A harmless defluorination method for electrolytic aluminum waste slag

Abstract

The present invention discloses a harmless defluorination method for electrolytic aluminum waste slag, belonging to the field of defluorination of electrolytic aluminum waste slag. The method adopts a coordinated treatment of turbulent flow crushing-ultrasonic activation-adsorption locking to replace strong acid leaching through the linkage coordination of components such as a multi-stage reactor, thereby avoiding the introduction of excessive salt, effectively reducing the amount of process wastewater, and realizing the recovery of NH4F aerosol. While effectively improving the recovery efficiency, the method can also be reused as an industrial raw material, greatly improving the resource utilization rate. At the same time, the method also realizes the full-phase capture of fluorine, that is, the liquid phase and gas phase fluorine are locked and captured by the multi-stage reactor, and the solid phase fluorine is locked and captured by the solidification reactor, thereby realizing efficient defluorination of electrolytic aluminum waste slag.

Description

Technical Field

[0001] The present invention relates to the field of fluorine removal from electrolytic aluminum waste slag, and in particular to a harmless fluorine removal method for electrolytic aluminum waste slag. Background Art

[0002] Electrolytic aluminum waste slag refers to the waste generated when bauxite undergoes the electrolytic aluminum process. It is mainly composed of various metal oxides, fluorides and other impurities. It is usually the ore residue that cannot be reduced by aluminum liquid during the electrolytic aluminum production process.

[0003] To address the above issues, a Chinese patent provides a method for recovering lithium from aluminum electrolysis solid waste (patent number: CN115872423A). This method uses sulfuric acid-aluminum salt mixed leaching and two-stage graded precipitation to achieve precise recovery of fluorine, aluminum, and lithium from aluminum electrolysis solid waste, yielding high-value-added products such as cryolite, aluminum fluoride, and lithium carbonate.

[0004] However, in actual use of the above technical solution, due to the introduction of a large amount of acid and alkali in the pre-process, the salt content of the filtrate is too high. The evaporation and concentration process causes excessive crystals, which easily causes the feed pump to become clogged, greatly affecting production efficiency. In addition, the tail liquid after crystallization precipitation contains a high amount of fluorine, which is very difficult to handle. Summary of the Invention

[0005] The purpose of the present invention is to provide a harmless defluorination method for electrolytic aluminum waste slag to solve the technical defects proposed in the background technology.

[0006] The purpose of the present invention can be achieved by the following technical solution: A harmless defluorination method for electrolytic aluminum waste slag, comprising the following steps:

[0007] Step 1: Waste slag crushing treatment, the electrolytic aluminum waste slag is transported to the crushing and screening machine, and the pH of the waste slag is adjusted during the crushing process;

[0008] Step 2: Slurry viscosity adjustment: start the screw feeder to feed the crushed waste residue into the slurry mixing tank, adjust the slurry viscosity, and then transport it to the multi-stage reactor through the diaphragm pump;

[0009] Step 3: Chemical precipitation treatment, which uses a multi-stage reactor to adjust the slurry flow rate and induce crystal breakage. Nano-calcium oxide suspension is added to generate new precipitates to reduce the fluorine concentration. Double alkali is added to the slurry to maintain the slurry pH range to promote co-precipitation and further reduce the fluorine concentration.

[0010] Step 4: Filler adsorption treatment, the residual F is adsorbed by the honeycomb ceramic filler in the multi-stage reactor - The Al-F complex is generated, which further reduces the fluorine concentration;

[0011] Step 5: Filter pressing treatment, using a curing reactor to heat the slurry and add a binder, while using a filter press to press and shape it;

[0012] The multi-stage reactor used in the above-mentioned defluorination method consists of a tank body filled with honeycomb ceramic filler and fixed pipes 1 and 2 for conveying slurry. The guide plates arranged in fixed pipes 1 and 2 are used to adjust the flow rate of the slurry.

[0013] Preferably, both the first fixed tube and the second fixed tube are provided with a tapered section, a sudden expansion cavity and a diameter reducing tube;

[0014] The sudden expansion cavity is located between the tapered section and the reducer. The tapered section of fixed tube one is fixedly connected to the diaphragm pump through a pipeline. The reducer of fixed tube one is fixedly connected to the tapered section of fixed tube two through a pipeline. The reducer of fixed tube two is fixedly connected to the tank body through a pipeline.

