An on-line detection product concentration control system and method for the steam pressure difference at the top of a rectifying column

Abstract

The present invention provides a control system and method for online detection of product concentration by using the pressure difference of vapor at the top of a distillation tower, belonging to the technical field of distillation towers. It solves the problem of inaccurate concentration control during product distillation in existing distillation towers. The distillation tower is connected to a first condenser via an outlet pipe, which is connected to the distillation tower via a reflux pipe. A first regulating valve is provided on the reflux pipe. A sample tube is fixedly connected to the distillation tower and partially extends into the cavity at the top of the distillation tower. A first pressure gauge is connected to the sample tube and is used to detect the pressure of the vapor inside the sample tube. A second pressure gauge is connected to the distillation tower and is used to detect the pressure of the vapor at the top of the distillation tower. A thermometer is connected to the distillation tower and is used to detect the temperature of the vapor at the top of the distillation tower. A data acquisition and control unit controls the opening of the first regulating valve based on the pressure difference between the first and second pressure gauges and the temperature of the thermometer. The present control system has the advantages of accurately controlling product concentration and improving product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of distillation towers and relates to a control system and method for online detection of product concentration of vapor pressure difference at the top of a distillation tower. Background Art

[0002] A distillation tower is a tower-type vapor-liquid contact device that performs rectification. By utilizing the different volatilities of the components in a mixture, i.e., the different vapor pressures of the components at the same temperature, low-boiling substances in the liquid phase are transferred to the gas phase, while high-boiling substances in the gas phase are transferred to the liquid phase, thereby achieving separation.

[0003] There are existing devices that use distillation towers for separation. For example, Chinese patent literature discloses a methanol recovery device [application number: 202220092132.1; authorization announcement number: CN216777951U], which includes a distillation tower, a temporary storage tank, a distillation outlet pipe, a condenser and a first reflux pipe. The upper part of the distillation tower is formed with a gas phase outlet and a liquid phase inlet, and the lower part is formed with a first gas phase inlet and a liquid phase outlet. The gas phase outlet is connected to the temporary storage tank through the distillation outlet pipe. The condenser is arranged on the distillation outlet pipe to cool the methanol vapor after distillation. The first reflux pipe connects the temporary storage tank and the liquid phase inlet, and the liquid methanol in the temporary storage tank is refluxed into the distillation tower.

[0004] This type of methanol recovery device, based on the fact that the boiling point of methanol is 64.7°C and the boiling point of water is 100°C under standard atmospheric pressure, controls the temperature at the distillation end of the distillation tower between 64.7-100°C, such as 65-70°C. This condenses water vapor into liquid and collects it at the bottom of the distillation tower, while the methanol remains in a gaseous state, achieving separation of methanol and water. However, after methanol is separated and recovered, the methanol recovery device with this structure requires sampling and testing of the product to determine whether the methanol quality is qualified. This makes testing cumbersome, and the concentration of the separated and recovered methanol cannot be accurately controlled, resulting in a certain deviation between the concentration of the separated and recovered methanol and the required concentration, thereby reducing product quality. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and propose a control system and method for online detection of product concentration by vapor pressure difference at the top of a distillation tower. The technical problem to be solved is how to accurately control the concentration of the product and improve the quality of the product.

[0006] The objectives of the present invention can be achieved through the following technical solutions: a control system for online detection of product concentration of vapor pressure difference at the top of a distillation tower, wherein the gas outlet of the distillation tower is connected to a first condenser through an gas outlet pipe, the liquid outlet of the first condenser is connected to the distillation tower through a reflux pipe, and the reflux pipe is provided with a first regulating valve, characterized in that the control system includes a data acquisition and control unit, a first pressure gauge, a second pressure gauge, a thermometer, and a sample tube for storing a set concentration product, the sample tube being fixedly connected to the distillation tower and partially extending into a cavity at the top of the distillation tower, the first pressure gauge being connected to the sample tube and being used to detect the pressure of the vapor inside the sample tube, the second pressure gauge being connected to the distillation tower and being used to detect the pressure of the vapor at the top of the distillation tower, the thermometer being connected to the distillation tower and being used to detect the temperature of the vapor at the top of the distillation tower, the first pressure gauge, the second pressure gauge, the thermometer, and the first regulating valve are all connected to the data acquisition and control unit, and the data acquisition and control unit controls the opening of the first regulating valve according to the pressure difference between the first and second pressure gauges and the temperature of the thermometer.

