A treatment device and method for high-concentration slicing wastewater in the photovoltaic industry

Abstract

The present invention discloses a treatment device and a treatment method for high-concentration slicing wastewater in the photovoltaic industry, and relates to the technical field of high-concentration slicing wastewater, including a treatment device, wherein the treatment device includes an organic separation membrane device, a separation membrane concentrated water treatment device, a catalytic wet oxidation device, and an aerobic biochemical reaction device; the organic separation membrane device includes a membrane water inlet box, a membrane water inlet pump, a security filter, a membrane booster pump, and a membrane assembly, and the membrane water inlet box, the membrane water inlet pump, the security filter, the membrane booster pump, and the membrane assembly are connected in sequence through pipelines. The biochemical method of the present invention is relatively simple, and only aerobic biochemistry is used. The HRT of the biochemical section is 2d, while the total HRT of the biochemical section of the traditional method is as high as 6~8d, that is, the reaction tank of the biochemical method section of the present invention has a small capacity, a small footprint, and low investment cost and operating costs.

Description

Technical Field

[0001] The present invention relates to the technical field of high-concentration slicing wastewater, and in particular to a treatment device and a treatment method for high-concentration slicing wastewater in the photovoltaic industry. Background Art

[0002] Cutting single crystal silicon rods into ultra-thin silicon wafers is an important production link for photovoltaic companies. With the upgrading of photovoltaic production methods, the diamond wire method with a finer wire diameter is currently used to replace the traditional sand wire cutting method. This production method produces wastewater containing cutting fluid, which is slicing wastewater. The main organic pollutants in the wastewater include polyether compounds and alcohol compounds. The typical wastewater quality is shown in Table 1:

[0003] Table 1 Typical water quality of high-concentration slicing wastewater in the photovoltaic industry

[0004]

[0005] Figure 4 The figure shows a typical method for treating slicing wastewater. Since polyether is a difficult-to-biodegrade organic matter, the existing photovoltaic slicing wastewater treatment technology usually adopts the idea of ​​combining advanced oxidation with biological treatment: first, decompose and remove polyether compounds through Fenton oxidation, iron-carbon micro-electrolysis, or strong electrolytic oxidation to improve the biodegradability of wastewater, and then reduce the COD concentration of wastewater through biological treatment methods such as anaerobic biochemical, hydrolytic acidification, and aerobic biochemical. However, the actual engineering operation shows that the above-mentioned advanced oxidation methods have a low improvement in the biodegradability and COD removal rate of slicing wastewater, resulting in a heavy load on the biochemical treatment method and the COD of the treated effluent is still as high as 250~600mg / L, which is difficult to meet the indirect emission limit value of COD <150mg / L in the "Battery Industry Pollutant Emission Standard" (GB 30484-2013). It is often necessary to use ozone oxidation, ozone catalytic oxidation, membrane bioreactor (MBR) and other methods for deep treatment. Moreover, the biochemical treatment method has a large reaction tank capacity and floor space, a long hydraulic retention time, and high operating energy consumption.

[0006] The effective treatment of slicing wastewater to meet discharge standards or reuse has become an important constraint on the green and low-carbon development of the photovoltaic industry.

[0007] As mentioned above, we have designed a treatment device and method for high-concentration slicing wastewater in the photovoltaic industry to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a treatment device and method for high-concentration slicing wastewater in the photovoltaic industry.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A treatment device for high-concentration slicing wastewater in the photovoltaic industry, comprising a treatment device, wherein the treatment device comprises an organic separation membrane device, a separation membrane concentrated water treatment device, a catalytic wet oxidation device and an aerobic biochemical reaction device;

[0011] The organic separation membrane equipment comprises a membrane water inlet box, a membrane water inlet pump, a safety filter, a membrane booster pump and a membrane assembly, wherein the membrane water inlet box, the membrane water inlet pump, the safety filter, the membrane booster pump and the membrane assembly are connected in sequence through pipelines;

[0012] The separation membrane concentrated water treatment equipment comprises a membrane concentrated water tank, a concentrated water lifting pump, a coagulation reaction tank, a coagulation agitator, a flocculation reaction tank, a flocculation agitator, a chemical precipitation tank and a chemical precipitation tank scraper;

[0013] The catalytic wet oxidation equipment includes a catalytic wet oxidation water inlet tank, a catalytic wet oxidation water inlet pump, a high-pressure waste heat recovery heat exchanger, a thermal oil heat exchanger, a catalytic wet oxidation reactor, a pressure regulating valve, a gas-liquid separator, an oxidation liquid delivery pump, and a low-pressure waste heat recovery heat exchanger;

[0014] The aerobic biochemical reaction equipment includes an aerobic biochemical reactor, an aeration pipe, a biochemical sedimentation tank, and a biochemical sedimentation tank scraper;

[0015] The concentrated water produced by the membrane assembly flows into the membrane concentrated water tank through a pipeline, and is transported to the low-pressure waste heat recovery heat exchanger through a concentrated water lifting pump. The membrane concentrated water discharged from the low-pressure waste heat recovery heat exchanger enters the coagulation reaction tank, in which a coagulation agitator is provided for coagulation reaction. The effluent of the coagulation reaction tank flows into the flocculation reaction tank, in which a flocculation agitator is provided for flocculation reaction. The effluent of the flocculation reaction tank flows into the chemical precipitation tank for mud-water separation. A chemical precipitation tank scraper is installed inside the chemical precipitation tank.

[0016] The top of the chemical precipitation tank is connected to a catalytic wet oxidation water inlet tank, a catalytic wet oxidation water inlet pump is connected between the catalytic wet oxidation water inlet tank and the high-pressure waste heat recovery heat exchanger, the high-pressure waste heat recovery heat exchanger, the heat transfer oil heat exchanger, and the catalytic wet oxidation reactor are sequentially connected in series, the output end of the catalytic wet oxidation reactor is connected to the high-pressure waste heat recovery heat exchanger, a pressure regulating valve is installed between the high-pressure waste heat recovery heat exchanger and the gas-liquid separator, and an oxidizing liquid delivery pump is installed between the gas-liquid separator and the low-pressure waste heat recovery heat exchanger;

[0017] The output end of the low-pressure waste heat recovery heat exchanger is connected to an aerobic biochemical reactor, an aeration pipe is installed at the bottom of the aerobic biochemical reactor, and the output end of the aerobic biochemical reactor is connected to a biochemical sedimentation tank, and a biochemical sedimentation tank scraper is installed inside the biochemical sedimentation tank.

