Method and apparatus for the recovery and separation of vinyl chloride and vinyl acetate

Abstract

This invention relates to the field of vinyl chloride-vinyl acetate resin production and recycling technology, specifically a method and apparatus for the recovery and separation of vinyl chloride and vinyl acetate. The former uses unreacted vinyl chloride and vinyl acetate from vinyl chloride-vinyl acetate resin production as raw materials, employing high-temperature low-pressure desorption, filtration, compression condensation separation, and cryogenic condensation. It utilizes the difference in boiling points between vinyl chloride and vinyl acetate to achieve separation, and leverages the immiscibility of vinyl acetate with water and its density difference to separate water from the vinyl acetate. The latter includes a slurry tank, a foam trap, a gas phase filter, a gas-liquid separator, an intermediate vinyl acetate storage tank, a vinyl chloride condenser, a vinyl acetate recovery storage tank, and a vinyl chloride recovery storage tank. This invention features a simple process, convenient operation, high automation, and rapid recovery and separation of vinyl chloride and vinyl acetate, enabling resource recycling. It is safe, low-cost, simple, and efficient.

Description

Technical Field

[0001] This invention relates to the field of vinyl chloride resin production and recycling technology, and is a method and apparatus for the recovery and separation of vinyl chloride and vinyl acetate. Background Technology

[0002] The production of vinyl chloride-vinyl acetate resin can be divided into suspension polymerization, solution polymerization, and solvent polymerization. Among them, suspension polymerization has the advantages of lower production cost and mature production technology, and most domestic manufacturers of vinyl chloride-vinyl acetate copolymer resin use this method. Its feeding system can be modified based on general resin production to achieve the production of vinyl chloride-vinyl acetate resin. However, the recovery of vinyl chloride and vinyl acetate that did not participate in the reaction, especially the recovery and utilization of vinyl acetate, has always been a difficult problem in the production of vinyl chloride-vinyl acetate resin.

[0003] In actual production, the recovery rate of vinyl acetate is low, with most of it entering the wastewater treatment system. This not only poses a significant threat to the environment, but also, as the amount of vinyl acetate in the wastewater system increases, vinyl acetate accumulates in the wastewater storage tank. This causes the small amount of chlorovinyl acetate resin carried in the drainage from the polymerization reactor to swell, resulting in blockage of the wastewater system. Moreover, as continuous production continues, the blockage becomes more severe, seriously affecting the stable and continuous production of the equipment. Summary of the Invention

[0004] This invention provides a method and apparatus for the recovery and separation of vinyl chloride and vinyl acetate, which overcomes the shortcomings of the prior art. It can effectively solve the problems of difficulty in recovering and separating vinyl chloride and vinyl acetate in the production process of vinyl chloride and vinyl acetate, swelling and clogging of pipelines caused by vinyl chloride and vinyl acetate resin in wastewater, and environmental pollution.

[0005] One of the technical solutions of this invention is achieved through the following measures: a method for the recovery and separation of vinyl chloride and vinyl acetate, comprising the following steps: First, the slurry in the slurry tank is heated and recovered to remove unreacted gaseous vinyl chloride and vinyl acetate from the slurry; Second, the removed gaseous vinyl chloride, vinyl acetate, and water vapor are sequentially passed through a foam trap and a gas phase filter to remove a small amount of resin particles entrained in the gas phase; Third, the gas phase mixture after removing the resin particles enters a compressor for compression, and the compressed gas phase mixture undergoes gas-liquid separation in a gas-liquid separator, where the higher-boiling-point vinyl acetate and water vapor are liquefied. Subsequently, the liquid vinyl acetate and water accumulate in the lower part of the gas-liquid separator, while the gaseous vinyl chloride, with its lower boiling point, accumulates at the top of the gas-liquid separator. In the fourth step, the gaseous vinyl chloride is discharged from the top of the gas-liquid separator into the vinyl chloride condenser, where it is cooled and then sent to the vinyl chloride recovery storage tank for reuse. Of the liquid vinyl acetate and water, the denser water settles at the bottom of the gas-liquid separator and is discharged to the wastewater treatment system, while the relatively less dense vinyl acetate floats on top of the water and is discharged to the intermediate vinyl acetate storage tank after reaching the set liquid level. In the fifth step, the vinyl acetate undergoes further sedimentation and separation in the intermediate vinyl acetate storage tank to remove water, and then is discharged to the vinyl acetate recovery storage tank for reuse.

