Sulfur-iodine Cycle Research Articles

Experimental Study of the Characteristics of HI Distillation in the Thermochemical Iodine–Sulfur Cycle for Hydrogen Production

Experimental Study of the Characteristics of HI Distillation in the Thermochemical Iodine–Sulfur Cycle for Hydrogen Production

Integrated scheme analysis and thermodynamic performance study of advanced nuclear-driven hydrogen-electricity co-production systems with iodine-sulfur cycle and combined cycle

A promising method for massive clean hydrogen production is the Very High Temperature Reactor (VHTR)-driven Nuclear Hydrogen Production (NHP) system using the Iodine–Sulfur (IS) cycle. Research on integrated scheme and thermodynamic performance of the VHTR-driven NHP system using the IS cycle has, however, received little attention up to this point, particularly when the combined cycle is employed as the power generation cycle. In order to bridge this research gap, this work proposed and studied two distinct VHTR-driven hydrogen-electricity co-production systems with the IS cycle and combined cycle: the independent operating system and the coupled operating system. Thermodynamics was used to model these two systems, and system thermodynamic performance was examined under the baseline operating conditions. A parametric study was further conducted on how two important operating parameters affected system thermodynamic performance. The primary findings indicated that the coupled operating system outperformed the independent operating system in terms of thermodynamic performance. Additionally, both the independent and coupled operating systems could produce hydrogen at the same rate of 289.8 mol/s, with net electrical power outputs of 61.07 MW and 102.7 MW, respectively, under the baseline operating conditions. Furthermore, it was discovered that a rise in the mass flow ratio for both operating systems would result in a notable reduction in system efficiency.

Thermodynamic analysis of two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems under off-design operating conditions

This study conducts a thermodynamic analysis for two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems integrating an iodine-sulfur cycle and a helium turbine direct cycle under off-design operating conditions. Control strategies are proposed based on inventory control. The calculation model is established for the main components of the system under off-design conditions. Two operation modes are proposed, one is to maintain the split ratio at the reactor outlet at the rated value, and the other is to maintain the hydrogen generation rate at the rated value. The off-design performance of the two systems under partial load in two modes is analyzed. For Systems 1 and 2, the suggested lower limits of reactor thermal power are 68.80 % and 69.00 % of the rated value in mode 1, and 72.04 % and 64.98 % in mode 2. As the reactor thermal power decreases from the rated value to the suggested lower limit, in modes 1 and 2, the hydrogen-electricity efficiency of System 1 decreases from 37.46 % to 36.20 % and 31.81 %, and that of System 2 decreases from 42.40 % to 41.45 % and 35.21 %. The decrease in overall efficiency is more significant in mode 2.

Techno-Economic Analysis of Heat-Assisted Hydrogen Production from Nuclear Power

To play a full role in decarbonisation, hydrogen must be produced economically at scale; the role of nuclear power is interesting to national governments as it is capable of supplying both low-carbon electricity and high-quality heat. Depending on the hydrogen production technology choice, a plant may require electricity and/or heat input. This techno-economic evaluation considers not only the costs of the hydrogen plant itself but also the costs of the power supply it requires. This paper calculates cost estimates for HTSE (High Temperature Steam Electrolysis) coupled with nuclear heat and electricity, and a thermochemical SI (Sulphur Iodine) cycle coupled with nuclear heat, based on the predictions of technical process models. These estimates are then compared to estimates made elsewhere for the costs of using wind with low temperature liquid water electrolysis, and steam methane reformation with carbon capture. This analysis led to the identification of the conditions under which nuclear-heat-coupled hydrogen production would be competitively priced. Estimates for nuclear-coupled LCOH2 (levelised cost of hydrogen) in 2050 range from 2.14 to 1.24 £/kg for HTSE, and from 2.88 to 0.89 £/kg for the SI cycle. There is still a great deal of uncertainty around the efficiency of SI and how it may improve over time, and this limits the accuracy to which the LCOH2 can be predicted.

