Drum agglomeration behavior of nickel laterite ore: Effect of process variables

Abstract

Heap leaching is a promising, economically viable processing pathway for extracting nickel (Ni) and cobalt (Co) from complex, low grade laterite ores. Producing a stable heap with high permeability and sustainable lixiviant percolation rate is a key requirement to ensure efficient leaching operation for maximum value metal recovery. Agglomeration of fine ore particles to produce robust granules with desirable attributes (e.g., size distribution and strength and porosity) is a critically important precursor to the heap leaching process. In this study, the effect of binder type/composition and dosage, drum speed, temperature and batch time on drum agglomeration behavior of siliceous goethite (SG) Ni laterite ore was investigated. Isothermal, batch agglomeration performed with tap water and 30, 44 and 98%w/w H2SO4 solutions as binders revealed the key role of binder dosage and acidity in controlling ore particle wettability, granule nucleation and growth behavior. Increasing the binder acidity from zero (tap water) to 30, 44 and 98%w/w H2SO4 led to a higher binder dosage to initiate and maintain a moderate rate of agglomeration. This accordingly reflected decreasing growth rates with increasing binder acidity where 98%w/w H2SO4 resulted in complete suppression of granule growth. At a fixed binder acidity and dosage, both higher temperature and drum speeds led to faster agglomeration rates. The impact of binder acidity and dosage on agglomerates' wet strength appeared to be insignificant. Acid-bound, wet agglomerates' integrity/stability in solution was, however, greater at lower binder dosage and/or binder acidity. The findings foster our understanding of how various, primary process variables may be prudently controlled to produce Ni laterite agglomerates with desirable properties and behavior, as a key step to enhance heap leaching.