Role of liquid reactant volatility in gas absorption with an exothermic reaction

Abstract

AbstractA film‐theory model is presented for nonisothermal gas absorption with a second‐order exothermic reaction. The model accounts for the volatility of the liquid reactant and heat transfer from the liquid surface to the gas phase. The pertinent equations were solved numerically using B‐spline collocation. Results from this solution show that for intermediate values of Hatta number the liquid‐reactant volatility is deterimental to the enhancement of gas absorption. As Hatta number approaches zero or infinity, however, the effect of liquid‐reactant volatility becomes minor. Heat losses to the gas phase drastically reduce the interfacial temperature rise, which in turn enhances or inhibits the absorption rate depending on the effective activation energy being larger or less than zero, respectively. Approximate expressions for the enhancement factor and the interfacial temperature rise were also developed. Comparisons with the “exact” numerical solution verified the accuracy of these expressions over a reasonable spectrum of parameter values. The model developed was applied to two cases representing real conditions: the chlorination of toluene and the sulfonation of dodecylbenzene. Volatility effects are shown to be important for the former system, while the relatively nonvolatile dodecylbenzene served as a counter example.