Lime-process crystallization treatment process for photovoltaic wastewater and treatment system used by process

Abstract

The invention discloses a photovoltaic wastewater lime-process crystallization treatment process and a treatment system used by the same, which are characterized in that acid fluoride wastewater and alkali washing wastewater generated in a photovoltaic sheet production process are respectively collected by an acid fluoride wastewater collecting pool and an alkali washing wastewater collecting pool; the acid fluoride wastewater and a lime agent are subjected to a crystallization reaction in a crystallization fluidized bed to obtain calcium fluoride crystals, effluent of the crystallization fluidized bed and alkali washing wastewater are mixed in a secondary defluorination unit, and calcium chloride is added for a defluorination reaction after the pH value is adjusted; the effluent of the second-stage fluorine removal unit reacts with a fluorine removal agent or polyaluminum chloride in the third-stage fluorine removal unit to remove fluorine again, polyacrylamide is added into the third-stage fluorine removal unit to perform a flocculation reaction, and finally, the fluorine ion concentration in the effluent of the third-stage fluorine removal unit meets the discharge requirement. The agent input cost and the sludge treatment cost are reduced, the secondary pollution of chloride ions is avoided, and the effluent is ensured to stably reach the standard.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a photovoltaic wastewater lime crystallization treatment process and a treatment system used therein. Background Art

[0002] Chemical substances such as sodium hydroxide and HF are used in the production and cleaning of photovoltaic silicon wafers, thus generating fluorine-containing wastewater and silicon-containing wastewater. The pollutants in these wastewaters need to be treated to meet discharge standards.

[0003] At present, the typical method for treating wastewater in the photovoltaic and semiconductor industries is precipitation, which effectively captures fluoride ions in the wastewater by adding calcium chloride to the wastewater to form calcium fluoride precipitation. Under the current circumstances, photovoltaic semiconductor companies widely adopt a two-stage calcium addition reaction and precipitation defluorination process.

[0004] The above chemical precipitation defluorination process has the following disadvantages:

[0005] 1. The effluent quality is unstable. The fluoride content in the treated wastewater can generally only drop to 6-15 mg / L. The two-stage defluorination process is difficult to stably meet the emission requirements in the "Battery Industry Pollutant Emission Standard" (GB30484-2013) (the fluoride requirement for new enterprises is less than 8 mg / L, and the special emission limit for water pollution is less than 2 mg / L);

[0006] 2. A large amount of silicon dioxide precipitation will be formed during the reaction, resulting in the effective calcium fluoride in the precipitation product being less than 70%. The large amount of silicon dioxide makes the precipitation unable to be reused by the hydrofluoric acid enterprise and can only be treated as waste solid, resulting in a huge waste of resources;

[0007] 3. Since a large amount of calcium chloride is needed as a fluoride ion capture agent, a large amount of chloride ions will be brought in while removing fluoride, causing secondary pollution. Summary of the invention

[0008] In order to overcome the above-mentioned defects, the present invention provides a photovoltaic wastewater lime crystallization treatment process and a treatment system used therein. The photovoltaic wastewater lime crystallization treatment process and the treatment system used therein can ensure that the effluent is stable and meets the standards, and can also achieve resource processing, with low sludge output and low sewage treatment cost.

[0009] The technical solution adopted by the present invention to solve the technical problem is: a photovoltaic wastewater lime crystallization treatment process, the specific steps are as follows:

[0010] Step 1: Separately collect the acid-fluoride wastewater (containing trace silicon) and alkaline-washing wastewater (containing trace fluorine) generated during the production of photovoltaic panels;

[0011] Step 2: prepare lime reagent;

[0012] Step 3: The acid-fluoride wastewater (the alkaline washing wastewater is not included) is pumped into a crystallization fluidized bed together with lime reagent for crystallization reaction to obtain calcium fluoride crystals. Since the acid-fluoride wastewater contains only trace silicon, the silicon dioxide produced during the reaction between the acid-fluoride wastewater and the lime reagent in the crystallization fluidized bed is negligible, so high-purity calcium fluoride crystals can be obtained;

