Multistage deep fluorine removal device for fluorine-containing wastewater

Abstract

The utility model provides a multistage deep defluorination device for fluorine-containing wastewater. The multistage deep defluorination device comprises a crystallization tank, a coagulation tank, a coagulation aid tank, a flocculation tank, a precipitation water distribution tank and an efficient precipitation tank which are connected in sequence, a calcium chloride solution adding pipe is arranged in the crystallization tank; a first stirrer, a coagulant feeding pipe and an alkali liquor feeding pipe are arranged in the coagulation tank; a second stirrer and a particle medium adding mechanism are arranged in the coagulation aid tank; a flow guide cylinder is arranged in the flocculation tank, and a flocculant feeding pipe is arranged at the upper part of the flocculation tank; an inclined pipe and a water outlet collecting tank are arranged in the sedimentation water distribution tank; and a mud bucket and a mud scraper are arranged at the bottom of the efficient sedimentation tank. According to the technical scheme, the crystallization-adsorption-coordination-co-precipitation principle is utilized, fluorine is removed step by step, fluoride is efficiently and stably removed, meanwhile, the sludge yield is reduced, and calcium fluoride crystals can be recycled.

Description

TECHNICAL FIELD

[0001] The utility model relates to water treatment technical field especially relates to a multistage depth defluorination device of fluorine-containing wastewater. BACKGROUND

[0002] With the rapid development of industrialization, fluorine-containing wastewater pollution problem is increasingly serious. Fluoride widely exists in semiconductor manufacturing, photovoltaic industry, electroplating, metallurgy and other industrial processes, and the wastewater discharged by these industries often contains high concentration of fluoride ions (F-). Fluorine is one of the essential trace elements for human body, but excessive intake will cause diseases such as dental fluorosis and skeletal fluorosis, and the World Health Organization (WHO) stipulates that the limit value of fluoride ions in drinking water is 1.5 mg / L. Long-term drinking of high-fluorine water (>1.5 mg / L) can cause chronic diseases such as bone deformation and nervous system damage. If not effectively treated and directly discharged, it will not only threaten human health, but also damage soil structure and aquatic ecosystems, and even cause long-term environmental risks through food chain enrichment.

[0003] However, the concentration of fluoride in industrial wastewater is often as high as several tens to several hundred milligrams per liter, and fluorine-containing wastewater producing enterprises generally treat it to meet the industry standard (《Electronic Industry Water Pollutant Discharge Standard》(GB 39731-2020) requires fluoride ≤20 mg / L for indirect discharge, and fluoride ≤20 mg / L for direct discharge;《Integrated Wastewater Discharge Standard》(GB 8978-1996) requires fluoride concentration limit of 10 mg / L), but often fails to meet the water environmental quality of the receiving water body. According to《Surface Water Environmental Quality Standard》(GB3838-2002), the surface water III standard requires fluoride ≤1.0 mg / L (IV standard requires fluoride ≤1.5 mg / L). Therefore, the tail water discharged by enterprises needs further deep treatment.

[0004] Current deep defluorination technologies include membrane separation, adsorption method, etc. For fluorine-containing wastewater with low fluoride concentration (such as semiconductor enterprise tail water with fluoride ≤20 mg / L), traditional crystallization and coagulation process has poor treatment efficiency and is difficult to meet the strict requirements of surface water environmental quality standard for fluoride; although membrane separation and resin adsorption technology can achieve deep defluorination to meet water quality targets, there are problems such as membrane pollution, high energy consumption, low adsorption capacity, difficult regeneration, and high operating cost, which have limitations for large-scale application. UTILITY MODEL CONTENTS

[0005] In view of the above technical problems, the utility model discloses a multistage depth defluorination device for fluorine-containing wastewater, which utilizes the principles of crystallization-adsorption-complexation-co-precipitation to remove fluoride in stages, finally realizes deep defluorination of wastewater, and the effluent fluoride is ≤1.0 mg / L, while reducing sludge production, the operation is simple, and the investment and operation cost is low.

