A reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater

Abstract

This utility model provides a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater, relating to the field of reaction crystallization kettle technology. It includes: a shell, a stirring device and a material distribution structure at the lower end of the shell, a wire mesh in the middle of the shell, and an ultrasonic generator at the upper end of the shell. The stirring shaft of the stirring device is hollow, with a first feed inlet at the lower end of the stirring shaft. The material distribution structure forms a second feed inlet on the lower side wall of the shell. The upper side wall and bottom wall of the shell are respectively provided with a mother liquor outlet and a crystal slurry outlet. This invention solves the problems of poor reaction efficiency and equipment scaling in the current process of preparing cryolite from fluoride-containing wastewater.

Description

Technical Field

[0001] This utility model belongs to the field of reaction crystallization kettle technology, and more specifically, relates to a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater. Background Technology

[0002] With the rapid development of the semiconductor industry, represented by solar photovoltaics, the treatment and resource utilization of high-concentration fluoride-containing wastewater are receiving increasing attention from environmental protection companies. Cryolite is a crucial flux in the electrolytic aluminum industry and has high economic value, thus it is widely studied as a resource utilization product for high-concentration fluoride-containing wastewater. Current processes for preparing cryolite from fluoride-containing wastewater employ intermittent operation because cryolite crystallizes easily on the inner wall of the reaction crystallizer, the surface of the stirring shaft, and the impeller, leading to scaling and hindering continuous operation. In existing technologies, some reaction crystallizers have scrapers installed on the outer layer of the stirring paddle to remove scale from the reactor wall during cryolite preparation using mechanical force. This method is effective in removing scale from the reactor wall, but has virtually no effect on removing scale from the stirring shaft and impeller surfaces. In addition, the concentration of fluoride ions in fluoride-containing wastewater is generally around 10,000 mg / L. After the reaction, the proportion of cryolite product in the system is about 1-2%, the solid content is low, the particle collision frequency during the reaction is low, which leads to a high concentration of residual fluoride ions in the mother liquor after the reaction and poor reaction effect. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater, thereby solving the problems of poor reaction efficiency and equipment scaling in the current process of preparing cryolite from fluoride-containing wastewater.

[0004] To achieve the above objectives, this utility model provides a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater, comprising:

[0005] The shell has a stirring device and a cloth structure at its lower end, a wire mesh in its middle, and an ultrasonic generator at its upper end. The stirring shaft of the stirring device is hollow and has a first feed inlet at its lower end. The cloth structure forms a second feed inlet on the lower side wall of the shell. The upper side wall and the bottom wall of the shell are respectively provided with a mother liquor outlet and a crystal slurry outlet.

[0006] Optionally, the stirring device includes:

[0007] A drive motor is provided, which is located outside the housing, and the stirring shaft is connected to the drive motor via a transmission mechanism;

[0008] An impeller is connected to the stirring shaft. The impeller is a hollow structure that communicates with the internal space of the stirring shaft. The impeller has multiple first material distribution holes.

[0009] Optionally, the shell has a lower diameter smaller than the upper diameter, and the sidewalls of the shell form an angle with the vertical.

[0010] Optionally, the fabric structure includes an annular liquid distribution pipe, one side of which is connected to a feed pipe. The feed pipe penetrates the side wall of the housing and forms a second feed inlet. The liquid distribution pipe has multiple second material distribution holes.

[0011] Optionally, the fabric structure is located below the impeller, with the first material distribution hole and the second material distribution hole facing downwards and upwards, respectively.

[0012] Optionally, the impeller is a pusher impeller and is configured as a down-pressure type.

[0013] Optionally, the bottom wall of the housing has an upward protrusion in the middle so that the bottom wall cross-section of the housing forms a W shape, and the crystal slurry outlet is located at the lowest position of the bottom wall of the housing.

[0014] Optionally, the material of the wire mesh is polytetrafluoroethylene.

[0015] Optionally, a mechanical seal is provided at the location where the stirring shaft passes through the bottom wall of the housing.

[0016] Optionally, the outer periphery of the liquid distribution pipe is provided with a plurality of fixing lugs, the fixing lugs having mounting holes, and the fixing lugs being fixed to the inner wall of the housing by polytetrafluoroethylene bolts.