[0013] Step 4: The effluent from the crystallization fluidized bed and the alkali-washing wastewater are sent to the secondary defluorination unit together, the pH of the mixed water in the secondary defluorination unit is adjusted to 6-8, and calcium chloride is added to the secondary defluorination unit. The calcium chloride reacts with the fluoride ions in the mixed water, and the calcium fluoride produced by the reaction is removed by precipitation. The fluoride content in the effluent from the crystallization fluidized bed and the alkali-washing wastewater is relatively low. After reacting with calcium chloride, a small amount of calcium fluoride precipitation is produced, which realizes the effect of removing fluoride ions in the water again. Since the fluoride ion content in the wastewater is low at this time, the amount of calcium chloride to be added is also relatively small, which can avoid secondary pollution caused by excessive chloride ions in the effluent of the secondary defluorination unit;

[0014] Step 5: The effluent from the secondary defluorination unit enters the tertiary defluorination unit, and a defluorination agent or polyaluminium chloride (PAC) is added to the tertiary defluorination unit to remove the remaining fluorine. At the same time, polyacrylamide (PAM) is added to the tertiary defluorination unit for flocculation reaction. The mixed liquid after the reaction is precipitated to obtain effluent with a fluoride ion concentration that meets the discharge requirements.

[0015] The effluent from the secondary defluorination unit is subjected to the tertiary defluorination unit to adsorb and remove fluoride ions again, thereby ensuring that the effluent is clear and the fluoride ion concentration in the effluent is further reduced to 1-3 mg / L.

[0016] As a further improvement of the present invention, the lime reagent is lime water prepared by mixing lime and water, and the concentration of lime water includes but is not limited to 1%, 2%, 5% or 10%. The lime should be fully diluted and dissolved before entering the reactor to avoid excessive sludge production of the secondary defluorination unit due to undissolved lime, and also to avoid waste of lime and reduction of purity of calcium fluoride crystals.

[0017] As a further improvement of the present invention, part of the effluent in step 5 is refluxed as lime preparation water. Since the effluent of the three-stage defluorination unit is water with an ultra-low fluoride ion concentration, the effluent is used to prepare the lime preparation, which helps to fully dissolve and utilize the lime or calcium hydroxide, ensure the stability and controllability of the pH of the crystallization reaction in the crystallization fluidized bed, reduce the amount of lime added, and reduce the consumption of fresh water.

[0018] As a further improvement of the present invention, in step 3, the pickling wastewater and the lime reagent are added according to a calcium-fluorine molar ratio of 0.6 to 0.9, so as to ensure that the crystallization reaction is sufficient, and the lime reagent is not wasted, thereby avoiding affecting the crystal purity.

[0019] As a further improvement of the present invention, in step 3, a portion of calcium fluoride crystals are filled in the crystallization fluidized bed as an inducer, the particle size of the calcium fluoride crystals as the inducer is controlled to be 0.1-0.5 mm, the reaction pH value in the crystallization fluidized bed is controlled to be between 5 and 7, and the residence time of the acid fluoride wastewater and the lime reagent in the crystallization fluidized bed is controlled to be 30-120 minutes. Calcium fluoride crystallizes on the surface of the induced crystals, with a fast crystallization speed and high crystallization efficiency.

[0020] As a further improvement of the present invention, in step 4, sulfuric acid is added to the secondary defluorination unit to adjust the pH. The sulfuric acid reacts with the alkali washing wastewater to adjust the pH of the wastewater to 6-8 without introducing additional pollutants.

[0021] As a further improvement of the present invention, the precipitated sludge produced by the secondary defluorination unit and the tertiary defluorination unit is discharged regularly for general solid waste treatment, and the calcium fluoride crystals produced by the crystallization fluidized bed are discharged regularly, and after drying, a finished calcium fluoride crystal with a purity greater than 90% is obtained.

[0022] A photovoltaic wastewater lime crystallization treatment system, comprising an acid-fluorine wastewater collection tank, an alkali-washing wastewater collection tank, a crystallization fluidized bed, a secondary defluorination unit, a tertiary defluorination unit, an outlet water collection tank, a lime reagent configuration tank and a lifting pump, wherein the secondary defluorination unit and the tertiary defluorination unit both comprise a reaction zone, a precipitation zone and an outlet water zone, wherein the reaction zone is connected to the precipitation zone through a pipeline, and the upper clear liquid of the precipitation zone can be discharged into the outlet water zone, the acid-fluorine wastewater collection tank and the lime reagent configuration tank are respectively connected to the water inlet of the crystallization fluidized bed through a pipeline, and the acid-fluorine wastewater collection tank is ... The acid fluoride wastewater and the lime agent in the lime agent configuration pool can be sent into the crystallization fluidized bed through a lifting pump, the water outlet of the crystallization fluidized bed is connected with the water inlet of the reaction zone of the secondary defluorination unit through a gravity flow pipe, the water outlet area of ​​the secondary defluorination unit is connected with the water inlet of the reaction zone of the tertiary defluorination unit through a gravity flow pipe, the water outlet area of ​​the tertiary defluorination unit is connected with the effluent collection pool through a gravity flow pipe, the effluent collection pool is connected with the water inlet of the lime agent configuration pool through a reflux pipe, and the clean water in the effluent collection pool can be sent into the lime agent configuration pool through a lifting pump.

