Succinic acid hydrolysis reaction system and reaction liquid concentration control method

Abstract

The application provides a succinic acid hydrolysis reaction system and a reaction liquid concentration control method. The method comprises the following steps: S1, setting parameters; S2, controlling succinic anhydride to enter a hydrolysis kettle according to a fixed feed flow rate and controlling fresh water to enter the hydrolysis kettle according to a basic feed flow rate; S3, calculating a density deviation of a real-time density and a target density; S4, judging whether the absolute value of the density deviation is greater than the density deviation threshold value; and S5, repeatedly executing steps S3 to S4 to form a closed-loop control until the reaction liquid density is stabilized in a target range. Through density monitoring, indirect feedback of the reaction liquid concentration is realized, and in combination with flow proportion control, the fresh water addition amount is compensated in real time, so that the ratio of succinic anhydride to water in the hydrolysis kettle is stabilized, and then the succinic acid concentration of the reaction liquid is stabilized.

Description

Technical Field

[0001] This invention relates to the field of chemical reaction process control technology, and in particular to a succinic acid hydrolysis reaction system, and a method for controlling the concentration of the reaction solution based on density compensation in the succinic acid hydrolysis reaction. Background Technology

[0002] Succinic acid (also known as succinic acid) is an important chemical raw material widely used in pharmaceuticals, food, and new materials. In its preparation, the maleic anhydride hydrogenation method for succinic acid hydrolysate typically generates the hydrolysis solution from succinic anhydride and water in a hydrolysis reactor. The reaction equation is as follows:

[0003] This reaction is a quantitative reaction, and the ratio of succinic anhydride to water in the reaction system directly determines the degree of completeness of the reaction and the stability of the concentration of succinic acid in the final reaction solution.

[0004] Currently, during the hydrolysis of succinic acid, the succinic anhydride material entering the hydrolysis reactor is controlled at a fixed flow rate to ensure a stable supply of reaction raw materials. The water required for the reaction comes from two sources: most of the water comes from the return water from the subsequent system, and a small amount of water is supplemented by fresh water. Fresh water and succinic anhydride are added to the hydrolysis reactor in a preset flow rate ratio through automatic control, which can theoretically meet the quantitative ratio requirements of the reaction.

[0005] However, in actual industrial production, the amount of water returned to the hydrolysis reactor from the subsequent system is affected by various factors such as subsequent process fluctuations and equipment operating status, resulting in significant instability and making it impossible to maintain a stable total amount of water entering the hydrolysis reactor. Since the existing control method relies solely on a preset flow ratio of fresh water to succinic anhydride, it cannot compensate for the impact of fluctuations in the returned water volume in real time. This leads to deviations in the ratio of succinic anhydride to water in the hydrolysis reactor from the theoretical value, resulting in incomplete reaction or excess water. Ultimately, this causes large fluctuations in the succinic acid concentration in the reaction solution within the hydrolysis reactor, affecting product quality stability. Furthermore, additional separation and purification processes are required, increasing production costs and reducing production efficiency.

[0006] Succinic acid possesses specific physicochemical properties, with a clear correlation between the density and concentration of its aqueous solution (succinic acid has a relative density of 1.572 (25 / 4℃), and the higher the concentration in water, the greater the density of the aqueous solution). This characteristic provides a feasible method for indirect monitoring of the reaction solution concentration. Therefore, a density-based PID control method capable of compensating for fluctuations in the return water volume is urgently needed to achieve stable control of the succinic acid concentration in the hydrolysis reactor. Summary of the Invention

[0007] This invention provides a succinic acid hydrolysis reaction system and a method for controlling the concentration of the reaction solution to solve at least one of the above-mentioned technical problems.

[0008] This invention provides a method for controlling the concentration of a reaction solution, applied to a succinic acid hydrolysis reaction system, the method comprising the following steps: S1: Set the fixed feed flow rate of succinic anhydride The theoretical molar ratio of succinic anhydride to water corresponds to the flow rate ratio K, and the target concentration of succinic acid in the reaction solution. and the target concentration Corresponding target density of the reaction solution Density deviation threshold And the flow compensation coefficient k; S2: Control the succinic anhydride according to the fixed feed flow rate described above. Enter the hydrolysis reactor and follow the formula. = ×K calculates the basic feed flow rate of fresh water. Control the fresh water flow rate according to the basic feed rate. Enter the hydrolysis reactor; S3: Real-time detection of the density of the reaction solution inside the hydrolysis vessel. And calculate the real-time density With target density density deviation =ρ- ; S4: Determine density deviation Is the absolute value greater than the density deviation threshold? ; If | |≤ Then maintain the fresh water feed rate as ; If | |> According to the formula Calculate the fresh water compensation flow rate and change the fresh water feed flow rate from... Adjusted to = + ; S5: Repeat steps S3 to S4 to form a closed-loop control until the density of the reaction solution stabilizes within the target range.

