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

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