(335o) Chemical-Looping Cumbustion of Methane Using Fe2O3-Based Oxygen Carriers With a Thermal Storage Function

Chemical-looping cumbustion of methane using Fe₂O₃-based oxygen carriers with a thermal storage function

                       Li Kongzhai ^*, Wang Hua, Wei Yonggang, Zhu Xing, Liu Zisong          

(Faculty of Metallurgy and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China)

Abstract:The chemical-loopingcombustion is a new generation of combustion technology, which owns the advantages ofe high efficiency and low energy consumption for CO₂ capture. Chemical-looping combustion was perfprmed in two reactors: fuel reactor and air reactor. The heat exchange between the two reactors to provide sufficient heat for the endothermic reaction strongly affects the combustio effifiency 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, thephase change thermal storage technology was used in chemical-looping combustion process throughbuilding a thermal storage functional oxygen carrier, whichcan make the temperature of the oxygen carriers in the fixed bed more stable,and promote the heat exchange bwtween the two reacters.

A series of iron oxide-based oxygen carrierswere 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/Al₂O₃ oxygen carrier with a Fe₂O₃ loading of 60wt% prepared bycoprecipitation method revealed the best activity and redox stability for methane combustion. No obvious decline in the conversion of methane and the formation of CO₂ was observed over this oxygen carrier after the redox cycling in alternant methane/air atmosphere for 30 times.Acore-shell heat storage material (Al/AlN) was prepared via the gas-solid reaction between  aluminum powder and nitrogen, which were also characterized by TG, DSC, EDS and SEM. DSC results showed that adding of a lithium saltsand increasingthe reaction time could improve the formation of shell AlN. The Al/AlN material using Li₂CO₃ as an addtive and reaction time of 2 h showed a good high-temperature thermalstorageperformance and high anti-oxidation ability. The thermal storage capacity of this oxygen cattier is as high as 225J/g.

It also showed that the addtion of Al/AlN thermal storage material into Fe₂O₃/Al₂O₃oxygen carriers can significantly improve the seletiviry of CO₂in the combustion process of methane. With the Al/AlN content of 80wt%, the heat released in the oxidation step could be totally stored in the Fe₂O₃/Al₂O₃-Al/AlN oxygen carrier. This indiacates that the utilization of thermal storage materials in the chemical-looping combustion process to improve the heat exchange of oxygen carriers between the oxdation and the reduction steps is feasible.