Wall-To-Bulk Mass Transfer in a Gas Liquid Upflow Bubble Column

Abstract

Experiments have been carried out to investigate the effect of liquid and gas velocities, viscosity and gas hold-up on wall-to-bulk mass transfer coefficient in a gas–liquid upflow bubble column using limiting current technique. The system chosen was an electrolyte as liquid phase and inert nitrogen as gas phase. The electrolyte was an equimolar solution of potassium ferricyanide and potassium ferrocyanide of 0.01 N with 0.5 N sodium hydroxide as indifferent electrolyte. To vary the viscosity carboxy methyl cellulose sodium salt (CMC) in 0.1, 0.2 and 0.4 wt% was added to the electrolyte. The reaction considered was the reduction of ferricyanide ion. The experiments were carried out at constant temperature of 25 °C at which the physical property values of the electrolyte were known from literature. The mass transfer coefficient was computed from the measured limiting current. It was found that the mass transfer coefficient was relatively independent of liquid velocity with in the range covered in the present experiment. The kL increased with increasing gas velocity and gas holdup. The kL was observed to decrease with increasing CMC concentration. The entire experimental data have been correlated in terms of Colburn j-factor, Reynolds number and modified Froude number.