A method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag

Abstract

The invention provides a method for the coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, comprising the following steps: (1) mixing the aluminum electrolysis overhaul slag and carbon slag, crushing, ball milling, slurry mixing, pressurized alkali leaching, and introducing high-temperature water vapor and air to obtain an alkali leaching solution and an alkali leaching slag; (2) adding ozone, calcium hypochlorite, and modified polymer-grade aluminum chloride-aluminum sulfate to the alkali leaching solution in sequence, and filtering and separating; (3) washing the alkali leaching slag, and then acid leaching and settling to obtain an acid leaching solution and an acid leaching slag; (4) mixing the acid leaching solution and the alkali leaching solution treated in step (2) to carry out fluoride salt directional conversion, and separating the obtained product into a solid and a fluoride salt directional conversion liquid; (5) sending the fluoride salt directional conversion liquid obtained in step (4) to a water treatment system for treatment and then recycling it to the slurry mixing in step (1); washing and removing impurities from the solid and then drying it; the method can simultaneously realize the high-value utilization of valuable elements in the aluminum electrolysis overhaul slag and carbon slag, reduce the processing cost, and improve the efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization, and in particular to a method for coordinated processing and resource utilization of aluminum electrolysis overhaul slag and carbon slag. Background Art

[0002] The hazardous waste slag involved in the electrolytic aluminum industry in the national hazardous waste list released by the National Ecological and Environmental Department in 2020 includes overhaul slag, carbon slag, etc., and their main hazardous characteristics include toxicity (T) and reactivity (R).

[0003] Overhaul slag is the waste slag produced by the maintenance and replacement of the cathode lining of the electrolytic cell. According to the actual production of aluminum electrolysis, overhaul slag is further divided into three categories: waste cathode, waste refractory material, and mixed material. Waste cathode is the graphite cathode carbon block of the electrolytic cell. A large amount of electrolyte will penetrate into it during the long-term electrolysis production process. The main components of the graphite cathode carbon block corroded by the electrolyte are 50-70% C and about 30% fluoride. Fluoride exists in the form of Na3AlF6, NaF, CaF2, and contains a trace amount of NaCN. Waste refractory material is dry anti-seepage material corroded by electrolyte, including insulation bricks, refractory bricks, castables and silicate plates. Under normal circumstances, the electrolyte will only corrode the dry anti-seepage material and sinter it into a whole. Its main chemical component is NaAlSiO4, and fluoride basically exists in the form of NaF, containing a very small amount of Na3AlF6 and β-Al2O3. The mixed material is the electrolyte that has not been completely pumped out when the electrolytic cell is shut down, which is weathered into powder during the long-term storage process with waste cathodes and waste refractory materials. The main components of the mixed material are: NaF, SiO2, Al2O3, AlF3, and aluminosilicate.

[0004] Carbon slag is a substance produced by the uneven combustion and selective oxidation of carbon anodes, which leads to the shedding of carbon particles. The main components of aluminum electrolysis carbon slag are carbon and electrolyte, generally containing 20-30% carbon and 60-70% electrolyte. The main components of the electrolyte are Na3AlF6, Al2O3, CaF2, etc.

[0005] There are technologies available at home and abroad for the treatment and comprehensive resource utilization of aluminum electrolysis overhaul slag and carbon slag. The harmless disposal and comprehensive resource utilization of aluminum electrolysis overhaul slag can be divided into two categories: wet treatment and pyrolysis. The wet treatment process mainly includes water leaching, alkaline leaching, acid leaching, and acid-base combined leaching. The pyrolysis process mainly uses high-temperature oxygen-enriched combustion for harmless treatment, or uses the waste cathode as a carbonaceous material with usable calorific value resources, or recovers electrolytes at high temperature.

