Compositional Analysis + Hydrate Dissociation Conditions Measurements for Carbon Dioxide + Methane + Water System

摘要

A detailed description of an experimental “in-house” set-up based on the“static-analytic” technique with gas phase capillary sampling designed, built, and improved tomeasure phase equilibria (pressure, temperature, and compositions) under gas hydrate formationconditions is presented in this work. The apparatus is suitable for measurements at temperaturesranging from (233 to 373) K and pressures up to 60 MPa. It was used to study phase equilibria inthe carbon dioxide + methane + water system under hydrate formation conditions. An isochoricpressure-search method was used to measure hydrate dissociation conditions. The experimentaldata have been compared successfully with the literature data. The compositions of the gas phasein equilibrium with the hydrate and aqueous phases were measured using gas chromatographytechnique and compared successfully with the literature data. The compositions of the hydrateand aqueous phases were determined by applying material balance equations. The experimentaldata on the compositions of the hydrate have been compared successfully with the literature data.To solve the latter equations, the Newton’s numerical method coupled with the DifferentialEvolution optimization strategy was employed. All the aforementioned experimental data(hydrate dissociation conditions + compositions analysis) have been compared with thepredictions of two thermodynamic models, namely CSMGem and HWHYD. A discussion ismade on the reliabilities of the predictions of the latter models.