Microstructure analysis of Ni laterite agglomerates for enhanced heap leaching

Agglomeration is a process that is widely used in several industries (e.g., pharmaceuticals, fertilizers, minerals, food) to produce, from fine particles, large single or multiphase granules with desirable attributes. In the minerals industry, multi-mineral phase agglomerates are used in heap leaching operations to recover valuable metals such as copper, nickel and gold from finely ground, low grade ores. The key structural features of agglomerates that lead to enhanced leaching performance within full-scale heaps have been identified as their size and size distribution, internal porosity, bed permeability and mechanical strength. Knowledge of the agglomeration mechanisms and kinetics, together with the characterization of granule internal microstructures (e.g., porosity, spatial distribution of different mineral phases, pores and liquid phase distribution) are essential for greater understanding of leaching behaviour and correlation with the concomitant mechanical properties and robustness. In this paper, we demonstrate how a non-destructive micro-tomography analysis is used to study nickel laterite ore agglomeration behaviour and agglomerate microstructure. Specifically, its internal, multi-mineral component granule structure and pore volume spatial distribution are investigated. The results suggest that agglomerate microstructure analysis provide valuable information which may be used for possible agglomeration process optimization and improving final granule properties such as porosity, permeability, strength and re-wetting stability.

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► Non-destructive micro-tomography analysis is used in Ni laterite agglomerates.
► Granule growth during agglomeration mainly proceeds via random coalescence.
► Micro-CT image analysis enables porosity visualisation and measurement.
► Post-agglomeration curing leads to increased pore volume and pores interconnectivity.
► Concentrated CsCl solution is useful to evaluate agglomerate permeability.