Kinetics of the thermal dissociation of ZnO exposed to concentrated solar irradiation using a solar-driven thermogravimeter in the 1800–2100 K range
✍ Scribed by Lothar O. Schunk; Aldo Steinfeld
- Publisher
- American Institute of Chemical Engineers
- Year
- 2009
- Tongue
- English
- Weight
- 240 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0001-1541
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✦ Synopsis
Abstract
The two‐step H~2~O‐splitting thermochemical cycle based on the Zn/ZnO redox reactions is considered for solar H~2~ production, comprising the endothermal dissociation of ZnO followed by the exothermal hydrolysis of Zn. A solar‐driven thermogravimeter, in which a packed‐bed of ZnO particles is directly exposed to concentrated solar radiation at a peak solar concentration ratio of 2400 suns while its weight loss is continuously monitored, was applied to measure the thermal dissociation rate in a set‐up closely approximating the heat and mass transfer characteristics of solar reactors. Isothermal thermogravimetric runs were performed in the range 1834–2109 K and fitted to a zero‐order Arrhenius rate law with apparent activation energy 361 ± 53 kJ mol^−1^ K^−1^ and frequency factor 14.03 × 10^6^ ± 2.73 × 10^6^ kg m^−2^ s^−1^. Application of L‘vov’s kinetic expression for solid decomposition along with a convective mass transport correlation yielded kinetic parameters in close agreement with those derived from experimental data. © 2009 American Institute of Chemical Engineers AIChE J, 2009