A method for controlling draft ratio of raw yarn spinning process

Abstract

The present invention relates to the technical field of carbon fiber precursor production, and in particular to a method for controlling the draft ratio of a precursor spinning process. After a chemical liquid is pumped from a storage tank to a coagulation tank by a metering pump until it is full, the metering pump is controlled to keep each material pool in the coagulation tank in a constant overflow state. Specifically, the metering pump cooperates with an adjustment valve to accurately control the liquid level of the coagulation tank to be in a constant overflow state, thereby reducing liquid level fluctuations and providing a stable production environment for the spinning process. A liquid level sensor and a servo system are used to adjust the distance between the spinneret and the liquid level of the coagulation tank to ensure that the spinning solution maintains a consistent shape when entering the chemical liquid, thereby improving the spinning quality. The chemical liquid overflowing from the coagulation tank is collected and purified, and then pumped back to the storage tank for reuse, thereby saving resources. The liquid level in the storage tank is detected by a first liquid level gauge, and flow error compensation is performed by an adjustment valve based on the calculated flow difference, thereby further ensuring the stability and accuracy of the spinning process.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber precursor production, and in particular to a method for controlling the draft ratio of a precursor spinning process. Background Art

[0002] In the production of carbon fiber, the spinning of the precursor usually occurs after the polymerization reaction. The spinning solution is obtained through the polymerization reaction. Then the solution enters the coagulation tank through the spinneret under pressure to form gel fiber. After a series of post-processing steps, such as drawing, washing, densification, steam treatment, etc., PAN precursor is finally generated.

[0003] During the spinning process, the spinning solution is pressurized and introduced into the coagulation tank by a nozzle. The distance between the nozzle and the level of the chemical liquid below it affects the shape of the spinning solution when it enters the chemical liquid. Therefore, the distance between the nozzle and the level of the chemical liquid must be strictly controlled during the spinning process. During the spinning process, the coagulation tank carrying the chemical liquid must be kept in an overflow state. Therefore, the chemical liquid must be continuously fed into the coagulation tank. When the flow rate of the coagulation tank fluctuates or errors occur, it is easy to cause the water level to fluctuate, which in turn affects the spinning precision and reduces the quality of the raw yarn production. Summary of the Invention

[0004] The present invention provides a method for controlling the draft ratio of a raw silk spinning process, which can effectively solve the problems in the background technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for controlling the draft ratio of a raw yarn spinning process comprises the following steps:

[0007] Pumping the chemical liquid from the storage tank to the coagulation tank by a metering pump until it is full, and controlling the metering pump to keep each material tank in the coagulation tank in a constant overflow state;

[0008] The distance between the spinneret and the liquid level in the coagulation pool is detected by a liquid level sensor, and the servo system is used to control the spinneret to maintain a set distance from the liquid level in the coagulation pool;

[0009] The chemical liquid overflowing from the coagulation tank is collected in a transfer tank for purification, and then pumped to the storage tank by a water pump;

[0010] The liquid level in the storage tank is detected by a first liquid level meter, the flow difference is calculated, and the flow error is compensated in conjunction with the adjustment valve.

[0011] Furthermore, during the process of injecting liquid into the coagulation pool, the metering pump is first controlled to operate at a high flow rate until the coagulation pool is full, and the regulating valve disposed between the metering pump and the coagulation pool is simultaneously adjusted to a maximum opening state;

[0012] When the coagulation pool reaches an overflowing state, the flow rate of the metering pump is reduced and made higher than the reference value to maintain stable pumping to the coagulation pool. The actual flow rate pumped to the coagulation pool is maintained at the reference value by controlling the adjustment valve, and the flow error is compensated by further controlling the adjustment valve.

[0013] Furthermore, the height value of the liquid level drop in the storage tank during the monitoring period is collected by the first liquid level meter, and the actual flow rate of the liquid pumped from the storage tank to the coagulation pool during the corresponding period is calculated. The flow rate error is calculated by comparing it with the reference value of the stable pumping of liquid to the coagulation pool. Specifically, the following formula is used:

[0014] Q 1 =S 1 *ΔH 1 / Δt ;

[0015] ΔQ 1 =Q 0 -Q 1 ;

[0016] in, Q 1 represents the actual flow rate pumped from the storage tank to the coagulation tank, ΔH 1 Indicates the height of the liquid in the storage tank dropped during the monitoring period. S 1 represents the cross-sectional area inside the storage tank, Q 0 Indicates the base flow value, ΔQ 1 Indicates the flow error value, Δt Indicates the duration of the monitoring period.

