Kinetics of oxygen uncoupling of a copper based oxygen carrier
MetadataShow full item record
Hu, W., Donat, F., Scott, S., & Dennis, J. (2015). Kinetics of oxygen uncoupling of a copper based oxygen carrier. Applied Energy, 161 92-100. https://doi.org/10.1016/j.apenergy.2015.10.006
Here, an oxygen carrier consisting of 60 wt% CuO supported on a mixture of Al_2O_ 3 and CaO (23 wt% and 17 wt% respectively) was synthesised by wet-mixing powdered CuO, Al(OH)_3 and Ca(OH)_2, followed by calcination at 1000⁰C. Its suitability for chemical looping with oxygen uncoupling (CLOU) was investigated. After 25 repeated redox cycles in either a thermogravimetric analyser (TGA) or a laboratory-scale fluidised bed, (with 5 vol% H_2 in N_2 as the fuel, and air as the oxidant) no significant change in either the oxygen uncoupling capacity or the overall oxygen availability of the carrier was found. In the TGA, it was found that the rate of oxygen release from the material was controlled by intrinsic chemical kinetics and external transfer of mass from the surface of the particles to the bulk gas. By modelling the various resistances, values of the rate constant for the decomposition were obtained. The activation energy of the reaction was found to be 59.7 kJ/mol (with a standard error of 5.6 kJ/mol) and the corresponding pre-exponential factor was 632 m^3/mol/s. The local rate of conversion within a particle was assumed to occur either (i) by homogeneous chemical reaction, or (ii) in uniform, non-porous grains, each reacting as a kinetically-controlled shrinking core. Upon cross validation against a batch fluidised bed experiment, the homogeneous reaction mode l was found to be more plausible. By accurately accounting for the various artefacts (e.g. mass transfer resistances) present in both TGA and Fluidised bed experiments, it was possible to extract a consistent set of kinetic parameters which reproduced the rates of oxygen release in both experiments.
chemical-looping, CLOU, oxygen carrier, mass transfer, kinetics
This work is supported by the Engineering and Physical Sciences Research Council (EPSRC grant EP/I010912/1) and The Cambridge Commonwealth, European & International Trust as well as Selwyn College, University of Cambridge. The authors would also like to thank Mohammad Ismail for the XRD analysis and Zlatko Saracevic for the nitrogen adsorption analysis.
External DOI: https://doi.org/10.1016/j.apenergy.2015.10.006
This record's URL: https://www.repository.cam.ac.uk/handle/1810/251332
Creative Commons Attribution 4.0
Licence URL: http://creativecommons.org/licenses/by/4.0/
Recommended or similar items
The following licence files are associated with this item: