Evaluation of two CaMn1−x−yTixFeyO3−δ-based granules oxygen carriers for chemical looping applications

Abstract

AbstractUpscaling of the laboratory oxygen carriers while keeping comparable performance as laboratory powders remains a challenge in the field of chemical looping combustion (CLC). In this work, two perovskite compositions of CaMn0.375Ti0.5Fe0.125O3 (termed CMTF8341) and CaMn0.5Ti0.375Fe0.125O3 (CMTF8431) have been fabricated by means of spray granulation. The fabricated granules were evaluated by redox cycles under CLC conditions and showed comparable performance with laboratory-prepared powders, i.e. high oxygen transfer capacity and fast redox kinetics. Under chemical looping oxygen uncoupling (CLOU) conditions, it has been found that steam leads to a slower kinetics and lower oxygen transfer capacity for these two compositions. When it comes to sulphur effect on the oxygen carriers, redox cycles with deep reduction showed no influence with H2S since the CaSO4 formed in air decompose but it affected the materials under mild CLOU due to calcium sulphate formed under such condition. Nonetheless, redox performance can be recovered by deep reduction with an enhanced oxygen capacity. These two oxygen carriers showed no degradation as compared to other tested minerals in the field of CLC. Microstructure analyses from SEM showed high degree of structure integrity after redox cycles at temperatures up to 1050 °C for the CMTF8341. Good mechanical strength was evidenced from cold attrition test, and the lifetime of the two granules was also predicted based on a standard reference.