Development of an efficient numerical model for two-phase flows in air-lift pumps and its application to deep-sea mining

Abstract

Air-lift pump system has been selected as a potential application to convey the Rare-Earth mud in deep-sea mining processes due to the superior reliability and schematic simplicity. It is a major focus of current research to study the behavior and mechanism of the two-phase flow. Based on the drift flux model and modified Akawa pressure drop equation, mathematical model controlling the numerical simulation of two-phase flow within air-lift pump system is proposed and constructed. Comparison with experimental data concerning steady and unsteady two-phase flows in vertical pipes shows the high precision of the model. Combing with the robustness test results, it can be found that the present model can accurately predict the maximum flow rate of the two-phase flow at the outlet of the gas lift pump, as well as the average gas and liquid flow rates of the two-phase flow at the outlet in both steady and unsteady states. On this basis, several operation laws of the deep-sea mining airlift pump were studied. The relationship between input and output in the mining process is established and the output of the gas lift pump system is predicted. It is found that changing the position of the injected gas, the time for the two-phase flow in the vertical pipe to reach dynamic equilibrium varies equiprimordially. And changing the maximum amount of gas injected, the time required to reach dynamic equilibrium shows a symmetric relationship with the volume fraction after dynamic equilibrium. A series of laws closely related to the prediction of rare earth mud at the outlet of gas-lift pumps in deep-sea mining are investigated to be proposed for subsequent studies.