CN111825239A - Sodium hypochlorite wastewater treatment device and process - Google Patents

Abstract

The invention discloses a device and a process for treating sodium hypochlorite wastewater, which comprises a photocatalytic tank, an oxidation-reduction tank and a ceramic membrane filtration system which are sequentially connected; wherein, a UV irradiation system is arranged in the photocatalysis tank, a hydrogen peroxide feeding system is also arranged on a pipeline between the photocatalysis tank and the oxidation reduction tank, an aeration system is arranged in the oxidation reduction tank, and the water outlet of the ceramic membrane filtering system is connected with a production water tank. The method adopts the processes of photocatalysis, hydrogen peroxide reduction and ceramic membrane filtration to treat the sodium hypochlorite wastewater, and the treated sodium hypochlorite wastewater is mainly sodium chloride brine, has recycling value, can be used in chlor-alkali industry, and can realize the treatment, purification and recovery of the sodium hypochlorite wastewater.

Description

Sodium hypochlorite wastewater treatment device and process

technical field

The invention relates to the technical field of wastewater treatment, in particular to a treatment device and a process for sodium hypochlorite wastewater.

Background technique

In the C1 ₂ absorption process of tail gas treatment, the sodium hydroxide absorption method is generally used for treatment. This treatment process has a slow reaction speed. At the same time, due to the complex composition of the tail gas, it also contains other particulate matter and impurities. Wastewater containing sodium hypochlorite and various organic substances is inevitably generated. Such waste water is harmful to the environment and cannot be directly discharged. In the existing sodium hypochlorite treatment process, it is difficult to completely treat all sodium hypochlorite, other organic substances and impurity particles at the same time.

Chinese patent CN109879397A discloses a sodium hypochlorite wastewater treatment equipment and treatment process. The sodium hypochlorite wastewater is sequentially passed through sodium sulfite solution and oxalic acid solution with stirring, and finally the control index is achieved by adjusting the chloride of tap water. Although this patent can control the relevant discharge index However, the cost of treating chemicals is high, and the ratio of each solution must be strictly controlled, so the production practicability is not strong, and the power components with stirring devices are more likely to corrode and shorten the service life of the equipment.

Therefore, there is an urgent need for a sodium hypochlorite wastewater treatment process and equipment to solve the problem.

SUMMARY OF THE INVENTION

The invention provides a treatment device and process for sodium hypochlorite wastewater. The technology of photocatalysis + hydrogen peroxide reduction + ceramic membrane filtration is used to treat the sodium hypochlorite wastewater. The treated sodium hypochlorite wastewater is mainly sodium chloride brine, which has recycling value and can be used in the chlor-alkali industry It can realize the treatment, purification and recovery of sodium hypochlorite wastewater.

The technical scheme of the present invention is that a sodium hypochlorite wastewater treatment device comprises a photocatalytic pool, an oxidation-reduction pool and a ceramic membrane filtration system connected in sequence; wherein a UV irradiation system is arranged in the photocatalytic pool, and a space between the photocatalytic pool and the oxidation-reduction pool is provided. There is also a hydrogen peroxide feeding system on the pipeline, an aeration system in the oxidation-reduction tank, and the water outlet of the ceramic membrane filtration system is connected to the water production tank.

Further, the device further includes a waste water storage tank and a produced water storage tank; wherein the waste water storage tank is connected to the water inlet of the photocatalytic cell through a pipeline and a pump; the water production tank is connected to the produced water storage tank through a pipeline and a pump.

Further, the hydrogen peroxide feeding system comprises a hydrogen peroxide storage tank, which is merged into the pipeline between the photocatalytic pool and the redox pool through a pipeline, and a pipeline mixer is also provided at the entry place, and the pipeline between the hydrogen peroxide storage tank and the pipeline mixer. There is also a metering pump on it.

Further, the photocatalytic cell is divided into a plurality of regions by partitions, and the photocatalytic cell adopts a carbon steel lined glass fiber reinforced plastic anti-corrosion structure.

