The effects of morphology on the thermal reduction of nonstoichiometric ceria

• Published in: Chemical engineering science Vol. 111; pp. 231 - 243
• Main Authors: Keene, Daniel J., Lipiński, Wojciech, Davidson, Jane H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 24.05.2014
• Subjects: Ceria; Cerium oxide; Concentrating solar; Mass transfer; Mathematical models; Oxygen production; Porosity; Porous; Porous media; Redox cycle; Reduction; Sauter mean diameter; Synthetic fuel; Thermochemistry; Synthetic fuel; Thermochemistry; Redox cycle; Concentrating solar; Ceria; Porous
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2014.01.010

A numerical heat and mass transfer model is used to study the effects of the morphological features of a porous medium composed of ceria when it is placed in a cavity and exposed to high-flux solar irradiation to drive a nonstoichiometric reduction. The morphological features are described by the porosity and pore-level Sauter mean diameter. For porosities of 0.60, 0.75, and 0.90, the rate of oxygen production and the efficiency of solar-to-chemical energy conversion increase monotonically as the Sauter mean diameter is decreased from 1000 to 30µm. For a porosity of 0.90, these performance metrics continue to increase down to 10µm. The primary effect of the changes in porosity and Sauter mean diameter are through their influence on the permeability and the extinction coefficient of the medium. For appropriately selected time duration, an energy conversion efficiency of 10.9% is achieved with a Sauter mean diameter of 10µm and a porosity of 0.90. •The extinction coefficient and the permeability have the greatest impact on conversion efficiency.•The effects of morphology on the extinction coefficient and the permeability are strongly coupled.•For each porosity, there is an associated Sauter mean diameter that will optimize oxygen release.•Operational conditions are anticipated to impact the optimal morphological parameters.