MODELING A CIRCULATING FLUIDIZED-BED RISER REACTOR WITH GAS-SOLIDS DOWNFLOW AT THE WALL

A predictive model was developed for the fully developed zone of a cir culating fluidized bed (CFB) riser reactor operating in the fast fluid ization regime that overcomes limitations of existing models. The mode l accounts for the upward flow of gas and solids in the core and downw ard flow of the two phases in the annulus. Additionally, a numerical s olution methodology for the simulation of a riser reactor employing th e hydrodynamic model was devised. A simulation was performed using the fast, main Claus reaction to demonstrate the effects of backmixing in the fast fluidization regime. It was found that the molar flow rates of the reactants leaving a fast fluidized CFB riser reactor were signi ficantly higher than those leaving an identical reactor operating in t he pneumatic transport regime.