Optimal Ammonia Injection for Emissions Control in Power Plants

One of the effective devices to reduce NOx in power plants is the ammonia based selective catalyst reduction (SCR) system. In this paper, kinetic SCR model simulator is tuned and validated with representative site data from an actual combined-cycle power plant. This simulator is then used for the development and implementation of model predictive control (MPC) for SCR systems to control the plant startup NOx emissions along with maintaining ammonia slip within the acceptable limit. Also, the results of linear and nonlinear MPC are compared. The startup NOx reduction obtained in both cases is seen to be close to ~85%, but the computational effort required for both these approaches differ significantly.