Complete mixing type calcium fluoride crystal defluorination reactor and defluorination method

Abstract

The invention discloses a complete mixing type calcium fluoride crystallization defluorination reactor and a defluorination method, and relates to the field of fluorine-containing wastewater treatment and fluorine resource recovery, the reactor adopts a modular design, and comprises a seed crystal storage area, a mixing crystallization area and a clarification water outlet area, which are sequentially communicated from bottom to top and detachably connected, and are convenient to overhaul and assemble; the clarification water outlet area is connected with a water outlet pipe and is used for discharging treated water; the stirring paddle is coaxially arranged in the reactor, and one end of the stirring paddle is connected with the stirrer to ensure uniform mixing; the water inlet pipe is arranged on the peripheral side of the lower part of the mixed crystallization area, and the multiple dosing pipes are arranged at intervals in the axial direction and used for uniformly distributing chemicals; the stainless steel mesh is arranged between the mixed crystallization area and the clarification water outlet area to realize solid-liquid separation; and each pipeline is provided with a valve and a water distributor. According to the defluorination reactor and the defluorination method provided by the invention, effective treatment of fluorine-containing wastewater can be realized, operation and daily overhaul and maintenance are facilitated due to modular design, products can be reutilized, and the defluorination reactor and the defluorination method have certain economical efficiency.

Description

Technical Field

[0001] The present invention relates to the field of fluorine-containing wastewater treatment and fluorine resource recovery, and particularly to a completely mixed calcium fluoride crystallization defluorination reactor and a defluorination method. Background Art

[0002] In the production processes of the photovoltaic and electronic information manufacturing industries, a large amount of fluorine-containing wastewater is generated during the hydrofluoric acid etching process. Fluorine is a pollutant harmful to the human body, and long-term intake can cause health problems such as skeletal fluorosis, dental fluorosis, and metabolic system disorders in the human body. Therefore, the fluorine-containing wastewater generated during industrial production needs to be properly treated before being discharged.

[0003] Currently, the conventional methods for treating fluorine-containing wastewater mainly include adsorption method, chemical precipitation method, ion exchange method, etc., and all are finally disposed of in the form of solid waste, unable to achieve resource recovery and reuse. The induced crystallization method is an improvement of the precipitation method. By adding external seeds, fluoride ions react on the surface of the seeds to form a stable crystal structure. The product is crystalline pellets with a low water content and can be used for resource utilization.

[0004] Currently, the induced crystallization for defluorination mainly produces calcium fluoride, and fluidized bed reactors are mostly used in the reactors. Since the fluidized bed reactor mainly relies on the upward impact force of the water flow to achieve the fluidization of the seeds, the requirements for the seeds are relatively high. Smaller seed particles are convenient for fluidization but are also easily washed out of the reactor by the water flow, resulting in the lack of seeds in the reactor and the non-compliance of the effluent SS. Larger seed particles are difficult to fluidize, and at the same time, they have a small specific surface area and low reaction efficiency.

[0005] Therefore, it is necessary to propose a completely mixed calcium fluoride crystallization defluorination reactor and a defluorination method to solve the above problems, so as to achieve the efficient fluidization of the seeds, improve the defluorination efficiency, and ensure the long-term stable compliance of the effluent quality. Summary of the Invention

[0006] The purpose of the present invention is to provide a completely mixed calcium fluoride crystallization defluorination reactor and a defluorination method to achieve the effective treatment of fluorine-containing wastewater and the recycling and reuse of fluorine elements.

