燃尽风及生物质气对燃煤锅炉燃烧过程及NO_x排放影响的数值模拟
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摘要
为研究燃尽风以及掺烧生物质气对燃煤锅炉燃烧及NO_x排放的影响,对某电厂330 MW机组燃煤锅炉进行空气分级燃烧改造,在其主燃烧器上方5 m处增加3层分离式燃尽风(SOFA),基于FLUENT模拟软件,搭建了纯煤燃烧和煤粉掺烧生物质气模型,对锅炉无SOFA、有SOFA(15%和20%配风比)、有SOFA(15%和20%配风比)同时掺烧松木气等5种工况的炉内燃烧过程进行了数值模拟,分析不同工况下炉内速度场、温度场、组分场及污染物NOx排放特性。结果表明:在无SOFA和有15%SOFA工况下,一次风、二次风均能形成良好切圆,速度场稳定,在20%SOFA配比下,燃尽风切圆不太理想;与无SOFA纯煤燃烧工况相比,有SOFA工况下,主燃烧区中心温度均有所降低,分别降低了3. 31、27. 48、6. 78和40 K,而在SOFA区域温度有所上升,炉膛出口CO和O_2体积分数增大,CO2体积分数减小,与纯煤无SOFA工况相比,当SOFA配风比从15%增至20%时,NOx炉膛出口平均质量浓度在纯煤工况下分别降低了10. 76%和13. 28%,而在掺烧工况下分别降低了26%和28. 4%。
In order to investigate the effect of over-fire air,co-firing syngas and other factors on combustion and NOxemission,a 330 MW coal-fired boiler was reformed to air staged combustion by setting 3 layers separated over fire air nozzles at distance of 5 m above the primary burner. The pulverized coal combustion model and the co-firing models were built using the Fluent software,and the combustion processes under different conditions were simulated. The velocity field,temperature field,flue gas components and the NOxemission were measured. The five cases were studied; pure coal fired without SOFA,pure coal fired with SOFA of 15% and 20% wind rates,and co-firing with pine syngas setting SOFA of 15% and20% wind rates. The results showed that,in cases without SOFA and with 15% SOFA,both the primary air( pine syngas under co-firing condition) and the secondary air can form good tangential circles,and the flow fields stay stable. In the case with 20% SOFA rate,however,SOFA tangential circles become worse.Compared with coal-fired cases without SOFA,the maximum temperature of the furnace in the SOFA cases decreases by 3. 31,27. 48,6. 78 and 40 K,respectively,but then it has a certain rise at the SOFA region.The O_2 and CO volume fraction under co-firing conditions increase clearly than other cases,while the CO_2 volume fraction decreases. At the outlet,compared with pure coal fired without SOFA case,the average NOxmass concentration decreases by 10. 76% and 13. 28% in coal-fired setting SOFA cases,as well as26% and 28. 4% in co-firing setting SOFA cases.
In order to investigate the effect of over-fire air,co-firing syngas and other factors on combustion and NOxemission,a 330 MW coal-fired boiler was reformed to air staged combustion by setting 3 layers separated over fire air nozzles at distance of 5 m above the primary burner. The pulverized coal combustion model and the co-firing models were built using the Fluent software,and the combustion processes under different conditions were simulated. The velocity field,temperature field,flue gas components and the NOxemission were measured. The five cases were studied; pure coal fired without SOFA,pure coal fired with SOFA of 15% and 20% wind rates,and co-firing with pine syngas setting SOFA of 15% and20% wind rates. The results showed that,in cases without SOFA and with 15% SOFA,both the primary air( pine syngas under co-firing condition) and the secondary air can form good tangential circles,and the flow fields stay stable. In the case with 20% SOFA rate,however,SOFA tangential circles become worse.Compared with coal-fired cases without SOFA,the maximum temperature of the furnace in the SOFA cases decreases by 3. 31,27. 48,6. 78 and 40 K,respectively,but then it has a certain rise at the SOFA region.The O_2 and CO volume fraction under co-firing conditions increase clearly than other cases,while the CO_2 volume fraction decreases. At the outlet,compared with pure coal fired without SOFA case,the average NOxmass concentration decreases by 10. 76% and 13. 28% in coal-fired setting SOFA cases,as well as26% and 28. 4% in co-firing setting SOFA cases.