[0023] As a further improvement of the present invention, a sludge collection chamber is further provided, and a sludge discharge pipe is provided at the lower end of the sedimentation zone of the secondary defluorination unit and the tertiary defluorination unit, and the end of the sludge discharge pipe is connected to the sludge collection chamber. The sludge in the sedimentation zone of the secondary defluorination unit and the tertiary defluorination unit can be discharged into the sludge collection chamber through the sludge discharge pipe for collection and treated as waste solid. The secondary defluorination unit and the tertiary defluorination unit also include a first dosing device and a second dosing device. The first dosing device of the secondary defluorination unit is used to add dilute sulfuric acid to the reaction zone of the secondary defluorination unit, and the second dosing device of the secondary defluorination unit is used to add calcium chloride to the reaction zone of the secondary defluorination unit. The first dosing device of the tertiary defluorination unit is used to add a defluorinating agent or polyaluminum chloride to the reaction zone of the tertiary defluorination unit, and the second dosing device of the tertiary defluorination unit is used to add polyacrylamide to the reaction zone of the tertiary defluorination unit.

[0024] As a further improvement of the present invention, a dehydration workshop is also provided, wherein a crystal dehydration device is provided in the dehydration workshop, and the crystallization fluidized bed is connected to the feed port of the crystal dehydration device in the dehydration workshop through a crystal discharge pipeline, and the crystal dehydration device can dehydrate and dry the crystals. The calcium fluoride crystals discharged from the crystallization fluidized bed are mixed with water, and after entering the dehydration workshop, they are subjected to subsequent treatment, and finally dry and clean high-purity calcium fluoride particles are obtained for recycling.

[0025] The invention has the following beneficial effects: the invention collects and treats the acid fluoride wastewater and the alkali washing wastewater generated in the production process of photovoltaic panels respectively; in the crystallization fluidized bed process, the lime and the acid fluoride wastewater are reacted; the alkali washing wastewater does not enter the crystallization fluidized bed, thereby avoiding the entry of silicon ions; the purity of the generated calcium fluoride crystals is higher than 90%, and the calcium fluoride crystals can be reused by hydrofluoric acid enterprises, thereby realizing resource processing; and the invention adopts a three-stage treatment process to defluorinate the wastewater, thereby ensuring that the effluent is stable and meets the standards, and the effluent F content is less than 2 mg / L; the invention supplements the alkali washing wastewater in the secondary defluorination unit, thereby effectively reducing the amount of calcium chloride used, reducing the chloride ion content in the effluent, avoiding secondary pollution caused by chloride ions, and having a wide range of applications; the effluent of the three-stage defluorination unit of the invention is refluxed for lime preparation, thereby realizing the reuse of effluent, realizing the recycling of water resources, and reducing the process operation cost; and the lime is fully dissolved after the effluent preparation of the three-stage defluorination unit, thereby making full use of the lime, reducing the lime input cost, and reducing the sludge output of the two-stage defluorination unit, thereby reducing the sludge disposal cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] Embodiment: A photovoltaic wastewater lime crystallization treatment process, the specific steps are as follows:

[0028] (1) collecting the hydrofluoric acid-containing acid washing wastewater generated in the production process of the photovoltaic panel into an acid fluorine wastewater collection pool, homogenizing the hydrofluoric acid-containing acid washing wastewater in the acid fluorine wastewater collection pool, and testing the wastewater in the acid fluorine wastewater collection pool. At this time, the fluorine content of the wastewater in the acid fluorine wastewater collection pool is between 800 and 900 ppm; collecting the alkali washing wastewater generated in the cleaning process of the photovoltaic panel into an alkali washing wastewater collection pool. After the alkali washing wastewater is homogenized in the alkali washing wastewater collection pool, the wastewater in the alkali washing wastewater collection pool is tested. At this time, the silicon content of the wastewater in the alkali washing wastewater collection pool is between 20 and 60 ppm;

