Development of a flowsheet for iodine-sulfur thermo-chemical cycle based on optimized Bunsen reaction

Lee, B.J.,NO, H.C.,Yoon, H.J.,Jin, H.G.,Kim, Y.S.,Lee, J.I. Pergamon Press ; Elsevier Science Ltd 2009 International journal of hydrogen energy Vol.34 No.5

Based on the Bunsen reaction process whose operating conditions are optimized to yield an over-azeotropic HI liquid solution, we devised a new flowsheet of iodine-sulfur thermo-chemical cycle. A highly enriched hydrogen-iodide gas can be generated through a series of processes of liquid-liquid separation of product mixture from Bunsen reaction and flash of over-azeotropic HI solution. Operating temperature and pressure for HI enrichment need not to be increased as high as those for existing flowsheets; as a result, the operating conditions become less corrosive. Chance of pipe clogging due to iodine solidification is low because there is no process where iodine is concentrated that high. Enrichment of HI through spontaneous liquid-liquid separation and simple flash processes avoiding complicated separate process is considered to be an additional benefit. Analysis of overall and component material balances showed that excess amount of feed to each process to get a desired output depends on the efficiency of flash and decomposition processes. Compared to previous ones, the proposed flowsheet requires more recirculation flows throughout the whole cycle mainly because only a portion of HI content exceeding the azeotrope is allowed to evaporate in the flash without employing a separate HI enrichment process. Thermal efficiency of the proposed flowsheet was evaluated, together with a series of parametric analyses for the sensitivity to key operating parameters and component performances. It was observed that the thermal efficiency can be raised above 60% at optimal condition.

PUMP DESIGN AND COMPUTATIONAL FLUID DYNAMIC ANALYSIS FOR HIGH TEMPERATURE SULFURIC ACID TRANSFER SYSTEM

Choi, Jung-Sik,Shin, Young-Joon,Lee, Ki-Young,Yun, Yong-Sup,Choi, Jae-Hyuk Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.3

In this study, we proposed a newly designed sulfuric acid transfer system for the sulfur-iodine (SI) thermochemical cycle. The proposed sulfuric acid transfer system was evaluated using a computational fluid dynamics (CFD) analysis for investigating thermodynamic/hydrodynamic characteristics and material properties. This analysis was conducted to obtain reliable continuous operation parameters; in particular, a thermal analysis was performed on the bellows box and bellows at amplitudes and various frequencies (0.1, 0.5, and 1.0 Hz). However, the high temperatures and strongly corrosive operating conditions of the current sulfuric acid system present challenges with respect to the structural materials of the transfer system. To resolve this issue, we designed a novel transfer system using polytetrafluoroethylene (PTFE, $Teflon^{(R)}$) as a bellows material for the transfer of sulfuric acid. We also carried out a CFD analysis of the design. The CFD results indicated that the maximum applicable temperature of PTFE is about 533 K ($260^{\circ}C$), even though its melting point is around 600 K. This result implies that the PTFE is a potential material for the sulfuric acid transfer system. The CFD simulations also confirmed that the sulfuric acid transfer system was designed properly for this particular investigation.

Pump Design and Computational Fluid Dynamic Analysis for High Temperature Sulfuric Acid Transfer System

최정식,신영준,이기영,윤용섭,최재혁 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.3

In this study, we proposed a newly designed sulfuric acid transfer system for the sulfur-iodine (SI) thermochemical cycle. The proposed sulfuric acid transfer system was evaluated using a computational fluid dynamics (CFD) analysis forinvestigating thermodynamic/hydrodynamic characteristics and material properties. This analysis was conducted to obtainreliable continuous operation parameters; in particular, a thermal analysis was performed on the bellows box and bellows atamplitudes and various frequencies (0.1, 0.5, and 1.0 Hz). However, the high temperatures and strongly corrosive operatingconditions of the current sulfuric acid system present challenges with respect to the structural materials of the transfer system. To resolve this issue, we designed a novel transfer system using polytetrafluoroethylene (PTFE, Teflon®) as a bellows materialfor the transfer of sulfuric acid. We also carried out a CFD analysis of the design. The CFD results indicated that the maximumapplicable temperature of PTFE is about 533 K (260 °C), even though its melting point is around 600 K. This result impliesthat the PTFE is a potential material for the sulfuric acid transfer system. The CFD simulations also confirmed that the sulfuricacid transfer system was designed properly for this particular investigation.

