Extractive distillation system, control method and extractive distillation process

Abstract

This application provides an extractive distillation system, control method, and extractive distillation process, belonging to the field of chemical separation and purification technology. The extractive distillation system includes: an extractive distillation column, a first condenser, a first reboiler, a first reflux tank, an extractant recovery column, a second condenser, a second reboiler, a second reflux tank, a raw material preheater, multiple regulating valves, multiple material conveying pumps, and control equipment. The control equipment includes: a first pressure controller, a second pressure controller, a first reflux tank level controller, a first reboiler level controller, a second reflux tank level controller, a second reboiler level controller, a first reflux ratio controller, a first cascade control loop, a second cascade control loop, a third cascade control loop, and a fourth cascade control loop. This extractive distillation system can improve the purity of the obtained product.

Description

Technical Field

[0001] This application relates to the field of chemical separation and purification technology, specifically to the field of control technology for chemical separation systems, and particularly to an extractive distillation system, control method, and extractive distillation process. Background Technology

[0002] In the field of chemical separation and purification technology, trimethoxysilane is an intermediate in the synthesis of organosilicon and an important silane coupling agent, widely used in industry. During the preparation of trimethoxysilane, due to the excessive use of lower alcohols, it is necessary to recover and recycle them. However, the lower alcohol-trimethoxysilane system forms an azeotrope under normal pressure. Therefore, conventional distillation extraction methods cannot achieve high-purity separation of the two components in the lower alcohol-trimethoxysilane azeotrope system.

[0003] In the existing technology, an extraction tower and a recovery tower are required. The extractive distillation process for recovering trimethoxysilane from a trimethoxysilane-methanol mixture is carried out by using tetramethoxysilane as an extractant. That is, extractive distillation is performed using an extractant, and then the extractant is recovered using a recovery tower.

[0004] However, the inventors discovered that in actual use, when the distillation boundary causes disturbances in the composition of the distillation feed and the flow rate, it can lead to the inability to obtain high-purity trimethoxysilane and extractant simultaneously, resulting in low product purity from the extractive distillation system. Summary of the Invention

[0005] This application provides an extractive distillation system, control method, and extractive distillation process, which overcomes the limitation that high-purity trimethoxysilane and extractant cannot be obtained simultaneously due to the distillation boundary of the low-carbon alcohol-trimethoxysilane-extractant system by applying a fixed ratio control strategy, thereby achieving the technical effect of improving the purity of the product obtained by the extractive distillation system.

[0006] In a first aspect, embodiments of this application provide an extractive distillation system, comprising: an extractive distillation column, a first condenser, a first reboiler, a first reflux tank, an extractant recovery column, a second condenser, a second reboiler, a second reflux tank, a raw material preheater, multiple regulating valves, multiple material conveying pumps, and control equipment; the control equipment comprises: a first pressure controller, a second pressure controller, a first reflux tank level controller, a first reboiler level controller, a second reflux tank level controller, a second reboiler level controller, a first reflux ratio controller, a first cascade control loop, a second cascade control loop, a third cascade control loop, and a fourth cascade control loop;

[0007] The first pressure controller is connected to the first condenser, the second pressure controller is connected to the second condenser, the first reflux tank level controller is connected to a regulating valve on the reflux line of the first reflux tank, the first reboiler level controller is connected to a regulating valve on the drain line of the extractive distillation column, the second reflux tank level controller is connected to a regulating valve on the reflux line of the second reflux tank, the second reboiler level controller is connected to a regulating valve for replenishing the extractant feed, and the first reflux ratio controller is connected to a regulating valve on the extractive distillation column.

[0008] The first cascade control loop is connected to the first reboiler, the second cascade control loop is connected to a regulating valve on the reflux line of the extractant recovery tower, the third cascade control loop is connected to the second reboiler, and the fourth cascade control loop is connected to a regulating valve on the feed preheater.

[0009] In one possible implementation, the first cascade control loop includes a temperature difference controller and a temperature difference proportional controller; the second cascade control loop includes a first temperature controller and a second reflux ratio controller; the third cascade control loop includes a second temperature controller and a second temperature control proportional controller; and the fourth cascade control loop includes a proportional controller and a flow controller. The first pressure controller is connected to the first condenser; the second pressure controller is connected to the second condenser; the first reflux tank level controller is connected to a regulating valve on the reflux line of the first reflux tank; the first reboiler level controller is connected to a regulating valve on the drain line of the extractive distillation column; and the first reboiler level controller is connected to a regulating valve on the drain line of the extractive distillation column. The regulating valve on the reflux line of the second reflux tank is connected; the level controller of the second reboiler is connected to the regulating valve for replenishing the extractant feed; the feedstock controller is connected to the regulating valve for feeding; the feedstock controller is also connected to the temperature difference control proportional controller; the second reflux ratio controller is connected to the regulating valve connected to the extractant recovery tower; the temperature difference controller is connected to the temperature difference control proportional controller; the first temperature controller is connected to the second reflux ratio controller; the second temperature controller is connected to the second temperature control proportional controller; the extractant feedstock controller is connected to the regulating valve connected to the feedstock preheater; and the extractant feed proportional controller is connected to the extractant feedstock controller.

[0010] Secondly, embodiments of this application provide a control method using an extractive distillation system as described in the first aspect, the control method comprising:

[0011] Real-time acquisition and connection of flow data of regulating valves on the return pipeline of the second return tank;

[0012] When a change in the flow rate data is detected, the flow rate data is sent to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening based on the flow rate data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening, so as to adjust the amount of extractant.

[0013] In one possible implementation, the fourth cascade control loop includes a proportional controller and a flow controller. Accordingly, sending the flow data to the fourth cascade control loop so that the fourth cascade control loop obtains a target valve opening based on the flow data and controls a regulating valve connected to the feed preheater to open to the target valve opening to adjust the extractant dosage includes: sending the flow data to the proportional controller so that the proportional controller obtains a target extractant dosage based on the flow data and sends the target extractant dosage to the flow controller; the flow controller obtains the target valve opening based on the target extractant dosage and controls a regulating valve connected to the feed preheater to open to the target valve opening to adjust the extractant dosage.

[0014] In one possible implementation, the proportional controller calculates the target extractant dosage based on the flow data using the following formula:

[0015] FE=D2×f

[0016] In the formula, FE is the target extractant dosage, D2 is the flow rate data of the regulating valve connected to the reflux pipeline of the second reflux tank, and f is a preset fixed proportional coefficient.