[0018] Preferably, the method comprises the following steps:

[0019] Step S1, preliminary treatment of high-concentration wastewater: through the difference in the interception capacity of the separation membrane of the membrane module for organic matter of different molecular weights, the organic matter of low molecular weight passes through the separation membrane into the produced water side, while the organic matter of high molecular weight is intercepted on the concentrated water side of the separation membrane, thereby achieving the separation of organic matter of different molecular weights in the wastewater;

[0020] Step S2, treating the membrane produced water and membrane concentrated water after separation separately: directly performing aerobic biochemical treatment on the membrane produced water can reduce the COD concentration of the wastewater to below 100 mg / L, and performing "heating / destabilization-coagulation-flocculation-precipitation" treatment on the membrane concentrated water side of the separation membrane, and the polyether compounds in the concentrated water are converted from a dissolved state to an insoluble state at a temperature of 50°C to 80°C, and are removed from the membrane concentrated water in the form of a precipitate;

[0021] Step S3, the precipitated water in step S2 is treated: the precipitated water is subjected to catalytic wet oxidation treatment, and the difficult-to-degrade polyether compounds are oxidized and decomposed to be removed under the reaction conditions of 250°C to 260°C, and the biodegradability of the membrane concentrated water is improved, and it is combined with the membrane produced water for aerobic biochemical treatment;

[0022] Step S4: The COD concentration of the effluent from aerobic biochemical treatment can be reduced to below 100 mg / L, meeting the requirements for discharge standards or further treatment and reuse.

[0023] Preferably, the membrane assembly comprises a first separation membrane group and a second separation membrane group, and the first separation membrane group and the second separation membrane group are arranged in series;

[0024] The first separation membrane group and the second separation membrane group both have a plurality of separation membrane pressure vessels arranged in parallel, and the separation membrane pressure vessels are provided with 1-6 separation membranes;

[0025] The produced water of the first separation membrane group enters the produced water mother pipe, the output end of the produced water mother pipe is connected to the aerobic biochemical reactor, the concentrated water of the first separation membrane group enters the second separation membrane group, the produced water of the second separation membrane group enters the produced water mother pipe, and the concentrated water of the second separation membrane group enters the membrane concentrated water tank.

[0026] Preferably, the organic separation membrane in the membrane assembly is a composite membrane with an asymmetric structure, including a porous membrane for support and a dense membrane for separation, the membrane material is polyamide, and the structure of the organic separation membrane is one of a roll type, a tube type or a plate-and-frame type;

[0027] The molecular weight cutoff of the organic separation membrane is 200Da~500Da; the recovery rate of the membrane assembly is 70%~90%; the water production flux of the membrane assembly is 14~24 L / m2 ·h; the operating pressure of the membrane assembly is 0.3~0.6MPa.

[0028] Preferably, in the method of coagulating the membrane concentrate on the concentrate side of the separation membrane in step S2, the coagulant used is polyaluminium chloride, and the coagulant addition concentration is 200-400 mg / L; the flocculant used is polyacrylamide, and the flocculant addition concentration is 3-5 mg / L; the stirring speed of the coagulation agitator 2-4 is 70-90 rpm, and the stirring speed of the flocculation agitator is 35-45 rpm.

[0029] Preferably, in step S3, catalytic wet oxidation is a chemical process in which organic pollutants in wastewater are oxidized into CO2, H2O and small molecular organic matter using oxygen as an oxidant under the conditions of high temperature of 125°C to 320°C and high pressure of 0.5MPa to 10MPa.

[0030] Preferably, the method parameters of catalytic wet oxidation are as follows:

[0031] Catalytic wet oxidation reaction pressure: 5.5~6.5 MPa;

[0032] Catalytic wet oxidation reaction time: 3~4h.

[0033] Preferably, in the catalytic wet oxidation treatment, the oxidation heat of the membrane concentrate itself is used to continuously maintain the reaction temperature, and a group of heat exchangers are set at the inlet of the wet oxidation reactor to use the high-temperature oxidation liquid after the catalytic wet oxidation treatment as a heat source to heat exchange and heat the membrane concentrate before oxidation.

[0034] Compared with the existing technology,

[0035] (1) The conventional treatment method for photovoltaic slicing wastewater is mainly based on biochemical treatment, and advanced oxidation is used as a biochemical pretreatment to improve the biodegradability of slicing wastewater. However, the actual engineering operation shows that the effect is very limited. The present invention uses a separation membrane separation method as a slicing wastewater pretreatment method to separate the biodegradable organic matter from the difficult-to-biodegrade organic matter in the slicing wastewater at the source. The difficult-to-biodegrade organic matter is enriched in the membrane concentrated water, which is conducive to its targeted heating destabilization and advanced oxidation decomposition treatment; while the biodegradable organic matter enters the membrane produced water, making the biochemical treatment simple and feasible.

[0036] (2) The present invention utilizes the property of polyether compounds to destabilize and precipitate at high temperatures, and adopts the "heating / destabilization-coagulation-flocculation-precipitation" method to treat membrane concentrate, and obtains a COD removal rate of 30% to 50% through a relatively simple method, which reduces the processing load and processing energy consumption for the next step of catalytic wet oxidation treatment. In addition, it is generally believed that heating wastewater from room temperature (20℃~25℃) to 50℃~80℃ will consume a lot of heat energy, making wastewater treatment energy consumption high, but the present invention greatly reduces the energy consumption required for wastewater heating through two design schemes: First, the present invention only needs to heat and heat the membrane concentrate, and does not need to heat and heat all the sliced ​​wastewater, and the amount of membrane concentrate is only 10%~30% of the total amount of the sliced ​​wastewater. Second, the present invention can use the residual heat in the oxidation liquid after catalytic wet oxidation treatment to heat the membrane concentrate and implement heat recovery.

