Mechanistic Study on the Influence of Wax on Hydrate Formation Process.

To manage the interactions between wax and hydrate formation, a comprehensive understanding of the system's thermodynamics and flow characteristics is essential. Wax and hydrates coexist under low-temperature and high-pressure conditions, mutually influencing each other both thermodynamically and kinetically. This study focused on two main aspects: how wax affects the rate of hydrate formation in the oil-water system and how hydrate formation influences the thermodynamics of wax crystal precipitation. The presence of wax decreased the rate of hydrate formation, especially at higher wax contents. In systems with high wax content, over 70% of wax precipitated before hydrate formation, leading to less precipitation within the hydrate formation temperature range. With low water content, there were more nucleation sites for wax crystals in the oil phase, resulting in a greater difference in precipitation rates among different wax contents. For water content greater than 10%, the differences in precipitation rates were less significant, indicating a diminished effect of water content on wax crystal precipitation rates. Hydrates' hydrophilic nature had a limited impact on wax crystal nucleation and growth. Generally, wax crystals precipitate before hydrate formation, necessitating control measures for wax deposition during production processes.

Experimental study on particle movement and erosion behavior of the elbow in liquid-solid flow.

Recent investigations into the erosion of elbow junctions predominantly focus on identifying and predicting peak erosion points. Notably, these studies rely heavily on computational fluid dynamics methods, a valid approach but limited by its lack of empirical physical data. Additionally, the majority of these studies concentrate on the extrados, or outer curve of the elbow, neglecting the intrados or the inner curve. To provide a more comprehensive understanding of particle movements and the micro-mechanics of erosion on the elbow intrados, this study utilizes advanced observational technologies. High-speed camera technology, coupled with scanning electron microscopy, is employed to capture and record particle motion and micro-erosion patterns. The erosion rate is then estimated via the weight-loss method. The findings suggest that in low-speed liquid-solid flows (2.5 m/s), particles released from the intrados side of the elbow inlet exhibit a significant trajectory deviation from the centreline at an elbow angle of 60° from the inlet. Particles released from the extrados deviate towards the intrados side at an elbow angle of 30°. Secondary flow contributes to particle acceleration, unexpected trajectory deviation within the elbow, and an upward inclination in erosion on the intrados. The presence of partially overlapping scratches and cracks suggests that continuous ploughing and material fracturing are significant contributors to the micro-mechanics of erosion. When comparing the intrados and extrados, the extrados exhibits longer and shallower scratches, indicating a smaller impact angle. This research provides a more comprehensive understanding of particle trajectories and erosion patterns within elbow junctions during liquid-solid flows, offering new insights into the mechanisms underpinning these processes.