Hydrated lime (Ca(OH)(2)) is widely used as a sorbent in the dry and spray-drying flue gas desulfurization processes. The reaction of Ca(OH)(2) with SO2 at low temperatures in these processes is well described by the equations obtained from a surface coverage model. The model assumes that the rate is controlled by the chemical reaction occurring on the water-adsorbed sorbent surface and considers the surface coverage by the product. The results of this study are useful for the design and operation of dry and spray-drying processes using hydrated lime.