[0007] To achieve the above purpose, on the one hand, the present invention provides a completely mixed calcium fluoride crystallization defluorination reactor, including:

[0008] A reactor body, the reactor body includes a seed reserve area, a mixing and crystallization area, and a clarification and effluent area that are sequentially connected and detachably connected from bottom to top; the clarification and effluent area is connected to an outlet pipe;

[0009] A stirring paddle, the stirring paddle is coaxially arranged in the reactor body and penetrates through the seed reserve area, the mixing and crystallization area, and the clarification and effluent area; one end of the stirring paddle is connected to a stirrer;

[0010] An inlet pipe, the inlet pipe is arranged on the circumferential side of the lower part of the mixing and crystallization zone;

[0011] A chemical addition pipe, and a plurality of the chemical addition pipes are arranged at intervals along the axial direction of the mixing and crystallization zone;

[0012] A stainless steel mesh, the stainless steel mesh is arranged between the mixing and crystallization zone and the clarified water outlet zone for realizing solid-liquid separation;

[0013] Valves and water distributors are arranged on the inlet pipe, the chemical addition pipe, and the outlet pipe.

[0014] The above structure aims to provide a completely mixed calcium fluoride crystallization defluorination reactor with modular design. By optimizing the structure design, the defluorination efficiency is improved, and at the same time, the efficient fluidization and resource utilization of crystal seeds are realized.

[0015] Optionally, the crystal seed storage area is filled with fluorite particles with a particle size of 0.2 - 0.4 mm, and the filling volume is not less than 1 / 2 of the volume of the mixing and crystallization zone.

[0016] Optionally, n inlet pipes are circumferentially and uniformly distributed on the circumferential side of the mixing and crystallization zone, and the included angle between two adjacent inlet pipes is 360° / n, where n≥2.

[0017] Optionally, the number of the chemical addition pipes is m, and the m chemical addition pipes are arranged at equal intervals along the axial direction of the mixing and crystallization zone for uniformly distributing chemicals into the mixing and crystallization zone, where m≥3.

[0018] Optionally, an overflow weir is connected to the upper edge of the clarified water outlet zone, a collecting tank is arranged below the overflow weir, and an outlet pipe is connected to the bottom of the collecting tank.

[0019] Optionally, the crystal seed storage area, the mixing and crystallization zone, and the clarified water outlet zone are respectively connected by flanges.

[0020] Optionally, the stainless steel mesh is fixed between two flanges between the mixing and crystallization zone and the clarified water outlet zone.

[0021] Optionally, the stainless steel mesh adopts a mesh structure of 80 - 100 meshes.

[0022] Optionally, multiple groups of paddle blades are arranged at intervals along the length direction of the stirring paddle, and each group of paddle blades is uniformly distributed along the crystal seed storage area and the mixing and crystallization zone.

[0023] On the other hand, the present invention provides a completely mixed calcium fluoride crystallization defluorination method, using the completely mixed calcium fluoride crystallization defluorination reactor described in any one of the above, and the method includes the following steps:

[0024] Step S1: Open the inlet water valve, and the fluorine-containing wastewater enters the reactor through the inlet pipe.

[0025] Step S2: After the fluorine-containing wastewater fills the entire reactor, 50% calcium chloride solution enters the reactor through the chemical dosing pipe.

[0026] Step S3: Start the agitator to fluidize the calcium fluoride crystal seeds and evenly cover the entire mixing crystallization area and crystal seed storage area.

[0027] Step S4: Fluoride ions in the wastewater form a stable calcium fluoride crystal structure on the surface of fluorite particles in the presence of calcium ions, and the fluoride ions are removed.

[0028] Step S5: The mixed wastewater is subjected to solid-liquid separation under the interception of the stainless steel mesh.

[0029] Step S6: The effluent flows out from the clarified effluent area and is discharged through the outlet pipe.

[0030] Compared with the prior art, the present invention discloses at least the following beneficial effects:

[0031] The present invention is a completely mixed calcium fluoride crystallization defluorination reactor with a modular design, including a clarified effluent area, a mixing crystallization area, and a crystal seed storage area, which is convenient for maintenance and assembly; the solid-liquid separation is strengthened by the stainless steel mesh, making the effluent clear while ensuring that the crystal seeds will not be lost due to water flow impact; the induced crystallization principle is adopted to form a stable crystal structure of fluoride ions and calcium ions on the surface of fluorite, realizing the removal of fluoride ions while recovering high-quality calcium fluoride crystals; the overall form is an upflow, with a small floor area. Using the defluorination reactor and defluorination method provided by the present invention to treat fluorine-containing wastewater has remarkable effects, and the products can be reused, with certain economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 It is a structural schematic diagram of the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention;

