Editing Smelting (section)

===Sulfide ores===
[[File:Cowles furnace-2.jpg|thumb|[[Electric Smelting and Aluminum Company|Cowles Syndicate]] of [[Ohio]] in [[Stoke-upon-Trent]] [[England]], late 1880s. [[British Aluminium]] used the process of [[Paul Héroult]] about this time.<ref name=Minet>{{cite book|author=Minet, Adolphe|others=Leonard Waldo (translator, additions)|title=The Production of Aluminum and Its Industrial Use|url=https://archive.org/details/productionalumi01minegoog|year=1905|page=[https://archive.org/details/productionalumi01minegoog/page/n254 244] (Minet speaking) +116 (Héroult speaking)|publisher=John Wiley and Sons, Chapman & Hall|location=New York, London|ol=234319W}}</ref>]]

The ores of base metals are often sulfides. In recent centuries, [[reverberatory furnace]]s have been used to keep the charge being smelted separately from the fuel. Traditionally, they were used for the first step of smelting: forming two liquids, one an oxide slag containing most of the impurities, and the other a sulfide [[matte (metallurgy)|matte]] containing the valuable metal sulfide and some impurities. Such "reverb" [[Reverberatory furnace|furnace]]s are today about 40&nbsp;meters long, 3&nbsp;meters high, and 10&nbsp;meters wide. Fuel is burned at one end to melt the dry sulfide concentrates (usually after partial roasting) which are fed through openings in the roof of the furnace. The slag floats over the heavier matte and is removed and discarded or recycled. The sulfide matte is then sent to the [[converter (Metallurgical)|converter]]. The precise details of the process vary from one furnace to another depending on the mineralogy of the ore body.

While reverberatory furnaces produced slags containing very little copper, they were relatively energy inefficient and off-gassed a low concentration of [[sulfur dioxide]] that was difficult to capture; a new generation of copper smelting technologies has supplanted them.<ref>{{cite book|author=W. G. Davenport |contribution=Copper extraction from the 60s into the 21st century |title=Proceedings of the Copper 99–Cobre 99 International Conference |volume=I—Plenary Lectures/Movement of Copper and Industry Outlook/Copper Applications and Fabrication|editor1=G. A. Eltringham |editor2=N. L. Piret |editor3=M. Sahoo |publisher=The Minerals, Metals and Materials Society |location=Warrendale, Pennsylvania |year=1999 |pages=55–79 |oclc=42774618}}</ref> More recent furnaces exploit bath smelting, top-jetting lance smelting, [[flash smelting]], and blast furnaces. Some examples of bath smelters include the Noranda furnace, the [[Isasmelt]] furnace, the Teniente reactor, the Vunyukov smelter, and the SKS technology. Top-jetting lance smelters include the Mitsubishi smelting reactor. Flash smelters account for over 50% of the world's copper smelters. There are many more varieties of smelting processes, including the Kivset, Ausmelt, Tamano, EAF, and BF.