Computational and Experimental Studies on Gas-Solid Fluidized Bed Reactor for Treatment of Industrial Gaseous Effluent Containing Fluorides

Abstract

Fluidization with respect to abatement of fluorides is carried out experimentally using fluidized bed reactor (FBR). Treatment of gaseous effluent from Aluminium industry containing fluorides is considered as a case study. For knowing the optimum operating conditions of FBR, some hydrodynamic studies are carried out in a Perspex column. After which same conditions in addition to the temperature effects are maintained in a stainless steel reactor of same dimensions. Different bed materials are used at different temperatures to check the maximum reduction of fluorides from industrial effluent gas. The phase composition and structural transition of bed materials at different temperatures are investigated. Characterization of bed materials before and after the experiments are carried out from which abatement of fluorides from industrial effluents is confirmed.
For proper design of fluidized bed reactor CFD simulation is carried out by using the commercial CFD solver ANSYS/FLUENT 13.0 in the present work. All phases are described using an Eulerian approach to model the exchange of mass, energy and momentum. The appropriate model predictions are achieved, using Gidaspow drag model with restitution coefficient of 0.9, convergence criterions as 0.001, no slip boundary condition of specularity coefficient and first order discretization scheme. Hydrodynamic studies for the fluidized bed reactor are carried out computationally using fine i.e. Geldart-A particles. Effects of superficial velocity, static bed height, particle size and density of bed materials on bed pressure drop, bed expansion / fluctuation and fluidization index are studied. Results of experimental and computational studies are compared with each other. The comparison shows that CFD modeling is capable of predicting the hydrodynamic behaviors of gas–solid fluidized bed for fine particles with reasonable accuracy. CFD modeling is also carried out for thermal analysis. Velocity profile, bed expansion, solid movement, temperature profile are also focused in the present simulation work. Results of CFD simulation indicate that CFD modelling can be used to study the performance of fluidized bed reactor for high temperature reactions satisfactorily.