A Dynamic Study on the Impacts of Water Vapor and Impurities on Limestone Calcination and CaO Sulfurization Processes in a Microfluidized Bed Reactor Analyzer

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• 作者：Hui Wang ; Shuai Guo ; Dunyu Liu ; Yangzhou Guo ; Dingyi Gao ; Shaozeng Sun
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：30
• 期：6
• 页码：4625-4634
• 全文大小：680K
• 年卷期：0
• ISSN：1520-5029

文摘

In-furnace desulfurization technology is usually used in circulating fluidized bed (CFB) boilers, and natural limestone is the most common calcium-based sorbent for sulfur removal. Limestone desulfurization could be influenced by water vapor in the flue gas and also impurities such as SiO₂, Al₂O₃, and Fe₂O₃ contained in the natural limestone. The limestone desulfurization process can be divided into two steps: calcination to produce CaO and sulfurization of CaO formed. This paper studies the impacts of water vapor and impurities on the limestone calcination and sulfurization of CaO calcined in a microfluidized bed reactor analyzer (MFBRA). The apparent activation energy under different operating conditions was first calculated, and then the influence of water vapor and impurities on the activation energy was preliminarily discussed. The results show that reaction temperature, water vapor, and impurities all have influences on the indirect desulfurization of limestone under the condition of standard pressure and air atmosphere. For calcination, the apparent activation energy decreases slightly in the presence of water vapor, and it does not change with the impurities. It is speculated that the existence of water vapor may produce an intermediate product Ca(OH)₂, which has a lower activation energy for decomposition than that for CaCO₃. The impurities in the crystal structure of CaCO₃ may affect the connection of CaO*–CO₂ and improve the porosity of product layer which in turn accelerates the release of the gas product CO₂ without affecting the activation energy. For the sulfurization of CaO calcined, both water vapor and impurities decrease the apparent activation energy. This may result from the improvement in solid-state diffusion of Ca²⁺ ions in the presence of water vapor or impurities. Further investigations are needed in order to confirm these speculations.