The effect of particle size on the reflux performance of the lifting pumps

Deep-sea mining lifting pump differs from conventional solid–liquid two-phase flow pump, due to the complex and ever-changing operating environment. It is more likely to experience emergency shutdowns and particle reflux, leading to pump blockage and ultimately causing damage to the lifting system. Research on the influence of particle characteristic parameters on pump reflux performance can provide theoretical support for the design of high-performance deep-sea mining lifting pumps. The impact of particle size on the reflux performance of a mining lifting pump during shutdown was investigated in this study. The coupling method of CFD–DEM (computational fluid dynamics–discrete element method) was employed to simulate the reflux of spherical particles with different sizes (5 mm, 6 mm, 7 mm), and comparative analysis was conducted to the reflux performance of particles with varying sizes in the lifting pump. The results indicate that particles tend to accumulate at the junction between the impeller and guide vane when reflux occurs in the lifting pump. As the particle size increases, the distribution of particles in the first and second-stage pump becomes denser, resulting in less smooth reflux inside the pump and noticeable clogging. Moreover, particle accumulation gradually extends into the flow channel of the impeller and guide vane. The average velocity of particles gradually decreases with larger particle sizes; this leads to an increase in the time it takes for particles to pass through the pump and a gradual deterioration in the reflux performance of the lifting pump. Further analysis indicates that the ratio of collision number between particles to the total number of collisions increases continuously with the increase in particle size. Additionally, as the particle size increases, the proportion of collisions between the particles and the second guide vane significantly increases.