Nucleation granulation process for recycling calcium chloride cyclic regeneration reinforced fluorine resource

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a nucleation granulation process for calcium chloride cyclic regeneration reinforced fluorine resource recovery. According to the process, calcium hydroxide and a small amount of calcium chloride are compounded to serve as a crystal inducing agent, calcium ions in calcium chloride are consumed in the fluorine ion process, residual chloride ions exist in treated wastewater, the treated wastewater is subjected to circulating reflux, after calcium hydroxide is added again, the residual chloride ions can be combined with the calcium ions in the calcium hydroxide, and the calcium chloride is separated from the calcium hydroxide. And calcium chloride is formed and continuously reacts with fluorine ions to generate calcium fluoride, so that the purposes of calcium chloride regeneration reinforced fluorine resource recovery and treatment cost reduction are achieved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wastewater treatment, and in particular to a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery. Background Art

[0002] The amount of industrial wastewater discharged is increasing, and the amount of various pollutants discharged is also increasing; among them, hydrofluoric acid wastewater contains a large amount of fluoride ions and acidic and alkaline organic matter, which is very harmful to the environment and human body. It needs to be pre-purified before being discharged into the pipeline network or the environment in the factory.

[0003] The existing technology usually uses chemical dosing precipitation method to treat fluorine chemical wastewater, mainly using physical and chemical treatment, by adding chemical agents and fluoride ions to form precipitates, and then form precipitated sludge, which is removed in the sedimentation tank. The supernatant after fluoride removal enters the discharge pool, and the precipitated sludge enters the dehydration system to be dehydrated and dried before outsourcing. The existing purification process cannot completely remove fluoride ions, and a large amount of suspended matter remains in the supernatant, affecting the purified water quality, which needs further improvement.

[0004] In recent years, more and more studies have been conducted on the application of nuclear crystal granulation technology in fluoride-containing wastewater, and certain results have been achieved. This technology effectively reduces the dosage of chemical agents and avoids the production of high-water content sludge, while achieving efficient recovery of fluoride ions in wastewater, creating additional economic benefits for enterprises. The commonly used chemical agents for fluoride removal are calcium chloride and calcium hydroxide, but due to the high cost of calcium chloride, the water treatment cost is too high and the economic benefits are poor.

[0005] Therefore, it is of great significance to reduce the cost of adding chemical agents in treating fluoride-containing wastewater using nuclear crystal granulation technology. Summary of the invention

[0006] In order to solve the above technical problems, the present disclosure provides a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery. The core crystal granulation process reduces the water treatment cost by reducing the amount of calcium chloride used, while ensuring the treatment effect, and has good application prospects.

[0007] The present disclosure provides a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery, the core crystal granulation process comprising the following steps:

[0008] Under initial working condition:

[0009] The acidic fluorine-containing wastewater, calcium chloride, calcium hydroxide and seed crystals are mixed, and the seed crystals are placed in a fluidized state by controlling the hydraulic parameters of the water body; the seed crystals induce the fluoride ions in the acidic fluorine-containing wastewater to react with the calcium ions and nucleate and grow on the surface of the seed crystals in the form of calcium fluoride to form granules;

[0010] The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water obtained. A part of the treated water is discharged and a part is stored for subsequent reflux.

[0011] Wherein, the added molar amount of calcium chloride is 1 / 10 to 1 / 6 of the molar amount of fluoride ions in the reaction system;

[0012] The added molar amount of calcium hydroxide is 1 / 5 to 1 / 4 of the molar amount of fluoride ions in the reaction system;

[0013] When the amount of treated water to be stored reaches the set value:

[0014] The reflux ratio of the treated water is determined according to the fluoride ion concentration in the acidic fluoride-containing wastewater, and then the amount of the acidic fluoride-containing wastewater and the discharge amount of the treated water are adjusted to ensure that the calcium chloride addition ratio remains unchanged, increase the calcium hydroxide addition ratio, and control the stored treated water to reflux into the reaction system according to the determined reflux ratio; at this time, the hydrochloric acid in the reflux water reacts with the calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with the fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

[0015] In view of the high cost of crystallization inducing agents in the existing crystallization granulation process for treating fluorine-containing wastewater, the present invention designs a crystallization granulation process for strengthening fluorine resource recovery by recycling calcium chloride, aiming to reduce the cost of water treatment by reducing the amount of calcium chloride used. The process uses calcium hydroxide and a small amount of calcium chloride as crystallization inducing agents. Since the fluoride ions consume the calcium ions in the calcium chloride during the process, the residual chloride ions are present in the treated wastewater. The treated wastewater is circulated and refluxed. When calcium hydroxide is added again, the residual chloride ions will combine with the calcium ions in the calcium hydroxide to form calcium chloride, which will continue to react with the fluoride ions to form calcium fluoride, thereby achieving the purpose of strengthening fluorine resource recovery and reducing treatment costs by regenerating calcium chloride.

