Slurry washing and impurity removing process and device and application of slurry washing and impurity removing process and device

Abstract

The invention discloses a washing and impurity-removing process and device for desorbed slurry in a vinylidene chloride polymerization production process and application of the washing and impurity-removing process and device. The slurry washing and impurity-removing process comprises the following steps: transferring desorbed slurry into a washing kettle with an overflow port, spraying cold water to the top of the washing kettle, introducing hot water into the bottom of the washing kettle, swelling resin in the slurry to remove impurities by alternately carrying out cold and hot impact washing, and overflowing the impurities out of the washing kettle along with water through the overflow port under stirring, part of the resin flows out from the bottom of the washing kettle along with water and is circularly pumped back below the liquid level of the slurry washing mixed liquid in the washing kettle through the washing circulating pump. The slurry washing and impurity removing device comprises a washing kettle with an overflow port, a cold water spraying device is arranged at the top in the washing kettle, the bottom in the washing kettle is connected with a hot water inlet pipe and a discharging pipe, the discharging pipe is connected with one end of a washing circulating pump, and the other end of the washing circulating pump is connected with the washing kettle through a return pipe. And the outlet of the material return pipe is positioned below the liquid level of slurry washing mixed liquid in the washing kettle.

Description

Technical Field

[0001] The present invention relates to the field of vinylidene chloride (VDC) polymerization production, and in particular to a slurry washing and impurity removal process, a device and application thereof after separation in a vinylidene chloride polymerization production process. Background Art

[0002] Polyvinylidene chloride (PVDC) is a green packaging material, unique in the packaging industry, offering high barrier properties, strong toughness, low-temperature heat sealing, and excellent chemical stability. Multi-layer co-extruded PVDC-MA resins, produced by copolymerizing vinylidene chloride with monomers such as methyl acrylate (MA), are used in the manufacture of heat-shrinkable films, extruded films, composite PVDC films, as well as fresh-keeping bags, composite bags, blow-molded bottles, fishnet yarn, flame-retardant fabrics, and artificial turf.

[0003] The various steps of the conventional suspension polymerization process are exemplarily described as follows: 1) MA polymerization process: High-purity water, antioxidants, additives and dispersants from the dispersant tank are added to the polymerization kettle. After nitrogen replacement and vacuuming with a vacuum unit, materials such as vinylidene chloride and methyl acrylate monomer are introduced into the polymerization kettle in a certain proportion. Then, the weighed initiator is added to the polymerization kettle. The polymerization kettle is heated to a certain temperature through hot water in the jacket of the polymerization kettle. The temperature and pressure of the polymerization kettle are controlled to a certain level. After a period of reaction, when the pressure in the polymerization kettle drops to the specified pressure, the program determines that the reaction is over and automatically adds the terminator from the terminator tank into the polymerization kettle to terminate the reaction.

[0004] 2) MA desorption process: The polymerization reaction material obtained after the termination reaction in the polymerization kettle is transported to the desorption tank through the slurry discharge pump. Steam is introduced into the desorption tank to heat the residual monomers in the slurry for stripping and desorption. Epoxidized soybean oil (ESO) is added and stirred evenly. The desorbed slurry is transported to the centrifugal drying process through a centrifugal slurry delivery pump.

[0005] 3) MA tail gas treatment process: After the foam is removed from the precipitated mixed monomer in the defoaming collector, the non-condensable gas is compressed by the tail gas compressor unit and then sent to the primary and secondary condensers. The recovered condensed monomer is recovered into the mixed liquid tank and sent to the outside for treatment via the mixed liquid delivery pump. The non-condensable gas on the top of the secondary condenser is sent to the tail gas spray absorption tower for circulation absorption treatment with chilled brine and then discharged.

[0006] 4) Centrifugal drying and packaging process: The slurry after separation is sent to the centrifuge feed trough for stirring and buffering for a certain period of time, and then transported to the centrifuge by a centrifugal metering pump. After preliminary centrifugation, it is sent to the fluidized drying bed; after steam heating treatment, it is blown to the vibrating screen, and after the second screening treatment, it is sent to the fine material packaging plant for packaging. The gas phase of the fluidized drying bed passes through cyclone separator I, cyclone separator II, and bag dust collector to recover part of the material, and the qualified gas is discharged through the induced draft fan.