[0037] (3) The catalytic wet oxidation method is usually regarded as a high-cost, high-energy-consuming advanced oxidation treatment method. However, the present invention only needs to perform catalytic wet oxidation treatment on the membrane concentrate, without having to treat all the slicing wastewater. The amount of membrane concentrate is only 10% to 30% of the total amount of high-concentration slicing wastewater. Therefore, from the perspective of the overall cost and overall energy consumption of slicing wastewater treatment, the cost and energy consumption of the present invention can be controlled at a relatively low level. This is mainly due to the separation membrane treatment of high-concentration slicing wastewater at the front end, the separation and enrichment of the difficult-to-degrade organic matter in the slicing wastewater, the reduction of the catalytic wet oxidation treatment scale, and the increase of the catalytic wet oxidation influent COD concentration.

[0038] (4) The biochemical method in the method of the present invention is relatively simple, and only aerobic biochemistry is used. The HRT of the biochemical section is 2 days, while the total HRT of the biochemical section of the traditional method is as high as 6 to 8 days. That is, the reaction pool of the biochemical method section of the method of the present invention has a small capacity, saves space, and has low investment cost and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of a treatment device and method for high-concentration slicing wastewater in the photovoltaic industry proposed by the present invention;

[0040] Figure 2 This is a flow chart of a device and method for treating high-concentration slicing wastewater in the photovoltaic industry proposed by the present invention;

[0041] Figure 3 for Figure 2 Method: Molecular weight distribution test diagram of organic matter in high concentration slice wastewater;

[0042] Figure 4 The figure is a flow chart of the method of the prior art mentioned in the background technology.

[0043] In the figure: 1 organic separation membrane equipment, 1-1 membrane water inlet tank, 1-2 membrane water inlet pump, 1-3 security filter, 1-4 membrane booster pump, 1-5 membrane assembly, 2 separation membrane concentrated water treatment equipment, 2-1 membrane concentrated water tank, 2-2 concentrated water booster pump, 2-3 coagulation reaction tank, 2-4 coagulation agitator, 2-5 flocculation reaction tank, 2-6 flocculation agitator, 2-7 chemical sedimentation tank, 2-8 chemical sedimentation tank scraper, 3 catalytic wet oxidation equipment, 3-1 catalytic wet oxidation water inlet tank, 3-2 catalytic wet oxidation water inlet pump, 3-3 high-pressure waste heat recovery heat exchanger, 3-4 thermal oil heat exchanger, 3-5 catalytic wet oxidation reactor, 3-6 pressure regulating valve, 3-7 gas-liquid separator, 3-8 oxidation liquid delivery pump, 3-9 Low-pressure waste heat recovery heat exchanger, 4 aerobic biochemical reaction equipment, 4-1 aerobic biochemical reactor, 4-2 aeration pipe, 4-3 biochemical sedimentation tank, 4-4 biochemical sedimentation tank scraper. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0045] 1. Slicing wastewater treatment device

[0046] 1.1 The present invention slice wastewater treatment device refers to Figure 1 , described as follows:

[0047] After pretreatment to remove suspended solids, the photovoltaic high-concentration chip wastewater flows into the membrane inlet tank 1-1, and is transported to the security filter 1-3 for filtration through the membrane inlet pump 1-2. The security filter is filled with a filter element with a filtration accuracy of 5µm to intercept fine particles in the wastewater. The effluent from the security filter is transported to the membrane assembly 1-5 for treatment through the membrane booster pump 1-4;

[0048] Wherein, the membrane assembly 1-5 comprises a first separation membrane group and a second separation membrane group, and the first separation membrane group and the second separation membrane group are arranged in series;

[0049] The first separation membrane group and the second separation membrane group both have a plurality of separation membrane pressure vessels arranged in parallel, and the separation membrane pressure vessels are provided with 1-6 separation membranes;

[0050] The produced water of the first separation membrane group enters the produced water mother pipe, the output end of which is connected to the aerobic biochemical reactor 4-1, the concentrated water of the first separation membrane group enters the second separation membrane group, the produced water of the second separation membrane group enters the produced water mother pipe, and the concentrated water of the second separation membrane group enters the membrane concentrated water tank 2-1;

[0051] Through the above content, due to the difference in the retention capacity of the separation membrane for organic matter of different molecular weights, the low molecular weight alcohol compounds in the slicing wastewater pass through the separation membrane into the produced water side, while the high molecular weight polyether compounds are retained on the concentrated water side of the separation membrane. At the same time, through the above-mentioned membrane components 1-5, two first separation membrane groups and the second separation membrane group are connected in series, and the first separation membrane group and the second separation membrane group are internally connected with separation membranes arranged in parallel, which can achieve multiple filtration of the produced water and concentrated water of high-concentration slicing wastewater.

[0052] In this embodiment, the organic separation membrane in the membrane assembly 1-5 is a composite membrane with an asymmetric structure, including a porous membrane for support and a dense membrane for separation. The membrane material is polyamide. The structure of the organic separation membrane is one of a roll type, a tube type or a plate-and-frame type.

[0053] The molecular weight cutoff of the organic separation membrane is 200Da~500Da, and the preferred value is 300Da; the recovery rate of the separation membrane is 70%~90%, and the preferred value is 75%~80%; (Recovery rate = produced water flow rate ÷ inlet water flow rate)

[0054] The water flux of the separation membrane is 14~24 L / m 2 h, the preferred value is 18~20 L / m 2 ·h;

[0055] The operating pressure of the separation membrane is 0.3~0.6MPa.

