Analysis of reactivity of Fe-based oxygen carrier with coal during chemical-looping combustion

 The reactivity of using Fe₂O₃ as an oxygen carrier during chemical-looping combustion (CLC) of coal has been investigated experimentally at 800℃~950℃. The experiments were carried out in a fluidized bed, where the steam acted as the gasificationfluidization medium. The reactivity of Fe₂O₃ as a function of the reactor temperature, reaction time, and cyclic reduction number was discussed. The reactivity of Fe₂O₃ oxygen carriers was enhanced as temperature increased at 800℃~950℃. Moreover, the time of chemical reaction control between the oxygen carrier and coal gasification products decreased with increased reaction temperature. When the reaction temperature was above 900℃, the rate of carbon to form CO₂ was higher than 90%; however, it was lower than 75% below 850℃. At 900℃, the dry basis concentration of CO₂ decreased with increased cyclic reduction period, while that of CO and CH₄ increased. Moreover, the value of the CO concentration was less than that of CH₄. The performance of the reacted Fe₂O₃-based oxygen carriers was also evaluated using an X-ray diffractometer and a scanning electron microscope to characterize the solid residues of oxygen carrier. The results show that Fe₂O₃-based oxygen carriers are only reduced to Fe₃O₄. With the increase of cyclic reduction period, the oxygen carrier sinters gradually.