Study on the Adhesion Force between Wax Crystal Particles and Hydrate Particles

Abstract

In this work, to solve the problem of pipeline blockage caused by the accumulation of hydrate particles and wax particles and to explore the interaction characteristics of adhesive force between gas hydrate particles and wax particles as well as droplets, a high-pressure triaxial mobile device was used to measure the adhesion strength between cyclopentane hydrate particles and different commonly seen phases in the pipeline, including cyclopentane hydrate particles themselves, liquid droplets, and wax crystal particles. These experiments were conducted at different temperatures. The results showed that the adhesion between hydrate and wax particles was decreased with the increase in temperature; this is because the wax is amorphous, the heat absorbed when the temperature rises only increases its average kinetic energy, and the stronger the kinetic energy, the lower its viscosity, resulting in reduced adhesion between particles. Meanwhile, this adhesion was also affected by the concentration of wax. As the wax concentration increased from 1 to 5.32 wt % and then to 8.14 wt %, the adhesion between hydrate and wax particles was first decreased and then increased. This was because when the wax crystal concentration was below 5 wt %, a higher wax molecule concentration meant a more hydrophobic surface, which restricted the formation of a capillary liquid bridge between particles and thus reduced the interforce between wax crystal particles and hydrate particles. When the wax crystal concentration was between 5 and 8 wt %, the change of hydrophobicity was no longer the dominating factor, the increase in wax concentration blocked the hydrate molecular diffusion path, which caused a higher hydrate viscosity, therefore leading to a decreased hydrate molecular diffusion rate and a reduced conversion rate of the liquid bridge in hydrates, the lower conversion rate could subsequently lead to the increasing size of micropores in the hydrate shell, and adhesion between particles was increased.