Calcium fluoride crystallization method based on graded dosing in single reaction tank

Abstract

The invention discloses a calcium fluoride crystallization method based on graded dosing in a single reaction tank, which comprises the following steps: S1, introducing high-fluorine wastewater into a first-stage reaction zone of the reaction tank, and adding a precipitator to be mixed with the high-fluorine wastewater to form first slurry containing calcium fluoride coarse crystal nucleuses; s2, introducing the first slurry into a second-stage reaction zone of the reaction tank, and adding a calcium salt agent into the second-stage reaction zone to mix the calcium salt agent with the first slurry to form second slurry containing calcium fluoride crystals; and S3, introducing the second slurry into a separation area, carrying out solid-liquid separation on the second slurry, and recovering calcium fluoride crystals. The reaction area in the reaction tank is divided into the first-stage reaction area and the second-stage reaction area, and the three chemical adding units of the chemical adding device mounted at the top of the reaction tank are combined, so that the occupied area of the reaction area is reduced, the equipment structure is simplified, and meanwhile, two chemicals can be prevented from mutually competing and interfering; the fractional crystallization process is accurately controlled while the dosage of the medicament is reduced.

Description

Technical Field

[0001] This invention relates to the field of calcium fluoride crystallization technology, and in particular to a calcium fluoride crystallization method based on staged dosing in a single reaction tank. Background Technology

[0002] Fluoride-containing wastewater generated in industrial activities is due to its fluoride content (French fluoride). Excessive fluoride concentrations pose significant environmental and ecological toxicity and health risks (such as causing fluorosis and damaging the nervous system). Therefore, efficient, economical, and stable deep treatment of fluoride-containing wastewater is a major demand and a rigid constraint in the field of environmental protection. Among numerous fluoride-containing wastewater treatment technologies, chemical precipitation and its derived optimized processes (such as crystallization) have become the mainstream technology widely used in industry due to their advantages such as mature technology, relatively simple operation, and large treatment capacity. The core principle of this technology lies in adding specific chemical agents to the wastewater to induce fluoride ions (fluoride ions) to form fluoride ions (fluoride ions). The fluoride is converted into a sparingly soluble fluoride precipitate, which is then removed through solid-liquid separation. Among these, calcium salts (such as calcium chloride CaCl2 and calcium hydroxide Ca(OH)2) are widely recognized as indispensable core precipitants / nucleation inducers in this process system due to their significant economic and technological advantages, including wide availability, low cost, and suitable reactivity.

[0003] Currently, the traditional calcium fluoride crystallization process generally adopts a multi-stage series reaction or a single-tank reaction to carry out the crystallization reaction by adding different calcium sources. However, both methods have certain problems. For multi-stage series reactions, the following problems exist: (1) Large footprint: Each stage of the multi-stage series reaction tank needs to be set up with a separate tank and stirring device. Different calcium sources are added to different reaction tanks and then reacted. However, this method has problems such as large equipment footprint and high engineering investment costs. (2) Complex process and high equipment operation and maintenance costs: Multi-stage series reaction tanks have many equipment control points and complex processes, which requires high operation and maintenance personnel. For single-stage reaction tanks, the following problems exist: (1) Adding different calcium sources to the same tank can easily cause mutual interference, making it impossible to accurately control the graded crystallization process; (2) Mixed addition of chemicals in a single tank makes it difficult to achieve the graded fluoride control target. Summary of the Invention

[0004] To address the technical problems existing in the background art, this invention proposes a calcium fluoride crystallization method based on staged dosing in a single reaction tank.

[0005] The present invention proposes a calcium fluoride crystallization method based on staged dosing in a single reaction tank, comprising: S1, introducing high-fluoride wastewater into the primary reaction zone of the reaction tank, adding a precipitant and mixing it with the high-fluoride wastewater to form a first slurry containing coarse calcium fluoride crystal nuclei; S2, introducing the first slurry into a secondary reaction zone of the reaction tank, dynamically adjusting a dosing parameter of the precipitant according to the fluoride ion concentration at the outlet of the primary reaction zone; adding calcium salt agent into the secondary reaction zone to mix with the first slurry to promote the growth of the calcium fluoride coarse crystal nucleus, forming a second slurry containing calcium fluoride crystals; S3, introducing the second slurry into a separation zone, dynamically adjusting a dosing parameter of the calcium salt agent according to the fluoride ion concentration at the outlet of the secondary reaction zone; solid-liquid separating the second slurry to recover calcium fluoride crystals.

