A bloomery is a type of metallurgical furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. Bloomeries produce a porous mass of iron and slag called a bloom. The mix of slag and iron in the bloom, termed sponge iron, is usually consolidated and further forged into wrought iron. Blast furnaces, which produce pig iron, have largely superseded bloomeries.
A bloomery in operation. The bloom will eventually be drawn out of the bottom hole.
An iron bloom just removed from the furnace: Surrounding it are pieces of slag that have been pounded off by the hammer.
A drawing of a simple bloomery and bellows.
A Catalan furnace, with tuyere and bellows on the right
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.