Built-in calcium fluoride crystallizer based on coagulative precipitation tank

Abstract

The invention discloses a built-in calcium fluoride crystallizer based on a coagulative precipitation tank, a first guide cylinder and a second guide cylinder are respectively fixed on opposite side walls in the coagulative precipitation tank, a fluorine-containing wastewater inlet pipeline conveys fluorine-containing wastewater into the first guide cylinder, a calcium-containing medicament inlet pipeline conveys a calcium-containing medicament into the second guide cylinder, and the first guide cylinder and the second guide cylinder are communicated with each other. The first propeller and the second propeller are fixed in the first guide cylinder and the second guide cylinder respectively, the first propeller vertically pushes flow downwards, the second propeller vertically pushes flow upwards, the stirrer can stir liquid in the coagulating basin, and the crystal discharging device can regularly discharge crystal precipitates at the bottom of the coagulating basin into the cyclone separator. The cyclone separator can perform cyclone separation on large-particle crystals and small-particle crystals, the large-particle crystals are discharged from a crystal outlet of the cyclone separator, and the small-particle crystals are discharged from a water outlet of the cyclone separator along with water flow and enter the coagulating basin. The medicament cost is reduced, and the improvement cost is low.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a built-in calcium fluoride crystallizer based on a coagulation sedimentation tank. Background Technology

[0002] In the field of industrial wastewater treatment, the treatment of fluoride-containing wastewater has long relied on traditional chemical precipitation methods, namely, adding excess lime (Ca(OH)2) to form calcium fluoride (CaF2) precipitate. This method has significant drawbacks:

[0003] 1. High consumption of reagents: It is necessary to maintain a highly alkaline environment with the pH of the mixed solution between 10 and 11. The amount of lime added often exceeds the theoretical value by 30%-50%, resulting in high reagent costs.

[0004] 2. Low energy efficiency: It relies on mechanical stirring to maintain the uniformity of the reaction, and electricity consumption accounts for 15%-20% of the processing cost;

[0005] 3. Difficulty in sludge disposal: The generated amorphous CaF2 precipitate particles are small and have poor settling performance, requiring the addition of flocculants and the use of sludge dewatering equipment for subsequent treatment.

[0006] Currently, mainstream processes (such as the combination of neutralization reaction tank and sedimentation tank) do not integrate crystallization optimization devices, resulting in:

[0007] 1. Insufficient crystallinity of the reaction product affects the fluoride removal rate (usually only 80%-90%);

[0008] 2. The equipment occupies a large area, and the renovation requires production to be stopped for construction, which takes 2-4 weeks. Summary of the Invention

[0009] To overcome the above deficiencies, the present invention provides a built-in calcium fluoride crystallizer based on a coagulation sedimentation tank. This built-in calcium fluoride crystallizer based on a coagulation sedimentation tank can upgrade and transform the original tank, improve the fluoride recovery rate, and is simple and low in cost.

[0010] The technical solution adopted by this invention to solve its technical problem is: a built-in calcium fluoride crystallizer based on a coagulation sedimentation tank, comprising a coagulation tank and a sedimentation tank. The mixed liquid in the coagulation tank can be discharged into the sedimentation tank for sedimentation treatment. The upper side wall of the sedimentation tank is provided with an outlet for discharging the upper clear water. It also includes a fluoride wastewater inlet pipe, a calcium-containing reagent inlet pipe, a first guide cylinder, a second guide cylinder, a first propeller, a second propeller, a stirrer, a crystal discharge device, and a cyclone separator. The first and second guide cylinders are respectively fixedly installed on two opposite side walls inside the coagulation tank. The fluoride wastewater inlet pipe is fixedly inserted into the upper end of the first guide cylinder for conveying fluoride wastewater into the first guide cylinder. The calcium-containing reagent inlet pipe... A pipe is fixedly inserted into the upper end of the second guide tube to deliver calcium-containing agents into the second guide tube. The first and second propellers are fixedly installed in the first and second guide tubes, respectively. The first propeller pushes the flow vertically downward, and the second propeller pushes the flow vertically upward. The agitator is fixedly installed in the coagulation tank and can stir the liquid in the coagulation tank. The crystal discharge device can periodically discharge the crystal sediment at the bottom of the coagulation tank into the hydrocyclone separator. The hydrocyclone separator can separate large crystal particles from water and small crystal particles through hydrocyclone separation. Large crystal particles are discharged from the crystal outlet at the lower end of the hydrocyclone separator, and small crystal particles are discharged with the water flow from the drain outlet at the upper end of the hydrocyclone separator and enter the coagulation tank through the drainage pipe.

