Diluted alcohol solutions in bubble columns and draft tube airlift reactors with a single orifice sparger: Experiments and simple correlations

Abstract

BACKGROUND: Bubble columns (BCs) and airlift reactors (ALRs) have important applications as bioreactors, chemical reactors and as contactors in waste-water treatment. The liquid phase properties in these reactors significantly influence the main hydrodynamic and mass transfer characteristics. Dilute alcohol solutions can be used to simulate real industrial systems in bioreactors. However, only a few research studies have considered such systems. The aim of this paper is to broaden the existing experimental data related to the influence of alcohol addition on themain characteristics of draft tube airlift reactors (DT-ALRs), and to propose simple correlations for their prediction. RESULTS: New experiments were conducted in a DT-ALR with a single orifice sparger, and with dilute aliphatic alcohol solutions from methanol to n-octanol. Also, simple correlations were developed to predict the gas hold-up and volumetricmass transfer coefficients in BCs and DT-ALRs, but also the downcomer liquid velocity and liquid circulation time DT-ALRs with single orifice sparger and dilute alcohol solutions. The proposed correlations included, in addition to the superficial gas velocity, the surface tension gradient as the only factor to characterize the liquid phase. CONCLUSIONS: General conclusion can be made that the gas holdup increased, but the downcomer liquid velocity decreased in a DT-ALR, with increase in surface tension gradient of the alcohol solutions. Also, very good agreement was achieved between experimental and calculated data, by applying the developed correlations, with relative average errors less than 5%, except for gas hold-up, where it was in the range 8-32%. © 2009 Society of Chemical Industry.