Solid Fuel Conversion Via Chemical-Looping With Oxygen Uncoupling (CLOU) Using Co-Precipitation Derived Cu-Mn Oxygen Carriers

Chemical-looping combustion (CLC) is an emerging CO2 capture and storage (CCS) technology. In CLC oxygen derived from a solid oxygen carrier is used to completely combust a (hydro-) carbonaceous fuel to CO2 and H2O. Thus , in CLC CO2 is inherently separated from the nitrogen in air. Conventional CLC for solid fuels requires a prior , relatively slow gasification step to produce a synthesis gas containing mostly CO and H2. An alternative strategy is chemical-looping with oxygen uncoupling (CLOU) [1]. Here , oxygen is released via a decomposition reaction , with the combustion reaction of the solid fuel with molecular oxygen being very fast. A suitable oxygen carrier for CLOU , typically a transition metal oxide , must possess a high oxygen storage capacity , thermal stability and fast decomposition kinetics at typical operating temperatures (800-1000 ˚C). In addition , resistance to attrition and agglomeration , cost and environmental impact have to be taken into account. With regards to equilibrium thermodynamics CuO and Mn2O3 are arguably the most attractive oxygen carriers for CLOU [1]. However , both copper and manganese have some drawbacks. For the CuO/Cu2O system , agglomeration and a comparatively low oxygen partial pressure (at temperatures below 850 ˚C) are the main disadvantages , whereas Mn2O3/Mn3O4 has a low oxygen storage capacity and at temperatures above 900 ˚C Mn3O4 is thermodynamically stable and cannot be re-oxidized back to Mn2O3 using air. In this study , mixed metal oxide oxygen carriers containing manganese and copper oxides were synthesized using a co-precipitation technique. The synthesized oxygen carriers were fully characterized and assessed with regards to solid fuel conversion under CLOU conditions. A comparison with the performance of the individual metal oxides revealed that the optimized Cu-Mn mixed oxides possessed an improved resistance to agglomeration , a higher oxygen carrying capacity , a high solid fuel conversion and an improved physical and chemical stability. These favorable characteristics make the newly developed Cu-Mn mixed oxides promising oxygen carriers for CLOU. Reference[1] Mattisson , T. , Lyngfelt , A. , Leion , H. , Int. J. Greenhouse Gas Control 2009 , 3 (1) , 11-19