Integrated defluorination method and system based on fluidized bed

Abstract

The application patent belongs to the technical field of water treatment, and particularly relates to an integrated fluorine removal method and system based on a fluidized bed. The method comprises the following steps: delivering fluorine-containing wastewater to an inner fluidized bed bed body provided with fluorite seeds, and inputting a composite calcium salt crystallization agent in the inner fluidized bed bed body to induce crystallization to generate fluorite and perform primary fluorine removal; delivering the wastewater after the primary fluorine removal to an outer fluidized bed bed body provided with fluorapatite modified calcite seeds, and inputting di-potassium hydrogen phosphate and sodium hydroxide in the outer fluidized bed bed body to perform secondary fluorine removal; delivering the wastewater after the secondary fluorine removal to a water outlet collection tank after being treated by a porous adsorption filler, and the water outlet collection tank is communicated with a hydrochloric acid storage tank. The fluorine removal method and system combine high-concentration fluorine-containing wastewater fluorine removal and deep fluorine removal into integration, and can effectively improve the wastewater treatment effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and particularly relates to an integrated defluorination method and system based on a fluidized bed. BACKGROUND

[0002] A large amount of fluorine-containing wastewater is generated in the production processes of semiconductor, photovoltaic, rare earth smelting and other industrial enterprises. At present, the commonly used methods for treating fluorine-containing wastewater at home and abroad include chemical precipitation, electrocoagulation, reverse osmosis, ion exchange, membrane separation and adsorption. These methods have good removal effect, but a large amount of inorganic fluorine-containing sludge is generated, causing serious solid waste pollution and waste of fluorine resources.

[0003] Compared with the common chemical precipitation or coagulation precipitation method for treating fluorine-containing wastewater, the fluidized bed induced crystallization technology is used to recover fluorine resources from the fluorine-containing wastewater, which can solve the problem of fluorine-containing sludge disposal and also produce low-moisture and high-value products such as fluorite. However, the single-stage fluidized bed induced crystallization technology currently used for treating fluorine-containing wastewater can only control the fluorine concentration of the effluent to about 10-20 mg / L, which cannot meet the increasingly stringent environmental protection requirements, and an additional secondary treatment unit is needed to deeply remove fluorine from the fluidized bed effluent, resulting in a large overall equipment footprint and high operation and treatment cost. In addition, due to the fluctuation of fluoride concentration in the treatment process, the calcium salt dosage is difficult to accurately control, and the reaction process is easy to reach a supersaturated state, resulting in the generation of a large amount of small molecule calcium fluoride crystals in the reaction process, and further causing the turbidity of the effluent to increase.

[0004] Patent CN 101941752 B provides a treatment method and device for fluorine-containing wastewater, which uses a fluidized bed as a crystallization reactor, adds a certain amount of calcium fluoride seed crystals into the reactor, sends the fluorine-containing wastewater and the calcium-containing precipitator into the solid-liquid fluidized bed treatment device according to the reaction ratio, makes the fluoride ions precipitate on the surface of the calcium fluoride seed crystals, and recycles the sand-like calcium fluoride precipitate sludge obtained after settling. The first-stage treated water is discharged after further coagulation and sedimentation. However, the invention uses a batch operation, which involves the steps of supplementing calcium fluoride seed crystals, adjusting the reaction of raw water and precipitator, and discharging calcium fluoride sludge after the reaction is completed, and the operation is relatively complicated, which is not suitable for engineering practical application. The particle size of the produced sand-like calcium fluoride has no selectivity. The effluent from the fluidized bed is still subjected to flocculation for deep fluorine removal, which cannot avoid the secondary pollution of aluminum salt.

[0005] Patent CN 116947179 A provides a fluidized bed deep fluorine removal device and process, which is used for deep removal of fluorine, phosphorus and other pollutants. The outer cylinder, middle cylinder and inner cylinder are arranged from outside to inside, and the deep fluorine removal, flocculation, clarification, sedimentation and sludge concentration process units are integrated, realizing the integration of deep fluorine removal, flocculation and solid-liquid separation. But the fluorine removal principle of this process is mainly complexation and flocculation adsorption, mainly for the deep treatment of fluorine-containing wastewater, and does not involve the treatment of high-concentration fluorine-containing wastewater.

[0006] Patent CN 110627177 A constructs a defluorination method and defluorination fluidized bed crystallization separator for fluorine-containing wastewater. The system uses quartz sand or fluorapatite as crystal seed, CaHPO4·2H2O as defluorination agent for defluorination, sets up flow guide cylinder, screening device and reflux pipe to form crystallization separator, and realizes effective screening of different particle size crystals. But the CaHPO4·2H2O defluorination agent used in this invention has high cost, and the presence of phosphate may cause the effluent phosphorus to exceed the standard, which will seriously affect the grade of fluorite crystal; the structure of crystallization separator is complex, and it is easy to cause blockage in actual operation.

