Hydrodynamic Behaviour in a New Gas-Liquid-Solid Inverse Fluidization Airlift Bioreactor

Abstract

A gas-liquid-solid inverse fluidization airlift bioreactor was proposed by combining advantages of external-loop airlift reactors and inverse fluidized beds. This airlift bioreactor comprises a gas-liquid riser, a gas separator, a liquid-solid inverse fiuidized downcomer and a bottom connector. The effects of the gas velocity and the particle loading on the gas holdup in the riser and the liquid circulation velocity in the loop were investigated. Liquid-solid inverse fluidization in the downcomer was also studied. The gas holdup in the riser was experimentally found to increase with the increase in the particle loading and in the gas velocity. The liquid circulation velocity decreased with the increase in the particle loading whereas it increased with the gas velocity. It was found that the Richardson and Zaki model fitted experimental data of bed expansion of liquid-solid inverse fluidization in the downcomer well. Based on an energy balance, two hydrodynamic models were proposed to predict the liquid circulation velocity in the present bioreactor. It was shown that the present models gave a good fit to experimental data in this bioreactor.