[0015] Preferably, the inlet diameter of the tapered section of the fixed tube 1 is 200 mm, the outlet diameter is 80 mm, the sudden expansion cavity of the fixed tube 1 is hemispherical, with a diameter of 120 mm, and the sudden expansion ratio is 2.25;

[0016] The inlet diameter of the tapered section of the fixed pipe 2 is 200 mm, the outlet diameter is 100 mm, the sudden expansion cavity of the fixed pipe 2 is a flat ellipse with a major axis of 150 mm, a minor axis of 100 mm, and a sudden expansion ratio of 1.5.

[0017] Preferably, the fixed tube 1 is arranged horizontally, and the fixed tube 2 is arranged downwardly inclined, with the inclined direction being from the fixed tube 1 to the tank body, and the inclination angle is 5°;

[0018] The connection between the second fixed pipe and the tank body is tangentially arranged with an inclination angle of 45 degrees. A honeycomb ceramic filler is fixedly installed on the inner wall of the tank body. A flow groove is opened on the honeycomb ceramic filler, and the flow groove is spiral.

[0019] Preferably, a fixed plate is fixedly installed at the bottom of the tank body, a filler layer is fixedly installed on the fixed plate, a liquid outlet pipe is fixedly installed at the bottom of the tank body, the liquid outlet pipe is located below the fixed plate, and an air inlet pipe is fixedly installed on the outer wall of the tank body, and the air inlet pipes are evenly spaced on the filler layer.

[0020] Preferably, piezoelectric ceramic transducers are fixedly mounted on the sudden expansion cavities of fixed tube one and fixed tube two, and multiple piezoelectric ceramic transducers are provided, and the multiple piezoelectric ceramic transducers are evenly spaced on the outer wall of the sudden expansion cavity, and multiple guide plates are provided, and the multiple guide plates are evenly spaced in the tapered section.

[0021] Preferably, one end of the guide plate is movably connected to the inner walls of fixed tube one and fixed tube two through a rotating shaft, a magnetic block is fixedly installed on the guide plate, and electromagnets are fixedly installed on the outer walls of fixed tube one and fixed tube two, and the positions of the electromagnets are adapted to the magnetic blocks.

[0022] Preferably, a feeding pipe 1 is fixedly installed on fixed pipe 1, and feeding pipe 1 is located at the tapered section of fixed pipe 1. A feeding pipe 2 is fixedly installed on fixed pipe 2, and feeding pipe 2 is located at the sudden expansion cavity of fixed pipe 2. There are multiple feeding pipes 2, and the multiple feeding pipes 2 are evenly spaced on the outer wall of the sudden expansion cavity.

[0023] The beneficial effects of the present invention are as follows:

[0024] (1) The present invention uses a multi-stage reactor and other components in combination. The multi-stage reactor often uses a combination of an asymmetric hyperbolic tapered section and a hemispherical expanded cavity to make the waste slurry produce a three-dimensional spiral motion. On the one hand, it effectively improves the mixing efficiency of the reagents, and at the same time, by driving the waste slurry to move in a spiral motion, it avoids clogging the pipeline;

[0025] At the same time, piezoelectric ceramic transducers are arranged at equal intervals on the outer wall of the multi-stage reactor. The ultrasonic energy is focused on the center of the slurry vortex through the horn, reducing the fluoride crystal particle size to 5-10μm, effectively increasing the precipitation rate, reducing the processing pressure of subsequent equipment, and thus improving the fluorine removal efficiency;

[0026] (2) The present invention also pre-treats the electrolytic aluminum waste slag by using a crushing and screening machine and a slurry mixing tank, and then effectively reduces the fluorine content in the slurry through a gradient treatment process of a multi-stage reactor. At the same time, NH3 gas is input into the multi-stage reactor to capture the fluorine in the slurry to generate NH4F aerosol. While effectively improving the recovery efficiency, it can also be reused as an industrial raw material. The gas contacts the slurry in countercurrent, so that NH3 and PAC form a gas-liquid micro-interface reaction in the countercurrent flow field, effectively improving the fluorine removal efficiency and realizing efficient fluorine removal of electrolytic aluminum waste slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings;

[0028] Figure 1 It is a schematic flow diagram of the present invention;

[0029] Figure 2 It is a structural schematic diagram of the present invention;

