Advanced treatment and recycling system for polyvinyl chloride mother liquor

Abstract

The utility model discloses an advanced treatment and recycling system for polyvinyl chloride mother liquor. The advanced treatment and recycling system comprises a mother liquor pretreatment device, a mother liquor advanced treatment device and a recycling and pure water preparation device, the polymerization centrifugal mother liquor with the COD content of less than or equal to 350mg / L is recycled to prepare pure water, so that the overall pure water balance of the PVC device is realized, the use amount of surface water is reduced, the use efficiency of water in the mother liquor is improved, the waste of water resources is avoided, and the problems of resource waste and environmental pollution of the polymerization mother liquor are fundamentally solved. The reduction, harmlessness and resource utilization of the polymerization mother liquor are realized; obvious economic benefits, environmental benefits and social benefits are brought to enterprises, and meanwhile, the advanced concepts of low carbon, environmental protection, energy conservation and emission reduction at present are met.

Description

Technical Field

[0001] The utility model belongs to the technical field of water treatment and recovery devices, and in particular relates to a deep treatment and reuse system for polyvinyl chloride mother liquor water. Background Art

[0002] The suspension-process PVC production process requires that VCM oil droplets suspended in water polymerize under the action of dispersants and initiators. A large amount of soft water is used during the reaction, resulting in PVC particles suspended in water. During the centrifugal drying step, the PVC particles are separated by centrifugation, and the separated water is the mother liquor. Some unreacted dispersants, initiators, and other additives may remain in the mother liquor. These residual additives are organic matter, representing cyclic and macromolecular COD, and can only be reused after treatment. Currently, pretreated mother liquor water is sent to the utility circulating water system for replenishment. Due to low replenishment volumes in winter, mother liquor water is in excess. Currently, pure water is produced using surface water and evaporative condensate. To reduce surface water usage and improve its efficiency, the mother liquor water requires advanced treatment to achieve surface water quality of Class III or higher. This water is then sent to the utility's pure water station for pure water production, avoiding water waste and aligning with current low-carbon, environmentally friendly, energy-saving, and emission-reduction initiatives. In view of this, a polyvinyl chloride mother liquor water deep treatment and reuse system is designed to realize the recycling of water resources and reduce production costs.

[0003] For example, the process route proposed in the Chinese patent document with publication number 219217774 is to use ozone oxidation + carbon filtration + ion exchange method for the mother liquor water after pretreatment. The ion exchange method produces a large amount of recycled wastewater during operation, which does not conform to the original intention of water treatment reduction. Considering the properties of PVC mother liquor water itself, the mother liquor water after ozone oxidation + biochemical oxidation + filtration can be completely achieved by membrane method. Utility Model Content

[0004] The purpose of the utility model is to solve the problems of insufficient existing technology for purification and treatment of polymerization mother liquor water and to completely realize zero discharge and reuse of polymerization mother liquor water. It provides a polyvinyl chloride mother liquor water deep treatment and reuse system, reduces the use of surface water, improves the use efficiency of water in the mother liquor, avoids the waste of water resources, and fundamentally solves the problem of resource waste and environmental pollution of polymerization mother liquor water.

[0005] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0006] A polyvinyl chloride mother liquor water deep treatment and reuse system comprises a mother liquor water pretreatment device, a mother liquor water deep treatment device and a reuse pure water preparation device connected in sequence;

[0007] The mother liquor water pretreatment device includes a cooling tower, a hydrolysis and acidification tank, a contact oxidation tank, an inclined plate sedimentation tank, an intermediate water tank, a sand filter tank, a lifting water tank, and a mother liquor intermediate water tank. The aeration fan I sends air into the bottom of the contact oxidation tank for blowing; the hydrolysis and acidification tank is connected to a nitrogen and phosphorus dosing pipe; the inclined plate sedimentation tank is connected to a sedimentation agent dosing pipe;

