Computational Fluid Dynamic Modeling of SO3 Capture by Sorbents in Coal Flue Gas

摘要

Sulfur trioxide (SO3) is produced from the combustion of coal. Within a coalfired boiler, the concentration of SO3 in the coal combustion flue gas is low, typically less than 30 parts per million. However, even low concentrations of SO3 can cause corrosion at lower temperatures within the boiler and can result in the formation of ultra fine sulfuric acid particles in the stack exhaust gases. One method for reducing the concentration of SO3 is to inject powdered, alkaline sorbents into the flue gas. Both mixing of the sorbent with the flue gas and the sorbent reactivity are important in determining the reduction of SO3. In this study, two different types of powdered hydrated lime were injected at two different injection locations in a fullscale, bituminous coalfired boiler in which SO3 removal was measured. The SO3 adsorption process was incorporated into a computational fluid dynamic (CFD) model to account for the coupling between the flow gas dynamics, SO3 concentration in the gas phase and sorbent dispersion, SO3 adsorption. The model captured the effects of injection location, sorbent type and normalized stoichiometric ratio on SO3 removal. The predicted SO3 removal was in good agreement with measured data