Preparation of Fe2O3/Al2O3 and Fe2O3/TiO2 Pellets as Oxygen Carrier for Chemical Looping Process

Fe-based oxygen carriers supported by Al2O3 and TiO2 were prepared as pellets for chemical looping combustion in this study. Over 90% conversions were obtained for most experiments operated in the TGA; however, experiments conducted with FeTi320 pellets exhibited higher conversions than those with FeAl320. The prepared pellets sintered at higher temperatures always exhibited higher crush strength. The crush strength of prepared FeAl320 and FeTi320 pellets were decreased for experiments conducted with greater starch content, because the more pore spaces are formed in the original places of the starch grains. For experiments conducted in the fixed bed reactor, the prepared pellets exhibited relatively high conversion. The conversions of FeTi320 were remained to be about 80% with increasing starch content because high porosity (approximately 50%) was formed for 0-20% starch contents of FeTi320 pellets after 10 redox cycles. Less porosity was formed after 20 redox cycles for experiments conducted with FeAl320 pellets prepared with higher starch contents. Therefore, the conversion of FeAl320 pellets was elevated with increasing starch content. Iron content for inner part of prepared pellets was significantly decreased after operated for 20 redox cycles, while iron content for outer part of pellets were increased. It is suggested that the iron ions may diffuse onto the surface of oxygen carriers to react with oxygen during the oxidation period.