[0016] The specific cycle equation is as follows:

[0017] Ca(OH)2+2HF→CaF2+2H2O

[0018] Ca(Cl)2+2HF→CaF2+2HCl

[0019] 2HCl+Ca(OH)2→CaCl2+2H2O

[0020] In the present disclosure, hydraulic parameters such as flow rate can be adjusted by those skilled in the art according to relevant parameters such as seed dosage and wastewater quality.

[0021] The set value of the amount of stored treated water is adjusted according to the return ratio of the treated water.

[0022] The following are preferred technical solutions of the present disclosure, but are not intended to be limitations of the technical solutions provided by the present disclosure. Through the following technical solutions, the technical objectives and beneficial effects of the present disclosure can be better achieved and realized.

[0023] As a preferred technical solution of the present disclosure, before the mixing, the pH of the acidic fluorine-containing wastewater is adjusted to 4-5, such as 4, 4.2, 4.4, 4.6, 4.8 or 5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] Generally speaking, due to the strong initial acidity of acidic fluoride-containing wastewater, alkaline substances such as sodium hydroxide are usually used to pre-adjust its pH to avoid interaction with seed crystals, thereby causing seed loss and a decrease in fluorine resource recovery efficiency.

[0025] As a preferred technical solution of the present disclosure, the seed crystals include one or more of quartz sand, dolomite, brucite, ZSM-5 zeolite or marble powder.

[0026] As a preferred technical solution of the present disclosure, when the fluoride ion concentration in the acidic fluoride-containing wastewater does not exceed 1000 mg / L, the reflux rate of treated water is 1 to 1.2 times the amount of acidic fluoride-containing wastewater, for example, 1 time, 1.05 times, 1.1 times or 1.2 times, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0027] In the present disclosure, when the reflux amount of the treated water is 1 times the amount of the acidic fluorine-containing wastewater, it means that all the treated water obtained is refluxed.

[0028] As a preferred technical solution of the present disclosure, when the fluoride ion concentration in the acidic fluoride-containing wastewater is greater than 1000 mg / L and less than 5000 mg / L, the reflux rate of treated water is 3 to 3.2 times the amount of acidic fluoride-containing wastewater, for example, 3 times, 3.1 times or 3.2 times, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] As a preferred technical solution of the present disclosure, when the fluoride ion concentration in the acidic fluoride-containing wastewater is not less than 5000 mg / L, the reflux rate of treated water is 5 to 5.2 times the amount of acidic fluoride-containing wastewater, for example, 5 times, 5.1 times or 5.2 times, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] The present disclosure designs different reflux ratios according to the specific fluoride ion concentration of the acidic fluoride-containing wastewater. On the one hand, the residual chloride ions in the effluent can be fully utilized; on the other hand, the supersaturation of calcium fluoride in the system can be adjusted to improve the heterogeneous nucleation efficiency of calcium fluoride on the surface of the seed crystal. If the reflux ratio is too small, the supersaturation of the system will increase sharply, the self-nucleation effect will be enhanced, a large amount of high-water content sludge will be generated, and the fluoride ion recovery efficiency will be reduced.

[0031] As a preferred technical solution of the present disclosure, when the concentration of fluoride ions in the treated water is lower than 10 mg / L, the reflux is stopped and all the treated water is discharged.

