Spouted fluidized beds offer improved mixing and mass transfer performance needed for numerous process applications. In this work, the coupled computational fluid dynamics and discrete element method approach is used to study particle movement and mixing dynamics in a double-spouted fluidized bed considering five spout separations (10–50 mm) and three spouting velocities. The results indicate that at low spout velocities (10 m/s ≈7.4 Umf), there is little particle motion, while intermediate velocities (20 m/s ≈14.7 Umf) produce intermittent bursts of transverse movement, marking the onset of effective mixing. At higher velocities (30 m/s ≈22.1 Umf), vigorous and sustained large-scale convective flow and rotational motion emerge, promoting super-diffusive transport and efficient homogenization, with velocities expressed relative to the minimum fluidization velocity, Umf, of the bed. The spout separation distance is shown to play a critical role: small separations lead to merged, confined spouts with poor mixing; intermediate separations (20–30 mm) optimize inter-spout interactions and mixing efficiency; while large separations make the spouts behave independently, reducing overall mixing effectiveness. Analysis of the pressure drop signals using the Hilbert–Huang transform highlights dominant frequency bands and localized oscillations underpinning these dynamics. Overall, this work elucidates the cooperative interaction between spouting velocity and spout separation distance in balancing large-scale convection and small-scale diffusion in spouted fluidized beds, providing valuable guidance for optimizing operating conditions to achieve maximal mixing efficiency and process performance.
Radouan Boukharfane (Wed,) studied this question.