[0030] Figure 3 It is a schematic structural diagram of the multi-stage reactor in the present invention;

[0031] Figure 4 Schematic diagram of the structure of the fixed tube 1 and the fixed tube 2 in the present invention;

[0032] Figure 5 This is a schematic structural diagram of a fixed tube-expanding cavity in the present invention;

[0033] Figure 6This is a schematic structural diagram of the second protruding expansion cavity of the fixed tube in the present invention;

[0034] Figure 7 Schematic diagram of the internal structure of the fixed tube 1 and the fixed tube 2 in the present invention;

[0035] Figure 8 It is a schematic diagram of the structure inside the tank body of the present invention;

[0036] Figure 9 It is a structural schematic diagram of the honeycomb ceramic filler in the present invention.

[0037] Legend: 1. Slurry mixing tank; 101. Diaphragm pump; 2. Multi-stage reactor; 201. Fixed pipe 1; 202. Fixed pipe 2; 203. Tank body; 204. Honeycomb ceramic filler; 205. Flow trough; 206. Fixed plate; 207. Filling layer; 208. Liquid outlet pipe; 209. Air inlet pipe; 210. Piezoelectric ceramic transducer; 211. Guide vane; 212. Electromagnet; 213. Feeding pipe 1; 214. Feeding pipe 2. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1: Please refer to Figure 1 - Figure 8 As shown, this embodiment is a harmless defluorination method for electrolytic aluminum waste slag, which is implemented by a multi-stage reactor 2, including a fixed pipe 1 201, a fixed pipe 202 and a tank body 203. The fixed pipe 1 201 and the fixed pipe 202 are both provided with a tapered section, a sudden expansion cavity and a reducing pipe;

[0040] The sudden expansion cavity is located between the tapered section and the reducing pipe. The tapered section of the fixed pipe 201 is fixedly connected to the diaphragm pump 101 through a pipeline. The reducing pipe of the fixed pipe 201 is fixedly connected to the tapered section of the fixed pipe 202 through a pipeline. The reducing pipe of the fixed pipe 202 is fixedly connected to the tank body 203 through a pipeline.

[0041] Among them, the inlet diameter of the tapered section of the fixed tube 201 is 200mm, the outlet diameter is 80mm, the sudden expansion cavity of the fixed tube 201 is hemispherical, with a diameter of 120mm, and a sudden expansion ratio of 2.25; the inlet diameter of the tapered section of the fixed tube 202 is 200mm, the outlet diameter is 100mm, the sudden expansion cavity of the fixed tube 202 is a flat elliptical shape, with a major axis of 150mm, a minor axis of 100mm, and a sudden expansion ratio of 1.5.

[0042] Piezoelectric ceramic transducers 210 are fixedly installed on the sudden expansion cavities of fixed tube 1 201 and fixed tube 2 202. There are multiple piezoelectric ceramic transducers 210, and the multiple piezoelectric ceramic transducers 210 are evenly spaced on the outer wall of the sudden expansion cavity. Multiple guide vanes 211 are movably installed inside the tapered section, and the multiple guide vanes 211 are evenly spaced in the tapered section.

[0043] Fixed tube 1 201 is arranged horizontally, and fixed tube 202 is arranged downwardly inclined, with the inclination direction from fixed tube 1 201 to tank body 203, and the inclination angle is 5°. The connection between fixed tube 202 and tank body 203 is arranged tangentially, and the inclination angle is 45°. A honeycomb ceramic filler 204 is fixedly installed on the inner wall of tank body 203, and a flow groove 205 is opened on the honeycomb ceramic filler 204. The flow groove 205 is spiral. The main component of the honeycomb ceramic is cordierite or mullite. Its structural characteristics are: pore diameter of 2mm, allowing slurry to pass through while retaining particles greater than 50μm, wall thickness of 0.3mm, porosity of 85%, and open porosity greater than 95%.

[0044] That is, the slurry enters the tank body 203 tangentially through the pipeline, and under the action of the flow groove 205, the slurry flows in a spiral shape, effectively increasing the contact time and contact area between the slurry and the honeycomb ceramic filler 204, and effectively improving the adsorption effect.

