A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being supplied above atmospheric pressure.
Former AHM blast furnace in Port of Sagunt, Valencia, Spain
Blast furnaces of Třinec Iron and Steel Works in Czech Republic
Charcoal burning iron blast furnace in Jackson County, Ohio, 1923
Rising carbon monoxide reduces iron oxides to pure iron through a series of reactions that occur at different areas within a blast furnace.
A metallurgical furnace, often simply referred to as a furnace when the context is known, is an industrial furnace used to heat, melt, or otherwise process metals. Furnaces have been a central piece of equipment throughout the history of metallurgy; processing metals with heat is even its own engineering specialty known as pyrometallurgy.
Industrial furnace from 1907.
The Manufacture of Iron -- Filling the Furnace, an 1873 wood engraving
Modern TLS furnace used in copper smelting during heat up.