Unlocking additional value by optimising comminution strategies to process Grade Engineering® streams

Grade Engineering (R) comprises a range of techniques aiming to reject low grade uneconomic material (preconcentration) as early as possible within the mining value chain. It has been identified as an effective and feasible operating strategy whereby mining unit metal productivity can be significantly increased. Two Grade Engineering (G.E) levers have been assessed in a copper porphyry deposit: preferential grade by size response, and differential blasting for grade. Those are exploited through a modified blasting fragmentation coupled with screening based process on run-of-mine material to recover upgraded undersize fractions. Application of G.E inevitably alters comtninution circuit typical feed particle size distributions, and consequently impact semi-autogenous (SAG) milling performance. A factorial design approach has been employed to assess the extent of this effect. A wide range of different operating scenarios, representing the possible G.E strategies and dynamic processing rock attributes, were simultaneously assessed using the Integrated Extraction Simulator (IES), a new cloud-based process simulator. This enabled the development of a G.E throughput improvement model as function of blasting fragmentation, impact hardness (Axb) and grindability (BMWi), which can be employed to conduct more detailed process modelling as well as resource optimisation. Improvements up to 14% in throughput due to changes in mill feed particle size distributions were observed under the conditions examined. The impact of this effect upon the proportion of material that is amenable to G.E is also discussed. (C) 2016 Elsevier Ltd. All rights reserved.