Automatic reflux control device and method for intermittent vacuum distillation of high-purity α-thiophene derivatives

Abstract

The invention discloses an automatic reflux control device and method for intermittent vacuum distillation of high-purity α-thiophene derivatives. The device comprises a tower kettle reboiler, a distillation tower, a tower top condenser, a reflux distributor and a receiving tank, and also comprises a reflux control system composed of a PID cascade control unit and an intermittent distillation tower vacuum control system composed of a PID single-loop feedback control unit. The invention effectively separates a low-boiling point fore fraction on the basis of maintaining the stability of the distillation tower system, so as to achieve the purpose of producing high-purity α-thiophene derivatives by distillation.

Description

Technical Field

[0001] The invention relates to an automatic reflux control device and method for intermittent vacuum distillation, belonging to the field of pharmaceutical and chemical production. Background Art

[0002] In chemical production, distillation is a frequently used purification process. In the distillation tower, the material is vaporized and rises through the heating source at the bottom. In the entire distillation tower, the gas and liquid phases are in countercurrent contact and interphase mass transfer is carried out. The volatile components in the liquid phase enter the gas phase, and the non-volatile components in the gas phase are transferred to the liquid phase.

[0003] Distillation can be divided into two types: continuous distillation and intermittent distillation according to the production process. Continuous distillation has large production capacity and high tower efficiency, which is suitable for large-scale chemical production. Intermittent distillation is flexible and easy to operate, with small production capacity, which is suitable for small-scale production.

[0004] The synthesis of α-thiophene derivatives is mostly direct synthesis using thiophene as raw material. The purity of crude α-thiophene derivatives produced industrially is generally 90-95%. To obtain high-purity products above 99.5%, distillation is necessary. α-thiophene derivatives, which are pharmaceutical and chemical intermediates, have a high boiling point. In order to reduce energy consumption and increase relative volatility, intermittent vacuum distillation technology is generally used. Summary of the invention

[0005] Aiming at the distillation of high-purity α-thiophene derivatives, the present invention provides a device and method for automatically controlling the reflux ratio, which effectively realizes the stable operation of the distillation process and the high-purity distillation of the α-thiophene derivatives.

[0006] The technical solution of the present invention is as follows:

[0007] An automatic reflux control device for intermittent vacuum distillation, comprising: intermittent vacuum distillation equipment, a vacuum reflux control system;

[0008] The intermittent vacuum distillation equipment comprises: a tower kettle reboiler (1), a distillation tower (2), a tower top condenser (4), a buffer tank (6), an electric three-way regulating valve (5), and a receiving tank (7); the circulation inlet and outlet of the tower kettle reboiler (1) are respectively connected to the circulation inlet and outlet pipelines of the bottom of the distillation tower (2); the bottom of the distillation tower (2) is provided with a discharge port (21, used for discharging the kettle residue); the tower top condenser (4) is sequentially connected to the buffer tank (6) and the electric three-way regulating valve (5) pipeline; the top of the buffer tank (6) is provided with a vacuum port and a nitrogen pressure regulating pipe (61); the electric three-way regulating valve (5) is respectively connected to the distillation tower reflux pipe and the receiving tank (7) pipeline; the bottom of the receiving tank (7) is provided with a discharge port;

[0009] The vacuum reflux control system comprises: a reflux control system composed of a PID cascade control unit and a vacuum control system composed of a PID single-loop feedback control unit;

[0010] The reflux control system composed of the PID cascade control unit comprises: a tower top temperature sensor (103), a tower top pressure sensor (101), a tower top temperature controller (104), a tower top pressure controller (102) with two-way outputs, and an electric three-way regulating valve (5); the tower top pressure controller (102) and the tower top temperature controller (104) are connected in series, and the signal output of the tower top pressure controller (102) is used as the set value of the tower top temperature controller (104), thereby forming a PID cascade control; the detection heads of the tower top temperature sensor (103) and the tower top pressure sensor (101) extend into the tower top inner cavity of the distillation tower (2) The signal output end of the tower top temperature sensor (103) and the signal output end of the tower top pressure sensor (101) are electrically connected to the signal input end of the tower top temperature controller (104) and the signal input end of the tower top pressure controller (102) respectively; one signal output end of the tower top pressure controller (102) is electrically connected to the signal input end of the tower top temperature controller (104); the signal output end of the tower top temperature controller (104) is electrically connected to the control end of the electric three-way regulating valve (5), and the electric three-way regulating valve (5) regulates the reflux amount of the tower top, and the purpose of distilling high-purity α-thiophene derivatives is achieved by regulating the reflux amount of the tower top;