[0006] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0007] In the first step above, the temperature of the slurry tank is 70℃ to 75℃, and the pressure is -0.02MPa to -0.01MPa.

[0008] In the third step above, the gas mixture is compressed to a pressure of 0.2 MPa to -0.4 MPa.

[0009] In the fourth step above, the vapor-phase vinyl chloride is cooled down by 9°C to 11°C in the vinyl chloride condenser.

[0010] The second technical solution of the present invention is achieved through the following measures: an apparatus for implementing a method for recovering and separating vinyl chloride and vinyl acetate, comprising a slurry tank, a foam trap, a gas phase filter, a gas-liquid separator, an intermediate vinyl acetate storage tank, a vinyl chloride condenser, a vinyl acetate recovery storage tank, and a vinyl chloride recovery storage tank. A slurry feed pipeline is fixedly connected to the top inlet of the slurry tank; a foam feed pipeline is fixedly connected to the top outlet of the slurry tank and the upper inlet of the foam trap; a gas phase filter feed pipeline is fixedly connected to the top outlet of the foam trap and the upper inlet of the gas phase filter; and a foam discharge pipeline is fixedly connected to the bottom outlet of the foam trap and the upper inlet of the slurry tank. A gas-liquid separator feed line is fixedly connected between the lower outlet of the gas-liquid separator and the upper inlet of the gas-liquid separator. A compressor is fixedly installed on the gas-liquid separator feed line. A condenser feed line is fixedly connected between the top outlet of the gas-liquid separator and the top inlet of the vinyl chloride condenser. A vinyl chloride recovery line is fixedly connected between the bottom outlet of the vinyl chloride condenser and the top inlet of the vinyl chloride recovery storage tank. A gas-liquid separator overflow line is fixedly connected between the upper outlet of the gas-liquid separator and the top inlet of the vinyl acetate intermediate storage tank. A vinyl acetate recovery line is fixedly connected between the upper outlet of the vinyl acetate intermediate storage tank and the top inlet of the vinyl acetate recovery storage tank. A gas-liquid separator drain line is fixedly connected to the bottom outlet of the gas-liquid separator.

[0011] The following are further optimizations and / or improvements to the second technical solution of the above invention:

[0012] The bottom outlet of the aforementioned slurry tank is fixedly connected to a slurry discharge pipeline, and the gas-liquid separation drainage pipeline is fixedly connected to the bottom outlet of the vinyl acetate intermediate storage tank via an intermediate storage tank drainage pipeline.

[0013] The foam trap is equipped with a filter screen at the upper inlet and a spray device at the top, with a spray pipeline fixedly connected to the inlet of the spray device.

[0014] The gas-liquid separator is equipped with a first remote density meter and a first remote level meter from top to bottom, and the vinyl acetate intermediate storage tank is equipped with a second remote density meter and a second remote level meter from top to bottom.

[0015] A first automatic control valve is fixedly installed on the gas-liquid separation overflow pipeline. A second automatic control valve is fixedly installed on the gas-liquid separation drainage pipeline between the gas-liquid separator and the intermediate storage tank drainage pipeline. A third automatic control valve is fixedly installed on the vinyl acetate recovery pipeline. A fourth automatic control valve is fixedly installed on the intermediate storage tank drainage pipeline. An interlock is provided between the first automatic control valve and the first remote level gauge. An interlock is provided between the second automatic control valve and the first remote density gauge. An interlock is provided between the third automatic control valve and the second remote level gauge. An interlock is provided between the fourth automatic control valve and the second remote density gauge.

[0016] The lower shell-side inlet of the aforementioned vinyl chloride condenser is fixedly connected to a chilled brine supply line, and the upper shell-side outlet of the vinyl chloride condenser is fixedly connected to a chilled brine return line.

[0017] The present invention features a simple process, convenient equipment operation, and a high degree of automation. It quickly realizes the recovery and separation of vinyl chloride and vinyl acetate, enabling the recycling of resources. It is safe, low-cost, simple and efficient. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the process flow of Embodiment 5 of the present invention.

