HI Decomposition Research Articles

Quantitative evaluation of leakage flow rate in the sealing part using graphite gland packing to mount a hydrogen separation membrane tube for HI decomposition membrane reaction

The thermal efficiency of hydrogen production in the thermochemical iodine-sulfur (or sulfur-iodine) can be effectively enhanced using a membrane reactor for the HI decomposition reaction (about 500 °C) for hydrogen production. The attachment of ceramic tubes, made of brittle materials, for hydrogen separation membranes to a tube plate via sealing parts is a critical aspect of this process. A quantitative procedure was specified to make an expanded graphite grand packing exhibit sealing performance. The applicability of the method was tested during 50 thermal cycles ranging between 25°C-450 °C and gas pressure of 0.3–0.9 MPa. The leakage flow rate using a dummy membrane tube and helium gas (a tracer gas) was approximately 2 × 10−5 Pa m3 s−1. This value is comparable to the detection limit of the standard bubble leak test, indicating the effectiveness of this sealing procedure. Furthermore, the leakage flow rate was proportional to the differential pressure applied to the sealing part, suggesting a molecular flow type. This allows for estimating the leakage flow rate by introducing the conductance of flow paths, formulated based on the molecular kinetic theory of gases. An estimation method of the leakage flow rate at any packing size and any pressure difference is proposed, which can help design future practical membrane reactors.

Development of a hydrogen permselective silica membrane and its application to the thermochemical water splitting method

Abstract The thermochemical water splitting IS process is one of the hydrogen production method to use a heat directly. The temperature of the thermal decomposition of water (4000 K) can be reduced under 700 K by introducing I2 and SO2 as recycling catalysts. One of the problems in the IS process is that the conversion of the HI decomposition reaction is low at about 20%. If a membrane reactor with the H2 permselective membrane is applied to the HI decomposition reaction, the hydrogen can be extracted to improve the HI conversion. We focus on a counter diffusion CVD method for the preparation method of the membranes. Two reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and hybrid silica is deposited inside the pore of the substrate. The pore sizes are controlled by introducing organic functional groups to silica precursor. In this study, the silica hybrid membrane with high H2 permeation performance and high H2/HI selectivity were developed by introducing organic functional groups. Effects of the organic functional groups were summarized by using a pore model. The HI gas and other inorganic gases permeation performance were tested through silica hybrid membranes.

Ta–W metal alloy membrane reactor for HI decomposition in I–S thermochemical cycle for hydrogen production

HIx processing section of Iodine-Sulfur (IS) thermochemical cycle suffers from the drawbacks of highly corrosive environment and a low thermodynamic conversion of HI decomposition (∼22% at 450 °C). This study investigates, for the first time, the potential of tantalum-tungsten (Ta–W) metal alloy membrane reactor for the decomposition of HI. A thin film of Ta–W alloy was deposited on clay-alumina support by DC magnetron sputtering under optimized set of parameters. The corrosion resistance of the Ta–W membrane was evaluated through electrochemical corrosion studies and immersion coupon tests in azeotropic HI (57 wt % in water) environment. The results confirmed that Ta–W had a higher corrosion resistance than Ta. HI decomposition was carried out in Ta–W membrane reactor and suitable operating parameters were finalized. An enhanced conversion of ∼98% was obtained at 450 °C and 105 Pa, while no permeation of HI, water and iodine was observed across the membrane.

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.

S-TiO2/Ti as efficient and stable electrocatalysts electrode for decomposition of HI to produce hydrogen

S-TiO2/Ti as efficient and stable electrocatalysts electrode for decomposition of HI to produce hydrogen

Direct electrolysis of bunsen reaction product for hydrogen production: The continuous-flow operation

Hydrogen sulfide (H2S) emitted from oil industry's hydrotreating processes can be converted into hydrogen and used back to the same processes through a H2S splitting cycle, where the Bunsen reaction and HI decomposition are two participating reactions. To overcome the difficulties and complications posted in the scaling up of the cycle, direct electrolysis of the Bunsen reaction product solution was proposed and has been studied in a batch electrolysis cell in our earlier work. This paper studies the direct electrolysis using a customer-made, continuous-flow electrolysis cell. The effects of the operating parameters including the current density, the entering HI concentration and flow rate of the anolyte, the toluene to aqueous phase ratio and stirring speed in anolyte cell, the H2SO4 concentration and circulation rate of the catholyte on the performing parameters such as the conversion of iodide ions, the yield of iodine transferred to toluene, and the anodic and cathodic current efficiencies for iodide conversion and hydrogen production were carefully investigated. The results show that the cathodic current efficiency for hydrogen production is nearly 100% for all the runs and that the anodic current efficiency for iodide ion conversion to iodine is relatively low (20%–70%) and varies with the changes in operating parameters. Running at high levels of the current density, the volumetric ratio of toluene to aqueous phase in anolyte, or the stirring speed in anolyte, and low levels of the entering concentration of I− in anolyte or the flow rate of anolyte in electrolysis operation are in favor of having a high iodide conversion and high I2-toluene yield. Iodide anions at a few mmol L−1 level (a few thousandths of the entering concentration) are found in the cathodic chamber caused by its diffuse against the electric field and the proton exchange membrane. The continuous, direct electrolysis of the Bunsen product solution can be considered being adapted in the sulfur-iodine (S–I) water splitting cycle for hydrogen production.