[0056] Among them, the concentrated water produced by the membrane assembly flows into the membrane concentrated water tank 2-1 through the pipeline, and is transported to the low-pressure waste heat recovery heat exchanger 3-9 through the concentrated water lifting pump 2-2. The oxidized liquid separated by gas and liquid is used as the heat medium to heat the membrane concentrated water. The low-pressure heat exchanger is a shell-and-tube heat exchanger, which can be used alone or in series. The heat exchanger is made of 304 stainless steel. The cold material membrane concentrated water goes through the heat exchanger tube side, enters the low-pressure heat exchanger from the top, and flows out from the outlet on the other side of the top of the heat exchanger after heat exchange. The hot material oxidized liquid goes through the shell side, enters the low-pressure heat exchanger from the bottom, and flows out from the upper outlet of the side wall of the heat exchanger after heat exchange. After being heated by the low-pressure heat exchanger, the temperature of the cold material membrane concentrated water increases from 20~25℃ to 50~80℃, and at the same time, the temperature of the hot material oxidized liquid decreases from 85~95℃ to 35~45℃.

[0057] After the temperature of the membrane concentrate water rises to 50℃~80℃, the polyether compounds in the concentrate water are converted into insoluble state and precipitated; the membrane concentrate water discharged from the low-pressure waste heat recovery heat exchanger 3-9 enters the coagulation reaction tank 2-3, and the coagulant PAC is added to the coagulation reaction tank 2-3, and NaOH is added at the same time to adjust the pH value of the membrane concentrate water to neutral. A coagulation agitator 2-4 is provided in the coagulation reaction tank 2-3 for coagulation reaction. The effluent of the coagulation reaction tank 2-3 flows into the flocculation reaction tank 2-5, and the flocculant PAM is added to the flocculation reaction tank 2-5. A flocculation agitator 2-6 is provided in the flocculation reaction tank 2-5 for flocculation reaction. The polyether compounds precipitated by heating and destabilization form large-sized and dense sludge flocs after coagulation and flocculation reaction.

[0058] In this embodiment, the concentration of the coagulant PAC is 200-400 mg / L, the concentration of the flocculant PAM is 3-5 mg / L, the stirring speed of the coagulation stirrer is 70-90 rpm, and the stirring speed of the flocculation stirrer is 35-45 rpm.

[0059] The effluent from the flocculation reaction tank 2-5 flows into the chemical sedimentation tank 2-7 for mud-water separation, and the polyether compound sludge precipitated by thermal destabilization is scraped by the chemical sedimentation tank scraper 2-8 to the mud hopper at the bottom of the sedimentation tank, flows out of the sedimentation tank through a pipeline, and is transported to the sludge dewatering device for treatment.

[0060] The supernatant from the sedimentation tank flows into the catalytic wet oxidation water inlet tank 3-1, is pressurized by the catalytic wet oxidation water inlet pump 3-2 and transported to the high-pressure waste heat recovery heat exchanger 3-3, and the water inlet pump delivery pressure is 5.5~6.5MPa. In the high-pressure waste heat recovery heat exchanger 3-3, the high-pressure oxidation liquid flowing out of the catalytic wet oxidation reactor 3-5 is used as a heat medium to further heat the membrane concentrated water. The high-pressure waste heat recovery heat exchanger 3-3 is in the form of a shell and tube heat exchanger, which can be a single unit or two or more units in series. The material of the high-pressure waste heat recovery heat exchanger 3-3 is 2205 duplex steel or titanium. The cold material membrane concentrated water goes through the tube side, enters the high-pressure waste heat recovery heat exchanger 3-3 from the top, and flows out from the outlet on the other side of the top of the high-pressure waste heat recovery heat exchanger 3-3 after heat exchange. The hot material oxidation liquid goes through the shell side, enters the high-pressure waste heat recovery heat exchanger 3-3 from the bottom, and flows out from the outlet on the upper part of the side wall of the heat exchanger after heat exchange. After being heated by the high-pressure waste heat recovery heat exchanger 3-3, the temperature of the cold material membrane concentrated water increases from 50~80℃ to 210~230℃, and at the same time, the temperature of the hot material oxidation liquid decreases from 255~265℃ to 110~120℃.

[0061] After the membrane concentrate is heated by the high-pressure waste heat recovery heat exchanger 3-3, it enters the thermal oil heat exchanger 3-4 for further heating. The external thermal oil is used as the heat medium to heat the membrane concentrate. The thermal oil heat exchanger 3-4 is a shell-and-tube heat exchanger. The cold material membrane concentrate flows through the tube side and enters the thermal oil heat exchanger 3-4 from the top. After heat exchange, it flows out from the outlet on the other side of the top of the thermal oil heat exchanger 3-4. The heat medium thermal oil flows through the shell side and enters the thermal oil heat exchanger 3-4 from the bottom. After heat exchange, it flows out from the upper outlet of the side wall of the thermal oil heat exchanger 3-4. The tube side material of the thermal oil heat exchanger 3-4 is 2205 duplex steel or titanium, and the shell side material is carbon steel. After being heated by the thermal oil heat exchanger 3-4, the temperature of the membrane concentrate increases from 210~230℃ to 250~260℃. The thermal oil is cyclically heated and can be provided by an external electric heating thermal oil furnace.

[0062] After the membrane concentrate is heated by the heat transfer oil heat exchanger 3-4, it enters the catalytic wet oxidation reactor 3-5 for treatment. At the same time, high-pressure compressed air is introduced into the catalytic wet oxidation reactor 3-5. In the catalytic wet oxidation reactor 3-5, the reaction temperature is 250-260°C, the reaction pressure is 5.5-6.5MPa, and the reaction time is 2-4h. The polyether compounds in the membrane concentrate are oxidized and decomposed to be removed, and a large amount of oxidation heat is generated.

[0063] The catalytic wet oxidation reactor 3-5 adopts a vertical cylindrical reactor, which can be a single reactor or two or more reactors connected in series. The catalytic wet oxidation reactor 3-5 is made of 2205 duplex steel or titanium. The top of the catalytic wet oxidation reactor 3-5 is equipped with a bursting membrane and a safety valve, and is equipped with online monitoring instruments such as a thermometer and a pressure sensor.

[0064] The high-temperature oxidation liquid treated in the catalytic wet oxidation reactor 3-5 flows into the high-pressure waste heat recovery heat exchanger 3-3, and exchanges heat with the membrane concentrated water to be treated in the high-pressure waste heat recovery heat exchanger 3-3 to achieve heat recovery.

