Conventional “six-in-line” platinum smelting technology, though well understood, is at least 30 years old and has limitations in terms of chrome content in concentrate, PGM recoveries and SO2 emissions.
The development of the ConRoast process for PGMs over the past 12 years has been focused on improving the environment aspects (in terms of lower SO2 emissions) of PGM smelting, as well as the ability to treat PGM-containing materials that have very high chromium contents.
The ConRoast process is aimed at a very different smelter, using a DC-arc furnace for alloy smelting (from oxide) instead of matte (sulphide) smelting. Sulphur is removed at the beginning of the process (as a steady SO2 stream to an acid plant) by dead-roasting the concentrate.
The PGMs are collected in an iron-based alloy, which is more efficient than matte in collecting PGMs.
This flexible PGM processing route can handle a wide range of feeds, all the way to 100% UG2, as it has no need for much nickel and copper (or sulphur) in ore, as iron is the collector.
The reducing conditions in the furnace (and high temperatures) allow much higher levels of Cr2O3 in feed without causing a problem with spinel precipitation.
The iron is removed either by converting or hydro-metallurgically.
A feasibility study for a 10MW smelter for high chrome UG2 concentrates is due to be completed in March 2008.
An agreement signed with an emerging platinum miner was signed towards the end of calendar 2007, and others are envisaged in the near future.