Water Splitting by MnO x /Na 2 CO 3 Reversible Redox Reactions

Jia Liu, Shuo Li, Raf Dewil, Maarten Vanierschot, Jan Baeyens and Yimin Deng
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Jia Liu: Beijing Advanced Innovation Centre of Soft Matter Science and Engineering, Beijing University of Chemical Technology (BUCT), Chaoyang District, Beijing 100029, China
Shuo Li: Beijing Advanced Innovation Centre of Soft Matter Science and Engineering, Beijing University of Chemical Technology (BUCT), Chaoyang District, Beijing 100029, China
Raf Dewil: Process and Environmental Technology Lab, Department of Chemical Engineering, Katholieke Universiteit Leuven, 2860 Sint-Katelijne-Waver, Belgium
Maarten Vanierschot: Department of Mechanical Engineering, Group T Leuven Campus, Katholieke Universiteit Leuven, Celestijnenlaan 300, 3001 Heverlee, Belgium
Jan Baeyens: Beijing Advanced Innovation Centre of Soft Matter Science and Engineering, Beijing University of Chemical Technology (BUCT), Chaoyang District, Beijing 100029, China
Yimin Deng: Process and Environmental Technology Lab, Department of Chemical Engineering, Katholieke Universiteit Leuven, 2860 Sint-Katelijne-Waver, Belgium

Sustainability, 2022, vol. 14, issue 13, 1-15

Abstract: Thermal water splitting by redox reactants could contribute to a hydrogen-based energy economy. The authors previously assessed and classified these thermo-chemical water splitting redox reactions. The Mn 3 O 4 /MnO/NaMnO 2 multi-step redox cycles were demonstrated to have high potential. The present research experimentally investigated the MnO x /Na 2 CO 3 redox water splitting system both in an electric furnace and in a concentrated solar furnace at 775 and 825 °C, respectively, using 10 to 250 g of redox reactants. The characteristics of all reactants were determined by particle size distribution, porosity, XRD and SEM. With milled particle and grain sizes below 1 µm, the reactants offer a large surface area for the heterogeneous gas/solid reaction. Up to 10 complete cycles (oxidation/reduction) were assessed in the electric furnace. After 10 cycles, an equilibrium yield appeared to be reached. The milled Mn 3 O 4 /Na 2 CO 3 cycle showed an efficiency of 78% at 825 °C. After 10 redox cycles, the efficiency was still close to 60%. At 775 °C, the milled MnO/Na 2 CO 3 cycles showed an 80% conversion during cycle 1, which decreased to 77% after cycle 10. Other reactant compounds achieved a significantly lower conversion yield. In the solar furnace, the highest conversion (>95%) was obtained with the Mn 3 O 4 /Na 2 CO 3 system at 775 °C. A final assessment of the process economics revealed that at least 30 to 40 cycles would be needed to produce H 2 at the price of 4 €/kg H 2 . To meet competitive prices below 2 €/kg H 2 , over 80 cycles should be achieved. The experimental and economic results stress the importance of improving the reverse cycles of the redox system.

Keywords: H 2 yield; pilot-scale; thermochemical water splitting; redox reactions; cyclic operation; solar reactor (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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