Comparing Externally Excited Gas–Fluidized Beds from Structured Bubbling Viewpoint

With a wide spectrum of applications ranging from pharma to polymers to carbon sequestration to food–processing, granular material flows are everywhere. Both dense and dilute particle-laden flows within the gas–fluidized beds act to mix the solid constituents whilst exhibiting enhanced heat and mass transport characteristics. In these systems, the free–bubbling flow regime is disordered and chaotic, rendering mathematical description difficult. Recently (e.g. Guo et al., 2021, PNAS 118, e2108647118, Coppens, M. O- et al, J. Chem. Eng. 2003, 96) have shown that this hydrodynamics can be ordered into periodic, structured, triangulated arrays of rising bubbles, by imposing external excitations, such as vertical vibration and pulsed gas flow, respectively. This phenomenon is persistent across various system widths and particle properties and thus, opens opportunities to address issues related to scaling–up. Here, we compare the performance characteristics of these two excitation mechanisms from the structured bubbling viewpoint for both unary and binary–mixtures composed of different density ratios, different particle size ratios, and across different system sizes. The bubble structuring is accurately captured using CFD–DEM simulations besides a few results from preliminary Two-Fluid Model (TFM) simulations generated. The mixing/segregation is also quantified using a mixed entropy which reveals the tendency for more mixing under optimal conditions. Finally, the optically imaged experimental data is compared with all simulation predictions, and results have vital industrial design implications by selecting the appropriate mechanism and operating conditions.