[0006] From the existing technical achievements, the harmless disposal processes of aluminum electrolysis overhaul slag and carbon slag are independent technical routes. The Chinese patent with publication number CN113426807A discloses a method for the combined treatment of aluminum electrolysis hazardous waste slag and comprehensive resource utilization. Although it can achieve the combined treatment of aluminum electrolysis overhaul slag, carbon slag and aluminum ash, the alkaline leaching process is used for the treatment of overhaul slag, and the efficient leaching of valuable elements such as F, Na, Al, etc. cannot be achieved. In addition, the "aluminum salt leaching + fluoride salt directional conversion" of carbon slag is an independent route. In the process of combined disposal of overhaul slag and carbon slag, there are technical problems such as large equipment investment, low production efficiency, high processing cost, high labor intensity, and low resource utilization rate. Therefore, it is necessary to innovate and improve the existing technology to improve the efficiency of the disposal of aluminum electrolysis overhaul slag and carbon slag. Summary of the invention

[0007] The purpose of the present invention is to provide a method for the coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, which can simultaneously realize the high-value utilization of valuable elements such as F, Na, Al, etc. in the aluminum electrolysis overhaul slag and carbon slag, while significantly reducing the treatment cost of aluminum electrolysis overhaul slag and carbon slag, improving the efficiency of harmless disposal, and making the treatment process more simple and reliable.

[0008] The embodiments of the present invention are implemented by the following technical solutions:

[0009] A method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, comprising the following steps:

[0010] (1) mixing aluminum electrolysis overhaul slag and carbon slag in a mass ratio of 3:1-10:1, crushing and ball milling, adding NaOH solution for slurry preparation, and pressurizing alkali leaching to obtain alkali leaching solution and alkali leaching slag;

[0011] (2) adding ozone and calcium hypochlorite to the alkaline leaching solution obtained in step (1) in sequence for a period of time, adding modified polymer grade aluminum chloride-aluminum sulfate for a period of time, and finally filtering and separating;

[0012] (3) after the alkaline leaching residue obtained in step (1) is subjected to three-stage countercurrent washing, concentrated sulfuric acid is added for acid leaching for a period of time, and sedimentation washing is performed to obtain an acid leaching solution and acid leaching residue;

[0013] (4) mixing the acid leaching solution obtained in step (3) and the alkaline leaching solution treated in step (2) for directional conversion of fluoride salts, adding a NaOH solution with a concentration of 40%-50% to control the pH of the reaction system, and performing liquid-solid separation on the obtained product to obtain cryolite solid or aluminum fluoride + aluminum oxide mixed solid and directional conversion liquid of fluoride salts;

[0014] (5) The fluoride salt directional conversion liquid obtained in step (4) is sent to a water treatment system for treatment and then reused in step (1) for slurry preparation; the cryolite solid or aluminum fluoride + aluminum oxide mixed solid is subjected to three-stage countercurrent washing to remove impurities and then dried.

[0015] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0016] 1. The treatment method of the present invention can realize the efficient utilization of valuable elements such as F, Al, Na, etc. in aluminum electrolysis overhaul slag and carbon slag, while reducing the cost of disposal and comprehensive utilization of aluminum electrolysis overhaul slag and carbon slag, solving the technical problem of low utilization rate of valuable elements such as F, Al, Na, etc. in aluminum electrolysis overhaul slag and carbon slag, and can extract lithium salts from aluminum electrolysis overhaul slag and carbon slag, realizing clean regeneration and efficient utilization of secondary resources.

[0017] 2. The treatment method of the present invention can effectively increase the harmless slag carbon content of the overhaul slag mixture by mixing the aluminum electrolysis overhaul slag with the carbon slag, thereby realizing the productization and high value of the overhaul slag mixture; effectively reduce the carbon slag disposal cost and equipment investment, and at the same time purify the cumbersome process of independent disposal and comprehensive utilization of aluminum electrolysis overhaul slag and carbon slag, improve the harmless disposal and comprehensive utilization efficiency of overhaul slag and carbon slag, significantly reduce the labor intensity of workers, and improve the informationization, automation and intelligence level of its disposal process. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0019] The following is a specific description of a method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag provided in an embodiment of the present invention.