[0007] From the above content, it can be seen that the existing fluorine-containing wastewater treatment methods have some problems. When the chemical precipitation method is used for treatment, calcium salt is added for primary treatment, and defluorination agent is added for deep treatment, which has the problems of large amount of reagent addition and high operation cost; in addition, a large amount of fluorine-containing sludge is produced in the defluorination process, which has low purity and can only be landfilled, causing a large amount of waste of fluorine resources. The fluidized bed induced crystallization technology treats fluorine-containing wastewater, and the effluent concentration is 10~20mg / L. The turbidity of fluidized bed effluent is large, which cannot directly meet the discharge standard. SUMMARY

[0008] The present application provides an integrated defluorination method and system based on fluidized bed, which can realize the functions of primary treatment and deep treatment of high-concentration fluorine-containing wastewater with one set of fluidized bed equipment, replace the traditional deep treatment unit after fluidized bed treatment, and the effluent fluorine can be stably less than 1mg / L. In addition, the system can generate fluorite and calcium fluorophosphate crystals to realize the recycling of fluorine resources. The implementation of the system can improve the problems of incomplete fluorine treatment of primary fluidized bed process, high effluent turbidity, large amount of reagent addition and large equipment area, so that the fluidized bed technology for treating fluorine-containing wastewater has practical engineering value.

[0009] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0010] An integrated defluorination method based on fluidized bed, comprising the following steps:

[0011] The fluorine-containing wastewater is delivered to an inner fluidized bed bed body provided with fluorite seeds, and a composite calcium salt crystallization agent is input into the inner fluidized bed bed body to induce crystallization to generate fluorite, and primary fluorine removal is performed;

[0012] The wastewater after primary fluorine removal is delivered to an outer fluidized bed bed body provided with calcium fluorophosphate modified calcite seeds, and dipotassium hydrogen phosphate and sodium hydroxide are input into the outer fluidized bed bed body to perform secondary fluorine removal.

[0013] The wastewater after secondary fluorine removal is treated by the porous adsorption filler, and then delivered to a water outlet collection tank which is communicated with a hydrochloric acid storage tank.

[0014] Further, the wastewater after secondary fluorine removal is treated by the porous adsorption filler, and then a part of the water flows into the water outlet collection tank, and the remaining water enters the inner fluidized bed bed body under the action of a circulating pump.

[0015] Further, the preparation method of the composite calcium salt crystallization agent comprises the following steps: 10±1% calcium chloride solution and 1+0.1% calcium hydroxide solution are mixed in a molar ratio of 1:1.

[0016] Further, the preparation method of the calcium fluorophosphate modified calcite seed comprises the following steps: a dipotassium hydrogen phosphate solution, a calcium chloride solution and a sodium fluoride solution are mixed; the molar ratio of calcium ions, phosphate ions and fluoride ions is controlled to be 8-12:5:1, calcite seeds are added, calcium fluorophosphate is crystallized on the surface of the calcite seeds to form calcium fluorophosphate modified calcite seeds, supernatant is discharged after the reaction is completed and the precipitation is static, the dipotassium hydrogen phosphate solution, the calcium chloride solution and the sodium fluoride solution are added again, the above steps are repeated for multiple times, and the calcium fluorophosphate modified calcite seeds are taken out, washed and dried after the reaction is completed.

[0017] Further, the preparation method of the porous adsorption filler comprises the following steps: dolomite and kaolin are dried, ground, sieved, subjected to constant temperature heating and magnetic stirring, then hard stearic acid particles are added, fully mixed, granulated, dried and calcined to obtain the porous adsorption filler.

[0018] The application also provides an integrated fluorine removal system based on a fluidized bed, which is used for performing the above-mentioned integrated fluorine removal method based on a fluidized bed; the integrated fluorine removal system based on a fluidized bed comprises an outer fluidized bed bed body and an inner fluidized bed bed body; the outer fluidized bed bed body and the inner fluidized bed bed body are connected through an inner cylinder drainage pipeline or a circulating pump; the inner fluidized bed bed body is connected with a water outlet of a wastewater pool and a composite calcium salt storage tank, the outer fluidized bed bed body is connected with water outlets of a dipotassium hydrogen phosphate storage tank and a sodium hydroxide storage tank, a water outlet of the outer fluidized bed bed body is connected with a water outlet collection tank and the inner fluidized bed bed body, and the water outlet of the outer fluidized bed bed body is provided with an adsorption layer, and the adsorption layer is provided with a porous adsorption filler.

