System and method for producing polyvinyl chloride

Abstract

The invention relates to a system and a method for producing polyvinyl chloride, and belongs to the field of polyvinyl chloride production. According to the material transportation direction, the system comprises a storage configuration unit, a polymerization steam stripping unit, a vinyl chloride recovery unit, a polyvinyl chloride drying and packaging unit and a wastewater treatment unit, the polymerization stripping unit comprises a polymerization kettle, a kettle top condenser, a discharge tank, a stripping tower storage tank, a polymerization heat exchanger, a stripping tower, a stripping tower condenser and a mixing tank, and the wastewater treatment unit comprises a condensation separator, a water storage tank, a wastewater heat exchanger, a wastewater stripping tower, a wastewater stripping tower condenser and a pretreatment reactor. The kettle top condenser is arranged in the polymerization steam stripping unit, vinyl chloride generated in each link in the system is recycled, meanwhile, residual wastewater in the wastewater treatment unit is treated by using the pretreatment reactor to remove pollutants and then discharged, the vinyl chloride is recycled in the wastewater treatment process, and the wastewater treatment efficiency is improved. And the consumption of vinyl chloride is reduced.

Description

Technical Field

[0001] The invention relates to the field of polyvinyl chloride production, and in particular to a system and method for producing polyvinyl chloride. Background Art

[0002] Polyvinyl chloride (PVC) is a common plastic material that occupies an important position in the plastic industry and has been widely used in industries such as industry, agriculture, construction, electricity, automobiles, home appliances, packaging and public utilities. It is mainly obtained by polymerization of vinyl chloride (VCM) monomer. At present, in industrial production, the suspension method for preparing polyvinyl chloride is the most widely used process. In the process of preparing polyvinyl chloride by the suspension method, the vinyl chloride monomer is firstly polymerized by heating and catalysis. The vinyl chloride monomer will gradually connect to form long-chain polymer molecules during the polymerization reaction, and finally form polyvinyl chloride.

[0003] CN110078851B discloses a polyvinyl chloride suspension polymerization method, comprising the steps of: a) adding a terminator to a polyvinyl chloride suspension polymerization system to terminate the polymerization, centrifugally separating and purifying the aqueous reaction mixture of the suspension polymerization to obtain a centrifugal mother liquor; b) recycling the centrifugal mother liquor as a reaction raw material back to the polyvinyl chloride suspension polymerization system to continue polymerization; c) repeating steps a) and b) to prepare polyvinyl chloride.

[0004] CN209501640U discloses a suspension polyvinyl chloride continuous synthesis system, comprising a micro-reaction system, wherein the micro-reaction system comprises at least three stages of micro-reactors connected in series, the cross-sectional area of ​​the reaction micro-channels of the micro-reactors being 0.1-1 mm, the cross-sectional area of ​​the reaction micro-channel of the micro-reactor connected in series at the front end along the flow direction of the raw materials being smaller than the cross-sectional area of ​​the reaction micro-channels of the other micro-reactors connected in series thereafter, and the polymerization reaction is carried out in the micro-reactor.

[0005] The suspension process for producing polyvinyl chloride is already mature, but a large amount of by-products and unreacted vinyl chloride and other substances will be generated during the polymerization process. These substances need to be recycled and reused through post-processing methods to avoid pollution to the environment or harm to the safety of employees.

[0006] CN107365428A discloses a polyvinyl chloride paste resin monomer recovery system and method, comprising a polymerization kettle, a recovery gas holder and a latex storage tank, wherein the recovery gas holder is connected to the top of the polymerization kettle, the latex storage tank is connected to the bottom of the polymerization kettle, and the bottom of the polymerization kettle is also connected to a blow-off tank, the top of the blow-off tank is connected to the recovery gas holder, and the bottom of the blow-off tank is connected to the latex storage tank, thereby alleviating the technical problem that the existing micro-suspension method for preparing polyvinyl chloride paste resin monomers is carried out in the polymerization kettle, resulting in a long preparation cycle of polyvinyl chloride paste resin, low production efficiency and high cost, and achieving the technical effect of discharging the polyvinyl chloride latex mixture into the blow-off tank for recovering the vinyl chloride monomer, thereby improving the utilization rate of the polymerization kettle, shortening the production cycle of polyvinyl chloride paste resin, improving production efficiency and reducing production cost. In the existing vinyl chloride recovery process, the vinyl chloride monomer usually needs to be recovered before the next reaction can be carried out, which leads to a longer production cycle of polyvinyl chloride and low production efficiency. In addition, the method and equipment for recovering vinyl chloride are relatively complicated, the operating steps of the staff are difficult, and the production cost is high.

[0007] In summary, the suspension method for preparing polyvinyl chloride has been widely used in industry, but the problems of recovery of unreacted vinyl chloride and post-treatment of by-products in the preparation process have not been solved. The recovery and post-treatment processes are complicated, the recovery process takes a long time, and the low production efficiency is still a problem that needs to be solved urgently. Summary of the invention

[0008] In view of the above problems, the present invention provides a system and method for producing polyvinyl chloride, by-products and unreacted vinyl chloride in the reaction process are recovered through a condenser, and vinyl chloride is recovered simultaneously during the synthesis process of polyvinyl chloride, thereby improving production efficiency and shortening the reaction cycle. At the same time, the present invention also adds a wastewater treatment unit. Since vinyl chloride will still exist in the wastewater after condensation, and vinyl chloride will cause great harm to the environment after discharge, therefore, vinyl chloride is recovered during the wastewater treatment process, which reduces the consumption of vinyl chloride and ensures the environmental friendliness of the system for producing polyvinyl chloride in the present invention.

[0009] The present invention provides a system for producing polyvinyl chloride. According to the material transportation direction, the system includes a storage configuration unit, a polymerization stripping unit, a vinyl chloride recovery unit, a polyvinyl chloride drying and packaging unit, and a wastewater treatment unit; The storage configuration unit includes a desalted water tank, an additive storage tank, a fresh vinyl chloride storage tank and a recovered vinyl chloride storage tank; The polymerization stripping unit includes a polymerization kettle, a kettle top condenser, a discharge tank, a stripping tower storage tank, a polymerization heat exchanger, a stripping tower, a stripping tower condenser and a mixing tank; The vinyl chloride recovery unit includes a recovery separator, a compressor, a primary condenser and a secondary condenser; The polyvinyl chloride drying and packaging unit includes a centrifuge and a drying bed; The wastewater treatment unit includes a condensation separator, a water storage tank, a wastewater heat exchanger, a wastewater stripping tower, a wastewater stripping tower condenser and a pretreatment reactor; The additives in the additive storage tank include initiators, dispersants and buffers; The initiator is tert-butyl peroxyneodecanoate (BND) and tert-butyl peroxyneodecanoate (CND); The dispersant is polyvinyl alcohol with high alcoholysis degree and polyvinyl alcohol with low alcoholysis degree; The alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 78.5-81.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 40-45%.

[0010] Furthermore, the polyvinyl chloride drying and packaging unit also includes a cyclone separator and a bag filter.

[0011] Further, the desalted water tank includes a normal temperature desalted water tank, a high temperature desalted water tank and a low temperature desalted water tank; The normal temperature desalted water tank, the high temperature desalted water tank and the low temperature desalted water tank are all provided with a water inlet and a water outlet; Desalted water enters the water inlets of the normal temperature desalted water tank, the high temperature desalted water tank and the low temperature desalted water tank through pipelines; The low-temperature desalted water tank and the high-temperature desalted water tank are both equipped with heat exchangers to cool down and heat the desalted water in the low-temperature desalted water tank and the high-temperature desalted water tank.

[0012] Furthermore, the auxiliary agent storage tank is provided with a feed inlet and a discharge outlet, and a stirring device is also installed in the auxiliary agent storage tank.

[0013] Furthermore, the mass ratio of tert-butyl peroxyneodecanoate (BND) to polyvinyl chloride is (0.0003-0.0007):1, and the mass ratio of tert-butyl peroxyneodecanoate (CND) to polyvinyl chloride is (0.0006-0.0011):1.

[0014] Furthermore, the mass ratio of the polyvinyl alcohol with a high alcoholysis degree to the polyvinyl chloride is (0.0005-0.001):1, and the mass ratio of the polyvinyl alcohol with a low alcoholysis degree to the polyvinyl chloride is (0.0002-0.0006):1.

[0015] Furthermore, the buffer is sodium bicarbonate, and the mass ratio of the sodium bicarbonate to the polyvinyl chloride is (0.0002-0.0005):1.

[0016] Furthermore, the fresh vinyl chloride storage tank is provided with a feed inlet and a discharge outlet.

[0017] Furthermore, the recovered vinyl chloride storage tank is provided with a feed inlet and a discharge outlet.

