the tow; D. Intelligent Adjustment of Drying Room Humidity: Since moist air is generated during the drying process of the tow in the drying room 1, the moist air in the drying room 1 is discharged in sequence along the exhaust duct 8-1, the exhaust branch duct 8-4, the regulating air valve 8-2, and the moist air fan 8-3 installed on the top of the drying room under the action of the dehumidification fan 8-3; at the same time, the humidity in the drying room 1 is achieved by adjusting the opening of the regulating air valve 8-2 to adjust the flow rate of the exhausted moist air - that is, when the humidity transmitter WT connected to the upper inner cavity of the drying room 1 detects that the humidity of the drying room 1 deviates from the preset humidity value, the humidity transmitter WT promptly transmits the detected humidity signal to the humidity indication control WIC, and the humidity indication control WIC automatically adjusts the opening of the regulating air valve 8-2, thereby ensuring that the humidity of the drying room 1 is consistent with the preset humidity value; in this way, with the help of the drying room humidity control system 8, the humidity of the drying room can be accurately controlled, and an appropriate humidity that takes into account both water evaporation and the movement of internal macromolecular chains can be provided for the densification and drying of the tow; E. Intelligent regulation of the surface temperature of each hot roller: steam passes through the opened hot roller steam regulating valve 5-1, the hot roller steam inlet pipe 5-4, and the rotary joint 5-2 in sequence into the hollow shaft 2-3 and the roller 2-1, heats the roller wall and then dries the polyacrylonitrile carbon fiber precursor tow wound on the roller 2-1; the steam condenses into condensed water after heat exchange, and the condensed water is discharged through the siphon pipe 2-2, the hollow shaft 2-3, the rotary joint 5-2, the hot roller condensate outlet pipe 5-5 and the opened hot roller drain valve 5-3; at the same time, the surface temperature of the roller 2-1 is achieved by intelligently controlling the opening of the hot roller steam regulating valve 5-1 to regulate the steam flow entering the roller 2-1 - that is, when the surface temperature of the roller 2-1 deviates from the preset temperature value, the volume of the steam entering the inner cavity of the roller 2-1 will change when it condenses into condensed water, causing the pressure in the inner cavity of the roller 2-1 to change, and the pressure transmitter PT will detect the pressure change and signal it. The pressure is promptly transmitted to the pressure indicating control PIC, which automatically adjusts the opening of the hot roller steam regulating valve 5-1, thereby ensuring that the surface temperature of the roller 2-1 is consistent with the preset temperature value; in addition, a hot roller temperature transmitter TT-2 and a temperature alarm TA are installed on the hot roller condensate outlet pipe 5-5. When the hot roller temperature transmitter TT-2 detects that the condensate temperature is lower than the set value, the hot roller temperature transmitter TT-2 will promptly transmit the detected temperature signal to the temperature alarm TA, and the temperature alarm TA will issue a prompt alarm signal; in this way, with the help of each group of hot roller temperature control systems 5, each hot roller can be independently and accurately controlled and the temperature can be adjusted. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference required at each stage of the drying process, and the roller surface temperature uniformity of the hot roller can be ensured in the effective length direction, which effectively solves the technical problem of large temperature difference on the effective length direction of the traditional hot roller surface; F. Intelligent adjustment of fiber tension: The adjustment of fiber tension is achieved by controlling the speed difference of adjacent rollers 2-1 - that is, the reduction motor 6-1 in each group of fiber tension control systems 6 drives the hollow shaft 2-3 and roller 2-1 in the corresponding hot roller 2 to rotate, and the frequency converter VFD changes the motor working power frequency to keep the motor speed consistent with the set value, and the motor speed is detected in real time by the rotary encoder EC. In this way, the fiber tension change in the tow drying process can be maintained and stabilized by controlling the speed difference of adjacent rollers 2-1; in this way, with the help of each group of fiber tension control systems 6, each hot roller can be independently driven and accurately regulated, and the fiber tension of each hot roller can be flexibly adjusted according to the actual tow tension required by each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the precursor, enhancing the mechanical properties of the fiber, and thus obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor; G. Tow densification drying: When each control system operates to a normal working state, a uniform and stable drying environment is formed in the drying room 1, and has an appropriate humidity that takes into account water evaporation and internal macromolecular chain movement. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference, and the uniformity of the roller surface temperature in the effective length direction of the hot roller is guaranteed. The fiber tension of each hot roller can be flexibly adjusted according to the different tow tensions required by actual needs, and the fiber tension deviation between the rollers is greatly reduced. In this way, the water-containing polyacrylonitrile carbon fiber precursor tow entering the drying room 1 and passing through each hot roller 2 in turn can be accurately and uniformly densified and dried - that is, the internal moisture gradually evaporates from the micropores of the polyacrylonitrile carbon fiber and forms a negative pressure. The free movement of the macromolecular chain segments causes the micropores to shrink, fuse and close, making the internal structure of the fiber uniform and dense, and the mechanical properties of the fiber enhanced, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor.

