A photovoltaic wastewater zero discharge treatment system and treatment method

Abstract

The application relates to the photovoltaic manufacturing technical field, in particular to a photovoltaic wastewater zero-discharge treatment system and treatment method. The system comprises a dilute acid wastewater treatment device, a dilute alkali wastewater treatment device and a neutralized concentrated water filtering device. The dilute acid wastewater treatment device comprises a dilute acid wastewater filtering unit, an acid path concentrated water adjusting unit, a calcium fluoride crystallization unit and a calcium bicarbonate crystallization unit which are connected in sequence. The dilute acid wastewater treatment unit further comprises an adjusting pipeline which is connected between the upstream of the calcium fluoride crystallization unit, the calcium fluoride crystallization unit and the calcium bicarbonate crystallization unit and the downstream of the calcium bicarbonate crystallization unit. The adjusting pipeline can switch whether the concentrated water flowing out of the acid path concentrated water adjusting unit passes through the calcium fluoride crystallization unit and / or the calcium bicarbonate crystallization unit. The dilute alkali wastewater treatment device comprises a dilute alkali wastewater filtering unit and a silicic acid crystallization unit which are connected in sequence. The neutralized concentrated water filtering device is used for deep treatment of the crystallized concentrated water. The system can produce high-quality regenerated water and realize zero discharge while efficiently controlling energy consumption and chemical consumption.

Description

Technical Field

[0001] This application relates to the field of photovoltaic manufacturing technology, and in particular to a photovoltaic wastewater zero-discharge treatment system and treatment method. Background Technology

[0002] Solar cells (photovoltaic cells) are thin-film photovoltaic semiconductors that generate electricity directly from sunlight. Also known as "solar chips" or "photovoltaic cells," they can instantly output voltage and, in the presence of a circuit, generate current, provided certain illumination conditions are met. From 2012 to 2023, global photovoltaic cell production continued to grow, increasing from 38GW to 644GW. The rapid development of the photovoltaic cell industry has inevitably led to problems such as a rapid increase in water demand and wastewater discharge.

[0003] Photovoltaic wastewater is mainly generated from two processes: etching and texturing. It includes concentrated acid wastewater from etching, concentrated alkali wastewater from texturing, dilute acid wastewater from acid washing after texturing, and dilute alkali wastewater from alkaline rinsing after etching. All of these wastewaters are highly corrosive and have poor biodegradability. The concentrated and dilute acid wastewaters primarily contain pollutants such as hydrochloric acid, hydrofluoric acid, and fluorosilicic acid, along with small amounts of organic alcohols, surfactants, and suspended silica particles, with a pH of approximately 2.0-3.0. The concentrated and dilute alkali wastewaters primarily contain pollutants such as silicates, sodium hydroxide, and hydrogen peroxide, along with small amounts of fluorides, organic alcohols, surfactants, and suspended silica particles, with a pH of approximately 11.0-12.0. The concentrated acid and alkali wastewaters have extremely high levels of inorganic salt pollutants, with conductivity typically reaching 10. 5 While the inorganic salt pollutant content in dilute acid and dilute alkali wastewater is relatively low (above μs / cm), the conductivity can still reach 10. 4 μs / cm or higher.

[0004] In view of the different characteristics of the above four types of wastewater, different resource utilization technologies should be used for separate treatment and organic combination. This invention mainly provides a technical solution to simultaneously achieve the recycling and reuse of dilute acid wastewater and dilute alkali wastewater with zero discharge. Summary of the Invention

[0005] To address or at least partially address the aforementioned technical problems, this application provides a photovoltaic wastewater zero-discharge treatment system and method. This system treats dilute acid and dilute alkali wastewater generated during photovoltaic production, enabling their recycling and reducing the emission of harmful substances in the wastewater, thereby meeting environmental protection policy requirements.

[0006] The first aspect of this application provides a photovoltaic wastewater zero-discharge treatment system. A photovoltaic wastewater zero-discharge treatment system includes:

[0007] A dilute acid wastewater treatment device includes a dilute acid wastewater filtration unit, an acid concentrate adjustment unit, a dehydrator, a calcium fluoride crystallization unit, and a calcium bicarbonate crystallization unit connected in sequence. The dilute acid wastewater treatment unit also includes an adjustment pipeline connected upstream of the calcium fluoride crystallization unit, between the calcium fluoride crystallization unit and the calcium bicarbonate crystallization unit, and downstream of the calcium bicarbonate crystallization unit.