[0006] Preferably, S1 specifically includes: introducing the high-fluorine wastewater into the primary reaction zone of the reaction tank through the water inlet; adding the precipitant into the primary reaction zone through the first dosing unit of the agent dosing device arranged above the primary reaction zone; using the gas stripping stirring device to stir the high-fluorine wastewater and the precipitant in the primary reaction zone at high speed to form the first slurry containing calcium fluoride coarse crystal nucleus.

[0007] Preferably, S2 specifically includes: introducing the first slurry into the secondary reaction zone through the flow guide plate; monitoring the first fluoride ion concentration at the outlet of the primary reaction zone in real time; dynamically adjusting the precipitant dosing parameter according to the first fluoride ion concentration, the precipitant dosing parameter including the precipitant dosing flow and the number of precipitant dosing points; adding the calcium salt agent into the secondary reaction zone through the second dosing unit of the agent dosing device arranged above the secondary reaction zone; using the gas stripping stirring device to stir the calcium salt agent and the first slurry in the secondary reaction zone at low speed to promote the growth of the calcium fluoride coarse crystal nucleus to form the second slurry containing calcium fluoride crystals.

[0008] Preferably, S3 specifically includes: introducing the second slurry into the separation zone; monitoring the second fluoride ion concentration at the outlet of the secondary reaction zone in real time; dynamically adjusting the calcium salt agent dosing parameter according to the second fluoride ion concentration, the calcium salt agent dosing parameter including the calcium salt agent dosing flow and the number of calcium salt agent dosing points; using the sludge scraper to solid-liquid separate the second slurry to form calcium fluoride crystal precipitate and supernatant; using the lifting pump to recover the calcium fluoride crystals, and the supernatant flows to the water outlet area through the water outlet channel and is discharged.

[0009] Preferably, the agent dosing device further has a third dosing unit, the third dosing unit is arranged between the first dosing unit and the second dosing unit, the dosing points of the third dosing unit are divided into a first part of dosing points and a second part of dosing points, the first part of dosing points are uniformly arranged in the primary reaction zone, and the second part of dosing points are uniformly arranged in the secondary reaction zone; the third dosing unit adjusts the number of opened first part of dosing points and the number of opened second part of dosing points through a control valve.

[0010] Preferably, the number of dosing points of the precipitant includes the number of dosing points of the first dosing unit and the number of open dosing points of the first part of the third dosing unit; and the dynamic adjustment of the precipitant dosing parameters according to the first fluoride ion concentration is specifically: controlling the power of the first dosing pump of the first dosing unit to adjust the amount of precipitant dosing, and controlling the valve of the third dosing unit to adjust the number of open dosing points of the first part of the third dosing unit.

[0011] Preferably, the number of dosing points of the calcium salt medicament includes the number of dosing points of the second dosing unit and the number of open dosing points of the second part of the third dosing unit; and the dynamic adjustment of the calcium salt medicament dosing parameters according to the second fluoride ion concentration is specifically: controlling the power of the second dosing pump of the second dosing unit to adjust the amount of calcium salt medicament dosing, and controlling the valve of the third dosing unit to adjust the number of open dosing points of the second part of the third dosing unit.

[0012] Preferably, the valve of the third dosing unit is automatically controlled by a control unit; the control unit is configured to receive a first fluoride ion concentration signal from a first fluoride ion concentration detector at the outlet of the primary reaction zone and a second fluoride ion concentration signal from a second fluoride ion concentration detector at the outlet of the secondary reaction zone; based on the first fluoride ion concentration signal, the opening and closing of the valve on the first part of the dosing points of the third dosing unit is controlled, and based on the second fluoride ion concentration signal, the opening and closing of the valve on the second part of the dosing points of the third dosing unit is controlled.

[0013] Preferably, the control unit has a hierarchical control logic, which is specifically: first, based on the first fluoride ion concentration signal, the valve corresponding to the first part of the dosing points in the third dosing unit is controlled to open and close; then, based on the second fluoride ion concentration signal, the valve corresponding to the second part of the dosing points in the third dosing unit is controlled to open and close.

