THE ROLE OF NONIDEAL PHENOMENA IN INTERFACIAL MASS-TRANSFER WITH CHEMICAL-REACTION

The work investigates the role of non-ideality in interfacial multicom ponent mass transfer with chemical reaction. These effects are produce d by two different mechanisms. First non-ideal thermodynamics must be considered for the mixture, since it may affect both the diffusion rat e (the true driving force for diffusion being the chemical potential g radient) and the reaction rate. Moreover, the diffusion coefficients m ay vary with composition, due to the intrinsic kinetics of diffusion. In order to estimate the magnitude of these effects, approximate analy tical solutions are developed for the two extreme cases of fast bimole cular reactions, that is, pseudo first order and instantaneous reactio n, considering rather dilute mixtures. The diffusion process has been modelled through the generalised Maxwell-Stefan equation. For the pseu do first order reaction regime previous results by Valerio and Vanni [ 9] indicated that the main perturbation, with respect to the ideal cas e, was due to the modification of the reaction rate caused by non-idea l thermodynamics. This perturbation was analysed in detail and was sho wn to increase strongly with the Hatta number. In the instantaneous re action regime the obtained solutions confirm that the composition depe ndence of the diffusion coefficients has usually a small effect and th at the role of non-ideal thermodynamics may be significant only in the presence of very highly non-ideal systems.