[0034] Figure 2 It is a structural schematic diagram of the clarified effluent area in the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention;

[0035] Figure 3Schematic structural diagram of the mixing and crystallization zone in the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention;

[0036] Figure 4 Schematic structural diagram of the seed reserve zone in the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention;

[0037] Figure 5 Schematic diagram of the stainless steel in the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention;

[0038] Figure 6 Schematic diagram of the stirring paddle in the completely mixed calcium fluoride crystallization defluorination reactor provided by the present invention.

[0039] In the figure: 1, overflow weir; 2, water collecting tank; 3, water outlet pipe; 4, stainless steel mesh; 5, chemical adding pipe; 6, water inlet pipe; 7, bottom rotating shaft; 8, stirring paddle; 100, clarified water outlet area; 200, mixing and crystallization area; 300, seed reserve area. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0041] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0042] Refer to Figures 1 to 6As shown in the figure, an embodiment of the present invention provides a completely mixed calcium fluoride crystallization defluorination reactor, which includes a reactor body. The reactor body adopts a three-stage design and includes a seed storage area 300, a mixing crystallization area 200, and a clarification effluent area 100 that are connected in sequence from bottom to top. The top of the seed storage area 300 and the bottom of the mixing crystallization area 200 are connected by a flange. The top of the mixing crystallization area 200 and the bottom of the clarification effluent area 100 are connected by a flange. Using flange connection can make the device modular, facilitate disassembly and assembly, and is convenient for daily maintenance and repair. Moreover, the connection between the top of the seed storage area 300 and the bottom of the mixing crystallization area 200 can achieve rapid addition and discharge of seeds. A stirring paddle 8 that penetrates up and down is coaxially arranged inside the reactor body. A bottom rotating shaft 7 for fixing the lower end of the stirring paddle 8 is provided at the bottom of the seed storage area 300. The lower end of the stirring paddle 8 rotates on the bottom rotating shaft 7, and the upper end of the stirring paddle 8 is connected to a stirrer (not shown in the figure). Multiple groups of paddle blades are arranged at intervals along the length direction of the stirring paddle 8. The stirrer drives the stirring paddle 8 to rotate, and through agitation, the mixed substances inside the reactor body are fully contacted, improving the reaction effect. A water inlet pipe 6 is provided on the circumferential side of the reactor body at the lower part of the mixing crystallization area 200. Several medicine adding pipes 5 are arranged at intervals along the axial direction of the mixing crystallization area 200 above the water inlet pipe 6. The medicine adding pipes 5 are used for uniformly distributing medicine into the mixing crystallization area 200. An overflow weir 1 is connected to the upper edge of the clarification effluent area 100. A water collecting tank 2 is arranged below the overflow weir 1, and a water outlet pipe 3 is connected to the bottom of the water collecting tank 2. A stainless steel mesh 4 is arranged between the mixing crystallization area 200 and the clarification effluent area 100 to effectively intercept the seeds. Valves and water distributors are provided on the water inlet pipe 6, the medicine adding pipes 5, and the water outlet pipe 3.

[0043] In some optional embodiments, the seed storage area 300 is filled with fluorite particles with a particle size of 0.2 - 0.4 mm, and the filling volume is not less than 1 / 2 of the volume of the mixing crystallization area 200. The fluorite particles within this particle size range can provide a sufficient specific surface area for inducing the crystallization of calcium fluoride. At the same time, it is convenient for agitation to make them fully fluidized, and it can also avoid pipeline blockage caused by too small particles. The filling volume can enable the lattice building ions in the solution to fully contact the particle seeds, achieving effective removal of fluoride ions.

[0044] In some optional embodiments, the bottom rotating shaft 7 is arranged at the center position of the bottom of the seed storage area 300. Arranging the bottom rotating shaft 7 at this position can make the stirring paddle 8 rotate along the central axis of the reactor, avoiding physical collisions of the device caused by the deviation of the stirring paddle 8.

