高温条件下NH_3还原NO实验研究
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摘要
利用固定床实验系统,在800～1 500℃的反应温度范围内进行了NH_3还原NO实验,分析不同气氛条件下反应温度、氨氮摩尔比以及组分浓度对脱硝效率的影响。实验结果表明:氧化性气氛下最佳脱硝温度约为950℃,温度继续升高时脱硝效率开始下降,而还原性气氛下NH_3对NO的还原存在一个临界温度(约1 000℃),低于临界温度时,NH_3对NO没有脱除效果,反而会额外生成NO,超过临界温度后,脱硝效率随着温度的升高迅速跃升至最大,氨氮摩尔比为2.0时最大脱硝效率可达95%,且在1 200℃以上的高温条件下保持稳定;修正后的GADM98模型对NO浓度的预测与实验结果符合较好,活性基团对NH_2的消耗是高温氧化性气氛下脱硝效率下降的重要原因。
To study the rule of denitration by NH_3 under high temperature conditions,experimental and chemical kinetic model studies on denitration by NH_3 were carried out on a fixed bed experimental system in the temperature range of 800～1 500 ℃.The effects of reaction temperature,normalized stoichiometric ratio and components concentration on denitration efficiency were studied under different atmosphere conditions.The experimental results show that the optimum denitration temperature is about 950 ℃ under the oxidizing atmosphere,and the denitration efficiency begins to decrease as the temperature continues to increase.However,a critical temperature(about 1 000 ℃) of the denitration efficiency was found under the reducing atmosphere.When the temperature is below this critical temperature,NH_3 results in additional NO generation rather than reducing NO.And when the temperature is over this critical temperature,the denitration efficiency reaches the maximum level rapidly,then keeps steady above 1 200 ℃,meanwhile the maximum denitration efficiency could reach above 95% with the normalized stoichiometric ratio of 2.0.The calculation results of the modified GADM98 model turn out to be in good agreement with the experimental results.Finally,the consumption of NH_2 by active groups will decrease the denitration efficiency under the high temperature oxidizing atmosphere.
To study the rule of denitration by NH_3 under high temperature conditions,experimental and chemical kinetic model studies on denitration by NH_3 were carried out on a fixed bed experimental system in the temperature range of 800～1 500 ℃.The effects of reaction temperature,normalized stoichiometric ratio and components concentration on denitration efficiency were studied under different atmosphere conditions.The experimental results show that the optimum denitration temperature is about 950 ℃ under the oxidizing atmosphere,and the denitration efficiency begins to decrease as the temperature continues to increase.However,a critical temperature(about 1 000 ℃) of the denitration efficiency was found under the reducing atmosphere.When the temperature is below this critical temperature,NH_3 results in additional NO generation rather than reducing NO.And when the temperature is over this critical temperature,the denitration efficiency reaches the maximum level rapidly,then keeps steady above 1 200 ℃,meanwhile the maximum denitration efficiency could reach above 95% with the normalized stoichiometric ratio of 2.0.The calculation results of the modified GADM98 model turn out to be in good agreement with the experimental results.Finally,the consumption of NH_2 by active groups will decrease the denitration efficiency under the high temperature oxidizing atmosphere.
引文
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[20] ALZUETA M U,BILBAO R,MILLERA A,et al.Interactions between nitric oxide and urea under flow reactor conditions[J].Energy & Fuels,1998,12(5):1001-1007.
[21] ROTA R,ANTOS D,ZANOELO E F,et al.Experimental and modeling analysis of the NOxOUT process[J].Chemical Engineering Science,2002,57(1):27-38.
[2] GREUL U,SPLIETHOFF H,HEIN K R G.Pulverized coal combustion:Concept for the lowest NOx emissions[J].Chemical Engineering & Technology,1998,21(1):51-55.
[3] Cremer M,Adams B R,O′connor D C,et al.Design and demonstration of rich reagent injection(RRI)for NOx reduction at Conectiv′s BL England Station[C]//Proceedings of the EPRI-DOE-EPA Combined Power Plant Air Pollutant Control Symposium:The MEGA Symposium,USA,2001:20-23.
[4] LU Z,LU J.Influences of O2 concentration on NO reduction and N2O formation in thermal deNOx process[J].Combustion and Flame,2009,156(6):1303-1315.
[5] 张健,毕德贵,张忠孝,等.煤粉炉高温还原性氛围下NH3还原NOx[J].燃烧科学与技术,2017,23(5):406-411.ZHANG Jian,BI De-gui,ZHANG Zhong-xiao,et al.NOx reduction with NH3 reagent injected into high temperature and reducing atmosphere in PC-boiler[J].Journal of Combustion Science and Technology,2017,23(5):406-411.