[0017] In one possible implementation, the method further includes: real-time acquisition of tray temperature data for each tray in the extractive distillation column; sending the tray temperature data for each tray to a first cascade control loop, so that the first cascade control loop determines the target monitoring tray based on the tray temperature data of all trays; acquiring the standby temperature value of the target monitoring tray and sending the standby temperature value to the first cascade control loop, so that the first cascade control loop adjusts the heat load of the first reboiler based on the standby temperature value, thereby controlling the tray temperature in the extractive distillation column within a preset temperature range.

[0018] In one possible implementation, after real-time acquisition of tray temperature data for each tray in the extractive distillation column, the method further includes: sending the tray temperature data for each tray to a first cascade control loop, so that the first cascade control loop determines a first tray to be monitored and a second tray to be monitored based on the tray temperature data of all trays, wherein the temperature sensitivity of the first tray to be monitored is less than that of the second tray to be monitored under the same feed disturbance scenario; acquiring a first temperature value of the first tray to be monitored and a second temperature value of the second tray to be monitored, and sending the difference between the first temperature value and the second temperature value to the first cascade control loop, so that the first cascade control loop adjusts the heat load of the first reboiler according to the waiting temperature value to control the tray temperature in the extractive distillation column within a preset temperature range.

[0019] In one possible implementation, the method further includes: when the extractive distillation system is performing extractive distillation and there is a disturbance in the feed flow rate, adjusting the heat load of the first condenser through a first pressure controller to control the pressure stability within the extractive distillation column, and adjusting the heat load of the second condenser through a second pressure controller to control the pressure stability of the extractant recovery column; controlling the regulating valve connected to the reflux line of the first reflux tank through a first reflux tank level controller to control the liquid level stability in the first reflux tank; controlling the opening of the regulating valve connected to the drain line of the extractive distillation column through a first reboiler level controller to control the liquid level stability in the first reboiler; and controlling the opening of the regulating valve connected to the drain line of the second reflux tank through a second reflux tank level controller. The opening of the regulating valve on the reflux line of the first reflux tank is controlled to stabilize the liquid level in the second reflux tank; the opening of the regulating valve used to replenish the extractant feed is controlled by the second reboiler level controller to stabilize the liquid level in the extractant recovery tower; the opening of the regulating valve connected to the extractive distillation tower is controlled by the second reflux ratio controller to stabilize the reflux flow rate from the first reflux tank to the extractive distillation tower; the heat load of the first reboiler is adjusted by the first cascade control loop to stabilize the temperature difference in the extractive distillation tower; the opening of the regulating valve connected to the reflux line of the extractant recovery tower is controlled by the second cascade control loop to stabilize the reflux flow rate from the second reflux tank to the extractant recovery tower.

[0020] In one possible implementation, the feed disturbance ranges from [-20%, +20%], wherein the feed disturbance includes feed flow rate disturbance and feed composition disturbance.

[0021] Thirdly, embodiments of this application provide an extractive distillation process for extracting and distilling a low-carbon alcohol-trimethylsilane azeotrope, wherein the extractive distillation process uses the extractive distillation system described in the first aspect and includes the following steps:

[0022] The low-carbon alcohol-trimethoxysilane azeotrope and the extractant are used as raw materials and fed into the extractive distillation column from different trays;

[0023] The first reboiler heats the bottom of the extractive distillation column, so that the top vapor is condensed by the first condenser and enters the first reflux tank to obtain the product low carbon alcohol. Part of the product low carbon alcohol is pressurized by the material transfer pump and collected as the product, while the other part of the product low carbon alcohol is refluxed back to the extractive distillation column.

[0024] Part of the bottom material of the extractive distillation column is vaporized, and the other part of the bottom material is sent to the extractant recovery column by the material transfer pump. The top vapor of the extraction recovery column is condensed by the second condenser and enters the second reflux tank to obtain the product trimethoxysilane. Part of the product trimethoxysilane is pressurized by the material transfer pump and collected as the product, while the other part is refluxed to the extraction recovery column.

[0025] The extractant is collected from the bottom of the extraction recovery tower. After being pressurized by the material transfer pump and cooled by the raw material preheater, the extracted extractant enters the extractive distillation tower to be used as raw material again.

[0026] In one possible implementation, the product low-carbon alcohol is any one of methanol, ethanol, or propanol; the extractant is o-trimethylbenzene, pseudotrimethylbenzene, o-xylene, ethylbenzene, n-propanol, isopropylbenzene, o-methylethylbenzene, m-methylethylbenzene, or p-methylethylbenzene.

[0027] This application provides an extractive distillation system, control method, and extractive distillation process. First, it detects changes in the flow rate data of a regulating valve connected to the reflux pipeline of a second reflux tank, indicating a disturbance in the feed flow rate and composition. Then, the flow rate data is sent to a fourth cascade control loop. Based on the flow rate data, the fourth cascade control loop determines the target valve opening and controls the regulating valve connected to the feed preheater to open to the target valve opening. This adjusts the extractant dosage, ensuring sufficient extractant quantity, thereby achieving the goal of simultaneously obtaining high-purity TMS and extractant, and improving the product purity obtained by the extractive distillation system. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0029] Figure 1 Schematic diagram of the ternary phase diagram and distillation line of the n-propanol-trimethoxysilane-p-methylethylbenzene ternary system under normal pressure provided in the embodiments of this application. Figure 1 ;

[0030] Figure 2 This is a schematic diagram of the control principle of the extractive distillation system provided in the embodiments of this application;

[0031] Figure 3 A flowchart illustrating the control method provided in the application embodiments;

[0032] Figure 4 A schematic diagram of the dynamic response curves of the purity change, product flow rate change, and heat load of n-propanol and trimethoxysilane in the extractive distillation process of n-propanol-trimethoxysilane binary azeotrope provided in the embodiments of this application under ±20% feed flow rate disturbance.

[0033] Figure 5 A schematic diagram of the dynamic response curves of the purity changes, product flow rate changes, and heat load of n-propanol and trimethoxysilane in the extractive distillation process of n-propanol-trimethoxysilane binary azeotrope provided in the embodiments of this application under ±20% feed composition disturbance.

[0034] Figure 6 A schematic diagram illustrating the control principle when the feed composition is 50% n-propanol and the fixed ratio is 2.6, as provided in the embodiments of this application;

[0035] Figure 7 This is a schematic diagram illustrating the control principle when 40% n-propanol is used and the fixed ratio is 2.6, as provided in the embodiments of this application.

[0036] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0037] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0038] First, let me explain the terms used in this application:

[0039] The distillation boundary refers to the insurmountable limit in the separation process. It represents the degree of component separation achievable through distillation under current operating conditions. The distillation boundary is typically determined by various factors, including the composition of the feedstock, operating pressure, temperature, number of trays, and the design of the column internals.

