排烟温度热损失是燃气锅炉热损失中主要的一项，它主要取决于排烟温度与过量空气系数λ。λ与排烟热损失q1关系：根据经验公式：q1=(0.5+3.5λ)(T排烟-T环境温度)

The heat loss of exhaust gas temperature is one of the main heat losses of gas-fired boiler, which mainly depends on the exhaust gas temperature and excess air coefficient λ。λ Relationship with exhaust heat loss Q1: according to empirical formula: Q1 = (0.5 + 3.5) λ)( T smoke exhaust - t ambient temperature)

在运行中，要尽可能地在保证完全燃烧的条件下降低q1来提高锅炉的燃烧效率，锅炉排烟温度偏高就会导致锅炉的热效率降低。排烟热损失随排烟温度的升高和空气系数的增大而增大。燃气锅炉排烟中含有蒸汽，过热蒸汽是烟气中热量的主要携带者。因此，燃气锅炉排出的烟气中除显热外，还有大量潜热，这一部分热损失的大部分(约70%)可以通过接触式换热设备进行回收。低氮锅炉改造根据炉膛尺寸是否达标可分为以下两种方式：

During operation, it is necessary to reduce Q1 as low as possible under the condition of ensuring complete combustion to improve the combustion efficiency of the boiler. The high exhaust gas temperature of the boiler will reduce the thermal efficiency of the boiler. The heat loss of exhaust gas increases with the increase of exhaust gas temperature and air coefficient. The flue gas of gas-fired boiler contains steam, and superheated steam is the main carrier of heat in the flue gas. Therefore, in addition to sensible heat, there is also a large amount of latent heat in the flue gas discharged from the gas-fired boiler. Most of this part of heat loss (about 70%) can be recovered by contact heat exchange equipment. The transformation of low nitrogen boiler can be divided into the following two ways according to whether the furnace size meets the standard:

1、更换低氮燃烧器(全预混、烟气外循环、烟气内循环)

1. Replace low nitrogen burner (full premixing, flue gas external circulation, flue gas internal circulation)

2、更换锅炉(冷凝锅炉、三回程燃气锅炉+低氮燃烧头)由于冷凝炉更环保、更低氮，在低氮改造中，选择更换冷凝锅炉已然成为一种必然趋势：

2. Replacement of boiler (condensing boiler, three return gas boiler + low nitrogen combustion head) because the condensing boiler is more environmentally friendly and lower nitrogen, it has become an inevitable trend to choose to replace the condensing boiler in the low nitrogen transformation:

1).超率：冷凝锅炉比普通锅炉效率高20%至30%,冷凝锅炉热效率可达108.9%。

1) Ultra high efficiency: the efficiency of condensing boiler is 20% to 30% higher than that of ordinary boiler, and the thermal efficiency of condensing boiler can reach 108.9%.

2).冷凝锅炉排烟温度低：排烟温度低至35℃。

2) Low exhaust gas temperature of condensing boiler: the exhaust gas temperature is as low as 35 ℃.

3).供水温度可调范围大：冷凝锅炉自备先进的、质量好的水温控制系统及独特的结构和燃烧方式。

3) Large adjustable range of water supply temperature: the condensing boiler is equipped with advanced and high-quality water temperature control system and unique structure and combustion mode.

4).更加环保：冷凝锅炉氮氧化物(NOx)排放量只有30ppm，低于欧洲标准5级的56ppm。一氧化碳排放量大大低于一般锅炉排放标准。由于燃烧效率高，生成的二氧化碳远低于普通燃气锅炉。运行噪声小于40分贝。

4) More environmentally friendly: the nitrogen oxide (NOx) emission of condensing boiler is only 30ppm, which is lower than 56ppm of European standard level 5. Carbon monoxide emission is much lower than the general boiler emission standard. Due to high combustion efficiency, the generated carbon dioxide is much lower than that of ordinary gas-fired boilers. The operating noise is less than 40 dB.