增压富氧鼓泡床的NO生成特性

NO Emission Characteristics of Pressurized Oxy-Fuel Bubbling Fluidized Bed

搭建小型增压富氧燃烧鼓泡床试验台,以试验结果为基础结合偏最小二乘法对增压富氧燃煤NO生成特性进行了研究和分析.试验结果表明,压力对NO排放规律的影响与反应气氛中的氧体积分数有关.在增压空气燃烧时,随着系统总压的升高,燃烧过程中NO的生成量有明显降低,但在增压富氧燃烧时,系统总压升高后,燃煤NO生成量反而逐渐增加.分析显示,在加压燃烧过程中,挥发分燃烧速率增加对煤粉热解的促进作用与CO和焦炭对NO的还原作用共同决定了燃煤NO的生成特性.在低氧气体积分数时,系统总压升高后CO和焦炭对NO的还原作用强于燃料氮的氧化作用,导致燃料氮的NO转化率逐渐下降,但是在高氧体积分数时,系统总压升高后,快速燃烧的挥发分使得挥发分氮的释放和转化强于CO和焦炭的还原作用,导致燃料氮的NO转化率逐渐增加.

Based on experimental results obtained on a pressurized oxy-fuel bubbling fluidized bed,the emission characteristics of NO during pressurized oxy-fuel combustion were investigated with partial least square method. The results show that the effect of pressure on the NO emission characteristics depends on the oxygen volume fraction in the atmosphere. During pressurized air combustion,the NO formation decreases dramatically with the rise in system pressure. But during pressurized oxy-fuel combustion,the NO formation increases with the rise in system pressure.Further analysis indicates that during pressurized combustion,both of the promotion effect of the rise in volatile burning rate on coal pyrolysis and the NO reduction through CO and char determine NO emission characteristics. At lower oxygen volume fraction,the NO reduction through CO and char is stronger than the oxidation of fuel nitrogen with the increase of system pressure,which leads to the decrease of NO conversion rate. However,the faster burning rate of volatiles at higher oxygen volume fraction makes the release of volatile nitrogen stronger than the NO reduction with the increase of system pressure,which leads to an increase of NO conversion rate.