Further, the water production tank is connected to the backwash water inlet of the ceramic membrane filtration system through the pipeline and the backwash pump, the backwash water outlet is connected to the photocatalytic pool through the pipeline, and the pipeline between the backwash water outlet and the photocatalytic pool is also provided. There is a second bag filter.

Further, a first bag filter is provided on the front-end pipeline of the water inlet of the photocatalytic cell.

Further, the device also includes a chemical cleaning tank, which is connected to the backwash water inlet of the ceramic membrane filtration system through a pipeline.

The present invention also relates to adopting the device to carry out the process of sodium hypochlorite wastewater treatment, comprising the following steps:

1) The sodium hypochlorite wastewater is introduced into the photocatalytic tank, and the photocatalytic reaction is carried out under the irradiation of an ultraviolet lamp. The lamp power is ≥150W, the reaction time is ≥4h, and the water temperature is ≤50℃;

2) Add hydrogen peroxide to the water after the photocatalytic reaction for mixing, enter the redox tank, and control the ORP meter reading of the redox tank to be less than 160mv; hydrogen peroxide is added according to the content of free chlorine;

3) The water treated by the redox tank enters the ceramic membrane filtration system. The ceramic membrane has a porosity of 30% to 50% and a pore diameter of 50 nm to 15 μm. The effluent of the ceramic membrane filtration system is the treated water.

The ultraviolet lamp is equipped with a ballast, N=320W, the ultraviolet lamp adopts the UVC band, the ultraviolet wavelength class is 185-254nm, and the length is 1650mm.

Further, the ultraviolet lamp tube is arranged vertically, and the outer layer thereof is arranged with a quartz sleeve. Fouling can be prevented. The upper part of the UV lamp tube is provided with a lamp head, which is a ceramic lamp head, which has anti-ultraviolet function and is equipped with a silicone cable, which has a good high temperature resistance effect and prevents the aging of the outer sheath of the cable caused by ultraviolet radiation. The bottom of the UV lamp tube is provided with a lamp holder, and the lamp holder is made of PVC.

Further, the ceramic membrane filtration system needs to be backwashed at intervals. The backwashing liquid is the water produced by the ceramic membrane filtration system during normal operation, and the interval time is ≥ 0.5h. The catalytic cell is used for secondary use.

Further, the ceramic membrane filtration system needs to be chemically cleaned at intervals. The cleaning liquid during chemical cleaning is acid cleaning, alkali cleaning or pure water, and the cleaned liquid is neutralized and then discharged into a sewage pool.

After the sodium hypochlorite wastewater is collected in a centralized manner, it is input into the photocatalytic cell, and the UV irradiation system is used to generate valence band holes (h+) and conduction band electrons (e-) under the irradiation of ultraviolet light, of which the valence band holes are a strong oxidant , and the conduction band electron is a strong reducing agent, so most organic matter can be directly or indirectly oxidized or reduced by photogenerated carriers. At this time, the decomposition equation of sodium hypochlorite is as follows:

The wastewater that removes a large amount of sodium hypochlorite through the photocatalytic tank enters the redox tank. In the case of the participation of hydrogen peroxide, the aeration reaction, the residual sodium hypochlorite is reduced, and NaCl, water and oxygen are generated. The specific equation is as follows:

NaClO+H ₂ O ₂ ==NaCl+H ₂ O+O ₂ ↑;

The sodium hypochlorite wastewater after photolysis and redox enters the ceramic membrane filtration system to filter out colloids, suspended solids, particulate impurities SiO ₂ and turbidity, etc. The ceramic membrane filtration system is also equipped with a normal backwashing system and a chemical cleaning system to clean the membrane surface. fouling, restore the flux of the membrane.

