Sulfur Iodine Thermochemical Cycle Research Articles

Correction to: Catalytic Decomposition of Hydrogen-Iodide Over Nanocrystalline Ceria Promoted by Transition Metal Oxides for Hydrogen Production in Sulfur–Iodine Thermo-Chemical Cycle

In this study, CeO2, and CeO2-M (M=Fe, Co, and Ni) catalysts were prepared by sol–gel method for catalytic decomposition of hydrogen-iodide in sulfur–iodine (SI) cycle. These catalysts sample were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), and Raman spectroscopy. The powder XRD, and TEM results gave 4–5 nm average size particles of CeO2–Ni-300 sample. BET and Raman results showed a high specific surface area, and large number of oxygen vacancy in the Ni sample. The hydrogen-iodide decomposition experiments were carried out in the temperature range of 400–550 °C in a quartz-tube vertical fixed-bed reactor with 55 wt% HI feed over prepared CeO2-M catalysts using nitrogen as a carrier gas at atmospheric pressure. The experimental hydrogen-iodide decomposition results showed high catalytic activity of Ni sample as compared to Co and Fe samples. They followed the catalytic order: CeO2–Ni-300 > CeO2–Co-300 > CeO2–Fe-300 > CeO2-300. The effect of calcination temperatures (300, 500, and 700 °C) of CeO2–Ni sample (during sol–gel method) on hydrogen-iodide conversion was also studied and showed that the following catalytic order: CeO2–Ni-300 > CeO2–Ni-500 > CeO2–Ni-700. With increase in calcination temperatures the conversion decreased. CeO2–Ni-300 sample also gave a reasonable stability for time-on-stream of about 5 h. So, based on these results, CeO2–Ni-300 is an attractive candidate which has potential for producing large quantity of hydrogen in SI cycle.

Computational model of a sulfur-iodine thermochemical water splitting system coupled to a VHTR for nuclear hydrogen production

Sulfur-Iodine thermochemical water splitting cycle coupled is one of the most promising methods for hydrogen production using a nuclear reactor as the primary energy source. However, there are not references in the scientific publications of a test facility that allow to evaluate the efficiency of the overall process. A computational model for the evaluation and optimization of the sulfur-iodine cycle coupled to a very high temperature reactor for nuclear hydrogen production was developed using a chemical process simulator Aspen HYSYS®. Some operational and design parameters of the cycle sections can be optimized in order to obtain the maximum hydrogen production and higher efficiency. The optimized sections of the flowsheet are coupled to a very high temperature nuclear system (TADSEA) through a Brayton gas cycle for power cogeneration. It is proposed a closed flowsheet for the sulfur-iodine thermochemical water splitting cycle coupled to an accelerator driven system, considering a Brayton cycle for the energy production. It is obtained an acceptable value of global efficiency for the initial operating condition. Several parametric studies are conducted using the flowsheet proposed to evaluate important operating parameters in the overall process efficiency.

Catalytic Decomposition of Hydrogen-Iodide Over Nanocrystalline Ceria Promoted by Transition Metal Oxides for Hydrogen Production in Sulfur–Iodine Thermo-Chemical Cycle

Catalytic Decomposition of Hydrogen-Iodide Over Nanocrystalline Ceria Promoted by Transition Metal Oxides for Hydrogen Production in Sulfur–Iodine Thermo-Chemical Cycle

Kinetic analysis of Bunsen reaction with HI existence in the thermochemical sulfur–iodine cycle for hydrogen production

The sulfur–iodine (SI) cycle is considered as a promising method for large-scale and high-efficiency hydrogen production. The Bunsen reaction in the cycle dominates the following HI and H2SO4 decomposition section and even the whole SI flowsheet. In this work, the detailed kinetics of the Bunsen reaction at practical condition with HI recycled was studied. The effects of operating temperature and initial HI concentration on the overall reaction rate were explored. A SO42- production rate model was proposed based on three elementary reactions, and well described the kinetic process of Bunsen reaction. Both theoretical and experimental results indicated that increasing the initial HI concentration (0–3.08mol/kgH2O) or operating temperature (303–358K) enhanced the reaction rate, including the earlier appearance of liquid separation and thermodynamic equilibrium. But the recycled HI should be controlled within 6.17mol/kgH2O, so as to make the separation of H2SO4 and HIx phase possible. The calculated apparent activation energy for kinetics-controlled reactions (4) and (5) were 8.536 and 21.516kJ/mol, respectively. These results may contribute to the further optimization and reactor design of the Bunsen reaction in the SI cycle.

