Continuous resourceful treatment system for photovoltaic fluorine-containing wastewater

Abstract

The utility model belongs to the field of chemical raw material recovery, and discloses a continuous resourceful treatment system for photovoltaic fluorine-containing wastewater. The system comprises a first-stage fluorine removal unit, a second-stage fluorine removal unit and a silicon removal unit. According to the utility model, the fluorine element is subjected to resource recovery in the form of high-purity calcium fluoride with the purity of more than 95%, meanwhile, the consumption of a fresh sodium hydroxide solution is avoided, the purpose of treating waste with waste is realized, and the residual fluorine quantity in the effluent of the system is reduced to be less than 5mg / L.

Description

Technical Field

[0001] The utility model belongs to the field of chemical raw material recovery, and more specifically, relates to a continuous resource treatment system for photovoltaic fluorine-containing wastewater. Background Technique

[0002] The photovoltaic industry utilizes the photovoltaic effect to directly generate electricity when sunlight shines on silicon materials. The optoelectronic conversion industry formed by the application and development of silicon materials includes the production of high-purity polysilicon raw materials, solar cell production, solar cell module production, and the manufacturing of related production equipment. Its production process includes steps such as texturing, alkali washing, water washing, and acid washing. Among them, the alkali washing step uses a sodium hydroxide solution for cleaning, and a large amount of photovoltaic alkaline silicon-containing wastewater is generated after cleaning. The acid washing step uses hydrochloric acid and hydrofluoric acid for etching, and a large amount of acidic fluorine-containing wastewater is generated after cleaning. Fluorine is an accumulative poison. Fluorine in water will seriously pollute the soil and groundwater, and then damage the metabolic balance of plants, animals, and humans, resulting in huge toxic side effects. Existing wastewater defluorination methods include distillation method, adsorption method, ultraviolet method, lime method, calcium chloride method, etc. However, due to various conditions, it is difficult to industrialize.

[0003] Application No. 201610799160.6 proposes a method of first evaporating and then distilling to recover hydrofluoric acid. Since hydrofluoric acid forms a maximum azeotrope with water, almost all the water needs to be evaporated to recover hydrofluoric acid, resulting in huge energy consumption. Application No. 202311206292.X proposes a method of flocculation and adsorption, but the adsorption capacity of the adsorbent is small, the service life is short, the cost is high, and a large amount of solid waste is generated. Application No. 202410014006.8 proposes an ultraviolet on-line defluorination method, but the cost of the ultraviolet light source is high, and the defluorination efficiency of the ultraviolet method is low, and it is difficult to meet the discharge standards for the effluent. Application No. 201610197407.7 proposes a lime method for defluorination. Due to the low solubility of lime, the treatment process takes a long time, the operation difficulty is large, and the purity of the recovered calcium fluoride is low. Application No. 201610463012.7 proposes the co-removal of fluorine by sodium hydroxide and calcium chloride to recover calcium fluoride. The calcium chloride method has a fast reaction rate and a high purity of the recovered calcium fluoride; however, hydrochloric acid is generated after the reaction of calcium chloride and hydrofluoric acid, resulting in a stronger acidity in the wastewater, with pH < 1. At this pH value, the solubility of fluoride ions is high, making it difficult to completely precipitate, resulting in a low yield of calcium fluoride; at the same time, a large amount of sodium hydroxide needs to be consumed for neutralization, resulting in a deficit and making it difficult to industrialize.

[0004] In view of this, there is an urgent need to propose a continuous resource treatment system for photovoltaic fluorine-containing wastewater to solve the technical problem that it is difficult to industrialize existing defluorination technologies and processes. Summary of the Utility Model

[0005] The purpose of the present utility model is to propose a continuous resource treatment system for photovoltaic fluorine-containing wastewater in view of the deficiencies of the prior art. The present utility model recovers fluorine elements in the form of high-purity calcium fluoride with a purity > 95%, while avoiding the consumption of fresh sodium hydroxide solution, achieving the goal of treating waste with waste, and reducing the fluorine residue in the system effluent to < 5 mg / L.

[0006] To achieve the above purpose, the present utility model provides a continuous resource treatment system for photovoltaic fluorine-containing wastewater, and the system includes a primary defluorination unit, a secondary defluorination unit and a desiliconization unit;

[0007] Each defluorination unit includes a reaction flocculator, a sedimentation discharging device and a solid-liquid separator;

[0008] In the upper-middle part of the primary reaction flocculator, there are provided a photovoltaic acidic fluorine-containing wastewater inlet, a calcium chloride aqueous solution feed inlet, a primary lime milk feed inlet and a primary polyacrylamide aqueous solution feed inlet, and at the bottom, there is provided a primary reaction flocculation discharging outlet;

[0009] In the upper-middle part of the secondary reaction flocculator, there are provided a primary defluorination clear liquid mixture inlet, a desiliconization filtrate inlet and a secondary polyacrylamide aqueous solution feed inlet, and at the bottom, there is provided a secondary reaction flocculation discharging outlet;

[0010] Each sedimentation discharging device is provided with a bottom inlet, an upper clear liquid overflow outlet and a sedimentation outlet; each solid-liquid separator is provided with a solid-liquid feed inlet, a filter cake outlet and a filtrate outlet;

