Experimental and theoretical studies were made in order to discuss the characteristics of the mass transfer between gas and liquid in the gas-stirred system. Carbon dioxide was injected into water. The concentration of carbon dioxide in water was measured by the carbon-dioxide electrode.
The volumetric coefficient (
kLa) was defined by assuming the uniform concentration in the water, where
kL is mass-transfer coefficient, and a is the specific area of the gas-liquid interface. The coefficients were obtained from the concentration change with time under the following conditions: gas-flow rate=1.67 × 10
-51.67 × 10
-4 m
3/s, radius of vessel=0.0550.145 m, depth of water=0.10.4 m, and nozzle diameter=0.6 cm.
A mathematical model for the mass transfer was proposed under the assumptions that the both masstransfer coefficients (
kL) for bubbles and the free surface were given by the HIGBIE's penetration theory. The model consists of the equations for the continuity of solute with constant effective diffusivity and the equations for the flow field proposed previously. Although the computed concentration profiles were not uniform, it was shown that the relation between In((
Ceq-
Co)/(
Ceq-C)) and time was linear and that the slope of the straight line was independent of the location in the vessel, where
C is local concentration,
Ceq is equilibrium concentration, and
Co is initial concentration. Volumetric coefficients (
kLa) obtained from the slope under the various conditions were consistent with those calculated by the HIGBIE's model, and also were roughly consistent with observed ones.
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