富氧燃烧条件下炉内数值模拟研究

Numerical Simulation of Oxy-fuel Combustion Characteristics in a 300 MW Coal-fired Boiler

以300MW电站锅炉为研究对象，对燃烧过程的反应机理、物性参数和换热模型进行了修正，采用数值模拟方法对空气燃烧和富氧燃烧条件下炉膛的温度场和煤粉含碳量进行对比研究．结果表明：化学反应机理和物性参数对富氧燃烧有明显影响，煤粉着火延迟，火焰形状狭长，随着氧气体积分数的增大，煤粉颗粒在炉内的停留时间缩短，燃尽率增大；富氧燃烧条件下炉内烟气和颗粒的最高温度及炉膛换热能力均低于空气燃烧条件下，火焰中心高度上移；当氧气体积分数达到26％～29％时，富氧燃烧条件下炉内温度变化趋势与空气燃烧条件下炉内温度变化趋势一致；炉膛换热量数值模拟计算值比热力计算值低4％～11％．

Taking the 300 MW coal-fired boiler as an object of study, the models for reaction mechanism, physical parameters and heat transfer of the combustion process were revised, so as to comparatively inves- tigate the temperature field in the furnace and the carbon content in the pulverized coal by numerical meth- od respectively under air and oxy-fuel combustion conditions. Results show that the reaction mechanism and physical parameters have significant influence on the oxy-fuel combustion, when the ignition of pulver- ized coal is delayed, and the shape of the flame is narrowed and elongated. With the rise of oxygen concen- tration, the residence time of coal particles in the furnace reduces while the burnout rate increases. Com- pared to air combustion conditions, the peak temperature of flue gas and coal particles decreases, the heat- transfer capability reduces and the height of flame center moves upward under oxy-fuel combustion condi- tions. When the oxygen concentration increases from 26 ~//0 to 29 %, the oxy-fuel combustion has a good a- greement with the air combustion in trends of temperature variation. The capacity of heat transfer calculat- ed by numerical simulation is 4%-11% lower than that by thermal calculation.