[0065] The pressure of the oxidizing liquid flowing out of the high-pressure waste heat recovery heat exchanger 3-3 is 5.2~6.2MPa, and the pressure regulating valve 3-6 is used to reduce the pressure to 0.4~0.6MPa.

[0066] The decompressed oxidizing liquid enters the gas-liquid separator 3-7, where the pressure of the oxidizing liquid is reduced to normal pressure, and the generated tail gas flows out from the top of the gas-liquid separator, and is transported through a pipeline to an external tail gas cooling tower and a tail gas purification device for treatment before being discharged. The oxidizing liquid at the bottom of the gas-liquid separator is transported to the low-pressure waste heat recovery heat exchanger 3-9 through the oxidizing liquid delivery pump 3-8, and exchanges heat with the membrane concentrated water to be treated to achieve heat recovery.

[0067] The oxidized liquid and membrane produced water flowing out of the low-pressure waste heat recovery heat exchanger 3-9 flow into the aerobic biochemical reactor 4-1. The aeration pipe 4-2 is installed at the bottom of the aerobic biochemical reactor. Microorganisms degrade the low molecular weight organic matter in the membrane produced water and the catalytic wet oxidation treatment water into CO2 and H2O, reducing the COD concentration of the wastewater to below 100 mg / L. The effluent of the aerobic biochemical reactor 4-1 flows into the biochemical sedimentation tank 4-3. The sludge at the bottom of the sedimentation tank is pumped to the sludge dewatering device for treatment. The supernatant of the biochemical sedimentation tank 4-3 meets the discharge standards or is reused after further deep treatment.

[0068] 2. Treatment methods for high-concentration slicing wastewater

[0069] 2.1 Methods

[0070] The present invention proposes a new method for treating high-concentration slicing wastewater in the photovoltaic industry. The method route is as follows: Figure 2 shown.

[0071] First, a separation membrane is used to treat high-concentration slice wastewater. Due to the difference in the retention capacity of the separation membrane for organic matter of different molecular weights, low-molecular-weight alcohol organic matter passes through the separation membrane and enters the water production side, while high-molecular-weight polyether organic matter is retained on the concentrated water side of the separation membrane, thereby achieving the separation of organic matter of different molecular weights in the wastewater.

[0072] The membrane produced water directly enters the terminal aerobic biochemical treatment.

[0073] The membrane concentrate is treated with "heating / destabilization-coagulation-flocculation-precipitation". The polyether compounds in the concentrate are converted from dissolved to insoluble at a temperature of 50℃~80℃ and are removed from the membrane concentrate in the form of precipitates.

[0074] The precipitated water is then subjected to catalytic wet oxidation treatment. Under reaction conditions of 250°C to 260°C, the difficult-to-degrade polyether compounds are oxidatively decomposed and removed, and the biodegradability of the membrane concentrate is improved, and it is combined with the membrane produced water for aerobic biochemical treatment.

[0075] The COD concentration of the effluent from aerobic biochemical treatment can be reduced to below 100 mg / L, meeting the requirements for discharge standards or further treatment and reuse.

[0076] 2.2 Principle of the method

[0077] 2.2.1 Separation membrane

[0078] The molecular weight distribution of organic matter in the high-concentration slicing wastewater of a photovoltaic enterprise was tested. The results are as follows: Figure 3As shown, most of the molecular weights of organic matter in the slicing wastewater are between 600Da and 270Da, and a small part is around 1700Da. The present invention uses a separation membrane to treat slicing wastewater, and through the difference in the retention capacity of the separation membrane for organic matter of different molecular weights, the organic matter with low molecular weight passes through the separation membrane and enters the water production side, while the organic matter with high molecular weight is retained on the concentrated water side of the separation membrane, thereby achieving the separation of organic matter of different molecular weights in the wastewater.

[0079] Through the biodegradability test of membrane produced water and concentrated water, it was found that the organic matter in membrane produced water is mainly alcohol compounds with low molecular weight, which have good biodegradability. Direct aerobic biochemical treatment of membrane produced water can reduce the COD concentration of wastewater to below 100 mg / L. The organic matter in membrane concentrated water is mainly polyether compounds with high molecular weight, which have poor biodegradability and cannot be directly treated by biochemical methods.

[0080] The molecular weight cut-off of the separation membrane is 200Da-500Da, preferably 300Da.

[0081] The recovery rate of the separation membrane is 70% to 90%, preferably 75% to 80%. (Recovery rate = produced water flow rate ÷ inlet water flow rate)

[0082] The water production flux of the separation membrane is 14-24 L / m 2 h, the preferred value is 18~20 L / m 2 ·h.

[0083] The operating pressure of the separation membrane is 0.3-0.6 MPa, which is related to the salt content of the treated influent.

[0084] The research and development test results show that (refer to Figure 3 ), the COD concentration of the raw water of high-concentration slice wastewater is 17360~29220mg / L, the separation membrane is operated under the above method parameters, the COD concentration of the membrane produced water is 3360~7940mg / L, and the COD concentration of the membrane concentrated water is 30500~101520mg / L.

[0085] 2.2.2 Heating / destabilization-coagulation-flocculation-sedimentation

[0086] The solubility of polyether compounds in aqueous solutions decreases with increasing temperature. When an aqueous solution containing a certain concentration of polyether compounds is heated to a certain temperature, the polyether compounds are converted from a dissolved state to an insoluble state and precipitate, causing the solution to become turbid.

[0087] According to the unique properties of the above-mentioned polyether compounds, the technical solution heats the membrane concentrate water. When the temperature of the membrane concentrate water rises to 50°C~80°C, the polyether compounds in the concentrate water are converted into insoluble state and precipitated. Then, the turbid liquid is subjected to coagulation, flocculation and precipitation treatment, and the precipitated insoluble polyether compounds are removed from the membrane concentrate water in the form of precipitates, thereby reducing the COD concentration of the membrane concentrate water.

