Method for green recovery of aluminum electrolysis waste

Abstract

The invention belongs to the technical field of aluminum electrolysis waste treatment, and particularly relates to a method for green recovery of aluminum electrolysis waste. The method comprises the following steps: mixing and roasting aluminum electrolysis waste, aluminum-containing waste and sulfuric acid to prepare modified waste; the modified waste is smashed and stirred, and filter residues A and filtrate A are filtered and separated out; removing impurities from the filtrate A to obtain filter residues B and filtrate B; reacting the filtrate B with water-soluble carbonate or phosphate to prepare a lithium product; mixing and roasting the filter residue A, the filter residue B and a silicon-containing substance to generate aluminum oxide and silicon tetrafluoride gas; dissolving the aluminum oxide through hydrochloric acid, and reacting the silicon tetrafluoride gas with an aluminum chloride solution to form silicon tetrachloride gas and aluminum fluoride; the silicon tetrachloride gas is combusted to generate hydrogen chloride gas and silicon dioxide particles, and the hydrogen chloride gas is converted into a hydrochloric acid solution through water absorption. According to the method, recycling of aluminum and lithium resources in the aluminum electrolysis waste is effectively achieved, by-products are converted into valuable chemical substances, and resource recycling is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of processing aluminum electrolysis waste, and specifically relates to a green method for recycling aluminum electrolysis waste. Background Art

[0002] In the process of aluminum electrolysis, a large amount of waste is generated, which contains rich aluminum and lithium resources. However, the current treatment methods for these wastes are mainly landfill or simple incineration, which not only causes a huge waste of resources, but also causes serious pollution to the environment. Although there are some studies in the prior art dedicated to recovering aluminum and lithium from aluminum electrolysis waste, these methods usually have problems such as complex process, high cost, low recovery rate and serious environmental pollution.

[0003] As we all know, in the production process of electrolytic aluminum, an electrolyte system based on cryolite is mainly used. Changes in the physical and chemical properties of the electrolyte have an extremely important impact on the stable operation of the electrolytic cell. During the production process, in order to control the molecular ratio of the electrolyte, it is necessary to continuously add aluminum fluoride to the electrolytic cell, and add substances such as lithium fluoride to reduce the initial crystallization temperature of the electrolyte. Therefore, in the aluminum electrolytic cell, the electrolyte and its waste will continue to accumulate. The main components of these electrolytic wastes include sodium fluoride, aluminum fluoride, cryolite, and lithium-containing aluminum electrolytic waste, etc., among which the fluorine content is extremely high, so it needs to be utilized as a resource.

[0004] In addition, as a kind of available resource, the recycling of aluminum electrolytic waste containing lithium is of great significance to alleviate the shortage of lithium resources in my country. By effectively recycling and utilizing the aluminum and lithium resources in these wastes, not only can the pollution to the environment be reduced, but also the utilization rate of resources can be improved, thereby achieving the dual goals of economic benefits and environmental protection. Therefore, the development of an efficient, low-cost, and low-pollution aluminum electrolytic waste resource recycling technology is of great practical significance for promoting the sustainable development of the aluminum electrolysis industry.

[0005] The shortcomings of the existing technology are mainly reflected in the following aspects: The recycling process is complex and involves multiple steps, resulting in cumbersome operation and high energy consumption.

[0006] The recycling efficiency is low, and efficient utilization of aluminum and lithium resources cannot be achieved.

[0007] The problem of secondary pollution to the environment is prominent, such as the generation of harmful gases and waste residues.