[0008] The mother liquor water deep treatment device includes a mother liquor intermediate water tank, an ozone oxidation tower, a stripping tank, a biochemical tank, a secondary sedimentation tank, an intermediate water tank, a multi-media filter, an ultrafiltration raw water tank, an ultrafiltration device and an ultrafiltration water production tank and an aeration fan II connected in sequence; the aeration fan II sends air into the stripping tank and the bottom of the biochemical tank for blowing; an ozone aeration disk and a catalytic filler are arranged in the ozone oxidation tower; the mother liquor intermediate water treated by the pretreatment device is sent to the mother liquor intermediate water tank and then sent to the bottom of the ozone oxidation tower through a lifting pump. The bottom of the ozone oxidation tower is also connected to an ozone generator, and overflows from the top of the ozone oxidation tower into the stripping tank, the biochemical tank, the secondary sedimentation tank and the intermediate water tank in sequence. The mother liquor water in the intermediate water tank is transported to the multi-media filter I by the lifting pump and then flows into the ultrafiltration raw water tank. The mother liquor water in the ultrafiltration raw water tank is pumped to the ultrafiltration safety filter and then enters the ultrafiltration device. The filtered water enters the ultrafiltration water production tank;

[0009] The reuse pure water device includes a pure water source pool, a multi-media filter II, a reverse osmosis safety filter, a reverse osmosis device, a degassing tower, an intermediate water tank, a mixed bed, a resin trap and a pure water tank;

[0010] Furthermore, the ozone generator is connected to a liquid oxygen tank.

[0011] Furthermore, the ultrafiltration security filter and the reverse osmosis security filter use large-flux filter elements.

[0012] Furthermore, the biochemical pool is connected to a carbon source dosing tube.

[0013] The beneficial effects of the utility model are as follows: the utility model provides a polyvinyl chloride mother liquor water deep treatment and reuse system, which, through the mother liquor water pretreatment device, the mother liquor water deep treatment device and the reuse pure water preparation device, reuses the polymerization centrifugal mother liquor water with a COD content of ≤350 mg / L to prepare pure water, thereby achieving the overall pure water balance of the PVC device itself, reducing the use of surface water, improving the use efficiency of water in the mother liquor, avoiding the waste of water resources, and fundamentally solving the resource waste and environmental pollution problems of polymerization mother liquor water, achieving the reduction, harmlessness and resource utilization of polymerization mother liquor water; it also brings obvious economic benefits, environmental benefits and social benefits to the enterprise, and is in line with the current advanced concept of low carbon environmental protection, energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of the present utility model.

[0015] Figure 2 It is a structural diagram of the mother liquid water pretreatment device.

[0016] Figure 3 It is a structural diagram of the mother liquor water deep treatment device.

[0017] Figure 4 It is a structural diagram of a reuse pure water device.

[0018] Figure: 10. Cooling tower; 11. Hydrolysis and acidification tank; 111. Nitrogen and phosphorus dosing pipe; 12. Contact oxidation tank; 121. Aeration fan I; 13. Inclined plate settling tank; 131. Sedimentation agent dosing pipe; 14. Intermediate water tank; 15. Sand filter tank; 16. Lifting tank; 17. Mother liquor intermediate water tank; 20. Ozone oxidation tower; 201. Ozone generator; 202. Liquid oxygen tank; 21. Stripping tower; 22. Biochemical tank; 221. Carbon source dosing pipe ; 222. Aeration fan II; 23. Secondary sedimentation tank; 24. Intermediate water tank; 25. Multi-media filter I; 26. Ultrafiltration raw water tank; 27. Ultrafiltration safety filter; 28. Ultrafiltration device; 29. ​​Ultrafiltration water production tank; 30 Pure water raw water tank; 31. Multi-media filter II; 32. Reverse osmosis safety filter; 33. Reverse osmosis device; 34. Degassing tower; 35. Intermediate water tank; 36. Mixed bed; 37. Resin collector; 38. Pure water tank. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to more clearly and accurately understand the technical solution of the present invention, the following is a detailed explanation by way of examples. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0020] Example

