Screening of Equation-of-State Models for Pure Carbon Dioxide Properties and Binary Mixture (Carbon Dioxide/Water and Carbon Dioxide/Ethanol) Phase Equilibrium

An appropriate thermodynamic model is vital for simulating the multiple industrial processes involving carbon dioxide. This work used equations of state available in the Aspen Plus software to determine carbon dioxide's thermodynamic and transport properties (density, viscosity, and specific heat capacity) and its equilibrium in binary mixtures with water and ethanol. Results were compared with literature data for temperatures from 273 to 353 K and pressures up to 30 MPa. The best results for carbon dioxide's pure properties were given by the REFPROP and GERG-2008 models, with less than 0.5% overall relative error. Other models also produced accurate predictions within global average absolute value of the relative error of less than 5%. Nevertheless, these models must be cautiously used, as some zones might lead to significantly larger errors. Regarding the equilibrium of binary mixtures (carbon dioxide/water and carbon dioxide/ethanol), no model accurately covered the entire pressure and temperature range here considered. For the carbon dioxide/water binary system, the worst VLE prediction of the CO2-dense phase was usually given by the PRMHV2 model; GERG-2008 and PR-BM commonly overestimate the water mole fraction in the water-rich phase. PRMHV2 and REFPROP models typically fail VLE predictions regarding the carbon dioxide/ethanol binary system. Generally, better predictions were obtained at temperatures further from CO2's critical temperature.