[0027] The temperature difference of the surface temperature of the hot roller 2 in the effective length direction is not greater than 1 o C.

Claims

1. A system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor, characterized by: The system comprises a drying room (1) having serpentine heating tubes (3) and air-distributing plates (4) symmetrically distributed on the upper and lower layers, two upper and lower rows of hot rollers (2) arranged in parallel and staggered manner in the middle layer of the drying room (1) with steam as a heat source for sequentially winding and conveying polyacrylonitrile carbon fiber precursor tows (9), respectively connected to different positions of the upper and lower serpentine heating tubes (3), a plurality of drying room temperature control systems (7) for accurately controlling the drying room temperature, a drying room humidity control system (8) installed on the top of the drying room for accurately controlling the drying room humidity, and a plurality of hot roller temperature control systems (8) independently connected to each hot roller for independently controlling the temperature of each hot roller and accurately adjusting the temperature. A control system (5) is provided, wherein the plurality of fiber tension control systems (6) are independently connected to each heat roller and used for independently driving and accurately regulating the speed of each heat roller; the number of the heat roller temperature control systems (5) and the fiber tension control systems (6) is the same as the number of the heat rollers (2), and the fiber tension control systems (6) and the heat roller temperature control systems (5) of the same group are arranged in series at the same end of the corresponding heat roller (2); the heat roller (2) comprises a roller (2-1), a hollow shaft (2-3) installed on the central axis of the roller, and a siphon (2-2) installed in the inner cavity of the heat roller, with one end close to the wall of the heat roller and the other end connected to the hollow shaft at the input end.

2. The system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 1, characterized in that: The drying room temperature control system (7) comprises a drying room steam inlet pipe (7-3) and a drying room condensate outlet pipe (7-4) connected to the serpentine heating pipe (3), a drying room steam regulating valve (7-1) installed on the drying room steam inlet pipe (7-3), a drying room steam trap (7-2) installed on the drying room condensate outlet pipe, and a drying room temperature transmitter (TT-1) and a temperature indicating control (TIC) connected in series on a telecommunication line between the middle layer inner cavity of the drying room (1) and the drying room steam regulating valve (7-1).

3. The system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 1, characterized in that: The drying room humidity control system (8) comprises an exhaust duct (8-1) embedded in the top of the drying room, an exhaust branch duct (8-4) connected to the exhaust duct (8-1), a regulating air valve (8-2) and a dehumidifying fan (8-3) connected in series on the exhaust branch duct (8-4), and a humidity transmitter (WT) and a humidity indicating control (WIC) connected in series on a telecommunication line between the upper inner cavity of the drying room (1) and the regulating air valve (8-2). The drying room humidity control system (8) is divided into two rows, upper and lower, with at least three drying room humidity control systems (8) in each row.

4. The system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 1, characterized in that: The hot roller temperature control system (5) comprises a rotary joint (5-2) connected to the hollow shaft (2-3) at the input end, a hot roller steam inlet pipe (5-4) and a hot roller condensate outlet pipe (5-5) respectively connected to the other two interfaces of the rotary joint (5-2), a hot roller steam regulating valve (5-1) installed on the hot roller steam inlet pipe (5-4), a hot roller drain valve (5-3) installed on the hot roller condensate outlet pipe (5-5), a pressure transmitter (PT) and a pressure indicating control (PIC) installed in series on the telecommunication line between the outlet end of the hot roller steam inlet pipe (5-4) and the hot roller steam regulating valve (5-1), and a hot roller temperature transmitter (TT-2) and a temperature alarm (TA) installed on the telecommunication line drawn between the inlet end of the hot roller condensate outlet pipe (5-5) and the hot roller drain valve (5-3).

