The lateral film growth rate of CH4, C2H4, CO2, CH4 + C2H4, and CH4 + C3H8 hydrates in pure water were measured at four fixed temperatures of 273.4, 275.4, 277.4, and 279.4 K by means of suspending a single gas bubble in water. The results showed that the lateral growth rates of mixed-gas CH4 + C2H4 hydrate films were slower than that of pure gas (CH4 or C2H4) for the same driving force and that of mixed-gas CH4 + C3H8 hydrate film growth was the slowest. The dependence of the thickness of hydrate film on the driving force was investigated, and it was demonstrated that the thickness of hydrate film was inversely proportional to the driving force. It was found that the convective heat transfer control model reported in the literature could be used to formulate the lateral film growth rate v(f) with the driving force DeltaT perfectly for all systems after introduction of the assumption that the thickness of hydrate films is inversely proportional to the driving force DeltaT; i.e., v(f) = psiDeltaT(5/2) is correct and independent of the composition of gas and the type of hydrate. The thicknesses of different gas hydrate films were estimated, and it is demonstrated that the thicknesses of mixed-gas hydrate films were thicker than those of pure gases, which was qualitatively consistent with the experimental result.

No abstract

The anti-agglomeration performance of single or compounded commercial chemical additives with/without the addition of alcohol as a co-surfactant was evaluated using a sapphire cell and an autoclave reactor with a focused beam reflectance measurement (FBRM) probe. Five kinds of gas hydrate morphologies, clumpy-like, slush-like, flocculent-like, slurry-like, and powder-like, were found during evaluating the effect of the commercial additives in (water + oil) systems. The experimental results showed that AEO-3 combined with some commercial chemical additives, especially Span 20, exhibits good antiagglomeration performance. The hydrate slurry thus formed has a high stability and will not result in agglomeration for a long period of time. A compounded inhibition mechanism, in which one of the components disperses water droplet in the oil phase and the other component prevents formed hydrate from agglomeration, was proposed. A new structure of hydrate antiagglomerant was designed according to the evaluating results of the single or compounded commercial additives with/without the addition of alcohol material.