Effect of liquid phase rheology and gas–liquid interface property on mass transfer characteristics in bubble columns

Abstract

Gas–liquid mass transfer in non-Newtonian fluid systems is important in many chemical and biochemical processes. Having a good understanding of gas–liquid mass transfer contributes to achieving the optimization of design and the energy-efficient operation. The mass transfer performance in tap water and carboxyl methyl cellulose (CMC) aqueous solutions with different weight percentages (0.3wt%, 0.4wt%, 0.5wt% and 0.6wt%) were investigated experimentally. The CMC aqueous solution was shear-thinning non-Newtonian fluid. In this study the apparent viscosity of the solutions ranged from 0.01 to 0.1Pas. As expected, the liquid phase rheology had a great effect on the gas–liquid mass transfer performance. The volumetric mass transfer coefficients in CMC aqueous solutions were much smaller than those in tap water, and the value decreased from 3.04×10−3s−1 to 2.8×10−4s−1 with the increase of the weight percentage of CMC aqueous solutions. The mobility of the gas–liquid interface in tap water and CMC aqueous solutions was identified by the dimensionless diameter number. It was found that the mobile gas–liquid interface prevailed in tap water, while bubbles behaved as rigid particles in relatively high weight percentage of CMC aqueous solutions (0.5wt% and 0.6wt%). The liquid film mass transfer coefficient could be approximated by theories for mobile and immobile gas–liquid interfaces in tap water and CMC aqueous solutions, respectively. Based on the liquid phase rheology and the mobility of the gas–liquid interface, the dimensionless correlations were proposed to describe the mass transfer process in Newtonian and non-Newtonian fluids.