A model for the heat of absorption of CO2 using ammonia was established in the Aspen Plus software based on the e-NRTL model.The vapor liquid equilibrium and speciation of the NH3-CO2-H2O system were validated with the experimental data in literature.The heat of CO2 absorption was predicted and compared with the experimental data

combined with the analysis of liquid composition in the CO2 loaded aqueous ammonia.The results show that the model built in this paper can accurately calculate the vapor liquid equilibrium

speciation

as well as the heat of CO2 absorption in the ammonia based CO2 capture process.The heat of CO2 absorption is mainly affected by the dissociation of H2O and NH3

formation and hydrolysis of NH2COO- and dissolution of CO2 in the aqueous ammonia.The heat of H2O dissociation has the largest proportion in the overall heat of CO2 absorption

which is in restraint of the dissociation of NH3.The reaction related to NH2COO- is exothermic first and then endothermic with the increase of CO2 loading.As the temperature increases

the heat of CO2 absorption decreases.The average heat of CO2 absorption is 70.5 kJ·(mol CO2)-1

when the CO2 loading is between 0.2—0.5 mol CO2·(mol NH3)-1 and temperature is 80℃.