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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2019, Vol. 53 Issue (2): 220-227    DOI: 10.3785/j.issn.1008-973X.2019.02.003
Energy Engineering     
Effect of bowl-shaped secondary air distribution on combustion efficiency and NOx mass concentration
Xiao-qiang XIE1(),Jian-guo YANG1,*(),Chao-yang ZHU2,Chuan-huai LIU2,Hong ZHAO1,Zhi-hua WANG1
1. State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
2. Fengtai Power Generation Branch of Huaizhe Coal and Power Co. Ltd, Huainan 232131, China
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Abstract  

The combustion process in a 600 MW supercritical opposite-wall-firing boiler under the conditions of equal and bowl-shaped secondary air distribution (BSAD) was numerically simulated. The influence of varying secondary air distribution deviation on the particle mass concentration field, CO volume fraction field, furnace temperature and NOx generation was analyzed. The calculated results were compared with experimental data. The simulation results showed that BSAD enhanced the mixing between pulverized coal and air, decreased the bias of average CO volume fraction and particle mass concentration along the furnace width, reduced the average CO volume fraction in flue gas, carbon mass fraction in fly ash at the furnace exit, and improved the combustion efficiency of opposite-wall-firing boiler. BSAD did harm to the average NOx mass concentration in flue gas at the furnace exit, however, the NOx mass concentration varied within 3.5% when the deviation of the secondary air distribution was less than 20%. By combining the effects of BSAD on horizontal CO volume fraction distribution and average NOx mass concentration in flue gas at the furnace exit, the appropriate deviation of BSAD for the boiler is recommended to be 20% when the boiler utilizes frequently-fired coal. The variation trend of numerical results of average CO volume fraction in flue gas, carbon mass fraction in fly ash, average NOx mass concentration at the furnace exit is consistent with the in-situ experimental results. In practical operation, the effect of BSAD on declining average CO volume fraction is more significant, the reduction of average CO volume fraction at the economizer exit reaches 95% when the deviation of secondary air distribution equals to 20%.

Key words： boiler      opposite-wall-firing      bowl-shaped secondary air distribution (BSAD)      CO volume fraction      carbon mass fraction      NOx mass concentration     
Received: 01 January 2018      Published: 21 February 2019
CLC:  TK 224  
Corresponding Authors: Jian-guo YANG     E-mail: xiexiaoqiang@zju.edu.cn;yjg@zju.edu.cn
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Xiao-qiang XIE
Jian-guo YANG
Chao-yang ZHU
Chuan-huai LIU
Hong ZHAO
Zhi-hua WANG
Cite this article:

Xiao-qiang XIE,Jian-guo YANG,Chao-yang ZHU,Chuan-huai LIU,Hong ZHAO,Zhi-hua WANG. Effect of bowl-shaped secondary air distribution on combustion efficiency and NOx mass concentration. Journal of ZheJiang University (Engineering Science), 2019, 53(2): 220-227.

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http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2019.02.003     OR     http://www.zjujournals.com/eng/Y2019/V53/I2/220


碗式配风对燃烧效率与NOx质量浓度的影响

对600 MW超临界前后墙对冲燃烧锅炉在均等配风和碗式配风下的燃烧进行数值模拟，分析不同偏差程度碗式配风对炉内颗粒质量浓度场、CO体积分数场、炉膛温度、NOx生成的影响，并与试验结果进行对比. 模拟结果表明，燃烧器碗式配风改善了炉内宽度方向上的风、煤混合过程，减小了CO体积分数和煤粉颗粒质量浓度偏差，降低了炉膛出口烟气中CO的平均体积分数和飞灰中碳的质量分数，从而有效提高了前后墙对冲燃烧锅炉的燃烧效率. 燃烧器碗式配风对炉膛出口烟气中NOx的平均质量浓度有不利影响，但是当碗式配风风量偏差不大于20%时，NOx平均质量浓度变化不大于3.5%. 综合燃烧器碗式配风对水平截面CO分布特征和炉膛出口烟气中NOx的平均质量浓度的影响，在燃烧常用煤种的条件下，碗式配风的风量偏差宜控制在20%以内. 炉膛出口烟气中CO的平均体积分数、飞灰中碳的质量分数、NOx平均质量浓度的模拟值与热态试验值变化趋势一致. 在实际应用中碗式配风对CO平均体积分数的降低效果更加显著，当碗式配风的风量偏差达到20%时，省煤器出口烟气中CO的平均体积分数降低幅度达95%.


