Influence of Alkaline on Generating Aluminum Ammonium Sulfate inside an Air Preheater in a Coal-fired Power Plant

Abstract

Influence of alkaline compounds on generating aluminum ammonium sulfate, which was thought to be a main cause of rising differential pressure of an air preheater in a coal-fired power plant, was basically investigated. Performing thermodynamic equilibrium calculation based on the condition of coal combustion flue gas indicated that aluminum ammonium sulfate would be generated inside an air preheater. When alkaline component such as Ca or Na was added to the calculation condition, the production of aluminum ammonium sulfate was reduced by the formation of alkaline sulfates. Aluminum ammonium sulfate was experimentally synthesized by heating the mixture of coal ash, sulfuric acid, ammonium bisulfate, and a small amount of ionexchanged water at 150℃ which was equivalent to an outlet temperature of an air preheater. When alkaline compounds containing Ca or Na were added to the raw materials, the production of aluminum ammonium sulfate was reduced by the formation of alkaline sulfates as well as the calculation results. However, addition of insufficient amount of Na caused the formation of hard reaction products instead of sodium sulfate.