Thermodynamic performance assessment of solar based Sulfur-Iodine thermochemical cycle for hydrogen generation

Recent studies show that thermochemical cycles has a great potential for green hydrogen generation. In this study, the thermodynamic performance assessment of a solar based Sulfur-Iodine (S-I) thermochemical cycle for hydrogen generation is performed focusing on the energy and exergy methods. Moreover, we investigated that various reference environment and reaction temperatures effects on energy and exergy efficiencies of S-I cycle steps. The results of thermodynamic analyses indicated that energy and exergy efficiency of S-I cycle are found to be 43.85% and 62.39%, respectively. In addition, the overall energy and exergy efficiencies of cycle are computed as, 32.76% and 34.56%, respectively. It was concluded that the S-I thermochemical cycle offers a feasible and a diverse option for hydrogen generation and seems to be a promising cycle.

Multi-Scale Control of Bunsen Section in Iodine-Sulphur Thermochemical Cycle Process

Abstract Hydrogen is considered as an environmental friendly energy carrier but its actual impact on the environment depends on the way it is produced. A strategy of plant-wide modelling and advanced process control with optimization is currently developed for the Hydrogen production via the Iodine-Sulphur thermochemical cycle process. The objectives of this paper are two-folds: (1) to optimize the trade-off between steady-state profitability and dynamic operability of the Bunsen section subject to multiple constraints, and (2) to design practical control strategy based on the multi-scale control concept. A multi-scale modelling for the Bunsen section in the Hydrogen production via the Iodine-Sulphur thermochemical cycle process is presented. Based on this multi-scale model, a practical control design is developed and applied to Bunsen section. The suitable sets of control variables and manipulated variables are chosen via a sensitivity study incorporating the multivariate Response Surface Analysis method. By dint of simulation study, it can be shown that the proposed control strategy is able to produce a good closed-loop performance where its robustness depends strongly on the selected schemes of Bunsen section. It is worth highlighting that, the proposed multi-scale control strategy demonstrates robust performance in the face of the worst case uncertainty scenario.

DDR zeolite membrane reactor for enhanced HI decomposition in IS thermochemical process

The third section of closed loop Iodine Sulphur (IS) thermochemical cycle, dealing with HIx processing, suffers from low equilibrium decomposition of HI to hydrogen with a conversion value of only ∼22% at 700 K. Here, we report a significant enhancement in conversion of HI into hydrogen (up to ∼95%) using a zeolite membrane reactor for the first time. The all silica DDR (deca dodecasil rhombohedral) zeolite membrane with dense, interlocked structure was synthesized on the seeded clay alumina substrate by sonication mediated hydrothermal process. The synthesized membranes along with seed crystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDX). Corrosion studies were carried out by exposing the membrane samples to simulated HI decomposition reaction environment (at 450 °C) for different durations of time upto 200 h. The FESEM, EDX and XRD analyses indicated that no significant changes occurred in the morphology, composition and structure of the membranes. Iodine adsorption on to the membrane surface was observed which got increased with the exposure duration as confirmed by secondary ion mass spectrometry studies. A packed bed membrane reactor (PBMR) assembly was fabricated with integration of in-house synthesized zeolite membrane and Pt-alumina catalyst for carrying out HI decomposition studies. The tube side was chosen as reaction zone and the shell side as the permeation zone. The HI decomposition experiments were carried out for different values of temperature and feed flow rates. DDR zeolite based PBMR was found to enhance the single-pass conversion of HI up to ∼95%. The results indicate that for achieving optimal performance of PBMR, it should be operated with space velocities of 0.2–0.3 s−1 and temperature in the range of 650 K–700 K with permeate side vacuum of 0.12 kg/cm2. It is believed that the in-house developed zeolite PBMR shall be a potential technology augmentation in making the IS thermochemical cycle energy efficient.

Study on a new wet flue gas desulfurization method based on the Bunsen reaction of sulfur-iodine thermochemical cycle

A novel wet flue gas desulfurization method based on the Bunsen reaction of sulfur-iodine (SI) thermochemical cycle was investigated in this paper. I2 and HI absorption system was utilized to remove SO2 from simulated coal-fired flue gas. The SO2 removal efficiency was about 98.8% when the I2 concentration was 25.6mmol/L. The influences of reaction temperature, initial SO2 concentration and the other flue gas components on SO2 removal were investigated, respectively. The absorption products were H2SO4 and HI, which could be easily separated by distillation. Compared with the traditional wet flue gas desulfurization (FGD) byproducts, such as gypsum or magnesium sulfate, H2SO4 has better commercial value and application prospect. Moreover, HI could be used as the raw material for the hydrogen production in the SI thermochemical cycle. In short, it is a promising technology for the SO2 removal and recycling from coal-fired flue gas.