关键词： 锅炉,  前后墙对冲燃烧,  碗式配风 (BSAD),  CO体积分数,  碳质量分数,  NOx质量浓度 
工业分析wB/% Q/（MJ·kg?1） 元素分析wB/%
M A V C H O N S
7.00 26.00 26.13 21.30 56.37 3.72 5.54 1.00 0.37
Tab.1 Proximate and elemental analyses of coal used in boiler (as received basis)
Fig.2 Structural diagram of HT-NR3 low NOx swirl burner
名称 qm /（kg·s?1） θa / °C r/%
一次风 133.4 75 23.00
内二次风 62.8 345 10.83
外二次风 267.8 345 46.17
燃尽风 116.0 345 20.00
Tab.2 Main operating parameters of boiler under rated condition
工况 配风方式 D/%
中间燃烧器 两侧燃烧器
1 均等配风 0 0
2 10%碗式配风 ?5 +5
3 20%碗式配风 ?10 +10
4 30%碗式配风 ?15 +15
Tab.3 Outer secondary air distribution of burners under different BSAD conditions
Fig.1 Structure of boiler furnace and layouts of burners and over-fire air ports
截面 H/m 截面位置说明
Z1 17.5 冷灰斗与水冷壁衔接位置
Z2 19.9 第1层燃烧器中心
Z3 24.9 第2层燃烧器中心
Z4 29.8 第3层燃烧器中心
Z5 32.5 燃烧器区域出口
Z6 36.8 主燃尽风中心
Z7 42.5 燃尽风区域出口
Tab.4 Position description of furnace’s horizontal cross-sections
Fig.3 Comparison between measured and simulated average temperature at horizontal cross-sections along furance height
Fig.5 Effect of bowl-shaped air distribution on CO volume fraction field at exit of over fire air region
Fig.6 Effect of bowl-shaped air distribution on particle mass concentration field at exit of burner region
Fig.7 Effect of bowl-shaped air distribution on particle mass concentration field at exit of over fire air region
Fig.8 Variation of average CO volume fraction at horizontal cross-sections along furnace height
配风方式 $\overline \varphi_{\rm s}\left({\rm O}_2\right)$/
% 		$\overline \varphi_{\rm s}\left({\rm CO}\right)$/
% 		$w_{\rm s}\left({\rm C}\right)$/
% 		$\overline \rho_{\rm s}\left({\rm NO}_x\right)$/
（mg·m?3）1)
注：1）NOx质量浓度折算到6%O2体积分数
均等配风 2.17 0.435 6 3.27 314
10% 碗式配风 2.21 0.404 4 3.47 312
20% 碗式配风 2.08 0.285 6 2.21 325
30% 碗式配风 1.94 0.230 9 1.38 388
Tab.5 Numerical results of gas parameters at furnace exit under various air distribution conditions
Fig.9 Variation of average temperature at horizontal cross-sections along furnace height
Fig.10 Variation of average NOx volume concentration at horizontal cross-sections along furnace height
Fig.4 Effect of bowl-shaped air distribution on CO volume fraction field at exit of burner region
配风方式 $\overline \varphi_{\rm t}\left({\rm O}_2\right)$/
% 		$\overline \varphi_{\rm t}\left({\rm CO}\right)$/
% 		$w_{\rm t}\left({\rm C}\right)$/
% 		$\overline \rho_{\rm t}\left({\rm NO}_x\right)$/
（mg·m?3）1)
注：1）NOx质量浓度折算到6%O2体积分数
均等配风 2.10 0.232 4 3.34 302
10% 碗式配风 2.06 0.064 1 2.89 326
20% 碗式配风 2.01 0.012 0 2.14 306
Tab.6 Experimental results of gas parameters at economizer exit under various air distribution conditions
[1]   LIU H, TANG C, ZHANG L, et al Effect of two-level over fire air on the combustion and NOx emission characteristics in a 600 MW wall-fired boiler [J]. Numerical Heat Transfer Part A: Applications, 2015, 10 (6): 858- 875
[2]   仝营, 钟葳, 吴燕玲, 等 基于流体网络方法的超临界电站锅炉性能分析平台[J]. 中国电机工程学报, 2014, 34 (5): 748- 755
TONG Ying, ZHONG Wei, WU Yan-ling, et al Performance analysis platform of supercritical power station boilers based on the fluid network method[J]. Proceedings of the CSEE, 2014, 34 (5): 748- 755
[3]   刘建全. 超(超)临界机组锅炉燃烧特性试验与优化研究 [D]. 保定: 华北电力大学, 2012.
LIU Jian-quan. Combustion characteristics experimental and optimization on supercritical and ultra supercriticalunit boiler [D]. Baoding: North China Electric Power University, 2012.
[4]   李德波,沈跃良. 前后墙对冲旋流燃煤锅炉CO和NOx分布规律的试验研究 [J]. 动力工程学报, 2013, 33(7): 502-506.
LI De-bo, SHEN Yue-liang. Experimental study on CO and NOx emission of a swirl-opposed coal-fired boiler [J]. Journal of Chinese Society of Power Engineering, 2013, 33(7): 502-506.
[5]   周永刚, 李培, 敖翔, 等 基于燃烧均匀性的对冲燃烧锅炉高温腐蚀抑制[J]. 浙江大学学报: 工学版, 2015, 49 (9): 1769- 1775
ZHOU Yong-gang, LI Pei, AO Xiang, et al High temperature corrosion inhibition for opposed firing boiler based on combustion distribution evenness[J]. Journal of Zhejiang University: Engineering Science, 2015, 49 (9): 1769- 1775
