Penetration model for absorption with chemical reaction in the presence of heat generation, bulk flow and effects of the gaseous environment

A penetration model for gas absorption into a laminar liquid stream in the presence of chemical reaction and large heat generation was investigated theoretically, accounting for the presence of the gaseous environment, not considered in previous analyses, as well as the transverse bulk flow contribution to the total mass transfer. A complete formulation was performed which is based solely upon the conservation equations in both phases with the appropriate matching conditions at the gas-liquid interface. A boundary layer model was assumed for the fluid mechanical behaviour of the gaseous surroundings. The liquid stream initially had a uniform velocity in the axial direction. After being exposed to the absorbed gas, the flow field in the liquid stream was found to conform with a uniform axial velocity along with a transverse component, solely dependent on the axial distance. The numerical solution was demonstrated for the absorption of chlorine into toluene which has been investigated experimentally by others. It was found that the effect of heat conduction from the liquid stream surface to the gaseous surroundings is negligible as compared to other heat contributions. The contribution due to the bulk flow of the absorbed gas, previously neglected, to the total absorption flux was found significant. In all cases it was appreciable at the entrance region and of the order of 17%. Evaluation of the above-mentioned experimental results revealed a deviation of 25% in the total absorption flux of chlorine between calculations based on a simplified model and the more general one presented here. It is thus concluded that the a priori neglect of the effect of the gaseous environment as well as bulk flow contribution is not justified for absorption of gases with high solubilities and large heat effects.