Under the requirements of environmental protection policies, the industry also attaches great importance to energy conservation and emission reduction measures. Low nitrogen combustion technology has certain advantages in environmental protection, but at the same time, it also has a certain impact on the operation of boilers, so it is necessary to deal with problems arising from new environmental protection technologies. In terms of measures, we should further strengthen and strive for the greatest environmental protection mechanism for the sustainable development of the industry. This article discusses the relevant content, which has certain practical significance.

1. Analysis of burner connotation

The burner is the main combustion equipment of the boiler in the fuel power plant, and the burner is located on the four corners of the boiler furnace or on the wall. The burner will inject various fuels and the air necessary for combustion into the furnace in a certain way. The fuel and air will be fully mixed in the furnace, and will quickly ignite and maintain stable combustion under a certain airflow structure. . The burners used today are all electromechanical devices with a relatively high degree of automation. The burners mainly have five systems: air supply, ignition, monitoring, fuel and electronic control systems.

According to the type of fuel, burners can be divided into pulverized coal burners, gas burners and oil burners. The pulverized coal burner uses the primary air and the secondary air to inject the pulverized coal fuel into the furnace, and forms a special airflow structure while mixing the fuel and the air evenly, so that the fuel is stably ignited and completely burned in the furnace. The secondary air swirling jet is used to form a recirculation zone that is conducive to ignition, and the strong mixing in the swirling jet and between the swirling jet and the surrounding medium enhances the ignition characteristics of the pulverized coal gas flow. A tongue-shaped baffle is installed at the entrance of the secondary air volute to adjust the swirl intensity of the air flow. The volute pulverized coal burner has a simple structure and has a good effect on burning bituminous coal and lignite, and can also be used for burning lean coal.

2. Analysis of the influence of low-nitrogen burner modification on boilers

2.1 Influence of combustion stability

The stability of the boiler is reflected in many aspects, the most important of which is the stability of the temperature and the stability of the operation process. The low-nitrogen burner is equipped with a combination of concentration and lightness at the primary air outlet, and uses heat recirculation relay combustion and other technologies to design according to the principle of thermal and dynamic asymmetry during the combustion process, so that the pulverized coal at the nozzle is pyrolyzed and composited with the center of the boiler. The jet and large vortex are connected, and the higher recirculation rate of the hot return carbon powder makes the residence time longer, which increases the heat generated by the combustion in the ring vortex, so that the temperature rise affects the operation of the boiler.

The low-nitrogen transformation of the boiler also controls the amount of oxygen. During the combustion process, oxygen needs to meet the combustion conditions to generate heat. Since the number of oxygen is controlled, the generation of heat is suppressed, thus affecting the operation of the boiler. The existence of the two operation modes affects the stable operation of the boiler.

2.2 Influence of the internal environment of the boiler

低氮燃烧器中的喷口比传统的燃烧器喷口低，因此，在锅炉的运行中燃料产生的火焰也发生了移动，燃烧面积降低会使得锅炉对温度的接收程度变低，而在锅炉的内部产生的压力状况也发生了变化，会有一些不协调的现象产生。低氮燃烧器设备的改造使锅炉的部件也发生了改变，在运行上会发生不同状况。低氮燃烧器改造使锅炉内部的氧气量受到了一定的影响，通常会有一个最大运行氧量和一个最小运行氧量，机组的调节跟不上氧量调节而出现负氧情况，氧气量的变化与燃烧程度的变化使锅炉内外部压力发生变化，改变了内部环境，并且使相关人员需要对氧气量进行调整控制，直接造成送风工作不能及时进行调节，锅炉不能持续稳定的运行。

2.3 对锅炉再热气温的影响

低氮燃烧器在改造后将原来的燃烧器标高下移，对再热气温有很大的影响，低氮燃烧器改造后由于机组协调缓慢的问题使得锅炉压力的跟踪调整跟不上，容易造成超调现象，使得气温的变化幅度变大。改造后的低氮燃烧器有一组摆动火嘴，当喷口向上摆动蒸汽的温度会上升，喷口向下摆动时温度会下降，但因为只有一组摇动火嘴所以温度调整速度受限，调整的时间过长加上风次配比受到低氧条件的控制，影响着机器的效率。为了保证锅炉出口温度在规定范围内低负荷，需要使用制粉系统，这样又会导致受热面温度过高，很难再不超温的情况下还能保持出口温度保持在规定范围内，影响着锅炉的运行。