[0045] A fixed plate 206 is fixedly installed at the bottom of the tank body 203, a packing layer 207 is fixedly installed on the fixed plate 206, a liquid outlet pipe 208 is fixedly installed at the bottom of the tank body 203, and the liquid outlet pipe 208 is located below the fixed plate 206. An air inlet pipe 209 is fixedly installed on the outer wall of the tank body 203, and the air inlet pipes 209 are evenly spaced on the packing layer 207. During the process of the slurry passing through the honeycomb ceramic filler 204, NH3 gas is transported to the inside of the tank body 203 through the air inlet pipe 209. The NH3 gas forms microbubbles in the honeycomb channels of the packing layer 207, with a diameter of 0.5-1 mm. The rising process of the bubbles captures F - , generating NH4F aerosol, and realizing the synergistic purification of liquid phase fixation and gas phase removal of fluorine by integrating the triple functions of adsorption, reaction and gas capture.

[0046] At the same time, NH3 gas is used to backflush the pores of the packing layer 207, that is, impurities blocking the pores are flushed out by high-speed airflow, effectively avoiding blockage of the packing layer 207 and improving the working time of the equipment.

[0047] One end of the guide plate 211 is movably connected to the inner walls of the fixed tube 1 201 and the fixed tube 2 202 through a rotating shaft. A magnetic block is fixedly installed on the guide plate 211, and an electromagnet 212 is fixedly installed on the outer walls of the fixed tube 1 201 and the fixed tube 2 202. The position of the electromagnet 212 is adapted to the magnetic block. That is, in actual use, by energizing the electromagnet 212, it becomes magnetic, thereby generating a repulsive force on the magnetic block, thereby pushing multiple guide plates 211 to rotate and deflect at the same time.

[0048] The guide vane 211 in the fixed tube 201 has an adjustable angle range of 0-15°. The deflection of the guide vane 211 guides the slurry to form a three-dimensional spiral flow, and the flow rate is increased from 1.2 m / s to 4.5 m / s by reducing the cross-sectional area of ​​the fluid. Strong turbulence is used to ensure full contact between the nano-calcium oxide agent and the waste slag particles, shortening the reaction time. At the same time, the spiral flow field suppresses particle sedimentation to avoid blockage. At the same time, the guide vane 211 and the piezoelectric ceramic transducer 210 work in conjunction with each other to effectively improve the efficiency of CaF2 crystal crushing.

[0049] The guide plate 211 and the piezoelectric ceramic transducer 210 are specifically linked and coordinated as follows:

[0050] Through the linkage formula , where P is the ultrasonic power in W. That is, when the guide vane angle θ increases from 0° to 15°, the ultrasonic power P increases linearly from 800W to 2000W, achieving precise matching of flow field kinetic energy and acoustic field energy.

[0051] Example: When θ=10°, At this time, the turbulence intensity and the cavitation effect reach the best coordinated state. That is, when the deflection of the guide vane 211 increases, the shear force of the flow field is enhanced, the cavitation bubble distribution is more uniform, and the efficiency of CaF2 crystal crushing is improved. At this time, the ultrasonic energy is focused on the vortex center, and the cavitation energy density per unit volume reaches 12J / cm³.

[0052] The guide vane 211 in the fixed tube 202 can be adjusted in an angle range of 5-20°. The guide vane 211 can reduce the slurry flow rate to 3.1 m / s, extend the reaction time to 12 s, and promote the co-precipitation of CaF2 microcrystals and double alkali, effectively improving the fluorine removal rate. The guide vane 211 moves in an offset manner during adjustment to form a staggered vortex, further improving the slurry mixing efficiency.

[0053] A feeding pipe 213 is fixedly installed on the fixed pipe 201, and the feeding pipe 213 is located at the tapered section of the fixed pipe 201. A feeding pipe 214 is fixedly installed on the fixed pipe 202, and the feeding pipe 214 is located at the sudden expansion cavity of the fixed pipe 202. There are multiple feeding pipes 214, and the multiple feeding pipes 214 are evenly spaced on the outer wall of the sudden expansion cavity.

[0054] The feeding pipe 213 is used to add nano calcium oxide suspension into the slurry, with a CaO particle size of 50nm and a concentration of 10%, to react with the dissolved F - CaF2 precipitate is generated, and the feeding pipe 214 is used to add double alkali, namely NaOH and Na2CO3, to the slurry in the fixed pipe 202, with a concentration of 20%, to maintain pH = 6.5-7.0 and optimize the precipitation conditions.

