Oxygen carrier development of calcium manganite-based materials with perovskite structure for chemical looping combustion of methane

Chemical-looping combustion (CLC) of gaseous fuels could be of interest in industrial processes for heat, power or hydrogen production with carbon capture. For instance, production of steam or hydrogen from refinery gas are possible applications. A series of collaborate European projects has been carried out since 2002, which focused on oxygen-carrier development and upscaling of both the CLC process and oxygen-carrier production with methane or natural gas as fuel. Most recently, in the FP7 SUCCESS project (2013-2017), Ca-Mn-based materials with perovskite structure, CaMnO3, were produced at a larger scale and with cheap and commercial raw materials. The main advantage with this type of oxygen carrier is the ability to release oxygen to the gas phase, hence promoting reactivity in the fuel reactor. In the project, a significant number of such materials were produced and tested. It was found that a perovskite structure can be obtained relatively easy with widely different raw materials for Ca, Mn, Ti and Mg. The produced materials generally had high reactivities and high attrition resistances, but were prone to sulfur poisoning. In this paper, selected results are presented from the different stages of material development and upscaling, i.e., from bench-scale reactors with batch and continuous operation, respectively, as well as from a laboratory-scale unit with continuous operation and a nominal fuel input of 10 kWth. In the 10 kW unit, the gas velocities in the riser and in the grid jet zone of the gas distributor come close to gas velocities of industrial-scale units and, therefore, this unit is used to assess particle lifetime. Results from the 10 kW unit show that very high degrees of fuel conversion can be reached while achieving very high lifetimes