[0011] The primary reaction flocculation discharging outlet and the secondary reaction flocculation discharging outlet are respectively connected to the bottom inlet of the corresponding sedimentation discharging device; the sedimentation outlet of each sedimentation discharging device is connected to the solid-liquid feed inlet of the corresponding solid-liquid separator; the upper clear liquid overflow outlet of the primary sedimentation discharging device and the filtrate outlet of the primary solid-liquid separator converge and are connected to the primary defluorination clear liquid mixture inlet; the upper clear liquid overflow outlet of the secondary sedimentation discharging device and the filtrate outlet of the secondary solid-liquid separator converge and are connected to outside the plant;

[0012] The desiliconization unit includes a desiliconization reactor and a desiliconization solid-liquid separator; in the upper-middle part of the desiliconization reactor, there are provided a photovoltaic alkaline silicon-containing wastewater inlet and a desiliconization lime milk feed inlet, and at the bottom, there is provided a slurry outlet; the desiliconization solid-liquid separator is provided with a slurry inlet, a silicon-containing filter cake outlet and a desiliconization filtrate outlet; the slurry outlet of the desiliconization reactor is connected to the slurry inlet of the desiliconization solid-liquid separator; the desiliconization filtrate outlet of the desiliconization solid-liquid separator is connected to the desiliconization filtrate inlet of the secondary reaction flocculator;

[0013] Stirrers are independently arranged in the primary reaction flocculator, the secondary reaction flocculator and the desiliconization reactor respectively.

[0014] Preferably, the filter cake outlets of the solid-liquid separators at each level and the silicon-containing filter cake outlet of the silicon removal solid-liquid separator are each independently connected to outside the battery limits.

[0015] Preferably, the system further includes a high-level tank for lime milk;

[0016] A discharge control valve is provided at the discharge port of the high-level tank for lime milk, and the discharge port of the high-level tank for lime milk is divided into two paths, one path is connected to the first-stage lime milk inlet, and the other path is connected to the silicon removal lime milk inlet; the high-level tank for lime milk is used to achieve continuous feeding of lime milk; a stirrer is provided in the high-level tank for lime milk.

[0017] Preferably, the system further includes a photovoltaic acidic fluoride-containing wastewater feed pump, a photovoltaic alkaline silicon-containing wastewater feed pump, a calcium chloride aqueous solution feed pump, and a polyacrylamide aqueous solution feed pump;

[0018] The outlet of the photovoltaic acidic fluoride-containing wastewater feed pump is connected to the photovoltaic acidic fluoride-containing wastewater inlet; the photovoltaic acidic fluoride-containing wastewater feed pump is used to achieve continuous feeding of photovoltaic acidic fluoride-containing wastewater;

[0019] The outlet of the calcium chloride aqueous solution feed pump is connected to the calcium chloride aqueous solution inlet; the calcium chloride aqueous solution feed pump is used to achieve continuous feeding of calcium chloride aqueous solution;

[0020] The outlet of the polyacrylamide aqueous solution feed pump is divided into two paths, one path is connected to the first-stage polyacrylamide aqueous solution inlet, and the other path is connected to the second-stage polyacrylamide aqueous solution inlet; the polyacrylamide aqueous solution feed pump is used to achieve continuous feeding of polyacrylamide aqueous solution;

[0021] The outlet of the photovoltaic alkaline silicon-containing wastewater feed pump is connected to the photovoltaic alkaline silicon-containing wastewater inlet; the photovoltaic alkaline silicon-containing wastewater feed pump is used to achieve continuous feeding of photovoltaic alkaline silicon-containing wastewater.

[0022] Preferably, the sedimentation discharge devices at each level include a sedimentation discharger, a elutriation leg, and a screw discharger connected in sequence from top to bottom;

[0023] The sedimentation discharger is provided with the bottom inlet and an upper clear liquid overflow port;

[0024] The screw discharger is provided with the sedimentation outlet.

[0025] Preferably, the top of the reactor body of the reaction flocculators at each level is arranged on the same horizontal plane as the top of the reactor body of the corresponding-level sedimentation discharger.

[0026] Preferably, the height-to-diameter ratios of the first-stage reaction flocculator and the second-stage reaction flocculator are each independently 0.5-3:1.

[0027] Preferably, the diameter ratio of the primary sedimentation discharger to the primary reaction flocculator is 1:1 - 5.

[0028] Preferably, the diameter ratio of the secondary sedimentation discharger to the secondary reaction flocculator is 1:1 - 5.

[0029] Preferably, the diameter of the elutriation leg is 1 / 2 to 1 / 5 of the diameter of the sedimentation discharger.

[0030] The beneficial effects of the technical solution of the present utility model are as follows:

[0031] The present utility model adopts continuous operation, the system runs stably, realizes the continuous treatment of fluorine-containing wastewater in the photovoltaic industry, can recycle fluorine ions in the form of high-purity calcium fluoride with a purity ≥ 95% while reducing the fluorine ion concentration in the system effluent to < 5 mg / L.

[0032] The present utility model uses the photovoltaic alkaline silicon-containing wastewater in the factory to adjust the pH value of the acidic fluorine-containing wastewater, treating waste with waste, avoiding the consumption of fresh sodium hydroxide solution, and reducing the treatment cost of acidic fluorine-containing wastewater.

[0033] The present utility model designs a clear liquid overflow port and an elutriation leg in both two-stage sedimentation discharge devices, which can realize the extraction of clear liquid and recovered calcium fluoride from different positions. The clear liquid overflows from the upper-middle part of the sedimentation discharge device, and the flocculated calcium fluoride is thickened in the elutriation leg and then extracted, greatly reducing the working load and difficulty of the solid-liquid separator.

