Phase equilibrium for methane, ethane and carbon dioxide hydrates at pressures up to 100 MPa through high-pressure microcalorimetry: Experimental data, analysis and modeling

摘要

New experimental dissociation data for CH4, C2H6, and CO2 hydrates obtained by high-pressure microcalorimetry (HP-mu DSC) up to 100 MPa are presented. Deviations of onset, peak, and endset temperatures from predictions and their representativeness as equilibrium values are evaluated. For these systems, the onset temperatures provided good reproducibility and more accurate results than peak and endset temperatures, when compared to literature data. Predictions from CSMGem and Multiflash software packages are compared to the experimental results. Dynamic effects on gas hydrates formation are also evaluated by varying the water-sample size and the cooling-heating rate. Enthalpies of dissociation are determined by applying the Clapeyron equation, and new approaches are applied for the calculation of the hydrate volume and the hydration number estimation. The enthalpy of dissociation at conditions above the upper quadruple point is obtained for ethane and carbon dioxide hydrates for the first time. (C) 2020 Elsevier B.V. All rights reserved.