Modern Mining June 2015

MINING IN AFRICA

million when compared to a standalone Esaase plant and associated infrastructure. These sav- ings include a shared and expanded tailings storage facility (US$23 million), utilisation of the current power supply line being con- structed for Phase 1 (US$7 million), buildings such as workshops and offices (US$7 million), civils works and plant terraces (US$7 million) and savings in construction accommodation and facilities (US$9 million). An industry standard, troughed overland conveyor has been chosen as the ore trans- port method with a low operating cost of US$0,71 per tonne. The conveyor represents the most optimal method when compared to the various other options that were reviewed including trucking, rail or piping. Although the capital cost of the conveyor is significant, this is more than offset by the other savings that have been achieved, as well as its low operating costs, providing a net capital saving of US$17 million compared to the standalone 2013 PFS for Esaase. The Phase 2 study will be advanced to a full Definitive Feasibility Study (DFS), which will also seek to optimise the mining operations by more efficiently sequencing the six open pit deposits into one integrated mining schedule, as well as achieve process synergies and opti- misations. The DFS will commence during the current quarter, with an investment decision planned for Q2 2016. The US$270 million, Phase 2 expansion will take approximately 18 months to build, with production from Esaase targeted to come on stream in Q1 2018. This timetable is predicated on a positive investment decision from Asanko Gold’s board in Q2 2016. The Phase 1 processing plant is currently around 50 % complete. It includes single stage jaw crushing with reclaim from a live stockpile and open circuit SAG mill, feeding cyclones that in turn operate in a closed circuit with a ball mill. A pebble crusher will receive scats from the SAG mill, crush them and return them to the SAG for further grinding. The hydrocyclones will achieve the final product size of P80 106 µm. A gravity circuit will be utilised to treat a portion of the cyclone under- flow stream to recover coarse free gold, around 40 %, from the recirculating load. The milled product will gravitate to a trash screen before entering a pre-leach thickener followed by a conditioning tank. A seven-stage CIL circuit will be used to leach and adsorb gold from the milled ore onto activated carbon. An AARL elution circuit will be used to recover gold from loaded carbon.

Cyanide in the CIL tailings will be detoxified using the SO 2 /air method. The Phase 2 expansion project will expand the central processing facility with the addi- tion of a 5 Mt/a ball mill, gravity concentrator followed by a flotation circuit. The concentrate from the float circuit at a mass pull of plus/ minus 10 % will be reground and then trans- ferred to a new CIL circuit for leaching and then final gold production. Phase 2 further makes provision for the opportunity to optimise feed material streams to either the flotation or whole ore leach circuit via interlinking conveyors between the respec- tive mill feed circuits. In doing this, there is an opportunity to optimise recoveries and oper- ating costs depending on the ore types being

Machines belonging to mining contractor PW Ghana in action at the mine. Asanko Gold announced in November last year that it had selected PW for the Nkran pre-strip – Nkran is the main pit at Obotan – plus the first year of mining operations. The prestrip operations are well underway with the first ore having being already intercepted and stockpiled.

Genser Energy Ghana to build Asanko power plant Asanko Gold Inc announced in early June the signing of a binding Power Purchase Agreement (PPA) with Genser Energy Ghana Limited (Genser) for the supply of all the power required for Phase 1 of the Asanko Gold Mine. Genser is an es- tablished independent power pro- ducer and power plant operator in Ghana that provides power to large industrial and parastatal clients. fixed-price, life-of-mine contract. The initial contracted rates for the first two years (2016 and 2017) are slightly below the rates that were published in the Phase 1 Definitive Project Plan in November 2014. In 2018 and 2019 the contracted tar- iffs decrease in each year providing a benefit to the long term operat- ing cost profile of the mine.

Permitting and construction of the 19,2 MW plant will begin im- mediately, with power expected to be available in Q4 2015 in ad- vance of commissioning Phase 1 in early 2016. 

Under the agreement, Genser will build and operate a 19,2 MW liquid fuel power plant adjacent to the mine site and supply 17 MW of nominal power to Phase 1 on a

feature

June 2015  MODERN MINING  47