HYDRODYNAMICS AND MASS-TRANSFER STUDIES IN A PILOT-PLANT AIRLIFT REACTOR - NON-NEWTONIAN SYSTEMS

Experimental studies on the effects of surface active agents on the hy drodynamics and mass-transfer performance of a 700 dm(3) pilot-plant e xternal loop airlift reactor have been conducted. The effects of the a ddition of a silicone polymer antifoam agent on foaming caused by the viscous non-Newtonian solutions of xanthan gum and carboxymethyl cellu lose were examined. In general, the addition of the antifoam led to si gnificant reductions in all design parameters, i.e., gas holdup, liqui d circulation velocities, and volumetric mass-transfer coefficients re lative to the values determined for the air-water system. Presented in this paper are new correlations for riser gas holdup (epsilon(r)) and volumetric mass-transfer coefficient (k(1)a) with effective viscosity (eta eff) based on shear rate determined in this reactor. Also, it wa s found and/or confirmed that the geometric parameter A(d)/A(r) and V- sg had the most effect on the nonadjustable parameters such as riser a nd downcomer gas holdup, superficial liquid velocity, and specific int erfacial area. The disengagement section design has a profound effect on the rate of foaming.