Vacuum control system and control method for PAN-based carbon fiber vacuum tower

Abstract

The application provides a PAN-based carbon fiber vacuum tower vacuum control system and a control method thereof. The vacuum control system comprises a vacuum tower and a tower top condenser, a first gas phase channel for the flow of unreacted monomers or solvents is arranged between the vacuum tower and the tower top condenser, a spraying unit for spraying is arranged at the top end of the tower top condenser, the spraying liquid of the spraying unit flows out to a condensate tank through the gas path channel of the tower top condenser, and a circulating pipeline in communication with the spraying unit is arranged at the outlet of the condensate tank. The vacuum control system further comprises a vacuum control unit, which comprises a vacuum ejector and a working liquid tank connected to the pressure inlet and outlet of the vacuum ejector. When a pressure difference is generated between the pressure at the top of the vacuum tower and the suction port pressure of the vacuum ejector, the control valve can adjust the flow of the third gas phase channel, and the sum of the pressure at the top of the vacuum tower and the third gas phase channel is equal to the suction port pressure of the vacuum ejector. The application stabilizes the pressure at the top of the vacuum tower and ensures the uniformity of the polymerization stock solution.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber production technology, and in particular to a vacuum control system and control method for a PAN-based carbon fiber vacuum tower. Background Technology

[0002] In the current PAN-based carbon fiber production field, due to the characteristics of batch polymerization reactions, the vacuum level of the monomer removal and concentration system needs to be frequently adjusted. Since the lower the pressure in the vacuum tower, the lower the boiling point of the monomer, operating under certain vacuum conditions can lower the monomer boiling point. Furthermore, abnormal liquid levels in the vacuum tower can also cause vacuum fluctuations, as a large amount of polymer liquid entering the top of the vacuum tower reduces its gas phase space and decreases the vacuum level.

[0003] In existing technology, vacuum adjustment at the top of the vacuum tower and concentration tower is mainly achieved by adjusting the temperature of the top cooler and the outlet pressure of the vacuum pump. During the intermittent production of the polymerization solution, the properties of the polymerization solution change within the polymerization solution buffer tank, resulting in significant system vacuum fluctuations. This leads to large fluctuations in the properties of the polymerization solution, ultimately affecting the uniformity and stability of the spinning solution and impacting subsequent spinning processes.

[0004] Adjusting the temperature of the condenser at the top of the tower to control the pressure of the vacuum system has limited effect and can only be used as a fine-tuning method. Adjusting the pressure at the inlet of the ejector to adjust the vacuum at the top of the tower will cause large fluctuations in the pressure at the top of the vacuum tower and the concentration tower due to small changes in the outlet pressure of the vacuum pump, which is not conducive to the uniformity and stability of the spinning solution.

[0005] In addition, since the polymerization reaction is a batch reaction, the composition of the working fluid of the vacuum pump is constantly changing. The change in composition causes changes in the outlet pressure of the vacuum jet pump, which ultimately causes fluctuations in the vacuum at the top of the tower and affects the quality of the polymerization solution. Summary of the Invention

[0006] In view of this, the present invention aims to propose a vacuum control system for a PAN-based carbon fiber vacuum tower to improve the pressure stability at the top of the vacuum tower and ensure the uniformity and stability of the polymerization solution.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A vacuum control system for a PAN-based carbon fiber vacuum tower includes a vacuum tower and a top condenser.

[0009] A first gas phase channel for unreacted monomers or solvents to flow between the vacuum tower and the tower top condenser is provided, and a spray unit for spraying is provided at the top of the tower top condenser. The spray liquid of the spray unit flows out to the condensate tank through the gas passage of the tower top condenser, and the outlet of the condensate tank is provided with a circulation pipeline connected to the spray unit.