[0007] The data acquisition and control unit pre-collects various distillation data for various products and forms a database. When distilling a product, the distillation tower first adds a product of a desired concentration or pure product to a sample tube, based on the desired product concentration. The sample tube is then installed in the distillation tower. Since the product in the sample tube is of the desired concentration or pure product, the vapor pressure generated by the product in the sample tube during distillation at a set temperature is the pressure of the desired product of the desired concentration or pure product. The distillation tower generates steam, and the sample in the sample tube also generates steam. A second pressure gauge measures the pressure of the vapor at the top of the distillation tower, while a first pressure gauge measures the pressure of the vapor within the sample tube. The data acquisition and control unit collects the pressures of the first and second pressure gauges, as well as the temperature of the thermometer, and calculates the pressure difference between the first and second pressure gauges at that temperature to determine whether the pressure difference is within the desired range. If the pressure difference is within the desired range, the first regulating valve remains in its original position. If the pressure difference is outside the desired range, the data acquisition and control unit controls the opening of the first regulating valve until the pressure difference is adjusted to within the desired range. This application compares the pressure difference between qualified products and processed products under the same conditions during actual production with the data collected in the data acquisition and control unit, and determines in real time whether the product is qualified after production and processing, thereby accurately detecting and controlling the concentration of the product online in real time to improve the quality of the product. The data acquisition and control unit is a prior art, and the specific model and structure are not described in detail. When adding a sample to the sample tube, it needs to be added under a vacuum state or in a sample vapor atmosphere. This control system can be applied to normal pressure, reduced pressure, and pressurized distillation systems.

[0008] In the aforementioned online product concentration control system for detecting vapor pressure differential at the top of a distillation tower, the measuring ends of the first pressure gauge, the second pressure gauge, and the temperature gauge are positioned adjacent to each other. This structure allows all measuring ends to be as close as possible and to operate under the same conditions as much as possible, thereby improving test accuracy and thus enhancing product quality.

[0009] In the aforementioned system for online monitoring of product concentration using vapor pressure differential at the top of a distillation tower, the distillation tower includes a connecting pipe at the top. The sample tube is inserted through the connecting pipe, with the bottom of the sample tube extending into a cavity at the top of the distillation tower. A gap is provided between the outer wall of the sample tube and the inner wall of the connecting pipe. This structure allows the measuring ends of the first pressure gauge, the second pressure gauge, and the temperature gauge to operate under the same conditions as much as possible, improving test accuracy and thus enhancing product quality.

[0010] In the aforementioned online product concentration control system for monitoring vapor pressure differential at the top of a distillation tower, the water inlet of the first condenser is connected to a water inlet pipe, which is connected to a second regulating valve. The second regulating valve is connected to a data acquisition and control unit, which controls the opening of the second regulating valve based on the pressure differential between the first and second pressure gauges and the temperature of the thermometer. The provision of the second regulating valve provides the present vapor pressure differential control system with a second adjustment mode. Multiple adjustment modes ensure the regulation accuracy of the present vapor pressure differential control system and improve product quality.

[0011] In the aforementioned product concentration control system for online detection of distillation tower overhead vapor pressure differential, the gas outlet of the first condenser is connected to a second condenser, and the liquid outlet of the second condenser is connected to the reflux line. The second condenser assists the first condenser in its operation, ensuring that the product is converted from gas to liquid after passing through the condenser.

[0012] In the above-mentioned online detection product concentration control system for the top vapor pressure difference of the distillation tower, the power of the first condenser is greater than the power of the second condenser. Reasonable arrangement ensures processing requirements while reducing costs.

[0013] In the aforementioned online product concentration control system for detecting vapor pressure differential at the top of a distillation tower, a reboiler is connected to the bottom of the distillation tower, which is connected to a heat medium inlet pipe. A third regulating valve is connected to the heat medium inlet pipe. The third regulating valve is connected to a data acquisition and control unit, which controls the opening of the third regulating valve based on the pressure differential between the first and second pressure gauges and the temperature of the thermometer. The provision of the third regulating valve provides the present vapor pressure differential control system with a third and multiple adjustment modes, ensuring its adjustment accuracy and improving product quality.

