Transmission, Distribution & Storage
Understanding Corrosion Morphology of Duplex Stainless Steel Wire in Chloride Electrolyte
Jul 2021
Publication
The corrosion morphology in grade 2205 duplex stainless steel wire was studied to understand the nature of pitting and the causes of the ferrite phase’s selective corrosion in acidic (pH 3) NaCl solutions at 60 °C. It is shown that the corrosion mechanism is always pitting which either manifests lacy cover perforation or densely arrayed selective cavities developing selectively on the ferrite phase. Pits with a lacy metal cover form in concentrated chloride solutions whereas the ferrite phase’s selective corrosion develops in diluted electrolytes showing dependency on the chloride-ion concentration. The pit perforation is probabilistic and occurs on both austenite and ferrite grains. The lacy metal covers collapse in concentrated solutions but remain intact in diluted electrolytes. The collapse of the lacy metal cover happens due to hydrogen embrittlement. Pit evolution is deterministic and occurs selectively in the ferrite phase in light chloride solutions.
Analysis of Stress Corrosion Cracking in X80 Pipeline Steel: An Approach from the Theory of Critical Distances
Dec 2018
Publication
This paper presents an analysis of Stress Corrosion Cracking (SCC) based on the Theory of Critical Distances (TCD). The research is based on an experimental program composed of fracture specimens with notch radius varying from 0 mm (crack-like defect) up to 1 mm and tensile specimens. A pipeline steel was used in this work (X80). It has been analysed in one hydrogen embrittlement situation. The study has been completed with Finite Elements Simulation analysis. The capacity of the TCD to analyse SCC processes has been proven.
A Fracture Analysis of Ti-10Mo-8V-1Fe-3.5Al Alloy Screws during Assembly
Oct 2016
Publication
Titanium screws have properties that make them ideal for applications that require both a high strength-to-weight ratio and corrosion resistance such as fastener applications for aviation and aerospace. The fracture behavior of Ti-10Mo-8V-1Fe-3.5Al (TB3) alloy screws during assembly was explored. Besides visual examination other experimental techniques used for the investigation are as follows: (1) fracture characteristics and damage morphology via scanning electron microscopy (SEM); (2) chemical constituents via energy dispersive spectroscopy (EDS) and hydrogen concentration testing; (3) metallographic observation; (4) stress durability embrittlement testing; and (5) torsion simulation testing. Results show that the fracture mode of the screws is brittle. There is no obvious relation to hydrogen-induced brittle. The main reason for the fracture of titanium alloy screws is internal defects around which oxygen content is high increasing brittleness. The internal defects of screws result from grain boundary cracking caused by hot forging.
Controllable H2 Generation by Formic Acid Decomposition on a Novel Pd/Templated Carbon Catalyst
Nov 2020
Publication
A novel Pd/templated carbon catalyst (Pd/TC) was developed characterized and tested in the dehydrogenation of formic acid (FA) under mild conditions with the possibility to control the H2 generation rate in the absence or presence of HCOONa (SF) by adjusting the Pd:FA and/or FA:SF ratios. The characterization results of the templated carbon obtained by the chemical vapor deposition of acetylene on NaY zeolite revealed different structural and morphological properties compared to other C-based supports. Therefore it was expected to induce a different catalytic behavior for the Pd/TC catalyst. Indeed the TC-supported Pd catalyst exhibited superior activity in the decomposition of FA even at room temperature with turnover frequencies (TOFs) of up to 143.7 and 218.8 h−1 at 60 °C. The H2 generation rate increased with an increasing temperature while the H2 yield increased with a decreasing FA concentration. Constant generation of gaseous flow (H2 + CO2) was achieved for 11 days by the complete dehydrogenation of FA at room temperature using a 2 M FA solution and Pd:FA = 1:2100. The presence of SF in the reaction medium significantly enhanced the H2 generation rate (535 h−1 for FA:SF = 3:1 and 60 °C).