引文
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[15]刘联胜,赵荣煊,王高月,等.基于ASPEN PLUS的烟气气氛下生物质气化模拟[J].农业机械学报,2017,48(6):278-283.LIU Lian-sheng,ZHAO Rong-xuan,WANG Gao-yue,et al. Simu-lation on pyrolysis gasification of biomass in flue gas based onAspen Plus[J]. Transactions of The Chinese Society of Agricul-tural,2017,48(6):278-283.
[16]冯飞,宋国辉,沈来宏,等.加压串行汽化床制取生物质合成气的模拟[J].农业机械学报,2013,44(3):129-136.FENG Fei,SONG Guo-hui,Shen Lai-hong,et al. Simulation ofbio-syngas production from biomass gasification via pressurizedinterconnected fluidized beds[J]. Transactions of the ChineseSociety of Agricultural,2013,44(3):129-136.
[17]孙俊威. 600 MW超临界燃煤锅炉生物质气再热的数值模拟[D].保定:华北电力大学,2012.SUN Jun-wei. Numerical simulation of biomass gas reburning in600 MW supercritical coal-fired boiler[D]. Baoding:North Chi-na Electric Power University,2012.
[18]刘春元,罗永浩,张睿智,等.生物质气化气还原NO的化学反应动力学机制及数值模拟[J].中国电机工程学报,2011,31(5):120-124.LIU Chun-yuan,LUO Yong-hao,ZHANG Rui-zhi,et al. Chemi-cal kinetic mechanism and numerical simulation on NO reductionby biomass gasification gas[J]. Proceedings of the CSEE,2011,31(5):120-124.
[19]宋前进.生物质气煤混燃燃烧过程数值模拟及燃烧分析[J].信息技术,2016,36(8):25-28.SONG Qian-jin. Numerical simulation and combustion analysis ofbiomass gas and coal co-firing process[J]. Information Thchnolo-gy,2016,36(8):25-28.
[20]吕旭阳,张勇胜,李春曦,等.燃尽风率对锅炉燃烧特性影响的数值模拟[J].热力发电,2015,44(5):108-112.LU Xu-yang,ZHANG Yong-sheng,LI Chun-xi,et al. Effect of o-ver fire air rate on boiler combustion performance:a numericalsimulation[J]. Thermal Power Generation,2015,44(5):108-112.
[2]周俊虎,赵琛杰,许建华,等.电站锅炉空气分级低NOx燃烧技术的应用[J].中国电机工程学报,2010,30(23):19-23.ZHOU Jun-hu,ZHAO Chen-jie,XU Jian-hua,et al. Applicationofair-staged and low NOxemission combustion technology in plantboiler[J]. Proceedings of the CSEE,2010,30(23):19-23.
[3] ASKAROVAA S,MESSERLE V E,USTIMENKO A B,et al. Re-duction of noxious substance emissions at the pulverized fuel com-bustion in the combustion of the BKZ-160 boiler of Almaty heat e-lectric power station using the"Over fire Air"technology[J].Thermal physics and Aeromechanics,2016,23(1):1124-1133.
[4] Ma Lun,Fang Qing-yan,Tan Peng,et al. Effect of the separatedoverfire air location on the combustion optimization and NOxre-duction of a 600 MWeFW down-fired utility boiler with a novelcombustion system[J]. Applied Energy,2016,180(10):104-114.
[5]赵振宁,童家麟,叶学民,等.燃尽风对300 MW锅炉燃烧特性影响的数值模拟[J].华东电力,2013,41(1):214-219.ZHAO Zhen-ning,TONG Jia-lin,YE Xue-min,et al. Numericalsimulation on effects of over fire air on the combustion characteris-tics in 300 MW boiler[J]. East China Electric Power,2013,41(1):214-219.
[6]汪涂维.混煤掺烧方式对混煤燃尽率和NOx排放影响的实验研究[D].武汉:华中科技大学,2015.WANG Tu-wei. Influence of coal blending methods on the burnoutand NOxemissions of coal blends combustion[D]. Wuhan:Hua-zhong University of Science and Technology,2015.
[7]魏刚,樊孝华,王毅斌,等.生物质混燃与空气分级对NOx排放的影响[J].热力发电,2015,44(5):7-11.WEI Gang,FAN Xiao-hua,WANG Yi-bin,et al. Effect of biomassco-firing and air staging on NOxemissions[J]. Thermal PowerGeneration,2015,44(5):7-11.