The present invention has the following beneficial effects:

1. The present invention adopts the treatment process of photocatalysis + hydrogen peroxide reduction + ceramic membrane filtration to treat the sodium hypochlorite wastewater, and the treated product is mainly sodium chloride brine, which can be used in the chlor-alkali industry and has recycling value. Among them, the photocatalytic degradation speed is fast, generally only tens of minutes to a few hours can achieve good treatment effect, and the reaction is non-selective, and can quickly reduce most pollutants, the reaction conditions are mild, the investment is low, and the energy consumption is low. The pollutants are decomposed into harmless substances such as NaCl and _O2 , and there is no secondary pollution.

2. The ceramic membrane filtration system is equipped with a normal backwash system and a chemical cleaning system. The normal backwash system uses the water collected by the water production tank during normal operation as backwash water, and backwashes the ceramic membrane filtration system. The backwashed water After filtration, it enters the photocatalytic tank for reprocessing to avoid the efflux of backwash water; when the ceramic membrane filtration system works for a long time or the membrane flux is greatly reduced, the liquid in the chemical cleaning tank is used as the backwash liquid, generally acid The waste acid or alkali solution produced is neutralized and then discharged into the sewage pool, and it can be used normally after being cleaned with pure water. The normal backwash system and chemical cleaning system can remove the fouling and blockage on the membrane surface and restore the flux of the membrane.

3. The present invention also provides a treatment device for sodium hypochlorite wastewater, which can realize the treatment, purification and recovery of sodium hypochlorite wastewater, and the entire treatment process can realize automatic operation.

4. In the process of UV photocatalysis, in addition to the need to control the reaction time, the power of the UV lamp also has an impact. The power of the lamp is 300-320w to ensure the decomposition efficiency. The lamp of this power is set with an outer lamp with a quartz sleeve, which can prevent scaling on the outer wall of the lamp, reduce the decomposition efficiency of the lamp, increase the amount of hydrogen peroxide treated, increase the treatment cost, and try to avoid scaling. In addition, by setting the ceramic lamp cap and silicone cable, it has anti-ultraviolet function, good high temperature resistance effect, and prevents ultraviolet radiation from damaging the lamp cap and cable.

5. In the early stage of the redox tank aeration device, it is not easy to control the gas volume, resulting in insufficient decomposition of sodium hypochlorite. In the preferred scheme, the residual sodium hypochlorite can be fully reacted with hydrogen peroxide by increasing the control valve.

Description of drawings

FIG. 1 is a schematic structural diagram of a device provided by the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention.

Embodiment 1: as shown in Figure 1, a kind of treatment device of sodium hypochlorite waste water, comprises photocatalytic pond 4, redox pond 9 and ceramic membrane filtration system 12 connected in turn; wherein photocatalytic pond 4 is provided with UV irradiation system, The overflow port of the photocatalytic pool 4 is connected to the oxidation-reduction pool 9 through a pipeline. The pipeline between the photocatalytic pool 4 and the oxidation-reduction pool 9 is also provided with a hydrogen peroxide feeding system. The oxidation-reduction pool is provided with an aeration system and a ceramic membrane filtration system. 12 The water outlet is connected to the product water tank 13. The overflow port of the redox tank 9 is connected to the ceramic membrane filtration system through a pipeline and a second horizontal centrifugal pump 11 .

Preferably, the device further includes a waste water storage tank 1 and a produced water storage tank 15; wherein the waste water storage tank is connected to the water inlet of the photocatalytic cell 4 through pipes and the first horizontal centrifugal pump 3; The third horizontal centrifugal pump 14 is connected to the produced water storage tank 15 .

Wastewater storage tank 1 adopts glass fiber reinforced plastic lined with PVC structure, which is resistant to acid and alkali corrosion and has high structural strength.