[0029] (2) Add lime to the lime reagent preparation pool to prepare lime water with a mass percentage concentration of 1%. The lime water is a milky white liquid. Lime water can also be prepared with other concentrations, such as mass percentage concentrations of 1%, 2%, 5%, 10%, etc.;

[0030] (3) adding calcium fluoride particles with a particle size of 0.1 to 0.5 mm into the crystallization fluidized bed as inducing crystals, pumping acid fluoride wastewater in the acid fluoride wastewater collection pool and lime water in the lime reagent preparation pool into the crystallization fluidized bed by a lift pump, and adjusting the flow ratio of the acid fluoride wastewater and the lime reagent lift pump so that the calcium-fluoride ratio of the liquid mixture entering the crystallization fluidized bed is between 0.65 and 0.75, and the rising flow rate in the fluidized bed is controlled at 50 to 80 m / h. At the same time, the pH value in the crystallization fluidized bed is controlled at 6 to 8 by adding lime, and the residence time of the acid fluoride wastewater and the lime water in the crystallization fluidized bed is controlled at 30 to 120 minutes. The generated crystals are discharged into the dehydration workshop at regular intervals for dehydration and drying treatment, and finally calcium fluoride crystals with a purity greater than 90% are obtained, and the fluoride content of the effluent from the crystallization fluidized bed is below 30 ppm;

[0031] (4) The effluent from the crystallization fluidized bed flows by gravity into the reaction zone of the secondary defluorination unit, and the alkali-washing wastewater is simultaneously sent into the reaction zone of the secondary defluorination unit by a lifting pump. The alkali-washing wastewater is mixed with the effluent from the crystallization fluidized bed in the reaction zone of the secondary defluorination unit, and sulfuric acid is used to adjust the pH of the mixed solution in the reaction zone of the secondary defluorination unit to 6-8. Then, a calcium chloride solution is added to the reaction zone of the secondary defluorination unit to generate calcium fluoride. After the mixed solution is fully reacted in the reaction zone of the secondary defluorination unit, it enters the sedimentation zone of the secondary defluorination unit to achieve mud and water stratification and separation. The sludge is discharged into the sludge collection chamber, and the supernatant enters the effluent zone of the secondary defluorination unit. At this time, the fluoride ion in the effluent of the effluent zone of the secondary defluorination unit is below 8ppm;

[0032] (5) The effluent from the effluent area of ​​the secondary defluorination unit enters the reaction area of ​​the tertiary defluorination unit. At the same time, a high-efficiency defluorination agent or polyaluminium chloride (PAC) is added to the reaction area of ​​the tertiary defluorination unit. The fluoride ions are removed by the adsorption of the high-efficiency defluorination agent or polyaluminium chloride (PAC). The adsorption process is carried out in the reaction area of ​​the tertiary defluorination unit. Since the flocs formed by adsorption have poor settling performance, polyacrylamide (PAM) is added in the reaction area of ​​the tertiary defluorination unit to achieve the settling of the flocs. The mixed liquid after PAM) is subjected to floc sedimentation in the sedimentation area of ​​the tertiary defluorination unit, and the settled sludge is discharged into the sludge collection chamber. The upper clear water in the sedimentation area of ​​the tertiary defluorination unit enters the effluent area of ​​the tertiary defluorination unit. The effluent from the effluent area of ​​the tertiary defluorination unit is clarified. At this time, the fluorine content is less than 2ppm, which can stably meet the emission requirements of the "Battery Industry Pollutant Emission Standard" (GB30484-2013) (fluoride requirement is less than 8mg / L), and even meet the requirement that the special emission limit of water pollution is less than 2mg / L;

[0033] (6) The effluent from the effluent area of ​​the tertiary defluorination unit enters the effluent collection pool for storage. A portion of the water in the effluent collection pool is pumped back to the lime reagent preparation pool at the front end for lime reagent preparation, which can achieve water circulation and reduce operating costs. The other portion of the water is directly discharged;

[0034] (7) The sludge discharged into the sludge collection room from the secondary and tertiary defluorination units shall be disposed of as general solid waste.

