화학공학소재연구정보센터
Energy & Fuels, Vol.30, No.3, 2285-2294, 2016
In-Depth Investigation of Chemical Looping Combustion of a Chinese Bituminous Coal with CuFe2O4 Combined Oxygen Carrier
Coal is of heterogeneous nature with a complex chemical structure, which is closely associated with its reactivity. In this research, from the perspective of the chemical structure of coal, reaction characteristics of the as-synthesized CuFe2O4 oxygen carrier (OC) with a typical Chinese bituminous coal (designated as LZ) were deeply investigated using thermogravimetric analysis (TGA). Also, the effect of CuFe2O4 oxygen excess number Phi on the reaction behavior of LZ coal with CuFe2O4 was highlighted. TGA investigation of LZ coal reaction with CuFe2O4 at Phi = 1.0 displayed the enhanced reactivity of CuFe2O4, which was useful to conversion of the aromatic matrix in LZ coal. Furthermore, during LZ coal reaction with CuFe2O4 in the TGA, the gaseous products evolved from the condensed flue gas were in situ analyzed using Fourier transform infrared (FTIR), which indicated that most of the CO2 resulted from oxidation of CO by CuFe2O4 OC. Meanwhile, the solid product left after LZ coal reaction with CuFe2O4 was analyzed with X-ray photoelectron spectroscopy (XPS), which revealed that oxidation and conversion of the C-C/C-H groups was the limited step at the molecular scale for full conversion of coal. Finally, the effect of CuFe2O4 excess number Phi for LZ coal reaction with CuFe2O4 was investigated by TGA, and the solid product left was analyzed by XPS, which indicated that C-C/C-H was more effectively converted at CuFe2O4 Phi = 1.0 than Phi = 0.5 and 1.5 at the final reaction temperature of 900 degrees C. In addition, the mechanism of coal oxidation by CuFe2O4 was also explored, and the C-C/C-H involved in LZ coal was preferentially oxidized to form C-O groups and then further converted to O=C-O groups through the formed intermediate C=O groups. Overall, this research was much beneficial for a mechanistic understanding of the conversion of coal in a CLC system and promotion of the efficient utilization of coal.