[0018] Further, the polymerization kettle is provided with a hot desalted water inlet, a cold desalted water inlet, a feed port, a discharge port, a gas phase outlet and a water outlet; the hot desalted water inlet of the polymerization kettle is connected to the water outlets of the normal temperature desalted water tank and the high temperature desalted water tank; the cold desalted water inlet of the polymerization kettle is connected to the water outlet of the low temperature desalted water tank; the feed port of the polymerization kettle is connected to the discharge ports of the fresh vinyl chloride storage tank and the recovered vinyl chloride storage tank; The polymerization kettle is provided with a stirring device; The outer layer of the polymerization kettle is provided with a cooling water pipeline, and circulating cooling water flows through the cooling water pipeline.

[0019] Furthermore, the top condenser is installed on the top of the polymerization kettle to condense the reacted materials in the polymerization kettle.

[0020] Furthermore, the discharge tank is provided with a feed port, a discharge port and a gas phase outlet, and a stirring device is also provided in the discharge tank, and the feed port of the discharge tank is connected to the discharge port of the polymerization kettle.

[0021] Furthermore, the stripping tower storage tank is provided with a feed inlet, a discharge port and a gas phase outlet, and a stirring device is also provided in the stripping tower storage tank, and the feed inlet of the stripping tower storage tank is connected to the discharge port of the discharge tank.

[0022] Furthermore, the polymerization heat exchanger is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the polymerization heat exchanger is connected to the discharge port of the stripping tower storage tank.

[0023] Furthermore, the stripping tower is provided with a feed inlet, a discharge port and a gas phase outlet, the feed inlet of the stripping tower is connected to the cold material outlet of the polymerization heat exchanger, and the discharge port of the stripping tower is connected to the hot material inlet of the polymerization heat exchanger.

[0024] Furthermore, the stripping tower condenser is provided with a gas phase inlet and a liquid outlet, and the gas phase inlet of the stripping tower condenser is connected to the gas phase outlet of the stripping tower.

[0025] Furthermore, the mixing tank is provided with a feed inlet and a discharge port, and a stirring device is also provided in the mixing tank, and the feed inlet of the mixing tank is connected to the hot material outlet of the polymerization heat exchanger.

[0026] Furthermore, the recovery separator is provided with a feed port and a discharge port, and the feed port of the recovery separator is connected to the gas phase outlet of the polymerization kettle, the discharge tank and the stripping tower storage tank.

[0027] Furthermore, the compressor is provided with a feed port and a discharge port, and the feed port of the compressor is connected to the discharge port of the recovery separator.

[0028] Furthermore, the primary condenser is provided with a feed port, a discharge port and a gas phase outlet, the feed port of the primary condenser is connected to the discharge port of the compressor, and the discharge port of the primary condenser is connected to the feed port of the recovered vinyl chloride storage tank.

[0029] Furthermore, the secondary condenser is provided with a feed port, a discharge port and a gas phase outlet; the feed port of the secondary condenser is connected to the gas phase outlet of the primary condenser; the discharge port of the secondary condenser is connected to the feed port of the recovered vinyl chloride storage tank; and the gas phase outlet of the secondary condenser is connected to the tail gas treatment device.

[0030] Furthermore, the centrifuge is provided with a feed port, a discharge port and a wastewater outlet, and the feed port of the centrifuge is connected to the discharge port of the mixing tank.

[0031] Furthermore, the drying bed is provided with a feed port, a discharge port and a gas outlet, and the feed port of the drying bed is connected to the discharge port of the centrifuge; the material is packaged after being discharged from the discharge port of the drying bed.

[0032] Furthermore, the cyclone separator is provided with a feed inlet and a discharge inlet, and the feed inlet of the cyclone separator is connected to the gas outlet of the drying bed.

[0033] Furthermore, the bag filter is provided with a feed inlet and an air outlet, the feed inlet of the bag filter is connected to the discharge port of the cyclone separator, and the air outlet of the bag filter is connected to the exhaust gas treatment device.

[0034] Furthermore, the condensation separator is provided with a water inlet, a water outlet and a material outlet, the water inlet of the condensation separator is connected to the liquid outlet of the stripping tower condenser, and the material outlet of the condensation separator is connected to the feed inlet of the recovery separator.

[0035] Furthermore, the water storage tank is provided with a water inlet and a water outlet, the water inlet of the water storage tank is connected to the water outlet of the condensation separator, and the water inlet of the water storage tank is also connected to the wastewater outlet of the centrifuge and the water outlet of the polymerization kettle; The water storage tank is also filled with flushing wastewater and ground wastewater generated during the operation of the system.

[0036] Furthermore, the wastewater heat exchanger is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the wastewater heat exchanger is connected to the water outlet of the water storage tank.

[0037] Furthermore, the wastewater stripping tower is provided with a feed port, a discharge port and a gas phase outlet, the feed port of the wastewater stripping tower is connected to the cold material outlet of the wastewater heat exchanger, and the discharge port of the wastewater stripping tower is connected to the hot material inlet of the wastewater heat exchanger.

[0038] Furthermore, the wastewater stripping tower condenser is provided with a feed inlet and a discharge port, the feed inlet of the wastewater stripping tower condenser is connected to the gas phase outlet of the wastewater stripping tower, and the discharge port of the wastewater stripping tower condenser is connected to the feed inlet of the recovery separator.

[0039] Furthermore, the pretreatment reactor is provided with a water inlet and a water outlet, the water inlet of the pretreatment reactor is connected to the hot material outlet of the wastewater heat exchanger, and the water outlet of the pretreatment reactor is connected to the wastewater treatment device.

[0040] The present invention also provides a method for preparing polyvinyl chloride using the system for producing polyvinyl chloride, comprising the following steps: Step 1: Material storage configuration Desalted water enters a normal temperature desalted water tank, a high temperature desalted water tank and a low temperature desalted water tank through a pipeline, a heat exchanger is used to heat the desalted water in the high temperature desalted water tank, and a heat exchanger is used to cool the desalted water in the low temperature desalted water tank to obtain low temperature desalted water and high temperature desalted water; Step 2: Polymerization stripping An anti-sticking layer is provided in the polymerization kettle, vinyl chloride enters the polymerization kettle from the vinyl chloride storage tank, and at the same time, normal temperature desalted water, the high temperature desalted water and the low temperature desalted water are added to the reaction starting temperature, and the additives in the additive storage tank are stirred and reacted together in the polymerization kettle, the low temperature desalted water is continuously passed through the polymerization kettle during the reaction to cool down and seal the polymerization kettle, circulating water is passed through the cooling water pipeline of the outer layer of the polymerization kettle to cool down the polymerization kettle, the material in the polymerization kettle evaporates due to the temperature increase during the reaction, the evaporated material encounters the kettle top condenser at the top of the polymerization kettle for condensation, and falls back into the polymerization kettle to react repeatedly, the unreacted vinyl chloride and other impurity gases generated during the reaction enter the recovery separator from the polymerization kettle, and the waste water in the polymerization kettle is discharged into the water storage tank; The material generated after the reaction in the polymerization kettle is completed enters the discharge tank, and part of the unreacted vinyl chloride generated in the discharge tank enters the recovery separator, and the material enters the stripping tower storage tank from the discharge tank, and the material in the stripping tower storage tank enters the stripping tower through the polymerization heat exchanger to absorb heat and then enters the stripping tower, in the stripping tower, part of the unreacted vinyl chloride generated enters the condensation separator through the stripping tower condenser, and the stripped material enters the polymerization heat exchanger from the bottom of the stripping tower to recover heat, and then enters the mixing tank; Step 3: Vinyl chloride recovery The vinyl chloride in the recovery separator is compressed by a compressor and enters a primary condenser. The liquid vinyl chloride condensed in the primary condenser enters a recovery vinyl chloride storage tank, while the uncondensed gas enters a secondary condenser for condensation. The liquid vinyl chloride condensed in the secondary condenser enters the recovery vinyl chloride storage tank, while the uncondensed gas enters a tail gas treatment device to remove pollutants and is then discharged. The vinyl chloride in the recovery vinyl chloride storage tank enters the polymerization kettle along with the vinyl chloride in the fresh vinyl chloride tank. Step 4: PVC recycling packaging After the materials in the mixing tank are centrifuged by the centrifuge, the solid materials enter the drying bed, and after being dried in the drying bed, polyvinyl chloride is obtained. The polyvinyl chloride is packaged after being output from the drying bed, and the liquid water produced in the centrifuge enters the water storage tank; Step 5: Wastewater treatment The liquid condensed in the condensation separator enters the water storage tank, and the gaseous vinyl chloride enters the recovery separator. The water storage tank includes the wastewater in the polymerization kettle, the wastewater used for washing the ground during the production process, and the waste liquid in the centrifuge. All the wastewater in the water storage tank absorbs heat through the wastewater heat exchanger and enters the wastewater stripping tower. The stripped material recovers heat through the wastewater heat exchanger and enters the pretreatment reactor, and then enters the wastewater treatment device. The gas generated in the wastewater stripping tower is condensed by the wastewater stripping tower condenser and enters the recovery separator.

