Application of CFD Methods to the Analysis of the Flow in Air-Lift Pump

Abstract

In order to improve the understanding of the air-lift process a Computational Fluid Dynamics (CFD) model has been developed. A multi-fluid Eulerian approach is used in the modeling. Three independent interpenetrating phases are considered: a continuous liquid phase (water) and two discrete phases (air bubbles and solid particles). The simulations are conducted two-dimensionally. After the transient computational results have been obtained for a sufficiently long time period, averaging is done to obtain mean values of the flow rates for all the phases. The model has been verified by comparison with published experimental results for the air-lift pipes in the range of 300–450 m in height. Good agreement between experiment and computations has been obtained. The solution process proves to be sufficiently robust for a fairly wide range of particle sizes, densities, flow rates, pipe and injection depths, and inlet volume fractions. Flow analysis reveals the distribution of velocities and volume fractions for all phases inside the airlift pipe that improves our understanding of the process. The computational results highlight some interesting transient behavior of the multiphase flow in the pipe. The numerical model can be utilized during various stages of the design of the air-lift pumps to help answer fundamental questions on the process, and during their operation to select optimal process parameters and to address possible problems.