Sibanye-Stillwater owns and operate the Columbus Metallurgical Complex, a smelting facility and base metal refinery situated between our Stillwater mine and the town of Billings, Montana. It is one of the world’s largest producers of PGMs recycled from spent automotive catalytic converters.
The Columbus Metallurgical Complex produces a 2E PGM-rich filter cake (in addition to other by-product metals) which is further refined to palladium and platinum metal by a third-party precious metal refiner.
In 2022, the Columbus Metallurgical Complex processed and recycled a total of 598,774oz 3E PGM ounces from spent recycled catalytic converters, of which 7,336oz were processed on a tolled returned basis. In all, 643,200oz were sold to the market in 2022.
A closer look
The Columbus Metallurgical Complex consists of a smelter, that includes a concentrate drying plant, two electric furnaces, two top blown rotary convertors, a matte granulator, gas handling and solution regeneration systems. The smelter’s maximum design capacity is 20,000 lbs/hour (operates at 90% utilisation) which is presently limited until upgrades to the concentrate drying plant and convertor/granulation circuit are completed. These improvements are scheduled such that the capacity of the smelter aligns with the Blitz/East Boulder production increases.
At the smelter, the gases released from the smelting operations are routed through a state-of-the-art dual alkaline, gas/liquid scrubbing system. The scrubber is so efficient and effective that less than 3% of the smelter’s permitted emissions are discharged into the environment.
In addition to the smelter, the base metals refinery has a capacity of 1,300 lbs/hour of matte but is limited by overall copper electrowinning (EW) capacity. The copper EW circuit operates 24/7 even though the rest of plant operates approximately one half of a week, and therefore the copper circuit must be expanded to accommodate the increased quantities of copper that Blitz and East Boulder will deliver.
The base metal refinery utilises a sulphuric acid solution to dissolve out nickel, copper, cobalt and any residual iron from the PGM-bearing converter matter. The base metal refinery produces a palladium, platinum and rhodium-rich filter cake (from the recycling process), which is further processed to refined metal by a third-party refiner. Refined metals from our mine production are sold to Johnson Matthey, while refined metals from our recycling business are normally delivered to counterparties.
The Columbus Metallurgical Complex is one of the world’s largest recyclers of PGMs derived from spent catalytic converters and other industrial sources.
Spent catalytic converters are sourced from third-party suppliers, either by outright purchase or on a toll processing fee basis. Third-party suppliers collect recycling materials primarily from automobile repair shops and automobile yards that process scrapped vehicles. PGMs are also recycled from petroleum refinery catalysts and other PGM-bearing materials.
Prior to processing, recycling materials are weighed, crushed and sampled in a state-of-the-art assay lab at Columbus utilising an automated X-ray process that provides greater accuracy and faster processing times than conventional fire assay methods. Crushed catalyst material is blended and processed with concentrates from our Stillwater and East Boulder mines.
Blending materials from two different sources gives us a competitive advantage over other recycling facilities which lack access to mined production. It also provides processing efficiencies – the concentrates from our Montana mines contain quantities of nickel and copper which facilitate extraction of the PGMs from the recycled material.
Our recycling operations conserve natural resources, energy and landfill space, reducing the environmental impact associated with acquiring mined material. Recycling is not only resource-efficient and environmentally sound; it also contributes to the resilience, efficiency and predictability of our Columbus operation.