[0032] As a preferred technical solution of the present disclosure, the core crystal granulation process is carried out using a core crystal granulation device, and the core crystal granulation device includes a core crystal granulation reactor and a storage tank;

[0033] The lower end of the side wall of the nuclear crystal granulation reactor is respectively provided with a wastewater inlet for introducing acidic fluorine-containing wastewater; two crystal inducing agent injection ports, one for introducing calcium chloride solution and the other for introducing calcium hydroxide solution; and a reflux port for realizing the reflux of treated water;

[0034] The top end or the upper end of the side wall of the core crystal granulation reactor is provided with a water outlet for discharging the treated water in the core crystal granulation reactor;

[0035] The bottom end of the nuclear crystal granulation reactor is provided with a granulation body discharge port for discharging the granulation body;

[0036] The storage tanks are respectively provided with a water storage inlet for receiving part of the treated water from the water outlet of the core crystal granulation reactor; and a water storage outlet for discharging the treated water in the storage tank to the reflux port of the core crystal granulation reactor.

[0037] Preferably, the wastewater inlet, the crystal inducing agent addition port and the reflux port are located at the same height.

[0038] As a preferred technical solution of the present disclosure, the core crystal granulation process includes:

[0039] Under initial working condition:

[0040] Filling seed crystals into the nuclear crystal granulation reactor;

[0041] Adjust the pH of acidic fluoride-containing wastewater to 4-5;

[0042] The regulated acidic fluorine-containing wastewater, calcium chloride solution and calcium hydroxide solution are respectively introduced into the seed crystal granulation reactor to make the seed crystals in a fluidized state; the seed crystals induce the fluoride ions and calcium ions in the water to react and nucleate and grow on the surface of the seed crystals in the form of calcium fluoride to form granules;

[0043] The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water obtained. A part of the treated water is discharged and a part is stored for subsequent reflux.

[0044] The added molar amount of calcium chloride is 1 / 10 to 1 / 6 of the molar amount of fluoride ions in the reaction system;

[0045] The molar amount of calcium hydroxide added is 1 / 5 to 1 / 4 of the molar amount of fluoride ions in the reaction system;

[0046] After the water volume in the storage tank reaches the set value:

[0047] The reflux ratio of the treated water is determined according to the fluoride ion concentration in the acidic fluoride-containing wastewater, and then the water inlet of the acidic fluoride-containing wastewater and the discharge of the treated water are adjusted to ensure that the addition ratio of calcium chloride remains unchanged, increase the addition ratio of calcium hydroxide, and control the treated water in the storage tank to reflux to the nuclear crystal granulation reactor according to the determined reflux ratio; at this time, the hydrochloric acid in the reflux water reacts with the calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with the fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

[0048] As a preferred technical solution of the present disclosure, the filling height of the seed crystal is 20 to 40% of the effective height of the nuclear crystal granulation reactor, for example, 20%, 25%, 30%, 35% or 40%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0049] Preferably, the hydraulic retention time of the acidic fluorine-containing wastewater in the core crystal granulation reactor is not less than 5 minutes, for example 5 minutes, 6 minutes, 8 minutes, 10 minutes, 11 minutes, 12 minutes or 15 minutes, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0050] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0051] (1) The present invention aims to solve the problem of high cost of crystallization agents used in the existing crystallization granulation process for treating acidic fluorine-containing wastewater, and designs a crystallization granulation process for strengthening fluorine resource recovery by recycling calcium chloride. The process uses calcium hydroxide and a small amount of calcium chloride as crystallization agents. Since the fluoride ions consume the calcium ions in the calcium chloride during the process, the residual chloride ions are present in the treated wastewater. The treated wastewater is circulated and refluxed. When calcium hydroxide is added again, the residual chloride ions will combine with the calcium ions in the calcium hydroxide to form calcium chloride, which will continue to react with the fluoride ions to form calcium fluoride, thereby achieving the purpose of strengthening fluorine resource recovery and reducing treatment costs by regenerating calcium chloride.

[0052] (2) The core crystal granulation process disclosed in the present invention requires a small amount of reagent to be added, does not generate sludge, has a short treatment process, and recovers high-quality calcium fluoride. It simultaneously achieves water purification and resource recovery and utilization of fluoride, which is beneficial to production and application. DETAILED DESCRIPTION

[0053] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0054] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0055] The present disclosure provides a nucleus crystal granulation device, comprising a nucleus crystal granulation reactor and a storage tank;

[0056] The lower end of the side wall of the nuclear crystal granulation reactor is respectively provided with a wastewater inlet for introducing acidic fluorine-containing wastewater; two crystal inducing agent injection ports, one for introducing calcium chloride solution and the other for introducing calcium hydroxide solution; and a reflux port for realizing the reflux of treated water;

[0057] Furthermore, the wastewater inlet, the crystal inducing agent addition port and the reflux port are located at the same height;

[0058] The top end or the upper end of the side wall of the core crystal granulation reactor is provided with a water outlet for discharging the treated water in the core crystal granulation reactor;

[0059] The bottom end of the nuclear crystal granulation reactor is provided with a granulation body discharge port for discharging the granulation body;

[0060] The storage tanks are respectively provided with a water storage inlet for receiving part of the treated water from the water outlet of the core crystal granulation reactor; and a water storage outlet for discharging the treated water in the storage tank to the reflux port of the core crystal granulation reactor.