Using a simulation software to perform energy and exergy analyses of the sulfur-iodine thermochemical process

The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process. Exergy analysis, being a new and useful thermodynamics tool, will be applied to one of the newest research fields in hydrogen production. One of the many advantages of computer simulation is elimination of the need to construct a pilot plant. Presently, extensive research is underway to come up with the production and use of clean fuels. The research entails performing pilot studies and proof of concept experiments using validated models. The research is further extended to various analyses such as safety, economic sustainability and energy efficiency of the processes involved. The production of hydrogen through thermochemical water splitting processes is one of the newest technologies and is expected to compete with the existing technologies. Among a wide range of thermochemical cycles, the sulfur-iodine (SI) thermochemical cycle process has been proposed as a promising technology for the production of hydrogen. In this research, we demonstrate how a commercial simulator can be used to perform an energy and exergy analysis of the SI water splitting process. Using a commercial simulator, a process flowsheet is developed based on research findings presented by other authors and an energy-exergy analysis is carried out on the process. The method of energy–exergy analysis used in this presentation indicates that an energy and exergy efficiency of 17% and 24% can be attained, respectively, in the conceptual design of the SI cycle.

INET's catalysts study for HI decomposition in the thermochemical water-splitting iodine–sulfur process for hydrogen production

The iodine–sulfur thermochemical cycle (IS cycle) can be applied to realize water decomposition and hydrogen production by using the solar energy or the nuclear heat from High Temperature Gas-cooled Reactor as heat source. Among the three reactions of the IS process (Bunsen reaction, H2SO4 decomposition and HI decomposition), the HI decomposition has the slowest reaction rate and the lowest thermodynamic equilibrium conversion (about 23% at 500 °C). In order to make HI decompose at the workable reaction rate, catalysts had to be applied in the reaction system. This paper outlines our study on the monometallic and bimetallic catalysts for HI decomposition at INET (Institute of Nuclear and New Energy Technology, Tsinghua University, China). The influences of different supports, transition metals, bimetallic compositions, reaction time on the catalytic performance for HI decomposition were investigated. The optimized catalyst of 2.5 wt.%Pt–2.5 wt.%Ir/C was proposed and adopted to catalyze the HI decomposition in the close-cycle operation of IS-100 facility with the H2 production rate of 100 NL/h. Both the conversion of HI (21%) and the H2 production rate (60 NL/h) reached the technical targets of the nuclear hydrogen project (National S&T Major Projects 2010zx06901: Research on key technologies of hydrogen production from high temperature gas cooled reactor).

Carbon membrane performance on hydrogen separation in H2[sbnd]H2O[sbnd]HI gaseous mixture system in the sulfur-iodine thermochemical cycle

Sulfur-iodine thermochemical cycle is considered as a promising route for hydrogen production without CO2 emission. In this cycle, the hydrogen iodide conversion rate plays an important role in the total thermal efficiency to some extent. To improve the efficiency of HI decomposition, the homemade carbon membranes supported by α-alumina porous tubes were well-designed in a specific way and evaluated aiming at removing H2 from HI decomposition reaction side. Permeability, selectivity and stability of self-designed carbon membranes are investigated in some gaseous components in the present work. Firstly, single-component (H2/Ar) permeance was observed with differential pressure ranging from 0.05 to 0.2 Mpa. The result shows that differential pressure has little effect on H2 and Ar permeance. Secondly, the hydrogen and argon permeance through carbon membrane is 3.1 × 10−8 mol m−2 s−1 Pa−1 and 5.7 × 10−10 mol m−2 s−1 Pa−1 respectively at 300 °C. The separation factor of H2 and Ar is 54, which is greater than the theoretical value calculated by Knudsen diffusion equation. Thirdly, hydrogen permeability in the H2HIH2O gaseous mixture system owns nearly the same as that of the single-component (H2) at 300–500 °C. Due to the large molecule diameter, most of HI are stopped by carbon membrane. However, H2O molecules could pass through the carbon membrane obviously. The permselectivity of H2/HI is over 310 at 500 °C. Last, after 10 h of stability tests, some slight damage are observed on the surface of carbon membrane according to the scanning electron micrograph (SEM). The structure change of carbon membrane gave rise to a little increase of H2 permeance at 20–100 °C.

