CONCENTRIC-TUBE AIRLIFT BIOREACTORS PART-II - EFFECTS OF GEOMETRY ON LIQUID CIRCULATION

Liquid circulation velocity was investigated in three concentric-tube airlift reactors of different scales (RIMP, V-L = 0.07 m(3); RIS-1, V- L = 2.5 m(3); RIS-2, V-L = 5.20 m(3)). The effects of top and bottom c learance and resistance in flow pathway at downcomer entrance on the r iser liquid superficial velocity, the circulation time, the friction c oefficient and flow radial profiles of the gas holdup and the liquid s uperficial velocity in riser, using water-air as a biphasic system, we re studied. It was found that the riser liquid superficial velocity is affected by the analyzed geometrical parameters in different ways, de pending on their effects on the pressure loss. The riser liquid superf icial velocity, the friction coefficient and the parameters of the dri ft-flux model were satisfactorily correlated with the bottom spatial r atio (B), gas separation ratio (Y) and downcomer flow resistance ratio (A(d)/A(D)), resulting empirical models, with correlation coefficient s greater than 0.85.