A self-sustained one-dimensional experimental furnace for pulverized coal combustion was used to study the characteristics of air-staged combustion and NO_x emission of low-volatile lean coal. The investigation focuses on the influence of air-staged depth and over-fire air(OFA) nozzle position on the NO_x emission

so as to explore the optimal air-staged combustion arrangement to realize low NO_x emission of lean coal. The results show that

the NO_x mass concentration at the furnace outlet gradually decreased with the excess air coefficient αM in the primary combustion zone

and the NO_x reduction efficiency reached 33.1% when αM=0.70. With the increase of OFA nozzle position ratio Ms

the residence time of coal particles in the reduction zone prolonged

the NO_x mass emission further decreased

and there existed an optimal OFA nozzle position ratio. When αM=0.85

the optimal OFA nozzle position ratio was 0.47

and the corresponding NO_x reduction efficiency in the furnace was 37.7%.