Pilot tests were carried out on a 1 MW pulverized coal combustion furnace with a new type radial bias whirl burner to clarify the NOxemission and coal combustion characteristics.Two opposing dual channel whirl burners were applied

and the over fire air(OFA)nozzles were arranged above the burners along the furnace height.This type of burner had a cross-section changing primary air pipe

inside which the pulverized coal and air mixture was divided into two streams

namely the pulverized coal rich annular jet outside and the pulverized coal lean annular jet inside.Due to the inertial force

a dense-dilute pulverized coal concentration profile in the radial direction of the burner nozzle was formed.Hot state meld tests were performed on Shanbei Shenhua high rank bituminous coal(SH coal)

Shanxi Hejin low rank bituminous coal(HJ coal)and Shanxi Changzhi lean coal(CZ coal).The results showed that

the relative position of the OFA nozzle had a significant effect on NOx emission and carbon content in fly ash.When the relative position of the OFA nozzles and the burners was from near to far

NOx emission of all three coals first increased then dropped

while the carbon content in fly ash first decreased then rose.The OFA air staged combustion technology was beneficial to NOxreduction of the high volatile fuel and carbon content in fly ash drop of the low volatile fuel.Reasonable design and arrangement of the OFA nozzles can reduce the NOx emission and decrease the carbon content in fly ash simultaneously.