Heat, economic and multi-path safety (HEMPS) management on co-generation of hydrogen and sulfuric acid through modified sulfur-iodine cycle

This research suggests a novel framework for heat, safety, and economic management based on the leverage relationship among those analyses on polygeneration system of hydrogen and sulfuric co-production from flue gas and water using modified sulfur-iodine cycle. The exergy assessment is conducted to identify the useful energy available in the section. Following that, the heat integration and economic assessment are performed simultaneously to investigate the minimum cost corresponding minimum temperature difference. The novel leverage assessment between risk- costs, heating cost –cost, heating – risk were conducted to suggest optimal parameters. The results show that the minimum temperature difference is 25 °C for heat integration, indicating the capital + operating cost was expected to be reduced by 3%. The HI decomposition section reveals the low exergy efficiency and high exergy destruction. The expected accident probabilities of Bunsen reaction section and HI decomposition section are contributed to be 46% and 54%, respectively. The novel thermal risk coefficient method suggests 160 °C to be the minimal risk temperature. The total 23 safety pipes were optimal considering the cure cost for accident and pipe installation cost indicating a 35% total cost reduction.

CFD Development of a Silica Membrane Reactor during HI Decomposition Reaction Coupling with CO2 Methanation at Sulfur-Iodine Cycle.

In this work, a novel structure of a hydrogen-membrane reactor coupling HI decomposition and CO2 methanation was proposed, and it was based on the adoption of silica membranes instead of metallic, according to their ever more consistent utilization as nanomaterial for hydrogen separation/purification. A 2D model was built up and the effects of feed flow rate, sweep gas flow rate and reaction pressure were examined by CFD simulation. This work well proves the feasibility and advantage of the membrane reactor that integrates HI decomposition and CO2 methanation reactions. Indeed, two membrane reactor systems were compared: on one hand, a simple membrane reactor without proceeding towards any CO2 methanation reaction; on the other hand, a membrane reactor coupling the HI decomposition with the CO2 methanation reaction. The simulations demonstrated that the hydrogen recovery in the first membrane reactor was higher than the methanation membrane reactor. This was due to the consumption of hydrogen during the CO2 methanation reaction, occurring in the permeate side of the second membrane reactor system, which lowered the amount of hydrogen recovered in the outlet streams. After model validation, this theoretical study allows one to evaluate the effect of different operating parameters on the performance of both the membrane reactors, such as the pressure variation between 1 and 5 bar, the feed flow rate between 10 and 50 mm3/s and the sweep gas flow rate between 166.6 and 833.3 mm3/s. The theoretical predictions demonstrated that the best results in terms of HI conversion were 74.5% for the methanation membrane reactor and 67% for the simple membrane reactor.

Catalytic and Sulfur-Tolerant Performance of Bimetallic Ni–Ru Catalysts on HI Decomposition in the Sulfur-Iodine Cycle for Hydrogen Production

The sulfur-iodine (SI) cycle holds great promise as an alternative large-scale process for converting water into hydrogen without CO2 emissions. A major issue regarding the long-term stability and activity of the catalysts is their poor sulfur deactivation resistance in the HI feeding process. In this work, the effect of Ru addition for enhancing the activity and sulfur resistance of SiO2-supported Ni catalysts in the HI decomposition reaction has been investigated. The presence of H2SO4 molecules in the HI results in severe sulfur deactivation of the Ru-free Ni/SiO2 catalysts by blocking the active sites. However, Ni–Ru/SiO2 catalysts show higher catalytic activity without sulfur-poisoning by 25% and exhibit more superior catalytic performance than the Ru-free catalyst. The addition of Ru to the Ni/SiO2 catalyst promotes the stability and activity of the catalysts. The experimental trends in activity and sulfur tolerance are consistent with the theoretical modeling, with the catalytic activities existing in the order Ni/SiO2 < Ni–Ru/SiO2. The effect of Ru on the improvement in sulfur resistance over Ni-based catalysts is attributed to electronic factors, as evidenced by theory modeling analysis and detailed characterizations.

