Thermodynamic modeling of CO2 absorption in aqueous potassium carbonate solution with electrolyte NRTL model

Abstract

Aqueous potassium carbonate (K2CO3) solution is a favorable choice for CO2 removal due to low costs and lessened environmental impacts compared to amine solutions. To support process development of CO2 removal with aqueous solutions, we present a comprehensive thermodynamic model for the H2O + K2CO3 + CO2 ternary system using electrolyte Nonrandom Two-liquid (eNRTL) activity coefficient model. Experimental data of vapor-liquid equilibrium, heat capacity, excess enthalpy, mean ionic activity coefficient and osmotic coefficient are simultaneously used to determine the temperature dependent eNRTL binary interaction parameters for the ternary system and its binary subsystems. Covering a wide temperature range of 273.15–473.15 K, the K2CO3 concentration up to saturation, and the CO2 loading range of 0–3.6, the model satisfactorily represents all the thermodynamic properties for the system. The model should be a very useful tool in the research, development and design of CO2 capture processes involving concentrated K2CO3 solutions at elevated temperatures and pressures.