Gas–liquid–hydrate flow characteristics in vertical pipe considering bubble and particle coalescence and breakage

Abstract

The gas–liquid flow behavior laden by hydrate particles is significant for the flow assurance of submarine natural gas hydrate production. An integrated multiphase flow model considering the coalescence and breakage of bubbles and hydrate particles was developed to investigate the gas–liquid–hydrate flow problem in a vertical pipe. The population balance theory was adopted to describe the evolution of the bubble and hydrate particle sizes in a flow field. The effects of particle behavior on flow pattern transition were analyzed. The results indicated that the phase distribution became inhomogeneous during the flow process, and bubbles tended to aggregate at the central region of the pipe. Most hydrate particles agglomerated in the liquid film region, and the particle size increased. The coalescence and breakage of bubbles induced a flow pattern transition from a bubbly to slug and churn flows. However, the agglomeration of hydrate particles increased the viscosity of the liquid phase, further reduced the turbulent intensity, and enhanced the stability of the bubbles. Thus, a higher gas superficial velocity was required for the formation of slug and churn flows. An annular flow was easier to form because the hydrate particles entrained in the liquid phase stabilized the liquid film. This study contributes to the flow assurance of submarine natural gas hydrate production and relevant multiphase flow modeling studies with hydrate particles.