[0040] It should be noted that, in this embodiment, the described connection can be a connection capable of transmitting control signals, such as a wired communication connection, a wireless communication connection, or a Bluetooth connection. The controller adjusts the corresponding controlled variable by outputting control signals to the connected regulating valve. The described connectivity can be a fluid connection between two containers achieved through a pipeline.

[0041] Figure 1 Schematic diagram of the ternary phase diagram and distillation line of the n-propanol-trimethoxysilane-p-methylethylbenzene ternary system under normal pressure provided in the embodiments of this application. Figure 1 .

[0042] Regarding the existing technology, the inventors discovered that when the composition of n-propanol in the feed undergoes a certain range, such as -20%, maintaining a constant ratio of extractant dosage to feed dosage, the operating line D1-B1 of the extractive distillation column C1 ( Figure 1 Move the dashed line with a relatively large slope to, for example, Figure 1 As shown, due to the constraint of the distillation boundary, point B1 cannot fall on the line connecting D2 and B2. Figure 1 The bottom line segment (i.e., the operating line of the extractant recovery tower C2) is used in the distillation process design. A necessary principle for distillation process design is that D2-B1-D2 should be a straight line. However, in practice... Figure 1 The line that must pass through D2, B1, and D2 simultaneously can no longer be a straight line. This condition is no longer valid, indicating that it is impossible to obtain high-purity trimethoxysilane (TMS) and extractant simultaneously in the extractant recovery tower C2.

[0043] Based on the above scenarios, it can be seen that in the existing technology, when the distillation boundary causes disturbances in the composition and flow rate of the distillation feed, it will lead to the inability to obtain high-purity TMS and extractant simultaneously, resulting in low product purity from the extractive distillation system.

[0044] This application provides a control method for an extractive distillation process. By applying a fixed ratio control strategy, it overcomes the limitation that high-purity trimethoxysilane and extractant cannot be obtained simultaneously due to the distillation boundary of the low-carbon alcohol-trimethoxysilane-extractant system.

[0045] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0046] Figure 2 This is a schematic diagram of the control principle of the control device for the extractive distillation system provided in the embodiments of this application.

[0047] like Figure 2 As shown in the embodiment of this application, an extractive distillation system includes: an extractive distillation column C1, a first condenser E1, a first reboiler E2, a first reflux tank R1, an extractant recovery column C2, a second condenser E3, a second reboiler E4, a second reflux tank R2, a raw material preheater E5, multiple regulating valves (V1 to V9), multiple material conveying pumps (P1 to P4), and control equipment.

[0048] The extractive distillation column C1 is fed through both the extractant feed pipe and the raw material feed pipe. A regulating valve V1 for adjusting the supplementary extractant feed is installed on the extractant feed pipe. A regulating valve V9 for adjusting the raw material feed is installed on the extractant feed pipe. A raw material preheater E5 is installed on the raw material feed pipe between the regulating valve V9 and the extractive distillation column C1, and one discharge port of the raw material preheater E5 is connected to the extractant feed pipe via a pipe. The top of the extractive distillation column C1 is connected to the first condenser E1 via a steam pipe. The steam outlet of the first condenser E1 is connected to the first reflux tank R1 via a steam pipe. A material transfer pump P1 for discharging the product (such as low-carbon alcohols) is installed between the first reflux tank R1 and a regulating valve V2 for adjusting the product. A regulating valve V3 for adjusting the product reflux flow rate is installed on the reflux line of the extractive distillation column C1. The bottom of the extractive distillation column C1 is connected to the extractant recovery column C2 via a feed pipe to the recovery column. The second reboiler E2 is installed at the bottom of the extractive distillation column C1. The feed pipe to the recovery column is equipped with a material pump P2 for feeding the extractant recovery column C2, a regulating valve V4 for adjusting the flow rate of the feed to the extractant recovery column C2, and a regulating valve V5 near the extractant recovery column C2.

[0049] The top of the extractant recovery tower C2 is connected to the second condenser E3 via a discharge pipe. The discharge port of the second condenser E3 is connected to the second reflux tank R2 via a discharge pipe. The second reflux tank R2 is connected to a regulating valve V6 for adjusting product discharge via a product discharge pipe. A material transfer pump P3 for discharging product is installed on the discharge pipe between the second reflux tank R2 and the regulating valve V6. The material transfer pump P3 is also connected to the top of the extractant recovery tower C2 via a material reflux pipe, on which a regulating valve V7 for adjusting the reflux flow rate is installed. The second reboiler E4 is installed at the bottom of the extractant recovery tower C2 to heat the bottom of the extractant recovery tower C2. The bottom of the extractant recovery tower C2 is connected to the raw material preheater E5 through the extractant recovery pipeline. The extractant recovery pipeline is connected in sequence from the extractant recovery tower C2 to the raw material preheater E5. A material conveying pump P4 for supplying extractant circulation and a regulating valve V8 for adjusting the extractant recovery flow rate are installed on the pipeline.

[0050] Taking the separation of a low-carbon alcohol-trimethoxysilane binary mixture using an extractive distillation system as an example, the process of extractive distillation in the system is briefly described below:

[0051] The raw material, a binary mixture of low-carbon alcohol and trimethoxysilane, and the extractant enter the extractive distillation column C1 from different trays. The first reboiler E2 heats the bottom of column C1. The vapor at the top of the column is condensed by condenser E1 and enters the first reflux tank R1 to obtain the product low-carbon alcohol. Part of the product low-carbon alcohol is pressurized by the material circulation pump P1 and collected as product. The rest of the product low-carbon alcohol is refluxed to the extractive distillation column C1. Part of the bottom material of the extractive distillation column C1 is vaporized, and part of the bottom material is sent to the extractant recovery column C2 by the material transfer pump P2.

[0052] In an optional embodiment of this application, the low alcohol includes, but is not limited to, any one of methanol, ethanol or propanol, and the low alcohol and trimethoxysilane can form an azeotrope under normal pressure.

[0053] After the bottom material of the extractive distillation column C1 enters the extractant recovery column C2, the top vapor of the extractant recovery column C2 is condensed by the second condenser E3 and enters the reflux tank R2 to obtain the product trimethoxysilane. Part of the product trimethoxysilane is pressurized by the material transfer pump P3 and collected as the product, while the other part is refluxed to the extractant recovery column C2 through the regulating valve V7. The extractant is collected from the bottom of the extractant recovery column C2, pressurized by the material transfer pump P4 and cooled by the raw material heat exchanger E5, and then enters the extractive distillation jacket C1 for recycling.