Fluoride-Salt-cooled high-Temperature Advanced Reactor (FuSTAR): An integrated nuclear-based energy production and conversion system

Based on the analysis of energy structure and the development trends of advanced nuclear energy technology, combining the complementary advantages of nuclear energy and other energy sources in China, the Fluoride-Salt-cooled high-Temperature Advanced Reactor (FuSTAR) system has been proposed. FuSTAR system is designed to address production capacity issues in areas with energy shortages or resource concentration and can be combined with high-temperature process heat to achieve high-value-added processes such as hydrogen production. In this paper, the Tri-structural isotropic fuel combined with helical cruciform elements has been studied in detail on the neutron physics and thermal-hydraulic properties, and the flow and heat transfer experiment is carried out for the first time. The multilayer nonlinear programming method has been applied to the design of thermal transport systems. Then the optimal parameters and configuration of the thermoelectric conversion system are obtained by the superstructure optimization method. The inherent safety of FuSTAR is demonstrated through deterministic safety analysis. In addition, the iodine-sulfur cycle technology and the characteristics of tritium production are also analyzed. This study highlights the significant potential of integrating nuclear energy with other energy sources in an optimized energy-production system.

HI decomposition over the HI-100 test apparatus at a hydrogen production rate over 100 L/h

Studies on the iodine-sulfur (IS) thermochemical cycle for hydrogen production has been carried out since about 2005 by the Institute of Nuclear and New Energy Technology, Tsinghua University, China. The HI decomposition occupies the important position of hydrogen generation in the IS cycle. In this paper, the HI-100 test apparatus with a H2 production rate of 100 L/h was constructed and the HI decomposition was tested. First, the process and components for HI decomposition were designed. Then, the key components, including the feed tank, evaporator, gas heater, adiabatic reactor, condenser, and gas-liquid separator were made of industrial materials. After building this apparatus, the sealing test, heating water test, and HI decomposition have been conducted. The stable hydrogen production operation of more than 100 L/h had been achieved for 5 h, the maximum hydrogen production reached approximately 130 L/h, and the hydroiodic acid decomposition rate maintained about 22 %. The test results provide the design and experimental guidance for further amplification of HI decomposition for hydrogen production by the IS cycle.

Process modelling and assessment of thermochemical sulfur-iodine cycle for hydrogen production considering Bunsen reaction kinetics

Thermochemical sulfur-iodine (SI) cycle is one of the large-scale, clean, and efficient hydrogen production routes. The Bunsen reaction process is always simulated by a stoichiometric reaction, without considering the realistic Bunsen reaction kinetic process. Herein, a user-defined Fortran module concerning Bunsen reaction kinetics was developed and embedded into a continuous stirred tank reactor (RCSTR), and then a SI flowsheet with 100 L/h hydrogen production was modeled. The key parameter optimization, mass and energy balance were analyzed, the internal heat exchange network was created using the pinch point temperature difference analysis and the principle of energy cascade utilization, along with thermal efficiency evaluation. Bunsen reaction process reaches equilibrium after a period, which is consistent with experiments. The increase of H2SO4 decomposition ratio is beneficial to reduce the energy consumption of system. Increase in temperature has less effect on increasing the equilibrium decomposition ratio of HI. The theoretical thermal efficiency of system reaches 14.0–57.4 % considering the recovery of exothermic heat. This work provides a theoretical basis for the optimization of SI cycle.

Corrosion behavior of SiC coated HX with MoSi2 interlayer to be utilized in iodine–sulfur cycle for hydrogen production

