Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Acid gas re-injection or carbon capture and storage are two technologies now implemented for management of produced CO2 or reducing the industrial emission of CO2. For both technologies, impurities such as H2O, H2S, O2, and SO2 can find a way into a CO2 injectate stream. In addition to unwanted reactions, these impurities can alter the phase behavior and volumetric properties of the injectate stream. Measuring accurate densities associated with mixing various impurities and CO2 fluid is one method to optimize mixing coefficients for calculating reliable phase behavior and chemical activities for these systems. In this work, the volumetric influence and/or phase behavior of SO2, CS2, or O2 impurities in a dense CO2 phase were studied through high-precision density measurements. Densities of the CO2 mixtures were measured with a custom vibrating tube densimeter with an average uncertainty of +-0.07 kg m-3 for temperatures of T = 50 to 125 deg.C and pressures at p less than= 35 MPa. The densities were used in calculating the apparent molar volumes, which were subsequently used to (i) calibrate or verify mixing coefficients for reference quality reduced Helmholtz energy equations-of-state, and (ii) provide a fitted equation based on fluctuation solution theory which can be used to calculate fugacity coefficients and partial molar volumes of CS2 at infinite dilution. Validating our optimized mixing coefficients for the CO2 + SO2 mixture showed more reliable vapor-liquid equilibrium phase behavior when compared to those previously estimated in the literature.