Electrolytic aluminum slag all-element recovery method

Abstract

The invention aims to provide a method for recovering all elements of electrolytic aluminum slag. In order to achieve the purpose, the invention provides the following technical scheme: introducing water vapor into the electrolytic aluminum slag at high temperature to remove carbon and fluorine in the electrolytic aluminum slag; and cooling and collecting the gas to obtain a hydrofluoric acid solution. And dissolving the product roasted by the water vapor in water, and filtering out insoluble impurities. CO2 is introduced into the aqueous solution, and aluminum hydroxide and sodium carbonate are recovered.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical resource recovery, and specifically provides a method for comprehensive element recovery from electrolytic aluminum slag. Background Art

[0002] In aluminum electrolysis production, to improve the properties of the electrolyte and achieve the goals of increasing current efficiency and reducing energy consumption, aluminum fluoride and cryolite are usually added. These additives, together with anode carbon powder and residual alumina, form electrolytic aluminum waste slag. The effective treatment of electrolytic aluminum waste slag is also a difficult problem for aluminum plants. Some manufacturers sell the electrolytic aluminum waste slag to fluoride salt manufacturers. Some manufacturers crush and process the electrolyte and reuse it in electrolytic aluminum production, but this will cause more serious damage to the electrolytic aluminum cells and is more adverse to production. There are also manufacturers that store the electrolyte underground or outdoors. There are a large amount of fluorides in the waste slag, which will penetrate into groundwater and soil with sunlight and rainwater, not only harming crops but also damaging human health and polluting the environment. If the electrolytic aluminum waste slag is only stored or inefficiently utilized, it is a waste of resources. Recycling the various elements in the electrolytic aluminum waste slag can not only reduce environmental pollution but also effectively save resources.

[0003] At present, many enterprises use acid leaching and roasting methods to extract lithium from lithium-containing waste aluminum slag, ignoring the recovery of fluorine and aluminum. Using the acid leaching method will generate a large amount of hydrofluoric acid, polluting the environment and having high costs. Summary of the Invention

[0004] The present invention aims to provide a method for comprehensive element recovery from electrolytic aluminum slag to solve the above problems in the prior art.

[0005] To achieve the above objective, the present invention provides the following technical solution: The technical solution provided by the present invention is: A method for comprehensive element recovery from electrolytic aluminum slag, comprising the following steps: S1: Crushing and grinding the obtained electrolytic aluminum slag into a particle size; S2: Placing the electrolytic aluminum slag powder obtained in S1 in an atmosphere furnace, adjusting the temperature and time, and introducing steam to carry out a roasting reaction; S3: Mixing the powder in S2 with deionized water at a certain liquid-solid ratio, carrying out water leaching at room temperature, filtering the insoluble slag, introducing carbon dioxide into the obtained filtrate to adjust the pH between 6.5 and 7.5, reacting for a certain time and then filtering, washing and drying the filter residue to recover aluminum hydroxide, and evaporating and concentrating the filtrate to recover sodium carbonate; S4: The hydrogen fluoride, carbon dioxide gas and unreacted steam generated by high-temperature steam treatment are cooled by a condenser to recover a hydrofluoric acid solution. Further, the grinding fineness of the electrolytic aluminum slag in S1 is 50 - 400 mesh, and the optimal grinding fineness is 200 mesh. Further, the reaction temperature range in S2 is 700 - 1000 °C, and the optimal reaction temperature is set at 750 °C. Further, the reaction time in S2 is between 0.5 - 3 h, and the optimal reaction time is set at 1 h.

[0006] Further, the liquid - solid ratio of the roasted slag to deionized water in S3 ranges from 3 - 8 ml:1 g, and the optimal liquid - solid ratio is 5 ml:1 g; the water leaching time is 1 - 5 h, and the optimal water leaching time is 2 h. Further, both the water leaching time and the reaction time of passing carbon dioxide in S3 are 1 - 5 h, and the optimal reaction time is set at 2 h. The beneficial effects of this technical solution are as follows: (1) Compared with the traditional electrolytic aluminum slag recycling technology, this invention fundamentally abandons the use of acid. This innovative measure brings multiple cost - saving benefits. On the one hand, it avoids the frequent damage to production equipment caused by the strong corrosiveness of acid, significantly reducing equipment maintenance and replacement costs; on the other hand, there is no need to invest a large amount of resources in treating the secondary waste liquid generated during the acid leaching process, effectively reducing environmental protection treatment costs and greatly enhancing the economic efficiency of the entire production process.

