(2)Penetration depth and unleached core area within large zinc ore particles

摘要

The economics of heap leaching are strongly governed by the trade-offbetween the slow rate and limited extent of leaching from large particlesand the cost of ore crushing. X-ray Computed Tomography (CT) was used tofollow the progression of Zn leaching in a number of individual largesphalerite ore particles, which were subjected to a long-term simulatedheap bioleaching environment. The ore was prepared by two differentmodes of comminution-HPGR (at 45, 90 and 120 bar) and cone crusher andindividual particles were selected from three different size fractions.Investigation of the reacted fraction of Zn vs. distance from the center ofeach particle indicated that leaching from large particles leads to nearcomplete conversion close to the surface, but only partial conversion in thezones that are closer to the center of particles. The cores of the conecrushedparticles show hardly any conversion at all, especially in the largerparticle sizes. The results indicated that the penetration depth (Pd) is afunction of both the comminution mode and the particle size/radius (R).Density of cracks and particle porosity are important in increasing thepenetration depth, and these characteristics are more pronounced inHPGR-crushed particles.