Effects of the operation modes on the HIx phase purification in the iodine–sulfur thermochemical cycle for hydrogen production

In the iodine–sulfur thermochemical water-splitting process for hydrogen production, purification of hydriodic phase (HIx) had to be adopted to eliminate the minor components in the HIx phases (the mixture of mainly HI, H2O, I2 and small amounts of H2SO4), so as to avoid the undesirable side reactions between HI and H2SO4. In this work, experimental studies on HIx phase purification were carried out. Effects of the operation modes (such as batch operation, continuous operation and the mixed modes of the continuous and discontinuous operation), and process parameters (such as the reaction temperature, feed flowrate of the HIx solution, and the flowrate of the stripping gas N2) on the purification of HIx phase were investigated. The experimental results showed that increase of temperature and N2 flowrate, and decrease of feed flowrate of HIx solution favored the removal of H2SO4 from HIx phase. The purification efficiency would be improved by combining the continuous operation with the batch operation during the purification process. These results were favorable for achieving the closed operation of IS cycle.

Catalytic performance of bimetallic Ni-Pt nanoparticles supported on activated carbon, gamma-alumina, zirconia, and ceria for hydrogen production in sulfur-iodine thermochemical cycle

Bimetallic Ni-Pt nanoparticles supported on four different supports (activated carbon (AC)), γ-alumina, zirconia, and ceria) were prepared by modified impregnation-reduction technique for decomposition of hydrogen iodide to hydrogen and iodine, in the thermochemical water-splitting sulfur-iodine (SI) cycle. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) method to find their structure, morphology, and surface area, respectively. High metal dispersions (Ni-Pt) were obtained with particle sizes of the order of 10 nm or lesser, in the high-surface-area supports. The hydrogen iodide-decomposition results showed catalytic activity of Ni-Pt nanoparticles in the following order on different supports: Ni(2.5%)-Pt(2.5%)/AC > Ni(2.5%)-Pt(2.5%)/γ-alumina > Ni(2.5%)-Pt(2.5%)/Zirconia > Ni(2.5%)-Pt(2.5%)/Ceria. Bimetallic Ni(2.5%)-Pt(2.5%)/AC also showed excellent stability for 100 h in the hydrogen iodide-decomposition reaction, and with a higher performance relative to the corresponding Pt supported catalyst under the same operating conditions.

Catalytic performance and durability of Ni/AC for HI decomposition in sulfur–iodine thermochemical cycle for hydrogen production

This work reports the Ni content effect on the Ni/AC catalytic performance in the HI decomposition reaction of the sulfur–iodine (SI) thermochemical cycle for hydrogen production and the Ni/AC catalyst durability in a long-term test. Accordingly, five catalysts with the Ni content ranging from 5% to 15% were prepared by an incipient-wetness impregnation method. The activity of all catalysts was examined under the temperature range of 573–773K. The catalytic performance evaluation suggests that Ni content plays a significant role in the Ni dispersion, Ni particle size, and eventually the catalytic activity in HI decomposition. 12% is the optimal Ni content for Ni/AC catalysts in HI decomposition which is balanced between poor dispersion of Ni particles and increasing active center. The results of 24h durability test, which incorporated with BET and TEM investigations of the 12%Ni/AC catalyst before and after the reaction, indicate that establishing a better Ni particle dispersion pattern and improving the stability of Ni particles on the support should be considered in the future.

Effect of raw material sources on activated carbon catalytic activity for HI decomposition in the sulfur-iodine thermochemical cycle for hydrogen production

In order to study the effect of raw material sources on the catalytic performance of activated carbon, five activated carbon samples generated by steam activation of various raw materials (wood, coal, shell, bamboo and coconut shell) were investigated for their catalytic performance in HI decomposition for the sulfur–iodine (SI) thermochemical cycle. Their catalytic activities were evaluated from 573 K to 823 K. XRD, BET, SEM, proximate and ultimate analyses were used to characterize the catalysts. The results showed the raw materials of activated carbon played an important role in the catalytic activity of the activated carbon sample in HI decomposition. AC-CS and AC-SHELL exhibited the highest activity, followed by AC-BAMBOO, AC-COAL and AC-WOOD. AC-CS had the highest carbon content and the lowest ash content of the activated carbon samples. The catalytic activity of the activated carbon samples increased in coordination with increasing fixed carbon content and decreasing ash content. A long-term evaluation of catalytic performance was performed with AC-CS to assess its stability during extended use as an HI decomposition catalyst.

