Production system for producing fluoride salt particles from fluorine-containing wastewater

Abstract

The present invention discloses a production system for producing fluoride salt particles from fluorine-containing wastewater, which includes a preheater for heating high-concentration fluorine-containing wastewater, a seed mixing tank, a fluoride salt crystallizer, a slurry pump, a seed dosing device, and a precipitant dosing device. The fluorine-containing wastewater drain outlet of the preheater is communicated with the preheated wastewater inlet of the seed mixing tank through a pipeline. Induced seeds can be added into the seed mixing tank through the seed feed inlet. The slurry pump discharges the mixed wastewater in the seed mixing tank into the fluoride salt crystallizer through a pipeline. The precipitant can be input into the fluoride salt crystallizer through the precipitant dosing port. The fluoride salt crystal discharge port is located at the lower end of the fluoride salt crystallizer, and the fluoride salt crystal discharge port can discharge fluoride salt crystals outwards. The present invention realizes the direct use of high-concentration fluorine-containing wastewater for producing fluoride salt particles without dilution, and the obtained fluoride salt particles have large particle size, plump particles, and no broken slag, greatly improving the treatment efficiency of high-concentration fluorine-containing wastewater and the quality of fluoride salt particles.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a production system for producing fluoride salt particles from fluoride-containing wastewater. Background Art

[0002] Industrially, the treatment of fluoride-containing wastewater often uses the coagulation precipitation method. For example, precipitation agents such as calcium and sodium are added to the wastewater to convert fluoride ions into fluoride salt precipitates such as calcium fluoride and sodium fluoride. Since it is necessary to control the fluoride ion concentration in the discharged water, an excessive amount of precipitation agent often needs to be added. Therefore, the fluoride salt sludge such as calcium fluoride and sodium fluoride generated contains an excessive amount of calcium salt or sodium salt, and these salts are closely symbiotic with the fluoride salt and are difficult to separate, which restricts the resource recycling of the fluoride salt.

[0003] Applying a fluidized bed crystallizer to treat fluoride-containing wastewater can reduce the dosage of the precipitation agent, and the produced fluoride salt particles have high grade and low water content. The existing fluidized bed crystallizer is only suitable for treating low-concentration fluoride-containing wastewater. Under the condition of high fluoride ion concentration (generally, when the fluoride ion concentration in the wastewater reaches more than 1000 ppm, it is high-concentration fluoride-containing wastewater), it needs to be diluted to obtain a better crystallization effect. After dilution, the volume of the fluoride-containing wastewater is large, occupying a large storage space, and when performing fluidized bed crystallization treatment, it takes a long time and has low efficiency. Summary of the Invention

[0004] In order to overcome the above defects, the present invention provides a production system for producing fluoride salt particles from fluoride-containing wastewater. The production system for producing fluoride salt particles from fluoride-containing wastewater can achieve efficient treatment of high-concentration fluoride-containing wastewater, and the obtained fluoride salt particles have high purity, and can realize the resource recovery and utilization of the fluoride salt.

[0005] The technical solution adopted by the present invention to solve its technical problems: A production system for producing fluoride salt particles from fluoride-containing wastewater includes a preheater, a seed mixing tank, a fluoride salt crystallizer, a slurry pump, a seed feeding device, and a precipitant feeding device. The preheater is provided with a fluoride-containing wastewater inlet and a fluoride-containing wastewater outlet. The seed mixing tank is provided with a preheated wastewater inlet, a seed inlet, and a mixed wastewater outlet. The fluoride salt crystallizer is provided with a mixed wastewater inlet, a precipitant feeding port, and a fluoride salt crystal discharge port. The preheater can heat the high-concentration fluoride-containing wastewater therein. The fluoride-containing wastewater outlet of the preheater is communicated with the preheated wastewater inlet on the seed mixing tank through a pipeline. The induced seed can be fed into the seed mixing tank through the seed inlet. The slurry pump discharges the mixed wastewater in the seed mixing tank into the fluoride salt crystallizer through the mixed wastewater outlet and the mixed wastewater inlet through a pipeline. The precipitant can be fed into the fluoride salt crystallizer through the precipitant feeding port. The fluoride salt crystal discharge port is located at the lower end of the fluoride salt crystallizer, and the fluoride salt crystal discharge port can discharge the fluoride salt crystals outwards.

[0006] As a further improvement of the present invention, a stirrer is provided in the seed mixing tank, and the stirring blades of the stirrer can rotate and stir in the seed mixing tank.

[0007] As a further improvement of the present invention, the fluoride salt crystallizer includes a crystallization reaction chamber, a feed mixing chamber, and a crystallization discharge chamber. The feed mixing chamber is fixedly arranged at the upper end of the crystallization reaction chamber, and the crystallization discharge chamber is fixedly arranged at the lower end of the crystallization reaction chamber. A number of conical tube bundles arranged in parallel at intervals in the vertical direction are fixedly arranged in the crystallization reaction chamber. The inner diameter of the upper end of the conical tube bundle is larger than that of the lower end, and a sealed space is formed between the outer side wall of the conical tube bundle and the inner side wall of the crystallization reaction chamber. The upper openings of each conical tube bundle communicate with the feed mixing chamber, and the lower openings of each conical tube bundle communicate with the crystallization discharge chamber. The fluoride salt crystallization discharge port is located at the lower end of the crystallization discharge chamber, and the mixed wastewater inlet and the precipitant dosing port are respectively located on the feed mixing chamber.

