贫煤锅炉燃烧过程中，保证贫煤燃料的稳定着火、燃烧及燃尽特性，必须充分满足和保证燃烧过程温度、氧量等要求，这一定程度上与NO_x生成控制要求的低氧、低温条件存在矛盾。因此在贫煤锅炉应用低氮燃烧技术过程中，如何保证锅炉低氮燃烧，又不影响锅炉燃烧性能，一直以来都是低氮燃烧技术的难点。在锅炉低氮燃烧技术初步方案的基础上，通过系统分析与设计，提出了切实可行的低氮燃烧技术深度优化改造方案。针对某300 MW贫煤锅炉，通过数值模拟分析了空气分级低氮燃烧方式以及底二次风喷口面积对锅炉燃烧及NO_x排放的影响。在锅炉增设3层新型SOFA风进行低氮燃烧改造初步方案基础上，通过进一步计算与分析，提出了增大底二次风喷口面积1.5倍的低氮燃烧深度优化改造方案。模拟结果表明，NOx排放量由原先的473.4 mg/m³减少为265.3 mg/m³，改造后NO_x排放量减少了40%以上，同时能保证锅炉温度场和氧量场分布均匀。改造后锅炉实际运行结果表明，NO_x排放量由优化前的481.6 mg/m³降至269.1 mg/m³，NO_x排放量减少了44.1%，有效实现了贫煤锅炉安全、高效、低污染运行。

In the combustion process of lean coal boilers，in order to ensure the ignition，stable combustion and burnout of lean coal，the conditions such as temperature and oxygen content in the combustion process must be fully considered and guaranteed，which is obviously contradictory to the low oxygen and low temperature conditions required for NO_x emission control to a certain extent. Therefore，for the low nitrogen combustion technology of lean coal boiler，how to ensure the low nitrogen combustion without affecting the combustion performance of boiler has always been the difficulty of this technology. Based on the preliminary scheme of low nitrogen combustion technology of boiler，a feasible deep optimization transformation scheme of low nitrogen combustion technology was put forward through system analysis and design. In this paper，for a 300 MW lean coal boiler，the effects of air classification low-nitrogen combustion mode and the area of the bottom secondary air nozzle on NO_x emissions were analyzed through numerical simulation. Based on the preliminary plan of adding three layers of new SOFA wind to the boiler for low-nitrogen combustion reform，through further calculation and analysis，a low NO_x combustion depth optimization for increasing the area of the bottom secondary air nozzle by 1.5 times was proposed. The simulation results show that the NOx emission is reduced from 473.4 mg/m³ to 265.3 mg/m³. The NO_x emission can be reduced by more than 40% after the transformation，and the temperature field and oxygen field of the boiler can be evenly distributed. After the transformation，the actual operation results on site show that the NO_x emission is reduced from 481.6 mg/m³ before optimization to 269.1 mg/m³ after optimization，and the emission of nitrogen oxides is reduced by 44.1%，which has realized the safe，high efficient and low pollution operation of lean coal boilers.

0 引言

1 研究对象和方法

   1.1 锅炉结构及参数

   1.2 数值模拟方法

2 低氮燃烧初步方案

   2.1 原型锅炉燃烧及NO_x排放特性

   2.2 低氮改造初步方案

3 低氮改造优化

4 低氮改造效果

5 结论