[0054] In this embodiment, the extractant includes, but is not limited to: o-trimethylbenzene, pseudotrimethylbenzene, o-xylene, ethylbenzene, n-propanol, isopropylbenzene, o-methylethylbenzene, m-methylethylbenzene, or p-methylethylbenzene. The ternary phase diagram of the low-carbon alcohol-trimethoxysilane-extractant extractive distillation system has a distillation boundary.

[0055] The control equipment may include multiple controllers that control corresponding regulating valves and material delivery pumps respectively. The above process represents the normal operating scenario in the extractive distillation system where there are no disturbances in feed composition or feed flow rate. Under this normal operating scenario, the control equipment does not need to control the regulating valves or material delivery pumps; it only needs to maintain the original operating state. In abnormal operating scenarios where there are no disturbances in feed composition or feed flow rate, the control equipment controls the corresponding regulating valves and material delivery pumps to achieve robust control of the extractive distillation process under disturbances in flow rate and composition. This overcomes the limitation that the low-carbon alcohol-trimethoxysilane-extractant system cannot simultaneously obtain high-purity trimethoxysilane and extractant due to the distillation boundary.

[0056] The following will combine Figure 2Describe the composition and implementation principle of the control equipment, such as Figure 2 As shown in the figure, this application provides a control device, including: a first pressure controller PC1, a second pressure controller PC2, a first reflux tank level controller LC1, a first reboiler level controller LC2, a second reflux tank level controller LC3, a second reboiler level controller LC4, a first reflux ratio controller RR1, a first cascade control loop QR1 / FF-TC1, a second cascade control loop TC2-RR2, a third cascade control loop QR2 / B1-TC3, and a fourth cascade control loop FE / D2-FC2.

[0057] Specifically, the first pressure controller PC1 is connected to the first condenser E1, the second pressure controller PC2 is connected to the second condenser E3, the first reflux tank level controller LC1 is connected to the regulating valve V2 connected to the reflux pipeline of the first reflux tank R1, the first reboiler level controller LC2 is connected to the regulating valve V4 connected to the drain pipeline of the extractive distillation column C1, the second reflux tank level controller LC3 is connected to the regulating valve V6 connected to the reflux pipeline of the second reflux tank R2, the second reboiler level controller LC4 is connected to the regulating valve V1 used to replenish the extractant feed, and the first reflux ratio controller RR1 is connected to the regulating valve V3 connected to the extractive distillation column C1.

[0058] The first cascade control loop is connected to the first reboiler E2, the second cascade control loop is connected to the regulating valve V7 on the reflux line connected to the extractant recovery tower C2, the third cascade control loop is connected to the second reboiler E4, and the fourth cascade control loop is connected to the regulating valve V8 on the feed preheater E5.

[0059] In this embodiment, the described connection can be a connection that can transmit control signals, such as a wired communication connection, a wireless communication connection, or a Bluetooth connection.

[0060] Specifically, in an optional embodiment of this application, the first cascade control loop includes a temperature difference controller TC1 and a temperature difference control proportional controller QR1 / FF, the second cascade control loop includes a first temperature controller TC2 and a second reflux ratio controller RR2, the third cascade control loop includes a second temperature controller TC3 and a second temperature control proportional controller QR2 / B1, and the fourth cascade control loop includes a proportional controller FE / D2 and a flow controller FC2.

[0061] The first pressure controller PC1 is connected to the first condenser E1, the second pressure controller PC2 is connected to the second condenser E3, the first reflux tank level controller LC1 is connected to the regulating valve V2 connected to the reflux pipeline of the first reflux tank R1, the first reboiler level controller LC2 is connected to the regulating valve V4 connected to the drain pipeline of the extractive distillation column C1, the first reboiler level controller LC3 is connected to the regulating valve V6 connected to the reflux pipeline of the second reflux tank R2, and the second reboiler level controller LC4 is connected to the regulating valve V1 used to replenish the extractant feed.

[0062] The raw material feed controller FC1 is connected to the regulating valve V9 for feeding. The raw material feed controller FC1 is also connected to the temperature difference control proportional controller QR1 / FF. The second reflux ratio controller RR2 is connected to the regulating valve V7 connected to the extractant recovery tower C2. The temperature difference controller TC1 is connected to the temperature difference control proportional controller QR1 / FF. The first temperature controller TC2 is connected to the second reflux ratio controller RR2. The second temperature controller TC3 is connected to the second temperature control proportional controller QR2 / B1. The extractant feed controller FC2 is connected to the regulating valve V8 connected to the raw material preheater E5. The extractant feed proportional controller D2 / FE is connected to the extractant feed controller FC2.

[0063] Figure 3 This is a flowchart illustrating the control method provided in an embodiment of this application.

[0064] The following will combine Figure 2 and Figure 3 The control process of the control device in the above embodiments will be described.

[0065] like Figure 3 As shown, this control method uses the control device provided in the above embodiments, and the method includes:

[0066] S301: Real-time acquisition and connection of flow data of regulating valve V6 on the return pipeline of the second return tank R2.

[0067] In this embodiment, the regulating valve V6 connected to the reflux pipeline of the second reflux tank R2 can be a valve with a built-in flow meter. The flow data of the flow through the regulating valve V6 is collected by the flow meter. The changes in these flow data can reflect whether the output of products such as trimethoxysilane is disturbed by changes in the feed flow rate and feed composition.

[0068] S302: When a change in flow rate data is detected, the flow rate data is sent to the fourth cascade control loop so that the fourth cascade control loop can obtain the target valve opening based on the flow rate data and control the regulating valve V8 connected to the raw material preheater E5 to open to the target valve opening in order to adjust the amount of extractant.

[0069] As can be seen from the above embodiments, the fourth cascade control loop includes a proportional controller FE / D2 and a flow controller FC2. Accordingly, in an optional embodiment of this application, step S302 includes:

[0070] S302a: Send the flow data to the proportional controller FE / D2 so that the proportional controller FE / D2 can obtain the target extractant dosage based on the flow data and send the target extractant adjustment dosage to the flow controller FC2.

[0071] In this embodiment, the proportional controller FE / D2 can calculate the target extractant dosage from the input flow rate data. Further, in an optional embodiment of this application, the proportional controller FE / D2 calculates the target extractant dosage based on the flow rate data using the following formula:

[0072] FE=D2×f

[0073] In the formula, FE is the target extractant dosage, D2 is the flow rate data of the regulating valve V6 connected to the reflux pipeline of the second reflux tank R2, and f is a preset fixed proportional coefficient.