[0061] The following core crystal granulation processes are all carried out using the core crystal granulation device.

[0062] Example 1

[0063] This embodiment provides a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery, comprising:

[0064] Under initial working condition:

[0065] Filling dolomite into the core crystal granulation reactor, the filling height being 20% ​​of the effective height of the core crystal granulation reactor;

[0066] The pH of the acidic fluoride-containing wastewater with a fluoride ion concentration of 1000 mg / L was adjusted to 4 using sodium hydroxide;

[0067] The regulated acidic fluoride wastewater was heated to 30 m 3 / h flow rate into the nuclear crystal granulation reactor, at the same time, the calcium chloride solution at 0.3m 3 / h flow rate, calcium hydroxide solution at 0.3m 3 / h flow into the nuclear crystal granulation reactor, so that the dolomite is in a fluidized state; the dolomite induces the fluoride ions and calcium ions in the water to react and nucleate and grow on the surface of the dolomite in the form of calcium fluoride to form a granulation body;

[0068] The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water. A part of the treated water is discharged and the other part is stored for subsequent reflux.

[0069] The added molar amount of calcium chloride is 1 / 10 of the molar amount of fluoride ions in the reaction system;

[0070] The molar amount of calcium hydroxide added is 1 / 5 of the molar amount of fluoride ions in the reaction system;

[0071] When the water volume in the storage tank reaches 15m 3 back:

[0072] According to the fluoride ion concentration in the acidic fluoride-containing wastewater, the reflux ratio of the treated water is determined to be 100%, and then the inflow of the acidic fluoride-containing wastewater is adjusted to 15m 3 / h, the treated water discharge is 15m 3 / h, at the same time, the addition ratio of calcium chloride is kept unchanged, the addition ratio of calcium hydroxide is adjusted to 2 / 5, and the treated water in the storage tank is controlled to flow at 15m 3 / h flow rate back to the nuclear crystal granulation reactor; at this time, the hydrochloric acid in the reflux water reacts with calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

[0073] When the concentration of fluoride ions in the treated water is lower than 10 mg / L, the reflux is stopped and all the treated water is discharged.

[0074] Example 2

[0075] This embodiment provides a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery, comprising:

[0076] Under initial working condition:

[0077] Filling dolomite into the core crystal granulation reactor, the filling height being 30% of the effective height of the core crystal granulation reactor;

[0078] The pH of the acidic fluoride-containing wastewater with a fluoride ion concentration of 4900 mg / L was adjusted to 4 using sodium hydroxide;

[0079] The regulated acidic fluoride wastewater was heated to 40 m 3 / h flow rate into the nuclear crystal granulation reactor, at the same time, the calcium chloride solution at 0.4m 3 / h flow rate, calcium hydroxide solution at 0.4m 3 / h flow into the nuclear crystal granulation reactor, so that the dolomite is in a fluidized state; the dolomite induces the fluoride ions and calcium ions in the water to react and nucleate and grow on the surface of the dolomite in the form of calcium fluoride to form a granulation body;

[0080] The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water. A part of the treated water is discharged and the other part is stored for subsequent reflux.

[0081] The added molar amount of calcium chloride is 1 / 8 of the molar amount of fluoride ions in the reaction system;

[0082] The molar amount of calcium hydroxide added is 1 / 4 of the molar amount of fluoride ions in the reaction system;

[0083] When the water volume in the storage tank reaches 30m 3 back:

[0084] According to the fluoride ion concentration in the acidic fluoride-containing wastewater, the reflux ratio of the treated water is determined to be 300%, and then the inflow of the acidic fluoride-containing wastewater is adjusted to 10m 3 / h, the treated water discharge is 10m 3 / h, at the same time, ensure that the calcium chloride addition ratio remains unchanged, the calcium hydroxide addition ratio is adjusted to 1 / 3, and the treated water in the storage tank is controlled to flow at 30m 3 / h flow rate back to the nuclear crystal granulation reactor; at this time, the hydrochloric acid in the reflux water reacts with calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

[0085] When the concentration of fluoride ions in the treated water is lower than 10 mg / L, the reflux is stopped and all the treated water is discharged.

