A resource recycling system for mixed acid wastewater of a photovoltaic bc type cell

Abstract

The utility model belongs to photovoltaic wastewater treatment technical field especially relates to a kind of photovoltaic BC type battery mixed acid wastewater resource recovery system.The utility model includes the mixed acid dilution pond, primary mixed acid processing system and secondary mixed acid processing system connected in proper order, and the supernatant pipeline connection of secondary mixed acid processing system and primary mixed acid processing system;Primary mixed acid processing system includes first multistage reaction pool and the first adjusting device connected with first multistage reaction pool, and secondary mixed acid processing system includes second multistage reaction pool and the second adjusting device connected with second multistage reaction pool, and primary mixed acid processing system is connected with calcium fluoride sludge filter pressing system, and secondary mixed acid processing system is connected with calcium sulfate sludge filter pressing system.The utility model is recycled high-purity calcium sulfate by adopting hierarchical processing mode, to achieve the purpose of resource recovery.

Description

Technical Field

[0001] This utility model belongs to the field of photovoltaic wastewater treatment technology, and in particular relates to a resource recovery system for mixed acid wastewater from photovoltaic BC type batteries. Background Technology

[0002] In recent years, the photovoltaic, electronics and semiconductor industries have needed to use large amounts of alkaline solutions, hydrofluoric acid and their mixtures with sulfates, nitric acid and hydrochloric acid to etch and clean elemental silicon materials, as well as to wash acid mist and exhaust gases in the workshop, resulting in the discharge of large amounts of wastewater with high fluoride content.

[0003] The mixed acid wastewater generated during the production of photovoltaic BC-type cells mainly consists of hydrofluoric acid, sulfuric acid, and nitric acid. While photovoltaic BC-type cells, with their high energy conversion efficiency, are gradually replacing other processes, the high concentration of mixed acid cannot be recovered, resulting in significant resource waste and environmental burden. Previous treatment methods primarily involved the direct addition of lime, forming mixed sludge that could not be recycled and could only be disposed of as solid waste. Therefore, a resource-based recycling system for mixed acid wastewater from photovoltaic BC-type cells is urgently needed to solve these problems. Utility Model Content

[0004] To overcome the shortcomings of the existing technology, this invention provides a resource recovery system for mixed acid wastewater from photovoltaic BC-type cells. This invention achieves resource recovery by employing a staged treatment method to recover high-purity calcium sulfate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A resource recovery system for mixed acid wastewater from photovoltaic BC-type cells is disclosed. The system includes a mixed acid dilution tank, a primary mixed acid treatment system, and a secondary mixed acid treatment system connected in sequence. The secondary mixed acid treatment system is connected to the supernatant pipeline of the primary mixed acid treatment system. The primary mixed acid treatment system includes a first multi-stage reaction tank and a first regulating device connected to the first multi-stage reaction tank. The secondary mixed acid treatment system includes a second multi-stage reaction tank and a second regulating device connected to the second multi-stage reaction tank. The primary mixed acid treatment system is connected to a calcium fluoride sludge depressurization system, and the secondary mixed acid treatment system is connected to a calcium sulfate sludge depressurization system.

[0007] Preferably, the first multi-stage reaction tank includes a first-stage reaction tank 1, a second-stage reaction tank 2, a third-stage reaction tank 3, and a first-stage sedimentation tank connected in sequence. The inlet of the first-stage reaction tank 1 is connected to the outlet of the mixed acid dilution tank, and the sludge discharge outlet of the first-stage sedimentation tank is connected to the calcium fluoride sludge dewatering system.

[0008] Preferably, the second multi-stage reaction tank includes a second-stage reaction tank I, a second-stage reaction tank II, a third-stage reaction tank III, and a second-stage sedimentation tank connected in sequence. The inlet of the second-stage reaction tank I is connected to the outlet of the first-stage sedimentation tank through a supernatant pipe, and the sludge discharge outlet of the second-stage sedimentation tank is connected to a calcium sulfate sludge dewatering system.