In this era, renewable energy technologies are suitable to meet the challenges of fossil fuel depletion and global warming. Thus, hydrogen is gaining attention as an alternative clean energy carrier that can be produced from various methods, one of them is the iodine-sulfur (I–S) cycle which is a thermochemical process. The I–S cycle requires a material that can withstand an extremely corrosive environment at high temperatures. Immersion tests were conducted on bare superalloy Hastelloy X (HX), MoSi2, and SiC–MoSi2 coated HX, deposited in physical vapor deposition (PVD) to evaluate their corrosion resistance. Bare HX exhibited a high corrosion rate of 208.1 mm yr−1 when exposed to 98 wt% sulfuric acid at 300 °C. In contrast, HX with MoSi2 coating showed a much lower corrosion rate of 23.5 mm yr−1, and HX with SiC–MoSi2 coating demonstrated the lowest corrosion rate at 6.5 mm yr−1 under the same conditions. The coated samples were analyzed via FESEM before and after corrosion testing. The FESEM images reveal the formation of coalescent particles on the surface of the coating. The elemental analysis illustrates an increased concentration of silicon and oxygen in the corroded samples. Elemental mapping of these samples show a uniform distribution of elements over the sample. These findings contribute not only to materials science understanding but also to practical applications in hydrogen production via the I–S cycle, where corrosion-resistant materials are critical.

Design and evaluation of a novel process for green hydrogen production in the iodine–sulfur cycle via pressure-swing distillation of HIx (HI-I2-H2O)

In striving for carbon neutrality, hydrogen energy serves as a sustainable solution, and the iodine–sulfur (IS) cycle stands out as the most promising method for hydrogen production. The separation and purification of HI from the HIx (HI-I2-H2O) mixture holds significant research value, as they constitute the crucial aspect of the iodine–sulfur cycle in hydrogen production. Due to the azeotropic behavior of HI and H2O, the HIx system poses a considerable challenge. In this research, a technique for purifying HI via pressure-swing distillation was developed, exploiting the changes in azeotropic points under varying pressure conditions. The most effective method for HI purification was determined to be a three-column pressure-swing distillation configuration, as revealed by Aspen Plus phase diagrams and process topology mapping. It yielded H2O and I2 at the top of the first column, I2 at the bottom of the second column, and HI at the top of the third column with an HI recovery rate of 97 %. By analyzing the Bunsen reaction kinetics of the core reaction in the IS system, a comprehensive method for evaluating the separation and reaction coupling quality network of HIx cycle system using Bunsen-factor (B-factor) was proposed. The B-factor elucidates the correlation between the Bunsen reaction rate and the concentrations of [H+], [I-], [I3-], as well as the pH level. A comprehensive analysis of the B-factor was conducted for the pressure-swing distillation topologies of the HIx system, and the results were contrasted with those of alternative separation processes. The findings indicated that the three-column pressure-swing distallation is the most suitable option for both separation and reaction quality in a recycled network. The total energy consumption of the newly designed HIx three-column process is 352 MJ/kmol, rendering it more economical and beneficial than other processes. This study presents a pressure-swing distillation method for HI separation and purification, which is broadly applicable in IS cycles and aids in achieving large-scale production of green H2. This method enables the achievement of the dual-carbon objective, which seeks to mitigate carbon emissions while safeguarding the environment.

Insights into the stability of the iron oxide immobilized into mesoporous silica catalysts in iodine–sulfur cycle for hydrogen production

Insights into the stability of the iron oxide immobilized into mesoporous silica catalysts in iodine–sulfur cycle for hydrogen production

Advancing production of hydrogen using nuclear cycles - integration of high temperature gas-cooled reactors with thermochemical water splitting cycles

The usage of heat from the nuclear cogeneration plant and hydrogen production technologies based on thermochemical water splitting was analyzed. Two most promising ones – copper-chlorine (Cu–Cl) and sulfur-iodine (S–I) cycles have been studied. The main advantage of the two analyzed thermochemical technologies is that they can be completely or partially independent from the electricity required for the process. The Cu–Cl method has a high ability to reduce the enthalpy of technological heat even to temperatures of up to 120 °C, enabling high output of the produced hydrogen. It is not demonstrated by the S–I technology, which can reduce the temperature of the working medium to approximately 380 °C, although it exhibits the limited demand for electricity. Considering the working conditions of the planned demonstration plant it is recommended to install Cu–Cl cycle due to its high level of utilization of the available heat and no requirement for additional medium heating.