[0021] Reference Figure 1 As shown, a polyvinyl chloride mother liquor water deep treatment and reuse system includes a mother liquor water pretreatment device, a mother liquor water deep treatment device and a reuse pure water device connected in sequence;

[0022] The mother liquor water pretreatment device includes a cooling tower 10, a hydrolysis and acidification tank 11, a contact oxidation tank 12, an inclined plate sedimentation tank 13, an intermediate water tank 14, a sand filter tank 15, a lifting tank 16, and a mother liquor intermediate water tank 17. The aeration fan I 121 sends air into the bottom of the contact oxidation tank 12 for blowing; the hydrolysis and acidification tank 11 is connected to a nitrogen and phosphorus dosing pipe 111; the inclined plate sedimentation tank 13 is connected to a precipitant dosing pipe 131;

[0023] The mother liquor water deep treatment device comprises a mother liquor intermediate water pool 17, an ozone oxidation tower 20, a stripping tank 21, a biochemical tank 22, a secondary sedimentation tank 23, an intermediate water pool 24, a multi-media filter 25, an ultrafiltration raw water pool 26, an ultrafiltration device 28, an ultrafiltration water production pool 29 and an aeration fan II 222, which are connected in sequence; the aeration fan II 222 sends air into the bottom of the stripping tank 21 and the biochemical tank 22 for blowing; an ozone aeration disk and a catalytic filler are arranged in the ozone oxidation tower 20; the mother liquor intermediate water treated by the pretreatment device is sent to The mother liquor in the water pool 17 is pumped into the bottom of the ozone oxidation tower 20. The bottom of the ozone oxidation tower 20 is also connected to an ozone generator 201. The mother liquor overflows from the upper part of the ozone oxidation tower into the stripping tank 21, the biochemical tank 22, the secondary sedimentation tank 23 and the intermediate water pool 24 in sequence. The mother liquor water in the intermediate water pool 24 is transported to the multi-media filter I 25 by the lifting pump and then flows into the ultrafiltration raw water pool 26. The mother liquor water in the ultrafiltration raw water pool 26 is pumped to the ultrafiltration safety filter 27 and then enters the ultrafiltration device 28. The filtered product water enters the ultrafiltration product water pool 29.

[0024] The reuse pure water device includes a pure water source pool 30, a multi-media filter II 31, a reverse osmosis safety filter 32, a reverse osmosis device 33, a degassing tower 34, an intermediate water tank 35, a mixed bed 36, a resin trap 37 and a pure water tank 38;

[0025] Furthermore, the ozone generator 201 is connected to a liquid oxygen tank 202 .

[0026] Furthermore, the ultrafiltration safety filter 27 and the reverse osmosis safety filter 32 use large-flux filter elements.

[0027] Furthermore, the biochemical pool 22 is connected to a carbon source dosing pipe 221 .

[0028] The implementation process of this system:

[0029] (1) Pretreatment of mother liquor water

[0030] The centrifugal mother liquor wastewater (turbidity ≤ 100, COD ≤ 350 mg / L, temperature 25-65°C) transported from the polymerization drying station is cooled to 25-40°C in a cooling tower. Then, nitrogen and phosphorus nutrients are added according to a certain element ratio through the nitrogen and phosphorus dosing pipe 111 before entering the hydrolysis and acidification tank 11. After the high-concentration centrifugal mother liquor wastewater undergoes anaerobic reaction, the high-molecular-weight, long-chain organic matter contained in the water is decomposed into small-molecule, short-chain organic matter by anaerobic microorganisms, and then enters the contact oxidation tank 12. The aerobic microorganisms in the contact oxidation tank 12 consume the small-molecule, short-chain organic matter in the water through their own metabolism and growth and proliferation, releasing water and carbon dioxide. A small amount of undecomposed organic matter and partially detached biofilm flow into the inclined plate sedimentation tank 13 with the water. The undecomposed organic matter and detached biofilm fully react and mix with the flocculant added to the water to form flocs that enter the inclined plate sedimentation tank 13. In the inclined plate sedimentation tank 13, flocculent matter settles to the bottom of the tank under the action of gravity, forming sludge, and the supernatant flows into the intermediate water tank. The supernatant in the intermediate water tank is pressurized by the lift pump and enters the sand filter tank 15. After filtering out fine particles and impurities in the water, it enters the lift tank. The water in the lift tank flows into the mother liquor intermediate water tank 17. The mother liquor intermediate water (turbidity ≤ 4.5, COD ≤ 50 mg / L) is discharged into the sludge storage tank by the sludge discharge pump when the sludge at the bottom of the sedimentation area accumulates to a certain amount. Part of the sludge is returned to the hydrolysis acidification tank 11 and the contact oxidation tank 12 by the reflux pump, and the remaining part is sent to the sludge filter unit sludge tank for filtration.

