Relationship between gas-liquid-solid flow patterns and lifting performance of an airlift device

Abstract

Gas-liquid-solid three-phase flows in the airlift device have been mainly limited to laboratory scales. The present study aims to elucidate the relationship between flow characteristics and performance of an airlift device featuring a riser pipe of 200 mm in inner diameter. Both gas-liquid two-phase and gas-liquid-solid three-phase flows were investigated. Solid particles with diameters of 5.0 and 10.0 mm were separately adopted. A validated numerical scheme was employed to solve the multiphase flow field. The results show that before the highest liquid flow rate is reached, smaller particles impose high resistance to flow development. A synergistic effect among particle size, flow pattern, and lifting performance is identified. Compared to bubbly, churn and annular flows, the slug flow exhibits explicit periodicity, which contributes to continuous and stable lifting. Under the same superficial gas velocity, increasing particle size leads to decreased particle lifting rate but results in higher liquid lifting flow rate and efficiency. Although the bubbly flow corresponds to the highest lifting efficiency, low lifting rates of water and particles are evidenced. In contrast, the slug flow is responsible for high lifting performance under both gas-liquid and gas-liquid-solid flow conditions.