Numerical simulation on deposition evolution of natural gas hydrate in pipeline

Abstract

The traditional Euler-Euler fluid model is to predict the flow and deposition of two phases by approximating the hydrate particles as a fluid phase, but does not consider the effect of particle formation caused by phase change in the flow process. Herein, the Euler-Euler fluid mode, the interfacial area transport equation and the convection equation were implanted into the open source computing software OpenFoam 4.0, and the key phase change source term was introduced with consideration to the hydrate particle aggregation and breakage efficiency. The amount of hydrate formation was calculated in real time according to the temperature field distribution in the pipeline and taken into account in the subsequent flow deposition process. However, the thermal insulation effect brought by the deposition in the pipeline will have an effect on the temperature field distribution, resulting in the dynamic evolution of the deposits. The numerical simulation results show that: the hydrates are firstly deposited on the top of the pipeline with the increase of hydrate volume fraction in the pipeline inlet, showing the trend of marginalization and centripetal growth. More hydrates will be formed in the system as the degree of supercooling increases continuously, but there is an obvious threshold for the maximum particle size. Among different flow modes, it is found that uniform flow is the safest flow condition in the pipeline. It can provide theoretical basis for the exploitation, prevention and control of deep-sea hydrate slurry.

Keywords

• deep-sea pipeline
• natural gas hydrate
• interfacial area transport
• phase change
• deposition