煤粉和流化床燃烧方式下汞排放 及飞灰吸附特性研究

Mercury emission and adsorption characteristics of fly ash in PC and CFB boilers

Abstract

The mercury emission was obtained by measuring the mercury contents in flue gas and solid samples in pulverized coal (PC) and circulating fluidized bed (CFB) utility boilers. The relationship was obtained between the mercury emission and adsorption characteristics of fly ash. The parameters included unburned carbon content, particle size, and pore structure of fly ash. The results showed that the majority of mercury released to the atmosphere with the flue gas in PC boiler, while the mercury was enriched in fly ash and captured by the precipitator in CFB boiler. The coal factor was proposed to characterize the impact of coal property on mercury emissions in this paper. As the coal factor increased, the mercury emission to the atmosphere decreased. It was also found that the mercury content of fly ash in the CFB boiler was ten times higher than that in the PC boiler. As the unburned carbon content increased, the mercury adsorbed increased. The capacity of adsorbing mercury by fly ash was directly related to the particle size. The particle size corresponding to the highest content of mercury, which was about 560 ng/g, appeared in the range from 77.5 to 106 µm. The content of mesoporous (4–6 nm) of the fly ash in the particle size of 77.5–106 µm was the highest, which was beneficial to adsorbing the mercury. The specific surface area played a more significant role than specific pore volume in the mercury adsorption process.

Keywords

mercury / combustion modes / coal property / fly ash / particle size

参考文献

[1] Ito S, Yokoyama T, Asakura K. Emissions of mercury and other trace elements from coal-fired power plants in Japan. Science of the Total Environment, 2006, 368(1): 397–402

[2] Pudasainee D, Kim J, Seo Y. Mercury emission trend influenced by stringent air pollutants regulation for coal-fired power plants in Korea. Atmospheric Environment, 2009, 43(39): 6254–6259

[3] Glodek A, Pacyna J. Mercury emission form coal-fired power plants in Poland. Atmospheric Environment, 2009, 43(35): 5668–5673

[4] Jia L, Fan B G, Yao Y, Han F, Huo R, Zhao C, Jin Y. Study on the elemental mercury adsorption characteristics and mechanism of iron-based modified biochar materials. Energy & Fuels, 2018, 32(12): 12554–12566

[5] Yin L B, Zhuo Y Q, Xu Q S, Zhu Z W, Du W, An Z Y. Mercury emission from coal-fired power plants in China. Proceedings of the CSEE, 2013, 33(29): 1–9 (in Chinese)

[6] Han J, Xu M H. Zhan J, Cai M, Zhu W Y. Predicting the emission of mercury during coal combustion. Proceedings of the CSEE, 2003, 23(12): 208–212 (in Chinese)

[7] Streets D G, Hao J M, Wu Y, Jiang J, Chan M, Tian H, Feng X. Anthropogenic mercury emissions in China. Atmospheric Environment, 2005, 39(40): 7789–7806

[8] Zhao Y, Zhang Z L. Research reviews of mercury control technology in the coal-fired power plants. Electric Power Technology and Environmental Protection, 2010, 26(2): 31–33 (in Chinese)

[9] Dabrowski J M, Ashton P J, Murray K, Leaner J J, Mason R P. Anthropogenic mercury emissions in South Africa: coal combustion in power plants. Atmospheric Environment, 2008, 42(27): 6620–6626

[10] Wu C J, Duan Y F, Wang Y J, Jiang Y M, Wang Q, Yang L G. Characteristics of mercury emission and demercurization property of NID system of a 410 t/h pulverized coal fired boiler. Journal of Fuel Chemistry and Technology, 2008, 36(5): 540–544 (in Chinese)

[11] Lu P, Wu J, Pan W P. Mercury emission and its speciation from flue gas of an 860 MW pulverized coal-fired boiler. Journal of Power Engineering, 2009, 29(11): 1067–1072 (in Chinese)

[12] Zhu Z J, Xu L, Tan Y, Zhang C L, Li Y G, Zhang D L, Wang Q J, Pan L H, Ke J X. Research on characteristics of mercury distribution in combustion products for a 300 MW pulverized coal fired boiler. Journal of Power Engineering, 2002, 22(1): 1594–1607 (in Chinese)

[13] Guo X, Zheng C G, Jia X H, Lin Z, Liu Y M. Study on mercury speciation in pulverized coal fired flue gas. Proceedings of the CSEE, 2004, 24(6): 189–192 (in Chinese)

[14] Zhou J S, Zhang L, Luo Z Y, Hu C X, He S, Zheng J M, Cen K F. Study on mercury emission and its control for boiler of 300 MW unit. Thermal Power Generation, 2008, 37(4): 22–27 (in Chinese)

[15] Zhou J S, Wang G K, Luo Z Y, Cen K F. An experimental study of mercury emissions from a 600 MW pulverized coal-fired boiler. Journal of Engineering for Thermal Energy and Power, 2006, 21(6): 569–572 (in Chinese)

[16] Zhou J S, Wu X J, Gao H L, Luo Z Y, Cen K F. Experimental study on mercury emission and control for CFB boilers. Thermal Power Generation, 2004, (1): 72–75 (in Chinese)

[17] Wu C L, Cao Y, Li H X, Pan W P. Study on mercury migration in a circulating fluidized bed combustion boiler. Journal of Fuel Chemistry and Technology, 2012, 40(10): 1276–1280 (in Chinese)

[18] Wang P, Wu J, Ren J X, Zhang J H, Fang J H, Shi Z. Experimental study on influence of unburned carbon in fly ash on mercury adsorption in flue gas. Journal of Chinese Society of Power Engineering, 2012, 32(4): 332–337 (in Chinese)

