A novel approach for nature gas hydrate separation: Downhole spiral-cyclone coupled hydraulic in-situ separation

The weakly cemented mixture slurry which is formed by the natural gas hydrate (NGH) solid-state fluidization mining method that is composed of natural gas hydrate, sediment and water. The downhole cyclone of NGH needs to deal with such problems as high viscosity, narrow radial working space, and difficult to adjust the split ratio. Directly using the conventional solid-liquid cyclone structure for downhole sand removal cannot obtain good separation performance. And the conventional separator does not have a tubular structure suitable for solid fluidization exploitation of NGH. Therefore, in order to solve the problem of weak cementation between NGH and sediment due to large sand pro-duction during NGH exploitation, this study proposes a new method to separate weakly cemented natural gas hydrate based on the principle of spiral-cyclone coupling. And the model of spiral-cyclone separator was established. This method can break weakly ce-mented solid-phase particles in the slurry, and the effective separation and removal of ultra-fine sediment with cross-scale and micron size. The research also designs and op-timizes the separation device for NGH sand removal. According to numerical simulation and theoretical analysis, the separation efficiency is greater than 60% when the particle size is larger than 5 mu m and the inlet velocity is between 2 m/s and 10 m/s. The research results show that the proposed spiral-cyclone separation method has the characteristics of high separation efficiency, strong sand removal, and can break the cementation bond between the sediment and natural gas hydrate, which is a high-efficiency solid-liquid separation technology.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study proposes a new method for separating weakly cemented natural gas hydrate based on the principle of spiral-cyclone coupling. The method can effectively separate and remove ultra-fine sediment in the NGH slurry, and has a high separation efficiency and strong sand removal capability.