Method for recycling PVC mother liquor wastewater

Abstract

The invention relates to the technical field of wastewater recycling, and discloses a PVC mother liquor wastewater resource recycling method, which comprises: carrying out membrane filtration on PVC mother liquor wastewater to obtain a trapped fluid and a membrane filtration fluid; performing oxidation treatment on the membrane filtrate to obtain primary treated water; treating the primary treated water with activated carbon to obtain secondary treated water; and carrying out ion exchange treatment on the secondary treated water to obtain pure water. According to the method disclosed by the invention, the PVC particles in the PVC mother liquor wastewater are recycled by adopting the low-energy-consumption silicon carbide film, so that the problems of unstable operation in a catalytic ozonation process, pollution and blockage of activated carbon and the like in a PVC mother liquor wastewater treatment process are solved, and meanwhile, recycling is realized; the resin regeneration waste liquid and the activated carbon regeneration waste liquid are used as brine, so that no waste liquid retreatment and discharge exist in the whole technological process, and no secondary pollution exists.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater recycling, and particularly to a method for resource recycling of PVC mother liquor wastewater. Background Art

[0002] The PVC mother liquor wastewater discharged during the production process of the chlor-alkali chemical industry usually contains PVC particles, and this PVC mother liquor wastewater has the characteristics of low inorganic ion concentration and large water volume. At present, there are mainly two treatment methods for this type of wastewater. One is to meet the discharge standards or be recycled to the circulating water make-up system after processes such as cooling, precipitation, and biochemical treatment; the other is to enter the reverse osmosis membrane for advanced treatment after pretreatment and then be recycled as pure water to PVC production. However, in the existing treatment processes, the high-content PVC particles in the PVC mother liquor wastewater cannot be recycled, and at the same time, due to the difficult degradation of PVC particles, the treatment effect of the PVC mother liquor wastewater is affected. After the PVC mother liquor wastewater is treated by processes such as biochemical treatment, the COD only drops to about 50 mg / L, which will affect the system water quality when used as circulating water make-up, and membrane fouling will also occur during the reverse osmosis membrane treatment process, resulting in problems such as excessive COD concentration in the reverse osmosis concentrate water.

[0003] Therefore, there is an urgent need for a method for resource recycling of PVC mother liquor wastewater to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems in the existing treatment of PVC mother liquor wastewater, and provide a method for resource recycling of PVC mother liquor wastewater to achieve the recycling of PVC particles in the PVC mother liquor wastewater discharged from the chlor-alkali industry and the recycling of the wastewater, and at the same time, the resin regeneration waste liquid and activated carbon regeneration waste liquid during the treatment process can also be recycled to the primary brine.

[0005] To achieve the above purpose, the present invention is implemented according to the following technical scheme:

[0006] A method for resource recycling of PVC mother liquor wastewater includes the following steps:

[0007] S1, subjecting the PVC mother liquor wastewater to membrane filtration to obtain a retained liquid and a membrane filtrate;

[0008] S2, subjecting the membrane filtrate to oxidation treatment to obtain a primary treated water;

[0009] S3, treating the primary treated water with activated carbon to obtain a secondary treated water;

[0010] S4, subjecting the secondary treated water to ion exchange treatment to obtain pure water.

[0011] Specifically, an ion exchange device is used in the ion exchange treatment process. The ion exchange device includes a cation exchanger, a carbon removal device, an anion exchanger, and a mixed ion exchanger that are connected in sequence.

[0012] The PVC mother liquor wastewater is obtained by centrifuging the PVC mother liquor.

[0013] Preferably, in step S1, a membrane filtration device with a silicon carbide membrane is used for membrane filtration; the filtration accuracy of the silicon carbide membrane is 40 - 200 nm.

[0014] Specifically, this membrane filtration device is provided with a backwashing function. In the present invention, the PVC mother liquor wastewater does not need to be cooled and can directly enter the membrane filtration device. Specifically, the PVC mother liquor wastewater at a temperature of 60 - 70 °C directly enters the membrane filtration device for membrane filtration.

[0015] Preferably, the filtration method of the membrane filtration device is cross - flow filtration; the volume ratio of the retentate to the filtrate of the membrane filtration device is 1:9 - 1:20.

