Agglomeration of Fine Ores for Heap Leaching: Mechanisms, Design Parameters, and Scale-Up Limitations

Agglomeration of fine ores is a critical pre-treatment step in heap leaching, directly influencing permeability, fluid distribution, and overall metal recovery. Despite its widespread industrial adoption, the mechanistic understanding of agglomeration and its scale-up reliability remains limited. This review critically examines the physicochemical mechanisms governing agglomerate formation, including capillary forces, binder interactions, particle size distribution, and curing processes. The role of operational parameters—such as moisture content, binder type and dosage, mixing energy, and curing time—is analyzed in relation to agglomerate strength, stability, and resistance to degradation under leaching conditions. Particular attention is given to the evolution of agglomerate structure during irrigation, highlighting the impacts of fines migration, precipitation, and mechanical breakdown on long-term permeability and flow heterogeneity. A comparative assessment of laboratory, pilot, and industrial practices reveals systematic discrepancies that limit direct scale-up, especially due to differences in stress conditions, wetting regimes, and time-dependent transformations. The review identifies common sources of bias in agglomeration testing and proposes a scale-aware framework linking laboratory characterization to heap performance. It concludes that agglomeration effectiveness cannot be assessed solely by initial strength metrics, emphasizing the need for integrated evaluation under representative hydraulic and chemical conditions.