Papers by Keyword: Hydrogen

Abstract: The problems of stress corrosion or hydrogen blistering of gas pipelines are relevant and require careful study of the causes and factors that cause this type of corrosion-mechanical destruction of pipelines. The analysis of numerous publications on this problem revealed contradictions of information regarding the mechanism of stress corrosion and a lack of experimental materials on the substantiation of the nature and peculiarities of the nature of destruction on gas pipeline networks. Systematic experimental studies using different brands of pipe steels allowed to determine the brands of steels, which according to their characteristics are the most resistant to VBR in harsh operating conditions, including even in the most aggressive NACE environment with H₂S and CO₂ additives at a pressure of 10-15 atm. Moreover, the experimental studies were as close as possible to the operating conditions of pipelines of the gas transportation network. The obtained results of experimental studies can serve as a basis for developing methods of technical diagnostics and forecasting the actual state of pipelines, which will significantly prevent the occurrence of sudden destruction caused by stress corrosion. The influence of the service life of gas pipelines on the degree of flooding and microhardness of pipe steels was established, which made it possible to substantiate the embrittlement of the metal with the increase of service life. The values of impact toughness on samples with sharp and round notches and the amount of work of crack growth depending on the service life of the pipe steels were determined, which made it possible to choose steel grades characterized by the highest resistance to brittle fracture. It is shown that with the service life, the destruction occurs according to a brittle mechanism, which is confirmed by the increase in the share of the fibrous component in the fractured samples after impact tests. It was established that the lowest corrosion rate is possessed by new grades of improved steel grades 20А and 08 KhMChA.The PRFNV parameter proposed in the paper makes it possible to assess the susceptibility of pipe steels to stress corrosion cracking and provides an opportunity to regulate the corrosion crack resistance of pipelines by metallurgical methods.

Abstract: The article analyzes the cooling systems that have become stuck during the operation of high-power electric machines, the importance of using water-cooling systems for them has been dubbed. The main part of the research is devoted to the consideration of nutritional and detailed methods of rational cooling of turbogenerators based on the use of innovative environment protection technologies, namely metal hydride hydrogen storage technologies as an environmentally friendly alternative to motor fuel. It is shown that an alternative to the traditionally used devices for cooling of electric machines with hydrogen is the use of hydrides of intermetallic compounds to implement the working processes of thermosorption compressors, which is due to the ability of reversible hydrides of intermetallic compounds to repeatedly sorb and desorb hydrogen at significantly different pressures, the value of which is determined by the temperature potential of the thermal effect, i.e. thermochemical compression of hydrogen. The methods of calculating the parameters used in the designing such devices have been analyzed, and the method of determining the parameters of phase equilibria of hydrides of intermetallic compounds has been suggested. Mathematical modeling of hydrogen sorption by intermetallic compounds, performed on the basis of the mathematical apparatus of the thermodynamic perturbation theory improved in the study and on the example of the intermetallic hydride LaNi₅, based on the application of the lattice gas model for metal hydrides. At the same time, due to the presence of an unchanged crystal structure of the metal, an increase in the volume of the crystal lattice in the process of hydrogen sorption was taken into account, which leads to the appearance of additional components in the potential energy, and the interaction between absorbed hydrogen atoms has also been taken into account. The calculated temperature dependences of the pressure on the plateau of the hydrogen solubility isotherm are in good agreement with the experimental data available in the literature. The operation of the metal hydride cooling system of TG excludes the occurrence of fire and explosive situations, and it also significantly increases the level of ecological safety indicators.

Abstract: IIn a geothermal environment, cathodic protection is employed to improve resistance against corrosion fatigue. However, during the cathodic reactions under applied potential, hydrogen is generated and assimilated, leading to a reduced lifetime expectancy of high-alloyed steels. The corrosion fatigue mechanism of a standard duplex stainless steel X2CrNiMoN22-5-3 (1.4462) specimen loaded with hydrogen was studied in a corrosion chamber specifically designed for the purpose, surrounded by the electrolyte of the Northern German Basin at 369 K. The microstructural reactions resulting in hydrogen incorporation significantly decrease the number of cycles to failure of the specimen. This reduction is attributed to hydrogen enhancing crack propagation and causing early failure, primarily due to the deterioration of the mechanical properties of the ferritic phase rather than corrosion reactions or corrosive degradation.

