Optimizing airlift pumps for efficient solid-liquid transport: Effect of particle properties, submergence ratio, and injector design

Abstract

Airlift pumps have been widely utilized for liquid transport and have recently shown significant potential for efficiently handling slurry flows in many applications such as mining, wastewater treatment, dredging, and oil and gas, where the need for effective solid-liquid transport is critical for operations like removing sediments, transferring drilling mud, or managing slurries in pipelines. The present study experimentally investigates the performance of airlift pumps under three-phase solid-gas-liquid flow conditions, emphasizing the influence of particle properties (diameter and density), pump submergence ratio (SR), and injector design. The experimental setup involved two types of solid particles (glass and ceramic) with different densities (2835 kg/m³ and 2668 kg/m³) and sizes (1, 4, and 5 mm), three SRs (50 %, 70 %, and 90 %), and two injector designs (annular and swirl). High-speed imaging and flow measurements were used to assess the dynamics within the riser pipe and evaluate pump performance. It was found that the presence of solid particles significantly reduces the liquid phase deliverability, reducing the superficial velocity of the lifted liquid phase and therefore the pump's effectiveness, notably at smaller particle sizes due to momentum transfer to the solid phase and clogging effects. Pump performance was evaluated based on three key operational phases: start-up, transitional, and steady state. The results show that smaller, less dense particles and higher SRs significantly improve the solid production rate and effectiveness and accelerate the transition phase where the pump begins lifting solid particles. The swirl injector design that promotes angular momentum transfer to the liquid as the carrying medium for solids was found to increase solid particle discharge rates and consequently improve pumping effectiveness. The present results are correlated with the Stokes number to describe the inertia of the solid particles relative to viscous drag forces, determining how well the particles follow the liquid's motion. Consequently, the study introduces new performance curves that demonstrate the interaction between solid particle concentration, terminal velocity, and known airlift pump parameters such as lifting efficiency and effectiveness. These findings provide valuable insights for optimizing airlift pump system designs for a wide range of industrial applications, where efficient solid-liquid transportation is crucial.