Discovering the evolution of Jacques-Louis David\u2019s portrait of Antoine-Laurent and Marie-Anne Pierrette Paulze Lavoisier

Jacques-Louis David’s (1748–1825) iconic portrait of Antoine Laurent Lavoisier (1743–1794) and Marie-Anne Lavoisier (Marie-Anne Pierrette Paulze, 1758–1836) has come to epitomize a modern couple born of the Enlightenment. An analytical approach that combined macro-X-ray fluorescence with the examination and microanalysis of samples by Raman spectroscopy and scanning electron microscopy-energy dispersive X-ray spectrometry to investigate imprecise indications of changes to the composition observed by microscopy and infrared refectography allowed the visualization of a hidden composition with a high level of detail. The results revealed that the first version depicted not the progressive, scientific-minded couple that we see today, but their other identity, that of wealthy tax collectors and fashionable luxury consumers. The first version and the changes to the composition are placed in the context of David’s mastery of the oil painting technique by examining how he concealed colorful features in the first composition by using paint mixtures that allowed for maximum coverage with thin paint layers. The limitations of the analytical techniques used are also discussed. To our knowledge, this is the first in-depth technical study of a painting by J.-L. David.

Fabrication, permeation, and corrosion stability measurements of silica membranes for HI decomposition in the thermochemical iodine–sulfur process

In this study, a corrosion-stable silica membrane was developed to be used in H2 purification during the hydrogen iodide decomposition (2HI → H2 + I2), which is a new application of the silica membranes. From a practical perspective, the membrane separation length was enlarged up to 400 mm and one end of the membrane tubes was closed to avoid any thermal variation along the membrane length and sealing issues. The silica membranes consisted of a three-layer structure comprising a porous α-Al2O3 ceramic support, an intermediate layer, and a top silica layer. The intermediate layer was composed of γ-Al2O3 or silica, and the top silica layer that is H2 selective was prepared via counter-diffusion chemical vapor deposition of a hexyltrimethoxysilane.To the best of our knowledge, this is the first report of 400-mm-long closed-end silica membranes supported on Si-formed α-Al2O3 tubes produced via chemical vapor deposition method. A 400-mm-long closed-end membrane using a Si-formed α-Al2O3 tube exhibited a higher H2/SF6 selectivity of 1240 but lower H2 permeance of 1.4 × 10−7 mol Pa−1 m−2 s−1 with compared with the membrane using a γ-Al2O3-formed α-Al2O3 tube (907 and 5.6 × 10−7 mol Pa−1 m−2 s−1, respectively). The membrane using the Si-formed α-Al2O3 tube was more stable in corrosive HI gas than a membrane with a γ-Al2O3-formed α-Al2O3 tube after 300 h of stability tests. In conclusion, the developed silica membranes using the Si-formed α-Al2O3 tubes seem suitable for membrane reactors that produce H2 on large scale using HI decomposition in the thermochemical iodine–sulfur process.

Carbon derived from rice: application as a support for platinum catalysts for hydrogen generation by HI decomposition

Carbon derived from rice: application as a support for platinum catalysts for hydrogen generation by HI decomposition

Preparation and characterization of hollow carbon sphere supported catalysts (M@HCS [M=Pt, Ir, Ni]) for HI decomposition in the iodine–sulfur cycle for hydrogen production

Catalysts for HI decomposition are important in hydrogen production via the iodine–sulfur cycle. The catalysts should have a good activity, excellent thermal stability at 400 °C-500 °C, and corrosion resistance to HI and iodine. In this study, a series of hollow carbon sphere (HCS) supported mono-metallic catalysts M@HCS (M = Pt, Ir, Ni) were fabricated by coating the silica core with dopamine, carbonization, and sacrificial core technique. Active carbon-supported monometallic catalysts (M/C) were also prepared via the impregnation method. Catalytic activities of M@HCS and M/C during HI decomposition at 500 °C were compared. The composition, structure, specific surface area, morphology, and surface chemical states of M@HCS and M/C were characterized via inductively coupled plasma (ICP), X-ray diffraction (XRD), Brunauere-Emmette-Teller (BET) surface area, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the catalytic performance of M@HCS was better than that of M/C probably because of the synergistic effects between the active metals and HCSs.