Abstract: The abundance of rice husk in some regions of Southeast Asia makes it a potential feedstock for hydrogen synthesis. However, the information on economic and environmental feasibility of its conversion to hydrogen is lacking. This study aims to assess the techno-economic and life cycle sustainability of hydrogen production from rice husk via the thermochemical gasification method. The techno-economic analyses reveal that rice husk-based hydrogen conversion is more financially attractive than conventional hydrogen production technology. The results of the life cycle assessment are also promising, especially with the global warming potential of the rice husk-based hydrogen production being 99.7 % lower than that of natural gas steam reforming. Waste valorization of rice husk into hydrogen is therefore economically and environmentally viable.

Abstract: The production of the most abundant chemical element in the atmosphere, hydrogen, particularly green hydrogen (i.e. hydrogen in its cleanest and most sustainable form), is quickly becoming a priority for nations worldwide. This interest is mainly attributed to, among other factors, its potential to serve as a cornerstone of the global energy transition to low-carbon economies. Green hydrogen possesses the potential to decarbonize the so-called “hard-to-abate,” sectors i.e., energy-intensive sectors, such as heavy industries, iron and steel production, and transportation - including aviation and shipping, among other economic sectors.The growing focus on the adoption of green hydrogen as a viable decarbonization pathway must be viewed against the backdrop of global commitments and international imperatives to address the adverse effects of climate change. Such commitments emanate from instruments such as the Paris Agreement of 2015 and obligations towards meeting the United Nation's Sustainable Development Goals (SDGs). Further, the “Just Energy Transition" journey towards decarbonization must also be contextualized within different jurisdictions, in line with their situations and context-specific goals, geographic locations, and policy frameworks.Much like other nations worldwide, the South African regulatory framework for hydrogen is still emerging, as it is presently dominated by soft law instruments such as roadmaps, strategies and guiding documents, as opposed to binding and enforceable hard law instruments. For example, the South African Hydrogen Society Roadmap of 2022, the Integrated Resource Plan, the Integrated Energy Plan, and the Renewable Energy Policy, among other significant policy documents, highlight the fundamental role that green hydrogen would play in South Africa’s energy transition. Whilst other legal and policy documents may apply to the hydrogen value chain, such as the various safety requirements in the Occupational Health and Safety Act, 1996, there is a lacuna of hydrogen-specific hard law regulation, including, importantly, regulations regarding certification (which will need to be aligned internationally).In light of the above, this paper discusses the potential of green hydrogen in the context of South Africa and explores the current position in the country. It further canvasses emerging developments within the hydrogen space. This analysis aims to identify gaps or lacunas in the law, risks, and challenges for South Africa’s hydrogen economy. The article proceeds to provide recommendations for a policy and regulatory regime for hydrogen in Southern Africa. It draws on examples from countries and regions such as the European Union (EU), which are further along in terms of regulating hydrogen, but contextualizing this discussion within the African, and specifically Southern African context. This budding industry provides an opportunity to learn from past energy mistakes and create an appropriate regulatory and policy framework that works and benefits Africa.

Abstract: Natural gas has diverse content such as Methane, Ethane, Carbon dioxide, Hydrogen Sulfide, and other gases. In addition, natural gas is formed over a very long time, where it comes from fossil fuels. Natural gas that has been treated and produced products are called synthesis gas which can be used to make ammonia (NH₃). To produce ammonia, steam compounds (H₂O) are used which are reacted with natural gas to produce hydrogen (H₂) and Nitrogen (N₂) obtained from the air. Ammonia manufacturing can be done by several processes, namely desulfurization (natural gas purification), Steam Reforming, Shift Converter, CO₂ removal, methanation, and refrigeration units. The data used in this simulation is data on the ammonia plant at PT. Petrokimia Gresik. What is seen from this simulation is the influence of the composition of natural gas with variations in composition, namely 75% – 99% methane. The largest yield was obtained in the composition of 75% methane with an ammonia product yield of 82.34 tons/hour, this is because the division of the composition is divided propositionally into other compounds such as ethane, and propane, i-butane, etc. which have more H₂ content. Then there is the ratio of methane flow rate to steam using a variation of 1:3.5 - 1:7.5 where the largest ammonia product is obtained from a ratio of 1:7.5 with ammonia product yields of 84.79 tons/hour because more and more steam causes the formation of more hydrogen. Furthermore, there is a ratio of methane flow rate to air with a variation of 1:5.5 - 1:7.5 where the largest ammonia product is obtained from a ratio of 1:5.5 with an ammonia product yield of 84.87 tons/hour because the air content consists of N₂ and O₂, where if the O₂ content is a lot it will react with Methane so that the H₂ produced will be less if methane reacts also with O₂ not only with H₂O.

