No abstract

No abstract

No abstract

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

Consistent phase equilibrium data for cyclopentane hydrates in presence of salts are vitally important to many industries, with particular interest to the field of hydrate-based water separation via cyclopentane hydrate crystallization such as desalination. However, there are very little experimental equilibrium data, and no thermodynamic prediction tools. Hence, we set up a method to generate a great deal of much needed equilibrium data for cyclopentane hydrates in diverse saline solutions with a wide range of salt concentrations. Our method does furnish verified, reliable and accurate equilibrium data. Plus, three thermodynamic approaches are developed to predict equilibrium, and provide tools for simulations, by considering the kind of salt and concentrations. All three models are in very good accordance with experimental data. One method, using a new correlation between occupancy factor and water activity, might be the best way to obtain consistent, quick, and accurate dissociation temperatures of cyclopentane hydrate in brine.a Dh b2L w j T 0 ;P 0 5 Dl b2I w j T 0 ;P 0 -6011, where 6011 is the enthalpy of ice (J mol 21 ).

In the second part of this series, we introduce the mathematical model for the growth kinetics of gas hydrates in oil continuous flow. Mathematical description of the capillary filling-up process is given (porosity evolution), coupled with growth phenomena already described in the literature (gas absorption by the oil bulk, mass transfer particle/bulk, outer growth due to permeation). The range of closure parameters reported in the literature for CH 4 hydrates is used to understand the limiting steps of crystallization, the evolution of porosity being the controlling factor in the asymptotic trend of the gas consumed over time. Furthermore, gas absorption by the bulk and mass transfer particle/bulk is shown to be negligible for oil-continuous flow when considering a gas that is much more soluble in oil than in water. The model is simplified for engineering purposes, giving rise to an explicit semi-empirical equation for the gas consumption rate because of hydrate formation based on two independent parameters that are experimentally regressed. A criterion for the existence of wet or dry particles (the water layer covering the particles in oilcontinuous flow) is proposed in means of the competition of crystal integration in the outer surface versus water permeation through the porous hydrate.

No abstract

This article presents a systematic review on the past developments of Hydrate-Based Desalination process using Cyclopentane as hydrate guest. This is the first review that covers all required fundamental data, such as multiphase equilibria data, kinetics, morphology, or physical properties of cyclopentane hydrates, in order to develop an effective and sustainable desalination process. Furthermore, this state-of-the-art describes research and commercialization perspectives. When compared to traditional applications, cyclopentane hydrate-based desalination process could be a promising solution. Indeed, it operates under normal atmospheric pressure, lower operation energies are required, etc… However, there are some challenges yet to overcome. A decision aid in the form of a diagram is proposed for a new cyclopentane hydrates-based desalination process. Hopefully, concepts reviewed in this study will suggest new ideas to advance technical solutions in order to make commercial hydrate-based desalination processes a reality.