Extractive distillation system, control method and extractive distillation process

Abstract

The embodiment of the invention provides an extractive distillation system, a control method and an extractive distillation process, and belongs to the technical field of chemical separation and purification. The extractive distillation system comprises an extractive distillation tower, a first condenser, a first reboiler, a first reflux tank, an extraction agent recovery tower, a second condenser, a second reboiler, a second reflux tank, a raw material preheater, a plurality of regulating valves, a plurality of material conveying pumps and control equipment, the control equipment comprises a first pressure controller, a second pressure controller, a first reflux tank liquid level controller, a first reboiler liquid level controller, a second reflux tank liquid level controller, a second reboiler liquid level controller, a first reflux ratio controller, a first cascade control loop and a second cascade control loop, a third cascade control loop and a fourth cascade control loop. The extractive distillation system has the technical effect of improving the purity of the obtained product.

Description

Technical Field

[0001] The present application relates to the technical field of chemical separation and purification, specifically to the technical field of control of chemical separation systems, and in particular to an extraction and distillation system, a control method and an extraction and distillation process. Background Art

[0002] In the field of chemical separation and purification technology, trimethoxysilane is an intermediate for synthesizing organic silicon and an important silane coupling agent, and is widely used in industry. In the preparation process of trimethoxysilane, due to the excessive use of low-carbon alcohols, the low-carbon alcohols need to be recovered and recycled, but the low-carbon alcohol-trimethoxysilane system will form an azeotrope under normal pressure. Therefore, the conventional distillation extraction method cannot achieve high-purity separation of the two in the low-carbon alcohol-trimethoxysilane azeotrope system.

[0003] In the prior art, an extraction tower and a recovery tower are required to recover trimethoxysilane from a trimethoxysilane-methanol mixture by using tetramethoxysilane as an extractant in an extractive distillation process, that is, extractant is used for extractive distillation, and then a recovery tower is used to recover the extractant.

[0004] However, the inventors have found that in actual use, when the distillation boundary causes disturbances in the composition of the distillation feed and the flow rate, it will lead to the inability to simultaneously obtain high-purity trimethoxysilane and the extractant, resulting in the problem of low purity of the product obtained by the extraction distillation system. Summary of the invention

[0005] The embodiments of the present application provide an extractive distillation system, a control method and an extractive distillation process, which are used to overcome the limitation that high-purity trimethoxysilane and extractant cannot be obtained simultaneously due to the existence of a distillation boundary in the low-carbon alcohol-trimethoxysilane-extractant system by applying a fixed ratio control strategy, so as to achieve the technical effect of improving the purity of the product obtained by the extractive distillation system.

[0006] In a first aspect, an embodiment of the present application provides an extractive distillation system, the extractive distillation system comprising: an extractive distillation tower, a first condenser, a first reboiler, a first reflux tank, an extractant recovery tower, a second condenser, a second reboiler, a second reflux tank, a raw material preheater, a plurality of regulating valves, a plurality of material delivery pumps and a control device; the control device 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 the regulating valve on the reflux pipeline connected to the first reflux tank, the first reboiler level controller is connected to the regulating valve on the discharge pipeline connected to the extractive distillation tower, the second reflux tank level controller is connected to the regulating valve on the reflux pipeline connected to the second reflux tank, the second reboiler level controller is connected to the regulating valve for supplementing the extractant feed, and the first reflux ratio controller is connected to the regulating valve connected to the extractive distillation tower;

[0008] The first cascade control loop is connected to the first reboiler, the second cascade control loop is connected to the regulating valve on the reflux pipeline connected to the extractant recovery tower, the third cascade control loop is connected to the second reboiler, and the fourth cascade control loop is connected to the regulating valve on the raw material preheater.

[0009] In one possible implementation, the first cascade control loop includes a temperature difference controller and a temperature difference control ratio 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 ratio controller, and the fourth cascade control loop includes a ratio controller and a flow controller; wherein 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 the regulating valve on the reflux pipeline connected to the first reflux tank, the first reboiler level controller is connected to the regulating valve on the discharge pipeline connected to the extractive distillation tower, and the first reboiler level controller is connected to the regulating valve on the discharge pipeline connected to the first reflux tank. The second reflux tank is connected to the regulating valve on the reflux pipeline, the second reboiler liquid level controller is connected to the regulating valve for supplementing the extractant feed; the raw material feed controller is connected to the regulating valve for feeding, the raw material feed 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 controller proportional controller, the first temperature controller is connected to the second reflux ratio controller, the second temperature controller is connected to the first temperature control proportional controller, the extractant feed controller is connected to the regulating valve connected to the raw material preheater, and the extractant feed proportional controller is connected to the extractant feed controller.

