Errors in the determination of mass transfer in gas-liquid dispersions

Mass transfer behaviour of gas-liquid dispersions is usually characterized by the volumetric mass transfer coefficient β_La. For its experimental determination various methods exist which can be grouped into stationary and instationary (dynamic) methods. Very often volumetric mass transfer coefficients published in literature show surprisingly large scattering and divergence which cannot be explained by differences in properties of the systems. In order to find possible causes for these inconsistencies in experimental results, the two types of methods have been subjected to an analysis of errors. It is shown that deviations of real from assumed mixing behaviour in both phases as well as rather small errors in the concentration of the liquid phase may result in deviations up to a factor of 5–10. This may also be the case in the evaluation of results obtained by the dynamic method, if the approximations used are too rigorous. The limits of applicability of the two methods are discussed.