Abstract: Hydrogen is an impurity that is often present in LiXO₃ (X= Nb, Ta) single crystals and related materials. In this context, the diffusion of hydrogen is an important process because it may influence the overall conductivity of the material. We investigated the diffusional hydrogen uptake in LiNb_0.15Ta_0.85O₃ single crystals at 600 °C. For the experiments, O₂ is bubbled through liquid deuterated water (D₂O), which leads to a saturation of the gas atmosphere with D₂O that is incorporated into the crystal during isothermal annealing. The diffusivities of deuterium during uptake were determined by infra-red spectroscopy. We identified a fast process that can be associated with tracer diffusion and a second slower process with an almost three times lower diffusivity.

Abstract: Hydrogen embrittlement (HE) is a well-known issue, especially with ultrahigh-strength steels (UHSS). Various testing methods are utilised to study HE, but they typically require tensile test equipment, or are impractical due to limited stress control with standard geometries. We have developed a novel Tuning-fork test (TFT) to study HE susceptibility of steels with a new specimen geometry, which can be stressed accurately without tensile test equipment. The test method utilises in situ electrochemical hydrogen charging and constant displacement for stressing of the notched specimens by bending. Crack initiation and propagation are controlled with an isolated tensile stress region, and the failure process is monitored with a loadcell. TFT is a simple and fast testing method, which allows ranking of UHSSs, and to investigate, e.g., microstructural effects on susceptibility to HE and H-induced fracture processes. Here in this study, we present the state-of-the-art with the improved more precise second-generation TFT setup, which benefits from a more sensitive loadcell and a more stable fine-tuneable differential screw adjustment. We extend TFT to testing of martensitic steels with nominal hardness from 400 HBW to 600 HBW with the Incremental step loading technique (ISLT). The results show that TFT with ISLT is well applicable for ranking ultrahigh-strength steels based on their susceptibility to HE. Force-time data from ISLT can also be used for the determination of a material-specific threshold stress level, and the last step for the calculation of a crack initiation-time and time-to-fracture. However, the current manual operation of the loading screw can still limit maximum duration of a test.

Abstract: The primary barrier to hydrogen production through the aluminum-water reaction is the oxide layer which forms on the exterior surface of the aluminum. In this work, the passivation was minimized by optimizing the concentration of sodium hydroxide solution (0.3 - 0.5 M) promoted by NaAlO₂ at room temperature reaction conditions. The aluminum used is waste aluminum foil AA1235 chips having dimensions of 20 mm x 30 mm. The results showed that the hydrogen production rate increases as the NaOH solution concentration increases. The higher the solution’s pH, the shorter the hydrolysis process of the alumina layer, hence the hydrogen production is faster. Adding NaAlO₂ as a promoter could increase the hydrogen production rate compared to sole NaOH, i.e., 11.162 ml/minute and 9.86 ml/minute, respectively. This increase occurred significantly during the fast reaction stage. It indicates that the solution containing NaOH and NaAlO₂ work synergistically whereby NaOH can accelerate the reaction rate in the aluminum core and NaAlO₂ functions as the booster for producing Al(OH)₃.

Abstract: Utility of aluminum series AA5XXX, 6XXX, and 7XXX emerges. However, scrap waste remains unrecycled and ends up in municipal solid waste landfills. It is known that aluminum related reactions maybe problematic for landfill operations by generating undesired heat, liquid leachate, and gases. Aluminum produces hydrogen as it reacts readily with water at room temperature to form aluminum hydroxide. In most cases, it may not conventionally take place due to the presence of aluminum oxide that naturally coats the materials preventing it from direct contact with water. The layer can be detached using an acidic solution, such as HCl. HCl solution is prepared to remove the Al₂O₃ protective layer under acidic conditions. NaOH solution is added into the water to promote hydrogen production afterward. Aluminum scrap with a constant mass of 0.5 grams added to 250 ml of NaOH solution in which the concentrations varied by 0.5 M, 1.5 M, and 3 M. As the pretreatment, it was soaked into 1 M, 2 M, and 3 M HCl solutions for 1 minute. The measurement result shows that aluminum treated with 3 M HCl and reacted in 3 M NaOH yielded 532 ml of hydrogen gas. However, hydrogen concentration in total produced gas volume decreases as NaOH and HCl increase. This result is also confirmed using FTIR spectroscopy which shows the reaction with less NaOH concentration yielded more bayerite form.