Integrated real-time optimization of boiler and post-combustion system in coal-based power plants via extremum seeking

AES Cayuga Unit 1 is a 160MW unit, equipped with a low nitrogen oxide (NO_x) firing system and an anhydrous ammonia (NH₃), TiO₂=V₂O₅=WO₃ selective catalytic reduction (SCR) system for NO_x emission control. An ammonium bisulfate (ABS) probe was retrofit to the SCR to monitor ABS formation in real-time with the ultimate goal of minimizing air preheater (APH) plugging (ABS concentration) by regulating the APH bypass damper. Recent work on static optimization of coal-based power plants has played a crucial role in improving overall efficiency. However, static optimization falls short in dealing with real-time scenario changes (i.e., cycling unit load, coal quality, firing system maintenance conditions, subsystem failures, plant aging, etc.). Extremum seeking (ES) is proposed in this work to optimally tune boiler operation in order to minimize NO_x production in real-time. The effectiveness of the ES adaptive controller in keeping the system at an optimal operation point in presence of input disturbances and system changes is demonstrated through simulations based on identified models of the boiler, SCR and APH systems.