CFD Simulations On The Internal Loop Air-Lift Bioreactor

The air-lift reactor is a type of bioreactor for contacting multiple phases such as air, water, and biomass. The fluid motion in the reactor is induced by injected air. Typical applications of this kind of reactor can be found in chemical processes, especially aerobic processes.Efficiency of the internal loop air-lift bioreactor depends on the gas holdup, solid hold up, liquid circulation velocity, mass transfer coefficient, liquid diffusion coefficient and so on. Gas holdup and liquid circulation velocity in the reactor are two very important parameters. Reactor with a higher gas holdup and liquid circulation velocity will perform better in the production. The inner tube diameter has a direct impact to the gas hold up and liquid circulation velocity.In this study, taking a 16L center inject internal loop air-lift bioreactors and a 70L side inject internal loop air-lift bioreactor as example, air distribution, velocity and pressure distribution in the bioreactors are investigated with the CFD software Fluent 6.3. The gas holdup and the liquid circulation velocity under different inner tube diameters are also invested and compared. The results present the best inner tube diameters areas, demonstrate that the gas holdup and the liquid circulation velocity are higher with the inner tube diameters in the result areas. This thesis also taking a 70L side inject internal loop air-lift bioreactor as example, monitoring the liquid velocity changing in the riser and descender from the beginning to the steady state.