[0010] It also includes a vacuum control unit for adjusting the vacuum level at the top of the vacuum tower, the vacuum control unit including a vacuum ejector and a working liquid tank connected to the pressure inlet and outlet of the vacuum ejector;

[0011] The working liquid tank is provided with a liquid phase channel connected to the pressure inlet of the vacuum ejector, and a second gas phase channel is provided between the suction port of the vacuum ejector and the top condenser of the tower; the second gas phase channel (26) is used for the flow of uncondensed gas phase;

[0012] The working liquid tank is also provided with a third gas phase channel that communicates with the second gas phase channel; the third gas phase channel is provided with a control valve for controlling the flow rate of the third gas phase channel, and a first pressure sensor for detecting pressure is provided at the top of the vacuum tower;

[0013] When a pressure difference occurs between the pressure at the top of the vacuum tower and the pressure at the suction port of the vacuum ejector, the control valve is driven to adjust the flow rate of the third gas phase channel so that the sum of the pressure at the top of the vacuum tower and the pressure in the third gas phase channel is equal to the pressure at the suction port of the vacuum ejector.

[0014] Furthermore, the condenser at the top of the tower is connected to a first chilled water line and a first circulating water line for condensing the unreacted monomers or solvents. The first chilled water line is equipped with a first regulating valve for adjusting its own flow rate.

[0015] A first temperature transmitter (10) is provided on the connecting pipeline between the top condenser (2) and the condensate tank (3), and the first regulating valve (12) adjusts the flow rate of the first chilled water pipeline (14) according to the monitoring temperature of the first temperature transmitter (10).

[0016] Furthermore, the outlet of the condensate tank has a liquid phase channel communicating with the inlet of the spray unit, and the spray unit includes one or more spray heads, the spray head spraying the unreacted monomers or solvents from top to bottom.

[0017] Furthermore, the working fluid tank is connected to a condenser, and the inlet of the condenser is connected to a first pipeline and a second pipeline. The working fluid in the first pipeline and the second pipeline enters the liquid phase channel after being condensed by the condenser.

[0018] Furthermore, the first pipeline includes a second circulating water pipeline and a second chilled water pipeline. The working fluid tank is connected to a second temperature transmitter. The second cooling water pipeline is equipped with a second regulating valve for adjusting its own flow rate. The second regulating valve adjusts the flow rate of the second cooling water pipeline according to the temperature of the second temperature transmitter.

[0019] Furthermore, the outlet of the working fluid tank is provided with a first pump body for supplying working fluid to the injector, and the first pump body is a variable frequency water pump.

[0020] Furthermore, the third gas phase channel includes a first compensation gas path and a second compensation gas path. The first compensation gas path is connected to the nitrogen pipeline network, and the second compensation gas path is connected to the top of the working liquid tank, for transporting the gas phase in the working liquid tank (5).

[0021] Furthermore, the control valve includes a first control valve and a second control valve. The first control valve is connected to the first compensation gas line, and the second control valve is connected to the second compensation gas line. The first control valve and the second control valve are cascaded to adjust the output pressure of the third gas phase channel.

[0022] Furthermore, a first baffle is provided at one end of the top condenser near the second gas phase channel, allowing the gas phase of the top condenser to flow out through the first baffle, while the first baffle prevents the liquid phase inside the top condenser from flowing out.

[0023] A second baffle is provided inside the working liquid tank near the second compensation gas path. The gas phase inside the working liquid tank can pass through the second baffle, while the second baffle blocks the liquid phase inside the working liquid tank from flowing out.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The vacuum control system for the PAN-based carbon fiber vacuum tower of the present invention includes a vacuum control unit, a second gas phase channel between the vacuum ejector and the top condenser, a first pressure sensor at the top of the vacuum tower to detect the top pressure, and a third gas phase channel connected to the second gas phase channel with a control valve to control the flow rate of the third gas phase channel. This increases the compensating gas to ensure that the top pressure of the vacuum tower meets the pressure at the suction port of the vacuum ejector 6, thereby stabilizing the top pressure of the vacuum tower and ensuring the uniformity and stability of the polymerization solution.

[0026] Another objective of this invention is to provide a vacuum control method for a PAN-based carbon fiber vacuum tower, the specific steps of which are as follows:

[0027] Step 1: The polymerization liquid is pressurized and transported to the vacuum tower by an external gear pump. Under vacuum, unreacted monomers or solvents are removed to form the polymerization liquid, which is then pumped out of the vacuum tower to the subsequent processing unit.