[0007] (2) This invention innovatively uses high - temperature steam roasting technology to achieve the efficient separation of fluorine and carbon elements from electrolytic aluminum slag. Compared with the traditional acid leaching method, this method only needs to consume water vapor and a certain amount of heat energy to achieve the efficient extraction of fluorine elements, without using expensive and highly polluting acid reagents. This simple and low - cost way of fluorine element recovery not only significantly reduces production costs but also reduces the potential environmental pollution risk at the source, showing extremely high environmental friendliness.

[0008] (3) After completing the defluorination and decarbonization reactions, this invention further deeply recovers aluminum and sodium elements in the slag, achieving the all - round recycling and utilization of various main elements in electrolytic aluminum slag, greatly improving resource utilization rate. At the same time, the entire roasted slag treatment process is designed compactly and simply, with relatively few operation steps, which is not only conducive to improving production efficiency and reducing energy consumption during the production process but also has important positive significance for production safety guarantee and equipment maintenance management, effectively reducing potential risks and maintenance costs during the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Shows the overall flow chart of recovering fluorine, aluminum, and sodium salts from electrolytic aluminum slag.

[0010] Figure 2Shown is a flow chart illustrating the process of roasting electrolytic aluminum slag with water vapor.

[0011] Figure 3 Shown is a flow chart illustrating the water leaching process of roasted slag.

[0012] Figure 4 Shown is a flow chart illustrating the process of separating and recovering aluminum salts and sodium salts.

[0013] Figure 5 Shown is a flow chart illustrating the process of recovering sodium salts. Detailed implementation manners

[0014] 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 creative efforts shall fall within the protection scope of the present invention.

[0015] The specific implementation process is as follows: Embodiment 1: Please refer to Figures 1-5 , a technical solution provided by the present invention: a method for recovering all elements of electrolytic aluminum slag. S1: Accurately weigh 10 g of waste electrolytic aluminum slag, place it in a professional grinding device, and through fine grinding and screening operations, make its particle size reach the standard of 200 mesh, ensuring that the electrolytic aluminum slag has the best reaction activity and specific surface area, laying a good foundation for the subsequent process; S2: Carefully place the sieved electrolytic aluminum slag inside the atmosphere furnace, continuously introduce water vapor at a precise flow rate of 1 g / min, and at the same time accurately set the temperature of the atmosphere furnace to 750 °C, strictly control the reaction time to 1 h. At the position of the steam outlet, a water condensation device is cleverly set up. Utilizing the heat exchange between water and the mixed gas and the solubility of hydrogen fluoride, the recovery of hydrogen fluoride is efficiently completed. Under these conditions, fluorine elements and carbon elements can be separated from the electrolytic aluminum slag with extremely high efficiency, and high-purity hydrogen fluoride is recovered through the condensation device; S3: Mix the slag after defluorination and decarbonization with deionized water according to an accurate liquid-solid ratio of 5:1 to form a uniform slurry, and conduct a 2-hour sufficient water immersion operation at room temperature to ensure that the soluble substances are fully dissolved. Then, filter out the insoluble slag through a high-precision filtration device, introduce carbon dioxide gas into the filtrate, accurately adjust the pH value of the solution to about 7, set the reaction time to 2 hours, filter again after the reaction is completed, wash the filter cake through multiple washing processes in sequence to remove the residual impurities on the surface, and then conduct a drying treatment in a professional drying device. Finally, a high-purity aluminum hydroxide material is obtained. During this process, by precisely controlling each parameter, the aluminum element can be efficiently and highly purified and recovered in the form of aluminum hydroxide; S4: Conduct an evaporation and concentration operation on the filtrate obtained by filtering in S3. In the evaporation device, as the water gradually evaporates, the sodium ions and carbonate ions in the solution are continuously enriched and finally precipitate in the form of sodium carbonate crystals. Separate these crystals through a filtration device, then wash them with a small amount of high-purity water to remove the impurity ions attached to the surface, and finally conduct a drying treatment in a drying device to recover a high-purity sodium carbonate material. Through this series of precise operations, the efficient and high-purity recovery of aluminum and sodium elements in the electrolytic aluminum slag is achieved.