[0008] A dilute alkali wastewater treatment device includes a dilute alkali wastewater filtration unit and a silica crystallization unit connected in sequence;

[0009] A neutralized concentrate filtration device is connected downstream of the calcium bicarbonate crystallization unit and the silica crystallization unit.

[0010] In some embodiments, the dilute acid wastewater filtration unit includes a first inlet pipe, a first backwashable filter, a second inlet pipe, and a first reverse osmosis unit connected in sequence, and a booster pump is provided on the first inlet pipe and / or the second inlet pipe.

[0011] In some embodiments, the acid path concentrate conditioning unit includes a conditioning tank and a calcium carbonate dosing tank. The concentrate side of the first reverse osmosis unit is connected to the conditioning tank through a first outlet pipe. The calcium carbonate dosing tank is connected to the conditioning tank and is used to add calcium carbonate to the conditioning tank.

[0012] In some embodiments, the dehydrator has a first inlet, a first outlet, and a recovery port; the equalization tank is connected to the first inlet via a second outlet pipe; the first outlet is connected to the calcium fluoride crystallization unit via a third outlet pipe; and the recovery port is connected to the calcium carbonate dosing tank via a return pipe.

[0013] The calcium fluoride crystallization unit is connected to the calcium bicarbonate crystallization unit through a fourth water outlet pipe, and a first check valve is installed at the inlet of the fourth water outlet pipe. The calcium bicarbonate crystallization unit is connected to the neutralized concentrate filtration device through a fifth water outlet pipe, and a second check valve is installed at the inlet of the fifth water outlet pipe.

[0014] In some embodiments, the neutralized concentrate filtration device includes an electrocoagulation sedimentation tank, an ultrafiltration unit, a second reverse osmosis unit, and an evaporator crystallizer connected in sequence. A booster pump is provided between the ultrafiltration unit and the second reverse osmosis unit, and the evaporator crystallizer is connected to the concentrate side of the second reverse osmosis unit.

[0015] In some embodiments, the regulating pipeline includes a first branch pipe, a second branch pipe, a diversion pipe, a first valve, a second valve, a third valve, and a fourth valve. The inlet of the first branch pipe is connected to the third outlet pipe, the outlet of the first branch pipe is connected to the first end of the diversion pipe and the inlet of the second branch pipe, the second end of the diversion pipe is connected to the fourth outlet pipe, and the outlet of the second branch pipe is connected to the fifth outlet pipe.

[0016] The first valve is located on the first branch pipe, the second valve is located on the second branch pipe, the third valve is located on the third outlet pipe and downstream of the inlet of the first branch pipe, and the fourth valve is located on the fourth outlet pipe and downstream of the second end of the diversion pipe.

[0017] In some embodiments, the third outlet pipe is provided with a first fluoride detector and a first calcium ion detector, which are located upstream of the inlet of the first branch pipe.

[0018] The fourth water outlet pipe is equipped with a second calcium ion detector, which is located upstream of the first check valve.

[0019] In some embodiments, the system further includes a regenerated water tank. The product water side of the first reverse osmosis unit is connected to the regenerated water tank via a first product water pipe, and the product water side of the second reverse osmosis unit is connected to the regenerated water tank via a third product water pipe. The dilute alkali wastewater filtration unit includes a dilute alkali wastewater conditioning unit, a second backwashable filter, and a nanofiltration unit connected in sequence. A booster pump is provided between the second backwashable filter and the nanofiltration unit. The product water side of the nanofiltration unit is connected to the regenerated water tank via a second product water pipe, and the concentrate side of the nanofiltration unit is connected to the silica crystallization unit.

[0020] In some embodiments, the top of the conditioning tank is connected to the silica crystallization unit via a gas supply pipe.

[0021] A second aspect of this application provides a method for zero-discharge treatment of photovoltaic wastewater, employing a photovoltaic wastewater zero-discharge treatment system as described in any of the preceding claims, the method comprising:

[0022] S1. The first fluoride detector measures the fluoride content as F1 mg / L, the first calcium ion detector measures the calcium ion content as C1 mg / L, and the second calcium ion detector measures the calcium ion content as C2 mg / L.

[0023] S2. When F1 < 5.0, the third valve is closed, the first valve is opened, and the calcium fluoride crystallization unit stops operating.

[0024] S3. When F1≥5.0, the third valve opens and the first valve closes, and the calcium fluoride crystallization unit is in operation.

[0025] S3. When the second calcium ion detector does not trigger an empty tube alarm and C2 < 330, the fourth valve is closed, the second valve is opened, and the calcium bicarbonate crystallization unit stops operating.

[0026] When the second calcium ion detector does not trigger an empty tube alarm and C2≥330, the fourth valve opens, the second valve closes, and the calcium bicarbonate crystallization unit begins to operate.

