Experimental study of NO emission in coal-methanol co-combustion under air-staged condition

Application of renewable methanol as an alternative fuel is a promising method for both CO₂ and NO emission reduction in thermal power plants fueled by coal. This work gives the first insight into coal-methanol co-combustion from the perspective of NO emission control with a wide range of methanol blending ratio (0%–100 %) involved. Air-staged strategy commonly applied in thermal power plants fueled by coal was considered, and the effects of some key parameters, including burnout air ratio, burnout air injection position and furnace temperature, were analyzed. Experimental results show a significant potential of NO emission reduction in coal-methanol co-combustion, as NO emission from methanol combustion is less than 30 % of that from coal combustion. The correlation between NO emission and methanol blending ratio is approximately linear. Air-staged strategy is still effective for NO emission reduction in coal-methanol co-combustion, and the effects of the key parameter is similar to that in coal combustion. Increase of burnout air ratio and delay of burnout air injection are beneficial, and NO emission can be reduced by more than 70 % compared with that under unstaged condition. Furnace temperature rise is harmful, whereas the corresponding NO emission increase is lower than 30 ppm (@6 % O₂).