Distributions of fines during percolation segregation for varying bed depths in binary size mixtures of potash

The distribution profiles of percolated fines in binary size mixtures of blended fertilizer were evaluated during shear motion. Of the three main constituents used for preparing fertilizer blends, urea (near spherical shape), phosphate (somewhat aspherical), and potash (angular), potash was selected for experimentation because it is much more prone to segregation due to its angular shape. Based on particle size distribution of low analysis blends (such as 10-10-10), which are known to segregate, two absolute coarse size ranges of potash 3,500-4,000 μm and 2,800-3,500 μm, and three fine size ranges 2,000-2,360 μm, 1,700-2,000 μm, and 1,400-1,700 μm, were used to prepare binary mixtures. In all three different mixing proportions (coarse:fine = 67:33, 50:50, and 33:67) by weight of size ratios (coarse:fine particle size) 2.4, 2.0, 1.7, and 1.4 were formulated. 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) at two strains (6% and 2%). At both strains, for all the size ratios and bed depths, the majority of segregated fines were concentrated near the moving walls of the shear box of PSSC-II. For size ratio of 2.4 at 6% strain, the segregated fines were most uniformly distributed for a bed depth of 85 mm and mixing ratio of 33:67 based on ANOVA and variance metrics analyses. Similar results were obtained for other size ratios at both strains.