[0027] When the second calcium ion detector alarms for an empty tube and C1 < 330 + 10F1 / 19, the fourth valve closes, the second valve opens, and the calcium bicarbonate crystallization unit stops operating.

[0028] When the second calcium ion detector alarms for an empty tube and C1 ≥ 330 + 10F1 / 19, the fourth valve opens and the second valve closes, and the calcium bicarbonate crystallization unit begins operation.

[0029] The technical solution provided in this application has the following advantages compared with the prior art:

[0030] 1. To achieve full resource utilization of photovoltaic wastewater and valuable substances in the water, while producing high-quality reclaimed water that can be reused in photovoltaic cell production lines, as well as inorganic salt products such as silica, calcium fluoride, calcium bicarbonate, and sodium chloride.

[0031] 2. It can achieve acid-base neutralization and removal of organic pollutants while saving a significant number of biochemical treatment units, greatly reducing the generation of solid waste such as activated sludge and precipitated sludge. It is used in photovoltaic wastewater zero-discharge treatment systems and concentrated water filtration devices. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the photovoltaic wastewater zero-discharge treatment system described in the embodiments of this application;

[0035] Figure 2 This is a flowchart of the photovoltaic wastewater zero-discharge treatment method described in the embodiments of this application.

[0036] Among them, 1. dilute acid wastewater filtration unit; 101. first inlet pipe; 102. first backwashable filter; 103. first reverse osmosis unit; 104. second inlet pipe;

[0037] 2. Acid concentrate conditioning unit; 201. Conditioning tank; 202. Calcium carbonate dosing tank;

[0038] 3. Calcium fluoride crystallization unit;

[0039] 4. Calcium bicarbonate crystallization unit;

[0040] 5. Dilute alkali wastewater filtration unit; 501. Dilute alkali wastewater conditioning unit; 502. Second backwashable filter; 503. Nanofiltration unit;

[0041] 6. Silicate crystallization unit;

[0042] 7. Neutralization concentrate filtration device; 701. Electrocoagulation sedimentation tank; 702. Ultrafiltration unit; 703. Second reverse osmosis unit; 704. Evaporator crystallizer;

[0043] 8. Dehydrator;

[0044] 9. First calcium ion detector;

[0045] 10. First fluoride detector;

[0046] 11. Second calcium ion detector;

[0047] 12. First branch pipe; 121. First valve;

[0048] 13. Second branch pipe; 131. Second valve;

[0049] 14. Third water outlet pipe; 141. Third valve;

[0050] 15. Fourth water outlet pipe; 151. Fourth valve;

[0051] 16. First water outlet pipe;

[0052] 17. Second water outlet pipe;

[0053] 18. Return pipe;

[0054] 19. Fifth water outlet pipe;

[0055] 20. Third water production pipe;

[0056] 21. Reclaimed water tank;

[0057] 22. First water production pipe;

[0058] 23. Second water production pipe;

[0059] 24. Gas pipeline;

[0060] 25. Modify the flow pipe. Detailed Implementation

[0061] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0062] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0063] like Figure 1 As shown in the figure, this application provides a photovoltaic wastewater zero-discharge treatment system, including a dilute acid wastewater treatment device, a dilute alkali wastewater treatment device, and a neutralization concentrate filtration device 7. The dilute acid wastewater treatment device includes a dilute acid wastewater filtration unit 1, an acid path concentrate adjustment unit 2, a dehydrator 8, a calcium fluoride crystallization unit 3, a calcium bicarbonate crystallization unit 4, and a regulating pipeline. The dilute acid wastewater filtration unit 1, the acid path concentrate adjustment unit 2, the calcium fluoride crystallization unit 3, and the calcium bicarbonate crystallization unit 4 are connected in sequence, and the regulating pipeline is connected to the calcium fluoride crystallization unit. The upstream of unit 3, between calcium fluoride crystallization unit 3 and calcium bicarbonate crystallization unit 4, and downstream of calcium bicarbonate crystallization unit 4, and the regulating pipeline is configured to switch the solution flowing out from acid concentrate regulating unit 2 through calcium fluoride crystallization unit 3 and / or calcium bicarbonate crystallization unit 4; the dilute alkali wastewater treatment device includes a dilute alkali wastewater filtration unit 5 and a silicate crystallization unit 6 connected in sequence; the neutralization concentrate filtration device 7 is connected downstream of calcium bicarbonate crystallization unit 4 and silicate crystallization unit 6, and is used to precipitate and filter the crystallized acid and alkali solutions.