[0041] Furthermore, in step 1, the temperature of the normal temperature desalted water is 30-35°C, the temperature of the high temperature desalted water is 90-100°C, and the temperature of the low temperature desalted water is 23-25°C.

[0042] Furthermore, the steam pressure in the heat exchanger of the high-temperature desalted water tank in step 1 is 0.3-0.4 MPa and the temperature is 180-200°C.

[0043] Furthermore, the anti-sticking layer in step 2 is a layer of oleophobic and hydrophilic polymer, and the thickness of the anti-sticking layer is 1-3 nm.

[0044] Furthermore, the vinyl chloride storage tank in step 2 includes one or more of a fresh vinyl chloride storage tank and a recycled vinyl chloride storage tank.

[0045] Furthermore, the addition rate of the normal temperature desalted water, the high temperature desalted water and the low temperature desalted water in step 2 is 5m 3 / min.

[0046] Furthermore, in the step 2, the total volume ratio of the vinyl chloride to the total volume of the normal temperature desalted water and the high temperature desalted water is 1:(1.15-1.2).

[0047] Furthermore, the reaction starting temperature in step 2 is 55-60°C.

[0048] Furthermore, the auxiliary agent in step 2 includes an initiator, a dispersant and a buffer.

[0049] Furthermore, the initiator is tert-butyl peroxyneodecanoate (BND) and tert-butyl peroxyneodecanoate (CND).

[0050] Furthermore, the mass ratio of tert-butyl peroxyneodecanoate (BND) to polyvinyl chloride is (0.0003-0.0007):1, and the mass ratio of tert-butyl peroxyneodecanoate (CND) to polyvinyl chloride is (0.0006-0.0011):1.

[0051] Furthermore, the dispersant is polyvinyl alcohol with a high alcoholysis degree and polyvinyl alcohol with a low alcoholysis degree.

[0052] Furthermore, the alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 78.5-81.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 40-45%.

[0053] Furthermore, the mass ratio of the polyvinyl alcohol with a high alcoholysis degree to the polyvinyl chloride is (0.0005-0.001):1, and the mass ratio of the polyvinyl alcohol with a low alcoholysis degree to the polyvinyl chloride is (0.0002-0.0006):1.

[0054] Furthermore, the buffer is sodium bicarbonate, and the mass ratio of the sodium bicarbonate to the polyvinyl chloride is (0.0002-0.0005):1.

[0055] Furthermore, the stirring speed in step 2 is 90-120 r / min.

[0056] Furthermore, the reaction time in step 2 is 240-300 min.

[0057] Furthermore, the temperature of the circulating water in step 2 is 30-40°C.

[0058] Furthermore, in step 2, the top temperature of the stripping tower is 90-95°C, and the bottom temperature is 100-105°C.

[0059] Furthermore, the drying temperature of the drying bed in step 4 is 95-100°C.

[0060] Furthermore, the gaseous substances in the drying bed in step 4 may be sequentially introduced into a cyclone separator and a bag filter for separation.

[0061] Furthermore, in the step 5, the top temperature of the wastewater stripping tower is 70-75°C, and the bottom temperature is 80-85°C.

[0062] Furthermore, the pH value of the wastewater in step 5 is 6-7.5, the COD is 400-460 mg / L, the BOD is 160-200 mg / L, and the SS is 80-90 mg / L.

[0063] Furthermore, the viscosity of the polyvinyl chloride in step 5 is 110-120 ml / g, the number of impurity particles is 14-16, the volatile matter content is 0.25-0.4%, and the apparent density is 0.48-0.49 g / ml.

[0064] Beneficial effects of the present invention: 1. The system for producing polyvinyl chloride in the present invention comprises a vinyl chloride recovery unit and a wastewater treatment unit. A kettle top condenser is also provided in the polymerization stripping unit, and vinyl chloride generated in each link of the system is recovered. The recovered vinyl chloride enters the vinyl chloride recovery unit for condensation and recovery, and then continues to enter the polymerization stripping unit for reaction. On the basis of preventing pollution caused by vinyl chloride discharge, vinyl chloride is recovered, thereby improving the utilization rate of vinyl chloride and saving production costs; 2. In the process of preparing polyvinyl chloride, the wastewater generated still contains unreacted vinyl chloride or other pollutants. In the wastewater treatment unit of the present invention, the wastewater in the production process and ground sewage are passed through a wastewater stripping tower and a wastewater stripping tower condenser, and the unreacted vinyl chloride is first stripped and condensed and recovered into a vinyl chloride recovery unit, and then the remaining wastewater is treated with a pretreatment reactor to remove pollutants and then discharged. In the process of treating the wastewater, vinyl chloride is recovered, thereby reducing the consumption of vinyl chloride; 3. The systems for producing polyvinyl chloride in the present invention are all combinations of separate devices. During the reaction process, when any equipment is damaged, it is easy to repair and replace. At the same time, the heat in the present invention can be recovered through a heat exchanger, and the recovered heat is used for heating other systems. The preparation process of the systems for producing polyvinyl chloride in the present invention is smooth, no human intervention is required, and all are automated equipment, ensuring the safety of personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a structural schematic diagram of the system for producing polyvinyl chloride according to the present invention; The names of the numbers in the figure are: 2, auxiliary agent storage tank; 3, fresh vinyl chloride storage tank; 4, recycled vinyl chloride storage tank; 5, polymerization kettle; 6, kettle top condenser; 7, discharge tank; 8, stripping tower storage tank; 9, polymerization heat exchanger; 10, stripping tower; 11, stripping tower condenser; 12, mixing tank; 13, recovery separator; 14, compressor; 15, primary condenser; 16, secondary condenser; 17, centrifuge; 18, drying bed; 19, cyclone separator separator; 20. bag filter; 21. condensation separator; 22. water storage tank; 23. wastewater heat exchanger; 24. wastewater stripping tower; 25. wastewater stripping tower condenser; 26. pretreatment reactor; 101. normal temperature desalted water tank; 102. high temperature desalted water tank; 103. low temperature desalted water tank; A. storage configuration unit; B. polymerization stripping unit; C. vinyl chloride recovery unit; D. polyvinyl chloride drying and packaging unit; E. wastewater treatment unit. DETAILED DESCRIPTION

[0066] The invention is described in detail below with reference to the embodiments: The invention provides a system for producing polyvinyl chloride, which recovers by-products and unreacted vinyl chloride in the reaction process, greatly improves the utilization rate of vinyl chloride, and improves the environmental protection of the system.

[0067] Example 1 This embodiment provides a system for producing polyvinyl chloride. According to the material transportation direction, the system includes a storage configuration unit A, a polymerization stripping unit B, a vinyl chloride recovery unit C, a polyvinyl chloride drying and packaging unit D, and a wastewater treatment unit E; The storage configuration unit A includes a desalted water tank, an additive storage tank 2, a fresh vinyl chloride storage tank 3 and a recovered vinyl chloride storage tank 4; The polymerization stripping unit B includes a polymerization kettle 5, a kettle top condenser 6, a discharge tank 7, a stripping tower storage tank 8, a polymerization heat exchanger 9, a stripping tower 10, a stripping tower condenser 11 and a mixing tank 12; The vinyl chloride recovery unit C includes a recovery separator 13, a compressor 14, a primary condenser 15 and a secondary condenser 16; The polyvinyl chloride drying and packaging unit D includes a centrifuge 17 and a drying bed 18; The wastewater treatment unit E includes a condensation separator 21, a water storage tank 22, a wastewater heat exchanger 23, a wastewater stripping tower 24, a wastewater stripping tower condenser 25 and a pretreatment reactor 26; The additives in the additive storage tank 2 include initiators, dispersants and buffers; The initiator is tert-butyl peroxyneodecanoate and tert-butyl peroxyneodecanoate; The dispersant is polyvinyl alcohol with high alcoholysis degree (PVA-420H) and polyvinyl alcohol with low alcoholysis degree (LM-10HD); The alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 78.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 40%.

