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High Pressure Grinding Rolls (HPGR) technology is accepted as an energy-efficient and cost-effective alternative for treating specific mineral ore types. HPGR technology has been advancing within manufacturing facilities and research centers since its first installation in 1985. Over the last three decades much of the literature on HPGR have focused on the industrial applications and trade-off studies in comparison with semi-autogenous and ball milling circuits. Literature on fundamental studies of HPGR technology has been very limited. This paper aims to provide a review of the modeling of high pressure grinding rolls.

Agglomerate size distribution is a pretreatment step in low grade heap leach operations. The present work focuses on modeling the evolution of size distribution in batch agglomeration drum. Up to now there has been no successful work on modeling of crushed ore agglomeration although the framework for population balance modeling of pelletization and granulation is readily available. Different batch agglomeration drums were used to study the agglomeration kinetics of copper, gold and nickel ores. The agglomerate size distribution is inherently subject to random fluctuation due to the very nature of the process. Yet, with careful experimentation and size analysis the evolution of size distribution can be followed. The population balance model employing the random coalescence model with a constant rate kernel is shown to work well in a lab scale agglomerator experiments. It was observed that in a small drum agglomerates begin to break in a short time whereas the growth is uniform in the larger drum. The experimental agglomerate size distributions exhibit self-preserving size spectra which confirms the applicability of coalescence rate based model. The present work lays out the fundamentals for applying the population balance concept to batch agglomeration, specifically crushed ore agglomeration. The experimental difficulties and how to overcome them are described.

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