Effect of particle and fluid properties on the pickup velocity of fine particles

Systems involving fluid–particle flows are a key component of many industrial processes, but they are not well-understood. One important parameter to consider when designing a conveying system is pickup velocity, the minimum fluid velocity required for particle entrainment. Many theoretical and experimental analyses have been performed to better understand pickup velocity, but there is little consistency with regard to system conditions, fluid properties, and particle characteristics, which makes comparisons between these studies very difficult. Although the proper design of many conveying systems requires the utilization of expressions that are applicable across a broad range of operating parameters, most expressions are system specific, which means that they are not extendable to other conditions. Also, there is currently an absence of a universal expression to predict particle entrainment in both gases and liquids.In this work, the pickup velocity of glass spheres, crushed glass, and stainless steel spheres in water has been measured for particles less than 450 μm. The effects of particle size, particle shape, and particle density are discussed and compared to the pickup velocity trends previously determined for similar gas-phase systems. In addition, the experimental data are used to assess an existing force balance model previously developed for gas-phase systems.

The pickup velocities of various particles in water were experimentally measured and compared to gas–solids pickup velocities for the same particle types. Fluid type affects interparticle, buoyancy, and lift forces, resulting in a shift in the pickup velocity curves. The effects of particle size, shape, and density are explored and a simple force balance model is also discussed.Figure optionsDownload as PowerPoint slide