[0014] Preferably, it further comprises S4, which is specifically: during operation, periodically performing desilting through the crystallization reaction zone discharge port, and the primary reaction zone and the secondary reaction zone form the crystallization reaction zone.

[0015] The present application divides the reaction area inside the reaction tank into a primary reaction zone and a secondary reaction zone, which can form two independent reaction areas while meeting the requirements of reducing the floor area and simplifying the equipment structure, can be used for adding different calcium salt medicaments, thereby forming calcium fluoride crystalline products of different levels, and the three dosing units of the medicament dosing device installed on the top of the reaction tank can also prevent mutual competition and interference between the two medicaments, thereby achieving precise control of the fractional crystallization process while reducing the amount of medicament. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flowchart of the calcium fluoride crystallization method based on fractional dosing in a single reaction tank is provided. Figure 2 A plan view of a crystallization device used in the calcium fluoride crystallization method based on staged dosing in a single reaction tank according to the present application. DETAILED DESCRIPTION

[0017] Reference Figure 1 The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to the present application is performed in a crystallization device 1 as shown in Figure 2 The crystallization device 1 includes a reaction zone 11, a crystallization separation zone 12, and a water outlet zone 13. The reaction zone 11 is divided into an upstream first-stage reaction zone 111 and a downstream second-stage reaction zone 112 by a downwardly-inverted baffle. A passage is left between the bottom of the baffle and the bottom of the tank, forcing the water flow from the bottom of the first-stage reaction zone 111 into the second-stage reaction zone 112.

[0018] A reagent dosing device 2 is also provided at the top of the reaction zone 11. The reagent dosing device 2 is mainly used to dose the calcium source, i.e., the precipitant (calcium hydroxide) and the calcium salt reagent (calcium chloride), required for the calcium fluoride crystallization reaction into the reaction zone 11. The precipitant and the calcium salt reagent are respectively stored in two dosing tanks upstream of the reaction zone 11, so as to facilitate the dosing of different calcium sources into the first-stage reaction zone 111 and the second-stage reaction zone 112. The calcium hydroxide and the calcium chloride can also be respectively subjected to crystallization reaction with the fluorine-containing wastewater in the single tank. Compared with the existing multi-stage series reaction tank structure, the calcium fluoride crystallization method based on staged dosing in a single reaction tank according to the present application has the advantages of small footprint, simple equipment structure, simple control process, and low engineering investment cost.

[0019] In this embodiment, the reagent dosing device 2 is divided into a first dosing unit 21, a second dosing unit 22, and a third dosing unit 23 along the water flow direction. The third dosing unit 23 is arranged between the first dosing unit 21 and the second dosing unit 22. The first dosing unit 21, the second dosing unit 22, and the third dosing unit 23 are each provided with multiple dosing points. The dosing service area of each dosing point is between 0.25 m2 and 0.64 m2 per unit area of the reaction zone 11, and the dosing amount of each dosing point is between 4 L / min and 8 L / min.

[0020] The first dosing unit 21, located in the first third of the section, is connected to a dosing tank containing a precipitant. The dosing point of the first dosing unit 21 is located at the top of the primary reaction zone 111, allowing calcium hydroxide to be added into the primary reaction zone 111. The second dosing unit 22, located in the last third of the section, is connected to a dosing tank containing a calcium salt reagent. The dosing point of the second dosing unit 22 is located at the top of the secondary reaction zone 112, used to add calcium chloride into the secondary reaction zone 112. The third dosing unit 23, located in the middle third of the section, is connected to both dosing tanks. The dosing point of the dosing unit 23 is arranged between the primary reaction zone 111 and the secondary reaction zone 112. The dosing point is divided into a first dosing point located above the primary reaction zone 111 and a second dosing point located above the secondary reaction zone 112. The first dosing point and the second dosing point are connected to the calcium hydroxide dosing pipe or calcium chloride dosing pipe on the two dosing tanks through pipelines. Thus, the purpose of supplementing calcium hydroxide into the primary reaction zone 111 or calcium chloride into the secondary reaction zone 112 can be achieved by controlling the valve on the third dosing unit 23.

