四角切圆燃煤锅炉变SOFA风量下燃烧特性数值模拟

Numerical Simulation on Combustion Characteristics in a Tangentially-fired Boiler with Variable Volumes of SOFA

对某电厂660MW四角切圆燃煤锅炉增加了分离燃尽风(SOFA)的低氮改造,利用Ansys Fluent14.0软件进行了改造后燃烧特性的数值模拟,并将数值模拟结果与实际测量数据进行对比,研究了炉膛速度场、温度场、组分场和NOx质量浓度的分布规律,分析了不同SOFA风门开度下燃烧器区域以及沿炉膛高度方向NOx质量浓度的变化.结果表明:低氮改造中增加SOFA后的温度分布较均匀,切圆形成较好,没有出现火焰贴墙现象;当SOFA风门开度由30%增大到100%时,燃烧器区域最高温度由1 803K降低到1 684K,最高温度降低119K;燃烧器区域NOx最高质量浓度由388 mg/m3降低到259 mg/m3,降低了129 mg/m3;炉膛出口NOx质量浓度由487.9mg/m3降低到307.4mg/m3,降低了180.5mg/m3;通过调节SOFA风门开度可有效降低炉膛出口NOx质量浓度.

To reduce the NOxemission from a 660 MW tangentially-fired boiler,a low NOxretrofit was carried out by adding separated overfire air(SOFA)to the boiler,after which numerical simulation was conducted to the combustion characteristics using Ansys Fluent 14.0software,and subsequently a comparison was made between the simulation results and actual measurements.Meanwhile,the in-furnace velocity distribution,temperature field,species field and NOxconcentration distribution were studied,and the NOx concentration distribution in combustion zone and along furnace height were analyzed at different volumes of SOFA.Results show that after the low NOxretrofit by adding SOFA to the boiler,uniform temperature distribution and ideal tangential firing are achieved without flame adhering to the wall.When the damper opening of SOFA varies from 30%to 100%,the maximum temperature in combustion zone reduces from1 803 Kto 1 684 K,with a reduction of 119K;the maximum NOxconcentration in combustion zone reduces from 388mg/m3 to 259mg/m3,with a reduction of 129mg/m3;the NOxconcentration at furnace exit reduces from 487.9 mg/m3 to 307.4 mg/m3,with a reduction of 180.5 mg/m3,indicating that the NOxconcentration at furnace exit can be effectively reduced by changing the damper opening of SOFA.