No abstract

No abstract

in Wiley InterScience (www.interscience.wiley.com).CH 4 -CO 2 replacement in CH 4 hydrate with high pressure CO 2 was studied with insitu laser Raman spectroscopy at 273.2 K and at initial pressures of 3.2, 5.4, and 6.0 MPa. Replacement rates increased with increasing pressures up to 3.6 MPa and did not change at higher pressures (;6.0 MPa). These results showed that the replacement rates were dependent on pressure and phase conditions with the driving force being strongly related to fugacity differences of the two guest components between fluid and hydrate phases. When CH 4 hydrate was contacted with CO 2 under flow conditions, in-situ Raman measurements of the hydrate phase showed differences of cage decomposition rates between the Medium-cage (M-cage) and the Small-cage (S-cage) in the CH 4 hydrate with decomposition of the M-cage being faster than that of the S-cage. The van der Waals-Platteeuw model was applied to the measurements of the transient data and it is shown that the theory allows estimation of occupancies of each component during replacement.

No abstract

No abstract

No abstract

in Wiley InterScience (www.interscience.wiley.com).Binary H 2 -THF clathrate hydrate formation kinetics were investigated with a pressure decay method at temperatures from 266.7 to 275.1 K, at initial pressures from 3.6 to 8.4 MPa, and at stoichiometric THF hydrate concentrations for particle sizes between 212 and 1,400 lm. Formation rate increased for smaller particle sizes, higher pressures and lower-temperatures. A hydrogen delocalization model and a proposed hydrogen hydrate phase diffusion (HHPD) model were used to analyze the formation mechanisms. The HHPD model assumes that the H 2 -THF hydrate phase is formed due to hydrogen adsorption onto the particle surface that is followed by subsequent diffusion of hydrogen into the clathrate hydrate. The HHPD model could express the kinetics quantitatively at the experimental conditions studied. Values of the hydrogen diffusion coefficient in the clathrate hydrate estimated from the bulk data and the phase thickness in the HHPD model agreed well with the literature.

No abstract