| In this study, a Computational Fluid Dynamic (CFD) model with chemical reaction was developed to study the effect of hydrodynamics. The model is based on the principles of conservation of mass and momentum. For the solid phase, three different models of solid viscosity: constant coefficient, semi-empirical and kinetic theory, were applied to study the flow behavior in the IIT's circulating fluidized bed (CFB).; In the first case, the hydrodynamics and sorption of SO{dollar}sb2{dollar} with calcined limestone were studied in a PYROFLOW type CFB loop. The effect of gas velocity and CFB geometry on the sorption of SO{dollar}sb2{dollar} was studied. At a velocity of 3 m/s, reported to be a typical velocity by PYROPOWER, there is reasonably good SO{dollar}sb2{dollar} removal. However, the SO{dollar}sb2{dollar} removal was poor when the gas velocity was increased. This is due to the mixing and gas bypassing at the left wall of the reactor caused by the asymmetric solid inlet. Simulation of the PYROPOWER loop with a symmetrical inlet gave us a considerable improvement over the conventional PYROPOWER system.; Next, these hydrodynamic models were used to simulate the flow behavior in the IIT's CFB. The time-average solid velocity, solid concentration and solid viscosity were compared with Miller's experimental data (1991). Both open-loop (only riser was considered) and closed-loop (both riser and downcomer were considered) simulations were performed.; In the open-loop simulation, only constant coefficient and semi-empirical models were used. The solid volume fraction for this case was much lower than the experiment, because there was less internal circulation of solid in the riser. For the closed-loop simulation, all three models of solid viscosity were employed. The constant coefficient model predicted the high solid volume fraction at both sides of the CFB, while the solid velocity for this model is somewhat overpredicted. The kinetic theory model gave a good agreement with the experiments for the solid velocity. The solid viscosities predicted from the new kinetic theory model with high values of restitutive coefficients matched with Miller and Gidaspow experimental data. |
