Ammoniation system for polyacrylonitrile spinning solution

Abstract

The utility model discloses an ammoniation system for polyacrylonitrile spinning solution, and belongs to the technical field of ammoniation of spinning solution in the carbon fiber industry. The temperature sensor is positioned below the ammonia gas bottle to measure the temperature of the ammonia gas bottle and is interlocked with the heat preservation water regulating valve to stabilize the temperature of the ammonia gas bottle; the weight sensor is used for measuring the total weight of the ammonia gas bottle and the external structure thereof, and is in interlocking control with the ammonia gas regulating valve to regulate the adding speed of the ammonia gas; the ammonia gas distributor expands the contact surface between ammonia gas and the spinning solution through a porous structure, so that the ammonia gas is in better contact with the spinning solution, and the static mixer ensures that the solution is fully mixed with the ammonia gas after ammonia addition; the problem of insufficient pressure of an ammonia gas pipeline caused by frosting at the bottom of an ammonia gas bottle in an ammonia adding process can be solved; the ammonia adding amount is generally small, the measuring error of a flowmeter is large and unstable, the system optimizes the detection mode of the ammonia adding amount, and the accuracy of the ammonia adding amount is improved; and the ammonia adding structure mode is optimized, so that the ammonia gas and the spinning solution are mixed more uniformly.

Description

Technical Field

[0001] This utility model belongs to the field of amination technology of spinning dope in the carbon fiber industry, and specifically relates to an amination system for polyacrylonitrile-based carbon fiber spinning dope. Background Technology

[0002] Polyacrylonitrile-based carbon fiber is a high-performance fiber material with excellent properties such as high specific strength, high specific modulus, low density, and chemical stability. It is widely used in aerospace, automotive, and sporting goods industries.

[0003] The quality of the precursor fiber is the key to determining the various properties of carbon fiber. A large part of the defects in the precursor fiber come from the coagulation bath. The core-sheath structure and large pores generated in the coagulation bath are important factors affecting the performance of carbon fiber.

[0004] Ammoniation of spinning solutions increases their hydrophilicity and effectively reduces the core-sheath structure and macropores during the coagulation bath stage, contributing to the production of high-quality yarn. However, current ammoniation systems for spinning solutions suffer from frost formation on the ammonia cylinders during the ammonia addition process. This frost formation can lead to a series of problems, such as reduced ammonia vaporization, pressure fluctuations in the ammonia pipeline, even cessation of ammonia supply, and problems like solution backflow or blockage of the ammonia pipeline. Furthermore, due to the generally high viscosity of the spinning solution, achieving uniform mixing of ammonia with the spinning solution is a significant challenge in ammoniation. Summary of the Invention

[0005] The present invention aims to solve the technical problems existing in the prior art and provides an amination system for polyacrylonitrile spinning dope.

[0006] The above-mentioned technical problems of this utility model are mainly solved by the following technical solution: an ammoniation system for polyacrylonitrile spinning dope. To solve the above problems, this utility model provides an ammoniation system for polyacrylonitrile spinning dope, including: an ammonia cylinder insulation device, the outside of which is an open insulation cotton, which is tightened and loosened with Velcro; a rubber heat tracing pipe is installed inside, which is arranged in a dense lower part and sparse upper part on the insulation cotton, and the heat tracing pipe is insulated with hot water; a hot water regulating valve is on the hot water inlet pipe of the device, and a temperature sensor is located on the lower side of the ammonia cylinder. The temperature sensor transmits the temperature signal of the ammonia cylinder to the PLC module, and the PLC module controls the opening of the hot water regulating valve to maintain the temperature stability of the lower side of the ammonia cylinder.

[0007] The weight sensor is placed on the lower side of the ammonia cylinder. There is an ammonia regulating valve on the ammonia pipeline. The weight sensor transmits the weight signal of the ammonia cylinder and its accessories to the PLC module in real time. The PLC converts the weight signal into a weight loss signal per unit time, i.e., a mass flow signal. Then, the PLC module controls the valve flow of the ammonia regulating valve to control the ammonia addition rate.