[0017] This invention provides a reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater. Its advantages are as follows: This reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater is designed for the relatively low concentration of fluoride ions in the wastewater. It adopts a semi-continuous operation, with continuous feeding of fluoride-containing wastewater, continuous discharge of the mother liquor, and intermittent discharge of cryolite slurry. This ensures a higher solids content within the reaction crystallization vessel, increases particle collision efficiency, improves the reaction crystallization effect, and results in lower residual fluoride ion content in the discharged mother liquor. Compared to current intermittent reaction crystallization vessels, it offers higher processing efficiency, requires less volume, and reduces equipment investment. The bottom-entry stirring method results in a shorter stirring shaft, with the stirring device completely below the liquid surface, eliminating the need for a frame or other stirring shaft fixing devices. Compared to top-entry stirring, this effectively avoids scaling on the stirring shaft surface caused by material splashing during the rising of the feed liquid. Simultaneously, an ultrasonic generator is installed at the upper end of the shell. Under the action of ultrasound, cavitation occurs on the inner wall of the shell and the surfaces of the stirring paddle and cloth structure, making it difficult for cryolite to nucleate on the surface, effectively preventing scaling.

[0018] Other features and advantages of this invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally represent like parts.

[0020] Figure 1 A schematic diagram of the overall structure of a reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to an embodiment of the present invention is shown.

[0021] Figure 2 A schematic diagram of the stirring device of a reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to an embodiment of the present invention is shown.

[0022] Figure 3 A schematic diagram of the fabric structure of a reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to an embodiment of the present invention is shown.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Shell; 2. Stirring device; 21. Gear motor; 22. Bevel gear transmission mechanism; 23. Stirring shaft; 24. Impeller; 3. Wire mesh; 4. Ultrasonic generator; 5. First feeding device; 51. First feed inlet; 52. First material distribution hole; 6. Second feeding device; 61. Second feed inlet; 62. Liquid distribution pipe; 63. Second material distribution hole; 64. Fixed ear plate; 7. Mother liquor outlet; 8. Crystal slurry outlet. Detailed Implementation

[0025] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0026] like Figure 1 As shown, this utility model provides a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater, comprising:

[0027] The shell 1 has a stirring device 2 and a cloth structure at its lower end, a wire mesh 3 in the middle, and an ultrasonic generator 4 at its upper end. The stirring shaft 23 of the stirring device 2 is hollow, and a first feed inlet 51 is formed at the lower end of the stirring shaft 23. The cloth structure forms a second feed inlet 61 on the lower side wall of the shell 1. The upper side wall and the bottom wall of the shell 1 are respectively provided with a mother liquor outlet 7 and a crystal slurry outlet 8.

[0028] Specifically, to address the problems of poor reaction efficiency and equipment scaling in the current process of preparing cryolite from fluoride-containing wastewater, this utility model provides a reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater. Designed specifically for the relatively low fluoride ion concentration in fluoride-containing wastewater, it employs a semi-continuous operation: continuous feeding of fluoride-containing wastewater, continuous discharge of clarified mother liquor, and intermittent discharge of cryolite slurry. This ensures a higher solids content within the reaction crystallization kettle, increases particle collision efficiency, improves the reaction crystallization effect, and results in lower residual fluoride ion content in the discharged mother liquor. Compared to current intermittent reaction crystallization kettles, this method offers significant advantages. It offers higher processing efficiency, requires less volume, and reduces equipment investment. The bottom-entry stirring method of the housing 1 results in a shorter stirring shaft 23, with the stirring device 2 completely submerged below the liquid surface. This eliminates the need for a frame or other fixing devices for the stirring shaft 23, effectively preventing scaling on the stirring shaft 23 caused by material splashing during the rising liquid level compared to top-entry stirring. Furthermore, an ultrasonic generator is installed at the top of the housing 1. Under the action of ultrasonic waves, cavitation occurs on the inner wall of the housing 1 and the surfaces of the stirring paddle and cloth structure, making it difficult for cryolite to nucleate on the surface and effectively preventing scaling.

[0029] Optionally, the stirring device 2 includes:

[0030] The drive motor is located outside the housing 1, and the stirring shaft 23 is connected to the drive motor through a transmission mechanism;

[0031] Impeller 24 is connected to stirring shaft 23. Impeller 24 is a hollow structure that communicates with the internal space of stirring shaft 23. Impeller 24 has multiple first material distribution holes 52.

