Reversed air staging - a method to reduce nitrous oxide emissions from circulating fluidized bed boilers

Reversed air staging is a method to reduce nitrous oxide (N2O)emissions from circulating fluidized bed boilers (FBBs). Tests in a 12 MW circulating FBB show that the N20 emission can be lowered to one fourth without affecting the emissions of NO,SO2 or CO and without adverse effects on the combustion efficiency. The focus of the paper is on the conditions in the combustion chamber. Measurements inside the combustion chamber reveal how the combustion conditions are affected by reversed air staging compared to normal air staging. These measurements confirm the working principle of reversed air staging, namely to provide more oxidizing conditions in the lower part of the combustion chamber and lower stoichiometry in the upper part of the combustion chamber