Effect of stratified stacks on extraction and surface morphology of copper sulfides

Due to the obvious differences of particle size, the ore particle segregation and stratification like fine interlayers (FIs) widely appeared in non-agglomerated heaps. In this paper, stratified stacks were set up by inserting FIs at the top, middle and bottom positions of stack, which were named TFIs, MFIs and BFIs respectively. The effect of these fine interlayers on copper extraction, pore evolution and surface damage were studied via the CT and SEM-EDS scanning methods. The results showed that the inserted FIs could be detrimental to the extraction efficiency. The peak extraction rate reached 73.2% in C4 (a uniform coarse stack), which was obviously higher than the peak extraction rate in stacks containing FIs, especially C3 (BFIs, 58.2%). Even though the average porosities of C1 similar to C5 all increased after a 60-day leaching period, the bottom porosity of the stack tended to decrease whereas the top porosity increased, especially for the TFIs in Cl. The damage to the ores surface negatively correlated with the located depth of FIs and was classified as severe damage (TFIs), extensive damage (MFIs) and pore-dominated damage (BFIs). This result shows that selective dissolution of minerals could have much more severe consequences in TFIs than in BFIs. Ore agglomerations that formed spontaneously during the leaching process could easily be observed in regions with undeveloped porosity especially in the BFIs.