Supercritical pressure–density–temperature measurements on CO2–N2, CO2–O2 and CO2–Ar binary mixtures

This paper presents new supercritical volumetric measurements on three binary mixtures mainly composed of carbon dioxide. The interest in the tested mixtures derives primarily from carbon capture and storage applications. In particular, CO2-rich streams with low amounts of nitrogen, oxygen and argon are representative of the flows that are treated by the compression units and the purification units employed in the oxy-fuel fired power plants. These flows are then transported from power plants to storage sites in supercritical conditions. For each type of binary mixture, two different molar compositions are here considered. Isothermal pressure–density–temperature measurements are performed for all the mixtures in a temperature range from 303 K to 383 K and in a pressure range from 1 MPa to 20 MPa by way of a vibrating tube densimeter-based apparatus. The experimental data are used subsequently for the regression of new binary interaction coefficients for two types of cubic equations of state, the Peng–Robinson and the Redlich–Kwong–Soave–Peneloux, and a multi-parameter equation, the Benedict–Webb–Rubin–Starling. The absolute deviations with respect to experimental data are in the range 2.10–2.56%, 3.05–4.07% and 1.71–1.97% for the three equations respectively. The results confirm the superiority of the multi-parameter equation of state over the cubic models in the supercritical region.