Numerical analysis of effects of over-fired air on NO reduction in a down-fired furnace

To investigate effects of over- fired air on NO reduction in a down- fired furnace,Fluent6. 3. 26 which was used to calculate fluid mechanics was adopted to simulate the combustion process of pulverized coal in a down- fired furnace. Parameters in the furnace were obtained at three kinds of over- fire air position,including temperature fields,velocity fields and concentration fields. The interaction of bluff body and over- fire air formed a lean- oxygen area which prohibited the formation of NO. As the over- fire air moved downward,and a larger recirculating zone of pulverized coal appeared. NO content at the outlet of the furnace reduced. The NO at the outlet of the furnace were compared to the experimental data in reference,the error were less than 18. 4%.