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

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%O 2 –79%CO 2 , 30%O 2 –70%CO 2 and 35%O 2 –65%CO 2 ), were compared with those produced in air. The replacement of CO 2 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 O 2 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.