[0019] Further, the wastewater tank is filled with fluorine-containing wastewater, and a raw water lifting pump is arranged at the outlet of the wastewater tank to pump the fluorine-containing wastewater into the built-in fluidized bed body; the dibasic potassium phosphate storage tank is filled with potassium dihydrogen phosphate solution, and a dibasic potassium phosphate metering pump is arranged at the water outlet of the dibasic potassium phosphate storage tank to control the flow rate of the potassium dihydrogen phosphate solution; the sodium hydroxide storage tank is filled with sodium hydroxide solution, and a sodium hydroxide metering pump is arranged at the water outlet of the sodium hydroxide storage tank to control the flow rate of the sodium hydroxide solution; the composite calcium salt storage tank is provided with a composite calcium salt crystallization agent, and a composite calcium salt metering pump is arranged at the water outlet of the composite calcium salt storage tank to control the flow rate of the composite calcium salt crystallization agent; and the hydrochloric acid storage tank is filled with hydrochloric acid, and a hydrochloric acid metering pump is arranged at the water outlet of the hydrochloric acid storage tank to control the flow rate of the hydrochloric acid solution.

[0020] Further, the bottom of the built-in fluidized bed body is provided with a first crystallization discharge port and a second crystallization discharge port, the first crystallization discharge port is used to discharge the fluorite crystals formed by the fluorine-containing wastewater in the wastewater tank and the composite calcium salt crystallization agent in the composite calcium salt storage tank, and the second crystallization discharge port is used to discharge the calcium fluorophosphate crystals.

[0021] Further, the water outlet collecting tank is connected with the water outlet of the hydrochloric acid storage tank.

[0022] Further, a buffer zone and a settling zone are arranged above the external fluidized bed body to reduce the flow rate of the water flow. Beneficial effects

[0023] (1) The traditional fluorine removal fluidized bed usually adopts a Woerden, Amsterdam type single-cylinder fluidized bed, and the effluent concentration of the treated high-concentration fluorine-containing wastewater is high, and a subsequent deep fluorine removal unit is needed to achieve standard discharge, which occupies a large area and has poor effluent effect. The patent constructs a double-cylinder integrated fluidized bed defluorination system, which combines high-concentration fluorine-containing wastewater defluorination and deep defluorination into an integrated system. The inner cylinder adopts a fluorite induced crystallization technology, and the fluorine content in the high-concentration fluorine-containing wastewater is reduced from about 800 mg / L to about 10-20 mg / L by adding a composite calcium salt crystallization agent, and the effluent of the inner cylinder enters the outer cylinder of the fluidized bed under the action of 4 drainage pipes. The outer cylinder fluidized bed uses modified calcite as a crystal seed and dibasic potassium phosphate as a crystallization agent for deep defluorination, and the effluent fluorine concentration can be <1 mg / L. Compared with the traditional single fluidized bed defluorination system, about 50% of the land area can be saved, and about 20% of the defluorination reagent usage can be saved.

[0024] (2) For low concentration of fluoride wastewater with fluoride concentration <20 mg / L after primary treatment, usually add fluoride removal agent for advanced treatment, these treatment methods need to add a large amount of agent to ensure that the effluent fluoride is reduced to below 2 mg / L, and also produce solid waste such as fluoride-containing sludge, causing secondary pollution. In addition, low concentration of fluoride wastewater after primary treatment with calcium salt still contains 200~300 mg / L of Ca 2+ , which also needs further treatment. This patent uses fluorapatite with low solubility product and easy to reach the required supersaturation for precipitation as the seed of modified calcite, di-potassium hydrogen phosphate as the phosphorus source, and the residual Ca 2+ in the wastewater as the calcium source, to induce crystallization of the effluent from the inner cylinder fluidized bed, realizing deep fluoride removal of the wastewater, and also fully utilizing Ca 2+ . When the phosphate precipitant is added to the effluent from the inner cylinder, it reacts with Ca 2+ and F - in the wastewater, the fluorapatite on the surface of the modified calcite provides active sites, promoting the newly generated precipitate to nucleate on it for secondary nucleation, and the F - concentration in the effluent after treatment can be <1 mg / L. Compared with traditional deep fluoride removal by adding fluoride removal agent, deep fluoride removal by fluorapatite induced crystallization has better fluoride removal effect and does not produce solid waste such as fluoride-containing sludge.

