准东高铁煤与稻草秆热解NO_x前驱物释放规律研究
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摘要
氨(NH_3)和氰氢酸(HCN)是燃料热解过程中的主要含氮化合物,也是燃烧过程中重要的NO_x前驱物,因此研究热解过程中HCN/NH_3的释放规律与转化机制,对降低NO_x排放意义重大。借助热重-质谱联用(TG-MS)系统开展实验研究,探讨了准东高铁煤与稻草秆热解过程中NO_x前驱物的释放规律。研究表明:准东高铁煤与稻草秆的热解产物中,NH_3是主要的NO_x前驱物;NH_3与HNCO、HCN与CH_3CN的释放规律趋同;同等实验条件下,稻草秆热解的NO_x前驱物释放量明显高于准东高铁煤的;准东高铁煤与稻草秆混合热解时,当稻草杆掺混质量百分比从10%增加至40%时,NO_x前驱物的释放量呈先减少后增加的趋势,NO_x前驱物释放量最低时的掺混比为30%,说明稻草秆与准东高铁煤共热解时,二者对NO_x前驱物的释放具有一定的协同耦合抑制作用。
NH_3 and HCN are the main nitrogen containing compound in the pyrolysis process and important NO_x precursors in the combustion process of solid fuel. The conversion and control rules of HCN and NH_3 during the pyrolysis process are of great significance to reduce the NO_x emission.Experiments using the TG-MS technique were carried out to analyze the release behaviors of NO_x precursors in the pyrolysis process of Zhun Dong high-iron content coal and straw stalk. The results indicate that the NH_3 is the main NO_x precursors product in the pyrolysis process of Zhun Dong highiron content coal and straw stalk. The release behaviors of NH_3 with HNCO and HCN with CH_3 CN are similar. The emission of NO_x precursors in the straw stalk pyrolysis process is apparently more than in that of Zhun Dong high-iron content coal. The experiments show that iron compounds and minerals in coal have reduction effects on the NO_x precursors release. In co-pyrolysis process of Zhun Dong highiron content coal and straw stalk, with the mass percent of straw stalk increased from 10% to 40%, the emission of NO_x precursors is firstly reduced then increased. The emission is the lowest at the mass percent of 30%. It is shown there is synergistic effect on the reduction of NO_x precursors release by the co-pyrolysis of Zhun Dong high-iron content coal and straw stalk.
NH_3 and HCN are the main nitrogen containing compound in the pyrolysis process and important NO_x precursors in the combustion process of solid fuel. The conversion and control rules of HCN and NH_3 during the pyrolysis process are of great significance to reduce the NO_x emission.Experiments using the TG-MS technique were carried out to analyze the release behaviors of NO_x precursors in the pyrolysis process of Zhun Dong high-iron content coal and straw stalk. The results indicate that the NH_3 is the main NO_x precursors product in the pyrolysis process of Zhun Dong highiron content coal and straw stalk. The release behaviors of NH_3 with HNCO and HCN with CH_3 CN are similar. The emission of NO_x precursors in the straw stalk pyrolysis process is apparently more than in that of Zhun Dong high-iron content coal. The experiments show that iron compounds and minerals in coal have reduction effects on the NO_x precursors release. In co-pyrolysis process of Zhun Dong highiron content coal and straw stalk, with the mass percent of straw stalk increased from 10% to 40%, the emission of NO_x precursors is firstly reduced then increased. The emission is the lowest at the mass percent of 30%. It is shown there is synergistic effect on the reduction of NO_x precursors release by the co-pyrolysis of Zhun Dong high-iron content coal and straw stalk.
引文
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[2]LI C Z,LI T.Formation of NOx and SOx precursors during the pyrolysis of coal and biomass(Part III):Further discussion on the formation of HCN and NH3 during pyrolysis[J].Fuel,2000,79(15):1899-1906.
[3]TIAN F J,LI B Q,CHEN Y,et al.Formation of NOx precursors during the pyrolysis of coal and biomass(Part V):Pyrolysis of a sewage sludge[J].Fuel,2002,81(17):2203-2208.
[4]孙志向.生物质热解过程中燃料氮转化及碱/碱土金属离子催化转化的实验研究[D].北京:华北电力大学,2014.
[5]TSUBOUCHI N,OHTSUKA Y.Nitrogen chemistry in coal pyrolysis:catalytic roles of metal cations in secondary reactions of volatile nitrogen and char nitrogen[J].Fuel Processing Technology,2008,89(4):379-390.
[6]杨凯,丁志江,肖立春,李强.城市污泥耦合锯末共热解特性及动力学分析[J].热能动力工程,2018,33(3):112-118.
[7]REN Q,ZHAO C,XIN W,et al.Effect of mineral matter on the formation of NOx precursors during biomass pyrolysis[J].Journal of Analytical&Applied Pyrolysis,2009,85(1/2):447-453.
[8]AHMAD T,AWAN I A,NISAR J,et al.Influence of inherent minerals and pyrolysis temperature on the yield of pyrolysates of some Pakistani coals[J].Energy Conversion&Management,2009,50(5):1163-1171.
[9]徐秀峰,顾永达.铁催化剂对煤热解过程中氮元素迁移的影响[J].燃料化学学报,1998,26(1):18-23.
[10]顾颖,刘小伟,乔瑜,等.煤热解过程中FeCl3对氮分布规律的影响[J].中国电机工程学报,2011,31(35):59-64.
[11]GUAN R,LI W,CHEN H,et al.The release of nitrogen species during pyrolysis of model chars loaded withdifferent additives[J].Fuel Processing Technology,2004,85 (8/9/10):1025-1037.
[12]LIU Y,CHE D,XU T.Effects of minerals on the release of nitrogen species from anthracite[J].Energy Sources,Part A:Recovery,Utilization&Environmental Effects,2007,29(4):313-327.
[13]侯封校,金晶,林郁郁,等.Fe2O3对污泥热解特性及部分NOx前驱物转化规律的影响[J].燃烧科学与技术,2017,23(1):90-95.
[14]张守玉.高钠煤燃烧利用现状[J].中国电机工程学报,2013,33(5):1-12.
[15]DOUGHTY A,MACKIE J C.Kinetics of pyrolysis of a coal model compound,2-picoline,the nitrogen heteroaromatic analogue of toluene(2):The 2-picolyl radical and kinetic modeling[J].Journal of PhysicalChemistry,1992,96(25):100339-100348.
[16]HA·MA·LA·INEN J P,AHO M J Effect of fuel composition on theconversion of volatile solid fuel-N to N2O and NO[J].Fuel,1995,74(12):1922-1924.
[17]柏继松.生物质燃烧过程氮和硫的迁移、转化特性研究[D].杭州:浙江大学,2012.
[18]HANSSON K M,SAMUELSSON J,TULLIN C,et al.Formation of HNCO,HCN,and NH3 from the pyrolysis of bark and nitrogen-containing model compounds[J].Combustion&Flame,2004,137(3):265-277.
[19]李尚,金晶,林郁郁,等.准东煤与污泥共热解过程中NOx前驱物释放规律[J].化工学报,2017,68(5):2089-2095.
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