Optimization of Separated Overfire Air System for a Utility Boiler from a 3-MW Pilot-Scale Facility

详细信息    查看全文

• 作者：Jianwen Zhang ; Kai Chen ; Chang鈥檃n Wang ; Kun Xiao ; Xueyuan Xu ; Defu Che
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：February 21, 2013
• 年：2013
• 卷：27
• 期：2
• 页码：1131-1140
• 全文大小：616K
• 年卷期：v.27,no.2(February 21, 2013)
• ISSN：1520-5029

文摘

A 3-MW pilot-scale facility was used to study the effect of separated overfire air (SOFA) on NO_x emissions from utility boilers. Experiment results showed that NO_x emissions decreased as the excess air ratio in the main combustion zone first decreased, but remained unchanged when the excess air ratio was above a certain value; the carbon content in fly ash increased with the decrease of the excess air ratio in the main combustion zone; NO_x emissions decreased and the heat loss due to unburned carbon increased as the residence time in the reduction zone (the zone in the furnace from the middle of combustion zone to the middle of the SOFA zone) increased. Based on the experiment results, a residence time of 2.12鈥?.68 s is recommended for the reduction zone. Besides, numerical simulations were conducted about the pilot-scale facility and a 600-MW boiler firing the blended coal of Shenhua coal (80 wt鈥?) and Baode coal (20 wt鈥?). The simulations, together with the experiments, showed that there was a critical excess air ratio with value of 0.8 for the minimum NO_x emissions with relatively low unburned carbon. This critical value, together with the residence time of 2.35 s, which is in the range recommended by our experiments, were used in the retrofit of the 600-MW boiler by SOFA technology, leading to a reduction of NO_x emissions as high as 60%.