[0006] The utility model discloses the technical scheme that adopts for this,

[0007] A multistage deep fluorine removal device for fluorine-containing wastewater, comprising, in sequence, a crystallization tank, a coagulation tank, a coagulant aid tank, a flocculation tank, a sedimentation and water distribution tank, and a high-efficiency sedimentation tank; the lower part of the crystallization tank is provided with a wastewater inlet, and the upper part is provided with a supernatant outlet; a calcium chloride solution dosing pipe is arranged in the crystallization tank, and the calcium chloride solution dosing pipe is uniformly provided with dosing holes; the coagulation tank is provided with a first stirrer, a coagulant dosing pipe, and an alkali dosing pipe; the coagulant aid tank is provided with a second stirrer and a micro-particle medium feeding mechanism; the flocculation tank is provided with a flow guide cylinder, and the upper part of the flow guide cylinder is provided with a flocculant dosing pipe; the sedimentation and water distribution tank is provided with a plurality of inclined pipes filled with fillers and a water outlet collecting tank, and the outlets of the inclined pipes are communicated with the water outlet collecting tank; and the bottom of the high-efficiency sedimentation tank is provided with a sludge hopper and a sludge scraper, and the outlet of the sludge hopper is connected with a sludge discharge pipe.

[0008] As a further improvement of the utility model, the crystallization tank is filled with calcium carbonate or hydroxyapatite crystal seeds. Further, the particle size of the calcium carbonate or hydroxyapatite crystal seeds is 0.1-0.2 mm. Further, the filling volume of the calcium carbonate or hydroxyapatite crystal seeds accounts for 40-50% of the volume of the crystallization tank.

[0009] As a further improvement of the utility model, the calcium chloride solution dosing pipe comprises a double-layer annular structure. Further, the double-layer spacing of the calcium chloride solution dosing pipe is 0.8-1 m.

[0010] As a further improvement of the utility model, the dosing holes are uniformly distributed on the inner and outer sides of the double-layer annular structure, and the orifices of the dosing holes are obliquely downward arranged. Further, the orifices of the dosing holes are obliquely downward arranged at an angle of 45 degrees. Further, the diameter of the dosing holes is 5-10 mm. Further, the diameter of the dosing holes is 8 mm.

[0011] As a further improvement of the utility model, the wastewater inlet of the crystallization tank is provided with a water distribution plate.

[0012] As a further improvement of the utility model, the crystallization tank has a regular octahedral structure.

[0013] As a further improvement of the utility model, the pipe diameter of the double-layer annular structure is 32 mm.

[0014] As a further improvement of the utility model, the supernatant outlet is provided with a triangular weir, the outlet of the triangular weir is directed toward a ring-shaped collecting tank, and the water outlet hole of the ring-shaped collecting tank is communicated with the inlet of the coagulation tank.

[0015] As a further improvement of the utility model, the alkali dosing pipe is arranged above the coagulant dosing pipe.

[0016] As a further improvement of this utility model, the outlet holes of the coagulant dosing pipe and the alkali dosing pipe are arranged downwards and evenly distributed. Further, the diameter of the outlet holes of the coagulant dosing pipe and the alkali dosing pipe is 10-20 mm, more preferably 15 mm.

[0017] As a further improvement of this utility model, the upper part of the coagulation aid tank is provided with a water inlet and the bottom part with a water outlet; the particulate medium dosing mechanism is located in the middle of the coagulation aid tank.

[0018] As a further improvement of this utility model, the outlet of the coagulation aid tank is connected to the bottom inlet of the flocculation tank through a bottom connecting pipe. The bottom inlet of the flocculation tank is a funnel-shaped opening facing into the guide tube.

[0019] As a further improvement of this utility model, the flocculant dosing pipe is annular, and the outlet holes of the flocculant dosing pipe are uniformly arranged downwards.

[0020] As a further improvement of this utility model, the guide tube is connected and supported to the inner wall of the flocculation tank by a support rod.

[0021] As a further improvement of this utility model, the outlet of the inclined tube is provided with a water outlet weir, which faces the water outlet collection trough.

[0022] As a further improvement of this utility model, the bottom of the high-efficiency sedimentation tank is inclined towards the sludge hopper, and the outlet of the sludge hopper is connected to the sludge discharge pipe through a sludge pump.

