Control system and method for continuous and accurate spraying of glyoxal solution in cellulose ether production

Abstract

The invention relates to a control system and method for continuous and accurate spraying of a glyoxal solution in cellulose ether production. The control system comprises a glyoxal aqueous solution preparation tank; the soft water feeding pipeline, the glyoxal feeding pipeline and the glyoxal mixed solution discharging pipeline are respectively connected with the preparation tank; regulating valves and flowmeters are respectively arranged on the pipelines to respectively form a first flow control loop, a second flow control loop and a third flow control loop; the controller system is connected with the three flow control loops; and the ratio controller is used for automatically calculating and setting a flow set value of the controller system according to the set proportionality coefficient K. Three groups of PID control systems are used for tracking and controlling three PIDs, the ratio devices K and Q3 are set, the ratio devices can automatically set PID set values, track and rectify deviation, corresponding valves are opened for tracking and controlling, inlet and outlet balance is achieved, and the problems that manual calculation is inaccurate in feeding, uneven in proportion, discontinuous in production and unstable in product quality are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cellulose ether production, and particularly relates to a control system and method for continuous and accurate spraying of glyoxal solution in cellulose ether production. BACKGROUND

[0002] In the production process of some cellulose ether products (such as cross-linked sodium carboxymethyl cellulose (CCMC), slow-release HPMC, water-resistant HEC, thermal gel type MC, and other functional and modified cellulose ethers), glyoxal aqueous solution needs to be uniformly sprayed into the material during the granulation stage to achieve specific chemical modification. The traditional solution preparation method usually adopts intermittent operation: glyoxal is first injected into a preparation tank, then a certain proportion of soft water is manually calculated and added, and after stirring and mixing, the mixture is pumped to the spraying system for use. After the solution is used up, manual preparation is performed again.

[0003] This traditional method has the following significant defects: first, manual calculation and feeding cannot guarantee the accuracy of each preparation ratio, resulting in fluctuations in the concentration of the mixed solution and affecting the stability of the final product quality; second, the solution preparation process is intermittent, which cannot realize continuous solution supply, causing interruption of the production process and affecting production efficiency and continuity; third, frequent manual operation increases labor costs and poses safety risks.

[0004] Therefore, there is an urgent need for a control system that can accurately, continuously, and automatically mix and transport glyoxal and soft water. SUMMARY

[0005] The present application aims to overcome the defects of inaccurate glyoxal mixed solution preparation, discontinuous production, and reliance on manual operation in the prior art, and provides a control system and method for continuous and accurate spraying of glyoxal solution in cellulose ether production, which realizes accurate proportioning, continuous mixing, and stable transportation of glyoxal and soft water, and improves product quality stability and production automation.

[0006] In a first aspect, the present application provides a control system for continuous and accurate spraying of glyoxal solution in cellulose ether production, comprising: a glyoxal aqueous solution preparation tank; a soft water feed pipe, a glyoxal feed pipe, and a glyoxal mixed solution discharge pipe connected to the preparation tank, respectively; adjustment valves and flow meters arranged on the soft water feed pipe, the glyoxal feed pipe, and the discharge pipe, respectively, to form first, second, and third flow control circuits; a controller system connected to the three flow control circuits, comprising: a first PID controller (PID1) acting on the first flow control circuit for controlling soft water flow; a second PID controller (PID2) acting on a second flow control loop for controlling the flow of glyoxal; a third PID controller (PID3) acting on a third flow control loop for controlling the total flow of the glyoxal mixed solution; a ratio controller for automatically calculating and setting the flow set values of PID1 and PID2 according to a set proportional coefficient K and PID3, to realize three-closed-loop flow ratio control.

[0007] As preferred, the ratio controller automatically calculates the soft water flow Q1 and the glyoxal flow Q2 according to the set total flow Q3 and the proportional coefficient K, to meet the following relationships: Q2 = K×Q1 Q3 = Q1+Q2 = Q1×(1+K) Q1 = Q3 / (1+K) Q2 = K×Q3 / (1+K).

[0008] As preferred, the PID controller adopts a reaction control mode and realizes real-time correction of flow deviation through closed-loop fine tuning.

