Hidrodynamics, heat and mass transfer characteristics of three-phase fluidized beds of floating bubble breakers

Abstract

Hydrodynamic properties (phase holdups, wake to mean bubble volume(k), local gas phase holdup, bubble chord length), gas-liquid interfacial area, heat transfer and mass transfer characteristics in three-phase fluidized beds with and without floating bubble beakers ($\rho$f:1,500-2,280 kg/$m^3$, Vf: $2.03.85\times10^{-6}m^3$) have been determined in a 0.142 m-ID $\times$ 2.0 m-high Plexiglas column. The flow pattern of floating bubble beakers and bubble breakage phenomena by the beakers in the beds have been studied by using the photographic technique in a 2-dimensional acryl column (0..25 m-thickness $\times$ 0.44 m-width $\times$ 1.80 m-height). The effects of superficial velocities of gas (0.0-0.20 m/s) and liquid phases (0.02-0.10 m/s), particle size (0.0-6.0 mm) and the volume ratio of floating bubble beakers to solid particles (0.0-0.030), properties of floating bubble beakers (density, contact angle, projected area) and of liquid phase (surface tension) on phase holdups, wake to mean bubble volume (k), local gas phase holdup, bubble chord length, gas-liquid interfacial area, heat transfer and mass transfer coefficients have been determined. In the bubble coalescing regime, three-phase fluidized beds having the volume ratio ($V_f/V_s$) of 0.15 produced a maximum increase in heat transfer coefficient of about 20\% in comparison to that in the beds without floating bubble beakers. Also, beds having a volume ratio ($V_f/V_s$) of about 0.15 showed a maximum increase in both the volumetric mass transfer coefficient ($k_1a$) and gas-liquid interfacial area (a) of about 40\% in comparison to those in the corresponding bed without floating bubble beakers. The bed porosity in the bubble coalescing beds without floating bubble beakers decreases with increasing gas velocity up to around 0.04 m/s, thereafter, it increases with an increase in gas velocity. In contrast, the bed porosity in the bubble disintegrating beds increases with increasing gas velocity from 0.0 to...