FLOW ANALYSIS OF RISING SHALLOW METHANE HYDRATE IN GAS-LIFT SYSTEM WITH A TAPERED PIPE AND MULTIPLE GAS INJECTIONS

Three-phase flows of rising shallow methane hydrate (MH) in a gas-lift system are numerically studied. The relevance of a tapered section and multiple gas injections in the vertical pipe is discussed. One-dimensional simulations of the motion driven by compressed gas injection into the pipe are performed using a simplified marker-and-cell (SMAC) method, in which the gas compressibility and the phase change are considered. We investigate the relationship between the MH volumetric flow rate <i>Q<sub>s</sub></i> and the injection gas one <i>Q<sub>g,inj</sub></i> with varying the pipe form, the depth of gas injection <i>L<sub>g,inj</sub></i>, and the number of the gas injection points. For the same gas injection points, <i>Q<sub>s</sub></i> increased significantly in the tapered pipe compared to the straight one. Additionally, the combination of multiple gas injections and tapered pipe leads to a substantial reduction in the peak value of liquid velocity <i>u<sub>l</sub></i> at the pipe outlet. The value at fully developed is also decreased, suggesting a new design condition.