5. The system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 1, characterized in that: The fiber tension control system (6) includes a reduction motor (6-1) connected to a hollow shaft (2-3) at an input end, and a rotary encoder (EC) for detecting the motor speed and a frequency converter (VFD) for changing the motor working power frequency to keep the motor speed consistent with a set value are connected to the reduction motor (6-1).

6. The system for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 1, characterized in that: The wind uniforming plate (4) is covered with wind uniforming holes that penetrate the thickness of the plate.

7. A process for uniformly densifying and drying polyacrylonitrile carbon fiber precursor using the system of claim 1, characterized in that: The steps of the process are as follows: A. Tow winding: The water-containing polyacrylonitrile carbon fiber raw yarn tow is wound from top to bottom and from front to back in sequence through two rows of hot rollers (2) arranged in parallel and staggered manner in the middle layer of the drying room (1); B. Start each control system: Start a plurality of drying room temperature control systems (7) connected to the upper and lower serpentine heating tubes (3) for accurately controlling the drying room temperature; start a drying room humidity control system (8) installed on the top of the drying room for accurately controlling the drying room humidity; start each set of heating roller temperature control systems (5) independently connected to each heating roller for independently controlling and accurately adjusting the temperature of each heating roller; start each set of fiber tension control systems (6) independently connected to each heating roller for independently driving and accurately adjusting the speed of each heating roller; C. Intelligent regulation of drying room temperature: After the drying room steam regulating valve (7-1) is opened, the steam in the drying room steam inlet pipe (7-3) enters the serpentine heating pipe (3) to heat the air in the upper and lower layers of the drying room (1); the steam condenses into condensed water after heat exchange, and the condensed water is discharged through the drying room condensate outlet pipe (7-4) and the opened drying room drain valve (7-2); and the hot air is evenly blown to the polyacrylonitrile carbon fiber raw yarn bundle located in the middle layer of the drying room (1) through the uniform air holes on the uniform air plate (4); at the same time, the temperature in the drying room (1) is regulated by intelligently controlling the opening of the drying room steam regulating valve (7-1). This is achieved by regulating the steam flow entering the drying room (1) - that is, when the drying room temperature transmitter (TT-1) detects that the temperature of the middle layer cavity of the drying room (1) deviates from the preset temperature value, the drying room temperature transmitter (TT-1) promptly transmits the detected temperature signal to the temperature indication control (TIC), and the temperature indication control (TIC) automatically adjusts the opening of the steam regulating valve (7-1), thereby ensuring that the temperature of the middle layer cavity of the drying room (1) is consistent with the preset temperature value; in this way, the temperature of the drying room can be accurately controlled with the help of the drying room temperature control system (7), and a uniform and stable drying environment can be provided for the densification drying of the tow; D. Intelligent regulation of drying room humidity: Since wet air is generated during the drying process of the tow in the drying room (1), the wet air in the drying room (1) is discharged in sequence along the exhaust pipe (8-1) embedded in the top of the drying room, the exhaust branch pipe (8-4), the regulating air valve (8-2), and the dehumidification fan (8-3) under the action of the dehumidification fan (8-3); at the same time, the humidity in the drying room (1) is achieved by regulating the opening of the regulating air valve (8-2) to adjust the flow rate of the discharged wet air - that is, when the air valve (8-2) is connected to the upper inner cavity of the drying room (1), the wet air in the drying room (1) is discharged in the following order. When the humidity transmitter (WT) detects that the humidity of the drying room (1) deviates from the preset humidity value, the humidity transmitter (WT) promptly transmits the detected humidity signal to the humidity indication control (WIC), and the humidity indication control (WIC) automatically adjusts the opening of the air valve (8-2) to ensure that the humidity of the drying room (1) is consistent with the preset humidity value; thus, the humidity of the drying room can be accurately controlled with the help of the drying room humidity control system (8), and can provide a suitable humidity for the densification drying of the yarn bundle, which takes into account both water evaporation and the movement of the internal macromolecular chains; E. Intelligently adjust the surface temperature of each hot roller: steam passes through the opened hot roller steam regulating valve (5-1), the hot roller steam inlet pipe (5-4), the rotary joint (5-2) and enters the