Gas-liquid mass transfer studies with triple impeller system on a laboratory scale bioreactor

The gas-liquid mass transfer coefficient KLa in a fermentor is known to be a strong function of the mode of energy dissipation and physicochemical properties of the liquid media. Three impeller combinations namely, single, double and triple impellers, respectively have been tested in the laboratory bioreactor (2 l) for their gas-liquid mass transfer performance. The liquid phase physico-chemical properties have been varied using distilled water, aqueous solutions of sodium carboxymethyl cellulose and simulated fermentation medium. The effects of the process variables such as the impeller speed, gas flow rate and the liquid phase physico-chemical properties on the volumetric liquid phase mass transfer coefficient of oxygen, KLa in a stirred bioreactor were investigated by static gassing out method. Correlations have been developed for the predictions of the gas-liquid mass transfer coefficient with liquids having different physico-chemical properties. It has been observed that triple impeller system gave highest values of gas-liquid mass transfer coefficient with the least power consumption.