A comprehensive evaluation integrating thermodynamics and mechanism kinetics for the Bunsen reaction in a sustainable iodine–sulfur cycle

Carbon neutrality makes hydrogen a promising alternative source of energy. Iodine-sulfur cycle shows the greatest potential among hydrogen production methods. Bunsen reaction holds significant research value as the core reaction of the iodine-sulfur cycle. This paper presents an innovative method for evaluating Bunsen reactions, integrating equilibrium thermodynamics and kinetics to explore the influence of temperature, pressure, and reactant concentration on the Bunsen reaction. The thermodynamic results show that the influence of pressure on reaction balance is weak; with the gradual excess of I2, the amount of H2O required for Bunsen reaction decreases; the optimal operation ratio of H2O:I2:SO2 is 16:4:1 at 360K; the Bunsen reaction system should be carried out in an acidic system, while H2O promotes the spontaneous exothermic reaction of Bunsen. Additionally, we propose 8 reactions as Bunsen reaction mechanisms, and derive the rate equation. Bunsen reaction rates are promoted by [I2], [I3−], and [SO2] concentrations, inhibited by [I−] and [H+] concentrations, and the reaction rate of the whole solution system is sensitive to pH, [I−] and [H+] concentration changes. Added H2O improves pH, whereas acidic systems benefit from higher pH. Lastly, the interconnection of thermodynamic and kinetic results is discussed and compared with other literature. The method proposed in this study has universal application value for Bunsen reaction. It contributes to system process optimization and Bunsen reactor amplification, and facilitating carbon neutralization and hydrogen energy.

Evaluation and comparison of hydrogen production potential of the LIFE fusion reactor by using copper–chlorine (Cu–Cl), cobalt–chlorine (Co–Cl) and sulfur–iodine (S–I) cycles

In this paper, the hydrogen production and neutronic analysis of the Laser Inertial Confinement Fusion-Fission Engine (LIFE) fusion reactor have been analyzed. The potential of hydrogen production from unit integrated of the reactor with three different hydrogen production methods which has copper-chlorine (Cu–Cl) cycle, cobalt-chlorine (Co–Cl) cycle and sulfur-iodine (S–I) cycle have been investigated. Neutronic performance analysis for various parameters was calculated statically by using Monte Carlo N-Particle Nuclear Code and determined optimum reactor operation conditions. The hydrogen production potential for all conditions was investigated as statically. And also, the production potential with determining optimum conditions was performed over operation plant. Tristructural isotropic (TRISO) coated thorium carbide (ThC) was used as fuel of LIFE fusion reactor. Natural lithium and FLiNaBe (LiF + NaF + BeF2) were used first and second coolant, respectively. In the statistical analysis, effects of ThC fuel ratio, 1st and 2nd coolant zone thicknesses were examined. As a consequence of the neutronic analysis, tritium breeding values and energy multiplication values (M) was attained and according to M values, hydrogen production amount, required thermal power and thermal power ratios were acquired. Among the used hydrogen production methods, Cu–Cl cycle produced the highest hydrogen amount, while the Co–Cl cycle has the lowest H2 amount. At the end of the reactor operation time for determining optimum conditions, the produced hydrogen amounts are 9.00, 4.80 and 7.36 kg/s for Cu–Cl, Co–Cl and S–I cycles, respectively.

Experimental and numerical investigation of sulfuric acid decomposition for hydrogen production via iodine–sulfur cycle

