smeltning

Smeltning is a pyrometallurgical process in which metal is extracted from its ore by heating the material to high temperatures in the presence of a reducing agent. The aim is to separate the desired metal from oxides, sulfides, or other compounds, producing a molten metal and a waste slag.

Process overview: ore concentrates are mixed with fluxes such as limestone or silica and a reducing agent, typically carbon in the form of coke, coal, or charcoal. This mixture is heated in a furnace suitable for the metal being produced, such as a blast furnace for iron, a reverberatory or flash furnace for other metals, or an electric arc furnace for certain applications. Oxides are reduced to metal (for example, Fe2O3 + 3CO → 2Fe + 3CO2), while gangue compounds combine with flux to form slag. In sulfide smelting, sulfide minerals are converted to oxide and then reduced or directly reduced, with sulfur released as a gas or captured in byproducts.

Products and byproducts: the primary product is the metal, while slag is formed from the non-metallic components and fluxes. Gases such as CO2, CO, and, depending on ore composition, SO2, may be emitted and are subject to emission controls. Smelting is energy-intensive and can impact air quality and landscape through slag heaps and tailings.

Applications and history: smelting is central to producing base metals such as iron, copper, lead, zinc, tin, and nickel, as well as some precious metals. It has a long history, from early bloomery furnaces in ancient times to modern large-scale blast furnaces and electric smelters, enabling large-volume metal production with subsequent refining and alloying.