An innovative device for quantification of percolation and sieving segregation patterns - Single component and multiple size fractions

Segregation occurs during most particulate materials-related unit operations including mixing, conveying, discharging, filling, and compaction. A redesigned second-generation primary segregation shear cell (PSSC-II) was fabricated to simulate and quantify percolation and sieving mechanisms-based segregation. Several binary mixtures were tested to quantify the effect of size ratios and absolute size. The constituents of binary mixtures studied were spherical glass beads. Three binary size ratios, 4:1, 6:1, and 8:1, were tested. For a given size ratio, three different absolute coarse (710-850, 1000-1200, and 1400-1700 μm) to fine particle sizes were studied. The experimental results showed that the PSSC-II was capable of quantifying segregation potential for various materials. Several physical parameters such as segregation rate (SR), phase of segregation rate (PSR), distribution of segregation rate (DSR), maximum segregation rate (MSR), and normalized segregation rate (NSR) were created to describe the quantity of segregation to a certain level. It was concluded that: (1) Generally, the segregation rates increase with the increase in size ratio. A linear relationship between NSR and size ratio exists for glass beads (R² = 0.99). (2) Segregation rate also increases with absolute size. NSR increases linearly with absolute size for glass beads (R² = 0.99). Furthermore, a quantitative relationship exists between certain size ratios and segregation rates, i.e., while size ratio increased two-fold from 4:1 to 8:1, the NSR increased approximately six-fold. (3) The largest magnitude of the NSR occurred where both absolute size and size ratio were at their largest values. (4) The DSR for the binary mixture of glass beads was mainly concentrated in the center region of the shear box for larger size ratios such as 8:1 and 6:1, whereas, for smaller size ratios such as 4:1, the DSR is approximately uniformly distributed. (5) Both duration of lag phase (DLP) and duration of acceleration phase (DAP) decrease with increase in size ratios and in absolute sizes. The smaller the DLP and DAP, the larger the MSR.