排煙溫度熱損失是燃氣鍋爐熱損失中主要的一項，它主要取決於排煙溫度與過量空氣係數λ。λ與排煙熱損失q1關係：根據經驗公式：q1=(0.5+3.5λ)(T排煙-T環境溫度)

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)

在運行中，要盡可能地在保證完全燃燒的條件下降低q1來提高鍋爐的燃燒效率，鍋爐排煙溫度偏高就會導致鍋爐的熱效率降低。排煙熱損失隨排煙溫度的升高和空氣係數的增大而增大。燃氣鍋爐排煙中含有蒸汽，過熱蒸汽是煙氣中熱量的主要攜帶者。因此，燃氣鍋爐排出的煙氣中除顯熱外，還有大量潛熱，這一部分熱損失的大部分(約70%)可以通過接觸式換熱設備進行回收。低氮鍋爐改造根據爐膛尺寸是否達標可分為以下兩種方式：

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、更換低氮燃燒器(全預混、煙氣外循環、煙氣內循環)

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

2、更換鍋爐(冷凝鍋爐、三回程燃氣鍋爐+低氮燃燒頭)由於冷凝爐更、更低氮，在低氮改造中，選擇更換冷凝鍋爐已然成為一種必然趨勢：

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：冷凝鍋爐比普通鍋爐效率高20%30%,冷凝鍋爐熱效率可達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).冷凝鍋爐排煙溫度低：排煙溫度低35℃。

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

3).供水溫度可調範圍大：冷凝鍋爐自備的、質量好的水溫控製係統及獨特的結構和燃燒方式。

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：冷凝鍋爐氮氧化物(NOx)排放量隻有30ppm，低於歐洲標準5級的56ppm。一氧化碳排放量大大低於一般鍋爐排放標準。由於燃燒效率高，生成的二氧化碳遠低於普通燃氣鍋爐。運行噪聲小於40分貝。

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.