Macroscopic investigation of hydrate film growth at the hydrocarbon/water interface

Abstract

Clathrate hydrate film growth has been investigated at the hydrocarbon/water interface for cyclopentane and methane hydrate, using video microscopy combined with gas consumption measurements. Hydrate formation was characterized by the film thickness, propagation rate across the hydrocarbon/water interface, and gas consumption. The film formation processes of cyclopentane and methane hydrate were measured over the temperature range of 260–273 K and pressure range of atmospheric to 8.3 MPa. Hydrate formation was initiated by the propagation of a thin, porous film across the hydrocarbon/water interface. This thickening rate was strongly dependent on the hydrate former solubility in the aqueous phase, in the absence and presence of hydrate. The methane hydrate film thickness began at about 5 μ m and grew to a final thickness (20– 100 μ m ) which increased with subcooling. The cyclopentane hydrate film thickness began at about 12 μ m and grew to a final thickness (15– 40 μ m ) which again increased with subcooling. The hydrate film grew into the water phase. Gas consumption indicated that the aqueous phase supplied hydrate former during the initial hydrate growth, and the free gas supplied the hydrate former for film thickening.