[0023] As a further improvement of this utility model, the crystallization tank, coagulation tank, coagulation aid tank, flocculation tank, sedimentation and water distribution tank and high-efficiency sedimentation tank are constructed as an integrated steel structure.

[0024] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0025] The technical solution of this utility model integrates crystallization, adsorption, complexation, and co-precipitation, and utilizes the principle of crystallization-adsorption-coordination-co-precipitation to remove fluoride in a step-by-step manner, achieving efficient and stable removal of fluoride. The fluoride content in the effluent is consistently below 1 mg / L, while reducing sludge production. Calcium fluoride crystals can be recycled, making it environmentally friendly, highly efficient in removing fluoride, and easy to operate. It also requires minimal land use and has low treatment costs, making it highly valuable for widespread application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the partitioned structure of the multi-stage deep defluorination device according to an embodiment of this utility model.

[0027] Figure 2This is a lower plan view of the multi-stage deep defluorination device according to an embodiment of the present invention.

[0028] Figure 3 This is a top plan view of an embodiment of the present utility model.

[0029] Figure 4 yes Figure 3 Sectional view along the AA direction.

[0030] Figure 5 for Figure 3 Cross-sectional view along the BB direction.

[0031] Figure 6 for Figure 3 Cross-sectional view along the CC direction.

[0032] Figure 7 for Figure 3 Cross-sectional view along the DD direction.

[0033] Figure 8 for Figure 3 Cross-sectional view of the EE direction.

[0034] Figure 9 for Figure 3 Cross-sectional view along the FF direction.

[0035] Figure 10 This is a schematic diagram of the calcium chloride solution dosing pipeline and the annular dosing pipe in the embodiment of this utility model; wherein, a) is a schematic diagram of the connection between the main dosing pipe, the branch dosing pipe and the annular dosing pipe, and b) is a schematic diagram of the structure of the annular dosing pipe.

[0036] Figure 11 This is a schematic diagram of the structure of the flocculant dosing pipeline and the flocculant annular dosing pipe in the embodiment of this utility model; wherein, a) is a schematic diagram of the connection between the main flocculant dosing pipe, the branch flocculant dosing pipe and the annular dosing pipe, and b) is a schematic diagram of the structure of the annular dosing pipe.

[0037] The reference numerals in the figures include:

[0038] 1-Crystallization tank, 2-Coagulation tank, 3-Coagulation aid tank, 4-Flocculation tank, 5-Sedimentation and distribution tank, 6-High-efficiency sedimentation tank, 7-Effluent area, 8-Inlet main pipe, 9-Inlet branch pipe, 10-Drain pipe, 11-Sludge pipe, 12-Chemical dosing main pipe, 13-Chemical dosing branch pipe, 14-Chemical ring dosing pipe, 15-Chemical outlet, 16-Coagulant dosing pipe, 17-Coagulant outlet, 18-Alkali dosing pipe, 19-Alkali outlet, 20-Flocculant dosing main pipe, 21-Flocculant dosing branch pipe, 22-Flocculant ring dosing pipe, 23-Flocculant outlet, 24-Guide cylinder, 25 - Sludge scraper, 26- Sludge discharge pipe, 27- Sludge pump, 28- Water distribution plate, 29- Distributed water inlet, 30- Supernatant outlet, 31- Confluence outlet, 32- Rapid coagulation mixer, 33- Rapid coagulation aid mixer, 34- Slow flocculation mixer, 35- Bottom connecting hole, 36- Bottom connecting pipe, 37- Hydrocyclone, 38- Inclined tube packing, 39- Effluent triangular weir, 40- Effluent pipe, 41- Trumpet mouth, 42- Support rod, 43- Triangular weir, 44- Annular water collection tank, 45- Crystal nucleus packing, 46- Crystal discharge port, 47- Transparent observation window, 48- Effluent water collection tank. Detailed Implementation

[0039] The preferred embodiments of this utility model will be described in further detail below.

[0040] like Figures 1-11 As shown, a multi-stage deep defluorination device includes a frame and a crystallization tank 1, a coagulation tank 2, a coagulation aid tank 3, a flocculation tank 4, a sedimentation and distribution tank 5, and a high-efficiency sedimentation tank 6 connected sequentially on the frame. The crystallization tank 1, coagulation tank 2, coagulation aid tank 3, flocculation tank 4, sedimentation and distribution tank 5, and high-efficiency sedimentation tank 6 are constructed as an integrated steel structure.

