Roasting is a metallurgical process involving gas–solid reactions to remove sulfur and impurities such as Arsenic, Antimon, Mercury and Halogenides from concentrates and ore bearing material. Outotec utilizes fluidized bed technology, which is the BAT (Best Available Technology) for the main minerals. During the process, sulfides (e.g. ZnS, FeS2) are transformed into oxidic forms (e.g. ZnO, Fe2O3) and SO2(g). The product of roasting is called calcine (e.g. zinc calcine).
Outotec roasting technology for zinc, copper, gold ore and pyrite concentrates is characterized by lowest operating costs, minimum waste material, safe and simple operation at high availability and the production of useful side products as steam and sulfuric acid. The most strict environmental regulations are met for solid, liquid and gaseous products or emissions.