Gaseous PVTx Properties of the CO₂-N₂O Binary Mixture: Experiment and Simulation

Anthropogenic greenhouse gases are mainly CO₂, CH₄, N₂O, and fluorinated gases. However, due to the toxicity of the CO₂-N₂O mixture, there are few experimental pressure-volume-temperature-composition (PVTx) data available in the literature, which do not meet the temperature-pressure conditions for the applications of carbon capture and storage (CCS). In this work, the gaseous PVTx data of the CO₂-N₂O mixture with molar ratios of 0.6:0.4 and 0.8:0.2 were measured by using a constant-volume vapor phase density apparatus, over a temperature-pressure range of 298.15-473.15 K and 1.0-100.0 bar. The relative standard uncertainty of density ranged from 0.15 to 0.35%. Based on experimental data, a Helmholtz free energy equation of state (EOS) for the CO₂-N₂O mixture was developed, which can accurately reproduce the PVTx properties of the CO₂-N₂O fluid mixture. The EOS reveals that as the N₂O content increases, the density of the CO₂-N₂O fluid mixture initially decreases and then increases. The overall trend shows that the density decreases with increasing temperature and increases with increasing pressure. The EOS can be used to quantitatively estimate the effect of impurity N₂O on the CO₂ storage capacity in the CCS process.