[0068] In this embodiment, the polyvinyl chloride drying and packaging unit D further includes a cyclone separator 19 and a bag filter 20; The desalted water tank comprises a normal temperature desalted water tank 101, a high temperature desalted water tank 102 and a low temperature desalted water tank 103; the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 are all provided with a water inlet and a water outlet; the desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through a pipeline; the low temperature desalted water tank 103 and the high temperature desalted water tank 102 are both provided with a heat exchanger to cool and heat the desalted water in the low temperature desalted water tank 103 and the high temperature desalted water tank 102; The auxiliary agent storage tank 2 is provided with a feed inlet and a discharge port, and is also provided with a stirring device; the mass ratio of tert-butyl peroxyneodecanoate (BND) to polyvinyl chloride is 0.0003:1, and the mass ratio of tert-butyl peroxyneodecanoate (CND) to polyvinyl chloride is 0.0006:1; the mass ratio of high alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.0005:1, and the mass ratio of low alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.0002:1; the buffer is sodium bicarbonate, and the mass ratio of sodium bicarbonate to polyvinyl chloride is 0.0002:1; The fresh vinyl chloride storage tank 3 is provided with a feed inlet and a discharge outlet; The recovered vinyl chloride storage tank 4 is provided with a feed inlet and a discharge outlet; The polymerizer 5 is provided with a hot desalted water inlet, a cold desalted water inlet, a feed port, a discharge port, a gas phase outlet and a water outlet. The hot desalted water inlet of the polymerizer 5 is connected to the water outlets of the normal temperature desalted water tank 101 and the high temperature desalted water tank 102, the cold desalted water inlet of the polymerizer 5 is connected to the water outlet of the low temperature desalted water tank 103, and the feed port of the polymerizer 5 is connected to the discharge ports of the fresh vinyl chloride storage tank 3 and the recovered vinyl chloride storage tank 4; a stirring device is provided in the polymerizer 5; a cooling water pipeline is provided on the outer layer of the polymerizer 5, and circulating cooling water is passed through the cooling water pipeline; The top condenser 6 is installed on the top of the polymerization kettle 5 to condense the materials reacted in the polymerization kettle 5; The discharge tank 7 is provided with a feed port, a discharge port and a gas phase outlet, and a stirring device is also provided in the discharge tank 7. The feed port of the discharge tank 7 is connected to the discharge port of the polymerization kettle 5; The stripping tower storage tank 8 is provided with a feed inlet, a discharge port and a gas phase outlet, and a stirring device is also provided in the stripping tower storage tank 8. The feed inlet of the stripping tower storage tank 8 is connected to the discharge port of the discharge tank 7; The polymerization heat exchanger 9 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the polymerization heat exchanger 9 is connected to the discharge port of the stripping tower storage tank 8; The stripping tower 10 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the stripping tower 10 is connected to the cold material outlet of the polymerization heat exchanger 9, and the discharge port of the stripping tower 10 is connected to the hot material inlet of the polymerization heat exchanger 9; The stripping tower condenser 11 is provided with a gas phase inlet and a liquid outlet, and the gas phase inlet of the stripping tower condenser 11 is connected to the gas phase outlet of the stripping tower 10; The mixing tank 12 is provided with a feed inlet and a discharge port, and a stirring device is also provided in the mixing tank 12. The feed inlet of the mixing tank 12 is connected to the hot material outlet of the polymerization heat exchanger 9; The recovery separator 13 is provided with a feed port and a discharge port, and the feed port of the recovery separator 13 is connected to the discharge tank 7 of the polymerization kettle 5 and the gas phase outlet of the stripping tower storage tank 8; The compressor 14 is provided with a feed port and a discharge port, and the feed port of the compressor 14 is connected to the discharge port of the recovery separator 13; The primary condenser 15 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the primary condenser 15 is connected to the discharge port of the compressor 14, and the discharge port of the primary condenser 15 is connected to the feed port of the recovered vinyl chloride storage tank 4; The secondary condenser 16 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the secondary condenser 16 is connected to the gas phase outlet of the primary condenser 15, the discharge port of the secondary condenser 16 is connected to the feed port of the recovered vinyl chloride storage tank 4, and the gas phase outlet of the secondary condenser 16 is connected to the tail gas treatment device; The centrifuge 17 is provided with a feed port, a discharge port and a wastewater outlet, and the feed port of the centrifuge 17 is connected to the discharge port of the mixing tank 12; The drying bed 18 is provided with a feed port, a discharge port and a gas outlet, and the feed port of the drying bed 18 is connected to the discharge port of the centrifuge 17; the material is packaged after being discharged from the discharge port of the drying bed 18; The cyclone separator 19 is provided with a feed inlet and a discharge port, and the feed inlet of the cyclone separator 19 is connected to the gas outlet of the drying bed 18; The bag filter 20 is provided with a feed inlet and an air outlet. The feed inlet of the bag filter 20 is connected to the discharge port of the cyclone separator 19, and the air outlet of the bag filter 20 is connected to the exhaust gas treatment device. The condensation separator 21 is provided with a water inlet, a water outlet and a material outlet. The water inlet of the condensation separator 21 is connected to the liquid outlet of the stripping tower condenser 11, and the material outlet of the condensation separator 21 is connected to the feed inlet of the recovery separator 13; Furthermore, the water storage tank 22 is provided with a water inlet and a water outlet, the water inlet of the water storage tank 22 is connected to the water outlet of the condensation separator 21, and the water inlet of the water storage tank 22 is also connected to the wastewater outlet of the centrifuge 17 and the water outlet of the polymerization kettle 5; the water storage tank 22 is also filled with flushing wastewater and ground wastewater during the operation of the system; The wastewater heat exchanger 23 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the wastewater heat exchanger 23 is connected to the water outlet of the water storage tank 22; The wastewater stripping tower 24 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the wastewater stripping tower 24 is connected to the cold material outlet of the wastewater heat exchanger 23, and the discharge port of the wastewater stripping tower 24 is connected to the hot material inlet of the wastewater heat exchanger 23; The wastewater stripping tower condenser 25 is provided with a feed port and a discharge port, the feed port of the wastewater stripping tower condenser 25 is connected to the gas phase outlet of the wastewater stripping tower 24, and the discharge port of the wastewater stripping tower condenser 25 is connected to the feed port of the recovery separator 13; The pretreatment reactor 26 is provided with a water inlet and a water outlet. The water inlet of the pretreatment reactor 26 is connected to the hot material outlet of the wastewater heat exchanger 23, and the water outlet of the pretreatment reactor 26 is connected to the wastewater treatment device.

[0069] This embodiment also provides a method for preparing polyvinyl chloride using the system for producing polyvinyl chloride, comprising the following steps: Step 1: Material storage configuration Desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through the pipeline, and the desalted water in the high temperature desalted water tank 102 is heated by a heat exchanger at 0.3 MPa and 180°C, and the desalted water in the low temperature desalted water tank 103 is cooled by a heat exchanger to obtain high temperature desalted water at 90°C and low temperature desalted water at 23°C. The temperature of the normal temperature desalted water in the normal temperature desalted water tank 101 is 30°C; Step 2: Polymerization stripping In the polymerization reactor 5, a layer of oleophobic hydrophilic polymer with a thickness of 2.5 nm is sprayed by steam method, and 49.5 nm 3 Fresh vinyl chloride enters the polymerization kettle 5 from the fresh vinyl chloride storage tank 3, and at the same time, the 3 The room temperature desalted water, the high temperature desalted water and the low temperature desalted water are added at a rate of 58.41 m / min. 3 , until the reaction starting temperature is 56.8°C, and the additives in the additive storage tank 2 enter the polymerization kettle 5 together, stir and react at 90r / min, the reaction time is 240min, the low-temperature desalted water is continuously passed through the polymerization kettle 5 to cool and seal the polymerization kettle 5 during the reaction, and 30°C circulating water is passed through the cooling water pipeline of the outer layer of the polymerization kettle 5 to cool the polymerization kettle 5. During the reaction, the material in the polymerization kettle 5 evaporates due to the increase in temperature, and the evaporated material encounters the kettle top condenser 6 on the top of the polymerization kettle 5 for condensation, and falls back to the polymerization kettle 5 to react repeatedly. The unreacted vinyl chloride and other impurity gases generated during the reaction enter the recovery separator 13 from the polymerization kettle 5, and the waste water in the polymerization kettle 5 is discharged into the water storage tank 22; The material generated after the reaction in the polymerization kettle 5 is completed enters the discharge tank 7, and part of the unreacted vinyl chloride generated in the discharge tank 7 enters the recovery separator 13. The material enters the stripping tower storage tank 8 from the discharge tank 7. The material in the stripping tower storage tank 8 enters the stripping tower 10 for stripping after absorbing heat through the polymerization heat exchanger 9. The top temperature of the stripping tower 10 is 95° C., and the bottom temperature is 105° C. In the stripping tower 10, part of the unreacted vinyl chloride is generated and enters the condensation separator 21 through the stripping tower condenser 11, and the stripped material enters the polymerization heat exchanger 9 from the bottom of the stripping tower 10 to recover heat, and then enters the mixing tank 12; Step 3: Vinyl chloride recovery The vinyl chloride in the recovery separator 13 is compressed by the compressor 14 and enters the primary condenser 15. The liquid vinyl chloride condensed in the primary condenser 15 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the secondary condenser 16 for condensation. The liquid vinyl chloride condensed in the secondary condenser 16 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the tail gas treatment device to remove pollutants and then is discharged. The vinyl chloride in the recovery vinyl chloride storage tank 4 enters the polymerization kettle 5 along with the vinyl chloride in the fresh vinyl chloride tank 3; Step 4: PVC recycling packaging After the materials in the mixing tank 12 are centrifuged by the centrifuge 17, the solid materials enter the drying bed 18, and are dried at 95°C in the drying bed 18 to obtain polyvinyl chloride, which is then packaged after being output from the drying bed 18. The liquid water produced in the centrifuge 17 enters the water storage tank 22, and the gaseous materials dried in the drying bed 18 are sequentially passed into the cyclone separator 19 and the bag filter 20 for separation. Step 5: Wastewater treatment The liquid condensed in the condensation separator 21 enters the water storage tank 22, and the gaseous vinyl chloride enters the recovery separator 13. The water storage tank 22 includes the wastewater in the polymerization kettle 5, the wastewater used to wash the ground during the production process, and the waste liquid in the centrifuge 17. All the wastewater in the water storage tank 22 absorbs heat through the wastewater heat exchanger 23 and then enters the wastewater stripping tower 24 for stripping. The top temperature of the wastewater stripping tower 24 is 75°C and the bottom temperature is 85°C. The stripped material recovers heat through the wastewater heat exchanger 23 and then enters the pretreatment reactor 26, and then enters the wastewater treatment device. The gas generated in the wastewater stripping tower 24 is condensed by the wastewater stripping tower condenser 25 and then enters the recovery separator 13.