[0011] As a further improvement of the present invention, the first and second propellers have the same power and the same flow velocity, and the flow rate of the first and second propellers is 10-20 times the flow rate of the fluoride-containing wastewater inlet.

[0012] As a further improvement of the present invention, the cross-sections of the first guide tube, the second guide tube, the first thruster, and the second thruster are all rectangular structures.

[0013] As a further improvement of the present invention, a conical sedimentation inner barrel with an upper inner diameter larger than the lower inner diameter is fixedly installed in the sedimentation tank. An overflow weir is formed at the upper edge of the conical sedimentation inner barrel. A water outlet is provided on the upper side wall of the coagulation tank. The height of the water outlet is lower than the height of the overflow weir by a set distance. The water outlet of the coagulation tank is connected to the upper end of the conical sedimentation inner barrel in the sedimentation tank through a water pipe. The mixed liquid in the coagulation tank can enter the conical sedimentation inner barrel of the sedimentation tank through the water pipe for sedimentation treatment. A row of mud pipes is installed at the lower end of the conical sedimentation inner barrel.

[0014] As a further improvement of the present invention, a central cylinder is fixedly installed at the center of the conical sedimentation inner tank in the sedimentation tank. The lower end of the central cylinder is open, and there is a set distance between the lower end of the central cylinder and the side wall and bottom surface of the conical sedimentation inner tank. The height of the upper end of the central cylinder is not higher than the height of the upper end of the conical sedimentation inner tank.

[0015] As a further improvement of the present invention, a three-way pipe is further provided. One path of the three-way pipe is connected to the sludge discharge pipe, the second path forms a sludge discharge channel, and a reflux pipe is connected to the third path. The liquid outlet of the reflux pipe is located above the opening of the coagulation tank. Control valves are respectively installed on the second path and the third path of the three-way pipe. The two control valves can control the on / off and flow rate of the second path and the third path of the three-way pipe. A reflux pump is also provided. The reflux pump can send the calcium fluoride crystals deposited at the bottom of the conical sedimentation inner barrel into the coagulation tank along the sludge discharge pipe, the third path of the three-way pipe and the reflux pipe.

[0016] As a further improvement of the present invention, the crystal discharging device includes an air-lift crystal discharging pipe and an external air supply pipeline. One end of the air-lift crystal discharging pipe extends into the bottom of the coagulation tank, and the other end of the air-lift crystal discharging pipe is connected to the liquid inlet of the hydrocyclone separator. An air inlet pipe extending obliquely downward is provided on the side wall of one end of the air-lift crystal discharging pipe. The air inlet pipe is connected to the external air supply pipeline through a reduced-diameter air nozzle. The air flow in the external air supply pipeline enters the air-lift crystal discharging pipe obliquely upward through the air inlet pipe. The air flow flowing in the direction of the other end of the air-lift crystal discharging pipe makes one end of the air-lift crystal discharging pipe form a negative pressure. The negative pressure at one end of the air-lift crystal discharging pipe can adsorb the crystal precipitate deposited at the bottom of the coagulation sedimentation tank.

[0017] As a further improvement of the present invention, a "king" - shaped air-lift branch pipe is fixedly installed at the bottom of the coagulation tank. There is a set distance between the lower side surface of the air-lift branch pipe and the bottom of the coagulation tank. Absorbing crystal holes are opened at the bottom of the air-lift branch pipe at intervals, and the opening direction of the absorbing crystal holes is vertically downward. The air-lift branch pipe is fixedly connected to one end of the air-lift crystal discharging pipe and is connected to the air-lift crystal discharging pipe.

