A method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag

Abstract

The present invention relates to a method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag. The preparation process is: firstly, the overhaul slag or carbon slag is ball-milled into powder, and the fineness is greater than 200 meshes; sodium hydroxide solution is prepared, and the concentration is 3%-15%, and the ground powder is added to the sodium hydroxide solution, and the solid content is controlled to be 3%-10%; stirring at 60℃-90℃ for 2h-5h; filtering to obtain filter residue and filtrate, and carbon dioxide is introduced into the filtrate under stirring conditions for carbonization to obtain cryolite slurry, and cryolite and sodium carbonate solution are obtained by filtration and separation; the filter residue is subjected to secondary alkaline leaching with calcium hydroxide slurry, and the filter residue and filtrate are obtained by filtration and separation, and the filter residue is sent to a cement plant as a raw material for making cement, and the filtrate is added to the above sodium carbonate solution to precipitate lithium to obtain lithium carbonate, so as to realize the comprehensive recovery and utilization of lithium, sodium, aluminum and fluorine in the overhaul slag / carbon slag. The comprehensive recovery rates of lithium and fluorine are 85% and 80% respectively.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive recovery of waste materials, and relates to a technical method and application thereof for comprehensive recovery of lithium carbonate and cryolite from lithium-containing overhaul slag and carbon slag. Background Art

[0002] In aluminum electrolysis production, in order to improve the properties of the electrolyte, improve current efficiency and reduce energy consumption, in addition to adding aluminum fluoride or cryolite to the electrolyte, some fluoride or chloride salts are also added to the electrolyte. One of the commonly used additives is lithium fluoride. Lithium fluoride salts are currently used in the aluminum electrolysis industry to good effect. They can effectively reduce the electrolyte initial crystallization temperature and reduce fluorine emissions, which promotes energy conservation and consumption reduction in aluminum electrolysis enterprises.

[0003] The destination of lithium fluoride in the process is mainly in overhaul slag, electrolyte and carbon blocks. The total amount of waste slag reaches 1.8 million tons / year, with a lithium content of 1%-3% and a fluorine content of 15%-40%. With the development of lithium batteries, metallic lithium has become a necessary product. Therefore, the comprehensive recovery and utilization of valuable lithium, sodium, aluminum and fluorine in electrolytic aluminum waste slag has great commercial value.

[0004] The invention adopts a two-step alkaline leaching method to extract lithium and fluorine, adopts sodium hydroxide to extract fluorine, and calcium hydroxide to extract lithium, and recovers cryolite and lithium carbonate, with a comprehensive yield of more than 80%.

[0005] Table 1 Main chemical components of electrolytic aluminum carbon slag element(%) Li F Na <![CDATA[Al2O3]]> K CaO MgO S Fe C Ni Carbon residue 1.56 37.25 18.81 16.21 0.96 0.54 0.12 0.98 0.31 17.02 0.32 Summary of the invention

[0006] The invention adopts a two-step alkaline leaching method to extract lithium and fluorine, adopts sodium hydroxide to extract fluorine, and calcium hydroxide to extract lithium, and recovers cryolite and lithium carbonate.

[0007] 1. First grind the overhaul slag / carbon slag into powder, the fineness is >200 mesh.

[0008] 2. Prepare a sodium hydroxide solution with a concentration of 3%-15%, add the powder into the sodium hydroxide solution, stir and leach, control the solid content to 3%-10%, and the leaching temperature to 60℃-90℃.

[0009] 3. Filter to obtain filter residue and filtrate, introduce carbon dioxide into the filtrate under stirring conditions for carbonization to obtain cryolite slurry, and filter and separate to obtain cryolite and sodium carbonate solution.

[0010] 4. The filter residue is subjected to secondary alkaline leaching with calcium hydroxide slurry, and the filter residue and filtrate are separated by filtration. The filter residue is sent to a cement plant as a raw material for making cement, and the filtrate is added with the above-mentioned sodium carbonate solution to obtain lithium carbonate.

[0011] 5. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that the overhaul slag and carbon slag have a lithium content of 1%-3% and a fluorine content of 15%-40%.

[0012] 6. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that the carbonization endpoint pH is 9-12 and the carbonization temperature is 50°C-80°C.

[0013] 7. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that the solid content of the cryolite slurry obtained by carbonization is 3%-8%, and the sodium carbonate concentration is 5%-10%.

[0014] 8. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1 is characterized in that the amount of calcium hydroxide used in the secondary alkaline leaching of the filter residue is 0.5-1 times the dry basis of the filter residue, the leaching temperature is 50°C-90°C, and the leaching time is 1h-3h.

