Effect of impeller vertical position on drop sizes in agitated dispersions

The effect of impeller height relative to the vessel bottom was studied by measuring the drop size distributions of kerosene dispersions in water at t wo positions inside a stirred tank. Measurements were taken at 1/3, 1/2, an d 2/3 of total vessel height for rotational speeds 250, 300, 350 and 400 RP M and for hold-up fractions 0.02 and 0.04. Results show an influence of imp eller height on drop sizes ranging from a Sauter mean diameter decrease of 7.8 % to an increase of 35 % relative to the ones obtained with the impelle r at the center of the vessel.