[0018] As a further improvement of the present invention, the air-lift branch pipe is installed at a height of 10 cm - 50 cm from the bottom of the coagulation tank. The air-lift crystal discharging pipe is of an L-shaped structure, and its vertical section is inserted into the coagulation tank from top to bottom. The lower end of its vertical section is connected to the air-lift branch pipe. The air inlet pipe is fixedly installed on the side wall of the vertical section of the air-lift crystal discharging pipe at a 45 ° oblique angle, and the position where the air inlet pipe is installed on the vertical section of the air-lift crystal discharging pipe is 10 cm - 30 cm above the air-lift branch pipe.

[0019] As a further improvement of the present invention, the stirrer is located at the central position of the coagulation tank. The stirrer includes a stirring motor, a stirring shaft and stirring fan blades. The stirring motor drives the stirring shaft to rotate, and the stirring fan blades are fixedly installed on the stirring shaft.

[0020] The beneficial technical effects of this invention are as follows: This invention transforms the coagulation and sedimentation tanks of traditional coagulation and sedimentation processes into a crystallization fluidized bed process by adding prefabricated components. By forming an annular fluidized reaction zone within the coagulation tank, the crystallinity of calcium fluoride is significantly improved, reducing the amount of calcium-containing reagents required. The annular fluidized reaction zone generated by the first and second propellers in the coagulation tank of this invention can enhance mixing efficiency, reduce energy consumption, and promote crystal growth. The guide cylinder and agitator in the coagulation tank, as well as the conical sedimentation inner tank and central cylinder in the sedimentation tank, are all modularly designed, enabling rapid integration into existing treatment systems within 48 hours. During the modification, only installation space needs to be reserved on the tank wall, making the modification convenient, quick, and cost-effective. Attached Figure Description

[0021] Figure 1 This is a three-dimensional diagram illustrating the structural principle of the present invention;

[0022] Figure 2 This is a front view illustrating the structural principle of the present invention;

[0023] Figure 3 This is a top view illustrating the structural principle of the present invention;

[0024] Figure 4 This is a perspective view of the coagulation tank of the present invention;

[0025] Figure 5 This is a front view of the coagulation tank of the present invention;

[0026] Figure 6 for Figure 5 Sectional view along line AA;

[0027] Figure 7 This is a front view of the crystal arranging device of the present invention;

[0028] Figure 8 for Figure 7 Enlarged view of section B in the middle;

[0029] Figure 9 This is a top view of the crystal arranging device of the present invention. Detailed Implementation

[0030] Example: A built-in calcium fluoride crystallizer based on a coagulation sedimentation tank includes a coagulation tank 100 and a sedimentation tank 400. The mixed liquor in the coagulation tank 100 can be discharged into the sedimentation tank 400 for sedimentation treatment. The upper side wall of the sedimentation tank 400 is provided with an outlet for discharging the upper clear water. It also includes a fluoride wastewater inlet pipe 140, a calcium-containing reagent inlet pipe 150, a first guide tube 111, a second guide tube 112, a first propeller 121, a second propeller 122, a stirrer 130, a crystal discharge device 200, and a cyclone separator 300. The first guide tube 111 and the second guide tube 112 are respectively fixedly installed on two opposite side walls inside the coagulation tank 100. The fluoride wastewater inlet pipe 140 is fixedly inserted into the upper end of the first guide tube 111 for conveying fluoride wastewater into the first guide tube 111. The calcium-containing reagent inlet pipe 150 is fixedly inserted into the second guide tube 111. The upper end of the guide tube 112 is used to convey calcium-containing agents into the second guide tube 112. The first propeller 121 and the second propeller 122 are respectively fixedly installed in the first guide tube 111 and the second guide tube 112. The first propeller 121 pushes the flow vertically downward, and the second propeller 122 pushes the flow vertically upward. The agitator 130 is fixedly installed in the coagulation tank 100. The agitator 130 can stir the liquid in the coagulation tank 100. The crystal discharge device 200 can periodically discharge the crystal sediment at the bottom of the coagulation tank 100 into the hydrocyclone separator 300. The hydrocyclone separator 300 can separate large crystal particles from water and small crystal particles by hydrocyclone separation. Large crystal particles are discharged from the crystal outlet 303 at the lower end of the hydrocyclone separator 300, and small crystal particles are discharged with the water flow from the drain outlet 302 at the upper end of the hydrocyclone separator 300 and enter the coagulation tank 100 through the drainage pipe.