[0008] Pressure sensor and check valve: The pressure sensor is mainly used to detect the pressure value on the ammonia pipeline and the spinning solution pipeline, and the check valve prevents the spinning solution on the solution pipeline from flowing into the ammonia pipeline.

[0009] The ammonia distributor is a short flanged pipe with a jacket. The inner pipe of the jacket has holes of the same size evenly distributed. The center of the outer pipe of the short pipe is connected to the ammonia pipeline, which increases the contact area between the ammonia and the spinning solution, so as to achieve the purpose of uniform contact between the ammonia and the solution. The flange on the ammonia distributor is bolted to the flange on the main pipeline, and the flange on the ammonia pipeline is bolted to the check valve. The ammonia distributor can be disassembled and cleaned at any time.

[0010] The static mixer is used to further mix ammonia and spinning solution after they are mixed, so as to achieve uniform mixing of ammonia and spinning solution.

[0011] Preferably, in the above-mentioned amination system, the amination system is used in any process after polymerization and before spinning; the viscosity of the spinning solution from the upstream side is ≤150,000 cP.

[0012] Preferably, in the above-mentioned ammoniation system, the ammonia cylinder and its associated ammonia cylinder insulation device, temperature sensor, weight sensor, hot water regulating valve, and pressure reducing valve are all configured in a one-in-one standby configuration. When the ammonia cylinder weight sensor detects that the weight no longer changes, it immediately switches to the standby ammonia cylinder to provide ammonia to ensure the continuity of the system.

[0013] Preferably, in the above-mentioned ammoniation system, the temperature below the ammonia cylinder is ≤30°C and the temperature of the hot water in the heat tracing pipe is ≤35°C.

[0014] Preferably, in the above-mentioned ammoniation system, the pressure measured on the ammonia pipeline is greater than the pressure measured on the raw liquid pipeline.

[0015] Preferably, in the above-mentioned ammoniation system, the hot water in the ammonia cylinder insulation device enters from the bottom and exits from the top, with the lower heat tracing pipes being dense and the upper heat tracing pipes being relatively sparse.

[0016] Preferably, in the above-mentioned ammonia system, the weight sensor has an accuracy of 0.01g or higher and a range of 500kg or higher. The PLC continuously receives the weight signal and converts it into a weight reduction signal per unit time, i.e., a mass flow rate signal, such as 2.5kg / h. The converted mass flow rate signal is interlocked with the ammonia regulating valve, and the ammonia flow rate can be adjusted according to the production line's capacity.

[0017] Preferably, in the above-mentioned ammoniation system, the ammonia distributor is connected to both the main pipeline and the ammonia pipeline by flanges, allowing for timely disassembly and cleaning.

[0018] Preferably, in the above-mentioned ammonia system, the static mixer is a combination of SX and SK types.

[0019] This invention has the following advantages: it solves the problem of frost forming at the bottom of ammonia cylinders due to heat absorption during ammonia vaporization, and controls the temperature to make ammonia vaporization more stable; it uses the weight reduction method to measure the ammonia addition rate, making the measurement more accurate and the amount of ammonia added more precise; the ammonia distributor makes the ammonia addition more uniform, and can be quickly disassembled for cleaning when not in use for a long time. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the amination system for the polyacrylonitrile spinning dope of this invention.

[0021] In the diagram: 1. Weight sensor LT1; 2. Temperature sensor TT1; 3. Hot water regulating valve TV1; 4. Ammonia cylinder; 5. Ammonia cylinder outlet pressure reducing valve; 6. Ammonia cylinder insulation device; 7. Weight sensor LT2; 8. Temperature sensor TT2; 9. Hot water regulating valve TV2; 10. Spare ammonia cylinder; 11. Spare ammonia cylinder outlet pressure reducing valve; 12. Ammonia regulating valve LV1; 13. Pressure sensor PT1; 14. Check valve; 15. Ammonia distributor; 16. Pressure sensor PT2; 17. Static mixer. Detailed Implementation

[0022] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. However, it should be understood that the scope of protection of this utility model is not limited to the specific embodiments.