[0088] The method parameters are as follows:

[0089] Membrane concentrate water heating temperature: 50℃~80℃, preferably 55℃~60℃.

[0090] Coagulant: Polyaluminium Chloride (PAC)

[0091] Coagulant concentration: 200~400mg / L, preferably 300mg / L

[0092] Flocculant: Polyacrylamide (PAM)

[0093] Flocculant concentration: 3~5mg / L

[0094] After treatment by the "heating / destabilization-coagulation-flocculation-sedimentation" method, the COD concentration of membrane concentrate was reduced to 21350mg / L~49500mg / L, and the COD removal rate was 30%~50%.

[0095] 2.2.3 Catalytic wet oxidation

[0096] Catalytic wet oxidation is a method for treating toxic, harmful, and high-concentration organic wastewater. It is a chemical process that uses oxygen as an oxidant to oxidize organic pollutants in wastewater into CO2, H2O, and small molecular organic matter under high temperature (125℃~320℃) and high pressure (0.5MPa~10MPa). In practical applications, air is often used as an oxidant because of its low price, no danger, and mature boosting equipment.

[0097] The present invention adopts a catalytic wet oxidation method to further treat the membrane concentrated water after the coagulation and sedimentation treatment, thereby reducing the COD concentration of the concentrated water and improving the biodegradability of the wastewater.

[0098] The method parameters are as follows:

[0099] Catalytic wet oxidation reaction pressure: 5.5~6.5 MPa

[0100] Catalytic wet oxidation reaction temperature: 250℃~260℃

[0101] Catalytic wet oxidation reaction time: 3~4h

[0102] After treatment by catalytic wet oxidation method, the COD concentration of membrane concentrate was reduced to 3206mg / L~8290mg / L, and the COD removal rate was 82%~96%.

[0103] In the catalytic wet oxidation treatment, it is preferred to use the oxidation heat of the membrane concentrate to continuously maintain the reaction temperature. The specific method is to set a group of heat exchangers at the inlet of the wet oxidation reactor, and use the high-temperature oxidation liquid after catalytic wet oxidation treatment as a heat source to heat the membrane concentrate before oxidation. The higher the concentration of organic matter in the concentrate, the higher the oxidation reaction heat generated. Insufficient heat can be supplemented by external high-temperature heat transfer oil heating.

[0104] The catalytic wet oxidation method can not only significantly reduce the COD concentration of membrane concentrate, but also improve the biodegradability of wastewater. Aerobic biochemical treatment of catalytic wet oxidation effluent can reduce the COD of wastewater to below 200 mg / L.

[0105] 2.2.4 Aerobic biochemistry

[0106] By combining the membrane produced water with the membrane concentrate after thermal destabilization, coagulation sedimentation and catalytic wet oxidation for biochemical treatment, the COD concentration of the slice wastewater can be directly reduced to below 100 mg / L by aerobic biochemical methods without the need for anaerobic biochemical, hydrolysis acidification and other forms. The hydraulic retention time (HRT) of the aerobic biochemical method only requires 2 days.

[0107] In addition, the above-mentioned membrane water and concentrated water can be combined with other organic wastewater from the wastewater station (such as low-concentration chip wastewater) for aerobic biochemical treatment, and the effluent COD concentration can be reduced to below 100 mg / L, meeting the indirect emission limit requirement of COD < 150 mg / L in the "Battery Industry Pollutant Emission Standard" (GB 30484-2013).

[0108] 2.3 Comparison with traditional methods

[0109] The method of the present invention is compared with the traditional slicing wastewater treatment method:

[0110] (1) The treatment effect of the method of the present invention is better than that of the traditional treatment method. The method of the present invention can stably remove the COD concentration of the slicing wastewater to below 100 mg / L; while the COD concentration of the effluent treated by the traditional method is 100~200 mg / L, which is difficult to stably meet the discharge standard requirements.

[0111] (2) The biochemical method in the method of the present invention is relatively simple, and only aerobic biochemistry is used. The HRT of the biochemical section is 2 days, while the total HRT of the biochemical section of the traditional method is as high as 6 to 8 days. That is, the reaction pool of the biochemical method section of the method of the present invention has a small capacity, saves space, and has low investment cost and operating costs.

[0112] (3) Although the operating cost of the high-concentration slice wastewater in the method of the present invention is higher than that of the traditional method, the operating cost of the method of the present invention is lower than that of the traditional method in terms of the overall operating cost of the wastewater station.

[0113] Table 2 Table 2 Comparison between the method of the present invention and the traditional method

[0114]

[0115] 3. Effects of the Implementation of the Invention

[0116] The slicing wastewater discharged from a photovoltaic solar energy factory is used as the treatment object to illustrate the treatment effect of the device and method of the present invention. The water quality data of the high-concentration slicing wastewater to be treated is shown in Table 1.

[0117] 3.1 Separation membrane

[0118] 3.1.1 Operation status under different separation membrane recovery rates

[0119] The slice wastewater was treated by using the membrane assembly of the present invention, and the data of membrane water production and concentrate water quality under different recovery rate conditions, as well as separation operation pressure and chemical cleaning cycle are listed in Table 3.

[0120] It can be concluded from Table 3 that the separation membrane can operate within the recovery range of 70% to 90%. As the recovery rate increases, the COD concentration of the concentrated water increases accordingly, and the operating pressure also increases accordingly. Under the premise that the membrane assembly can operate stably, the recovery rate should be increased as much as possible to reduce the membrane concentrated water flow rate, thereby reducing the subsequent thermal destabilization coagulation precipitation and catalytic wet oxidation device processing scale. However, when the recovery rate reaches 85% and 90%, the chemical cleaning cycle of the membrane assembly is greatly reduced to 10d and 6d. More frequent chemical cleaning means that the operation and maintenance volume is large, and the separation membrane device is prone to fouling when operating at a high recovery rate. Therefore, the preferred separation recovery rate range is 75% to 80%.