Sulphonated (PVDF-co-HFP)-graphene oxide composite polymer electrolyte membrane for HI decomposition by electrolysis in thermochemical iodine-sulphur cycle for hydrogen production

In overall iodine-sulphur (I-S) cycle (Bunsen reaction), HI decomposition is a serious challenge for improvement in H2 production efficiency. Herein, we are reporting an electrochemical process for HI decomposition and simultaneous H2 and I2 production. Commercial Nafion 117 membrane has been generally utilized as a separator, which also showed huge water transport (electro-osmosis), and deterioration in conductivity due to dehydration. We report sulphonated poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) (SCP) and sulphonated graphene oxide (SGO) composite stable and efficient polymer electrolyte membrane (PEM) for HI electrolysis and H2 production. Different SCP/SGO composite PEMs were prepared and extensively characterized for water content, ion-exchange capacity (IEC), conductivity, and stabilities (mechanical, chemical, and thermal) in comparison with commercial Nafion117 membrane. Most suitable optimized SCP/SGO-30 composite PEM exhibited 6.78 × 10−2 S cm−1 conductivity in comparison with 9.60 × 10−2 S cm−1 for Nafion® 117. The electro-osmotic flux ofSCP/SGO-30 composite PEM (2.53 × 10−4 cm s−1) was also comparatively lower than Nafion® 117 membrane (2.75 × 10−4 cm s−1). For HI electrolysis experiments, SCP/SGO-30 composite PEM showed good performance such as 93.4% current efficiency (η), and 0.043 kWh/mol-H2 power consumption (Ψ). Further, intelligent architecture of SCP/SGO composite PEM, in which hydrophilic SGO was introduced between fluorinated polymer by strong hydrogen bonding, high efficiency and performance make them suitable candidate for electrochemical HI decomposition, and other diversified electrochemical processes.

Modeling and simulation of non-isothermal packed-bed membrane reactor for decomposition of hydrogen iodide

HI decomposition using a membrane reactor is one of the important steps in hydrogen production by the thermal splitting of water using the Sulfur–Iodine cycle. Though, this reaction is endothermic. The mathematical model available to study the performance of such a reactor is an isothermal model. In this study, a non-isothermal mathematical model is developed by microscopic material and energy balance across the length of the membrane reactor. Experimental results from the literature are used for validation of the developed model. Comparing the simulations from the developed model and already reported isothermal model showed significant differences, which endorses the importance of the developed model. Later, the effects of different operating and design parameters were analyzed. Higher feed temperature (950–1000 K), lower feed pressure (100,000–150,000 Pa), lower feed flow rate (<200 ml/min), lower permeate pressure (<2500 Pa) and low to moderate N 2 /HI ratio (0.3–0.4) were found to be the optimum operating conditions. Similarly, the conversion also increased with increasing reactor length, membrane area, and membrane permeance but eventually became constant. Reactor length around 0.4 m, membrane area around 0.008 m 2 and membrane permeance around 2 × 10 −7 mol m 2 Pa −1 s −1 were estimated to be the optimum design conditions for the maximum HI decomposition. • A non-isothermal model for HI decomposition using membrane reactor is developed. • Developed model is validated using experimental results. • Performances of developed model are significantly different from isothermal model. • Operating and design parameters are optimize using developed model.

Multi-tube tantalum membrane reactor for HIx processing section of IS thermochemical process

HIx processing section of Iodine-Sulphur (IS) thermochemical cycle dictates the overall efficiency of the cycle, which poses extremely corrosive HI–H2O–I2 environment, coupled with a very low equilibrium conversion (~22%) of HI to hydrogen at 450 °C. Here, we report the fabrication, characterization and operation of a 4-tube packed bed catalytic tantalum (Ta) membrane reactor (MR) for enhanced HI decomposition. Gamma coated clay-alumina tubes were used as supports for fabrication of Ta membranes. Clay-alumina base support was fabricated with 92% alumina (~8 μm particle size) and 8% clay (~10 μm particle size), sintered at a temperature of 1400 °C. An intermediate gamma alumina coating was provided with 4% polyvinyl butyral as binder for a 10% solid loading. Composite alumina tubes were coated with thin films of Ta metal of thickness <1 μm using DC magnetron sputter deposition technique. The 4-tube Ta MR assembly was designed and fabricated with integration of Pt-alumina catalyst for carrying out the HI decomposition studies, which offered >80% single-pass conversion of HI to hydrogen at 450 °C. The hydrogen throughput of the reactor was ~30 LPH at a 2 bar trans-membrane pressure, with >99.95% purity. This is the first time a muti-tube MR is reported for HIx processing section of IS process.