[0025] (3) In order to effectively remove fluoride ions, the fluoride ions and calcium ions in the solution must reach supersaturation, which means that the amount of calcium and phosphorus precipitant must be higher than the Ca / P / F composition of Ca5(PO4)3F, and the excess Ca 2+ and PO4 3- cannot be utilized and remain in the solution, and the wastewater after secondary treatment by the outer cylinder still contains more than 100 mg / L of Ca 2+ and more than 30 mg / L of residual phosphorus. The high calcium and phosphorus content in the effluent increases the difficulty of subsequent treatment. This patent developed a porous adsorption filler to adjust the pH of the wastewater to 10~12 with NaOH, to treat the residual Ca 2+ and PO4 3- in the solution after fluorapatite induced crystallization. When the residual Ca 2+ and PO4 3- pass through the filler, Ca3(PO4)2 precipitate is generated under alkaline conditions, and the porous structure of the filler itself has adsorption effect, which can make the Ca3(PO4)2 precipitate be adsorbed, and the final effluent Ca 2+ concentration is <30 mg / L, and PO4 3-<0.2mg / L. When the filler is saturated with adsorption, the adsorbed Ca3(PO4)2 can be removed by treating the filler with 4% HCl, and then pre-treating with alkali to regenerate the adsorption filler. The use of porous adsorption filler solves the problem of high calcium and phosphorus content in the effluent, which affects subsequent treatment. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Process flow chart of integrated fluorine removal system.

[0027] Reference signs: 1, wastewater pool; 2, dipotassium hydrogen phosphate storage tank; 3, sodium hydroxide storage tank; 4, raw water lifting pump; 5, dipotassium hydrogen phosphate metering pump; 6, sodium hydroxide metering pump; 7, circulating pump; 8, first crystallization discharge port; 9, second crystallization discharge port; 10, inner cylinder drainage pipeline; 11, external fluidized bed bed body; 12, reaction zone; 13, buffer zone; 14, adsorption layer; 15, sedimentation zone; 16, internal fluidized bed bed body; 17, composite calcium salt storage tank; 18, composite calcium salt metering pump; 19, effluent collection pool; 20, hydrochloric acid metering pump; 21, hydrochloric acid storage tank. DETAILED DESCRIPTION

[0028] An integrated fluorine removal system based on fluidized bed, comprising an external fluidized bed bed body 11 and an internal fluidized bed bed body 16; the external fluidized bed bed body 11 and the internal fluidized bed bed body 16 are connected through an inner cylinder drainage pipeline 10 or a circulating pump 7; the internal fluidized bed bed body 16 is connected with the effluent outlet of a wastewater pool 1 and a composite calcium salt storage tank 17, the external fluidized bed bed body 11 is connected with the effluent outlet of a dipotassium hydrogen phosphate storage tank 2 and a sodium hydroxide storage tank 3, the effluent outlet of the external fluidized bed bed body 11 is connected with an effluent collection pool 19 and the internal fluidized bed bed body 16, and the effluent outlet of the external fluidized bed bed body 11 is provided with an adsorption layer 14, and the adsorption layer 14 is provided with porous adsorption filler.

[0029] The wastewater pool 1 contains fluorine-containing wastewater, the outlet of the wastewater pool 1 is provided with a raw water lifting pump 4 for pumping the fluorine-containing wastewater into the internal fluidized bed bed body 16; the dipotassium hydrogen phosphate storage tank 2 contains potassium dihydrogen phosphate solution, and the effluent outlet of the dipotassium hydrogen phosphate storage tank 2 is provided with a dipotassium hydrogen phosphate metering pump 5 for controlling the flow rate of the potassium dihydrogen phosphate solution; the sodium hydroxide storage tank 3 contains sodium hydroxide solution, and the effluent outlet of the sodium hydroxide storage tank 3 is provided with a sodium hydroxide metering pump 6 for controlling the flow rate of the sodium hydroxide solution; the composite calcium salt storage tank 17 is provided with a composite calcium salt crystallizing agent, and the effluent outlet of the composite calcium salt storage tank 17 is provided with a composite calcium salt metering pump 18 for controlling the flow rate of the composite calcium salt crystallizing agent; the hydrochloric acid storage tank 21 contains hydrochloric acid, and the effluent outlet of the hydrochloric acid storage tank 21 is provided with a hydrochloric acid metering pump 20 for controlling the flow rate of the hydrochloric acid solution.

[0030] The bottom of the built-in fluidized bed body 16 is provided with a first crystalline discharge port 8 for discharging fluorite crystals and a second crystalline discharge port 9 for discharging calcium fluorophosphate crystals. The water outlet collection tank 19 is connected to the water outlet of the hydrochloric acid storage tank 21.