[0034] Other features and advantages of the present utility model will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0035] By describing the exemplary embodiments of the present utility model in more detail in conjunction with the drawings, the above and other objects, features, and advantages of the present utility model will become more obvious. Among them, in the exemplary embodiments of the present utility model, the same reference numerals generally represent the same components.

[0036] Figure 1 Shows a schematic diagram of a continuous resource treatment system for photovoltaic fluorine-containing wastewater provided in Embodiment 1 of the present utility model.

[0037] Figure 2 Shows a schematic diagram of a primary defluorination unit in a continuous resource treatment system for photovoltaic fluorine-containing wastewater provided in Embodiment 2 of the present utility model.

[0038] The description of the reference numerals in the drawings is as follows:

[0039] 101 - Photovoltaic acidic fluorine-containing wastewater feed pump; 102 - Calcium chloride aqueous solution feed pump; 103 - Polyacrylamide aqueous solution feed pump; 104 - Lime milk elevated tank; 105 - Primary reaction flocculator; 106 - Primary sedimentation discharge device; 107 - Primary elutriation leg; 108 - Primary screw discharge device; 109 - Primary solid-liquid separator; 110 - Primary filter cake outlet; 111 - Primary filtrate outlet; 112 - Primary upper clear liquid overflow port;

[0040] 201 - Photovoltaic alkaline silicon-containing wastewater feed pump; 202 - Silicon removal reactor; 203 - Silicon removal solid-liquid separator; 204 - Silicon-containing filter cake outlet; 205 - Silicon removal filtrate outlet;

[0041] 301 - Secondary reaction flocculator; 302 - Secondary sedimentation discharge device; 303 - Secondary elutriation leg; 304 - Secondary screw discharge device; 305 - Secondary solid-liquid separator; 306 - Secondary filter cake outlet; 307 - Upper clear liquid overflow port; 308 - Secondary filtrate outlet; 309 - Fluoride-removed discharged mixed wastewater;

[0042] 401 - Photovoltaic acidic fluorine-containing wastewater feeding device; 402 - Photovoltaic alkaline silicon-containing wastewater feeding device; 403 - Calcium chloride aqueous solution feed pump device; 404 - Polyacrylamide aqueous solution feeding device. Detailed implementation mode

[0043] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0044] The present invention provides a continuous resource treatment system for photovoltaic fluorine-containing wastewater, and the system includes a primary defluorination unit, a secondary defluorination unit and a silicon removal unit;

[0045] Each defluorination unit includes a reaction flocculator, a sedimentation discharge device and a solid-liquid separator;

[0046] The upper middle part of the primary reaction flocculator is provided with a photovoltaic acidic fluorine-containing wastewater inlet, a calcium chloride aqueous solution feed inlet, a primary lime milk feed inlet and a primary polyacrylamide aqueous solution feed inlet, and the bottom is provided with a primary reaction flocculation discharge outlet;

[0047] The upper middle part of the secondary reaction flocculator is provided with a primary defluorination clear liquid mixture inlet, a silicon removal filtrate inlet and a secondary polyacrylamide aqueous solution feed inlet, and the bottom is provided with a secondary reaction flocculation discharge outlet;

[0048] Each stage of the sedimentation discharge device is provided with a bottom inlet, an upper clear liquid overflow port, and a sedimentation outlet; each stage of the solid-liquid separator is provided with a solid-liquid feed port, a filter cake outlet, and a filtrate outlet;

[0049] The outlet of the first-stage reaction flocculation and the outlet of the second-stage reaction flocculation are respectively connected to the bottom inlets of the sedimentation discharge devices at the corresponding stages; the sedimentation outlets of each stage of the sedimentation discharge device are connected to the solid-liquid feed ports of the solid-liquid separators at the corresponding stages; the upper clear liquid overflow port of the first-stage sedimentation discharge device and the filtrate outlet of the first-stage solid-liquid separator are merged and then connected to the first-stage defluorinated clear liquid mixture inlet; the upper clear liquid overflow port of the second-stage sedimentation discharge device and the filtrate outlet of the second-stage solid-liquid separator are merged and then connected to outside the boundary;

[0050] The silicon removal unit includes a silicon removal reactor and a silicon removal solid-liquid separator; a photovoltaic alkaline silicon-containing wastewater inlet and a silicon removal lime milk feed port are arranged in the upper middle part of the silicon removal reactor, and a slurry outlet is arranged at the bottom; the silicon removal solid-liquid separator is provided with a slurry inlet, a silicon-containing filter cake outlet, and a silicon removal filtrate outlet; the slurry outlet of the silicon removal reactor is connected to the slurry inlet of the silicon removal solid-liquid separator; the silicon removal filtrate outlet of the silicon removal solid-liquid separator is connected to the silicon removal filtrate inlet of the second-stage reaction flocculator.

[0051] Agitators are independently arranged in the first-stage reaction flocculator, the second-stage reaction flocculator, and the silicon removal reactor respectively.

[0052] In one example, the filter cake outlets of each stage of the solid-liquid separators and the silicon-containing filter cake outlet of the silicon removal solid-liquid separator are independently connected to outside the boundary.

[0053] In one example, the system further includes a lime milk elevated tank;

[0054] An outlet control valve is arranged at the outlet of the lime milk elevated tank, and the outlet of the lime milk elevated tank is divided into two paths, one path is connected to the first-stage lime milk feed port, and the other path is connected to the silicon removal lime milk feed port; the lime milk elevated tank is used to achieve continuous feeding of lime milk; an agitator is arranged in the lime milk elevated tank.