[0070] In this embodiment, the pH value of the wastewater is 7.4, the COD is 439 mg / L, the BOD is 174 mg / L, and the SS is 82 mg / L; The viscosity of the polyvinyl chloride is 110 ml / g, the number of impurity particles is 14, the volatile matter content is 0.29%, and the apparent density is 0.485 g / ml.

[0071] Example 2 This embodiment provides a system for producing polyvinyl chloride. According to the material transportation direction, the system includes a storage configuration unit A, a polymerization stripping unit B, a vinyl chloride recovery unit C, a polyvinyl chloride drying and packaging unit D, and a wastewater treatment unit E; The storage configuration unit A includes a desalted water tank, an additive storage tank 2, a fresh vinyl chloride storage tank 3 and a recovered vinyl chloride storage tank 4; The polymerization stripping unit B includes a polymerization kettle 5, a kettle top condenser 6, a discharge tank 7, a stripping tower storage tank 8, a polymerization heat exchanger 9, a stripping tower 10, a stripping tower condenser 11 and a mixing tank 12; The vinyl chloride recovery unit C includes a recovery separator 13, a compressor 14, a primary condenser 15 and a secondary condenser 16; The polyvinyl chloride drying and packaging unit D includes a centrifuge 17 and a drying bed 18; The wastewater treatment unit E includes a condensation separator 21, a water storage tank 22, a wastewater heat exchanger 23, a wastewater stripping tower 24, a wastewater stripping tower condenser 25 and a pretreatment reactor 26; The additives in the additive storage tank 2 include initiators, dispersants and buffers; The initiator is tert-butyl peroxyneodecanoate and tert-butyl peroxyneodecanoate; The dispersant is polyvinyl alcohol with high alcoholysis degree (PVA-420H) and polyvinyl alcohol with low alcoholysis degree (LM-10HD); The alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 81.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 45%.

[0072] In this embodiment, the polyvinyl chloride drying and packaging unit D further includes a cyclone separator 19 and a bag filter 20; The desalted water tank comprises a normal temperature desalted water tank 101, a high temperature desalted water tank 102 and a low temperature desalted water tank 103; the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 are all provided with a water inlet and a water outlet; the desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through a pipeline; the low temperature desalted water tank 103 and the high temperature desalted water tank 102 are both provided with a heat exchanger to cool and heat the desalted water in the low temperature desalted water tank 103 and the high temperature desalted water tank 102; The auxiliary agent storage tank 2 is provided with a feed inlet and a discharge port, and is also provided with a stirring device; the mass ratio of tert-butyl peroxyneodecanoate (BND) to polyvinyl chloride is 0.0003:1, and the mass ratio of tert-butyl peroxyneodecanoate (CND) to polyvinyl chloride is 0.0006:1; the mass ratio of high alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.0005:1, and the mass ratio of low alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.0002:1; the buffer is sodium bicarbonate, and the mass ratio of sodium bicarbonate to polyvinyl chloride is 0.0002:1; The fresh vinyl chloride storage tank 3 is provided with a feed inlet and a discharge outlet; The recovered vinyl chloride storage tank 4 is provided with a feed inlet and a discharge outlet; The polymerizer 5 is provided with a hot desalted water inlet, a cold desalted water inlet, a feed port, a discharge port, a gas phase outlet and a water outlet. The hot desalted water inlet of the polymerizer 5 is connected to the water outlets of the normal temperature desalted water tank 101 and the high temperature desalted water tank 102, the cold desalted water inlet of the polymerizer 5 is connected to the water outlet of the low temperature desalted water tank 103, and the feed port of the polymerizer 5 is connected to the discharge ports of the fresh vinyl chloride storage tank 3 and the recovered vinyl chloride storage tank 4; a stirring device is provided in the polymerizer 5; a cooling water pipeline is provided on the outer layer of the polymerizer 5, and circulating cooling water is passed through the cooling water pipeline; The top condenser 6 is installed on the top of the polymerization kettle 5 to condense the materials reacted in the polymerization kettle 5; The discharge tank 7 is provided with a feed port, a discharge port and a gas phase outlet, and a stirring device is also provided in the discharge tank 7. The feed port of the discharge tank 7 is connected to the discharge port of the polymerization kettle 5; The stripping tower storage tank 8 is provided with a feed inlet, a discharge port and a gas phase outlet, and a stirring device is also provided in the stripping tower storage tank 8. The feed inlet of the stripping tower storage tank 8 is connected to the discharge port of the discharge tank 7; The polymerization heat exchanger 9 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the polymerization heat exchanger 9 is connected to the discharge port of the stripping tower storage tank 8; The stripping tower 10 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the stripping tower 10 is connected to the cold material outlet of the polymerization heat exchanger 9, and the discharge port of the stripping tower 10 is connected to the hot material inlet of the polymerization heat exchanger 9; The stripping tower condenser 11 is provided with a gas phase inlet and a liquid outlet, and the gas phase inlet of the stripping tower condenser 11 is connected to the gas phase outlet of the stripping tower 10; The mixing tank 12 is provided with a feed inlet and a discharge port, and a stirring device is also provided in the mixing tank 12. The feed inlet of the mixing tank 12 is connected to the hot material outlet of the polymerization heat exchanger 9; The recovery separator 13 is provided with a feed port and a discharge port, and the feed port of the recovery separator 13 is connected to the discharge tank 7 of the polymerization kettle 5 and the gas phase outlet of the stripping tower storage tank 8; The compressor 14 is provided with a feed port and a discharge port, and the feed port of the compressor 14 is connected to the discharge port of the recovery separator 13; The primary condenser 15 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the primary condenser 15 is connected to the discharge port of the compressor 14, and the discharge port of the primary condenser 15 is connected to the feed port of the recovered vinyl chloride storage tank 4; The secondary condenser 16 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the secondary condenser 16 is connected to the gas phase outlet of the primary condenser 15, the discharge port of the secondary condenser 16 is connected to the feed port of the recovered vinyl chloride storage tank 4, and the gas phase outlet of the secondary condenser 16 is connected to the tail gas treatment device; The centrifuge 17 is provided with a feed port, a discharge port and a wastewater outlet, and the feed port of the centrifuge 17 is connected to the discharge port of the mixing tank 12; The drying bed 18 is provided with a feed port, a discharge port and a gas outlet, and the feed port of the drying bed 18 is connected to the discharge port of the centrifuge 17; the material is packaged after being discharged from the discharge port of the drying bed 18; The cyclone separator 19 is provided with a feed inlet and a discharge port, and the feed inlet of the cyclone separator 19 is connected to the gas outlet of the drying bed 18; The bag filter 20 is provided with a feed inlet and an air outlet. The feed inlet of the bag filter 20 is connected to the discharge port of the cyclone separator 19, and the air outlet of the bag filter 20 is connected to the exhaust gas treatment device. The condensation separator 21 is provided with a water inlet, a water outlet and a material outlet. The water inlet of the condensation separator 21 is connected to the liquid outlet of the stripping tower condenser 11, and the material outlet of the condensation separator 21 is connected to the feed inlet of the recovery separator 13; Furthermore, the water storage tank 22 is provided with a water inlet and a water outlet, the water inlet of the water storage tank 22 is connected to the water outlet of the condensation separator 21, and the water inlet of the water storage tank 22 is also connected to the wastewater outlet of the centrifuge 17 and the water outlet of the polymerization kettle 5; the water storage tank 22 is also filled with flushing wastewater and ground wastewater during the operation of the system; The wastewater heat exchanger 23 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the wastewater heat exchanger 23 is connected to the water outlet of the water storage tank 22; The wastewater stripping tower 24 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the wastewater stripping tower 24 is connected to the cold material outlet of the wastewater heat exchanger 23, and the discharge port of the wastewater stripping tower 24 is connected to the hot material inlet of the wastewater heat exchanger 23; The wastewater stripping tower condenser 25 is provided with a feed port and a discharge port, the feed port of the wastewater stripping tower condenser 25 is connected to the gas phase outlet of the wastewater stripping tower 24, and the discharge port of the wastewater stripping tower condenser 25 is connected to the feed port of the recovery separator 13; The pretreatment reactor 26 is provided with a water inlet and a water outlet. The water inlet of the pretreatment reactor 26 is connected to the hot material outlet of the wastewater heat exchanger 23, and the water outlet of the pretreatment reactor 26 is connected to the wastewater treatment device.

