Roasting (metallurgy)

Roasting is a process of heating a sulfide ore to a high temperature in the presence of air.

More specifically, roasting is often a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component(s).

[1] Roasting consists of thermal gas–solid reactions, which can include oxidation, reduction, chlorination, sulfation, and pyrohydrolysis.

Early sulfide roasting was practiced in this manner in "open hearth" roasters, which were manually stirred (a practice called "rabbling") using rake-like tools to expose unroasted ore to oxygen as the reaction proceeded.

Some metals such as uranium, titanium, beryllium and some rare earths are processed in their chloride form.

Reduction roasting partially reduces an oxide ore before the actual smelting process.