hollow shaft (2-3), the roller (2-1), heats the roller wall and then dries the polyacrylonitrile carbon fiber precursor tow wound on the roller (2-1); the steam condenses into condensed water after heat exchange, and the condensed water passes through the siphon (2-2), the hollow shaft (2-3), the rotary joint (5-2), the hot roller condensed water outlet pipe (5- 5) and the opened hot roller steam trap (5-3); at the same time, the surface temperature of the roller (2-1) is achieved by adjusting the opening of the hot roller steam regulating valve (5-1) to adjust the steam flow entering the roller (2-1) - that is, when the surface temperature of the roller (2-1) deviates from the preset temperature value, the volume of the steam entering the inner cavity of the roller (2-1) will change when it condenses into condensed water, causing the pressure in the inner cavity of the roller (2-1) to change, and the pressure transmitter (PT) will detect the pressure. The change detection signal is promptly transmitted to the pressure indication control (PIC), and the pressure indication control (PIC) automatically adjusts the opening of the hot roller steam regulating valve (5-1), thereby ensuring that the surface temperature of the roller (2-1) is consistent with the preset temperature value; in addition, a hot roller temperature transmitter (TT-2) and a temperature alarm (TA) are installed on the hot roller condensate outlet pipe (5-5). When the hot roller temperature transmitter (TT-2) detects that the condensate temperature is lower than the set value, the hot roller temperature transmitter (TT-2) will promptly transmit the detected temperature signal to the temperature alarm (TA), and the temperature alarm (TA) will issue a prompt alarm signal; in this way, with the help of each group of hot roller temperature control systems (5), each hot roller can be independently controlled and accurately adjusted in temperature, and the roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference required in each stage of the drying process, so as to ensure the uniformity of the roller surface temperature of the hot roller in the effective length direction, and effectively solve the technical problem of large temperature difference of the traditional hot roller surface in the effective length direction; F. Intelligent adjustment of fiber tension: The adjustment of fiber tension is achieved by controlling the speed difference of adjacent rollers (2-1) - that is, the reduction motor (6-1) in each group of fiber tension control systems (6) drives the hollow shaft (2-3) and roller (2-1) in the corresponding hot roller (2) to rotate, and the frequency converter (VFD) changes the motor working power frequency to keep the motor speed consistent with the set value, and the motor speed is detected in real time by the rotary encoder (EC). In this way, the fiber tension change during the drying process of the tow can be maintained and stabilized by controlling the speed difference of adjacent rollers (2-1); in this way, with the help of each group of fiber tension control systems (6), each hot roller can be independently driven and accurately regulated, and the fiber tension of each hot roller can be flexibly adjusted according to the actual tow tension required by each hot roller in the production process, thereby reducing the fiber tension deviation between the rollers, ensuring the uniformity and density of the internal structure of the raw yarn, and enhancing the mechanical properties of the fiber, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber raw yarn; G. Tow densification drying: When each control system is running to normal working state, a uniform and stable drying environment is formed in the drying room (1), and the humidity is suitable for taking into account the evaporation of water and the movement of internal macromolecular chains. The roller surface temperature of each hot roller can be flexibly adjusted according to the temperature difference, and the uniformity of the roller surface temperature in the effective length direction of the hot roller is guaranteed. The fiber tension of each hot roller can be flexibly adjusted according to the different tow tensions required, and the fiber tension deviation between the rollers is greatly reduced. In this way, the water-containing polyacrylonitrile carbon fiber precursor tow entering the drying room (1) and winding around each hot roller (2) in turn can be accurately and uniformly densified and dried - that is, the internal water gradually evaporates from the micropores of the polyacrylonitrile carbon fiber and forms a negative pressure. The free movement of the macromolecular chain segments causes the micropores to shrink, fuse and close, making the internal structure of the fiber uniform and dense, and the mechanical properties of the fiber enhanced, thereby obtaining uniform, dense, stable, reliable and high-performance polyacrylonitrile carbon fiber precursor.

8. The process for uniformly densifying and drying polyacrylonitrile carbon fiber precursor according to claim 7, characterized in that: The temperature difference of the surface temperature of the hot roller (2) in the effective length direction is not greater than 1 o C.

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