[0009] In some embodiments, a target density of the reaction solution is set. Specifically, it includes: Standard solutions of succinic acid of different concentrations were prepared under the same temperature and pressure conditions as in actual production. The densities of each standard solution were measured, and a curve showing the relationship between succinic acid concentration and density was established. According to the target concentration The target density is obtained by querying the corresponding relationship curve. .

[0010] In some embodiments, setting the traffic compensation coefficient k specifically includes: Under different return water flow fluctuation conditions, the corresponding data of density deviation and required fresh water compensation flow are recorded, and the flow compensation coefficient k is obtained by linear fitting.

[0011] In some embodiments, in step S4, the fresh water feed rate is adjusted gradually, with each adjustment not exceeding the basic fresh water feed rate. 5%.

[0012] In some embodiments, the method further includes: When the density deviation The absolute value is greater than the density deviation threshold. And continue for a preset duration, or the succinic anhydride feed flow rate. When the deviation from the fixed value exceeds 3%, the controller issues an abnormal alarm signal.

[0013] In some embodiments, in step S4, when If the concentration is >0, the reaction solution concentration is determined to be too high, and the amount of fresh water added should be increased; when If the concentration is less than 0, the concentration of the reaction solution is determined to be too low, and the amount of fresh water added should be reduced.

[0014] The present invention also provides a succinic acid hydrolysis reaction system, comprising: A hydrolysis reactor, which is equipped with a feed inlet and a discharge outlet; The succinic anhydride feed pipeline is connected to the feed inlet of the hydrolysis reactor and is used to deliver succinic anhydride into the hydrolysis reactor. A fresh water inlet pipeline is connected to the inlet of the hydrolysis reactor and is used to deliver fresh water into the hydrolysis reactor; A return water feed pipeline is connected to the feed inlet of the hydrolysis reactor and is used to introduce the returned process water into the hydrolysis reactor. A density detection device is installed on the hydrolysis vessel to detect the density of the reaction liquid inside the hydrolysis vessel in real time. The flow detection device includes at least a first flow detection device for detecting the flow rate of succinic anhydride feed and a second flow detection device for detecting the flow rate of fresh water feed. The controller is electrically connected to the density detection device, the flow detection device, and the regulating valves of each feed pipeline; the controller is configured to execute the control method described above.

[0015] In some embodiments, the density detection device is a high-precision density meter, which is installed in the lower middle region of the hydrolysis vessel; the detection frequency of the density detection device is 1-5 times / minute.

[0016] In some embodiments, the first flow detection device is a mass flow meter, which is installed on the succinic anhydride feed pipeline.

[0017] In some embodiments, the system further includes an electric stirring device disposed inside the hydrolysis vessel for mixing succinic anhydride, fresh water, and returned water.

[0018] In one or more of the above specific embodiments, the density-compensated reaction solution concentration stabilization control method provided by the present invention is applied to a succinic acid hydrolysis reaction system. The succinic acid hydrolysis reaction system includes a hydrolysis reactor, a succinic anhydride feed pipeline, a fresh water feed pipeline, a return water feed pipeline, a density detection device, a flow detection device, and a controller. The succinic anhydride feed pipeline, the fresh water feed pipeline, and the return water feed pipeline are all connected to the hydrolysis reactor. The density detection device is used to detect the real-time density of the reaction solution in the hydrolysis reactor. The flow detection device is used to detect the succinic anhydride feed flow rate and the fresh water feed flow rate, respectively. The controller collects the signals from the density detection device, the flow detection device, and the valves of each feed pipeline, processes and calculates them accordingly, and then adjusts the fresh water feed valve through PID control to control the fresh water flow rate, thereby achieving the control objective. The present invention provides a method for controlling the concentration stability of reaction solution based on density compensation. It achieves indirect feedback of reaction solution concentration through density monitoring, and combines flow ratio control to compensate for the amount of fresh water added in real time, so as to ensure the stability of the ratio of succinic anhydride to water in the hydrolysis vessel, thereby ensuring the stability of succinic acid concentration in the reaction solution. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart of the reaction solution concentration control method provided by the present invention; Figure 2 This is a schematic diagram of the succinic acid hydrolysis reaction system provided by the present invention.

[0021] Explanation of reference numerals in the attached figures: Figure 2 In the middle: 1-hydrolysis kettle, 2-succinic anhydride feed pipe, 3-fresh water feed pipe, 4-return water feed pipe, 5-density detection device, 6-succinic anhydride flow detection device, 7-fresh water flow detection device, 8-electric stirring device, 9-succinic anhydride flow regulating valve, 10-fresh water flow regulating valve, 11-controller; Figure 1 In the diagram, solid lines represent control flow and dashed lines represent feedback flow. Figure 2 In the diagram, arrows indicate the direction of material flow, and signal lines are represented by dashed lines. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In one specific embodiment, the reaction solution concentration control method provided by the present invention is applied to a succinic acid hydrolysis reaction system. This method is based on density compensation and can ensure stable reaction solution concentration. Figure 1 As shown, the method includes the following steps: S1: Set the fixed feed flow rate of succinic anhydride The theoretical molar ratio of succinic anhydride to water corresponds to the flow rate ratio K, and the target concentration of succinic acid in the reaction solution. and the target concentration Corresponding target density of the reaction solution Density deviation threshold And the flow compensation coefficient k. In other words, S1 is the preset parameter setting step, specifically setting the fixed feed flow rate of the succinic anhydride raw material. The theoretical molar ratio (1:1) of succinic anhydride to water corresponds to the flow rate ratio K, and the target concentration of succinic acid in the reaction solution. and the target concentration Corresponding target density of the reaction solution Simultaneously set a density deviation threshold. and the flow compensation coefficient k, the density deviation threshold To allow the real-time density of the reaction solution to be close to the target density The maximum difference, the flow compensation coefficient k is used to calculate the fresh water compensation flow based on the density deviation.

