E Hashtochahar - Department of Chemical Engineering, school of Chemical, Gas and Petroleum Engineering, Semnan University, semnan, Iran.
A Haghighi Asl - Department of Chemical Engineering, school of Chemical, Gas and Petroleum Engineering, Semnan University, semnan, Iran.
S . J Safdari - Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, Iran.
M Napeida - Department of Chemical Engineering, school of Chemical, Gas and Petroleum Engineering, Semnan University, semnan, Iran.

Characteristic velocity was obtained in a pilot plant Hanson mixer-settler extraction column of seven stages using three systems. In this paper, a set of previous characteristic velocity models presented in the past literatures were examined. Comparison between these models and the experimental results showed that although some of these equations may have satisfactory results, but they have to be more accuracy for design. So, a model for prediction of slip velocity was suggested in terms of total holdup and characteristic velocity which depends onphysical properties of liquid systems and operating variables. The comparison of experimental values of slip velocity was demonstrated good agreement with results of proposed model.

Slip velocity, characteristic velocity, dispersed phase holdup, Hanson mixer-settler