A process for reducing an amount of sulfur trioxide present in a flue gas stream (20), including the steps of processing an alkaline material (24) to comprise a predetermined percentage of particles, based on the mass of alkaline material introduced into a flue gas stream (20), having a size less than a predetermined dimension and introducing the processed alkaline material (24) to the flue gas stream (20), wherein the processed alkaline material (24) reduces the amount of sulfur trioxide present in the flue gas stream (20).