[0007] The current process has the following disadvantages: 1) During the centrifugal process, the powder resin in the slurry after separation may wear out the transmission position, resulting in unstable product quality. Due to the influence of foam material after polymerization and precipitation of PVDC-MA resin, the pores of resin particles still contain a large amount of powder fine materials (dispersants, additives, etc.). When centrifuged at high speed, the powder will produce adsorption, agglomeration and other phenomena, which are easy to accumulate in the centrifuge. After a certain period of time, it is easy to contact with the centrifuge drum, causing drum wear, and black and yellow spots will appear on the resin.

[0008] 2) High energy consumption: Since a large amount of powder remains in the slurry after separation, the powder tends to turn yellow more easily as the fluidized bed temperature rises during the next drying process, which also increases the energy consumption required for drying. This process requires a large amount of utility and electricity consumption, resulting in high production and operating costs.

[0009] 3) The centrifuge cleaning time is short and produces a lot of three wastes: Due to the easy accumulation of lumps, the drum is severely worn. The centrifuge cleaning time is basically 45 days per time. Each cleaning will generate a large amount of wastewater and waste, which not only produces three wastes, but also increases the loss of PVDC products.

[0010] 4) The powder in the slurry after desorption is prone to clumping due to static electricity and other reasons during the drying, vibration, mixing and other stages. The high content of powder resin has a greater impact on product quality. Summary of the Invention

[0011] In view of the above technical problems and the shortcomings in the art, the present invention provides a process, device and application of washing and removing impurities from slurry after separation in the production process of vinylidene chloride polymerization.

[0012] The specific technical solutions are as follows: In the first aspect, the present invention provides a process for washing and removing impurities from slurry after desorption in a vinylidene chloride polymerization production process, comprising: transferring the desorbed slurry to a washing kettle with an overflow port, spraying cold water on the top of the washing kettle, and introducing hot water at the bottom, and performing alternating cold and hot shock washing to swell the resin in the slurry and remove impurities; under stirring, the impurities overflow the washing kettle through the overflow port with the water, and part of the resin flows out from the bottom of the washing kettle with the water and is circulated back to below the liquid level of the slurry washing mixture in the washing kettle through a washing circulation pump.

[0013] The present invention returns the circulating material to below the liquid level of the slurry washing mixed liquid in the washing kettle, thereby avoiding resin overflow loss.

[0014] In some embodiments, the slurry washing and impurity removal process can result in the vinylidene chloride polymerization product accounting for 32% to 35% of the slurry after separation, water accounting for 57% to 60%, and impurities accounting for 5% to 8% by mass. Furthermore, the sum of the mass percentages of the vinylidene chloride polymerization product, water, and impurities in the slurry after separation is 100%.

[0015] In some embodiments, in the slurry washing and impurity removal process, the amount of slurry transferred to the washing tank is 30 to 40 tons, for example, 35 tons.

[0016] In some preferred embodiments, the slurry washing and impurity removal process has a spraying cold water flow rate of 5 to 10 m 3 / h, for example 8m 3 / h, etc.

[0017] In some preferred embodiments, the slurry washing and impurity removal process has a circulation flow rate of 50-100 m 3 / h, 70 m 3 / h, etc.

[0018] In some embodiments, in the slurry washing and impurity removal process, the cold water is room temperature water and the hot water temperature exceeds 60°C.

[0019] In some preferred examples, in the slurry washing and impurity removal process, the slurry washing temperature in the washing kettle is controlled at 35~60°C.

[0020] In some preferred embodiments, in the slurry washing and impurity removal process, the cold shock washing in the hot and cold shock washing refers to controlling the slurry washing temperature in the washing kettle at 35-45°C, for example, 35-40°C, and the hot shock washing refers to controlling the slurry washing temperature in the washing kettle at 45-60°C, for example, 55-60°C. It is understandable that the hot shock washing temperature is higher than the cold shock washing temperature.

[0021] In the present invention, cold and hot shock washing can be achieved by adjusting the amount of cold water sprayed and the amount of hot water introduced. For example, cold shock washing can be achieved by reducing or not introducing hot water, maintaining cold water spraying, and lowering the washing temperature; while hot shock washing can be achieved by increasing the amount of hot water introduced and raising the washing temperature.

