Integrated Exhaust System for Simple Cycle Power Plants

Simple cycle power plants are frequently utilized as peaking power plants which generate electricity typically during a high demand. To comply with environmental standards simple cycle power plants are equipped with emission control catalysts reducing emissions of nitrogen oxides, carbon monoxide and other pollutants. In some applications ambient air (so called tempering air) is injected into the exhaust duct to control temperature of the flue gas prior to entering environmental catalysts. Such catalytic treatment of pollutants present in the flue gas requires exhaust systems with substantial footprints to accommodate the emission control catalysts and tempering air injection systems. This paper discusses a new compact exhaust system and efficient arrangement of the tempering air system for simple cycle power plants. The proposed system includes transitioning hot exhaust flue gas into pre-oxidation section of the exhaust system, passing hot exhaust gas through the oxidation catalyst for the CO emissions control, injecting tempering air stream into the post-oxidation section of the exhaust system, and passing cooled flue gas through the reduction catalyst for the NO_x emissions control. The resultant benefit of this newly designed process is a more effective use of catalysts, a smaller exhaust footprint of equipment and a lower capital cost to the end user.