[0015] 9. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that the lithium carbonate synthesis temperature is 80°C-95°C, the synthesis pH is greater than 13, and the main content is greater than 90%.

[0016] The method of the present invention has the following advantages: 1. Turn waste into treasure and recycle resources; 2. Short process flow, low cost and high recovery rate; 3. The recovered cryolite meets the process grade standard and can be directly returned to the electrolytic aluminum process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a process flow chart of a comprehensive recovery and treatment method of lithium-containing overhaul slag and carbon slag. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the examples, which are merely further supplements and explanations of the present invention, rather than limitations of the invention.

[0019] Example 1 The carbon slag is ground into powder, 800kg of 6% sodium hydroxide solution is prepared, 100kg of carbon powder is weighed, added to the sodium hydroxide solution and stirred for leaching, the leaching temperature is 80℃, and the leaching time is 4h; the leached slurry is filtered to obtain the leachate and leached slag, the leached liquid is transferred to the reactor, carbon dioxide is introduced and the reaction is continued with stirring, the reaction temperature is 60℃, and the reaction pH reaches 9-10 as the reaction end point. Filter and separate to obtain 60kg of cryolite product, and the sodium carbonate concentration of the filtrate is 8%. The filter residue is prepared into 150kg of slurry with 30kg of calcium hydroxide for secondary leaching, the leaching time is 2h, and the leaching temperature is 90℃. Filter and separate to obtain the secondary filter residue, which is washed with water and sent to the cement plant as cement raw material. The filtrate lithium concentration is 6g / L. After lithium is precipitated with sodium carbonate solution, it is filtered and separated, and the obtained mother liquor is returned to the sodium hydroxide batching for leaching, in which the sodium hydroxide concentration is 3%, and the filter cake is lithium carbonate with a main content of 92%.

[0020] Example 2 Grind the overhaul slag into powder, prepare 800kg of 4% sodium hydroxide solution, weigh 100kg of overhaul slag, add it to the sodium hydroxide solution and stir for leaching, the leaching temperature is 85℃, and the leaching time is 3h; filter the leached slurry to obtain the leachate and leached slag, transfer the leached liquid to the reactor, introduce carbon dioxide and continue to stir the reaction, the reaction temperature is 65℃, and the reaction pH reaches 9-10 as the reaction end point. Filter and separate to obtain 40kg of cryolite product, and the sodium carbonate concentration of the filtrate is 6%. The filter residue is prepared into 150kg of slurry with 40kg of calcium hydroxide for secondary leaching, the leaching time is 2h, and the leaching temperature is 90℃. Filter and separate to obtain the secondary filter residue, which is washed with water and sent to the cement plant as cement raw material. The filtrate lithium concentration is 5.5g / L. After lithium is precipitated with sodium carbonate solution, it is filtered and separated, and the obtained mother liquor is returned to the sodium hydroxide batching for leaching, in which the sodium hydroxide concentration is 2%, and the filter cake is lithium carbonate with a main content of 91%.

Claims

1. A method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag, characterized in that: The preparation method comprises the following steps: (1) First, grind the overhaul slag / carbon slag into powder with a fineness of >200 mesh; (2) Prepare a sodium hydroxide solution with a concentration of 3%-15%, add the powder into the sodium hydroxide solution, stir and leaching, control the solid content to 3%-10%, and the leaching temperature to 60℃-90℃; (3) filtering to obtain a filter residue and a filtrate, introducing carbon dioxide into the filtrate under stirring conditions for carbonization to obtain cryolite slurry, and filtering and separating to obtain cryolite and sodium carbonate solution; (4) The filter residue is subjected to secondary alkaline leaching with calcium hydroxide slurry, and the filter residue and filtrate are separated by filtration. The filter residue is sent to a cement plant as a raw material for making cement, and the filtrate is added with the above-mentioned sodium carbonate solution to obtain lithium carbonate.

2. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that The overhaul slag and carbon slag have a lithium content of 1%-3% and a fluorine content of 15%-40%.

3. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that The carbonization end point pH is 9-12, and the carbonization temperature is 50°C-80°C.

4. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that The solid content of the cryolite slurry obtained by carbonization is 3%-8%, and the sodium carbonate concentration is 5-10%.

5. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that The amount of calcium hydroxide used in the secondary alkaline leaching of the filter residue is 0.5-1 times the dry basis of the filter residue, the leaching temperature is 50°C-90°C, and the leaching time is 1h-3h.

6. The method for comprehensive recovery and treatment of lithium-containing overhaul slag and carbon slag according to claim 1, characterized in that The synthesis temperature of lithium carbonate is 80℃-95℃, the synthesis pH is greater than 13, and the main content is greater than 90%.

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