Jay N. Bruggeman

Effect of Open Holes in the Crust on Gaseous Fluoride Evolution from Pots

Changes in fluoride evolution from aluminum smelting pots have direct consequences on pot gas scrubber loads and resultant smelter emissions. Changes in fluoride evolution can also have dramatic implications on bath chemistry control and the resulting pot performance. Both of these factors motivate continuing efforts to quantify the effect of pot operating practices on fluoride evolution in order to prioritize the amount of effort to place on any given practice to minimize fluoride evolution. Gaseous fluoride evolution measurements were made at several smelters and demonstrate a strong correlation between the amount of gaseous fluoride evolved from an individual pot and the total area of open holes in the crust. Data from pots of different types suggest that it is possible to normalize the data to allow predictions for other pot sizes and geometries. In almost every case, the additional fluorides lost due to holes in the crust comprise the largest fraction of the total gaseous evolution.