[0032] Specifically, the drive motor drives the stirring shaft 23 and impeller 24 to rotate through the transmission mechanism, forming a stirring at the bottom of the housing 1. After the material is fed into the first feed port 51 at the lower end of the stirring shaft 23, it is distributed in the housing 1 through multiple first material distribution holes 52 on the impeller 24.

[0033] In this embodiment, as Figure 2 As shown, the drive motor is a geared motor 21, and the transmission mechanism is a bevel gear transmission mechanism 22, which includes a first bevel gear connected to the geared motor 21 and a second bevel gear connected to the stirring shaft 23. The first bevel gear and the second bevel gear mesh and drive each other, driving the stirring shaft 23 to rotate and facilitating the opening and exposure of the first feed port 51.

[0034] Optionally, the shell 1 has a lower diameter smaller than the upper diameter, and the sidewalls of the shell 1 form an angle with the vertical.

[0035] Specifically, the shell 1 adopts a structure design that is thicker at the top and thinner at the bottom, which allows the paddle diameter ratio of the bottom stirring device 2 to be relatively larger. Combined with the W-shaped design of the bottom wall of the shell 1, it can effectively avoid the occurrence of stirring dead corners and material settling and clumping, thus enhancing the material mixing effect.

[0036] Optionally, the sidewall of the housing 1 is inclined at an angle of 1° to 30° with respect to the vertical direction.

[0037] Optionally, the ratio of the height of the housing 1 to the diameter of the lower end of the side wall of the housing 1 is 1:1 to 3:1.

[0038] In this embodiment, the inclination angle of the side wall of the housing 1 to the vertical direction is 10°, and the ratio of the height of the housing 1 to the diameter of the lower end of the side wall of the housing 1 is 1.5:1.

[0039] Optionally, the fabric structure includes an annular liquid distribution pipe 62, with a feed pipe connected to one side of the liquid distribution pipe 62. The feed pipe penetrates the side wall of the housing 1 and forms a second feed inlet 61. The liquid distribution pipe 62 has multiple second material distribution holes 63.

[0040] Optionally, the fabric structure is located below the impeller 24, with the first material distribution hole 52 and the second material distribution hole 63 facing downwards and upwards, respectively.

[0041] Specifically, the first feed inlet 51 and the first material distribution hole 52 located at the lower part of the impeller 24 form the first feeding device 5, and the second feed inlet 61, the liquid distribution pipe 62 and the second material distribution holes 63 evenly distributed on the upper part of the liquid distribution pipe 62 form the second feeding device 6.

[0042] Optionally, the impeller 24 is a pusher impeller 24 and is configured as a down-pressure type.

[0043] Optionally, the impeller 24 is a three- or four-bladed propulsion design, and the ratio of the diameter of the impeller 24 to the diameter of the lower end of the side wall of the housing 1 is 0.5:1 to 0.8:1.

[0044] In this embodiment, the ratio of the diameter of the impeller 24 to the diameter of the lower end of the side wall of the housing 1 is 0.75:1, and the lowest point of the W-shaped structure at the bottom of the housing 1 is flush with the outer end of the impeller 24 in the vertical direction.

[0045] Optionally, an upward protrusion is provided in the middle of the bottom wall of the housing 1 so that the bottom wall cross section of the housing 1 forms a W shape, and the crystal slurry outlet 8 is located at the lowest position of the bottom wall of the housing 1.

[0046] Specifically, the bottom of the shell 1 has a W-shaped structure, and the lowest point of the W-shaped structure is where the crystal slurry outlet 8 of the cryolite is located.

[0047] Optionally, the material of the wire mesh 3 is polytetrafluoroethylene.

[0048] Optionally, the mesh count of screen 3 is 80-240.

[0049] In this embodiment, the wire mesh 3 is positioned at a height with a diameter ratio of 1:1 to the lower end of the side wall of the housing 1, and is made of 240-mesh polytetrafluoroethylene. The mother liquor outlet 7 is located on the upper part of the wire mesh 3.

[0050] In this embodiment, the ultrasonic generator 4 is disposed on the outer surface of the upper end of the housing 1.

[0051] Optionally, a mechanical seal is provided at the location where the stirring shaft 23 passes through the bottom wall of the housing 1.

[0052] Optionally, the outer periphery of the liquid distribution pipe 62 is provided with a plurality of fixing lugs 64, the fixing lugs 64 having mounting holes, and the fixing lugs 64 being fixed to the inner wall of the housing 1 by polytetrafluoroethylene bolts.