Energy optimization of a Sulfur-Iodine thermochemical nuclear hydrogen production cycle

Juarez-Martinez, L.C.,Espinosa-Paredes, G.,Vazquez-Rodriguez, A.,Romero-Paredes, H. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.6

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.

황-요오드 수소 생산 공정의 분젠 반응 부분에서 부반응 제어

이광진,홍동우,김영호,박주식,배기광 한국수소및신에너지학회 2008 한국수소 및 신에너지학회논문집 Vol.19 No.6

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 I2/H2O molar ratio of 0.094∼0.297 under a continuous flow of SO2 gas. As the result, sulfur formed predominantly with increasing temperature and decreasing I2/H2O molar ratios. The molar ratios of H2O/H2SO4 and HI/H2SO4 in global system were decreased as the more side reaction occurred. A side reactions did not appear at I2/H2O molar ratios, saturated with I2, irrespective of the temperature change. We concluded that it caused by the increasing stability of an I2xH+ complex and a steric hindrance with increasing I2/HI molar ratios.

황-요오드 수소 제조 공정의 분젠 반응 부분에서 O2의 역할

홍동우,김효섭,김영호,박주식,배기광 한국수소및신에너지학회 2010 한국수소 및 신에너지학회논문집 Vol.21 No.4

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 H2SO4 decomposition section and the HI decomposition section. To identify the role of oxygen that can be supplied to the Bunsen reaction section via the H2SO4 decomposition section, Bunsen reactions with a SO2, SO2-O2 mixture and SO2-N2 mixture as feed gases were carried out using a stirred reactor in the presence of I2/H2O mixture. As the results, the amounts of I2 unreacted under the feed of mixture gases were higher than those under the feed of SO2 gas only, and the amount of HI produced was relatively decreased. The results of Bunsen reaction using SO2-O2mixture were similar to those using SO2-N2 mixture. It may be concluded that an oxygen in SO2-O2 mixture has a role as a carrier gas like a nitrogen in SO2-N2 mixture. The effects of oxygen were decreased with increasing temperature and decreasing oxygen content in SO2-O2 mixture.

H₂SO₄-HI-H₂O-I₂계의 2 액상 분리특성에 관한 연구(I)

이태천,정헌도,김태환,배기광,Lee, Tae-Cheon,Jeong, Heon-Do,Kim, Tae-Hwan,Bae, Gi-Gwang 한국공업화학회 2005 공업화학 Vol.16 No.6

Iodine-sulfur 사이클의 연속 공정 운전을 위해서는 분젠반응에서 생성되어진 황산과 요오드화수소의 분리와 일정한 조성을 유지시키는 기술이 필요하다. 그러나 황산과 요오드화수소는 황과 황화수소를 생성시키는 부반응이 일어나므로 부반응을 억제하며 두 개의 산을 분리시키는 기술이 요구된다. 따라서 본 연구는 부반응이 최소화되는 조건에서 2 액상 분리에 관한 물의 영향에 관하여 조사하였다. 물 몰분율이 0.86에서 0.91까지 범위에서 2 액상 분리가 일어나고 물의 증가에 따라 황화수소의 생성이 억제되었으나 물아 몰분율이 0.92 이상에서 2 액상 분리 현상은 관찰되지 않았다. The two important problems to solve before the industrialization of the iodine-sulfur (IS) process are (i) methods to separate $H_2SO_4$ and HI and (ii) to maintain constant components. However undesired reaction was occurred and $H_2S$ and S were formed during the Bunsen reaction. It is necessary to forbid the undesired reaction between $H_2SO_4$ and HI by separating the two acids into two different layers. The experimental conditions for the present study was chosen in such a way that to achieve the separation between the two acids and minimize the side reaction. $H_2S$ formation was reduced and the separations of the two liquids were occurred at $H_2O$ molar fraction from 0.86 to 0.909. But the separations between the two liquids were not occurred at $H_2O$ molar fraction more than 0.92.

