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UBC Theses and Dissertations

Assessing efficiency of macro particle classification using tilted structured pillar arrays Joel, Ikechukwu David


The biomedical and pharmaceutical industries have explored the use of pillar arrays for microparticle separation of cancer cells, blood cells, and droplets extensively. Over the recent years, other sectors such as the powder industry are beginning to apply devices with structured pillar arrays for particle classification due to their small footprint, passive nature, and ability to achieve multiple cut points within a single device. This thesis investigates if the structured pillar arrays can have utility for the size-based classification of macro-and mesoscale spherical glass beads and crushed ore particles. Multiple pillar array designs are evaluated in this work on a small bench-scale apparatus that allows manipulation of the array tilt angle, which is a parameter used to control the separation cut point. The experiments with target samples are conducted individually, first considering monosized glass beads and then crushed ore samples over the particle size range between 2000 and 8000 microns. The scope of this research work is constrained by the size of the structured pillar array used in this study, which is designed for coarse particle classification (>500 microns and <8 millimetres). Separation is a dry process, driven only by gravity, where the separation efficiency depends on particle-particle and particle-pillar interactions. In the current application, particle-wall interactions also play a crucial role due to the relatively small size of the separation device. Separated particles are collected from the device outlets (five distinct bins), and further quantitative analysis is done by calculating the particle recovery in each bin. Further research is carried out to determine device separation efficiency by using the partition modelling approach for the fractions of particles that underwent separation and select the most effective array design (D1, D2, D3) and tilt angle (25.6°, 30.6°, 35.6°) for the range of particle sizes considered. The experiment results showed that as the tilt angle is manipulated in an increasing order, particle separation efficiency improves with D1 and D2 but not D3. The partition model used in this research determined that the tilt angle and array design with the best separation efficiency for particles is D1 at 35.6°.

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