[0028] Step 2: The unreacted monomers or solvents that have been released are condensed by the top condenser and collected in the condensate tank. During the flow of the gaseous material from the tube side of the top condenser, it is cooled by the chilled water transported by the first chilled water pipeline. The condensed liquid phase flows into the condensate tank and is then transported to the top condenser by an external pressurized pump to spray the subsequent gas phase. The condensed gas phase is connected to the vacuum ejector through the second gas phase channel.

[0029] Step 3: The working fluid in the working fluid tank and the mixture cooled by the condenser are sent to the inlet of the vacuum ejector by the first pump body to form a vacuum. Based on the pressure value detected by the first pressure sensor, the first gas path and the second gas path adjust their own gas flow through the control of the first control valve and the second control valve, respectively, so that the sum of the pressure at the top of the vacuum tower and the pressure in the third gas phase channel is equal to the pressure at the suction port of the vacuum ejector.

[0030] The vacuum control method for the PAN-based carbon fiber vacuum tower of the present invention improves the condensation effect by mixing chilled water and circulating water in step two to cool the gas phase, and then collecting the condensed liquid phase and sending it back to the top condenser for spraying to ensure thorough mixing of the absorbent liquid and the gas phase. Furthermore, by testing the pressure at the top of the vacuum tower and controlling the flow rate of the third gas phase channel via a control valve, fluctuations in the pressure at the vacuum ejector intake port are prevented from causing pressure fluctuations at the top of the vacuum tower. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a production flow diagram of the vacuum control system for the PAN-based carbon fiber vacuum tower described in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Vacuum tower; 2. Tower top condenser; 3. Condensate tank; 4. Condenser; 5. Working liquid tank; 6. Vacuum ejector; 7. First pump body; 8. Second pump body; 9. Third pump body; 10. First temperature transmitter; 11. Second temperature transmitter; 12. First regulating valve; 13. Second regulating valve; 14. First chilled water pipeline; 15. First circulating water pipeline; 16. Second chilled water pipeline; 17. Second circulating water pipeline; 18. First compensation gas line; 19. Second compensation gas line; 20. First control valve; 21. Second control valve; 22. First baffle; 23. Second baffle; 24. Spray head; 25. First gas phase channel; 26. Second gas phase channel; 27. Third gas phase channel; 28. First pressure sensor; 29. ​​Second pressure sensor. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0036] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "back," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] Furthermore, in the description of this invention, unless otherwise explicitly defined, the terms "installation," "connection," "linking," and "connector" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] This embodiment relates to a vacuum control system for a PAN-based carbon fiber vacuum tower, including a vacuum tower 1 and a top condenser 2. A first gas phase channel 25 for unreacted monomers or solvents to flow between the vacuum tower 1 and the top condenser 2 is provided. The top of the top condenser 2 is provided with a spray unit for spraying. The spray liquid of the spray unit flows out through the gas passage of the top condenser 2 into a condensate tank 3. The outlet of the condensate tank 3 is provided with a circulation pipeline connected to the spray unit.

[0040] The vacuum control system of the PAN-based carbon fiber vacuum tower also includes a vacuum control unit for adjusting the vacuum level at the top of the vacuum tower 1. The vacuum control unit includes a vacuum ejector 6 and a working liquid tank 5 connected to the pressure inlet and outlet of the vacuum ejector 6. The working liquid tank 5 is provided with a liquid phase channel 28 communicating with the pressure inlet of the vacuum ejector 6. A second gas phase channel 26 is provided between the suction port of the vacuum ejector 6 and the condenser 2 at the top of the tower. The working liquid tank 5 is also provided with a third gas phase channel 27 communicating with the second gas phase channel 26. A control valve for controlling the flow rate of the third gas phase channel 27 is provided on the third gas phase channel 27. A first pressure sensor 28 for detecting pressure is provided at the top of the vacuum tower 1.

