Redox kinetics of CaMg0.1Ti0.125Mn0.775O2.9-δ for Chemical Looping Combustion (CLC) and Chemical Looping with Oxygen Uncoupling (CLOU)

The objective of this study was to establish the kinetic of reactions involved in redox cycles of an oxygen carrier material based on a perovskite type structure with the formula CaMg0.1Ti0.125Mn0.775O2.9-delta. The oxygen transport capacity and reactivity of this material during reduction with gaseous fuels (CH4, H-2 and CO) and the subsequent oxidation with oxygen are studied in a TGA apparatus. Besides, the oxygen uncoupling properties of this material are analysed. Thus, kinetics for relevant reactions involved in Chemical Looping Combustion (CLC) and Chemical Looping with Oxygen Uncoupling (CLOU) were determined. CaMg0.1Ti0.125Mn0.775O2.9-delta reactivity increased with the number of redox cycles, whereas the total oxygen transport capacity decreased from 8.5 to 8.0 wt.%. Particles that reached the maximum reactivity were denoted as activated material. Kinetics for both fresh and activated particles was determined. Conversion vs. time curves at different temperatures (973-1273 K), and reacting gas concentration (5-60 vol.% for CH4, H-2 or CO; 5-21 vol.% for O-2) were obtained for both fresh and activated material. For kinetics determination, the shrinking core model with control by chemical reaction and diffusion through the product layer was used to obtain the kinetic parameters. (C) 2015 Elsevier B.V. All rights reserved.