Evaluation of crushed ore agglomeration, liquid retention capacity, and column leaching

In heap leaching operations, large fractions of fines and clays in ores may cause uneven solution distribution and plugging at the bottom of a heap. Agglomeration is a processing step that reduces the mobility of fine particles by agglomerating them with other particles. Agglomeration is used as a pretreatment step in many gold and copper heap leaching operations. Agglomeration is achieved by addition of moisture, and in many case binder in agglomeration equipment. Agglomeration often results in reduced fine particle migration and reduced leaching time. The objectives of this thesis research are to improve the fundamental understanding of agglomeration and to develop quality control methods for agglomeration. Agglomerated ore size distribution, electro conductivity, permeability and soak tests have been developed to evaluate the quality of the agglomerates. Scanning electron microscope (SEM), Quantitative Evaluation of Minerals by Scanning electron microscopy (QEMSCAN), and X-ray computed tomography (CT) were used as agglomerates analysis techniques. Initial binding mechanisms in the agglomeration process involve interfacial forces such as capillary forces. Capillary forces depend on three-phase contact, such as a solid-liquid-gas interface. Therefore, appropriate liquid or moisture content plays a very important role in agglomerate formation. This thesis research shows optimal moisture needed for acidic or nonacidic solution based ore agglomeration can be estimated using liquid retention capacity measurements. Column leaching was also performed to evaluate the effect of agglomeration on fine particle migration and leaching recovery.