Effect of preheating air equivalent ratio on preheating combustion of coal slime mixed in a circulating fluidized bed
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 compre-hensive 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 re-sults 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 circu-lating ash.With the increasing of equivalence ratio for preheating air from 0.36 to 0.51,there is a rise of preheating temperature,the vol-ume fraction of CO2 and HCN in the preheated gas increase,and the volume fractions of CO,H2,CH4 and NH3 decrease,with the heat-ing value of coal gas from 2.02 MJ/m3 to 1.49 MJ/m3.Also,with the increasing of the preheating air equivalence ratio,the volume frac-tion of NO along the height of circulating fluidized bed gradually increases,and the volume fraction of CO shows the atmosphere with high-er at the bottom and lower at the upper part.The NOx emission increases from 172 mg/m3 to 242 mg/m3(6％O2).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 bitu-minous coal,which provides a new technical route and data support for the development and application with coal slime utilization.
万方数据
维普