[0009] Preferably, the calcium fluoride sludge filter press system includes a first sludge storage tank and a first filter press. The sludge inlet of the first sludge storage tank is connected to the sludge outlet of the first-stage sedimentation tank, and the sludge outlet of the first sludge storage tank is connected to the first filter press. The outlet of the first filter press is connected to the inlet of the first-stage reaction tank through a first filter liquid return pipe, which facilitates the timely removal of sludge from the first-stage sedimentation tank, frees up space in the first-stage sedimentation tank, increases the retention time of sewage, and improves the sedimentation effect.

[0010] Preferably, the calcium sulfate sludge filter press system includes a second sludge storage tank and a second filter press. The sludge inlet of the second sludge storage tank is connected to the sludge outlet of the secondary sedimentation tank, and the sludge outlet of the second sludge storage tank is connected to the second filter press. The outlet of the second filter press is connected to the inlet of the first secondary reaction tank through a second filter liquid return pipe, which facilitates the timely removal of sludge from the secondary sedimentation tank, frees up space in the secondary sedimentation tank, increases the retention time of wastewater, and improves the sedimentation effect.

[0011] Preferably, the first regulating device includes a first lime slurry dosing tank and a first flocculant dosing tank, the first lime slurry dosing tank being connected to a first-stage reaction tank 1 and a second-stage reaction tank 2, and the first flocculant dosing tank being connected to a third-stage reaction tank; the second regulating device includes a second lime slurry dosing tank and a second flocculant dosing tank, the second lime slurry dosing tank being connected to a second-stage reaction tank 1 and a second-stage reaction tank 2, and the second flocculant dosing tank being connected to a third-stage reaction tank.

[0012] Preferably, the sludge discharge port of the primary sedimentation tank is connected to the primary reaction tank 1 through a first sludge return pipe; the sludge discharge port of the secondary sedimentation tank is connected to the secondary reaction tank 1 through a second sludge return pipe. The sludge returned to the reaction tank provides a nucleus for crystal attachment, which helps crystal growth, and also washes and reacts the residual trace amounts of unreacted lime. Furthermore, the sludge returned to the primary reaction tank 1 will precipitate the calcium sulfate that has already been produced in the primary reaction tank 1 and react with the fluoride in the raw water to replace and generate calcium fluoride, thereby improving the purity of the sludge.

[0013] Preferably, the inner walls of the first primary reaction tank, the second primary reaction tank, the third primary reaction tank, the first primary sedimentation tank, the first secondary reaction tank, the second secondary reaction tank, the third secondary reaction tank, and the second secondary sedimentation tank are all coated with an anti-corrosion layer to prevent the treated highly acidic wastewater from corroding the system.

[0014] Preferably, both the primary and secondary sedimentation tanks are equipped with sludge scrapers, and both the first and second sludge storage tanks are equipped with stirring devices. The stirring method is mechanical stirring or aeration stirring, which can stir the sludge and partially adjust the pH value.

[0015] Preferably, the first sludge storage tank is connected to a third regulating device containing lime slurry or sodium hydroxide, which is used to adjust the pH value in the first sludge storage tank to 6-7 to ensure the safety of sludge treatment. The slightly acidic pH can reduce costs and reduce the generation or residue of calcium hydroxide, thereby improving sludge purity.

[0016] The advantages of this utility model are:

[0017] (1) This utility model utilizes the large difference in solubility product constants between calcium fluoride and calcium sulfate, controls the dosage of calcium salt, and uses a graded processing system to first precipitate fluoride ions to recover higher purity calcium fluoride, and then precipitate sulfate ions to recover higher purity calcium sulfate, thereby achieving the purpose of resource recovery.

[0018] (2) This utility model adopts a segmented sedimentation method to precipitate and recycle sludge. The returned sludge can provide a core for crystal attachment and help crystal growth. On the other hand, it can clean and react the residual trace amount of unreacted lime. At the same time, the calcium sulfate that has been generated is precipitated in the first-stage reaction tank and reacts with the fluoride in the raw water to replace and generate calcium fluoride, which improves the purity of sludge. The mechanism is simple and highly operable, making it easy to implement.

[0019] (3) This invention recycles the calcium ions remaining in the filtrate, the fluoride ions remaining under saturation, and the fine calcium fluoride particles in the permeate into the system, thereby reducing the cost of medication and increasing the recovery rate. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the system of this utility model. Figure 1 .