[0010] In a second aspect, an embodiment of the present application provides a control method, using the extractive distillation system described in the first aspect, the control method comprising:

[0011] Real-time collection of flow data of a regulating valve on a reflux pipeline connected to the second reflux tank;

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

[0013] In a 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 according to the flow data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of the extractant, including: sending the flow data to the proportional controller so that the proportional controller obtains a target amount of the extractant according to the flow data, and sending the target adjusted amount of the extractant to the flow controller; the flow controller obtains a target valve opening according to the target amount of the extractant, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of the extractant.

[0014] In a possible implementation manner, the proportional controller obtains the target amount of extractant according to the flow data, and the calculation formula is:

[0015] FE=D2×f

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

[0017] In a possible implementation, it also includes: collecting the plate temperature data of each plate in the extractive distillation tower in real time; sending the plate temperature data of each plate to the first cascade control loop, so that the first cascade control loop determines the target monitoring plate according to the plate temperature data of all plates; collecting the standby temperature value of the target monitoring plate, 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 according to the standby temperature value to control the plate temperature in the extractive distillation tower within a preset temperature range.

[0018] In a possible embodiment, after the real-time acquisition of the plate temperature data of each plate in the extractive distillation tower, the method further includes: sending the plate temperature data of each plate to the first cascade control loop, so that the first cascade control loop determines a first plate to be monitored and a second plate to be monitored according to the plate temperature data of all plates, wherein the temperature sensitivity of the first plate to be monitored is less than the temperature sensitivity of the second plate to be monitored under the same feed disturbance scenario; acquiring a first temperature value of the first plate to be monitored and a second temperature value of the second plate 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 standby temperature value to control the plate temperature in the extractive distillation tower within a preset temperature range.

[0019] In a possible embodiment, the invention further includes: when the extractive distillation system performs extractive distillation and there is a feed flow disturbance, the heat load of the first condenser is adjusted by the first pressure controller to control the pressure stability in the extractive distillation tower, and the heat load of the second condenser is adjusted by the second pressure controller to control the pressure stability of the extractant recovery tower; the regulating valve on the reflux pipeline connected to the first reflux tank is controlled by the first reflux tank liquid level controller to control the liquid level stability in the first reflux tank; the opening of the regulating valve on the discharge pipeline connected to the extractive distillation tower is controlled by the first reboiler liquid level controller to control the liquid level stability in the first reboiler; the regulating valve on the discharge pipeline connected to the second reflux tank is controlled by the second reflux tank liquid level controller to control the liquid level stability in the first reboiler; the regulating valve on the reflux pipeline connected to the second reflux tank is controlled by the second reflux tank liquid level controller to control the liquid level stability in the first reboiler. The opening of the regulating valve on the reflux pipeline of the tank is controlled to stabilize the liquid level in the second reflux tank; the opening of the regulating valve used to supplement 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 amount from the first reflux tank to the extractive distillation tower; the heat load of the first reboiler is controlled by the first cascade control loop to stabilize the temperature difference in the extractive distillation tower; the opening of the regulating valve on the reflux pipeline connected to the extractant recovery tower is controlled by the second cascade control loop to stabilize the reflux amount from the second reflux tank to the extractant recovery tower.

[0020] In a possible implementation manner, the range of the feed disturbance is [-20%, +20%], wherein the feed disturbance includes feed flow disturbance and feed composition disturbance.

[0021] In a third aspect, an embodiment of the present application provides an extractive distillation process for extractive distillation of a low-carbon alcohol-trimethylsilane azeotrope, wherein the extractive distillation process uses the extractive distillation system described in the first aspect, and comprises the following steps:

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

[0023] The first reboiler heats the kettle of the extractive distillation tower, so that the top steam is condensed by the first condenser and enters the first reflux tank to obtain product low-carbon alcohol, wherein part of the product low-carbon alcohol is extracted as the product after being pressurized by the material delivery pump, and the other part of the product low-carbon alcohol is refluxed to the extractive distillation tower;

[0024] The bottom material of the extractive distillation tower is partially vaporized, and the other part of the bottom material is sent to the extractant recovery tower through the material delivery pump; the top steam of the extraction recovery tower is condensed by the second condenser and enters the second reflux tank to obtain the product trimethoxysilane, wherein part of the product trimethoxysilane is extracted as the product after being pressurized by the material delivery pump, and the other part is refluxed to the extraction recovery tower;

[0025] The extractant is taken out from the kettle of the extraction recovery tower, and after being pressurized by the material delivery pump and cooled by the raw material preheater, it enters the extraction distillation tower and is used as raw material again.

