Numerical Simulation Study on Solid‐Carrying Capacity of Mixed Hydrate Slurry in Horizontal Pipe

ABSTRACT Solid fluidization method is a green mining method developed for non‐diagenetic gas hydrate deposits on the sea floor. The gas hydrate can be safely and controllably transported to land through safe conveying, and the system includes seabed mining, closed fluidization, and gas–liquid–solid multiphase lifting. However, many technical problems are involved in the process of multiphase lifting, such as hydrate and sediment fluidification, and the improvement of pipeline transport capacity. Based on the above problems, taking seawater, solid hydrates and sediment as the research objects, a numerical simulation study was carried out on the hydrate sediment mixed slurry in a horizontal tube with the guide strip rotating throughout the whole process, so as to explore the solid‐carrying capacity of spiral flow, expand the safety boundary of multiphase flow, and make a comparison and analysis with the ordinary light tube. The effects of hydrate volume fraction and Reynolds number on the average density, velocity, solid phase volume fraction distribution and pressure of hydrate slurry were studied. The results show that the mean slurry density decreases with the increase of hydrate volume fraction, and the effect of Reynolds number on the axial flow velocity is greater than that on the tangential flow velocity. When centrifugal force is dominant, solid hydrates are mainly distributed in the pipeline axis, while sediment particles are mainly distributed in the windward side of the diversion strip. In the ordinary pipe, solid hydrates are mainly distributed at the top of the pipe, while sediment particles are mainly distributed at the bottom of the pipe. When Re = 30,000, the critical volume fraction of hydrate plugging in the horizontal spin‐tube is 57%, and that in the horizontal optical tube is 31%. The transport capacity of the spin‐tube for solid hydrates increases by 84% under the same conditions. The pressure drop of the full spinning tube is about 14% higher than that of the ordinary optical tube.