Thermodynamics of carbon dioxide mixtures at cryogenic conditions

Carbon capture and sequestration / utilization using cryogenic conditions have found attention due to lower energy penalty compared to other separation methods. In cryogenic processes, carbon dioxide is likely to desublimate from a vapor phase or freezes out from a liquid phase. This study deals with phase equilibrium calculations where solid carbon dioxide forms in the presence of vapor phase (SLV), liquid phase (SLE), or both (SLVE). Two of the successful solid fugacity models are used with predictive cubic equations of state (EOSs) in calculating the phase equilibrium of carbon dioxide mixtures. The advantages and limitations of the models are discussed. In addition, a new fugacity model which describes solid carbon dioxide along solid–liquid coexistence curve is developed. This model remedies the previous models and is used from low to very high pressure. This model reduces to an analytical expression for describing carbon dioxide melting curve. When coupled with the predictive cubic EOSs, this model satisfactorily describes the SVE, SLE, and SVLE of carbon dioxide mixtures.