Three-dimensional Eulerian modeling of gas–liquid–solid flow with gas hydrate dissociation in a vertical pipe

The pipe transportation of gas hydrate-bearing sediments (GHBS)1 is one of the key problems in mechanical–thermal exploitation of gas hydrate (GH)2 in marine stratum. It is a gas–liquid–solid (methane gas–seawater–GHBS particles) three-phase flow, accompanied by GH dissociation. In this study, a three-dimensional Eulerian model combined with the kinetic theory of granular flow (KTGF) was adopted to simulate the gas–liquid–solid flow with GH dissociation. The commercial CFD software FLUENT 16.2 was employed, considering the hydrodynamics, heat and mass transfer, and GH dissociation simultaneously. A kinetic model for GH dissociation in the GHBS particles is presented, considering the influence of multiphase flow on dissociation rate. The model can capture the transition from the initial liquid–solid two-phase flow to gas–liquid–solid three-phase flow, describing the distribution of the phase volume fraction, velocity, temperature, and dissociation rate. The interaction between GH dissociation and multiphase flow is discussed. The simulation results indicate that the continuous production of gas bubbles by GH dissociation leads to more violent fluctuations in the pressure gradient and a more marked elevation of the solid particles compared with the liquid–solid two-phase flow without GH dissociation. In addition, the effect of GH dissociation on the multiphase flow under different hydrate saturations was analyzed.