Partial Roasting of High-Arsenic Copper Concentrates

The partial roasting of high-arsenic copper concentrates at 973 K/998 K (700 °C/725 °C) under controlled atmosphere can remove > 95 pct of the arsenic contained in the concentrates, leaving a calcine with 52 to 68 wt pct bornite, 10 to 13 wt pct chalcopyrite and 2 to 5 wt pct magnetite, with 8 to 24 wt pct remnant chalcocite. The mineralogic composition of the calcine obtained is consistent with the calculated mineralogic composition based on the chemical analysis of the calcine and the gaseous phase in equilibrium with the calcine. The formation of the new solid phases present in the calcine (bornite and chalcopyrite) should take place in the emulsion phase of the fluidized bed, while the oxidation of part of the gaseous sulfur generated by thermal decomposition of the sulfides present in the concentrate could occur in the evolving cloud and wake surrounding the air bubbles in the emulsion phase of the fluidized bed.