A mechanochemical transformation and recovery method of sodium-containing and fluorine-containing compounds in spent cathode carbon blocks of aluminum electrolytic cells

Abstract

The invention relates to a method for mechanochemical conversion and recovery of sodium-containing and fluorine-containing compounds in waste cathode carbon blocks of aluminum electrolytic cells. First, the waste cathode blocks of aluminum electrolytic cells are crushed, pulverized and homogenized to obtain waste cathodes with particles ≤ 200 μm carbon powder, and then add waste cathode carbon powder, sodium compound and fluorine compound conversion agent, cyanide conversion agent, grinding aid and water into the conversion mill. Under the synchronous action of high-energy mechanical force, the content of waste cathode carbon powder Sodium compounds are transformed into fluorine-free soluble sodium compounds, fluorine-containing compounds are transformed into insoluble and harmless mineral fluoride compounds, cyanide-containing compounds are oxidized into harmless N 2 or NH 3 and CO 2 , so as to completely remove the hazards of fluoride and cyanide in the waste cathode carbon blocks of aluminum electrolysis, and realize the harmless and resourceful recycling of the waste cathode carbon blocks of aluminum electrolysis. The invention has the advantages of simple process, easy large-scale production, low production cost, no three wastes pollution and environmental friendliness.

Description

technical field [0001] The invention relates to a method for mechanochemical conversion and recovery of sodium-containing and fluorine-containing compounds in waste cathode carbon blocks of aluminum electrolytic cells, and belongs to the technical field of harmless and resourceful utilization of solid waste in the electrolytic aluminum industry. Background technique [0002] By 2017, China has built about 45 million tons of aluminum electrolytic production capacity, and the actual output exceeds 36 million tons, accounting for more than 50% of the global electrolytic aluminum production capacity. During the production process of aluminum electrolysis, the carbon cathode expands due to the penetration of fluorine-containing salts, which further causes damage to the electrolytic cell and scraps it. Aluminum electrolytic cells generally need to be shut down for overhaul after about 4 to 6 years of use, and all waste tank lining materials (referred to as overhaul slag) are taken...

AI Technical Summary

Problems solved by technology

[0025] The current wet treatment technology has at least the following main problems: first, the large amount of salty and fluorine-containing wastewater produced has not been effectively treated, causing secondary pollution; the produced H 2 、CH 4 , NH 3 The gas is not controlled and utilized, and the generated HF causes serious pollution

Second, the recovered electrolyte and carbon materials contain too many impurities and cannot be used directly

Third, the process route is cumbersome, the technology is complicated, the equipment is severely corroded, and the processing cost is too high

Fourth, due to the influence of factors such as the difference in the capacity and age of the electrolytic aluminum tank, the fluctuation of the composition, and the particle size of the powder, it is difficult to control the process

[0026] The current fire treatment technology has at least the following main problems: First, the tail gas that produces a large amount of entrained HF and dust needs to be treated

Second, the recovery of the electrolyte is not complete, and the residue in the carbon material or slag needs further treatment

Third, the electrolyte with a low melting point melts and agglomerates in the furnace, resulting in a large residual amount of incomplete oxidation and combustion of the carbon material. The melting and agglomeration of the electrolyte in the furnace leads to deterioration of production conditions and poor production stability

Fourth, it is difficult for the reaction materials to achieve uniform mixing at the molecular level, resulting in incomplete conversion reactions

Fifth, the equipment is seriously corroded and the energy consumption is high

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