Influence of alcohol addition on gas hold-up in bubble columns: Development of a scale up model

Measurements were carried out in bubble columns with diameters of 0.1, 0.15 and 0.38 m with air-water system to which ethanol was added in concentrations ranging from 0.03-1 volume %. Alcohol addition results in a significant increase in the gas hold-up, ϵ. This increase in ϵ can be attributed to a delay in the point of transition from homogeneous to heterogeneous flow regime. The model of Krishna et al. (Chem. Eng. Sci., 54, 171 (1999)) was found applicable for the range of column diameters studied, after accounting for the influence of alcohol addition on the regime transition parameters.