[0014] In the aforementioned product concentration control system for online detection of vapor pressure differential at the top of a distillation tower, the reflux pipe is connected to a liquid outlet pipe, the liquid inlet of which is located between the first regulating valve and the first condenser. The outlet of the liquid outlet pipe is connected to several tanks to be inspected. The tops of all the tanks to be inspected are connected to balancing pipes, the other ends of which are connected to a vacuum pump or an exhaust structure. The tanks to be inspected temporarily store product, and the provision of the balancing pipes balances the pressure of the product in the tanks to be inspected, thereby improving the stability of the distillation.

[0015] A method for controlling product concentration by online detection of vapor pressure difference at the top of a distillation tower, characterized in that the method comprises the following steps:

[0016] Step 1: Collect distillation data of different products through experiments, and store the data in a data acquisition control unit to form a database;

[0017] Step 2: During the product distillation process, the steam pressure in the sample tube is measured by a first pressure gauge, the steam pressure at the top of the distillation tower is measured by a second pressure gauge, and the steam temperature at the top of the distillation tower is measured by a thermometer, and the data are transmitted to a data acquisition control unit;

[0018] Step 3: The data acquisition and control unit identifies and calculates the collected data and compares it with the data in the database. When the pressure difference is within the qualified range, the distillation tower works normally and the concentration of the distillation tower top product meets the requirements. When the pressure difference is outside the qualified range and the concentration of the distillation tower top product does not meet the requirements, the data acquisition and control unit sends a signal to adjust the first regulating valve, the second regulating valve and the third regulating valve individually or jointly to return the pressure difference to a reasonable range.

[0019] In the above-mentioned method for online detection of product concentration control of the vapor pressure difference at the top of a distillation tower, in step 1, it can be known from Raoult's law and Dalton's law of partial pressure that as long as the saturated vapor pressure P of the pure components A and B is A 0 and P B 0 The relationship between liquid phase composition and bubble point is known, and the molar fraction of liquid phase A component X is directly calculated. A and the mole fraction of component B X B , P is the steam pressure at the top of the distillation tower,

[0020]

[0021] Since the gas and liquid are in equilibrium when the top of the distillation tower boils, the quantitative relationship between the gas phase composition and the dew point can also be determined. The molar fraction Y of the gas phase component A can also be calculated by knowing the dew point. A and the mole fraction Y of component B B ,

[0022]

[0023] The relationship between the saturated vapor pressures of pure components A and B at different temperatures is usually expressed by the Antoine equation:

[0024] Where a, d, and c are the antoine constants of the component. Commonly used a, d, and c can be found in the Handbook of Basic Chemical Materials, and t is the temperature.

[0025] Compared with the prior art, the online detection product concentration control system for distillation tower top vapor pressure difference provided by the present invention has the following advantages:

[0026] 1. This steam pressure difference control system collects various data in advance through the data acquisition and control unit. During distillation, the data acquisition and control unit identifies the pressure difference between the first pressure gauge and the second pressure gauge and the temperature of the thermometer to control the opening of the first regulating valve, the second regulating valve and the third regulating valve to maintain the pressure difference within the qualified range, thereby accurately controlling the concentration of the product and improving the quality of the product.

[0027] 2. This vapor pressure difference control system places qualified products or pure products in the sample tube so that the products in the sample tube and the processed products in the distillation tower are under the same conditions, thereby accurately controlling the concentration of the products and improving the quality of the products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the distillation tower top vapor pressure difference control system.

[0029] Figure 2 This is a schematic diagram of the installation structure of the sample tube and the connecting tube.

[0030] Figure 3 This is a graph showing the relationship between the saturated vapor pressure difference and concentration of methanol in distillation at normal pressure at different temperatures.

[0031] In the figure, 1, distillation tower; 101, connecting pipe; 2, air outlet pipe; 3, first condenser; 4, reflux pipe; 5, first regulating valve; 6, data acquisition and control unit; 7, first pressure gauge; 8, second pressure gauge; 9, thermometer; 10, sample tube; 11, water inlet pipe; 12, second regulating valve; 13, second condenser; 14, heat medium inlet pipe; 15, third regulating valve; 16, liquid outlet pipe; 17, tank to be inspected; 18, balance pipe; 19, reboiler. DETAILED DESCRIPTION

[0032] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0033] like Figure 1 As shown, the distillation device includes a distillation tower 1, a first condenser 3, a second condenser 13, a tank to be inspected 17 and a vapor pressure difference control system. The vapor pressure difference control system includes a data acquisition control unit 6, a first pressure gauge 7, a second pressure gauge 8, a temperature gauge 9, a sample tube 10, a first regulating valve 5, a second regulating valve 12 and a third regulating valve 15.