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

[0027] The embodiment of the present application provides an extractive distillation system, control method and extractive distillation process, which first detects the change in the flow data of the regulating valve on the reflux pipeline connected to the second reflux tank collected in real time to determine that the raw material feed flow rate change and feed composition change disturbance have also occurred. Then the flow data is sent to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening according to the flow data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of extractant, thereby ensuring that the amount of extractant is sufficient, thereby achieving the purpose of simultaneously obtaining high-purity TMS and extractant, and improving the purity of the product obtained by the extractive distillation system. BRIEF DESCRIPTION OF THE DRAWINGS

[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 The ternary phase diagram and distillation operation line diagram of the n-propanol-trimethoxysilane-p-methylethylbenzene ternary system at normal pressure provided in the embodiment of the present application are shown in FIG. Figure 1 ;

[0030] Figure 2 A schematic diagram of the control principle of the extraction and distillation system provided in the embodiment of the present application;

[0031] Figure 3 A flow chart of a control method provided for an application embodiment;

[0032] Figure 4 A schematic diagram of a dynamic response curve of the purity change of n-propanol and trimethoxysilane, the product flow change, and the heat load of the extractive distillation process of the n-propanol-trimethoxysilane binary azeotrope provided in an embodiment of the present application under a feed flow disturbance of ±20%;

[0033] Figure 5 A schematic diagram of a dynamic response curve of the n-propanol and trimethoxysilane purity change, product flow change, and heat load under a ±20% feed composition disturbance in the extractive distillation process of the n-propanol-trimethoxysilane binary azeotrope provided in an embodiment of the present application;

[0034] Figure 6 A schematic diagram of the control principle when the feed composition is 50% n-propanol and the fixed ratio is 2.6 provided in an embodiment of the present application;

[0035] Figure 7 This is a schematic diagram of the control principle when 40% n-propanol and a fixed ratio of 2.6 are provided in an embodiment of the present application.

[0036] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0037] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0038] First, the terms involved in this application are explained:

[0039] Distillation boundary: refers to the boundary that cannot be exceeded during the separation process. It represents the degree of component separation that can be achieved by distillation under the current operating conditions. The distillation boundary is usually determined by many factors, including the composition of the raw materials, operating pressure, temperature, number of plates, and the design of the tower internals.

[0040] It should be noted that in this embodiment, the connection described may be a connection relationship that can transmit control signals, such as a wired communication connection, a wireless communication connection, or a Bluetooth connection, and the controller adjusts the corresponding controlled variable by outputting a control signal to act on a regulating valve connected thereto. The communication described may be fluid communication between two containers achieved through a pipeline.

[0041] Figure 1 The ternary phase diagram and distillation operation line diagram of the n-propanol-trimethoxysilane-p-methylethylbenzene ternary system at normal pressure provided in the embodiment of the present application are shown in FIG. Figure 1 .

[0042] Regarding the prior art, the inventors found that when the n-propanol in the feed undergoes a composition change within a certain range, such as -20%, the ratio of the amount of the extractant to the amount of the feed is maintained unchanged, and the operating line D1-B1 ( Figure 1 The dotted line with a larger slope in the middle) moves to Figure 1 The position shown is limited by the distillation boundary, and point B1 cannot fall on the D2-B2 connecting line ( Figure 1 The bottom line in the figure is the operating line of the extractant recovery tower C2. A necessary principle for the design of the distillation process is that D2-B1-D2 should be a straight line. Figure 1 The line that passes through D2, B1 and D2 at the same time cannot be a straight line. This is no longer true, which means that high-purity trimethoxysilane (TMS) and extractant cannot be obtained simultaneously in the extractant recovery tower C2.

[0043] In combination with the above scenario, it can be seen that in the prior art, when the distillation boundary causes disturbances in the composition change of the distillation feed and the flow change, it will lead to the inability to simultaneously obtain high-purity TMS and extractant, resulting in the problem of low purity of the product obtained by the extraction distillation system.

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

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

[0046] Figure 2 A schematic diagram of the control principle of a control device for an extractive distillation system provided in an embodiment of the present application.

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

[0048] Among them, the feed port of the extractive distillation tower C1 is fed through the extractant feed pipeline and the raw material feed pipeline respectively, and the regulating valve V1 for adjusting the supplementary extractant feed is installed on the extractant feed pipeline. The regulating valve V9 for adjusting the raw material feed is installed on the extractant feed pipeline, and the raw material preheater E5 is installed on the raw material feed pipe at a position between the regulating valve V9 for adjusting the raw material feed and the extractive distillation tower C1, and a discharge port of the raw material preheater E5 is connected to the extractant feed pipeline through a pipeline. The top of the extractive distillation tower C1 is connected to the first condenser E1 through a steam pipeline, and the steam discharge port of the first condenser E1 is connected to the first reflux tank R1 through a steam pipeline. A material delivery pump P1 for discharging the product is installed between the first reflux tank R1 and the regulating valve V2 for adjusting the product such as low-carbon alcohol, and a regulating valve V3 for adjusting the product reflux amount is installed on the reflux pipeline of the extractive distillation tower C1. The bottom of the extractive distillation tower C1 is connected to the extractant recovery tower C2 through a recovery tower feed pipeline. The second reboiler E2 is installed at the bottom of the extractive distillation tower C1. The recovery tower feed pipeline is sequentially installed with a material delivery pump P2 for feeding the extractant recovery tower C2, a regulating valve V4 for adjusting the feed flow rate to the extractant recovery tower C2, and a regulating valve V5 close to the extractant recovery tower C2 from the extractive distillation tower C1 to the extractant recovery tower C2.

