Hydrodynamics and flow regimes in external loop airlift reactors

The hydrodynamic behaviour of airlift reactors strongly depends on the flow regime in the riser. Representing the slip velocity of the gas as a functi on of the overall fluid velocity (U-gr + U-lr) in the riser of an airlift r eactor allows to distinguish between homogeneous and heterogeneous flow reg imes. The transition between the flow regimes depends on the resistance to liquid circulation; this resistance has been varied by changing the downcom er diameter and by inserting a valve on the downcomer. The flow regime also strongly depends on the initial gas distribution and on the size of the pl ant: improving the sparger and increasing the column height lead to a more homogeneous flow. This is confirmed by estimating the parameters of the cla ssic Zuber and Findlay model for the present results and for these of liter ature. (C) 1999 Elsevier Science Ltd. All rights reserved.