2.4 对炉膛结焦的影响

低氮燃烧器改造时虽然采用了横向双区、纵向分级、加贴壁风和逆风向射流等措施用，来控制受热面结焦情况，但在运行中，仍能发现燃烧器喷口处有结焦情况，特别是当启动下层制粉系统时，会明显影响着负压，说明燃烧区状况不好，而由于主燃烧区进行缺氧燃烧，所以燃烧器附近会出现冷壁结焦现象，并且比较严重，而且在降负荷中还会经常出现掉焦现象，恶化主燃烧区影响锅炉的运行。

2.5 对炉渣可燃物的影响

改造后的低氮燃烧器，虽然 NO 的产量得到了降低，但是同时也增加了炉渣可燃物。低氮燃烧技术采用的是低温低氧条件燃烧，燃烧区温度下降越多煤粉着火受到的影响就越大，燃烧区的氧气量降低煤粉燃尽能力就下降，燃烧的过程也就被加长了使得炉渣可燃物变多，而且有些燃烧器的喷口面积改变使得混合风推迟不利于锅炉内煤粉的气流流动使燃烧不完全增加炉渣可燃物，炉渣可燃物的不断增加会使锅炉的尾部磨损增加，从而减少锅炉的使用寿命。

3、低氮燃烧器的具体改造措施分析

3.1 一次风的改造设计

1）在本次改造中的 A、B、C、D 以及 E 层的一次风作全部的更换，并且采用上部和下部浓淡不同形式的射流形式布置。

2）浓淡分离采取一次风弯头惯性分离结合煤粉风室百叶窗分离装置。

3）对一次风的喷口进行加装波纹形稳定燃烧顿体，对烟气的回流量进行加大处理，钝体向火侧采用特殊的焊条堆焊工艺，达到耐高温和防磨的效果。

4）对一次风的弯头进行改造设计：对一次风的弯头进行全部的重新设置更换，并采用低阻力的空间钢板和内壁贴陶瓷的弯头，和原来的煤粉燃料管道法兰相连接。

3.2 二次风的改造设计

1）主燃区域的二次风喷口相比较改造之前有所缩小，并保持射流方向和一次风之间形成 3°的夹角。

2）二次风仍取风自原大风箱。

3）将主燃区原上下部大风箱进行联通处理。

3.3 燃尽风的改造设计

燃尽风的改造主要是对主燃烧器的上面部分区域并且和上一次风标高距离约 6.99m 处增加四层燃尽风设备，燃尽风的风源来自于大风箱，风源的位置位于大风箱的顶部，将燃尽风的风箱重新改造设计并安装与两侧墙上，并且将连接方式改为和主燃烧器的大风箱相同的连接方式。

将燃尽风的风箱管道延长到燃尽风的风箱标高处，风道与燃尽风的挡板风箱通过燃尽风相连接，并且利用使用附加防磨衬不锈钢制作的膨胀节对燃尽风的热膨胀进行膨胀补偿，不锈钢膨胀节的壁厚要超过十五毫米。

Multi-nozzle arrangement is adopted for the exhaust air nozzles, and the exhaust air nozzles in the form of vertical and horizontal multi-direction swing are used. For the control method, the vertical swing direction should be controlled by remote control, and the horizontal swing direction should be controlled manually. .

The modification of the over-burning air fixture: The modification of the over-burning air fixture adopts the same linking and fixing method as the original burner.

Renovation in terms of thermal insulation: The thermal insulation method of the overburning wind is the same as the thermal insulation method adopted by the main burner. That is, the newly added overburning wind bellows and the connected air ducts are wrapped with aluminum silicate plates, and corrugated plates are installed on the outside.