[0008] As a further improvement of the present invention, a fluorine-containing wastewater water distribution pipe and a precipitant dosing pipe are also fixedly arranged in the feed mixing chamber. The fluorine-containing wastewater water distribution pipe includes a main water distribution pipe and a branch water distribution pipe. One end of the main water distribution pipe communicates with the mixed wastewater inlet on the side wall of the feed mixing chamber. The branch water distribution pipe extends in the horizontal direction to form an annular pipe structure. The branch water distribution pipe and the main water distribution pipe are communicated to form an integral structure. A number of water distribution holes are arranged on the side wall of the branch water distribution pipe. The mixed wastewater entering the branch water distribution pipe can enter the feed mixing chamber through each water distribution hole. The precipitant dosing pipe includes a main dosing pipe and a branch dosing pipe. One end of the main dosing pipe communicates with the precipitant dosing port on the side wall of the feed mixing chamber. The branch dosing pipe extends in the horizontal direction to form an annular pipe structure. The branch dosing pipe and the main dosing pipe are communicated to form an integral structure. A number of dosing holes are arranged on the side wall of the branch dosing pipe. The precipitant entering the branch dosing pipe can enter the feed mixing chamber through each dosing hole. The branch water distribution pipe and the branch dosing pipe are arranged at intervals in the vertical direction, and the water distribution holes and the dosing holes are arranged in one-to-one correspondence.

[0009] As a further improvement of the present invention, a water distribution spray head is fixedly installed on the water distribution hole, and a dosing spray head is fixedly installed on the dosing hole. The water distribution spray head and the dosing spray head are arranged in a one-to-one spraying manner.

[0010] As a further improvement of the present invention, at least two water distribution branch pipes with different diameters are arranged concentrically at intervals, and each water distribution branch pipe is respectively communicated with the main water distribution pipe. At least two dosing branch pipes with different diameters are arranged concentrically at intervals, and each dosing branch pipe is respectively communicated with the main dosing pipe. The projections of the water distribution branch pipe and the dosing branch pipe on the horizontal plane are in a nested ring structure arranged in a staggered manner.

[0011] As a further improvement of the present invention, a first steam inlet and a first condensate drain outlet are further provided on the side wall of the crystallization reaction chamber. The first steam inlet is communicated with an external steam supply pipeline, and the first condensate drain outlet can discharge the condensate in the crystallization reaction chamber. A secondary steam discharge outlet is further provided on the feed mixing chamber, and the steam generated by the evaporation of the high-concentration fluorine-containing wastewater solvent in the conical tube bundle can be discharged through the secondary steam discharge outlet on the feed mixing chamber for reuse.

[0012] As a further improvement of the present invention, a compressed air inlet is further provided on the feed mixing chamber. The compressed air inlet is connected to a compressed air generating device through a pipeline, and the compressed air generating device can supply compressed air to the feed mixing chamber in a pulsed manner.

[0013] As a further improvement of the present invention, the preheater includes a preheating housing, a heat exchanger, a second steam inlet and a second condensate drain outlet. The fluorine-containing wastewater inlet is located on the upper side wall of the preheating housing, and the fluorine-containing wastewater drain outlet is located on the lower side wall of the preheating housing. A cavity for accommodating high-concentration fluorine-containing wastewater is formed inside the preheating housing. The heat exchanger is fixedly arranged inside the preheating housing. The second steam inlet and the second condensate drain outlet are respectively located at both ends of the heat exchanger. The second steam inlet is communicated with an external steam supply pipeline, and the second condensate drain outlet can discharge the condensate in the heat exchanger to the outside of the preheating housing.

[0014] The beneficial effects of the present invention are as follows: The present invention preheats the high-concentration fluorine-containing wastewater through a preheater so that it can obtain a relatively high initial temperature before entering the fluoride salt crystallizer. Before the high-concentration fluorine-containing wastewater enters the fluoride salt crystallizer, the induction seeds are evenly distributed in the high-concentration fluorine-containing wastewater through the seed mixing tank, so as to provide more reaction contact surfaces for the subsequent fluoride salt crystallization process. After the high-concentration fluorine-containing wastewater mixed with the induction seeds enters the fluoride salt crystallizer, in the presence of the initial induction seeds, the cations in the high-concentration fluorine-containing wastewater react with the precipitation agent to generate fluoride salts. The steam continuously entering the crystallization reaction chamber of the fluoride salt crystallizer exchanges heat with the fluoride salt solution in the conical tube bundle, evaporating the solvent in the fluoride salt solution into water vapor. Along with the reduction of the solvent in the fluoride salt solution, the supersaturation of the fluoride salt increases from top to bottom in the conical tube bundle. When the fluoride salt reaches the lower end of the conical tube bundle, it will precipitate crystals on the surface of the induction seeds. The present invention combines induced crystallization nucleation and evaporation crystallization, greatly improving the crystallization efficiency of fluoride salts. The concentration of the fluoride salt solution forms a gradient from top to bottom through the conical tube bundle, which is more conducive to the crystallization of fluoride salts on the surface of the seeds. The inner wall of the conical tube bundle is also cleaned by pulsed compressed air, avoiding the blockage caused by the adhesion of fluoride salt crystals or precipitates on the inner side wall of the conical tube bundle. The present invention realizes the direct use of high-concentration fluorine-containing wastewater for the production of fluoride salt particles without dilution, and the obtained fluoride salt particles have large particle size, plump particles and no debris, greatly improving the treatment efficiency of high-concentration fluorine-containing wastewater and the quality of fluoride salt particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the production system for producing fluoride salt particles from fluorine-containing wastewater according to the present invention;

