Chapter 23 – Roasting Developments – Especially Oxygenated Roasting

Roasting of ores and concentrates can be defined as the heating of a material to cause reaction and the expelling of volatile matter without causing fusion. Oxidative roasting is used extensively to pretreat base and precious metal–bearing materials and to oxidize iron sulfides to generate sulfur dioxide for fixation with lime or sulfuric acid production. For the recovery of gold from refractory ores and concentrates, roasting has been used extensively for decades. For severe refractory gold ores, it was the exclusive pretreatment process and, accordingly, its development is presented in detail in this chapter, finishing with the most recent technology: oxygenated roasting for whole ores. Commercially, four important steps have been witnessed in the development of roaster equipment. The development of new technologies was driven by increased throughput requirements, improving efficiencies, reducing costs, and increasing environmental concerns. Oxygenated roasting in fluidized beds also improves throughput per unit area as well as reducing the size of gas-cleaning equipment.