[6] MILLER J A,BOWMAN C T.Mechanism and modeling of nitrogen chemistry in combustion[J].Progress in Energy and Combustion Science,1989,15(4):287-338.
[7] GLARBORG P,ALZUETA M U,DAM-JOHANSEN K,et al.Kinetic modeling of hydrocarbon/nitric oxide interactions in a flow reactor[J].Combustion and Flame,1998,115(1):1-27.
[8] Coda ZABETTA E,KILPINEN P,HUPA M,et al.Kinetic modeling study on the potential of staged combustion in gas turbines for the reduction of nitrogen oxide emissions from biomass IGCC plants[J].Energy & Fuels,2000,14(4):751-761.
[9] ZABETTA E C,HUPA M.A detailed kinetic mechanism including methanol and nitrogen pollutants relevant to the gas-phase combustion and pyrolysis of biomass-derived fuels[J].Combustion and Flame,2008,152(1):14-27.
[10] SAXENA P,WILLIAMS F A.Testing a small detailed chemical-kinetic mechanism for the combustion of hydrogen and carbon monoxide[J].Combustion and Flame,2006,145(1/2):316-323.
[11] LI Y,FAN W.Experimental research on the NOx evolvement of pulverized coal combusted in CO2,Ar and N2 atmospheres[J].Energy Conversion and Management,2015,106:457-465.
[12] 任鹏,范卫东,李宇,等.温度对燃煤挥发分和焦炭NO生成及相互关系的影响研究[J].锅炉技术,2013,44(2):74-80.REN Peng,FAN Wei-dong,LI Yu,et al.Effect of temperature and volatile-char interaction on ratio of volatile-NO and char-NO during coal combustion[J].Boiler Technology,2013,44(2):74-80.
[13] 卢志民,周俊虎,岑可法,等.不同O2浓度下NH3选择非催化还原NO的实验和模型研究[J].中国电机工程学报,2008,28(29):78-82.LU Zhi-min,ZHOU Jun-hu,CEN Ke-fa,et al.Flow reactor experiments and kinetics modeling on selective non-catalytic removal of NOx under different O2 atmospheres [J].Proceedings of the Chinese Society for Electrical Engineering,2008,28(29):78-82.
[14] CREMER M A,WANG H D,BOLL D E,et al.Improved rich reagent injection (RRI) performance for NOx control in coal fired utility boilers[C]//US DOE Conference on SCR and SNCR for NOx Control,Pittsburgh,2003.
[15] 梁秀进,仲兆平,金保升,等.气态氨作还原剂的SNCR脱硝工艺的试验研究与模拟[J].热能动力工程,2009,24(6):796-802.LIANG Xiu-jin,ZHONG Zhao-ping,JIN Bao-sheng,et al.Experimental study and simulation of SNCR(Selective Non-catalytic reduction) denitrification process with gas-state ammonia serving as a reducing agent[J].Journal of Engineering for Thermal Energy&Power,2009,24(6):796-802.
[16] JAVED M T,IRFAN N,GIBBS B M.Control of combustion-generated nitrogen oxides by selective non-catalytic reduction[J].Journal of Environmental Management,2007,83(3):251-289.
[17] 齐飞,李玉阳,曾美容,等.燃烧反应动力学研究进展与展望[J].中国科学技术大学学报,2013,43(11):948-958.QI Fei,LI Yu-yang,ZENG Mei-rong,et al.Progress and perspectives in combustion chemistry[J].Journal of University of Science and Technology of China,2013,43(11):948-958.
[18] PARK J,LIN M C.Laser-initiated NO reduction by NH3:Total rate constant and product branching ratio measurements for the NH2+ NO reaction[J].The Journal of Physical Chemistry A,1997,101(1):5-13.
[19] BAULCH D L,COBOS C J,COX R A,et al.Evaluated kinetic data for combustion modelling[J].Journal of Physical and Chemical Reference Data,1992,21(3):411-734.
[20] ALZUETA M U,BILBAO R,MILLERA A,et al.Interactions between nitric oxide and urea under flow reactor conditions[J].Energy & Fuels,1998,12(5):1001-1007.
[21] ROTA R,ANTOS D,ZANOELO E F,et al.Experimental and modeling analysis of the NOxOUT process[J].Chemical Engineering Science,2002,57(1):27-38.