Carbon dust refers to carbon particles, originating from carbon inputs into the smelting process like anodes, that float on top of the bath, below anodes or suspended in the bath. The phenomenon has a deleterious effect on the specific energy consumption of cells and can lead to anode deformations, hot cells out of the process window and stoppage of cells.
Trials were conducted in the TRIMET Hamburg Smelter focusing on the effect of dust at anode changes. The conditions were chosen to be best and worst practice as assessed by a visual carbon dust assessment in the taphole. Contrasting with published literature, there was no relation in the experiments between spike formation and carbon dust in anodes after 8 hours. Anodes set in cells with a high carbon level in the taphole did not behave differently when compared to anodes with a low carbon dust content in the taphole. Samples obtained from the frozen bath layer underneath the anodes showed carbon contents in the range of 0.0315 to 6.29 %.