阅读说明：本技术 再生冰晶石转化氟化铝的方法 (Method for converting regenerated cryolite into aluminum fluoride ) 是由 刘向前 李海 郑斌 王玉强 于 2020-05-19 设计创作，主要内容包括：本发明提供了再生冰晶石转化氟化铝的方法,解决了采用硝酸铝对碳渣中的氟元素进行浸出和沉淀成本较高的问题。本发明采用氢氧化钠对碳渣中分离出的冰晶石进行氟元素和氯元素的分离,得到氟化钠和铝酸钠混合溶液,然后采用加酸型溶液的方式,使氟化钠与酸性溶液中反应得到氟化氢和钠盐,氟化氢与溶液中的水反应得到氢氟酸,得到的氢氟酸与铝酸钠反应得到氟化铝沉淀物。本发明一是实现了对碳渣进行了回收再利用,二是所采用的反应物：氢氧化钠,相对于硝酸铝的价格很低,目前市场上的一吨氢氧化钠的价格仅为一吨硝酸铝价格的三分之一左右,大大降低了氟化铝的工业生产成本,利于大规模工业推广。(The invention provides a method for converting regenerated cryolite into aluminum fluoride, which solves the problem of high cost of leaching and precipitating fluorine in carbon slag by adopting aluminum nitrate. The method comprises the steps of separating fluorine and chlorine from cryolite separated from carbon slag by using sodium hydroxide to obtain a sodium fluoride and sodium aluminate mixed solution, reacting sodium fluoride with an acidic solution in an acid solution adding mode to obtain hydrogen fluoride and sodium salt, reacting the hydrogen fluoride with water in the solution to obtain hydrofluoric acid, and reacting the obtained hydrofluoric acid with sodium aluminate to obtain an aluminum fluoride precipitate. The invention realizes the recycling of the carbon slag, and adopts the following reactants: the price of sodium hydroxide is very low compared with that of aluminum nitrate, and the price of one ton of sodium hydroxide in the current market is only about one third of that of one ton of aluminum nitrate, so that the industrial production cost of aluminum fluoride is greatly reduced, and the large-scale industrial popularization is facilitated.)

1. The method for regenerating cryolite converted aluminum fluoride is characterized by comprising the following steps of:

(1) ball-milling electrolytic aluminum carbon slag by a ball mill to obtain carbon slag powder, and performing flotation and solid-liquid separation on the carbon slag powder to obtain a precipitate mainly composed of a carbon material and a solution containing cryolite;

(2) injecting the solution containing cryolite obtained in the step (1) into a reaction kettle, adding a sodium hydroxide solution into the reaction kettle, and heating, stirring and fully reacting to obtain a mixed solution with main components of sodium aluminate and sodium fluoride;

(3) injecting the mixed solution obtained in the step (2) into another reaction kettle, adding an acidic solution into the reaction kettle, fully reacting under the conditions of heating and stirring, and then carrying out precipitation, cooling and solid-liquid separation to obtain a supernatant liquid with a main component of sodium salt and a precipitate with a main component of crude crystals of aluminum fluoride;

(4) and (4) washing, filtering and drying the crude crystal precipitate of the aluminum fluoride obtained in the step (3) to obtain a pure aluminum fluoride product.

2. The process for regenerating cryolite converted aluminum fluoride of claim 1, wherein: the reaction time in the step (2) and the step (3) is 1-3 hours.

3. The process for regenerating cryolite converted aluminum fluoride of claim 1, wherein: the reaction temperature in the step (2) and the step (3) is 60 ℃ to 100 ℃.

4. The process for regenerating cryolite converted aluminum fluoride of claim 1, wherein: the mass ratio of the solution containing cryolite to the sodium hydroxide solution in the step (2) is 1:7, and the mass ratio of sodium hydroxide to water in the sodium hydroxide solution is 0.75: 6.25.

5. The process for regenerating cryolite converted aluminum fluoride as claimed in claim 4, wherein: and (3) completely reacting 1 part of cryolite-containing solution in the step (2) with nitric acid solution under the condition of 30 mass percent of nitric acid solution, wherein the required nitric acid solution is 1.8 parts.

6. The process for regenerating cryolite converted aluminum fluoride as claimed in claim 4, wherein: the acid solution in the step (3) is hydrochloric acid solution, 1 part of cryolite-containing solution in the step (2) and the hydrochloric acid solution completely react under the condition of 30% mass concentration of the hydrochloric acid solution, and 1 part of nitric acid solution is needed.

Technical Field

The invention relates to the technical field of recycling electrolytic aluminum carbon slag, in particular to a method for converting regenerated cryolite into aluminum fluoride.

Background

During the aluminum electrolysis process, unburned aggregate particles enter the electrolyte solution to form carbon slag due to selective oxidation. Carbon slag contains carbon powder and fluoride salt, the industry mainly adopts the flotation method to separate the fluoride salt in the carbon slag at present, and after flotation, fluorine is leached and precipitated to obtain aluminum fluoride, thereby realizing the recycling of electrolytic aluminum carbon slag.

