分级燃烧低排放燃烧器数值模拟与参数优化

Numerical simulation and parameter optimization of staged combustion low emission combustors

为了研究轧制加热工序中的能源消耗和污染排放问题,对其核心部件燃烧器在燃烧过程中温度和产物的影响因素和分布规律进行了研究。采用CFD建立了全尺寸的某型天然气燃烧器和加热中试炉的三维模型并进行了数值模拟计算,对燃烧产物的影响因素进行了分析,通过对燃烧器参数进行优化,建立了排放产物浓度与空气预热温度、空气分级比例的数学关系。结果表明:燃烧器产生的污染产物主要为热力型一氧化氮,提高空气预热温度可以提高燃烧速率,提高加热炉的整体温度,但氮氧化物的排放量也急剧升高,当空气预热温度不超过100℃,此时炉内温度高且氮氧化物排放量为76.42 mg/m^(3),燃烧性能良好,加热炉膛出口一氧化氮浓度与空气预热温度呈指数正相关关系;通过数学拟合,加热炉出口一氧化氮浓度与一次空气比例、二次空气比例呈二元幂值正相关关系,降低一次空气和二次空气进气量,适当提高三次空气进气量可以减少氮氧化物的排放,当分级空气比例为15%-45%-40%时,氮氧化物排放量最低为41.93 mg/m^(3)。燃烧产物浓度与空气参数的数学方程对于实际燃烧器和加热炉的进一步设计、控制和优化过程有着十分重要的意义。

In order to study the problems of energy consumption and pollution emission in the billet heating process,the influence factors and distribution rules of temperature and products in the combustion process of the core component combustor were investigated.A full-size three-dimensional model of a natural gas combustor and a heating pilot furnace was established by CFD and numerical simulation was carried out to analyze the influencing factors of combustion products.By optimizing combustor parameters,the mathematical relationship between emission product concentration,air preheating temperature and air classification ratio was established.The results show that the pollution products produced by the combustor are mainly thermal nitric oxide.Increasing the air preheating temperature can improve the combustion rate and improve the overall temperature of the heating furnace,but the emission of nitrogen oxides also increases sharply.When the air preheating temperature does not exceed 100℃,the temperature in the furnace is high and the emission of nitrogen oxides is 76.42 mg/m^(3),and the combustion performance is good.The nitric oxide concentration at the outlet of heating furnace is positively correlated with the air preheating temperature.The nitric oxide concentration at the outlet of the heating furnace is positively correlated with the proportion of primary air and secondary air through mathematical fitting.Reducing the intake volume of primary air and secondary air and appropriately increasing the intake volume of tertiary air can reduce the emission of nitrogen oxides.When the proportion of classificated air is 15%-45%-40%,the emission of nitrogen oxides is the lowest at 41.93 mg/m^(3).The mathematical equations of combustion product concentration and air parameters are very important for the further design,control and optimization of actual combustors and reheating furnaces.