Kinetics and modeling of hydrogen iodide decomposition for a bench-scale sulfur-iodine cycle

Nguyen, T.D.B.,Gho, Y.K.,Cho, W.C.,Kang, K.S.,Jeong, S.U.,Kim, C.H.,Park, C.S.,Bae, K.K. Applied Science Publishers 2014 APPLIED ENERGY Vol.115 No.-

In this work, the decomposition of hydrogen iodide (HI) over platinum catalyst in a frame work of the development of a bench-scale Sulfur-Iodine (S-I) cycle is studied. The catalyst Pt/γ-alumina 1.0wt% is prepared by impregnation-calcination method. The experiments of HI decomposition over the as-prepared catalyst are conducted at the temperature range of 350-550<SUP>o</SUP>C and at the atmospheric pressure. The experimental data are then used to estimate new kinetic parameters for HI decomposition on the basis of Langmuir-Hinshelwood type where the surface reaction is considered as the rate-limiting step. The kinetics with the estimated parameters shows a reasonable agreement with the experimental data. It also reflects the fact that, HI conversion is significantly decreased with a small amount of iodine present in the feeding solution. Thereafter, the kinetic model is applied to the modeling of a HI decomposer for the hydrogen production rate of 1Nm<SUP>3</SUP>/h in which hot helium gas is used to provide heat for the decomposition. Effects of heat-exchanger reactor configuration and composition of the feeding solution on the reactor size and the heat consumed are examined using the proposed model. Calculation results show that heat consumed for the co-current configuration is less than that for the counter-current configuration of the reactor. I<SUB>2</SUB> impurity and high water content in the feeding solution also result in an increase of reactor size and the heat required.

Iodine-Sulfur 수소제조 공정에서 H2SO4-HI-H2O-I2 계의 고온 상분리

이동희,박주식,황갑진,배기광,이광진,김영호,강영한 한국수소및신에너지학회 2006 한국수소 및 신에너지학회논문집 Vol.17 No.4

Iodine-sulfur(IS) hydrogenation production process consists of three sections, which are so called a Bunsen reaction section, a HI decomposition section and a H2SO4 decomposition section as a closed cycle. For highly efficient operation of a Bunsen reaction section, we investigated the phase separation characteristics of H2SO4-HI-H2O-I2 system into two liquid phases(H2SO4-rich phase and HIx-rich phase) in the high temperature ranges, mainly from 353 to 393 K, and in the H2SO4/HI/H2O/I2 molar ratio of 1/2/14~30/0.3~13.50. The desired results for the minimization of impurities in each phase were obtained in conditions with the higher temperature and the higher I2 molar composition. On the basis of the distribution of H2O to each phase, it is appeared that the affinity between HIx and H2O was more superior to that between H2SO4 and H2O.

황-요오드 수소 제조 공정에서 저온 분젠 반응의 상 분리 특성

한상진,이광진,김효섭,김영호,박주식,배기광,이종규 한국수소및신에너지학회 2011 한국수소 및 신에너지학회논문집 Vol.22 No.4

The Sulfur-Iodine(SI) thermochemical hydrogen production process consists of three sections, which are so called the Bunsen reaction section, the H_2SO_4 decomposition section and the HI decomposition section. In order to identify the phase separation characteristics in the reaction conditions with the high solubility of SO_2, we conducted the Bunsen reaction at the low temperatures, ranging from 283 to 298K, with the I_2/H_2O molar ratios of 2.5/16.0 and 3.5/16.0. The molar ratios of HI/H_2SO_4 products obtained from low temperature Bunsen reactions were ca. 2, indicating that there were no side reactions. The amount of reacted SO_2 was increased with decreasing the temperature, while the amounts of unreacted I_2 and H_2O were decreased. In the phase separation of the products, the amount of a H_2SO_4 impurity in HI_x phase was increased with decreasing the temperature, though the temperature has little affected on HI and I_2 impurities in H_2SO_4 phase.