Analysis of Mine Call Factor at Meli Gold Mine (Ezana): Implementing an Ore Reconciliation System Considering Key Performance Indicators
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Date
2020-06-03
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Addis Ababa University
Abstract
The study area is located in the promising geological region, the ANS, where the first gold mining started in human history which also hosts the VMS deposit that yields multiple metals from single ore like Au, Cu, and Zn. Mining helps for sustainable development, however, involves high levels of complexity and uncertainty which require huge capital investment and risk.
The most profitable way to exploit a mineral deposit requires continuous evaluation and planning. One practical method is to compare what was planned and what is achieved using MCF. It is the ratio, expressed as a percentage, of the gold called for to the gold accounted for.
If everything went well, the comparison of what the mine delivered to the plant and what the plant received and processed must be as close as possible equal or an MCF of approximately 100%, a situation that is impossible in practice, hence an MCF of 85% was considered reasonable for shortfalls as per different practices in different mining operation. Using additional data and study, this case study will help to draw a national standard in the MCF acceptable values.
The design capacity of the plant is 35 tonnes per hour. Considering the designed plant schedule, the crusher has a capacity of 12,500 tonnes per month crushing. The actual total crushed tonne is 175,742, with an average of 5,325 tonnes per month. Considering the crusher plant design capacity plan, the achievement is 42.6%. The total reconciled total mined and hauled ore were 281,246 tonnes with an average monthly of 8,523 tonnes, indicating that the shortfall is not due to ore supply; instead, it linked to the process plant related to various factors, mainly frequent and extended shutdown of the mill due to many reasons which are not the scope of this research.
With the assumption of a metal recovery of 90.6%, the assumed metal recovered is 25,565 ounces which contributes to an MCF of 85.9%. Though the operation is within the acceptable range of MCF values, it requires studying and addressing the shortfalls. The MCF suggests that gold losses averaged at 14.1%, which implies a 14.1% of the expected revenue was not realized and this translates into negative financial underperformance.
Total ore reserve is estimated at 515,837t@4.81 Au g/t contained 79,748.38 Oz of gold; with the design 92% recovery, the expected gold recovered is 73,368.51 Oz. As at March 2020, the mine extracted 55% (281,246t) of the reserve mass, indicating a 45% (234,591t) tonnes still remain on the ground. The plant processed 62.5% of the tonnes hauled from ROM stockpile, which is only 34% of the total reserve in terms of tonnes.
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Analysis of Mine, Call Factor at Meli Gold Mine (Ezana), Implementing, Ore Reconciliation System Considering, Performance Indicators