Mineral liberation - The key to unlock the optimisation problem of separation processes

Industrial plant operators recognise the benefits of process control to reduce the variability of key process variables. However, the actual financial value for the operation often remains elusive. There are no clear answers to apparently simple questions like what standard deviation can be tolerated on a flotation feed rate or more broadly, what is the cost of variability? A similar vague understanding reigns among metallurgists about optimisation. Is it better to maximise the plant feed rate or the recovery? Stage objectives can hardly make sense without considering the global performance, but even then, defining the optimal plant target raises questions. Quantifying the effect of the grinding product attributes on the separation process performance indicators has also posed significant practical challenges. The recent technological developments of automated quantitative mineralogy introduced new capabilities to solve this conundrum. As the mineral liberation distribution determines the ultimate grade and recovery curve, it seems natural to consider it for process control and optimisation applications. This paper examines the introduction of mineral liberation in the quest to generalise the solution of the process control and optimisation problem of separation plants. It reviews the advances of the last decade, focusing on model, simulation, control and optimisation developments. It also provides a prospective outlook of promising research work and technologies that will bring closer the materialisation of plant-wide or even mine-wide control.