Vapor-liquid equilibrium data for the carbon dioxide and nitrogen (CO₂+N2) system at the temperatures 223, 270, 298 and 303 K and pressures up to 18 MPa

A new setup for the measurement of vapor-liquid phase equilibria of CO₂-rich mixtures relevant for carbon capture and storage (CCS) transport conditions is presented. An isothermal analytical method with a variable volume cell is used. The apparatus is capable of highly accurate measurements in terms of pressure, temperature and composition, also in the critical region. Vapor-liquid equilibrium (VLE) measurements for the binary system CO₂+N2 are reported at 223, 270, 298 and 303 K, with estimated standard uncertainties of maximum 0.006 K in the temperature, maximum 0.003 MPa in the pressure, and maximum 0.0004 in the mole fractions of the phases. These measurements are verified against existing data. Although some data exists, there is little trustworthy data around critical conditions, and our data indicate a need to revise the parameters of existing models. A fit made against our data of the vapor-liquid equilibrium prediction of GERG-2008/EOS-CG for CO₂+N2 is presented. At 223 and 298 K, the critical region of the isotherm are fitted using a scaling law, and high accuracy estimates for the critical composition and pressure are found.