Cost reduction through mine to mill optimisation – a case study at Newmont Akyem Mine

Abstract

Recent economic factors have negatively influenced the mining operations of the Newmont Akyem Mine of Newmont Golden Ridge Limited, leading to major concerns on sustainability and profitability. In an operating mine, the main cost driver in the operating cost is influenced mainly by the cost of mining and processing. The size reduction processes from the mine until the mineral is liberated contribute immensely to these cost levels. Effective ways of reducing mining and processing cost significantly while delivering desired results in fragmentation for shovel loading, hauling and milling purposes was the focus of this research. The cost reduction technique used in this research was testing of the cost implication of seven blast scenarios by varying the drill and blast parameters and the use of a more potent explosive and also comparing their effect downstream on crusher energy use (electrical power). In addition to the existing blast pattern 4 m × 4 m at Akyem, additional six pattern scenarios were considered and tested. Patterns 3 m × 3 m, 3 m × 3.5 m, 3.5 m × 3.5 m, 3.5 m × 4 m, 4 m × 4 m, 4 m × 4.5 m and 4.5 m × 4.5 m under similar geological conditions at Akyem main pit resulted in a drill and blast cost savings ranging from $ 0.50/tonne to $ 0.22/tonne and crushing energy cost savings ranging from $ 2.14/tonne to $ 4.05/tonne. All simulated patterns produced good fragmentation with the ground vibration and air over pressure levels within acceptable limits. Using pattern 4 m × 4 m costs as baseline representing budget cost, the current pattern size 4.5 m × 4.5 m results in total crushing and drilling and blasting cost percentage variance of -8% implying a loss. However, pattern 3 m x 3 m resulted in +40% variance implying a gain and therefore was found to be the most cost effective.