Roasting (metallurgy)

Roasting is the heating of ore in air or oxygen to remove volatile substances or convert its compounds into forms more suitable for extraction.

Sulfide mineral oxidation: The reaction of sulfide minerals with oxygen, producing oxides or sulfates and often sulfur dioxide. Roasting commonly converts metal sulfides into oxides while releasing sulfur dioxide.
Copper extraction: The industrial recovery of copper from ores and concentrates by pyrometallurgical or hydrometallurgical processes. Copper sulfide concentrates may be roasted before smelting or further treatment.
Sulfide mineral: A mineral in which sulfur is chemically combined with one or more metals or semimetals. Many roasting processes begin with sulfide minerals such as zinc blende or chalcopyrite.
Sulfuric acid: A strong mineral acid with the formula H₂SO₄, widely used in chemical manufacture and metal processing. Captured sulfur dioxide from sulfide roasting can be converted into sulfuric acid.
Calcination: Heating a solid to cause thermal decomposition, usually with little or no air supplied. Unlike roasting, calcination generally relies on heat rather than oxidation by air.
Zinc extraction: The production of zinc metal from zinc-bearing ores, chiefly by roasting and leaching or by smelting. Roasting zinc sulfide concentrate produces zinc oxide for subsequent reduction or leaching.
Metal oxide: A compound formed from oxygen and a metal or metalloid. Oxide formation is a common chemical outcome of roasting metal sulfide ores.
Air pollution: The presence of harmful substances in the atmosphere at concentrations that damage health or ecosystems. Uncaptured sulfur dioxide from roasting contributes to air pollution and acid deposition.
Fluidized bed reactor: A vessel that suspends solid particles in an upward flow of gas, enabling intensive heat and mass transfer. Fluidized beds roast finely ground sulfide concentrates with controlled gas flow.
Gold cyanidation: A gold-recovery process that dissolves gold in a dilute cyanide solution before recovering it from the solution. Roasting can open refractory sulfide ores so cyanide solution can reach enclosed gold.

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