NanoSIMS Analysis of Hydrogen and Deuterium in Metallic Alloys: Artefacts and Best Practice
Apr 2021
Publication
Hydrogen embrittlement can cause catastrophic failure of high strength alloys yet determining localised hydrogen in the microstructure is analytically challenging. NanoSIMS is one of the few techniques that can map hydrogen and deuterium in metal samples at microstructurally relevant length scales. Therefore it is essential to understand the artefacts and determine the optimum methodology for its reliable detection. An experimental methodology/protocol for NanoSIMS analysis of deuterium (as a proxy for hydrogen) has been established uncovering unreported artefacts and a new approach is presented to minimise these artefacts in mapping hydrogen and deuterium in alloys. This method was used to map deuterium distributions in electrochemically charged austenitic stainless steel and precipitation hardened nickel-based alloys. Residual deuterium contamination was detected in the analysis chamber as a result of deuterium outgassing from the samples and the impact of this deuterium contamination was assessed by a series of NanoSIMS experiments. A new analysis protocol was developed that involves mapping deuterium in the passive oxide layer thus mitigating beam damage effects that may prevent the detection of localised deuterium signals when the surface is highly deuterated.
Hydrogen-Based Energy Storage Systems for Large-Scale Data Center Applications
Nov 2021
Publication
Global demand for data and data access has spurred the rapid growth of the data center industry. To meet demands data centers must provide uninterrupted service even during the loss of primary power. Service providers seeking ways to eliminate their carbon footprint are increasingly looking to clean and sustainable energy solutions such as hydrogen technologies as alternatives to traditional backup generators. In this viewpoint a survey of the current state of data centers and hydrogen-based technologies is provided along with a discussion of the hydrogen storage and infrastructure requirements needed for large-scale backup power applications at data centers.
Formation Criterion of Hydrogen-Induced Cracking in Steel Based on Fracture Mechanics
Nov 2018
Publication
A new criterion for hydrogen-induced cracking (HIC) that includes both the embrittlement effect and the loading effect of hydrogen was obtained theoretically. The surface cohesive energy and plastic deformation energy are reduced by hydrogen atoms at the interface; thus the fracture toughness is reduced according to fracture mechanics theory. Both the pressure effect and the embrittlement effect mitigate the critical condition required for crack instability extension. During the crack instability expansion the hydrogen in the material can be divided into two categories: hydrogen atoms surrounding the crack and hydrogen molecules in the crack cavity. The loading effect of hydrogen was verified by experiments and the characterization methods for the stress intensity factor under hydrogen pressure in a linear elastic model and an elastoplastic model were analyzed using the finite-element simulation method. The hydrogen pressure due to the aggregation of hydrogen molecules inside the crack cavity regularly contributed to the stress intensity factor. The embrittlement of hydrogen was verified by electrolytic charging hydrogen experiments. According to the change in the atomic distribution during crack propagation in a molecular dynamics simulation the transition from ductile to brittle fracture and the reduction in the fracture toughness were due to the formation of crack tip dislocation regions suppressed by hydrogen. The HIC formation mechanism is both the driving force of crack propagation due to the hydrogen gas pressure and the resisting force reduced by hydrogen atoms.
Metastable Metal Hydrides for Hydrogen Storage
Oct 2012
Publication
The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however many of the high capacity “reversible” hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. On the other hand the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.
Evaluation of Corrosion, Mechanical Properties and Hydrogen Embrittlement of Casing Pipe Steels with Different Microstructure
Dec 2021
Publication
In the research the corrosion and mechanical properties as well as susceptibility to hydrogen embrittlement of two casing pipe steels were investigated in order to assess their serviceability in corrosive and hydrogenating environments under operation in oil and gas wells. Two carbon steels with different microstructures were tested: the medium carbon steel (MCS) with bainitic microstructure and the medium-high carbon steel (MHCS) with ferrite–pearlite microstructure. The results showed that the corrosion resistance of the MHCS in CO2-containing acid chloride solution simulating formation water was significantly lower than that of the MCS which was associated with microstructure features. The higher strength MCS with the dispersed microstructure was less susceptible to hydrogen embrittlement under preliminary electrolytic hydrogenation than the lower strength MHCS with the coarse-grained microstructure. To estimate the embrittlement of steels the method of the FEM load simulation of the specimens with cracks was used. The constitutive relations of the true stress–strain of the tested steels were defined. The stress and strain dependences in the crack tip were calculated. It was found that the MHCS was characterized by the lower plasticity on the stage of the neck formation of the specimen and the lower fracture toughness than the other one. The obtained results demonstrating the limitations of the usage of casing pipes made of the MHCS with the coarse-grained ferrite/pearlite microstructure in corrosive and hydrogenating environments were discussed.
