Influence of coalescence behaviour of the liquid and of gas sparging on hydrodynamics and bubble characteristics in a bubble column

This experimental study is aimed at investigating the effect of liquid phase properties and gas distribution on bubble and hydrodynamic characteristics in bubble columns. With the various measuring techniques used, systematic measurements of bubble size, velocity and frequency and gas hold-up are possible. Bubble size distribution and shape factors which are rarely found in literature, are also available. Water–alcohol solutions are used to simulate the behaviour of industrial non-coalescing organic mixtures. The experimental results obtained with three different spargers in the coalescence inhibiting solutions are compared with data on standard coalescing air–water system. Evolutions of bubble characteristics and gas hold-up have been interpreted successfully by considering the simultaneous influence of the hydrodynamic regime of the gas–liquid flow and of the operating regime of the distributor. It has also been put into evidence that bubble frequency measurements are good tools to evaluate distributor efficiency. The influence of the distributor has been shown to be enhanced in non-coalescing media. Bubble shape and bubble size distributions are dramatically modified by addition of minute quantities of alcohol in water. Bimodal distributions can be observed even in the homogeneous regime with orifice nozzle spargers.