[0053] Specifically, the liquid distribution tube 62 is connected to the inner wall of the housing 1 through the fixing lug 64, and the lug can also be provided on the inner wall of the housing 1.

[0054] In this embodiment, the parts that come into contact with the material, such as the shell 1, stirring device 2, wire mesh 3, first feeding device 5, second feeding device 6, clear mother liquor outlet 7, and crystal slurry outlet 8, are all provided with a polytetrafluoroethylene (PTFE) liner or made of PTFE material.

[0055] In summary, when the reaction crystallization kettle for preparing cryolite from fluoride-containing wastewater provided by this utility model is in operation, taking the treatment of high-concentration fluoride-containing wastewater as an example: Mother liquor is added into the shell 1 until it submerges the impeller 24. The stirring device 2 and the ultrasonic generator 4 are turned on. The rotation direction of the impeller 24 is set to downward pressure. Fluoride-containing wastewater, aluminum salts such as aluminum hydroxide, aluminum chloride, and polyaluminum chloride, as well as crystallization aids such as sodium polyacrylate, are continuously fed into the solution from the first feeding device 5. The solution is thoroughly mixed with aluminum salts such as aluminum hydroxide, aluminum chloride, and polyaluminum chloride, and crystallization aids such as sodium polyacrylate until homogeneous. The feed pipe can be rotatably connected to the first feed port 51 through a dynamic sealing component. The first material distribution hole 52 at the bottom of the impeller 24 achieves material distribution. The solution is fed from the second feeding device 6... The process involves continuously feeding sodium chloride, sodium carbonate, sodium sulfate, sodium nitrate, sodium hydroxide, and other sodium salt solutions into the container. The materials are distributed through the second material distribution hole 63 at the top of the annular distribution pipe 62. Under the action of downward stirring, the two materials are fully mixed, resulting in high molecular weight cryolite with gradually increasing particle size. After the liquid level rises to the clear mother liquor outlet 7, the clear mother liquor outlet 7 is opened to discharge the clear mother liquor. At the same time, the material continues to be fed into the shell 1 until the solid content of the cryolite in the lower part reaches 15-20%. Then, the cryolite slurry is intermittently discharged until the remaining solid content is 5-10%. The discharged cryolite slurry undergoes solid-liquid separation steps such as centrifugation to obtain a sandy high molecular weight cryolite product.

[0056] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater, characterized in that, include: The shell has a stirring device and a cloth structure at its lower end, a wire mesh in its middle, and an ultrasonic generator at its upper end. The stirring shaft of the stirring device is hollow and has a first feed inlet at its lower end. The cloth structure forms a second feed inlet on the lower side wall of the shell. The upper side wall and the bottom wall of the shell are respectively provided with a mother liquor outlet and a crystal slurry outlet.

2. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 1, characterized in that, The stirring device includes: A drive motor is provided, which is located outside the housing, and the stirring shaft is connected to the drive motor via a transmission mechanism; An impeller is connected to the stirring shaft. The impeller is a hollow structure that communicates with the internal space of the stirring shaft. The impeller has multiple first material distribution holes.

3. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 1, characterized in that, The shell has a lower diameter smaller than the upper diameter, and the sidewalls of the shell form an angle with the vertical.

4. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 2, characterized in that, The fabric structure includes an annular liquid distribution pipe, one side of which is connected to a feed pipe. The feed pipe penetrates the side wall of the housing and forms a second feed inlet. The liquid distribution pipe has multiple second material distribution holes.

5. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 4, characterized in that, The fabric structure is located below the impeller, with the first material distribution hole and the second material distribution hole facing downwards and upwards, respectively.

6. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 2, characterized in that, The impeller is a propeller impeller and is configured as a downward-pressing impeller.

7. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 1, characterized in that, The bottom wall of the housing has an upward protrusion in the middle so that the bottom wall cross-section of the housing forms a W shape, and the crystal slurry outlet is located at the lowest position of the bottom wall of the housing.

8. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 1, characterized in that, The material of the wire mesh is polytetrafluoroethylene.

9. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 1, characterized in that, A mechanical seal is provided at the location where the stirring shaft passes through the bottom wall of the housing.

10. The reaction crystallization vessel for preparing cryolite from fluoride-containing wastewater according to claim 4, characterized in that, The outer periphery of the liquid distribution pipe is provided with multiple fixing lugs, each fixing lug having an installation hole, and the fixing lugs are fixed to the inner wall of the housing by polytetrafluoroethylene bolts.

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