[0020] A method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, comprising the following steps:

[0021] (1) Aluminum electrolysis overhaul slag and carbon slag are mixed in a mass ratio of 3:1-10:1, and then crushed and ball-milled to 150-200 meshes; the crushing process consists of a jaw crusher, a double-toothed roller crusher and an impact crusher connected in series, and iron removal facilities are set at the inlet and outlet of the jaw crusher and the outlet of the impact crusher to reduce the entry of impurity iron elements into the system; the ball milling method is wet grinding, and water is used as the medium in the wet grinding process to avoid the phenomenon that the material to be ground (overhaul slag, carbon slag) adheres to the steel ball, which can greatly improve the ball milling efficiency; the graphite process is provided with an exhaust gas collection device to collect and process the gases (NH3, CH4, H2) released during the reaction. The main reaction equation is as follows:

[0022] AlN+3H2O=Al(OH)3+NH3↑

[0023] 2Al+2NaOH+2H2O=2NaAlO2+3H2↑

[0024] Al4C3+6H2O=2Al2O3+3CH4↑

[0025] (2) The wet-ground overhaul slag and carbon slag mixture in step (1) is conveyed into a slurry mixing tank, and a NaOH solution with a concentration of 50-100 g / L is added to adjust the slurry solid content to 20%-30%, and stirred at room temperature for 2-3 hours; the stirring frequency is: 200-300 rpm;

[0026] (3) The overhaul slag and carbon slag mixture treated in step (2) above is sent to a pressure autoclave, where it stays for 3-4 hours under the process conditions of temperature: 90℃-95℃ and pressure 0.3-0.5MPa, and then enters the regulating tank, where high-temperature steam and air are introduced at the same time. A small amount of gas generated during the leaching process is sent to the tail gas treatment facility through a pipeline, and the alkali leaching slurry is sent to the alkali leaching sedimentation and washing system. The supernatant separated from the sedimentation tank is the alkali leaching liquid, which is pumped to the oxidation and cyanide removal process. The bottom flow is the leached slag, which is subjected to three-stage countercurrent washing and then enters the acid leaching process for further treatment. The main chemical reaction principle of the alkali leaching process is as follows:

[0027] Al2O3+2NaOH→2NaAlO2+H2O

[0028] Na4Fe(CN)6+2NaOH→6NaCN+Fe(OH)2

[0029] NaF is partially hydrolyzed, NaF+H2O→NaOH+HF

[0030] 2NaCN+5H2O2→2NaHCO3+N2↑+4H2O

[0031] Na3AlF6+4NaOH→6NaF+NaAlO2+2H2O

[0032] (4) The alkaline leaching solution obtained in the above step (3) is pumped into a cyanide-breaking tank, and ozone and calcium hypochlorite are added to perform oxidation and cyanide removal for 2-3 hours. The reaction is as follows:

[0033] 5O3+2NaCN+H2O=5O2+NaCNO+N2+2NaHCO3;

[0034] Then add modified polymer grade aluminum chloride-aluminum sulfate for 2-3 hours, and finally filter and separate;

[0035] The preparation method of modified polymer-grade aluminum chloride-aluminum sulfate is as follows: after nano-silicon dioxide is immersed in a polymer-grade aluminum chloride solution for a period of time, 1 / 3-1 / 2 of a mixed solution of tannic acid and aluminum sulfate is added thereto, and then dried for a period of time to obtain an intermediate, and then the remaining mixed solution of tannic acid and aluminum sulfate is sprayed on the surface of the intermediate, and further dried for a period of time to obtain the intermediate; the mass ratio of nano-silicon dioxide, polymer-grade aluminum chloride, tannic acid and aluminum sulfate is 10:30-50:1-5:1-5;

[0036] Polymer grade aluminum chloride is adsorbed inside the pores of nano-silica and filled outside the voids. Tannic acid is then used to interact with aluminum ions to form a complex, which is then combined with the adsorbed nano-silica, so that the defluoridation agent can more efficiently and stably exert its defluoridation effect. In the alkaline leaching solution, a large amount of aluminum hydroxy polymer is produced during hydrolysis, which undergoes a directional conversion effect of adsorption and electrofluoride salt with fluoride ions, forming a larger floc sedimentation, thereby achieving the purpose of defluoridation.