[0055] That is, the multi-stage reactor 2 often uses a combination of an asymmetric hyperbolic tapered section and a hemispherical expanded cavity to make the waste slurry produce a three-dimensional spiral motion, which effectively improves the mixing efficiency of the reagents and at the same time avoids clogging of the pipeline by driving the waste slurry to move in a spiral motion;

[0056] At the same time, piezoelectric ceramic transducers 210 are arranged at equal intervals on the outer wall of the multi-stage reactor 2. The ultrasonic energy is focused on the center of the slurry vortex through the amplitude rod, so that the fluoride crystal particle size is reduced to 5-10μm, the precipitation rate is increased by 3 times, the subsequent equipment processing pressure is reduced, and the fluorine removal efficiency is effectively improved.

[0057] Example 2: Please refer to Figure 1 As shown, a harmless defluorination method for electrolytic aluminum waste slag comprises the following steps:

[0058] Step 1: Waste slag crushing treatment: The electrolytic aluminum waste slag with a moisture content of less than 5% is transported to a crushing and screening machine, crushed to less than 80 mesh by a jaw crusher and a ball mill, and 5% dilute sulfuric acid is sprayed into the crushing process to adjust the pH to 4.5-5.0;

[0059] The physical shear force of the jaw crusher and the ball mill destroys the crystal structure of the waste residue, increases the specific surface area, and exposes the wrapped fluoride. During the process, 5% dilute sulfuric acid is sprayed in to react with the metal fluoride (such as CaF2, Na3AlF6) in the waste residue to generate soluble fluoride ions (F - ) and sulfate precipitation.

[0060] That is, it dissociates the encapsulated fluoride, improves the availability of fluoride ions in subsequent reactions, and avoids traditional strong acid leaching, reducing acid usage by 80%, thus controlling salt generation from the source.

[0061] Step 2: Slurry viscosity adjustment: Start the screw feeder to feed the crushed waste residue into the slurry preparation tank 1 at a solid-liquid ratio of 1:3, adjust the slurry viscosity to 300-500mPa.s, and transport it to the multi-stage reactor 2 via the diaphragm pump 101;

[0062] By preparing the slurry with a solid-liquid ratio of 1:3, the viscosity is reduced to 300-500mPa·s (thixotropic fluid), ensuring pipeline transportation stability. At the same time, the pH is maintained at 4.5-5.0 to inhibit the re-precipitation of CaF2 and avoid the introduction of excessive acid.

[0063] That is, it provides a homogenized reaction medium for the subsequent multi-stage reactor 2-stage defluorination, reduces the alkali consumption in the subsequent neutralization link, and effectively reduces the salt load.

[0064] Step 3: Chemical precipitation treatment: The slurry flow rate is adjusted through the multi-stage reactor 2, and the CaF2 crystals are induced to break down to less than 5μm. Nano-calcium oxide suspension is added to generate new CaF2 precipitation, reducing the fluorine concentration from 8% to 2.5%;

[0065] In this process, the slurry enters the fixed tube 201 and induces a three-dimensional spiral flow through the asymmetric hyperbolic tapering section. The slurry flow rate reaches 4.5m / s. At the same time, cavitation bubbles are generated by 28kHz ultrasonic waves to break the CaF2 crystals to less than 5μm. Nano calcium oxide (CaO, 50nm) suspension is added to the F - Producing microcrystalline CaF2.

[0066] That is, fluorine removal is completed quickly, and microcrystalline CaF2 is used as the seed of the secondary reaction, reducing the amount of subsequent reagents added;

[0067] At the same time, NaOH / Na2CO3 double alkali is added to the slurry through the multi-stage reactor 2 to maintain the slurry pH range of 6.5-7.0 to promote co-precipitation and further reduce the fluorine concentration to 0.8%;

[0068] In this process, the slurry enters the fixed pipe 202, the outlet of the tapered section is expanded to Φ100mm, the flow rate is reduced to 3.1m / s, the reaction time is extended to 12s, and Na2CO3 is preferentially added to precipitate excess Ca 2+ (anti-scaling), then switch to NaOH to adjust pH=6.5-7.0 to promote F - With residual Ca 2+ / Al 3+ Co-precipitation.

[0069] That is, it avoids the salt accumulation caused by a single alkaline agent, and further reduces the fluoride concentration, thereby reducing the amount of salt generated.