[0031] (2) Deep treatment of mother liquor water

[0032] The mother liquor water with turbidity ≤ 4.5 and COD ≤ 50 mg / L is pumped into the bottom of the ozone oxidation tower 20. The ozone aeration disk and catalytic filler (COD degradation catalyst) are set in the ozone oxidation tower 20. The ozone (generated by the ozone generator) and the PVC mother liquor water are completely mixed through the ozone aeration disk. The strong oxidizing property of ozone is used to kill bacteria in the water. At the same time, the COD degradation catalyst decomposes the macromolecular chain organic pollutants that are difficult to biodegrade, thereby improving the biodegradability of the mother liquor water and providing favorable conditions for the subsequent biochemical system to degrade organic matter. Overflow from the top of the ozone oxidation tower flows sequentially into the stripping tank 21 to remove excess ozone. Biochemical tank 22 undergoes further biochemical reactions to further degrade organic pollutants in the wastewater's molecular chains, reducing the pollutant content. The wastewater then flows sequentially into the secondary sedimentation tank 23 and the intermediate water tank 24. The biochemical mother liquor in intermediate water tank 24 is pumped by a lift pump to a multi-media filter 1 25, which uses quartz sand and anthracite as filter media. This filter, through interception and adsorption, removes suspended matter, colloids, particulate matter, and other solids from the water, extending the service life of the ultrafiltration system. After a period of operation, the multi-media filter is backwashed regularly. After removing suspended matter and colloids, the mother liquor flows into the ultrafiltration raw water tank 26. The mother liquor from the ultrafiltration raw water tank 26 is pumped to the ultrafiltration safety filter 27 and then into the ultrafiltration unit 28. Further interception of organic pollutants, suspended matter, colloids, and other substances in the water results in the product water entering the ultrafiltration product water tank 29, providing a buffer for subsequent processes. The effluent meets surface water standards IIII.

[0033] (3) Recycling to produce pure water

[0034] After pretreatment and advanced treatment, the mother liquor, meeting surface water IIII standards, is fed into the pure water raw water tank 30. It is pumped through the raw water pump into the multi-media filter II 31. As it flows downward through the filter media layer, suspended solids, impurities, and particulate matter are removed, reducing the water's turbidity. It then enters the reverse osmosis safety filter 32. After being pressurized by a high-pressure pump, it enters the reverse osmosis unit 33, where most inorganic ions (such as calcium, magnesium, and sulfate) are removed. It also removes most organic matter, bacteria, heat-causing viruses, and particulates. The filtered water enters the degassing tower 34, where carbon dioxide is removed. It then enters the intermediate water tank 35, passes through the mixed bed 36, and flows downward through the mixed resin layer. The cations in the water are replaced by hydrogen ions from the cation resin, while the anions are replaced by hydroxide ions from the anion resin. The hydrogen and hydroxide ions in the water then form water molecules. After passing through the resin trap 37, it enters the pure water tank 38 and is pumped to various pure water users.

