Effect of Highly Viscous Non-Newtonian Liquids on Gas Holdup in a Concurrent Upflow Bubble Column
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia;
tel.: +386 1 24 19 514; fax: +386 1 24 19 530
In a bubble column the effect of gas velocity and consequently the effective viscosity of the selected non-Newtonian liquids on gas holdup as the most important hydrodynamic parameter was studied. Experiments were carried out in a bubble column of 0.14 I. D. and 2.4 m of total height. A perforated plate served as the gas distributor. The column operated in a two-phase concurrent upflow mode and also as the liquid-batch. Different concentrations of aqueous solutions of carboxyl methyl cellulose and xanthan took the role of non-Newtonian liquids, and air was used as the gas phase. Due to the experimental conditions most of these experiments were taken in the heterogeneous hydrodynamic regime. The superficial gas velocity affected the gas hold-up most, for both polymer solutions, while the impact of the effective viscosity was much more pronounced in the case of xanthan solutions. The liquid flow rate showed a minor effect on the measured parameter. Finally, empirical correlations for the gas holdup prediction as a function of gas velocity and effective viscosity of the liquid were developed for CMC solutions. The xanthan solutions exhibit a more complex dependence on the prevailing effective liquid viscosity, which still needs to be studied.
Keywords: Bubble column, non-Newtonian liquids, gas holdup, cocurrent upflow