Hydrodynamics in an internal loop airlift reactor with a convergence-divergence draft tube

Gas holdup and liquid circulation of one conventional draft tube and three different convergence-divergence draft tubes in an internal loop airlift re actor were investigated. Experiments were carried out in two-phase systems with air;water and air-CMC (carboxyl methylcellulose) solution and three-ph ase system with air-water-resin particles. The two-phase drift-flux model w as used to estimate gas holdup for three-phase Newtonian and two-phase non- Newtonian systems. It is shown that gas holdup in convergence-divergence dr aft tubes is higher than that in a conventional draft tube and increases wi th superficial gas velocity. Variation of the structural parameters of conv ergence-divergence draft tubes has little effect on gas holdup in the two-p hase and three-phase system. The mathematical model, which is based on a dr ift-flux model, was developed to describe the liquid circulation velocity i n the reactor satisfactorily.