[0016] Figure 2 is a three-dimensional view of the fluoride salt crystallizer according to the present invention;

[0017] Figure 3 is the front view of the fluoride salt crystallizer according to the present invention;

[0018] Figure 4 is Figure 3 the cross-sectional view taken along the line A-A in

[0019] Figure 5 is a three-dimensional view of the internal structure of the crystallization reaction chamber of the fluoride salt crystallizer;

[0020] Figure 6 is a three-dimensional schematic diagram of the fluorine-containing wastewater distribution pipeline;

[0021] Figure 7 is a three-dimensional schematic diagram of the precipitation agent dosing pipeline. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solution of the present invention will be described in detail below through specific embodiments. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Embodiment: A production system for producing fluoride salt particles from fluorine-containing wastewater, comprising a preheater 1, a seed mixing tank 2, a fluoride salt crystallizer 3, a slurry pump 4, a seed addition device and a precipitant addition device. The preheater 1 is provided with a fluorine-containing wastewater inlet 11 and a fluorine-containing wastewater drain outlet 12. The seed mixing tank 2 is provided with a preheated wastewater inlet 21, a seed inlet 22 and a mixed wastewater drain outlet 23. The fluoride salt crystallizer 3 is provided with a mixed wastewater inlet 31, a precipitant addition port 32 and a fluoride salt crystal discharge outlet 33. The preheater 1 can heat the high-concentration fluorine-containing wastewater therein. The fluorine-containing wastewater drain outlet 12 of the preheater 1 is communicated with the preheated wastewater inlet 21 on the seed mixing tank 2 through a pipeline. The induced seed can be added into the seed mixing tank 2 through the seed inlet 22. The slurry pump 4 discharges the mixed wastewater in the seed mixing tank 2 into the fluoride salt crystallizer 3 through the mixed wastewater drain outlet 23 and the mixed wastewater inlet 31 through a pipeline. The precipitant can be put into the fluoride salt crystallizer 3 through the precipitant addition port 32. The fluoride salt crystal discharge outlet 33 is located at the lower end of the fluoride salt crystallizer 3, and the fluoride salt crystal discharge outlet 33 can discharge the fluoride salt crystals outwards.

[0024] The high-concentration fluorine-containing wastewater enters the preheater 1 through the fluorine-containing wastewater inlet 11. The preheater 1 heats the high-concentration fluorine-containing wastewater, so that the high-concentration fluorine-containing wastewater has a relatively high initial temperature. Then, the high-concentration fluorine-containing wastewater with a relatively high initial temperature is discharged from the fluorine-containing wastewater drain outlet 12 of the preheater 1 and enters the seed mixing tank 2 through the preheated wastewater inlet 21. The preheated high-concentration fluorine-containing wastewater is fully mixed with the induced seed in the seed mixing tank 2. After the induced seed is evenly dispersed in the high-concentration fluorine-containing wastewater, it is sent into the fluoride salt crystallizer 3 together with the high-concentration fluorine-containing wastewater by the slurry pump 4. The fluoride ions in the high-concentration fluorine-containing wastewater react chemically with the precipitant to generate fluoride salts. The fluoride salts dissolve in the solvent of the high-concentration fluorine-containing wastewater to form a fluoride salt solution with a relatively high temperature. After the fluoride salt solution is evaporated in the fluoride salt crystallizer 3, as the solvent decreases, the supersaturation of the fluoride salts gradually increases. Finally, with the induced seed as the nucleus, crystals precipitate on the surface of the induced seed to form fluoride salt particles. The fluoride salt particles are discharged from the fluoride salt crystal discharge outlet 33 at the lower end of the fluoride salt crystallizer 3, and the staff can bag and recycle the discharged fluoride salt particles for reuse.

[0025] The preheater 1 generally heats the high-concentration fluorine-containing wastewater to 80°C - 100°C. The high-concentration fluorine-containing wastewater at this temperature is close to the boiling temperature. After reacting with the precipitant in the fluoride crystallizer 3 to produce fluoride salts, the fluoride salt solution is further heated, and the solvent of the fluoride salt solution will quickly reach the boiling temperature and evaporate, realizing the efficient crystallization of fluoride salts.