[0011] The vacuum control system composed of the PID single-loop feedback control unit comprises: a tower top pressure sensor (101), a tower top pressure controller (102) with two-way output, and an electric regulating valve (3); the detection head of the tower top pressure sensor (101) extends into the tower top inner cavity of the distillation tower (2), the signal output end of the tower top pressure sensor (101) is electrically connected to the signal input end of the tower top pressure controller (102); the other signal output end of the tower top pressure controller (102) is electrically connected to the control end of the electric regulating valve (3); the electric regulating valve (3) is arranged on a nitrogen pressure regulating pipe (61), and the vacuum degree of the tower top is adjusted by injecting nitrogen to maintain the stability of the vacuum degree of the distillation tower.

[0012] The present invention automatically controls the reflux ratio by using a PID cascade control unit and automatically controls the vacuum degree by using a PID single-loop feedback control unit, thereby effectively separating the low-boiling point front fraction on the basis of maintaining the stability of the distillation tower system, and achieving the purpose of producing high-purity alpha-thiophene derivatives by distillation.

[0013] When the device of the present invention is working, the tower top PID single-loop feedback control unit controls the tower top vacuum degree within a set range, and can achieve accurate fraction separation by determining the boiling point. Different α-thiophene derivatives have different boiling points. By adjusting the set value of the tower top pressure controller, the output value of the tower top pressure controller and the input value of the tower top temperature controller are matched, so that the PID cascade control unit can automatically adjust the reflux ratio of the distillation tower to achieve efficient separation of the front fraction and obtain a high-purity α-thiophene derivative finished product.

[0014] In the present invention, the pressure control loop constitutes both the outer loop unit of the cascade reflux control and the single loop unit of the vacuum control. The tower top pressure controller sets the vacuum degree to 100-5000 Pa. For different α-thiophene derivatives, the tower top pressure controller sets the vacuum degree in different ranges, for example: 800-1100 Pa for 2-thiophene ethanol and 1800-2200 Pa for 2-thiophene ethylamine.

[0015] The tower top pressure controller and tower top temperature controller are connected in series. One signal output of the tower top pressure controller is used as the set value of the tower top temperature controller. The output of the tower top temperature controller controls the electric three-way regulating valve, and the electric three-way regulating valve controls the reflux volume of the tower top. Another signal output of the tower top pressure controller controls the electric regulating valve to maintain the stability of the vacuum degree of the distillation tower.

[0016] The beneficial effects of the present invention are:

[0017] The present invention provides a reflux automatic control device and method for intermittent vacuum distillation of high-purity α-thiophene derivatives, the device comprising a tower bottom reboiler, a distillation tower, a tower top condenser, a reflux distributor and a receiving tank, and also comprising a reflux control system composed of a PID cascade control unit and an intermittent distillation tower vacuum control system composed of a PID single-loop feedback control unit. The present invention effectively separates a low-boiling point fore fraction on the basis of maintaining the stability of the distillation tower system, thereby achieving the purpose of producing high-purity α-thiophene derivatives by distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0019] Figure 2 It is a block diagram of the PID control system of the present invention;

[0020] In the figure, 1-tower kettle reboiler, 2-rectifying tower, 3-electric regulating valve, 4-tower top condenser, 5-electric three-way regulating valve, 6-buffer tank, 7-receiving tank, 21-discharge port, 61-nitrogen pressure regulating pipe, 101-tower top pressure sensor, 102-tower top pressure controller, 103-tower top temperature sensor, 104-tower top temperature controller, A represents nitrogen inlet (to adjust vacuum degree), B represents vacuum port (to connect vacuum pump), C represents discharging, and D represents kettle residue;

[0021] Figure 1 The meanings of the instrument legend symbols are as follows:

[0022]

[0023] Specifically, Figure 1 TC stands for temperature controller, TT stands for temperature sensor, PC stands for pressure controller, and PT stands for pressure sensor;

[0024] Figure 2 The "+" and "-" in the PID operation represent the "given value" and "measured value" required for PID operation respectively. DETAILED DESCRIPTION

[0025] The present invention is further described below by means of specific embodiments in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited thereto.

