Case study

Cobalt Alloy Production at KCM - Breaking New Grounds

As a standard practice, from the copper mining reserves, the copper concentrate is made and from that the copper metal is produced with other minerals being lost in the form of tailings / slag.

The ore at Zambia, besides being rich in copper also has cobalt in it. In a bid to drive change through innovation, KCM emerged with a new development in the metallurgical complex by recovering cobalt from the process molten slag in form of an alloy of copper, iron and cobalt. This is achieved through the adoption of a two stage electric slag-cleaning furnace system - the first of its kind. The cobalt in the concentrates is fixed in the slag from the flash furnace after smelting. The slag also contains an appreciable amount of copper. The primary slag-cleaning furnace utilizes carbothermic reduction using metallurgical coke as a reducing agent to recover copper only in the first electric furnace.

Cobalt is recovered in the second stage electric furnace (also called the Cobalt Recovery Furnace (CRF)), which handles slag from first slag-cleaning furnace. Apart from the molten slag, a bone dry concentrate feed mixture is injected to induce sulfur, which helps in the adjustment of the liquidus temperature. The metal droplets in the SCF slag and the reduction products settle through the slag layer and form the CRF metallic alloy. The highly reduced slag from the CRF is tapped from the slag tapping holes via launders into the granulation pond. The cobalt alloy design spec of 63% Cu, 23.6%Fe, 6.3%Co and the rest sulphur is tapped through launders directly for granulation. The cobalt alloy production at peak rate is expected to be 70tpd.

We expect to have a cobalt recovery of 37% and produce about 4.4 tonnes per day of cobalt in the form of cobalt copper alloy.