Single and mixed oxide and clay particle agglomeration: Influence of feed mineralogy and percent drum volume loading

Abstract

Agglomeration of fine particles into coarse and robust product with desired attributes is a key precursor to a number of industrial processes and unit operations. This study investigates isothermal, batch, drum agglomeration behaviour and agglomerate attributes of model, single and mixed oxide (hematite and quartz) and clay (kaolinite and smectite) minerals, the nature of which reflects mineral feed ore preparation for heap leaching. Particularly, the influence of per cent drum volume loading and feed mineralogical composition on agglomeration behaviour and product structural properties was examined. 5–40mm size agglomerates produced with 30% w/w H2SO4 solution as a binding medium displayed drum volume loading and mineralogy dependent structure and properties. Increasing the per cent drum volume loading from 2.9 to 8.6 led to the formation of larger agglomerates due to a concomitant increase in particles' collision frequency. Furthermore, clay-rich (single and mixed minerals) feeds exhibited slower growth rates than the oxide-rich ones, despite the higher binder dosages used in the agglomeration of the former. For mineral type (clay vs. oxide) particle–binder interactions during agglomeration, NMR analysis showed that H2SO4 adsorption by kaolinite was considerably greater than that of quartz. On equivalent feed masses, the differences in agglomerate growth rates of the oxide and clay minerals can be attributed to the differences in their intrinsic properties (e.g., plasticity, ore mineralogy/chemistry). Dry agglomerates' compressive strengths for kaolinite and hematite were quite similar and greater than those for quartz and smectite. Their re-wetting stability, however, decreased in the order: kaolinite>quartz>hematite=smectite. Oxide and clay minerals mixing and synergistic particles' interactions resulted in agglomerates which displayed markedly enhanced compressive strength and re-wetting stability.