Modelling of gas-liquid reactors - implementation of the penetration model in dynamic modelling of gas-liquid processes with the presence of a liquid bulk

Analytical solution of models for gas-liquid reactors is restricted to a few asymptotic cases, while most numerical models make use of the physically less realistic stagnant film model. A model was developed that simulates the dynamic behaviour of gas-liquid tank reactors by simultaneously solving the Higbie penetration model for the phenomenon of mass transfer accompanied by chemical reaction and the dynamic gas and liquid phase component balances. The model makes it possible to implement an alternative for the well known Hinterland concept, which is usually used together with the stagnant film model. In contrast to many other numerical and analytical models the present model can be used for a wide range of conditions, the entire range of Hatta numbers, (semi-)batch reactors, multiple complex reactions and equilibrium reactions, components with different diffusion coefficients and also for systems with more than one gas phase component. By comparing the model results with analytical asymptotic solutions it was concluded that the model predicts the dynamic behaviour of the reactor satisfactorily. It is shown that under some circumstances substantial differences exist between the exact numerical and existing approximate results. It is also shown that for some special cases, differences can exist between the results obtained using the stagnant film model with Hinterland concept and the implementation of the Higbie penetration model. (C) 2000 Elsevier Science S.A. All rights reserved.