[0021] The specific steps of the calcium fluoride crystallization method based on the above-mentioned crystallization apparatus are as follows: S1. High-fluoride wastewater is introduced into the primary reaction zone 111 of reaction zone 11 through the inlet; calcium hydroxide is added into the primary reaction zone 111 through the first dosing unit 21 of the reagent dosing device 2 set above the primary reaction zone 111 to control the pH of the liquid in the primary reaction zone 111 between 7 and 8. The high-fluoride wastewater and calcium hydroxide in the primary reaction zone 111 are stirred at high speed (e.g., 200-300 rpm) by an air-lift stirring device, so that the high-fluoride wastewater and calcium hydroxide can be quickly mixed to form coarse calcium fluoride crystal nuclei. At this time, the mixture of liquid in the primary reaction zone 111 and coarse calcium fluoride crystal nuclei is the first slurry.

[0022] S2. The first slurry in the primary reaction zone 111 is introduced into the secondary reaction zone 112 through a guide plate. During its entry into the secondary reaction zone 112, it flows through the fluoride ion concentration monitor at the outlet of the primary reaction zone 111, which monitors the fluoride ion concentration at the outlet of the primary reaction zone 111 in real time. During this process, the system control unit receives the first fluoride ion concentration signal (C1) fed back by the fluoride ion concentration monitor in real time and compares C1 with the system's preset threshold range (e.g., 25 mg / L-30 mg / L).

[0023] If C1 > 30 mg / L at this time, the control unit issues the following commands: Command 1: Control the power of the first dosing pump of the first dosing unit 21 to increase the total amount of calcium hydroxide added; Command 2: Link control the valve of the third dosing unit 23 to open one or more valves of the first part of the dosing point connected to the calcium hydroxide pipeline in the third dosing unit 23 that were originally closed, open the first part of the dosing point of the third dosing unit 23, and use the third dosing unit 23 to add calcium hydroxide into the primary reaction zone 111 to increase the number of precipitant dosing points in the primary reaction zone 111 and prolong the calcium hydroxide reaction time; If C1 < 25 mg / L at this time, the control unit issues the following commands: Command 1: Control the first dosing pump to reduce the amount of calcium hydroxide added; Command 2: Close one or more valves of the first part of the dosing point that have been opened in the third dosing unit 23, reduce the number of opening first part dosing points in the third dosing unit 23, and shorten the reaction time of calcium hydroxide. If the concentration of C1 is between 25 mg / L and 30 mg / L, then the current dosage should be maintained.

[0024] After the first slurry enters the secondary reaction zone 112, the second dosing unit 22 at the top of the secondary reaction zone 112 adds calcium chloride solution to replenish calcium ions, thereby promoting fine crystallization and further crystal growth. During this process, the calcium chloride solution and the first slurry in the secondary reaction zone 112 are stirred at a low speed (e.g., 50-100 rpm) using an air-lift stirring device to promote the continued growth of coarse calcium fluoride crystal nuclei, forming a second slurry containing calcium fluoride crystals.

[0025] S3. The second slurry is introduced into the separation zone. A fluoride ion concentration monitor is also installed at the outlet of the secondary reaction zone 112 to monitor the fluoride ion concentration at the outlet of the secondary reaction zone 112 in real time. Similarly, the system control unit will receive the second fluoride ion concentration signal (C2) fed back by the fluoride ion concentration monitor at this location in real time, and compare C2 with another preset threshold range (e.g., 10 mg / L-15 mg / L).

[0026] If C2 > 15 mg / L at this time, the control unit issues the following commands: Command 1: Increase the power of the second dosing pump in the second dosing unit 22 to increase the calcium chloride dosage; Command 2: Link control the valves of the third dosing unit 23 to open one or more valves in the third dosing unit 23 that were originally closed and connected to the second part of the calcium chloride pipeline, so that the third dosing unit 23 can be connected to the calcium chloride dosing tank, thereby opening the second part of the dosing points in the third dosing unit 23, increasing the number of calcium salt reagent dosing points in the secondary reaction zone 112, and prolonging the calcium chloride reaction time; If C2 < 10 mg / L at this time, the control unit will issue the following commands: Command 1: Reduce the frequency of the second dosing pump and reduce the amount of calcium chloride added; Command 2: When linked, adjust the valve of the third dosing unit 23, close the valve of one or more of the second part dosing points that have been opened in the third dosing unit 23, reduce the number of open second part dosing points, and shorten the calcium chloride reaction time. If 10 mg / L ≤ C2 ≤ 15 mg / L at this time, then maintain the current dosage.

