High-efficiency alkali washing device for recovering monomers from polyvinyl chloride polymerization kettle by suspension method

Abstract

The invention relates to the technical field of chemical production processes, and particularly discloses an efficient alkali washing device for recycling monomers from a suspension method polyvinyl chloride polymeric kettle, which comprises a polymeric kettle, a valve F10 and a pipeline C are arranged at the bottom of the polymeric kettle, the top of the polymeric kettle is connected with a foam catcher through a pipeline G1, the top of the foam catcher is connected with an alkali washing tower through a pipeline G3, and the alkali washing tower is connected with a pipeline G4 through a pipeline G5. The top of the alkaline washing tower is connected with a gas holder through a pipeline G4, the gas holder is connected with a water separator through a pipeline G5, the water separator is connected with an alkaline liquor circulating tank through a pipeline G11, the top of the alkaline liquor circulating tank is provided with a pipeline J1 and a valve F8, the bottom of the alkaline liquor circulating tank is connected with the alkaline washing tower through a pipeline J3, and the pipeline J3 is provided with an alkaline liquor circulating pump. The bottom of the alkaline washing tower is connected with the alkaline liquor circulating tank through a pipeline J2, a pipeline J4 is arranged on one side of the bottom of the alkaline liquor circulating tank, a valve F11 is arranged on the pipeline J4, and the efficient alkaline washing technology of the suspension method polyvinyl chloride polymerization kettle recycled monomer is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production processes, and in particular to a high-efficiency alkali washing device for recovering monomers from a suspension-process polyvinyl chloride polymerization kettle. Background Art

[0002] In the current suspension polyvinyl chloride production process, a polymerization kettle is mainly used to add monomers, desalted water and various auxiliary materials and small additives for reaction. The polyvinyl chloride slurry after the reaction is completed is transported to the subsequent stripping device through a discharge pump to remove residual vinyl chloride, and then enters the drying system for drying and air conveying packaging.

[0003] In this production process, especially when using processes such as suspension polymerization, some monomers in the polymerization kettle are not completely converted into polymers, but exist in the polymerization reaction mixture in the form of unreacted gas. At the same time, in the stripping process, the residual vinyl chloride monomer is efficiently removed from the PVC slurry. Since vinyl chloride is a toxic and volatile organic compound, the residue in the PVC product not only affects the performance of the product, but also poses a threat to the environment and human health. Therefore, in order to improve the utilization rate of monomers, reduce the waste of raw materials, reduce production costs and reduce environmental pollution, the monomer recovery step in the polymerization kettle and the stripping tower becomes particularly important. Usually, a recovery system is set up in the polymerization device to recycle vinyl chloride.

[0004] During the operation of the recovery system, the pH value of vinyl chloride was low. The main reasons are as follows. If the catalyst or initiator used in the polymerization reaction is not completely neutralized or removed, acid residues will be left in the recovered monomer, resulting in a decrease in pH value; some monomers may have a certain acidity, or acidic by-products may be generated during the reaction, affecting the pH value of the recovered monomer; metal parts of the polymerization equipment or recovery system (such as iron, copper, etc.) may release metal ions due to corrosion, and these metal ions may react with water to generate acidic substances, thereby reducing the pH value; if the pH value of the cooling water or washing water used is low, it may also affect the pH value of the recovered monomer; at the same time, the low pH value of the recovered monomer will have the following effects on continuous production: 1. A low pH value of the recycled monomer will accelerate the corrosion of the metal equipment and pipelines in the recycling system, shorten the life of the equipment, and increase maintenance costs.

[0005] 2. If the acidic substances in the recycled monomers are not effectively removed, re-putting them into production may cause performance problems of the new polymer products, such as color changes, decreased mechanical properties, etc.