[0024] S2: Control the succinic anhydride according to the fixed feed flow rate described above. Enter the hydrolysis reactor and follow the formula. = ×K calculates the basic feed flow rate of fresh water. Control the fresh water flow rate according to the basic feed rate. It enters the hydrolysis reactor. In other words, S2 is the basic flow control step; specifically, the controller controls the succinic anhydride feed line to maintain a fixed feed flow rate. Succinic anhydride is continuously fed into the hydrolysis reactor; the feed flow rate of succinic anhydride is determined according to the flow ratio K and the feed flow rate of succinic anhydride. Calculate the basic fresh water feed flow rate F2basic = F1 × K. The controller controls the fresh water feed pipeline to deliver fresh water into the hydrolysis reactor according to F2basic. The return water of the subsequent system flows naturally into the hydrolysis reactor through the return water feed pipeline.

[0025] S3: Real-time detection of the density of the reaction solution inside the hydrolysis vessel. And calculate the real-time density With target density density deviation =ρ- In other words, step S3 is the real-time density detection and deviation calculation step, which uses a density detection device to detect the real-time density of the reaction liquid in the hydrolysis vessel. The controller calculates the real-time density. With target density density deviation .

[0026] S4: Determine density deviation Is the absolute value greater than the density deviation threshold? ; If | |≤ Then maintain the fresh water feed rate as ; If | |> According to the formula Calculate the fresh water compensation flow rate and change the fresh water feed flow rate from... Adjusted to = + ; In other words, step S4 is the density compensation control step; specifically, the controller determines the density deviation. Is the absolute value greater than the density deviation threshold? : If | |≤ This indicates that the concentration of the reaction solution is within a stable range, and no additional flow compensation is required. The controller maintains the fresh water feed flow rate at [value missing]. ; If | |> This indicates that the concentration of the reaction solution deviates from the target range, and the controller adjusts the density deviation accordingly. Calculate the compensation flow rate of fresh water using the flow compensation coefficient k. ; when A value >0 indicates that the real-time density of the reaction solution is greater than the target density, meaning the succinic acid concentration in the reaction solution is too high. When the value is positive, the controller adjusts the fresh water feed flow rate to... = + Increase the amount of fresh water added to compensate for insufficient return water. when A value less than 0 indicates that the real-time density of the reaction solution is less than the target density, meaning the succinic acid concentration in the reaction solution is too low. When the value is negative, the controller adjusts the fresh water feed flow rate to... = + This reduces the amount of fresh water added and compensates for the excessive amount of returned water.

[0027] S5: Repeat steps S3 to S4 to form a closed-loop control until the reaction solution density stabilizes within the target range. In other words, step S5 is a cyclic feedback adjustment step. Specifically, repeating steps S3-S4 involves real-time detection of the reaction solution density, calculation of density deviation, and adjustment of the fresh water feed rate to form a closed-loop PID dynamic control until the real-time reaction solution density... The deviation from the target density ρ0 is within the density deviation threshold Δρ range. Maintaining a stable fresh water feed flow rate ensures a stable succinic acid concentration in the reaction solution within the hydrolysis reactor.

[0028] This method employs a dual closed-loop control approach combining basic flow ratio control and density feedback compensation. By converting the succinic acid concentration, which is difficult to detect in real time, into an easily detectable and fast-responding density parameter, it achieves indirect and accurate monitoring of the reaction solution concentration. This method can detect changes in the reaction solution concentration caused by fluctuations in the return water volume in real time, and by dynamically adjusting the amount of fresh water added, it ensures that the ratio of succinic anhydride to water in the hydrolysis reactor remains stable near the theoretical reaction ratio. This effectively controls the fluctuation range of succinic acid concentration in the reaction solution within a small range, significantly improving product quality stability, reducing the load on subsequent separation and purification processes, and lowering production energy consumption and costs.

[0029] In some embodiments, a target density of the reaction solution is set. Specifically, it includes: Standard solutions of succinic acid of different concentrations were prepared under the same temperature and pressure conditions as in actual production. The densities of each standard solution were measured, and a curve showing the relationship between succinic acid concentration and density was established. According to the target concentration The target density is obtained by querying the corresponding relationship curve. .

[0030] In other words, in step S1, the target density Obtained through experimental calibration. Under the same reaction conditions (temperature, pressure) as actual production, succinic acid standard solutions of different concentrations were prepared, and the density of each standard solution was measured to establish a curve relating succinic acid concentration to density. Based on the target concentration... Query the corresponding relationship curve to obtain the target density. .

