Agglomeration behaviour and product structure of clay and oxide minerals

Agglomeration of fine mineral particle into robust and porous granules is an essential precursor to heap leaching and valuable metal recovery from low grade lateritic ores. In this paper, isothermal, batch agglomeration behavior of selected model clay (kaolinite and smectite) and oxide (hematite and quartz) minerals which constitute the predominant host gangue phases of typical low-grade nickel (Ni) lateritic ores is investigated. Specifically, the influential role of feed particle size and mineralogy on H2SO4 binder dosage requirement and agglomeration behavior was studied. Granules of 5-40 mm size range were produced within 8-14 min and their mechanical/structural properties examined. The results showed that for equivalent wetting and saturation, finer feed particles required higher binder dosage and led to dry agglomerates of higher compressive strength and re-wetting stability in acidic solution than coarser feed particles. Furthermore, binder dosages required for effective agglomeration were greater for the clays than the oxide minerals. Quartz, kaolinite and smectite displayed markedly slower growth behavior in comparison with hematite. The internal micro-structural analysis showed that the pore volumes (porosities) of the oxide granules were noticeably more than those of the clay granules these increased markedly (20-30% for clays and 30-40% for oxides) upon drying due to stresses/strains resulting from particle shrinkage after solvent (water) loss. Agglomerate dry compressive strengths for kaolinite and hematite were found to be similar and greater than those for quartz and smectite whilst the corresponding re-wetting stability decreased in the order: kaolinite>quartz>hematite=smectite. These findings, which indicate that the correlation between granule mineralogy, structural and behavior is quite complex, provide a useful basis for benchmarking the agglomeration behavior and granule properties of lateritic mineral ores. (c) 2013 Elsevier Ltd. All rights reserved.