Visualization of TBAB Hydrate in Confined Small Channels

Abstract

AbstractTBAB (tetrabutylammonium bromide) can generate semi-cage hydrate at atmospheric pressure, which has high energy storage density and can be applied to cold storage technology. Small channel has the characteristics of high heat exchange efficiency and can generate hydrate more efficiently. In this paper, 2 mm and 3 mm quartz tubes with inner diameter were used as experimental tubes. The hydrate crystal morphology and agglomeration morphology generated by the flow in the tube were captured by industrial microscope. The effects of undercooling degree and diameter of solution concentration and flow rate on the blockage time and agglomeration process of hydrate morphology were studied. It was found that the density of single crystal hydrate formed by TBAB (10 wt%–20 wt%) at the same undercooling is low, and its front end is needle or sword, which is beneficial to mass and heat transfer and continues to grow. High concentration TBAB solution (30 wt%–40 wt%) formed hydrate crystals closely, and the tip effect was significantly weakened. For low concentration TBAB solution, the increase of flow rate can accelerate the formation of new nuclei and inhibit the growth of large crystals. Adjusting the flow rate can help to obtain slurry solutions with different particle sizes. The growth and aggregation process of TBAB hydrate were reviewed, and the microscopic physical model of TBAB hydrate growth and aggregation process was established. It is found that the initial morphology of TBAB hydrate crystal includes spherical and columnar, and the morphology evolution process of single hydrate crystal is similar. The optimal solution concentration and flow rate range for continuous hydrate formation can be preliminarily determined by experiments, which has reference significance for the development of efficient and continuous hydrate formation process.KeywordsTBAB hydrateMorphologyFlowSmall channel