[0070] Step 4: Filler adsorption treatment: NH3 gas is introduced into the multi-stage reactor 2 and contacts the slurry in countercurrent, while the honeycomb ceramic filler 204 adsorbs the residual F - The Al-F complex is formed, and the fluorine concentration is finally reduced to 0.15%;

[0071] In this process, the slurry enters the tank 203 and rotates downward from the top tangential inlet (inclination angle 45°), and contacts with the NH3 gas introduced from the bottom in countercurrent, forming a gas-liquid micro-interface reaction. At the same time, the honeycomb ceramic filler 204 locks the residual F through chemical adsorption. - ;

[0072] That is, to achieve deep defluorination, solve the problem of high fluorine residue in the tail liquid of traditional processes, and at the same time recover NH4F aerosol to increase resource utilization benefits.

[0073] Step 5: Filter press treatment: the slurry after being treated by the multi-stage reactor 2 is transported to the curing reactor, the microwave module of the curing reactor is started, the slurry is heated to 150°C and sodium silicate binder is added, and the filter press is formed at a pressure of 8-15MPa.

[0074] The solidified body obtained by microwave crystallization and high-pressure filtration can be directly and safely buried. Microwave crystallization refers to inducing the transformation of CaF2 crystal form into α phase (thermodynamically stable state) through 2.45GHz microwave field. High-pressure filtration refers to removing moisture under 8-15MPa pressure. The pre-buried nano-Al2O3 crystal seeds form an Al2O3-SiO2-CaF2 eutectic network with silicate. The slurry that does not meet the standards is refluxed to step one through the reflux pipe for secondary treatment.

[0075] First, the electrolytic aluminum waste slag is pretreated, and then the fluorine content in the slurry is effectively reduced through the gradient treatment process of the multi-stage reactor 2. At the same time, NH3 gas is input into the multi-stage reactor 2 to capture the fluorine in the slurry to generate NH4F aerosol. While effectively improving the recovery efficiency, it can also be reused as an industrial raw material. The gas and slurry are in countercurrent contact, so that NH3 and PAC form a gas-liquid micro-interface reaction in the countercurrent flow field, and the fluorine removal efficiency is increased by 40%, thereby achieving efficient fluorine removal from electrolytic aluminum waste slag.

[0076] Combining Example 1 and Example 2, it can be seen that by coordinating the multi-stage reactor 2 and other components, a turbulent flow crushing-ultrasonic activation-adsorption locking coordinated treatment is adopted to replace the strong acid leaching, thereby avoiding the introduction of excessive salt, effectively reducing the amount of process wastewater, and realizing the recovery of NH4F aerosol. While effectively improving the recovery efficiency, it can also be reused as an industrial raw material, greatly improving the resource utilization rate, and at the same time realizing the full-phase capture of fluorine, that is, the liquid phase and gas phase fluorine are locked and captured by the multi-stage reactor 2, and the solid phase fluorine is locked and captured by the solidification reactor, thereby realizing efficient fluorine removal from electrolytic aluminum waste slag.

[0077] The above is only an explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A harmless defluorination method for electrolytic aluminum waste slag, characterized in that: The following steps are involved: Step 1: Waste slag crushing treatment, the electrolytic aluminum waste slag is transported to the crushing and screening machine, and the pH of the waste slag is adjusted during the crushing process; Step 2: Slurry viscosity adjustment: start the screw feeder to feed the crushed waste residue into the slurry preparation tank (1), adjust the slurry viscosity, and then transport it to the multi-stage reactor (2) via the diaphragm pump (101); Step 3: Chemical precipitation treatment, adjusting the slurry flow rate through the multi-stage reactor (2) and inducing crystal breakage, adding nano calcium oxide suspension to generate new precipitates to reduce the fluorine concentration, and adding double alkali to the slurry to maintain the slurry pH range to promote co-precipitation and reduce the fluorine concentration; Step 4: Filler adsorption treatment, the honeycomb ceramic filler in the multi-stage reactor (2) adsorbs the residual F - The Al-F complex is generated, which reduces the fluorine concentration; Step 5: Filter pressing treatment, using a curing reactor to heat the slurry and add a binder, while using a filter press to press and shape it; The multi-stage reactor (2) used in the above-mentioned defluorination method is composed of a tank body (203) filled with honeycomb ceramic filler and a fixed pipe (201) and a fixed pipe (202) for conveying slurry. The guide plate (211) provided in the fixed pipe (201) and the fixed pipe (202) is used to adjust the flow rate of the slurry.