[0041] The crystallization tank 1 has a wastewater inlet at the bottom and a supernatant outlet at the top. A ring-shaped dosing pipe 14 for adding calcium chloride solution is installed inside the crystallization tank 1, and the ring-shaped dosing pipe 14 is uniformly provided with dosing holes 15. The coagulation tank 2 is equipped with a first stirrer, a coagulant dosing pipe 16, and an alkali dosing pipe 18. The coagulation aid tank 3 is equipped with a second stirrer and a particulate medium dosing mechanism, i.e., a hydrocyclone 37. The flocculation tank 4 is equipped with a guide tube 24, and a flocculant ring-shaped dosing pipe 22 is installed above the guide tube 24. The sedimentation distribution tank 5 is equipped with several inclined tubes filled with packing material, i.e., inclined tube packing 38, and an effluent collection tank. The outlet of the inclined tubes is connected to the effluent collection tank. The bottom of the high-efficiency sedimentation tank 6 is equipped with a sludge hopper and a sludge scraper 25, and the outlet of the sludge hopper is connected to a sludge discharge pipe 26.

[0042] Fluorine-containing wastewater first enters crystallization tank 1. To avoid dead zones in the flow, crystallization tank 1 is constructed with a regular octagonal shape, with an equivalent diameter ranging from 1.2m to 2.5m and a height of 4.5m to 6m. The pressurized inlet water flows through the main inlet pipe 8 and the branch inlet pipe 9, and then through the distributed inlet holes 29 of the water distribution plate 28, and enters the fluidized crystallization tank 1 evenly, with an upward flow velocity of 8-10m / h.

[0043] Crystallization tank 1 is filled with crystal nucleus filler 45, namely calcium carbonate or hydroxyapatite seed crystals, with a seed crystal particle size of 0.1-0.2mm and a volume filling rate of 40-50%. The seed crystals are recycled and replenished periodically. During the upward flow of water, precipitation and crystallization occur with the added calcium chloride solution.

[0044] The calcium chloride solution is added using a double-layered ring-shaped dosing pipe 14, with a spacing of 0.8-1m between the two layers. The calcium chloride solution is connected to the double-layered ring-shaped dosing pipe 14 via the main dosing pipe 12 and the branch dosing pipe 13. The diameter of the ring-shaped dosing pipe 14 is 32mm. The dosing outlet holes 15 are evenly distributed on both the inner and outer sides of the octagonal ring-shaped dosing pipe 14. Each segment of the octagon has two holes on the outer edge and one hole on the inner edge, with the orifices angled downwards at 45 degrees and having a diameter of 8mm.

[0045] Fluoride ions in the fluoride-containing wastewater are uniformly mixed with calcium ions in the calcium chloride solution added through reagent outlet 15. Under the induction of calcium carbonate seed crystals, the supersaturation of calcium ions required for nucleation is effectively reduced. The dosage of calcium chloride solution is controlled according to a calcium ion to fluoride ion molar ratio of 1.2-1.5:1. Under the conditions of concentration gradient and turbulent flow, calcium and fluoride ions in the water are adsorbed on the crystal surface and embedded in the crystal lattice, continuously forming calcium fluoride crystals and growing continuously, eventually forming stable crystals. The crystallization tank 1 is divided into two groups operating in parallel. The crystals are periodically discharged through the crystal discharge port 46. Seed crystals are added directly from the top for replenishment. The replenishment of seed crystals and the fluidization and crystal formation of the water during operation are observed and confirmed through the transparent observation window 47. During maintenance, the water is drained through the drain pipe 10.

[0046] The effluent from crystallization tank 1 flows through triangular weir 43 to annular collection tank 44, and from the two supernatant outlets 30 it flows to the confluence outlet 31 before entering the next stage. The fluoride concentration in the effluent from crystallization tank 1 is controlled at 5-8 mg / L.

