Mercury Transformation and NO Emission of Coal Combustion with CaCl2 and NH4Cl Additives in a 6 kW CFB Combustor

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• 作者：Qiang Zhou ; Yu-Feng Duan ; Shi-Lin Zhao ; Hong-Fei Du ; Chun Zhu ; Min She ; Hong-Qi Wei
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：29
• 期：8
• 页码：5267-5273
• 全文大小：410K
• ISSN：1520-5029

文摘

Combustion experiments of anthracite with different amounts of CaCl₂ and NH₄Cl additives were conducted in a 6 kW circulating fluidized bed (CFB) combustor. Mercury transformation resulted by the addition of CaCl₂ and NH₄Cl, and the side effects on NO emission were explored. Mercury species existing in flue gas and fly ash were determined, respectively, by the Ontario Hydro Method (OHM) and thermal decomposition experiments, to explore the mercury transformation pathway and mechanism. Results show that the initial Hg⁰ and Hg²⁺ emission concentrations in flue gas are 2.276 and 2.572 渭g/Nm³, respectively, as the anthracite is combusted in the CFB combustor. The proportion of gas-phase mercury is 22.65% and that of particle-bound mercury is 77.35%. The gas-phase mercury emission concentration decreases continuously with the increase of CaCl₂ or NH₄Cl addition amount and is also affected by the unburned carbon content of fly ash. Mercury compounds species existing in fly ashes are mainly HgCl₂ and HgS with little amounts of HgSO₄/HgO. The addition of CaCl₂ or NH₄Cl leads to the significant increase of HgCl₂ content in fly ash with a slight change on HgS and HgSO₄/HgO contents. Anthracite combustion with CaCl₂ or NH₄Cl additives can promote more Hg⁰ and Hg²⁺ in flue gas transformation to HgCl₂ adsorbed on fly ash by homogeneous and heterogeneous reactions. The addition of NH₄Cl reduces 5鈥?0% NO emission, but the addition of CaCl₂ increases NO emission within 10%.