[0022] In some preferred examples, in the slurry washing and impurity removal process, the slurry is washed in the washing tank for 2 to 5 hours, for example, 3 hours.

[0023] In some preferred examples, in the slurry washing and impurity removal process, the total time of the cold shock washing in the cold and hot shock washing is 1 to 4 hours, such as 2 hours, 3 hours, etc., and the total time of the hot shock washing is 1 to 4 hours, such as 2 hours, 3 hours, etc.

[0024] In some preferred examples, in the slurry washing and impurity removal process, the time of a single cold shock washing and a single hot shock washing in the cold and hot shock washing is 0.5 to 2 hours, such as 1 hour, 1.5 hours, etc.

[0025] In some preferred examples, in the slurry washing and impurity removal process, the ratio of the total time of cold shock washing to the total time of hot shock washing in the cold and hot shock washing is 0.25~4:1, for example, 0.5:1, 1:1, 2:1, etc.

[0026] In some preferred examples, in the slurry washing and impurity removal process, the cold shock washing and the hot shock washing are alternated 2 to 5 times, for example, 3 times, 4 times, etc., wherein changing from cold shock washing to hot shock washing or from hot shock washing to cold shock washing is counted as one alternation.

[0027] In some preferred examples, the stirring speed of the slurry washing and impurity removal process is 20-60 rpm, for example, 40 rpm.

[0028] In the second aspect, the present invention provides a vinylidene chloride polymerization production process, including a polymerization process, a desorption process and a centrifugation process. The vinylidene chloride polymerization production process also includes a washing and impurity removal process located between the desorption process and the centrifugation process. The washing and impurity removal process adopts the slurry washing and impurity removal process described in the first aspect. The slurry washing and impurity removal process receives the slurry after desorption in the desorption process, and the output of the slurry washing and impurity removal process is sent to the centrifugation process.

[0029] In the third aspect, the present invention provides a slurry washing and impurity removal device after separation in the production process of vinylidene chloride polymerization, comprising a washing kettle with an overflow port, a cold water spray device arranged on the top of the washing kettle, a hot water inlet pipe and a discharge pipe connected to the bottom of the washing kettle, the discharge pipe being connected to one end of a washing circulation pump, and the other end of the washing circulation pump being connected to the washing kettle through a return pipe, the return pipe outlet being located below the liquid level of the slurry washing mixture in the washing kettle, and a stirring device being further provided in the washing kettle.

[0030] The invention arranges the outlet of the return pipe below the liquid level of the slurry washing mixed liquid in the washing kettle, so that the circulating material can be returned below the liquid level of the slurry washing mixed liquid in the washing kettle to avoid resin overflow loss.

[0031] The slurry washing and impurity removal device described in the third aspect can be used to perform the slurry washing and impurity removal process described in the first aspect.

[0032] The slurry washing and impurity removal process described in the first aspect can be carried out using the slurry washing and impurity removal device described in the third aspect.

[0033] In a fourth aspect, the present invention provides a vinylidene chloride polymerization production device, comprising a polymerization device, a desorption device and a centrifugal device. The vinylidene chloride polymerization production device also includes the slurry washing and impurity removal device described in the third aspect, the washing kettle in the slurry washing and impurity removal device is connected to the desorption device, and the other end of the washing circulation pump in the slurry washing and impurity removal device is also connected to the centrifugal device.

[0034] The vinylidene chloride polymerization production apparatus described in the fourth aspect can be used to implement the vinylidene chloride polymerization production process described in the second aspect.

[0035] The vinylidene chloride polymerization production process described in the second aspect can be carried out using the vinylidene chloride polymerization production device described in the fourth aspect.

[0036] Compared with the prior art, the present invention has the following beneficial effects: 1) Uniform particle size distribution.

[0037] The present invention aims to provide a process for separating a foam material (containing dispersants, additives, etc.) from a polymerization reaction product (such as a PVDC-MA slurry). Compared to existing processes, this process incorporates a new washing and impurity removal step. High-speed water flow creates a high-speed rotating flow field within a washing tank. The slurry and foam material swell and separate under alternating hot and cold impact washing. Compared to the existing process, the final product particle size distribution is improved from ≥92% of the original 32-120 mesh to ≥95% of the 32-120 mesh. This more uniform particle size distribution improves resin flowability and thermal uniformity during processing, resulting in a more optimal melt processing state, resulting in better processing stability, significantly improved film quality, and a reduction in processing losses from 5-8% in the original process to 2-4%.