[0031] Thus, the method provided by this invention experimentally calibrates the relationship between succinic acid concentration and density by simulating the temperature and pressure conditions under actual production conditions, ensuring that the established concentration-density relationship curve can truly reflect the actual situation under industrial production conditions. The resulting target density value corresponding to the target concentration has extremely high reference value, avoiding density-concentration conversion errors caused by differences in operating conditions. This provides relatively accurate benchmark data for subsequent concentration control based on density feedback, thereby ensuring the accuracy and reliability of concentration control.

[0032] In some embodiments, setting the traffic compensation coefficient k specifically includes: Under different return water flow fluctuation conditions, the corresponding data of density deviation and required fresh water compensation flow are recorded, and the flow compensation coefficient k is obtained by linear fitting.

[0033] In other words, in step S1, the flow compensation coefficient k is obtained through experimental calibration. Under different return water flow fluctuation conditions, the corresponding data of density deviation and required fresh water compensation flow are recorded, and the flow compensation coefficient k is obtained through linear fitting to ensure that the compensation flow can accurately offset the impact of return water flow fluctuation.

[0034] Thus, the method provided by this invention addresses the actual characteristics of return water flow fluctuations in industrial production by determining the flow compensation coefficient through linear fitting of multiple sets of experimental data under various operating conditions. This coefficient is designed to match the dynamic response characteristics of a specific production system. This calibration method based on measured data ensures that the calculation of the compensation flow accurately offsets the impact of return water flow fluctuations on the reaction ratio, avoiding the problem of theoretical calculations being out of sync with actual operating conditions. This significantly improves the accuracy of compensation control and the system's anti-interference capability, making the control strategy more targeted and practical.

[0035] In some embodiments, in step S4, the fresh water feed rate is adjusted gradually, with each adjustment not exceeding the basic fresh water feed rate. The flow rate is adjusted to 5%, avoiding sudden changes that could cause drastic fluctuations in the reaction system and ensuring a stable reaction. This gradual fine-tuning strategy limits the magnitude of single flow rate adjustments, effectively preventing drastic fluctuations in the reaction system caused by sudden changes in fresh water flow. This gentle adjustment method helps maintain the stability of the flow and concentration fields within the hydrolysis vessel, preventing localized over-concentration or over-dilute conditions, ensuring the smooth progress of the succinic anhydride hydrolysis reaction. It also reduces frequent and large-amplitude movements of the regulating valve, extends the service life of the actuator, and improves the operational stability and safety of the entire control system.

[0036] Furthermore, the method also includes an anomaly alarm step: When the density deviation The absolute value is greater than the density deviation threshold. And continue for a preset duration (e.g., 10-15 minutes), or the succinic anhydride feed flow rate. When the deviation from the fixed value exceeds 3%, the controller issues an abnormal alarm signal to remind staff to troubleshoot the fault in a timely manner.

[0037] Thus, the method provided by this invention adds an abnormal operating condition monitoring and alarm function. By setting reasonable duration and deviation thresholds, it can effectively distinguish between short-term random fluctuations and real fault conditions, avoiding false alarms caused by momentary interference. This promptly alerts operators to problems such as flow detection failure, feed pump malfunction, density meter abnormality, or severe process disturbances, facilitating rapid troubleshooting and handling of faults, preventing the mass production of defective products, and significantly improving the level of automation management and safety assurance capabilities of the production process.

[0038] In step S4 above, when If the concentration is >0, the reaction solution concentration is determined to be too high, and the amount of fresh water added should be increased; when If the concentration is less than 0, the reaction solution concentration is determined to be too low, and the amount of fresh water added is reduced. Based on the physicochemical property that the higher the concentration of succinic acid aqueous solution, the higher the density, the system automatically adds fresh water to dilute the reaction solution when the real-time density is higher than the target value; conversely, it reduces the amount of fresh water added. This control logic, which conforms to the process principle, is simple and reliable, with accurate response direction, ensuring the stable operation of the closed-loop control system. It can quickly and effectively correct concentration deviations and achieve dynamic balance of reaction solution concentration.

[0039] In addition to the methods described above, the present invention also provides a succinic acid hydrolysis reaction system, such as... Figure 2 As shown, the system includes: Hydrolysis reactor 1, which is equipped with a feed inlet and a discharge outlet; The succinic anhydride feed pipe 2 is connected to the feed inlet of the hydrolysis reactor 1 and is used to feed succinic anhydride into the hydrolysis reactor 1. Fresh water inlet pipe 3 is connected to the inlet of the hydrolysis vessel 1 and is used to deliver fresh water into the hydrolysis vessel 1; The return water inlet pipe 4 is connected to the inlet of the hydrolysis reactor 1 and is used to introduce the returned process water into the hydrolysis reactor 1. A density detection device 5 is installed on the hydrolysis vessel 1 to detect the density of the reaction liquid inside the hydrolysis vessel 1 in real time. The density detection device is a high-precision density meter, which is installed in the lower middle part of the hydrolysis vessel to ensure that the detected density of the reaction liquid is representative and to avoid detection errors caused by material stratification inside the vessel. The detection frequency of the density detection device is 1-5 times / minute to ensure real-time capture of changes in the density of the reaction liquid.

