Polyvinylidene fluoride resin slurry monomer recovery and washing device

Abstract

The utility model provides a kind of polyvinyl fluoride resin slurry monomer recovery and washing device, including polymerizer, the bottom end of the polymerizer is connected with infusion tube, the infusion tube is connected with washing tank, infusion valve is equipped on infusion tube, the top of the polymerizer is connected with first gas pipe, the first gas pipe is connected with gas storage tank, first cut-off valve and first vacuum pump are equipped on first gas pipe, the top of the washing tank is connected with second gas pipe, the second gas pipe is connected with gas storage tank, second cut-off valve and cyclone separator are equipped on second gas pipe, the bottom end of the washing tank is connected with liquid outlet pipe, liquid outlet valve is equipped on liquid outlet pipe.The utility model sets up gas pipe with vacuum pump in the top of polymerizer and washing tank, the gas phase remaining in polymerizer and washing tank is extracted by vacuum pump, effectively improve the recovery effect of gas, ensure that there is no VDF gas residue.

Description

Technical Field

[0001] This utility model belongs to the field of polyvinylidene fluoride (PVDF) production technology, and relates to a device for recovering monomers from PVDF resin slurry and washing it with water. Background Technology

[0002] The suspension polymerization process for polyvinylidene fluoride (PVDF) resin uses PVDF monomer with a purity ≥99.99% as raw material and deoxygenated and desalinated water as the dispersion medium. Under precisely controlled temperature and pressure parameters and stable stirring conditions, a free radical polymerization reaction is initiated through the synergistic effect of the dispersant and initiator. When the polymerization reaction reaches its endpoint, the resulting slurry system contains not only the target product, PVDF resin, but also unreacted VDF monomer, dispersant, catalyst, terminator, and other functional additives. Currently, the process uses a self-pressurized recovery mode in the polymerization reactor to treat unreacted monomer. Recovery is terminated when the pressure inside the reactor drops to a critical value. After removing residual VDF through a nitrogen purging process, the slurry is discharged into a pretreatment tank for washing. The process suffers from the following technical bottlenecks: 1. Limited monomer recovery efficiency: The self-pressure recovery process relies on natural pressure drop, which is time-consuming and seriously affects the turnover efficiency of the polymerization reactor; 2. Inadequate residue control: The VDF residue in the finished resin is generally >50ppm. The nitrogen replacement process not only increases gas consumption but also leads to excessive VOC emissions; 3. Additive residues affect quality: Dispersants and other organic additives undergo thermal degradation during fluidized bed drying. The resulting oligomers increase the resin yellowing index and increase the fluctuation range of melt flow rate, significantly reducing the product grade. Utility Model Content

[0003] The purpose of this invention is to provide a device for recovering and washing monomers from polyvinylidene fluoride resin slurry, addressing the problems existing in the prior art.

[0004] Therefore, the present invention adopts the following technical solution: A device for recovering monomers from polyvinylidene fluoride (PVDF) resin slurry and washing it includes a polymerization reactor. A liquid delivery pipe is connected to the bottom of the polymerization reactor, and the liquid delivery pipe is connected to a washing tank. A liquid delivery valve is installed on the liquid delivery pipe. A first gas delivery pipe is connected to the top of the polymerization reactor, and the first gas delivery pipe is connected to a gas storage tank. A first shut-off valve and a first vacuum pump are installed on the first gas delivery pipe. A second gas delivery pipe is connected to the top of the washing tank, and a second shut-off valve and a cyclone separator are installed on the second gas delivery pipe. A liquid outlet pipe is connected to the bottom of the washing tank, and a liquid outlet valve is installed on the liquid outlet pipe.

[0005] Furthermore, the top of the washing tank is connected to an air extraction pipe, which is connected to the first air supply pipe. A second vacuum pump is installed on the air extraction pipe, and an exhaust pipe is connected to the middle of the air extraction pipe. A third shut-off valve is installed near the washing tank and a fourth shut-off valve is installed near the first air supply pipe. An exhaust valve is installed on the exhaust pipe.

[0006] Furthermore, the liquid outlet pipe is connected to a plate and frame filter press, and a plate and frame screw conveyor is provided at the bottom of the plate and frame filter press.

[0007] Furthermore, the plate and frame filter press is connected to a waste discharge pipe, which is connected to a wastewater tank.