[0026] The induced crystal seeds are generally sodium fluoride, quartz sand or calcium fluoride. In addition to the above three materials, the induced crystal seeds can also be other slightly soluble or insoluble substances. By adding slightly soluble or insoluble substances to form induced crystal seeds, when fluoride salts crystallize, the induced crystal seeds form crystal nuclei. Since the crystal form or three-dimensional configuration of the induced crystal seeds and the fluoride salt crystals are enantiomers, the induced crystal seeds can promote the rapid growth of fluoride salt crystals, thereby realizing the rapid crystallization of fluoride salts, greatly improving the crystallization efficiency, and the crystal particles after crystallization are large in particle size and plump.

[0027] When adding the induced crystal seeds, the molar amount of the induced crystal seeds: the molar amount of all fluoride ions in the high-concentration fluorine-containing wastewater converted into fluoride salts = 3:1. The dosage of the induced crystal seeds is proportional to the molar amount of fluoride salts in the final fluoride salt solution, realizing the efficient crystallization of fluoride salts while avoiding over-dosage or under-dosage of the induced crystal seeds. Among them, the molar amount of all fluoride ions in the high-concentration fluorine-containing wastewater converted into fluoride salts can be calculated based on the amount of fluoride ions in the high-concentration fluorine-containing wastewater.

[0028] A stirrer 24 is provided in the crystal seed mixing tank 2, and the stirring blades 25 of the stirrer 24 can rotate and stir in the crystal seed mixing tank 2.

[0029] The stirrer 24 fully stirs the mixture of the high-concentration fluorine-containing wastewater and the induced crystal seeds in the crystal seed mixing tank 2, making the induced crystal seeds evenly dispersed in the high-concentration fluorine-containing wastewater, which is beneficial to efficient crystallization in the subsequent fluoride crystallizer 3. The stirrer 24 can be installed on the lid at the upper end of the crystal seed mixing tank 2. The rotating shaft of the stirrer 24 extends downward into the crystal seed mixing tank 2, and the stirring blades 25 on the rotating shaft of the stirrer 24 stir the mixed liquid in the crystal seed mixing tank 2. The stirrer 24 can also be installed at the bottom of the crystal seed mixing tank 2, and the rotating shaft of the stirrer 24 extends upward. The crystal seed feed inlet 22 and the preheated wastewater inlet 21 are preferably both set on the lid at the upper end of the crystal seed mixing tank 2 to form a top-down feeding, thereby improving the mixing uniformity of the induced crystal seeds and the high-concentration fluorine-containing wastewater. In addition, the crystal seed feed inlet 22 and the preheated wastewater inlet 21 can also be set on the side wall at the upper end of the crystal seed mixing tank 2.

[0030] The fluoride salt crystallizer 3 includes a crystallization reaction chamber 34, a feed mixing chamber 35, and a crystallization discharge chamber 36. The feed mixing chamber 35 is fixedly arranged at the upper end of the crystallization reaction chamber 34, and the crystallization discharge chamber 36 is fixedly arranged at the lower end of the crystallization reaction chamber 34. A number of conical tube bundles 37 arranged in parallel at intervals along the vertical direction are fixedly arranged in the crystallization reaction chamber 34. The inner diameter of the upper end of the conical tube bundle 37 is larger than that of the lower end. A sealed space is formed between the outer side wall of the conical tube bundle 37 and the inner side wall of the crystallization reaction chamber 34. The upper openings of the conical tube bundles 37 communicate with the feed mixing chamber 35, and the lower openings of the conical tube bundles 37 communicate with the crystallization discharge chamber 36. The fluoride salt crystallization discharge port 33 is located at the lower end of the crystallization discharge chamber 36, and the mixed wastewater inlet 31 and the precipitant dosing port 32 are respectively located in the feed mixing chamber 35.

[0031] The high-concentration fluoride-containing wastewater containing induced crystal seeds is mixed with the precipitant in the feed mixing chamber 35. The fluoride ions in the high-concentration fluoride-containing wastewater chemically react with the precipitant to form fluoride salts. The fluoride salt solution enters each conical tube bundle 37. The high-temperature fluoride salt solution is prone to gradually evaporate in the conical tube bundle 37, making the supersaturation of the fluoride salt gradually increase from the upper end to the lower end of the conical tube bundle 37. When the fluoride salt reaches the lower end of the conical tube bundle 37, crystals will precipitate on the surface of the induced crystal seeds, forming fluoride salt crystals with the induced crystal seeds as the core. After the fluoride salt crystals enter the crystallization discharge chamber 36, they are discharged from the fluoride salt crystallization discharge port 33 at the lower end thereof. Among them, the crystallization discharge chamber 36 is preferably a conical cylinder structure with an inner diameter of the upper end larger than that of the lower end. The fluoride salt crystals falling from the lower end of the conical tube bundle 37 slide down along the inner side wall of the conical cylinder structure, gather at the fluoride salt crystallization discharge port 33, and finally are discharged to the outside of the fluoride salt crystallizer 3. A control switch can also be arranged on the fluoride salt crystallization discharge port 33 for the automatic control of the discharge of the fluoride salt crystals. The switch can include a sensor and a control valve. By sensing the amount of fluoride salt crystals in the crystallization discharge chamber 36 through the sensor, the automatic opening and closing of the control valve are realized. When the control valve is opened, the fluoride salt crystallization discharge port 33 discharges the fluoride salt crystals. When the control valve is closed, the fluoride salt crystallization discharge port 33 waits for the crystals to gather.