[0086] Example 3

[0087] This embodiment provides a core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery, comprising:

[0088] Under initial working condition:

[0089] Filling dolomite into the core crystal granulation reactor, the filling height being 30% of the effective height of the core crystal granulation reactor;

[0090] The pH of the acidic fluoride-containing wastewater with a fluoride ion concentration of 10000 mg / L was adjusted to 4 using sodium hydroxide;

[0091] The regulated acidic fluoride wastewater was heated to 30 m 3 / h flow rate into the nuclear crystal granulation reactor, at the same time, the calcium chloride solution at 0.6m 3 / h flow rate, calcium hydroxide solution at 0.6m 3 / h flow into the nuclear crystal granulation reactor, so that the dolomite is in a fluidized state; the dolomite induces the fluoride ions and calcium ions in the water to react and nucleate and grow on the surface of the dolomite in the form of calcium fluoride to form a granulation body;

[0092] The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water. A part of the treated water is discharged and the other part is stored for subsequent reflux.

[0093] The added molar amount of calcium chloride is 1 / 9 of the molar amount of fluoride ions in the reaction system;

[0094] The added molar amount of calcium hydroxide is 9 / 40 of the molar amount of fluoride ions in the reaction system;

[0095] When the water volume in the storage tank reaches 25m 3 back:

[0096] According to the fluoride ion concentration in the acidic fluoride-containing wastewater, the reflux ratio of the treated water is determined to be 500%, and then the inflow of the acidic fluoride-containing wastewater is adjusted to 5m 3 / h, the treated water discharge is 5m 3 / h, at the same time, the addition ratio of calcium chloride is kept unchanged, the addition ratio of calcium hydroxide is adjusted to 2 / 5, and the treated water in the storage tank is controlled to flow at 25m 3 / h flow rate back to the nuclear crystal granulation reactor; at this time, the hydrochloric acid in the reflux water reacts with calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

[0097] When the concentration of fluoride ions in the treated water is lower than 10 mg / L, the reflux is stopped and all the treated water is discharged.

[0098] The use of the calcium chloride recycling regeneration and enhanced fluorine resource recovery core crystal granulation process disclosed in the present invention can save more than 30% of the amount of calcium chloride crystal inducer and reduce the processing cost by more than 38%.

[0099] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0100] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A core crystal granulation process for calcium chloride recycling and enhanced fluorine resource recovery, characterized in that: The core crystal granulation process comprises the following steps: Under initial working condition: Acidic fluoride-containing wastewater, calcium chloride, calcium hydroxide and seed crystals are mixed, and the seed crystals are placed in a fluidized state by controlling the hydraulic parameters of the water body; the seed crystals induce fluoride ions and calcium ions in the water body to react and nucleate and grow on the surface of the seed crystals in the form of calcium fluoride to form granules; The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water obtained. A part of the treated water is discharged and a part is stored for subsequent reflux. Wherein, the added molar amount of calcium chloride is 1 / 10 to 1 / 6 of the molar amount of fluoride ions in the reaction system; The added molar amount of calcium hydroxide is 1 / 5 to 1 / 4 of the molar amount of fluoride ions in the reaction system; When the amount of treated water to be stored reaches the set value: The reflux ratio of the treated water is determined according to the fluoride ion concentration in the acidic fluoride-containing wastewater, and then the amount of the acidic fluoride-containing wastewater and the discharge amount of the treated water are adjusted to ensure that the addition ratio of calcium chloride remains unchanged, increase the addition ratio of calcium hydroxide, and control the stored treated water to reflux into the reaction system according to the determined reflux ratio; at this time, the hydrochloric acid in the reflux water reacts with the calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with the fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

2. The core crystal granulation process according to claim 1, characterized in that: Before the mixing, the pH of the acidic fluorine-containing wastewater is adjusted to 4-5.

3. The core crystal granulation process according to claim 1, characterized in that: The seed crystals include one or more of quartz sand, dolomite, brucite, ZSM-5 zeolite or marble powder.

