Study on Residence Time Distribution of Particles in a Quasi-Two-Dimensional Batch Discharge Silo Using the Multi-Simulation Averaging Method

Abstract

As the primary carrier for storing and transporting particles, the silo is widely used in the production process. The RTD is a promising method for studying the silo discharge process and has not been studied enough. This paper presents a study on the residence time distribution (RTD) and flow pattern of particles in a two-dimensional flat-bottom batch discharge silo under gravity using experiments and the discrete element method (DEM). Meanwhile, a multi-simulation averaging method is proposed to eliminate local fluctuations in the residence time. The results are as follows. The mean flow rate is 16.85 g·s−1 in simulations, which is only 2.7% larger than the experimental value. In the central area of the silo, the residence time contour lines take on elliptical shapes and the trajectories of particles are straight lines. The particles are distributed along the elliptical residence time contour lines all the time during the discharge process until they flow out of the silo. The particles near the side wall of the silo swiftly flow with a constant acceleration to the central line of the silo along the upper horizontal surface, which has become avalanche slopes, and then flow down the outlet together with the particles in the radial flow region. In this study, an elliptical distribution law during the silo discharge process was funded for the first time. An improved radial flow model was proposed with a higher accuracy and clearer physical meaning, which will be helpful in silo design and scaling up in industrial applications.