Simulation of sulfur-dioxide removal via hydrated lime slurries in a spray dryer absorber flue gas desulfurization system

The objective of this study was to numerically analyze an SO{dollar}sb2{dollar} removal process by combining a two phase gas-solid reaction (dry particle) stage with a three phase gas-liquid-solid reaction (wet particle) stage. The SO{dollar}sb2{dollar} removal process in a spray dryer absorber flue gas desulfurization system was simulated and studied by the mathematical model developed. This model involves the simulation of the evaporation of water from atomized slurry droplets, the absorption/reaction of SO{dollar}sb2{dollar} in the slurry droplets, and the transport phenomena in both wet and dry particle stages. Two stages of evaporation which include a constant-drying period and a falling-rate drying period were described by the corresponding mass and heat transfer rate relations. The absorption/reaction of SO{dollar}sb2{dollar} in the wet particle stage was modeled using the modified Ramachandran and Sharma's film model. The grain model was adopted to evaluate the SO{dollar}sb2{dollar} removal rate in the dry particle stage.; The model predictions were compared with experimental data taken over a wide range of operating conditions. These data were collected from three different pilot scale test programs. The predictions made by the developed model show satisfactory agreement with experimental data. The influence of high inlet flue gas temperature on the dry particle stage is not nearly as significant as that of approach to saturation temperature. It was concluded from this research that the dry particle stage exhibits a strong effect on SO{dollar}sb2{dollar} removal and should be included in the simulation model of SO{dollar}sb2{dollar} removal by a spray dryer absorber.