[0006] 3. The pH value deviating from the optimal range may affect the efficiency of subsequent processes, such as affecting the efficiency of the initiator and reducing the speed and selectivity of the polymerization reaction. Summary of the invention

[0007] The purpose of the present invention is to provide a high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle in view of the problems existing in the above-mentioned prior art.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: A high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle comprises a polymerization kettle, a valve F10 and a pipeline C are provided at the bottom of the polymerization kettle, a foam collector is connected to the top of the polymerization kettle via a pipeline G1, a alkali washing tower is connected to the top of the foam collector via a pipeline G3, a gas holder is connected to the top of the alkali washing tower via a pipeline G4, the gas holder is connected to a water separator via a pipeline G5, the water separator is connected to an alkali liquid circulation tank via a pipeline G11, a pipeline J1 and a valve F8 are provided at the top of the alkali liquid circulation tank, the bottom of the alkali liquid circulation tank is connected to the alkali washing tower via a pipeline J3, an alkali liquid circulation pump is provided on the pipeline J3, the bottom of the alkali washing tower is connected to the alkali liquid circulation tank via a pipeline J2, a pipeline J4 is provided on one side of the bottom of the alkali liquid circulation tank, and a valve F11 is provided on the pipeline J4.

[0009] Preferably, the top of the water separator is connected to a recovery compressor via a pipeline G6, the recovery compressor is connected in series with a primary condenser and a secondary condenser via pipelines G7 and G8, the bottoms of the primary condenser and the secondary condenser are connected to a recovery monomer tank via a pipeline G12, a pipeline and a valve F7 are provided at the bottom of the recovery monomer tank, the recovery monomer tank is connected to a recovery monomer pump via a pipeline G14, the liquid outlet of the recovery monomer pump is connected to the polymerization kettle via a pipeline G14, and a valve F4 is provided on the pipeline G14.

[0010] Preferably, the bottom of the secondary condenser is connected to a pressure swing adsorption device through a pipeline, the top of the pressure swing adsorption device is connected to the gas cabinet through a pipeline G9, a valve F9 is provided on the pipeline G9, and a pipeline G10 is provided on one side of the pressure swing adsorption device.

[0011] Preferably, a pressure gauge P1 and a pressure gauge P2 are respectively provided on the gas phase outlet pipes of the first-stage condenser and the second-stage condenser, and pipes are respectively provided at the bottoms of the first-stage condenser and the second-stage condenser, and regulating valves F5 and F6 are respectively provided on the pipes, and the pressure gauge P1, the pressure gauge P2, the regulating valve F5 and the regulating valve F6 are connected to a PLC controller via signals.

[0012] Preferably, a pressure gauge P is provided on the top of the polymerization kettle, a regulating valve F1 and a pressure gauge P3 are sequentially provided on the pipeline G1, a bypass pipeline G2 is provided on the pipeline G1, a regulating valve F2 and a recovery vacuum pump are sequentially provided on the pipeline G2, a liquid outlet of the recovery vacuum pump is connected to the position of the regulating valve F1 of the pipeline G1 through a pipeline, and the regulating valve F1, the regulating valve F2, the pressure gauge P, the recovery pressure gauge P3 and the recovery vacuum pump are connected to a PLC controller through signals.

[0013] Preferably, the bottom of the foam collector is connected to a foam pump via a pipeline, the foam pump is connected to a monomer tank via a pipeline G15, the bottom of the monomer tank is connected to a monomer pump via a pipeline G16, the liquid outlet of the monomer pump is connected to a pipeline G18 via a pipeline G17, the end of the pipeline G18 is connected to the top of the polymerization kettle, and a valve F4 is provided at the connection between the pipelines G17 and G18.

[0014] The beneficial effects of the present invention are: The polymerization kettle of the present invention is a 108m³ vertical reactor, which is the core equipment for realizing efficient and controllable polymerization reaction. The kettle is equipped with temperature and pressure sensors and corresponding control systems to monitor the reaction conditions in real time to ensure the safety and stability of the reaction process. The monomers of the polymerization kettle are added from the top of the polymerization kettle, and a discharge port and a regulating valve are arranged at the bottom, and a recovery pipeline is arranged at the top of the polymerization kettle.

[0015] A recovery pipeline is set at the outlet of the polymerization kettle to the foam trap, and a recovery vacuum pump is set in parallel on the recovery pipeline of the polymerization kettle to the foam trap. The principle adopted is that in the initial stage of polymerization kettle recovery, due to the high pressure in the kettle, the vinyl chloride monomer is recovered to the foam trap by relying on the pressure in the kettle. In the later stage of recovery, as the pressure of the polymerization kettle decreases, the recovery vacuum pump is started to vacuum and recover to the foam trap. The regulating valve on the recovery pipeline, the recovery vacuum pump inlet regulating valve, the polymerization kettle pressure, and the PLC controller are interlocked. During the recovery process, when the polymerization kettle pressure is less than 0.2Mpa, the recovery pipeline regulating valve is closed, the recovery vacuum pump inlet regulating valve is opened, and the recovery vacuum pump is started. When the polymerization kettle pressure is ≤-60Kpa, the recovery vacuum pump stops running, the recovery pipeline regulating valve and the recovery vacuum pump inlet regulating valve are closed, and the recovery is completed.