[0040] The flow detection device includes at least a first flow detection device 6 for detecting the flow rate of succinic anhydride feed and a second flow detection device 7 for detecting the flow rate of fresh water feed; the flow detection device of the succinic anhydride feed pipeline adopts a mass flow meter, which can accurately detect the flow data of the feed pipeline and provide a reliable basis for control.

[0041] The controller 11 is electrically connected to the density detection device 5, the flow detection device, and the regulating valves of each feed pipeline; the controller 11 is configured to execute the control method described above.

[0042] Thus, the system provided by this invention integrates material conveying, online density detection, flow monitoring, and intelligent control functions, providing a hardware platform for density-compensated concentration control methods. Through the controller's comprehensive processing of various detection signals and coordinated control of various regulating valves, the system can automatically execute a closed-loop regulation strategy, achieving real-time monitoring and dynamic adjustment of the reaction solution concentration. This system is compact, highly automated, and adaptable to continuous production needs without extensive manual intervention. It effectively solves the problem of concentration instability caused by fluctuations in return water, making it particularly suitable for the construction or renovation of large-scale industrial succinic acid production lines.

[0043] The density detection device 5 described above employs a high-precision densitometer, which is installed in the lower-middle region of the hydrolysis reactor 1. The detection frequency of the density detection device 5 is 1-5 times per minute. Installing the high-precision densitometer in the lower-middle position of the hydrolysis reactor effectively avoids the upper layer of foam and any possible sediment at the bottom. The detected density data best represents the overall concentration level of the reaction liquid inside the reactor, avoiding detection deviations caused by improper sampling location. Combined with a high detection frequency of 1 to 5 times per minute, the system can quickly capture subtle changes in the density of the reaction liquid, providing high-frequency and reliable data support for the controller's real-time decision-making, significantly improving the response speed and adjustment accuracy of the entire control system.

[0044] The first flow detection device 6 is a mass flow meter, installed on the succinic anhydride feed pipeline 2. Using a mass flow meter to detect the succinic anhydride feed flow rate is more efficient than using a volumetric flow meter, as the mass flow meter is unaffected by changes in material temperature, pressure, viscosity, and density. It can directly and accurately measure the mass flow rate, providing a high-precision data source for fixed flow control and flow ratio calculation, thereby improving the accuracy of the reaction raw material ratio.

[0045] Furthermore, the system also includes an electric stirring device 8, which is installed inside the hydrolysis vessel 1 and is used to mix succinic anhydride, fresh water, and returned water. The stirring device inside the hydrolysis vessel ensures thorough mixing of the succinic anhydride, fresh water, and returned water, resulting in a uniform density of the reaction solution. This avoids density detection deviations caused by excessively high or low local concentrations, and simultaneously promotes the complete hydrolysis reaction of succinic anhydride.

[0046] In one or more of the above specific embodiments, the density-compensated reaction solution concentration stabilization control method provided by the present invention is applied to a succinic acid hydrolysis reaction system. The succinic acid hydrolysis reaction system includes a hydrolysis reactor, a succinic anhydride feed pipeline, a fresh water feed pipeline, a return water feed pipeline, a density detection device, a flow detection device, and a controller. The succinic anhydride feed pipeline, the fresh water feed pipeline, and the return water feed pipeline are all connected to the hydrolysis reactor. The density detection device is used to detect the real-time density of the reaction solution in the hydrolysis reactor. The flow detection device is used to detect the succinic anhydride feed flow rate and the fresh water feed flow rate, respectively. The controller collects the signals from the density detection device, the flow detection device, and the valves of each feed pipeline, processes and calculates them accordingly, and then adjusts the fresh water feed valve through PID control to control the fresh water flow rate, thereby achieving the control objective. The present invention provides a method for controlling the concentration stability of reaction solution based on density compensation. It achieves indirect feedback of reaction solution concentration through density monitoring, and combines flow ratio control to compensate for the amount of fresh water added in real time, so as to ensure the stability of the ratio of succinic anhydride to water in the hydrolysis vessel, thereby ensuring the stability of succinic acid concentration in the reaction solution.

[0047] To facilitate understanding, the technical solutions and effects provided by the present invention will be further described in detail below with reference to specific embodiments.

