Method for preparing cryolite by alkaline leachate of cathode carbon block of aluminum electrolytic cell

Abstract

The invention relates to a method for preparing cryolite by alkaline leachate of a cathode carbon block of an aluminum electrolytic cell, and belongs to a leachate preparation method. The method comprises the steps of grinding the cathode carbon block of the aluminum electrolytic cell to a certain particle size, mixing the ground cathode carbon block with alkaline liquid, carrying out size mixing, carrying out stirring leaching at a heating temperature of 20-90 DEG C, filtering to obtain first filtrate and a first filter residue, adding sodium fluoride and a small amount of Na3AlF6 solids into the first filtrate, controlling the introducing velocity of CO2-rich gas to generate precipitates while heating and stirring, after the reaction is finished, filtering to obtain second filtrate and a second filter residue, and drying the second filter residue at 100-150 DEG C, so as to obtain a cryolite product. According to the method, acidy leaching is replaced with alkaline leaching, so that the equipment requirements in the production process are reduced, processing processes such as flotation are omitted, an absorption process of hydrogen fluoride is omitted, and the processing process is simplified; a high-temperature processing process is saved, so that the energy consumption is reduced; and by adding crystal seeds, high-quality cryolite with the uniform particle size is generated when airflow rate is controlled. The method has the beneficial effects that the process is simple, a closed loop is utilized, the resource utilization rate is high, and the secondary pollution is avoided.

Description

technical field [0001] The invention belongs to a method for preparing cryolite, in particular to a method for preparing cryolite by using the alkaline leaching solution of cathode carbon block of an aluminum electrolytic cell as a raw material. [0002] technical background [0003] 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...

AI Technical Summary

Problems solved by technology

[0007] 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 existing in the 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