[0031] Fluoride-containing wastewater enters the first guide tube 111 through the fluoride-containing wastewater inlet pipe 140, while calcium-containing reagent enters the second guide tube 112 through the calcium-containing reagent inlet pipe 150. The fluoride-containing wastewater is pushed downwards by the first propeller 121, flowing down the first guide tube 111 to the bottom of the coagulation tank 100, and then flowing below the second guide tube 112, where it is pushed upwards by the second propeller, forming a vertical circulation. Simultaneously, the liquid in the coagulation tank 100, driven by the agitator 130, flows around the agitator 130, forming a vortex on the horizontal plane. Thus, the fluid direction in the coagulation tank 100 forms both horizontal vortices and vertical circulation, improving the thorough mixing of the fluoride-containing wastewater and calcium-containing reagent in the mixed liquid. At the same time, it causes small calcium fluoride crystals to float up and down in the coagulation tank 100, forming a uniform distribution. The seed crystals provided by the cloth facilitate the adhesion of newly formed calcium fluoride to the surface of the seed crystals, allowing the calcium fluoride crystal particles to grow rapidly and form large calcium fluoride crystals. The large calcium fluoride crystals settle in the coagulation tank 100, while the small calcium fluoride crystals enter the sedimentation tank 400 with the water flow. While continuing to grow in the sedimentation tank 400, they settle to the bottom of the sedimentation tank 400. The supernatant leaves the system through the outlet. The calcium fluoride crystals that have settled to the bottom of the coagulation tank 100 enter the hydrocyclone separator 300 through the crystal discharge device 200 for hydrocyclone separation. The larger calcium fluoride crystals leave the system through the crystal outlet 303 at the lower end of the hydrocyclone and can be further dewatered to form calcium fluoride crystal products. The smaller calcium fluoride crystals return to the coagulation tank 100 through the drain outlet 302 at the upper end of the hydrocyclone to continue growing as seed crystals.

[0032] The first thruster 121 and the second thruster 122 have the same power and the same flow velocity. The flow rate of the first thruster 121 and the second thruster 122 is 10-20 times the flow rate of the fluoride-containing wastewater influent. The above scheme is conducive to forming a stable vertical circulation in the coagulation tank 100.

[0033] The cross-sections of the first guide tube 111, the second guide tube 112, the first propeller 121, and the second propeller 122 are all rectangular. Ideally, they should be flat rectangular structures, which allows them to fit more closely to the sidewalls of the coagulation tank 100, providing sufficient space within the coagulation tank 100 to ensure thorough mixing of the fluoride-containing wastewater and the calcium-containing reagent, and also facilitates the placement of the agitator 130.

[0034] The sedimentation tank 400 is fixedly installed with a conical sedimentation inner tank 401 whose upper inner diameter is larger than its lower inner diameter. An overflow weir 402 is formed on the upper edge of the conical sedimentation inner tank 401. A water outlet 101 is provided on the upper side wall of the coagulation tank 100. The height of the water outlet 101 is lower than the height of the overflow weir 402 by a set distance. The water outlet 101 on the coagulation tank 100 is connected to the upper end of the conical sedimentation inner tank 401 in the sedimentation tank 400 through a water pipe 102. The mixed liquid in the coagulation tank 100 can enter the conical sedimentation inner tank 401 of the sedimentation tank 400 through the water pipe 102 for sedimentation treatment. A row of mud pipes 403 is installed at the lower end of the conical sedimentation inner tank 401.

