The hedge fired boilers in a certain 330 MW power plant appeared to high concentration of nitrogen oxides after commissioning. Through the analysis of the test data and design values

the results show that the OFA（ over fire air） cannot be put into

and low steam temperature

high primary air ratio and oxygen-enriched combustion in primary combustion zone is the main cause of the high concentration of nitrogen oxides on furnace outlet. By taking a series measurement of increasing the flame center

improving steam parameters and adjusting the OFA

furnace outlet nitrogen oxides emission concentration was reduced.