[0019] The codes in the attached diagram are as follows: 1 for slurry tank, 2 for foam collector, 3 for gas phase filter, 4 for compressor, 5 for gas-liquid separator, 6 for vinyl acetate intermediate storage tank, 7 for vinyl acetate recovery storage tank, 8 for vinyl chloride condenser, 9 for vinyl chloride recovery storage tank, 10 for slurry feed line, 11 for slurry discharge line, 12 for foam feed line, 13 for foam discharge line, 14 for spray line, 15 for gas phase filter feed line, 16 for gas-liquid separation feed line, and 17 for vinyl chloride. The pipeline includes: 18 is the gas-liquid separation overflow pipeline; 19 is the vinyl acetate recovery pipeline; 20 is the gas-liquid separation drainage pipeline; 21 is the intermediate storage tank drainage pipeline; 22 is the condensate feed pipeline; 23 is the first automatic control valve; 24 is the chilled brine supply pipeline; 25 is the chilled brine return pipeline; 26 is the first remote density meter; 27 is the second remote density meter; 28 is the first remote level gauge; 29 is the second remote level gauge; 30 is the second automatic control valve; 31 is the third automatic control valve; and 32 is the fourth automatic control valve. Detailed Implementation

[0020] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art. Unless otherwise specified, the equipment and apparatus used in this invention are all well-known and commonly used equipment and apparatus in the art.

[0021] The present invention will be further described below with reference to embodiments:

[0022] Example 1: As Figure 1As shown, the method for recovering and separating vinyl chloride and vinyl acetate is carried out according to the following steps: First, the slurry in the slurry tank 1 is heated and recovered to remove the unreacted gaseous vinyl chloride and vinyl acetate from the slurry; Second, the removed gaseous vinyl chloride, vinyl acetate, and water vapor are sequentially passed through a foam trap 2 and a gas phase filter 3 to remove a small amount of resin particles entrained in the gas phase; Third, the gas phase mixture after removing the resin particles enters the compressor 4 for compression, and the compressed gas phase mixture undergoes gas-liquid separation in the gas-liquid separator 5. After the higher boiling point vinyl acetate and water vapor are liquefied, the liquid phase vinyl acetate and water... The lower-boiling-point vaporized vinyl chloride accumulates in the lower part of the gas-liquid separator 5, while the upper part of the gas-liquid separator 5 accumulates at the top. In the fourth step, the vaporized vinyl chloride is discharged from the top of the gas-liquid separator 5 into the vinyl chloride condenser 8, where it is cooled and then sent to the vinyl chloride recovery storage tank 9 for reuse. In the liquid phase, the higher-density water settles at the bottom of the gas-liquid separator 5 and is discharged to the wastewater treatment system, while the relatively lower-density vinyl acetate floats on top of the water and is discharged to the intermediate vinyl acetate storage tank 6 after reaching the set liquid level. In the fifth step, the vinyl acetate in the intermediate vinyl acetate storage tank 6 undergoes further sedimentation and separation to remove water, and then is discharged to the vinyl acetate recovery storage tank 7 for reuse.

[0023] This invention uses slurry containing unreacted vinyl chloride and vinyl acetate from the production of vinyl chloride-vinyl acetate resin as raw material. Through high-temperature and low-pressure desorption, filtration, compression condensation separation, and deep cryogenic condensation, the difference in boiling points between vinyl chloride and vinyl acetate is utilized to separate vinyl chloride and vinyl acetate. Furthermore, the immiscibility of vinyl acetate with water and the density difference are used to achieve stratification, thereby separating water and vinyl acetate from vinyl acetate.

[0024] Example 2: As an optimization of the above examples, such as Figure 1 As shown, in the first step, the temperature of the slurry tank 1 is 70℃ to 75℃, and the pressure is -0.02MPa to -0.01MPa.

[0025] Example 3: As an optimization of the above example, in the third step, the gas phase mixture is compressed to a pressure of 0.2 MPa to -0.4 MPa.

[0026] Example 4: As an optimization of the above example, in the fourth step, the vapor-phase vinyl chloride is cooled down by 9°C to 11°C in the vinyl chloride condenser 8.