[0064] In practice, the dilute acid wastewater generated during the photovoltaic production process is first passed into the dilute acid wastewater filtration unit 1 to remove suspended particulate matter such as silica from the dilute acid wastewater. Then it is passed into the acid concentrate adjustment unit 2 to adjust the pH value of the wastewater so that it meets the optimal conditions for the subsequent crystallization reaction. The regulating pipeline has three switching modes. For example, in the first mode, the calcium fluoride crystallization unit 3 and the calcium bicarbonate crystallization unit 4 are connected sequentially. The wastewater treated by the acid-path concentrate regulating unit 2 crystallizes in the calcium fluoride and calcium bicarbonate crystallization units 3 and 4 before entering the neutralization concentrate filtration device 7. In the second mode, the calcium fluoride crystallization unit 3 is connected, and the calcium bicarbonate crystallization unit 4 is closed. The wastewater treated by the acid-path concentrate regulating unit 2 crystallizes in the calcium fluoride crystallization unit 3 and then directly enters the neutralization concentrate filtration device 7. In the third mode, the calcium fluoride crystallization unit 3 is closed, and the calcium bicarbonate crystallization unit 4 is connected. The wastewater treated by the acid-path concentrate regulating unit 2 bypasses the calcium fluoride crystallization unit 3 and enters the calcium bicarbonate crystallization unit 4 for crystallization before directly entering the neutralization concentrate filtration device 7. The optimal mode is selected based on real-time monitored parameters during wastewater treatment (such as wastewater pH, fluoride ion concentration, and calcium ion concentration) to ensure treatment effect and efficiency.

[0065] In some embodiments of this application, the regulating pipeline includes a first branch pipe 12, a second branch pipe 13, a diversion pipe 25, a first valve 121, a second valve 131, and a third valve 141. The first branch pipe 12 has a first inlet and two first outlets. The first inlet is connected to the upstream pipe of the calcium fluoride crystallization unit 3. The diversion pipe 25 is connected between one of the first outlets and the upstream pipe of the calcium bicarbonate crystallization unit 4. The second branch pipe 13 is connected between the other first outlet and the downstream pipe of the calcium bicarbonate crystallization unit 4. The first valve 121 is disposed on the first branch pipe 12, the second valve 131 is disposed on the second branch pipe 13, and the third valve 141 is disposed on the upstream pipe of the calcium fluoride crystallization unit 3.

[0066] In specific implementation, the upstream pipeline of the calcium fluoride crystallization unit 3 includes a third outlet pipe 14, which is connected between the acid concentrate regulating unit 2 and the calcium fluoride crystallization unit 3. The first inlet of the first branch pipe 12 is connected to the third outlet pipe 14. The first valve 121 is installed on the first branch pipe 12, and the third valve 141 is installed on the third outlet pipe 14. When the first valve 121 is open and the third valve 141 is closed, the first branch pipe 12 is opened and the calcium fluoride crystallization unit 3 is closed. When the first valve 121 is closed and the third valve 141 is open, the first branch pipe 12 is closed and the calcium fluoride crystallization unit 3 is opened. One end of the diversion pipe 25 is connected to one of the outlets of the first branch pipe 12, and the other end is connected to the upstream pipe of the calcium bicarbonate crystallization unit 4, allowing the solution to bypass the calcium fluoride crystallization unit 3 and directly enter the calcium bicarbonate crystallization unit 4. The upstream pipe of the calcium bicarbonate crystallization unit 4 includes a fourth outlet pipe 15, which is equipped with a fourth valve 151. When the fourth valve 151 is open, the calcium bicarbonate crystallization unit 4 is open; when the fourth valve 151 is closed, the calcium bicarbonate crystallization unit 4 is closed. One end of the second branch pipe 13 is connected to another first outlet, and the other end is connected to the downstream pipe of the calcium bicarbonate crystallization unit 4. Specifically, the downstream pipe of the calcium bicarbonate crystallization unit 4 includes a fifth outlet pipe 19, which connects the calcium bicarbonate crystallization unit 4 and the neutralization concentrate filtration device 7. When the second valve 131 on the second branch pipe 13 is open, the solution bypasses the calcium bicarbonate crystallization unit 4 and directly enters the neutralization concentrate filtration device 7.

[0067] Furthermore, in some embodiments of this application, the dilute acid wastewater filtration unit 1 includes a first inlet pipe 101, a first backwashable filter 102, a second inlet pipe 104 and a first reverse osmosis unit 103 connected in sequence, and a booster pump is provided on the first inlet pipe 101 and / or the second inlet pipe 104.