[0031] The bottom of the built-in fluidized bed body 16 extends in part to provide water inlet, medicine inlet pipeline and crystalline discharge port. The top of the built-in fluidized bed body 16 is provided with a cover for sealing, and about 5 cm below the top, two water outlet pipelines are arranged on the left and right sides respectively. The water after the first-stage defluorination of the built-in fluidized bed body 16 flows into the bottom of the external fluidized bed body 11 along the pipelines. The upward flow rate = water inlet flow rate / water inlet area, and it is necessary to control the upward flow rates of the built-in fluidized bed body 16 and the external fluidized bed body 11 to be consistent, so the diameter of the external fluidized bed body 11 is set to be 1.41 times the diameter of the built-in fluidized bed body 16. The middle part of the external fluidized bed body and the built-in fluidized bed body is provided with a reaction zone 12 for defluorination reaction and crystallization. The buffer zone 13 and the sedimentation zone 15 are arranged above the external fluidized bed body 11 to reduce the flow rate of the water flow and allow the crystal seeds to settle and not be washed out by the water flow. The height of the buffer zone 13 is half of the height of the sedimentation zone 15, and the diameter of the sedimentation zone 15 is 1.5 times the diameter of the reaction zone 12. The sedimentation zone 15 is provided with a layer of porous adsorption filler for removing residual phosphate and reducing the turbidity of the outlet water. A reflux pipeline is installed above the filler to reflux the water after the defluorination of the external cylinder to the bottom of the built-in fluidized bed body 16.

[0032] Preparation method of composite calcium salt crystallization agent: the composite calcium salt crystallization agent is prepared by mixing 10% calcium chloride solution and 1% calcium hydroxide solution in a molar ratio of 1:1 (the above percentages are mass percentages).

[0033] Preparation method of calcium fluorophosphate modified calcite seed: first, 5L of 0.5 mol / L dipotassium hydrogen phosphate solution, 5L of 1 mol / L calcium chloride solution and 25L of 0.5 mmol / L sodium fluoride solution are prepared by using ultrapure water. The molar ratio of calcium ions, phosphate ions and fluoride ions is controlled to be 10:5:1, and the 0.5 mmol / L sodium fluoride solution is added to the 5L beaker with dipotassium hydrogen phosphate and calcium chloride solution for reaction. The calcite seed is added, the reaction water temperature is controlled to be stable at 25℃, the reaction time is 1h, the calcium fluorophosphate is crystallized on the surface of the calcite seed to form the calcium fluorophosphate modified calcite seed, and the supernatant is discharged after standing and precipitating for 30 min. The raw water containing fluorine, dipotassium hydrogen phosphate and calcium chloride solution are added again, and the above steps are repeated for 6 times. After the reaction is completed, the calcium fluorophosphate modified calcite seed is taken out, washed with ultrapure water for 3 times, then put into a 105~110℃ air drying oven for drying for 12 h, taken out and packed.

[0034] Preparation method of porous adsorption filler: taking dolomite as main raw material, kaolin as binder and stearic acid as pore forming agent to prepare porous adsorption filler. After drying and grinding, the dolomite and kaolin are sieved through a 200 mesh sieve. 30 g of dolomite and 20 g of kaolin are placed in a 70℃ constant temperature heating magnetic stirrer. 7% stearic acid particles are added to the mixed material, and then stirred uniformly. The granulator speed is set to 60r / min for granulation. A small amount of 10-15 mL ultrapure water is added to make it easier to form in the rolling process. After the ball is formed, the raw material ball with a particle size of 5-11 mm is sieved and dried in an electric heating constant temperature air oven. After drying, it is transferred to a high temperature box furnace with a heating rate of 10℃ / min for calcination. After calcination, it is cooled to room temperature for 120 min to obtain the porous adsorption filler.

[0035] Specific operation process: fluorite with a purity of 85-95% and a particle size of 100-120 mesh is added to the built-in fluidized bed body 16 as a crystal seed, and the fluorite also contains 5-15% of silicon dioxide and calcium carbonate, and the crystal seed has a stacking height of 15 cm. The calcium fluoride modified calcite crystal seed is added to the external fluidized bed body 11, and the crystal seed has a stacking height of 15 cm. The high-concentration fluorine-containing wastewater in the wastewater tank 1 is transported to the built-in fluidized bed body 16 by the raw water lifting pump 4 at a flow rate of 0.5 m 3 / h. The composite calcium salt crystallization agent in the composite calcium salt storage tank 17 reacts with the fluorine-containing wastewater under the transportation of the composite calcium salt metering pump 18 to induce the formation of fluorite crystals. The fluorine-containing wastewater after reaction in the built-in fluidized bed body 16 flows into the bottom of the external fluidized bed body 11 from the inner cylinder drainage pipeline 10. The potassium dihydrogen phosphate in the potassium hydrogen phosphate storage tank 2 enters the external fluidized bed body 11 under the action of the potassium hydrogen phosphate metering pump 5. The sodium hydroxide in the sodium hydroxide storage tank 3 enters the external fluidized bed body 11 under the action of the sodium hydroxide metering pump 6, and the low-concentration fluorine-containing wastewater is subjected to deep fluorine removal reaction. The wastewater after deep fluorine removal reaction flows through the adsorption layer 14, and the residual PO4 3- and Ca 2+ small molecules are effectively intercepted. Part of the effluent flows into the effluent collection tank 19, and part of the effluent enters the built-in fluidized bed body 16 under the action of the circulating pump 7. The circulating pump functions to dilute the high-concentration influent with the low-concentration effluent to reduce the supersaturation degree and make the reaction more complete. The hydrochloric acid metering pump 20 introduces hydrochloric acid in the hydrochloric acid storage tank 21 into the effluent collection tank 19 to neutralize the effluent with a pH of 9-10. When the equipment is discharged, the first crystal discharge port 8 at the bottom of the built-in fluidized bed 16 is opened to discharge fluorite crystals, and the second crystal discharge port 9 at the bottom of the external fluidized bed 11 is opened to discharge calcium fluoride phosphate crystals. Example

