An improved method for smelting copper ores such as chalcocite (cu2s) is presented. The improvement involves the use of calcium sulfate and iron as smelting additives. Conventional smelting of such ores requires the addition of pyrite (fes2) or chalcopyrite (cufes2), both expensive and often not available close to the smelter site. The present invention substitutes inexpensive and readily available gypsum (caso4.2H2o) or anhydrite (caso4) and scrap iron (turnings, borings, auto body scrap, etc.). The reactions by which sulfur is made available for matte formation are believed to be: (1) 4fe + caso4 -> cas + 4feo; (2) 3cas + caso4 -> 4cao + 2s2; (3) 2cu + s2 -> 2cus; and (4) 2feo + 1.5S2 -> 2fes + so2. (Cao formed in reaction 2 lowers the requirement for limestone as a fluxing reagent.) The amounts of ingredients to be used depends on the mineralogical and chemical composition of the ore to be processed, the quantity and grade of secondary materials such as converter slags, dusts, and scrap fed to the smelter, the grade of matte desired, and the analysis of calcium sulfate and iron added to the charge. The smelting charge should have a composition cu 13-16, fe 4-10, s 4-12, cao 14-16, al2o3 9-12, and sio2 wt pct. Smelting temperature is preferably 1,300 deg-1,400 deg c.
U.S. Pat. 3,533,779, Oct. 13, 1970, Chem. Abstr. Not Found