[0008] Furthermore, the side wall of the washing tank is connected to an overflow pipe, the overflow pipe is connected to a buffer tank, the buffer tank is connected to a return pipe, the return pipe is connected to a plate and frame filter press, the return pipe is equipped with a return pump, and the overflow pipe is equipped with an overflow valve.

[0009] Furthermore, the washing tank is equipped with a mesh plate, a first water supply pipe and a second water supply pipe. The first water supply pipe is located at the upper part of the washing tank and is equipped with multiple first nozzles. One end of the first water supply pipe extends out from the side wall of the washing tank, and the outer end of the first water supply pipe is connected to a main water supply pipe. The second water supply pipe is located at the lower part of the washing tank and is equipped with multiple second nozzles. One end of the second water supply pipe extends out from the side wall of the washing tank and is connected to the main water supply pipe. A water supply valve is provided on the second water supply pipe.

[0010] The beneficial effects of this utility model are as follows: a gas supply pipe and a vacuum pump are installed at the top of the polymerization reactor and the washing tank to extract the residual gas phase in the polymerization reactor and the washing tank, effectively improving the gas recovery effect and ensuring that there is no VDF gas residue; the washing tank is drawn to a negative pressure state by the vacuum pump, which allows the slurry in the polymerization reactor to be quickly input into the washing tank, which is efficient and fast; water supply pipes are installed at the top and bottom of the washing tank to effectively improve the washing effect and efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this utility model; In the diagram, 1-polymerization reactor, 2-infusion pipe, 3-washing tank, 4-infusion valve, 5-first gas infusion pipe, 6-gas storage tank, 7-first shut-off valve, 8-first vacuum pump, 9-second gas infusion pipe, 10-second shut-off valve, 11-cyclone separator, 12-mesh plate, 13-first water infusion pipe, 14-second water infusion pipe, 15-main water infusion pipe, 16-second nozzle, 17-water infusion valve, 18-liquid outlet pipe, 19-liquid outlet valve, 20-plate and frame filter press, 21-plate and frame screw conveyor, 22-waste discharge pipe, 23-wastewater tank, 24-extraction pipe, 25-second vacuum pump, 26-exhaust pipe, 27-third shut-off valve, 28-fourth shut-off valve, 29-exhaust valve, 30-overflow pipe, 31-buffer tank, 32-return pipe, 33-return pump, 34-first nozzle, 35-overflow valve. Detailed Implementation

[0012] The present invention will now be described in detail with reference to the accompanying drawings: like Figure 1As shown, a polyvinylidene fluoride (PVDF) resin slurry monomer recovery and washing device includes a polymerization reactor 1. The polymerization reactor 1 is a conventional polymerization reactor used for polymerization reaction to produce PVDF. A liquid delivery pipe 2 is connected to the bottom of the polymerization reactor 1, and the liquid delivery pipe 2 is connected to a washing tank 3. A liquid delivery valve 4 is installed on the liquid delivery pipe 2. The solution produced after the reaction in the polymerization reactor 1 can be transported to the washing tank 3 through the liquid delivery pipe 2 for washing. A first gas delivery pipe 5 is connected to the top of the polymerization reactor 1, and the first gas delivery pipe 5 is connected to a gas storage tank 6. The gas storage tank 6 is used for... The system collects residual VDF gas. A first shut-off valve 7 and a first vacuum pump 8 are installed on the first gas supply pipe 5. A second gas supply pipe 9 is connected to the top of the washing tank 3 and is connected to the gas storage tank 6. A second shut-off valve 10 and a cyclone separator 11 are installed on the second gas supply pipe 9. A mesh plate 12 is installed inside the washing tank 3. A first water supply pipe 13 and a second water supply pipe 14 are also installed inside the washing tank 3. The first water supply pipe 13 is located at the top of the washing tank 3 and is equipped with multiple first nozzles 34. One end of the first water supply pipe 13 extends from the side of the washing tank 3. The first water pipe 13 extends through the wall and is connected to the main water pipe 15. The second water pipe 14 is located at the bottom of the washing tank 3 and is equipped with multiple second nozzles 16. One end of the second water pipe 14 extends through the side wall of the washing tank 3 and is connected to the main water pipe 15. A water supply valve 17 is provided on the second water pipe 14. The main water pipe 15 is used to supply hot water to the first water pipe 13 and the second water pipe 14. A liquid outlet pipe 18 is connected to the bottom of the washing tank 3, through which the slurry after washing can be discharged. The liquid outlet pipe 18 is equipped with... The liquid outlet valve 19 and liquid outlet pipe 18 are connected to a plate and frame filter press 20. The solution in the washing tank 3 can be transported to the plate and frame filter press 20 through the liquid outlet pipe 18 for filtration to remove waste liquid and obtain vinylidene fluoride resin. The bottom of the plate and frame filter press 20 is equipped with a plate and frame screw conveyor 21. The vinylidene fluoride resin obtained after filtration can be transported through the plate and frame screw conveyor 21. The plate and frame filter press 20 is connected to a waste discharge pipe 22, which is connected to a wastewater tank 23. The wastewater generated after filtration can be discharged into the wastewater tank 23 for collection through the waste discharge pipe 22.

