Vibration-induced dynamics of granular materials in the vibro-compaction of carbon anodes

Vibro-compaction is a key stage in carbon anode production for aluminum manufacturing, where vertical vibration is used to rearrange particles, increase density, and enhance homogeneity. To simulate this process, we experimentally investigate the flow dynamics of representative dry and wet granular materials in a transparent container subjected to vertical vibration. Mixtures of calcined petroleum coke particles and glycerin simulate the behavior of anode paste. Using ultra-high-speed imaging, we analyze the effects of particle size, concentration, and vibration amplitude on flowability, characterized by bulk average height, angle of repose, frequency ratio, and phase lag. Our findings reveal a non-monotonic effect of particle concentration on the average height and angle of repose, with a peak at 85% concentration. In addition, increasing particle concentration decreases energy transfer efficiency between the vibration table and the material, resulting in complex subharmonic responses with significant deviations from sinusoidal behavior, particularly at higher vibration amplitudes. These subharmonic responses are visualized as so-called multi-loop Lissajous patterns, which describe the motion of the bulk material relative to the vibration table. Our findings enhance understanding of vibro-compaction and have implications for other vibration-based industrial processes, including pharmaceuticals, food processing, sediment transport, and powder metallurgy.