[0049] The top of the extractant recovery tower C2 is connected to the second condenser E3 through a discharge pipe, the discharge port of the second condenser E3 is connected to the second reflux tank R2 through a discharge pipe, the second reflux tank R2 is connected to the regulating valve V6 for regulating product discharge through a product discharge pipe, and a material delivery pump P3 for discharging the product is installed between the second reflux tank R2 and the regulating valve V6 for regulating product discharge on the discharge pipe. The material delivery pump P3 is also connected to the top of the extractant recovery tower C2 through a material reflux pipe, and a regulating valve V7 for regulating the reflux amount is also installed on the material reflux pipe. 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 an extractant recovery pipeline. A material delivery pump P4 for circulating the extractant and a regulating valve V8 for adjusting the extractant recovery flow rate are sequentially installed on the extractant recovery pipeline from the extractant recovery tower C2 to the raw material preheater E5.

[0050] Taking the extraction distillation system to separate the low-carbon alcohol-trimethoxysilane binary mixture as an example, the process of the extraction distillation system performing the extraction distillation process is briefly described as follows:

[0051] The raw material low-carbon alcohol-trimethoxysilane binary mixture and the extractant enter the extractive distillation tower C1 from different tower plates, the first reboiler E2 heats the bottom of the C1 tower, the top vapor is condensed by the 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 then extracted as the product, part of the product low-carbon alcohol is refluxed to the extractive distillation tower C1, the bottom material of the extractive distillation tower C1 is partially vaporized, and part of the bottom material is sent to the extractant recovery tower C2 through the material delivery pump P2.

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

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

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

[0055] The control device may include multiple controllers to respectively control the corresponding regulating valves and material delivery pumps. The above process is a normal working scenario in which no disturbance of feed composition change and feed flow change occurs in the extractive distillation system. In this normal working scenario, the control device does not need to control the regulating valve or the material delivery pump, and only needs to maintain the original working state. In an abnormal working scenario in which no disturbance of feed composition change and feed flow change occurs in the extractive distillation system, the control device controls the corresponding regulating valves and material delivery pumps to achieve robust control of the extractive distillation process under flow change and composition change disturbances, thereby overcoming 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.

[0056] The following will be combined Figure 2Describe the composition and implementation principle of the control equipment, such as Figure 2 As shown, an embodiment of the present application provides a control device, including: a first pressure controller PC1, a second pressure controller PC2, a first reflux tank liquid level controller LC1, a first reboiler liquid level controller LC2, a second reflux tank liquid level controller LC3, a second reboiler liquid 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] Among them, 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 liquid level controller LC1 is connected to the regulating valve V2 on the reflux pipeline connected to the first reflux tank R1, the first reboiler liquid level controller LC2 is connected to the regulating valve V4 on the discharge pipeline connected to the extractive distillation tower C1, the second reflux tank liquid level controller LC3 is connected to the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2, the second reboiler liquid level controller LC4 is connected to the regulating valve V1 for supplementing the extractant feed, and the first reflux ratio controller RR1 is connected to the regulating valve V3 connected to the extractive distillation tower 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 pipeline 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 connected to the raw material preheater E5.

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

[0060] Specifically, in an optional embodiment of the present application, the first cascade control loop includes a temperature difference controller TC1 and a temperature difference control ratio 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 ratio controller QR2 / B1, and the fourth cascade control loop includes a ratio 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 liquid level controller LC1 is connected to the regulating valve V2 on the reflux pipeline connected to the first reflux tank R1, the first reboiler liquid level controller LC2 is connected to the regulating valve V4 on the discharge pipeline connected to the extraction distillation tower C1, the first reboiler liquid level controller LC3 is connected to the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2, and the second reboiler liquid level controller LC4 is connected to the regulating valve V1 for supplementing the extractant feed.

[0062] The raw material feed controller FC1 is connected to the regulating valve V9 used for feeding, and 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 controller 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 first 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, and the extractant feed proportional controller D2 / FE is connected to the extractant feed controller FC2.

[0063] Figure 3 A flow chart of a control method provided in an embodiment of the present application.

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

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

[0066] S301: Collecting flow data of the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2 in real time.

[0067] In this embodiment, the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2 can be a valve with its own flow meter. The flow data flowing 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 raw material feed flow and feed composition.

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

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

[0070] S302a: Send the flow data to the proportional controller FE / D2, so that the proportional controller FE / D2 obtains the target amount of the extractant according to the flow data, and sends the target amount of the extractant to the flow controller FC2.

