Numerical simulation of hydrate slurry flow behaviors with micron-sized sand in the transport pipe based on the population balance model

Both micron-sized sand particles flowing into the pipe and the secondary formation of natural gas hydrate will pose a great threat to the flow assurance of the pipeline for hydrate exploitation. Therefore, based on the population balance model considering the aggregation and breakage of hydrate and micron-sized sand particles, the flow characteristics coupling hydrate and micron-sized sand are studied, and the effects of flow velocity are discussed. The results show that the slurry viscosity increases significantly at the lower part of the horizontal pipe where the solid particles tend to aggregate. After the slurry enters the elbow pipe, the viscosity, hydrate concentration, and particle size gradually decrease, while the sand concentration first increases and then decreases. Solid particles with relatively high concentration and large particle size appear on the outside of the first half of the elbow. In the vertical pipe, the hydrate concentration and particle size gradually increase again, and the hydrate with high concentration and large particle size appears on the inside. Besides, the coupling aggregation of hydrate and sand particles is concentrated near the wall of the bottom of the horizontal pipe, near the wall of the outside of the elbow pipe and the inside of the second half of the elbow, and near the wall of the vertical pipe. The high flow velocity has a great ability to carry the hydrate with high concentration and large size.