On the scale-up of external loop airlift reactors: Newtonian systems

Hydrodynamic and mass transfer experiments have been carried out in three g eometrically similar external loop airlift reactors. The ratio of the cross -sectional area of the downcomer to riser, i.e., A(d)/A(r) is used as a sca le-up factor to distinguish the reactors (i.e., A(d)/A(r) = 0.25, 0.44 and 1.0 for the small, medium and large reactors respectively). At constant gas throughputs, increasing the area ratio results in an increase in liquid ci rculation velocity and reduction in both gas hold-up and mass transfer coef ficient. New empirical correlations which incorporate the most important pa rameters that affect the performance of airlift reactors have been develope d for gas hold-up, liquid circulation velocity and volumetric mass transfer coefficients. The predictions of the proposed correlations compare favoura bly with the present experimental results for all reactors. (C) 1998 Elsevi er Science Ltd. All rights reserved.