[0041] When a pressure difference occurs between the top pressure of vacuum tower 1 and the suction port pressure of vacuum ejector 6, the control valve is driven to adjust the flow rate of the third gas phase channel 27 so that the sum of the pressure at the top of vacuum tower 1 and the pressure in the third gas phase channel 27 is equal to the suction port pressure of vacuum ejector 6.

[0042] The vacuum control system for the PAN-based carbon fiber vacuum tower described in this embodiment includes a vacuum control unit. A second gas phase channel 26 is provided between the vacuum ejector 6 and the top condenser 2. Uncondensed gas from the top condenser 2 flows through this second gas phase channel to the suction port of the vacuum ejector 6. Furthermore, a first pressure sensor 28 is installed at the top of the vacuum tower 1 to detect the pressure at the top. A third gas phase channel 27 is connected to the second gas phase channel 26, and the flow rate of the third gas phase channel 27 is controlled by a control valve. This increases the amount of compensating gas, ensuring that the pressure at the top of the vacuum tower 1 meets the pressure at the suction port of the vacuum ejector 6. This stabilizes the pressure at the top of the vacuum tower 1, guaranteeing the uniformity and stability of the polymerization solution.

[0043] Based on the above overall introduction, this embodiment presents an exemplary structure of the vacuum control system for a PAN-based carbon fiber vacuum tower, as follows: Figure 1 As shown, the vacuum control system of the PAN-based carbon fiber vacuum tower consists of a vacuum tower 1, a tower top condenser 2, a condensate tank 3, and a vacuum control unit. In this embodiment, the vacuum tower 1 can be a de-monopolymerization tower or a concentration tower. The vacuum control system of the PAN-based carbon fiber vacuum tower in this embodiment will be described below using a de-monopolymerization tower as an example.

[0044] Furthermore, it should be noted that, based on Figure 1 As shown in the status. Figure 1 The dashed line in the diagram is used to indicate a dependency relationship between the two ends of the dashed line, as explained in the following text.

[0045] The outlet of vacuum column 1 is connected to the top condenser 2. Unreacted monomers or solvents are transported to the top of the top condenser 2 through the first gas phase channel. In this embodiment, the top condenser 2 includes a feed zone, a condensation zone, and a discharge zone. The feed zone has two inlets, one of which is connected to the first gas phase channel 25, and the other is connected to a circulation pipeline. A spray unit is provided at the inlet of the circulation pipeline in the feed zone. Figure 1 As shown, in this embodiment, the vacuum tower 1 is pressurized by the third pump body 9 and then sent to the subsequent unit.

[0046] The spray liquid in the spray unit is dimethyl sulfoxide (DMSO). After being pressurized by the second pump body 8, the absorbent in the condensate tank 3 is transported to the top condenser 2. The output end of the second pump body 8 also has a collection pipeline to the tank area, thus ensuring the liquid pressure balance of the condensate tank 3. Both the second pump body 8 and the third pump body 9 are pressurization pumps.

[0047] As Figure 1 As shown, unreacted monomers or solvents are drawn in from the side of the top condenser 2, and the spray liquid is sprayed downwards, making perpendicular contact with the gas phase. This spraying ensures sufficient contact between the gas and liquid phases, increasing the absorption effect. Furthermore, a flow meter and a flow regulating valve are installed on the first gas phase channel 25 to detect the flow rate and ensure a constant flow of the spray liquid, preventing pressure fluctuations in the top condenser 2.

[0048] In addition, the top condenser 2 is connected to a first chilled water line 14 and a first circulating water line 15 for condensing unreacted monomers or solvents. The first chilled water line 14 is equipped with a first regulating valve 12 for adjusting its own flow rate. The connecting pipe between the top condenser 2 and the condensate tank 3 is equipped with a first temperature transmitter 10. The first regulating valve 12 adjusts the flow rate of the first chilled water line 14 according to the temperature monitored by the first temperature transmitter 10.

