【作者】 杨蓓；

【导师】 方庆艳； 周怀春；

【作者基本信息】 华中科技大学 ， 动力工程， 2012， 硕士

【摘要】 目前，燃煤发电仍然是我国电力供应的主要来源。然而，由于煤炭市场的变化，许多燃煤电站在实际运行时偏离原设计煤种，而煤质对锅炉的安全及经济性存在较大的影响，因此，研究煤种变化对锅炉运行的影响是至关重要的。本文针对一台135MW改烧烟煤的四角切圆锅炉开展了锅炉燃烧特性、NO_X排放特性的模拟研究，并以额定工况下的模拟结果为基础，进行了改变制粉系统运行方式及烟气再循环率的变工况模拟计算。额定工况的计算结果显示，模拟的煤粉燃尽率为99.78%，炉膛出口NO_X浓度为580.96mg/m~3，与电厂试验报告结果相比，其相对误差分别为2.94%、19.24%。该结果表明，该模型能够较合理地预测锅炉的燃尽率，但在计算NO_X浓度上存在着一定误差。变工况模拟结果显示，制粉系统对炉膛燃烧影响较大，制粉系统对角运行或者不运行，炉膛内部温度都会有一定程度的增加，相比与额定工况，制粉系统对角运行、不运行时最高温度分别升高了50K、100K，且壁面最大热负荷区域明显扩大，同时，制粉系统的改变，增大了炉膛出口NO_X浓度，其值分别增大了38.9%、49.8%；当改变烟气再循环率时，二次风风量增大，炉膛燃烧区域内的温度升高，但燃尽区温度降低，而壁面热负荷则没有显著的变化；由于燃尽区温度的降低，且存在一定量的水蒸气与CO2，有利于氮氧化物的脱除，因此NO_X排放量有了较大幅度下降，对比额定工况下，烟气再循环率分别为10.07%与11.48%时，NO_X排放量降低了19.1%、16.1%。更多还原

【Abstract】 Currently, coal-fired power generation is still the main source of the power supply.However, due to changes in the coal market, it is deviated from the original designed coalthat in the running condition the coal are used in the coal-fired power plant, while coalcharacteristic has a critical impact on boiler safety and economic. Therefore, it is essentialto study the effect of coal changes on the combustion of boiler.In this paper, the combustion and NO_Xemission characteristics in a135MWtangentially fired boiler with burning bituminous coal were studied. Based on thesimulation results of the rated conditions, it was studied that simulation results changedwith the difference of operating mode of the milling system and the variable flue gasrecirculation rate. The calculation results of rated operating condition indicated that theprediction of pulverized coal burn-out rate is99.78%, and NO_Xconcentration of furnaceexit is580.96mg/m3. Compared with the power plant testing report results, the relativeerrors were2.94%and19.24%, respectively. The results suggested that the model canaccurately predict the burn-out rate of the boiler, but there were large errors between theprediction and test data of NO_Xconcentration.Simulated results of changes of operating conditions showed that, the milling systemplayed an important role on combustion characteristics. The milling system operatedopposed or did not operate, the furnace internal temperature would have increased to someextent, compared with results of rated operating condition, the maximum temperatureincreased by50K and100K, respectively. And the region of maximum wall heat loadsignificantly expanded. Meanwhile, the increase of temperature resulted in higher thermalNO_Xformation, which value increased by38.9%,49.8%, respectively. As the flue gasrecirculation rate rising, secondary air volume increased and caused temperature growing incombustion zone, but temperature in the burnout zone was slightly lower, and there was nosignificant change of the wall heat load. Due to burnout zone temperature decreased andthere were more water vapor and CO2in this zone, which did a favour to the reduction ofNO_X, and NO_Xemission had decreased significantly, in comparison with rated conditions,when the flue gas recirculation rate was10.07%,11.48%, NO_Xemissions were reduced by19.1%,16.1%, respectively.更多还原