Heap leaching, a process by which base metals such as gold, silver, nickel, uranium, and copper are recovered from ore, has been in long been the method of choice for ore beneficiation. While this process has proven to be an efficient process, often chosen for its cost-effectiveness, the efficiency of the heap leaching process relies heavily on the process of agglomeration.
Upon removal from the ground, ore is sent through a crusher to break the ore down into fines. The ore fines are then “heaped,” or piled, into a large pile. This mound is irrigated with a special solution that is dependent upon the type of ore being extracted. In the case of copper, sulfuric acid is used, because it reacts with the copper to create Copper Sulfate, a by-product that has many potential reuse applications. The irrigated solution is allowed to sit for several days, permeating through the ore, and draining to the bottom of the heap. The ore pile sits over a permeable layer, such as plastic, that collects the leached material as it drains through. Once the solution is collected, it can be purified to extract the valuable copper material.
While this process is efficient on its own, efficiency is greatly improved by adding an agglomeration drum to the process. Heap leaching relies on the ability of the leaching solution to penetrate through the mound, around particles.
When the ore is not properly agglomerated, fines can vary in size, severely reducing the ability for the solution to penetrate through the heap. Using a rotary drum agglomerator to agglomerate the ore fines will ensure crushed ore particles are uniform in size, making it easier for the leaching solution to travel through the channels between particles (See Figure 1). In addition to the benefit of increased percolation, adding a rotary drum agglomerator into the process also allows for an added opportunity to mix the leaching solution with the ore fines. As the ore fines are agglomerated, the solution can be sprayed throughout the drum and mixed thoroughly with the ore fines. This creates further increased efficiency benefits, as the solution can begin to concentrate around the ore fine agglomerates, furthering the efficiency of the leach.
Left: Ore fines pre-agglomeration, Right: Agglomerated ore fines
FEECO has been a leader in the agglomeration industry for over 60 years, and provides rotary ore agglomerators to heap leaching operations around the world. Our custom built, superior quality rotary drum agglomerators are robust, and built for longevity.