[0016] The foam collector is mainly used to remove excess foam or vinyl chloride droplets suspended in the gas during the vinyl chloride recovery process to maintain the stability of the process and improve product quality. It is usually made of porous materials (such as metal mesh, fiber membrane or ceramic, etc.), which have a certain pore structure. When the gas containing foam or droplets passes through the collector, the foam or droplets hit and adhere to the surface of the collector or are intercepted in the pores due to inertia, diffusion force and surface tension. In the area where the gas flow slows down, the droplets settle and gather into larger droplets due to gravity, and finally settle at the bottom of the collector. The foam collector is equipped with a level gauge and a foam pump at the bottom. The deposited liquid vinyl chloride monomer is pumped to the monomer tank for reuse through the foam pump.

[0017] A pipeline is set at the outlet of the foam collector to connect to the alkali washing tower, which is mainly used to remove the acidic gas and impurities carried by the recycled vinyl chloride, and ensure that the pH value of the recycled vinyl chloride monomer is controlled between 6 and 9 through chemical neutralization reaction. The alkali washing tower is equipped with an air inlet, a packing layer, a spray layer, a demisting layer and a top outlet from bottom to top.

[0018] The air inlet of the alkali washing tower is the position where the recovered vinyl chloride enters the tower and is set at the bottom of the tower. The packing layer needs to be designed with Raschig rings, Pall rings, etc. to increase the gas-liquid contact area and promote the mass transfer process. The spray layer is provided with nozzles for evenly spraying alkali solution onto the packing layer to ensure that the alkali solution and the recovered vinyl chloride gas are fully in contact and reacted. The demisting layer recovers the droplets carried by vinyl chloride through a demister (such as a wire mesh demister) to prevent the alkali solution from being discharged with the gas and keep the recovered vinyl chloride gas clean. The top outlet of the alkali washing tower is convenient for the purified vinyl chloride gas to be discharged from here. The design operating pressure of the alkali washing tower is in the range of 0.1Mpa-0.5Mpa. This pressure can be achieved by adjusting the outlet pressure of the polymerization kettle recovery regulating valve and the recovery vacuum pump.

[0019] The alkali washing tower is equipped with an alkali liquid circulation tank. Alkali distribution pipelines and valves are set on the top of the alkali liquid circulation tank. An alkali liquid circulation pump is set at the bottom of the alkali liquid circulation tank. The alkali liquid in the circulation tank is pumped to the top of the alkali washing tower. After spraying, it flows into the alkali liquid circulation tank from the bottom of the tower for recycling. A gas phase balance pipe must be set between the alkali liquid circulation tank and the top of the alkali tower to facilitate the normal alkali washing cycle. The contact reaction between the recovered vinyl chloride gas and the alkali liquid can ensure that the pH value of the vinyl chloride at the outlet of the alkali washing tower is stable between 6 and 9. The designed alkali liquid concentration is required to be 5%-15%. If the alkali concentration is lower than 5%, the alkali liquid needs to be replaced.

[0020] The top outlet of the alkali washing tower is connected to the recovery gas holder through a pipeline. The gas holder is a wet single-section gas holder. The vinyl chloride gas holder serves as an intermediate storage device, which can balance the difference between the vinyl chloride recovery volume and the subsequent recovery compressor suction volume. When the recovery volume exceeds the compressor suction volume, the gas holder liquid level rises. When the recovery compressor suction volume is greater than the recovery volume, the gas holder liquid level drops, thereby ensuring the continuity and stability of the production process.

[0021] The vinyl chloride gas holder is a wet gas holder, which results in a higher moisture content in the exported recycled vinyl chloride. A water separator is installed after the recovery gas holder is connected through a pipeline. Its main function is to separate and remove moisture from the vinyl chloride gas flow, ensure the dryness of the gas, ensure the moisture content of the recovered vinyl chloride monomer, and improve the gas utilization efficiency and the overall reliability of the system.

