Paul J. Marcantonio

Converting practices at the stillwater precious metals smelter

At the Stillwater Mining Company’s precious metals smelter in Columbus, Montana, flotation concentrates containing copper, nickel, and platinum-group metals are smelted in a submerged-arc electric furnace. The matte, containing 30% copper plus nickel, is granulated, dried, remelted in a top-blown rotary converter, and blown with oxygen to ”white metal” containing approximately 75% copper plus nickel and 2.5% precious metals. For the first month of converter operation (July 1990), conventional fluxing with quartz was practiced. An excessive number of slag foams and heavy accretion formation at the mouth of the converter led to a switch to lime fluxing as a replacement for silica. This resulted in eliminating slag foams and decreasing accretion build-up. It is believed that the Stillwater works is the only commercial smelter in the world following this practice.