[0008] There is a lack of means to effectively transform and utilize by-products, resulting in serious waste of resources. Summary of the invention

[0009] The purpose of the present invention is to provide a green method for recycling aluminum electrolysis waste to solve the problems existing in the prior art, improve the recovery efficiency of aluminum and lithium resources, reduce environmental pollution, and achieve effective conversion and utilization of by-products.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions: A green method for recycling aluminum electrolysis waste comprises the following steps: Step 1: fully mixing the electrolytic waste particles, aluminum-containing waste and sulfuric acid, and then calcining and modifying them to obtain modified electrolytic waste; Step 2: crushing the modified electrolytic waste in step 1, mixing with water, stirring and reacting, and filtering to obtain filter residue A and filtrate A; Step 3: removing impurities from the filtrate A detected in step 2, removing the remaining hydrogen ions, fluoride ions, and aluminum ions in the solution, and obtaining filter residue B and filtrate B after separation and filtration; Step 4: passing the filtrate B of step 3 into a water-soluble carbonate or phosphate, heating and stirring, and performing a lithium precipitation reaction; after separation and filtration, a lithium carbonate or lithium phosphate product and a lithium precipitation mother liquor are obtained; Step 5: the filter residue obtained in step 2 and step 3 is fully mixed with the silicon-containing material and then calcined at high temperature to obtain aluminum oxide and a mixed gas containing silicon tetrafluoride; the aluminum oxide is dissolved in hydrochloric acid to generate an aluminum chloride solution and acid-insoluble matter; Step 6: absorbing the mixed gas obtained in step 5 with concentrated sulfuric acid to obtain a mixed solution of pure silicon tetrafluoride gas and sulfuric acid; the silicon tetrafluoride gas reacts with the aluminum chloride solution obtained in step 5 to generate silicon tetrachloride gas and a high-purity aluminum fluoride product; Step 7: hydrogen is introduced into the silicon tetrachloride gas for combustion reaction to generate a mixed gas of hydrogen chloride gas and fumed silica particles, and after gas-solid separation, hydrogen chloride gas and fumed silica products are obtained; the hydrogen chloride gas is used with water to obtain a hydrochloric acid solution, which is returned to step 5 for repeated use.

[0011] Preferably, the aluminum electrolysis waste includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte.

[0012] Preferably, the aluminum-containing waste is one or more of aluminum ash, aluminum water and aluminum oxides in molten salt, limestone, coal ash, etc., aluminum scrap products, waste slag in aluminum processing, etc.

[0013] Preferably, the mass ratio of the electrolytic waste: the aluminum-containing waste: the sulfuric acid is 1:0.2-0.5:0.3-1.

[0014] Preferably, the mass ratio of the electrolytic waste: the aluminum-containing waste: the sulfuric acid is 1:0.2-0.4:0.4-0.6.

[0015] Preferably, the temperature range of the calcination reaction is 200-800° C., and the reaction time is 30-150 min.

[0016] Preferably, the reaction temperature range is 400-600° C., and the reaction time is 60-90 min.

[0017] Preferably, the temperature range of the mixing and stirring reaction with water is 0-80°C, and the reaction time is 30-120min.

[0018] Preferably, the temperature range of the mixing and stirring reaction with water is 20-60° C., and the reaction time is 60-90 min.

[0019] Preferably, the impurity removal step is divided into two stages: the first stage uses one or more of calcium oxide, calcium hydroxide, and sodium carbonate to adjust the solution pH to 6-7 to remove excess aluminum ions and fluoride ions in the solution; the second stage uses one or more of calcium oxide, calcium hydroxide, and sodium hydroxide to adjust the pH to 10 to remove calcium and magnesium, or uses ion exchange resin to remove magnesium and calcium.

[0020] Preferably, the silicon-containing substance is one or more of silicon dioxide, fly ash, bauxite, coal gangue, mullite, refractory bricks and thermal insulation bricks; the roasting temperature is 400-900°C; the mass ratio of the silicon addition to the filter residue is 1:0.3-0.8.

[0021] Preferably, the calcination temperature is 600-800°C, and the mass ratio of the silicon addition to the filter residue is 1:0.4-0.6. The reaction equation is: Preferably, the concentration of sulfuric acid is 50%-98%; the concentration of aluminum chloride solution is ≥10g / L.

[0022] Preferably, the volume content of hydrogen is 10-50%.

