Agitated vessel particle-liquid mass transfer: A comparison between theories and data

Mass transfer from suspended solids in agitated vessels has been explained by both the Kolmogoroff and the terminal velocity-slip velocity theories.It is shown that data plots using the dimensionless groupings obtained from the Kolmogoroff theory are unsatisfactory, because of the swamping effect in the groups of the enormous range of particle size as compared to the ranges of the other variables. These dimensionless groupings are misleading, since they suggest equal power input leads to equal mass transfer coefficients. Experimental evidence shows, that different impeller-vessel configurations enable complete suspension to be achieved at significantly different power inputs, whilst the mass transfer coefficient remains the same. This observation complies with the terminal velocity-slip velocity theory.However, though the fundamental concepts underlying the two theories are different, the resultant numerical values of the mass transfer coefficients are approximately the same.