1025t/h旋流燃烧器煤粉炉降低NO_x生成的数值模拟

Numerical Simulation of Decreasing NO_x Emission in a Swirling Combustion Pulverized Coal Boiler

针对某电厂运行中NOx排放量过高的问题,通过对NOx生成机制以及电厂实际燃用煤质的分析,采用去除部分卫燃带以及将主燃区内部分三次风移至主燃区上方的空气分级燃烧技术,对炉内进行降低NOx排放的改造。利用数值计算软件对改造前后的炉内温度水平、组分分布及NOx生成规律进行研究。计算结果表明,改造后,主燃区内氧量降低,炉内整体温度分布水平下降,缺氧燃烧造成主燃区内还原性气氛增强,有效地抑制了燃烧过程中NOx的生成。改造后的试验结果也表明,上移三次风后,炉内NOx生成量显著降低。继续增大上移三次风量的比例,NOx排放浓度持续降低,但飞灰含碳量逐渐升高。综合改造后的试验结果,上移三次风比例为70%时,炉膛出口NOx浓度较改造前降低了40%且对炉内燃烧影响较小,改造效果较好。

By analyzing the mechanism of NOx formation and the coal quality from practical operation in furnace,air-staged combustion was adopted to low the NOx emissions.The characteristics of the temperature,the distribution of species concentrations and NOx emissions in the furnace were numerically studied.The predicted results show that moving parts of jets of the tertiary air to the top of primary combustion zone can reduce the oxygen concentration in the primary combustion zone and decreasing the distribution of the temperature in the furnace.Incomplete combustion will result in increasing the reducing atmosphere in the primary combustion zone.It will inhibit the formation of NOx and increasing the volume of the top tertiary air can reduce the formation of NOx.The experimental results show that in the different proportion of the top tertiary air the thermal efficiency of the boiler don＇t have any obvious variation,the concen-tration of NOx continue decreasing,but the carbon content in fly ash is increased.Comprehensive results show that when the proportion of the top tertiary air is 70%,the concentration of NOx in the export of air preheater is reduced to 40%.It can achieve a better effect than before.