2. The harmless defluorination method for electrolytic aluminum waste slag according to claim 1, characterized in that: The fixed pipe 1 (201) and the fixed pipe 2 (202) are both provided with a tapered section, a sudden expansion cavity and a diameter reducing pipe; The sudden expansion cavity is located between the tapered section and the reducing pipe, the tapered section of the fixed pipe 1 (201) is fixedly connected to the diaphragm pump (101) via a pipeline, the reducing pipe of the fixed pipe 1 (201) is fixedly connected to the tapered section of the fixed pipe 2 (202) via a pipeline, and the reducing pipe of the fixed pipe 2 (202) is fixedly connected to the tank body (203) via a pipeline.

3. The harmless defluorination method for electrolytic aluminum waste slag according to claim 2, characterized in that: The inlet diameter of the tapered section of the fixed tube (201) is 200 mm, the outlet diameter is 80 mm, the sudden expansion cavity of the fixed tube (201) is hemispherical, the diameter is 120 mm, and the sudden expansion ratio is 2.25; The inlet diameter of the tapered section of the second fixed tube (202) is 200 mm, and the outlet diameter is 100 mm. The sudden expansion cavity of the second fixed tube (202) is a flat ellipse with a major axis of 150 mm, a minor axis of 100 mm, and a sudden expansion ratio of 1.

5.

4. The harmless defluorination method for electrolytic aluminum waste slag according to claim 3, characterized in that: The fixed pipe 1 (201) is arranged horizontally, and the fixed pipe 2 (202) is arranged to be tilted downward, with the tilting direction being from the fixed pipe 1 (201) to the tank body (203), and the tilting angle is 5°; The connection between the second fixed pipe (202) and the tank body (203) is tangentially arranged with an inclination angle of 45 degrees. A honeycomb ceramic filler (204) is fixedly installed on the inner wall of the tank body (203). A flow groove (205) is provided on the honeycomb ceramic filler (204). The flow groove (205) is spiral.

5. The harmless defluorination method for electrolytic aluminum waste slag according to claim 4, characterized in that: A fixing plate (206) is fixedly mounted on the bottom of the tank body (203), a packing layer (207) is fixedly mounted on the fixing plate (206), a liquid outlet pipe (208) is fixedly mounted on the bottom of the tank body (203), the liquid outlet pipe (208) is located below the fixing plate (206), and an air inlet pipe (209) is fixedly mounted on the outer wall of the tank body (203), the air inlet pipes (209) are evenly spaced and distributed on the packing layer (207).

6. The harmless defluorination method for electrolytic aluminum waste slag according to claim 2, characterized in that: A piezoelectric ceramic transducer (210) is fixedly mounted on the sudden expansion cavity of the fixed tube 1 (201) and the fixed tube 2 (202), a plurality of the piezoelectric ceramic transducers (210) are provided, and the plurality of the piezoelectric ceramic transducers (210) are evenly spaced and distributed on the outer wall of the sudden expansion cavity, and a plurality of the guide plates (211) are provided, and the plurality of the guide plates (211) are evenly spaced and distributed in the tapered section.

7. The harmless defluorination method for electrolytic aluminum waste slag according to claim 6, characterized in that: One end of the guide plate (211) is movably connected to the inner walls of the fixed tube 1 (201) and the fixed tube 2 (202) via a rotating shaft. A magnetic block is fixedly mounted on the guide plate (211). Electromagnets (212) are fixedly mounted on the outer walls of the fixed tube 1 (201) and the fixed tube 2 (202). The positions of the electromagnets (212) are adapted to the magnetic blocks.

8. The harmless defluorination method for electrolytic aluminum waste slag according to claim 7, characterized in that: A feeding pipe 1 (213) is fixedly installed on the fixed pipe 1 (201), and the feeding pipe 1 (213) is located at the tapered section of the fixed pipe 1 (201). A feeding pipe 2 (214) is fixedly installed on the fixed pipe 2 (202), and the feeding pipe 2 (214) is located at the sudden expansion cavity of the fixed pipe 2 (202). There are multiple feeding pipes 2 (214), and the multiple feeding pipes 2 (214) are evenly spaced and distributed on the outer wall of the sudden expansion cavity.

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