Preferably, the hydrogen peroxide feeding system includes a hydrogen peroxide storage tank 7, which is merged into the pipeline between the photocatalytic pool 4 and the redox pool 9 through a pipeline, and a pipeline mixer 5 is also provided at the entrance, so that the waste water after photocatalysis Fully mixing and reacting with hydrogen peroxide, a metering pump 6 is also provided on the pipeline between the hydrogen peroxide storage tank 7 and the pipeline mixer 5 . The oxidation-reduction tank is made of carbon steel lined with glass fiber reinforced plastic for anti-corrosion, and contains 3 sets of partitions, ORP meter, online pH detector, liquid level meter and aeration system. The aeration system can accelerate the reaction speed of hydrogen peroxide and sodium hypochlorite; the aeration system includes The aeration source 10 outside the redox tank and the aerator 8 arranged in the redox tank. The aeration air source 10 is 0.6Mpa dry compressed air, which is connected to the aerator through a pipeline. The hydrogen peroxide feeding system accurately adds the hydrogen peroxide ratio through the metering pump 6 according to the ORP value in the redox tank, so that the sodium hypochlorite removal rate can reach more than 99%.

Preferably, the photocatalytic cell 4 is divided into a plurality of regions by partitions, and the photocatalytic cell adopts a carbon steel lined glass fiber reinforced plastic anti-corrosion structure.

Preferably, the water production tank 13 is connected to the backwash water inlet of the ceramic membrane filtration system through pipes and the backwash pump 16 , the backwash water outlet is connected to the photocatalytic cell 4 through pipes, and the backwash water outlet and the photocatalytic cell 4 are connected between There is also a second bag filter 18 on the pipeline. Use the filtered water in the produced water buffer tank 13 to backwash the ceramic membrane, set the flushing time and parameters, remove the fouling and blockage on the membrane surface, and restore the flux of the membrane. The backwashed sewage passes through the second bag filter 18 Afterwards, it is returned to the photocatalytic cell 4 for secondary use.

Preferably, a first bag filter 2 is provided on the front-end pipeline of the water inlet of the photocatalytic cell 4 . The sodium hypochlorite wastewater is pumped into the photocatalytic cell 4 after passing through the first bag filter for ultraviolet photocatalytic degradation.

The structure of the photocatalytic cell is made of carbon steel lined with FRP anti-corrosion, and contains several sets of partitions, FRP lamp holders, 80-100 UV lamps, fuses and rectifiers. Detect the residual amount of sodium hypochlorite, PH value and liquid level, and master the wastewater data in real time. The photocatalytic cell is about 13.6m ³ , and 100 lamps are divided into 20 groups, 5 in each group, and the power is 320W. After photocatalytic treatment, the removal rate of sodium hypochlorite reaches 80%.

The shells of the first and second bag filters are made of PP material, and the filter bag is made of PTFE material, which is anti-corrosion. The pump flow parts used in this device are all lined with tetrafluoride to prevent corrosion, and use silicon carbide mechanical seal to prevent leakage.

Preferably, the device further includes a chemical cleaning tank 17, which is connected to the backwash water inlet of the ceramic membrane filtration system through a pipeline. Ceramic membrane separation is a membrane separation technology. The ceramic membrane is made of a ceramic carrier with a porosity of 38% and a pore size of 50 nm to 15 μm, and is an asymmetric composite membrane made by the sol-gel method or other processes. The structure of ceramic membranes used for separation is usually sandwich type: support layer (also known as carrier layer), transition layer (also known as intermediate layer), membrane layer (also known as separation layer). The pore size distribution of the entire membrane gradually decreases from the support layer to the membrane layer, forming an asymmetric structure distribution, and its purpose is to filter out colloid, suspended solids, particulate impurities SiO ₂ and turbidity, and the water output of the ceramic membrane device in the present invention is: ≥72m ³ /d, recovery rate ≥90%, during normal operation, the system starts and stops automatically according to the water level of waste water storage tank 1 and the water level of produced water storage tank 15, or it can be switched to manual mode at the operator station as needed Remote manual control.