[0074] In this embodiment, the preset fixed ratio coefficient can be a value pre-set in the proportional controller FE / D2. For example, when the content of n-propanol in the feed composition decreases, the amount of extractant is increased accordingly. At this time, the preset fixed ratio coefficient can be fixed to adjust the amount of extractant to ensure that the amount of extractant is sufficient, thereby achieving the purpose of obtaining high-purity TMS and extractant at the same time.

[0075] S302b: The flow controller FC2 obtains the target valve opening based on the target extractant dosage and controls the regulating valve V8 connected to the raw material preheater E5 to open to the target valve opening in order to adjust the extractant dosage.

[0076] In this embodiment, the flow controller FC2 is used to calculate the target valve opening of the regulating valve V8 connected to the raw material preheater E5 by using the existing correspondence between the target extractant dosage and the valve opening. Then, the flow controller FC2 controls the regulating valve V8 to open to the target valve opening so that the flow rate of the extractant circulating back from the regulating valve V8 and the supplemented extractant reaches the target extractant dosage.

[0077] In summary, the control method provided in this application first detects changes in the flow rate data of the regulating valve V6 connected to the reflux pipeline of the second reflux tank R2, thus determining that changes in the raw material feed flow rate and feed composition have also occurred. The flow rate data is then sent to the fourth cascade control loop, which determines the target valve opening based on the flow rate data and controls the regulating valve V8 connected to the raw material preheater E5 to open to the target valve opening. This adjusts the extractant dosage, ensuring sufficient extractant quantity and thereby achieving the goal of simultaneously obtaining high-purity TMS and extractant, thus improving the purity of the product obtained from the extractive distillation system.

[0078] Based on the above embodiments, the control method provided in an optional embodiment of this application further includes:

[0079] Step A: Collect the tray temperature data of each tray in the extractive distillation column C1 in real time.

[0080] In this embodiment, the tray temperature data can be obtained by detecting the temperature sensor in the extractant recovery column C2. The temperature data of each tray in the extractive distillation column C1 indicates whether the tray is sensitive to temperature differences caused by changes in the composition of the distillation feed. The temperature data of each tray can be obtained by calculating the temperature change of the tray by changing the composition of the distillation feed, the heat load of the first reboiler E2, and the reflux ratio. The temperature change of the tray can be calculated using a sensitivity criterion method.

[0081] Based on the above embodiments, in an optional embodiment of this application, the number of trays in the extractive distillation column C1 is 30 to 60, for example, 35, 45, 50, or any value between 35 and 50. The feed inlet is located at any position between the 20th and 30th trays of the extractive distillation column C1, and the extractant inlet is located at any position between the 5th and 20th trays.

[0082] Step B: Send the tray temperature data of each tray to the first cascade control loop QR1 / FF-TC1 so that the first cascade control loop QR1 / FF-TC1 can determine the target monitoring tray based on the tray temperature data of all trays.

[0083] In this embodiment, after receiving the temperature data of each tray, the temperature difference controller TC1 in the first cascade control loop can calculate the temperature difference sensitivity of each tray to feed composition disturbances based on the temperature data. The tray with the highest temperature difference sensitivity to feed composition disturbances among all trays can be determined as the target monitoring tray. Of course, the temperature difference sensitivity of the target monitoring tray should be greater than a preset fixed value. The temperature difference value of the target monitoring tray can be used as the controlled variable of the first cascade control loop.

[0084] Step C: Collect the standby temperature value of the target monitoring tray and send the standby temperature value to the first cascade control loop QR2 / B1-TC3, so that the first cascade control loop adjusts the heat load of the first reboiler E2 according to the standby temperature value, so as to control the tray temperature in the extractive distillation column C1 within the preset temperature range.

[0085] In this embodiment, the temperature difference controller in the first cascade control loop calculates and processes the temperature difference of the target monitoring tray based on the collected standby temperature value of the target monitoring tray. The temperature difference control proportional controller QR1 / FF in the first cascade control loop uses the temperature difference of the target monitoring tray as the controlled variable to adjust the heat load of the first reboiler E2 in order to control the tray temperature in the extractive distillation column C1 within the preset temperature range.

[0086] The above describes the control process for trays in extractive distillation column C1 when their sensitivity to feed disturbance composition is greater than a fixed value. When the trays are not sensitive to temperature differences under feed composition disturbances, the control method provided in an optional embodiment of this application, based on the above embodiments, further includes, after real-time acquisition of tray temperature data for each tray in extractive distillation column C1 in step A:

[0087] Step D: Send the tray temperature data of each tray to the first cascade control loop QR1 / FF-TC1, so that the first cascade control loop QR1 / FF-TC1 can determine a first tray to be monitored and a second tray to be monitored based on the tray temperature data of all trays, wherein the temperature sensitivity of the first tray to be monitored is less than that of the second tray to be monitored under the same feed disturbance scenario.

[0088] In this embodiment, the process of determining the first and second monitoring trays is as follows: first, the temperature difference sensitivity of each monitoring tray to feed composition disturbance is determined according to the method in step B; then, the tray with the lowest temperature sensitivity is selected as the first monitoring tray, and the tray with the highest temperature sensitivity is selected as the second monitoring tray.

[0089] Step E: Collect the first temperature value of the first monitoring tray and the second temperature value of the second monitoring tray, and send the difference between the first temperature value and the second temperature value to the first cascade control loop QR1 / FF-TC1, so that the first cascade control loop adjusts the heat load of the first reboiler E2 according to the temperature value to be used, so as to control the tray temperature in the extractive distillation column C1 within the preset temperature range.

[0090] In this embodiment, the difference from step C in the above embodiment is that the controlled variable of the first cascade control loop is the temperature difference between the first and second monitored trays. The remaining control process and principle are similar to those in step C, so they will not be described again here.

[0091] In an optional embodiment of this application, the control method further includes a control process for a third cascade control loop. This third cascade control loop, consisting of a second temperature controller TC3 and a second temperature control proportional controller QR2 / B1, controls the stripping section (the process stage for separating the extractant and trimethoxysilane) by adjusting the heat load of the second reboiler E4, as follows:

[0092] Step F: Collect the tray temperature data of each tray in the extractant recovery tower C2 in real time.

[0093] Step G: Send the tray temperature data of each tray to the third cascade control loop QR2 / B1-TC3 so that the third cascade control loop QR2 / B1-TC3 can determine the target monitoring tray based on the tray temperature data of all trays.