[0016] Preferably, the retentate is precipitated by a precipitation device to obtain a concentrated solution and a clear solution; the concentrated solution is refluxed to the PVC mother liquor centrifugation device; the clear solution is refluxed in front of the membrane filtration device.

[0017] Specifically, the concentrated solution is refluxed to the PVC mother liquor centrifugation device to be centrifuged together with the PVC mother liquor; the clear solution is refluxed in front of the membrane filtration device to be membrane - filtered together with the PVC mother liquor wastewater.

[0018] Preferably, in step S2, an ozone contact oxidation device is used for oxidation treatment; the pH of the membrane filtrate is adjusted to 8 - 9 before oxidation treatment.

[0019] Specifically, sodium hydroxide is used to adjust the pH of the membrane filtrate.

[0020] Preferably, in step S4, the secondary treated water is cooled before ion exchange.

[0021] Furthermore, the secondary treated water is cooled to 35 - 40 °C before ion exchange.

[0022] Preferably, the resin regeneration waste liquid generated during the regeneration of the resin in the ion exchange process in step S4 is used as brine.

[0023] Preferably, the activated carbon regeneration waste liquid generated during the regeneration of the activated carbon in the activated carbon treatment process in step S3 is used as brine.

[0024] The regeneration process of activated carbon involved in the present invention is a prior art; similarly, the regeneration of resin involved in the ion exchange process also belongs to the prior art, and those skilled in the art are clear about the process and will not be described in detail herein.

[0025] Specifically, the resin regeneration waste liquid and the activated carbon regeneration waste liquid can be discharged into the brine dissolving tank in the brine dissolving process section of the ion-exchange membrane electrolysis for producing sodium hydroxide solution and used as brine.

[0026] The present invention recovers PVC particles in the mother liquor, realizes the reuse of wastewater at the same time, reduces the amount of wastewater, improves the utilization rate, saves the operation cost, and achieves the goals of energy conservation, consumption reduction, and green and clean production.

[0027] Beneficial effects:

[0028] (1) By using a low-energy consumption silicon carbide membrane to recover and utilize PVC particles in the PVC mother liquor wastewater, the method of the present invention not only reduces the problems such as unstable operation in the ozone catalytic oxidation process and fouling of activated carbon during the treatment of PVC mother liquor wastewater, but also realizes the resourceful reuse.

[0029] (2) The resin regeneration waste liquid and the activated carbon regeneration waste liquid are used as brine, so that there is no re-treatment and discharge of waste liquid in the whole process, and there is no secondary pollution. Description of the drawings

[0030] Figure 1 It is the process flow diagram of Embodiment 1 of the present invention. Specific embodiments

[0031] The following further describes the present invention in detail with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] For all raw materials of the present invention, there is no special limitation on their purity, and the present invention preferably uses industrial purity or the conventional purity used in the art.

[0033] For the devices used in the present invention, those without special limitations are all the commonly used devices in the art.

[0034] Embodiment 1

[0035] As Figure 1 shown, a method for resourceful reuse of PVC mother liquor wastewater includes the following steps:

[0036] S1. Subject the PVC mother liquor wastewater to membrane filtration to obtain a retentate and a filtrate; the membrane filtration is carried out using a membrane filtration device with a silicon carbide membrane; the filtration accuracy of the silicon carbide membrane is 40 to 200 nm. The membrane filtration device is provided with a backwashing function. The PVC mother liquor wastewater at a temperature of 60 to 70 °C enters the membrane filtration device directly without cooling. The filtration method of the membrane filtration device is cross-flow filtration; the volume ratio of the retentate to the filtrate of the membrane filtration device is 1:9 to 1:20. The retentate is precipitated by a precipitation device to obtain a concentrated liquid and a clear liquid; the concentrated liquid is refluxed to the PVC mother liquor centrifugation device and centrifuged together with the PVC mother liquor; the clear liquid is refluxed to before the membrane filtration device and subjected to membrane filtration together with the PVC mother liquor wastewater.

