High Hydrogen Content Research Articles

Numerical Modeling of Swirl Stabilized Lean-Premixed H2–CH4 Flames With the Artificially Thickened Flame Model

Abstract The lean premixed technology is a very convenient combustion strategy to progressively move from natural gas to high hydrogen content fuels in gas turbines limiting the pollutants emissions at the same time. The enabling process that will allow the combustor to manage a full H2 operation requires relevant design modifications, and in this framework, the numerical modeling will be a pivotal tool that will support this transition. In this work, high-fidelity simulations of perfectly premixed swirl stabilized flames have been performed varying the H2 content in the fuel from 0 to 100% to investigate the effect of the hydrogen addition on the methane flame. The artificially thickened flame model (ATFM) has been used to treat the turbulent chemistry interaction. The numerical results have been compared with the detailed experimental data performed at Cardiff University's Gas Turbine Research Center. After the numerical model validation against experimental OH* chemiluminescence maps has been presented, a deep numerical investigation of the effect of the H2 addition on the flame has been performed. In this way, the work aims to highlight the good prediction capability of the ATFM, and, at the same time, highlight the change in the different contributions that govern the flame reactivity moving from 100% CH4 to 100% H2 in very lean conditions.

A simplified chemical kinetic model with a reaction mechanism based on a multidimensional average error iteration method for ammonia and ammonia/hydrogen combustion

A NH3/H2 kinetics model was developed, which is analyzed using MATI method. The combustion chemistry of NH3 under various conditions regimes are intensive studied and the new significant reaction pathways for NOx formation was elucidated.

Advances in electrocatalytic dehydrogenation of ethylamine to acetonitrile.

The electrocatalytic dehydrogenation of ethylamine (EDH), owing to its high hydrogen content, holds broad prospects in electrochemical hydrogen (H2) production, H2 storage, and addressing energy issues, thus deserving wide attention. In this feature article, we first summarized the fundamentals of thermocatalytic and electrocatalytic EDH and reviewed the recent state-of-the-art advances in catalyst research, specifically platinum group metal (PGM) catalysts and non-PGM catalysts. We systematically discussed the potential applications of electrocatalytic EDH in energy storage and conversion. Finally, we provide our perspective on the key challenges and future developments in this field. We believe this feature article will offer helpful guidance for oriented design and optimization of stable and efficient catalysts for electrocatalytic EDH and related energy applications.

Pure ammonia flames with high thermal intensities through fuel and air staging under extreme rich-to-lean conditions

Ammonia combustion has gained significant attention due to its high hydrogen content and zero carbon emissions. It poses a challenge for stabilization due to their low energy content and limited flammability range, with the added concern of fuel NOx emissions. In the current study, a novel burner design equipped with four series of reactors is proposed to achieve stable pure ammonia-air flames with reduced NOx emissions. The impact of thermal intensity (∼0.7 MW/m3 to ∼4 MW/m3), number of stages, equivalence ratio (0.5–1.2), and fuel staging on flame stabilization and emissions were investigated in the proposed burner. Comprehensive emissions analysis is performed at various burner levels. Numerical simulations incorporating Large Eddy Simulation (LES) modeling are employed to enhance understanding of the impact of thermal intensity and equivalence ratios on ammonia dissociation, mixedness, and NO emissions. The results indicated that the present burner design improved reactant mixing, and flame stability, reduced NH3 emissions (∼ 0 PPM), and lowered NOx levels in non-premixed ammonia-air flames. The computational and experimental results demonstrated that the implementation of fuel staging is crucial for reducing NOx emissions for the flames with lean global equivalence ratios. Lower NO emissions were identified at a global equivalence ratio of 1.1 for all the considered flames in the range of 0.5–1.2. In the four-stage rich-lean combustion strategy employed in this study; it was observed that higher thermal intensity (4 MW/m3) with fuel staging resulted in lower NOx emissions per kW of energy input compared to lower thermal intensities 0.7 MW/m3. This finding underscores the significance of achieving uniform mixtures and ensuring local flame in rich conditions for achieving low NOx emissions in ammonia combustion. Exhaust gas analysis is conducted at three stages of the burner to enhance the understanding of emissions at various levels of the burner. The proposed combustor design has achieved a substantial reduction in NOx to ∼1 PPM/kW and ∼2.8 PPM/kW with and without fuel staging, respectively. This impressive outcome is attributed to the controlled ammonia consumption facilitated by uniform mixing generated through the use of tangential air inlets.

