Gas–liquid mass transfer in a high pressure bubble column reactor with different sparger designs

Abstract

The gas–liquid mass transfer in a 0.162 m high pressure stainless steel bubble column was investigated using three different gas sparger designs. An oxygen-enriched-air dynamic method and an optical oxygen probe technique were implemented to measure k 1 a values in the bubble column reactor. Using the interfacial area ( a ) values measured by a four-point optical probe technique at similar conditions ( Xue, 2004), the k 1 values were estimated. Axial dispersion model (ADM) and continuous stirred tank reactor (CSTR) model were used to calculate k 1 a as a fitted parameter with the measured data. The ADM gave better fits to the experimental data than the CSTR model, especially at high axial locations for the bubble column used with a large L / d c ratio. The sparger design was found to have a noticeable effect on k 1 a in the low gas velocity range ( u g < 0.15 m / s ) but only a slight effect in the high gas velocity range ( u g > 0.20 m / s ) . The sparger design showed almost no effect on the liquid side mass transfer coefficient, k 1 , at high gas velocity ( u g = 0.30 m / s ) , where no significant variations of the bubble size distribution and hydrodynamics were obtained using different sparger designs. Although the k 1 a values increased with the operating pressure, the pressure change from 0.1 to 0.4 MPa yielded lower k 1 values, as a result of the reduced bubble size. However, as the pressure further increased to 1.0 MPa, the a and k 1 a values increased, while the k 1 values negligibly decreased. In addition to the pressure and sparger design effects, the superficial gas velocity had effect of increasing the k 1 values, while such effect became small and flattened out at high superficial gas velocities.