[0023] The green method for recycling aluminum electrolytic waste of the present invention effectively solves the problems of low recycling efficiency, serious environmental pollution and incomplete treatment in the prior art, and has the following advantages: Through modified roasting and multi-step reactions, efficient recovery of aluminum and lithium resources was achieved.

[0024] The purity and recovery rate of lithium products are improved by combining impurity removal and chemical reaction.

[0025] By using the mixed roasting of silicon-containing substances and filter residues, the waste residues can be effectively converted into valuable aluminum oxides and silicon tetrafluoride.

[0026] Through the combustion treatment of silicon tetrachloride and the water absorption of hydrogen chloride, the recycling of hydrogen chloride is achieved and environmental pollution is reduced.

[0027] The entire recycling process realizes the circular utilization of resources and has good economic and environmental benefits. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0029] A green method for recycling aluminum electrolysis waste comprises the following steps: Step 1: fully mixing the electrolytic waste particles, aluminum-containing waste and sulfuric acid, and then calcining and modifying them to obtain modified electrolytic waste; Step 2: crushing the modified electrolytic waste in step 1, mixing with water, stirring and reacting, and filtering to obtain filter residue A and filtrate A; Step 3: removing impurities from the filtrate A detected in step 2, removing the remaining hydrogen ions, fluoride ions, and aluminum ions in the solution, and obtaining filter residue B and filtrate B after separation and filtration; Step 4: passing the filtrate B of step 3 into a water-soluble carbonate or phosphate, heating and stirring, and performing a lithium precipitation reaction; after separation and filtration, a lithium carbonate or lithium phosphate product and a lithium precipitation mother liquor are obtained; Step 5: the filter residue obtained in step 2 and step 3 is fully mixed with the silicon-containing material and then calcined at high temperature to obtain aluminum oxide and a mixed gas containing silicon tetrafluoride; the aluminum oxide is dissolved in hydrochloric acid to generate an aluminum chloride solution and acid-insoluble matter; Step 6: absorbing the mixed gas obtained in step 5 with concentrated sulfuric acid to obtain a mixed solution of pure silicon tetrafluoride gas and sulfuric acid; the silicon tetrafluoride gas reacts with the aluminum chloride solution obtained in step 5 to generate silicon tetrachloride gas and a high-purity aluminum fluoride product; Step 7: hydrogen is introduced into the silicon tetrachloride gas for combustion reaction to generate a mixed gas of hydrogen chloride gas and fumed silica particles, and after gas-solid separation, hydrogen chloride gas and fumed silica products are obtained; the hydrogen chloride gas is used with water to obtain a hydrochloric acid solution, which is returned to step 5 for repeated use.

[0030] Preferably, the aluminum electrolysis waste includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte.

[0031] Preferably, the aluminum-containing waste is one or more of aluminum ash, aluminum water and aluminum oxides in molten salt, limestone, coal ash, etc., aluminum scrap products, waste slag in aluminum processing, etc.

[0032] Preferably, the mass ratio of the electrolytic waste: the aluminum-containing waste: the sulfuric acid is 1:0.2-0.5:0.3-1.

[0033] Preferably, the mass ratio of the electrolytic waste: the aluminum-containing waste: the sulfuric acid is 1:0.2-0.4:0.4-0.6.

[0034] Preferably, the temperature range of the calcination reaction is 200-800° C., and the reaction time is 30-150 min.

[0035] Preferably, the reaction temperature range is 400-600° C., and the reaction time is 60-90 min.

[0036] Preferably, the temperature range of the mixing and stirring reaction with water is 0-80°C, and the reaction time is 30-120min.

[0037] Preferably, the temperature range of the mixing and stirring reaction with water is 20-60° C., and the reaction time is 60-90 min.

[0038] Preferably, the impurity removal step is divided into two stages: the first stage uses one or more of calcium oxide, calcium hydroxide, and sodium carbonate to adjust the solution pH to 6-7 to remove excess aluminum ions and fluoride ions in the solution; the second stage uses one or more of calcium oxide, calcium hydroxide, and sodium hydroxide to adjust the pH to 10 to remove calcium and magnesium, or uses ion exchange resin to remove magnesium and calcium.

