Xstrata Process Services (XPS) and Xstrata Nickel – Sudbury Operations recently undertook a characterisation program of the low sulphur-high PGE (platinum group element) zones within the newly discovered Nickel Rim South deposit in Canada. These zones of low sulphur and elevated PGE signatures do not behave the same as high sulphide ores at the Strathcona mill. These zones are low in sulphide mineralogy and appear to be waste rock but for their impressive PGE grades!
A testwork program was designed to characterise the mineralogy of the zones, benchmark the flotation behaviour of the ore through the standard Strathcona flowsheet and optimise the metallurgical performance with rougher-scavenger regrinding and PGM promoter concepts.
XPS geoscientists reviewed the Nickel Rim South resource block model to build a representative composite of the zone, matching target grades and spatial distribution within the deposit, for subsequent mineralogy and metallurgical testwork. Bench scale rougher-scavenger flotation tests were carried out on a set of test charges, blended using XPS’ proprietary ‘Odds and Evens” blending technique, to benchmark the performance of the ore to the standard Strathcona flowsheet. A staged approach was taken in the optimisation of the metallurgical performance. First various PGM promoters were tested with the Strathcona flowsheet and the best performer used in subsequent stages of optimisation. Secondly, a staged fine-grinding approach was taken with tests performed on two regrind sizes both with and without the best performing PGM promoter.
Comparing the results of the optimisation phase with the Strathcona benchmark, a fine-regrind with the best performing PGM promoter showed between 10 % and 15 % recovery improvements of precious metal phases for the low sulphur-high PGE ore! Further work is required to optimise conditions for additional improvements in concentrate grade; in turn improving economics by increasing recovery of fine liberated PGM.
Mineralogical work was completed using QEMSCAN (Quantitative Evaluation of Materials by Scanning Electron Microscopy). These results clearly showed the improvement of PGM liberation with the finer regrind.
This project presented baseline recoveries as well as flowsheet optimisation with both low and high capital cost additions and their corresponding recovery improvements. This will allow Nickel Rim South and the Strathcona mill to complete an economic analysis of options relating to the processing low sulphur-high PGE ore.
Techniques such as staged grinding and flotation, and reagent optimisation can be used to recover PGM from similar orebodies to potentially maximise the profitability of the ore.
Please note IM’s forthcoming feature on flotation in the July issue. We are interested in interesting technical reports on new technologies, new reagents and improved methods. Send to [email protected]