[0036] A certain photovoltaic factory in Hebei Province: fluorine ion concentration 800~1200mg / L, pH 1.3, silicon 160mg / L, ammonia nitrogen 103.7mg / L, chloride 35.9mg / L, sulfate ion 162.2mg / L, water volume 2m 3 / h, running time 24h.

[0037] The specific implementation steps of the synchronous recovery system are as follows:

[0038] (1) The dipotassium hydrogen phosphate is loaded into the dipotassium hydrogen phosphate storage tank 2; the sodium hydroxide is loaded into the sodium hydroxide storage tank 3; and the composite calcium salt crystallization agent is loaded into the composite calcium salt storage tank 17.

[0039] (2) The fluorite seed is put into the built-in fluidized bed bed body 16; and the calcium fluoro-phosphate modified calcite seed is added to the external fluidized bed bed body 11.

[0040] (3) The high-concentration fluorine-containing wastewater in the wastewater pool 1 is transported to the built-in fluidized bed bed body 16 by the raw water lifting pump 4 at a flow rate of 2m 3 / h, and the composite calcium salt crystallization agent in the composite calcium salt storage tank 17 is transported under the composite calcium salt metering pump 18 to react with the fluorine-containing wastewater to induce the formation of fluorite.

[0041] (4) The fluorine-containing wastewater after reaction in the built-in fluidized bed bed body 16 flows into the bottom of the external fluidized bed bed body 11 from the inner cylinder drain pipe 10, the dipotassium hydrogen phosphate in the dipotassium hydrogen phosphate storage tank 2 enters the external fluidized bed bed body 11 under the action of the metering pump 5, and the sodium hydroxide in the sodium hydroxide storage tank 3 enters the external fluidized bed bed body 11 under the action of the sodium hydroxide metering pump 6 to carry out deep defluorination reaction with the low-concentration fluorine-containing wastewater. After the deep defluorination reaction, the wastewater flows through the adsorption layer 14, and the residual PO4 3- and Ca 2+ small molecules in the wastewater are effectively intercepted, part of the effluent flows into the effluent collection pool 19, and part of the effluent enters the built-in fluidized bed bed body 16 under the action of the circulating pump 7. The hydrochloric acid metering pump 20 introduces the hydrochloric acid in the hydrochloric acid storage tank 21 into the effluent collection pool 19 to neutralize the effluent with pH of 9~10.

[0042] (5) The first crystallization discharge port 8 at the bottom of the built-in fluidized bed bed body 16 is opened to discharge fluorite crystals, and the second crystallization discharge port 9 at the bottom of the external fluidized bed bed body 11 is opened to discharge calcium fluoro-phosphate crystals.

[0043] Treatment conclusion: After the integrated defluorination system treatment, the F- concentration of the fluorine-containing wastewater raw water is reduced to 0.5~1.0mg / L, the Ca 2+ concentration of the effluent is <30mg / L, and the PO4 3- concentration is <0.2mg / L; the purity of the recovered fluorite and calcium fluoro-phosphate is >85%.

[0044] Comparative Example 1:

[0045] Comparative Example 1 provides a secondary mixed treatment system for treating the waste acidic cleaning liquid from a certain photovoltaic factory in Hebei Province described in Example 1. The wastewater quality is as follows: fluoride ion concentration 800-1200 mg / L, pH 1.3, silicon 160 mg / L, ammonia nitrogen 103.7 mg / L, chloride ion 35.9 mg / L, and sulfate ion 162.2 mg / L.

