基于变工况运行超超临界锅炉NO_x排放的数值模拟研究

Numerical Simulation Study on NO_x Emissions of the Ultra-supercritical Utility Boiler on Varying Operation Conditions

基于变工况运行,采用计算流体力学(CFD)模拟方法,对某电厂1000MW超超临界锅炉炉膛内CO、O_2、NO浓度场和温度场进行计算和分析.影响该锅炉NO_x排放浓度主要运行因素有燃用煤质、附加风量(AA风量)和过剩空气系数等.CFD数值模拟计算结果表明:锅炉通过合理组织炉内燃烧,实现了主燃烧区的较均匀的温度分布,主燃区的燃烧方式属于还原态燃烧方式;大量AA风的深度空气分级燃烧和锅炉低过量空气系数的有机结合及PM燃烧器的应用是该型锅炉NO_x排放浓度低的主要原因.

Computational fluid dynamics （CFD） approach was applied to simulate the combustion and NOx formation processes in the furnace of a 1000 MW ultra-supercritical boiler so as to study the impacts of varying the operation conditions on its NOx emission as well as combustion characteristics. With the help of CFD simulation, the distributions of CO, 02 and NO concentrations and the combustion temperature were calculated and analyzed. The main influential operation parameters include coal type, additional air flow rate and excess air level. The CFD simulations indicated that the main reasons of low NOx emission from the boiler are on two aspects： rationally organizing combustion process to achieve relatively uniform temperature distribution and reducing combustion environment in the main combustion zone, and combining the utilizations of the large amount of additional air to achieve deep air stage and the low excess air level as well as PM burners.