[0068] The first inlet pipe 101 connects at one end to the dilute acid wastewater source generated during photovoltaic production, and at the other end to the inlet of the first backwashable filter 102, conveying the raw dilute acid wastewater to the filtration unit. The first backwashable filter 102 removes large particulate suspended pollutants (such as silica particles and a small amount of solid impurities) from the dilute acid wastewater, protecting the subsequent precision first reverse osmosis unit 103. The second inlet pipe 104 connects at one end to the outlet of the first backwashable filter 102, and at the other end to the inlet of the first reverse osmosis unit 103, conveying the pre-filtered wastewater to the first reverse osmosis unit 103. The first reverse osmosis unit 103 further retains colloidal and dissolved impurities, producing high-quality reclaimed water.

[0069] The first reverse osmosis unit 103 includes a reverse osmosis membrane element, a pressure vessel, and a sealing ring. The reverse osmosis membrane element is made of inert materials such as sulfonated polyethersulfone and polyvinylidene fluoride, which have extremely high chemical stability, preventing the membrane element from being corroded and degraded. Other components such as the pressure vessel and sealing ring are made of acid-resistant materials such as SS316L stainless steel. SS316L stainless steel contains molybdenum, and its corrosion resistance is far superior to ordinary stainless steel (such as 304 stainless steel), which can prevent the inner wall of the vessel and the sealing ring from being corroded by acid and leaking.

[0070] Furthermore, in some embodiments of this application, the acid concentrate adjustment unit 2 includes an adjustment tank 201 and a calcium carbonate dosing tank 202. The adjustment tank 201 is connected to the first reverse osmosis unit 103 through a first outlet pipe 16, and the calcium carbonate dosing tank 202 is connected to the adjustment tank 201 and is used to add calcium carbonate into the adjustment tank 201.

[0071] The inlet of the equalization tank 201 is connected to the outlet of the first reverse osmosis unit 103 via the first outlet pipe 16. The outlet of the equalization tank 201 is connected to the upstream pipe of the calcium fluoride crystallization unit 3. The equalization tank 201 serves as a reaction vessel for pH adjustment, providing space for the mixing and reaction of wastewater and calcium carbonate. The calcium carbonate dosing tank 202 is connected to the equalization tank 201 via a dosing pipeline (including a dosing pump and flow meter) (usually connected to the middle or bottom of the tank to ensure uniform mixing). The calcium carbonate dosing tank 202 stores solid calcium carbonate (or calcium carbonate suspension) and precisely adds it to the equalization tank 201.

[0072] The equalization tank 201 is typically equipped with a stirring device (such as a mechanical agitator or aeration device) and an online pH monitor; the dosing pipeline is equipped with a dosing pump and a flow regulating valve. The online pH monitor provides real-time feedback on the water's pH value and, in conjunction with the dosing pump, adjusts the dosage.

[0073] In some embodiments of this application, a dehydrator 8 is provided between the equalization tank 201 and the calcium fluoride crystallization unit 3. The dehydrator 8 has a second inlet, a second outlet and a recovery port. The second inlet is connected to the outlet of the equalization tank 201 through a second outlet pipe 17. The second outlet is connected to the calcium fluoride crystallization unit 3 through a third outlet pipe 14. The recovery port is connected to the calcium carbonate dosing tank 202 through a return pipe 18.

[0074] Specifically, the second inlet of the dewatering machine 8 is connected to the outlet of the equalization tank 201 via the second outlet pipe 17, and the second outlet is connected to the calcium fluoride crystallization unit 3 via the third outlet pipe 14. The recovery port is connected to the calcium carbonate dosing tank 202 via the return pipe 18. The outlet of the dewatering machine 8 is equipped with a solid-liquid separation filter screen or filter membrane; the return pipe 18 is equipped with a transfer pump and a filter; and the second outlet pipe 17 is equipped with a flow regulating valve. The dewatering machine 8 uses centrifugal dewatering, pressure filtration dewatering, and other methods to separate and recover unreacted calcium carbonate precipitate in the equalization tank 201. The precipitate flows out through the recovery port and is sent back to the calcium carbonate dosing tank 202 via the return pipe 18 (pressurized by a submersible pump) to achieve recycling.

[0075] In some embodiments of this application, the third water outlet pipe 14 is connected to the first fluoride detector 10 and / or the first calcium ion detector 9, and the fourth water outlet pipe 15 is connected to the second calcium ion detector 11.

[0076] In some embodiments of this application, the neutralized concentrate filtration device 7 includes an electrocoagulation sedimentation tank 701, an ultrafiltration unit 702, a second reverse osmosis unit 703, and an evaporator crystallizer 704 connected in sequence.

