Continuous sulphur drossing process

A continuous sulphur drossing process for the decoppering of lead which comprises:

• continuously flowing lead bullion into the first of a series of at least two reaction vessels;
• continuously agitating the lead bullion in the first reaction vessel;
• continuously adding sulphur to the lead bullion in the first reaction vessel during the continuing agitation;
• continuously and concurrently transferring the lead bullion, dross arising from copper reacted with the sulphur, and any unreacted sulphur from each reaction vessel to the next in the series, without backmixing;
• continuously agitating the contents of each reaction vessel;
• maintaining the average total residence time of the materials in the reaction vessels below that within which a significant amount of reversion to elemental copper would occur, thereby substantially preventing re-solution of copper in the bullion;
• continuously and concurrently transferring decoppered bullion and dross from the final reaction vessel in the series to an unagitated dross separation vessel;
• removing the dross from the surface of the decoppered bullion in the dross separation vessel;
• and
• continuously withdrawing decoppered bullion from the dross separation vessel.