[0035] A photovoltaic wastewater lime crystallization treatment system, comprising an acid-fluorine wastewater collection tank 1, an alkali-washing wastewater collection tank 2, a crystallization fluidized bed 3, a secondary defluorination unit 4, a tertiary defluorination unit 5, an outlet water collection tank 6, a lime reagent configuration tank 7 and a lifting pump, wherein the secondary defluorination unit 4 and the tertiary defluorination unit 5 both comprise a reaction zone, a precipitation zone and an outlet water zone, wherein the reaction zone is connected to the precipitation zone through a pipeline, and the upper clear liquid of the precipitation zone can be discharged into the outlet water zone, the acid-fluorine wastewater collection tank 1 and the lime reagent configuration tank 7 are respectively connected to the water inlet of the crystallization fluidized bed 3 through a pipeline, and ... The acid fluoride wastewater in pool 1 and the lime agent in lime agent preparation pool 7 can be sent into the crystallization fluidized bed 3 through a lifting pump, the water outlet of the crystallization fluidized bed 3 is connected with the water inlet of the reaction zone of the secondary defluorination unit 4 through a gravity flow pipe, the water outlet area of ​​the secondary defluorination unit 4 is connected with the water inlet of the reaction zone of the tertiary defluorination unit 5 through a gravity flow pipe, the water outlet area of ​​the tertiary defluorination unit 5 is connected with the effluent collecting pool 6 through a gravity flow pipe, the effluent collecting pool 6 is connected with the water inlet of the lime agent preparation pool 7 through a reflux pipe, and the clean water in the effluent collecting pool 6 can be sent into the lime agent preparation pool 7 through a lifting pump.

[0036] A sludge collecting chamber 8 is also provided. A sludge discharge pipe is provided at the lower end of the sedimentation zone of the secondary defluorination unit 4 and the tertiary defluorination unit 5. The end of the sludge discharge pipe is communicated with the sludge collecting chamber 8. The sludge in the sedimentation zone of the secondary defluorination unit 4 and the tertiary defluorination unit 5 can be discharged into the sludge collecting chamber 8 through the sludge discharge pipe for collection and treated as waste solid. The secondary defluorination unit 4 and the tertiary defluorination unit 5 also include a first dosing device and a second dosing device. The first dosing device of the secondary defluorination unit 4 is used to add dilute sulfuric acid to the reaction zone of the secondary defluorination unit 4, the second dosing device of the secondary defluorination unit 4 is used to add calcium chloride to the reaction zone of the secondary defluorination unit 4, the first dosing device of the tertiary defluorination unit 5 is used to add a defluorinating agent or polyaluminum chloride to the reaction zone of the tertiary defluorination unit 5, and the second dosing device of the tertiary defluorination unit 5 is used to add polyacrylamide to the reaction zone of the tertiary defluorination unit 5.

[0037] A dehydration workshop 9 is also provided, in which a crystal dehydration device is provided. The crystallization fluidized bed 3 is connected to the feed port of the crystal dehydration device of the dehydration workshop 9 through a crystal discharge pipeline, and the crystal dehydration device can dehydrate and dry the crystals. The calcium fluoride crystals discharged from the crystallization fluidized bed 3 are mixed with water, and after entering the dehydration workshop 9, subsequent treatment is performed to finally obtain dry and clean high-purity calcium fluoride particles for recycling.

Claims

1. A photovoltaic wastewater lime crystallization process, characterized in that: The specific steps are as follows: Step 1: Separately collect the acid-fluoride wastewater and alkaline-washing wastewater generated during the production of photovoltaic panels; Step 2: prepare lime reagent; Step 3: The acid-fluoride wastewater and lime reagent are pumped into a crystallization fluidized bed for crystallization reaction to obtain calcium fluoride crystals; Step 4: The effluent from the crystallization fluidized bed and the alkali washing wastewater are sent to the secondary defluorination unit together, the pH of the mixed water in the secondary defluorination unit is adjusted to 6-8, and calcium chloride is added to the secondary defluorination unit. The calcium chloride reacts with the fluoride ions in the mixed water, and the calcium fluoride produced by the reaction is removed by precipitation; Step 5: The effluent from the secondary defluorination unit enters the tertiary defluorination unit, and a defluorination agent or polyaluminium chloride is added to the tertiary defluorination unit to remove the remaining fluorine. At the same time, polyacrylamide is added to the tertiary defluorination unit for flocculation reaction. The mixed liquid after the reaction is precipitated to obtain effluent with a fluoride ion concentration that meets the discharge requirements.

2. The photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: The lime agent is lime water prepared by mixing lime and water, and the concentration of the lime water includes but is not limited to 1%, 2%, 5% or 10%.