[0027] It is worth emphasizing that the crystallization treatment of fluoride-containing wastewater is a series of irreversible physicochemical processes. The wastewater must first undergo a preliminary reaction with calcium hydroxide in the primary reaction zone 111 (forming coarse crystal nuclei and removing most of the fluoride) before the resulting slurry can enter the secondary reaction zone 112 for refined crystal growth. Therefore, the aforementioned control unit's reception and comparison process for C2 only begins after C1 has taken effect. This design prioritizes the stability and optimization of the reaction within the primary reaction zone 111. Furthermore, within each control cycle, the adjustment decisions for the parameters of the primary reaction zone 111 are made independently based on its own effluent quality, without being simultaneously affected by cross-influenced feedback signals from the secondary reaction zone 112. This allows the system to independently optimize the secondary reaction zone 112 based on new steady-state conditions after adjustments in the primary reaction zone 111 have taken effect, thus avoiding conflicts in action execution.

[0028] S4. The sedimentation scraper 121 located upstream of the separation zone 12 is used to perform solid-liquid separation on the second slurry, separating calcium fluoride crystal precipitate and supernatant; the separated calcium fluoride crystal precipitate is recovered by a booster pump, and the supernatant after removing the calcium fluoride crystal flows by gravity to the effluent zone 13 through the effluent channel and is then discharged from the system.

[0029] S5. During operation, sludge is discharged periodically through the vent of the crystallization reaction zone. The primary reaction zone 111 and the secondary reaction zone 112 constitute the crystallization reaction zone.

[0030] The apparatus and method described in this embodiment were used to treat fluoride-containing wastewater (initial fluoride ion concentration approximately 500 mg / L) from a photovoltaic enterprise. After the system stabilized, the addition of calcium hydroxide and calcium chloride was precisely optimized through the aforementioned intelligent feedback control. This enabled independent dosing calculations for two-stage fluoride treatment within a single tank, avoiding competition and interference between the two calcium sources. This reduced reagent consumption while precisely controlling the staged crystallization process. The fluoride ion concentration in the effluent from the primary reaction zone 111 was stably controlled at 28±2 mg / L, and the fluoride ion concentration in the effluent from the secondary reaction zone 112 (final) was stably controlled at 12±2 mg / L, far below the emission limit of 15 mg / L. Simultaneously, due to the ideal staged crystallization conditions, the formed calcium fluoride crystals were large with good settling properties, allowing for effective separation in the crystallization separation zone, resulting in high-purity recovered calcium fluoride. The entire system uses only one reaction tank, reducing the floor space by approximately 40% compared to traditional two-stage series processes. It also features a high degree of automation and reduces reagent consumption by approximately 15% compared to traditional empirical dosing methods.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for calcium fluoride crystallization based on staged dosing in a single reaction tank, characterized in that, include: S1. High-fluoride wastewater is introduced into the primary reaction zone of the reaction tank, and a precipitant is added and mixed with the high-fluoride wastewater to form a first slurry containing coarse calcium fluoride crystal nuclei. S2. Introduce the first slurry into the secondary reaction zone of the reaction tank, and dynamically adjust the addition parameters of the precipitant according to the fluoride ion concentration at the outlet of the primary reaction zone; add calcium salt reagent to the secondary reaction zone to mix with the first slurry to promote the continued growth of the coarse calcium fluoride crystal nuclei and form a second slurry containing calcium fluoride crystals; S3. Introduce the second slurry into the separation zone, and dynamically adjust the addition parameters of the calcium salt reagent according to the fluoride ion concentration at the outlet of the secondary reaction zone; separate the second slurry into solid and liquid phases, and recover calcium fluoride crystals.

2. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 1, characterized in that, Specifically, S1 involves introducing high-fluoride wastewater into the primary reaction zone of the reaction tank through an inlet; and adding a precipitant into the primary reaction zone through the first dosing unit of the reagent dosing device located above the primary reaction zone. The high-fluoride wastewater and precipitant in the primary reaction zone are stirred at high speed using an air-lift stirring device to form the first slurry containing coarse calcium fluoride crystal nuclei.

3. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 1, characterized in that, S2 specifically involves: introducing the first slurry into the secondary reaction zone through a guide plate; monitoring the concentration of the first fluoride ion at the outlet of the primary reaction zone in real time; dynamically adjusting the precipitant addition parameters based on the first fluoride ion concentration, the precipitant addition parameters including the precipitant addition flow rate and the number of precipitant addition points; adding calcium salt reagent into the secondary reaction zone through the second dosing unit of the reagent dosing device located above the secondary reaction zone; and using an air-lift stirring device to stir the calcium salt reagent and the first slurry in the secondary reaction zone at low speed to promote the continued growth of coarse calcium fluoride crystal nuclei to form a second slurry containing calcium fluoride crystals.

4. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 3, characterized in that, S3 specifically involves: introducing the second slurry into the separation zone; monitoring the concentration of the second fluoride ions at the outlet of the secondary reaction zone in real time; dynamically adjusting the calcium salt reagent dosing parameters based on the concentration of the second fluoride ions, including the calcium salt reagent dosing flow rate and the number of calcium salt reagent dosing points; performing solid-liquid separation on the second slurry using a sedimentation scraper to form calcium fluoride crystal precipitate and supernatant; recovering the calcium fluoride crystals using a lift pump, and discharging the supernatant through the effluent channel to the effluent area.

5. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 4, characterized in that, The drug dosing device also has a third dosing unit, which is arranged between the first dosing unit and the second dosing unit. The dosing points of the third dosing unit are divided into a first part dosing point and a second part dosing point. The first part dosing points are evenly distributed in the primary reaction zone, and the second part dosing points are evenly distributed in the secondary reaction zone. The third dosing unit adjusts the number of the first part dosing points and the number of the second part dosing points by controlling the valve.

6. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 5, characterized in that, The number of precipitant dosing points includes the number of dosing points in the first dosing unit and the number of dosing points in the first part of the third dosing unit that are opened; the dynamic adjustment of precipitant dosing parameters according to the first fluoride ion concentration specifically involves controlling the power of the first dosing pump in the first dosing unit to adjust the amount of precipitant added, and controlling the valves in the third dosing unit in conjunction to adjust the number of dosing points in the first part of the third dosing unit that are opened.

7. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 6, characterized in that, The number of calcium salt dosing points includes the number of dosing points in the second dosing unit and the number of dosing points in the second part of the third dosing unit that are open; the dynamic adjustment of calcium salt dosing parameters according to the second fluoride ion concentration specifically involves controlling the power of the second dosing pump in the second dosing unit to adjust the calcium salt dosing amount, and controlling the valve of the third dosing unit in conjunction to adjust the number of dosing points in the second part of the third dosing unit that are open.

8. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 7, characterized in that, The valves of the third dosing unit are automatically controlled by a control unit. The control unit is configured to: receive a first fluoride ion concentration signal from a first fluoride ion concentration detector at the outlet of the primary reaction zone and a second fluoride ion concentration signal from a second fluoride ion concentration detector at the outlet of the secondary reaction zone; control the opening and closing of the valves at the first dosing points of the third dosing unit based on the first fluoride ion concentration signal, and control the opening and closing of the valves at the second dosing points of the third dosing unit based on the second fluoride ion concentration signal.

9. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 8, characterized in that, The control unit has hierarchical control logic, which specifically involves: firstly, controlling the opening and closing of valves corresponding to the first part of the dosing points in the third dosing unit based on the first fluoride ion concentration signal; and then controlling the opening and closing of valves corresponding to the second part of the dosing points in the third dosing unit based on the second fluoride ion concentration signal.

10. The calcium fluoride crystallization method based on staged dosing in a single reaction tank according to claim 1, characterized in that, It also includes S4, which specifically refers to the periodic sludge discharge operation through the vent of the crystallization reaction zone during operation. The primary reaction zone and the secondary reaction zone constitute the crystallization reaction zone.

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