[0037] (5) The leached residue obtained in the above step (3) is re-pulped and then pumped into an acid leaching tank, and a certain amount of concentrated sulfuric acid is added to adjust the solid content of the slurry to 15%-20%. After being kept in the continuous acid leaching tank at 50°C-70°C for 5-7 hours, it is sent to the acid leaching sedimentation washing system. The supernatant separated in the sedimentation tank is the acid leaching liquid. The acid leaching liquid is pumped through the fluoride salt directional conversion process to react with the alkaline leaching liquid to produce regenerated aluminum fluoride, regenerated cryolite and other products; the bottom flow is the acid leaching residue, and the acid leaching residue is subjected to three-stage countercurrent washing with the system. Lime is added during the washing process as appropriate to further reduce the fluoride content therein to meet the standard of "GB / T5085.1-2007 "Identification Standard for Hazardous Wastes Corrosiveness Identification"". After the final washing is completed, it is pumped to the product filter press and storage device.

[0038] (6) introducing the alkaline leaching solution and the acid leaching solution obtained by filtering the above steps (3) and (5) into a fluoride salt directional conversion tank, causing a fluoride salt directional conversion reaction, and controlling the pH of the reaction system by adding a NaOH solution to control the production of products, mainly cryolite, aluminum fluoride + alumina, etc.; the concentration of the NaOH solution is 40%-50%; the pH of the cryolite production process is 8-10, the reaction temperature is 60°C-80°C, the reaction time is 4-6h, and the stirring rate is: 200-300rpm; the aluminum fluoride + alumina production process The pH value of the process is 4-5, the reaction temperature is 60℃-80℃, the reaction time is 4-6h, and the stirring rate is 200-300rpm; after the above reaction is completed, it is sent to the product sedimentation washing system, and the supernatant is the liquid after the directional conversion of the fluoride salt. It is sent to the water treatment facility for treatment and then reused in the above step (2) for slurry mixing. The product is then pumped into the product drying and storage device after three-stage countercurrent washing to remove impurities; the water treatment facility includes a nanofiltration system, a freezing crystallization system, an evaporation crystallization system, etc.; the evaporation concentrate is used to extract valuable elements such as valuable Li. The main chemical reaction principles of the directional conversion process of fluoride salts are as follows:

[0039] Chemical reactions in the production of recycled cryolite:

[0040] 12NaF+Al2(SO4)3=2Na3AlF6↓+3Na2SO4

[0041] Chemical reactions when producing regenerated sodium fluoride:

[0042] 0.76Al 3+ +3.24AlF 2+ +2H + +7.52NaOH→2Al2F 3.24 (OH) 2.76 ·H2O↓+7.52Na +

[0043] Al(OH) 4- +1.24F - +AlF2++1.24H + →Al2F 3.24 (OH) 2.76 ·H2O↓+0.24H2O

[0044] (7) The concentrated solution obtained by evaporation and crystallization in step (6) is further concentrated and purified, and after impurity removal and freeze crystallization, sodium carbonate is finally added to precipitate lithium, and industrial-grade lithium carbonate is prepared after washing and drying; the impurity removal is carried out by adding hydrogen peroxide, resin, etc.

[0045] The treatment method of the present invention comprises the following steps: (1) mixing overhaul slag and carbon slag in proportion, and then subjecting the mixture to alkaline leaching, acid leaching, fluoride salt directional conversion, and valuable metal extraction, thereby realizing efficient extraction of valuable metals from aluminum electrolysis overhaul slag and carbon slag. At the same time, the invention makes up for the fact that in the independent treatment of aluminum electrolysis overhaul slag, the fluoride salt directional conversion process to produce regenerated spar and aluminum fluoride + alumina requires the additional addition of elements such as F and Al to meet the requirements of synthesizing regenerated spar and aluminum fluoride + alumina and other products. While realizing efficient utilization of valuable elements such as F, Al, and Na in aluminum electrolysis overhaul slag and carbon slag, the cost of treatment and comprehensive utilization of aluminum electrolysis overhaul slag and carbon slag is reduced, thereby solving the technical problem of low utilization rate of valuable elements such as F, Al, and Na in aluminum electrolysis overhaul slag and carbon slag. The valuable metal elements contained therein are extracted and lithium carbonate products are prepared, thereby realizing clean regeneration and efficient utilization of secondary resources of metallic lithium in aluminum electrolysis overhaul slag and carbon slag.