[0034] like Figure 2 As shown, the distillation tower 1 includes a connecting pipe 101 at the top, and the sample tube 10 is detachably fixedly connected to the connecting pipe 101. The sample tube 10 is inserted into the connecting pipe 101 and the bottom of the sample tube 10 extends into the cavity at the top of the distillation tower 1. There is a gap between the outer wall of the sample tube 10 and the inner wall of the connecting pipe 101.

[0035] The gas outlet of the distillation tower 1 is connected to the first condenser 3 through the gas outlet pipe 2, the liquid outlet of the first condenser 3 is connected to the distillation tower 1 through the reflux pipe 4, the reflux pipe 4 is provided with a first regulating valve 5, the water inlet of the first condenser 3 is connected to the water inlet pipe 11, the water inlet pipe 11 is connected to the second regulating valve 12, the gas outlet of the first condenser 3 is connected to the second condenser 13, the liquid outlet of the second condenser 13 is connected to the reflux pipe 4, and the power of the first condenser 3 is greater than the power of the second condenser 13.

[0036] The reflux pipe 4 is connected to a liquid outlet pipe 16, and the liquid inlet of the liquid outlet pipe 16 is located between the first regulating valve 5 and the first condenser 3. In this embodiment, the liquid outlet of the liquid outlet pipe 16 is connected to three tanks to be inspected 17, and the tops of all the tanks to be inspected 17 are connected to a balancing pipe 18, and the other end of the balancing pipe 18 is connected to a vacuum pump. In actual production, the liquid outlet of the liquid outlet pipe 16 is connected to two or four tanks to be inspected 17, and the other end of the balancing pipe 18 is connected to the emptying structure.

[0037] The bottom of the distillation tower 1 is connected to a reboiler 19 , the reboiler 19 is connected to a heat medium inlet pipe 14 , the heat medium inlet pipe 14 is connected to a third regulating valve 15 , and the third regulating valve 15 is connected to the data acquisition control unit 6 .

[0038] The first pressure gauge 7 is connected to the sample tube 10 and is used to detect the pressure of the steam inside the sample tube 10. The second pressure gauge 8 is connected to the distillation tower 1 and is used to detect the pressure of the top steam in the distillation tower 1. The thermometer 9 is connected to the distillation tower 1 and is used to detect the temperature of the top steam in the distillation tower 1. The measuring ends of the first pressure gauge 7, the second pressure gauge 8 and the thermometer 9 are arranged adjacent to each other. The first pressure gauge 7, the second pressure gauge 8, the thermometer 9, the first regulating valve 5, the second regulating valve 12 and the third regulating valve 15 are all connected to the data acquisition and control unit 6. In this embodiment, the data acquisition and control unit 6 controls the openings of the first regulating valve 5, the second regulating valve 12 and the third regulating valve 15 according to the pressure difference between the first pressure gauge 7 and the second pressure gauge 8 and the temperature of the thermometer 9. In actual production, the openings of the first regulating valve 5, the second regulating valve 12 and the third regulating valve 15 can be adjusted separately.

[0039] During operation, when the data acquisition and control unit 6 detects that the pressure differential between the first pressure gauge 7 and the second pressure gauge 8 is within a reasonable range and at a set temperature, the openings of the first regulating valve 5, the second regulating valve 12, and the third regulating valve 15 remain at their current levels. When the data acquisition and control unit 6 detects that the pressure differential between the first pressure gauge 7 and the second pressure gauge 8 is within an unreasonable range and at a set temperature, the data acquisition and control unit 6 can control the first regulating valve 5, the second regulating valve 12, and the third regulating valve 15 to operate independently or in coordination with each other to return the pressure differential to a reasonable range. When the temperature is detected to be outside the set range, the data acquisition and control unit 6 can control the first regulating valve 5, the second regulating valve 12, and the third regulating valve 15 to operate independently or in coordination with each other to return the temperature to the set temperature.

