NOx Reduction in a Carbon Monoxide Boiler by Reburning

Abstract

Reburning technology is one of the most promising and cost-effective NOx reduction strategies for combustion systems. In this study, NOx reduction in a CO boiler by reburning is investigated. This study adopts a CO boiler from the Formosa Petrochemical Corporation (FPC) in Taiwan as the model for numerical investigation. It is found that NOx reduction occurs mainly behind the DeNOx section where recirculation is strong. Without reburn air, the size of reburn fuel hole does not significantly influence the NOx reduction, although a larger size is a little better. Without reburn air, a larger reburn fuel hole yields a higher temperature near the reburn fuel hole and leads to a better NO reduction. Injection of reburn fuel without reburn air results in higher CO emission. For a “richer” primary fuel without reburn air, reburn fuel fraction and injection location do not significantly influence the NOx reduction. The reburn air closer to the reburn fuel yields a lower NO emission. Temperature decreases first and arises then near the reburn air injection location. Combustion is more complete when the inlet air flow rate is increased. Increase of inlet air flow rate yields a higher NO emission and a lower CO emission. The cross- sectional average temperature decreases with the inlet air flow rate.