Investigation of Chemical Looping Combustion of Coal with CuFe2O4 Oxygen Carrier

详细信息    查看全文

• 作者：Baowen Wang ; Rong Yan ; Haibo Zhao ; Ying Zheng ; Zhaohui Liu ; Chuguang Zheng
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：July 21, 2011
• 年：2011
• 卷：25
• 期：7
• 页码：3344-3354
• 全文大小：1180K
• 年卷期：v.25,no.7(July 21, 2011)
• ISSN：1520-5029

文摘

Chemical looping combustion (CLC) has great advantages to obtain pure CO₂ from coal combustion flue gas at a manageable cost. CuFe₂O₄ was put forward as a novel oxygen carrier, which integrated Cu and Fe metals into one oxide matrix with superior characteristics over single metal oxide of either CuO or Fe₂O₃ and had a high potential to be used in CLC. In this study, the reaction of CuFe₂O₄ with two Chinese coals of different ranks [Liu Pan Shui (LPS) sub-bituminous coal and Yang Quang (YQ) anthracite] was performed in a thermogravimetric analyzer (TGA). Fourier transform infrared (FTIR) spectroscopy was used to detect in situ the emitted gases from the TGA. Field scanning electron microscopy/energy-dispersive X-ray spectrometry (FSEM/EDX) was used to study the morphology and elemental compositions present in the solid residues, and the related phases were further identified by X-ray diffraction (XRD). Meanwhile, to explore the reaction mechanisms involved for the reaction of CuFe₂O₄ with coal, a more realistic simulation system with 376 species was designed for thermodynamic analysis. Through all of these measures, it was found that the reaction of LPS lean coal with CuFe₂O₄ underwent two distinct reaction stages at 300鈥?00 and 600鈥?50 掳C, respectively. At these two reaction stages, CuFe₂O₄ was dominantly reduced into Cu and Fe₃O₄ by transfer of the lattice oxygen [O] in CuFe₂O₄, and then the formed Fe₃O₄ was further reduced into Fe_2.962O₄. However, above 800 掳C, CuFeO₂ and Cu₂O were produced through direct decomposition of CuFe₂O₄ into CuFeO₂ and then further partial decomposition of CuFeO₂ into Cu₂O. Especially, O₂ generated was greatly beneficial to the full conversion of the remaining coal. Different from LPS, the reaction of YQ with CuFe₂O₄ presented only one discernible reaction stage above 600 掳C. Besides Cu and CuFeO₂, Fe_2.957O₄ was also generated. Furthermore, four cycles of reduction of CuFe₂O₄ with H₂ and then oxidation with air displayed a good reaction stability of synthesized CuFe₂O₄. However, if coal was used, iron silicates were formed from the interaction of the reduced CuFe₂O₄ with ash and resulted in the insufficient reoxidation of reduced CuFe₂O₄. As such, effective separation of coal ash should be included in the CLC process to ensure the full regeneration of reduced CuFe₂O₄.