Controlling product quality at high production rates as applied to BHP Billiton Iron Ore Yandi fines operation

BHP Billiton Iron Ore has replaced the conventional product quality control batch system at Yandi with the continuous stockpile management system (CSMS) centred on a fully integrated 'continuous' stockpile flow from mine planning through to port reclaiming. With increasing tonnage rates, tight operational coupling associated with the original batch system caused production interference which achieved final product quality but in an increasingly inefficient manner. This innovative approach places a continuous emphasis on product grade control and takes full advantage of the most appropriate blending opportunities of the mine to port planning and production system to reduce the natural variability of the ore to an acceptable level. To implement continuous control, product variability throughout the process is classified as long term and short term. Long term variability is best controlled through the monthly mine planning process which determines monthly grade targets while taking into account optimum mine development. In the past, attempts to control long term variability were made at the port through selective stockpiling and reclaiming, which reduced operational efficiency. Short term variability is best controlled around the monthly mine grade target by daily mine production scheduling, train sequencing, stacking into port stockpiles of appropriate size and systematic stockpile reclaiming. The implementation of the new system has maintained customer accepted shipping grades and has provided significant improvements in resource utilisation, operational efficiencies and costs.