Due to their anisotropic permeability for different particle sizes, ordered tilted pillar arrays have shown a high potential for effective particle separation based on size. The key factors controlling the particle separation efficiency in such arrays include viscosity and velocity of the carrying fluid, particle size and density, and pillar arrangement. In this study, particle separation dynamics in different tilted pillar arrays is investigated using coupled computational fluid dynamics – discrete element method (CFD-DEM) approach. Simulations are carried out using a 12x20 pillar array with a fixed tilt angle of 26.5˚. Particles with sizes ranging from 1 to 9 mm are released from the top of the pillar array filled with water, and both fluid drag and gravitational forces are considered. Particle trajectories and exit positions are obtained for particles with three different densities (1.2, 2.7, and 7.6 SG) and resulting residence times are calculated.
To validate numerical findings, a lab-scale device is built and particle movement inside six different pillar arrays is recorded. Spherical particles with three different densities (1.2, 2.7, and 7.6 SG) and five discrete sizes (1, 2, 3, 4, and 5 mm) are used. The effects of particle size, particle density, fluid velocity, and fluid viscosity on particle movement dynamics and residence times are studied and compared with numerical results.
It is found that both particle density and pillar array tilt angle affect particle separation performance. Particle diffusion within pillar array is shown to increase significantly with an increase in particle density and particle loading rate. Finally, an increase in fluid viscosity is found to dampen random collisions between particles and pillars and, therefore, improve the separation efficiency.
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