预热空气当量比对循环流化床掺混煤泥预热燃烧的影响

Effect of preheating air equivalent ratio on preheating combustion of coal slime mixed in a circulating fluidized bed

煤泥灰含量大、颗粒细、热值低,煤泥的高效清洁燃烧是固废资源化利用的重要方式之一。采用煤粉流态化预热耦合循环流化床燃烧技术,在30 kW预热燃烧综合评价试验台上,控制煤泥掺混比、给料量、还原区当量比、二/三次风比例及过剩空气系数等参数不变,并借助煤气分析仪和烟气分析仪等测量仪器,开展了循环流化床烟煤掺混煤泥的预热燃烧试验。结果表明,循环流化床预热燃烧系统运行稳定可靠,预热温度800℃以上,预热燃料可持续稳定输送到循环流化床中;烟煤掺混高灰分的煤泥,循环灰量增加,循环流化床燃烧室温差小,温度均匀;预热空气当量比由0.36增至0.51时,预热器内温度增加,预热煤气中CO_(2)、HCN体积分数增加,CO、H_(2)、CH_(4)及NH_(3)体积分数降低,煤气热值由2.02 MJ/m^(3)降至1.49 MJ/m^(3);且随着预热空气当量比的增加,循环流化床燃烧室沿程NO体积分数增加,CO体积分数底部高、上部低,NO_(x)排放量由172 mg/m^(3)增至242 mg/m^(3)(6%O_(2)),可见,较低预热当量比有利于烟煤掺混煤泥的高效清洁燃烧。研究结果可为煤泥的高效燃烧利用提供新型技术路线和数据支持。

The high-efficient and clean combustion of coal slime is one of the most important ways for solid waste resource utilization as coal slime has the characteristics of high ash content,fine particle,and low heating value.Using a novel technology with the coupling of circulating fluidized bed combustion and fluidizing preheating for pulverized coal,and some experiments were performed in a comprehensive evaluation test bench for 30 kW.The preheating combustion experiment of circulating fluidized bed bituminous coal blended with coal slime was carried out by keeping some parameters unchanged,including mixing ratio,feed rate,equivalence ratio,the ratio of secondary air to tertiary air,and excess air ratio,and using measurement instruments such as gas analyzer and flue gas analyzer.The results show that this new process is in a quite stable running,and with a preheating temperature above 800℃,and the preheating fuel can be continuously and stably transported to the circulating fluidized bed.The temperature profile in the circulating fluidized bed is uniform with an extremely small temperature difference,as mixing bituminous coal with high ash content coal slime increases the amount of circulating ash.With the increasing of equivalence ratio for preheating air from 0.36 to 0.51,there is a rise of preheating temperature,the volume fraction of CO_(2) and HCN in the preheated gas increase,and the volume fractions of CO,H_(2),CH_(4) and NH_(3) decrease,with the heating value of coal gas from 2.02 MJ/m^(3) to 1.49 MJ/m^(3).Also,with the increasing of the preheating air equivalence ratio,the volume fraction of NO along the height of circulating fluidized bed gradually increases,and the volume fraction of CO shows the atmosphere with higher at the bottom and lower at the upper part.The NO x emission increases from 172 mg/m^(3) to 242 mg/m^(3)(6%O_(2)).It can be concluded that the lower equivalence ratio for preheating air benefits to achieve high-efficient and clean combustion with coal slime mixed into bituminous coal,which provides a new technical route and data support for the development and application with coal slime utilization.