初始氧浓度对锅炉富氧燃烧和NOx排放的影响

The Influence of the Initial Oxygen Concentration on Boiler Oxygen-enriched Combustion and NOx Emissions

针对某电站300MW燃煤锅炉,基于专门开发的CFX-TASCFLOW软件平台,将额定负荷下空气气氛、不同初始氧浓度φ(O2=21%、30%、35%、40%)的O2/CO2气氛,共五种工况下的炉内流动、燃烧及污染物生成进行了数值模拟。计算结果表明:O2/CO2燃烧方式下,炉膛出口烟气中CO2的浓度均可达到90%以上,便于CO2的回收;随着初始氧浓度的增大,炉内的火焰温度提高,沿炉膛高度方向温度的降低幅度增高,炉膛出口烟气温度降低,NOx的生成量小于空气气氛;飞灰可燃物在初始氧浓度为21%时最高,在初始氧浓度增至30%～40%时,飞灰可燃物大幅度下降;30%的初始氧浓度是比较合理的富氧燃烧浓度。

For a 300 MW coal-fired boiler in a power plant and on the basis of a specially developed software platform CFX-TASC Flow, numerically studied were the flow, combustion and pollutant production in the furnace under the rated-load air environment in the O2/CO2 atmosphere of various initial oxygen concentrations φ(O2)=21%, 30%, 35% and 40% totaling five operating conditions. The calculation results show that under the O2/CO2 combustion mode, the CO2 concentration of the flue gas at the outlet of the furnace can reach over 90%, facilitating the recovery of CO2. With an increase of the initial oxygen concentration, the in-furnace flame temperature will go up, the temperature drop margin along the furnace height direction, increase,and the flue gas temperature at the outlet of the furnace, go down. The amount of NOx product being generated will be less than the air quantity. The combustible content of the flying ash will be the highest when the initial oxygen concentration is 21%. It will drop by a great margin when the initial oxygen concentration increases to 30%~40%. Thus, 30% initial oxygen concentration is considered as a comparatively rational choice for the oxygen-enriched combustion.