Flow Characteristics of Air-lift Pumps for Deep-sea Mining Using Enlargement Conveying Pipe and/or Back-pressure Device

摘要

In deep-sea mining conditions, abrasion on periphery units of the outlet is predicted at large flow rates of supplied air because the velocity of solid-phase becomes very large toward the outlet of the conveying pipe owing to very great expansion of the air and corresponding velocities. In this paper, we present flow characteristics of air-lift pumps for deep-sea mining and discuss methods of the countermeasure. That is, some numerical simulations are performed for the flow conditions of air-lift pumps applied one-stepped enlargement pipe in the end part of conveying pipe and/or added excess pressure using back-pressure device at the outlet of conveying pipe. Consequently, it is found to reduce the velocity of solid-phase at the outlet considerably, almost remaining flow rate of lifting slurry. And we demonstrate most appropriate length of enlargement conveying pipe that maximum velocities of solid-phase became equal in main conveying pipe section and enlargement conveying pipe section. As a result, a guideline and fundamental data to design air-lift pumps for deep-sea mining more practically could be shown.