MASS-TRANSFER STUDIES IN PNEUMATIC REACTORS

Local mass transfer studies have been carried out in an external loop airlift reactor and indicated the existence of significant non-uniform ities in aeration capacity in the various sections of the reactor. The traditional assumption of a single well mixed unit with a single k(L) a value for external loop airlift reactors was found to be poor and c annot represent adequately the reactor as a whole. The liquid head in the gas/liquid separator was found to have a significant negative effe ct on the local mass transfer coefficient k(L) a. Visualization of flo w patterns showed the existence of strong vortices in the riser and do wncomer which contributed to a reduction in local aeration capacity. M ass transfer experiments in an aerated tank showed that the aeration c apacity can be reduced by half in viscous media but improved significa ntly in the presence of salts.