[0121] Table 3 Treatment effect of membrane modules at different recovery rates

[0122]

[0123] 3.1.2 Operation of different separation membrane water fluxes

[0124] The membrane assembly of the present invention was used to treat slicing wastewater, and the data of membrane produced water and concentrated water quality at different separation membrane fluxes, as well as separation operating pressure and chemical cleaning cycle are listed in Table 4; the separation recovery rate at each produced water flux was 75%.

[0125] From Table 4, it can be seen that the membrane module has a water production flux of 16~24 L / m 2·h range, the device can operate, with the separation membrane flux increases, the device operating pressure gradually increases. Under the premise that the membrane assembly can operate stably, the membrane flux should be increased as much as possible to reduce the engineering cost of the membrane assembly. However, when the separation membrane flux is increased to 20L / m 2 When the chemical cleaning cycle is more than 1 hour, the chemical cleaning cycle is reduced to less than 20 days. Frequent chemical cleaning means a large amount of operation and maintenance, and the separation membrane device is prone to fouling when operating at a high membrane flux. Therefore, the preferred separation membrane water flux range is 18~20L / m 2 ·h.

[0126] Table 4 Treatment effect of membrane modules at different membrane fluxes

[0127]

[0128] 3.2 Heating / destabilization-coagulation-flocculation-precipitation

[0129] When the temperature of membrane concentrate is raised to 50℃~80℃, polyether compounds will precipitate. Coagulation and flocculation precipitation method is used for treatment at different temperatures. The PAC addition concentration is 300 mg / L and the PAM addition concentration is 5 mg / L. Different COD removal rates are obtained. The data are shown in Table 5.

[0130] As shown in Table 5, as the temperature of membrane concentrated water increases, the removal rate of COD in concentrated water by coagulation and sedimentation increases accordingly, but when the temperature rises to above 70°C, the COD removal rate no longer increases further with the increase in temperature. In addition, it was found in the research and development test that when the reaction temperature rises to above 60°C, the flocculation effect of the organic polymer flocculant will be affected by the high temperature, the generated flocs will become loose, the sedimentation effect will deteriorate, and in severe cases, mud will occur in the sedimentation tank. Therefore, the preferred thermal desiccation stable operation temperature range designed by the present invention is 55°C~60°C.

[0131] Table 5 Removal of COD from membrane concentrate by thermal destabilization coagulation and precipitation at different reaction temperatures

[0132]

[0133] 3.3 Catalytic wet oxidation

[0134] After treatment by the “heating / destabilization-coagulation-flocculation-precipitation” method, the COD concentration of membrane concentrate was reduced to 21350 mg / L~49500 mg / L. It was treated by catalytic wet oxidation. The reaction conditions and COD removal are shown in Table 6 (the treated influent COD was 49380 mg / L).

[0135] It can be seen from Table 6 that when the catalytic wet oxidation reaction time is maintained at 4h, the reaction pressure and reaction temperature are in the range of 5.5~6.5MPa and 250℃~260℃ respectively, the reaction pressure and reaction temperature have little effect on the COD removal effect of catalytic wet oxidation. The main factor affecting the COD removal effect of catalytic wet oxidation is the reaction time. When the reaction time is 4h, the COD removal rate can reach up to 93.5%; when the reaction time is reduced to 3h and 2h, the COD removal rate is reduced to 90% and 83.2% respectively. Therefore, the preferred reaction time of this embodiment is 3~4h.

[0136] Table 6 COD removal by catalytic wet oxidation under different reaction conditions

[0137]

[0138] 3.4 Aerobic biochemical treatment

[0139] The membrane water and the concentrated water after catalytic wet oxidation treatment are combined for aerobic biochemical treatment, and the effluent COD can reach below 100 mg / L, as shown in Table 7.

[0140] Table 7 COD treatment effect of slice wastewater

[0141]

[0142] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A treatment device for high-concentration slicing wastewater in the photovoltaic industry, comprising a treatment device, characterized in that: The treatment device comprises an organic separation membrane device (1), a separation membrane concentrated water treatment device (2), a catalytic wet oxidation device (3) and an aerobic biochemical reaction device (4); The organic separation membrane device (1) comprises a membrane water inlet box (1-1), a membrane water inlet pump (1-2), a security filter (1-3), a membrane booster pump (1-4) and a membrane assembly (1-5); the membrane water inlet box (1-1), the membrane water inlet pump (1-2), the security filter (1-3), the membrane booster pump (1-4) and the membrane assembly (1-5) are connected in sequence through pipelines; The separation membrane concentrated water treatment equipment (2) comprises a membrane concentrated water tank (2-1), a concentrated water lifting pump (2-2), a coagulation reaction tank (2-3), a coagulation agitator (2-4), a flocculation reaction tank (2-5), a flocculation agitator (2-6), a chemical precipitation tank (2-7) and a chemical precipitation tank scraper (2-8); The catalytic wet oxidation equipment (3) comprises a catalytic wet oxidation water inlet tank (3-1), a catalytic wet oxidation water inlet pump (3-2), a high-pressure waste heat recovery heat exchanger (3-3), a thermal oil heat exchanger (3-4), a catalytic wet oxidation reactor (3-5), a pressure regulating valve (3-6), a gas-liquid separator (3-7), an oxidation liquid delivery pump (3-8), and a low-pressure waste heat recovery heat exchanger (3-9); The aerobic biochemical reaction equipment (4) comprises an aerobic biochemical reactor (4-1), an aeration pipe (4-2), a biochemical sedimentation tank (4-3), and a biochemical sedimentation tank scraper (4-4); The concentrated water generated by the membrane assembly (1-5) flows into the membrane concentrated water tank (2-1) through a pipeline, and is transported to the low-pressure waste heat recovery heat exchanger (3-9) through a concentrated water lifting pump (2-2). The membrane concentrated water discharged from the low-pressure waste heat recovery heat exchanger (3-9) enters the coagulation reaction tank (2-3), and a coagulation agitator (2-4) is provided in the coagulation reaction tank (2-3) to perform a coagulation reaction. The effluent of the coagulation reaction tank (2-3) flows into the flocculation reaction tank (2-5), and a flocculation agitator (2-6) is provided in the flocculation reaction tank (2-5) to perform a flocculation reaction. The effluent of the flocculation reaction tank (2-5) flows into the chemical precipitation tank (2-7) for mud and water separation, and a chemical precipitation tank scraper (2-8) is installed inside the chemical precipitation tank (2-7); The top of the chemical precipitation tank (2-7) is connected to the catalytic wet oxidation water inlet tank (3-1), a catalytic wet oxidation water inlet pump (3-2) is connected between the catalytic wet oxidation water inlet tank (3-1) and the high-pressure waste heat recovery heat exchanger (3-3), the high-pressure waste heat recovery heat exchanger (3-3), the heat transfer oil heat exchanger (3-4), and the catalytic wet oxidation reactor (3-5) are sequentially connected in series, the output end of the catalytic wet oxidation reactor (3-5) is connected to the high-pressure waste heat recovery heat exchanger (3-3), a pressure regulating valve (3-6) is installed between the high-pressure waste heat recovery heat exchanger (3-3) and the gas-liquid separator (3-7), and an oxidation liquid delivery pump (3-8) is installed between the gas-liquid separator (3-7) and the low-pressure waste heat recovery heat exchanger (3-9); The output end of the low-pressure waste heat recovery heat exchanger (3-9) is connected to the aerobic biochemical reactor (4-1), an aeration pipe (4-2) is installed at the bottom of the aerobic biochemical reactor (4-1), the output end of the aerobic biochemical reactor (4-1) is connected to the biochemical sedimentation tank (4-3), and a biochemical sedimentation tank scraper (4-4) is installed inside the biochemical sedimentation tank (4-3).