[0040] A method for controlling product concentration by online detection of vapor pressure difference at the top of a distillation tower, the method comprising the following steps:

[0041] Step 1: Collect the distillation data of different products through experiments, and record the data into the data acquisition control unit 6 to form a database. According to Raoult's law and Dalton's law of partial pressure, as long as the saturated vapor pressure P of pure components A and B is A 0 and P B 0 The relationship between liquid phase composition and bubble point is known, and the molar fraction of liquid phase A component X is directly calculated. A and the mole fraction of component B X B , P is the steam pressure at the top of the distillation tower 1,

[0042]

[0043] Since the gas and liquid are in equilibrium when the top of the distillation tower 1 boils, the quantitative relationship between the gas phase composition and the dew point can also be determined. The molar fraction Y of the gas phase component A can also be calculated by knowing the dew point. A and the mole fraction Y of component B B ,

[0044]

[0045] The relationship between the saturated vapor pressures of pure components A and B at different temperatures is usually expressed by the Antoine equation:

[0046] Where a, d, and c are the antoine constants of the component. Commonly used a, d, and c can be found in the Handbook of Basic Chemical Materials, and t is the temperature.

[0047] like Figure 3 As shown, taking methanol as an example, in this embodiment, component A is methanol and component B is water, and the relationship between the saturated vapor pressure difference and concentration of methanol in distillation at normal pressure at different temperatures is shown. In actual production, the distillation data is obtained through experiments and stored in the data acquisition and control unit 6.

[0048] Step 2: During the product distillation process, the steam pressure in the sample tube 10 is measured by the first pressure gauge 7, the steam pressure at the top of the distillation tower 1 is measured by the second pressure gauge 8, and the steam temperature at the top of the distillation tower 1 is measured by the thermometer 9, and the data are transmitted to the data acquisition and control unit 6.

[0049] Step three, the data acquisition and control unit 6 identifies and calculates the collected data and compares it with the data in the database. When the pressure difference is within the qualified range, the distillation tower 1 works normally and the concentration of the top product of the distillation tower 1 meets the requirements. When the pressure difference is outside the qualified range and the concentration of the top product of the distillation tower does not meet the requirements, the data acquisition and control unit 6 sends a signal to adjust the first regulating valve 5, the second regulating valve 12 and the third regulating valve 15 individually or jointly to return the pressure difference to a reasonable range.

[0050] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

[0051] Although this document frequently uses terms such as distillation column 1, connecting pipe 101, gas outlet pipe 2, first condenser 3, reflux pipe 4, first regulating valve 5, data acquisition and control unit 6, first pressure gauge 7, second pressure gauge 8, thermometer 9, sample pipe 10, water inlet pipe 11, second regulating valve 12, second condenser 13, heat medium inlet pipe 14, third regulating valve 15, liquid outlet pipe 16, tank to be inspected 17, balancing pipe 18, and reboiler 19, the use of other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

Claims

1. A product concentration control system for online detection of vapor pressure difference at the top of a distillation tower, wherein the gas outlet of the distillation tower (1) is connected to a first condenser (3) via a gas outlet pipe (2), the liquid outlet of the first condenser (3) is connected to the distillation tower (1) via a reflux pipe (4), and a first regulating valve (5) is provided on the reflux pipe (4), characterized in that: The control system comprises a data acquisition control unit (6), a first pressure gauge (7), a second pressure gauge (8), a thermometer (9) and a sample tube (10) for storing a product with a set concentration, wherein the sample tube (10) is fixedly connected to the distillation tower (1) and a portion of the sample tube (10) extends into a cavity at the top of the distillation tower (1), the first pressure gauge (7) is connected to the sample tube (10) and is used to detect the pressure of steam inside the sample tube (10), the second pressure gauge (8) is connected to the distillation tower (1) and is used to detect the pressure of steam at the top of the distillation tower (1), the thermometer (9) is connected to the distillation tower (1) and is used to detect the temperature of steam at the top of the distillation tower (1), the first pressure gauge (7), the second pressure gauge (8), the thermometer (9) and the first regulating valve (5) are all connected to the data acquisition control unit (6), and the data acquisition control unit (6) controls the opening of the first regulating valve (5) according to the pressure difference between the first pressure gauge (7) and the second pressure gauge (8) and the temperature of the thermometer (9).

2. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, characterized in that: The measuring ends of the first pressure gauge (7), the second pressure gauge (8) and the temperature gauge (9) are arranged adjacent to each other.

3. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, characterized in that: The distillation tower (1) comprises a connecting pipe (101) at the top, the sample tube (10) is inserted into the connecting pipe (101), and the bottom of the sample tube (10) extends into the cavity at the top of the distillation tower (1), and a gap is formed between the outer wall of the sample tube (10) and the inner wall of the connecting pipe (101).

4. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, 2 or 3, characterized in that: The water inlet of the first condenser (3) is connected to a water inlet pipe (11), the water inlet pipe (11) is connected to a second regulating valve (12), the second regulating valve (12) is connected to a data acquisition control unit (6), and the data acquisition control unit (6) controls the opening of the second regulating valve (12) according to the pressure difference between the first pressure gauge (7) and the second pressure gauge (8) and the temperature of the thermometer (9).

5. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, 2 or 3, characterized in that: The gas outlet of the first condenser (3) is connected to the second condenser (13), and the liquid outlet of the second condenser (13) is connected to the reflux pipe (4).

6. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 5, characterized in that: The power of the first condenser (3) is greater than the power of the second condenser (13).

7. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, 2 or 3, characterized in that: The bottom of the distillation tower (1) is connected to a reboiler (19), the reboiler (19) is connected to a heat medium inlet pipe (14), the heat medium inlet pipe (14) is connected to a third regulating valve (15), the third regulating valve (15) is connected to a data acquisition control unit (6), and the data acquisition control unit (6) controls the opening of the third regulating valve (15) according to the pressure difference between the first pressure gauge (7) and the second pressure gauge (8) and the temperature of the thermometer (9).

8. A distillation tower top vapor pressure difference online detection product concentration control system according to claim 1, 2 or 3, characterized in that: The reflux pipe (4) is connected to a liquid outlet pipe (16), the liquid inlet of the liquid outlet pipe (16) is located between the first regulating valve (5) and the first condenser (3), the liquid outlet of the liquid outlet pipe (16) is connected to a plurality of tanks to be inspected (17), the tops of all the tanks to be inspected (17) are connected to a balancing pipe (18), and the other end of the balancing pipe (18) is connected to a vacuum pump or an exhaust structure.

9. A method for controlling product concentration by online detection of vapor pressure difference at the top of a distillation tower, characterized in that: The method comprises the following steps: Step 1: Collect distillation data of different products through experiments, and store the data in a data acquisition control unit (6) to form a database; Step 2: During the product distillation process, the steam pressure in the sample tube (10) is measured by the first pressure gauge (7) as described in claims 1 to 8 above, the steam pressure at the top of the distillation tower (1) is measured by the second pressure gauge (8), and the steam temperature at the top of the distillation tower (1) is measured by the thermometer (9), and the data are transmitted to the data acquisition control unit (6); Step 3: The data acquisition control unit (6) identifies and calculates the collected data and compares it with the data in the database. When the pressure difference is within the qualified range, the distillation tower (1) operates normally and the concentration of the product at the top of the distillation tower (1) meets the requirements. When the pressure difference is outside the qualified range and the concentration of the product at the top of the distillation tower (1) does not meet the requirements, the data acquisition control unit (6) sends a signal to adjust the first regulating valve (5), the second regulating valve (12) and the third regulating valve (15) individually or jointly to return the pressure difference to a reasonable range.

10. The method for controlling product concentration by online detection of vapor pressure difference at the top of a distillation tower according to claim 9, characterized in that: In step 1, according to Raoult's law and Dalton's law of partial pressure, as long as the saturated vapor pressure P of pure components A and B is A 0 and P B 0 The relationship between liquid phase composition and bubble point is known, and the molar fraction of liquid phase A component X is directly calculated. A and the mole fraction of component B X B , P is the steam pressure at the top of the distillation tower (1), Since the gas and liquid are in equilibrium when the top of the distillation tower (1) boils, the quantitative relationship between the gas phase composition and the dew point can also be determined. The molar fraction Y of the gas phase component A can also be calculated by knowing the dew point. A and the mole fraction Y of component B B , The relationship between the saturated vapor pressures of pure components A and B at different temperatures is usually expressed by the Antoine equation: Where a, d, and c are the antoine constants of the component. Commonly used a, d, and c can be found in the Handbook of Basic Chemical Materials, and t is the temperature.

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