Review of agglomeration practice and fundamentals in heap leaching

This article reviews agglomeration practices for precious metal and copper heap leaching. Both industries prefer drum to conveyor agglomeration, particularly for clayey ore or ore having a high fines content. Precious metal heap leaching operations opt for cement in a dosage from 2.5 to 10 kg cement/t of ore ( 5 - 20 lb/ton) added to a cyanide solution. Copper ores are agglomerated with water and up to 40 kg sulfuric acid/t of ore ( 80 lb/ton) without binder. The agglomerate physical characteristics, with the exception of their strength, can be measured precisely and automatically. The impact of agglomeration on the in situ physical characteristics of the heap, other than the observable ponding and slumping, is not understood well. The most substantial benefits of agglomeration include up to 90% metal recovery from poorly permeable ores, shorter leach cycles, extra metal recovery from already-leached tailings, and better environmental heap closure.