[0077] The electrocoagulation sedimentation tank 701 has two inlets and one outlet. One inlet is connected to the outlet of the calcium bicarbonate crystallization unit 4 via the fifth outlet pipe 19, and the other inlet is connected to the outlet of the silica crystallization unit 6. The outlet of the electrocoagulation sedimentation tank 701 is connected to the ultrafiltration unit 702. The electrocoagulation sedimentation tank 701 generates metal cations such as iron or aluminum ions through electrode electrolysis. These cations combine with hydroxide ions, mainly from the concentrated alkaline water, to form water-insoluble iron hydroxide or aluminum hydroxide flocs. The positively charged flocs capture negatively charged impurities in the water through adsorption bridging, forming easily settling "lumps," thereby removing residual fluoride ions, fluorosilicate ions, silica ions, silica flocs, and other impurities.

[0078] The ultrafiltration unit 702 is used to remove fine flocs, colloids, and large organic molecules that have not been completely settled in the electrocoagulation sedimentation tank 701, preventing these impurities from entering the second reverse osmosis unit 703 and scratching or clogging the reverse osmosis membrane. The second reverse osmosis unit 703 removes residual dissolved inorganic salt ions (such as Na+). + Cl - ).

[0079] The evaporator crystallizer 704 uses steam heating or heat pump heating to evaporate the water in the reverse osmosis concentrate, causing salts such as sodium chloride to crystallize and precipitate after reaching saturation, thus achieving zero discharge and full resource utilization of valuable substances in wastewater.

[0080] Furthermore, in some embodiments of this application, the photovoltaic wastewater zero-discharge treatment system further includes a regenerated water tank 21, with the first reverse osmosis unit 103 connected to the regenerated water tank 21 via a first water pipe 20; the second reverse osmosis unit 703 connected to the regenerated water tank 21 via a second water pipe 22; and the dilute alkali wastewater filtration unit 5 including a dilute alkali wastewater regulating unit 501, a second backwashable filter 502, and a nanofiltration unit 503 connected in sequence, with the nanofiltration unit 503 connected to the regenerated water tank 21 via a third water pipe 23.

[0081] The reclaimed water tank 21 is used to store qualified reclaimed water, realizing the recycling and reuse of water resources. Water generated by the first reverse osmosis unit 103, the second reverse osmosis unit 703, and the nanofiltration unit 503 is all fed into the reclaimed water tank 21 for storage. The dilute alkaline wastewater conditioning unit 501 removes hydrogen peroxide by adding manganese dioxide catalyst to the dilute alkaline wastewater, catalyzing the self-oxidation and reduction reaction of hydrogen peroxide to decompose it into oxygen and water.

[0082] The nanofiltration membrane element used in nanofiltration unit 503 is made of inert materials such as sulfonated polyethersulfone and polyvinylidene fluoride, and coated with alkali-resistant polymers such as polyvinyl alcohol as a protective layer. Nanofiltration unit 503 utilizes a dual mechanism of "membrane pore size sieving + charge repulsion" to retain colloidal and dissolved impurities, producing high-quality reclaimed water.

[0083] Furthermore, in some embodiments of this application, the top of the regulating tank 201 is connected to the silica crystallization unit 6 via a gas supply pipe 24. The acid concentrate regulating unit 2 removes acid through the reaction of carbonates with hydrogen ions. The carbon dioxide gas generated by the reaction is supplied to the silica crystallization unit 6 through the gas supply pipe 24, where it reacts with free silicates to generate silica crystals. The silica crystals can be calcined to produce silica products.

[0084] This application also provides a method for zero-discharge treatment of photovoltaic wastewater. The method uses the photovoltaic wastewater zero-discharge treatment system described in the above embodiments to treat dilute acid wastewater and dilute alkali wastewater generated during photovoltaic production, so as to meet the emission standards required by environmental protection requirements.

[0085] Specifically, such as Figure 2 As shown, the zero-discharge treatment method for photovoltaic wastewater includes:

[0086] The fluoride content F1 at the inlet of the calcium fluoride crystallization unit 3 is detected by the first fluoride detector 10, the calcium ion content C1 at the inlet of the calcium fluoride crystallization unit 3 is detected by the first calcium ion detector 9, and the calcium ion content C2 at the outlet of the calcium fluoride crystallization unit 3 is detected by the second calcium ion detector 11.

