Lead is separated from pbs concentrates without air pollution by so2. Its first step is vaporizing pbs from the concentrate to 900 deg-1,100 deg c in a chamber having only a small opening through which the vapor is carried by a stream of he, ar, or preferably n2, into another similar chamber at 750 deg-1,200 deg c. Excess h2 is also admitted to convert the s to h2s, leaving pb to condense to liquid in an externally cooled extension to the chamber. The inert gas stream carries the h2s out for recovery of elemental s. Molten pb is drawn off from a trap in the bottom of the cooled end of the chamber. Byproducts such as cu, ag, and zn, if present in the concentrates, can be recovered from the residue in the first chamber; if its temperature is kept below 1,100 deg c, zns is vaporized very little to contaminate the pb vapor. In applying the process to a concentrate containing 88.2 pct pbs in a horizontal externally heated glass apparatus, 3 h at 950 deg c resulted in 97.94 pct recovery of pb (99.9 pct pure).
U.S. Pat. 3,891,430; June 24, 1975; Chem. Abstr. 81:P80,933s