Volumetric mass transfer coefficient, power input and gas hold-up in viscous liquid in mechanically agitated fermenters. Measurements and scale-up

Abstract

Transport characteristics such as volumetric mass transfer coefficients, kLa, power input, P and gas hold-up, εG, are the key parameters in the design of mechanically agitated gas-liquid contactors. For their successful design, values of the key parameters can be estimated using empirical correlations. The goal of this work is to complete a complex study to investigate the behavior of kLa, P and εG in multiple-impeller vessels in non-coalescent viscous batch. We used the dynamic pressure method (DPM).The experiments were conducted in multiple-impeller vessels of both laboratory and pilot-plant scale, which enabled the scale-up studies. Several impeller types with different diameters and their combinations on a common shaft were used in the vessel, under various impeller tip speeds and gassing rates. For all impeller combinations, the gassed and ungassed power consumption, gas hold-up and volumetric mass transfer coefficient were measured in viscous batch.The measured transport characteristics were summarized into correlations. Several literature correlations were judged, using these extensive datasets. In addition to this, new correlation shapes were also established. The correlation given by and PgVL=K1PuVLK2vsK3 gave fairly good prediction of the impeller power. The correlation of this shape can also be employed to calculate the power dissipated in the bottom and upper stages of the multiple-impeller vessel.Correlation εG=K1PgVLK2vsK3, based on the theory of isotropic turbulence was shown to be reliable for various impeller types.For non-coalescent viscous batch, it is worth using correlation based on power dissipation kLa=K1(PTOT)K2vsK3 This correlation shape can be used to predict transport characteristics in industrial-scale vessels under a wide range of operational conditions.