[0009] As preferred, the ratio controller is further configured to dynamically fine tune the proportional coefficient K according to the actual flow deviation of soft water and glyoxal, to compensate for raw material concentration fluctuation or equipment response delay, and to ensure long-term stability of the mixing ratio.

[0010] As preferred, the flow meter for glyoxal is a mass flow meter, and the flow meter for soft water is an electromagnetic flow meter.

[0011] As preferred, the regulating valve is a high-response pneumatic V-type ball valve or an electric regulating valve, with a response time less than 2 seconds.

[0012] The present application is applicable to the glyoxal modification process of various cellulose ether products, and through the establishment of a product-formulation database, the system can automatically call corresponding K values and Q3 set values, to realize one-key switching and precise control, and significantly improve production flexibility and product quality consistency.

[0013] In the second aspect of the present application, a control method for continuous and precise spraying of a glyoxal solution in cellulose ether production is provided, including the following steps: S1: setting a total flow target value Q3 of the glyoxal mixed solution and a proportional coefficient K of soft water and glyoxal; S2: calculating a soft water target flow Q1 = Q3 / (1+K) and a glyoxal target flow Q2 = K×Q3 / (1+K) through a ratio controller; S3: Q1, Q2, Q3 are respectively taken as the set value of the first PID control loop (PID1), the second PID control loop (PID2), and the third PID control loop (PID3); S4: each PID controller adjusts the opening of the corresponding regulating valve according to the deviation of the actual flow from the set value, so as to realize accurate control of the flow; S5: the system continuously collects actual flow data, and dynamically corrects the proportional coefficient K through closed-loop feedback, so as to ensure stable mixing ratio.

[0014] As preferred, in step S1, the setting method of the proportional coefficient K comprises: According to the target mixed liquid concentration Cmix and the glyoxal stock solution concentration Cgly, the following formula is used to calculate: .

[0015] As preferred, in step S1, the proportional coefficient K is further corrected through experiments on the basis of the theoretical value obtained by the above formula, and the corrected K value is taken as the final K value.

[0016] Each specific product corresponds to a K value, and the K value is calculated and corrected and then recorded in a system formula database, so that when the product needs to be produced, the corresponding parameters can be selected.

[0017] Through implementation of the above technical solution, compared with the prior art, the present application has the following beneficial effects: the present application sets the proportional coefficient K through three groups of PID control systems for tracking control of three PIDs, sets Q3, and the proportional coefficient K automatically sets the set value of the PID and performs tracking correction, and opens the corresponding valve for tracking control. The balance of in and out is achieved, and the material is discharged uniformly and continuously. The problems of inaccurate manual calculation, uneven mixing ratio, discontinuous production, and unstable product quality are solved.

[0018] The K value and Q3 setting of different product formulas are supported, one-key switching is realized through a formula database, the present application is suitable for CCMC, HPMC, HEC and other cellulose ether products, the flow control precision is better than ±1%, the mixed liquid concentration fluctuation is less than ±0.5%, and the batch consistency of key indicators such as product crosslinking degree and viscosity is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a structural schematic diagram of the control system shown in the present application; Figure 2 FIG. 2 is a control principle block diagram of the control system shown in the present application. DETAILED DESCRIPTION

[0020] The present application will be further described in detail through specific embodiments.

[0021] It should be noted that the following embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0022] Example 1 The control system in this embodiment is used for the continuous and precise spraying of glyoxal solution in cellulose ether production, such as... Figure 1 , 2 As shown, the system includes a glyoxal aqueous solution preparation tank 100 and three PID flow control loops. Soft water enters the preparation tank 100 through a first pipe, on which a first regulating valve FV1 and a first flow meter FT1 are installed, forming a PID1 control loop. Glyoxal enters the preparation tank 100 through a second pipe, on which a second regulating valve FV2 and a second flow meter FT2 are installed, forming a PID2 control loop. The mixed glyoxal solution is output through a third pipe, on which a third regulating valve FV3 and a third flow meter FT3 are installed, forming a PID3 control loop.

[0023] A separate control cabinet is configured, which includes a built-in PID control module, a ratio calculation function block (ratio controller), and a human-machine interface.