[0055] In one example, the system further includes a photovoltaic acidic fluorine-containing wastewater feed pump, a photovoltaic alkaline silicon-containing wastewater feed pump, a calcium chloride aqueous solution feed pump, and a polyacrylamide aqueous solution feed pump;

[0056] The outlet of the photovoltaic acidic fluorine-containing wastewater feed pump is connected to the photovoltaic acidic fluorine-containing wastewater inlet; the photovoltaic acidic fluorine-containing wastewater feed pump is used to achieve continuous feeding of photovoltaic acidic fluorine-containing wastewater;

[0057] The outlet of the calcium chloride aqueous solution feed pump is connected to the calcium chloride aqueous solution feed port; the calcium chloride aqueous solution feed pump is used to achieve continuous feeding of calcium chloride aqueous solution;

[0058] The outlet of the polyacrylamide aqueous solution feed pump is divided into two paths, one path is connected to the first-stage polyacrylamide aqueous solution inlet, and the other path is connected to the second-stage polyacrylamide aqueous solution inlet; the polyacrylamide aqueous solution feed pump is used to achieve continuous feeding of the polyacrylamide aqueous solution;

[0059] The outlet of the photovoltaic alkaline silicon-containing wastewater feed pump is connected to the photovoltaic alkaline silicon-containing wastewater inlet; the photovoltaic alkaline silicon-containing wastewater feed pump is used to achieve continuous feeding of the photovoltaic alkaline silicon-containing wastewater.

[0060] In one example, each stage of the sedimentation discharge device includes a sedimentation discharger, a elutriation leg, and a screw discharger connected in sequence from top to bottom;

[0061] The sedimentation discharger is provided with the bottom inlet and the upper clear liquid overflow port;

[0062] The screw discharger is provided with the sedimentation outlet.

[0063] In one example, the top of the body of each stage of the reaction flocculator (excluding the height of the motor of the stirrer) and the top of the body of the corresponding stage of the sedimentation discharger are arranged on the same horizontal plane.

[0064] In one example, the height-diameter ratios of the first-stage reaction flocculator and the second-stage reaction flocculator are each independently 0.5 - 3:1.

[0065] In one example, the diameter ratio of the first-stage sedimentation discharger to the first-stage reaction flocculator is 1:1 - 5.

[0066] In one example, the diameter ratio of the second-stage sedimentation discharger to the second-stage reaction flocculator is 1:1 - 5.

[0067] In one example, the diameter of the elutriation leg is 1 / 2 to 1 / 5 of the diameter of the sedimentation discharger.

[0068] In the present utility model, the pipelines and equipment in the first-stage defluorination unit are all made of anti-corrosion materials, or a lining is provided on the surface of the pipelines and equipment, and the lining is made of polytetrafluoroethylene or enamel material.

[0069] The present utility model also provides a continuous resource treatment method for photovoltaic fluorine-containing wastewater. The method uses the above system and includes the following steps:

[0070] S1: Continuously feed the photovoltaic acidic fluoride-containing wastewater, calcium chloride aqueous solution, polyacrylamide aqueous solution, and lime milk into the upper-middle part of the first-stage reaction flocculator to obtain the first-stage reaction material; feed the first-stage reaction material into the first-stage sedimentation discharging device for flocculation sedimentation to obtain the first-stage clear liquid and the first-stage sediment; feed the first-stage sediment into the first-stage solid-liquid separator for filtration to obtain the first-stage filtrate and a calcium fluoride filter cake with a purity > 95%.

[0071] S2: Continuously feed the photovoltaic alkaline silicon-containing wastewater and lime milk into the upper-middle part of the silicon removal reactor, keep the liquid level in the silicon removal reactor constant, and obtain the silicon removal reaction slurry; feed the silicon removal reaction slurry into the silicon removal solid-liquid separator for filtration to obtain a calcium silicate sludge filter cake and a silicon removal alkaline filtrate.

[0072] S3: Mix the first-stage clear liquid and the first-stage filtrate obtained in step S1 to form a first-stage defluorination clear liquid mixture; feed the first-stage defluorination clear liquid mixture, the silicon removal alkaline filtrate, and the polyacrylamide aqueous solution into the upper-middle part of the second-stage reaction flocculator to obtain the second-stage reaction material; feed the second-stage reaction material into the second-stage sedimentation discharging device for flocculation sedimentation to obtain the second-stage clear liquid and the second-stage sediment; feed the second-stage sediment into the second-stage solid-liquid separator for filtration to obtain the second-stage filtrate and a calcium fluoride filter cake with a purity > 80%; mix and discharge the second-stage clear liquid and the second-stage filtrate out of the boundary.

[0073] In one example, the lime milk is provided by a lime milk elevated tank, and the calcium hydroxide content in the slaked lime for preparing the lime milk is > 90%.

[0074] In one example, the polyacrylamide in the polyacrylamide aqueous solution is cationic polyacrylamide; the mass fraction of the polyacrylamide aqueous solution is 0.08 - 0.12%; the addition amounts of polyacrylamide in the first-stage reaction flocculator and the second-stage reaction flocculator are independently determined according to the concentration of polyacrylamide in the photovoltaic acidic fluoride-containing wastewater being 1 - 50 ppm.

[0075] In one example, the reactions in the first-stage reaction flocculator, the second-stage reaction flocculator, and the silicon removal reactor are all carried out under stirring.

