Oxy-fuel combustion has an advantage of easy CO2 recovery due to its high CO2 concentration in exhausted gas.It is a promising combustion method for coal.In this work

the change of conversion ratio of fuel-N to NO with CO2 concentration

reduction ratio of recycled NO in the reducing zone of volatile matter combustion

and the influence of recycled NO on conversion ratio of fuel-N to NO were investigated

and corresponding correlations were obtained.With these experimental results and theoretical analysis on the material balance in the system

the conversion ratio of fuel-N to NO in the system was derived.The results revealed that much less NO was released in a dry-recycle system than in a wet-recycle system

due to a higher gas recirculation ratio in the dry-recycle system.With oxy-fuel combustion

NO emission can be reduced to about only 1/7 of conventional air combustion.This effect is mainly attributed to the reduction of recycled NO.NO concentration increases with nitrogen content

but the increase in NO concentration is less than that in nitrogen content.As nitrogen content increases

the conversion ratio of fuel-N to NO of the system decreases.