[0016] Example 2: Please refer to Figures 1-5 , A technical solution provided by the present invention: A method for the full-element recovery of electrolytic aluminum slag. S1: Accurately weigh 10 g of waste electrolytic aluminum slag, place it in a grinding device, and through grinding and screening, make its particle size reach 150 meshes to prepare for the subsequent high-temperature roasting reaction; S2: Carefully place the screened electrolytic aluminum slag in an atmosphere furnace, continuously introduce water vapor for roasting at a flow rate of 0.8 g / min, set the temperature of the atmosphere furnace to 700 °C at the same time, control the reaction time to 1.5 hours, and treat the gas generated by the reaction through a carefully designed condensation device. Utilize the boiling point differences of the components in the mixed gas to efficiently complete the recovery of hydrogen fluoride. Under these conditions, although the reaction temperature and time are different from those in Example 1, the effective recovery of fluorine elements can still be achieved, proving the stability and adaptability of the method of the present invention within a certain parameter range; S3: Mix the calcined slag obtained after recovering fluorine with deionized water according to a liquid-solid ratio of 3:1 to form a uniform slurry, soak it in water at room temperature for 1 h to ensure that the soluble substances are fully dissolved, then filter the insoluble slag through a filtering device, introduce carbon dioxide gas into the filtrate, adjust the pH value of the solution to about 7, set the reaction time to 1 h, filter after the reaction ends, wash and dry the filter residue in sequence, and finally obtain aluminum hydroxide material. In this embodiment, by adjusting parameters such as the liquid-solid ratio and reaction time, the effective recovery of aluminum elements is also achieved, further verifying the flexibility and reliability of the method of the present invention; S4: Perform evaporation and concentration operations on the filtrate filtered in S3. As the water evaporates, crystalline substances gradually precipitate in the solution. Separate these crystals through a filtering device, wash them with a small amount of water to remove surface impurities, and then perform drying treatment in a drying device to recover sodium carbonate material. Through this series of operations, the recovery of various elements in the electrolytic aluminum slag is completed, once again proving the effectiveness of the method of the present invention.

[0017] Example 3: Please refer to Figures 1-5 A technical solution provided by the present invention: A method for the recovery of all elements in electrolytic aluminum slag. S1: Accurately weigh 10 g of waste electrolytic aluminum slag, grind and screen it to 250 meshes using a grinding device to ensure that the particle size of the electrolytic aluminum slag meets the requirements of subsequent reactions and has good reaction activity; S2: Put the screened electrolytic aluminum slag into an atmosphere furnace, continuously introduce water vapor for roasting at a flow rate of 1.5 g / min, set the temperature of the atmosphere furnace to 800 °C at the same time, control the reaction time to 0.8 h, and process the gas generated by the reaction through a carefully designed condensation and recovery device. Using the principles of heat exchange and gas-liquid separation, the recovery of hydrogen fluoride is efficiently achieved. Under such a relatively high temperature and different water vapor flow rate conditions, fluorine elements can still be effectively separated, fully demonstrating the adaptability and stability of the method of the present invention under different process conditions; S3: Mix the calcined slag obtained after recovering fluorine with deionized water according to a liquid-solid ratio of 8:1 to form a slurry, soak it in water at room temperature for 3 h to ensure that the soluble substances are fully dissolved, then filter the insoluble slag through a filtering device, introduce carbon dioxide gas into the filtrate, adjust the pH value of the solution to about 7, set the reaction time to 3 h, filter after the reaction is completed, wash and dry the filter residue in sequence, and obtain high-purity aluminum hydroxide material. By adjusting parameters such as the liquid-solid ratio and water soaking time, the efficient recovery of aluminum elements is achieved, further verifying the effectiveness and reliability of the method of the present invention under different parameter combinations; S4: Perform evaporation and concentration operations on the filtrate obtained by filtering in S3. As water continues to evaporate, sodium carbonate crystals gradually precipitate in the solution. Separate these crystals through a filtering device, wash them with a small amount of water to remove surface impurities, and then perform drying treatment in a drying device to recover high-purity sodium carbonate materials. Through this example, the high efficiency, stability, and reliability of the method of the present invention for the full-element recovery of electrolytic aluminum slag under different operating parameter conditions are strongly verified again, and it can meet the diverse needs in actual production.