[0021] Figure 2 This is a schematic diagram of the system of this utility model. Figure 2 .

[0022] The meanings of the symbols in the diagram are as follows:

[0023] 1-Mixed acid dilution tank, 2-Primary mixed acid treatment system, 3-Secondary mixed acid treatment system, 4-Calcium fluoride sludge filter press system, 5-Calcium sulfate sludge filter press system, 6-Primary reaction tank one, 7-Primary reaction tank two, 8-Primary reaction tank three, 9-Primary sedimentation tank, 10-Secondary reaction tank one, 11-Secondary reaction tank two, 12-Secondary reaction tank three, 13-Secondary sedimentation tank, 14-First sludge storage tank, 15-First filter press, 16-First filtrate return pipe, 17-Third regulating device, 18-First sludge return pipe, 19-Secondary sludge return pipe, 20-Secondary sludge storage tank, 21-Secondary filter press, 22-Secondary filtrate return pipe. Detailed Implementation

[0024] like Figure 1-2 As shown, a photovoltaic BC-type battery mixed acid wastewater resource recovery system includes a mixed acid dilution tank 1, a primary mixed acid treatment system 2, and a secondary mixed acid treatment system 3 connected in sequence. The secondary mixed acid treatment system 3 is connected to the supernatant pipeline of the primary mixed acid treatment system 2. The primary mixed acid treatment system 2 includes a first multi-stage reaction tank and a first regulating device connected to the first multi-stage reaction tank. The secondary mixed acid treatment system 3 includes a second multi-stage reaction tank and a second regulating device connected to the second multi-stage reaction tank. The primary mixed acid treatment system 2 is connected to a calcium fluoride sludge filter press system 4, and the secondary mixed acid treatment system 3 is connected to a calcium sulfate sludge filter press system 5. In the mixed acid dilution tank 1, mixed acid and dilute acid are stirred and diluted at a volume ratio of 1:(5-20), and the fluoride ion concentration is detected.

[0025] Specifically, the first regulating device includes a first lime slurry dosing tank and a first flocculant dosing tank. The first lime slurry dosing tank is connected to primary reaction tank 6 and primary reaction tank 7, respectively, and the first flocculant dosing tank is connected to primary reaction tank 8. The second regulating device includes a second lime slurry dosing tank and a second flocculant dosing tank. The second lime slurry dosing tank is connected to secondary reaction tank 10 and secondary reaction tank 11, respectively, and the second flocculant dosing tank is connected to secondary reaction tank 12. The first sludge storage tank 14 is connected to a third regulating device 17 containing lime slurry or sodium hydroxide.

[0026] Furthermore, the first multi-stage reaction tank includes a first-stage reaction tank 6, a second-stage reaction tank 7, a third-stage reaction tank 8, and a first-stage sedimentation tank 9 connected in sequence. The inlet of the first-stage reaction tank 6 is connected to the outlet of the mixed acid dilution tank 1, and the sludge discharge outlet of the first-stage sedimentation tank 9 is connected to the calcium fluoride sludge filter press system 4. The calcium fluoride sludge filter press system 4 includes a first sludge storage tank 14 and a first filter press 15. The sludge inlet of the first sludge storage tank 14 is connected to the sludge discharge outlet of the first-stage sedimentation tank 9, and the sludge discharge outlet of the first sludge storage tank 14 is connected to the first filter press 15.

[0027] Furthermore, the second multi-stage reaction tank includes a second-stage reaction tank 10, a second-stage reaction tank 21, a second-stage reaction tank 312, and a second-stage sedimentation tank 13 connected in sequence. The inlet of the second-stage reaction tank 10 is connected to the outlet of the first-stage sedimentation tank 9 through a supernatant pipe, and the sludge outlet of the second-stage sedimentation tank 13 is connected to the calcium sulfate sludge dewatering system 5.