[0024] During system operation, the operator sets the target total output flow rate Q3 of the glyoxal mixture in the control system and sets the ratio coefficient K between soft water and glyoxal. After receiving Q3 and K, the ratio controller 200 calculates the target flow rates Q1 and Q2 of soft water and glyoxal according to the formulas Q1 = Q3 / (1+K) and Q2 = K×Q3 / (1+K), and uses Q1, Q2, and Q3 as the setpoints for PID1, PID2, and PID3, respectively.

[0025] Application Example 1 Using the control system of Example 1, sustained-release hydroxypropyl methylcellulose (HPMC-K100M) was produced. This sustained-release hydroxypropyl methylcellulose is used as the matrix material for oral sustained-release tablets. Key quality indicators include: crosslinking degree 85% ± 3%, viscosity 4000–5000 mPa·s, and a glyoxal mixture concentration of 8.0% w / w.

[0026] Raw material parameters: Glyoxal stock solution concentration: 40.0% (w / w) (industrial grade, 25℃) Soft water: Deionized water K value calculation: According to the mass balance formula: , substituting , we get K = 0.25.

[0027] Finally, K = 0.25 is determined as the standard setting value for this product.

[0028] Q3 setting and flow distribution: The total flow of the mixed solution Q3 = 1.2 m 3 / h is set.

[0029] According to the formula , Q1 and Q2 are calculated: , .

[0030] The first PID controller (PID1) setting value: Q1 = 0.96 m 3 / h; The second PID controller (PID2) setting value: Q2 = 0.24 m 3 / h; The third PID controller (PID3) setting value: Q3 = 1.2 m 3 / h.

[0031] Control process The operator selects the product "HPMC-K100M" on the HMI, and the system automatically calls K = 0.25, Q3 = 1.2 m 3 / h The ratio controller automatically calculates Q1 = 0.96 m 3 / h, Q2 = 0.24 m 3 / h PID1, PID2, PID3 control three flows respectively, the system runs stably, and the actual mixed solution concentration fluctuates <±0.3%.

[0032] After 8 hours of continuous spraying, the crosslinking degree of the product is stable at 85.2% ± 0.8%, meeting the product requirements.

[0033] Application Example 2 Using the control system of Example 1, crosslinked sodium carboxymethyl cellulose is produced, which is used as a super disintegrant for tablets. The key quality indicators are: disintegration time < 30 seconds, water absorption expansion rate > 12 mL / g, and the required glyoxal mixed solution concentration is 6.0% w / w.

[0034] Raw material parameters Glyoxal stock solution concentration: 40.0% (w / w) (industrial grade, 25℃) Soft water: deionized water K value calculation According to the formula K is calculated as 0.1765.

[0035] Experiment verification and K value correction Since the theoretically calculated K = 0.1765 is the initial value, the K value needs to be verified and corrected through small or pilot test in actual production to ensure that the final product meets the quality requirements of "disintegration time < 30 seconds, water absorption expansion rate > 12 mL / g".

[0036] Specifically includes the following steps: (1) Calculate the initial K value according to the target mixed liquid concentration; (2) According to the K value, carry out trial production, take samples and detect the product disintegration time and water absorption expansion rate; (3) If it does not meet the requirements, adjust the K value step by step and repeat the experiment until the product quality meets the requirements; (4) Set the K value that meets the requirements as the standard value of the product and store it in the control system formula library.

[0037] Finally, K = 0.2 is determined as the standard set value of the product.

[0038] Q3 setting and flow distribution Using the corrected K = 0.20 and Q3 = 0.8m 3 / h, calculate the soft water flow Q1, Q2: .

[0039] Control process The operator selects the product "HPMC-K100M" on the HMI, and the system automatically calls K = 0.2, Q3 = 0.8m 3 / h The ratio controller automatically calculates Q1 = 0.6667m 3 / h, Q2 = 0.1333m 3 / h PID1, PID2, PID3 control three flows respectively, the system runs stably, and the actual mixed liquid concentration fluctuation is < ± 0.3%.

[0040] Spray continuously for 6 hours, the product disintegration time is stable at 27-29 seconds, and the water absorption expansion rate is > 12.4 mL / g, which meets the product requirements.

[0041] Application example 3 Using the control system of Example 1, water-resistant hydroxyethyl cellulose was produced for use in exterior wall paint thickener, with key quality indicators: water resistance time > 48 hours, viscosity 2000-3000 mPa·s, and required glyoxal mixture concentration: 10.0% w / w.