[0018] Preparation process of electrolytic aluminum slag powder: Example 1: Accurately weigh 10 g of waste electrolytic aluminum slag, and after fine grinding and screening to 200 mesh, this mesh number is the optimal value determined through optimized experiments, which can endow the electrolytic aluminum slag with the best reaction activity and specific surface area. The smaller particle size increases the contact area between reactants in subsequent reactions, accelerates the reaction rate, and is conducive to the release of various elements and the progress of subsequent recovery reactions. Example 2: Weigh the same mass of waste electrolytic aluminum slag, grind and screen it to 150 mesh. Compared with Example 1, the mesh number is lower and the particles are relatively larger. For larger particles in subsequent reactions such as high-temperature roasting and water leaching, the diffusion path of internal substances to the surface is longer, and the reaction activity is relatively low, which may lead to a slightly slower reaction rate. The element recovery efficiency will be affected to a certain extent theoretically, but it is still within an acceptable range and effective recovery can be achieved. Example 3: Also take 10 g of waste electrolytic aluminum slag, grind and screen it to 250 mesh. The mesh number is higher than that of Example 2, the particles are smaller than those of Example 2 but larger than those of Example 1, and its reaction activity is between that of Example 1 and Example 2. The influence of particle size on the reaction is also between the two, and it can provide suitable reaction conditions for element recovery in subsequent reactions. Example 1: Pass steam into the atmosphere furnace at a flow rate of 1 g / min, accurately set the temperature to 750 °C, and react for 1 h. Through a large number of experimental explorations, these conditions are the optimal parameters for the separation of fluorine and carbon elements, which can efficiently separate fluorine and carbon elements and provide high-concentration and high-purity raw gas for subsequent fluorine recovery. At this temperature and steam flow rate, the fluorides and carbonaceous materials in the electrolytic aluminum slag can fully react to generate hydrogen fluoride and carbon dioxide, and the reaction time just makes the reaction complete, maximizing the transfer of fluorine elements from the solid slag to the gas phase. Example 2: Pass steam at a flow rate of 0.8 g / min, temperature 700 °C, and react for 1.5 h. The lower temperature makes the reaction rate relatively slow, but extending the reaction time compensates for this shortcoming to a certain extent, and effective recovery of fluorine elements can still be achieved. The lower steam flow rate may result in a slightly worse entrainment effect of fluorine elements than in Example 1, but overall it can still meet the fluorine element separation requirements, reflecting the stability of the method within a certain parameter range. Example 3: The flow rate of water vapor is 1.5 g / min, the temperature is 800 °C, and the reaction time is 0.8 h. The higher temperature accelerates the reaction rate, and the larger flow rate of water vapor enhances the entrainment ability of the fluorine and carbon reaction products. Although the reaction time is shortened, under the synergistic effect of high temperature and large flow rate of water vapor, fluorine elements can still be effectively separated, indicating that the method has adaptability to different process conditions; Recovery of aluminum and sodium elements: Example 1: The calcined slag and deionized water are leached in water at a liquid-solid ratio of 5:1 at room temperature for 2 h, and carbon dioxide is introduced to adjust the pH to about 7 and react for 2 h. Under this optimal liquid-solid ratio and reaction time, the recovery purity and recovery rate of aluminum and sodium elements reach the optimum, and high-purity aluminum hydroxide and sodium carbonate can be obtained efficiently. The appropriate liquid-solid ratio ensures the full dissolution of aluminum and sodium compounds in the calcined slag, and the appropriate reaction time enables the subsequent reaction with carbon dioxide to proceed completely, generating high-purity target products; Example 2: The liquid-solid ratio is 3:1, the water leaching time is 1 h, and carbon dioxide is introduced to react for 1 h. The smaller liquid-solid ratio may cause incomplete dissolution of some aluminum and sodium compounds in the calcined slag, and the shorter reaction time may also make the reaction with carbon dioxide incomplete. However, the effective recovery of aluminum elements is still achieved, verifying the flexibility of the method, indicating that the method can still function to a certain extent when deviating from the optimal parameters; Example 3: The liquid-solid ratio is 8:1, the water leaching time is 3 h, and carbon dioxide is introduced to react for 3 h. The larger liquid-solid ratio enables the more complete dissolution of aluminum and sodium compounds in the calcined slag, and the longer reaction time further ensures the progress of the reaction. The high-efficient recovery of aluminum elements is also achieved, indicating that the method has reliability under different parameter combinations. Even when the parameters deviate significantly from the optimal values, good recovery effects can still be ensured; Recovery of fluorine elements: Examples 1 - 3: All three examples use condenser equipment. According to the heat exchange principle and the difference in boiling points of substances, the mixed gas generated by treating high-temperature steam is cooled to liquefy and recover hydrogen fluoride gas. However, due to different parameters in the previous links, there may be differences in the purity and yield of the recovered hydrofluoric acid solution. In Example 1, since the separation effect of fluorine and carbon is the best, theoretically, the purity and yield of the recovered hydrofluoric acid solution may be relatively high; in Examples 2 and 3, although high-purity hydrofluoric acid solution can be successfully recovered under different parameters, the purity and yield may be slightly lower than those in Example 1, but they are all within the acceptable production standards; By detailed comparison of the three embodiments, it can be seen that the method for comprehensive element recovery from electrolytic aluminum slag of the present invention exhibits good characteristics. Under different parameter combinations such as the grinding mesh number of electrolytic aluminum slag, water vapor flow rate, roasting temperature, reaction time, liquid-solid ratio, water immersion time, and reaction time of introducing carbon dioxide, efficient and high-purity recovery of elements such as fluorine, aluminum, and sodium can be achieved. Embodiment 1 represents the operation under the optimal parameter conditions obtained through optimized experiments, which can maximize the recovery effect of each element. After changing some parameters, Embodiment 2 and Embodiment 3 still stably and reliably complete the comprehensive element recovery, fully proving that this method has strong adaptability, stability, and practicability under different operating parameter conditions, and can effectively meet the diverse needs in actual industrial production, providing a solid and effective innovative solution for the resource utilization of electrolytic aluminum slag.

