Crystal growth behaviour of clathrate hydrate in flowing liquid water saturated with natural gas

Abstract

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.This paper reports the visual observation on the growth and formation of clathrate hydrate crystals in the stream of flowing liquid water presaturated with simulated natural gas: methane + ethane + propane gas mixture. The composition of the methane + ethane + propane gas mixtures were 90:7:3 and 98.5:1.4:0.1 in molar ratio. The morphology (the geometric configuration of crystal such as crystal size or shape) of natural gas hydrate crystals grown in liquid water stream varied depending on the system’s subcooling temperature. The subcooling temperature is defined as the difference between equilibrium temperature of the hydrate and experimental temperature. At subcooling temperature larger than 6.0 K, the crystals grew from the porous pipe surface into the bulk of liquid water in both gas mixture systems. At a lower subcooling condition, polygonal flat plate crystals were observed. At ~9.0 K to ~12.0 K, the crystal morphology enters the transition phase, where the polygonal flat plate crystals started to change into dendritic crystals with increase in subcooling. When the subcooling temperature is greater than 12.0 K, polygonal crystals were completely replaced by the dendritic crystals.