Crystallization Behavior of the Hydrogen Sulfide Hydrate Formed in Microcapillaries.

There are no reports on the hydrogen sulfide hydrate growth process and morphology in micropores due to the toxicity of hydrogen sulfide. In this study, the experimental measurements and dissociation enthalpies were provided to assess the effect of the microcapillary silica tube size on hydrogen sulfide hydrate dissociation conditions. To simulate micropore sediments, the H2S hydrate growth processes and morphologies at different supercooling temperatures were observed in this study. The dissociation temperature depression of the hydrate crystal in the microcapillary was less than 0.001 °C, which shows that the stability of the hydrate is less affected by the microcapillary pore used in this study. The mass transfer from the gas phase to the liquid phase is easily blocked when the hydrogen sulfide hydrate shell covers the gas-water meniscus, causing the growth of the gas hydrate to be inhibited. The hydrate crystal morphology can be divided into fibrous, needle-like crystals and dendritic crystals when ΔTsub > 12.7; the hydrate crystal morphology can be categorized as dendritic crystals and columnar crystals when ΔTsub = 7.9-8.9, and the hydrate crystals can form polyhedral crystals when ΔTsub = 7.9-8.9. Additionally, a new "bridging effect" that a hollow crystal which was filled with the gas phase can connect with two separated gas phases was found at low supercooling temperature.