Transformation of Alkali Metals during Pyrolysis and Gasification of a Lignite

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• 作者：Xiaofang Wei ; Jiejie Huang ; Tiefeng Liu ; Yitian Fang ; Yang Wang
• 刊名：Energy & Fuels
• 出版年：2008
• 出版时间：May 2008
• 年：2008
• 卷：22
• 期：3
• 页码：1840 - 1844
• 全文大小：137K
• 年卷期：v.22,no.3(May 2008)
• ISSN：1520-5029

文摘

Transformation of Na and K in a lignite was investigated during pyrolysis and gasification in a fixed-bed by using a serial dissolution method with H₂O, CH₃COONH₄, and HCl solutions. The evolution of the fractions of four forms in solid and alkali volatilization during pyrolysis and gasification was determined. The results show that a different mode of occurrence between Na and of K in coal existed. Na in coal can be nearly completely dissolved by H₂O, CH₃COONH₄, and HCl solution. However, K in coal exists almost in the stable forms. Both H₂O soluble and CH₃COONH₄ soluble Na and K fractions decline during pyrolysis and early gasification stage and increase a little with the process of char gasification. The stable form Na in the char produced during pyrolysis is transferred to other forms during char gasification via the pore opening and a series of chemical reactions. Na₂SO₄ (K₂SO₄) may play an important role in producing stable forms such as Na₂O·Al₂O₃·2SiO₂ and K₂O·Al₂O₃·2SiO₂ during pyrolysis. The fraction of HCl soluble K increases during pyrolysis but decreases markedly during the early gasification stage.