CaFe₂O₄ reduced during chemical looping coal gasification can be oxidized with steam for production of hydrogen. The conversion and equilibrium data of the oxidation of reduced CaFe₂O₄ with steam were analyzed using steam concentrations of 10–25 vol % with a balance of helium and the temperature range of 1023–1123 K. Experimental data were evaluated to characterize H₂ production rates and oxidation isotherms. The film diffusion was the controlling step for the oxygen uptake process, and its parameters were determined on the basis of the uptake rate model. The steady-state oxygen uptake data were also evaluated with Langmuir, Temkin, Freundlich, and Dubinin–Radushkevich isotherms. The Langmuir isotherm model correlated the oxidation isotherms best, and the peak uptake capacity decreased with increasing temperatures, which suggests an exothermic process. The negative Gibbs free energy values (−ΔG°) implied the spontaneous nature of the uptake process at 1023–1123 K.

中文翻译：

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化学循环煤气化过程中蒸汽氧化还原CaFe ₂ O _4产生的氢气：平衡和动力学分析

在化学循环煤气化过程中还原的CaFe ₂ O ₄可以被蒸汽氧化以产生氢气。使用浓度为10–25 vol％，平衡氦气和温度范围为1023–1123 K的蒸汽，分析了还原的CaFe ₂ O ₄被蒸汽氧化的转化率和平衡数据。评估了实验数据以表征H ₂生产率和氧化等温线。膜扩散是氧吸收过程的控制步骤，其参数根据吸收速率模型确定。还使用Langmuir，Temkin，Freundlich和Dubinin-Radushkevich等温线评估了稳态氧吸收数据。Langmuir等温线模型与氧化等温线最相关，并且峰值吸收能力随温度升高而降低，这表明存在放热过程。负的吉布斯自由能的值（-Δ ģ °）隐含的摄取过程的自发性质在1023年至1123年K.