The intensification of pyrometallurgical processescarries a price: valuable metals are potentially lost in the discardslags. Slags from copper flash smelting furnaces producing highgrade mattes must be cleaned by milling and flotation orreduction smelting in electric furnaces. Outokumpu Oy's newsingle-step nickel flash smelting process oxidizes all of the ironin the feed into the slag. Converting is eliminated, but slagcleaning is mandated to avoid high losses of nickel and cobalt.Similarly, dedicated cleaning is required for the slags producedin the high intensity Noranda Reactors and El Teniente Modified Converters.However, "process intensification" is an arbitrary phase. For theeasily oxidized metals such as iron, cobalt, and molybdenum,conventional copper smelting is intensive, as all of these metalsare intentionally or unintentionally driven into the slag. Thispaper reviews the sulphide smelting behaviour of one of thesemetals -- molybdenum-- and the technology for its recovery,including some recent pilot plant results.
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