[0027] Example 5: Figure 1As shown, the apparatus for implementing the method of recovering and separating vinyl chloride and vinyl acetate includes a slurry tank 1, a foam trap 2, a gas phase filter 3, a gas-liquid separator 5, a vinyl acetate intermediate storage tank 6, a vinyl chloride condenser 8, a vinyl acetate recovery storage tank 7, and a vinyl chloride recovery storage tank 9. A slurry feed pipeline 10 is fixedly connected to the top inlet of the slurry tank 1. A foam feed pipeline 12 is fixedly connected between the top outlet of the slurry tank 1 and the upper inlet of the foam trap 2. A gas phase filter feed pipeline 15 is fixedly connected between the top outlet of the foam trap 2 and the upper inlet of the gas phase filter 3. A foam discharge pipeline 13 is fixedly connected between the bottom outlet of the foam trap 2 and the upper inlet of the slurry tank 1. The lower outlet of the gas phase filter 3 is connected to the gas-liquid separator... A gas-liquid separator feed line 16 is fixedly connected between the upper inlet of gas-liquid separator 5 and the upper inlet of vinyl chloride condenser 8. A compressor 4 is fixedly installed on the gas-liquid separator feed line 16. A condensation feed line 22 is fixedly connected between the top outlet of gas-liquid separator 5 and the top inlet of vinyl chloride condenser 8. A vinyl chloride recovery line 17 is fixedly connected between the bottom outlet of vinyl chloride condenser 8 and the top inlet of vinyl chloride recovery storage tank 9. A gas-liquid separator overflow line 18 is fixedly connected between the upper outlet of gas-liquid separator 5 and the top inlet of vinyl acetate intermediate storage tank 6. A vinyl acetate recovery line 19 is fixedly connected between the upper outlet of vinyl acetate intermediate storage tank 6 and the top inlet of vinyl acetate recovery storage tank 7. A gas-liquid separator drain line 20 is fixedly connected between the bottom outlet of gas-liquid separator 5.

[0028] Example 6: As an optimization of the above embodiments, such as Figure 1 As shown, the bottom outlet of the slurry tank 1 is fixedly connected to the slurry discharge pipeline 11, and the gas-liquid separation drainage pipeline 20 is fixedly connected to the bottom outlet of the vinyl acetate intermediate storage tank 6 via the intermediate storage tank drainage pipeline 21.

[0029] Example 7: As an optimization of the above embodiments, such as Figure 1 As shown, a filter screen is installed at the upper inlet of the foam trap 2, and a spray device is installed at the top of the foam trap 2. The inlet of the spray device is fixedly connected to the spray pipeline 14.

[0030] Example 8: As an optimization of the above embodiments, such as Figure 1 As shown, the gas-liquid separator 5 is equipped with a first remote density meter 26 and a first remote level meter 28 arranged sequentially from top to bottom, and the vinyl acetate intermediate storage tank 6 is equipped with a second remote density meter 27 and a second remote level meter 29 arranged sequentially from top to bottom.

[0031] Example 9: As an optimization of the above embodiments, such as Figure 1As shown, a first automatic control valve 23 is fixedly installed on the gas-liquid separation overflow pipeline 18; a second automatic control valve 30 is fixedly installed on the gas-liquid separation drainage pipeline 20 between the gas-liquid separator 5 and the intermediate storage tank drainage pipeline 21; a third automatic control valve 31 is fixedly installed on the vinyl acetate recovery pipeline 19; and a fourth automatic control valve 32 is fixedly installed on the intermediate storage tank drainage pipeline 21. An interlock is provided between the first automatic control valve 23 and the first remote level gauge 28; an interlock is provided between the second automatic control valve 30 and the first remote density gauge 26; an interlock is provided between the third automatic control valve 31 and the second remote level gauge 29; and an interlock is provided between the fourth automatic control valve 32 and the second remote density gauge 27.

[0032] As needed, the gas-liquid separator 5 is equipped with a first remote density meter 26 and a first remote level meter 28. When the water level in the gas-liquid separator 5 rises above the measuring point of the first remote density meter 26, that is, when the first remote density meter 26 displays a value exceeding the set value, the program will automatically open the second automatic control valve 30 to drain the water. When the water level in the gas-liquid separator 5 drops to the set value, the second automatic control valve 30 will automatically close.

[0033] The upper part of the gas-liquid separator 5 (below the inlet of the gas-liquid separation feed line 16) is equipped with a gas-liquid separation overflow line 18, which is equipped with a first automatic control valve 23. When the liquid level of the gas-liquid separator 5 exceeds the set value of the first remote level gauge 28, the program will automatically open the first automatic control valve 23 to discharge the liquid vinyl acetate in the upper part of the gas-liquid separator 5 into the vinyl acetate intermediate storage tank 6.

