贫煤直接混烧低氮稳燃研究

Research on Low Nitrogen Stable Combustion of Lean Coal Direct Co-firing

针对贫煤难稳燃,NOx生成量大的突出问题,采用热重分析法结合卧式炉燃烧研究,通过Testo 350在线烟气分析仪考察了贫煤及其与生物质等直接混烧的燃烧特性和NOx排放特性。结果表明:贫氧气氛下燃烧,氧浓度对焦炭氮的影响明显大于对挥发分氮的影响,氧浓度低于21%时,NOx转化率由27.4%降低至15%左右;在1100℃以下,温度升高促进燃料氮与挥发分同时释放,还原性气氛下含N中间体更容易向N2转化,NOx排放浓度及转化率降低。生物质可以促进燃烧,减少NOx排放,但容易出现挥发分与焦炭分段燃烧现象,影响焦炭稳定燃烧。为此,以烟煤煤矸石为调节燃料,将贫煤、玉米芯、煤矸石三者混配,配比为80∶5∶15(质量比)时,着火温度较贫煤单独燃烧降低100℃左右,最大失重峰温由670℃降低至600℃;氮转化率由28.5%下降至16.7%。

In view of the unstable combustion and large NOx production issue of lean coal,the horizontal static combustion furnace were used to investigate the combustion characteristics and NOx emission for lean coal and mixture with other fuel by means of thermogravimetric analysis.The results show that when the lean coal burns in lean-oxygen atmosphere condition,the oxygen concentration has greater influence on char nitrogen than that on volatile nitrogen.The NOx conversion rate decreases from 27.4%to 15%when the oxygen concentration decreases to below 21%.At 1100℃,the increase of temperature promotes the release of fuel nitrogen and volatilization simultaneously.Therefore,in the reductive atmosphere,N intermediates are more easily converted to N2,and NOx emission concentration and conversion rate decrease.Biomass promotes combustion and reduce NOx emissions,but it is easy to cause a phenomenon of piecewise combustion of volatiles and coke,which affects the stable combustion of coke.To solve this problem,bituminous coal gangue is used as a regulating fuel.The results illustrate that,when lean coal is directly co-fired with corn cob and coal gangue at ratio of 80∶5∶15(mass ratio),the ignition temperature is about 100℃lower than that when lean coal burns alone,and the temperature corresponding to maximum weight loss peak is reduced from 670℃to 600℃,and the nitrogen conversion rate decreases from 28.5%to 16.7%.