[0023] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments. Example

[0024] Please refer to Figure 1This embodiment provides an ammoniation system for polyacrylonitrile spinning dope. The polyacrylonitrile spinning dope from the upstream side has a viscosity of 150,000 cP, and the pressure sensor PT2 is 0.7 MPa. The ammonia cylinder's insulation device is supplied with 35°C hot water. The temperature TT1 below the ammonia cylinder is set to 25°C in the PLC and is interlocked with the hot water regulating valve TV1 through the PLC. The PLC automatically adjusts the valve opening of TV1 to stably control the temperature of the ammonia cylinder at 25°C, preventing frost from forming at the bottom of the ammonia cylinder.

[0025] Before opening the ammonia cylinder, record the initial total weight M1 of the ammonia cylinder and its accessories. Then, open the ammonia cylinder and the pressure reducing valve behind it to adjust the ammonia outlet pressure to 0.8MPa. The PLC converts the data collected by the weight sensor LT1 into mass flow rate data. Set the mass flow rate to 2.5kg / h in the PLC and interlock it with the ammonia regulating valve LV1. The PLC automatically adjusts the valve opening of LV1 to stabilize the mass flow rate at 2.5kg / h.

[0026] After passing through the check valve, the ammonia gas is evenly distributed in the raw liquid pipeline by the ammonia gas distributor, and then it is thoroughly mixed with the raw liquid in the static mixer. Example

[0027] Please refer to Figure 1 This embodiment provides an ammoniation system for polyacrylonitrile spinning dope. The polyacrylonitrile spinning dope from the upstream side has a viscosity of 120,000 cP, and the pressure sensor PT2 is 0.6 MPa. The ammonia cylinder's insulation device is supplied with 35°C hot water. The temperature TT1 below the ammonia cylinder is set to 25°C in the PLC and is interlocked with the hot water regulating valve TV1 through the PLC. The PLC automatically adjusts the valve opening of TV1 to stably control the temperature of the ammonia cylinder at 25°C, preventing frost from forming at the bottom of the ammonia cylinder.

[0028] Before opening the ammonia cylinder, record the initial total weight M2 of the ammonia cylinder and its accessories. Then, open the ammonia cylinder and the pressure reducing valve behind it to adjust the ammonia outlet pressure to 0.7MPa. The PLC converts the data collected by the weight sensor LT1 into mass flow rate data. Set the mass flow rate to 6.0kg / h in the PLC and interlock it with the ammonia regulating valve LV1. The PLC automatically adjusts the valve opening of LV1 to stabilize the mass flow rate at 6.0kg / h.

[0029] After passing through the check valve, the ammonia gas is evenly distributed in the raw liquid pipeline by the ammonia gas distributor, and then it is thoroughly mixed with the raw liquid in the static mixer. Example

[0030] Please refer to Figure 1This embodiment provides an ammoniation system for polyacrylonitrile spinning dope. The polyacrylonitrile spinning dope from the upstream side has a viscosity of 80,000 cP and a pressure sensor PT2 of 0.3 MPa. The ammonia cylinder's insulation device is supplied with 35°C hot water. The temperature TT1 below the ammonia cylinder is set to 20°C in the PLC and is interlocked with the hot water regulating valve TV1 through the PLC. The PLC automatically adjusts the valve opening of TV1 to stably control the temperature of the ammonia cylinder at 20°C, preventing frost from forming at the bottom of the ammonia cylinder.