[0049] like Figure 1 As shown, the condensation zone of the top condenser 2 in this embodiment is provided with inlets for chilled water and circulating water. In a preferred embodiment, the chilled water temperature in the first chilled water pipeline 14 is between 5-10°C, and the circulating water temperature in the first circulating water pipeline 15 is 25-32°C. The chilled water and circulating water from the first chilled water pipeline 14 and the first circulating water pipeline 15 are mixed before entering the top condenser 2. The first chilled water pipeline 14 is used to transport chilled water to the shell side of the top condenser 2 to cool the gas phase and spray liquid passing through the tube side, causing some of the gas phase to condense into a liquid phase, while some of the uncondensed gas phase is adsorbed onto the suction port of the vacuum ejector 6 through the second gas phase channel 26. The circulating water is used to increase the shell side temperature and prevent crystallization and blockage caused by excessively low temperatures.

[0050] Furthermore, the outlet of the condensate tank 3 has a liquid phase channel 28 that connects to the inlet of the spray unit. The spray unit includes one or more spray heads 24, and the spray direction of the spray heads 24 is from top to bottom to spray unreacted monomers or solvents. In this embodiment, multiple spray heads 24 are arranged circumferentially. The spraying effect of multiple spray heads 24 can increase the fusion effect between the spray liquid and the gas phase and improve the condensation effect.

[0051] In addition, the temperature of the spray liquid can be controlled to be no higher than 19℃-25℃. This temperature can prevent the polymerization of acrylonitrile monomers and also prevent DMSO from freezing and blocking the pipeline. The establishment of circulating water can facilitate the elimination of freezing blockage of the condenser 2 at the top of the tower when the pipeline freezes due to abnormal low temperature. The temperature of the spray liquid can be adjusted by adjusting the opening of the temperature self-regulating valve TV1, thereby achieving fine adjustment of the vacuum degree at the top of the tower.

[0052] In a preferred embodiment, the working fluid tank 5 is connected to a condenser 4, and the inlet of the condenser 4 is connected to a first pipeline and a second pipeline. The working fluid in the first pipeline and the second pipeline is condensed by the condenser 4 and then enters the liquid phase channel 28.

[0053] The first pipeline includes a second circulating water pipeline 17 and a second chilled water pipeline 16. The working fluid tank 5 is connected to a second temperature transmitter 11. The second cooling water pipeline is equipped with a second regulating valve 13 for adjusting its own flow rate. The second regulating valve 13 adjusts the flow rate of the second cooling water pipeline according to the temperature of the second temperature transmitter 11.

[0054] In terms of specific structure, such as Figure 1 As shown, the sprayed liquid is cooled by condenser 4. The second chilled water pipeline 16 is used to regulate the temperature of the sprayed liquid during normal production, and the temperature of the chilled water is 5-10℃. The second circulating water pipeline 17 is used to prevent the temperature of the chilled water pipeline from being too low and is used to thaw the pipeline when it is blocked. The temperature of the circulating water is 25-32℃.

[0055] In addition, by adjusting the flow rate of the second cooling water pipe 16, the temperature of the injection liquid entering the vacuum ejector 6 is controlled to be no higher than 19°C-25°C, thereby preventing the polymerization of the monomer acrylonitrile.

[0056] Meanwhile, the second pipeline on the condenser 4 is used to transport cooling water back to the outside. By installing a second temperature transmitter 11 in the working fluid tank 5, the temperature of the working fluid in the working fluid tank 5 is detected. The second regulating valve 13 adjusts the flow rate of the second chilled water pipeline 16 according to the detected temperature of the second temperature transmitter 11, thereby stabilizing the temperature of the injection liquid in the first pipeline and reducing the impact of temperature fluctuations on the system vacuum.

[0057] It should be noted that the vacuum control system of the PAN-based carbon fiber vacuum tower in this embodiment also includes a control unit. This control unit is used to receive the detected temperature signals from the first temperature transmitter 10 and the second temperature transmitter 11, compare the temperature signals with preset values, and then output electrical signals to the first regulating valve 12 and the second regulating valve 13 to drive the first regulating valve 12 and the second regulating valve 13 to automatically adjust the flow rate of their corresponding pipelines. The control unit in this embodiment refers to the controller used in the prior art, and will not be described in detail here.