[0039] Preferably, the silicon-containing substance is one or more of silicon dioxide, fly ash, bauxite, coal gangue, mullite, refractory bricks and thermal insulation bricks; the roasting temperature is 400-900°C; the mass ratio of the silicon addition to the filter residue is 1:0.3-0.8.

[0040] Preferably, the calcination temperature is 600-800°C, and the mass ratio of the silicon addition to the filter residue is 1:0.4-0.6. The reaction equation is: Preferably, the concentration of sulfuric acid is 50%-98%; the concentration of aluminum chloride solution is ≥10g / L.

[0041] Preferably, the volume content of hydrogen is 10-50%. Example 2

[0042] The green method for recycling aluminum electrolysis waste in Example 1 is used to recycle aluminum electrolysis waste, and the steps are as follows: Step 1: Weigh 500g of aluminum electrolyte, crush it, fully mix the electrolyte, aluminum ash and sulfuric acid according to the mass ratio of electrolytic waste: aluminum ash: sulfuric acid of 1:0.4:0.6, roast it at 600℃ for 90min, cool it down and crush it to obtain modified electrolytic waste particles; Step 2: Weigh 500 g of modified electrolytic waste, add water according to a solid-liquid ratio of 1:2, place at 60° C. and stir to react for 60 minutes, and after solid-liquid separation, obtain a lithium-containing solution and a filter residue; Step 3: adding sodium hydroxide and sodium carbonate to the filtrate to remove impurities, and precipitating a mixture of aluminum hydroxide, aluminum fluoride, cryolite, etc.; the lithium liquid is subsequently used to prepare lithium carbonate; Step 4: Concentrate the lithium solution in step 3 to obtain a high-concentration lithium salt solution. Add sodium carbonate at a lithium:carbonate molar ratio of 2:1 and react at 90°C for 60 minutes to obtain a lithium carbonate product; After testing, the purity of lithium carbonate is 99.50%, which meets the national standard requirements for battery-grade lithium carbonate; Step 5: calcine the filter residue obtained in step 2 and step 3 and the silicon-containing material at a mass ratio of 1:0.6 at 800° C. for 60 min to obtain a mixed gas whose main component is silicon tetrafluoride; dissolve the calcined residue in 1.5 mol / L dilute hydrochloric acid to generate an aluminum chloride solution; Step 6: The mixed gas from step 5 is absorbed by 80% sulfuric acid solution to obtain silicon tetrafluoride gas, which reacts with aluminum chloride solution to generate silicon tetrachloride gas and aluminum fluoride products; After testing, the prepared aluminum fluoride has a fluorine content of 59.88% and an aluminum content of 28.96%, which meets the national standard requirements for aluminum fluoride; Step 7: introducing silicon tetrachloride into a reactor with a hydrogen content of 30% for high temperature reaction to prepare fumed silicon dioxide and hydrogen chloride gas; the hydrogen chloride gas is recovered and reused via an acid absorption tower; After testing, the silicon dioxide content in the prepared fumed silicon dioxide is 99.84%, which meets the national standard requirements for fumed silicon dioxide. Example 3

