钝体关键参数对煤粉燃烧效率和NO排放量的影响

Influence of Blunt Body Key Parameters on Pulverized Coal Combustion Efficiency and NO Emission

钝体可以改变煤粉气流的流动状态,加速二次风和煤粉气流在燃烧室内部的混合,改善煤粉燃烧环境.提高煤粉燃烧效率,降低污染物排放,本文基于Fluent软件平台,以CO/CO2比值作为煤粉燃烧效率的评价指标,以NO的质量分数作为主要污染物的评价指标,合理简化并构建煤粉热燃烧行为的控制模型,以煤粉燃烧器和烘干筒作为分析系统进行数值模拟,研究煤粉燃烧器钝体关键参数对燃烧性能的影响.结果表明,端径比和钝体锥角显著影响煤粉燃烧性能,随着端径比的增大,NO质量分数和CO/CO2比值先降低后升高;钝体锥角对NO、CO、CO2的质量分数均具有显著影响,但对燃烧性能的影响无明显规律性;当端径比为0.55,钝体锥角为50°时,NO的质量分数最小;当端径比0.55,钝体锥角55°时,CO/CO2比值最小.从煤粉燃烧器燃烧效率和NO排放量的角度综合考虑,适宜选用端径比0.55和钝体锥角55°.

Blunt body can improve the combustion environment of pulverized coal by changing the dynamics of pulverized coal airflow so as to accelerate the mixing of secondary air and pulverized coal airflow in the combustion chamber.In order to improve the combustion efficiency of pulverized coal and reduce the emission of pollutants,based on the software platform Fluent,with the ratio of CO/CO2 as the evaluation index of pulverized coal combustion efficiency and the mass fraction of NO as the evaluation index of main pollutants,this paper reasonably simplifies and constructs the control model of pulverized coal thermal and combustion behavior,and uses the pulverized coal burner and drying drum as the analysis system to carry out numerical simulation to study the influence of the key parameters of the blunt body of the pulverized coal burner on combustion performance.The results show that end-diameter ratio and blunt cone angle significantly affect the combustion performance of pulverized coal.With the increase of end-diameter ratio,NO mass fraction and CO/CO2 ratio decrease first and then increase.Blunt cone angle has significant influence on the mass fractions of NO,CO and CO2,but has no obvious regularity on combustion performance.When the end-diameter ratio is 0.55 and the blunt cone angle is 50,the mass fraction of NO is the smallest.When the end-diameter ratio is 0.55 and the blunt cone angle is 55,the CO/CO2 ratio is the smallest.Considering combustion efficiency and NO emission of pulverized coal burner,it is desirable to choose the end-diameter ratio of 0.55 and the blunt cone angle of 55 as key parameters of the blunt body.