Heats of mixing of gaseous CO2/CH4 mixtures with aqueous solutions of methyldiethanolamine and diethanolamine

The heats of mixing of gaseous CO2/CH4 mixtures with aqueous solutions of methyldiethanolamine and diethanolamine have been determined using an isothermal flow calorimeter. Data were collected at 26.7, 76.7 and 126.7°C, at total pressures of 1.38, 3.45 and 6.90 MPa, with aqueous amine concentrations of 20, 35 and 50 wt%. The nominal partial pressure of CO2 in the gaseous feed stream was 0.069 MPa at a total pressure of 1.38 and 0.69 MPa at 3.45 and 6.90 MPa total pressure. A model developed to predict thermodynamic properties of these systems includes reaction equilibria, dissolution of methane, vapor-phase non-idealities, vaporization of water and amines in addition to the acid gas absorption.