[0045] In some alternative embodiments, there are n water inlet pipes 6 evenly distributed circumferentially along the periphery of the mixed crystallization zone 200, where n≥2, and the angle between two adjacent water inlet pipes 6 among the n water inlet pipes 6 is 360° / n. The uniform distribution of multiple water inlet pipes 6 along the circumference of the mixed crystallization zone 200 can make the water inlet more uniform. At the same time, the design of multiple water inlet pipes 6 can share the water inlet flow rate and avoid the local lack of crystal seeds caused by too high local flow velocity.

[0046] In some alternative embodiments, there are m chemical dosing pipes 5 evenly spaced along the axial direction of the mixed crystallization zone 200, where m≥3. The multiple chemical dosing pipes 5 arranged at equal intervals can achieve uniform chemical dosing along the entire length of the mixed crystallization zone 200 and avoid uneven chemical dosing.

[0047] In some alternative embodiments, the stainless steel mesh 4 adopts a mesh structure with 80 - 100 meshes. A round hole with a diameter ≤6 mm is opened in the center of the stainless steel mesh 4. The round hole with this diameter can allow the stirring paddle 8 to pass through and prevent the loss of crystal seeds.

[0048] In some alternative embodiments, the stainless steel mesh 4 is fixed between two flanges between the mixed crystallization zone 200 and the clarified water outlet zone 100. Fixing the stainless steel mesh 4 through the flanges is not only convenient for replacement but also enables the stainless steel mesh 4 to cover the entire cross-section of the device, achieving effective interception of crystal seeds.

[0049] In some alternative embodiments, there are at least 4 groups of paddle blades of the stirring paddle 8 arranged along its length direction, and each group of paddle blades is evenly distributed in the crystal seed storage zone 300 and the mixed crystallization zone 200. The quantity and spacing of the stirring paddle 8 can promote the complete solid-liquid mixing in the mixed crystallization zone 200 and avoid the reduction of the fluidity of crystal seeds and insufficient solid-liquid mixing caused by insufficient stirring power.

[0050] The embodiment of the present invention also provides a method for completely mixing calcium fluoride crystallization for defluorination, which uses a completely mixing calcium fluoride crystallization defluorination reactor described in any one of the above embodiments. The method includes the following steps:

[0051] Step S1: Open the valve of the water inlet pipe 6, and the fluorine-containing wastewater enters the reactor through the water inlet pipe 6;

[0052] Step S2: After the fluorine-containing wastewater fills the entire reactor, 50% of the CaCl₂ solution enters the reactor through the chemical dosing pipe 5;

[0053] Step S3: Start the stirrer to fluidize the calcium fluoride crystal seeds and evenly cover the entire mixed crystallization zone 200 and the crystal seed storage zone 300;

[0054] Step S4: The fluoride ions in the wastewater form a stable calcium fluoride crystal structure on the surface of the fluorite particles in the presence of calcium ions, and the fluoride ions are removed.

[0055] Step S5: Under the interception of the stainless steel mesh 4, the mixed wastewater realizes solid-liquid separation;

[0056] Step S6: After the effluent flows out from the overflow weir 1, it flows through the collection tank 2 and is discharged through the outlet pipe 3.

[0057] Compared with the prior art, the embodiments of the present invention disclose at least the following beneficial effects:

[0058] 1. The present invention adopts a modular design, and is provided with a clarified effluent area 100, a mixed crystallization area 200 and a seed reserve area 300, which is convenient for maintenance and assembly.

[0059] 2. The design of the three-section functional area facilitates the operations of seed addition and discharge. The solid-liquid separation is strengthened by the stainless steel mesh 4, so that the effluent is clarified while ensuring that the seeds will not be lost due to water flow impact.

[0060] 3. Through the design of the bottom rotating shaft 7, the stability of the stirring paddle 8 is enhanced, and the solid-liquid mass transfer in the mixed crystallization area 200 is strengthened.