Hydrogen Storage Behavior of TiFe Alloy Activated by Different Methods
Feb 2021
Publication
TiFe activation for hydrogen uptake was conducted through different methods and ball milling with ethanol proved to be the most effective one. TiFe alloy after activation could absorb 1.2 wt% hydrogen at room temperature with absorption and desorption plateaus of 0.5 MPa and 0.2 MPa respectively. Investigation on microstructure and chemical state of TiFe sample after milled with ethanol suggested that the well spread metallic Ti and Fe elements helped hydrogen uptake and release. The activation of TiFe alloy by milling with ethanol was achieved at ambient conditions with ease successfully and possibly can be used for large scale production
A Review on the Properties of Iron Aluminide Intermetallics
Jan 2016
Publication
Iron aluminides have been among the most studied intermetallics since the 1930s when their excellent oxidation resistance was first noticed. Their low cost of production low density high strength-to-weight ratios good wear resistance ease of fabrication and resistance to high temperature oxidation and sulfurization make them very attractive as a substitute for routine stainless steel in industrial applications. Furthermore iron aluminides allow for the conservation of less accessible and expensive elements such as nickel and molybdenum. These advantages have led to the consideration of many applications such as brake disks for windmills and trucks filtration systems in refineries and fossil power plants transfer rolls for hot-rolled steel strips and ethylene crackers and air deflectors for burning high-sulfur coal. A wide application for iron aluminides in industry strictly depends on the fundamental understanding of the influence of (i) alloy composition; (ii) microstructure; and (iii) number (type) of defects on the thermo-mechanical properties. Additionally environmental degradation of the alloys consisting of hydrogen embrittlement anodic or cathodic dissolution localized corrosion and oxidation resistance in different environments should be well known. Recently some progress in the development of new micro- and nano-mechanical testing methods in addition to the fabrication techniques of micro- and nano-scaled samples has enabled scientists to resolve more clearly the effects of alloying elements environmental items and crystal structure on the deformation behavior of alloys. In this paper we will review the extensive work which has been done during the last decades to address each of the points mentioned above.
Enhanced Hydrogen Storage Properties of Mg by the Synergistic Effect of Grain Refinement and NiTiO 3 Nanoparticles
May 2021
Publication
As a promising hydrogen storage material the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics. In this paper three kinds of NiTiO3 catalysts with different mole ratio of Ni to Ti were successfully synthesized and doped into nanocrystalline Mg to improve its hydrogen storage properties. Experimental results indicated that all the Mg-NiTiO3 composites showed prominent hydrogen storage performance. Especially the Mg-NiTiO3/TiO2 composite could take up hydrogen at room temperature and the apparent activation energy for hydrogen absorption was dramatically decreased from 69.8 ± 1.2 (nanocrystalline Mg) kJ/mol to 34.2 ± 0.2 kJ/mol. In addition the hydrogenated sample began to release hydrogen at about 193.2 °C and eventually desorbed 6.6 wt% H2. The desorption enthalpy of the hydrogenated Mg-NiTiO3 -C was estimated to be 78.6 ± 0.8 kJ/mol 5.3 kJ/mol lower compared to 83.9 ± 0.7 kJ/mol of nanocrystalline Mg. Besides the sample revealed splendid cyclic stability during 20 cycles. No obvious recession occurred in the absorption and desorption kinetics and only 0.3 wt% hydrogen capacity degradation was observed. Further structural analysis demonstrates that nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO3 -C composite which might serve as a reference for future design of highly effective hydrogen storage materials.