[0046] Moreover, by mixing aluminum electrolysis overhaul slag with carbon slag, the harmless slag carbon content of the overhaul slag mixture can be effectively increased, thereby realizing the productization and high value of the overhaul slag mixture; effectively reducing the carbon slag disposal cost and equipment investment, while purifying the cumbersome process of independent disposal and comprehensive utilization of aluminum electrolysis overhaul slag and carbon slag, improving the harmless disposal and comprehensive utilization efficiency of overhaul slag and carbon slag, significantly reducing the labor intensity of workers, and improving the informatization, automation and intelligence level of its disposal process.

[0047] Example 1

[0048] A method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, comprising the following steps:

[0049] (1) Aluminum electrolysis overhaul slag and carbon slag are mixed in a mass ratio of 5:1, and then crushed and ball-milled to 180 meshes; the crushing process is composed of a jaw crusher, a double-toothed roller crusher and an impact crusher connected in series, and iron removal facilities are set at the inlet and outlet of the jaw crusher and the outlet of the impact crusher to reduce the substitution of impurity iron elements into the system; the ball milling method is wet grinding, and water is used as the medium in the wet grinding process;

[0050] (2) The wet-ground overhaul slag and carbon slag mixture in step (1) was transported into a slurry mixing tank, and a NaOH solution with a concentration of 80 g / L was added to adjust the slurry solid content to 25%, and stirred at room temperature for 2.5 h; the stirring frequency was 250 rpm;

[0051] (3) The overhaul slag and carbon slag mixture treated in step (2) above is sent to a pressure autoclave, where it stays for 3.5 hours under the process conditions of temperature: 90° C. and pressure: 0.4 MPa, and then enters a regulating tank, where high-temperature steam and air are introduced simultaneously. A small amount of gas generated during the leaching process is sent to an exhaust gas treatment facility through a pipeline, and the alkali leaching slurry is sent to an alkali leaching sedimentation and washing system. The supernatant separated in the sedimentation tank is the alkali leaching liquid, which is pumped to the oxidation and cyanide removal process, and the bottom flow is the leaching slag. The leaching slag is subjected to three-stage countercurrent washing and then enters the acid leaching process for further treatment;

[0052] (4) The alkaline leaching solution obtained in the above step (3) is pumped into a cyanide breaking tank, ozone and calcium hypochlorite are added to perform oxidation and cyanide removal for 2.5 hours, and then modified polymer-grade aluminum chloride-aluminum sulfate is added for treatment for 2.5 hours, and finally filtered and separated; wherein the preparation method of the modified polymer-grade aluminum chloride-aluminum sulfate is: after nano-silicon dioxide is immersed in a polymer-grade aluminum chloride solution for a period of time, 1 / 3 of a mixed solution of tannic acid and aluminum sulfate is added thereto, and then dried for a period of time to obtain an intermediate, and then the remaining mixed solution of tannic acid and aluminum sulfate is sprayed on the surface of the intermediate, and continued to be dried for a period of time to obtain; the mass ratio of nano-silicon dioxide, polymer-grade aluminum chloride, tannic acid and aluminum sulfate is 10:40:3:3;

