Abstract:
Through mechanical-mixing, impregnating and sol-gel methods, Fe
2O
3-based oxygen carriers (OC) were prepared with natural attapulgite (ATP) as an inert support and characterized by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and nitrogen adsorption-desorption measurements. The reactivity of Fe
2O
3-based oxygen carriers (Fe
2O
3/ATP OCs) in coal chemical looping combustion (CLC) was investigated in a fluidized-bed reactor at 900 ℃ by using steam as the gasification agent. The results indicated that the surface area and attrition resistance of Fe
2O
3/ATP OCs are improved significantly by using ATP as the support. Owing the synergy between ATP and Fe
2O
3, both are catalytic active, carbon conversion is enhanced significantly. ATP is an appropriate support for Fe
2O
3 oxygen carriers, whereas the sol-gel method gives the carriers best performance. U-Fe4ATP6 prepared by the sol-gel method, with a surface area of 4.920 7 m
2/g and Ca content of 4.3%, exhibits much better performance than other two oxygen carriers. When used in CLC, the initial carbon conversion rate reaches 0.168 min
-1, with an average CO
2 concentration of 98.6% and a combustion efficiency of 98.7%. The catalytic activity of U-Fe4ATP6 is slightly decreased after twenty cycles; the initial carbon conversion rate is decreased to 0.108 min
-1 and the residence time (
t95) is extended to 18 min, whereas the CO
2 capture efficiency and combustion efficiency remain at about 98.6% and 96.7%, respectively.