[19] Chen P, Tang X Y. The research on the adsorption of nitrogen in low temperature and micro-pore properties in coal. Journal of China Coal Society, 2001, 26(5): 552–556 (in Chinese)

[20] Pavlish J H, Sondreal E A, Mann M D, Olson E S, Galbreath K C, Laudal D L, Benson S A. Status review of mercury control options for coal-fired power plants. Fuel Processing Technology, 2003, 82(2–3): 89–165

[21] Hower J C, Senior C L, Suuberg E M, Hurt R H, Wilcox J L, Olson E S. Mercury capture by native fly ash carbons in coal-fired power plants. Progress in Energy and Combustion Science, 2010, 36(4): 510–529

[22] Gbor P K, Wen D, Meng F, Yang F, Zhang B, Sloan J. Improved model for mercury emission, transport and deposition. Atmospheric Environment, 2006, 40(5): 973–983

[23] Zeng H, Jin F, Guo J. Removal of elemental mercury from coal combustion flue gas by chloride-impregnated activated carbon. Fuel, 2004, 83(1): 143–146

[24] Yang L G, Duan Y F, Fan X X. Enrichment characteristics of mercury in solid products of coal-fired power plants and influencing factors. Journal of Combustion Science and Technology, 2010, 16(6): 485–490 (in Chinese)

[25] Jiang Y M, Duan Y F, Yang X H, Yang L G, Wang Y J. Adsorption characterization of coal fired flue gas mercury by ESP fly ashes. Journal of Southeast University (Natural Science Edition), 2007, 37(3): 436–440

[26] Huang H W, Luo J J. Effect of various fly ash compositions on mercury speciation transformation. Proceedings of CSEE, 2010, 30: 70–75 (in Chinese)

[27] Zhao Y, Hao R J. The research on morphological transformation and factors of mercury in coal-fired power plants. Thermal Power Generation, 2010, 39(1): 6–10 (in Chinese)

[28] Jia L, Fan B G, Huo R, Li B, Yao Y, Han F, Qiao X, Jin Y. Study on quenching hydration reaction kinetics and desulfurization characteristics of magnesium slag. Journal of Cleaner Production, 2018, 190: 12–23

[29] Jia L, Fan B G, Li B, Huo R P, Zhao R, Qiao X L, Jin Y. Effects of pyrolysis mode and particle size on the microscopic characteristics and mercury adsorption characteristics of biomass char. BioResources, 2018, 13(3): 5450–5471

[30] Hower J C, Maroto-Valer M, Taulbee D N, Sakulpitakphon T. Mercury capture by distinct fly ash carbon forms. Energy & Fuels, 2000, 14(1): 224–226

[31] Wu J, Cao Y, Pan W, Shen M, Ren J, Du Y, He P, Wang D, Xu J, Wu A, Li S, Lu P, Pan W P. Evaluation of mercury sorbents in a lab-scale multiphase flow reactor, a pilot-scale slipstream reactor and full-scale power plant. Chemical Engineering Science, 2008, 63(3): 782–790

[32] Zhou Q, Duan Y F. Mao Y Q, Zhu C. Kinetics and mechanism of activated carbon adsorption for mercury removal. Proceedings of the CSEE, 2013, 33(29): 10–17 (in Chinese)

[33] Dai X W, Wu J, Qi X M, Wu Q, He P, Li X. Preparation of Fe-doped titania by sol-gel method and photocatalytic removal of gaseous mercury. Research of Environmental Sciences, 2014, 27(8): 827–834 (in Chinese)

[34] Zhao Y, Liu S T, Ma X Y, Yu H H, Zang Z Y. Removal of elemental Hg by modified fly ash absorbent. Proceedings of the CSEE, 2008, 28(20): 55–60 (in Chinese)

[35] Cao Y, Chen B, Wu J, Cui H, Smith J, Chen C K, Chu P, Pan W P. Study of mercury oxidation by a selective catalytic reduction catalyst in a pilot-scale slipstream reactor at a utility boiler burning bituminous coal. Energy & Fuels, 2007, 21(1): 145–156

[36] Clarkson C R, Solano N, Bustin R M, Bustin A M M, Chalmers G R L, He L, Melnichenko Y B, Radliński A P, Blach T P. Pore structure characterization of North American shale gas reservoirs using USANS/SANS, gas adsorption, and mercury intrusion. Fuel, 2013, 103(1): 606–616

[37] Wu H L, Wei S N, Cui S L. Introduction and application of adsorption isotherm. Textile Dyeing and Finishing Journal, 2006, 28(10): 12–14

[38] Zhou Z J, Liu X W, Zhao B, Chen Z G, Shao H Z, Wang L L, Xu M H. Effects of existing energy saving and air pollution control devices on mercury removal in coal-fired power plants. Fuel Processing Technology, 2015, 131: 99–108

[39] Zhou Z J, Cao T, Liu X, Xu S, Xu Z, Xu M. Vanadium silicate (EVS)-supported silver nanoparticles: a novel catalytic sorbent for elemental mercury removal from flue gas. Journal of Hazardous Materials, 2019, 375: 1–8

[40] Zhou Z J, Leng E, Li C, Zhu X, Zhao B. Insights into the inhibitory effect of H₂O on Hg-catalytic oxidation over the MnO_x-based catalysts. ChemistrySelect, 2019, 4(11): 3259–3265

[41] Jin Y, Liu J J, Qiao X L, Feng C Y. Experimental study of the pore structure of the flying ash particles in a CFB boiler. Journal of Engineering for Thermal Energy and Power, 2012, 27(1): 71–75 (in Chinese)

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant Nos. U1510135, U1810126, and U1910214).

版权

2020 Higher Education Press