[0087] When F1 is less than the first set value F 11At this time, there is no need to start the calcium fluoride crystallization unit 3, avoiding unnecessary energy consumption and reagent waste. At this time, the regulating pipeline is switched, the third valve is closed, and the first valve is opened, so that the concentrated water flowing from the acid line concentrated water regulating unit 2 bypasses the calcium fluoride crystallization unit 3.

[0088] When F1 is greater than or equal to F 11 When this occurs, it indicates that the calcium fluoride crystallization unit 3 must be activated. At this time, the regulating pipeline is switched, the third valve is opened, and the first valve is closed, so that the concentrated water flowing from the acid line concentrated water regulating unit 2 flows through the calcium fluoride crystallization unit 3.

[0089] When the second calcium ion detector 11 does not trigger an empty tube alarm and C2 is less than the second set value C 11 If the reaction fails, it indicates that the calcium bicarbonate crystallization reaction cannot be supported. At this point, the regulating pipeline is switched, the fourth valve is closed, and the second valve is opened, so that the concentrated water flowing from the calcium fluoride crystallization unit 3 bypasses the calcium bicarbonate crystallization unit 4 and enters the neutralized concentrated water filtration device 7.

[0090] When the second calcium ion detector 11 does not trigger an empty tube alarm and C2 is greater than or equal to C 11 When the flow rate is 10, it indicates that the calcium bicarbonate crystallization reaction is supported. At this time, the regulating pipeline is switched, the fourth valve is opened, and the second valve is closed to ensure that the concentrated water flowing out of the calcium fluoride crystallization unit 3 can flow through the calcium bicarbonate crystallization unit 4.

[0091] When the second calcium ion detector 11 triggers an empty tube alarm and C1 is less than the third set value C 12 At this time, the calcium bicarbonate crystallization reaction is not supported. The regulating pipeline is switched, the fourth valve is closed, and the second valve is opened, allowing the concentrated water flowing from the acid circuit concentrated water regulating unit 2 to bypass the calcium bicarbonate crystallization unit 4 and enter the neutralized concentrated water filtration device 7.

[0092] When the second calcium ion detector 11 triggers an empty tube alarm and C1 is greater than or equal to C 12 When the indicator shows that the calcium bicarbonate crystallization reaction is supported, the regulating pipeline is switched, the fourth valve is opened, and the second valve is closed to ensure that the concentrated water flowing from the acid concentrate regulating unit 2 can flow through the calcium bicarbonate crystallization unit 4.

[0093] Specifically, in some embodiments, the first set value F 11 =5.0 mg / L, second set value C 11 =300 mg / L, third set value C 12 = 300 mg / L + 10F1 / 19.

[0094] A real-time water quality monitoring system is constructed using a first fluoride detector 10, a first calcium ion detector 9, and a second calcium ion detector 11. Key indicators (fluoride content F1, inlet calcium ion content C1, and outlet calcium ion content C2) serve as the core control basis to achieve dynamic adaptation of the treatment process and efficiently control energy and chemical consumption.

[0095] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0096] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for zero-discharge treatment of photovoltaic wastewater, characterized in that, The wastewater is treated using a photovoltaic wastewater zero-discharge treatment system, which includes: A dilute acid wastewater treatment device includes a dilute acid wastewater filtration unit, an acid concentrate conditioning unit, a dehydrator, a calcium fluoride crystallization unit, and a calcium bicarbonate crystallization unit connected in sequence. The dilute acid wastewater treatment unit further includes a regulating pipeline connected upstream of the calcium fluoride crystallization unit, between the calcium fluoride crystallization unit and the calcium bicarbonate crystallization unit, and downstream of the calcium bicarbonate crystallization unit. The regulating pipeline is configured to switch the solution flowing out of the acid concentrate conditioning unit through the calcium fluoride crystallization unit and / or the calcium bicarbonate crystallization unit. A dilute alkali wastewater treatment device includes a dilute alkali wastewater filtration unit and a silica crystallization unit connected in sequence; A neutralized concentrate filtration device is connected downstream of the calcium bicarbonate crystallization unit and the silica crystallization unit; The zero-discharge treatment method for photovoltaic wastewater includes: S1. The first fluoride detector measures the fluoride content as F1 mg / L, the first calcium ion detector measures the calcium ion content as C1 mg / L, and the second calcium ion detector measures the calcium ion content as C2 mg / L. S2. When F1 < 5.0, the third valve is closed, the first valve is opened, and the calcium fluoride crystallization unit stops operating. S3. When F1≥5.0, the third valve opens and the first valve closes, and the calcium fluoride crystallization unit is in operation. S3. When the second calcium ion detector does not trigger an empty tube alarm and C2 < 330, the fourth valve is closed, the second valve is opened, and the calcium bicarbonate crystallization unit stops operating. When the second calcium ion detector does not trigger an empty tube alarm and C2≥330, the fourth valve opens, the second valve closes, and the calcium bicarbonate crystallization unit begins to operate. When the second calcium ion detector alarms for an empty tube and C1 < 330 + 10F1 / 19, the fourth valve closes, the second valve opens, and the calcium bicarbonate crystallization unit stops operating. When the second calcium ion detector alarms for an empty tube and C1 ≥ 330 + 10F1 / 19, the fourth valve opens and the second valve closes, and the calcium bicarbonate crystallization unit begins operation.

