Method for recovering fluoride salt from aluminum electrolysis overhaul slag through pressurized alkaline leaching

Abstract

A method for recovering fluoride salt from aluminum electrolysis overhaul slag through pressurized alkaline leaching comprises the steps that waste cathodes and waste tank linings are subjected to two-stage crushing, NaOH solutions are added for wet ball milling, and waste cathode slurry and waste tank lining slurry are obtained; the waste cathode slurry and the waste tank lining slurry are respectively added into NaOH solutions to carry out pressurized alkaline leaching, and a cyanide breaking agent H2O2 which is 0.2-0.4% of the volume of a leaching solution is added in the pressurized alkaline leaching process to carry out cyanide breaking treatment; the pressure is released after pressurized alkaline leaching is completed, and the discharged ammonia gas is washed with sulfuric acid to form ammonium sulfate which can be used as a chemical fertilizer; the extract is filtered to obtain a leaching solution and leaching residues, countercurrent washing is connducted on the leaching residues, and then the leaching residues are dried to be used as an additive for smelting iron and steel, preparing cement and preparing a refractory material; the leaching solution is filtered after neutralized and precipitated, and filter residues are calcinated to form aluminum fluoride; and a filtrate is frozen and crystallized to obtain mirabilite. According to the method, the waste cathode carbon blocks and the waste tank linings can be subjected to harmless treatment and comprehensive resource utilization, and fluoride salt is obtained through recovery.

Description

technical field [0001] The invention belongs to the technical field of harmless disposal of aluminum electrolysis overhaul slag and comprehensive utilization of resources, and specifically relates to a method for recovering fluoride salt in aluminum electrolysis overhaul slag. Background technique [0002] Overhaul slag is the process of aluminum electrolysis production, due to the penetration and corrosion of the lining of the aluminum electrolytic cell by the high-temperature electrolyte, the lining structure of the aluminum electrolytic cell is deformed, cracked, etc., and the high-temperature aluminum liquid and electrolyte penetrate into the cell from these deformed and cracked cracks Lining, resulting in the failure of normal production of the electrolytic cell and the repair of the cell. Since the new aluminum electrolytic cell needs to be shut down for overhaul after 3 to 6 years of use, the lining of the electrolytic cell has electrochemically reacted with the elect...

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Problems solved by technology

[0008] A comprehensive analysis of the above prior art shows that the existing technology only focuses on the disposal of spent cathode carbon blocks, and there is no better treatment method for waste tank linings, and there is no harmless treatment of both waste cathode carbon blocks and waste tank linings. It is a feasible method for disposal and comprehensive utilization of resources. At the same time, the existing technology also has many technical problems such as complex process, large equipment investment, and difficulty in large-scale ultrasonic devices, which restricts the further promotion of the pressure alkaline leaching process.

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