Experimental and empirical investigation of mass transfer enhancement in multi-scale modified airlift reactors

Abstract

The modified airlift reactor (MALR) was previously developed to enhance the oxygen transfer coefficient, KLa by optimizing internal configurations and operational conditions. Although MALR mass transfer and gas–liquid hydrodynamic performance have been investigated, scaling has not yet been examined. Therefore, this work studies scale effects and defined scaling criteria to construct empirical correlations for multi-scale MALRs. Five different MALR working volumes or scales were examined (2.2, 4.4, 6.6, 17.5, and 140 dm3) in similar geometries. The results of scale effect on KLa and hydrodynamics showed that every MALR scale provided better KLa compared with regular reactors. Moreover, 1.1- to 1.6-fold higher KLa was obtained from the 140 dm3 reactor compared with 17.5 dm3. Scaling criteria analysis was divided into three types: multi-dimensional, liquid height, and combined processes. The KLa coefficient was defined as the scaling criteria compared to investigated parameters, i.e., oxygen transfer rate and efficiency, and aeration efficiency, for all three scaling types. Thus, KLa prediction correlations were constructed with respect to reactor configuration and operating conditions. KLa was well presented by all considered models, with R2 = 92–99% and discrepancy = 10–20%.