As International Mining’s annual copper extraction update is finalised, one item for which there was not enough editorial space concerns a new process to extract value from undeveloped copper deposits. This may be the most economically and environmentally feasible option for using a particular untapped resource, a Minerals Down Under Flagship evaluation has found. Although significant undeveloped copper deposits exist in Australia and overseas, many of these contain arsenic at levels smelters consider too high to use. However, a CSIRO developed process could change this.

The proposed flowsheet separates copper minerals that are high in arsenic from other copper minerals via a two-stage flotation process and an extra roasting stage. It has fewer environmental impacts – because of reduced arsenic emissions and dispersion to the biosphere – than existing processes, but requires new capital (a roaster and extra flotation units) and additional operating costs. However, these costs are offset by eliminating
the arsenic penalty that would otherwise be imposed.

To gauge economic viability, CSIRO research scientists Dr Nawshad Haque and Terry Norgate, working through the Cooperative Research Centre for Sustainable Resource Processing, undertook a techno-economic
evaluation. This combines estimates for materials, energy inputs and outputs and capital, with variables – including labour – to determine the total cost of a production process.

Using information from CSIRO’s constantly updated database, Haque found that the new process was economically feasible with the potential to use under developed copper deposits and significantly reduce the penalty for arsenic content in copper concentrates. “Also, if a smelter cannot accept concentrates with arsenic levels above 5,000 ppm, the economics of the new process means it could be the only option for using this ore.”