Hydrodynamic Studies of Coarse, Fine and Nano Particles in a Cylindrical Fluidized / Spouted Bed: CFD Simulation

Abstract

The fluidization characteristics or hydrodynamic behaviours of coarse (regular / irregular), fine and nano particles have been studied in a fluidized and/or spouted bed for gas-solid system. A stirrer and external force (equivalent centrifugal force) have been used with fine and nano particles respectively for smooth fluidization. The speed of rotation of stirrer with fine particles and frequency of application of external force (magnitude of force) with nano particles were also varied for analyzing the fluidization characteristics. Experiments were carried out in a cylindrical column by varying different system parameters (viz. static bed height, particle size, particle density and superficial velocity of the medium, speed of rotation of stirrer and spout diameter). Fluidization characteristics, such as bed expansion ratio, bed fluctuation ratio, bed pressure drop, minimum fluidizing/spouting velocity and fluidization index of coarse (regular / irregular), fine and nano particleshave been tried to be analyzed by developing correlations on the basis of dimensional less analysis. Finally calculated values of different fluidization characteristics have been compared against the experimentally observed values. The comparison results show a good agreement among the experimental and calculated values thereby indicating the application of these developed correlations over a wide range of parameters.CFD simulation has also been carried out for the hydrodynamic behaviours. Finally calculated values of these fluidization characteristics obtained through CFD simulation have been compared against the experimentally observed values. The results show a good agreement thereby implying the design of fluidizer for gas-solid systems can be optimum design for many chemical industries. The technique of external force application can also be suitably used in industries for handling nano particles with increased efficiencies.