2. A treatment device for high-concentration slicing wastewater in the photovoltaic industry according to claim 1, characterized in that: The membrane assembly (1-5) comprises a first separation membrane group and a second separation membrane group, wherein the first separation membrane group and the second separation membrane group are arranged in series; The first separation membrane group and the second separation membrane group both have a plurality of separation membrane pressure vessels arranged in parallel, and the separation membrane pressure vessels are provided with 1-6 separation membranes; The produced water of the first separation membrane group enters the produced water mother pipe, the output end of the produced water mother pipe is connected to the aerobic biochemical reactor (4-1), the concentrated water of the first separation membrane group enters the second separation membrane group, the produced water of the second separation membrane group enters the produced water mother pipe, and the concentrated water of the second separation membrane group enters the membrane concentrated water tank (2-1).

3. A treatment method based on the treatment device for high-concentration slicing wastewater in the photovoltaic industry according to claim 1, characterized in that: The following steps are involved: Step S1, preliminary treatment of high-concentration wastewater: through the difference in the interception capacity of the separation membrane of the membrane assembly (1-5) for organic matter of different molecular weights, the organic matter of low molecular weight passes through the separation membrane into the produced water side, while the organic matter of high molecular weight is intercepted on the concentrated water side of the separation membrane, thereby achieving the separation of organic matter of different molecular weights in the wastewater; Step S2, treating the membrane produced water and membrane concentrated water after separation separately: directly performing aerobic biochemical treatment on the membrane produced water can reduce the COD concentration of the wastewater to below 100 mg / L, and performing "heating destabilization-coagulation-flocculation-precipitation" treatment on the membrane concentrated water side of the separation membrane, and the polyether compounds in the concentrated water are converted from a dissolved state to an insoluble state at a temperature of 50°C to 80°C, and are removed from the membrane concentrated water in the form of precipitates; Step S3, the precipitated water in step S2 is treated: the precipitated water is subjected to catalytic wet oxidation treatment, and the refractory polyether compounds are oxidatively decomposed and removed under the reaction conditions of 250° C. to 260° C., and the biodegradability of the membrane concentrated water is improved, and the concentrated water is combined with the membrane produced water for aerobic biochemical treatment; Step S4: The COD concentration of the effluent from aerobic biochemical treatment can be reduced to below 100 mg / L, meeting the requirements for discharge standards or further treatment and reuse.

4. The processing method according to claim 3, characterized in that: The organic separation membrane in the membrane assembly (1-5) is a composite membrane with an asymmetric structure, comprising a porous membrane for support and a dense membrane for separation, the membrane material is polyamide, and the structure of the organic separation membrane is one of a roll type, a tube type or a plate-and-frame type; The molecular weight cutoff of the organic separation membrane is 200Da to 500Da; the recovery rate of the membrane assembly (1-5) is 70% to 90%; the water production flux of the membrane assembly (1-5) is 14 to 24L / m 2 ·h; the operating pressure of the membrane assembly (1-5) is 0.3-0.6MPa.

5. The processing method according to claim 3, characterized in that: In the step S2, in the method for coagulating the membrane concentrate on the concentrate side of the separation membrane, the coagulant used is polyaluminium chloride, and the coagulant addition concentration is 200-400 mg / L; the flocculant used is polyacrylamide, and the flocculant addition concentration is 3-5 mg / L; the stirring speed of the coagulation agitator (2-4) is 70-90 rpm, and the stirring speed of the flocculation agitator (2-6) is 35-45 rpm.

6. The processing method according to claim 3, characterized in that: In step S3, catalytic wet oxidation is a chemical process in which organic pollutants in wastewater are oxidized into CO2, H2O and small molecular organic matter using oxygen as an oxidant under the conditions of high temperature of 125°C to 320°C and high pressure of 0.5MPa to 10MPa.

7. The processing method according to claim 6, characterized in that: The process parameters for catalytic wet oxidation are as follows: Catalytic wet oxidation reaction pressure: 5.5~6.5MPa; Catalytic wet oxidation reaction time: 3 to 4 hours.

8. The processing method according to claim 7, characterized in that: In the catalytic wet oxidation treatment, the oxidation heat of the membrane concentrate is first used to continuously maintain the reaction temperature. A group of heat exchangers are set at the inlet of the wet oxidation reactor, and the high-temperature oxidation liquid after the catalytic wet oxidation treatment is used as a heat source to exchange heat and heat up the membrane concentrate before oxidation.

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