[0094] Step H: Collect the standby temperature value of the target monitoring tray and send the standby temperature value to the third cascade control loop QR2 / B1-TC3 so that the third cascade control loop adjusts the heat load of the second reboiler E4 according to the standby temperature value, so as to control the tray temperature in the extractant recovery tower C2 within the preset temperature range.

[0095] In this embodiment, the difference from the above embodiments is that the number of trays in the extractant recovery tower C2 is 12 to 30, for example, 15, 20, 25, or any value from 15 to 25. The feed inlet of the extractant recovery tower C2 is located at the position of the 5th to 10th tray.

[0096] In this embodiment, the control principle in steps F to H is similar to that in steps A to C in the above embodiment, so it will not be described again here.

[0097] Based on the above embodiments, the control method provided in an optional embodiment of this application further includes, after step F:

[0098] Step 1: Send the tray temperature data of each tray to the third cascade control loop QR2 / B1-TC3, so that the third cascade control loop QR2 / B1-TC3 can determine a first tray to be monitored and a second tray to be monitored based on the tray temperature data of all trays. The temperature sensitivity of the first tray to be monitored is less than that of the second tray to be monitored under the same feed composition disturbance scenario.

[0099] Step J: Collect the first temperature value of the first monitoring tray and the second temperature value of the second monitoring tray, and send the difference between the first temperature value and the second temperature value to the third cascade control loop QR2 / B1-TC3, so that the third cascade control loop QR2 / B1-TC3 adjusts the heat load of the second reboiler E4 according to the temperature value to be used, so as to control the tray temperature in the extractive distillation column C1 within the preset temperature range.

[0100] In this embodiment, the control principles of steps I to J are similar to those of steps D and E in the above embodiments, so they will not be described again here.

[0101] The control method provided in an optional embodiment of this application further includes:

[0102] Step K: When the extractive distillation system is performing extractive distillation and there is a disturbance in the feed flow rate, the heat load of the first condenser E1 is adjusted by the first pressure controller PC1 to control the pressure stability in the extractive distillation column C1, and the heat load of the second condenser E3 is adjusted by the second pressure controller PC2 to control the pressure stability in the extractant recovery column C2.

[0103] Step L: Control the regulating valve V2 connected to the return pipeline of the first return tank R1 through the first return tank level controller LC1 to stabilize the liquid level in the first return tank R1.

[0104] Step M: The opening of the regulating valve V4 connected to the drain line of the extractive distillation column C1 is controlled by the first reboiler level controller LC2 to stabilize the liquid level in the first reboiler E2.

[0105] Step N: Control the opening of the regulating valve V6 connected to the return pipeline of the second return tank R2 by the liquid level controller LC3 of the second return tank to stabilize the liquid level in the second return tank R2.

[0106] Step O: The opening of the regulating valve V1 used for replenishing the extractant feed is controlled by the second reboiler level controller LC4 to stabilize the liquid level in the extractant recovery tower C2.

[0107] Step P: The opening of the regulating valve V3 connected to the extractive distillation column C1 is controlled by the second reflux ratio controller RR1 to stabilize the reflux flow rate from the first reflux tank R1 to the extractive distillation column C1.

[0108] Step Q: Adjust the heat load of the first reboiler E2 through the first cascade control loop to control the temperature difference stability in the extractive distillation column C1.

[0109] Step R: The opening of the regulating valve connected to the reflux pipeline of the extractant recovery tower C2 is controlled by the second cascade control loop to stabilize the reflux flow rate from the second reflux tank R2 back to the extractant recovery tower C2.

[0110] In this embodiment, when the extractive distillation system is performing extractive distillation and there is a disturbance in the feed flow rate, the corresponding control process can be carried out based on the monitoring data collected by the original sensors or detection instruments in each device of the extractive distillation system. The controlled variables and control variables are different for different devices.

[0111] For example: Figure 2 As shown, when the liquid level collected by the level gauge in the first return tank R1 rises, it indicates that there is a disturbance in the feed flow rate. After receiving the liquid level data collected by the level gauge, the liquid level controller LC1 of the first return tank can calculate the valve opening data that needs to be increased or decreased, and then control the regulating valve V2 connected to the return pipeline of the first return tank R1 according to the calculated valve opening data to stabilize the liquid level in the first return tank R1.

[0112] In an optional embodiment of this application, the range of the feed disturbance in the above embodiment is [-20%, +20%], wherein the feed disturbance includes feed flow rate disturbance and feed composition disturbance.

[0113] In summary, the control method provided in this application embodiment achieves robust control of the low-carbon alcohol-trimethoxysilane azeotropic extractive distillation process under ±20% feed flow rate and feed composition disturbances, and can still obtain high-purity products without using expensive online composition analysis equipment, while having a short response time.

[0114] Based on the above embodiments, in an optional embodiment of this application, the heat load of the first condenser E1 is adjusted by the first pressure controller PC1 to control the pressure in the extractive distillation column C1 to be stable within the range of 0.3 to 4 standard atmospheres, and the reflux ratio of the extractive distillation column C1 is 1.3 to 6; the heat load of the second condenser E3 is adjusted by the second pressure controller PC2 to control the pressure in the extractant recovery column C2 to be stable within the range of 0.3 to 3 standard atmospheres, and the reflux ratio of the extractant recovery column C2 is 1.5 to 3.

[0115] In this embodiment, pressure and reflux ratio are process characteristics. Therefore, the pressure value in the above embodiment should be a constant value rather than a wide range, for example, stable at 2 standard atmospheres out of 0.3 to 4 standard atmospheres.

[0116] In summary, the control method provided in this application can form multiple control loops around the extractive distillation column C1 and the extractant recovery column C2, which are used to control the extractive distillation system using different control processes and principles to separate the low-carbon alcohol-trimethoxysilane mixture and obtain high-purity low-carbon alcohol and trimethoxysilane, thus solving the problem of the difficulty in separating low-carbon alcohol-trimethoxysilane azeotropes.

[0117] This application also provides an extractive distillation process for extractive distillation of low-carbon alcohol-trimethylsilane azeotropes, using the extractive distillation system described above. The extractive distillation process includes the following steps:

[0118] (1): The low-carbon alcohol-trimethoxysilane azeotrope and the extractant were fed into the extractive distillation column C1 from different trays.

[0119] (2): The first reboiler E2 is controlled to heat the bottom of the extractive distillation column C1 so that the top vapor is condensed by the first condenser E1 and enters the first reflux tank R1 to obtain the product low carbon alcohol. Part of the product low carbon alcohol is pressurized by the material transfer pump P1 and collected as the product, while the other part of the product low carbon alcohol is refluxed back to the extractive distillation column C1.

