Bubble breakage phenomena, phase holdups and mass transfer in three-phase fluidized beds with floating bubble breakers

Abstract

The individual phase holdups and mass transfer characteristics in three-phase fluidized beds with different floating bubble breakers have been determined in a 2.0 m high Plexiglas column of inner diameter 0.142 m. The bubble breaking phenomena by the breakers have been studied via a photographic method in a two-dimensional Plexiglas column. The volumetric mass transfer coefficient k L a in three-phase fluidized beds with hexagonal-shaped breakers is up to 40% greater than that in beds without floating bubble breakers. The bed porosity ε L + ε g, gas-phase holdup ε g, and volumetric mass transfer coefficient k L a increase with an increase in the volume ratio of floating bubble breakers to solid particles, V f/ V s, up to around 0.15, and thereafter decrease with V f/ V s in three-phase fluidized beds with floating bubble breakers. Also, k L a increases with increasing breaker density, projected area and contact angle between the floating bubble breakers and the water. The volumetric mass transfer coefficients in terms of the Sherwood number in three-phase fluidized beds with the various floating bubble breakers have been correlated with the volume ratio of floating bubble breakers to solid particles, the particle Reynolds number based on the local isotropic turbulence theory and the modified Weber number.