• Journal of Hydrogen and New Energy
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• v.17 no.1
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• pp.90-97
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• 2006

Hydrogen is used as a chemical feedstock in several important industrial processes, including oil refineries and petro-chemical production. But, nowadays hydrogen is focused as energy carrier on the rising of problems such as exhaustion of fossil fuel and environmental pollution. Thermochemical hydrogen production by nuclear energy has potential to efficiently produce large quantities of hydrogen without producing greenhouse gases, and research of nuclear hydrogen, therefore, has been worked with goal to demonstrate commercial production in 2020. The oil refineries and petro-chemical plant are very large, centralized producers and users of industrial hydrogen, and high-potential early market for hydrogen produced by nuclear energy. Therefore, it is essential to investigate and analyze for state of domestic hydrogen market focused on industrial users. Hydrogen market of petro-chemical industry as demand site was investigated and worked for demand forecast of hydrogen in 2020. Also we suggested possible supply plans of nuclear hydrogen considered regional characteristics and then it can be provided basis for determination of optimal capacity of nuclear hydrogen plant in 2020.

• Journal of Hydrogen and New Energy
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• v.19 no.2
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• pp.111-117
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• 2008

A Bunsen reaction section is a primary stage of Sulfur-iodine thermochemical hydrogen production cycle. This section is important, because it decides the efficiency of next stages. In order to produce hydrogen very efficiently, the characteristics of Bunsen reaction were investigated via two experimental methods. The one is a phase separation of $H_2SO_4-HI-H_2O-I_2$ mixture system, and the other is a direct Bunsen reaction. The characteristics of each method were investigated and compared. As the result of this study, the amount of HI and $I_2$ in $H_2SO_4$ phase via Bunsen reaction was more decreased than that via $H_2SO_4-HI-H_2O-I_2$ mixture system with increasing $I_2$ concentration. However, the amount of $H_2SO_4$ in $HI_x$ phase via Bunsen reaction was remarkably increased with increasing $I_2$ concentration, while that via $H_2SO_4-HI-H_2O-I_2$ mixture system was decreased. On the other hand, the range of initial composition which is able to separate into two liquid phases without $I_2$ solidification was almost alike.

• Journal of Hydrogen and New Energy
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• v.19 no.4
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• pp.305-312
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• 2008

ZnO/Zn redox cycle is the one of the promising thermochemical cycles for hydrogen production via water splitting with high temperature heat source like a concentrated solar energy. This paper reports the particle size effect of Zinc on water splitting behavior. Water splitting reaction experiments were carried out at isothermal conditions of 350 and 400$^{\circ}C$ in TGA (Thermo Gravimetric Analyzer) using four commercial Zinc powders (nano, <10 ${\mu}m$, <150 ${\mu}m$ and $150{\sim}600\;{\mu}m$ particle sizes). Before the experiments, average particle size of Zinc powders was analyzed by PSA (Particle Size Analysis). After the experiments, XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscope) analyses were conducted on the samples. The experimental results showed that particle size had a effect on the conversion of Zinc to ZnO. Zinc conversion was increased, as the particle size decreased. Especially, the nano size particles were aggregated and the particle's morphology changed on the surface during hydrolysis reaction.

• Journal of Hydrogen and New Energy
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• v.17 no.4
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• pp.353-361
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• 2006

As one of the thermochemical water splitting hydrogen production cycles, which could be operated at the lower temperature below 1200 K, we investigated the feasibility of the cyclic operation of Ispra Mark 2 cycle with the addition of $ZrO_2$. The cycle is theoretically composed of three reaction steps; (1) 1st step($2MnO_2{\rightarrow}Mn_2O_3+0.5O_2$), (2) 2nd step($Mn_2O_3+4NaOH{\rightarrow}2Na_2O{\cdot}MnO_2+H_2+H_2O$) and (3) 3rd step($2Na_2O{\cdot}MnO_2H_2O{\rightarrow}4NaOH+2MnO_2$). From the TPR tests, the temperature ranges for $O_2$ production in 1st step and $H_2$ production in 2nd step were $550{\sim}750^{\circ}C$ and $650{\sim}750^{\circ}C$, respectively. In $MnO_2/Mn_2O_3/NaOH$ system, the formation of molten products due to the reaction between manganese oxides and NaOH were greatly decreased with the addition of $ZrO_2$. In addition, the results of a cyclic test were discussed with the viewpoint of $H_2$ production amounts and the feasibility of the process improvement.

