Effect of Preoxidation O2 Concentration on the Reduction Reaction of NO by Char at High Temperature

Abstract

Preoxidation experiments were carried out to determine the effect of temperature, ranging from 1000 to 1600 °C, on the O2 enhancement of NO reduction by a bituminous coal char. The results showed that there is a critical O2 concentration that gives a maximum amount of NO reduced by char. The effect of O2 on the reduction of NO indicates a balance between the oxidation reaction and the formation of surface complexes on the char. A large number of C(O) surface complexes can form during the gasification process of char but cannot stably exist at high temperature. The presence of active vacant sites in the complexes is an important factor affecting the reduction of NO and char. This analysis provides a theoretical foundation for further reducing NO emissions during coal combustion. In recent work, we found that a four-level air-staged combustion technology realized ultralow NOx emissions of ∼100 mg/Nm3 at 6% O2, which is much lower than that obtained by the current single-level air-staged technology with NOx ...