Experimental study on visualization of TBAB hydrate formation in confined small channels

Abstract

Hydrate crystals' microscopic characteristics and agglomerating morphologies play an important role in the hydrate reaction equipment's flow assurance and heat transfer. In order to study the formation process of hydrate, experimental quartz tubes with small diameters were selected, and a fully visualized flow loop system was established. The study investigated the effects of supercooling, solution concentration, tube diameter, and flow rate on hydrate blockage time and agglomeration morphology. The results show that under the same supercooling conditions, the density of single crystal hydrate formed in 10 wt%-20 wt% TBAB (Tetra-n-butylammonium bromide) hydrate solution is low, and the crystal front appears needle-like or sword-like, which is conducive to mass and heat transfer. High concentration TBAB solution(30 wt%-40 wt%) can form dense hydrate crystals, and the tip effect was significantly weakened. For low concentration TBAB solution, the increased flow rate can accelerate the formation of new nuclei and inhibit the growth of large crystals. Grout solutions with different particle sizes can be obtained by adjusting the flow rate. It was found that the initial morphology of TBAB hydrate crystals included spherical and cylindrical shapes, and the morphological evolution process of a single hydrate crystal was similar. Finally, a microscopic physical model of the TBAB hydrate growth and aggregation process was established.