[0022] A height difference is set between the water separator and the alkali liquid circulation tank. The on-site height of the water separator is higher than the top of the alkali liquid circulation tank. By setting a U-shaped liquid seal pipe at the bottom of the water separator, the water collected in the water separator flows to the alkali liquid circulation tank through gravity sedimentation.

[0023] A recovery compressor is set at the outlet of the water separator to suck in the vinyl chloride gas and compress it into a smaller volume. In this process, the vinyl chloride gas molecules are forced to move closer, and the pressure and temperature of the vinyl chloride gas rise accordingly. The purpose of compression is to increase the pressure of the vinyl chloride gas, make it easier to liquefy, and prepare for the subsequent condensation recovery. The designed outlet pressure of the recovery compressor is 0.4Mpa-0.6Mpa, which can be achieved through the interlocking circulating water and 5℃ water regulating valves of the first and second condenser outlet pressure transmitters.

[0024] The recovery compressor is designed with a water ring compressor, which fully utilizes the advantages of the water ring compressor, such as simple structure, reliable operation, easy maintenance, environmental protection, oil-free, and strong adaptability, to compress the vinyl chloride gas phase from the water separator to facilitate subsequent condensation recovery.

[0025] The outlet of the recovery compressor is equipped with a primary condenser and a secondary condenser in sequence. The condenser is a shell-and-tube heat exchanger, and the high-temperature and high-pressure vinyl chloride at the outlet of the compressor passes through the primary condenser and the secondary condenser tubes in sequence. The vinyl chloride monomer is condensed by introducing circulating water and 5°C water into the shell of the primary condenser and the secondary condenser. The condensate flows into the recovery monomer tank through the bottom of the primary condenser and the secondary condenser. After the uncondensed gas is adsorbed by the pressure swing adsorption device, the vinyl chloride is recovered to the gas cabinet for reuse, and the inert gas is discharged through the pressure swing adsorption discharge port in compliance with the standards.

[0026] Pressure swing adsorption is based on the differences in the adsorption capacity of adsorbents for different gas components and the characteristic that this adsorption capacity changes with pressure. The adsorption tower is filled with adsorbents with a higher affinity for vinyl chloride, and the vinyl chloride is returned to the gas holder for reuse through desorption. The unabsorbed inert gas is discharged in compliance with emission standards.

[0027] A decanter is set at the bottom of the recovery monomer tank to facilitate the sedimentation of trace water in the recovery monomer, which is discharged into the sewage treatment system manually and regularly. The monomers in the recovery monomer tank can be added to the polymerization kettle through the recovery monomer pump for repeated utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the present invention; In the figure: 1-polymerization kettle; 2-recovery vacuum pump; 3-foam collector; 4-foam pump; 5-monomer tank; 6-monomer pump; 7-gas cabinet; 8-alkali washing tower; 9-alkali solution circulation pump; 10-alkali solution circulation tank; 11-water separator; 12-recovery compressor; 13-primary condenser; 14-secondary condenser; 15-pressure swing adsorption; 16-recovery monomer tank; 17-recovery monomer pump; 18-PLC controller. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments: like Figure 1 The shown embodiment shows a high-efficiency alkali washing device for recovering monomers from a suspended polyvinyl chloride polymerization kettle, comprising a polymerization kettle 1, a valve F10 and a pipeline C being provided at the bottom of the polymerization kettle 1, a foam collector 3 being connected to the top of the polymerization kettle 1 via a pipeline G1, a alkali washing tower 8 being connected to the top of the alkali washing tower 8 via a pipeline G3, a gas holder 7 being connected to the top of the alkali washing tower 8 via a pipeline G4, a water separator 11 being connected to the gas holder 7 via a pipeline G5, a alkali liquid circulation tank 10 being connected to the water separator 11 via a pipeline G11, a pipeline J1 and a valve F8 being provided at the top of the alkali liquid circulation tank 10, the bottom of the alkali liquid circulation tank 10 being connected to the alkali washing tower 8 via a pipeline J3, a alkali liquid circulation pump 9 being provided on the pipeline J3, the bottom of the alkali washing tower 8 being connected to the alkali liquid circulation tank 10 via a pipeline J2, a pipeline J4 being provided on one side of the bottom of the alkali liquid circulation tank 10, and a valve F11 being provided on the pipeline J4. The alkali washing tower 8 is equipped with an alkali liquid circulation tank 10. An alkali preparation pipeline J1 and a valve F8 are arranged on the top of the alkali liquid circulation tank 10. An alkali liquid circulation pump 9 is arranged at the bottom of the alkali liquid circulation tank 10. The alkali liquid in the circulation tank is pumped to the top of the alkali washing tower 8 through a pipeline J3. After spraying, the alkali liquid flows from the bottom of the tower into the alkali liquid circulation tank 10 for recycling. The alkali preparation alkali liquid concentration is required to be 5%-15%. If the alkali concentration is lower than 5%, the alkali liquid needs to be replaced. Fresh alkali liquid can be replaced after being discharged from the pipeline J2 and the valve F11 at the bottom of the alkali liquid circulation tank. After the above operations, the pH value of vinyl chloride at the outlet of the alkali washing tower 8 can be guaranteed to be stable between 6 and 9.

