Abstract: A smelting furnace, the refractory sole (3) of which is contained in a metallic casing (5) having expansion joints (6, 7, 7'), comprises means (18, 19) for cooling the expansion joints, these means enabling to solidify actually any liquid phase that might tend to infiltrate into the joints.

Abstract: Non-ferrous metals are extracted from molten slags 9 by treating the latter in an electric furnace with submerged electrodes 2 under a layer of a solid reducing agent 8. During the extraction, a non-oxidizing gas is injected into the molten material at a flow rate of between 0.5 and 10 Nm3/h/ton of material treated (FIG. 1).

Abstract: Lead-copper-sulphur charges (e.g., ores and concentrates) containing at least one of the elements Fe, Ag, Bi, Zn and Sn are treated pyrometallurgically to recover their metal values by a process comprising the steps of (a) smelting the charge to produce a slag phase containing at least about 10% Pb, a copper matte phase containing less than about 65% Cu, and a lead bullion phase; (b) separating the slag, matte and bullion phases formed in step (a); (c) reducing the molten slag separated in step (b) to decrease the lead content thereof to less than about 2% and form thereby a lead bullion phase; and (d) separating the slag and bullion phases formed in step (c).

Abstract: A process for the pyrometallurgical extraction of bismuth from a bismuth-bearing material (e.g., ores and concentrates of bismuth in the roasted or unroasted states), in an electric furnace with submerged electrodes in which the sulphur content of the charge constituted of the bismuth-bearing material is controlled so that a matte phase is produced having a bismuth content of between 3 and 20% by weight and a slag phase is produced which is separated from the matte. Under these conditions cheap fluxes (e.g., sand, limestone, iron oxide) can be used whereby the resulting slag has a relatively low corrosivity and high melting point (e.g., 1150.degree.-12000.degree. C.) without excessive losses of bismuth by volatilization.