Critical Review of Models for H2-permeation Through Polymers with Focus on the Differential Pressure Method
May 2021
Publication
To reduce loss of hydrogen in storage vessels with high energy-to-weight-ratio new materials especially polymers have to be developed as barrier materials. Very established methods for characterization of barrier materials with permeation measurements are the time-lag and flow rate method along with the differential pressure method which resembles the nature of hydrogen vessel systems very well. Long measurement durations are necessary to gain suitable measurement data for these evaluation methods and often restrictive conditions have to be fulfilled. For these reasons common models for hydrogen permeation through single-layer and multi-layer membranes as well as models for hydrogen gas properties were collected and reviewed. Using current computer power together with these models can reduce measurement time for characterization of the barrier properties of materials while additional information about the quality of the measurement results is obtained.
Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review
Jan 2021
Publication
Hydrogen is receiving increasing attention as a versatile energy vector to help accelerate the transition to a decarbonised energy future. Gas turbines will continue to play a critical role in providing grid stability and resilience in future low-carbon power systems; however it is recognised that this role is contingent upon achieving increased thermal efficiencies and the ability to operate on carbon-neutral fuels such as hydrogen. An important consideration in the development of gas turbine combustors capable of operating with pure hydrogen or hydrogen-enriched natural gas are the significant changes in thermoacoustic instability characteristics associated with burning these fuels. This article provides a review of the effects of burning hydrogen on combustion dynamics with focus on swirl-stabilised lean-premixed combustors. Experimental and numerical evidence suggests hydrogen can have either a stabilising or destabilising impact on the dynamic state of a combustor through its influence particularly on flame structure and flame position. Other operational considerations such as the effect of elevated pressure and piloting on combustion dynamics as well as recent developments in micromix burner technology for 100% hydrogen combustion have also been discussed. The insights provided in this review will aid the development of instability mitigation strategies for high hydrogen combustion.
Sizing Hydrogen Energy Storage in Consideration of Demand Response in Highly Renewable Generation Power Systems
May 2018
Publication
From an environment perspective the increased penetration of wind and solar generation in power systems is remarkable. However as the intermittent renewable generation briskly grows electrical grids are experiencing significant discrepancies between supply and demand as a result of limited system flexibility. This paper investigates the optimal sizing and control of the hydrogen energy storage system for increased utilization of renewable generation. Using a Finnish case study a mathematical model is presented to investigate the optimal storage capacity in a renewable power system. In addition the impact of demand response for domestic storage space heating in terms of the optimal sizing of energy storage is discussed. Finally sensitivity analyses are conducted to observe the impact of a small share of controllable baseload production as well as the oversizing of renewable generation in terms of required hydrogen storage size.
Hydrogen - A Sustainable Energy Carrier
Jan 2017
Publication
Hydrogen may play a key role in a future sustainable energy system as a carrier of renewable energy to replace hydrocarbons. This review describes the fundamental physical and chemical properties of hydrogen and basic theories of hydrogen sorption reactions followed by the emphasis on state-of-the-art of the hydrogen storage properties of selected interstitial metallic hydrides and magnesium hydride especially for stationary energy storage related utilizations. Finally new perspectives for utilization of metal hydrides in other applications will be reviewed.
Influence of Synthesis Gas Components on Hydrogen Storage Properties of Sodium Aluminium Hexahydride
Feb 2021
Publication
A systematic study of different ratios of CO CO2 N2 gas components on the hydrogen storage properties of the Na3AlH6 complex hydride with 4 mol% TiCl3 8 mol% aluminum and 8 mol% activated carbon is presented in this paper. The different concentrations of CO and CO2in H2 and CO CO2 N2 in H2 mixture were investigated. Both CO and CO2gas react with the complex hydride forming Al oxy-compounds NaOH and Na2CO3 that consequently cause serious decline in hydrogen storage capacity. These reactions lead to irreversible damage of complex hydride under the current experimental condition. Thus after 10 cycles with 0.1 vol % CO + 99.9 vol %H2 and 1 vol % CO + 99 vol %H2 the dehydrogenation storage capacity of the composite material decreased by 17.2% and 57.3% respectively. In the case of investigation of 10 cycles with 1 vol % CO2 + 99 vol % H2 gas mixture the capacity degradation was 53.5%. After 2 cycles with 10 vol % CO +90 vol % H2 full degradation was observed whereas after 6 cycles with 10 vol % CO2+ 90 vol % H2 degradation of 86.8% was measured. While testing with the gas mixture of 1.5 vol % CO + 10 vol % CO2+ 27 vol % H2 + 61.5 vol % N2 the degradation of 94% after 6 cycles was shown. According to these results it must be concluded that complex aluminum hydrides cannot be used for the absorption of hydrogen from syngas mixtures without thorough purification.
