Decomposition of Zn-ferrite for O2 generation by concentrated solar radiation

Kaneko, Hiroshi; Kodama, Tetsuya; Gokon, Nobuyuki; Tamaura, Yutaka; Lovegrove, Keith; Luzzi, Andreas

doi:10.1016/j.solener.2003.08.034

Cited by 67 publications

(38 citation statements)

References 20 publications

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“…Mixed-metal ferrites that incorporate transition metals in the ferrite structure can be reduced at lower reduction temperatures and are being studied intensively. Such metals are Mn [10,11], Co [12,13], Ni [14,15] and Zn [16][17][18] and several comparative studies were performed [19,20]. Different approaches on solar receiver concepts, which use mixed ferrites [21][22][23][24][25][26][27][28][29][30], have been developed and already tested.…”

Section: Introductionmentioning

confidence: 99%

Kinetic investigations of the hydrogen production step of a thermochemical cycle using mixed iron oxides coated on ceramic substrates

Neises

Roeb

Schmücker

et al. 2009

Int. J. Energy Res.

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SUMMARYA two-step thermochemical cycle for solar hydrogen production using mixed iron oxides as the metal oxide redox system has been investigated. The ferrite is coated on a honeycomb structure, which serves as the absorber for solar irradiation and provides the surface for the chemical reaction. Coated honeycomb structures have already been tested in a solar receiver reactor in the solar furnace of DLR in Cologne with respect to their water splitting capability and their long-term stability. The concept of this new reactor design has proven feasible and constant hydrogen production during repeated cycles has been shown.For a further optimization of the process and in order to gain reliable performance predictions more information about the process especially concerning the kinetics of the oxidation and the reduction step are essential.To examine the hydrogen production during the water splitting step a test rig has been built up on a laboratory scale. In this test rig small coated honeycombs are heated by an electric furnace. The honeycomb is placed inside a tube reactor and can be flushed with water vapour or with an inert gas. A homogeneous temperature within the sample is reached and testing conditions are reproducible. Through analysis of the product gas the hydrogen production is monitored and a reaction rate describing the hydrogen production rate per gram ferrite can be formulated. Using this test set-up, SiC honeycombs coated with zinc ferrite have been tested. The influences of the temperature and the water concentration on the hydrogen production during the water splitting step have been investigated. An analysis of the ferrite conversion was performed using the Shrinking Core Model. A mathematical approach for the peak reaction rate at the beginning of the water splitting step was formulated and the activation energy was calculated from the experimental data. An activation energy of 110 kJ mol À1 was found.

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Section: Introductionmentioning

confidence: 99%

Kinetic investigations of the hydrogen production step of a thermochemical cycle using mixed iron oxides coated on ceramic substrates

Neises

Roeb

Schmücker

et al. 2009

Int. J. Energy Res.

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“…The peak positions of Zn2p 3/2 and Zn2p 1/2 shift to the lower binding energy side after mechanochemical reduction with Fe, which is evidence for the decomposition of zinc ferrite and formation of ZnxFe 3 -xO 4 solid solution (Hou , 2014;Kaneko, 2004).…”

Section: Effect Of Fe:znfe 2 O 4 Ratiomentioning

confidence: 99%

Extraction of zinc from zinc ferrites by alkaline leaching: enhancing recovery by mechanochemical reduction with metallic iron

Zhang

Wang

et al. 2016

J. South. Afr. Inst. Min. Metall.

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“…The activation was conducted at 1,373 K in presence of Ar and reactivation was conducted in presence of (steam ? Ar) flow at 573 K. In the case of ZnFe 2 O 4 , reduction follows two pathways [16] as shown in Eqs. 9 and 10.…”

Section: Introductionmentioning

confidence: 99%

“…The minimum values of x that the authors obtained experimentally were 1.91, 1.86 and 1.83 for temperatures of 2,300, 2,500, and 2,700 K, respectively, in an Ar atmosphere at 1 bar. They used the latter material to reduce ZnO to produce Zn as indicated in reaction (16). It is to be noted that the higher the degree of decomposition, the greater the vaporization of TiO 2 , this limits the efficiency of the water-splitting cycle using TiO 2 system.…”

Section: Introductionmentioning

confidence: 99%

Thermochemical hydrogen production from water using reducible oxide materials: a critical review

D’Souza

2013

Mater Renew Sustain Energy

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This review mainly focuses on summarizing the different metal oxide systems utilized for water-splitting reaction using concentrated solar energy. Only two or three cyclic redox processes are considered. Particle size effect on redox reactions and economic aspect of hydrogen production via concentrated solar energy are also briefly discussed. Among various metal oxides system CeO 2 system is emerging as a promising candidate and researchers have demonstrated workability of this system in the solar cavity-receiver reactor for over 500 cycles. The highest solar thermal process efficiency obtained so far is about 0.4 %, which needs to be increased for real commercial applications. Among traditionally studied oxides, thin-film ferrites looks more promising and could meet US Department of energy target of $2.42/kg H 2 by 2025. The cost is mainly driven by high heliostat cost which needs to reduced significantly for economic feasibility. Overall, more work needs to be done in terms of redox material engineering, reactor technology, heliostat cost reduction and gas separation technologies before commercialization of this technology.

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Decomposition of Zn-ferrite for O2 generation by concentrated solar radiation

Cited by 67 publications

References 20 publications

Kinetic investigations of the hydrogen production step of a thermochemical cycle using mixed iron oxides coated on ceramic substrates

Kinetic investigations of the hydrogen production step of a thermochemical cycle using mixed iron oxides coated on ceramic substrates

Extraction of zinc from zinc ferrites by alkaline leaching: enhancing recovery by mechanochemical reduction with metallic iron

Thermochemical hydrogen production from water using reducible oxide materials: a critical review

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