• Journal of Hydrogen and New Energy
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• v.19 no.5
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• pp.386-393
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• 2008

The Sulfur-iodine(SI) thermochemical cycle is one of the most promising methods for massive hydrogen production. For the purpose of continuous operation of SI cycle, phase separation characteristics into two liquid phases ($H_2SO_4$-rich phase and $HI_x$-rich phase) were directly investigated via Bunsen reaction. The experiments for Bunsen reaction were carried out in the temperature range, from 298 to 333 K, and in the $I_2/H_2O$ molar ratio of $0.109{\sim}0.297$ under a continuous flow of $SO_2$ gas. As the results, solubility of $SO_2$, decreased with increasing the temperature, had considerable influence on the global composition in the Bunsen reaction system. The amounts of impurity in each phase(HI and $I_2$ in $H_2SO_4$-rich phase and $H_2SO_4$ in $HI_x$-rich phase) were decreased with increasing $H_2SO_4$ molar ratio and temperature. To control the amounts of impurity in $HI_x$-rich phase, temperature is a factor more important than $I_2/H2_O$ molar ratio. On the other hand, the affinity between $HI_x$ and $H_2O$ was increased with increasing $I_2/H2_O$molar ratio.

• Journal of Institute of Convergence Technology
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• v.7 no.1
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• pp.19-22
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• 2017

SI process is one of the most advanced thermochemical water splitting cycles enabling mass production of hydrogen without emitting carbon dioxide when coupled to nuclear heat energy. The highest temperature (close to $1000^{\circ}C$) required in SI process is well matched with the outlet temperature of a coolant circulating a high-temperature gas-cooled reactor at around $950^{\circ}C$. In Section 3, some heat exchangers are included to recover heats from process flows at high temperature. In this work, we designed a heat exchanger based on the $1Nm^3/hr$ $H_2$ production capacity using commercial tools for chemical process design.

• Journal of Hydrogen and New Energy
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• v.14 no.4
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• pp.298-304
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• 2003

The thermal behavior of $NiFe_2O_4$ prepared by a solid-state reaction was investigated for $H_2$ generation by the thermochemical cycle. The reduction of $NiFe_2O_4$ started from $800^{\circ}C$, and the weight loss was 0.2-0.3 wt% up to $1000^{\circ}C$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidation of reduced $NiFe_2O_4$. The crystal structure of $NiFe_2O_4$ maintained during the redox reaction of 5 cycles. From this observation, the lattice oxygen in $NiFe_2O_4$ is released without the structural change during the thermal reduction and oxygen deficient $NiFe_2O_4$ can be restored to the spinel structure of $NiFe_2O_4$.

• Journal of Hydrogen and New Energy
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• v.13 no.2
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• pp.143-150
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• 2002

The thermal behavior of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ prepared by a co-precipitation wasinvestigated for Hz generation by the thermochemical cycle. The reduction reaction of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ started from $480^{\circ}C$, and the weight loss was 1.6 wt% up to $1100^{\circ}C$. At this reaction, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ was reduced by release of oxygen bonded with the $Fe^{3+}$ ion in the B site of ($CO_{0.5}$ $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidationof reduced $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. The crystal structure of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ for reduction reaction maintained spinel structure and the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ ($8.41\AA$) was enlarged to $8.45\AA$. But the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ after $H_2O$ decomposition reaction did not change to $8.45\AA$. Then, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ is excellent material in the thermochemical cyclic reaction due to release oxygen at low temperature for the reduction reaction and produce $H_2$ maintaining crystal structure for redox reaction.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1122-1123
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• 2006

Mn-Fe oxide and Mn-Fe oxide/$ZrO_2$(50wt%/50wt%) were prepared by ball milling method. XRD data of the prepared samples revealed that hematite and ferrite phase coexisted. Water splitting at 1273K, after thermal reduction at 1573K, was performed 4 times for the samples. Hydrogen production amount was analyzed by GC with TCD detector. Water splitting capacity of Mn-Fe oxide was improved by ball milling with $ZrO_2$.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.463-469
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• 2012

Solar thermochemical syngas and hydrogen production process bv redox system of metal oxide was performed under direct irradiation of the metal oxide on the SiC ceramic foam device using solar simulator. $CeO_2/ZrO_2$ nanotube has been synthesized by anodic oxidation method. Syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. The produced syngas had the $H_2/CO$ ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. After ten cycles of redox reaction, $CeO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.