International audienceIn this paper, a set of experimental data on the phase equilibrium of gas hydrates in the presence of binary gas mixtures comprising CO2 is presented. The procedure established allows for the determination of both the composition of the gas phase as well as the hydrate phase without the need to sample the hydrate. The experimental results obtained in these measurements have been described by means of the classical model of van der Waals and Platteeuw. The values of internal parameters of the reference state and the Kihara parameters have been re-discussed and their interdependency is pointed. Finally the new set of parameters is validated against experimental data from other sources available in the literature, or invalidated against other sources. Finally, we conclude on the difference of experimental data between laboratories. The differences are not on the classical (pressure, temperature, gas composition) data which appear equivalent between laboratories. The difference stands on the measurement composition of the hydrate phase

In this work, the effects of Al 2 O 3 , SiO 2 , Ag and Cu nanoparticles on the kinetics of CO 2-CH 4 hydrate formation process were experimentally studied by measuring the amount of gas consumed and the rate of gas consumption. A suspension of 0.1wt%, 0.2wt % and 0.3wt% of each nanoparticle was injected into the hydrate formation reactor, while pressure and temperature were maintained at 4.0 MPa and 274.15 K, and the magnetic stirrer speed was set at 350 rpm. The CO-CH 4 hydrate formation process was studied in both pure water and water containing a 0.1wt%, 0.2wt% and 0.3wt% of each nanoparticle suspension. The results showed that these nanoparticles had a positive effect on hydrate formation. These effects varied from one nanoparticle to another. It was observed that nanoparticles of SiO 2 had the most positive effect on CO 2 gas consumption, particularly at a concentration of 0.3wt%. At this concentration the average amount of gas consumed was about 45% higher than that in pure water during the dissolution and 77% during crystallization. Cu and Al 2 O 3 nanoparticles had an intermediate effect with improvement in gas consumption by 1% to 15% during dissolution; while it had an important impact on gas consumption during hydrate crystallization with an improvement of 30% to 65%. Ag nanoparticles had no significant effect during these two phases.

International audienceIn this study the dry coating experiments were performed with two different processes using a high energy impact coater “Hybridizer” (Nara) and a high shear mixer “Cyclomix” (Hosokawa). Silica gel particles (d50 = 55µm) were coated with fine particles of magnesium stearate (d50 = 4.6µm) at two different weight ratio of magnesium stearate, 5% and 15%. Several methods of characterization were used to study the effect of dry coating of the silica gel powder. The uncoated and coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). The images have shown that a more uniform coating was obtained in the case of Hybridizer. The flowability of the different samples obtained with Hybridizer and Cyclomix have been characterized by measurements of the tapped and aerated densities. It has been shown that the flowability of silica gel treated in Hybridizer was not significantly affected whereas the flowability was reduced after treatment in the Cyclomix. The wettability of silica gel was determined by measurements of the contact angle between a water drop and a powder bed prepared for each sample. The results obtained have shown that the coating of silica gel powder by hydrophobic magnesium stearate in the two different devices, Hybridizer and Cyclomix, can improve its hydrophobic properties. The results of the different characterizations have been compared with those concerning the simple mixtures prepared by using a Turbula mixer. To investigate the stability and the ageing of silica gel particles after coating, three samples of silica gel coated with 15% (w/w) of magnesium stearate in the Hybridizer device have been stored under different relative humidities (RH). The temporal evolution of the contact angle and the volume of the drop water on the surface of the bed powder have been determined after 10 days or 36 days storage. The results have shown the influence of the relative humidity on the evolution of the coated silica gel particles. The surface of the host particles recovers its hydrophilic nature after 10 or 36 days storage under different relative humidity. No significant variations of the contact angle and the volume of the drop were recorded for the sample stored under dry atmosphere (RH < 12%). The ESEM observations of the different samples confirmed the results. A mechanism that can explain these ageing effects is proposed