MPES Conference 2017

Event: International Symposium on Mine Planning & Equipment Selection (MPES2017)

Date: 29-31 August 2017

Location: Lulea, Sweden

Paper: Economic Benefits and Technical Complexities of Grade Engineering® in Strategic Mine Planning of Metalliferous Projects



Economic Benefits and Technical Complexities of Grade Engineering® in Strategic Mine Planning of Metalliferous Projects


Grade Engineering




Carlos Espejel







Abstract text:

Grade Engineering® (GE) is a concept created by CRC ORE (Cooperative Research Centre for Optimising Resource Extraction) to describe a range of pre-concentration technologies and operating methods to improve head grades and throughput (TPH) to processing destinations. This is achieved through the early rejection of low value material prior to energy and cost intensive activities (e.g. milling and flotation). Grade Engineering pre-concentration technologies include; particle and bulk sensor based sorting, differential blasting to induce deportment of grade to finer size fractions to be separated by screening and screening for the preferential deportment of grade by size.

It is estimated that if the entire mining system is optimised incorporating Grade Engineering, the global financials of a project could be significantly improved by 3 to 15% in Net Present Value (NPV). Furthermore, total ore reserves could be increased and the geological resource could be utilised in a more efficient and sustainable manner. Although Grade Engineering offers flexibility and added value to a mining asset, it also comes with associated technical and operational complexities that must be addressed. One of the main technical complexities is the characterisation of the geological resource by pre-concentration (separation) properties. A new dimensionless geometallurgical attribute has been created to describe separation potential named Response Ranking (RR).

The separation behavior of each GE technique and rock type as Response Ranking (RR) attributes must be incorporated in the fundamental input data (Block Model) to facilitate assessment in all optimisation stages for strategic mine planning, including: final pit and production schedule/cut-off grade optimisation. This is required to assess the delta in economics achieved by Grade Engineering, and to use it as a strategic tool to reach objective indicators set by the mining project such as; net present value, internal rate of return, metal production, and life of mine.

To incorporate Grade Engineering economic benefits and complexities into the main optimisation stages of mine planning, Lane’s value and cut-off grade equations have been revised and updated for Grade Engineering and pre-concentration. This paper provides a discussion of GE economic block modelling, GE final pit optimisation, GE value and cut-off grade equations and GE production schedule optimisation at a metalliferous project. The optimisation of the case study incorporating Grade Engineering improved the NPV from developing the mineralised deposit through open pit mining.

Keywords: Mine Planning Optimisation for NPV, Grade Engineering, Sensor Based Sorting, Mining Economics, Strategic Mine Planning.




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