[0026] Example 1

[0027] A reflux automatic control device for intermittent vacuum distillation (such as Figure 1 As shown), it includes: a tower kettle reboiler 1, a distillation tower 2, a tower top condenser 4, an electric three-way regulating valve 5, a buffer tank 6 and a receiving tank 7. The circulation inlet and outlet of the tower kettle reboiler 1 are respectively connected to the circulation inlet and outlet pipelines at the bottom of the distillation tower 2; the bottom of the distillation tower 2 is provided with a discharge port 21 for discharging the kettle residue, and the top of the tower is provided with a reflux port; the liquid outlet of the tower top condenser 4 is connected to the buffer tank 6 and then to the electric three-way regulating valve 5, one outlet of the electric three-way regulating valve 5 is connected to the tower top reflux port, and the other outlet of the electric three-way regulating valve 5 is connected to the liquid inlet pipeline of the receiving tank 7, and the liquid outlet of the receiving tank 7 discharges the material; the top of the buffer tank 6 is provided with a vacuum pipe connected to the vacuum system, and the pressure regulating pipe 61 is connected to nitrogen.

[0028] The device also includes a reflux control system composed of a PID cascade control unit and a vacuum control system composed of a PID single-loop feedback control unit.

[0029] The reflux control system composed of the PID cascade control unit includes: a tower top pressure sensor 101, a tower top temperature sensor 103, a tower top pressure controller (with two-way output) 102, a tower top temperature controller 104 and an electric three-way regulating valve 5; the tower top pressure controller 102 and the tower top temperature controller 104 are connected in series, and the signal output of the tower top pressure controller 102 is used as the set value of the tower top temperature controller 104 to form a PID cascade control. The detection heads of the tower top pressure sensor 101 and the tower top temperature sensor 103 extend into the tower top inner cavity of the distillation tower, and the signal output end of the tower top pressure sensor 101 and the signal output end of the tower top temperature sensor 103 are electrically connected to the signal input end of the tower top pressure controller 102 and the signal input end of the tower top temperature controller 104 respectively, the signal output end of the tower top pressure controller 102 is electrically connected to the signal input end of the tower top temperature controller 104, and the signal output end of the tower top temperature controller 104 is electrically connected to the control end of the electric three-way regulating valve 5, and the electric three-way regulating valve 5 controls the reflux amount of the tower top, and the purpose of distilling high-purity α-thiophene derivatives is achieved by controlling the reflux amount of the tower top.

[0030] The vacuum control system composed of the PID single-loop feedback control unit includes: a tower top pressure sensor 101, a tower top pressure controller 102 (with two-way output) and an electric regulating valve 3. The detection head of the tower top pressure sensor 101 extends into the tower top inner cavity of the distillation tower, the signal output end of the tower top pressure sensor 101 is electrically connected to the signal input end of the tower top pressure controller 102, the signal output end of the tower top pressure controller 102 is electrically connected to the control end of the electric regulating valve 3, and the electric regulating valve 3 is arranged on the pressure regulating pipe 61 at the top of the buffer tank 6, and the vacuum degree of the tower top is adjusted to remain stable by injecting nitrogen.

[0031] When the device of the present invention is working, the tower top vacuum control system composed of the tower top pressure sensor, the tower top pressure controller and the tower top electric regulating valve controls the tower top vacuum within a set range, and can achieve accurate fraction separation by a determined boiling point. The tower top pressure sensor, the tower top temperature sensor, the tower top pressure controller (with two-way output), the tower top temperature controller and the electric three-way regulating valve constitute a PID cascade control system, which automatically adjusts and controls the reflux ratio of the distillation tower to achieve efficient separation of the front fraction and obtain a high-purity α-thiophene derivative finished product.

[0032] Example 2

[0033] The α-thiophene derivative 2-thiophene ethanol was distilled to produce high-purity 2-thiophene ethanol. The control device of Example 1 was used to perform intermittent vacuum distillation on the α-thiophene derivative 2-thiophene ethanol. The crude 2-thiophene ethanol with a GC purity of about 93% was pumped into a stainless steel wire mesh corrugated packing distillation kettle (28 theoretical plates). The vacuum pump was turned on, and the vacuum degree of the tower top pressure controller was set to 900 Pa. The front fraction was distilled. When the top temperature reached 83 degrees, the finished product was transferred. The purity of the finished product was greater than 99.7%.

