Feedstream jet intermittency phenomenon in a continuous stirred tank reactor

A feedstream jet intermittency phenomenon and its onset conditions in a con tinuous stirred tank reactor are detected for the first time using a laser sheet induced fluorescence visualisation technique. The aim of the present investigation is to determine the operating conditions for which the interm ittency phenomenon occurs in stirred tank reactors The jet intermittency pa rameters studied are: stirrer type (Rushton and 45 degrees pitched blade tu rbines, profiled Mixel TTP propeller), stirrer rotational speed, fluid visc osity, feeding rate and the feed point location in the tank. In the case of the Rushton turbine stirred tank reactor, diagrams of intermittency occurr ence are reported. These diagrams represent the feeding jet velocity as a f unction of specific power input or local fluid velocity in the tank. It was not possible to derive from these diagrams any valuable correlation. In or der to predict and scale-up the occurrence of intermittency in industrial s tirred reactors, dimensionless correlations characterising intermittency oc currence in these devices have been modelled for the three types of stirrer s. The dominant variables determining the occurrence of intermittency is th e ratio of the jet velocity v(J) to the tip velocity v(tip). (C) 1999 Elsev ier Science S.A. All rights reserved.