Process for the thermal treatment of spent potlinings from Hall-Heroult electrolytic cells.

摘要

The invention relates to a process for the thermal treatment of ground pot-linings consisting both of carbonaceous products and of aluminosilicate products impregnated with fluorinated inorganic compounds as a mixture with a pulverulent inorganic additive capable of combining while hot, with or without melting, with the impregnating fluorinated compounds in order to form new, stable and insoluble compounds. The pulverulent mixture is injected at the upper part of a reactor in a gas flow at a temperature not exceeding 1100 DEG C. After having adjusted the contact time of the solid particles with the gas flow so that these achieve a temperature of between 400 DEG C and 750 DEG C at the base of the reactor before they are extracted, the temperature of the gas flow at the base of the reactor is maintained at a set value by adjustment of the flow rate of pulverulent mixture. At the outlet of the reactor, after cooling, the gas flow is separated from the particles then constituting a stabilised residue whose leachable cyanide content is less than 0.0005% and whose leachable fluorine content does not exceed 0.2%.