[0046] The specific treatment steps are as follows:

[0047] (1) The fluoride-containing raw wastewater is directly added with 10% mass concentration of calcium hydroxide for primary treatment, and the fluoride concentration of the effluent is reduced to 10-20 mg / L;

[0048] (2) 10% mass concentration of PAC (polyaluminum chloride) is added to the primary fluoride-containing wastewater for secondary treatment, and the fluoride concentration of the effluent is reduced to 5-6 mg / L;

[0049] The treatment conclusion is that after the fluoride-containing wastewater is treated by the mixed treatment, the fluoride ion concentration is 5-6 mg / L, the Ca 2+ concentration is 200-300 mg / L, and the purity of the fluoride-containing sludge is <40%, which has no recycling value.

[0050] Comparative Example 2:

[0051] Comparative Example 2 provides a single-pole fluorite fluidized bed defluorination system for treating the waste acidic cleaning liquid from a certain photovoltaic factory in Hebei Province described in Example 1. The wastewater quality is as follows: fluoride ion concentration 800-1200 mg / L, pH 1.3, silicon 160 mg / L, ammonia nitrogen 103.7 mg / L, chloride ion 35.9 mg / L, and sulfate ion 162.2 mg / L.

[0052] The specific treatment steps are as follows:

[0053] (1) Fluorite seed with 90% purity of calcium fluoride is added to the single-pole fluorite fluidized bed defluorination system;

[0054] (2) The fluoride-containing raw wastewater is directly added with 10% mass concentration of calcium hydroxide for induced crystallization;

[0055] The treatment conclusion is that after the fluoride-containing wastewater is treated by the single-pole fluorite fluidized bed, the fluoride ion concentration is 15-20 mg / L, the Ca 2+ concentration is 200-300 mg / L, and compared with the inner cylinder fluidized bed in Example 1, the calcium salt consumption exceeds 20%.

[0056] Comparative Example 3:

[0057] The comparative example 3 provides a deep fluorine removal system based on fluidized bed, which is used to treat the first-stage fluorine removal effluent of the chemical mixing of the Hebei photovoltaic factory. The wastewater quality is as follows: the fluorine ion concentration is 15-20 mg / L, and the pH is 7.3.

[0058] The specific treatment steps are as follows:

[0059] (1) The first-stage fluorine removal effluent of the chemical mixing is treated by adding sodium phosphate dibasic and calcium chloride in a ratio of Ca: P: F = 10: 5: 1, respectively, for deep fluorine removal;

[0060] (2) 10% mass concentration of liquid alkali is added to the effluent treated by the fluidized bed deep fluorine removal system, for Ca and P precipitation;

[0061] The treatment conclusion is as follows: after the fluorine-containing wastewater is treated by the fluidized bed deep fluorine removal system, the fluorine ion concentration is reduced to 2-3 mg / L, the Ca 2+ concentration is 50-70 mg / L, and the PO4 3- concentration is about 4-5 mg / L. The comparative example 3 is used to compare the effect of deep fluorine removal. The fluorine removal effect of the comparative example 3 is poor. In addition, only liquid alkali is used for Ca and P precipitation, and the removal effect is not complete. A large amount of Ca 2+ and PO4 3- still remains in the effluent.

[0062] As can be seen from the above examples and comparative examples, the integrated fluorine removal method and system based on the fluidized bed provided by the present application combines high-concentration fluorine-containing wastewater fluorine removal and deep fluorine removal into one, which can effectively improve the wastewater treatment effect: the fluorine concentration of the effluent is <1.0 mg / L, the Ca 2+ concentration of the effluent is <30 mg / L, and the PO4 3- concentration is <0.2 mg / L; the use amount of fluorine removal reagent can be saved by 20% by using composite calcium salt crystallization. The fluorine-containing sludge yield is reduced by adding fluorite seed and modified calcite seed for induced crystallization, and the fluorine resources are effectively recovered. The purity of the recovered fluorite and calcium fluoride phosphate is >85%. The integrated fluorine removal system combines high-concentration fluorine-containing wastewater fluorine removal and deep fluorine removal into one, and the land area is saved by about 50%.

[0063] For those skilled in the art, some modifications can be directly derived or inferred from the patent concept and specific examples, and the ordinary skilled in the art will realize that other methods or commonly known technologies in the prior art can be used instead, and the dosage of the added reagent, the reaction time and other parameters can be changed, or slightly exceed the range, and other non-essential changes can also be applied, which can achieve the functions and effects described in the patent and will not be described in detail. All of the above are within the protection scope of the present patent.

