Abstract: A process for changing spent anodes while recovering the majority of the gaseous compounds evolved by the spent anodes and by the bath crust removed from the electrolytic pots during the cooling phase uses an effluent-collection device for electrolytic pots. A device for collecting gaseous effluents from pots for the production of aluminum by igneous electrolysis allows the recovery of the gaseous compounds evolved by the spent anodes and by the crust which they contain during the replacement and cooling of these anodes and this crust. The device preferably includes a degassing and cooling container located at one of the ends of the hooding device of the pots. The container can be made to communicate with the suction produced by the gas collection device.

Abstract: Process for insolubilizing and consolidating in pellet form the spent linings from electrolysis cells for the production of aluminium comprising grinding said spent linings and mixing them thoroughly with various pulverulent refractory additives before heating, characterized in that after the addition of:a first additive intended to fix the alkali metals during firing, which is chosen from the group of aluminosilicates,and subsequently a second additive intended firstly to combine with the impregnating fluoride compounds during firing to form new stable, insoluble compounds, and secondly through its non-combined excess part to assure the consolidation of the mixture, and is chosen from the group of calcium oxides and salts, preferably limestone cements and mortars,the intimate mixture of ground, spent linings and said first and second pulverulent additives is agglomerated into pellet form before firing at a temperature in the range of from 700.degree. C. to 950.degree. C.

Abstract: A process for heat treating spent pot linings from Hall-Heroult electrolytic cells which comprise carbon and silico-aluminous materials impregnated with fluorides. The pot linings are ground to a particle size less than 5 mm, and formed into an intimate mixture with calcium sulfate or calcium sulfate dihydrate having a particle size less than 1 mm. The mixture is injected into the center of a vortex formed by a flow of circulating hot gas at the top part of a reactor at a temperature between 700.degree. and 1100.degree. C., and extracted from the bottom part of the reaction at a temperature between 400.degree. and 750.degree. C. after a contact time of less than 2 seconds.

Abstract: The invention relates to a thermal shock treatment in a reactor of ground spent pot linings, constituted both by carbon-containing products and silico-aluminous products impregnated with fluorine-containing mineral compounds, mixed with a pulverulent mineral additive able to combine hot, with or without melting or fusion, with the fluorine-containing impregnating compounds in order to form new stable and insoluble compounds such as CaF.sub.2, binary, ternary or quaternary compounds of NaF, CaF.sub.2, SiO.sub.2, Al.sub.2 O.sub.3, CaSO.sub.4, Na.sub.2 SO.sub.4, of the nephelite, hauynite or similar type.