Effect of Gas Volume Expansion on Bubble Behavior in Fluidized Catalyst Beds

Many industrially useful reactions involve changes in the total number of moles, resulting in changes in gas volume and superficial gas velocity. These changes influence hydrodynamics of fluidized beds, particularly bubble size, a critical parameter in the design because it affects the mass transfer rates between the bubble and emulsion phases. However, the effects of gas volume changes on bubble size remain largely unexplored. In this study, the effects of increasing molar number were investigated by experimentally simulating gas volume expansion through liquid evaporation within porous particles. In a three-dimensional fluidized bed, water-impregnated particles were fluidized with air, and the resulting pressure fluctuations were analyzed. Additionally, a two-dimensional fluidized bed was used to observe bubble behavior via video recording while ethanol-impregnated particles were fluidized with air. In catalytic reactions, the gas composition in the emulsion phase differs from the feed gas. Similarly, in the liquid evaporation studied here, the gas in the emulsion phase contains water vapor or ethanol in addition to air, affecting the properties of the mixed gas and the voidage of the emulsion phase and, consequently, bubble behavior. This research investigates the impact of gas volume expansion on bubble behavior while considering these effects.