[0035] The mixed liquor in the coagulation tank 100 enters the conical sedimentation tank 401 of the sedimentation tank 400 through the water inlet 101 and the water pipe 102. After the calcium fluoride crystals hit the inclined side wall of the conical sedimentation tank 401, they will slide down the inclined side wall of the conical sedimentation tank 401 quickly and concentrate at the center of the conical sedimentation tank 401. This is conducive to the rapid discharge of calcium fluoride crystals in the later stage, and at the same time, it prevents them from sticking to the side wall of the conical sedimentation tank 401. The clear water on the upper layer of the conical sedimentation tank 401 flows into the annular space between the sedimentation tank 400 and the conical sedimentation tank 401 through the overflow weir 402, and is finally discharged.

[0036] A central cylinder 404 is fixedly installed at the center of the conical sedimentation tank 401 within the sedimentation tank 400. The lower end of the central cylinder 404 is open, and there is a set distance between the lower end of the central cylinder 404 and the side wall and bottom of the conical sedimentation tank. The upper end of the central cylinder 404 is no higher than the upper end of the conical sedimentation tank 401. After the mixed liquid enters the central cylinder 404, it will quickly sink, preventing small calcium fluoride crystals in the mixed liquid from diffusing in the upper layer, thus fully achieving the separation of calcium fluoride crystals from water.

[0037] A three-way pipe 405 is also provided. One of the three-way pipes 405 is connected to the sludge discharge pipe 403, the second path forms a sludge discharge channel, and the third path is connected to the return pipe 406. The outlet of the return pipe 406 is located at the upper end of the opening of the coagulation tank 100. Control valves are installed on the second and third paths of the three-way pipe 405 respectively. The two control valves can control the opening and closing and the flow rate of the second and third paths of the three-way pipe 405. A return pump is also provided. The return pump can send the calcium fluoride crystals deposited at the bottom of the conical sedimentation tank 401 into the coagulation tank 100 along the sludge discharge pipe 403, the third path of the three-way pipe 405, and the return pipe 406.

[0038] A return pipe 406 is added to the sludge discharge pipe 403 at the bottom of the sedimentation tank 400 through a three-way pipe 405. The calcium fluoride crystals discharged from the sludge discharge pipe 403 at the bottom of the sedimentation tank 400 can be pumped back above the coagulation tank 100. The sludge discharge at the bottom of the sedimentation tank 400 can control the reflux flow rate and reflux time at any time according to the process conditions through a control valve, and the control valve can be a manual valve or a solenoid valve.

[0039] The crystal discharging device 200 includes an air-lift crystal discharging pipe 201 and an external air supply pipeline. One end of the air-lift crystal discharging pipe 201 extends into the bottom of the coagulation tank 100, and the other end of the air-lift crystal discharging pipe 201 is connected to the liquid inlet of the cyclone separator 300. An air inlet pipe 220 extending obliquely downward is provided on the side wall of one end of the air-lift crystal discharging pipe 201. The air inlet pipe 220 is connected to the external air supply pipeline through a reduced-diameter air nozzle 221. The air flow in the external air supply pipeline enters the air-lift crystal discharging pipe 201 obliquely upward through the air inlet pipe 220. The air flow flowing in the direction of the other end of the air-lift crystal discharging pipe 201 makes one end of the air-lift crystal discharging pipe 201 form a negative pressure, and the negative pressure at one end of the air-lift crystal discharging pipe 201 can adsorb the crystal precipitate deposited at the bottom of the coagulation sedimentation tank. The gas is discharged from an air compressor or other gas sources through a hose, along the hose fixed on the pool wall, and then enters the main air-lift pipe through the reduced-diameter air nozzle 221. The air-lift crystal discharging pipe 201 lifts the calcium fluoride crystals deposited at the bottom of the coagulation tank 100 to the cyclone separator 300 through negative pressure. The crystal discharging device 200 can also be realized by a pump and a pipeline. The above structure is convenient to install and does not damage the original structure of the coagulation tank 100.