[0032] Inside the feed mixing chamber 35, there are also fixedly installed a fluorine-containing wastewater distribution pipeline and a precipitant dosing pipeline. The fluorine-containing wastewater distribution pipeline includes a main distribution pipe 351 and distribution branch pipes 352. One end of the main distribution pipe 351 is connected to the mixed wastewater inlet 31 on the side wall of the feed mixing chamber 35. The distribution branch pipes 352 extend in the horizontal direction to form an annular pipeline structure. The distribution branch pipes 352 are connected to the main distribution pipe 351 to form an integral structure. A number of water distribution holes 353 are provided on the side wall of the distribution branch pipes 352. The mixed wastewater entering the distribution branch pipes 352 can enter the feed mixing chamber 35 through each water distribution hole 353. The precipitant dosing pipeline includes a main dosing pipe 354 and dosing branch pipes 355. One end of the main dosing pipe 354 is connected to the precipitant dosing port 32 on the side wall of the feed mixing chamber 35. The dosing branch pipes 355 extend in the horizontal direction to form an annular pipeline structure. The dosing branch pipes 355 are connected to the main dosing pipe 354 to form an integral structure. A number of dosing holes 356 are provided on the side wall of the dosing branch pipes 355. The precipitant entering the dosing branch pipes 355 can enter the feed mixing chamber 35 through each dosing hole 356. The distribution branch pipes 352 and the dosing branch pipes 355 are arranged at intervals in the vertical direction, and the water distribution holes 353 and the dosing holes 356 are arranged in one-to-one correspondence.

[0033] The mixed wastewater enters the distribution branch pipes 352 along the main distribution pipe 351 and flows out from the water distribution holes 353 on the distribution branch pipes 352 to form uniform water discharge; the precipitant enters the dosing branch pipes 355 along the main dosing pipe 354 and flows out from the dosing holes 356 on the dosing branch pipes 355 to form uniform dosing; at the same time, due to the one-to-one correspondence between the water distribution holes 353 and the dosing holes 356, the mixed wastewater and the precipitant are quickly mixed and chemically react to generate fluorinated salts.

[0034] A water distribution nozzle is fixedly installed on the water distribution hole 353, and a dosing nozzle is fixedly installed on the dosing hole 356. The water distribution nozzles and the dosing nozzles spray against each other one by one. The mixed wastewater and the precipitant are fully contacted by the way of spraying against each other, further improving the reaction efficiency of the mixed wastewater and the precipitant, avoiding the residue of unreacted fluoride ions, and at the same time enabling the medicament to fully react, saving the medicament more.

[0035] At least two distribution branch pipes 352 with different diameters are arranged concentrically at intervals, and each distribution branch pipe 352 is respectively connected to the main distribution pipe 351. At least two dosing branch pipes 355 with different diameters are arranged concentrically at intervals, and each dosing branch pipe 355 is respectively connected to the main dosing pipe 354. The projections of the distribution branch pipes 352 and the dosing branch pipes 355 on the horizontal plane are an interleaved and spaced ring structure. The multiple distribution branch pipes 352 and the multiple dosing branch pipes 355 are arranged in an interleaved manner. The mixed wastewater coming out of the water distribution holes 353 and the precipitant coming out of the dosing holes 356 are sprayed and mixed with each other along the inclined direction, which is beneficial to improving the mixing uniformity of the mixed wastewater and the precipitant, improving the reaction efficiency, and saving space at the same time.

[0036] A first steam inlet 38 and a first condensate drain outlet 39 are also provided on the side wall of the crystallization reaction chamber 34. The first steam inlet 38 is connected to the external steam supply pipe 5, and the first condensate drain outlet 39 can discharge the condensate in the crystallization reaction chamber 34. A secondary steam outlet 40 is also provided on the feed mixing chamber 35. The steam generated by the evaporation of the high-concentration fluorine-containing wastewater solvent in the conical tube bundle 37 can be discharged through the secondary steam outlet 40 on the feed mixing chamber 35 for reuse.

[0037] The high-temperature external steam is introduced into the crystallization reaction chamber 34. Through the heat exchange between the continuously incoming steam and the fluoride salt solution in the conical tube bundle 37, the solvent in the fluoride salt solution is evaporated into water vapor. The water vapor formed by the evaporation of the solvent in the fluoride salt solution is discharged through the secondary steam outlet 40 on the feed mixing chamber 35. The secondary steam can be recovered and reused. In addition to using steam to heat and evaporate the high-concentration fluorine-containing wastewater in the conical tube bundle 37, heating methods such as electric heating wires can also be used to heat and evaporate the high-concentration fluorine-containing wastewater in the conical tube bundle 37, or the preheating temperature of the high-concentration fluorine-containing wastewater itself can be used for evaporation. Such are all equivalent replacement schemes that those skilled in the art can think of according to this application and belong to the protection scope of this application.

