Method for preparing cryolite from aluminum reduction cell cathode carbon block alkali leachate

Abstract

The invention relates to a method for preparing cryolite from aluminum reduction cell cathode carbon block alkali leachate and belongs to a cryolite preparation method. The method disclosed by the invention comprises the steps: levigating an aluminum reduction cell cathode carbon block to a certain particle size, mixing with alkali liquor to perform pulp mixing, mixing and leaching under a heatingtemperature of 20 to 90 DEG C and then filtering to obtain first filtrate and first filter residue; adding sodium fluoride and a little Na3AlF6 solid into the first filtrate, then controlling a speedfor inflating NH3-enriched gas or adding NH4F, generating precipitate under the heating and stirring action and filtering to obtain second filtrate and second filter residue after reaction finishes;drying the second filter residue under 100 to 150 DEG C to obtain a cryolite product. According to the method disclosed by the invention, acid leaching is replaced by alkali leaching, so that a requirement of a production process for equipment is reduced; furthermore, treating processes of flotation and the like are reduced, a hydrogen fluoride absorption process is reduced, and the treating technology is simplified; a high-temperature treating technology is prevented from being used, and energy consumption is reduced; high-quality cryolite with an even particle size is generated by adding seed crystal under the condition of controlling an air flow rate. The method disclosed by the invention has the advantages of simple technology, closed loop, high resource utilization rate and no secondary pollution.

Description

technical field [0001] The invention belongs to a method for preparing cryolite, in particular to a method for producing cryolite by using the alkaline leaching solution of cathode carbon block of an aluminum electrolytic cell as a raw material. Background technique [0002] During the production process of aluminum electrolysis, the cathode carbon block expands due to the penetration of impurities such as sodium and cryolite, which further causes damage to the electrolytic cell. Domestic aluminum electrolytic cells need to be overhauled when they are about 2000 days old. The waste cathode carbon blocks produced during the overhaul process are one of the main solid pollutants in the aluminum electrolysis industry. The statistical results of the fluorine balance survey of industrial aluminum electrolytic cells show that for every ton of electrolytic aluminum produced, about 10kg of waste cathode carbon blocks will be produced. Taking 2015 as an example, the output of electro...

AI Technical Summary

Problems solved by technology

[0006] In order to solve the pollution problem of the alkaline leaching solution of the cathode carbon block of the aluminum electrolytic cell, and the problems in the above-mentioned prior art, the present invention proposes a method for producing cryolite with the alkaline leaching solution of the cathode carbon block of the aluminum electrolytic cell, to achieve The purpose of treating waste, reducing energy consumption, shortening the process, and reducing equipment loss