Hydrodynamic, mixing and mass transfer characteristics of multiphase reactors

The multiphase reactors such as solid-liquid fluidized beds and bubble columns are widely used chemical, petrochemical and allied industries. Their application ranges from manufacturing processes such as catalytic hydrogenation, oxidation, fermentation, waste water treatment, Fischer-Tropsch Synthesis and Chromatographic separations etc. The performance of these multiphase reactors depends on hydrodynamic, mixing and mass transfer characteristics. With this objective, in the present research work, an attempt has been made to understand the rational design procedures for multiphase reactors such as solid-liquid fluidized bed (SLFB), Solid-liquid multistage fluidized bed (SLMFB), Solid-liquid circulating multistage fluidized bed (SLCMFB) and Bubble column reactors. Liquid phase residence time distribution (RTD) studies have been performed in conventional SLFB and SLCMFB. RTD experiments for SLFB were carried out in the column having the same diameter as the downcomer of SLCMFB. RTD has been estimated for both the riser column and the multistage downcomer column of SLCMFB. Computational fluid dynamic (CFD) simulations of SLFB and riser section of SLCMFB have been performed to predict the RTD. In all the above cases, good agreement was found between the CFD predictions and the experimental measurements. Based on the experimental data, empirical correlations have been proposed for liquid phase axial dispersion coefficient. Solid-liquid mass transfer coefficient (kSL) was measured in both conventional SLFB and SLMFB by using the system of dissolution of benzoic acid in water. The dependence of kSL on important variables associated with the distributor design and the effect of inerts has also been studied. Based on the experimental data, generalized correlation has been proposed for the estimation kSL for both SLFB and SLMFB. Radioactive Particle Tracking (RPT) technique was employed to quantify the hydrodynamic parameters in 120 mm diameter bubble column with and without internals using air/water systemat different superficial gas velocities ranging from 15 mm/s to 265 mm/s. Experiments were performed for two internal configurations with percentage obstruction area in the range from 0 (no internals) to 11.7%. It is found that, the liquid phase hydrodynamics depends strongly on the superficial gas velocity and the internals. Suggestions have also been made for the future work.by Dinesh Kumar KalagaPh.D