CO2 ABSORPTION DESORPTION IN MIXTURES OF METHYLDIETHANOLAMINE WITH MONOETHANOLAMINE OR DIETHANOLAMINE

This paper presents a compilation of data and model interpretation of CO2 absorption/desorption with mixtures of MDEA (methyldiethanolamine), MEA (monoethanolamine) and DEA (diethanolamine). The electrolyte-NRTL model is used to represent the activity coefficients of the species in solution. The simplified eddy diffusivity theory is used to simulate liquid-phase hydrodynamic characteristics. Binary interaction parameters for the equilibrium model and kinetic rate constants have been regressed from literature and currently obtained experimental data. The data presented in this work include both absorption and desorption conditions and temperatures ranging from 288 to 313 K. The results indicate that the combined mass transfer/equilibrium model can effectively represent CO2 mass transfer rates for the mixtures MEA/MDEA and DEA/MDEA under a wide range of conditions. Using a generalized framework for consistency between kinetics and reaction equilibria in nonideal systems, absorption and desorption data have been reconciled by allowing the forward rate constants to "increase" with ionic strength. It is shown that MDEA promotes the DEA reaction rate, but not the MEA reaction rate. Both of these phenomena can be explained in terms of the zwitterion mechanism for amine carbamate formation.