[0048] Example 1 A method for controlling the concentration stability of the reaction solution based on density compensation is applied to a hydrolysis reaction system with an annual production capacity of 10,000 tons of succinic acid. The system includes a hydrolysis reactor (10 m³ volume), succinic anhydride feed pipeline, fresh water feed pipeline, return water feed pipeline, a high-precision density meter (detection accuracy ±0.001 g / cm³), a mass flow meter, flow regulating valves, and a PLC controller. The density meter is installed in the lower middle part of the hydrolysis reactor, and the stirring device rotates at 60 r / min. Each flow detection device is installed in its corresponding feed pipeline, and the controller is electrically connected to the density meter, each flow detection device, and the electric regulating valve of each feed pipeline. The specific control steps are as follows: S1. Preset parameter settings: Set the fixed feed flow rate of succinic anhydride. =1000kg / h (succinic anhydride molar mass 100g / mol, corresponding to a molar flow rate of 10kmol / h); based on the theoretical molar ratio of succinic anhydride to water of 1:1 (water molar mass 18g / mol), the flow rate ratio K is calculated as K = (10kmol / h × 18g / mol) ÷ (10kmol / h × 100g / mol) = 0.18, that is, the ratio of the basic fresh water flow rate to the succinic anhydride flow rate is 0.18; the target concentration of succinic acid in the reaction solution is set. =30wt%; Through experimental calibration, succinic acid standard solutions with concentrations of 25-35wt% were prepared at a reaction temperature of 80℃ and a pressure of 0.1MPa (consistent with actual production conditions). The densities of each standard solution were measured, and a concentration-density correlation curve was established. The target density corresponding to the target concentration of 30wt% was then obtained by looking up the value. =1.120 g / cm³; Set density deviation threshold =±0.005g / cm³, and the flow compensation coefficient k=50kg / (h·g / cm³) was obtained through experimental calibration.

[0049] S2. Basic Flow Control: The PLC controller controls the regulating valve of the succinic anhydride feed pipeline to maintain a fixed feed flow rate. =1000 kg / h of succinic anhydride is fed into the hydrolysis reactor; calculate the basic fresh water feed flow rate. = ×K=1000kg / h×0.18=180kg / h. The controller controls the regulating valve of the fresh water inlet pipeline to deliver fresh water into the hydrolysis reactor at a flow rate of 180kg / h. The return water from the subsequent system flows naturally into the hydrolysis reactor through the return water inlet pipeline.

[0050] S3. Real-time density detection and deviation calculation: A high-precision density meter detects the real-time density ρ of the reaction liquid in the hydrolysis vessel at a frequency of 3 times / minute. The PLC controller collects density data in real time and calculates the density deviation. =ρ- .

[0051] S4. Density Compensation Control: The controller determines density deviation. Is the absolute value greater than 0.005 g / cm³? When real-time density is detected When =1.126 g / cm³, =1.126-1.120=0.006g / cm³, | |> This indicates that the succinic acid concentration in the reaction solution is too high; calculate the compensation flow rate. =50kg / (h·g / cm³)×0.006g / cm³=0.3kg / h, at this time the fresh water feed flow rate is adjusted to =180 + 0.3 = 180.3 kg / h, increasing the amount of fresh water added to compensate for the insufficient return water volume; When real-time density is detected When =1.113 g / cm³, =1.113-1.120=-0.007g / cm³,| |> This indicates that the concentration of succinic acid in the reaction solution is too low; calculate the compensation flow rate. =50×(-0.007)=-0.35kg / h, at this time the fresh water feed flow rate is adjusted to =180-0.35=179.65kg / h, reducing the amount of fresh water added to compensate for the excessive amount of returned water; When real-time density is detected When =1.122 g / cm³, =0.002g / cm³| |≤ Maintain a fresh water feed flow rate of 180 kg / h.

[0052] S5. Cyclic Feedback Regulation: Repeat steps S3-S4, detect, calculate and adjust in real time to form a closed-loop control, so that the real-time density of the reaction solution is always maintained in the range of 1.115-1.125 g / cm³, and the corresponding succinic acid concentration is maintained in the range of 29.5-30.5 wt%, thus achieving stable concentration control.

[0053] S6, Abnormal Alarm: When density deviation... If the absolute value of the succinic anhydride feed exceeds 0.005 g / cm³ for 10 minutes, or if the feed flow rate deviates from 1000 kg / h by more than 30 kg / h, the PLC controller will issue an audible and visual alarm signal to remind staff to troubleshoot the fault.

[0054] Example 2 The difference between Example 2 and Example 1 is: target concentration =25wt%, the corresponding target density was obtained through experimental calibration. =1.100 g / cm³, density deviation threshold Δρ=±0.004 g / cm³, flow compensation coefficient k=45 kg / (h·g / cm³); succinic anhydride fixed feed flow rate =800kg / h, fresh water basic feed flow rate =800×0.18=144kg / h.

[0055] During the control process, when the real-time density When =1.105 g / cm³, =0.005g / cm³| |> Compensation flow =45×0.005=0.225kg / h, fresh water feed flow rate adjusted to 144.225kg / h; when real-time density When =1.095g / cm³, =-0.005g / cm³, compensation flow rate =45×(-0.005)=-0.225kg / h, the fresh water feed flow rate was adjusted to 143.775kg / h; after circulation adjustment, the reaction liquid density was maintained in the range of 1.096-1.104g / cm³, and the corresponding succinic acid concentration was maintained in the range of 24.6-25.4wt%, with good concentration stability.