[0013] A vacuum pipe 24 is connected to the top of the washing tank 3, and the vacuum pipe 24 is connected to the first gas supply pipe 5. A second vacuum pump 25 is installed on the vacuum pipe 24, and an exhaust pipe 26 is connected to the middle of the vacuum pipe 24. The vacuum pipe 24 and the exhaust pipe 26 are used to perform a vacuum operation in the washing tank 3, so that a negative pressure state is formed in the washing tank 3. In addition, the vacuum pipe 24 can also draw the residual VDF gas in the washing tank 3 into the gas storage tank 6 for storage. A third shut-off valve 27 is installed near the washing tank 3 on the vacuum pipe 24, and a second shut-off valve 28 is installed near the first gas supply pipe 5. Four shut-off valves 28, an exhaust valve 29 on the exhaust pipe 26, an overflow pipe 30 connected to the side wall of the washing tank 3, an overflow pipe 30 connected to a buffer tank 31, an overflow valve 35 on the overflow pipe 30, a return pipe 32 connected to the buffer tank 31, the return pipe 32 connected to the plate and frame filter press 20, and a return pump 33 on the return pipe 32. When there is too much slurry in the washing tank 3, it can overflow into the buffer tank 31 through the overflow pipe 30, and then be transported back to the plate and frame filter press 20 for filtration under the action of the return pump 33.

[0014] The method of using this utility model is as follows: Various raw materials for producing polyvinylidene fluoride (PVDF) are placed into polymerization reactor 1 to produce a slurry. Then, the third shut-off valve 27, exhaust valve 29, and second vacuum pump 25 are opened to create a vacuum in washing tank 3, forming a negative pressure state. After confirming that the combustible gas content in the washing tank is within acceptable limits, the liquid inlet valve 4 is opened, allowing the slurry in polymerization reactor 1 to enter washing tank 3 through liquid inlet pipe 2. Under negative pressure, the VDF in the slurry is rapidly vaporized. After the slurry enters washing tank 3, the liquid inlet valve 4 and the water inlet valve are closed. 17. Hot water is supplied to the first water pipe 13 through the main water supply pipe 15. The hot water is sprayed onto the mesh plate 12 through the first nozzle 34, so that the foam generated during vaporization is liquefied to prevent a large amount of resin foam from being mixed in the gas phase. At this time, the second shut-off valve 10 is opened, so that the VDF gas is transported to the gas storage tank 6 through the second gas supply pipe 9 for storage, and the VDF gas is initially recovered. When the gas passes through the second gas supply pipe 9, the cyclone separator 11 can remove the resin foam mixed in the gas. After the initial recovery is completed, the second shut-off valve 10 is closed.

[0015] After the initial recovery is completed, the infusion valve 4 and the first shut-off valve 7 are opened, and then the first vacuum pump 8 is started. The residual VDF gas in the polymerization kettle 1 and washing tank 3 is extracted by the first vacuum pump 8 and transported to the gas storage tank 6 through the first gas transmission pipe 5 for storage, thus completing the deep recovery.

[0016] After deep recovery is completed, the third shut-off valve 27 and the fourth shut-off valve 28 are opened (while the exhaust valve 29 is kept closed). At the same time, the first vacuum pump 8 and the second vacuum pump 25 are turned on to extract the small amount of residual VDF gas in the polymerization kettle 1 and the washing tank 3 into the gas storage tank 6, thus completing the ultimate recovery and ensuring the recycling of VDF gas.

