Investigation of sintered iron ore fines as an oxygen carrier in chemical looping combustion

Sintered iron ore fines were selected as oxygen carriers in chemical looping combustion. The reactivity of the sintered iron ore was investigated in redox cycles using thermogravimetric methods under isothermal or non-isothermal conditions. The used sintered iron ore samples from the redox cycles in isothermal tests, which were chosen to evaluate their structural changes, were characterized using the N-2 adsorption-desorption, SEM-EDS, XRD and Raman spectroscopy. Results revealed that multiple redox cycle was an activation process of the selected sintered iron ore to promote its redox kinetics, as well as formations of the new crystalline phase. This was attributed to variations of the sintered iron ore in both their physical and chemical structural changes during redox cycles. The N-2 adsorption-desorption analysis indicated an increase of its surface areas of sintered iron ore during redox cycles. The SEM-EDS results revealed the appearance of tiny cracks on the tested ore sample surfaces. Both XRD and Raman results presented appearance of a new crystalline phase, such as the lepidocrocite (gamma-FeOOH), which was apparently generated in the reduction reaction of chemical looping cycles. The formation of the new lepidocrocite phase seemed correlated with the decrease of the oxygen transport capacity of the sintered iron ore. The sintered iron ore performed properly in the carbon-laden atmospheres, and there was no carbon deposition on its surface.