In this embodiment, the ceramic membrane module adopts an internal pressure structure design, and the effective membrane area is 19m ² (205ft 2 ). The influent water can enter the membrane module from the bottom or top of the membrane according to the design requirements. The raw water flows into the capillary channel after being pressurized, and the suspended solids are trapped on the surface of the inner wall of the capillary. The structure is then collected into the permeate flow channel inside the container, and finally flows out from the side outlet of the module. The retained suspended solids will build up a contaminant layer on the membrane surface.

When treating sodium hypochlorite wastewater, first open the water inlet valve of the photocatalytic pool, start the first horizontal centrifugal pump on the spot, adjust the pressure gauge at the outlet of the first horizontal centrifugal pump 3, the operating pressure is 0.15-0.35MPa, and the flow rate is 4- 6m ³ /h, when the liquid level of the photocatalytic cell fully covers the effective light source of the lamp, turn off the first horizontal centrifugal pump 3, turn on the UV irradiation system of the photocatalytic cell, and stay in the reaction for 4 h under the irradiation of the UV lamp. The decomposed waste brine overflows into the redox tank 9, the aeration system on the redox tank is properly opened, and the amount of hydrogen peroxide added is adjusted to 10-20L/h according to the ORP meter reading of the redox tank, and the ORP meter reading is controlled to be less than 150mv. The waste brine overflows into the back-end buffer space, and its liquid level reaches a certain height. The ceramic membrane filtration system starts the second horizontal centrifugal pump 11 to adjust the water flow rate of 2.5--3.5m ³ /h, when the buffer spacer level When it reaches the set position, the first horizontal centrifugal pump 3 will start to feed water again, and it will be turned off when it reaches the set liquid level. Set the water making time 30-60min and the backwashing time 1-2min. In the later stage, the running time can be adjusted according to the water quality, and backwashing and positive washing can be carried out after running for a certain period of time. The ceramic membrane produced water enters the water production tank 13. After the liquid level of the water production tank 13 reaches the high liquid level, the third horizontal centrifugal pump 14 is started to transport it to the produced water storage tank 15. When the liquid level reaches the low liquid level, the third horizontal centrifugal pump 14 is turned off. Type centrifugal pump pump 14.

For chemical cleaning of ceramic membrane filtration system, acid, lye or pure water can be used for cleaning. The specific operation examples are as follows:

1. Pure water washing: fill 50-100L of pure water in the chemical cleaning tank, open the ceramic membrane chemical cleaning valve, close other valves, after the cleaning pump exhausts, start the cleaning pump, adjust the cleaning flow to 6-8m ³ /h, rinse 15- After 30 minutes, stop the pump and open the lower drain valve of the chemical cleaning tank to empty it.

2. Pickling: prepare 50-100L hydrochloric acid solution with pH 1-2 in the chemical cleaning tank, rinse for 15 minutes in the same way, soak for 30 minutes, repeat 2-3 times, open the lower drain valve of the chemical cleaning tank to empty it, use alkali After the liquid is neutralized, it is discharged into the sewage tank, and then the residual acid liquid is removed according to the same pure water cleaning method.

3. Alkaline washing: prepare 50-100L of sodium hydroxide solution with pH 11-13 in the chemical cleaning tank, rinse for 15 minutes in the same way, soak for 30 minutes, repeat 2-3 times, open the lower drain valve of the chemical cleaning tank to empty, use After neutralization with hydrochloric acid, it is discharged into the sewage tank, and then the residual lye is removed according to the same pure water cleaning method, and the cleaning is completed.

The water before and after treatment by the device and process provided by the present invention is detected, and the specific information is shown in Table 1 and Table 2 below. Among the standards for testing reference, there are mainly sodium hypochlorite GB/T19106-2003, industrial sodium chlorate GB/T1618-2008).

Table 1 Influent water quality water meter

Table 2 Product water quality and water quantity table

NOTE: Sodium hypochlorite exists as free chlorine.