[0073] This embodiment also provides a method for preparing polyvinyl chloride using the system for producing polyvinyl chloride, comprising the following steps: Step 1: Material storage configuration Desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through the pipeline, and the desalted water in the high temperature desalted water tank 102 is heated by a heat exchanger at 0.4 MPa and 200° C., and the desalted water in the low temperature desalted water tank 103 is cooled by a heat exchanger to obtain high temperature desalted water at 95° C. and low temperature desalted water at 25° C. The temperature of the normal temperature desalted water in the normal temperature desalted water tank 101 is 35° C. Step 2: Polymerization stripping In the polymerization reactor 5, a layer of oleophobic hydrophilic polymer with a thickness of 1 nm is sprayed by steam method, and 49.5 nm 3 Fresh vinyl chloride enters the polymerization kettle 5 from the fresh vinyl chloride storage tank 3, and at the same time, the 3 The room temperature desalted water, the high temperature desalted water and the low temperature desalted water are added at a rate of 57 m / min. 3 , until the reaction starting temperature is 56.8°C, and the additives in the additive storage tank 2 enter the polymerization kettle 5 together, stir and react at 120r / min, the reaction time is 280min, the low-temperature desalted water is continuously passed through the polymerization kettle 5 to cool and seal the polymerization kettle 5 during the reaction, and 40°C circulating water is passed through the cooling water pipeline of the outer layer of the polymerization kettle 5 to cool the polymerization kettle 5. During the reaction, the material in the polymerization kettle 5 evaporates due to the increase in temperature, and the evaporated material encounters the kettle top condenser 6 on the top of the polymerization kettle 5 for condensation, and falls back to the polymerization kettle 5 to react repeatedly. The unreacted vinyl chloride and other impurity gases generated during the reaction enter the recovery separator 13 from the polymerization kettle 5, and the waste water in the polymerization kettle 5 is discharged into the water storage tank 22; The material generated after the reaction in the polymerization kettle 5 is completed enters the discharge tank 7, and part of the unreacted vinyl chloride generated in the discharge tank 7 enters the recovery separator 13. The material enters the stripping tower storage tank 8 from the discharge tank 7. The material in the stripping tower storage tank 8 enters the stripping tower 10 for stripping after absorbing heat through the polymerization heat exchanger 9. The top temperature of the stripping tower 10 is 90° C. and the bottom temperature is 100° C. In the stripping tower 10, part of the unreacted vinyl chloride generated enters the condensation separator 21 through the stripping tower condenser 11, and the stripped material enters the polymerization heat exchanger 9 from the bottom of the stripping tower 10 to recover heat, and then enters the mixing tank 12; Step 3: Vinyl chloride recovery The vinyl chloride in the recovery separator 13 is compressed by the compressor 14 and enters the primary condenser 15. The liquid vinyl chloride condensed in the primary condenser 15 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the secondary condenser 16 for condensation. The liquid vinyl chloride condensed in the secondary condenser 16 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the tail gas treatment device to remove pollutants and then is discharged. The vinyl chloride in the recovery vinyl chloride storage tank 4 enters the polymerization kettle 5 along with the vinyl chloride in the fresh vinyl chloride tank 3; Step 4: PVC recycling packaging After the materials in the mixing tank 12 are centrifuged by the centrifuge 17, the solid materials enter the drying bed 18, and are dried at 100° C. in the drying bed 18 to obtain polyvinyl chloride, which is then packaged after being output from the drying bed 18. The liquid water produced in the centrifuge 17 enters the water storage tank 22, and the gaseous materials dried in the drying bed 18 are sequentially passed into the cyclone separator 19 and the bag filter 20 for separation. Step 5: Wastewater treatment The liquid condensed in the condensation separator 21 enters the water storage tank 22, and the gaseous vinyl chloride enters the recovery separator 13. The water storage tank 22 includes the wastewater in the polymerization kettle 5, the wastewater used to wash the ground during the production process, and the waste liquid in the centrifuge 17. All the wastewater in the water storage tank 22 absorbs heat through the wastewater heat exchanger 23 and then enters the wastewater stripping tower 24 for stripping. The top temperature of the wastewater stripping tower 24 is 75°C and the bottom temperature is 85°C. The stripped material recovers heat through the wastewater heat exchanger 23 and then enters the pretreatment reactor 26, and then enters the wastewater treatment device. The gas generated in the wastewater stripping tower 24 is condensed by the wastewater stripping tower condenser 25 and then enters the recovery separator 13.

[0074] In this embodiment, the pH value of the wastewater is 7.1, the COD is 408 mg / L, the BOD is 160 mg / L, and the SS is 90 mg / L; The viscosity of the polyvinyl chloride is 108 ml / g, the number of impurity particles is 14, the volatile matter content is 0.31%, and the apparent density is 0.48 g / ml.

[0075] Example 3 This embodiment provides a system for producing polyvinyl chloride. According to the material transportation direction, the system includes a storage configuration unit A, a polymerization stripping unit B, a vinyl chloride recovery unit C, a polyvinyl chloride drying and packaging unit D, and a wastewater treatment unit E; The storage configuration unit A includes a desalted water tank, an additive storage tank 2, a fresh vinyl chloride storage tank 3 and a recovered vinyl chloride storage tank 4; The polymerization stripping unit B includes a polymerization kettle 5, a kettle top condenser 6, a discharge tank 7, a stripping tower storage tank 8, a polymerization heat exchanger 9, a stripping tower 10, a stripping tower condenser 11 and a mixing tank 12; The vinyl chloride recovery unit C includes a recovery separator 13, a compressor 14, a primary condenser 15 and a secondary condenser 16; The polyvinyl chloride drying and packaging unit D includes a centrifuge 17 and a drying bed 18; The wastewater treatment unit E includes a condensation separator 21, a water storage tank 22, a wastewater heat exchanger 23, a wastewater stripping tower 24, a wastewater stripping tower condenser 25 and a pretreatment reactor 26; The additives in the additive storage tank 2 include initiators, dispersants and buffers; The initiator is tert-butyl peroxyneodecanoate and tert-butyl peroxyneodecanoate; The dispersant is polyvinyl alcohol with high alcoholysis degree (PVA-420H) and polyvinyl alcohol with low alcoholysis degree (LM-10HD); The alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 78.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 40%.

