Latest Developments in GTC Design to Reduce Fluoride Emissions

The emission of fluorine from aluminium smelters to the atmosphere remains a serious environmental concern and requires special considerations during Gas Treatment Centre (GTC) engineering phase for greenfield or creeping projects. In order to achieve the lowest emission of Hydrogen Fluorine (HF), Fives has developed several innovations and demonstrated their benefits at industrial scale: (1) An alumina recirculation gas scrubber named OZEOS designed to allow adjustments of the alumina residence time optimizing the HF adsorption. (2) Fives patented process of alumina Cascade with specific air gravity conveyor ensuring an improved scrubbing efficiency in very warm areas. (3) A dedicated flow-control valve installed at pots outlet ducts allowing the adjustment of the pot gas suction with cell operation requirements. (4) A digital solution combining multi-location measurements of hydrogen fluoride (potroom and stack). The current paper describes the R&D works, the industrial implementation, and the industrial results obtained thanks to these innovations.