In conducting technical due diligences, SRK’s recent experience has found the majority of projects to be “metallurgicallychallenged”. This is often due to low grade or complex mineralogy or at times, ore hardness; sometimes it is a matter of inadequate power, water or tailings handling.
Problems arise when the selected flowsheet is not appropriate for the range of ore properties – a “one size does not fit all” situation. Very often, companies do not appreciate or acknowledge the potential for variations in metallurgical performance, expecting the operations team to make the best of it.
How often does a company truly understand their ore variability – both now and in the future? Can they predict (to a reasonable level of accuracy) the expected changes in performance and have a plan in place to mitigate them? This may not be the case as confidence in these predictions is low and therefore, can be ignored.
Of course, the common term for this is geometallurgy – but does this include the potential for changes in the process flowsheet? In the figure below, a typical 16-year mine plan shows six metallurgical domains.
How were these domains derived and are they metallurgically-relevant? What will happen in the middle of the mine life when Domain 4 arrives at the mill? Does it justify a change in process flowsheet or an expectation that problems will be dealt with at that time?
SRK is assisting clients stuck with a fixed flowsheet and anticipating variable feed conditions: can feed quality be improved (e.g. blast fragmentation) or can the principles of Grade Engineering® be applied? That is, by blending/sorting ahead of the process plant or methods of pre-concentration, including coarse beneficiation.
SRK is advocating flexible process flowsheet design including “staged reduction in size and progressive upgrade” – recovery of product at every opportunity and removal of waste at every stage.
Remember: all ore is not created equal and equal grade does not mean equivalent performance. One thing is for certain – with an inflexible flowsheet, your metal recovery will not remain constant for the life of mine.
