低氮燃烧器的NOx排放性能及运行优化

doi:10.16085/j.issn.1000-6613.2020-0708

摘要/Abstract

摘要：

为降低锅炉氮氧化物（NO_x）排放浓度，综合利用烟气内外循环、旋流燃烧、稳焰技术等原理，本文设计出一种适合燃气锅炉的扩散式低氮燃烧器。在2.8MW燃气锅炉上进行了工业试验，同时展开了数值计算。通过工业试验及数值计算表明：燃料消耗量、过量空气系数和烟气外循环率都影响着NO_x的排放浓度，但三者影响程度不同。随着锅炉燃料消耗量的增加，NO_x排放浓度增加；随着过量空气系数的增加，NO_x排放浓度先增加而后降低；随着烟气外循环率的增加，NO_x排放浓度降低。针对本燃烧器，当烟气外循环率控制在28%～40%范围内，过量空气系数只需满足燃气充分燃烧，NO_x排放浓度都会低于30mg/m³；当烟气外循环率超过40%易出现燃烧不稳定现象，低于28%时，NO_x排放浓度会高于30mg/m³，不能满足排放要求。

关键词: 天然气, 低氮燃烧器, 烟气循环, 污染, 数值模拟

Abstract:

In order to reduce NO_x emission concentration of the boiler, a diffused low-nitrogen burner suitable for gas-fired boiler was designed by using the principles of flue gas internal and external circulation, swirl combustion and flame stabilization technology. The industrial experiment was carried out on the 2.8MW gas-fired boiler, and the numerical calculation was carried out at the same time. The industrial experiment and numerical calculation showed that fuel consumption, excess air coefficient and flue gas circulation rate all affect NO_x emission concentration, but the influence degrees of the three are different. With the increase of fuel consumption, NO_x emission concentration increases. With the increase of excess air coefficient, NO_x emission concentration first increases and then decreases. With the increase of flue gas external circulation rate, NO_x emission concentration decreases. For the burner here, when the flue gas external circulation rate is controlled within the range of 28% to 40%, the excess air coefficient only needs to meet the requirement of fuel complete combustion,the NO_x emission concentration will be lower than 30mg/m³. When the flue gas external circulation rate is more than 40%, it is prone to combustion instability, and when it is lower than 28%, the NO_x emission concentration will be higher than 30mg/m³, which cannot meet the emission requirements.

Key words: natural gas, low nitrogen burner, flue gas recirculation, pollution, numerical simulation

中图分类号:

TK16

陈旭, 朱永郁, 陶军, 王春华. 低氮燃烧器的NO_x排放性能及运行优化[J]. 化工进展, 2021, 40(2): 1069-1076.

Xu CHEN, Yongyu ZHU, Jun TAO, Chunhua WANG. NO_x emission performance and operation optimization of low nitrogen burner[J]. Chemical Industry and Engineering Progress, 2021, 40(2): 1069-1076.

图/表 18

图1 低氮燃烧器的结构1—燃气进口；2—封挡板；3—主气管；4—中空管；5—空气旋流器；6—燃气喷嘴；7—助燃剂入口

图2 喷嘴的结构

图3 旋流叶片结构

图4 稳焰装置结构

图5 安有本燃烧器的燃气锅炉工作过程1—燃气入口；2—燃烧器；3—锅炉；4—排烟口；5—外部烟气循环管；6—空气入口；7—脱水装置；8—鼓风机；9—烟风混合管

图6 工业锅炉试验测试平台

图7 燃料流量对NOx排放浓度的影响

图8 过量空气系数对NOx排放浓度的影响

图9 烟气外循环率对NOx排放浓度的影响

图10 不同网格数计算对比结果

图11 网格划分

图12 不同过量空气系数下炉膛内（X=0平面）温度分布

图13 过量空气系数对炉膛中心线上温度和NO物质的量分数的影响

图14 炉膛内最高温度和炉膛出口处NO排放浓度的关系（不同过量空气系数）

图15 不同烟气循环率下炉膛内（X=0平面）温度分布

图16 烟气外循环率对炉膛中心线上温度的影响

图17 烟气外循环率对炉膛中心线上NO物质的量分数的影响

图18 炉膛内最高温度和炉膛出口处NO排放浓度的影响（不同烟气外循环率）

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