NOX selective catalytic reduction control based on simple models

In the paper, a new approach to the control of the selective catalytic reduction process of NOX is presented. The reduction pro- cess can be eciently controlled using a combination of feed-forward and feed-back control structures. However, this approach requires expensive measurement equipment. It is shown that measurement of nitric oxide concentration at the input of the catalytic converter and measurement of the ¯ue gas ¯ow rate can be successfully substituted by corresponding ``software sensorsʹʹ. The software sensors are based on simple mathematical models and on measurements of excess oxygen concentration in ¯ue gas and the fuel ¯ow rate which are usually parts of already available standard combustion control system equipment. In the paper the com- plete derivation of the required mathematical models is given, and the proposed new control structure is described. The structure is tested using simulation and implemented on an industrial pilot plant.