[0076] In this embodiment, the polyvinyl chloride drying and packaging unit D further includes a cyclone separator 19 and a bag filter 20; The desalted water tank comprises a normal temperature desalted water tank 101, a high temperature desalted water tank 102 and a low temperature desalted water tank 103; the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 are all provided with a water inlet and a water outlet; the desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through a pipeline; the low temperature desalted water tank 103 and the high temperature desalted water tank 102 are both provided with a heat exchanger to cool and heat the desalted water in the low temperature desalted water tank 103 and the high temperature desalted water tank 102; The auxiliary agent storage tank 2 is provided with a feed inlet and a discharge port, and is also provided with a stirring device; the mass ratio of tert-butyl peroxyneodecanoate (BND) to polyvinyl chloride is 0.0007:1, and the mass ratio of tert-butyl peroxyneodecanoate (CND) to polyvinyl chloride is 0.0011:1; the mass ratio of high alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.001:1, and the mass ratio of low alcoholysis degree polyvinyl alcohol to polyvinyl chloride is 0.0006:1; the buffer is sodium bicarbonate, and the mass ratio of sodium bicarbonate to polyvinyl chloride is 0.0005:1; The fresh vinyl chloride storage tank 3 is provided with a feed inlet and a discharge outlet; The recovered vinyl chloride storage tank 4 is provided with a feed inlet and a discharge outlet; The polymerizer 5 is provided with a hot desalted water inlet, a cold desalted water inlet, a feed port, a discharge port, a gas phase outlet and a water outlet. The hot desalted water inlet of the polymerizer 5 is connected to the water outlets of the normal temperature desalted water tank 101 and the high temperature desalted water tank 102, the cold desalted water inlet of the polymerizer 5 is connected to the water outlet of the low temperature desalted water tank 103, and the feed port of the polymerizer 5 is connected to the discharge ports of the fresh vinyl chloride storage tank 3 and the recovered vinyl chloride storage tank 4; a stirring device is provided in the polymerizer 5; a cooling water pipeline is provided on the outer layer of the polymerizer 5, and circulating cooling water is passed through the cooling water pipeline; The top condenser 6 is installed on the top of the polymerization kettle 5 to condense the materials reacted in the polymerization kettle 5; The discharge tank 7 is provided with a feed port, a discharge port and a gas phase outlet, and a stirring device is also provided in the discharge tank 7. The feed port of the discharge tank 7 is connected to the discharge port of the polymerization kettle 5; The stripping tower storage tank 8 is provided with a feed inlet, a discharge port and a gas phase outlet, and a stirring device is also provided in the stripping tower storage tank 8. The feed inlet of the stripping tower storage tank 8 is connected to the discharge port of the discharge tank 7; The polymerization heat exchanger 9 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the polymerization heat exchanger 9 is connected to the discharge port of the stripping tower storage tank 8; The stripping tower 10 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the stripping tower 10 is connected to the cold material outlet of the polymerization heat exchanger 9, and the discharge port of the stripping tower 10 is connected to the hot material inlet of the polymerization heat exchanger 9; The stripping tower condenser 11 is provided with a gas phase inlet and a liquid outlet, and the gas phase inlet of the stripping tower condenser 11 is connected to the gas phase outlet of the stripping tower 10; The mixing tank 12 is provided with a feed inlet and a discharge port, and a stirring device is also provided in the mixing tank 12. The feed inlet of the mixing tank 12 is connected to the hot material outlet of the polymerization heat exchanger 9; The recovery separator 13 is provided with a feed port and a discharge port, and the feed port of the recovery separator 13 is connected to the discharge tank 7 of the polymerization kettle 5 and the gas phase outlet of the stripping tower storage tank 8; The compressor 14 is provided with a feed port and a discharge port, and the feed port of the compressor 14 is connected to the discharge port of the recovery separator 13; The primary condenser 15 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the primary condenser 15 is connected to the discharge port of the compressor 14, and the discharge port of the primary condenser 15 is connected to the feed port of the recovered vinyl chloride storage tank 4; The secondary condenser 16 is provided with a feed port, a discharge port and a gas phase outlet. The feed port of the secondary condenser 16 is connected to the gas phase outlet of the primary condenser 15, the discharge port of the secondary condenser 16 is connected to the feed port of the recovered vinyl chloride storage tank 4, and the gas phase outlet of the secondary condenser 16 is connected to the tail gas treatment device; The centrifuge 17 is provided with a feed port, a discharge port and a wastewater outlet, and the feed port of the centrifuge 17 is connected to the discharge port of the mixing tank 12; The drying bed 18 is provided with a feed port, a discharge port and a gas outlet, and the feed port of the drying bed 18 is connected to the discharge port of the centrifuge 17; the material is packaged after being discharged from the discharge port of the drying bed 18; The cyclone separator 19 is provided with a feed inlet and a discharge port, and the feed inlet of the cyclone separator 19 is connected to the gas outlet of the drying bed 18; The bag filter 20 is provided with a feed inlet and an air outlet. The feed inlet of the bag filter 20 is connected to the discharge port of the cyclone separator 19, and the air outlet of the bag filter 20 is connected to the exhaust gas treatment device. The condensation separator 21 is provided with a water inlet, a water outlet and a material outlet. The water inlet of the condensation separator 21 is connected to the liquid outlet of the stripping tower condenser 11, and the material outlet of the condensation separator 21 is connected to the feed inlet of the recovery separator 13; Furthermore, the water storage tank 22 is provided with a water inlet and a water outlet, the water inlet of the water storage tank 22 is connected to the water outlet of the condensation separator 21, and the water inlet of the water storage tank 22 is also connected to the wastewater outlet of the centrifuge 17 and the water outlet of the polymerization kettle 5; the water storage tank 22 is also filled with flushing wastewater and ground wastewater during the operation of the system; The wastewater heat exchanger 23 is provided with a cold material inlet, a cold material outlet, a hot material inlet and a hot material outlet, and the cold material inlet of the wastewater heat exchanger 23 is connected to the water outlet of the water storage tank 22; The wastewater stripping tower 24 is provided with a feed inlet, a discharge port and a gas phase outlet. The feed inlet of the wastewater stripping tower 24 is connected to the cold material outlet of the wastewater heat exchanger 23, and the discharge port of the wastewater stripping tower 24 is connected to the hot material inlet of the wastewater heat exchanger 23; The wastewater stripping tower condenser 25 is provided with a feed port and a discharge port, the feed port of the wastewater stripping tower condenser 25 is connected to the gas phase outlet of the wastewater stripping tower 24, and the discharge port of the wastewater stripping tower condenser 25 is connected to the feed port of the recovery separator 13; The pretreatment reactor 26 is provided with a water inlet and a water outlet. The water inlet of the pretreatment reactor 26 is connected to the hot material outlet of the wastewater heat exchanger 23, and the water outlet of the pretreatment reactor 26 is connected to the wastewater treatment device.

[0077] This embodiment also provides a method for preparing polyvinyl chloride using the system for producing polyvinyl chloride, comprising the following steps: Step 1: Material storage configuration Desalted water enters the normal temperature desalted water tank 101, the high temperature desalted water tank 102 and the low temperature desalted water tank 103 through the pipeline, and the desalted water in the high temperature desalted water tank 102 is heated by a heat exchanger at 0.4 MPa and 180°C, and the desalted water in the low temperature desalted water tank 103 is cooled by a heat exchanger to obtain high temperature desalted water at 95°C and low temperature desalted water at 25°C. The temperature of the normal temperature desalted water in the normal temperature desalted water tank 101 is 30°C; Step 2: Polymerization stripping In the polymerization reactor 5, a layer of oleophobic hydrophilic polymer with a thickness of 3 nm is sprayed by steam method, and 49.5 nm 3 Fresh vinyl chloride enters the polymerization kettle 5 from the fresh vinyl chloride storage tank 3, and at the same time, the 3 The room temperature desalted water, the high temperature desalted water and the low temperature desalted water are added at a rate of 59.4 m / min. 3 , until the reaction starting temperature is 56.8°C, and the additives in the additive storage tank 2 enter the polymerization kettle 5 together, stir and react at 90r / min, the reaction time is 300min, the low-temperature desalted water is continuously passed through the polymerization kettle 5 to cool and seal the polymerization kettle 5 during the reaction, and 30°C circulating water is passed through the cooling water pipeline of the outer layer of the polymerization kettle 5 to cool the polymerization kettle 5. During the reaction, the material in the polymerization kettle 5 evaporates due to the increase in temperature, and the evaporated material encounters the kettle top condenser 6 on the top of the polymerization kettle 5 for condensation, and falls back to the polymerization kettle 5 to react repeatedly. The unreacted vinyl chloride and other impurity gases generated during the reaction enter the recovery separator 13 from the polymerization kettle 5, and the waste water in the polymerization kettle 5 is discharged into the water storage tank 22; The material generated after the reaction in the polymerization kettle 5 is completed enters the discharge tank 7, and part of the unreacted vinyl chloride generated in the discharge tank 7 enters the recovery separator 13. The material enters the stripping tower storage tank 8 from the discharge tank 7. The material in the stripping tower storage tank 8 enters the stripping tower 10 for stripping after absorbing heat through the polymerization heat exchanger 9. The top temperature of the stripping tower 10 is 95° C., and the bottom temperature is 105° C. In the stripping tower 10, part of the unreacted vinyl chloride is generated and enters the condensation separator 21 through the stripping tower condenser 11, and the stripped material enters the polymerization heat exchanger 9 from the bottom of the stripping tower 10 to recover heat, and then enters the mixing tank 12; Step 3: Vinyl chloride recovery The vinyl chloride in the recovery separator 13 is compressed by the compressor 14 and enters the primary condenser 15. The liquid vinyl chloride condensed in the primary condenser 15 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the secondary condenser 16 for condensation. The liquid vinyl chloride condensed in the secondary condenser 16 enters the recovery vinyl chloride storage tank 4, and the uncondensed gas enters the tail gas treatment device to remove pollutants and then is discharged. The vinyl chloride in the recovery vinyl chloride storage tank 4 enters the polymerization kettle 5 along with the vinyl chloride in the fresh vinyl chloride tank 3; Step 4: PVC recycling packaging After the materials in the mixing tank 12 are centrifuged by the centrifuge 17, the solid materials enter the drying bed 18, and are dried at 95°C in the drying bed 18 to obtain polyvinyl chloride, which is then packaged after being output from the drying bed 18. The liquid water produced in the centrifuge 17 enters the water storage tank 22, and the gaseous materials dried in the drying bed 18 are sequentially passed into the cyclone separator 19 and the bag filter 20 for separation. Step 5: Wastewater treatment The liquid condensed in the condensation separator 21 enters the water storage tank 22, and the gaseous vinyl chloride enters the recovery separator 13. The water storage tank 22 includes the wastewater in the polymerization kettle 5, the wastewater used to wash the ground during the production process, and the waste liquid in the centrifuge 17. All the wastewater in the water storage tank 22 absorbs heat through the wastewater heat exchanger 23 and then enters the wastewater stripping tower 24 for stripping. The top temperature of the wastewater stripping tower 24 is 70°C and the bottom temperature is 80°C. The stripped material recovers heat through the wastewater heat exchanger 23 and then enters the pretreatment reactor 26, and then enters the wastewater treatment device. The gas generated in the wastewater stripping tower 24 is condensed by the wastewater stripping tower condenser 25 and then enters the recovery separator 13.

