High-Temperature Conversion of SO2 to SO3: Homogeneous Experiments and Catalytic Effect of Fly Ash from Air and Oxy-fuel Firing

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• 作者：Lawrence P. Belo ; Liza K. Elliott ; Rohan J. Stanger ; Reinhold Sp枚rl ; Kalpit V. Shah ; J枚rg Maier ; Terry F. Wall
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：28
• 期：11
• 页码：7243-7251
• 全文大小：441K
• ISSN：1520-5029

文摘

The reaction of SO₂ with fly ash in the presence of O₂ and H₂O involves a series of reactions that lead to the formation of SO₃ and eventually H₂SO₄. Homogeneous experiments were conducted to evaluate the effects of the procedural variables, i.e., temperature, gas concentrations, and residence time, on the post-combustion conversion of SO₂ to SO₃. The results were compared to existing global kinetics and found to be dependent upon SO₂, O₂, residence time, and temperature and independent of H₂O content. For a residence time of 1 s, temperatures of about 900 掳C are needed to have an observable conversion of SO₂ to SO₃. Literature suggested that the conversion of SO₂ to SO₃ is dependent upon the iron oxide content of the fly ash. Experiments using three different fly ash samples from Australian sub-bituminous coals were used to investigate the catalytic effects of fly ash on SO₂ conversion to SO₃ at a temperature range of 400鈥?000 掳C. It was observed that fly ash acts as a catalyst in the formation of SO₃, with the largest conversion occurring at 700 掳C. A homogeneous reaction at 700 掳C, without fly ash present, converted 0.10% of the available SO₂ to SO₃. When fly ash was present, the conversion increased to 1.78%. The catalytic effect accounts for roughly 95% of the total conversion. Average SO₃/SO₂ conversion values between fly ash derived from air and oxy-fuel firing and under different flue gas environments were found to be similar.