[0053] (5) The leached residue obtained in the above step (3) is re-pulped and then transported to an acid leaching tank by a pump, and a certain amount of concentrated sulfuric acid is added at the same time to adjust the solid content of the slurry to 18%. After being kept in the continuous acid leaching tank at 60° C. for 6 hours, it is sent to the acid leaching sedimentation washing system. The supernatant separated in the sedimentation tank is the acid leaching liquid. The acid leaching liquid is transported by a pump to the fluoride salt directional conversion process to react with the alkaline leaching liquid to produce regenerated aluminum fluoride, regenerated cryolite and other products; the bottom flow is the acid leaching residue, and the acid leaching residue is subjected to three-stage countercurrent washing with the system. Lime is added during the washing process as needed. After the final washing is completed, it is pumped to the product filter press and storage device;

[0054] (6) introducing the alkaline leaching solution and the acid leaching solution obtained by filtering the above steps (3) and (5) into a fluoride salt directional conversion tank, causing a fluoride salt directional conversion reaction, and controlling the pH of the reaction system to 9 by adding NaOH solution to produce cryolite, the NaOH solution concentration is 45%, the reaction temperature is 70°C, the reaction time is 5h, and the stirring rate is 250rpm; after the above reaction is completed, the product is sent to a product sedimentation washing system, and the supernatant is the fluoride salt directional conversion liquid, which is sent to a water treatment facility for treatment and then reused for slurry preparation in the above step (2), and the product is subjected to three-stage countercurrent washing to remove impurities and then pumped into a product drying and storage device; the water treatment facility includes a nanofiltration system, a freezing crystallization system, an evaporation crystallization system, etc.; the evaporated concentrate is used to extract valuable elements such as valuable Li;

[0055] (7) The concentrated solution obtained by evaporation and crystallization in step (6) is further concentrated and purified, and after impurities are removed by adding hydrogen peroxide, resin, etc., and frozen crystallized, sodium carbonate is finally added to precipitate lithium, and industrial-grade lithium carbonate is prepared after washing and drying.

[0056] In this embodiment, the yield of lithium carbonate is 83.2%, the yield of cryolite is 93.6%, the fluoride extraction rate is 90.3%, the Al2O3 dissolution rate is 92.1%, and the sodium recovery rate is 90.2%.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that: in step (1), during the pressurized alkali leaching, the temperature is 95° C. and the pressure is 0.5 MPa for 4 hours; in step (2), the mass ratio of the nano-silicon dioxide, polymer-grade aluminum chloride, tannic acid and aluminum sulfate in the modified polymer-grade aluminum chloride-aluminum sulfate is 10:50:5:3; in step (4), the pH is controlled to be 5, the reaction temperature is 60° C.-80° C., the reaction time is 4-6 hours, and the stirring rate is 200-300 rpm to produce aluminum fluoride + aluminum oxide.

[0059] In this embodiment, the yield of lithium carbonate is 83.0%, the yield of cryolite is 93.5%, the fluoride extraction rate is 90.5%, the Al2O3 dissolution rate is 92.0%, and the sodium recovery rate is 90.3%.

[0060] Example 3

[0061] The difference between this embodiment and embodiment 1 is that: in step (1), when adjusting the slurry: add a NaOH solution with a concentration of 100 g / L, keep the adjusted slurry solid content at 30%, and stir the reaction at room temperature for 2 hours; the stirring frequency is 300 rpm; in step (2), the mass ratio of the nano-silica, polymer-grade aluminum chloride, tannic acid and aluminum sulfate in the modified polymer-grade aluminum chloride-aluminum sulfate is 10:30:3:5; in step (4), the mass ratio of the acid leaching solution to the alkaline leaching solution is 1:6; the reaction temperature is 80°C, and the reaction time is 5 hours.

[0062] In this embodiment, the yield of lithium carbonate is 83.1%, the yield of cryolite is 93.6%, the fluoride extraction rate is 90.3%, the Al2O3 dissolution rate is 92.0%, and the sodium recovery rate is 90.0%.

