Two perovskite type oxygen carriers, for the application in chemical looping combustion, called C14 and C28 are investigated. The composition of C14 is CaMn0.9Mg0.1O3-δ and CaMn0.775Mg0.1Ti0.125O3-δ for C28, respectively. Both oxygen carriers allow chemical looping with oxygen uncoupling (CLOU), they release oxygen under conditions with low oxygen partial pressure. The materials are tested in a 120 kWth pilot plant at TU Wien. Operating temperatures from 800 °C to 960 °C are investigated, further the influence of active inventory and air equivalence number is reviewed. In addition to the experiments in the pilot plant, particle analysis is performed. In total, the CLC operation for C14 was 29.5 h and 22.7 h for C28, resulting in 75 different operating points. Both oxygen carrier materials are able to fully convert the natural gas, used as fuel. A temperature dependency is noticeable for both, the best results are achieved at 960 °C, the highest investigated temperature. Both, C14 and C28 are able to release about 10 % of the total available oxygen via oxygen uncoupling. The performance of both oxygen carriers is strongly linked to the air equivalence number and the resulting amount of excess oxygen in the air reactor. Low oxygen partial pressures lead to incomplete fuel conversion.
Keywords: CLOU; Mn based oxygen carrier; chemical looping combustion; pilot study.