• Nuclear Engineering and Technology
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• 제53권6호
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• pp.2066-2073
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• 2021

The use of nuclear reactors is a large studied possible solution for thermochemical water splitting cycles. Nevertheless, there are several problems that have to be solved. One of them is to increase the efficiency of the cycles. Hence, in this paper, a thermal energy optimization of a Sulfur-Iodine nuclear hydrogen production cycle was performed by means a heuristic method with the aim of minimizing the energy targets of the heat exchanger network at different minimum temperature differences. With this method, four different heat exchanger networks are proposed. A reduction of the energy requirements for cooling ranges between 58.9-59.8% and 52.6-53.3% heating, compared to the reference design with no heat exchanger network. With this reduction, the thermal efficiency of the cycle increased in about 10% in average compared to the reference efficiency. This improves the use of thermal energy of the cycle.

• 에너지공학
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• 제15권2호
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• pp.127-137
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• 2006

화학연료 사용으로 야기된 환경문제, 경제문제를 해결하기 위한 방안으로 수소경제가 추진되고 있다. 원자력을 이용한 대량수소생산은 수소경제를 뒷받침하기 위한 현실적인 방안이다. 본 논문에서는 원자력수소 생산에 사용할 초고온가스로의 특징과 개발현황, 초고온가스로로부터 발생하는 고온의 열을 이용한 수소생산방법 중 유력시 되는 기술로서 요오드-황 열화학법, 황산하이브리드법, 고온전기분해법의 기술개발 현황과 방향을 소개한다.

• 한국수소및신에너지학회논문집
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• 제19권3호
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• pp.226-231
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• 2008

Cu/Fe/$Al_2O_3$ granules with various sizes have been prepared by a combination of sol-gel and oil drop method for the use in sulfur trioxide decomposition, a subcycle in thermochemical sulfur-iodine cycle to split water in the hydrogen and oxygen. The size of composite granules have been mainly changed by the flow-rate of the gel mixture before dropping in the synthesis. The structural properties of the samples were comparable with granule size. In the reaction, the catalytic activity was enhanced by decreasing size in the entire reaction temperature ranges.

• 한국수소및신에너지학회논문집
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• 제1권1호
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• pp.40-47
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• 1989

The sulfur-iodine thermochemical water splitting process of GA(General atomic) cycle was studied to produce hydrogen from water by $H_2-I_2-SO_2$ reactions. The experimental scale was 500g based on iodine. The reaction took 100 minutes, products could be separated two liquid phases due to their density difference:HI solution had a density of 2.39~2.61g/cc, and $H_2SO_4$ solution had 1.37~1.38g/cc. The condition of reaction was when weight ratio of $I_2/H_2O$ was 2/1 resulting in good phase separation and productivity.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.633-638
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• 2008

열화학적 물분해에 의한 수소 생산 공정 중의 하나인 IS(Iodine-sulfur) 사이클에서 요오드와 이산화황, 그리고 물을 반응물로 하여 요오드화수소와 황산을 제조하는 분젠 반응에 대한 연구를 수행하였다. 요오드의 투입 몰수에 관계없이 황산의 생성량은 일정하였으나 요오드화수소의 생성량은 요오드의 투입 몰수가 증가함에 따라 감소하는 경향을 나타내었다. 이는 생성된 요오드화수소와 미 반응된 요오드가 $HI_3$ $HI_5$ or $HI_7$와 같은 착화합물인 polyiodide를 형성하기 때문인 것으로 생각된다. 이들 착화합물의 형성은 생성물의 2액상 분리 특성의 향상을 가져온다. 또한 요오드 투입 몰수의 증가함에 따라 반응 속도는 향상되었다. 반응물인 요오드의 투입 몰수 및 반응 온도가 증가함에 따라 생성 용액의 2액상 분리 특성이 향상되었으며 모든 실험의 조건 하에서 부반응은 발생 되지 않는 것으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제19권5호
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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.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.139-151
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• 2011

The sulfur-iodine (SI) thermochemical water splitting cycle is one of promising hydrogen production methods from water using high-temperature heat generated from a high temperature gas-cooled nuclear reactor (HTGR). The SI cycle consists of three main units, such as Bunsen reaction, HI decomposition, and $H_2SO_4$ decomposition. The feasibility of continuous operation of a series of subunits for $H_2SO_4$ decomposition was investigated with a bench-scale facility working at ambient pressure. It showed stable and reproducible $H_2SO_4$ decomposition by steadily producing $SO_2$ and $O_2$ corresponding to a capacity of 1 mol/h $H_2$ for 24 hrs.

• 한국수소및신에너지학회논문집
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• 제19권6호
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• pp.490-497
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• 2008

For continuous operation of the sulfur-iodine(SI) thermochemical cycle, which is expected practical method for massive hydrogen production, suggesting operation conditions at steady state is very important. Especially, in the Bunsen reaction section, the Bunsen reaction as well as side reactions is occurring simultaneously. Therefore, we studied on the relation between the variation of compositions in product solution and side reactions. The experiments for Bunsen reaction were carried out in the temperature range, from 268 to 353 K, and in the $I_2/H_2O$ molar ratio of $0.094{\sim}0.297$ under a continuous flow of $SO_2$ gas. As the result, sulfur formed predominantly with increasing temperature and decreasing $I_2/H_2O$ molar ratios. The molar ratios of $H_2O/H_2SO_4$ and $HI/H_2SO_4$ in global system were decreased as the more side reaction occurred. A side reactions did not appear at $I_2/H_2O$ molar ratios, saturated with $I_2$, irrespective of the temperature change. We concluded that it caused by the increasing stability of an $I_{2x}H^+$ complex and a steric hindrance with increasing $I_2/HI$ molar ratios.

• 한국수소및신에너지학회논문집
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• 제19권2호
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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.

• 한국수소및신에너지학회논문집
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• 제21권4호
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• pp.278-285
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• 2010

The Sulfur-Iodine (SI) thermochemical hydrogen production process of a closed cycle consists of three sections, which are so called the Bunsen reaction section, the $H_2SO_4$ decomposition section and the HI decomposition section. To identify the role of oxygen that can be supplied to the Bunsen reaction section via the $H_2SO_4$ decomposition section, Bunsen reactions with a $SO_2,\;SO_2-O_2$ mixture and $SO_2-N_2$ mixture as feed gases were carried out using a stirred reactor in the presence of $I_2/H_2O$ mixture. As the results, the amounts of $I_2$ unreacted under the feed of mixture gases were higher than those under the feed of $SO_2$ gas only, and the amount of HI produced was relatively decreased. The results of Bunsen reaction using $SO_2-O_2$ mixture were similar to those using $SO_2-N_2$ mixture. It may be concluded that an oxygen in $SO_2-O_2$ mixture has a role as a carrier gas like a nitrogen in $SO_2-N_2$ mixture. The effects of oxygen were decreased with increasing temperature and decreasing oxygen content in $SO_2-O_2$ mixture.