Mass transfer accompanied with complete reversible chemical reactions in gas-liquid systems: an overview

In many processes in the chemical industry mass transfer accompanied with reversible, complex chemical reactions in gas-liquid systems are frequently encountered. In point of view of design purposes it is very important that the absorption rates of the transferred reactants can estimated sufficiently accurate. Moreover, mass transfer phenomena can also affect substantially important process variables like selectivity and yield. Therefore large amounts of research effort has been invested in describing these processes and in the development of models that can be used for the calculation of the mass transfer rates and other parameters. The description of the absorption of a gas followed by a single first order irreversible reaction is simple and straightforward. For all mass transfer models, e.g. film, penetration and surface renewal respectively, this process can be analytically solved. For other processes however, only for a limited number of special cases analytical solutions are possible and therefore numerical techniques must be used for the description of these phenomena. Besides numerically solved absorption models the mass transfer rates often can be calculated satisfactory accurate by simplifying the actual process by means of approximations and/or linearizations. In this paper an overview will be given of the absorption models that are available for the calculation of the mass transfer rates in gas-liquid systems with (complex) reversible reactions. Both numerically solved and approximated models respectively will be treated and conclusions on the applicability and restrictions will be presented. Also perspectives and white spots will be indicated.