[0076] In one example, the method further includes independently discharging the calcium fluoride filter cake with a purity > 95%, the calcium silicate sludge filter cake, and the calcium fluoride filter cake with a purity > 80% out of the boundary.

[0077] In one example, the residence time of the materials in the first-stage reaction flocculator and the second-stage reaction flocculator is 5 - 60 min, preferably 10 - 40 min.

[0078] In one example, in the primary reaction flocculator, the ratio of the total number of moles of calcium ions in the calcium chloride aqueous solution and lime milk to the number of moles of fluoride ions in the photovoltaic acidic fluoride-containing wastewater is 0.5 - 0.6:1; in the primary reaction flocculator, the molar ratio of the calcium chloride aqueous solution to lime milk is 0.5 - 2:1.

[0079] In one example, the silicon content in the desiliconized alkaline filtrate < 20 mg / L.

[0080] In one example, the pH of the reaction materials in the secondary reaction flocculator is 6 - 9, and new calcium fluoride precipitate is produced.

[0081] In one example, the fluoride ion content in the liquid after mixing the secondary supernatant and the secondary filtrate < 5 mg / L.

[0082] In one example, the supernatant liquids at each level (primary supernatant, secondary supernatant) are obtained by overflow from the upper middle part of the sedimentation discharge device at each level of the supernatant in the reaction materials at each level; the sedimentation products at each level (primary sedimentation product, secondary sedimentation product) are obtained by the solid precipitation in the reaction materials at each level flocculating and settling into the thickening legs at each level, and then discharged through the screw discharge devices at each level.

[0083] The following examples and comparative examples:

[0084] The photovoltaic acidic fluoride-containing wastewater and photovoltaic alkaline silicon-containing wastewater generated at the production site of a photovoltaic enterprise in Anhui were used, Ca 2+ The detection method used EDTA titration method for F - The detection method for soluble SiO2 used the silicomolybdate yellow spectrophotometry method, the pH value was detected using a pH meter, and the calcium fluoride purity detection was carried out according to GB / T 27804 - 2011.

[0085] The composition of the photovoltaic acidic fluoride-containing wastewater and photovoltaic alkaline silicon-containing wastewater used is shown in Table 1.

[0086] The calcium chloride solution used Ca 2+ The concentration was 161126 mg / L, and the concentration of lime milk was 2 mol / L.

[0087] Table 1

[0088] Name <![CDATA[Cl - mg / L]]> <![CDATA[F - mg / L]]> <![CDATA[SiO2 (soluble) mg / L]]> pH Photovoltaic acidic fluoride-containing wastewater 277 17591 14 3.0 Photovoltaic alkaline silicon-containing wastewater 11 43 7194 13.3

[0089] Example 1

[0090] This example provides a continuous resource treatment system for photovoltaic fluoride-containing wastewater, as Figure 1As shown, the system includes a primary defluorination unit, a secondary defluorination unit, a desilication unit, a high-level milk of lime tank 104, a photovoltaic acidic fluorine-containing wastewater feed pump 101, a photovoltaic alkaline silicon-containing wastewater feed pump 201, a calcium chloride aqueous solution feed pump 102, and a polyacrylamide aqueous solution feed pump 103;

[0091] Each defluorination unit includes a reaction flocculator, a sedimentation discharge device, and a solid-liquid separator;

[0092] In the upper middle part of the primary reaction flocculator 105, there are a photovoltaic acidic fluorine-containing wastewater inlet, a calcium chloride aqueous solution inlet, a primary milk of lime inlet, and a primary polyacrylamide aqueous solution inlet, and at the bottom there is a primary reaction flocculation discharge outlet;

[0093] In the upper middle part of the secondary reaction flocculator 301, there are a primary defluorination clarified liquid mixed liquid inlet, a desilication filtrate inlet, and a secondary polyacrylamide aqueous solution inlet, and at the bottom there is a secondary reaction flocculation discharge outlet;

[0094] Each sedimentation discharge device includes a sedimentation discharger, a elutriation leg, and a screw discharger connected in sequence from top to bottom; the sedimentation discharger is provided with a bottom inlet and an upper clarified liquid overflow port; the screw discharger is provided with the sedimentation outlet;

[0095] Each solid-liquid separator is provided with a solid-liquid feed inlet, a filter cake outlet, and a filtrate outlet;

[0096] The top of the body of each reaction flocculator and the top of the body of the corresponding sedimentation discharge device at the corresponding level are arranged on the same horizontal plane;

[0097] The primary reaction flocculation discharge outlet and the secondary reaction flocculation discharge outlet are respectively connected to the bottom inlets of the corresponding sedimentation discharge devices at the corresponding levels; the sedimentation outlets of each sedimentation discharge device are connected to the solid-liquid feed inlets of the corresponding solid-liquid separators at the corresponding levels; the primary upper clarified liquid overflow port 112 of the primary sedimentation discharge device and the primary filtrate outlet 111 of the primary solid-liquid separator are merged and then connected to the primary defluorination clarified liquid mixed liquid inlet; the secondary upper clarified liquid overflow port 307 of the secondary sedimentation discharge device and the secondary filtrate outlet 308 of the secondary solid-liquid separator are merged and then connected to outside the boundary;

