Effect of solids on gas-liquid mass transfer and bubble characteristics in three-phase systems

Abstract

The effect of the solids on the mass transfer characteristics in a bubble column was studied experimentally for the system air/water/beads of calcium alginate. Volumetric liquid side mass transfer coefficient, kLα, specific interfacial area, α, and liquid side mass transfer coefficient, kL, were determined under different solid concentrations, gas flow rates and solid sizes. Bubble characteristics were obtained using an image analysis technique. The presence of solids affect negatively kLα, decreasing both α and kL and the effect is more pronounced for the smaller particles. For these particles the variation of kLα is due to the variation of its two components, while for larger particles kLα variation is due, essentially, to changes in kL as no significant differences in α were observed. An optical probe technique was also used to obtain gas holdup radial profiles for higher solids loadings and gas flow rates. It was observed that increasing the solids loading, the gas holdup decreases and the shape of the gas holdup profiles is also influenced by the solids concentration.