Carbothermic

Carbothermic, in metallurgy, describes reduction processes in which carbon or carbon-containing materials act as the primary reducing agent at elevated temperatures to convert metal oxides into metals. The term covers a range of techniques that rely on carbon’s ability to donate electrons by forming carbon monoxide or carbon dioxide.

In a typical carbothermic reaction, a metal oxide reacts with carbon to produce the metal and either CO or CO2. Examples include Fe2O3 + 3 CO → 2 Fe + 3 CO2 and Fe2O3 + 3 C → 2 Fe + 3 CO. For silica, SiO2 + 2 C → Si + 2 CO, and under certain conditions SiO2 + 3 C → SiC + 2 CO, yielding silicon carbide.

Applications include the historical and ongoing production of iron and steel, where coke provides both heat and reducing power in blast furnaces. Carbothermic routes also enable the production of silicon, ferroalloys, and silicon carbide, especially at industrially high temperatures.

Key considerations include the high temperatures required, carbon activity, and gas-phase equilibria such as the Boudouard reaction (C + CO2 ⇌ 2 CO), which influence efficiency and gas emissions. Impurities in carbon sources can affect product quality.

Environment and history: Carbothermic processes have played a central role in metallurgy since the early industrial era; today they are often complemented or replaced by alternative reductants and energy-efficient methods to reduce carbon emissions.