不同负荷下变SOFA风率对低NO_x燃烧特性影响分析

Analysis of the Influence of the Variable SOFA Air Ratio on Low NO_x Combustion Characteristics

SOFA(分离燃尽风)风率是决定燃尽风技术降低NOx排放浓度的关键因素。运用FLUENT(流体计算软件),对1台采用立体分级低氮燃烧技术的300 MW四角切圆燃烧锅炉炉内燃烧过程进行了数值计算,得出了300 MW、240MW、180 MW负荷SOFA风率分别为28%、20%和15%共9个工况下炉内水平截面的平均温度、组分浓度和NOx浓度随锅炉高度的变化曲线,并进行了详细分析。计算结果表明:随着SOFA风率的增大,同一机组负荷下主燃区内温度水平和平均氧浓度均有所降低,平均CO浓度升高,NOx浓度亦降低,同时煤粉颗粒的燃尽率有所减小。分析结果可为锅炉机组在不同负荷下运行时采用合理的SOFA风率以实现环保经济性运行提供一定的理论参考。

The SOFA air ratio is regarded as the key factor to lower the NOxemissions concentration by using the OFA technology. By using the software Fluent,a numerical calculation of the in-furnace combustion process in a 300 MW tangentially-fired boiler using the stereo-staged low nitrogen combustion technology was performed,during which the variation curves showing the average temperature,concentrations of constituents and NOxemissions concentration in a horizontal section in the furnace under nine operating conditions at the SOFA air ratios of 28%,20% and 15% at the load of 300 MW,240 MW and 180 MW respectively were obtained and a detailed analysis was performed. The calculation results show that with an increase of the SOFA air ratio,both the temperature and average oxygen concentration in the main combustion zone will somewhat decrease,the average CO concentration will increase and the NOxconcentration will also decrease and at the same time,the burn-out rate of the pulverized coal particles will somehow decrease. The analytic results can offer certain theoretical reference for boiler units to use rational SOFA air ratios operating at different loads to realize an environmental protection and economic operation.