The invention patent with application publication number CN109759423A discloses a comprehensive utilization method of aluminum electrolysis carbon slag, which comprises the following steps: crushing and screening: carrying out coarse crushing, ball milling and screening on the aluminum electrolysis carbon slag to obtain carbon slag powder; (2) flotation: putting the carbon residue powder into a flotation tank, and mixing slurry to obtain slurry; then adding inhibitor water glass and collecting agent kerosene into slurry of a flotation tank in sequence for flotation; drying the foam scraped by flotation to obtain carbon; and (3) filtering: filtering the electrolyte discharged from the bottom flow of the flotation tank to obtain a filtered substance; (4) dissolution: adding a mixed solution containing LHNO3 and Al (NO3)3 with the final concentration of 0.01-0.05 mol/L and 0.3-0.36 mol/L into the filtered substance, and reacting for 1-1.5 h at the temperature of 60-65 ℃ to obtain a solid-liquid mixture; in the step, aluminum reacts with fluorine to generate AlF2(OH) precipitate, and sodium and calcium form a mixed solution of sodium nitrate and calcium nitrate; (5) separating: carrying out solid-liquid separation on the solid-liquid mixture to obtain filter residue; wherein the main component of the filter residue is AlF2 (OH); (6) acid leaching: mixing the filter residue with a hydrofluoric acid solution with the pH value of 0.1-0.3, and then reacting for 1-1.5 h to obtain a solid-liquid mixture; (7) separation: and carrying out solid-liquid separation on the solid-liquid mixture to obtain AlF 3. The method adopts a flotation mode to separate carbon powder from filtered substances, at the moment, the carbon powder still contains partial fluorine, harmless carbon powder is not obtained, the carbon powder after flotation generally needs secondary treatment to obtain the harmless carbon powder, and the harmless treatment of carbon slag is not realized. After flotation, the fluorine is leached and precipitated, and at the moment, the filtrate contains more impurities. In addition, the method adopts aluminum nitrate to leach and precipitate fluorine, and the aluminum nitrate is high in price and is not suitable for industrial production.

Disclosure of Invention

In order to solve the problem of high leaching and precipitation cost of aluminum nitrate for fluorine in carbon slag in the background technology, the invention provides a method for converting regenerated cryolite into aluminum fluoride.

The technical scheme of the invention is as follows: the method for regenerating cryolite converted aluminum fluoride comprises the following steps:

(5) ball-milling electrolytic aluminum carbon slag by a ball mill to obtain carbon slag powder, and performing flotation and solid-liquid separation on the carbon slag powder to obtain a precipitate mainly composed of a carbon material and a solution containing cryolite;

(6) injecting the solution containing cryolite obtained in the step (1) into a reaction kettle, adding a sodium hydroxide solution into the reaction kettle, and heating, stirring and fully reacting to obtain a mixed solution with main components of sodium aluminate and sodium fluoride;

(7) injecting the mixed solution obtained in the step (2) into another reaction kettle, adding an acidic solution into the reaction kettle, fully reacting under the conditions of heating and stirring, and then carrying out precipitation, cooling and solid-liquid separation to obtain a supernatant liquid with a main component of sodium salt and a precipitate with a main component of crude crystals of aluminum fluoride;

(8) and (4) washing, filtering and drying the crude crystal precipitate of the aluminum fluoride obtained in the step (3) to obtain a pure aluminum fluoride product.

The reaction time in the step (2) and the step (3) is 1-3 hours.

The reaction temperature in the step (2) and the step (3) is 60-100 ℃.

The mass ratio of the solution containing cryolite to the sodium hydroxide solution in the step (2) is 1:7, and the mass ratio of sodium hydroxide to water in the sodium hydroxide solution is 0.75: 6.25.

The acidic solution in the step (3) is a nitric acid solution, 1 part of cryolite-containing solution in the step (2) and the nitric acid solution completely react under the condition of 30% mass concentration of the nitric acid solution, and the required nitric acid solution is 1.8 parts.

The acid solution in the step (3) is hydrochloric acid solution, 1 part of cryolite-containing solution in the step (2) and the hydrochloric acid solution completely react under the condition of 30% mass concentration of the hydrochloric acid solution, and 1 part of nitric acid solution is needed.

The invention has the advantages that: the method comprises the steps of separating fluorine and chlorine from cryolite separated from carbon slag by using sodium hydroxide to obtain a sodium fluoride and sodium aluminate mixed solution, reacting sodium fluoride with an acidic solution in an acid solution adding mode to obtain hydrogen fluoride and sodium salt, reacting the hydrogen fluoride with water in the solution to obtain hydrofluoric acid, and reacting the obtained hydrofluoric acid with sodium aluminate to obtain an aluminum fluoride precipitate. The invention realizes the recycling of the carbon slag, and adopts the following reactants: the price of sodium hydroxide is very low compared with that of aluminum nitrate, and the price of one ton of sodium hydroxide in the current market is only about one third of that of one ton of aluminum nitrate, so that the industrial production cost of aluminum fluoride is greatly reduced, and the large-scale industrial popularization is facilitated.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.