[0078] In this embodiment, the pH value of the wastewater is 6.6, COD is 452 mg / L, BOD is 191 mg / L, and SS is 88 mg / L; The viscosity of the polyvinyl chloride is 116 ml / g, the number of impurity particles is 15, the volatile matter content is 0.37%, and the apparent density is 0.489 g / ml.

[0079] Table 1 shows the properties of wastewater and polyvinyl chloride in Examples 1-3

[0080] Based on the above, it can be seen that the system for producing polyvinyl chloride described in the present invention has a wide range of applications, low cost and extremely high market prospects.

[0081] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A system for producing polyvinyl chloride, characterized in that: According to the material transportation direction, the system includes a storage configuration unit (A), a polymerization stripping unit (B), a vinyl chloride recovery unit (C), a polyvinyl chloride drying and packaging unit (D) and a wastewater treatment unit (E); The storage configuration unit (A) includes a desalted water tank, an additive storage tank (2), a fresh vinyl chloride storage tank (3) and a recovered vinyl chloride storage tank (4); The polymerization stripping unit (B) comprises a polymerization kettle (5), a kettle top condenser (6), a discharge tank (7), a stripping tower storage tank (8), a polymerization heat exchanger (9), a stripping tower (10), a stripping tower condenser (11) and a mixing tank (12); The vinyl chloride recovery unit (C) comprises a recovery separator (13), a compressor (14), a primary condenser (15) and a secondary condenser (16); The polyvinyl chloride drying and packaging unit (D) comprises a centrifuge (17) and a drying bed (18); The wastewater treatment unit (E) comprises a condensation separator (21), a water storage tank (22), a wastewater heat exchanger (23), a wastewater stripping tower (24), a wastewater stripping tower condenser (25) and a pretreatment reactor (26); The additives in the additive storage tank (2) include an initiator, a dispersant and a buffer; The initiator is tert-butyl peroxyneodecanoate and tert-butyl peroxyneodecanoate; The dispersant is polyvinyl alcohol with high alcoholysis degree and polyvinyl alcohol with low alcoholysis degree; The alcoholysis degree of the high alcoholysis degree polyvinyl alcohol is 78.5-81.5%, and the alcoholysis degree of the low alcoholysis degree polyvinyl alcohol is 40-45%.

2. The system according to claim 1, characterized in that The desalted water tank comprises a normal temperature desalted water tank (101), a high temperature desalted water tank (102) and a low temperature desalted water tank (103); The normal temperature desalted water tank (101), the high temperature desalted water tank (102) and the low temperature desalted water tank (103) are all provided with a water inlet and a water outlet; Desalted water enters the water inlets of the normal temperature desalted water tank (101), the high temperature desalted water tank (102) and the low temperature desalted water tank (103) through pipelines; The low-temperature desalted water tank (103) and the high-temperature desalted water tank (102) are both equipped with heat exchangers for cooling and heating the desalted water in the low-temperature desalted water tank (103) and the high-temperature desalted water tank (102).

3. The system according to claim 1, characterized in that The mass ratio of the tert-butyl peroxyneodecanoate to polyvinyl chloride is (0.0003-0.0007):1, and the mass ratio of the tert-butyl peroxyneodecanoate to polyvinyl chloride is (0.0006-0.0011):

1.

4. The system according to claim 1, characterized in that The mass ratio of the polyvinyl alcohol with high alcoholysis degree to polyvinyl chloride is (0.0005-0.001):1, and the mass ratio of the polyvinyl alcohol with low alcoholysis degree to polyvinyl chloride is (0.0002-0.0006):

1.

5. The system according to claim 1, characterized in that The buffer is sodium bicarbonate, and the mass ratio of the sodium bicarbonate to the polyvinyl chloride is (0.0002-0.0005):

1.

6. The system according to claim 1, characterized in that The top condenser (6) is installed on the top of the polymerization kettle (5) to condense the materials reacting in the polymerization kettle (5).

7. The system according to claim 1, characterized in that The recovery separator (13) is provided with a feed inlet and a discharge inlet, and the feed inlet of the recovery separator (13) is connected to the gas phase outlet of the polymerization kettle (5), the discharge tank (7) and the stripping tower storage tank (8).

8. The system according to claim 1, characterized in that The drying bed (18) is provided with a feed inlet, a discharge port and a gas outlet, and the feed inlet of the drying bed (18) is connected to the discharge port of the centrifuge (17); the material is packaged after being discharged from the discharge port of the drying bed (18).

9. A method for preparing polyvinyl chloride using the system for producing polyvinyl chloride according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Material storage configuration Desalted water enters a normal temperature desalted water tank (101), a high temperature desalted water tank (102) and a low temperature desalted water tank (103) through a pipeline, a heat exchanger is used to heat the desalted water in the high temperature desalted water tank (102), and a heat exchanger is used to cool the desalted water in the low temperature desalted water tank (103), thereby obtaining low temperature desalted water and high temperature desalted water; Step 2: Polymerization stripping An anti-sticking layer is provided in the polymerization kettle (5), vinyl chloride enters the polymerization kettle (5) from a vinyl chloride storage tank, and at the same time, normal temperature desalted water, the high temperature desalted water and the low temperature desalted water are added to the reaction starting temperature, and the additives in the additive storage tank (2) are added to the polymerization kettle (5) together with the additives to stir and react. During the reaction, the low temperature desalted water is continuously passed through to cool and seal the polymerization kettle (5), and circulating water is passed through the cooling water pipe of the outer layer of the polymerization kettle (5) to cool the polymerization kettle (5). During the reaction, the material in the polymerization kettle (5) evaporates due to the increase in temperature, and the evaporated material encounters the kettle top condenser (6) on the top of the polymerization kettle (5) to condense, and then falls back into the polymerization kettle (5) to repeatedly react. Unreacted vinyl chloride and other impurity gases generated during the reaction enter the recovery separator (13) from the polymerization kettle (5), and the waste water in the polymerization kettle (5) is discharged into the water storage tank (22); The material generated after the reaction in the polymerization kettle (5) is completed enters the discharge tank (7), and part of the unreacted vinyl chloride generated in the discharge tank (7) enters the recovery separator (13). The material enters the stripping tower storage tank (8) from the discharge tank (7). The material in the stripping tower storage tank (8) enters the stripping tower (10) after absorbing heat through the polymerization heat exchanger (9). In the stripping tower (10), part of the unreacted vinyl chloride generated enters the condensation separator (21) through the stripping tower condenser (11), and the stripped material enters the polymerization heat exchanger (9) from the bottom of the stripping tower (10) to recover heat, and then enters the mixing tank (12); Step 3: Vinyl chloride recovery The vinyl chloride in the recovery separator (13) is compressed by a compressor (14) and enters a primary condenser (15). The liquid vinyl chloride condensed in the primary condenser (15) enters a recovery vinyl chloride storage tank (4), while the uncondensed gas enters a secondary condenser (16) for condensation. The liquid vinyl chloride condensed in the secondary condenser (16) enters the recovery vinyl chloride storage tank (4), while the uncondensed gas enters an exhaust gas treatment device to remove pollutants and is then discharged. The vinyl chloride in the recovery vinyl chloride storage tank (4) enters the polymerization kettle (5) along with the vinyl chloride in the fresh vinyl chloride tank (3); Step 4: PVC recycling packaging After the material in the mixing tank (12) is centrifuged by the centrifuge (17), the solid material enters the drying bed (18), and after being dried in the drying bed (18), polyvinyl chloride is obtained. The polyvinyl chloride is packaged after being output from the drying bed (18), and the liquid water produced in the centrifuge (17) enters the water storage tank (22); Step 5: Wastewater treatment The liquid condensed in the condensation separator (21) enters the water storage tank (22), and the gaseous vinyl chloride enters the recovery separator (13). The water storage tank (22) includes wastewater in the polymerization kettle (5), wastewater used for washing the ground during the production process, and waste liquid in the centrifuge (17). All wastewater in the water storage tank (22) absorbs heat through the wastewater heat exchanger (23) and then enters the wastewater stripping tower (24). The stripped material recovers heat through the wastewater heat exchanger (23) and then enters the pretreatment reactor (26), and then enters the wastewater treatment device. The gas generated in the wastewater stripping tower (24) is condensed by the wastewater stripping tower condenser (25) and then enters the recovery separator (13).

10. The method according to claim 9, characterized in that The viscosity of the polyvinyl chloride in step 5 is 110-120 ml / g, the number of impurity particles is 14-16, the volatile content is 0.25-0.4%, and the apparent density is 0.48-0.49 g / ml.

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