[0030] The top of the water separator 11 is connected to a recovery compressor 12 through a pipeline G6, and the recovery compressor 12 is connected in series with a primary condenser 13 and a secondary condenser 14 through pipelines G7 and G8. The bottoms of the primary condenser 13 and the secondary condenser 14 are connected to a recovery monomer tank 16 through a pipeline G12. A pipeline and a valve F7 are provided at the bottom of the recovery monomer tank 16. A drainage pipeline is provided at the bottom of the recovery monomer tank, and drainage is performed by opening the valve F7 regularly. The recovery monomer tank 16 is connected to a recovery monomer pump 17 through a pipeline G14. The liquid outlet of the recovery monomer pump 17 is connected to the polymerization kettle 1 through a pipeline G14, and a valve F4 is provided on the pipeline G14.

[0031] The bottom of the secondary condenser 14 is connected to a pressure swing adsorption 15 through a pipeline. The top of the pressure swing adsorption 15 is connected to the gas cabinet 7 through a pipeline G9. A valve F9 is provided on the pipeline G9. A pipeline G10 is provided on one side of the pressure swing adsorption 15.

[0032] Pressure gauges P1 and P2 are respectively provided on the gas phase outlet pipelines of the primary condenser 13 and the secondary condenser 14. Pipes are respectively provided at the bottom of the primary condenser 13 and the secondary condenser 14. Regulating valves F5 and F6 are respectively provided on the pipelines. The pressure gauges P1, P2, regulating valves F5 and F6 are respectively connected to the PLC controller 18 through signals. A pipeline G5 is provided at the outlet of the gas cabinet 7 to connect to the inlet of the water separator 11. The bottom of the water separator 6 is connected to the alkali liquid circulation tank 10 after a U-shaped liquid seal is provided through the pipeline G11. The outlet of the water separator 11 is connected to the inlet of the recovery compressor 12 through the pipeline G6, and the outlet of the recovery compressor 12 is connected to the pipelines of the primary condenser 13 and the secondary condenser 14 in sequence through the pipelines G7 and G8. Pressure gauges P1 and P2 are respectively arranged on the gas phase outlet pipelines of the primary condenser 13 and the secondary condenser 14. The PLC controller 18 is interlocked with P1, P2, the circulating water regulating valve F5, and the 5°C water regulating valve F6 (interlocking 2), and the system automatically adjusts the opening of the F5 and F6 valves to control the recovery system pressure to be stable at 0.4Mpa-0.6Mpa.

[0033] A pressure gauge P is provided on the top of the polymerization kettle 1, a regulating valve F1 and a pressure gauge P3 are provided on the pipeline G1 in sequence, a bypass pipeline G2 is provided on the pipeline G1, a regulating valve F2 and a recovery vacuum pump 2 are provided on the pipeline G2 in sequence, and the liquid outlet of the recovery vacuum pump 2 is connected to the pipeline G1 after the regulating valve F1 is located through a pipeline, and the regulating valve F1, regulating valve F2, pressure gauge P, recovery pressure gauge P3 and recovery vacuum pump 2 are connected to the PLC controller 18 through signals. The regulating valves F1, F2, pressure gauge P, recovery pressure gauge P3 and recovery vacuum pump 2 are interlocked through the PLC controller 18, and the interlocking logic is as follows: 1. The recovery pressure gauge P3 is pressure-interlocked with the regulating valve F1 and the regulating valve F2 through the PLC controller 18, and the operating pressure of the alkali washing tower is controlled to be 0.1Mpa-0.5Mpa through the regulating valve switch.