[0017] Furthermore, based on the flow error calculated during the monitoring period, the flow error is compensated by controlling the adjustment valve. If the calculated flow error value is positive, the valve of the corresponding adjustment valve is increased; if the calculated flow error value is negative, the valve of the corresponding adjustment valve is decreased.

[0018] Furthermore, the height value of the liquid level rise in the transfer tank during the monitoring period is collected by a second liquid level meter and converted into the amount of liquid pumped from the transfer tank to the storage tank. The time interval for replenishing the chemical liquid to the storage tank is set according to the warning height value of the liquid in the storage tank.

[0019] Furthermore, the loss rate of the chemical liquid in the storage tank is calculated in combination with the pumping volume from the transfer tank to the storage tank, and the setting value of the time interval for replenishing the chemical liquid is calculated according to the consumption rate. T , specifically using the following formula:

[0020] T = H * (ΔH 1 -S 2 *ΔH 2 / S 1 ) * Δt ;

[0021] in, H Indicates the warning value of the liquid level drop in the storage tank, ΔH 2 Indicates the rising height of the liquid in the transfer tank during the monitoring period. S 2 Represents the cross-sectional area inside the transfer tank.

[0022] Furthermore, the liquid level sensors are respectively installed on the coagulation tank and the spinneret to detect the height value of the liquid level in the coagulation tank, and the distance b between the spinneret and the liquid level is calculated, specifically by the following formula:

[0023] b=h+△ha;

[0024] Among them, h represents the installation height of the liquid level sensor on the coagulation tank, Δh represents the difference between the height values ​​collected by the liquid level sensor, and a represents the difference between the installation height of the liquid level sensor on the spinneret and the height of the spinneret.

[0025] Furthermore, the spinneret is driven by a servo system to move to a set distance b1 from the liquid surface. The driving distance s1 of the servo system is calculated using the following formula:

[0026] s1=b-b1+s;

[0027] Wherein, s represents the current position height value recorded by the servo system during detection by the liquid level sensor.

[0028] Furthermore, the liquid level sensor collects and calculates the distance between the spinneret above each material pool in the coagulation pool and the liquid level in the corresponding material pool in sequence, and the servo system controls the spinneret above the material pool to move to a set distance height from the liquid level.

[0029] Furthermore, an overflow plate is provided on one side of the coagulation tank in the longitudinal direction, and a liquid collecting trough is provided below the corresponding overflow plate, and the liquid in the liquid collecting trough is pumped to the transfer tank by a pump body.

[0030] The beneficial effects of the present invention are:

[0031] In the present invention, a metering pump is used in conjunction with an adjustment valve to accurately control the liquid level in the coagulation tank to be in a constant overflow state, thereby reducing liquid level fluctuations and providing a stable production environment for the spinning process; a liquid level sensor and a servo system are used to adjust the distance between the spinneret and the liquid level in the coagulation tank to ensure that the spinning solution maintains a consistent shape when entering the chemical liquid material, thereby further improving the spinning quality.

[0032] The chemical liquid overflowing from the coagulation tank is collected, purified, and pumped back to the storage tank for reuse, saving resources and reducing production costs; the liquid level in the storage tank is detected by a first liquid level gauge, and the flow error is compensated by adjusting the valve based on the calculated flow difference, further ensuring the stability and accuracy of the spinning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 Schematic diagram of the structure of the coagulation tank in the present invention;

[0035] Figure 2 This is a schematic diagram of the installation of the liquid level sensor in the present invention;

[0036] Figure 3 Schematic diagram of the liquid level control in the coagulation tank in the present invention.

