Hydrodynamics and mixing in highly viscous pseudo-plastic non-Newtonian solutions in bubble columns

Abstract

Gas hold-up structures in highly viscous pseudo-plastic carboxymethyl cellulose (CMC) solutions were measured in 0.10, 0.20, 0.38 and 1.0 m diameter batch bubble columns. A correlation for the gas hold-up based on a large number of data and covering a wide range of viscosities and column diameters is presented in the churn turbulent regime. εG=0.171 V_G^0.6μ_eff^−0.22D^−0.15. A flow transition chart for the churn turbulent and slug flow regimes is also presented for highly viscous pseudo-plastic solutions. Transient conductivity measurements were carried out in 0.20 and 0.38 m i.d. bubble columns with CMC solutions to measure mixing time. A "tanks in series with interstage recirculation" model was used to predict mixing times in the churn turbulent regime. Reasonably good agreement was found between the predicted and experimental values of mixing time.