[0034] 2. During the recovery process of the polymerization kettle, when the pressure P of the polymerization kettle 1 is less than 0.2Mpa, the recovery pipeline regulating valve F1 is closed, the recovery vacuum pump 2 inlet regulating valve F2 is opened, and the recovery vacuum pump 2 starts to run. When the polymerization kettle pressure P is equal to -60Kpa, the recovery vacuum pump 2 stops running, the recovery pipeline G1 regulating valve F1 and the recovery vacuum pump 2 inlet regulating valve F2 are closed, and the recovery is completed. Multiple polymerization kettles can interlock the recovery pipeline related instruments with the PLC control system and the recovery vacuum pump 2.

[0035] The bottom of the foam trap 3 is connected to a foam pump 4 through a pipeline, and the foam pump 4 is connected to a monomer tank 5 through a pipeline G15. The bottom of the monomer tank 5 is connected to a monomer pump 6 through a pipeline G16. The liquid outlet of the monomer pump 6 is connected to a pipeline G18 through a pipeline G17. The end of the pipeline G18 is connected to the top of the polymerization kettle 1. A valve F4 is provided at the connection between the pipeline G17 and the pipeline G18. The pipeline G1 is connected to the foam trap 3. The liquid vinyl chloride deposited at the bottom of the foam trap 3 is transported to the monomer tank 5 through the pipeline G15 by setting the foam pump 5. The bottom outlet of the monomer tank 5 is provided with a pipeline G16 connected to the monomer pump 6. The outlet of the monomer pump 6 is provided with a pipeline G17, and is sent to the monomer feeding pipeline G18 of the polymerization kettle after passing through the regulating valve F3. The foam trap 3 is provided with a pipeline G3 to the feed port of the alkali washing tower 8. The top outlet of the alkali washing tower 8 is connected to the gas cabinet 7 through a pipeline G4 and a valve F10.

[0036] The uncondensed gas at the gas phase outlet of the secondary condenser 14 is transported to the pressure swing adsorption system 15 through a pipeline, and the adsorbed vinyl chloride gas is transported to the inlet of the gas cabinet 7 through a pipeline G9 and a valve F9 to merge with the pipeline G4, so that the vinyl chloride is recovered and utilized, and the unabsorbed inert gas is discharged in compliance with the standards through a pipeline G10.

[0037] The present invention is achieved by the following operation method: 1. Open all valves related to the system and connect nitrogen to conduct pressure test and leak test on the whole system. The pressure test is qualified at 1.0Mpa.

[0038] 2. Use nitrogen to replace the entire system and take samples at multiple points. The oxygen content is required to be ≤0.2%.

[0039] 3. Open valve F8 and use pipeline J1 to configure alkali solution in alkali solution circulation tank 10. The alkali solution concentration is required to be 5%-15%, and the liquid level is controlled at 70%-80%.

[0040] 4. Turn on the alkali solution circulation pump 9 to establish circulation between the alkali washing tower 8 and the alkali solution circulation tank 10.

[0041] 5. After the polymerization kettle starts to discharge materials and valve F10 is opened, the polymerization kettle is recovered and put into use.

[0042] 6. When the liquid level in the gas tank 7 reaches 65%, start the recovery compressor 12, put the compressor pressure control interlock into use, and start the pressure swing adsorption device.

[0043] 7. When the liquid level in the foam collector 3 reaches 60%, start the foam pump 4 to transport the liquid monomer to the monomer tank 5.

[0044] 8. Observe the liquid level of the monomer recovery tank 16, and promptly open the monomer recovery pump 17 to add the monomer in the monomer recovery tank 16 to other polymerization reactors to be fed.

[0045] 9. Timely check the pH value of vinyl chloride at the outlet of the alkali tower, regularly drain the bottom of the monomer recovery tank 16, and timely check the pressure swing adsorption air discharge index.