[0043] The green method for recycling aluminum electrolysis waste in Example 1 is used to recycle aluminum electrolysis waste, and the steps are as follows: Step 1: Weigh 500g of aluminum covering material, crush it, fully mix the electrolyte, aluminum ash and sulfuric acid according to the mass ratio of electrolytic waste: aluminum ash: sulfuric acid of 1:0.4:0.5, roast it at 550℃ for 90min, cool it down and crush it to obtain modified electrolytic waste particles; Step 2: Weigh 500 g of modified electrolytic waste, add water according to a solid-liquid ratio of 1:2, place at 50° C. and stir to react for 60 minutes, and after solid-liquid separation, obtain a lithium-containing solution and a filter residue; Step 3: adding sodium hydroxide and sodium carbonate to the filtrate to remove impurities, and precipitating a mixture of aluminum hydroxide, aluminum fluoride, cryolite, etc.; the lithium liquid is subsequently used to prepare lithium carbonate; Step 4: Concentrate the lithium solution in step 3 to obtain a high-concentration lithium salt solution. Add sodium carbonate at a lithium:carbonate molar ratio of 2:1 and react at 90°C for 60 minutes to obtain a lithium carbonate product; After testing, the purity of lithium carbonate is 99.57%, which meets the national standard requirements for battery-grade lithium carbonate; Step 5: calcine the filter residue obtained in step 2 and step 3 and the silicon-containing material at a mass ratio of 1:0.5 at 750° C. for 90 minutes to obtain a mixed gas whose main component is silicon tetrafluoride; dissolve the calcined residue in 1.5 mol / L dilute hydrochloric acid to generate an aluminum chloride solution; Step 6: The mixed gas from step 5 is absorbed by a 98% sulfuric acid solution to obtain silicon tetrafluoride gas, which reacts with an aluminum chloride solution to generate silicon tetrachloride gas and aluminum fluoride products; After testing, the prepared aluminum fluoride has a fluorine content of 59.64% and an aluminum content of 29.27%, which meets the national standard requirements for aluminum fluoride; Step 7: introducing silicon tetrachloride into a reactor with a hydrogen content of 30% for high temperature reaction to prepare fumed silicon dioxide and hydrogen chloride gas; the hydrogen chloride gas is recovered and reused via an acid absorption tower; After testing, the silicon dioxide content in the prepared fumed silicon dioxide is 99.81%, which meets the national standard requirements for fumed silicon dioxide. Example 4

[0044] The green method for recycling aluminum electrolysis waste in Example 4 is basically the same as that in Example 2, except that: The aluminum electrolyte is replaced with overhaul slag, and the ratio of the three is 1:0.2:0.4; Sodium carbonate was added according to the ratio of lithium to carbonate 2:1.1, and the mixture was reacted at 80°C for 90 minutes. The lithium carbonate product was obtained after separation and washing. After testing, the purity of lithium carbonate is 99.50%, which meets the national standard requirements for battery-grade lithium carbonate; The prepared aluminum fluoride product has a fluorine content of 58.75% and an aluminum content of 29.33%, which meets the national standard requirements for aluminum fluoride; The silicon dioxide content in the prepared fumed silicon dioxide is 99.80%, which meets the national standard requirements for fumed silicon dioxide. Example 5

[0045] The green method for recycling aluminum electrolysis waste in Example 5 is basically the same as that in Example 3, except that: 1. Aluminum ash is replaced with aluminum scrap, and the ratio of the three is 1:0.4:0.6; 2. Add sodium carbonate at a ratio of lithium to carbonate of 2.05:1, react at 80°C for 90 minutes, separate and wash to obtain lithium carbonate product; After testing, the purity of lithium carbonate is 99.61%, which meets the national standard requirements for battery-grade lithium carbonate; The prepared aluminum fluoride product has a fluorine content of 60.12% and an aluminum content of 29.47%, which meets the national standard requirements for aluminum fluoride; The silicon dioxide content in the prepared fumed silicon dioxide is 99.80%, which meets the national standard requirements for fumed silicon dioxide. Example 6

[0046] The green method for recycling aluminum electrolysis waste in Example 6 is basically the same as that in Example 2, except that: 1. Aluminum ash is replaced with aluminum processing waste slag, and the ratio of the three is changed to 1:0.3:0.6; 2. Sodium phosphate was added at a ratio of lithium to phosphate of 3:1.06, and the mixture was reacted at 80°C for 90 minutes. The lithium phosphate product was obtained after separation and washing; After testing, the purity of lithium phosphate is 90.51%; 3. The prepared aluminum fluoride product has a fluorine content of 59.84% and an aluminum content of 30.12%, which meets the national standard requirements for aluminum fluoride; 4. The silicon dioxide content in the prepared fumed silicon dioxide is 99.81%, which meets the national standard requirements for fumed silicon dioxide.

