Proof of concept to investigate a cost effective, environmentally safe closed loop system, to recover metals from spent pot liners / crucibles used in the melting of all types of metals, either during the initial smelting stage or metal purification stage

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Spent pot linings (SPL’s) are the waste material generated in the de-lining of crucibles/potsfollowing the aluminium (and other metal) smelting electrolysis process. The SPL iscomposed of carbon & various inert elements but also fluoride and cyanide and is thushazardous waste. It is regarded as a difficult and expensive waste stream to deal with because:• It has a propensity to combine with water and generate explosive gases.• The presence of cyanide at toxic levels potentially lethal for humans and other livingorganisms.SPL's are highly regulated as a hazardous waste in most parts of the world & are subject to:• The Basel Convention on the Control of Trans-boundary Movements of HazardousWastes and their Disposal.• Increasingly onerous regulatory requirements when shipped beyond the smelter.• Bans on landfill in an increasing number of countriesEffective disposal of SPL’s from aluminium reduction cell cathodes is a significantenvironmental challenge for the aluminium industry but is also a commercial opportunitybecause of the residual metal & the potential to reuse the inert residual material for makingnew pot liners or as input for other manufacturing e.g. aggregates. Such reuse has beenunattractive previously due to the toxicity of the material.Our idea is to conduct further research with some of the novel methods we are developing formaterials separation and applying these to SPL’s. We have carried out simple tests whichshowed a degree of preferential reduction & separation of the metals. Further research &experimentation will enable us to explore these novel processes more fully for SPL’s. Wepropose that the residual, de metalled material can be treated on a Wilfley table (or similar)and with the addition of calcium hypochlorite to render the trace amount of cyanides into inertcyanites at the same time converting the fluoride to inert calcium fluoride.The inert material can then be safely re used in manufacturing.