Abstract: The content of O2，CO，NOx and other gases，and the furnace temperature at different axial and radial positions in the downstream main combustion zone of a burner were measured in a 300 kW thermal pilot test furnace.Accordingly，the influence of the extensive angle of an once-through boiler´s blunt body on the ignition characteristics of Shenmu semi-coke and Shenhua bituminous coal co-combustion（semi-coke and bituminous coal were blended with a mass ratio of 45∶55）and NOx emissions was investigated. The results show that with the enlarging of the extensive angle，the ignition position gradually moves towards the upper chamber of the furnace，and the valley value of O2 volume fraction and the peak value of CO mass concentration，namely the strong reducing atmosphere，gradually move towards the furnace wall along the radical direction. When the extensive angle is 29°，the overall temperature of the furnace is considerably high，and the combustion is stable and the NOx emission is reduced.

Key words: semi-coke, bituminous coal, co-combustion, burner with blunt body, extensive angle, ignition characteristics, NOx emission