[0034] Similarly, a second remote density gauge 27 and a second remote level gauge 29 are installed in the vinyl acetate intermediate storage tank 6. When the water level in the vinyl acetate intermediate storage tank 6 rises above the measuring point of the second remote density gauge 27, that is, when the second remote density gauge 27 displays a value exceeding the set value, the program will automatically open the fourth automatic control valve 32 to drain the water. When the liquid level in the gas-liquid separator 5 drops to the set value, the fourth automatic control valve 32 will automatically close.

[0035] The upper part of the vinyl acetate intermediate storage tank 6 is equipped with a vinyl acetate recovery pipeline 19, which is equipped with a third automatic control valve 31. When the liquid level of the vinyl acetate intermediate storage tank 6 exceeds the set value of the second remote level gauge 29, the program will automatically open the third automatic control valve 31 to discharge the liquid vinyl acetate in the upper part of the vinyl acetate intermediate storage tank 6 into the vinyl acetate recovery storage tank 7.

[0036] Example 10: As an optimization of the above embodiments, such as Figure 1 As shown, the lower shell-side inlet of the vinyl chloride condenser 8 is fixedly connected to a chilled brine supply line 24, and the upper shell-side outlet of the vinyl chloride condenser 8 is fixedly connected to a chilled brine return line 25.

[0037] As needed, vinyl chloride condenser 8 uses chilled brine to cool and condense the gaseous vinyl chloride.

[0038] Depending on the needs, the pipelines and equipment of the apparatus for implementing the method for recovering and separating vinyl chloride and vinyl acetate may also be equipped with conventional valves, thermometers, and pressure gauges known in the art, as required by production needs.

[0039] In summary, the present invention features a simple process, convenient equipment operation, and a high degree of automation. It rapidly achieves the recovery and separation of vinyl chloride and vinyl acetate, enabling resource recycling and possessing the characteristics of safety, low cost, simplicity, and high efficiency.

[0040] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for the recovery and separation of vinyl chloride and vinyl acetate, characterized in that... Follow these steps: The first step is to heat and recover the slurry in the slurry tank, so that the unreacted gaseous vinyl chloride and vinyl acetate are separated from the slurry. The second step involves passing the desorbed vinyl chloride, vinyl acetate, and water vapor in the gas phase through a foam trap and a gas phase filter to remove any small amount of resin particles entrained in the gas phase. The third step is to remove the resin particles from the gas phase mixture and then compress it in the compressor. The compressed gas phase mixture is then separated into gas and liquid phases in the gas-liquid separator. After the higher boiling point vinyl acetate and water vapor are liquefied, the liquid phase vinyl acetate and water accumulate in the lower part of the gas-liquid separator, while the lower boiling point gas phase vinyl chloride accumulates in the top of the gas-liquid separator. In the fourth step, the gaseous vinyl chloride is discharged from the top of the gas-liquid separator to the vinyl chloride condenser. After cooling, it is sent to the vinyl chloride recovery storage tank for reuse. The gas-liquid separator is equipped with a first remote density meter and a first remote level meter. The liquid phase consists of vinyl acetate and water, with the denser water settling at the bottom of the gas-liquid separator. When the first remote density meter reading exceeds the set value, the program will automatically open the second automatic control valve to drain the water to the wastewater treatment system. When the liquid level in the gas-liquid separator drops to the set value, the second automatic control valve will automatically close. The gas-liquid separator is equipped with a gas-liquid separation overflow pipeline with a first automatic control valve. When the liquid level in the gas-liquid separator exceeds the set value of the first remote level meter, the program will automatically open the first automatic control valve to discharge the liquid vinyl acetate in the upper part of the gas-liquid separator into the vinyl acetate intermediate storage tank. Fifth, a second remote density meter and a second remote level meter are installed in the intermediate vinyl acetate storage tank. A vinyl acetate recovery pipeline is installed at the top of the intermediate vinyl acetate storage tank, which is equipped with a third automatic control valve. Vinyl acetate, which has a relatively low density, floats on top of the water. When the second remote density meter shows a value exceeding the set value, the program will automatically open the fourth automatic control valve to drain water to the wastewater treatment system. When the liquid level in the gas-liquid separator drops to the set value, the fourth automatic control valve will automatically close. When the liquid level in the intermediate vinyl acetate storage tank exceeds the set value of the second remote level meter, the program will automatically open the third automatic control valve. After the liquid phase vinyl acetate in the upper part of the intermediate vinyl acetate storage tank is separated and the water is removed by sedimentation again, it is discharged into the vinyl acetate recovery storage tank for reuse.