[0034] When the distillation tower is rectifying 2-thiopheneethanol, the tower top pressure controller sets the vacuum degree to 900Pa. When the vacuum degree rises above the set value, the output control electric regulating valve opening increases, and the injection of nitrogen is increased to reduce the vacuum degree, so that the vacuum degree is restored to the set value. When the vacuum degree drops above the set value, the output control electric regulating valve opening decreases, and the injection of nitrogen is reduced to increase the vacuum degree, so that the vacuum degree is restored to the set value.

[0035] Another output of the tower top pressure controller is used as the set value of the tower top temperature controller of the inner loop of the PID cascade control, corresponding to the boiling point of 2-thiopheneethanol under this vacuum degree. When distilling 2-thiopheneethanol, the tower top temperature of the front fraction is lower than the tower top temperature of 2-thiopheneethanol. The temperature controller output controls the electric three-way regulating valve to increase the amount of reflux, increase the reflux ratio, and separate the front fraction more efficiently; as the front fraction is separated, the tower top temperature gradually rises to the boiling point of 2-thiopheneethanol, and the temperature controller automatically controls the electric three-way regulating valve to reduce the reflux ratio, increase the discharge amount, receive high-purity 2-thiopheneethanol products, and reduce energy consumption.

[0036] Example 3

[0037] The high-purity 2-thiopheneethylamine was produced by distillation. The α-thiophene derivative 2-thiopheneethylamine was subjected to intermittent vacuum distillation using the control device of Example 1. The crude 2-thiopheneethylamine with a GC purity of about 92% was pumped into a stainless steel wire mesh corrugated packing distillation kettle (20 theoretical plates). The vacuum pump was turned on, and the vacuum degree of the tower top pressure controller was set to 2200Pa. The front fraction was distilled. When the top temperature reached 83 degrees, the finished product was transferred. The purity of the finished product was greater than 99.7%.

[0038] When the distillation tower is rectifying 2-thiopheneethylamine, the tower top pressure controller sets the vacuum degree to 2200Pa. When the vacuum degree rises above the set value, the output control electric regulating valve opening increases, and the injection of nitrogen is increased to reduce the vacuum degree, so that the vacuum degree is restored to the set value. When the vacuum degree drops above the set value, the output control electric regulating valve opening decreases, and the injection of nitrogen is reduced to increase the vacuum degree, so that the vacuum degree is restored to the set value.

[0039] Another output of the tower top pressure controller is used as the set value of the tower top temperature controller of the inner loop of the PID cascade control, corresponding to the boiling point of 2-thiopheneethylamine under this vacuum degree. When distilling 2-thiopheneethylamine, the tower top temperature of the front fraction is lower than the tower top temperature of 2-thiopheneethylamine. The output of the temperature controller controls the electric three-way regulating valve to increase the amount of reflux, increase the reflux ratio, and separate the front fraction more efficiently; as the front fraction is separated, the tower top temperature gradually rises to the boiling point of 2-thiopheneethylamine, and the temperature controller automatically controls the electric three-way regulating valve to reduce the reflux ratio, increase the discharge amount, receive high-purity 2-thiopheneethylamine finished products, and reduce energy consumption.