[0120] (3): Part of the bottom material of the extractive distillation column C1 is vaporized, and the other part of the bottom material is sent to the extractant recovery column C2 via the material transfer pump P2; the top vapor of the extraction recovery column C2 is condensed by the second condenser E3 and enters the second reflux tank R2 to obtain the product trimethoxysilane. Part of the product trimethoxysilane is pressurized by the material transfer pump and collected as a product, while the other part is refluxed to the extraction recovery column C2.

[0121] (4): The extractant is taken out from the bottom of the extraction recovery tower C2. After being pressurized by the material transfer pump and cooled by the raw material preheater E5, the extracted extractant enters the extraction distillation tower C1 as raw material again.

[0122] In an optional embodiment of this application, the product low-carbon alcohol is any one of methanol, ethanol, or propanol; the extractant is any one of o-trimethylbenzene, pseudotrimethylbenzene, o-xylene, ethylbenzene, n-propanol, cumene, o-methylethylbenzene, m-methylethylbenzene, or p-methylethylbenzene. It should be noted that the types of extractants and low-carbon alcohols include, but are not limited to, those described above. Those skilled in the art, after considering the specification and practicing the invention disclosed herein, will readily conceive of other embodiments of the invention. Therefore, the extractants and low-carbon alcohols in the above embodiments should not be considered as limitations on the technical solutions of this application.

[0123] The following will further describe the results of controlling the extractive distillation system according to the steps of the above method embodiment with specific examples. Assumptions: feed flow rate 100 kmol / h, feed temperature 50°C, molar fraction of n-propanol in the feed 50%, molar fraction of trimethoxysilane 50%. Extractive distillation column C1 has 33 trays, feed material is fed from tray 22, extractant p-methylethylbenzene is fed from tray 21, extractant flow rate is 100 kmol / h, reflux ratio is 2, operating pressure is 1.0 atm; extractant recovery column C2 has a pressure of 1.0 atm, 13 trays, feed position is tray 5, reflux ratio is 2, and the concentration of n-propanol and trimethoxysilane product after separation is 99.6 mol%.

[0124] Example 1:

[0125] Figure 4 This is a schematic diagram showing the dynamic response curves of the purity changes, product flow rate changes, and heat load of n-propanol and trimethoxysilane in the extractive distillation process of the n-propanol-trimethoxysilane binary azeotrope provided in the embodiments of this application under ±20% feed flow rate disturbance.

[0126] like Figure 4 As shown, a flow rate disturbance of ±20% was added to the initial steady-state process. Specifically, after 1 hour of stable operation, the feed flow rates were adjusted to 120 kmol / h and 80 kmol / h, respectively. After adding the disturbance, the product quality, product flow rate, and heat load of the two towers for n-propanol and trimethoxysilane were monitored and recorded. The dynamic response results are shown below. Figure 2 As shown, the overshoot of n-propanol purity was 0.056, the settling time was 3.5 h, and the residual error was 0.00118; the overshoot of trimethoxysilane purity was 0.004, the settling time was 4 h, and the residual error was -0.00238, indicating that the process can handle the disturbance of ±20% feed flow rate well.

[0127] Example 2:

[0128] Figure 5 This is a schematic diagram of the dynamic response curves of the purity changes, product flow rate changes, and heat load of n-propanol and trimethoxysilane in the extractive distillation process of the n-propanol-trimethoxysilane binary azeotrope provided in the embodiments of this application under ±20% feed composition disturbance.

[0129] like Figure 5As shown, a ±20% compositional perturbation was added to the initial steady-state process. Specifically, after 1 hour of stable operation, the feed composition was adjusted to 40% n-propanol and 60% trimethoxysilane, and 60% n-propanol and 40% trimethoxysilane, respectively. After adding the perturbation, the product quality and flow rate of n-propanol and trimethoxysilane, as well as the heat load of the two towers, were monitored and recorded. The dynamic response results are as follows. Figure 3 As shown, the overshoot of n-propanol purity was 0.093, the settling time was 5 hours, and the residual error was 0.00068; the overshoot of trimethoxysilane purity was 0.00059, the settling time was 4 hours, and the residual error was -0.00024. This indicates that the process can effectively handle disturbances in the ±20% feed composition.

[0130] Example 3:

[0131] Figure 6 This is a schematic diagram illustrating the control principle when the feed composition is 50% n-propanol and the fixed ratio is 2.6, as provided in the embodiments of this application.

[0132] Figure 7 This is a schematic diagram illustrating the control principle when 40% n-propanol is used and the fixed ratio is 2.6, as provided in the embodiments of this application.

[0133] like Figure 6 and Figure 7 The ratio of the fixed proportional controller FE / D2 is the fixed value stored in the proportional controller FE / D2 in the above method embodiment, which ensures that the amount of extractant is sufficient, so that point B1 falls on the connection line of B2-D2, and achieves the purpose of obtaining high-purity TMS and extractant at the same time.

[0134] In the above embodiments, the controller may be a control chip including a processor and memory, or a related computer device, server, or programmable controller. By automatically storing pre-edited program code into memory, the processor executes the steps described in the above method embodiments.

[0135] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0136] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0137] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0138] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0139] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0140] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0141] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0142] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0143] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0144] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0145] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0146] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0147] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An extractive distillation system, characterized in that, The extractive distillation system includes: an extractive distillation column, a first condenser, a first reboiler, a first reflux tank, an extractant recovery column, a second condenser, a second reboiler, a second reflux tank, a feed preheater, multiple regulating valves, multiple material conveying pumps, and control equipment; the control equipment includes: a first pressure controller, a second pressure controller, a first reflux tank level controller, a first reboiler level controller, a second reflux tank level controller, a second reboiler level controller, a first reflux ratio controller, a first cascade control loop, a second cascade control loop, a third cascade control loop, and a fourth cascade control loop; the first cascade control loop includes a temperature difference controller, a temperature difference proportional controller, and a feed controller; the second cascade control loop includes a first temperature controller and a second reflux ratio controller; the third cascade control loop includes a second temperature controller and a second temperature proportional controller; the fourth cascade control loop includes a proportional controller and a flow controller; the first pressure controller is connected to the first condenser, the second pressure controller is connected to the second condenser, and the first... A reflux tank level controller is connected to a regulating valve on the reflux line of the first reflux tank; a first reboiler level controller is connected to a regulating valve on the drain line of the extractive distillation column; a second reflux tank level controller is connected to a regulating valve on the reflux line of the second reflux tank; a second reboiler level controller is connected to a regulating valve for replenishing the extractant feed; a first reflux ratio controller is connected to a regulating valve on the extractive distillation column; a feedstock controller is connected to a regulating valve for feeding; the feedstock controller is also connected to a temperature difference control proportional controller; a second reflux ratio controller is connected to a regulating valve on the extractant recovery column; a temperature difference controller is connected to a temperature difference control proportional controller; a first temperature controller is connected to the second reflux ratio controller; a second temperature controller is connected to the second temperature control proportional controller; an extractant feed controller is connected to a regulating valve on the feed preheater; and an extractant feed proportional controller is connected to the extractant feed controller. The first cascade control loop is connected to the first reboiler, the second cascade control loop is connected to a regulating valve on the reflux line of the extractant recovery tower, the third cascade control loop is connected to the second reboiler, and the fourth cascade control loop is connected to a regulating valve on the feed preheater.

