Construction of Heap Leaching

The formation of the heap leaching is a critical point in the operation, which requires cares, not only for avoiding damages on the floor, but also to aobtain a porous and permeable bed where the particles will be uniformly distributed by size. The mineral can be deposited over the floor with a belt, truck or frontal loader. In the two last cases, the mineral remains more or less homogenous, but the loading with a blet (stacker type) normally produces a natural segregation, acumulating the fine material in the points of unloading, while the thick fragments roll in cascades. The resulting heap leaching stays with preferential routes of percolation in the areas of thick material, with scarce penetration of the solution in areas of low permeability where the fines have been concentrated.

An interesting technique described by Chamberlin (3) consists in depositing the mineral by layers, according to the natural angle of rest, being for such effect emptied in the top border of the heap leaching with the objective of making it roll in a cascade style by the pendant. Until a certain height (4 or 5 m.), the mineral can be placed with a frontal loader, but for superior heights, the transit of vehicles over the heap leaching is made necessary. In such a case, with the intention of minimizing the compactation of the bed, the mineral is first unloaded in a special place and, afterwards, pushed until the border with a leveller equipped with rockets, of higher surface of upholding. The material must previously be moistened, or aglomerated if it were necessary, to avoid the segregation by size.