Flow of non-spherical particles within a belt-driven hopper: simulations and experiments*

The repeatable, steady mass flow rate of pellets is desired in order to maintain a consistent energy conversion or provide the required rate of reactant for a chemical process. A discrete element method was used to model pellet-shaped granular flow within a bottom-driven conveyor belt as a function of the exit area; the size of the opening fluctuates as a result of the conveyor flights passing through the exit. Simulations and experiments were evaluated to demonstrate that greater uniformity in mass flow rates are possible with smaller opening area. The limitation in exit size due to the flights passing through the exit causes some circulation within the hopper reducing the efficiency of the transport process. Larger openings resulted in gravity dominated flow rather than the control via the belt speed. Frequency analysis of the fluctuations of the mass flow rate indicate correlation with the velocity of the flights on the belt. Simulations also considered the orientation of the 3:1 aspect ratio pellets showing the pattern of plug flow transitioning to pseudo-stationary material on top of the storage hopper. The overlapping performance of experiments confirmed the predictive nature of simulations to aid design of future poly-disperse systems of non-uniform materials.