Through the data comparison of Table 1 and Table 2, through the device and process provided by the present invention, the sodium hypochlorite has been completely decomposed, and each index of the produced water all meets the sodium chloride salt water recycling requirements, resulting in economic benefits.

Claims (10)

1. The utility model provides a processing apparatus of sodium hypochlorite waste water which characterized in that: comprises a photocatalysis tank (4), an oxidation-reduction tank (9) and a ceramic membrane filtering system (12) which are connected in sequence; wherein, a UV irradiation system is arranged in the photocatalysis tank (4), a hydrogen peroxide feeding system is also arranged on a pipeline between the photocatalysis tank (4) and the oxidation reduction tank (9), an aeration system is arranged in the oxidation reduction tank, and the water outlet of the ceramic membrane filtering system (12) is connected with a production water tank (13).

2. The apparatus of claim 1, wherein: the device also comprises a waste water storage tank (1) and a water production storage tank (15); wherein the waste water storage tank is connected to the water inlet of the photocatalytic tank (4) through a pipeline and a pump; the water production tank (13) is connected to the water production storage tank through a pipeline and a pump.

3. The apparatus of claim 1, wherein: the hydrogen peroxide charging system comprises a hydrogen peroxide storage tank (7), the hydrogen peroxide storage tank converges into a pipeline between the photocatalysis tank (4) and the oxidation and reduction tank (9) through a pipeline, a pipeline mixer (5) is further arranged at the confluence position, and a metering pump (6) is further arranged on the pipeline between the hydrogen peroxide storage tank (7) and the pipeline mixer (5).

4. The apparatus of claim 1, wherein: the photocatalysis tank (4) is divided into a plurality of areas by partition plates, and the photocatalysis tank adopts a carbon steel lining glass fiber reinforced plastic anti-corrosion structure.

5. The apparatus of claim 1, wherein: the water production tank (13) is connected to a backwashing water inlet of the ceramic membrane filtering system through a pipeline and a backwashing pump, a backwashing water outlet is connected to the photocatalytic tank (4) through a pipeline, and a second bag filter (18) is further arranged on the pipeline between the backwashing water outlet and the photocatalytic tank (4).

6. The apparatus of any one of claims 1-5, wherein: a first bag type filter (2) is arranged on the pipeline at the front water inlet end of the photocatalytic tank (4).

7. The apparatus of claim 5, wherein: the device also comprises a chemical cleaning pool (17) which is connected to the back washing water inlet of the ceramic membrane filtration system through a pipeline.

8. The process for treating sodium hypochlorite wastewater by using the device of any one of claims 1 to 7, is characterized by comprising the following steps:

1) introducing sodium hypochlorite wastewater into a photocatalysis tank, and carrying out photocatalytic reaction under the irradiation of an ultraviolet lamp, wherein the power of a lamp tube is more than or equal to 150W, the reaction time is more than or equal to 4h, and the water temperature is less than or equal to 50 ℃;

2) adding hydrogen peroxide into the water after the photocatalytic reaction, mixing, and feeding the water into an oxidation-reduction pool, wherein the reading of an ORP meter in the oxidation-reduction pool is controlled to be less than 160 mv; adding hydrogen peroxide according to the content of free chlorine;

3) and (3) the water treated by the redox pool enters a ceramic membrane filtration system, the porosity of the ceramic membrane is 30-50%, the pore diameter is 50 nm-15 mu m, and the effluent of the ceramic membrane filtration system is the treated water.

9. The process according to claim 8, characterized in that: the ceramic membrane filtration system carries out automatic back washing, the back washing liquid is produced water when the ceramic membrane filtration system normally works, the interval time is more than or equal to 0.5h, and the water after back washing is treated by the bag type filter and enters the photocatalysis pool for secondary utilization.

10. The process according to claim 8, characterized in that: the ceramic membrane filtering system needs to be chemically cleaned at intervals, cleaning liquid during chemical cleaning is acid washing, alkali washing or pure water, and the cleaned liquid is neutralized and then discharged into a sewage tank.

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