[0071] In this embodiment, the proportional controller FE / D2 can calculate the input flow data to obtain the target amount of extractant. Further, in an optional embodiment of the present application, the proportional controller FE / D2 obtains the target amount of extractant according to the flow data, and the calculation formula is:

[0072] FE=D2×f

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

[0074] In this embodiment, the preset fixed proportional coefficient may 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 the extractant is increased accordingly. At this time, the preset fixed proportional coefficient may be fixed to adjust the amount of the extractant to ensure that the amount of the extractant is sufficient, thereby achieving the purpose of simultaneously obtaining high-purity TMS and the extractant.

[0075] S302b: The flow controller FC2 obtains the target valve opening according to the target amount of the extractant, and controls the regulating valve V8 connected to the raw material preheater E5 to open to the target valve opening to adjust the amount of the extractant.

[0076] In this embodiment, the flow controller FC2 is used to calculate the target extractant dosage using the existing correspondence between the extractant dosage and the valve opening, and obtain the target valve opening at which the regulating valve V8 connected to the raw material preheater E5 will be opened. The flow controller FC2 then controls the regulating valve V8 to open to the target valve opening, so that the flow rate of the extractant circulated back from the regulating valve V8 and the supplementary extractant reaches the target extractant dosage.

[0077] In summary, the control method provided by the embodiment of the present application first detects the change in the flow data of the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2 collected in real time to determine that the raw material feed flow rate change and feed composition change disturbance have also occurred. Then the flow data is sent to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening according to the flow data, and controls the regulating valve V8 connected to the raw material preheater E5 to open to the target valve opening to adjust the amount of extractant, thereby ensuring that the amount of extractant is sufficient, thereby achieving the purpose of simultaneously obtaining high-purity TMS and extractant, and improving the purity of the product obtained by the extraction and distillation system.

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

[0079] Step A: collecting the plate temperature data of each plate in the extractive distillation tower C1 in real time.

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

[0081] Based on the above embodiment, in an optional embodiment of the present application, the number of plates of the extractive distillation tower C1 is 30 to 60, such as 35, 45, 50 or any value between 35 and 50. The raw material feed port is set at any position between the 20th and 30th plates of the extractive distillation tower C1, and the extractant feed port is set at any position between the 5th and 20th plates.

[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 determines the target monitoring tray according to 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 the feed composition disturbance according to the temperature data, and the tray with the highest temperature difference sensitivity to the feed composition disturbance 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 tower plate, 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 to control the tower plate temperature in the extractive distillation tower C1 within a 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 tower plate based on the collected standby temperature value of the target monitoring tower plate, and the temperature difference control proportional controller QR1 / FF in the first cascade control loop uses the temperature difference of the target monitoring tower plate as the controlled variable to adjust the heat load of the first reboiler E2 to control the tower plate temperature in the extractive distillation tower C1 within a preset temperature range.

[0086] The above is a control process for when the sensitivity of the tray in the extractive distillation column C1 to the feed disturbance composition is greater than a fixed value. When the tray is not sensitive to the temperature difference under the feed composition disturbance, based on the above embodiment, the control method provided in an optional embodiment of the present application, after collecting the tray temperature data of each tray in the extractive distillation column C1 in real time in step A, also includes:

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

[0088] In this embodiment, the process of determining the first tower plate to be monitored and the second tower plate to be monitored is to first determine the temperature difference sensitivity of each tower plate to be monitored under the feed composition disturbance according to the method in step B, then select a tower plate with the smallest temperature sensitivity among all the tower plates as the first tower plate to be monitored, and then select a tower plate with the largest temperature sensitivity as the second tower plate to be monitored.

[0089] Step E: Collect the first temperature value of the first tower plate to be monitored and the second temperature value of the second tower plate to be monitored, 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 standby temperature value to control the tower plate temperature in the extractive distillation tower C1 within a 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 tray to be monitored and the second tray to be monitored. The rest of the control process and principle are similar to those in step C, so this embodiment will not be repeated here.

[0091] The control method provided in an optional embodiment of the present application further includes a control process of a third cascade control loop, wherein the third cascade control loop includes a second temperature controller TC3 and a second temperature control ratio controller QR2 / B1. The third cascade control loop can control the process of the stripping section (process stage of separating the extractant and trimethoxysilane) by adjusting the heat load of the second reboiler E4 as follows:

[0092] Step F: collecting 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 determines the target monitoring tray according to 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 to control the tray temperature in the extractant recovery tower C2 within a preset temperature range.

[0095] In this embodiment, the difference from the above embodiment is that the number of plates of the extractant recovery tower C2 is 12 to 30, such as 15, 20, 25 or any number between 15 and 25. The feed inlet of the extractant recovery tower C2 is arranged at the position of the 5th to 10th plate.

[0096] In this embodiment, the control principles in step F to step H are similar to the control principles in step A to step C in the above embodiment, so they will not be described in detail in this embodiment.

