Critical Shear Stress of Clathrate and Semiclathrate Hydrates on Solid Substrates

Abstract

The adhesive force of gas hydrates to a solid surface is an important factor that influences the likelihood of a blockage of oil and natural gas pipelines by a hydrate plug. In this work, we investigated the adhesive shear strength of Structure II (sII)-forming tetrahydrofuran (THF) hydrate on substrates with different hydrophobicity. Five solid substrates with the contact angle of water in air ranging from 0° to 117 ± 3° were used. The critical shear stress (tangential adhesive strength) of THF hydrate was compared to that of tetrabutylammonium bromide (TBAB) semiclathrate hydrate on the same five substrates. We also investigated the impact of a common kinetic hydrate inhibitor (KHI), polyvinylpyrrolidone (PVP), on the critical shear stress of these hydrates. The results showed that the critical shear stress diminished with heating and became unmeasurably small just below the dissociation temperature of the hydrates. This lowering of the critical shear stress with heating is in contrast to the normal adhesive strength between a gas hydrate particle and a solid surface that has been known to increase with heating due to capillary action. Addition of PVP increased the critical shear stress of both THF clathrate hydrate and TBAB semiclathrate hydrate on all substrates. Interestingly, the critical shear stress of the hydrates was higher on the hydrophobic substrates than on the hydrophilic ones. Our results imply that the quasi-liquid layer may have acted as an effective lubricant layer that reduced the static friction. Our findings may be valuable to flow assurance related to hydrate deposition on pipeline walls during hydrodynamic transport.

Relationship between the Orientation of the (100) Crystal Plane and Elongation in Ultrathin Electrolytic Copper Foils

“…The author, in a quest to uncover the theoretical intrinsic connection between texture and mechanical properties, takes a single face-centered cubic crystal cell as the focal point and attempts to calculate the Schmid factor size under various textures, aiming to delve into the impact of crystal orientation on mechanical properties. According to the mechanism of metal single crystal tensile deformation and the critical shear stress law, the Schmid factor (m) can be expressed as follows − m = cos nobreak0em0.25em⁡ φ nobreak0em0.1em⁡ cos nobreak0em0.25em⁡ λ In the equation, where m is the Schmid factor, φ is the angle between the normal direction of the slip plane and the tensile direction ( F ), and λ is the angle between the slip direction of the slip plane and the tensile direction. While eq indicates that m is related to the tensile direction, the actual tensile direction of ECF is generally unidirectional during the tensile test process.…”

Prospect and Challenges of Hydrate-Based Hydrogen Storage in the Low-Carbon Future

“…In addition to gas storage, − gas hydrates are relevant to other sectors of the environmental and energy industry such as a cleaner energy source, ,− gas separation and carbon capture, ,− carbon sequestration, − desalination of saline water, − and cold energy storage . Gas hydrates also present a long-standing hazard to the flow assurance in oil and gas industry as they tend to cause flow blockage. − Owing to such scientific and application significances, research in gas hydrates has grown strongly over recent decades.…”