The Corrosion Behavior of Ni3(Si,Nb) Alloys in Boiling 70 wt.% Sulfuric Acid

Corrosion-resistant Ni3(Si,Nb) alloys are promising materials of construction for hydrogen-production systems based on the sulfur-iodine thermochemical cycle. In this work, the corrosion rates of three different Ni3(Si,Nb) alloys were measured in boiling 70 wt.% sulfuric acid and a three-stage corrosion mechanism was identified, based on the composition and morphology of surface scale that developed. The α(Ni) + β(Ni3Si) eutectic constituent of the alloy microstructure was selectively attacked by acid and, when present, is detrimental to corrosion resistance. The G-phase (Ni16Si17Nb6) is more passive than the β-matrix and seems to contribute to a lower steady-state corrosion rate.

Effect of agitation speed and fluid velocity on heat transfer performance in agitated Bunsen reactor of iodine-sulphur thermo-chemical cycle

Agitated Bunsen reactor (ABR) is one of the reactor alternatives to carry out Bunsen reaction of iodine-sulphur thermo-chemical process for hydrogen production. It is a tubular reactor with multiple agitating blades on a common shaft to enhance the radial mixing and with an inside helical coil arrangement to remove the exothermic Bunsen reaction heat. The effective heat removal from the reactor depends on the agitation speed and velocity of fluids flowing inside the reactor and through the helical coil. Experiments are carried out in ABR, for heat transfer study with water as reactor fluid as well as helical coil fluid and also Bunsen reaction heat transfer study, by varying the operating parameters such as agitation speed, velocity of reactor fluid and velocity of helical coil fluid. It has been observed that the overall heat transfer coefficient increases with increase in agitation speed and fluid velocities. Combined effect of agitation speed and fluid velocities on heat transfer rate, in shell side/reactor side of ABR, has been presented in the form of modified correlation.

Pt/graphite catalyst for hydrogen generation by HI decomposition reaction in S-I thermochemical cycle

Hydrogen is an attractive energy carrier for future because of various reasons. Therefore its large scale production is the need of the hour. One of the ways to achieve this is sulfur iodine thermochemical cycle and HI decomposition reaction is one of the three reactions constituting the cycle. Pt/graphite catalysts with different loading of platinum were prepared by impregnating colloidal graphite with hexachloroplatinic acid solution followed by reduction under N2 flow. The catalysts prepared have been characterized by X-ray diffraction, Raman, scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller surface area. These catalysts have been employed for liquid phase HI decomposition under different conditions. To evaluate the stability of this catalyst against noble metal leaching under the reaction conditions, the eluent was analyzed by using ICP-OES. Platinum loaded catalysts (0.5%, 1% and 2%) show 8.4%, 17.5% and 23.4% conversion respectively. From the present study we conclude that Pt/graphite is a suitable and stable catalyst for liquid phase HI decomposition reaction. Copyright © 2015 John Wiley & Sons, Ltd.

Predicting phase equilibrium of a ternary feed to the hydroiodic acid section of SI thermochemical cycle

This work presents a comparative study in predicting the vapor–liquid equilibrium (VLE) properties of a ternary feed, consisting of HI, H2O and I2, to the hydroiodic acid section of SI (sulfur-iodine) thermochemical cycle. Three binary interaction parameters sets are proposed for an activity-based NRTL (non-random two liquid) model and two equation of state models, namely SRK (Soave–Redlich–Kwong) and PR (Peng–Robinson). A comparative performance of these three VLE models is evaluated based on their single parameters set by using the available experimental data points.

Catalytic membrane reactors for SO3 decomposition in Iodine–Sulfur thermochemical cycle: A simulation study

The possibility of applying a catalytic membrane reactor (CMR) to SO3 decomposition in a low-temperature range was theoretically evaluated with the purpose of producing CO2-free hydrogen in an Iodine–Sulfur thermochemical cycle. A one-dimensional, isothermal and plug-flow model was developed for a cocurrent membrane reactor with selective permeation from the reactant stream to the permeate stream. Simulation results have revealed that CMRs can greatly reduce the reaction temperature for SO3 decomposition from the conventional 1200–1400 K to about 900 K. We predicted that porous inorganic membranes with a high O2 permeability and with selectivities of more than 50 for O2/SO3 and less than 10 for O2/SO2 had the potential to effectively improve SO3 conversion. CMRs were simulated to carry out SO3 decomposition at different catalyst weights, reaction temperatures, and SO3 feed flow rates as well as pressures in feed and permeate streams. SO3 conversion at 900 K was increased to 0.93 beyond the equilibrium conversion of 0.28 due to a shift in thermodynamic equilibrium.