2. A control method, characterized in that, Using the extractive distillation system as described in claim 1, the control method includes: Real-time acquisition and connection of flow data of regulating valves on the return pipeline of the second return tank; When a change in the flow rate data is detected, the flow rate data is sent to the fourth cascade control loop so that the fourth cascade control loop can obtain the target valve opening based on the flow rate data and control the regulating valve connected to the raw material preheater to open to the target valve opening in order to adjust the amount of extractant. When the extractive distillation system is performing extractive distillation and there is feed disturbance, the heat load of the first condenser is adjusted by the first pressure controller to control the pressure stability in the extractive distillation column, and the heat load of the second condenser is adjusted by the second pressure controller to control the pressure stability in the extractant recovery column. The level in the first return tank is controlled by a regulating valve connected to the return pipeline of the first return tank through a level controller. The opening of the regulating valve connected to the drain line of the extractive distillation column is controlled by the level controller of the first reboiler to stabilize the liquid level in the first reboiler. The opening of the regulating valve connected to the return pipeline of the second return tank is controlled by the liquid level controller of the second return tank to stabilize the liquid level in the second return tank. The liquid level in the extractant recovery tower is stabilized by controlling the opening of the regulating valve used to replenish the extractant feed through the second reboiler level controller. The opening of the regulating valve connected to the extractive distillation column is controlled by the second reflux ratio controller to stabilize the reflux flow rate from the first reflux tank to the extractive distillation column. The heat load of the first reboiler is adjusted by the first cascade control loop to stabilize the temperature difference in the extractive distillation column. The opening of the regulating valve connected to the reflux line of the extractant recovery tower is controlled by the second cascade control loop to stabilize the reflux flow rate from the second reflux tank back to the extractant recovery tower.

3. The control method according to claim 2, characterized in that, The fourth cascade control loop includes a proportional controller and a flow controller; Accordingly, sending the flow data to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening based on the flow data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening, so as to adjust the extractant dosage, includes: The flow rate data is sent to the proportional controller, so that the proportional controller obtains the target extractant dosage based on the flow rate data, and sends the target extractant adjustment dosage to the flow controller. The flow controller determines the target valve opening based on the target extractant dosage and controls the regulating valve connected to the raw material preheater to open to the target valve opening, thereby adjusting the extractant dosage.

4. The control method according to claim 3, characterized in that, The proportional controller obtains the following formula for calculating the target extractant dosage based on the flow rate data: FE=D2×f In the formula, FE is the target extractant dosage, D2 is the flow rate data of the regulating valve connected to the reflux pipeline of the second reflux tank, and f is a preset fixed proportional coefficient.

5. The control method according to claim 2, characterized in that, Also includes: Real-time acquisition of tray temperature data for each tray in the extractive distillation column; The tray temperature data of each tray is sent to the first cascade control loop so that the first cascade control loop can determine the target monitoring tray based on the tray temperature data of all trays. The standby temperature value of the target monitoring tray is collected and sent to the first cascade control loop, so that the first cascade control loop adjusts the heat load of the first reboiler according to the standby temperature value, so as to control the tray temperature in the extractive distillation column within the preset temperature range.

6. The control method according to claim 5, characterized in that, After acquiring the real-time temperature data of each tray in the extractive distillation column, the method further includes: The tray temperature data of each tray is sent to the first cascade control loop so that the first cascade control loop determines a first tray to be monitored and a second tray to be monitored based on the tray temperature data of all trays, wherein the temperature sensitivity of the first tray to be monitored is less than that of the second tray to be monitored under the same feed disturbance scenario. The system collects a first temperature value of the first tray to be monitored and a second temperature value of the second tray to be monitored, and sends the difference between the first temperature value and the second temperature value to a first cascade control loop. This allows the first cascade control loop to adjust the heat load of the first reboiler according to the desired temperature value, thereby controlling the tray temperature in the extractive distillation column within a preset temperature range.

7. The control method according to claim 2, characterized in that, The range of the feed disturbance is [-20%, +20%], wherein the feed disturbance includes feed flow rate disturbance and feed composition disturbance.

8. An extractive distillation process for the distillation extraction of low-carbon alcohol-trimethylsilane azeotropes, characterized in that, The extractive distillation process uses the control method described in claim 2, including the following steps: The low-carbon alcohol-trimethoxysilane azeotrope and the extractant are used as raw materials and fed into the extractive distillation column from different trays; The first reboiler is controlled to heat the bottom of the extractive distillation column, so that the top vapor of the column is condensed by the first condenser and enters the first reflux tank to obtain the product low carbon alcohol. Part of the product low carbon alcohol is pressurized by the material transfer pump and collected as the product, while the other part of the product low carbon alcohol is refluxed back to the extractive distillation column. Part of the bottom material of the extractive distillation column is vaporized, and the other part of the bottom material is sent to the extractant recovery column by the material transfer pump. The top vapor of the extraction recovery column is condensed by the second condenser and enters the second reflux tank to obtain the product trimethoxysilane. Part of the product trimethoxysilane is pressurized by the material transfer pump and collected as the product, while the other part is refluxed to the extraction recovery column. The extractant is collected from the bottom of the extraction recovery tower. After being pressurized by the material transfer pump and cooled by the raw material preheater, the extracted extractant enters the extractive distillation tower to be used as raw material again.

9. The extractive distillation process according to claim 8, characterized in that, The product, a low-carbon alcohol, is any one of methanol, ethanol, or propanol. The extractant is o-trimethylbenzene, pseudotrimethylbenzene, o-xylene, ethylbenzene, n-propanol, cumene, o-methylethylbenzene, m-methylethylbenzene, or p-methylethylbenzene.

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