[0047] Water from crystallization tank 1 enters coagulation tank 2. Coagulant is mixed with the wastewater through coagulant outlet 17 of coagulant dosing pipe 16. Coagulant outlet 17 has eight vertically downward-facing holes, each 15mm in diameter. The coagulant and fluoride-containing wastewater are thoroughly mixed under the rapid stirring of coagulation mixer 32. The added coagulant is an aluminum-based coagulant, which hydrolyzes in water to generate various aluminum hydroxide complexes, adsorbing negatively charged fluoride ions and forming stable Al-F complexes with fluoride. Simultaneously, fluoride ions are removed through electrostatic adsorption and trapping. After the coagulant is added, the solution is generally acidic. To control the reaction conditions, sodium hydroxide solution is added through alkaline outlet 19 of alkaline dosing pipe 18 located above it. Alkaline dosing pipe 18 has 12 vertically downward-facing holes, evenly distributed, each 10mm in diameter. The optimal pH for the mixed solution is adjusted to between 6.5 and 6.8 by adding alkali. The molar ratio of aluminum ions to fluoride ions is controlled at 1:2.5-4, the residence time in the coagulation reaction zone is 4-5 minutes, and the effluent enters the coagulation aid tank 3 from bottom to top through the baffle.

[0048] The coagulation aid tank 3 has an inlet at the top and an outlet at the bottom; the particulate medium dosing mechanism is located in the middle of the coagulation aid tank 3. Wastewater enters the coagulation aid tank 3 from the top and, under the stirring of the rapid coagulation aid mixer 33, is thoroughly mixed with the particulate medium added by the hydrocyclone 37. The particulate medium consists of micro-sand with a particle size of 0.1-0.15 mm. By adding the particulate medium, the aggregation and sedimentation separation capacity of fluorides after coagulation is enhanced. The residence time of the wastewater in the coagulation aid tank 3 is 4-5 minutes, and the effluent enters the flocculation tank 44 through the bottom connecting hole 35.

[0049] The bottom inlet of the flocculation tank 4 is a funnel-shaped opening 41, facing into the guide tube 24. Water enters the flocculation tank 44 through the bottom connecting pipe 36, and the water flows upward and diffuses into the guide tube 24 through the funnel-shaped opening 41.

[0050] The flocculant enters the annular flocculant dosing pipe 22 through the main flocculant dosing pipe 20 and the branch flocculant dosing pipe 21. Eight vertically downward-facing, evenly distributed flocculant outlet holes 23, each with a diameter of 15mm, are used for dosing. Inside the guide tube 24, the flocculant and incoming water are thoroughly mixed under the slow stirring of the slow-speed flocculation mixer 34. The water then slowly flows out from the upper edge of the guide tube 24, which has a diameter of 0.9-1.2m and is supported by support rods 42 connected to the four walls of the flocculation tank 4. The water retention time in the flocculation tank 4 is 15-20 minutes, and the flocculant dosage is 1-2 mg / L. The flocculant forms a network structure in the water, capturing fluoride and other suspended particles through adsorption bridging and trapping. The effluent enters the sedimentation and distribution tank 5 through the bottom.

[0051] Wastewater flows upward from the bottom of sedimentation and distribution tank 5, settles in the inclined tube packing 38 of sedimentation and distribution tank 5, and after solid-liquid separation, it exits through the effluent triangular weir 39 and is collected and converged into the effluent collection tank 48 before flowing into the effluent zone 7. The sedimentation zone of the high-efficiency sedimentation tank 66 is square, and the bottom sludge zone is a circular sludge hopper with an inclined bottom. The sludge is scraped into the sludge hopper by a sludge scraper 25, and then pumped by a sludge pump 27 and discharged into the sludge pipe 11 through the sludge discharge pipe 26. The particulate media in the sludge is separated by a hydrocyclone 37 and added to the coagulation aid tank 3 for recycling. The remaining fluoride-containing sludge is discharged for disposal. The effluent after the final deep defluorination of the system is discharged from the effluent pipe 40.

[0052] This patented multi-stage high-efficiency deep defluoridation system utilizes the principles of crystallization-adsorption-coordination-co-precipitation to remove fluoride in a step-by-step, tiered manner, ultimately achieving deep defluoridation of wastewater with effluent fluoride levels ≤1.0 mg / L. Simultaneously, it reduces sludge production and yields CaF2 crystals. This patent is applicable to deep purification projects of fluoride-laden wastewater requiring ultra-low fluoride emissions.