[0061] 4. Adopting the principle of induced crystallization, fluoride ions and calcium ions form a stable crystal structure on the surface of fluorite. While realizing the removal of fluoride ions, high-quality calcium fluoride crystals can be recovered. The whole adopts the form of upflow, and the floor area is small.

[0062] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0063] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A fully mixed calcium fluoride crystallization defluorination reactor, characterized in that, Including: A reactor body, which includes a seed reserve area (300), a mixing and crystallization area (200), and a clarified effluent area (100) that are connected in sequence from bottom to top and are detachably connected; the clarified effluent area (100) is connected to a water outlet pipe (3); A stirring paddle (8), which is coaxially arranged inside the reactor body and penetrates through the seed reserve area (300), the mixing and crystallization area (200), and the clarified effluent area (100); one end of the stirring paddle (8) is connected to a stirrer; A water inlet pipe (6), which is arranged on the circumferential side of the lower part of the mixing and crystallization area (200); A chemical addition pipe (5), and a plurality of chemical addition pipes (5) are arranged at intervals along the axial direction of the mixing and crystallization area (200); A stainless steel mesh (4), which is arranged between the mixing and crystallization area (200) and the clarified effluent area (100) for solid-liquid separation; Valves and water distributors are provided on the water inlet pipe (6), the chemical addition pipe (5), and the water outlet pipe (3).

2. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, The seed reserve area (300) is filled with fluorite particles with a particle size of 0.2 - 0.4 mm, and the filling volume is not less than 1 / 2 of the volume of the mixing and crystallization area (200).

3. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, There are n water inlet pipes (6) evenly distributed circumferentially along the circumferential side of the mixing and crystallization area (200), and the included angle between two adjacent water inlet pipes (6) is 360° / n, where n ≥ 2.

4. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, The number of the chemical addition pipes (5) is m, and the m chemical addition pipes (5) are arranged at equal intervals along the axial direction of the mixing and crystallization area (200) for uniformly distributing chemicals into the mixing and crystallization area (200), where m ≥ 3.

5. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, An overflow weir (1) is connected to the upper edge of the clarified effluent area (100), a collecting tank (2) is arranged below the overflow weir (1), and the bottom of the collecting tank (2) is connected to the water outlet pipe (3).

6. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, The seed reserve area (300), the mixing and crystallization area (200), and the clarified effluent area (100) are respectively connected by flanges.

7. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 6, characterized in that, The stainless steel mesh (4) is fixed between two flanges between the mixing and crystallization area (200) and the clarified effluent area (100).

8. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 7, characterized in that, The stainless steel mesh (4) adopts a mesh structure with 80 - 100 meshes.

9. The completely mixed calcium fluoride crystallization defluorination reactor according to claim 1, characterized in that, Multiple groups of paddle blades are arranged at intervals along the length direction of the stirring paddle (8), and each group of paddle blades is evenly distributed along the seed reserve area (300) and the mixing and crystallization area (200).

10. A method for removing fluorine by complete mixing type calcium fluoride crystallization, using the complete mixing type calcium fluoride crystallization fluorine removal reactor described in any one of claims 1 to 9, characterized in that, Including the following steps: Step S1: Open the valve of the water inlet pipe (6), and the fluoride-containing wastewater enters the reactor through the water inlet pipe (6); Step S2: After the fluoride-containing wastewater fills the entire reactor, 50% of the CaCl₂ solution enters the reactor through the chemical addition pipe (5); Step S3: Start the stirrer to fluidize the calcium fluoride seeds and evenly cover the entire mixing and crystallization area (200) and the seed reserve area (300); Step S4: The fluoride ions in the wastewater form a stable calcium fluoride crystal structure on the surface of the fluorite particles in the presence of calcium ions, and the fluoride ions are removed; Step S5: The mixed wastewater is subjected to solid-liquid separation under the interception of the stainless steel mesh (4); Step S6: After the effluent flows out from the clarified effluent area (100), it is discharged through the outlet pipe (3).

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