[0040] A "king" - shaped air-lift branch pipe 210 is fixedly installed at the bottom of the coagulation tank 100. There is a set distance between the lower side of the air-lift branch pipe 210 and the bottom of the coagulation tank 100. The bottom of the air-lift branch pipe 210 is provided with suction crystal holes 211 distributed at intervals, and the opening direction of the suction crystal holes 211 is vertically downward. The air-lift branch pipe 210 is fixedly connected to one end of the air-lift crystal discharging pipe 201 and is connected to the air-lift crystal discharging pipe 201.

[0041] The air-lift branch pipe 210 uniformly and comprehensively covers the bottom of the coagulation tank 100, and can suck away all the calcium fluoride crystals at the bottom of the coagulation tank 100 through negative pressure. The air-lift branch pipe 210 can also be of an annular structure or other structures, as long as it comprehensively covers the bottom of the coagulation tank 100.

[0042] The air-lift branch pipe 210 is installed at a height of 10 cm - 50 cm from the bottom of the coagulation tank 100. The air-lift crystal discharging pipe 201 is of an L-shaped structure, and its vertical section is inserted into the coagulation tank 100 from top to bottom. The lower end of its vertical section is connected to the air-lift branch pipe 210. The air inlet pipe 220 is fixedly installed on the side wall of the vertical section of the air-lift crystal discharging pipe 201 at a 45 ° oblique angle, and the position where the air inlet pipe 220 is installed on the vertical section of the air-lift crystal discharging pipe 201 is 10 cm - 30 cm above the air-lift branch pipe 210.

[0043] The agitator 130 is located at the center of the coagulation tank 100. The agitator 130 includes an agitator motor, an agitator shaft, and agitator blades. The agitator motor drives the agitator shaft to rotate, and the agitator blades are fixedly installed on the agitator shaft.

Claims

1. A built-in calcium fluoride crystallizer based on a coagulation sedimentation tank, comprising a coagulation tank (100) and a sedimentation tank (400), wherein the mixed liquor in the coagulation tank can be discharged into the sedimentation tank for sedimentation treatment, and the upper side wall of the sedimentation tank is provided with an outlet for discharging the upper clear water, characterized in that: It also includes a fluoride wastewater inlet pipe (140), a calcium-containing agent inlet pipe (150), a first guide tube (111), a second guide tube (112), a first propeller (121), a second propeller (122), a stirrer (130), a crystal removal device (200), and a cyclone separator (300). The first and second guide tubes are respectively fixedly installed on two opposite side walls inside the coagulation tank. The fluoride wastewater inlet pipe is fixedly inserted into the upper end of the first guide tube to transport fluoride wastewater into the first guide tube. The calcium-containing agent inlet pipe is fixedly inserted into the upper end of the second guide tube to transport calcium-containing agent into the second guide tube. The first propeller and the second propeller are fixedly installed in the first guide tube and the second guide tube, respectively. The first propeller pushes the flow vertically downward and the second propeller pushes the flow vertically upward. The agitator is fixedly installed in the coagulation tank. The agitator can stir the liquid in the coagulation tank. The crystal discharge device can periodically discharge the crystal sediment at the bottom of the coagulation tank into the hydrocyclone separator. The hydrocyclone separator can separate large crystal particles from water and small crystal particles by hydrocyclone separation. Large crystal particles are discharged from the crystal outlet (303) at the lower end of the hydrocyclone separator. Small crystal particles are discharged with the water flow from the drain outlet (302) at the upper end of the hydrocyclone separator and enter the coagulation tank through the drainage pipe.

2. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 1, characterized in that: The first and second thrusters have the same power and the same flow velocity. The flow rate of the first and second thrusters is 10-20 times that of the influent flow rate of the fluoride-containing wastewater.

3. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 1, characterized in that: The cross-sections of the first guide tube, the second guide tube, the first thruster, and the second thruster are all rectangular.

4. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 1, characterized in that: The sedimentation tank is fixedly installed with a conical sedimentation inner barrel (401) whose upper inner diameter is larger than its lower inner diameter. An overflow weir (402) is formed on the upper edge of the conical sedimentation inner barrel. A water outlet (101) is provided on the upper side wall of the coagulation tank. The height of the water outlet is lower than the height of the overflow weir by a set distance. The water outlet on the coagulation tank is connected to the upper end of the conical sedimentation inner barrel in the sedimentation tank through a water pipe (102). The mixed liquid in the coagulation tank can enter the conical sedimentation inner barrel of the sedimentation tank through the water pipe for sedimentation treatment. A row of mud pipes (403) is installed at the lower end of the conical sedimentation inner barrel.

5. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 4, characterized in that: A central cylinder (404) is fixedly installed at the center of the conical sedimentation tank. The lower end of the central cylinder is open, and there is a set distance between the lower end of the central cylinder and the side wall and bottom of the conical sedimentation tank. The height of the upper end of the central cylinder is not higher than the height of the upper end of the conical sedimentation tank.

6. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 4, characterized in that: It is also equipped with a three-way pipe (405), one of which is connected to the sludge discharge pipe, the second of which forms a sludge discharge channel, and the third of which is connected to a return pipe (406). The outlet of the return pipe is located at the upper end of the coagulation tank opening. Control valves are installed on the second and third of the three-way pipe respectively. The two control valves can control the opening and closing and flow rate of the second and third of the three-way pipe. It is also equipped with a return pump, which can send the calcium fluoride crystals deposited at the bottom of the conical sedimentation tank into the coagulation tank along the sludge discharge pipe, the third of the three-way pipe and the return pipe.

7. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 1, characterized in that: The crystal discharging device includes an air-lift crystal discharging pipe (201) and an external air supply pipeline. One end of the air-lift crystal discharging pipe extends into the bottom of the coagulation tank, and the other end of the air-lift crystal discharging pipe is connected to the liquid inlet of the hydrocyclone. An air inlet pipe (220) extending obliquely downward is provided on the side wall of one end of the air-lift crystal discharging pipe. The air inlet pipe is connected to the external air supply pipeline through a reduced-diameter air nozzle (221). The air flow in the external air supply pipeline enters the air-lift crystal discharging pipe obliquely upward through the air inlet pipe. The air flow flowing towards the other end of the air-lift crystal discharging pipe makes one end of the air-lift crystal discharging pipe form a negative pressure. The negative pressure at one end of the air-lift crystal discharging pipe can adsorb the crystal precipitate deposited at the bottom of the coagulation sedimentation tank.

8. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 7, characterized in that: A "king"-shaped air-lift branch pipe (210) is fixedly installed at the bottom of the coagulation tank. There is a set distance between the lower side of the air-lift branch pipe and the bottom of the coagulation tank. Absorbing crystal holes (211) are opened at intervals at the bottom of the air-lift branch pipe. The opening direction of the absorbing crystal holes is vertically downward. The air-lift branch pipe is fixedly connected to one end of the air-lift crystal discharging pipe and is connected to the air-lift crystal discharging pipe.

9. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 8, characterized in that: The air-lift branch pipe is installed at a height of 10 cm - 50 cm from the bottom of the coagulation tank. The air-lift crystal discharging pipe is of an L-shaped structure. Its vertical section is inserted into the coagulation tank from top to bottom. The lower end of its vertical section is connected to the air-lift branch pipe. The air inlet pipe is fixedly installed on the side wall of the vertical section of the air-lift crystal discharging pipe at a 45° angle. And the position of the vertical section of the air-lift crystal discharging pipe where the air inlet pipe is installed is 10 cm - 30 cm above the air-lift branch pipe.

10. The built-in calcium fluoride crystallizer based on a coagulation sedimentation tank according to claim 1, characterized in that: The stirrer is located at the central position of the coagulation tank. The stirrer includes a stirring motor, a stirring shaft and stirring fan blades. The stirring motor drives the stirring shaft to rotate. The stirring fan blades are fixedly installed on the stirring shaft.

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