[0038] 2) PVDC products have a high yield rate.

[0039] The temperature of the slurry after extraction is typically between 50 and 70°C. If centrifugal drying is performed directly according to existing techniques, powder adsorption and agglomeration are more severe, easily resulting in lumps and a high probability of black and yellow specks in the product. Furthermore, experiments have found that if the slurry after extraction is naturally cooled by more than 10 to 15°C before centrifugal drying, the particle size of the resin product becomes more dispersed and uneven. This present invention utilizes a new washing and impurity removal process, controlling the slurry washing temperature in the washing kettle at 35 to 60°C. Compared to the previous method, the slurry system is cooled by more than 10 to 15°C before entering the centrifuge and drying fluidized bed. This significantly reduces powder adsorption and agglomeration, making it less likely to produce lumps and significantly reducing the probability of black and yellow specks in the product. While maintaining the operating conditions of the reaction and extraction systems, the PVDC product yield rate has been increased from 93% to over 96% (inclusive).

[0040] 3) Reduced energy consumption.

[0041] By using alternating hot and cold impact swelling and washing to remove media such as suspension polymerization additives and organic dispersants, the resin is heated more evenly during the drying process, and the drying efficiency is significantly improved, thereby achieving the goal of reducing heat energy consumption during the drying process. Steam consumption has dropped from the original 1.48t / t to 1.38t / t, and the by-product resin rate of PVDC products has dropped to below 4%.

[0042] 4) The cleaning cycle of centrifugal equipment is extended.

[0043] The lower PVDC slurry temperature reduces the amount of lumps, thereby significantly reducing the subsequent centrifuge drum wear rate and the probability of black and yellow spots in the product. The centrifuge cleaning cycle is reduced from the original 15 days / time to more than 3 months / time, effectively improving production efficiency while reducing labor costs.

[0044] 5) Reduction of three wastes.

[0045] A. The present invention improves the product yield during operation, can further reduce the original product waste rate, and reduce the amount of solid waste generated.

[0046] B. The present invention prolongs the centrifuge cleaning cycle by about 1 time during operation, which can significantly reduce the annual wastewater volume generated by centrifuge cleaning.

[0047] C. The present invention can recycle and reuse the waste water after washing during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a structural schematic diagram of a slurry washing and impurity removal device after separation in a vinylidene chloride polymerization production process in a specific embodiment. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0050] like Figure 1 As shown, a slurry washing and impurity removal device after separation in the vinylidene chloride polymerization production process includes a washing kettle 1 with an overflow port 2 on the side, a cold water spray device 3 is arranged on the top of the washing kettle 1, a hot water inlet pipe 4 and a discharge pipe 5 are connected to the bottom of the washing kettle 1, the discharge pipe 5 is connected to one end of a washing circulation pump 6, and the other end of the washing circulation pump 6 is connected to the washing kettle 1 through a return pipe 7, the outlet of the return pipe 7 is lower than the overflow port 2 and is located below the liquid level of the slurry washing mixture in the washing kettle 1, and a stirring device 8 is also provided in the washing kettle 1.

[0051] A vinylidene chloride polymerization production device, comprising a polymerization device, a separation device and a centrifugal device, the vinylidene chloride polymerization production device further comprising Figure 1 In the slurry washing and impurity removal device shown above, the washing kettle 1 in the slurry washing and impurity removal device is connected to the desorption device, and the other end of the washing circulation pump 6 in the slurry washing and impurity removal device is also connected to the centrifugal device.

[0052] A process for washing and removing impurities from the slurry after separation in the production process of vinylidene chloride polymerization, using Figure 1 The above-mentioned slurry washing and impurity removal device shown includes: transferring the desorbed slurry to a washing kettle 1 with an overflow port 2 on the side, spraying cold water through a cold water spray device 3 on the top of the washing kettle 1, and introducing hot water through a hot water inlet pipe 4 at the bottom. The resin in the slurry is swollen and impurities are removed through alternating cold and hot shock washing. Under the stirring of the stirring device 8, the impurities overflow out of the washing kettle 1 through the overflow port 2 along with the water, and part of the resin flows out from the discharge pipe 5 at the bottom of the washing kettle 1 along with the water and is circulated back to below the liquid level of the slurry washing mixture in the washing kettle 1 through the washing circulation pump 6 and the return pipe 7.

