Modern Mining January 2019

GOLD

to connect Esaase to the processing plant at Obotan via a 27 km overland conveyor which will take 22 months (from contract award) to build and commission; in the interim, oxide ore from Esaase will be trucked to Obotan at a rate of 1,5 Mt/a over a haul road which has recently been completed. “The plant has a conventional flowsheet comprising a SAG, ball mill and crusher (SABC) with gravity gold and CIL recovery,” says Bradford. “Within three months of being fully commissioned, it was working at its design capacity and, in fact, exceeding it. What also became clear was that the SABC circuit could handle a much bigger throughput than the downstream section. This presented an opportunity for a low-cost capacity increase as modifications and upgrades to achieve a greater throughput would not require any additional milling capacity.” In 2017 an execution plan (P5M) was put in place to deliver 5 Mt/a by Q3 2017 while maintaining metallurgical performance. The metallurgical upgrades required included an additional Knelson concentrator and an additional Intensive Leach Reactor (ILR), an additional 5 t/day oxygen plant, expanded electrowinning capacity and a larger water- handling tank. On the volumetric side,

Left: The processing plant at Asanko Gold Mine. Its original throughput capacity of 3 Mt/a has been increased to 5 Mt/a for a very small capex of just US$29 million. Below: The MillSlicer is an instrument that monitors – via a number of vibration sensors – the SAG mill load position and toe angle and optimises the SAG mill power conditions.

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January 2019 _ MODERN MINING _ 61