Sulfonated porous organic polymer supported Ziegler-Natta catalysts for the synthesis of ultra-high molecular weight polyethylene.

Porous organic polymers (POPs) are attracting attention for their easy functionalization and potential as catalyst supports in olefin polymerization. In this study, sulfonated POP (s-POP) supported Ziegler-Natta catalysts were used for ethylene polymerization, producing ultra-high molecular weight polyethylene, with M ν reaching up to 6.83 × 106 g mol-1. The maximum M ν of polyethylene was achieved by Cat-3 with DIBP as the internal donor, albeit with a partial loss of catalytic activity. Polymerization conditions also play a pivotal role in determining the molecular weight of polyethylene. Hydrogen, being the most efficient chain transfer agent, can decrease the molecular weight to 9.68 × 104 g mol-1 at higher hydrogen concentrations ([H2] : [C2H4] = 0.83), and the s-POP-supported ethylene polymerization catalysts were observed to exhibit high sensitivity to hydrogen response. The effects of polymerization temperature, [Al] : [Ti] molar ratio, and ethylene pressure on ethylene polymerization were thoroughly investigated.

Mechanistic studies of HF/BF3-catalyzed anthracene polymerization to prepare mesophase pitch.

The mesophase pitch prepared by acid catalytic method typically had the advantages of low softening point and high solubility. To fully understand the mechanism of acid-catalyzed reactions and gain a deeper understanding of the microstructure of mesophase pitch, this article studied the mechanism of hydrofluoride/boron trifluoride (HF/BF3)-catalyzed anthracene using molecular simulation methods. The results showed that there might be two types of carbocations present in the system: classical and non-classical carbocations, and five reactions might occur, protonation reaction, chain elongation reaction, intramolecular cyclization reaction, deprotonation reaction, and dehydrogenation reaction. Classical carbocations acted as reactive intermediates in the chain elongation reaction and intramolecular cyclization reaction. When anthracene occurred chain elongation reactions with carbocations to form polymers, the generation of the tetramer required lager energy barriers than that of the dimer and trimer. The stiffness and flatness of molecules could be increased via intramolecular cyclization reactions. The polymers of anthracene might also occurred dehydrogenation reactions when the non-classical carbocations played the role of reactive intermediates. The dehydrogenation reactions required large energy barriers, which might be the reason for the product having a high aliphatic hydrogen content. The Materials Studio (MS) 2020 software was used to complete the simulation. The atomic charge distribution calculation and the structure optimization of molecules were carried out using the B3LYP functional and DNP basis. The DFT-D (TS) dispersion corrections were added to calculate the dispersion interaction between aromatic molecules. The complete LST/QST method was used to search the transition states and calculate the reaction energy barrier.

Hydrogen therapy: recent advances and emerging materials.

Hydrogen therapy, leveraging its selective attenuation of hydroxyl radicals (˙OH) and ONOO-, has emerged as a pivotal pathophysiological modulator with antioxidant, anti-inflammatory, and antiapoptotic attributes. Hydrogen therapy has been extensively studied both preclinically and clinically, especially in diseases with an inflammatory nature. Despite the substantial progress, challenges persist in achieving high hydrogen concentrations in target lesions, especially in cancer treatment. A notable breakthrough lies in water/acid reactive materials, offering enhanced hydrogen generation and sustained release potential. However, limitations include hydrogen termination upon material depletion and reduced bioavailability at targeted lesions. To overcome these challenges, catalytic materials like photocatalytic and sonocatalytic materials have surfaced as promising solutions. With enhanced permeability and retention effects, these materials exhibit targeted delivery and sustained stimuli-reactive hydrogen release. The future of hydrogen therapy hinges on continuous exploration and modification of catalytic materials. Researchers are urged to prioritize improved catalytic efficiency, enhanced lesion targeting effects, and heightened biosafety and biocompatibility in future development.

Highly active internal catalyst promoting the efficient ammonia decomposition and durability of protonic ceramic fuel cells

Direct ammonia protonic ceramic fuel cells (DA-PCFCs) have attracted extensive attention by virtue of their high hydrogen content, superior energy density, and zero carbon emissions. However, the practical application of DA-PCFCs is impeded by their unsatisfactory catalytic activity and limited durability. This study aims to evaluate the feasibility of utilizing ammonia solution as a fuel for PCFCs. In the hope of enhancing performance and reducing costs, a low-cost iron catalyst layer was proposed and fabricated within cells, with a structure of NiO–BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb)| NiO-BZCYYb| BZCYYb| PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF)-BZCYYb. The introduction of the iron catalyst layer yields promising results, achieving a remarkable increase (from 165 mW/cm2 to 300 mW/cm2 by 81.8 %) in maximum power density at 600 °C and a significant lengthening of durability. The enhanced electrochemical performance and durability can be attributed to the presence of the iron catalyst layer, which improves the catalytic activity for ammonia decomposition while preventing the formation of nitride.