[6]   YANG J, KIM J, HONG J, et al Effects of detailed operating parameters on combustion in two 500 MWe coal-fired boilers of an identical design[J]. Fuel, 2015, 144: 145- 156
doi: 10.1016/j.fuel.2014.12.017
[7]   LUO R, LI N, ZHANG Y, et al Effect of the adjustable inner secondary air-flaring angle of swirl burner on coal-opposed combustion[J]. Journal of Energy Engineering, 2016, 142 (1): 04010518
[8]   SUNG Y, LEE S, EOM S, et al Optical non-intrusive measurements of internal recirculation zone of pulverized coal swirling flames with secondary swirl intensity[J]. Energy, 2016, 102: 61- 74
[9]   LI S, LI Z, JIANG B, et al Effect of secondary air mass flow rate on the airflow and combustion characteristics and NOx formation of the low-volatile coal-fired swirl burner [J]. Asia-Pacific Journal of Chemical Engineering, 2015, 10 (6): 858- 875
doi: 10.1002/apj.1923
[10]   ZENG L, LI Z, ZHAO G, et al The influence of swirl burner structure on the gas/particle flow characteristics[J]. Energy, 2011, 36 (10): 6184- 6194
doi: 10.1016/j.energy.2011.07.044
[11]   CHEN Z, WANG Q, WANG B, et al Anthracite combustion characteristics and NOx formation of a 300 MWe down-fired boiler with swirl burners at different loads after the implementation of a new combustion system [J]. Applied Energy, 2017, 189: 133- 141
doi: 10.1016/j.apenergy.2016.12.063
[12]   YAN L, HE B, YAO F, et al Numerical simulation of a 600 MW utility boiler with different tangential arrangements of burners[J]. Energy and Fuels, 2012, 26: 5491- 5502
[13]   ADAMCZYK W, KOZOLUB P, WECEL G, et al Simulations of the PC boiler equipped with complex swirling burners[J]. International Journal of Numerical Methods for Heat and Fluid Flow, 2014, 24 (4): 845- 860
[14]   GANDHI M, VUTHALURU R, VUTHALURU H, et al CFD based prediction of erosion rate in large scale wall-fired boiler[J]. Applied Thermal Engineering, 2012, 42: 90- 100
doi: 10.1016/j.applthermaleng.2012.03.015
[15]   VUTHALURU R, VUTHALURU H Modelling of a wall fired furnace for different operating conditions using FLUENT[J]. Fuel Processing Technology, 2006, 87 (7): 633- 639
doi: 10.1016/j.fuproc.2006.01.004
[16]   VIKHANSKY A, BAR-ZIV E, CHUDNOSKY B, et al Measurements and numerical simulations for optimization of the combustion process in a utility boiler[J]. International Journal of Energy Research, 2004, 28 (5): 391- 401
doi: 10.1002/(ISSN)1099-114X
[17]   方庆艳, 汪华剑, 陈刚, 等 超超临界锅炉磨煤机组合运行方式优化数值模拟[J]. 中国电机工程学报, 2011, 31 (5): 1- 6
FANG Qing-yan, WANG Hua-jian, CHEN Gang, et al Optimal simulation on the combustion mode of mills for an ultra-supercritical utility boiler[J]. Proceedings of the CSEE, 2011, 31 (5): 1- 6
[18]   XU X, WANG Z, ZHUO Y, et al False diffusion in numerical simulation of combustion processes in tangential-fired furnace[J]. Journal of Mechanical Science and Technology, 2007, 21 (11): 1828- 1846
doi: 10.1007/BF03177439
[19]   李想.1000 MW超超临界前后墙旋流对冲锅炉燃烧数值模拟[D]. 武汉: 华中科技大学, 2012.
LI Xiang. Numerical simulation of coal combustion in a 1000 MW ultra-supercritical [D]. Wuhan: Huazhong University of Science and Technology, 2012.
[20]   HILL S, SMOOT L Modeling of nitrogen oxides formation and destruction in combustion systems[J]. Progress in Energy and Combustion Science, 2000, 26 (4): 417- 458
[21]   DE S Overall reaction rates of NO and N2 formation from fuel nitrogen [J]. Symposium on Combustion, 1975, 15 (1): 1093- 1102
doi: 10.1016/S0082-0784(75)80374-2
[22]   CHOI C, KIM C Numerical investigation on the flow, combustion and NOx emission characteristics in a 500 MWe tangentially fired pulverized-coal boiler [J]. Fuel, 2009, 88 (9): 1720- 1731
doi: 10.1016/j.fuel.2009.04.001
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