Hydrocyclone used for in-situ sand removal of natural gas-hydrate in the subsea

Abstract

The extraction of natural gas hydrates (NGH) for using as an alternative energy source necessitates the separation of sands from the mixed slurry of gas hydrates and backfill of the sand slurry onto the seafloor. Conventional hydrocyclones used for mining cannot be applied to such conditions due to the limited space of the mining pipeline. Therefore, here we propose a hydrocyclone suitable for subsea gas hydrate extraction. This study is intended to study the effects of operating parameters and geometric parameters on the performance of the hydrocyclone by experiment and computational fluid dynamics (CFD) method, and to improve the performance of the hydrocyclone. The results show that the optimal flow rate of the hydrocyclone separator is 7 m3/h; as the solid content of the inlet increases, the separation efficiency will decrease, and the pressure drop will increase. The energy consumption caused by the vortex in the blind zone can be reduced and the separation efficiency increases as the X/D decreases. The separation efficiency first increases and then decreases with the increase of L/D. The separation efficiency reaches its maximum when L/D is 1.2, but further increases in the L/D will increase the resistance loss along the journey, and the pressure drop will continue to increase. This study is applicable to solid-liquid separation in underground mining pipelines. The purpose of this study is to achieve real-time sand removal and the backfilling of sand slurry in addition to guiding industrial design.