350MW电站燃煤锅炉NO_x反应特性研究

Study of NO_x Reaction in 350 MW Utility Coal Fired Boiler

对350 MW电站四角切圆燃煤锅炉的NOx反应特性进行了试验和数值模拟.结果表明：燃烧器氧的体积分数从3%增大到5%,NOx排放体积分数从392×10^-6上升到535×10^-6（氧占6%）,上升幅度为33.8%.出口氧量（体积分数）为4%时,锅炉的飞灰含碳量最小,燃烧效率最高.随着氧量的增大,炉膛中心温度、炉膛截面平均温度和炉膛截面最高温度等沿高度的分布有减小的趋势,氧量从3%增大到5%,炉膛中心火焰温度的最大减小幅度为180℃.而随着氧量的增大,炉膛中心NOx体积分数、炉膛截面平均NOx体积分数和炉膛截面最大NOx体积分数等沿高度的分布有增大的趋势.炉膛截面最高温度和最大NOx体积分数沿高度的分布出现在燃烧器区域.截面平均温度和截面平均NOx体积分数沿高度分布的最大值出现在燃烧器上方5-10 m处.燃烧器区域炉膛横截面上NOx最大值出现在旋转火焰的环形区域,中心和四周的NOx体积分数较小,炉膛纵截面上的NOx最大值出现在燃烧器组喷口附近.燃煤锅炉的NOx主要在燃烧器区域生成,燃烧器区域的NOx生成速率是燃尽区域的3-5倍.

A profound study is conducted on NO. emission and its reaction characteristics of a 350 MW utility tangentially fired pulverized-coal boiler with experiments and numerical simulation. The results show： with the increase of the O2 volume fraction from 3% to 5%, NO. emission increases from 392 ppm to 535×10^-6（6%02）,which is up to at 33.8%. When the O2 fraction equals to 4%, the boiler runs in the state of the lowest carbon content of fly ash and the highest burning efficiency. When O2 fraction changes from 3 % to 5 %, all of the central temperature, highest temperature and average temperature of different cross sections of the furnace decrease continuously, the maximum difference of central flame temperature is 180 ℃, but the central NO. concentration, the average NO. concentration and highest NO. concentration of different cross sections keep increasing when O2 fraction is added from 3 % to 5 %. The highest temperature and the highest NO. concentration of furnace are located in burner＇s zone, but the maximum of average temperature distribution and average NO. concentration distribution occurs at the height of 5 - 10 meters. The highest NOx concentration appeares in the annular area of cross sections in burner＇s zone, and nearby the burners＇ outlet in vertical sections. The NOx amount is produced mostly in the burner＇s zone,and its generating rate is 3 or 5 times as many as that in the burnout zone.