Semipyritic Smelting

in copper metallurgy, the processing in shaft furnaces of pyrite ore containing 15–30 percent S. Any sulfide deficiency in the ore is offset by adding to the charge a quantity of coke (10–12 percent the weight of the charge) larger than for pyritic smelting. The degree of oxidation of the ferric sulfide depends on the oxygen excess. The amount of sulfur oxidized during the smelting process, 60–95 percent, depends on coke consumption given a specific quantity of air; the more coke, the lower the degree of desulfurization. In pyritic smelting, a large quantity of iron must be slagged by adding quartz to the charge, and in semipyritic smelting the silicon in the ore is slagged; for this purpose, limestone is added to the charge when there is an iron deficiency.