3. The photovoltaic wastewater lime crystallization treatment process according to claim 2, characterized in that: Part of the effluent in step 5 is returned as water for preparing lime reagent.

4. The photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: In step three, the pickling wastewater and lime reagent are added according to a calcium-fluoride molar ratio of 0.6 to 0.

9.

5. The photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: In step three, a portion of calcium fluoride crystals is loaded into the crystallization fluidized bed as an inducer, the particle size of the calcium fluoride crystals serving as the inducer is controlled to be 0.1-0.5 mm, the reaction pH value in the crystallization fluidized bed is controlled to be between 5 and 7, and the residence time of the acid fluoride wastewater and the lime reagent in the crystallization fluidized bed is controlled to be 30-120 min.

6. The photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: In step 4, sulfuric acid is added to the secondary defluorination unit to adjust the pH.

7. The photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: The precipitated sludge produced by the secondary defluorination unit and the tertiary defluorination unit is discharged regularly for general solid waste treatment, and the calcium fluoride crystals produced by the crystallization fluidized bed are discharged regularly, and after drying, a finished calcium fluoride crystal with a purity greater than 90% is obtained.

8. A photovoltaic wastewater lime crystallization treatment system used in the photovoltaic wastewater lime crystallization treatment process according to claim 1, characterized in that: The invention comprises an acid-fluorine wastewater collection tank (1), an alkali-washing wastewater collection tank (2), a crystallization fluidized bed (3), a secondary defluorination unit (4), a tertiary defluorination unit (5), an outlet water collection tank (6), a lime reagent configuration tank (7) and a lifting pump, wherein the secondary defluorination unit and the tertiary defluorination unit both comprise a reaction zone, a precipitation zone and an outlet water zone, the reaction zone is connected to the precipitation zone through a pipeline, the upper clear liquid of the precipitation zone can be discharged into the outlet water zone, the acid-fluorine wastewater collection tank and the lime reagent configuration tank are respectively connected to the water inlet of the crystallization fluidized bed through a pipeline, and the acid-fluorine wastewater collection tank is connected to the water inlet of the crystallization fluidized bed through a pipeline. The acid fluoride wastewater in the water collection pool and the lime agent in the lime agent preparation pool can be sent into the crystallization fluidized bed through a lifting pump, the water outlet of the crystallization fluidized bed is connected with the water inlet of the reaction zone of the secondary defluorination unit through a gravity flow pipe, the water outlet area of ​​the secondary defluorination unit is connected with the water inlet of the reaction zone of the tertiary defluorination unit through a gravity flow pipe, the water outlet area of ​​the tertiary defluorination unit is connected with the effluent collection pool through a gravity flow pipe, the effluent collection pool is connected with the water inlet of the lime agent preparation pool through a reflux pipe, and the clean water in the effluent collection pool can be sent into the lime agent preparation pool through a lifting pump.

9. The photovoltaic wastewater lime crystallization treatment system according to claim 8, characterized in that: A sludge collection chamber (8) is also provided. A sludge discharge pipe is provided at the lower end of the sedimentation zone of the secondary defluorination unit and the tertiary defluorination unit. The end of the sludge discharge pipe is communicated with the sludge collection chamber. The sludge in the sedimentation zone of the secondary defluorination unit and the tertiary defluorination unit can be discharged into the sludge collection chamber through the sludge discharge pipe for collection and as solid waste treatment. The secondary defluorination unit and the tertiary defluorination unit also include a first dosing device and a second dosing device. The first dosing device of the secondary defluorination unit is used to add dilute sulfuric acid to the reaction zone of the secondary defluorination unit. The second dosing device of the secondary defluorination unit is used to add calcium chloride to the reaction zone of the secondary defluorination unit. The first dosing device of the tertiary defluorination unit is used to add a defluorinating agent or polyaluminium chloride to the reaction zone of the tertiary defluorination unit. The second dosing device of the tertiary defluorination unit is used to add polyacrylamide to the reaction zone of the tertiary defluorination unit.

10. The photovoltaic wastewater lime crystallization treatment system according to claim 8, characterized in that: A dehydration workshop (9) is also provided, wherein a crystal dehydration device is provided in the dehydration workshop, and the crystallization fluidized bed is connected to the feed port of the crystal dehydration device in the dehydration workshop through a crystal row pipeline, and the crystal dehydration device can perform dehydration and drying treatment on the crystals.

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