Abstract In this paper

some research and test work on NO x emission characteristics in a 300MW lean coal-fired boiler are described in detail.Particularly

the effects of combustion conditions

such as load swinging

excess air ratio

OFA and its tilt angle

circumferential air as well as fuel distribution on NO x emission in exhaust gas

are studied.The NO x emission was changed greatly in response to excess air ratio.It was also found that NO x reduction was promoted by OFA positioned at the top of the burner.When OFA was increased and tilting angle was upward

the NO x emission was decreased while unburned carbon in fly ash was increased.In addition

the effect of coal distribution among coal burner layers on NO x emission was studied.With concentrated coal flow in lower layers and weak coal flow in higher layers

both low NO x and high efficiency performance could be obtained.However

NO x emission was still over the standard requirement and further investigation must be strengthened.