Converters are part of the sequenced smelting process, converting furnace matte into bessemer matte
, and removing more iron and sulphur to send precious metals downstream to the refinery to begin the first stages of copper-nickel separation.
The smelter produces blister copper (98% Cu) for shipment to the copper refinery and a slow-cooled Bessemer matte (75% Cu + Ni) which is separated at the matte separation plant into nickel sulfides (mainly heazlewoodite), metallics and copper sulfide (chalcocite).
Prior to 1991, all of the nickel concentrate (10-12% Ni, 2-4% Cu) was roasted in multiple hearth roasters, smelted in oxy-fuel fired reverb furnaces to a matte of 30-34% CuNiCo and further oxidized in Peirce-Smith converters to a low iron Bessemer matte at about 75% CuNiCo and 21-22% S.
The copper from the Bessemer matte is recovered at matte separation and processed in the smelter by oxygen flash converting.