FLUORIDE EVOLUTION/EMISSION FROM ALUMINUM SMELTING POTS - IMPACT OF ORE FEEDING AND COVER PRACTICES

摘要

Aluminum electrolysis pots evolve gaseous fluoride (HF) owing to hydrolysis of the molten salt bath. Nearly all of the evolved fluoride is captured using dry scrubbers that employ smelting grade alumina (SGA) as the active adsorbent so that the captured fluoride can be returned to the smelting pots. A range of smelter-owned factors such as pot chemistry, operating practice, pot tending practice and ore feeding affect the dynamics of this recovery process. Real-time HF monitoring was performed on operating smelting pots to show the impact of ore feeding practices on HF evolution and emission. The mechanism of fluoride evolution during feeding was studied by varying the rate and dynamics of the ore feed cycle. The purpose of this effort was to gain a better understanding of the root-cause origins of gaseous fluorides evolved during ore feeding in actual production cells.