Thermodynamic analysis of hydrate-based pre-combustion capture of CO2

Abstract

Abstract This paper presents the phase equilibria of quaternary CO 2 + H 2 + cyclopentane ( CP ) + water systems containing gas hydrates and proposes a staged-separation scheme based on the thermodynamic data. The phase equilibria of HLLV of quaternary CO 2 + H 2 + CP + water systems are determined by using a high-pressure differential scanning calorimeter (DSC). The equilibrium dissociation pressures are dependent on the vapor composition and they shift to lower values with the increase in the CO 2 mole fraction. The difference in the dissociation pressures between various CO 2 fractions vanishes as the temperature approaches the melting point of CP hydrates at 0.1 MPa. The hydrate dissociation enthalpy is independent of vapor compositions and it is 144 kJ mol ( gas ) - 1 over the temperature range. Experimental data are compared to the calculated ones from John–Holder's three-shell model. The prediction matches well with experimental data. The presence of CP reduces the operation pressure of a hydrate-based CO 2 capturing process from the pre-combustion stream. Two equilibrium stages of hydrate crystallization and dissociation can enrich CO 2 in the vapor-phase significantly from 0.4 of CO 2 mole fraction to 0.98 at 282 K. This thermodynamic analysis provides a conceptual design for developing a new process of pre-combustion CO 2 capture in IGCC plants.