[0037] Figure numerals: 11, metering pump; 12, regulating valve; 13, water pump; 14, pump body; 2, storage tank; 21, first liquid level gauge; 3, transfer tank; 31, second liquid level gauge; 4, coagulation tank; 41, material tank; 5, liquid level sensor; 6, spinneret. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0039] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] like Figures 1 to 3 A method for controlling the draft ratio of a raw silk spinning process is shown, comprising the following steps:

[0042] The chemical liquid is pumped from the storage tank 2 to the coagulation pool 4 by the metering pump 11 until it is full, and then the metering pump 11 is controlled to keep each material pool 41 in the coagulation pool 4 in a constant overflow state; the distance between the spinneret 6 and the liquid surface in the coagulation pool 4 is detected by the liquid level sensor 5, and then the spinneret 6 and the liquid surface in the coagulation pool 4 are controlled by the servo system to maintain a set distance; the chemical liquid overflowing from the coagulation pool 4 is collected in the transfer tank 3 for purification, and then pumped to the storage tank 2 by the water pump 13; the liquid level height in the storage tank 2 is detected by the first liquid level meter 21, the flow difference is calculated, and the flow error is compensated in conjunction with the adjustment valve 12.

[0043] In the present invention, the metering pump 11 is used in conjunction with the adjustment valve 12 to accurately control the liquid level of the coagulation tank 4 to be in a constant overflow state, thereby reducing liquid level fluctuations and providing a stable production environment for the spinning process; the liquid level sensor 5 and the servo system are used to adjust the distance between the spinneret 6 and the liquid level of the coagulation tank 4 to ensure that the spinning solution maintains a consistent shape when entering the chemical liquid material, thereby further improving the spinning quality.

[0044] The chemical liquid overflowing from the coagulation tank 4 is collected and purified and then pumped back to the storage tank 2 for reuse, saving resources and reducing production costs; the liquid level in the storage tank 2 is detected by the first liquid level meter 21, and the flow error is compensated by the adjustment valve 12 based on the calculated flow difference, further ensuring the stability and accuracy of the spinning process.

[0045] In the raw silk spinning process disclosed in this embodiment, the inlet and outlet liquid balance of the coagulation pool 4 is maintained. First, the chemical liquid is injected into the storage tank 2 to reach the set height, and the metering pump 11 starts to transport the solution to the coagulation pool 4 until the coagulation pool 4 is full and begins to overflow. The overflow solution is concentrated and transported to the transfer tank 3 and begins to be purified. The treated solution is then transported to the storage tank 2 again through the water pump 13 to keep the coagulation pool 4 in a constant overflow state. In this way, the inlet and outlet liquid balance in the coagulation pool 4 is achieved through reciprocating circulation.

[0046] During the process of injecting liquid into the coagulation pool 4, the metering pump 11 is first controlled to run at a high flow rate until the coagulation pool 4 overflows, and the regulating valve 12 set between the metering pump 11 and the coagulation pool 4 is synchronously adjusted to the maximum opening state; when the coagulation pool 4 reaches the overflow state, the flow rate of the metering pump 11 is reduced and made higher than the reference value to maintain stable pumping to the coagulation pool 4, and the actual flow rate pumped to the coagulation pool 4 is maintained at the reference value by controlling the regulating valve 12, and the flow error is compensated by further controlling the regulating valve 12.

[0047] During the specific implementation process, the coagulation tank 4 is first filled to overflowing with a high flow rate, and then the flow rate is reduced while maintaining steady pumping. This can quickly reach working conditions and then smoothly transition to a stable state, improving production efficiency. The valve 12 opening is dynamically adjusted based on the calculated flow error, forming a negative feedback control system that can effectively reduce the impact of external interference on the pumping flow.

[0048] An overflow plate is provided on one side of the coagulation tank 4 in the longitudinal direction, and a liquid collecting tank is provided below the corresponding overflow plate. The liquid in the liquid collecting tank is pumped to the transfer tank 3 by the pump body 14 .

[0049] The height value of the liquid level drop in the storage tank 2 during the monitoring period is collected by the first liquid level meter 21, and the actual flow rate of the liquid pumped from the storage tank 2 to the coagulation pool 4 during the corresponding period is calculated. The flow rate error is calculated by comparing it with the reference value of the stable pumping of liquid to the coagulation pool 4. The specific formula is as follows:

[0050] Q 1 =S 1 *ΔH 1 / Δt ;

[0051] ΔQ 1 =Q 0 -Q 1 ;

[0052] in, Q 1 Indicates the actual flow rate pumped from the storage tank to the solidification pool.ΔH 1 It represents the height of the liquid in the storage tank dropped during the monitoring period. It is obtained by the difference between the liquid level data collected by the first level gauge at the beginning and end of the monitoring period. S 1 represents the cross-sectional area inside the storage tank, Q 0 Indicates the base flow value, ΔQ 1 Indicates the flow error value, Δt Indicates the duration of the monitoring period.

