Abstract: Fluidized preheating combustion technology used in rotary kilns can effectively reduce the fuel consumption per unit product and has advantages such as wide fuel adaptability and low NOx emissions. However, compared to pulverized coal, the combustion characteristics of preheated fuel are significantly different. This work employs computational fluid dynamics (CFD) to study the effects of preheating temperature, excess air coefficient within the rotary kiln, and the momentum of the axial flow air passage of the burner on the combustion process of high-temperature preheated fuel within the rotary kiln. Combining the author's previous research on the swirl number of multi-channel burners, an orthogonal design method combined with matrix analysis is used to obtain the importance of the effects of these four factors on combustion characteristics and the optimal parameter combination for comprehensive combustion performance. The results show that as the preheating temperature increases, the flame becomes thicker and shorter; as the excess air coefficient increases, the flame first becomes longer, then shorter; as the momentum of the axial flow air passage of the burner increases, the flame first becomes shorter and thicker, then longer and thinner. The importance of the effects of these four factors on combustion characteristics is in the order of preheating temperature>momentum of the axial flow air passage of the burner>swirl number>excess air coefficient. The optimal parameter combination is a swirl number of 0.2, a preheating temperature of 850℃, an excess air coefficient of 1.1, and a momentum of the axial flow air passage of the burner of 0.5 N/MW. The optimized conditions, compared to the original conditions, result in a 47% increase in flame length, a 37% increase in the average heat flux of the wall in the firing zone, and an 80% increase in the maximum heat flux of the wall in the firing zone.

Key words: cement, preheating combustion, rotary kiln, combustion characteristics, numerical simulation

摘要： 流态化预热燃烧技术用于回转窑燃烧可以有效降低单位产品燃料消耗且具有燃料适应性广和NOx排放低等优点。但与煤粉相比，预热燃料的燃烧特性具有显著差异。本工作采用计算流体力学研究了预热温度、回转窑内过量空气系数和多通道燃烧器轴流风通道动量等因素对高温预热燃料在回转窑内燃烧过程的影响，并结合课题组前期对多通道燃烧器旋流数的研究，通过正交设计法结合矩阵分析法获得了四个因素对燃烧特性影响的重要程度以及综合燃烧性能最佳的参数组合。结果表明，随着预热温度增大，火焰变粗和变短；随着过量空气系数增大，火焰先变长后变短；随着燃烧器轴流风通道动量增加，火焰先变短变粗后变长变细。四个因素对燃烧特性影响的重要程度分别为预热温度>燃烧器轴流风通道动量>旋流数>过量空气系数，最佳参数组合为旋流数0.2、预热温度850℃、过量空气系数1.1、燃烧器轴流风通道动量0.5 N/MW。优化后的工况相较于原始工况火焰长度增长了47%、烧成带区域壁面平均热通量提高37%、烧成带区域壁面最大热通量提高80%。

关键词: 水泥, 预热燃烧, 回转窑, 燃烧特性, 数值模拟