Wa. Almasry et Ar. Dukkan, THE ROLE OF GAS DISENGAGEMENT AND SURFACE-ACTIVE AGENTS ON HYDRODYNAMIC AND MASS-TRANSFER CHARACTERISTICS OF AIRLIFT REACTORS, Chemical engineering journal, 65(3), 1997, pp. 263-271
The hydrodynamics and mass transfer characteristics of a 0.7 m(3) exte
rnal loop airlift reactor were experimentally investigated for superfi
cial gas velocities between 0.02 and 0.18 m s(-1). The reactor was mad
e of QVF glass sections with 6.5 m in height and 0.225 m in diameter o
f both riser and downcomer. The effects of the addition of minute quan
tities of silicone polymer, polypropylene glycol and octanol, on air-w
ater systems were examined. In general, the addition of surface active
agents led to significant reductions in volumetric mass transfer coef
ficients and liquid circulation velocities, relative to the values det
ermined for the air-water system. However, for the gas hold-up, gas di
sengagement section was found to have a great effect on the reactor pe
rformance, especially when foaming increased in the system. Of the two
gas disengagement sections used (namely, closed and open channel) the
closed channel configuration failed to remove the increasing small bu
bbles and the reactor continuity disrupted at high gas throughputs. In
contrast, the open channel configuration improved the reactor perform
ance with substantial reduction in downcomer gas hold-up and increase
in volumetric mass transfer coefficient. (C) 1997 Published by Elsevie
r Science S.A.