[0017] After VDF gas recovery is complete, the water supply valve 17 is opened, and 60-65℃ hot water is supplied to the first water supply pipe 13 and the first water supply pipe 14 through the main water supply pipe 15. The hot water is sprayed from the top and bottom of the washing tank 3 through the first nozzle 34 and the second nozzle 16 to wash the slurry, ensuring washing effect and washing speed. When the liquid level in the washing tank 3 reaches the overflow height, the main water supply pipe 15 stops supplying water and lets it stand for 5 minutes. During the standing process, the resin powder separates from the washing liquid wastewater, and the resin powder settles to the bottom of the washing tank 3. Then, the overflow valve 35 can be opened to release some of the wastewater. The washing wastewater overflows into the buffer tank 31 through the overflow pipe, and then the liquid outlet valve 19 is opened. The resin powder with washing water is also transported to the plate and frame filter press 20 through the liquid outlet pipe 18 for filtration. The washing water in the resin powder is discharged through the filtration and discharged into the wastewater tank 23 through the waste discharge pipe 22 for collection. The filtered resin powder enters the plate and frame screw conveyor 21 for transport and collection. If the washing does not meet the requirements in one wash, the above washing operation can be repeated multiple times. After the corresponding requirements are met, the washed resin powder can be transported to the corresponding drying system for drying again.

[0018] In addition, the wastewater stored in the wastewater tank 23 can also be returned to the plate and frame filter press 20 for filtration through the return pipe 32 under the action of the return pump 33, and the residual resin powder can be collected.

Claims

1. A device for recovering monomers from polyvinylidene fluoride resin slurry and washing it, characterized in that, The apparatus includes a polymerization reactor (1), with a liquid delivery pipe (2) connected to the bottom end of the polymerization reactor (1), a washing tank (3) connected to the liquid delivery pipe (2), a liquid delivery valve (4) provided on the liquid delivery pipe (2), a first gas delivery pipe (5) connected to the top end of the polymerization reactor (1), a gas storage tank (6) connected to the first gas delivery pipe (5), a first shut-off valve (7) and a first vacuum pump (8) provided on the first gas delivery pipe (5), a second gas delivery pipe (9) connected to the top end of the washing tank (3), the second gas delivery pipe (9) connected to the gas storage tank (6), a second shut-off valve (10) and a cyclone separator (11) provided on the second gas delivery pipe (9), and an outlet pipe (18) connected to the bottom end of the washing tank (3), an outlet valve (19) provided on the outlet pipe (18).

2. The polyvinylidene fluoride resin slurry monomer recovery and washing device according to claim 1, characterized in that, The washing tank (3) is connected to a suction pipe (24) at the top. The suction pipe (24) is connected to the first gas supply pipe (5). A second vacuum pump (25) is provided on the suction pipe (24). An exhaust pipe (26) is connected to the middle of the suction pipe (24). A third shut-off valve (27) is provided near the washing tank (3) and a fourth shut-off valve (28) is provided near the first gas supply pipe (5). An exhaust valve (29) is provided on the exhaust pipe (26).

3. The polyvinylidene fluoride resin slurry monomer recovery and washing device according to claim 1, characterized in that, The liquid outlet pipe (18) is connected to a plate and frame filter press (20), and a plate and frame screw conveyor (21) is provided at the bottom of the plate and frame filter press (20).

4. The polyvinylidene fluoride resin slurry monomer recovery and washing device according to claim 3, characterized in that, The plate and frame filter press (20) is connected to a waste discharge pipe (22), and the waste discharge pipe (22) is connected to a wastewater tank (23).

5. The polyvinylidene fluoride resin slurry monomer recovery and washing device according to claim 1, characterized in that, The side wall of the washing tank (3) is connected to an overflow pipe (30), the overflow pipe (30) is connected to a buffer tank (31), the buffer tank (31) is connected to a return pipe (32), the return pipe (32) is connected to a plate and frame filter press (20), the return pipe (32) is equipped with a return pump (33), and the overflow pipe (30) is equipped with an overflow valve (35).

6. The polyvinylidene fluoride resin slurry monomer recovery and washing device according to claim 1, characterized in that, The washing tank (3) is provided with a mesh plate (12), a first water supply pipe (13) and a second water supply pipe (14). The first water supply pipe (13) is located at the upper part of the washing tank (3). The first water supply pipe (13) is provided with multiple first nozzles (34). One end of the first water supply pipe (13) passes through the side wall of the washing tank (3). The outer end of the first water supply pipe (13) is connected to a water supply main pipe (15). The second water supply pipe (14) is located at the lower part of the washing tank (3). The second water supply pipe (14) is provided with multiple second nozzles (16). One end of the second water supply pipe (14) passes through the side wall of the washing tank (3) and is connected to the water supply main pipe (15). The second water supply pipe (14) is provided with a water supply valve (17).

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