Distribution of fines during percolation segregation for varying particle bed depths

Percolation segregation mechanism is one of the most commonly observed but one of the lesser understood segregation mechanisms in powder industry. In percolation mechanism, the finer particles move downward through the pores of the coarser particles during shear and vibration. In this study, the distribution of fines during percolation segregation for varying depths of binary mixtures bed was studied during shear motion. Angular shaped potash fertilizer was selected for experimentation purpose. One absolute coarse size range of potash: 3,350-4,000 μm and two absolute fine size ranges of potash: 1,400-1,700 μm and 2,000-2,360 μm were mixed in three different mixing proportions (67:33, 50:50, and 33:67) by weight to make binary size mixtures of size ratios 2.4 and 1.7 (Coarse fine). The binary mixtures were tested for three bed depths (85 mm, 65 mm, and 42 mm) using the second generation primary segregation shear cell (PSSC-II). It was observed that for a particular mixing ratio and bed depth, majority of segregated fines were concentrated near the moving walls of shear box of PSSC-II. The segregated fines were most uniformly distributed for bed depth of 85 mm and mixing ratio of 33:67. The initial higher concentration of fines particles in the binary mixture for bed depth of 85 mm and for mixing ratio of 33:67 followed a free-fall convective segregation mechanism, resulting in uniform distribution of segregated fines across the collection pan. These qualitative observations were tested using two statistical approaches: the variance metrics and the ANOVA analyses.