Drop size distribution in batch stirred tank at high organic to aqueous phase ratios

Abstract

Hydrodynamic studies were carried out at high organic to aqueous (O/A) phase ratios in a liquid-liquid batch stirred tank. Minimum mixing speed for complete dispersion, Sauter mean diameter, and drop size distribution have been measured with Rushton turbine and pitched blade turbine for three different liquid-liquid systems. Experiments have been performed at various impeller speeds and organic-to-aqueous phase ratios. Minimum mixing speed for complete dispersion (Nmin) was measured by visual observation as well as by sample withdrawal technique. Surfactant stabilization technique has been used to measure the drop size. Minimum mixing speed was found to be strongly dependent on impeller type and organic-to-aqueous phase ratios. About 10–40% decrease in minimum mixing speed was observed when organic to aqueous phase ratio was increased from 10 to 50. Sauter mean diameter was significantly affected by impeller speed, physical properties of the liquid systems, and dispersed phase holdup. Experimental drop size distributions were fitted with the log-normal distribution. Empirical correlations have been developed to predict minimum mixing speed and Sauter mean diameter at various operating conditions. Absolute Average Relative Error for the prediction of minimum mixing speed and Sauter mean diameter using developed correlations were found to be 18.45% and 11.06%, respectively.