Chemical-Looping Combustion of Solid Fuels Using Manganese Ores as Oxygen Carriers

In chemical looping combustion (CLC), the choice of the oxygen carrier material is crucial with respect to overall system performance and cost. Materials based on manganese ores are promising candidates due to their favorable thermodynamic properties, high availability, and low price. As these ores tend to be comparably soft and prone to attrition, the challenge is to find materials which combine the above-mentioned advantages with sufficient mechanical durability. In this study, three manganese materials were screened for their suitability as oxygen carriers in the chemical looping process. The materials were subjected to continuous operation with fuel in a 10 kW chemical looping unit and evaluated in terms of gas conversion, carbon capture efficiency, and particle lifetime. All oxygen carriers showed good performance and reached more than 90% gas conversion at relevant conditions. Particle lifetime based on fines production was in the range of 99-284 h, which is a considerable improvement compared to a manganese ore previously tested in this unit. One material was ruled out as a potential candidate for up-scaling due to agglomeration tendencies.