[0040] The contents described in the embodiments of this specification are merely an enumeration of implementation forms of the inventive concept. The protection scope of the present invention should not be deemed to be limited to the specific forms described in the embodiments. The protection scope of the present invention also includes equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for distilling α-thiophene derivatives using an automatic reflux control device for intermittent vacuum distillation, characterized in that: The reflux automatic control device for intermittent vacuum distillation comprises: intermittent vacuum distillation equipment and a vacuum reflux control system; The intermittent vacuum distillation equipment comprises: a tower bottom reboiler (1), a distillation tower (2), a tower top condenser (4), a buffer tank (6), an electric three-way regulating valve (5), and a receiving tank (7); the circulation inlet and outlet of the tower bottom reboiler (1) are respectively connected to the circulation inlet and outlet pipelines of the bottom of the distillation tower (2); the bottom of the distillation tower (2) is provided with a discharge port (21); the tower top condenser (4) is sequentially connected to the buffer tank (6) and the electric three-way regulating valve (5) pipeline; the top of the buffer tank (6) is provided with a vacuum port and a nitrogen pressure regulating pipe (61); the electric three-way regulating valve (5) is respectively connected to the distillation tower reflux pipe and the receiving tank (7) pipeline; the bottom of the receiving tank (7) is provided with a discharge port; The vacuum reflux control system comprises: a reflux control system composed of a PID cascade control unit and a vacuum control system composed of a PID single-loop feedback control unit; The reflux control system composed of the PID cascade control unit comprises: a tower top temperature sensor (103), a tower top pressure sensor (101), a tower top temperature controller (104), a tower top pressure controller (102) with two-way outputs, and an electric three-way regulating valve (5); the tower top pressure controller (102) and the tower top temperature controller (104) are connected in series, and the signal output of the tower top pressure controller (102) is used as the set value of the tower top temperature controller (104), thereby forming a PID cascade control; the detection heads of the tower top temperature sensor (103) and the tower top pressure sensor (101) extend into the tower top inner cavity of the distillation tower (2) The signal output end of the tower top temperature sensor (103) and the signal output end of the tower top pressure sensor (101) are electrically connected to the signal input end of the tower top temperature controller (104) and the signal input end of the tower top pressure controller (102) respectively; one signal output end of the tower top pressure controller (102) is electrically connected to the signal input end of the tower top temperature controller (104); the signal output end of the tower top temperature controller (104) is electrically connected to the control end of the electric three-way regulating valve (5), and the electric three-way regulating valve (5) regulates the reflux amount of the tower top, and the purpose of distilling high-purity α-thiophene derivatives is achieved by regulating the reflux amount of the tower top; The vacuum control system composed of the PID single-loop feedback control unit comprises: a tower top pressure sensor (101), a tower top pressure controller (102) with two-way output, and an electric regulating valve (3); the detection head of the tower top pressure sensor (101) extends into the tower top inner cavity of the distillation tower (2), the signal output end of the tower top pressure sensor (101) is electrically connected to the signal input end of the tower top pressure controller (102); the other signal output end of the tower top pressure controller (102) is electrically connected to the control end of the electric regulating valve (3); the electric regulating valve (3) is arranged on the nitrogen pressure regulating pipe (61), and the vacuum degree of the tower top is adjusted by injecting nitrogen to maintain the stability of the vacuum degree of the distillation tower; The method is: When the distillation tower is used to rectify α-thiophene derivatives, the tower top pressure controller and the tower top temperature controller are connected in series, and one signal output of the tower top pressure controller is used as the set value of the tower top temperature controller. The output of the tower top temperature controller controls the electric three-way regulating valve, and the electric three-way regulating valve controls the reflux amount at the tower top; another signal output of the tower top pressure controller controls the electric regulating valve to maintain the stability of the vacuum degree of the distillation tower; The tower top pressure controller sets the vacuum degree to 100-5000Pa. When the vacuum degree rises above the set value, the output control electric regulating valve opening increases, and the nitrogen injection is increased to reduce the vacuum degree, so that the vacuum degree returns to the set value. When the vacuum degree drops above the set value, the output control electric regulating valve opening decreases, and the nitrogen injection is reduced to increase the vacuum degree, so that the vacuum degree returns to the set value. Another output of the tower top pressure controller is used as the set value of the tower top temperature controller of the inner loop of the PID cascade control, corresponding to the boiling point of the α-thiophene derivative under this vacuum degree; when distilling the α-thiophene derivative, the tower top temperature of the front fraction is lower than the tower top temperature of the α-thiophene derivative, and the temperature controller output controls the electric three-way regulating valve to increase the reflux amount, increase the reflux ratio, and separate the front fraction; as the front fraction is separated, the tower top temperature gradually rises to the boiling point of the α-thiophene derivative, and the temperature controller automatically controls the electric three-way regulating valve to reduce the reflux ratio, increase the discharge amount, and receive the α-thiophene derivative finished product.

2. The method according to claim 1, characterized in that The α-thiophene derivative is 2-thiopheneethanol, and the vacuum degree of the tower top pressure controller is set to 800-1100 Pa.

3. The method according to claim 1, characterized in that The α-thiophene derivative is 2-thiopheneethylamine, and the vacuum degree of the tower top pressure controller is set to 1800-2200Pa.

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