A lab-scale air-lift pumping system with 3.64 m straight pipe is designed and manufactured to analyze and understand operational performance and characteristics of the air-lift pump. The experiments for air-liquid-solid three-phase flow in vertical pipe are performed by systematically changing experimental parameters, such as air injection rate, air injection points, pipe diameters, solid particle size and density, and solid injection rate. From the experiments, it is confirmed that the variables, such as superficial velocity of seawater and solid particle, in-situ velocity and volume fraction of solid particle in the suction pipe, and pumping efficiency, are inevitably affected by these parameters. An Optimization of these parameters is necessary to design and operate such a system adequately. Also, the effect of air-injection point rather than submergence ratio on the small-scale air-lift pump can be examined and the optimum efficiency of gas-liquidsolid 3-phase air-lift pump by extending the theory of gas-liquid 2- phase air-lift pump can be obtained.
Recently the world is developing the plan for the use of deep-sea metallic resources because of the reduction of land resources. However, it is essential to have integrated mining technology for developing deepsea manganese nodules. To lift the manganese nodules from deep seabeds, the hydraulic pumping system (Chung et al., 1998; Yoon et al., 1999) and the air-lift pumping system are recommended for commercial lifting. In the past, the small-scale air-lift pump was used to lift corrosive and/or toxic liquid, so the main concern was how the submergence ratio of the liquid in a vertical pipe affects the gas-liquid two-phase flow. Recently, the utilization of a large-scale air-lift pump with about 1.0 of submergence ratio is anticipated and examined in the lifting of manganese nodules from about 5,000 m in depth of seabed.
