Quantitative characterization of mixing of dry powders in V-blenders



Experiments were conducted to determine the effect of rotation rate, fill level, and total number of revolutions on the mixing performance of a V-blender. The experiments were performed using 66-μm red and green glass beads. Mixture uniformity was quantified after each experiment by infiltrating the mixtures with a binder, and using image analysis to examine slices of the solidfied mixture. The mixing rate (as a function of total revolutions) was not affected by changing the rotation rate between 8 and 24 rpm. The mixing rate increased significantly as the fill percentage was decreased from 60% to 40% of the total vessel volume. In a symmetric blender such as a V-blender, the rate of mixing is limited by the rate of mass transfer across the vessel plane of symmetry orthogonal to the axis of rotation. A one-parameter model based on the amount of material that crossed the plane of symmetry per revolution displayed good agreement with the experimental data.