Effect of initial droplet size distribution on sulfur removal efficiency in FGD SDA

Dry scrubbing with lime slurry in a spray dryer [spray dryer absorber (SDA) ] has been an important technology for flue gas desulfurization (FGD). Math ematical models based on the heat and mass balances are used to predict SO2 removal in the SDA as a function of initial size distribution of slurry dr oplets. Since the existence of moisture in the droplets appreciably enhance s the SO2 removal, its removal efficiency depends on the rate of drying as well as that of SO, removal itself, both depending on droplet diameter. Wit h the increase in the geometric standard deviation (GSD) of the initial dro plet size distribution, the efficiency of SO2 removal first increases and t hen decreases, showing a maximum at a certain value of GSD. This trend is a ltered by the sorbent content of the droplets, expressed as stoichiometric ratio (SR). The decrease in SR makes the maximum move to higher GSD and red uces the variation in the efficiency with respect to GSD. For SR<0.73, a mi nimum efficiency also appears, ahead of the maximum. The results are well e xplained by the specific rates of both drying and SO2 removal of the drople ts.