[0047] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A green method for recycling aluminum electrolysis waste, characterized in that: The following steps are involved: Step 1: fully mixing the electrolytic waste particles, aluminum-containing waste and sulfuric acid, and then calcining and modifying them to obtain modified electrolytic waste; Step 2: crushing the modified electrolytic waste in step 1, mixing with water, stirring and reacting, and filtering to obtain filter residue A and filtrate A; Step 3: removing impurities from the filtrate A detected in step 2, removing the remaining hydrogen ions, fluoride ions, and aluminum ions in the solution, and obtaining filter residue B and filtrate B after separation and filtration; Step 4: passing the filtrate B of step 3 into a water-soluble carbonate or phosphate, heating and stirring, and performing a lithium precipitation reaction; after separation and filtration, a lithium carbonate or lithium phosphate product and a lithium precipitation mother liquor are obtained; Step 5: the filter residue obtained in step 2 and step 3 is fully mixed with the silicon-containing material and then calcined at high temperature to obtain aluminum oxide and a mixed gas containing silicon tetrafluoride; the aluminum oxide is dissolved in hydrochloric acid to generate an aluminum chloride solution and acid-insoluble matter; Step 6: absorbing the mixed gas obtained in step 5 with concentrated sulfuric acid to obtain a mixed solution of pure silicon tetrafluoride gas and sulfuric acid; the silicon tetrafluoride gas reacts with the aluminum chloride solution obtained in step 5 to generate silicon tetrachloride gas and a high-purity aluminum fluoride product; Step 7: hydrogen is introduced into the silicon tetrachloride gas for combustion reaction to generate a mixed gas of hydrogen chloride gas and fumed silica particles, and after gas-solid separation, hydrogen chloride gas and fumed silica products are obtained; the hydrogen chloride gas is used with water to obtain a hydrochloric acid solution, which is returned to step 5 for repeated use.

2. A green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The aluminum electrolysis waste includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte. The aluminum-containing waste in step 1 is one or more of aluminum ash, aluminum water and aluminum oxides in molten salt, limestone, coal ash, etc., aluminum scrap products, waste slag in aluminum processing, etc. The mass ratio of electrolytic waste: aluminum-containing waste: sulfuric acid in step 1 is 1:0.2-0.5:0.3-1.

3. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: In the step 1, the mass ratio of electrolytic waste: aluminum-containing waste: sulfuric acid is 1:0.2-0.4:0.4-0.

6.

4. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The temperature range of the calcination reaction in step 1 is 200-800° C., and the reaction time is 30-150 min.

5. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The temperature range of the calcination reaction in step 1 is 400-600° C., and the reaction time is 60-90 min. The temperature range of the mixing and stirring reaction with water in step 2 is 0-80° C., and the reaction time is 30-120 min.

6. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The temperature range of the mixing and stirring reaction with water in step 2 is 20-60° C., and the reaction time is 60-90 min.

7. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: In step 3, the impurity removal step is divided into two stages: the first stage uses one or more of calcium oxide, calcium hydroxide, and sodium carbonate to adjust the solution pH to 6-7 to remove excess aluminum ions and fluoride ions in the solution; the second stage uses one or more of calcium oxide, calcium hydroxide, and sodium hydroxide to adjust the pH to 10 to remove calcium and magnesium, or uses ion exchange resin to remove magnesium and calcium.

8. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The silicon-containing substance in step 5 is one or more of silicon dioxide, fly ash, bauxite, coal gangue, mullite, refractory bricks and thermal insulation bricks; the roasting temperature is 400-900°C; the mass ratio of the silicon addition amount to the filter residue is 1:0.3-0.

8.

9. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: In the step 5, the calcination temperature is 600-800° C., and the mass ratio of the silicon addition to the filter residue is 1:0.4-0.

6.

10. The green method for recycling aluminum electrolysis waste according to claim 1, characterized in that: The concentration of sulfuric acid in step 6 is 50%-98%; the concentration of the aluminum chloride solution is ≥10g / L, and the volume content of hydrogen in step 7 is 10-50%.