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

[0098] Step I: 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 determines a first tray to be monitored and a second tray to be monitored according to the tray temperature data of all trays, wherein the temperature sensitivity of the first tray to be monitored is less than the temperature sensitivity 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 tower plate to be monitored and the second temperature value of the second tower plate to be monitored, 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 stand-by temperature value to control the tower plate temperature in the extractive distillation tower C1 within a preset temperature range.

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

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

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

[0103] Step L: The regulating valve V2 connected to the reflux pipeline of the first reflux tank R1 is controlled by the first reflux tank liquid level controller LC1 to control the liquid level in the first reflux tank R1 to be stable.

[0104] Step M: The first reboiler liquid level controller LC2 controls the opening of the regulating valve V4 on the discharge pipeline connected to the extractive distillation tower C1 to control the liquid level in the first reboiler E2 to be stable.

[0105] Step N: The second reflux tank liquid level controller LC3 controls the opening of the regulating valve V6 on the reflux pipeline connected to the second reflux tank R2 to control the liquid level in the second reflux tank R2 to be stable.

[0106] Step O: The second reboiler liquid level controller LC4 controls the opening of the regulating valve V1 for supplementing the extractant feed to stabilize the liquid level in the extractant recovery column C2.

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

[0108] Step Q: The heat load of the first reboiler E2 is adjusted through the first cascade control loop to control the temperature difference in the extractive distillation column C1 to be stable.

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

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

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

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

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

[0114] Based on the above embodiment, in an optional embodiment of the present 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 tower C1 to be stable within the range of 0.3 to 4 standard atmospheric pressure values, and the reflux ratio of the extractive distillation tower C1 is 1.3 to 6; the second pressure controller PC2 adjusts the heat load of the second condenser E3 to control the pressure of the extractant recovery tower C2 to be stable within the range of 0.3 to 3 standard atmospheric pressure values, and the reflux ratio of the extractant recovery tower C2 is 1.5 to 3.

[0115] In this embodiment, the pressure and the 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: 0.3 to 4 standard atmospheric pressure values ​​are stabilized at 2 standard atmospheric pressure values.

[0116] In summary, the control method provided in the embodiment of the present application can form multiple control loops around the extractive distillation tower C1 and the extractant recovery tower C2, and is used to control the extractive distillation system using different control processes and principles to separate the low-carbon alcohol-trimethoxysilane mixture to obtain high-purity low-carbon alcohol and trimethoxysilane, thereby solving the problem that the low-carbon alcohol-trimethoxysilane azeotrope is difficult to separate.

[0117] The present application also provides an extractive distillation process for extractive distillation of a low-carbon alcohol-trimethylsilane azeotrope, using the extractive distillation system as described above. The extractive distillation process comprises the following steps:

[0118] (1): Low carbon alcohol-trimethoxysilane azeotrope and extractant are used as raw materials and enter the extractive distillation tower C1 from different tower plates.

[0119] (2): Control the first reboiler E2 to increase the temperature of the bottom of the extractive distillation tower C1, so that the top steam is condensed by the first condenser E1 and enters the first reflux tank R1 to obtain product low-carbon alcohols. Part of the product low-carbon alcohols is pressurized by the material delivery pump P1 and then extracted as the product, and the other part of the product low-carbon alcohols is refluxed to the extractive distillation tower C1.

[0120] (3): Part of the bottom material of the extractive distillation tower C1 is vaporized, and the other part of the bottom material is sent to the extractant recovery tower C2 through the material delivery pump P2; the top vapor of the extractive recovery tower C2 is condensed by the second condenser E3 and enters the second reflux tank R2 to obtain the product trimethoxysilane, of which part of the product trimethoxysilane is extracted as the product after being pressurized by the material delivery pump, and the other part is refluxed to the extractive recovery tower C2.

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

[0122] In an optional embodiment of the present application, the product low-carbon alcohol is any one of methanol, ethanol or propanol; the extractant is any one of o-trimethylbenzene, unsymmetrical trimethylbenzene, o-xylene, ethylbenzene, n-propanol, isopropylbenzene, 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 the above-described contents. After considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other embodiments of the present invention. Therefore, the extractants and low-carbon alcohols in the above embodiments cannot be used as limitations on the technical solutions of the present application.

[0123] The following will further describe the results of controlling the extractive distillation system with the steps of the above method embodiment in combination 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%. The number of plates of the extractive distillation tower C1 is 33, the raw material is fed from the 22nd plate, the extractant p-methylethylbenzene is fed from the 21st plate, the amount of extractant is 100 kmol / h, the reflux ratio is 2, and the operating pressure is 1.0 standard atmospheric pressure value atm; the pressure of the extractant recovery tower C2 is 1.0 atm, the number of plates is 13 plates, the feed position is the 5th plate, the reflux ratio is 2, and the concentration of n-propanol obtained after separation is 99.6 mol%, and the concentration of trimethoxysilane product is 99.6 mol%.

