Abstract: Lead refining drosses are fed to a furnace containing molten slag that is heated to at least about 1200.degree. C. by the resistance to electric current flowing between at least two electrodes immersed in the slag. The drosses are smelted to separate matte and metal phases which are tapped from the furnace.The process is particularly advantageous for smelting drosses containing significant amounts of nickel or cobalt and arsenic which react to form speisses. The speisses have densities between that of the matte and the metal and melting points that are high compared to the matte and metal. Resistance heating of the slag insures that any speiss formed is maintained in the molten state thereby minimizing precipitation of the speiss on the furnace walls.

Abstract: A method is provided for producing blister copper from calcined copper-iron concentrates wherein the calcine containing copper ferrite is mixed with particulate carbonaceous reducing agent and charged into a rotary furnace, slag-forming ingredients being also added to slag off iron oxide. The charge is heated to a smelting temperature above the melting point of copper by directing a combusting stream of oxygen and hydrocarbon fuel axially into the rotatable furnace while causing said charge to cascade by rotating the furnace, the ratio of oxygen to the fuel being sufficient to effect substantially complete combustion and provide excess oxygen. Following reduction of the copper to molten blister copper, it is separated from the slag for further purification treatment, the slag being further treated when necessary to recover contained copper therefrom.

Abstract: A method is provided for producing blister copper from calcined copper-iron sulfide concentrates wherein the calcine containing copper ferrite is mixed with particulate carbonaceous reducing agent and charged into a smelting furnace, slag-forming ingredients being also added to slag off iron oxide. The charge, in the form of a shallow bed, is smelted by applying heat whereby the temperature is raised to above the melting point of copper, the copper oxide being selectively reduced to form blister copper, the iron oxide being reduced to form substantial amounts of ferrous oxide, the iron oxide combining with SiO.sub.2 present in the charge to form a slag and assure a low-iron copper product. Following reduction of the copper to molten blister copper, it is separated from the slag for further purification treatment, the slag being further treated when necessary to recover contained copper therefrom.