[0053] The above-mentioned post-desorption slurry washing and impurity removal process in the vinylidene chloride polymerization production process, in this embodiment, involves separating impurities such as methyl acrylate (MA), vinylidene chloride (VDC), and dispersant from a high-performance polyvinylidene chloride (PVDC) barrier material mixture containing methyl acrylate (MA), vinylidene chloride (VDC), and dispersant, thereby obtaining high-purity polyvinylidene chloride (PVDC). This washing and impurity removal process is added between the existing MA desorption process and the centrifugal drying process. The desorbed resin slurry is pumped into a washing kettle 1 using a centrifugal slurry delivery pump. High-pressure, high-purity water is then circulated and washed for a specified period of time using a wash circulation pump 6 at a controlled temperature, with a controlled spray flow rate and stirring speed. The overflow of the wash water is collected in a wash liquid collection tank and then pumped to other processes for wastewater recycling. The qualified slurry after washing is then delivered to the next centrifugal drying process using the wash circulation pump 6.

[0054] In this example, a mixture (PVDC slurry weight percentage composition: PVDC 35%, water 60%, impurity foam material 5%) at 50-70°C is added to the washing tank 1 at a feeding rate of 5 t / h. The mass of the mixture in one batch is 35 tons. High-purity water is used in the range of 35-60°C for alternating hot and cold shock washing. The spray flow rate of the cold water spray device 3 is controlled to 8 m 3 / h and stirring device 8 stirring speed 40 rpm, combined with washing circulation pump 6 for 3 hours 70 m 3 / h circulation washing, the upper washing water overflows to the washing liquid collection tank for collection, and is then pumped to other processes for related wastewater recycling by a washing liquid delivery pump. PVDC high-efficiency slurry is obtained at the bottom of the washing kettle 1 and delivered to the next centrifugal drying process by a washing circulation pump 6. In this embodiment, the cold water sprayed by the cold water spray device 3 is room temperature water, and the hot water introduced by the hot water inlet pipe 4 has a temperature exceeding 60°C. In this embodiment, the alternating hot and cold shock washing is specifically a first cold shock washing of 1 hour - a hot shock washing of 1 hour - a second cold shock washing of 1 hour, for a total of 3 hours. The cold shock washing refers to the slurry washing temperature in the washing kettle 1 being controlled at 35-40°C, and the hot shock washing refers to the slurry washing temperature in the washing kettle being controlled at 55-60°C.

[0055] A vinylidene chloride polymerization production process includes a polymerization process, a separation process and a centrifugation process. The vinylidene chloride polymerization production process also includes a washing and impurity removal process located between the separation process and the centrifugation process. The washing and impurity removal process adopts the above-mentioned slurry washing and impurity removal process. The above-mentioned slurry washing and impurity removal process receives the slurry separated by the separation process, and the output of the slurry washing and impurity removal process is sent to the centrifugation process.

[0056] This cleaning method improves the particle size distribution of the final product obtained by centrifugal drying from the original 32-120 mesh (≥92%) to 32-120 mesh (≥95%). Using this washing and impurity removal method, the slurry system is cooled to 35-40°C before entering the centrifuge and fluidized bed drying process, significantly reducing powder adsorption and agglomeration. The yield of PVDC products has increased from 93% to over 96%. The subsequent centrifuge cleaning cycle has been reduced from 15 days to over 3 months, effectively improving production efficiency while reducing labor costs.

[0057] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A process for washing and removing impurities from slurry after separation in a vinylidene chloride polymerization production process, characterized in that: include: The precipitated slurry is transferred to a washing kettle with an overflow port. Cold water is sprayed on the top of the washing kettle and hot water is introduced at the bottom. The resin in the slurry is swollen and impurities are removed through alternating cold and hot shock washing. Under stirring, the impurities overflow out of the washing kettle through the overflow port along with the water, and part of the resin flows out from the bottom of the washing kettle along with the water and is circulated back to below the liquid level of the slurry washing mixture in the washing kettle through the washing circulation pump.

