Method for reclaiming electrolyte in carbon dross of aluminium electrolysis

Abstract

A method for retrieving electrolyte form aluminum electrolysis carbon residue, characterized in that the aluminum electrolysis carbon residue is mixed with calcium fluoride serving as disperser with a weight of 1 to 10 wt. % of the carbon residue, and coal serving as combustion catalyst with a weight of 1 to 10 wt. % of the carbon residue, and then is roasted for 1 to 3 hours under a temperature of 650 to 850 degree C.. The method has the advantages of low process cost, high retrieving rate of electrolyte, easy implementation. The retrieved electrolyte has little impurity, and can be directly and completely returned to the electrolysis cell for use without negative effect to the quality of the electrolyte and aluminum melt.

Description

technical field [0001] The invention relates to a method for recovering electrolyte in aluminum electrolysis carbon slag. Background technique [0002] At present, about 3-10 kg of carbon slag is discharged for every ton of primary aluminum produced. Due to the immersion and penetration of electrolytes, the electrolyte content in the carbon slag is very high, accounting for about 60% to 70% of the weight of the carbon slag, mainly due to fluorination. Sodium, cryolite, sub-cryolite and a small amount of alumina. Electrolyte is an extremely valuable raw material for electrolysis. If it can be effectively recovered and returned to the electrolytic cell for use, it will be of great benefit to reduce the production cost per ton of aluminum and the consumption of fluoride salt, and can produce obvious economic benefits. [0003] The currently reported technology for processing aluminum electrolytic carbon slag is mainly the flotation method, and the process is complicated. 6 Or...

AI Technical Summary

Problems solved by technology

The recovery rate of this method is low, and the recovered electrolyte contains high content of carbon powder and other impurities, which cannot be directly returned to the electrolytic cell for use.

The flotation method has the following deficiencies: (1) contains about 9% of the electrolyte in the flotation charcoal powder, and cannot return to the carbon production system; (2) contains high carbon in the flotation electrolyte, reaching more than 5%, and cannot return to the electrolyzer for use; ( 3) The flotation electrolyte is mixed with flotation agent, sticky, and easy to block the feeder. It cannot be used for dense phase transportation. It must be roasted to remove carbon and flotation agent before it can be used; (4) Fluoride ion content in flotation wastewater About 100mg / L, which is 10mg / L higher than the allowable limit of discharged industrial wastewater, cannot be discharged directly, and must be treated with wastewater

[0005] However, the above-mentioned method has difficulties such as high processing cost, large pollution, low electrolyte recovery rate, difficult disposal of waste liquid, etc., and poor industrial operability.