[0056] Comparative experiment: Using existing technology (controlling only the flow rate ratio of fresh water to succinic anhydride without density compensation) for succinic acid hydrolysis, under the same succinic anhydride feed flow rate and return water fluctuation conditions, the succinic acid concentration in the reaction solution fluctuated between 27-33 wt% (Example 1 condition) and 22-28 wt% (Example 2 condition), with a large fluctuation range. However, after adopting the control method of the present invention, the concentration fluctuation range was reduced to within ±0.5 wt%, significantly improving the concentration stability, increasing product purity by 1.2-1.5%, and reducing energy consumption of subsequent separation and purification processes by 8-10%.

[0057] It should be noted that the core innovation of this invention lies in breaking through the limitations of traditional control methods that rely solely on flow ratios. By combining the quantitative characteristics of the succinic acid hydrolysis reaction with the physicochemical properties of succinic acid aqueous solution, a dual closed-loop control system with real-time compensation for both basic flow ratio and density is constructed. The specific innovations are as follows: 1. Innovatively adopting density as an indirect monitoring and compensation basis for succinic acid concentration, utilizing the inherent correspondence between succinic acid concentration and aqueous solution density, the concentration parameter, which is difficult to detect directly in real time, is transformed into a density parameter that is easy to detect, has a fast response, and is highly accurate, thus solving the industry pain point of high difficulty and high cost in real-time monitoring of succinic acid concentration. 2. A targeted density deviation compensation logic was designed. The flow compensation coefficient was calibrated through experiments to achieve precise dynamic adjustment of the amount of fresh water added. This can offset the impact of fluctuations in the return water volume of the subsequent system in real time, breaking the shortcomings of traditional control methods that cannot cope with feed fluctuations and realizing dynamic balance of the reaction ratio. 3. It integrates basic flow control, real-time density detection, deviation calculation, compensation adjustment and abnormal alarm into one system to build a fully automated closed-loop control system, which not only ensures the stability of control, but also improves the level of intelligence in industrial production, and is adapted to the actual needs of continuous production of succinic acid hydrolysis.

[0058] Based on the above-mentioned innovations, this invention has the following significant technical advantages and beneficial effects compared with the prior art: 1. High monitoring accuracy and fast response speed, with outstanding technical advantages: Compared with traditional concentration detection methods (such as titration and chromatography), density detection does not require complex pretreatment, and the detection frequency can reach 1-5 times / minute. It can capture the concentration changes of the reaction solution in real time. Combined with a high-precision density meter and mass flow meter, the detection error is small, providing reliable support for accurate compensation. It effectively solves the problems of complex operation, slow response and high cost of traditional concentration detection. 2. Strong anti-interference ability and excellent control stability: Through the density compensation mechanism, the interference of subsequent system return water fluctuations can be offset in real time, ensuring that the ratio of succinic anhydride to water in the hydrolysis kettle is always close to the theoretical reaction ratio of 1:1, so that the succinic acid concentration fluctuation is controlled within ±0.5wt%. Compared with the existing uncompensated control method, the concentration stability is improved by more than 60%, which significantly improves the consistency of product quality, while reducing the load of subsequent separation and purification processes and reducing production costs by 8-10%. 3. High degree of automation, suitable for industrial production: No frequent manual intervention is required. The entire process can be closed-loop controlled by preset parameters. At the same time, an abnormal alarm function is added to promptly detect abnormal conditions such as flow fluctuations and equipment failures, avoid production accidents, improve production safety and continuity, adapt to the needs of large-scale industrial continuous production, and reduce manual operation and maintenance costs. 4. Highly targeted and practical: Specifically adapted to the process characteristics of succinic acid hydrolysis reaction, it fully utilizes the quantitative reaction characteristics of succinic anhydride hydrolysis and the physicochemical properties of succinic acid. The control logic is aligned with actual production conditions. Compared with general concentration control methods, it does not require complex parameter adjustments, has stronger adaptability and more precise compensation, and can be directly applied to the transformation of existing succinic acid hydrolysis production lines. The transformation is simple and cost-effective, and it has broad industrial application prospects.

[0059] 5. This invention combines the inherent correspondence between the density and concentration of succinic acid aqueous solution, using density as an indirect monitoring indicator of the reaction solution concentration. Real-time feedback of the reaction solution concentration is achieved through density detection, solving the problems of complex operation, high cost, and slow response when directly detecting succinic acid concentration. At the same time, the use of high-precision density meters and mass flow meters ensures the accuracy of the detection data, providing a reliable basis for control.

[0060] 6. Based on traditional flow ratio control, this invention adds density compensation control, which can compensate for the impact of fluctuations in the return water volume of the subsequent system in real time. By adjusting the amount of fresh water added through closed-loop feedback, it ensures that the ratio of succinic anhydride to water in the hydrolysis vessel is always close to the theoretical reaction ratio (1:1), thereby ensuring the stability of succinic acid concentration in the reaction solution, improving product quality stability, reducing the load on subsequent separation and purification processes, and lowering production costs.