4. The core crystal granulation process according to claim 1 or 2, characterized in that: When the fluoride ion concentration in the acidic fluoride-containing wastewater does not exceed 1000 mg / L, the reflux amount of the treated water is 1 to 1.2 times the amount of the acidic fluoride-containing wastewater.

5. The core crystal granulation process according to claim 1 or 2, characterized in that: When the fluoride ion concentration in the acidic fluoride-containing wastewater is greater than 1000 mg / L and less than 5000 mg / L, the reflux amount of the treated water is 3 to 3.2 times the amount of the acidic fluoride-containing wastewater.

6. The core crystal granulation process according to claim 1 or 2, characterized in that: When the fluoride ion concentration in the acidic fluoride-containing wastewater is not less than 5000 mg / L, the reflux amount of the treated water is 5 to 5.2 times the amount of the acidic fluoride-containing wastewater.

7. The core crystal granulation process according to any one of claims 1 to 6, characterized in that: When the concentration of fluoride ions in the treated water is lower than 10 mg / L, the reflux is stopped and all the treated water is discharged.

8. The core crystal granulation process according to any one of claims 1 to 7, characterized in that: The core crystal granulation process is carried out by using a core crystal granulation device, and the core crystal granulation device includes a core crystal granulation reactor and a storage tank; The lower ends of the side walls of the nuclear crystal granulation reactor are respectively provided with wastewater inlets for introducing acidic fluorine-containing wastewater; 2 crystal inducing agent injection ports, one for introducing calcium chloride solution and the other for introducing calcium hydroxide solution; and a reflux port for achieving reflux of treated water; The top end or the upper end of the side wall of the core crystal granulation reactor is provided with a water outlet for discharging the treated water in the core crystal granulation reactor; The bottom end of the nuclear crystal granulation reactor is provided with a granulation body discharge port for discharging the granulation body; The storage tanks are respectively provided with water storage inlets for receiving part of the treated water from the water outlet of the core crystal granulation reactor; and, a water storage outlet for discharging the treated water in the storage tank to a reflux port of the core crystal granulation reactor; Preferably, the wastewater inlet, the crystal inducing agent addition port and the reflux port are located at the same height.

9. The core crystal granulation process according to claim 8, characterized in that: The core crystal granulation process comprises: Under initial working condition: Filling seed crystals into the nuclear crystal granulation reactor; Adjust the pH of acidic fluoride-containing wastewater to 4-5; The regulated acidic fluorine-containing wastewater, calcium chloride solution and calcium hydroxide solution are respectively introduced into the seed crystal granulation reactor to make the seed crystal in a fluidized state; the seed crystal induces the fluoride ions in the acidic fluorine-containing wastewater to react with the calcium ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride to form a granulation body; The residual chloride ions after the reaction react with the residual hydrogen ions in the water to form hydrochloric acid which is stored in the treated water obtained. A part of the treated water is discharged and a part is stored for subsequent reflux. The added molar amount of calcium chloride is 1 / 10 to 1 / 6 of the molar amount of fluoride ions in the reaction system; The molar amount of calcium hydroxide added is 1 / 5 to 1 / 4 of the molar amount of fluoride ions in the reaction system; After the water volume in the storage tank reaches the set value: The reflux ratio of the treated water is determined according to the fluoride ion concentration in the acidic fluoride-containing wastewater, and then the water inlet of the acidic fluoride-containing wastewater and the discharge of the treated water are adjusted to ensure that the addition ratio of calcium chloride remains unchanged, increase the addition ratio of calcium hydroxide, and control the treated water in the storage tank to reflux to the nuclear crystal granulation reactor according to the determined reflux ratio; at this time, the hydrochloric acid in the reflux water reacts with the calcium hydroxide to generate calcium chloride, and the calcium ions in the obtained calcium chloride continue to react with the fluoride ions and nucleate and grow on the surface of the seed crystal in the form of calcium fluoride, thereby realizing the cyclic regeneration of calcium chloride and strengthening the recovery of fluorine resources.

10. The core crystal granulation process according to claim 9, characterized in that: The filling height of the seed crystal is 20-40% of the effective height of the nuclear crystal granulation reactor; Preferably, the hydraulic retention time of the acidic fluorine-containing wastewater in the core crystallization granulation reactor is not less than 5 minutes.