[0038] A compressed air inlet 41 is also provided on the feed mixing chamber 35. The compressed air inlet 41 is connected to a compressed air generating device 6 through a pipe, and the compressed air generating device 6 can supply compressed air to the feed mixing chamber 35 in a pulsed manner.

[0039] After the fluoride salt crystallizer 3 stops operating, the fluoride salt crystallizer 3 is emptied, and pulsed compressed air is injected into the feed mixing chamber 35 to blow out the fluoride salt crystals or precipitates remaining on the conical tube bundle 37, realizing the cleaning of the conical tube bundle 37. By regularly injecting pulsed compressed air into the feed mixing chamber 35 of the emptied fluoride salt crystallizer 3, it is possible to prevent fluoride salt crystals or precipitates from adhering to the inner wall of the conical tube bundle 37, thereby avoiding blockage inside the conical tube bundle 37 and ensuring the normal discharge of fluoride salt crystals in the conical tube bundle 37.

[0040] The preheater 1 includes a preheating housing, a heat exchanger 13, a second steam inlet 14, and a second condensate discharge port 15. The fluorine-containing wastewater inlet 11 is located on the upper side wall of the preheating housing, and the fluorine-containing wastewater discharge port 12 is located on the lower side wall of the preheating housing. A cavity for accommodating high-concentration fluorine-containing wastewater is formed inside the preheating housing. The heat exchanger 13 is fixedly arranged inside the preheating housing. The second steam inlet 14 and the second condensate discharge port 15 are respectively located at both ends of the heat exchanger 13. The second steam inlet 14 is communicated with an external steam supply pipe 5, and the second condensate discharge port 15 can discharge the condensate water in the heat exchanger 13 to the outside of the preheating housing.

[0041] Using high-temperature external steam as a heat source, heat exchange is carried out between the heat exchanger 13 and the high-concentration fluorine-containing wastewater to realize preheating of the high-concentration fluorine-containing wastewater. In addition, the preheater 1 can also heat the high-concentration fluorine-containing wastewater through heating devices such as heating wires, which is an equivalent replacement structure that can be easily thought of by those skilled in the art according to this application and belongs to the protection scope of this patent.

[0042] The method for producing fluoride salt particles from high-concentration fluorine-containing wastewater using the present invention is described in detail through the following examples:

[0043] Example 1: A production method for producing fluoride salt particles from fluorine-containing wastewater, the specific steps are as follows:

[0044] 1) Collect the high-concentration fluorine-containing wastewater generated during the production process of solar cell wafers into a storage tank. The fluorine ion concentration of this high-concentration fluorine-containing wastewater is about 20,000 mg / L;

[0045] 2) Feed 100 L of high-concentration fluorine-containing wastewater into the preheater 1 for preheating. After heating to 80 °C, pour the high-concentration fluorine-containing wastewater into the seed mixing tank 2. At the same time, add 12.6 kg of sodium fluoride to induce seeds into the seed mixing tank 2 and stir. The molar ratio of sodium fluoride-induced seeds to fluorine ions is 3:1;

[0046] 3) Feed the high-concentration fluorine-containing wastewater and the sodium fluoride-induced seed mixed solution obtained in step 2) into the mixed wastewater inlet 31 of the fluoride salt crystallizer 3 using a slurry pump 4. At the same time, add 30 L of a sodium chloride solution with a mass percentage concentration of 20% to the precipitant dosing port 32 of the fluoride salt crystallizer 3;

[0047] 4) Steam is introduced into the fluoride salt crystallizer 3. The high-concentration fluoride-containing wastewater reacts with the cations in the precipitant in the fluoride salt crystallizer 3 to generate sodium fluoride. Sodium fluoride crystallizes with the sodium fluoride induced seed as the nucleus in the fluoride salt crystallizer 3. A solution containing sodium fluoride crystal particles is obtained at the bottom of the fluoride salt crystallizer 3. The obtained sodium fluoride crystal particles and part of the solution are discharged together outside the fluoride salt crystallizer 3. After solid-liquid separation, the sodium fluoride crystal particles are collected. The sodium fluoride crystal particles are washed and dried to obtain 17 kg of sodium fluoride particle products.

[0048] In this example, the recovery rate of fluorine is 99%, and the grade of sodium fluoride is about 99.2%.

[0049] Example 2: A production method for producing fluoride salt particles from fluoride-containing wastewater, the specific steps are as follows:

[0050] 1) The high-concentration fluoride-containing wastewater generated in the production process of the semiconductor factory is sent into the regulating tank for stable regulation of water quality and water volume. The fluoride ion concentration of the high-concentration fluoride-containing wastewater is about 2100 mg / L.

