Mass transfer with complex chemical reaction in gas-liquid systems - I. Consecutive reversible reactions with equal diffusivities

A fundamental description of gas-liquid mass transfer with reversible conse cutive reaction has been derived. The Higbie penetration theory has been us ed and numerical simulations were carried out for isothermal absorption. Al though the model can be adapted to reactions of general stoichiometric and kinetic orders, results in this paper have been limited to unit orders only . The model has been applied for a wide range of process conditions to inve stigate the effect of reversibility of both reaction steps and the effect o f the use of (partially) loaded solutions on the mass transfer characterist ics. For consecutive reactions with both steps irreversible, the approximat e solutions of Onda (1970, 1972) have been found to be sufficiently accurat e (maximum deviation of 4.3 % for the penetration theory solution). It has also been shown that the overall enhancement factor can be regarded as the summation of the enhancement factors of the individual reaction steps. This has been quantitatively shown for the case where the first step is irrever sible while the second is reversible. Finally, an approximate technique to determine infinite enhancement factors for reversible consecutive reactions has been given. This approximation is based on the method described by DeC oursey (1982). Deviations from numerical calculations for both loaded and u nloaded solutions were found to be less than 1.3%. Part I of this paper dea ls with the case of equal diffusivities of the chemical species involved wh ereas the effect of unequal diffusivities on the overall absorption rate an d enhancement will be dealt with in Part II. (C) 1998 Elsevier Science Ltd. All rights reserved.