[0035] The technical indicators of PVC mother liquor water treated by the device of the utility model are shown in Tables 1, 2 and 3. The annual processing capacity is about 1.6 million tons (operating time is 8000 hours / year), which reduces the annual use of surface water by about 1.6 million tons, improves the utilization efficiency of water in the mother liquor, and completely solves the production and environmental protection problems of the treatment and reuse of polyvinyl chloride mother liquor water.

[0036] Table 1 Main water quality of polymerization centrifugal mother liquor

[0037] Serial number project unit Control indicators 1 pH / 6.5～8.5 2 Turbidity NTU ≤100 3 <![CDATA[BOD5]]> mg / L ≤80 4 <![CDATA[COD Cr ]]> mg / L ≤350

[0038] Table 2 Main water quality of deep treated mother liquor water

[0039] Serial number project unit Control indicators 1 pH / 6.5～8.5 2 Turbidity NTU - 3 <![CDATA[BOD5]]> mg / L ≤4 4 <![CDATA[COD Cr ]]> mg / L ≤10

[0040] Table 3 Pure water quality table

[0041] Serial number project unit Control indicators 1 pH / 6.5～7.5 2 hardness mg / kg ≤5 3 Chloride mg / kg ≤5 4 Conductivity S / cm ≤1.5×10-6 5 <![CDATA[Fe 3+ ]]> mg / l ≤0.1 6 <![CDATA[Ca 2+ 、Mg 2+ ]]> mg / l ≤0.03 Si mg / l ≤0.1

[0042] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A polyvinyl chloride mother liquor water deep treatment and reuse system, characterized by: It includes a mother liquid water pretreatment device, a mother liquid water deep treatment device and a reuse pure water device connected in sequence; The mother liquor water pretreatment device includes a cooling tower, a hydrolysis acidification tank, a contact oxidation tank, an inclined plate sedimentation tank, an intermediate water tank, a sand filter tank, a lifting water tank and a mother liquor intermediate water tank. The aeration fan I sends air into the bottom of the contact oxidation tank for blowing; the hydrolysis acidification tank is connected to a nitrogen and phosphorus dosing pipe; the inclined plate sedimentation tank is connected to a sedimentation agent dosing pipe; The mother liquor water deep treatment device includes a mother liquor intermediate water tank, an ozone oxidation tower, a stripping tank, a biochemical tank, a secondary sedimentation tank, an intermediate water tank, a multi-media filter, an ultrafiltration raw water tank, an ultrafiltration device and an ultrafiltration water production tank and an aeration fan II connected in sequence; the aeration fan II sends air into the stripping tank and the bottom of the biochemical tank for blowing; an ozone aeration disk and a catalytic filler are arranged in the ozone oxidation tower; the mother liquor intermediate water treated by the pretreatment device is sent to the mother liquor intermediate water tank and then sent to the bottom of the ozone oxidation tower through a lifting pump. The bottom of the ozone oxidation tower is also connected to an ozone generator, and overflows from the top of the ozone oxidation tower into the stripping tank, the biochemical tank, the secondary sedimentation tank and the intermediate water tank in sequence. The mother liquor water in the intermediate water tank is transported to the multi-media filter I by the lifting pump and then flows into the ultrafiltration raw water tank. The mother liquor water in the ultrafiltration raw water tank is pumped to the ultrafiltration safety filter and then enters the ultrafiltration device. The filtered water enters the ultrafiltration water production tank; The reuse pure water device comprises a pure water source pool, a multi-media filter II, a reverse osmosis safety filter, a reverse osmosis device, a degassing tower, an intermediate water tank, a mixed bed, a resin catcher and a pure water tank.

2. A polyvinyl chloride mother liquor water deep treatment and reuse system according to claim 1, characterized in that: The ozone generator is connected to the liquid oxygen tank.

3. The polyvinyl chloride mother liquor water deep treatment and reuse system according to claim 1, characterized in that: The ultrafiltration safety filter and the reverse osmosis safety filter use large-flux filter elements.

4. The polyvinyl chloride mother liquor water deep treatment and reuse system according to claim 1, characterized in that: The biochemical pool is connected with a carbon source dosing tube.

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