Optimisation of the strategic mine plan provides a holistic approach to capture all impacts of new technologies and operational strategies deployed across the mining value chain, over the entire life of the operation. The optimisation is value driven, with the primary objective to maximise net present value within specified operational and processing constraints. For these reasons, optimisation of the strategic mine plan is the preferred method to evaluate preconcentration techniques.
Inputs into strategic mine planning include the resource block model, operational parameters, constraints and economic assumptions. From these inputs, the value of each block in the resource model is calculated for each processing destination including waste storage facilities. The maximum value of the block is assigned, and the Lerchs-Grossman algorithm is applied to develop a series of nested shells by adjusting the revenue factor applied to each block. These nested shells provide guidance to the selection of the ultimate pit and design of phases to be mined. The material can then be scheduled, and cut-off optimised, for all processing destinations in the operation.
The inclusion of preconcentration techniques offer flexibility and opportunity for optimisation in their application and operational settings, such as screen aperture or sorting cut-off. These options can be included in the optimisation of the strategic mine plan in much the same way trade-offs between throughput and recovery with grind size have traditionally been assessed.
Once an optimal schedule and cut-off grade policy is produced, the resultant material movement and cashflow provides the best estimate of economic benefits relating to the scenario modelled. In addition, the material movements can be combined with power, fuel, steel and water consumption (from process and haulage models) to provide environmental metrics relating to planned production and quantity the waste rock and tailings generated. A comparison of the strategic mine plan with and without preconcentration techniques provides a robust quantification of anticipated economic and environmental impacts due to preconcentration.
Complete strategic mine plan optimisations for preconcentration techniques have been performed with Whittle Consulting Enterprise Optimisation, Geovia Whittle™, COMET Strategy and COMET Scheduler and Datamine NPV Scheduler.