[0031] Before opening the ammonia cylinder, record the initial total weight M3 of the ammonia cylinder and its accessories. Then, open the ammonia cylinder and the pressure reducing valve behind it to adjust the ammonia outlet pressure to 0.4MPa. The PLC converts the data collected by the weight sensor LT1 into mass flow rate data. Set the mass flow rate to 10.0kg / h in the PLC and interlock it with the ammonia regulating valve LV1. The PLC automatically adjusts the valve opening of LV1 to stabilize the mass flow rate at 10.0kg / h.

[0032] After passing through the check valve, the ammonia gas is evenly distributed in the raw liquid pipeline by the ammonia gas distributor, and then it is thoroughly mixed with the raw liquid in the static mixer.

[0033] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the present invention to the precise forms disclosed, and many changes and variations can be made based on the above embodiments. The selection of parameters in the embodiments is intended to explain the practical application of the present invention, thereby enabling those skilled in the art to implement and utilize various different embodiments and various choices and modifications of the present invention. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. An amination system for polyacrylonitrile spinning dope, characterized in that, include: The ammonia cylinder insulation device has an open insulation cotton exterior, which is tightened and loosened with Velcro. Inside, there is a plastic heat tracing pipe that is filled with hot water for insulation. The device has a hot water regulating valve on the inlet hot water pipe and a temperature sensor on the lower side of the ammonia cylinder. The temperature sensor transmits the temperature signal of the ammonia cylinder to the PLC module. The weight sensor is placed directly below the ammonia cylinder. There is an ammonia regulating valve on the ammonia pipeline. The weight sensor transmits the weight signal of the ammonia cylinder and its accessories to the PLC module in real time. The PLC converts the weight signal into a weight loss signal per unit time, i.e., a mass flow signal. Then, the PLC module controls the valve flow of the ammonia regulating valve. Pressure sensor and check valve: The pressure sensor is mainly used to detect the pressure value on the ammonia pipeline and the spinning solution pipeline, and the check valve prevents the spinning solution on the solution pipeline from flowing into the ammonia pipeline. The ammonia distributor is a short flanged pipe with a jacket. The inner pipe of the jacket has holes of the same size evenly distributed. The center of the outer pipe of the short pipe is connected to the ammonia pipeline to increase the contact area between the ammonia and the spinning solution, so as to achieve the purpose of uniform contact between the ammonia and the solution. The flange on the ammonia distributor is bolted to the flange on the main pipeline, and the flange on the ammonia pipeline is bolted to the check valve. The static mixer is used to further mix ammonia and spinning solution after they are mixed, so as to achieve uniform mixing of ammonia and spinning solution.

2. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The ammonia cylinder and its associated ammonia cylinder insulation device, temperature sensor, weight sensor, hot water regulating valve, and pressure reducing valve are all configured in a one-in-one-backup configuration. When the ammonia cylinder weight sensor detects that the weight is no longer changing, it immediately switches to the backup ammonia cylinder to supply ammonia to ensure the continuity of the system.

3. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The temperature below the ammonia cylinder is ≤30℃, and the temperature of the hot water is ≤35℃.

4. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The pressure in the ammonia pipeline must be greater than the pressure in the main spinning solution pipeline.

5. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The ammonia cylinder insulation device has hot water entering from the bottom and exiting from the top; the heat tracing pipes at the bottom are dense, while those at the top are relatively sparse.

6. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The weight sensor has an accuracy of over 0.01g and a range of over 500kg. The PLC continuously receives the weight signal and converts it into a weight reduction signal per unit time, i.e., a mass flow rate signal, such as 2.5kg / h. The converted mass flow rate signal is interlocked with the ammonia regulating valve, and the ammonia flow rate can be adjusted according to the production line's capacity.

7. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The ammonia distributor is connected to both the main pipeline and the ammonia pipeline by flanges, allowing it to be disassembled and cleaned promptly.

8. The amination system for polyacrylonitrile spinning solution according to claim 1, characterized in that, The static mixer is a combination of SX and SK types.

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