[0098] The desilication unit includes a desilication reactor 202 and a desilication solid-liquid separator 203; in the upper middle part of the desilication reactor 202, there are a photovoltaic alkaline silicon-containing wastewater inlet and a desilication milk of lime inlet, and at the bottom there is a slurry outlet; the desilication solid-liquid separator 203 is provided with a slurry inlet, a silicon-containing filter cake outlet 204, and a desilication filtrate outlet 205; the slurry outlet of the desilication reactor is connected to the slurry inlet of the desilication solid-liquid separator; the desilication filtrate outlet 205 of the desilication solid-liquid separator is connected to the desilication filtrate inlet of the secondary reaction flocculator;

[0099] The filter cake outlets of the solid-liquid separators at all levels and the silicon-containing filter cake outlet of the silicon removal solid-liquid separator are each independently connected to outside the battery limits;

[0100] Agitators are independently arranged in the first-stage reaction flocculator 105, the second-stage reaction flocculator 301, and the silicon removal reactor 202;

[0101] An outlet control valve is arranged at the outlet of the lime milk elevated tank 104, and the outlet of the lime milk elevated tank 104 is divided into two paths, one path is connected to the first-stage lime milk inlet, and the other path is connected to the silicon removal lime milk inlet; the lime milk elevated tank 104 is used to achieve continuous feeding of lime milk; a stirrer is arranged in the lime milk elevated tank 104;

[0102] The outlet of the photovoltaic acidic fluoride-containing wastewater feed pump 101 is connected to the photovoltaic acidic fluoride-containing wastewater inlet; the photovoltaic acidic fluoride-containing wastewater feed pump 101 is used to achieve continuous feeding of photovoltaic acidic fluoride-containing wastewater;

[0103] The outlet of the calcium chloride aqueous solution feed pump 102 is connected to the calcium chloride aqueous solution inlet; the calcium chloride aqueous solution feed pump 102 is used to achieve continuous feeding of the calcium chloride aqueous solution;

[0104] The outlet of the polyacrylamide aqueous solution feed pump 103 is divided into two paths, one path is connected to the first-stage polyacrylamide aqueous solution inlet, and the other path is connected to the second-stage polyacrylamide aqueous solution inlet; the polyacrylamide aqueous solution feed pump 103 is used to achieve continuous feeding of the polyacrylamide aqueous solution;

[0105] The outlet of the photovoltaic alkaline silicon-containing wastewater feed pump 201 is connected to the photovoltaic alkaline silicon-containing wastewater inlet; the photovoltaic alkaline silicon-containing wastewater feed pump 201 is used to achieve continuous feeding of photovoltaic alkaline silicon-containing wastewater.

[0106] The diameters of the first-stage sedimentation discharger 106, the first-stage reaction flocculator 105, the second-stage sedimentation discharger 302, and the second-stage reaction flocculator 301 are all 200 mm, and the height-to-diameter ratios are all 2:1;

[0107] The diameters of the first-stage elutriation leg 107 and the second-stage elutriation leg 303 are both 80 mm, and the height-to-diameter ratios are both 3:1.

[0108] This embodiment further provides a continuous resource treatment method for photovoltaic fluoride-containing wastewater. The method uses the above system and includes the following steps:

[0109] S1: Turn on the stirrer of the primary reaction flocculator 105. According to the residence time of 30 min of the materials in the primary reaction flocculator 105, continuously feed 20 L / h (feed rate) of photovoltaic acidic fluorine-containing wastewater, 1.2 L / h of calcium chloride aqueous solution, 1 L / h of polyacrylamide aqueous solution (mass fraction of 0.1%) and 2.2 L / h of lime milk into the middle-upper part of the primary reaction flocculator 105. The feeding temperature is 25 °C to obtain the primary reaction materials.

[0110] Feed the primary reaction materials into the primary sedimentation discharging device. The solid precipitate in the primary reaction materials flocculates and settles from the primary sedimentation discharger 106 into the primary elutriation leg 107 for thickening, and then is discharged through the primary screw discharger 108 to obtain the primary sediment; the clear liquid in the primary reaction materials overflows from the middle-upper part of the primary sedimentation discharger 106 to obtain the primary clear liquid; feed the primary sediment into the primary solid-liquid separator 109 for filtration to obtain the primary filtrate and the primary calcium fluoride filter cake (primary calcium fluoride filter cake: 620 g / h, purity 95.4%, yield 90.3%).

[0111] S2: Turn on the stirrer of the silicon removal reactor 202. Continuously feed 22.2 L / h of photovoltaic alkaline silicon-containing wastewater and 3 L / h of lime milk into the middle-upper part of the silicon removal reactor 202, and keep the liquid level in the silicon removal reactor 202 constant to obtain the silicon removal reaction slurry; feed the silicon removal reaction slurry into the silicon removal solid-liquid separator 203 for filtration to obtain 460 g / h of calcium silicate sludge filter cake and the silicon removal alkaline filtrate (the soluble SiO2 concentration in the silicon removal alkaline filtrate is 12.7 mg / L).

[0112] S3: Mix the primary clear liquid and the primary filtrate obtained in step S1 to form a primary defluorination clear liquid mixture (where the Ca 2+ concentration is 1691 mg / L and the F - concentration is 1547 mg / L); turn on the stirrer of the secondary reaction flocculator 301. According to the residence time of 20 min of the materials in the secondary reaction flocculator 301, feed 15.1 L / h of the primary defluorination clear liquid mixture, 22.2 L / h of the silicon removal alkaline filtrate and 0.25 L / h of polyacrylamide aqueous solution into the middle-upper part of the secondary reaction flocculator. The pH of the reaction materials in the secondary reaction flocculator 301 is 6.5 to obtain the secondary reaction materials.