[0124] Example 1:

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

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

[0127] Example 2:

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

[0129] like Figure 5As shown in Figure 1, a ±20% composition change disturbance is added to the initial steady-state process, that is, when the stable operation is 1h, the feed composition is adjusted to 40% n-propanol, 60% trimethoxysilane and 60% n-propanol, 40% trimethoxysilane. After adding the disturbance, the product quality, product flow rate and heat load of the two towers of n-propanol and trimethoxysilane are monitored and recorded. The dynamic response results are shown in Figure 1. Figure 3 As shown, the purity overshoot of n-propanol is 0.093, the adjustment time is 5h, and the residual is 0.00068; the purity overshoot of trimethoxysilane is 0.00059, the adjustment time is 4h, and the residual is -0.00024, which shows that the process can better handle the disturbance of ±20% feed composition.

[0130] Example 3:

[0131] Figure 6 Schematic diagram of the control principle for a feed composition of 50% n-propanol and a fixed ratio of 2.6 provided in an embodiment of the present application.

[0132] Figure 7 This is a schematic diagram of the control principle when 40% n-propanol and a fixed ratio of 2.6 are provided in an embodiment of the present application.

[0133] like Figure 6 and Figure 7 The ratio of the fixed ratio controller FE / D2 is the fixed value stored in the ratio controller FE / D2 in the above method embodiment, which ensures that the amount of extractant is sufficient, so that the point B1 can fall on the B2-D2 connecting line, thereby achieving the purpose of simultaneously obtaining high-purity TMS and extractant.

[0134] In the above embodiment, the controller may be a control chip including a processor and a memory or a related computer device, server or programmable controller. The pre-edited program code is automatically stored in the memory so that the processor executes the steps described in the above method embodiment.

[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 (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the invention can be directly implemented as a hardware processor, or can be implemented by a combination of hardware and software modules in the processor.

[0136] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (NVM), such as at least one disk storage.

[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. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0138] The present application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0139] The present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When a processor executes the computer-executable instructions, the above method is implemented.

[0140] The above-mentioned 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 memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0141] An exemplary readable storage medium is coupled to a processor so that the processor can read information from the readable storage medium 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 be located in an application specific integrated circuit (Application Specific Integrated Circuits, referred to as: ASIC). Of course, the processor and the readable storage medium can also exist in the device as discrete components.

[0142] The division of units is only a logical function division, and there may be other divisions in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

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

[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 the function is implemented in the form of 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 the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0146] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0147] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. An extractive distillation system, characterized in that: The extractive distillation system comprises: an extractive distillation tower, a first condenser, a first reboiler, a first reflux tank, an extractant recovery tower, a second condenser, a second reboiler, a second reflux tank, a raw material preheater, a plurality of regulating valves, a plurality of material delivery pumps and control equipment; the control equipment comprises: a first pressure controller, a second pressure controller, a first reflux tank liquid level controller, a first reboiler liquid level controller, a second reflux tank liquid level controller, a second reboiler liquid 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 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 the regulating valve on the reflux pipeline connected to the first reflux tank, the first reboiler level controller is connected to the regulating valve on the discharge pipeline connected to the extractive distillation tower, the second reflux tank level controller is connected to the regulating valve on the reflux pipeline connected to the second reflux tank, the second reboiler level controller is connected to the regulating valve for supplementing the extractant feed, and the first reflux ratio controller is connected to the regulating valve connected to the extractive distillation tower; The first cascade control loop is connected to the first reboiler, the second cascade control loop is connected to the regulating valve on the reflux pipeline connected to the extractant recovery tower, the third cascade control loop is connected to the second reboiler, and the fourth cascade control loop is connected to the regulating valve on the raw material preheater.

2. The extractive distillation system according to claim 1, characterized in that: The first cascade control loop includes a temperature difference controller and a temperature difference control ratio 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 ratio controller, and the fourth cascade control loop includes a ratio 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 the regulating valve on the reflux pipeline connected to the first reflux tank, the first reboiler level controller is connected to the regulating valve on the discharge pipeline connected to the extractive distillation tower, the first reboiler level controller is connected to the regulating valve on the reflux pipeline connected to the second reflux tank, and the second reboiler level controller is connected to the regulating valve for supplementing the extractant feed; The raw material feed controller is connected to the regulating valve for feeding, and the raw material feed controller is also connected to the temperature difference control ratio 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 controller ratio controller, the first temperature controller is connected to the second reflux ratio controller, the second temperature controller is connected to the first temperature control ratio controller, the extractant feed controller is connected to the regulating valve connected to the raw material preheater, and the extractant feed ratio controller is connected to the extractant feed controller.

3. A control method, characterized in that: Using the extractive distillation system as claimed in claim 2, the control method comprises: Real-time collection of flow data of a regulating valve on a reflux pipeline connected to the second reflux tank; When a change in the flow data is detected, the flow data is sent to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening according to the flow data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of the extractant.