Ammonia as an Energy Carrier for Renewable Energy Conversion and Storage

An emerging energy carrier, ammonia (NH3), has attracted ever-increasing attention due to its high hydrogen content (17.65 wt. %) and its ease of storage, transportation, and handling [1,2]. This work aims to investigate the feasibility of utilizing ammonia as an energy carrier for intermittent renewable energy conversion and storage via an electrochemical flow cell, which includes two independent electrocatalytic processes (Fig. 1): ammonia production via nitrogen reduction and electricity generation via ammonia oxidation [3,4]. Firstly, the effects of structural design and operating parameters on the flow cell performance are investigated. Our preliminary results have shown that the ammonia yield reaches 27.9 μg h−1 mg−1 and the power density reaches 20.7 mW cm-2. Secondly, an in-depth analysis and discussion on the simultaneous transport of mass and charge through the flow cell are conducted. Thirdly, a techno-economic assessment for using ammonia as an energy carrier is performed. These research findings will provide crucial insights into the utilization of ammonia as an energy carrier for renewable energy conversion and storage.AcknowledgementThis work was fully supported by a grant from the National Natural Science Foundation of China (Project No. 52022003)References[1] Y. Zhao, B.P. Setzler, J. Wang, J. Nash, T. Wang, B. Xu, Y. Yan, An efficient direct ammonia fuel cell for affordable carbon-neutral transportation, Joule, 3 (2019) 2472–2484.[2] Y. Guo, Z. Pan, L. An, Carbon-free sustainable energy technology: Direct ammonia fuel cells, J. Power Sources, 476 (2020) 228454.[3] Y. Liu, Z. Pan, O.C. Esan, X. Xu, L. An, Performance characteristics of a direct ammonia fuel cell with an anion exchange membrane, Energy Fuels, 36 (2022) 13203-13211.[4] Y. Liu, Z. Pan, O.C. Esan, X. Liu, H. Wang, L. An, Efficient electrocatalytic nitrogen reduction to ammonia with FeNi-Co/carbon mat electrodes, J. Alloys Compd, 927 (2022) 166973.Figure 1. Ammonia as an energy carrier for renewable energy conversion and storage. Figure 1

Photoelectrochemical Nitrate Reduction to Ammonia Using Metal Oxide Based Photosensitisers

Ammonia is one of the most important chemicals synthesised presently. It supports the lives of billions around the world through its utilisation as a precursor for fertilisers, enhancing agricultural yield. It has also been proposed that ammonia could be employed as a carbon free hydrogen storage molecule due to its high hydrogen content (40% higher than methanol).Currently, ammonia primarily is synthesised through the energy-intensive Haber Bosch process. This entails combining dinitrogen and hydrogen under high temperatures (300-500 °C) and high pressures (150-200 atm). These strenuous conditions are due to the extreme difficulty in cleaving the dinitrogen triple bond. This process, in addition to using steam reforming to produce hydrogen, results in large carbon dioxide output.Therefore, it is necessary to devise alternative methods to synthesise green ammonia. Photoelectrochemical synthesis of ammonia is one such route that couples electrochemical and photochemical processes to reduce the overpotential needed. Additionally, from the economic and environmental perspective, nitrate reduction to produce ammonia is a better option. Nitrates are present in the environment naturally or contaminated from run off fertilisers. These present a threat that if consumed in large quantities can lead to cancers and if left to accumulate in waters, lead to environmental issues such as eutrophication.This work thus focuses on the synthesis of materials to reduce nitrates to ammonia photoelectrochemically. P-type semiconductors with a conduction band position that encompass the reduction potential of nitrate to ammonia are employed. Utilising different p-type metal oxide photosensitisers such as copper oxide, nickel oxide and cobalt oxide, the surfaces are modified with metal catalysts to improve the conversion efficiency of nitrate to ammonia. The concentration of nitrite (the first reductive product) and ammonia formed is evaluated using ion chromatography. Additionally, the concentration of hydrogen and nitrogen formed will be evaluated using gas chromatography. To further evaluate the efficacy of these materials, the faradaic efficiency and yield rates for nitrate reduction are evaluated. The quality of the materials chosen are be judged on their selectivity for adsorption and reduction, and their stability.