2. The slurry washing and impurity removal process according to claim 1, characterized in that: In terms of mass percentage, the vinylidene chloride polymerization product in the slurry after desorption accounts for 32% to 35%, water accounts for 57% to 60%, and impurities account for 5% to 8%.

3. The slurry washing and impurity removal process according to claim 2, characterized in that: In the slurry after separation, the sum of the mass percentages of vinylidene chloride polymerization product, water and impurities is 100%.

4. The slurry washing and impurity removal process according to claim 1, characterized in that: The amount of slurry transferred to the washing tank is 30~40 tons.

5. The slurry washing and impurity removal process according to claim 1, characterized in that: The cold water flow rate of the spray is 5~10 m 3 / h.

6. The slurry washing and impurity removal process according to claim 1, characterized in that: The circulation flow of the washing circulation pump is 50~100 m 3 / h.

7. The slurry washing and impurity removal process according to claim 1, characterized in that: The cold water is room temperature water and the hot water temperature is over 60℃.

8. The slurry washing and impurity removal process according to claim 1, characterized in that: The slurry washing temperature in the washing kettle is controlled at 35~60℃.

9. The slurry washing and impurity removal process according to claim 1, characterized in that: The cold shock washing in the cold and hot shock washing refers to controlling the slurry washing temperature in the washing kettle at 35-45°C, and the hot shock washing refers to controlling the slurry washing temperature in the washing kettle at 45-60°C.

10. The slurry washing and impurity removal process according to claim 9, characterized in that: The cold shock washing in the cold and hot shock washing refers to controlling the slurry washing temperature in the washing kettle at 35-40°C, and the hot shock washing refers to controlling the slurry washing temperature in the washing kettle at 55-60°C.

11. The slurry washing and impurity removal process according to claim 1, characterized in that: The slurry is washed in the washing kettle for 2 to 5 hours.

12. The slurry washing and impurity removal process according to claim 1, characterized in that: The total time of the cold shock washing in the cold and hot shock washing is 1 to 4 hours, and the total time of the hot shock washing is 1 to 4 hours.

13. The slurry washing and impurity removal process according to claim 1, characterized in that: The time of a single cold shock washing and a single hot shock washing in the cold and hot shock washing is 0.5 to 2 hours.

14. The slurry washing and impurity removal process according to claim 1, characterized in that: The ratio of the total time of the cold shock washing to the total time of the hot shock washing in the cold and hot shock washing is 0.25-4:

1.

15. The slurry washing and impurity removal process according to claim 1, characterized in that: In the cold and hot shock washing, the cold shock washing and the hot shock washing are alternated 2 to 5 times.

16. The slurry washing and impurity removal process according to claim 1, characterized in that: The stirring speed is 20~60 rpm.

17. A process for producing vinylidene chloride by polymerization, comprising a polymerization step, a separation step and a centrifugation step, characterized in that: The vinylidene chloride polymerization production process also includes a washing and impurity removal process located between the separation process and the centrifugation process. The washing and impurity removal process adopts the slurry washing and impurity removal process described in any one of claims 1 to 16. The slurry washing and impurity removal process receives the slurry separated by the separation process, and the output of the slurry washing and impurity removal process is sent to the centrifugation process.

18. A device for washing and removing impurities from slurry after separation in a vinylidene chloride polymerization production process, characterized in that: It includes a washing kettle with an overflow port, a cold water spray device is arranged on the top of the washing kettle, a hot water inlet pipe and a discharge pipe are connected to the bottom of the washing kettle, the discharge pipe is connected to one end of the washing circulation pump, and the other end of the washing circulation pump is connected to the washing kettle through a return pipe. The return pipe outlet is located below the liquid level of the slurry washing mixture in the washing kettle, and a stirring device is also provided in the washing kettle.

19. A vinylidene chloride polymerization production device, comprising a polymerization device, a separation device and a centrifugal device, characterized in that: The vinylidene chloride polymerization production device also includes the slurry washing and impurity removal device according to claim 8, the washing kettle in the slurry washing and impurity removal device is connected to the separation device, and the other end of the washing circulation pump in the slurry washing and impurity removal device is also connected to the centrifugal device.

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