Hydrogen Embrittlement and Oxide Layer Effect in the Cathodically Charged Zircaloy-2
Apr 2020
Publication
Poland The present paper is aimed at determining the less investigated effects of hydrogen uptake on the microstructure and the mechanical behavior of the oxidized Zircaloy-2 alloy. The specimens were oxidized and charged with hydrogen. The different oxidation temperatures and cathodic current densities were applied. The scanning electron microscopy X-ray electron diffraction spectroscopy hydrogen absorption assessment tensile and nanoindentation tests were performed. At low oxidation temperatures an appearance of numerous hydrides and cracks and a slight change of mechanical properties were noticed. At high-temperature oxidation the oxide layer prevented the hydrogen deterioration of the alloy. For nonoxidized samples charged at different current density nanoindentation tests showed that both hardness and Young’s modulus revealed the minims at specific current value and the stepwise decrease in hardness during hydrogen desorption. The obtained results are explained by the barrier effect of the oxide layer against hydrogen uptake softening due to the interaction of hydrogen and dislocations nucleated by indentation test and hardening caused by the decomposition of hydrides. The last phenomena may appear together and result in hydrogen embrittlement in forms of simultaneous hydrogen-enhanced localized plasticity and delayed hydride cracking.
Assessment of Operational Degradation of Pipeline Steels
Jun 2021
Publication
This paper summarizes a series of the authors’ research in the field of assessing the operational degradation of oil and gas transit pipeline steels. Both mechanical and electrochemical properties of steels are deteriorated after operation as is their resistance to environmentally-assisted cracking. The characteristics of resistance to brittle fracture and stress corrosion cracking decrease most intensively which is associated with a development of in-bulk dissipated microdamages of the material. The most sensitive indicators of changes in the material’s state caused by degradation are impact toughness and fracture toughness by the J-integral method. The degradation degree of pipeline steels can also be evaluated nondestructively based on in-service changes in their polarization resistance and potential of the fracture surface. Attention is drawn to hydrogenation of a pipe wall from inside as a result of the electrochemical interaction of pipe metal with condensed moisture which facilitates operational degradation of steel due to the combined action of operating stresses and hydrogen. The development of microdamages along steel texture was evidenced metallographically as a trend to the selective etching of boundaries between adjacent bands of ferrite and pearlite and fractographically by revealing brittle fracture elements on the fracture surfaces namely delamination and cleavage indicating the sites of cohesion weakening between ferrite and pearlite bands. The state of the X52 steel in its initial state and after use for 30 years was assessed based on the numerical simulation method.
Validation of Selected Optical Methods for Assessing Polyethylene (PE) Liners Used in High Pressure Vessels for Hydrogen Storage
Jun 2021
Publication
A polyethylene (PE) liner is the basic element in high-pressure type 4 composite vessels designed for hydrogen or compressed natural gas (CNG) storage systems. Liner defects may result in the elimination of the whole vessel from use which is very expensive both at the manufacturing and exploitation stage. The goal is therefore the development of efficient non-destructive testing (NDT) methods to test a liner immediately after its manufacturing before applying a composite reinforcement. It should be noted that the current regulations codes and standards (RC&S) do not specify liner testing methods after manufacturing. It was considered especially important to find a way of locating and assessing the size of air bubbles and inclusions and the field of deformations in liner walls. It was also expected that these methods would be easily applicable to mass-produced liners. The paper proposes the use of three optical methods namely visual inspection digital image correlation (DIC) and optical fiber sensing based on Bragg gratings (FBG). Deformation measurements are validated with finite element analysis (FEA). The tested object was a prototype of a hydrogen liner for high-pressure storage (700 bar). The mentioned optical methods were used to identify defects and measure deformations.
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