Modeling of the CO2 Absorption in a Wetted Wall Column by Piperazine Solutions

Theoretical and experimental investigations on the reactive absorption of CO2 in aqueous solutions of PZ using a wetted wall column are presented. A rigorous two dimensional absorption model, accounting for kinetics, hydrodynamics and thermodynamics, has been developed for a wetted wall column. Major innovative features of the model, compared to previous work, are the account on the variation of the gas-side CO2 concentration over the reactor height as well as the computation of the gas-liquid equilibrium by a thermodynamically consistent approach. A laboratory-scale wetted wall column was conceived and constructed and the gas-side mass-transfer coefficient was estimated. CO2 absorption experiments were carried out on unloaded and loaded aqueous solutions of PZ over the range of 298-331 K, and for total PZ concentrations varying from 0.2 to 1 M. The reactor model permitted to predict the absorption fluxes in loaded as well as in unloaded solutions with an excellent accuracy, i.e. 3.2% AAD. In loaded solutions, the gas-side CO2 concentration gradient, as well as the dicarbamate formation reaction has to be taken into account.