A flow assurance model for hydrates in natural gas pipelines based on spiral flow

The spiral flow in pipelines is characterized by uniform concentration distribution at sections, low energy consumption, long distance transportation and strong carrying capacity. Therefore, it is necessary to research and develop flow assurance technology of hydrates in natural gas pipelines based on spiral flow, which is promising in making up the deficiency of existing prevention and control technologies, improving the carrying capacity of hydrates and expanding the flow assurance boundary. Based on the suspension characteristics of hydrate particles in spiral flow, the circumferential critical velocity necessary for the effective "suspension" of hydrate particles in spiral flow was obtained after the dynamic equilibrium analysis was performed on hydrate particles. Then, the attenuation law of spiral flow was discussed. Finally, the criteria on flow assurance of hydrates in spiral-flow gas pipelines and the computing model for the safety delivery distance of hydrate particles were developed on the basis of motion equation of hydrate particles. It is indicated from the analysis on case computation that the spiral strength at horizontal straight sections attenuates along the axis exponentially. The effect of spiral flow generation parameters on spiral strength attenuation was studied by controlling the variables. Accordingly, the installation location of the continuous device is determined. It provides the theoretical basis for the spiral flows in pipelines to transport hydrates continuously and effectively.