Experimental investigation on the flow behavior during the solid particles lifting in a micro-bubble generator type airlift pump system

Abstract

The airlift pump system includes the both air and liquid inlet sections, and the vertical pipe as the transporting medium. The low performance of the concurrent airlift pump systems has promoted efforts to further improve performance in implementation of these devices in various conditions of real sediment transport on sea and lakebeds. In the present experimental study, we have modified the conventional airlift pump system by equipped our developed micro-bubble generators in the system. Here the three-phase flow behavior during the solid particle lifting of the micro-bubble generator type airlift pump system during the transient conditions is reported. The inner diameter of the vertical pipe of this airlift pump system was 50 mm. Several inclination angles of micro-bubble injection were used: 15°, 30°, and 45° from the horizontal. The working fluids were air and water. The tested solid particles were solid and coal with the averaged of particle diameters were 0.33 mm, 0.52 mm, and 0.81 mm. The ranges of supplied flow rates of liquid and air, QL and QG, were 7.0 m3/h–9.0 m3/h., 0.3 l/min–0.8 l/min, respectively. The obtained visualization images were analyzed by using the developed image processing technique.As a result, it was obtained that (1) the optimum solid lifting performance was found under the slug flow pattern due to their buoyancy force, (2) main parameters such as the injected inclination angle of the micro-bubble generator, the liquid and gas volumetric flow rates, the averaged particle diameters, and the density of the lifted particles affect the ability of the micro-bubble generator type of the airlift pump system, (3) The used of micro-bubble generators in the air lift pump system will increase their capability to bring the solid particles upward at least 17% compared to conventional airlift pump systems. Keywords: Airlift pump, Micro-bubble generator, Visualization study, Image processing technique, Slug flow