Modeling of gas absorption accompanied by chemical reaction in downflow co-current packed columns

A mathematical model is presented for gas absorption accompanied by chemical reaction in downflow cocurrent packed columns. The model incorporates an axial dispersed plug flow for the bulk gas and dynamic liquid phases and a Fickian type equation for the stagnant liquid phase. The reaction is considered to be occurring in both the dynamic and stagnant liquid phases. Numerical simulations have been carried out to investigate the effect of various parameters of practical significance for absorption of CO₂ from air into an alkaline solution of NaOH. The results of the numerical simulation show that the axial dispersion in the liquid phase do not affect the gas phase concentration profile, while dispersion in the gas phase affects both the liquid and gas phase concentration profiles. Increase in liquid and gas phase Peclet number, Reynolds number and the Stanton number results in enhanced absorption. The effect of dimensionless reaction rate constant K_R* is only pronounced for values of K_R* < 100. Beyond this value, the reaction can be considered instantaneous. Theoretical predictions using parametric values obtained from the literature are compared with the experimental data at three different flow rates for absorption of CO₂ in an alkaline solution of NaOH and are found to agree well.