This paper is concerned with constructing the numerical model for steady gas-liquid-solid threephase mixture flow in a lifting pipe. Air lift pumps are regardedas one of the convenient means of lifting slurries and solid particles such as manganese nodules from the deep-sea bed of about 5, 000m to the sea surface.
Here, the case is treated where the three-phase fluid is the slurry consisting of very small air bubble phase and solid particle phase mixed in water phase. The equations governing the gas-liquid-solid threephase slurry flow are formed by three continuity equations, only one momentum equation, a gas equation of state andan equation for three-phase volume fractions. These six equations are cooperatedinto the only one equation to find the change in the gas-phase volume fraction according to the vertical position. Thereby, the remaining flow parameters can quantitatively be determined in the present model.
Again, some numerical experiments are performed using this model. When the gas-phase volume fraction is given at the deep-sea bed, the corresponding solid-phase volume fraction can be determined between the upper and lower limits. It is shown that the solid-phase volume fraction near the lower limits leads to increasing the lifting efficiency of the solid-phase. Furthermore, it is demonstrated that there is a limiting curve to predict the maximum solid-phase mass flux against the solid-phase volume fraction at the deep sea bed.