[0058] In this embodiment, the first temperature transmitter 10 and the second temperature changer adopt the structure of the prior art, and the first regulating valve 12 and the second regulating valve 13 are automatic flow regulating valves.

[0059] In addition, the outlet of the working fluid tank 5 is equipped with a first pump body 7 for supplying working fluid to the injector. The first pump body 7 is a variable frequency water pump. The first pump body 7 is controlled by a frequency converter, which is connected to the aforementioned control unit. The outlet of the first pump body 7 is equipped with a second pressure sensor 29, and the pressure value detected by the second pressure sensor 29 is sent to the control unit. The control unit can send a frequency conversion signal to the first pump body 7.

[0060] By setting up a variable frequency water pump, the outlet pressure of the first pump body 7 can be kept stable, thereby ensuring the inlet pressure of the vacuum ejector 6 remains stable. This eliminates the impact of fluctuations in the ejector pump outlet pressure caused by changes in the composition of the ejector liquid due to intermittent polymerization feeding and variations in the polymer liquid's properties. Furthermore, using a variable frequency water pump achieves energy saving and consumption reduction, allowing the first pump body 7 to adjust its frequency according to the system load.

[0061] The third gas phase channel 27 includes a first compensation gas path 18 and a second compensation gas path 19. The first compensation gas path 18 is connected to the nitrogen pipeline network, and the second compensation gas path 19 is connected to the top of the working liquid tank 5. Figure 1 As shown, the other end of the second compensating gas path 19 is connected to the second gas phase channel 26. The first compensating gas path 18 is connected to the second compensating gas path 19, and after mixing, it is connected to the third gas phase channel 27. The first compensating gas path 18 delivers nitrogen, preferably at a pressure of 0.6 MPa.

[0062] Furthermore, the control valves include a first control valve 20 and a second control valve 21. The first control valve 20 is connected to the first compensating gas path 18, and the second control valve 21 is connected to the second compensating gas path 19. The first control valve 20 and the second control valve 21 are cascaded to adjust the output pressure of the third gas phase channel 27. Specifically, in this embodiment, both the first control valve 20 and the second control valve 21 are connected to the control unit. The first control valve 20 and the second control valve 21 are automatic flow control valves.

[0063] By monitoring the pressure of the first pressure sensor 28 at the top of the vacuum tower 1, the control unit receives the pressure value and obtains the vacuum value of the suction port of the vacuum ejector 6 through the second pressure sensor 29 located at the outlet end of the first pump body 7. The control unit receives the vacuum value and compares it with the pressure value to adjust the flow rate of the first control valve 20 and the second control valve 21, thereby stabilizing the pressure at the suction port of the vacuum ejector 6 and preventing pressure fluctuations inside the vacuum tower 1.

[0064] Furthermore, the second compensation gas path 19 serves as the non-condensable gas at the top of the working liquid tank 5, with the second compensation gas path 19 as the main input and nitrogen as the auxiliary input. The top of the working liquid tank 5 is also sealed with nitrogen to ensure a slight positive pressure in the working liquid tank 5 and prevent negative pressure from entering other gas phases and causing danger.

[0065] Furthermore, a first baffle 22 is provided at one end of the top condenser 2 near the second gas phase passage 26, allowing the gas phase of the top condenser 2 to flow out through the first baffle 22, while preventing the liquid phase from flowing out of the top condenser 2. A second baffle 23 is provided in the working liquid tank 5 near the second compensation gas passage 19, allowing the gas phase in the working liquid tank 5 to pass through the second baffle 23, while the second baffle 23 prevents the liquid phase in the working liquid tank 5 from flowing out. By setting the first baffle 22 and the second baffle 23, the gas phase and liquid phase in the tank can be separated, preventing the gas phase from being entrained by liquid phase and causing unstable gas phase pressure.

