Grade Engineering derives value from exploiting orebody heterogeneity. Current GEOA techniques utilise assessments of intrinsic heterogeneity to calculate realised value from deployment of specific coarse separation techniques. Any change to intrinsic heterogeneity prior to presentation at a given separation stage represents a known unknown variable discount to GE value. Quantifying this change in heterogeneity (whether a positive or negative influence) is key in understanding true GE value.
Standard mining practice at times introduces several stages of mixing in material delivery to generate an idealised homogenous feed for processing. These include:
- Truck loading
- Multiple active dig faces (feed sources)
- Truck delivery sequencing
These have a cumulative effect on heterogeneity characteristics at each step and can result in intrinsic heterogeneity profiles at GE plants that are significantly different than expected from initial observations and evaluations. Predicting grade heterogeneity, and its modification, across the mining chain allows for increased accuracy and a lower risk profile of GE value propositions. It also enables new optimisation options with the goal of minimising mixing, in order to maximise value.
Mixing throughout the value chain is unavoidable in practice; mining processes deal with multicomponent materials that are subjected to multiple mixing events as ore moves from the dig face. In addition, this will also invariably result in segregation-related problems. Design and operational decisions are routinely made without a fundamental understanding of these phenomena. CRC ORE has found that there are two key areas that are most at risk when it comes to this mixing; Bulk sorting away from the mining face, and trials of mine-to-mill optimisation approaches.