摘要
循环流化床锅炉具有煤种适应性广,负荷调节能力强,污染物超低排放等优点,被广泛应用于煤的清洁燃烧。为探究循环流化床污染物生成和排放规律,以0.3 MWthCFB燃煤中试装置系统为实际模型,利用Aspen Plus对煤燃烧和污染物控制装置全流程建模。采用Gibbs最小自由能热力学分析方法对煤燃烧产物进行了分析计算,并利用软件自带的灵敏度分析工具,对不同的操作参数进行了灵敏度分析,预测了锅炉运行参数对烟气组分、选择性催化还原脱硝效率和石灰石-石膏湿法烟气脱硫效率的影响规律,获得了过量空气系数、烟气温度、氨氮比和钙硫比对NOx和SOx脱除效率以及SO3生成的影响曲线。结果表明,在循环流化床煤燃烧条件下,温度变化对NOx和SOx的生成影响显著,温度升高会促进NH3、HCN等前驱物的转化,促进燃料氮生成NOx;高温条件下,SO2生成反应的化学平衡向正方向移动,但反应速率会随温度和浓度的升高而降低,SO3则与之相反。在选择性催化还原脱硝过程中,较低温度时,脱硝率随温度升高而增加,最佳活性温度在360℃左右;SCR反应温度低于380℃时,SO3含量呈显著上升趋势,380℃出现一极大值点,而后趋于平缓并略有下降。NSR<1时,脱硝率随氨氮比增加而增加,最佳氨氮比在1.05。湿法烟气脱硫过程中,增加钙硫比能明显提高脱硫效率,最佳钙硫比在1.05左右,并降低SO3排放;脱硫系统入口烟气温度升高会导致脱硫效率降低,但促进了SO3的生成。
Circulating fluidized bed(CFB)boiler has the advantages of wide adaptability of coal type,strong load regulation ability,ultra-low emission of pollutants,etc,which is widely used in clean combustion of coal.In order to explore the generation and emission of pollutants in CFB,a systematical modelling and prediction of a 0.3 MW th CFB coal-fired pilot facility based on the Aspen Plus scheme were conducted,including the sub-models of coal combustion and pollutant control devices.The Gibbs minimum free energy thermodynamic analysis method was used to analyze and calculate the coal combustion products,and the sensitivity analysis tool included in the software was used to analyze the sensitivity of different operating parameters.The effects of operational parameters of the combustion system on flue gas components,denitrition of selective catalytic reduction(SCR)and desulfurization of limestone-gypsum wet flue gas were predicted.The variable process of NOx,SOx removal efficiency and generation of SO3 versus the excess air coefficient,flue gas temperature,ammonium to nitrogen ratio and calcium to sulfure ratio was simulated.The results show that under the conditions of circulating fluidized bed coal combustion,the changes of temperature have a significant effect on the formation of NOx and SOx.The increase of temperature will promote the conversion of NH 3,HCN and other precursors,and promote the production of fuel nitrogen to NO x;under high temperature conditions,the chemical equilibrium of the SO2 formation reaction moves to the positive direction,but the reaction rate decreases with the increasing of temperature and concentration,while SO3 is the opposite.During the SCR denitration process,the denitration rate increases with the increase of temperature at lower temperatures,and the optimal active temperature is around 360℃.Before the reaction temperature of SCR is 380℃,the content of SO3 increases significantly,and there is a maximum value point at 380℃,and then tends to be gentle and slightly decreases.When th
作者
明祥栋
段钰锋
柳帅
胡鹏
MING Xiangdong;DUAN Yufeng;LIU Shuai;HU Peng(Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,School of Energy and Environment,Southeast University,Nanjing 210096,China)
出处
《洁净煤技术》
CAS
2020年第3期38-45,共8页
Clean Coal Technology
基金
国家重点研发计划资助项目(2016YFB0600203)。