Experimental studies on renewable hydrogen production by steam reforming of glycerol over zirconia promoted on Ni/Al2O3 catalyst

Abstract The impact of ZrO2 as a catalytic promoter for nickel-based alumina supported catalysts has been studied for the hydrogen synthesis via glycerol steam reforming. Hydrogen is a promising contender of clean fuel and has a key significance in the quest of an environment-preservation, low emission and more sustainable energy approach. Glycerol is a by-product produced during production of biodiesel by trans-esterification of vegetable oils. The higher hydrogen content in glycerol makes it the potential renewable feedstock for hydrogen production. Steam reforming process is the best method available which is highest in energy efficiency and most importantly most economical. The production of catalysts was based on the wet impregnation and co-precipitation methods. The majority of the bulk and surface properties of different synthesized catalysts were considered and determined by several characterization techniques like X-ray diffraction technique, BET surface area and scanning electron microscopy. The performance of catalyst is based on glycerol conversion and hydrogen yield obtained from the steam reforming process taking place in the fixed bed catalytic reactor. The effect of different operating conditions like contact time, temperature, metal loading, and steam to glycerol ratio were investigated to produce maximum hydrogen and glycerol conversion. The results show that the incorporation of promoter 2 % ZrO2 improved the activity of Ni/Al2O3 catalysts significantly resulting 96 % glycerol conversion, 84 % hydrogen production and greater stability at contact time = 15 kg cat s/mol, temperature = 800 °C, steam to glycerol ratio = 9:1 mol/mol, and pressure = 1 atm.

Study of thermal effects in ammonia-fueled solid oxide fuel cells

Ammonia is regarded as a promising alternative to hydrogen because of its high hydrogen content, ease of transportation and storage, and other favorable properties. However, in ammonia-fueled solid oxide fuel cell (SOFC), the intense heat absorption and excretion of ammonia decomposition and electrochemical reactions can lead to inhomogeneous temperatures inside the cell, which restricts long-life operation. For this reason, a three-dimensional tubular solid oxide fuel cell thermo-electrochemical model is established to explore the thermal characteristics when using ammonia as the fuel. The errors between the power density and voltage obtained from the numerical model and the experimental data in the literature are less than 5 %, which proves the accuracy of the model in this paper. Further parametric simulations reveal that the electrochemical performance and heat production rate are strongly affected by the operating voltage. And a peak power density of 66.4 mW/cm2 is obtained at an operating voltage of 0.45 V. Additionally, increasing the inlet temperature and increasing the fuel flow rate are beneficial for improving cell efficiency, although achieving temperature uniformity remains a challenge. The ammonia pre-reforming degree can be adjusted to effectively improve the temperature distribution uniformity within the cell and improve its internal heat balance. The maximum temperature difference in 96 % pre-reformed SOFC is only 22 K, while it reaches 167 K in direct ammonia SOFC. The temperature and electrochemical performance laws revealed in this study provide a theoretical basis for the optimization of ammonia-fueled SOFC.

Highly air-stable magnesium hydrides encapsulated by nitrogen-doped graphene nanospheres with favorable hydrogen storage kinetics

Severe surface oxidation and sluggish kinetic rates of Mg hydrides (MGHs) are the main bottlenecks for their industrial applications. Herein, we present a strategy to simultaneously tackle these problems. The nano-size MGHs were encapsulated in nitrogen-doped graphene nanospheres (NGNSs) via a facile wet-chemical method. This configuration not only prevented the MGHs from oxidation when exposed to air even after a long duration, but also stimulated faster kinetic rates of hydrogen absorption and desorption owing to the nano-size effect of MGHs and the unique electronic structure of NGNSs. As a result, MGHs of ca. 20 nm were coated by a few layered NGNSs to form MGH@NGNSs nanocomposite. A high hydrogen absorption capacity of 6.5 wt% was achieved at 200 °C within 0.4 h, with a releasing hydrogen capacity of 5.5 wt% at 300 °C within 0.5 h, indicating that this composite has obtained remarkably hydrogen storage performance. Density Functional Theory (DFT) based calculations suggested that the hydrogen adsorption/desorption kinetics were significantly fast at the interface of Mg surface and NGNSs with pyridinic configuration. This strategy paves a way for the development of high-performance Mg-based hydrogen storage materials for industrial applications.