Claims

1. An integrated defluorination method based on fluidized bed, characterized in that, It comprises the following steps: The fluorine-containing wastewater is transported to the built-in fluidized bed bed body provided with fluorite seeds, and a composite calcium salt crystallization agent is input into the built-in fluidized bed bed body to induce crystallization to generate fluorite, and primary fluorine removal is performed; The wastewater after primary fluorine removal is transported to the external fluidized bed bed body provided with calcium fluoride phosphate modified calcite seeds, and dipotassium hydrogen phosphate and sodium hydroxide are input into the external fluidized bed bed body to perform secondary fluorine removal; The wastewater after secondary fluorine removal is transported to the effluent collection tank after being treated by the porous adsorption filler, and the effluent collection tank is communicated with the hydrochloric acid storage tank. The preparation method of the composite calcium salt crystallization agent comprises: mixing 10±1% calcium chloride solution and 1+0.1% calcium hydroxide solution at a molar ratio of 1:1; The preparation method of the calcium fluoride phosphate modified calcite seed comprises: mixing dipotassium hydrogen phosphate solution, calcium chloride solution and sodium fluoride solution; the molar ratio of calcium ions, phosphate ions and fluoride ions is controlled to be 8-12:5:1, calcite seeds are added, calcium fluoride phosphate is crystallized on the surface of the calcite seeds to form calcium fluoride phosphate modified calcite seeds, and the supernatant is discharged after the reaction is completed and the precipitation is static; dipotassium hydrogen phosphate solution, calcium chloride solution and sodium fluoride solution are added again, and the above steps are repeated for multiple times, and the calcium fluoride phosphate modified calcite seeds are taken out after the reaction is completed, and are washed and dried; The preparation method of the porous adsorption filler comprises: drying and grinding dolomite and kaolin, sieving, constant-temperature heating and magnetic stirring, adding stearic acid particles, fully mixing, granulating, drying and baking to obtain the porous adsorption filler.

2. The fluidized bed-based integrated defluorination method according to claim 1, characterized by, After the wastewater after secondary fluorine removal is treated by the porous adsorption filler, part of the effluent flows into the effluent collection tank, and the remaining effluent enters the built-in fluidized bed bed body under the action of the circulating pump.

3. A fluidized bed-based integrated defluorination system, characterized by, The integrated fluorine removal system based on the fluidized bed is used to perform the integrated fluorine removal method based on the fluidized bed in claims 1 or 2; the integrated fluorine removal system based on the fluidized bed comprises an external fluidized bed bed body and a built-in fluidized bed bed body; the external fluidized bed bed body and the built-in fluidized bed bed body are connected through an inner cylinder drainage pipeline or a circulating pump; the built-in fluidized bed bed body is connected with the effluent outlet of the wastewater tank and the composite calcium salt storage tank, the external fluidized bed bed body is connected with the effluent outlet of the dipotassium hydrogen phosphate storage tank and the sodium hydroxide storage tank, the effluent outlet of the external fluidized bed bed body is connected with the effluent collection tank and the built-in fluidized bed bed body, and the effluent outlet of the external fluidized bed bed body is provided with an adsorption layer, and the adsorption layer is provided with the porous adsorption filler.

4. The fluidized bed based integrated defluorination system according to claim 3, wherein, The wastewater tank is filled with fluorine-containing wastewater, and a raw water lifting pump is arranged at the outlet of the wastewater tank to pump the fluorine-containing wastewater into the built-in fluidized bed body; the dipotassium hydrogen phosphate storage tank is filled with dipotassium hydrogen phosphate solution, and a dipotassium hydrogen phosphate metering pump is arranged at the water outlet of the dipotassium hydrogen phosphate storage tank to control the flow rate of the dipotassium hydrogen phosphate solution; the sodium hydroxide storage tank is filled with sodium hydroxide solution, and a sodium hydroxide metering pump is arranged at the water outlet of the sodium hydroxide storage tank to control the flow rate of the sodium hydroxide solution; the composite calcium salt storage tank is provided with a composite calcium salt crystallization agent, and a composite calcium salt metering pump is arranged at the water outlet of the composite calcium salt storage tank to control the flow rate of the composite calcium salt crystallization agent; and the hydrochloric acid storage tank is filled with hydrochloric acid, and a hydrochloric acid metering pump is arranged at the water outlet of the hydrochloric acid storage tank to control the flow rate of the hydrochloric acid solution.

5. The fluidized bed based integrated defluoridation system as claimed in claim 3, wherein, The bottom of the built-in fluidized bed body is provided with a first crystallization discharge port and a second crystallization discharge port, the first crystallization discharge port is used to discharge fluorite crystals formed by the fluorine-containing wastewater in the wastewater tank and the composite calcium salt crystallization agent in the composite calcium salt storage tank, and the second crystallization discharge port is used to discharge calcium fluophosphate crystals.

6. The fluidized bed based integrated defluoridation system as claimed in claim 3, wherein, The water outlet collecting tank is connected with the water outlet of the hydrochloric acid storage tank.

7. The fluidized bed based integrated defluoridation system as claimed in claim 3, wherein, The top of the external fluidized bed body is provided with a buffer zone and a sedimentation zone to reduce the flow rate of water flow.

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