[0051] 2) After heating 2 m³ of high-concentration fluoride-containing wastewater to 80 °C through the preheater 1, it is poured into the seed mixing tank 2. At the same time, 26.5 kg of sodium fluoride induced seeds are added to the seed mixing tank 2 for stirring. The molar ratio of sodium fluoride induced seeds to fluoride ions is 3:1.

[0052] 3) The mixed solution of high-concentration fluoride-containing wastewater obtained in step 2) is sent into the mixed wastewater inlet 31 of the fluoride salt crystallizer 3 by the slurry pump 4. At the same time, 63.6 L of sodium chloride solution with a mass percentage concentration of 20% is added to the precipitant feeding port 32 of the fluoride salt crystallizer 3.

[0053] 4) Steam is introduced into the fluoride salt crystallizer. The high-concentration fluoride-containing wastewater reacts with the cations in the precipitant in the fluoride salt crystallizer 3 to generate sodium fluoride. Sodium fluoride crystallizes with the sodium fluoride induced seed as the nucleus in the fluoride salt crystallizer 3. A solution containing sodium fluoride crystal particles is obtained at the bottom of the fluoride salt crystallizer 3. The obtained sodium fluoride crystal particles and part of the solution are discharged together outside the fluoride salt crystallizer 3. After solid-liquid separation, the sodium fluoride crystal particles are collected. The sodium fluoride crystal particles are washed and dried to obtain 35.3 kg of sodium fluoride particle products.

[0054] In this example, the recovery rate of fluorine is 97%, and the grade of sodium fluoride is about 98.2%.

[0055] Example 3: A production method for producing fluoride salt particles from fluoride-containing wastewater, the specific steps are as follows:

[0056] 1) Feed the high-concentration fluorine-containing wastewater generated in the polysilicon production process into the regulation tank for stable regulation of water quality and quantity. The fluoride ion concentration of this high-concentration fluorine-containing wastewater is about 3,200 mg / L.

[0057] 2) After heating 2 m³ of high-concentration fluorine-containing wastewater to 85 °C through the preheater 1, pour it into the seed mixing tank 2. At the same time, add 39.5 kg of calcium fluoride to induce seeds and stir in the seed mixing tank 2. The molar ratio of calcium fluoride-induced seeds to fluoride ions is 3:1.

[0058] 3) Feed the high-concentration fluorine-containing wastewater mixed solution obtained in step 2) into the mixed wastewater inlet 31 of the fluoride salt crystallizer 3 with a slurry pump 4. At the same time, add 93.5 L of calcium chloride solution with a mass percentage concentration of 20% to the precipitant dosing port 32 of the fluoride salt crystallizer 3.

[0059] 4) Pass steam into the fluoride salt crystallizer. The high-concentration fluorine-containing wastewater reacts with the cations in the precipitant in the fluoride salt crystallizer 3 to generate calcium fluoride. Calcium fluoride crystallizes with the calcium fluoride-induced seeds as nuclei in the fluoride salt crystallizer 3. A solution containing calcium fluoride crystal particles is obtained at the bottom of the fluoride salt crystallizer 3. Discharge the obtained calcium fluoride crystal particles and part of the solution together outside the fluoride salt crystallizer 3. After solid-liquid separation, collect the calcium fluoride crystal particles. The calcium fluoride crystal particles are washed and dried to obtain 58.1 kg of calcium fluoride particle products.

[0060] In this example, the fluorine recovery rate is 97.1%, and the grade of calcium fluoride is about 98.22%.