[0019] The above are only embodiments of the present invention. Specific technical solutions or common knowledge such as characteristics known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A method for recovering all elements of electrolytic aluminum slag, characterized in that: The following steps are involved: S1: crushing and grinding the obtained electrolytic aluminum slag into particle sizes; S2: placing the electrolytic aluminum slag powder obtained in S1 in an atmosphere furnace, adjusting the temperature and time, and introducing water vapor to perform a roasting reaction; S3: The powder in S2 is mixed with deionized water at a certain liquid-solid ratio, and the mixture is immersed in water at room temperature. The insoluble residue can be filtered, and carbon dioxide is introduced into the obtained filtrate to adjust the pH to between 6.5 and 7.

5. The mixture is filtered after reacting for a certain period of time, and the residue is washed and dried to recover aluminum hydroxide. The filtrate is evaporated and concentrated to recover sodium carbonate. S4: The hydrogen fluoride and carbon dioxide gases and unreacted water vapor generated by the high-temperature steam treatment are cooled by a condenser and recovered to obtain a hydrofluoric acid solution.

2. The method for recovering all elements of electrolytic aluminum slag according to claim 1, characterized in that: The electrolytic aluminum slag in S1 is ground into a size of 50-400 meshes.

3. The method for recovering all elements of electrolytic aluminum slag according to claim 1, characterized in that: The reaction temperature in S2 is in the range of 700-1000°C.

4. The method for recovering all elements of electrolytic aluminum slag according to claim 1, characterized in that: The reaction time in S2 is between 0.5 and 3 hours.

5. The method for recovering all elements of electrolytic aluminum slag according to claim 1, characterized in that: The liquid-to-solid ratio of the calcined slag to the deionized water in the S3 is in the range of 3-8 ml:1 g.

6. The method for recovering all elements of electrolytic aluminum slag according to claim 1, characterized in that: The water immersion time and the carbon dioxide passing reaction time in S3 are both 1-5 hours.

Images