Local gas hydrodynamics in an external-loop airlift reactor: newtonian and non-newtonian fluids

Abstract

Measurements of local gas phase characteristics are obtained in an external-loop airlift reactor ®lled with newtonian or viscous non-newtonian liquids. A doubleoptical ®ber probe technique is used. It allows the determination of the axial and radial pro®les of gas hold-up, bubbling frequency, bubble size and velocity. In the case of air-water system, the results show a strong effect of radial liquid velocity variation on the gas¯ow characteristics at the bottom of the riser. In the case of highly viscous nonnewtonian solution, the gas¯ow is strongly affected by the gas distribution just above the gas sparger. This study also points out the bubble coalescence and the break-up phenomena in different liquids and levels in the reactor. Furthermore, the local measurements of bubble size and velocity allows to gain more detailed information on the dynamics of the bubble-¯ow and shows a tendency of large bubbles to circulate in the column center.

Hydrodynamics of a Multi‐Stage Internal Loop Airlift Reactor

“…Fan et al [8] examined the hydrodynamic behavior of an annular three-phase fluidized bed and pointed out that the addition of a concentrically located inner column promoted bubble coalescence. Bentifraouine et al [9] measured the local gas-phase characteristics in an ELALR filled with Newtonian or viscous nonNewtonian liquids.…”

Prediction of gas holdup in a combined loop air lift fluidized bed reactor using Newtonian and non-Newtonian liquids

“…Blazej et al [5] studied the circulation velocity, overall riser and down comer gas holdup using three airlift reactors of different scale. Bentifraouine et al [7] studied the hydrodynamics of external loop airlift reactor using Newtonian and non-Newtonian liquids and they found that for highly viscous non-Newtonian solutions, the gas flow was strongly influenced by the gas distributor. Kilonzo et al [6] studied the influence of baffle clearance on the liquid circulation velocity, gas hold-up and pressure drop in a two riser rectangular airlift reactor with inverse internal loop and expanded gas-liquid separator using different concentrations of CMC solutions and developed gas holdup and liquid circulation velocity correlations using experimental data based on dimensional analysis.…”

Liquid velocity in a three and two phase external loop airlift reactors

“…Осим тога реактори са механичким мешањем имају мању ефикасност (однос преноса масе и унете снаге у систем) у односу на АЛР [20]. Исто тако, у овом типу реактора није лако постићи услове високе стерилности, која је неопходна посебно код фармацеутских процеса, док је код АЛР то врло једноставно остварити услед непостојања покретних делова реактора [21].…”