In the context of global warming and the greenhouse effect, the iodine–sulfur cycle is an important method of producing hydrogen on a large scale with low carbon emissions using nuclear energy for future applications. The sulfuric acid decomposition reaction is a key step in this process. A sulfuric acid decomposer with good performance usually has the characteristics of high decomposition rate, small pressure drop loss and reasonable temperature distribution, which can ensure the efficient and stable process of sulfuric acid decomposition. Therefore, an accurate evaluation of the performance of the sulfuric acid decomposer unit and the reproducibility of the whole process is of utmost importance for designing and engineering an actual system for hydrogen generation. In this work, two sets of experimental systems were designed to measure the important kinetic parameters of sulfuric acid decomposition reaction and to determine the thermal hydraulics and chemical reaction performance indicators of the system. Then, a multi-field coupling model in which the phase change and chemical reactions were coupled by user-defined functions was developed based on the experimental kinetic parameters to account for the whole process. The thermal–hydraulic characteristics and the chemical reaction indexes predicted by the model are in good agreement with the experimental results. The maximum errors of the sulfuric acid decomposition fraction and pressure drop do not exceed 5% and 10%, respectively. Overall, this work provided a complete model for predicting the performance of the sulfuric acid decomposer.

Highly active and stable copper ferrite supported on β–SiC foam for decomposition of SO3 in the Sulfur–Iodine cycle for H2 production

Highly active and stable copper ferrite supported on β–SiC foam for decomposition of SO3 in the Sulfur–Iodine cycle for H2 production

Exergy study of hydrogen cogeneration and seawater desalination coupled to the HTR-PM nuclear reactor

This work presents a novel integration system of the high-temperature gas-cooled reactor-pebble bed module project to a hydrogen production process using the iodine-sulfur cycle in cogeneration with seawater desalination. The current approach includes a Rankine cycle, a sulfur-iodine thermochemical cycle for hydrogen production and a multi-stage flash desalination process. The use of a catalyst that allows the H2SO4 decomposition reaction to being carried out at temperatures compatible with the nuclear reactor project is considered. The residual heat from the acid decomposition reactions is used to desalinate seawater through the multi-stage flash process. A chemical process simulator is used to create a computational model that allows estimates of global and local efficiencies of the proposed flow diagram. Some operating parameters were sized, and their influence on the efficiency is also reported. The proposed model for the sulfur-iodine cycle can produce 0.41 kg/s of hydrogen with partial energy and exergetic efficiency of 37.35% and 38.64%. The desalination process can process 40.70 kg/s with energy and exergy efficiencies of 58.78% and 82.66%, respectively. The higher exergy destruction share is obtained in the heat exchangers (36.55%), chemical reactors (16.56%) and separators (12.80%). The global system showed efficiencies of 40.13% and 52.04%, respectively.

Directional introduction of pyridine nitrogen functional groups in activated carbon catalysts for the catalytic production of hydrogen: An experimental and DFT calculation

With the increase in global energy consumption, it has become difficult for traditional energy (re)sources to meet our basic needs. Hydrogen energy is an important component of a low-carbon or carbon-free energy strategy, and the thermochemical sulfur-iodine cycle is considered to be one of the most promising methods for hydrogen production. Nitrogen-doped activated carbon catalysts (NACCs) can improve the decomposition efficiency of hydrogen iodide (HI). However, the investigation of the active nitrogen-containing functional group (NFG) is still in progress. In this study, results from experiments and density functional theory (DFT) calculations were combined to achieve a pyridine nitrogen targeted modification, with the idea that pyridine nitrogen is the catalytically active center.Using ammonia-carbon dioxide co-activation, the samples contained a maximum of 7.79 % N content, and 77.28 % pyridine nitrogen content. An increase in the pyridine nitrogen content resulted in an increase in the catalytic decomposition efficiency. Bipyridine was used to increase the pyridine nitrogen content to complement the nitrogen-modulation mechanism. The N-6 content reached a maximum when the bipyridine solution concentration was in the range of 0.3–0.35 g/L; this resulted in the highest catalytic efficiency. The transition state and reaction path energies were calculated at the B3LYP/def2-TZVP level and combined with thermodynamic enthalpy correction quantities to improve accuracy. According to the DFT calculations, the models for pyridine nitrogen substitution all reduced the activation energy of HI decomposition reaction compared to the other models.