Claims

1. A production system for producing fluoride salt particles from fluorine-containing wastewater, characterized in that: It includes a preheater (1), a seed mixing tank (2), a fluoride salt crystallizer (3), a slurry pump (4), a seed adding device and a precipitant adding device. The preheater (1) is provided with a fluoride-containing wastewater inlet (11) and a fluoride-containing wastewater drain outlet (12). The seed mixing tank (2) is provided with a preheated wastewater inlet (21), a seed inlet (22) and a mixed wastewater drain outlet (23). The fluoride salt crystallizer (3) is provided with a mixed wastewater inlet (31), a precipitant adding port (32) and a fluoride salt crystal discharge outlet (33). The preheater (1) can heat the high-concentration fluoride-containing wastewater therein. The fluoride-containing wastewater drain outlet (12) of the preheater (1) is communicated with the preheated wastewater inlet (21) of the seed mixing tank (2) through a pipeline. Induced seeds can be added into the seed mixing tank (2) through the seed inlet (22). The slurry pump (4) discharges the mixed wastewater in the seed mixing tank (2) into the fluoride salt crystallizer (3) through the mixed wastewater drain outlet (23) and the mixed wastewater inlet (31) by a pipeline. The precipitant can be input into the fluoride salt crystallizer (3) through the precipitant adding port (32). The fluoride salt crystal discharge outlet (33) is located at the lower end of the fluoride salt crystallizer (3), and the fluoride salt crystal discharge outlet (33) can discharge fluoride salt crystals outwards. The fluoride salt crystallizer (3) includes a crystallization reaction chamber (34), a feed mixing chamber (35) and a crystal discharge chamber (36). The feed mixing chamber (35) is fixedly arranged at the upper end of the crystallization reaction chamber (34), and the crystal discharge chamber (36) is fixedly arranged at the lower end of the crystallization reaction chamber (34). A plurality of conical tube bundles (37) arranged in parallel at intervals in the vertical direction are fixedly arranged in the crystallization reaction chamber (34). The inner diameter of the upper end of the conical tube bundle (37) is larger than that of the lower end, and a sealed space is formed between the outer side wall of the conical tube bundle (37) and the inner side wall of the crystallization reaction chamber (34). The upper openings of each conical tube bundle (37) are communicated with the feed mixing chamber (35), and the lower openings of each conical tube bundle (37) are communicated with the crystal discharge chamber (36). The fluoride salt crystal discharge outlet (33) is located at the lower end of the crystal discharge chamber (36). The mixed wastewater inlet (31) and the precipitant adding port (32) are respectively located on the feed mixing chamber (35). A first steam inlet (38) and a first condensed water drain outlet (39) are further arranged on the side wall of the crystallization reaction chamber (34). The first steam inlet (38) is communicated with an external steam supply pipeline (5), and the first condensed water drain outlet (39) can discharge the condensed water in the crystallization reaction chamber (34). A secondary steam discharge outlet (40) is further arranged on the feed mixing chamber (35). The steam generated by the evaporation of the high-concentration fluoride-containing wastewater solvent in the conical tube bundle (37) can be discharged through the secondary steam discharge outlet (40) on the feed mixing chamber (35).

2. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 1, wherein: A stirrer (24) is arranged in the seed mixing tank (2), and the stirring blades (25) of the stirrer (24) can rotate and stir in the seed mixing tank (2).

3. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 1, wherein: Inside the feed mixing chamber (35), a fluorine-containing wastewater distribution pipe and a precipitant dosing pipe are also fixedly arranged. The fluorine-containing wastewater distribution pipe includes a main distribution pipe (351) and distribution branches (352). One end of the main distribution pipe (351) is communicated with the mixed wastewater inlet (31) on the side wall of the feed mixing chamber (35). The distribution branches (352) extend in the horizontal direction to form an annular pipe structure. The distribution branches (352) are communicated with the main distribution pipe (351) to form an integral structure. A number of water distribution holes (353) are arranged on the side wall of the distribution branches (352). The mixed wastewater entering the distribution branches (352) can enter the feed mixing chamber (35) through each water distribution hole (353). The precipitant dosing pipe includes a main dosing pipe (354) and dosing branches (355). One end of the main dosing pipe (354) is communicated with the precipitant dosing port (32) on the side wall of the feed mixing chamber (35). The dosing branches (355) extend in the horizontal direction to form an annular pipe structure. The dosing branches (355) are communicated with the main dosing pipe (354) to form an integral structure. A number of dosing holes (356) are arranged on the side wall of the dosing branches (355). The precipitant entering the dosing branches (355) can enter the feed mixing chamber (35) through each dosing hole (356). The distribution branches (352) and the dosing branches (355) are arranged at intervals in the vertical direction, and the water distribution holes (353) and the dosing holes (356) are arranged in one-to-one correspondence.

4. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 3, wherein: A water distribution nozzle is fixedly installed on the water distribution hole (353), and a dosing nozzle is fixedly installed on the dosing hole (356). The water distribution nozzles and the dosing nozzles spray against each other one by one.

5. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 3, wherein: At least two distribution branches (352) with different diameters are arranged concentrically at intervals, and each distribution branch (352) is respectively communicated with the main distribution pipe (351). At least two dosing branches (355) with different diameters are arranged concentrically at intervals, and each dosing branch (355) is respectively communicated with the main dosing pipe (354). The projection of the distribution branches (352) and the dosing branches (355) on the horizontal plane is a nested ring structure arranged at staggered intervals.

6. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 1, characterized in that: The feed mixing chamber (35) is also provided with a compressed air inlet (41). The compressed air inlet (41) is connected to a compressed air generating device (6) through a pipe. The compressed air generating device (6) can supply compressed air to the feed mixing chamber (35) in a pulsed manner.

7. The production system for producing fluoride salt particles from fluorine-containing wastewater according to claim 1, characterized in that: The preheater (1) includes a preheating housing, a heat exchanger (13), a second steam inlet (14), and a second condensate drain outlet (15). The fluorine-containing wastewater inlet (11) is located on the upper side wall of the preheating housing, and the fluorine-containing wastewater drain outlet (12) is located on the lower side wall of the preheating housing. A cavity for accommodating high-concentration fluorine-containing wastewater is formed inside the preheating housing. The heat exchanger (13) is fixedly arranged inside the preheating housing. The second steam inlet (14) and the second condensate drain outlet (15) are respectively located at both ends of the heat exchanger (13). The second steam inlet (14) is communicated with an external steam supply pipeline, and the second condensate drain outlet (15) can discharge the condensate water in the heat exchanger (13) to the outside of the preheating housing.

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