To solve the NO

x

concentration is higher（900-1 000 mg/Nm

3

） when burn lean coal on storage type pulverizing system

four way tangential firing boiler of 300 MW

the chamber of a stove or furnace outlet NO

x

concentration to 550 mg/Nm

3

after burner alteration. National and local environmental standards improve need to further reduce

after tertiaryair then ran a burner wind to rearrange

part tertiaryair into the main combustion zone combustion-supporting renovation

the chamber of a stove or furnace outlet NO

x

concentration down to about 480 mg/Nm

3

low nitrogen combustion retrofit for similar boiler provides reference.