Discovery and material study of the missing feet part from Magritte\u2019s L\u2019\xe9vidence \xe9ternelle of 1954

One of the two missing canvases from L’évidence éternelle of 1954, the one of the feet, has been discovered beneath a small woman portrait painted in 1958, La toile de Pénélope. Indeed, the underlying woman’s feet revealed through the IRR and XRR images leave little doubt about the identity of the hidden composition. All the more so as the canvas dimensions perfectly match with the format ascribed to the feet part in the diagram Magritte made of the 1954 variant of L’évidence éternelle. This paper presents the main results of the material study conducted on La toile de Pénélope by means of non-invasive and complementary imaging and analytical techniques. Furthermore, it proposes a virtual colorized reconstruction of the hidden picture, built on the basis of the XRR and IRR images, the elemental information provided by the MA-XRF analysis, the Raman results and the microscope examination of the painting surface.

Leather Thermal and Environmental Parameters in Fire Conditions

The thermal decomposition of leather-product combustion produces some inflammable and harmful compounds after tanning, fat liquoring, dyeing, and finishing processes. These organic compounds are ignited and release a lot of toxic gases and smoke in fire conditions, polluting the atmosphere air. On this account, it is very important to know leather safety performance for fire prevention. The flammability and thermal stability of types of leather at thermal expositions stimulating fire conditions were analyzed. Five types of leather were used in experimental testing, four of animal origin and an artificial one. Results showed that, in the analyzed heat exposure, the highest average heat-release rate (174 kW/m2) and smoke generation, and the lowest temperature of the beginning of thermal decomposition, were recorded for the artificial leather. Leather flammability essentially depends on the type of applied energy stimulus, as well as hide composition and origin. A possible cause for differences in the obtained results of the leather analyses is the percentage of certain leather components and their chemical composition.

Comparison of experimental and simulation results on catalytic HI decomposition in a silica-based ceramic membrane reactor

In this study, the catalytic decomposition of hydrogen iodide was theoretically and experimentally investigated in a silica-based ceramic membrane reactor to assess the reactor's suitability for thermochemical hydrogen production. The silica membranes were fabricated by depositing a thin silica layer onto the surface of porous alumina ceramic support tubes via counter-diffusion chemical vapor deposition of hexyltrimethoxysilane. The performance of the silica-based ceramic membrane reactor was evaluated by exploring important operating parameters such as the flow rates of the hydrogen iodide feed and the nitrogen sweep gas. The influence of the flow rates on the hydrogen iodide decomposition conversion was investigated in the lower range of the investigated feed flow rates and in the higher range of the sweep-gas flow rates. The experimental data agreed with the simulation results reasonably well, and both highlighted the possibility of achieving a conversion greater than 0.70 at decomposition temperature of 400 °C. Therefore, the developed silica-based ceramic membrane reactor could enhance the total thermal efficiency of the thermochemical process.

The Stain of the Original Salt: Red Heats on Chrome Tanned Leathers and Purple Spots on Ancient Parchments Are Two Sides of the Same Ecological Coin.

Animal hides are one of man’s earliest and mostly used materials; many rawhide products, primarily leather, have for centuries been used for several purposes. The peculiar mechanical properties of leather depend on the hide composition, a dense collagen feltwork. Unfortunately, due to their proteic composition, rawhides may undergo microbial attack and biodeterioration. Over centuries, different processes and treatments (brining, vegetal or chrome tanning, tawing, etc.) were set up to face the biological attack and modify/stabilise the hide’s mechanical properties. Nevertheless, even present-day rawhides are subjected to biological colonisation, and traces of this colonisation are clearly shown in Chrome(III) tanned leathers (in the wet blue stage), with obvious economic damages. The colonisation traces on tanned leathers consist of isolated or coalescent red patches, known as red heat deterioration. Parchments are rawhide products, too; they derive from another manufacturing procedure. Even parchments undergo microbial attack; the parchment biodeterioration seems comparable to leather red heat deterioration and is known as purple spots. Recently, an ecological succession model explained the process of historical parchment purple spot deterioration; the haloarchaea Halobacterium salinarum is the pioneer organism triggering this attack. The marine salt used to prevent rawhide rotting is the carrier of haloarchaea colonisers (Migliore et al., 2019). The aim of this study was to investigate the dynamics of biodeterioration on Chrome(III) tanned leathers and its effects on the stability/integrity of collagen structure. To this end, standard cultivation methods were integrated with three updated technologies, Next-Generation Sequencing (NGS), Raman spectroscopy, and Light Transmitted Analysis (LTA). A bioinformatic comparison between chrome tanned leather vs. historical parchment colonisers was performed to evaluate if leather and parchment share common culprits; furthermore, the effect of the biodeterioration on the physical properties of the hide product was evaluated.