OS6A-4:HOW TO EXPLAIN THE HYDRATE COMPOSITION FROM CO2-C1-C2-C3-C4 GAS MIXTURES: TOWARD A KINETIC UNDERSTANDING VERSUS THERMODYNAMIC AND CONSEQUENCES ON THE EVALUATION OF THE KIHARA PARAMETERS.

Jean-Michel HERRI (1*), Duyen LE QUANG(1), Matthias KWATERSKI (1),Baptiste BOUILLOT (1),GLENAT Philippe (2) DUCHET-SUCHAUX, Pierre3)
1. Gas Hydrate Dynamics Centre, Ecole Nationale Supérieure des Mines de Saint-Etienne, France ; 2. TOTAL S.A., CSTJF, France ; 3. TOTAL S.A., France

    This work is a contribution to the global understanding of the coupling between kinetic and thermodynamic to explain the clathrate hydrates composition during their crystallization from a water liquid phase and a hydrocarbon gas phase. We faced new experimental facts that opened questioning after comparing the classical modeling of clathrate hydrates following the approach of van der Waals and Platteeuw with our experimental data following a new procedure allowing determining the hydrate composition during crystallization and at equilibrium. In the model (Herri et al, 2012), the enclathratation is described by means of a Langmuir absorption where the composition if fixed from kinetic consideration based on the balance between the absorption rate and desorption rate. In addition, they turn out to become dependent on the gas diffusion around the hydrate crystals, and so, the geometry of the system needs to be taken into account, especially the mass transfer at the Gas/liquid interface. The procedure results in the definition of a non-equilibrium hydrate composition with a new analytical expression of the composition.

    In this work, our contribution is to extract self-coherent experimental results from literature, or from us (Le Quang et al, 2014) to re-evaluate properly the Kihara parameters. This step implies to compile and implement all the literature data in a data base of a modeling program, called GasHyDyn. Then, we can optimize Kihara parameters from a procedure that can be trivial in some cases where literature data are rich enough to optimize directly the parameters, but the procedure is complex as the literature data are rare or not coherent together.

    Herri, J.M., Kwaterski, M., 2012, Derivation of a Langmuir type of model to describe the intrinsic growth rate of gas hydrates during crystallization from gas mixtures, Chemical Engineering Science (81)28-37

    Le Quang et al, 2014, ICGH8, Experimental procedure and results to measure to composition of gas hydrate, during crystallization and at equilibrium, from CO2-C1-C2-C3-C4 gas mixtures