[0061] 7. The control method of the present invention is simple to operate and highly automated, requiring no frequent manual intervention. By setting parameters and automatic feedback adjustment, stable control of the reaction solution concentration can be achieved, adapting to the continuous needs of industrial production. At the same time, an abnormal alarm function is set up to detect equipment failures or abnormal operating conditions in a timely manner, avoid production accidents, and improve production safety and stability.

[0062] 8. The control method of the present invention is highly targeted and specifically adapted to the process characteristics of succinic acid hydrolysis reaction. It utilizes the quantitative characteristics of succinic anhydride hydrolysis reaction and the physicochemical properties of succinic acid, with reasonable control logic and precise compensation. Compared with general concentration control methods, it is more practical and targeted, and can effectively solve the problem of concentration instability caused by fluctuations in return water volume in the prior art.

[0063] Finally, it should be noted that the above 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 modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the concentration of a reaction solution, applied to a succinic acid hydrolysis reaction system, characterized in that, The method includes the following steps: S1: Set the fixed feed flow rate of succinic anhydride The theoretical molar ratio of succinic anhydride to water corresponds to the flow rate ratio K, and the target concentration of succinic acid in the reaction solution. and the target concentration Corresponding target density of the reaction solution Density deviation threshold And the flow compensation coefficient k; S2: Control the succinic anhydride according to the fixed feed flow rate described above. Enter the hydrolysis reactor and follow the formula. = ×K calculates the basic feed flow rate of fresh water. Control the fresh water flow rate according to the basic feed rate. Enter the hydrolysis reactor; S3: Real-time detection of the density of the reaction solution inside the hydrolysis vessel. And calculate the real-time density With target density density deviation =ρ- ; S4: Determine density deviation Is the absolute value greater than the density deviation threshold? ; If | |≤ Then maintain the fresh water feed flow rate as ; If | |> According to the formula Calculate the fresh water compensation flow rate and change the fresh water feed flow rate from... Adjusted to = + ; S5: Repeat steps S3 to S4 to form a closed-loop control until the density of the reaction solution stabilizes within the target range.

2. The control method according to claim 1, characterized in that, Set the target density of the reaction solution Specifically, it includes: Standard solutions of succinic acid of different concentrations were prepared under the same temperature and pressure conditions as in actual production. The densities of each standard solution were measured, and a curve showing the relationship between succinic acid concentration and density was established. According to the target concentration The target density is obtained by querying the corresponding relationship curve. .

3. The control method according to claim 1, characterized in that, Setting the traffic compensation coefficient k specifically includes: Under different return water flow fluctuation conditions, the corresponding data of density deviation and required fresh water compensation flow are recorded, and the flow compensation coefficient k is obtained by linear fitting.

4. The control method according to claim 1, characterized in that, In step S4, the fresh water feed rate is adjusted gradually, with each adjustment not exceeding the basic fresh water feed rate. 5%.

5. The control method according to claim 1, characterized in that, The method further includes: When the density deviation The absolute value is greater than the density deviation threshold. And continue for a preset duration, or the succinic anhydride feed flow rate. When the deviation from the fixed value exceeds 3%, the controller issues an abnormal alarm signal.

6. The control method according to claim 1, characterized in that, In step S4, when If the concentration is >0, the reaction solution concentration is determined to be too high, and the amount of fresh water added should be increased; when If the concentration is less than 0, the concentration of the reaction solution is determined to be too low, and the amount of fresh water added should be reduced.

7. A succinic acid hydrolysis reaction system, characterized in that, include: Hydrolysis reactor (1), which is equipped with a feed inlet and a discharge outlet; The succinic anhydride feed pipeline (2) is connected to the feed inlet of the hydrolysis vessel (1) and is used to feed succinic anhydride into the hydrolysis vessel (1); A fresh water inlet pipe (3) is connected to the inlet of the hydrolysis vessel (1) and is used to deliver fresh water into the hydrolysis vessel (1); The return water feed pipe (4) is connected to the feed port of the hydrolysis vessel (1) and is used to introduce the returned process water into the hydrolysis vessel (1). A density detection device (5) is installed on the hydrolysis vessel (1) to detect the density of the reaction liquid in the hydrolysis vessel (1) in real time. The flow detection device includes at least a first flow detection device (6) for detecting the flow rate of succinic anhydride feed and a second flow detection device (7) for detecting the flow rate of fresh water feed. The controller (11) is electrically connected to the density detection device (5), the flow detection device, and the regulating valve of each feed pipeline; the controller (11) is configured to perform the control method as described in any one of claims 1-6.

8. The succinic acid hydrolysis reaction system according to claim 1, characterized in that, The density detection device (5) is a high-precision density meter, which is installed in the lower middle part of the hydrolysis vessel (1); the detection frequency of the density detection device (5) is 1-5 times / minute.

9. The succinic acid hydrolysis reaction system according to claim 1, characterized in that, The first flow detection device (6) is a mass flow meter, which is installed on the succinic anhydride feed pipeline (2).

10. The succinic acid hydrolysis reaction system according to claim 1, characterized in that, It also includes an electric stirring device (8), which is located inside the hydrolysis vessel (1) and is used to mix succinic anhydride, fresh water and returned water.

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