Pyrorefining process

A process for the production of a first lead-tin based metal composition, comprising the following steps:

• a) providing a black copper composition comprising at least 50% wt of copper together with at least 1.0% wt of tin and at least 1.0% wt of lead,
• b) partially oxidizing the black copper composition, thereby forming a first enriched copper metal phase and a first copper refining slag, both occurring as liquid molten phases, followed by separating the first copper refining slag from the first enriched copper metal phase,
• c) partially reducing the first copper refining slag thereby forming a first lead-tin based metal composition and a first spent slag, both occurring as liquid molten phases, followed by separating the first spent slag from the first lead-tin based metal composition, the latter forming the basis for a first liquid bath,
• whereby a total furnace content in step c) comprises an amount of copper that is at least 1.5 times as high as the sum of Sn plus Pb present, and
• whereby the first spent slag comprises at most 20% wt total of copper, tin and lead together.