[0046] By using the above technical invention and operation, a highly efficient alkaline washing process for recovering monomers from a suspended polyvinyl chloride polymerization kettle can be realized, which can effectively eliminate the problems arising from the above background.

Claims

1. An efficient alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle, comprising a polymerization kettle, characterized in that: A valve F10 and a pipeline C are provided at the bottom of the polymerization kettle (1); a foam collector (3) is connected to the top of the polymerization kettle (1) via a pipeline G1; a caustic washing tower (8) is connected to the top of the foam collector (3) via a pipeline G3; a gas holder (7) is connected to the top of the caustic washing tower (8) via a pipeline G4; the gas holder (7) is connected to a water separator (11) via a pipeline G5; the water separator (11) is connected to an alkali liquid circulation tank (10) via a pipeline G11; a pipeline J1 and a valve F8 are provided at the top of the alkali liquid circulation tank (10); the bottom of the alkali liquid circulation tank (10) is connected to the alkali washing tower (8) via a pipeline J3; an alkali liquid circulation pump (9) is provided on the pipeline J3; the bottom of the alkali washing tower (8) is connected to the alkali liquid circulation tank (10) via a pipeline J2; a pipeline J4 is provided on one side of the bottom of the alkali liquid circulation tank (10); a valve F11 is provided on the pipeline J4.

2. The high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle according to claim 1, characterized in that: The top of the water separator (11) is connected to a recovery compressor (12) via a pipeline G6; the recovery compressor (12) is connected in series to a primary condenser (13) and a secondary condenser (14) via pipelines G7 and G8; the bottoms of the primary condenser (13) and the secondary condenser (14) are connected to a recovery monomer tank (16) via a pipeline G12; a pipeline and a valve F7 are provided at the bottom of the recovery monomer tank (16); the recovery monomer tank (16) is connected to a recovery monomer pump (17) via a pipeline G14; the liquid outlet of the recovery monomer pump (17) is connected to the polymerization kettle (1) via a pipeline G14; and a valve F4 is provided on the pipeline G14.

3. The high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle according to claim 1 or 2, characterized in that: The bottom of the secondary condenser (14) is connected to a pressure swing adsorbent (15) via a pipeline. The top of the pressure swing adsorbent (15) is connected to a gas cabinet (7) via a pipeline G9. A valve F9 is provided on the pipeline G9. A pipeline G10 is provided on one side of the pressure swing adsorbent (15).

4. The high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization kettle according to claim 2, characterized in that: A pressure gauge P1 and a pressure gauge P2 are respectively provided on the gas phase outlet pipelines of the first-stage condenser (13) and the second-stage condenser (14); pipelines are respectively provided at the bottoms of the first-stage condenser (13) and the second-stage condenser (14); regulating valves F5 and F6 are respectively provided on the pipelines; the pressure gauge P1, the pressure gauge P2, the regulating valve F5 and the regulating valve F6 are connected to a PLC controller (18) via signals.

5. The high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization reactor according to claim 1, characterized in that: A pressure gauge P is provided on the top of the polymerization kettle (1), a regulating valve F1 and a pressure gauge P3 are provided on the pipeline G1 in sequence, a bypass pipeline G2 is provided on the pipeline G1, a regulating valve F2 and a recovery vacuum pump (2) are provided on the pipeline G2 in sequence, a liquid outlet of the recovery vacuum pump (2) is connected to the pipeline G1 after the regulating valve F1 is located via a pipeline, and the regulating valve F1, the regulating valve F2, the pressure gauge P, the recovery pressure gauge P3 and the recovery vacuum pump (2) are connected to a PLC controller (18) via signals.

6. The high-efficiency alkali washing device for recovering monomers from a suspension polyvinyl chloride polymerization reactor according to claim 1, characterized in that: The bottom of the foam collector (3) is connected to a foam pump (4) via a pipeline, the foam pump (4) is connected to a monomer tank (5) via a pipeline G15, the bottom of the monomer tank (5) is connected to a monomer pump (6) via a pipeline G16, the liquid outlet of the monomer pump (6) is connected to a pipeline G18 via a pipeline G17, the end of the pipeline G18 is connected to the top of the polymerization kettle (1), and a valve F4 is provided at the connection between the pipeline G17 and the pipeline G18.

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