2. The method for recovering and separating vinyl chloride and vinyl acetate according to claim 1, characterized in that... In the first step, the temperature of the slurry tank is 70℃ to 75℃, and the pressure is -0.02MPa to -0.01MPa.

3. The method for recovering and separating vinyl chloride and vinyl acetate according to claim 1 or 2, characterized in that... In the third step, the gas-phase mixture is compressed to a pressure of 0.2 MPa to -0.4 MPa.

4. The method for recovering and separating vinyl chloride and vinyl acetate according to claim 3, characterized in that... In the fourth step, the vaporized vinyl chloride is cooled down by 9°C to 11°C in the vinyl chloride condenser.

5. An apparatus for implementing the method for recovering and separating vinyl chloride and vinyl acetate according to any one of claims 1 to 4, characterized in that... The system includes a slurry tank, a foam trap, a gas-phase filter, a gas-liquid separator, a vinyl acetate intermediate storage tank, a vinyl chloride condenser, a vinyl acetate recovery storage tank, and a vinyl chloride recovery storage tank. A slurry feed pipeline is fixedly connected to the top inlet of the slurry tank. A foam feed pipeline is fixedly connected between the top outlet of the slurry tank and the upper inlet of the foam trap. A gas-phase filter feed pipeline is fixedly connected between the top outlet of the foam trap and the upper inlet of the gas-phase filter. A foam discharge pipeline is fixedly connected between the bottom outlet of the foam trap and the upper inlet of the slurry tank. A gas-liquid separator feed line is fixedly connected between the lower outlet of the filter and the upper inlet of the gas-liquid separator. A compressor is fixedly installed on the gas-liquid separator feed line. A condenser feed line is fixedly connected between the top outlet of the gas-liquid separator and the top inlet of the vinyl chloride condenser. A vinyl chloride recovery line is fixedly connected between the bottom outlet of the vinyl chloride condenser and the top inlet of the vinyl chloride recovery storage tank. A gas-liquid separator overflow line is fixedly connected between the upper outlet of the gas-liquid separator and the top inlet of the vinyl acetate intermediate storage tank. A gas-liquid separator overflow line is fixedly connected between the upper outlet of the vinyl acetate intermediate storage tank and the vinyl acetate... A vinyl acetate recovery pipeline is fixedly connected to the top inlet of the vinyl acetate recovery storage tank. A gas-liquid separator drainage pipeline is fixedly connected to the bottom outlet of the gas-liquid separator. A slurry discharge pipeline is fixedly connected to the bottom outlet of the slurry tank. A drainage pipeline for the intermediate vinyl acetate storage tank is fixedly connected to the gas-liquid separator drainage pipeline and the bottom outlet of the intermediate vinyl acetate storage tank. A first remote density meter and a first remote level meter are installed sequentially from top to bottom inside the gas-liquid separator. A second remote density meter and a second remote level meter are installed sequentially from top to bottom inside the intermediate vinyl acetate storage tank. A first automatic control valve is fixedly installed on the overflow pipeline; a second automatic control valve is fixedly installed on the gas-liquid separation drainage pipeline between the gas-liquid separator and the intermediate storage tank drainage pipeline; a third automatic control valve is fixedly installed on the vinyl acetate recovery pipeline; and a fourth automatic control valve is fixedly installed on the intermediate storage tank drainage pipeline. An interlock is provided between the first automatic control valve and the first remote level gauge; an interlock is provided between the second automatic control valve and the first remote density gauge; an interlock is provided between the third automatic control valve and the second remote level gauge; and an interlock is provided between the fourth automatic control valve and the second remote density gauge.

6. The apparatus according to claim 5, characterized in that... A filter screen is installed at the upper inlet of the foam trap, and a spray device is installed at the top of the foam trap. The inlet of the spray device is fixedly connected to a spray pipeline.

7. The apparatus according to claim 5 or 6, characterized in that... The lower shell-side inlet of the vinyl chloride condenser is fixedly connected to a chilled brine supply line, and the upper shell-side outlet of the vinyl chloride condenser is fixedly connected to a chilled brine return line.

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