[0053] According to the flow error calculated during the monitoring period, the flow error is compensated by controlling the adjustment valve 12. If the calculated flow error value is positive, the valve of the corresponding control adjustment valve 12 is increased. If the calculated flow error value is negative, the valve of the corresponding control adjustment valve 12 is decreased.

[0054] In the spinning process, although the pumping flow from the storage tank 2 to the coagulation pool 4 can be accurately controlled by the metering pump 11, the flow may change under different process conditions during the actual implementation. At this time, in order to ensure the stable operation of the process, a flow adjustment valve 12 is added behind the metering pump 11 to further achieve more stable and accurate flow control, thereby reducing the water surface fluctuation and improving the spinning quality.

[0055] In the present invention, the height value of the liquid level rise in the transfer tank 3 during the monitoring period is collected by the second liquid level meter 31 and converted into the amount of liquid pumped from the transfer tank 3 to the storage tank 2. The time interval for replenishing the chemical liquid to the storage tank 2 is set according to the warning height value of the liquid in the storage tank 2.

[0056] Calculate the loss rate of chemical liquid in the storage tank based on the pumping volume from the transfer tank to the storage tank, and calculate the set value of the time interval for replenishing chemical liquid based on the consumption rate T , specifically using the following formula:

[0057] T = H * (ΔH 1 -S 2 *ΔH 2 / S 1 ) * Δt ;

[0058] in, H Indicates the warning value of the liquid level drop in the storage tank. ΔH 2 It indicates the height of the liquid in the transfer tank during the monitoring period. It is obtained by the difference between the liquid level data collected by the second level meter at the beginning and end of the monitoring period.S 2 Indicates the cross-sectional area inside the transfer tank.

[0059] By calculating the change in the liquid level in the storage tank during the monitoring period, the liquid consumption during the monitoring period is obtained. Combined with the warning value of the liquid level drop in the storage tank, the set value for the time interval for replenishing the chemical liquid in the storage tank is calculated. The operator can arrange the manual loading time of the storage tank according to the set value.

[0060] In the present invention, see Figure 2 As shown, liquid level sensors are installed on the coagulation tank and the spinneret respectively to detect the height value of the liquid level in the coagulation tank, and the distance b between the spinneret and the liquid level is calculated by the following formula:

[0061] b=h+△ha;

[0062] Where h represents the installation height of the liquid level sensor above the coagulation tank, Δh represents the difference in height between the liquid level sensor and the spinneret, and a represents the difference between the installation height of the liquid level sensor and the spinneret height. The liquid level sensor sequentially collects and calculates the distance between the spinneret above each material pool in the coagulation tank and the liquid surface in the corresponding material pool. The servo system then controls the spinneret above each material pool to move to the set distance from the liquid surface.

[0063] The spinneret is driven by the servo system to move to a set distance b1 from the liquid surface. The driving distance s1 of the servo system is calculated using the following formula:

[0064] s1=b-b1+s;

[0065] Where s represents the current position height value recorded by the servo system during liquid level sensor detection.

[0066] In the specific control process of the spinneret, the draft ratio of the spinning stage is controlled by adjusting the distance between the spinneret and the liquid surface of the material pool to ensure the spinning quality. The specific requirement is to control the distance between the spinneret and the liquid surface as small as possible, and at the same time, avoid the spinneret from contacting the liquid surface to prevent the spinneret from being scrapped.

[0067] In the present invention, the metering pump cooperates with the liquid level sensor installed on the coagulation tank to perform PID control on the pumping flow rate, such as Figure 3 In the spinning control process, the draft ratio is related to the spinning speed, the number of spinneret holes, and the hole size of the spinneret. Specifically, under a constant spinning pressure, the spinneret hole size and the number of spinneret holes are inversely proportional to the spinning speed.