[0113] Feed the secondary reaction materials into the secondary sedimentation discharge device. The solid precipitate in the secondary reaction materials flocculates and settles from the secondary sedimentation discharger 302 to the secondary elutriation leg 303 for thickening, and then is discharged through the secondary screw discharger 304 to obtain the secondary sediment; the clear liquid in the secondary reaction materials overflows from the upper middle part of the secondary sedimentation discharger 302 to obtain the secondary clear liquid; Feed the secondary sediment into the secondary solid-liquid separator 305 for filtration to obtain the secondary filtrate and the secondary calcium fluoride filter cake (secondary calcium fluoride filter cake: 51 g / h, purity 82.3%);

[0114] Mix the secondary clear liquid and the secondary filtrate and discharge them outside the boundary. The concentration of Ca in the liquid after mixing the secondary clear liquid and the secondary filtrate is 0 mg / L, and the concentration of F is 4.6 mg / L. 2+ concentration 0 mg / L, F - concentration 4.6 mg / L.

[0115] Example 2

[0116] This example provides a continuous resource treatment system for photovoltaic fluorine-containing wastewater. As shown, the difference between this example and Example 1 is only that: Figure 2 The diameters of the primary reaction flocculator 105, the secondary sedimentation discharger 302 and the secondary reaction flocculator 301 are all 200 mm, and the height-diameter ratios are all 2:1;

[0117] The diameter of the primary sedimentation discharger 106 is 100 mm, and the height-diameter ratio is 4:1;

[0118] The diameter of the primary elutriation leg 107 is 40 mm, and the height-diameter ratio is 3:1;

[0119] The diameter of the secondary elutriation leg 303 is 80 mm, and the height-diameter ratio is 3:1.

[0120] The diameter of the secondary elutriation leg 303 is 80 mm, and the height-diameter ratio is 3:1.

[0121] This example also provides a continuous resource treatment method for photovoltaic fluorine-containing wastewater. The difference between the method of this example and Example 1 is only that:

[0122] Primary calcium fluoride filter cake: 616 g / h, purity 95.6%, yield 90%;

[0123] In the primary defluorination clear liquid mixture, the concentration of Ca is 1702 mg / L, and the concentration of F is 1589 mg / L; 2+ concentration 1702 mg / L, F - concentration 1589 mg / L;

[0124] Secondary calcium fluoride filter cake: 52 g / h, purity 82.1%;

[0125] The concentration of Ca in the liquid after mixing the secondary clear liquid and the secondary filtrate is 0 mg / L, and the concentration of F is 4.5 mg / L. 2+ concentration 0 mg / L, F - concentration 4.5 mg / L.

[0126] Comparative Example 1

[0127] This comparative example provides a continuous treatment method for photovoltaic fluorine-containing wastewater. The difference between this comparative example and Example 1 is only that: this comparative example does not adjust the pH after removing silicon from photovoltaic alkaline silicon-containing wastewater, and uses 30% sodium hydroxide solution for secondary defluorination. Specifically:

[0128] Step S1 of this Comparative Example 1 is the same as Step S1 of Example 1;

[0129] This Comparative Example 1 does not have Step S2 of Example 1;

[0130] Step S3 of this Comparative Example 1: Mix the primary supernatant and the primary filtrate obtained in Step S1 to form a primary defluorination supernatant mixture (where the concentration of Ca 2+ is 1691 mg / L, and the concentration of F - is 1547 mg / L); start the stirrer of the secondary reaction flocculator 301, and according to the residence time of 20 min of the materials in the secondary reaction flocculator 301, feed 33.3 L / h of the primary defluorination supernatant mixture, 4 L / h of 30% sodium hydroxide aqueous solution, and 0.55 L / h of polyacrylamide aqueous solution into the secondary reaction flocculator 301 from the upper middle part of the secondary reaction flocculator. The pH of the reaction materials in the secondary reaction flocculator 301 is 6.5 to obtain secondary reaction materials;

[0131] Feed the secondary reaction materials into the secondary sedimentation and discharging device. The solid precipitate in the secondary reaction materials flocculates and settles from the secondary sedimentation discharger 302 into the secondary elutriation leg 303 for thickening, and then is discharged through the secondary screw discharger 304 to obtain secondary sediment; the supernatant in the secondary reaction materials overflows from the upper middle part of the secondary sedimentation discharger 302 to obtain secondary supernatant; feed the secondary sediment into the secondary solid-liquid separator 305 for filtration to obtain secondary filtrate and secondary calcium fluoride filter cake (secondary calcium fluoride filter cake: 112 g / h, purity 81.6%);

[0132] Mix the secondary supernatant and the secondary filtrate and discharge them out of the boundary. The concentration of Ca 2+ in the liquid after mixing the secondary supernatant and the secondary filtrate is 0 mg / L, and the concentration of F - is 4.8 mg / L.

[0133] This comparative example uses 30% sodium hydroxide aqueous solution for secondary defluorination reaction. Treating one ton of photovoltaic acidic fluorine-containing wastewater requires consuming 120 kg of fresh 30% sodium hydroxide solution, and the cost increases greatly.