[8] MLADENOVIC M,PAPRIKA M,MARINKOVIC A. Denitrifica-tion techniques for biomass combustion. Renewable and Sustain-able Energy Reviews,2017,38(14):1364-1378.
[9] KUMAR H,MOHAPATRA S K,INDER R. Study of a 30 MWbubbling fluidized bed combustor based on co-firing biomass andcoal[J]. Sadahana,2015,44(4):1283-1298.
[10] WANG Xue-bin,TAN Hou-zhang,NIU Yang-qing,et al. Experi-mental investigation on biomass co-firing in a 300MW pulverizedcoal-fired utility furnace in China[J]. Science Direct,2011,43(33):2725-2732.
[11]路建伟. 350 MW煤粉高炉煤气混燃锅炉燃烧数值模拟[D].保定:华北电力大学,2016.LU Jian-wei. Numerical simulation of mixed combustion of pul-verized coal and blast furnace gas in 350 MW utility boiler[D].Baoding:North China Electric Power University,2016.
[12]梁占伟,陈鸿伟,杨新,等.混燃煤气气氛下NOx排放特性与建模预测[J].化工进展,2017,36(11):4265-4271.LIANG Zhan-wei,CHEN Hong-wei,YANG Xin,et al. Character-istics of NOxemissions in co-firing gases and modeling prediction[J]. Chemical Industry and Engineering Progress,2017,36(11):4265-4271.
[13]赵贵林,李荣花,黄琼英.燃气锅炉过量空气系数对锅炉效率的影响研究[J].工艺与设备,2017,343(8):123-124.ZHAO Gui-lin,LI Rong-hua,HUANG Qiong-ying. Study on theinfluence of excess air coefficient of gas-fired boiler on boiler ther-mal efficiency[J]. Technology and Equipment,2017,343(8):123-124.
[14]任静浩. WNS型燃气锅炉内燃烧与传热的数值模拟研究[D].北京:北京石油化工学院,2015.Ren Jing-hao. The Study of Numerical Simulation of Combustionand Heat Transfer in the WNS gas-fired boiler[D]. Beijing:Bei-jing Institute of Petrochemical Thchnology,2015.
[15]刘联胜,赵荣煊,王高月,等.基于ASPEN PLUS的烟气气氛下生物质气化模拟[J].农业机械学报,2017,48(6):278-283.LIU Lian-sheng,ZHAO Rong-xuan,WANG Gao-yue,et al. Simu-lation on pyrolysis gasification of biomass in flue gas based onAspen Plus[J]. Transactions of The Chinese Society of Agricul-tural,2017,48(6):278-283.
[16]冯飞,宋国辉,沈来宏,等.加压串行汽化床制取生物质合成气的模拟[J].农业机械学报,2013,44(3):129-136.FENG Fei,SONG Guo-hui,Shen Lai-hong,et al. Simulation ofbio-syngas production from biomass gasification via pressurizedinterconnected fluidized beds[J]. Transactions of the ChineseSociety of Agricultural,2013,44(3):129-136.
[17]孙俊威. 600 MW超临界燃煤锅炉生物质气再热的数值模拟[D].保定:华北电力大学,2012.SUN Jun-wei. Numerical simulation of biomass gas reburning in600 MW supercritical coal-fired boiler[D]. Baoding:North Chi-na Electric Power University,2012.
[18]刘春元,罗永浩,张睿智,等.生物质气化气还原NO的化学反应动力学机制及数值模拟[J].中国电机工程学报,2011,31(5):120-124.LIU Chun-yuan,LUO Yong-hao,ZHANG Rui-zhi,et al. Chemi-cal kinetic mechanism and numerical simulation on NO reductionby biomass gasification gas[J]. Proceedings of the CSEE,2011,31(5):120-124.
[19]宋前进.生物质气煤混燃燃烧过程数值模拟及燃烧分析[J].信息技术,2016,36(8):25-28.SONG Qian-jin. Numerical simulation and combustion analysis ofbiomass gas and coal co-firing process[J]. Information Thchnolo-gy,2016,36(8):25-28.
[20]吕旭阳,张勇胜,李春曦,等.燃尽风率对锅炉燃烧特性影响的数值模拟[J].热力发电,2015,44(5):108-112.LU Xu-yang,ZHANG Yong-sheng,LI Chun-xi,et al. Effect of o-ver fire air rate on boiler combustion performance:a numericalsimulation[J]. Thermal Power Generation,2015,44(5):108-112.
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