[0066] This embodiment also relates to a vacuum control method for a PAN-based carbon fiber vacuum tower, the specific steps of which are as follows:

[0067] Step 1: The polymerization liquid is pressurized and transported to vacuum tower 1 by an external gear pump. Unreacted monomers or solvents are removed under vacuum to form the polymerization liquid, which is then pumped out of vacuum tower 1 and transported to subsequent processing units.

[0068] Step 2: The unreacted monomers or solvents that have been released are condensed by the top condenser 2 and collected in the condensate tank 3. As the gaseous material flows from the tube side of the top condenser 2, the chilled water from the first chilled water line 14 flows into the shell side to cool the gaseous material in the tube side. The condensed liquid phase flows into the condensate tank 3 and is then pumped to the top condenser 2 by an external pressurization pump to spray the subsequent gas phase. The condensed gas phase enters the vacuum ejector 6 through the second gas phase channel 26.

[0069] Step 3: The working liquid in the working liquid tank 5 and the mixture cooled by the condenser 4 are sent to the inlet of the vacuum ejector 6 by the first pump body 7 to form a vacuum. Based on the pressure value detected by the first pressure sensor, the first gas path and the second gas path adjust their own gas flow rate through the control of the first control valve 20 and the second control valve 21, respectively, so that the sum of the pressure at the top of the vacuum tower 1 and the pressure in the third gas phase channel 27 is equal to the pressure at the suction port of the vacuum ejector 6. By compensating for changes in the gas volume, the pressure at the top of the vacuum tower is automatically adjusted to achieve precise adjustment of the top of the vacuum tower 1 and ensure the stability of the pressure at the top of the vacuum tower 1.

[0070] The vacuum control method for the PAN-based carbon fiber vacuum tower of the present invention improves the condensation effect by mixing chilled water and circulating water in step two to cool the gas phase, and then collecting the condensed liquid phase and sending it back to the top condenser for spraying to ensure thorough mixing of the absorbent liquid and the gas phase. Furthermore, by testing the pressure at the top of the vacuum tower and controlling the flow rate of the third gas phase channel via a control valve, fluctuations in the pressure at the vacuum ejector intake port are prevented from causing pressure fluctuations at the top of the vacuum tower.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vacuum control system for a PAN-based carbon fiber vacuum tower, comprising a vacuum tower (1) and a top condenser (2), characterized in that: A first gas phase channel (25) for unreacted monomers or solvents to flow between the vacuum tower (1) and the tower top condenser (2), and a spray unit for spraying the unreacted monomers or solvents is provided at the top of the tower top condenser (2). The spray liquid of the spray unit flows out into the condensate tank (3) through the gas passage of the tower top condenser (2), and the outlet of the condensate tank (3) is provided with a circulation pipeline connected to the spray unit. It also includes a vacuum control unit for adjusting the vacuum level at the top of the vacuum tower (1), the vacuum control unit including a vacuum ejector (6) and a working liquid tank (5) connected to the pressure inlet and outlet of the vacuum ejector (6). The working liquid tank (5) is provided with a liquid phase channel connected to the pressure water inlet of the vacuum ejector (6). A second gas phase channel (26) is provided between the suction port of the vacuum ejector (6) and the top condenser (2). The second gas phase channel (26) is used for the flow of uncondensed gas phase. The working liquid tank (5) is also provided with a third gas phase channel (27) that is connected to the second gas phase channel (26); the third gas phase channel (27) is provided with a control valve for controlling the flow rate of the third gas phase channel (27), and a first pressure sensor (28) for detecting pressure is provided at the top of the vacuum tower (1). When a pressure difference occurs between the top pressure of the vacuum tower (1) and the suction port pressure of the vacuum ejector (6), the control valve adjusts the flow rate of the third gas phase channel (27) so that the sum of the pressure at the top of the vacuum tower (1) and the pressure in the third gas phase channel (27) is equal to the suction port pressure of the vacuum ejector (6).

2. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 1, characterized in that: The top condenser (2) is connected to a first chilled water pipeline (14) and a first circulating water pipeline (15) for condensing the unreacted monomers or solvents. The first chilled water pipeline (14) is equipped with a first regulating valve (12) for adjusting its own flow rate. The connecting pipeline between the top condenser (2) and the condensate tank (3) is equipped with a first temperature transmitter (10). The first regulating valve (12) adjusts the flow rate of the first chilled water pipeline (14) according to the temperature monitored by the first temperature transmitter (10).

3. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 2, characterized in that: The spraying unit includes one or more spray heads (24), which spray the unreacted monomers or solvents from top to bottom.

4. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 2, characterized in that: The working fluid tank (5) is connected to a condenser (4). The inlet of the condenser (4) is connected to a first pipeline and a second pipeline. The working fluid in the first pipeline and the second pipeline enters the liquid phase channel after being condensed by the condenser (4).

5. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 4, characterized in that: The first pipeline includes a second circulating water pipeline (17) and a second chilled water pipeline (16). The working liquid tank (5) is connected to a second temperature transmitter (11). The second chilled water pipeline (16) is provided with a second regulating valve (13) for adjusting its own flow rate. The second regulating valve (13) adjusts the flow rate of the second chilled water pipeline (16) according to the temperature of the second temperature transmitter (11).

6. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 1, characterized in that: The outlet of the working fluid tank (5) is provided with a first pump body (7) for supplying working fluid to the injector, and the first pump body (7) is a variable frequency water pump.

7. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 1, characterized in that: The third gas phase channel (27) includes a first compensation gas path (18) and a second compensation gas path (19), wherein the first compensation gas path (18) is connected to the nitrogen pipeline network; The second compensation gas path (19) is connected to the top of the working liquid tank (5) and is used to transport the gas phase in the working liquid tank (5).

8. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 7, characterized in that: The control valve includes a first control valve (20) and a second control valve (21). The first control valve (20) is connected to the first compensation gas path (18), and the second control valve (21) is connected to the second compensation gas path (19). The first control valve (20) and the second control valve (21) are cascaded to adjust the output pressure of the third gas phase channel (27).

9. The vacuum control system for the PAN-based carbon fiber vacuum tower according to claim 7, characterized in that: The top condenser (2) is provided with a first baffle (22) at one end near the second gas phase channel (26). The gas phase of the top condenser (2) can flow out from the first baffle (22), and the first baffle (22) can prevent the liquid phase in the top condenser (2) from flowing out. A second baffle (23) is provided inside the working liquid tank (5) near the second compensation gas passage (19). The gas phase inside the working liquid tank (5) can pass through the second baffle (23), and the second baffle (23) blocks the liquid phase inside the working liquid tank (5) from flowing out.

10. The vacuum control method for the PAN-based carbon fiber vacuum tower according to claim 1, characterized in that: Step 1: The polymer liquid is pressurized and transported to the vacuum tower (1) by an external gear pump. Unreacted monomers or solvents are removed under vacuum to form the polymer liquid, which is then pumped out of the vacuum tower (1) and transported to the subsequent unit for processing. Step 2: The unreacted monomers or solvents that have been released are condensed by the top condenser (2) and collected in the condensate tank (3). During the flow of the gaseous material from the tube side of the top condenser (2), it is cooled by the chilled water transported by the first chilled water pipeline (14). The condensed liquid phase flows into the condensate tank (3) and is transported to the top condenser (2) by an external pressurizing pump to spray the subsequent gas phase. The condensed gas phase is connected to the vacuum ejector (6) through the second gas phase channel (26). Step 3: The working liquid in the working liquid tank (5) and the mixture cooled by the condenser (4) are sent to the inlet of the vacuum ejector (6) by the first pump body (7) to form a vacuum. Based on the pressure value detected by the first pressure sensor (28), the first gas path and the second gas path adjust their own gas flow rate by the control of the first control valve (20) and the second control valve (21) respectively, so that the sum of the pressure at the top of the vacuum tower (1) and the pressure of the third gas phase channel (27) is equal to the pressure at the suction port of the vacuum ejector (6).

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