[0042] Raw material parameters Glyoxal stock solution concentration: 40.0% (w / w) (industrial grade, 25°C) K value calculation Through formula calculation and correction, the final determination of K = 0.36 as the standard set value for this product.

[0043] Q3 setting and flow distribution Set Q3 = 1.5 m 3 / h, using the corrected K = 0.36 and Q3 = 1.5 m 3 / h, calculate soft water flow Q1, Q2: .

[0044] Control process The operator selects the product "HPMC-K100M" on the HMI, the system automatically calls K = 0.36, Q3 = 1.5 m 3 / h The ratio controller automatically calculates Q1 = 1.1029 m 3 / h, Q2 = 0.3971 m 3 / h.

[0045] PID1, PID2, PID3 control three-way flow respectively, the system runs stably, the actual mixture concentration fluctuation <±0.3% Continuous spraying for 12 hours, the product performance is stable, meeting the product requirements.

Claims

1. A control system for continuous and precise spraying of glyoxal solution in cellulose ether production, characterized in that, include: Glyoxal aqueous solution preparation tank; The soft water inlet pipe, the glyoxal inlet pipe, and the glyoxal mixed solution outlet pipe are respectively connected to the configuration tank; The regulating valves and flow meters installed on the soft water inlet pipe, the glyoxal inlet pipe and the outlet pipe respectively constitute the first, second and third flow control loops; The controller system connected to the three flow control loops includes: The first PID controller operates in the first flow control loop to control the soft water flow rate; The second PID controller operates in the second flow control loop to control the glyoxal flow rate. The third PID controller operates in the third flow control loop to control the total flow rate of the glyoxal mixed solution; The ratio controller is used to automatically calculate and set the flow setpoints of the first PID controller and the second PID controller based on the set proportional coefficient K and the third PID controller, so as to realize three-closed-loop flow ratio control.

2. The control system for continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 1, characterized in that, The ratio controller automatically calculates the soft water flow rate Q1 and the glyoxal flow rate Q2 based on the set total flow rate Q3 and the proportional coefficient K, satisfying the following relationship: Q2 = K×Q1; Q3 = Q1 + Q2 = Q1 × (1 + K); Q1 = Q3 / (1+K); Q2 = K×Q3 / (1+K).

3. The control system for continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 1, characterized in that, The PID controller adopts a reaction control method and achieves real-time correction of flow deviation through closed-loop fine-tuning.

4. The control system for continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 1, characterized in that, The ratio controller is also configured to dynamically fine-tune the ratio coefficient K based on the actual flow deviation between soft water and glyoxal, in order to compensate for fluctuations in raw material concentration or equipment response delays, and ensure long-term stability of the mixing ratio.

5. The control system for continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 1, characterized in that, The flow meter used for glyoxal is a mass flow meter, while the flow meter used for soft water is an electromagnetic flow meter.

6. The control system for continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 1, characterized in that, The regulating valve is a high-response pneumatic V-ball valve or an electric regulating valve.

7. A method for controlling the continuous and precise spraying of glyoxal solution in cellulose ether production, characterized in that, Includes the following steps: S1: Set the target total flow rate of the glyoxal mixed solution, Q3, and the ratio coefficient of soft water to glyoxal, K; S2: Calculate the target flow rate of soft water Q1 = Q3 / (1+K) and the target flow rate of glyoxal Q2 = K×Q3 / (1+K) using a ratio controller; S3: Use Q1, Q2, and Q3 as the setpoints for the first PID control loop, the second PID control loop, and the third PID control loop, respectively; S4: Each PID controller adjusts the opening of the corresponding regulating valve according to the deviation between the actual flow rate and the set value to achieve precise flow control; S5: The system continuously collects actual traffic data and dynamically corrects the proportional coefficient K through closed-loop feedback to ensure a stable mixing ratio.

8. The method for controlling the continuous and precise spraying of glyoxal solution in cellulose ether production according to claim 7, characterized in that, In step S1, the method for setting the scaling factor K includes: Calculated based on the target mixture concentration Cmix and the glyoxal stock solution concentration Cgly: .

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