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

• The reduction and oxidation kinetics of CaMg0.1Ti0.125Mn0.775O2.9−δ was determined by TGA.
• The presence of titanium improved the stability of the material during redox cycles.
• Oxygen transport via oxygen uncoupling was 1.4 wt.%; it was constant during redox cycles.
• Grain model with chemical reaction and diffusion through the product layer was suitable.
• Minimum solids in fuel reactor was 144 and 31 kg/MWCH4 for fresh and activated particles.

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−δ. The oxygen transport capacity and reactivity of this material during reduction with gaseous fuels (CH4, H2 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−δ 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, H2 or CO; 5–21 vol.% for O2) 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.

Schematic processes in air and fuel reactors () considered for redox kinetics of CaMg0.1Ti0.125Mn0.775O2.9−δ, including common CLC and CLOU with gaseous fuels.Figure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slide