Studies on hydrodynamic and mass transfer characteristics of bubble column reactor with and without stirrer

Abstract

Bubble column reactors are commonly used in the field of chemical, biochemical, petrochemical and wastewater treatment due to their simple construction, favourable heat and mass transfer and low operating cost. In the present study, an experimental investigation of the stirred bubble column on its hydrodynamic, mixing and mass transfer characteristics are analysed and compared with conventional bubble column in 0.14m i.d column with 2 m height. The experimental results show that the fractional gas hold-up increases with an increase in superficial gas velocity. The fractional gas hold up is found to decrease with viscosity of the solution for which a comparison is made between water and alcohol system for various concentrations. The mass transfer coefficient increases with an increase in H/D ratio, superficial gas velocity and stirrer speed. The mixing time increases with decrease in H/D ratio. The increase in mixing time is more for Carboxyl Methyl Cellulose (CMC) than Sodium Hydroxide (NaOH) and Barium Chloride (BaCl2) which is due to high viscosity of CMC. In addition, the effect of solid concentration and particle size on gas holdup, optimization of impeller combination and effect foaming agent are studied. Fractional gas holdup is less for solid-liquid-gas system than liquid-gas system. It decreases with an increase in particle diameter and solid concentration and increases with decrease in particle density. Hence it shows more holdup for quartz than sand particles. Critical velocity for solid suspension increases with increase in particle diameter and solid concentration and decreases with increases in rotational speed of the impeller. Among the impeller combination studied, turbine shows slightly higher gas holdup than paddle type. The fractional gas holdup increases by the addition of surfactant (Sodium Lauryl Sulphate) as well as increase in concentration of surfactant. Finally, correlations for fractional gas hold-up is developed for conventional and stirred bubble column. newline newline newline