[0037] S2. Subject the membrane filtrate to oxidation treatment to obtain primary treated water; the oxidation treatment is carried out using an ozone contact oxidation device; before the membrane filtrate is subjected to oxidation treatment, its pH is adjusted to 8 to 9 using sodium hydroxide.

[0038] S3. Treat the primary treated water with activated carbon to obtain secondary treated water;

[0039] S4. Cool the secondary treated water to 35 to 40 °C through a heat exchanger to obtain cooled secondary treated water; the cooled secondary treated water is subjected to ion exchange treatment to obtain pure water.

[0040] The resin regeneration waste liquid generated during the regeneration of the resin in the ion exchange process and the activated carbon regeneration waste liquid generated during the regeneration of the activated carbon in the activated carbon treatment process can both be discharged to the brine tank in the brine preparation process of the ion-exchange membrane electrolysis for producing sodium hydroxide solution and used as brine.

[0041] An ion exchange device is used in the ion exchange treatment process. The ion exchange device includes a cation exchanger, a carbon removal device, an anion exchanger, and a mixed ion exchanger connected in sequence.

[0042] As shown in Table 1, it is the water quality table of the PVC mother liquor wastewater in Example 1.

[0043] Table 1

[0044]

[0045]

[0046] As shown in Table 2, it is the water quality table of the membrane filtrate, primary treated water, cooled secondary treated water, and secondary treated water in Example 1.

[0047] Table 2

[0048] Temperature (°C) COD (mg / L) Turbidity (NTU) Membrane filtrate 55-65 100-150 ≤1 Primary treated water 48-57 10-15 ≤5 Secondary treated water after cooling 35-40 10-15 ≤5 Secondary treated water 34-39 ≤5 ≤3

[0049] As shown in Table 3, it is the water quality table of the pure water in Example 1.

[0050] Table 3

[0051]

[0052] As shown in Table 4, it is the data sheet of the concentrated solution.

[0053] Table 4

[0054] Project name Unit Content PVC particle content mg / L 30000

[0055] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for resource recycling of PVC mother liquor wastewater, characterized in that: It includes the following steps: S1. Subject the PVC mother liquor wastewater to membrane filtration to obtain a retentate and a membrane filtrate; S2. Subject the membrane filtrate to oxidation treatment to obtain a primary treated water; S3. Treat the primary treated water with activated carbon to obtain a secondary treated water; S4. Subject the secondary treated water to ion exchange treatment to obtain pure water.

2. The method for resource recycling of PVC mother liquor wastewater according to claim 1, characterized in that: In the step S1, the membrane filtration is carried out by using a membrane filtration device with a silicon carbide membrane; the filtration accuracy of the silicon carbide membrane is 40-200 nm.

3. A method for resource recycling of PVC mother liquor wastewater according to claim 2, characterized in that: The filtration mode of the membrane filtration device is cross-flow filtration; the volume ratio of the retentate to the membrane filtrate of the membrane filtration device is 1:9-1:

20.

4. A method for resource recycling of PVC mother liquor wastewater according to claim 3, characterized in that: The retentate is precipitated by a precipitation device to obtain a concentrated solution and a supernatant; the concentrated solution is refluxed to the PVC mother liquor centrifugation device; the supernatant is refluxed in front of the membrane filtration device.

5. A method for resource recycling of PVC mother liquor wastewater according to claim 1, characterized in that: In the step S2, the oxidation treatment is carried out by using an ozone contact oxidation device; the pH of the membrane filtrate is adjusted to 8-9 before the oxidation treatment.

6. A method for resource recycling of PVC mother liquor wastewater according to claim 1, characterized in that: In the step S4, the secondary treated water is cooled down before the ion exchange.

7. A method for resource recycling of PVC mother liquor wastewater according to claim 6, characterized in that: The secondary treated water is cooled down to 35-40 °C before the ion exchange.

8. A method for resource recovery and reuse of PVC mother liquor wastewater according to claim 1, characterized in that: The resin regeneration waste liquid generated during the regeneration of the resin in the ion exchange process of the step S4 is used as brine.

9. A method for resource recycling of PVC mother liquor wastewater according to claim 1, characterized in that: The activated carbon regeneration waste liquid generated during the regeneration of the activated carbon in the activated carbon treatment process of the step S3 is used as brine.

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