[0028] The mixed liquor from the mixed acid dilution tank 1 and the sludge from the primary sedimentation tank 9 are pumped into the primary reaction tank 6. According to the aforementioned fluoride ion concentration, 50%-90% of the molar equivalent of fluoride in lime slurry is added to the primary reaction tank 6 via the first lime slurry addition tank, with stirring time not less than 20 minutes. This process generates calcium fluoride sludge, which, along with the return sludge, provides nuclei for crystal formation and cleans the sludge, improving its purity and particle size for easier filtration. The mixed liquor from the primary reaction tank 6 flows by gravity into the secondary primary reaction tank 7. According to the aforementioned fluoride ion concentration, the remaining 50%-10% of lime slurry is added to the secondary lime slurry addition tank 7, with stirring time not less than 20 minutes. This process generates calcium fluoride sludge from all fluoride ions, simplifying the staged reaction control. Next, the solution from primary reaction tank 2 (7) flows by gravity into primary reaction tank 3 (8). PAM is added to primary reaction tank 3 (8) from the first flocculant dosing tank and stirred. The residence time is no less than 20 minutes, thereby flocculating the sludge and facilitating sedimentation. The solution from primary reaction tank 3 (8) then flows by gravity into primary sedimentation tank 9, where sludge-water separation occurs. The residence time in primary sedimentation tank 9 is no less than 4 hours, and the surface loading is no greater than 2 m³. 3 / (m 2 (h) and a sludge scraper is installed. Part of the sludge in the primary sedimentation tank 9 enters the first sludge storage tank 14, and the other part is returned to the primary reaction tank 6 through the second sludge return pipe 19. This facilitates thorough sedimentation, prevents sludge runoff, and improves the recovery efficiency of calcium fluoride. The returned sludge part, on the one hand, provides a nucleus for crystal attachment, aiding crystal growth; on the other hand, it washes and reacts residual trace amounts of unreacted lime. Simultaneously, the calcium sulfate already precipitated in the primary reaction tank 6 reacts with fluoride in the raw water, replacing it to generate calcium fluoride, thus improving sludge purity.

[0029] The calcium sulfate sludge filter press system 5 includes a second sludge storage tank 20 and a second filter press 21. The inlet of the second sludge storage tank 20 is connected to the outlet of the secondary sedimentation tank 13, and the outlet of the second sludge storage tank 20 is connected to the second filter press 21. The sludge cake pressed out by the plate and frame filter press is high-purity calcium fluoride, and the filtrate is returned to the primary reaction tank 6. Both the first filter press 15 and the second filter press 21 are plate and frame filter presses: residual calcium ions in the filtrate, residual fluoride ions under saturation conditions, and fine calcium fluoride particles that have passed through the filtrate are recycled back into the system through the first filtrate return pipe 16 / second filtrate return pipe 22, reducing chemical costs and improving recovery rate.

[0030] The supernatant from the primary sedimentation tank 9 flows by gravity into the secondary reaction tanks 1-10, 2-11, 3-12, and the secondary sedimentation tank. Lime slurry, lime milk, and PAM are added to secondary reaction tanks 1-10, 2-11, and 3-12 respectively. The pH values ​​of these tanks are controlled at 4-5, 6-7, and 6-7 respectively. Stirring devices are installed in secondary reaction tanks 1-10, 2-11, and 3-12. The reaction time is no less than 20 minutes for each tank. This staged control ensures a more complete reaction, saves reagents, and makes operation simpler and more convenient, with high operability.

[0031] The secondary reaction tank 3 (12) has the same structure and design as the primary sedimentation tank 9, and the supernatant is discharged after reaching the standard. The sludge discharge port of the primary sedimentation tank 9 is connected to the primary reaction tank 1 (6) through the first sludge return pipe 18. The inner walls of the primary reaction tank 1 (6), the primary reaction tank 2 (7), the primary reaction tank 3 (8), the primary sedimentation tank 9, the secondary reaction tank 1 (10), the secondary reaction tank 2 (11), the secondary reaction tank 3 (12), and the secondary sedimentation tank 13 are all coated with an anti-corrosion layer. No further chemicals are added to the second sludge storage tank 20.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A resource recovery system for mixed acid wastewater from photovoltaic BC type batteries, characterized in that: The system includes a mixed acid dilution tank (1), a primary mixed acid treatment system (2), and a secondary mixed acid treatment system (3) connected in sequence. The secondary mixed acid treatment system (3) is connected to the supernatant pipeline of the primary mixed acid treatment system (2). The primary mixed acid treatment system (2) includes a first multi-stage reaction tank and a first regulating device connected to the first multi-stage reaction tank. The secondary mixed acid treatment system (3) includes a second multi-stage reaction tank and a second regulating device connected to the second multi-stage reaction tank. The primary mixed acid treatment system (2) is connected to a calcium fluoride sludge filter press system (4). The secondary mixed acid treatment system (3) is connected to a calcium sulfate sludge filter press system (5).

2. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 1, characterized in that: The first multi-stage reaction tank includes a first-stage reaction tank (6), a second-stage reaction tank (7), a third-stage reaction tank (8), and a first-stage sedimentation tank (9) connected in sequence. The inlet of the first-stage reaction tank (6) is connected to the outlet of the mixed acid dilution tank (1), and the sludge outlet of the first-stage sedimentation tank (9) is connected to the calcium fluoride sludge dewatering system (4).

3. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 2, characterized in that: The second multi-stage reaction tank includes a second-stage reaction tank (10), a second-stage reaction tank (11), a third-stage reaction tank (12), and a second-stage sedimentation tank (13) connected in sequence. The inlet of the second-stage reaction tank (10) is connected to the outlet of the first-stage sedimentation tank (9) through a supernatant pipe, and the sludge outlet of the second-stage sedimentation tank (13) is connected to the calcium sulfate sludge dewatering system (5).

4. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 3, characterized in that: The calcium fluoride sludge filter press system (4) includes a first sludge storage tank (14) and a first filter press (15). The sludge inlet of the first sludge storage tank (14) is connected to the sludge outlet of the first sedimentation tank (9). The sludge outlet of the first sludge storage tank (14) is connected to the first filter press (15). The outlet of the first filter press (15) is connected to the inlet of the first reaction tank (6) through a first filter liquid return pipe (16).

5. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 4, characterized in that: The calcium sulfate sludge filter press system (5) includes a second sludge storage tank (20) and a second filter press (21). The sludge inlet of the second sludge storage tank (20) is connected to the sludge outlet of the secondary sedimentation tank (13). The sludge outlet of the second sludge storage tank (20) is connected to the second filter press (21). The outlet of the second filter press (21) is connected to the inlet of the secondary reaction tank (10) through the second filter liquid return pipe (22).

6. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 3, characterized in that: The first regulating device includes a first lime slurry addition tank and a first flocculant addition tank. The first lime slurry addition tank is connected to a first-stage reaction tank (6) and a second-stage reaction tank (7), respectively. The first flocculant addition tank is connected to a third-stage reaction tank (8). The second regulating device includes a second lime slurry addition tank and a second flocculant addition tank. The second lime slurry addition tank is connected to a second-stage reaction tank (10) and a second-stage reaction tank (11), respectively. The second flocculant addition tank is connected to a third-stage reaction tank (12).

7. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 3, characterized in that: The sludge discharge port of the primary sedimentation tank (9) is connected to the primary reaction tank (6) through the first sludge return pipe (18); the sludge discharge port of the secondary sedimentation tank (13) is connected to the secondary reaction tank (10) through the second sludge return pipe (19).

8. The photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 3, characterized in that: The inner walls of the first primary reaction tank (6), the second primary reaction tank (7), the third primary reaction tank (8), the first primary sedimentation tank (9), the first secondary reaction tank (10), the second secondary reaction tank (11), the third secondary reaction tank (12), and the second secondary sedimentation tank (13) are all coated with an anti-corrosion layer.

9. A photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 5, characterized in that: Sludge scrapers are installed in both the primary sedimentation tank (9) and the secondary sedimentation tank (13), and stirring devices are installed in both the first sludge storage tank (14) and the second sludge storage tank (20).

10. A photovoltaic BC-type battery mixed acid wastewater resource recovery system according to claim 4, characterized in that: The first sludge storage tank (14) is connected to a third regulating device (17) containing lime milk or sodium hydroxide.

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