Volume 24: Sustainable Energy Solutions for a Post-COVID Recovery towards a Better Future: Part VII

Growth Kinetics Behaviors of Hydrate Film on Gas Bubble Suspending in Water with Inhibitors Xin-Yang Zeng, Si Zhang*, Guozhong Wu, Jiang Wang, Zhifeng Yan, Jing-Chun Feng*

Abstract

Gas hydrate formation on gas bubble prefers to exist in the deep-sea pipelines during the oil-gas transportation, resulting into the clogging of pipelines. The hydrate inhibitors are generally added to deal with the huge threat and challenge. This study provided the growth kinetics behaviors of hydrate film on gas (CH4 – C3H8) bubble suspending in the water with the inhibitors (ethylene glycol: thermodynamic inhibitor of small molecular weight and LuviCap EG: kinetic inhibitor of big molecular weight, respectively) at extreme high undercooling degree (10 – 15 K), including the growth modes, the lateral growth rate, and the evolution of the morphology and mass transfer channels. The optical microscope was used to observe the kinetics growth phenomenon. Study showed the growth mode of pasty hydrate in the liquid phase instead of hydrated bubble when the inhibitor concentration increased to the critical 8000 ppm. For both inhibitors, the difference is that the craters embodied in the hydrate film were formed for LuviCap EG concentration from 500 to 4000 ppm. These craters were considered as the aggregative LuviCap EG molecules, which attached to the hydrate lattice in the lateral growth of hydrate film. Hence, the craters were a type of new mass transfer channels, accelerating the initial thickening growth of hydrate film. The craters quickly enlarged in the initial thickening and finally formed the uniform and coarse texture. The initial size and the enlarged rate of craters were determined by the concentration of LuviCap EG. In conclusion, the critical concentration indicated that the inhibitors should be added to more than 8000 ppm, which helps keep the good fluidity of oil-gas in the pipeline transportation. The morphology and kinetics behaviors of craters of new mass transfer channels on hydrate film on bubble shed light on the mechanism of hydrate formation in water with hydrate kinetics inhibitor, providing the theoretical basis of the hydrate anti-blockage mechanism for the oil gas transportation in the deep-sea pipelines.

Keywords Gas hydrate, hydrate inhibitors, clogging of pipelines in oil-gas transportation, mass transfer channel, growth kinetics behaviors of hydrate film, hydrate morphology