Effects of oxygen loading on the red-luminescence of non-bridging oxygen hole centers in γ-irradiated silica glasses

Ultra-high purity Corning 7980 and Corning 7979 silica glasses, respectively with high and low contents of hydroxyl and hydrogen, were specifically selected to investigate the effects of O2 loading on the 1.9 eV red luminescence of the gamma-ray induced non-bridging oxygen hole center (NBOHC), whose luminescence intensity is beneficial not only to predict the laser damage of silica but also to the targeted improvements in the preparation-treatment processes of silica. The UV trasmittance spectra, the UV excitation spectra, the visible emission spectra and the red emission lifetime decay curves were determined for these two types of the gamma-ray irradiated silica glasses before and after O2 loading. The content ratios of Si dangling bond (Si-E′) to NBOHC in silica glasses before and after O2 loading are estimated. The formation precursors and other related defects for NBOHC, such as Si-E′, Si-O-Si bond, Si-O-H bond, peroxy radical and linkage, oxygen-deficient centers ODC(I) and ODC(II), etc, are discussed. The bandwidths of the excitation and emission spectra before and after O2 loading are compared at the lower energy side of the spectra. The average emission lifetimes and especially the decay curves of the red luminescence before and after O2 loading are analyzed. There appear two types of NBOHCs with and without neighbouring hydrogen interaction at room temperature, respectively corresponding to the shorter and longer lifetime components. After O2 loading, the shorter lifetime component disappears and becomes the longer one, indicating that the hydrogen-bonded NBOHC is altered into the non-bonded. It is suggested that the analysis of the shorter and longer lifetime components of the red luminescence can be utilized in the laser damage prediction as well as the preparation and treatment processes of silica.

Recyclable ammonia uptake of CuCl2/graphite composite adsorbents with high adsorption capacity

Ammonia is considered a good hydrogen storage material due to its advantages of high hydrogen content density. At the same time, the characteristic of efficient heat transfer of ammonia makes it develop rapidly in many energy industries. However, unutilized NH3 can cause corrosion and poisoning, therefore, NH3 must be captured in time. Metal chloride is a green, efficient and sustainably utilized material for NH3 adsorption and capture. In this paper, a novel composite adsorbent was proposed by loading graphite to CuCl2 to enhance the NH3 adsorption·NH3 adsorption–desorption experiments of composite adsorbents were performed on the fixed bed. The results showed that the optimal loading of graphite on CuCl2 was 20 wt% and the optimal adsorption temperature was 25 ℃. The optimal adsorption of CuCl2-G (20) was 0.64 g NH3/g adsorbent. Moreover, the composite adsorbents showed good stability in NH3 adsorption properties during long-term cycling. The cumulative NH3 adsorption capacity of CuCl2-G (20) in the 10 cycles was up to 5.8 g NH3/g adsorbent, which was 0.07 g NH3/g adsorbent higher than that of CuCl2. Notably, all graphite-loaded composite adsorbents showed a stronger NH3 adsorption capacity than a single CuCl2 in the 2nd and subsequent cycles. Thus, CuCl2-G (20) is a promising adsorbent with potential application in the removal and enrichment of excess NH3 produced in industrial processes.

Analysis of Mechanical Properties of Welded Joint Metal from TPP Steam Piping after Its Operational Degradation and Hydrogenation.

In this paper, the mechanical properties of various zones of the welded joints of a heat-resistant steel 15Kh1M1F in different states (in the initial state, after an operation on the main steam piping of a thermal power plant (TPP) for 23 years) were determined, and the fracture surfaces were analyzed using scanning electron microscopy (SEM) images. The effect of hydrogen electrolytic charging on mechanical behavior and fracture mechanism was also studied. The long-term operation of welds resulted in a higher degradation degree of the weld metal compared to the base one, indicated by the deterioration of mechanical properties: decrease in hardness, strength characteristics, and reduction in area, which was accompanied by an atypical increase in elongation at fracture. All studied zones of the operated welded joints were characterized by higher hydrogen content, 2.5-3 times higher than that in the initial state. Additional hydrogen charging of the weld joint metal led to a decrease in the strength and ductility characteristics, more significantly for the operated weld compared with the non-operated one. This justified the possibility of using short-term tests of hydrogenated WM in the air to assess the degree of its damage during operation on a steam piping.

