Effects of Polyvinyl Alcohol on the Adhesion Force of Tetrahydrofuran Hydrate Particles

Effects of polyvinyl alcohol (PVA) on the adhesion force of tetrahydrofuran (THF) hydrate particles were investigated with the microscopic manipulating technique. The adhesion forces of THF hydrate particles with PVA concentration ranging from 0.1 to 1.0 wt % were measured at atmospheric pressure and -3 degrees C. The time-influence adhesion force of the 0.1 wt % PVA-THF hydrate particle was measured in 180 min. While the adhesion forces were measured, morphologies of the particles without PVA and with 0.1, 0.5, and 1.0 wt 96 PVA were observed. The surface property of the particles was investigated using droplets made from 19 wt % THF aqueous solution to contact THF hydrate particles containing 0.1, 0.5, and 1.0 wt 96 PVA. The adhesion forces of PVA-THF hydrate particles decreased by more than 50% compared to pure THF hydrate particles, which indicates an anti-agglomerating effect of PVA at low concentrations. The adhesion force of the 0.1 wt % PVA-THF hydrate particle was kept small with increasing time, revealing the effects of PVA on stabilizing the particle particle interaction and maintaining the low adhesion force. Morphologies show roughness on the surface of PVA-THF hydrate particles. The roughness leads to the decrease of the actual contact area between contacting particles, thus lowering the agglomeration tendency between hydrate particles. The reason for the morphological change and the occurrence of roughness is attributed to the hydrogen bonding between PVA molecules and water molecules. PVA was also found to change the surface property of THF hydrate particles by increasing the contact angle and weakening the wettability, which represents a decrease of the particle/medium liquid interfacial energy. Such an effect may alter the capillary bridge forming between the contacting particles. All results suggest that PVA may be a potential anti-agglomerant in lowering the hydrate plugging risk.