Iron-based Oxygen Carriers Regenerative Type Preparation And Chemical Looping Combustion Performance

The chemical-looping combustion is a new generation of clean, efficient combustion technology, which owns the advantages of high efficiency and low energy consumption for CO2capture. Chemical-looping combustion was performed in two reactors:fuel reactor and air reactor. The heat exchange between the two reactors to provide sufficient heat for the endothermic reaction strongly affect the combustion efficiency of the whole process. Thermal energy storage technology is very important to improve energy efficiency and move the gap between energy supply and request.. In this paper, the phase change thermal storage technology was used in chemical-looping combustion process through building a thermal storage functional oxygen carrier, which can make the temperature of the oxygen carriers in the fixed bed more stable, and promote the heat exchange between the two reacters.A series of iron oxide-based oxygen carriers prepared by different methods, and the oxygen carriers were characterized by XRD, BET, H2-TPR and O2-TPD techniques. The reactions between oxygen carriers and methane/air were also investigated in detail. The results show that the Fe2O3/Al2O3oxygen carrier with a Fe2O3loading of60wt%prepared by coprecipitation method revealed the best activity and redox stability for methane combustion. No obvious decline in the conversion of methane and the formation of CO2was observed over this oxygen carrier after the redox cycling in alternant methane/air atmosphere for30times.A core-shell heat storage material (Al/AlN) was prepared via the gas-solid reaction between aluminum powder and nitrogen characterized by TG, DSC, Raman, EDS and SEM. DSC results showed that adding of a lithium salts and increasing the reaction time could improve the formation of shell AlN. The Al/AlN material using Li2CO3as an additive and reaction time of2h showed a good high-temperature thermal storage performance and anti-oxidation ability. The regenerative heat value is as high as225J/g.It is also showed that introduced Al/AlN heat storage material into Fe2O3/Al2O3oxygen carriers can significantly improve the selectivity of CO2in the combustion process of methane. With the Al/AlN content of80wt%, the heat released in the oxidation step could be totally stored in the Fe2O3/Al2O3-Al/AlN oxygen carrier. This indicates that the utilization of thermal storage materials in the chemical-looping combustion process to improve the heat exchange of oxygen carriers between the oxidation and the reduction steps is feasible.