Hydrogen Production by Three-Step Solar Thermochemical Cycles Using Hydroxides and Metal Oxide Systems

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• 作者：Patrice Charvin ; Sté ; phane Abanades ; Florent Lemort ; Gilles Flamant
• 刊名：Energy & Fuels
• 出版年：2007
• 出版时间：September 2007
• 年：2007
• 卷：21
• 期：5
• 页码：2919 - 2928
• 全文大小：344K
• 年卷期：v.21,no.5(September 2007)
• ISSN：1520-5029

文摘

This paper presents a thermodynamic and experimental study of three-step thermochemical cycles for hydrogenproduction involving hydroxides (NaOH and KOH). Solar concentrated energy was successfully used to reducemanganese, cobalt, and iron oxides into lower valence metal oxides, MnO, CoO, Fe₃O₄, and FeO, in thetemperature range of 1300-1600 C. In the reaction with NaOH and KOH, MnO and CoO were stable anddid not produce hydrogen at 750 C even in a strong oxidizing media, whereas the iron oxides FeO and Fe₃O₄were able to generate hydrogen. For the NaOH activation reaction, the final chemical conversion rate was28% at about 400 C with FeO particles in the range of 30-50 m, and a passivating layer was observed,which reduced the H₂ production rate when the particle size increased. The reaction between Fe₃O₄ particlesand NaOH reached a final conversion higher than 70% after 7 min of the reaction for particle sizes in therange of 30-125 m. In addition, the reaction between Fe₃O₄ and KOH producing hydrogen was nearlycomplete. Although the three-step cycle based on FeO appears attractive in terms of theoretical productivity(156 mL_H2 g^-1 of FeO assuming a complete reaction) and energy efficiency (41.3%), it requires a high-temperature reduction reaction and a small particle size for the H₂-production reaction. Finally, the comparisonof iron oxide cycles highlights the high potential of the three-step cycle based on the Fe₂O₃/Fe₃O₄ pair, takinginto account experimental chemical conversions (37 mL_H2 g^-1 of Fe₃O₄ for a 75% chemical conversion).