2. The method for zero-discharge treatment of photovoltaic wastewater according to claim 1, characterized in that, The dilute acid wastewater filtration unit includes a first inlet pipe, a first backwashable filter, a second inlet pipe, and a first reverse osmosis unit connected in sequence, and a booster pump is provided on the second inlet pipe.

3. The method for zero-discharge treatment of photovoltaic wastewater according to claim 2, characterized in that, The acid path concentrate conditioning unit includes a conditioning tank and a calcium carbonate dosing tank. The concentrate side of the first reverse osmosis unit is connected to the conditioning tank through a first outlet pipe. The calcium carbonate dosing tank is connected to the conditioning tank and is used to add calcium carbonate into the conditioning tank.

4. The method for zero-discharge treatment of photovoltaic wastewater according to claim 3, characterized in that, The dehydrator has a first inlet, a first outlet, and a recovery port. The regulating tank is connected to the first inlet through a second outlet pipe. The first outlet is connected to the calcium fluoride crystallization unit through a third outlet pipe. The recovery port is connected to the calcium carbonate dosing tank through a return pipe. The calcium fluoride crystallization unit is connected to the calcium bicarbonate crystallization unit through a fourth water outlet pipe, and a first check valve is installed at the inlet of the fourth water outlet pipe. The calcium bicarbonate crystallization unit is connected to the neutralized concentrate filtration device through a fifth water outlet pipe, and a second check valve is installed at the inlet of the fifth water outlet pipe.

5. The method for zero-discharge treatment of photovoltaic wastewater according to claim 4, characterized in that, The neutralized concentrate filtration device includes an electrocoagulation sedimentation tank, an ultrafiltration unit, a second reverse osmosis unit, and an evaporator crystallizer connected in sequence. A booster pump is provided between the ultrafiltration unit and the second reverse osmosis unit, and the evaporator crystallizer is connected to the concentrate side of the second reverse osmosis unit.

6. The method for zero-discharge treatment of photovoltaic wastewater according to claim 5, characterized in that, The regulating pipeline includes a first branch pipe, a second branch pipe, a diversion pipe, a first valve, a second valve, a third valve, and a fourth valve. The inlet of the first branch pipe is connected to the third outlet pipe, the outlet of the first branch pipe is connected to the first end of the diversion pipe and the inlet of the second branch pipe, the second end of the diversion pipe is connected to the fourth outlet pipe, and the outlet of the second branch pipe is connected to the fifth outlet pipe. The first valve is located on the first branch pipe, the second valve is located on the second branch pipe, the third valve is located on the third outlet pipe and downstream of the inlet of the first branch pipe, and the fourth valve is located on the fourth outlet pipe and downstream of the second end of the diversion pipe.

7. The method for zero-discharge treatment of photovoltaic wastewater according to claim 6, characterized in that, The third outlet pipe is equipped with a first fluoride detector and a first calcium ion detector, which are located upstream of the inlet of the first branch pipe. The fourth water outlet pipe is equipped with a second calcium ion detector, which is located upstream of the first check valve.

8. The method for zero-discharge treatment of photovoltaic wastewater according to any one of claims 5-7, characterized in that, It also includes a reclaimed water tank, wherein the product water side of the first reverse osmosis unit is connected to the reclaimed water tank through a first product water pipe, and the product water side of the second reverse osmosis unit is connected to the reclaimed water tank through a third product water pipe; The dilute alkali wastewater filtration unit includes a dilute alkali wastewater conditioning unit, a second backwashable filter, and a nanofiltration unit connected in sequence. A booster pump is provided between the second backwashable filter and the nanofiltration unit. The product water side of the nanofiltration unit is connected to the regenerated water tank through a second product water pipe, and the concentrated water side of the nanofiltration unit is connected to the silica crystallization unit.

9. The method for zero-discharge treatment of photovoltaic wastewater according to claim 3, characterized in that, The top of the regulating tank is connected to the silica crystallization unit via a gas supply pipe.

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