NO emissions in oxy-coal combustion with the addition of steam in an entrained flow reactor

Abstract

The NO emissions of a semi-anthracite and a high-volatile bituminous coal were studied under oxy-fuel combustion conditions in an entrained flow reactor (EFR). The results obtained under oxy-fuel atmospheres (21%O2–79%CO2, 30%O2–70%CO2 and 35%O2–65%CO2), were compared with those produced in air. The replacement of CO2 by 5, 10, and 20% of steam in the oxy-fuel combustion atmospheres was also evaluated in order to study the wet recirculation of flue gas. The NO emissions during oxy-fuel combustion were lower than those in air-firing, and a slight increasing trend in NO emissions was observed as O2 concentrations in the oxy-fuel atmospheres increased. Similarly, the NO concentration was reduced by the addition of steam, both under air and under oxy-fuel atmospheres, but no relevant differences between the different steam concentrations were observed.