Fine and Ultrafine Particle Separation by Ordered Pillar Arrays
- Haidong Feng
- University of Utah, USA
- Metallurgical Engineering
- Sanja Miskovic, Ph.D
- Haidong defended his thesis in September 2014
Separation of fine and ultrafine particles is a common issue in pharmaceutical, medical, oil and gas, environmental, agricultural, and metallurgical fields. Different particle separation methods have been designed and used in the past to separate or classify bulk particles based on their size, density, and shape, namely screens, cyclones, centrifuges, elutriators, gravity separators, just to name a few. Each particle separation method offers many advantages, but can be successfully applied to particle mixtures of very narrow size and densities. Furthermore, obtained separation efficiencies of ultrafine/colloidal particles, with sizes less than ~30 microns, are typically very low.
In this study, we focused on the novel size based particle separation method using ordered pillar arrays. Numerical, CFD-DEM, study is performed in different scales with particle size ranging from 5 um to 9 mm. The particle separation using different operation modes, namely gravity driven and flow driven, have been performed using different pillar array designs. The particle movement trajectories, exit positions, and residence times are recorded to calculate particle separation efficiencies.
The CFD-DEM parallel coupling simulations are performed using the EDEM and ANSYS FLUENT. The CFD solver provides the information about the flow field inside the ordered pillar array, while the DEM solver simulates the particle movements considering gravity, flow drag force, particle-particle, and particle-geometry interactions.
Feng, H. and Miskovic, S., A numerical study of particle-fluid flow in different directional locking pillar arrays, (2014), 2014 SME Annual Meeting, Salt Lake City, USA.
Miskovic, S. and Feng, H., Feasibility of fine particle separation by tilted pillar arrays – numerical and experimental study, (2014), The International Mineral Processing Congress 2014, Santiago, Chile.
In the 2x2 pillar array, the pillar diameter and the gap between the pillars are 20 µm. The fluid flows horizontally in the device with velocity v = 0.01 m/s. The 5 µm particle is carried by the fluid flow and is able to penetrate through the pillar array. The 14 µm particle is guided in the shifted direction of the pillar array.
In the same 2x2 pillar array, with the pillar diameter and the gap between the pillars are 20 µm, the fluid flows horizontally in the device with velocity v = 0.01 m/s. here the 14 µm particle is guided in the shifted direction of the pillar array.
In the 5x5 pillar array, bulk particle release is investigated. A great number of particles of different sizes and same density (2.7 g/cm3) are released at the same time. All large particles move in shifted direction, while small particles have more random trajectories, which in average travel in the direction of the gravity.
For the 15x15 pillar array, particles with sizes ranging from 1 mm to 9 mm are released continuously. Particles fall through the pillar array driven only by gravity. In this video, particle density 1.2 g/cm3 is used.
The EDEM’s CFD-DEM coupling module is a powerful tool to simulate complex multi-phase systems. The single particle movement, subjected to flow drag force, particle-particle, and particle-geometry interactions, can be predicted precisely for course, fine, and ultrafine particles under either low or high flow Reynolds numbers. The user friendly coupling interface provides the opportunity to simulate various complex particulate processes.