POWER CONSUMPTION, IMPELLER COALESCENCE AND RECIRCULATION IN AERATED VESSELS.

In a turbine stirred aerated vessel the coalescence of recirculating bubbles with the cavity behind the blades has been determined from power measurements with and without recirculation. The contribution to the gas flow through the cavities is of the same order as the sparged gas inflow rate. The power consumption is reduced markedly as a result. For both tap water and ionic solutions the gas phase is well mixed as a result of impeller coalescence. The complexity of the relationship between impeller coalescence and operating conditions makes the simple Q/ND**3 relationship of doubtful value as a correlating variable. It is confirmed that scale up based on this group only will underestimate the power consumption of the larger system.