[0068] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the draft ratio of a raw silk spinning process, characterized in that: The following steps are involved: Pumping the chemical liquid from the storage tank to the coagulation tank by a metering pump until it is full, and controlling the metering pump to keep each material tank in the coagulation tank in a constant overflow state; The distance between the spinneret and the liquid level in the coagulation pool is detected by a liquid level sensor, and the servo system is used to control the spinneret to maintain a set distance from the liquid level in the coagulation pool; The chemical liquid overflowing from the coagulation tank is collected in a transfer tank for purification, and then pumped to the storage tank by a water pump; Detecting the liquid level in the storage tank by a first liquid level gauge, calculating the flow difference and coordinating with an adjustment valve to compensate for the flow error; During the process of injecting liquid into the coagulation pool, the metering pump is first controlled to operate at a high flow rate until the coagulation pool is full, and the regulating valve disposed between the metering pump and the coagulation pool is simultaneously adjusted to a maximum opening state; When the coagulation pool reaches an overflowing state, the flow rate of the metering pump is reduced to be higher than a reference value to maintain stable pumping to the coagulation pool, the actual flow rate pumped to the coagulation pool is maintained at the reference value by controlling the adjustment valve, and the flow rate error is compensated by further controlling the adjustment valve; The height value of the liquid level drop in the storage tank during the monitoring period is collected by the first liquid level meter, and the actual flow rate of the liquid pumped from the storage tank to the coagulation pool during the corresponding period is calculated. The flow rate error is calculated by comparing it with the reference value of the stable pumping of liquid to the coagulation pool. Specifically, the following formula is used: Q 1 =S 1 *ΔH 1 / Δt ； ΔQ 1 =Q 0 -Q 1 ； in, Q 1 represents the actual flow rate pumped from the storage tank to the coagulation tank, ΔH 1 Indicates the height of the liquid in the storage tank dropped during the monitoring period. S 1 represents the cross-sectional area inside the storage tank, Q 0 Indicates the base flow value, ΔQ 1 Indicates the flow error value, Δt Indicates the duration of the monitoring period.

2. The method for controlling the draft ratio of the raw silk spinning process according to claim 1, characterized in that: According to the flow error calculated during the monitoring period, the flow error is compensated by controlling the adjustment valve. If the calculated flow error value is positive, the valve of the adjustment valve is increased accordingly. If the calculated flow error value is negative, the valve of the adjustment valve is decreased accordingly.

3. The method for controlling the draft ratio of the raw silk spinning process according to claim 1, characterized in that: The height value of the liquid level rise in the transfer tank during the monitoring period is collected by a second liquid level meter and converted into the amount of liquid pumped from the transfer tank to the storage tank. The time interval for replenishing the chemical liquid to the storage tank is set according to the warning height value of the liquid in the storage tank.

4. The method for controlling the draft ratio of the raw silk spinning process according to claim 1, wherein: The liquid level sensors are respectively installed on the coagulation tank and the spinneret to detect the height value of the liquid level in the coagulation tank, and the distance b between the spinneret and the liquid level is calculated, specifically by the following formula: b=h+△ha; Among them, h represents the installation height of the liquid level sensor on the coagulation tank, Δh represents the difference between the height values ​​collected by the liquid level sensor, and a represents the difference between the installation height of the liquid level sensor on the spinneret and the height of the spinneret.

5. The method for controlling the draft ratio of the raw silk spinning process according to claim 4, characterized in that: The spinneret is driven by a servo system to move to a set distance b1 from the liquid surface. The driving distance s1 of the servo system is calculated using the following formula: s1=b-b1+s; Wherein, s represents the current position height value recorded by the servo system during detection by the liquid level sensor.

6. The method for controlling the draft ratio of the raw silk spinning process according to claim 5, characterized in that: The liquid level sensor collects and calculates the distance between the spinneret above each material pool in the coagulation pool and the liquid level in the corresponding material pool in sequence, and controls the spinneret above the material pool to move to a set distance height from the liquid level through the servo system.

7. The method for controlling the draft ratio of the raw silk spinning process according to claim 1, characterized in that: An overflow plate is provided on one side of the coagulation tank in the length direction, and a liquid collecting trough is provided below the corresponding overflow plate. The liquid in the liquid collecting trough is pumped to the transfer tank through a pump body.

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