OPEN PIT OPTIMIZATION AND PRODUCTION SCHEDULING OF OKOBO COAL MINE, CENTRAL NIGERIA

• Anthony T. Bolarinwa

  Department of Geology, University of Ibadan, Ibadan, Nigeria

• Gideon C. Nwafor

  Department of Geology, University of Ibadan, Ibadan, Nigeria

The Okobo coal in Enjema District of Ankpa Local Government Area of Kogi State, Nigeria is a near surface deposit that is mined through the open pit method. In this investigation, models and plans of the Okobo coal mine produced, using Minex® Gemcom Software, were aligned with depth, strip ratio and optimum pit limits with the aim of defining the most profitable extraction sequence of the coal that will produce maximum possible discounted profit under certain physical and operational constraints. Sandstones, shale and clays constitute the overburden. The topsoil thickness ranged from 0.1 to 0.5 m. Coal recovery was estimated from drill data to be 95%, with losses occurring primarily at the base of the coal seam. Eight (8) expansion pits from the most valuable to the least valuable material were identified using the optimizer. Parametric analysis of mining and processing costs generated an optimized pushback of 1.7 million tonnes of 20.79 Air Dried (AD) MJ/kg coal at 12.35 stripping ratio in the $65 incremental pit. Areas with higher stripping ratio might be more suitable for underground mining. Implementation of these application would reduce cost, improved the Net Present Value (NPV) of the operation and selection of the most economical areas for mining. It is recommended that the mine pits be developed from north to south for optimum productivity.

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