Experimental and modelling Studies of High Temperature HF Capture & Speciation on the Surface of SGA

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Aluminum metal is produced industrially by electrolysis of Smelter Grade Alumina (SGA) in a molten electrolyte, using the well-known Hall-Héroult process. Recovery of fluoride emissions are of primary importance to the environment and metal production costs. Emissions from the electrolytic cell are comprised of gaseous such as hydrogen fluoride (HF). The mechanics involved with the generation of HF by the electrolytic cell include thermal and electro-chemical hydrolysis of hydrogen entering the cell in the form of (predominately) loosely bound moisture on the surface of SGA, incomplete SGA calcination and, moisture from ambient air drawn into the electrolytic cell. To date, no economically viable alternatives (to conventional operating regimes) are known for recovering fluorides from the electrolytic cell process gases at the same, or better, capture efficiency that is achieved today. This project is focused on exploring methods for reducing HF formation at the source whilst enhancing HF capture and retention through SGA dehydration, and morphological change at elevated temperatures; minimizing or eliminating the conflict associated with current operating practices and the SGA specification for relatively high-water content. This work has the potential to radically change smelting practices which would improve the environment by reducing HF emissions while recovering energy. All research, process engineering and design development work to commercialize these systems would come from Bechtel Canada, thereby helping to create and maintain engineering excellence in Canada.