Thermodynamic analysis of two novel very high temperature gas-cooled reactor-based hydrogen-electricity cogeneration systems using sulfur-iodine cycle and gas-steam combined cycle

In this paper, two novel system layouts are proposed to improve the thermodynamic performance of the conventional very high temperature gas-cooled reactor (VHTR)-based hydrogen-electricity cogeneration system using sulfur-iodine (S–I) cycle and gas-steam combined cycle (GSCC). The heat and electricity consumption data of the S–I cycle are obtained from our previous Aspen Plus simulation results, and the thermodynamic model of the entire hydrogen-electricity cogeneration system is established using energy and exergy analysis methods. The performance of the system under benchmark conditions is analyzed, and the effects of several key operating parameters on system performance are investigated. The results show that with these two new system layouts, the thermal efficiency and exergy efficiency of the conventional system are improved by 8.56%–10.27% and 9.01%–10.82%, respectively. The largest exergy loss of the system occurs in the VHTR, and the exergy efficiency of the S–I cycle is very low, only about 50.8%. Therefore, when the hydrogen production load is large, it is very important to optimize the process flow and operating parameters of the S–I cycle. Besides this, it is found that the S–I cycle-based nuclear hydrogen production efficiencies are lower than the GSCC-based nuclear power generation efficiencies.

Analysis of internal heat exchange network and hydrogen production efficiency of iodine–sulfur cycle for nuclear hydrogen production

Nuclear energy enables large-scale carbon-free hydrogen production, and the coupling of the very-high-temperature gas-cooled reactor and iodine–sulfur (IS) cycle has the potential to achieve efficient hydrogen production. This study develops the flowsheet of IS process, performs process simulation, designs the internal heat exchange network using pinch point technology, and discusses the thermal efficiency of hydrogen production in detail. The results show that if all heat released by heat exchangers in H2SO4 and HI sections can be fully recovered and utilized, the upper bound of the thermal efficiency of the IS process is 51.9%. The pinch point temperature difference has little impact on the performance of the heat exchange network of the H2SO4 section, but greatly influences the performance of the heat exchange network of the HI section. When the pinch point temperature difference is 5°C to 20°C, the input heat duties required by the H2SO4 and HI sections are reduced by 23.9% to 25.0% and 20.8% to 50.8%, respectively, compared with those without heat exchange networks. After designing the heat exchange network, considering the recovery and utilization of a portion of waste heat, a more realistic hydrogen production efficiency of 30.0% to 37.1% corresponding to the pinch point temperature difference of 5°C to 20°C is given. Highlights Process simulation of IS cycle is conducted to analyze its energy consumption. Internal heat exchange network is designed using pinch point technology. Network performance is studied at different pinch point temperature differences. Thermal efficiency of hydrogen production is discussed in detail.

Simplified sulfur-iodine cycle process to hydrogen blast furnace: Techno-economic and CO2 mitigation analysis

In iron-making plants, the carbon emission problem is significant, and the existing reduction strategies focus on hydrogen utilization. Among the hydrogen production processes, a sulfur-iodine (SI) cycle is one of the most competitive candidates and there is a potential for the modification of the process design specifically targeted for the applications on blast furnaces (BF). We suggest a design for the SI process to produce H2 gas for use as a reductant in the BF during iron smelting. We first validated the conventional SI process by using a commercial process simulator with plant data and simplified the process to increase energy efficiency, profitability, and CO2 mitigation. We calculated the energy efficiency of the various process designs and derived the unit production cost of H2. We discussed the economic feasibility of the SI process in BF applications and showed the potential to mitigate global warming. The energy efficiency of the conventional SI process was estimated to be 32% and was increased to 38% by excluding a sulfuric acid decomposer. The unit production cost was estimated to be 1.22US$ kgH2−1 for the conventional SI process, and 0.80US$ kgH2−1 for the modified SI process of sulfuric acid co-production. The economic feasibility of the SI/MSI cycles was confirmed with a calculation of an internal rate of return and net present value. Also, generated H2 was utilized as an alternative fuel in BF, with an expected coke-replacement ratio of 0.168–0.232kgCoke mH2−3, and for the environmental prospects, an annual reduction was expected to 1077ktCO2-eq in the hot metal production scale of 3.8 Mt y−1.