4. The control method according to claim 3, characterized in that: The fourth cascade control loop includes a ratio controller and a flow controller; Correspondingly, the flow data is sent to the fourth cascade control loop, so that the fourth cascade control loop obtains the target valve opening according to the flow data, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of the extractant, including: Sending the flow data to a proportional controller, so that the proportional controller obtains a target amount of extractant according to the flow data, and sends the target amount of extractant to the flow controller; The flow controller obtains a target valve opening according to the target amount of the extractant, and controls the regulating valve connected to the raw material preheater to open to the target valve opening to adjust the amount of the extractant.

5. The control method according to claim 4, characterized in that: The proportional controller obtains the target amount of extractant according to the flow data, and the calculation formula is: FE=D2×f In the formula, FE is the target amount of extractant, D2 is the flow data of the regulating valve on the reflux pipeline connected to the second reflux tank, and f is the preset fixed proportional coefficient.

6. The control method according to claim 3, characterized in that: Also includes: Real-time collection of the plate temperature data of each plate in the extractive distillation tower; sending the tray temperature data of each tray to the first cascade control loop, so that the first cascade control loop determines the target monitoring tray according to the tray temperature data of all trays; The standby temperature value of the target monitoring tower plate 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 to control the tower plate temperature in the extractive distillation tower within a preset temperature range.

7. The control method according to claim 6, characterized in that: After the real-time acquisition of the tray temperature data of each tray in the extractive distillation tower, the method further comprises: Sending the tray temperature data of each tray 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 according to the tray temperature data of all trays, wherein the temperature sensitivity of the first tray to be monitored is less than the temperature sensitivity of the second tray to be monitored under the same feed disturbance scenario; A first temperature value of a first plate to be monitored and a second temperature value of a second plate to be monitored are collected, and a difference between the first temperature value and the second temperature value is sent to a 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 to control the plate temperature in the extractive distillation tower within a preset temperature range.

8. The control method according to claim 3, characterized in that: Also includes: When the extractive distillation system performs extractive distillation and there is a 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 tower, and the heat load of the second condenser is adjusted by the second pressure controller to control the pressure stability of the extractant recovery tower; The first reflux tank liquid level controller controls the regulating valve on the reflux pipeline connected to the first reflux tank to control the liquid level in the first reflux tank to be stable; The first reboiler liquid level controller controls the opening of the regulating valve on the liquid discharge pipeline connected to the extractive distillation tower to control the liquid level in the first reboiler to be stable; The second reflux tank liquid level controller controls the opening of the regulating valve on the reflux pipeline connected to the second reflux tank to control the liquid level in the second reflux tank to be stable; The liquid level in the extractant recovery tower is controlled to be stable by controlling the opening of the regulating valve for supplementing the extractant feed through the second reboiler liquid level controller; The opening of the regulating valve connected to the extractive distillation tower is controlled by the second reflux ratio controller to stabilize the reflux amount 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 control the temperature difference in the extractive distillation tower to be stable; The opening of the regulating valve on the reflux pipeline connected to the extractant recovery tower is controlled by the second cascade control loop to adjust the reflux amount from the second reflux tank to the extractant recovery tower to be stable.

9. The control method according to claim 8, characterized in that: The range of the feed disturbance is [-20%, +20%], wherein the feed disturbance includes feed flow disturbance and feed composition disturbance.

10. An extractive distillation process for the distillation extraction of a low-carbon alcohol-trimethylsilane azeotrope, characterized in that: The extractive distillation process uses the extractive distillation system as claimed in claim 2, comprising the following steps: The low-carbon alcohol-trimethoxysilane azeotrope and the extractant are used as raw materials and enter the extractive distillation tower from different trays; Controlling the first reboiler to heat the extractive distillation tower kettle, so that the top steam is condensed by the first condenser and then enters the first reflux tank to obtain product low-carbon alcohol, wherein part of the product low-carbon alcohol is extracted as the product after being pressurized by the material delivery pump, and the other part of the product low-carbon alcohol is refluxed to the extractive distillation tower; The bottom material of the extractive distillation tower is partially vaporized, and the other part of the bottom material is sent to the extractant recovery tower through the material delivery pump; the top steam of the extraction recovery tower is condensed by the second condenser and enters the second reflux tank to obtain the product trimethoxysilane, wherein part of the product trimethoxysilane is extracted as the product after being pressurized by the material delivery pump, and the other part is refluxed to the extraction recovery tower; The extractant is taken out from the kettle of the extraction recovery tower, and after being pressurized by the material delivery pump and cooled by the raw material preheater, it enters the extraction distillation tower and is used as raw material again.

11. The extractive distillation process according to claim 10, characterized in that: The product low-carbon alcohol is any one of methanol, ethanol or propanol; The extractant is o-trimethylbenzene, unsymmetrical trimethylbenzene, o-xylene, ethylbenzene, n-propanol, isopropylbenzene, o-methylethylbenzene, m-methylethylbenzene or p-methylethylbenzene.

Images