Effects of ignition position and hydrogen concentration on the flame propagation characteristics of hydrogen–air deflagration

In this study, the effects of hydrogen concentration and ignition position on the flame propagation characteristics of hydrogen–air deflagration in a pipe were investigated using a visual explosion propagation system. The change laws of propagation characteristics were analyzed at the microscopic level using free radical spectroscopy. The results indicated that the hydrogen flame had a lower velocity but higher explosion temperature and pressure under central ignition than under bottom ignition. However, the effect of ignition position weakened at higher hydrogen concentrations. As the hydrogen concentration was increased from 13 to 17 vol%, the differences in the maximum flame velocity, maximum temperature, and maximum pressure between central and bottom ignition decreased from 60.4%, 25.3%, and 17.8%, respectively, to 24.9%, 1.1%, and 4.6%, respectively. In addition, the maximum relative intensity and duration of the OH· spectral peak were more than 14% lower and shorter, respectively, under central ignition than under bottom ignition. As the hydrogen concentration was increased, the OH· spectral peak appeared earlier, the duration of this peak was shortened, and the explosion reaction was accelerated. OH· was consumed in the explosion reaction, which resulted in the release of heat; thus, the temperature and explosion pressure increased.

Stability of industrial gallium-doped Czochralski silicon PERC cells and wafers

The carrier lifetime stability of gallium-doped silicon wafers and performance stability of industrial PERC solar cells produced from sister wafers were investigated under four different illumination conditions and temperatures. The seven investigated materials feature a resistivity variation of 0.4–1.0 Ωcm and lifetime samples were processed to create high hydrogen content (with PECVD SiNx) or low hydrogen content (with ALD Al2O3 or HfO2). Our results confirm that the material itself is prone to light and elevated temperature induced degradation (LeTID), however experiments on PERC cells produced utilising the same silicon material indicate that the production process can successfully suppress LeTID. In contrast to earlier studies, we observe only small levels of degradation at the cell level, with some showing an improvement in cell parameters under LeTID testing conditions. Our results indicate that LeTID is not necessarily a major issue for the performance of modern passivated emitter and rear cells made from gallium-doped silicon substrates.

Colourless distributed combustion effects on a pre‐mixed coke oven gas flame

AbstractFuels consisting of high hydrogen concentration can be consumed under colourless distributed combustion (CDC) to suppress flashback tendency in premixed conditions. Higher NOX challenges can also be overcome through CDC. For those purposes, coke oven gas was consumed under CDC within the scope of this study. To achieve CDC, or diluents were introduced into the oxidizer so that oxygen concentration in the oxidizer would be decreased from 21% O2 to its lean blow‐off limits. Excess air ratios were determined as λ = 1.2 and λ = 1.5 along with a thermal power of 10 kW under premixed conditions. A commercial computational fluid dynamics code was used to predict temperature distribution and , CO, and emissions. 162‐step reactions created with GRI‐Mech 3.0 chemical kinetics was integrated to the eddy dissipation concept combustion model. The temperature and profiles predicted were compared with the experimental results. Consistency was achieved at ~95% for temperature profiles, and almost 100% for profiles between the measured and the predicted ones. According to the results, it is concluded that a more homogeneous temperature distribution with the ~21% decrease in the maximum temperature was observed, and there was about 96% decrease in level. It was also demonstrated that using as a diluent is more effective in terms of temperature distribution over the combustor and reduction, while dilution with is more effective in terms about 70% in decrease on CO.

Integration of a Microchannel Reactor in a CECE Process for H2 Removal from the O2 Stream Produced by the H2 Generator

A hydrogen generator is used in the combined electrolysis catalytic exchange process (CECE) for low-level tritiated water detritiation as a source of H2 (Q2) for the liquid-phase catalytic exchange column(s) within the process. To produce H2, the H2 generator employs an electrolytic process for H2O splitting into H2 and O2, resulting two streams: a hydrogen stream and an oxygen stream. During the detritiation of water, tritium is accumulated in the H2 generator in the form of tritiated water, and the effluent streams (hydrogen and oxygen) show in time an increased tritium concentration in the form of both tritiated water vapors and gas, which need to be recovered. The traditional methods for recovery present a risk of explosion due to the high concentration of hydrogen in oxygen (above 3%, while the explosion limit is 1%). In order to minimize this risk, a microchannel reactor with platinated channels has been developed and tested for the oxidation of tritiated hydrogen from the O2 electrolyzer stream in view of its recovery in a scrubber column and returned as tritiated water to the process. The reactor has been coupled to an electrolyzer and tested with regard to the operating temperature. It has been found that it reaches the highest oxidation efficiency of hydrogen when operated at 200°C. The design of the equipment is presented together with the results of the tests done with the equipment integrated in the CECE process.