The performance of Fe2O3-CaO Oxygen Carriers and the Interaction of Iron Oxides with CaO during Chemical Looping Combustion and H2 production

Chemical-looping combustion (CLC) has emerged as a promising and low cost carbon capture process which produces a pure stream of CO2. In CLC, oxygen from a solid oxygen carrier (OC) is used to combust fuels. Iron oxide is a promising material, being relatively cheap and environmentally benign. The thermodynamics of the Fe-O system allows reduced iron oxides to be also used for partial oxidation or hydrogen production. However, pure Fe2O3 has the problem of degradation in reactivity over repeated CLC cycles. This work is concerned with inclusion of a suitable CaO support material within the Fe-based OCs to increase its strength and cycle ability. OCs were made from Fe2O3 powder by granulation and followed by impregnation with Ca(NO3)2.4H2O. The reactivity and cyclic stability of the OCs were tested by being subjected to alternating reducing (using H2 or CO) and oxidizing environments (using air and / CO2) for many cycles, in a thermogravimetric analyser and a fluidized bed reactor at 850-950 °C. It was found that, for samples with a range of loading of CaO, from 2 to 30 mol%, the one containing 20 mol% CaO showed optimal performances, whereas others showed improvements in oxygen carrying capacity, cyclic stability and reactivity over unmodified iron oxide but to a lesser extent.