[0053] The above-mentioned device was used to treat the effluent discharged by a semiconductor integrated circuit company. The fluoride ion concentration was 14.22-27.76 mg / L. The system dosage of calcium chloride was 1.2:1 (calcium to fluoride molar ratio), the dosage of coagulant was 1:2.8 (aluminum to fluoride molar ratio), and the dosage of flocculant was 2 mg / L. After multi-stage purification, the final effluent fluoride ion concentration was stable at 0.45-0.93 mg / L, which is lower than the Class III standard for fluoride concentration of 1.0 mg / L for surface water.

[0054] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A multi-stage deep defluoridation device for fluoride-containing wastewater, characterized in that: The system comprises a crystallization tank, a coagulation tank, a coagulation aid tank, a flocculation tank, a sedimentation distribution tank, and a high-efficiency sedimentation tank, connected in sequence. The crystallization tank has a wastewater inlet at its lower part and a supernatant outlet at its upper part. A calcium chloride solution dosing pipe is installed inside the crystallization tank, and the dosing pipe has evenly distributed outlet holes. The coagulation tank contains a first agitator, a coagulant dosing pipe, and an alkali dosing pipe. The coagulation aid tank contains a second agitator and a particulate media dosing mechanism. The flocculation tank contains a guide tube, and a flocculant dosing pipe is located above the guide tube. The sedimentation distribution tank contains several inclined tubes filled with packing material and an effluent collection tank, with the outlet of the inclined tubes connected to the effluent collection tank. The high-efficiency sedimentation tank has a sludge hopper and a sludge scraper at its bottom, and the outlet of the sludge hopper is connected to a sludge discharge pipe.

2. The multi-stage deep defluorination device for fluoride-containing wastewater according to claim 1, characterized in that: The crystallization tank is filled with calcium carbonate or hydroxyapatite seed crystals, the particle size of which is 0.1-0.2 mm, and the filling volume accounts for 40-50% of the crystallization tank volume.

3. The multi-stage deep defluorination device for fluoride-containing wastewater according to claim 1, characterized in that: The calcium chloride solution dosing tube includes a dosing tube with an upper and lower double-ring structure; the dosing holes are evenly distributed on the inner and outer sides of the upper and lower double-ring structure dosing tube, and the openings of the dosing holes are set obliquely downward; the wastewater inlet of the crystallization tank is equipped with a water distribution plate; the crystallization tank has a regular octagonal structure.

4. The multi-stage deep defluoridation device for fluoride-containing wastewater according to claim 1, characterized in that: The supernatant outlet is equipped with a triangular weir, the outlet of which faces the annular water collection tank, and the outlet of the annular water collection tank is connected to the inlet of the coagulation tank; the alkali dosing pipe is located above the coagulant dosing pipe, and the outlets of the coagulant dosing pipe and the alkali dosing pipe are set downwards and evenly distributed.

5. The multi-stage deep defluorination device for fluoride-containing wastewater according to claim 1, characterized in that: The coagulation aid tank has an inlet at the top and an outlet at the bottom; the particulate medium dosing mechanism is located in the middle of the coagulation aid tank.

6. The multi-stage deep defluorination device for fluoride-containing wastewater according to claim 1, characterized in that: The outlet of the coagulation aid tank is connected to the bottom inlet of the flocculation tank via a bottom connecting pipe. The bottom inlet of the flocculation tank is a funnel-shaped opening facing inwards towards the guide tube. The flocculant dosing pipe is annular, and the outlet holes of the flocculant dosing pipe are evenly downwards. The guide tube is connected and supported to the inner wall of the flocculation tank via a support rod.

7. The multi-stage deep defluoridation device for fluoride-containing wastewater according to claim 1, characterized in that: The outlet of the inclined tube is provided with an outlet weir, which faces the outlet collection trough; the bottom of the high-efficiency sedimentation tank is an inclined surface that slopes towards the sludge hopper, and the outlet of the sludge hopper is connected to the sludge discharge pipe through a sludge pump.

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