Effect of particles on hydrodynamics and mass transfer in a slurry bubble column: Correlation of experimental data

The effects of particle concentration and size on hydrodynamics and mass transport in a slurry bubble column were experimentally studied. With increasing particle concentration, the averaged gas holdup, gas holdup of small bubbles and gas-liquid volumetric mass transfer coefficient decreased, while the gas holdup of large bubbles increased slightly. With increasing particle size, the averaged gas holdup and kla remained unchanged when the particle size increased from 55 to 92 m, but decreased significantly when the particle size was further increased to 206 m. A liquid turbulence attenuation model which could quantitatively describe the effects of particle concentration and size was first proposed. Semi-empirical correlations were obtained based on extensive experimental data in a wide range of operating conditions and corrected liquid properties. The gas holdup and mass transfer coefficient calculated by the correlations agreed with the experimental data from both two-phase and three-phase bubble columns

Kinetic-invariant analysis of dye degradation in an annular slurry bubble-column photo reactor

Heterogeneous photocatalysis refers to the series of oxidation and reduction reactions on a semiconductor surface by the electrons and holes generated by absorption of light by the catalyst. This method is widely used for the degradation of dyes and their mixtures present in the textile effluent, and involves two main aspects, viz. a photocatalyst, and a photoreactor. TiO2 nanoparticles are well explored and among the best known photocatalysts used worldwide. Annular slurry bubble-column reactor is a commonly used photoreactor for dye(s) degradation. This research paper explores the effects of different parameters like air-flow rate, photocatalyst loading, and initial dye concentration on the dye degradation in an annular slurry bubble-column photoreactor. The results showed that the best dye degradation efficiencies were reported at an aeration rate of 1.7 × 10−4 m3/s and at a catalyst loading of 1.5 kg/m3. Higher the initial concentration of dye, the greater is the time taken for complete degradation and mineralization. A kinetic-invariant method, which is based on the dimensionless representation of existing data to predict the new experimental results, is used to develop a semi-empirical reactor performance equation. It can be used to predict the concentration of dye undergoing degradation in the photocatalytic reactor at any time without a need for further experimentation.