[0134] The embodiments of the present utility model have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A continuous resource treatment system for photovoltaic fluorine-containing wastewater, characterized in that, The system includes a primary defluorination unit, a secondary defluorination unit and a desilication unit; Each defluorination unit includes a reaction flocculator, a sedimentation discharge device and a solid-liquid separator; At the upper-middle part of the primary reaction flocculator, there are provided a photovoltaic acidic fluorine-containing wastewater inlet, a calcium chloride aqueous solution feed inlet, a primary lime milk feed inlet and a primary polyacrylamide aqueous solution feed inlet, and at the bottom, there is provided a primary reaction flocculation discharge outlet; At the upper-middle part of the secondary reaction flocculator, there are provided a primary defluorination clear liquid mixture inlet, a desilication filtrate inlet and a secondary polyacrylamide aqueous solution feed inlet, and at the bottom, there is provided a secondary reaction flocculation discharge outlet; Each sedimentation discharge device is provided with a bottom inlet, an upper clear liquid overflow outlet and a sedimentation outlet; each solid-liquid separator is provided with a solid-liquid feed inlet, a filter cake outlet and a filtrate outlet; The primary reaction flocculation discharge outlet and the secondary reaction flocculation discharge outlet are respectively connected to the bottom inlets of the sedimentation discharge devices of the corresponding levels; the sedimentation outlets of each level of sedimentation discharge device are connected to the solid-liquid feed inlets of the corresponding level of solid-liquid separator; the upper clear liquid overflow outlet of the primary sedimentation discharge device and the filtrate outlet of the primary solid-liquid separator are joined and then connected to the primary defluorination clear liquid mixture inlet; the upper clear liquid overflow outlet of the secondary sedimentation discharge device and the filtrate outlet of the secondary solid-liquid separator are joined and then connected to outside the battery limits; The desilication unit includes a desilication reactor and a desilication solid-liquid separator; at the upper-middle part of the desilication reactor, there are provided a photovoltaic alkaline silicon-containing wastewater inlet and a desilication lime milk feed inlet, and at the bottom, there is provided a slurry outlet; the desilication solid-liquid separator is provided with a slurry inlet, a silicon-containing filter cake outlet and a desilication filtrate outlet; the slurry outlet of the desilication reactor is connected to the slurry inlet of the desilication solid-liquid separator; the desilication filtrate outlet of the desilication solid-liquid separator is connected to the desilication filtrate inlet of the secondary reaction flocculator; Stirrers are independently arranged in the primary reaction flocculator, the secondary reaction flocculator and the desilication reactor respectively.

2. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 1, wherein The filter cake outlets of each level of solid-liquid separator and the silicon-containing filter cake outlet of the desilication solid-liquid separator are independently connected to outside the battery limits.

3. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 1, characterized in that The system further includes a lime milk elevated tank; At the outlet of the lime milk elevated tank, there is provided an outlet control valve, and the outlet of the lime milk elevated tank is divided into two paths, one path is connected to the primary lime milk feed inlet, and the other path is connected to the desilication lime milk feed inlet; the lime milk elevated tank is used to achieve continuous feeding of lime milk; a stirrer is arranged in the lime milk elevated tank.

4. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 1, wherein The system further includes a photovoltaic acidic fluorine-containing wastewater feed pump, a photovoltaic alkaline silicon-containing wastewater feed pump, a calcium chloride aqueous solution feed pump and a polyacrylamide aqueous solution feed pump; The outlet of the photovoltaic acidic fluorine-containing wastewater feed pump is connected to the photovoltaic acidic fluorine-containing wastewater inlet; the photovoltaic acidic fluorine-containing wastewater feed pump is used to achieve continuous feeding of photovoltaic acidic fluorine-containing wastewater; The outlet of the calcium chloride aqueous solution feed pump is connected to the calcium chloride aqueous solution feed inlet; the calcium chloride aqueous solution feed pump is used to achieve continuous feeding of calcium chloride aqueous solution; The outlet of the polyacrylamide aqueous solution feed pump is divided into two paths, one path is connected to the primary polyacrylamide aqueous solution feed port, and the other path is connected to the secondary polyacrylamide aqueous solution feed port; the polyacrylamide aqueous solution feed pump is used to achieve continuous feeding of the polyacrylamide aqueous solution; The outlet of the photovoltaic alkaline silicon-containing wastewater feed pump is connected to the photovoltaic alkaline silicon-containing wastewater inlet; the photovoltaic alkaline silicon-containing wastewater feed pump is used to achieve continuous feeding of the photovoltaic alkaline silicon-containing wastewater.

5. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 1, characterized in that, Each stage of sedimentation discharge device includes a sedimentation discharger, a elutriation leg and a screw discharger connected in sequence from top to bottom; The sedimentation discharger is provided with the bottom inlet and the upper clear liquid overflow port; The screw discharger is provided with the sedimentation outlet.

6. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 5, characterized in that, The top of the body of each stage of reaction flocculator and the top of the body of the sedimentation discharger of the corresponding stage are arranged on the same horizontal plane.

7. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 5, wherein The height-diameter ratios of the primary reaction flocculator and the secondary reaction flocculator are each independently 0.5 - 3:

1.

8. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 5, characterized in that, The diameter ratio of the primary sedimentation discharger to the primary reaction flocculator is 1:1 - 5.

9. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 5, characterized in that, The diameter ratio of the secondary sedimentation discharger to the secondary reaction flocculator is 1:1 - 5.

10. The continuous resource treatment system for photovoltaic fluorine-containing wastewater according to claim 5, characterized in that, The diameter of the elutriation leg is 1 / 2 to 1 / 5 of the diameter of the sedimentation discharger.

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