Pyrometallurgical

Pyrometallurgy is a branch of extractive metallurgy that employs high-temperature chemical processes to extract metals from ores, concentrates, or scrap. Operating typically above 800°C, pyrometallurgical methods include roasting, calcination, smelting, and fire refining, as well as various smelting reductions. The approach contrasts with hydrometallurgy, which uses aqueous solutions for metal recovery.

Calcination and roasting decompose carbonates and oxidize sulfides, driving off volatile byproducts such as CO2 and sulfur oxides and converting minerals to oxides. In smelting, a reducing agent such as carbon or carbon monoxide reduces oxide materials to metal, producing liquid metal and a siliceous slag. Fire refining then adjusts composition and removes remaining impurities through controlled oxidation, reduction, or slag–metal separation. Slags, fluxes, and reductants are selected to optimize metal recovery and impurity control.

Pyrometallurgical processes are widely used to produce base and precious metals, including iron and steel, copper, lead, zinc, nickel, tin, and chromium. Copper and nickel smelting often yield matte and slag phases that are separated to obtain metal; iron and steel production typically relies on blast furnaces or direct-reduction routes, with secondary pyrometallurgical steps for refining. In modern industry, electric arc furnaces complement or substitute fossil-fuel furnaces in recycling and primary production.

Environmental and energy considerations are central to modern pyrometallurgy. Emissions of sulfur dioxide and other pollutants are controlled by gas cleaning and by recovering byproducts such as sulfuric acid. Advances focus on energy efficiency, continuous processing, and integration with hydrometallurgy and recycling to reduce environmental impact and improve overall metal yield.