[0063] It can be seen from the above embodiments 1-3 that the treatment method of the present invention can achieve efficient utilization of valuable elements such as F, Al, Na in aluminum electrolysis overhaul slag and carbon slag, while reducing the cost of disposal and comprehensive utilization of aluminum electrolysis overhaul slag and carbon slag, solving the technical problem of low utilization rate of valuable elements such as F, Al, Na in aluminum electrolysis overhaul slag and carbon slag, and can extract lithium salts from aluminum electrolysis overhaul slag and carbon slag, thereby realizing clean regeneration and efficient utilization of secondary resources.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for the coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag, characterized in that: The following steps are involved: (1) Aluminum electrolysis overhaul slag and carbon slag are mixed in a mass ratio of 3:1-10:1, crushed, ball-milled, and then NaOH solution is added for slurry preparation, pressurized alkali leaching is performed, and high-temperature steam and air are introduced at the same time, and alkali leaching solution and alkali leaching slag are obtained after a period of time; (2) adding ozone and calcium hypochlorite to the alkaline leaching solution obtained in step (1) in sequence for a period of time, adding modified polymer grade aluminum chloride-aluminum sulfate for a period of time, and finally filtering and separating; (3) after the alkaline leaching residue obtained in step (1) is subjected to three-stage countercurrent washing, concentrated sulfuric acid is added for acid leaching for a period of time, and sedimentation washing is performed to obtain an acid leaching solution and acid leaching residue; (4) mixing the acid leaching solution obtained in step (3) and the alkaline leaching solution treated in step (2) for directional conversion of fluoride salts, adding a NaOH solution with a concentration of 40%-50% to control the pH of the reaction system, and performing liquid-solid separation on the obtained product to obtain cryolite solid or aluminum fluoride + aluminum oxide mixed solid and directional conversion liquid of fluoride salts; (5) The fluoride salt directional conversion liquid obtained in step (4) is sent to a water treatment system for treatment and then reused in step (1) for slurry preparation; the cryolite solid or aluminum fluoride + aluminum oxide mixed solid is subjected to three-stage countercurrent washing to remove impurities and then dried.

2. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (1), when adjusting the slurry: add a NaOH solution with a concentration of 50-100 g / L, keep the solid content of the slurry adjusted to 20%-30%, and stir the reaction at room temperature for 2-3 hours; the stirring frequency is: 200-300 rpm.

3. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (1), during the pressurized alkali leaching, the mixture is kept at a temperature of 90°C-95°C and a pressure of 0.3-0.5 MPa for 3-4 hours.

4. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (2), the preparation method of modified polymer-grade aluminum chloride-aluminum sulfate is: after immersing nano-silicon dioxide in a polymer-grade aluminum chloride solution for a period of time, 1 / 3-1 / 2 of a mixed solution of tannic acid and aluminum sulfate is added thereto, and then dried for a period of time to obtain an intermediate, and then the remaining mixed solution of tannic acid and aluminum sulfate is sprayed on the surface of the intermediate, and continued to dry for a period of time to obtain the intermediate.

5. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 4 is characterized in that: The mass ratio of the nano silicon dioxide, polymer grade aluminum chloride, tannic acid and aluminum sulfate is 10:30-50:1-5:1-5.

6. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (4), the mass ratio of the acid leaching solution to the alkaline leaching solution is 1:5-6; the reaction temperature is 60°C-80°C, and the reaction time is 1-5h.

7. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (4), the cryolite solid is obtained when the pH is controlled to be 8-10, the reaction temperature is 60° C.-80° C., the reaction time is 4-6 h, and the stirring rate is 200-300 rpm.

8. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1 is characterized in that: In step (4), the cryolite solid is obtained when the pH is controlled to be 4-5, the reaction temperature is 60°C-80°C, the reaction time is 4-6h, and the stirring rate is 200-300rpm.

9. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 1, characterized in that: In step (5), the water treatment system includes a nanofiltration system, a freezing crystallization system, and an evaporation crystallization system.

10. The method for coordinated treatment and resource utilization of aluminum electrolysis overhaul slag and carbon slag according to claim 9, characterized in that: The concentrated liquid obtained by the evaporation crystallization system is further concentrated and purified. After impurity removal and freezing crystallization, sodium carbonate is added to precipitate lithium. After washing and drying, industrial-grade lithium carbonate is prepared.