Publications

In conjunction with John Zink Co. LLC the Chevron Energy Technology Company conducted a three part study evaluating potential issues with switching refinery process heaters from fuel gas to hydrogen fuel for the purpose of greenhouse gas emissions reduction via CO2 capture and storage.

The focus was on the following areas:

• Heater performance
• Burner performance and robustness
• Fuel gas system retrofit requirements

This paper will summarize the findings of the study.

The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However the hydrogen permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper various methods for consistent analysis of hydrogen permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of hydrogen permeability are introduced: (1) prediction of hydrogen flux under given conditions (2) comparability of hydrogen permeability (3) understanding of the anomalous temperature dependence of hydrogen permeability of Pd-Ag alloy membrane and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high hydrogen permeability together with strong resistance to hydrogen embrittlement.

Hydrogen recombiners (known in the nuclear industry as passive autocatalytic recombiners-PARs) in general can be utilized for mitigation of hydrogen in controlled areas where there is potential for hydrogen release and ventilation is not practical. Recombiners are widely implemented in the nuclear industry however there are other applications of recombiners outside the nuclear industry that have not yet been explored practically. The most notable benefit of recombiners over conventional hydrogen mitigation measures is their passive capability where power or operator actions are not needed for the equipment to remove hydrogen when it is present.

One of most significant concerns regarding the use of hydrogen recombiners in industry is their potential to ignite hydrogen at elevated concentrations (>6 vol%). The catalyst heated by the exothermal H2–O2 reaction is known to be a potential ignition source to cause hydrogen burns. An experimental program utilizing a full-size PAR at the Large-Scale Vented Combustion Test Facility (LSVCTF) has been carried out by Canadian Nuclear Laboratories (CNL) to investigate and understand the behaviour of hydrogen combustion induced by a PAR on a large-scale basis. A number of parameters external to the PAR have been explored including the effect of ambient humidity (steam) and temperature. The various aspects of this investigation will be discussed in this paper and examples of results are provided.

This study presents a computational fluid dynamic (CFD) study of Dimethyl Ether steam reforming (DME-SR) in a large scale Circulating Fluidized Bed (CFB) reactor. The CFD model is based on Eulerian–Eulerian dispersed flow and solved using commercial software (ANSYS FLUENT). The DME-SR reactions scheme and kinetics in the presence of a bifunctional catalyst of CuO/ZnO/Al₂O₃+ZSM-5 were incorporated in the model using in-house developed user-defined function. The model was validated by comparing the predictions with experimental data from the literature. The results revealed for the first time detailed CFB reactor hydrodynamics gas residence time temperature distribution and product gas composition at a selected operating condition of 300 °C and steam to DME mass ratio of 3 (molar ratio of 7.62). The spatial variation in the gas species concentrations suggests the existence of three distinct reaction zones but limited temperature variations. The DME conversion and hydrogen yield were found to be 87% and 59% respectively resulting in a product gas consisting of 72 mol% hydrogen. In part II of this study the model presented here will be used to optimize the reactor design and study the effect of operating conditions on the reactor performance and products.

In the context of the fatigue life design of components particularly those destined for use in hydrogen refuelling stations and fuel cell vehicles it is important to understand the hydrogen-induced fatigue crack growth (FCG) acceleration in steels. As such the mechanisms for acceleration and its influencing factors are reviewed and discussed in this paper with a special focus on the peculiar frequency dependence of the hydrogen-induced FCG acceleration. Further this frequency dependence is debated by introducing some potentially responsible elements along with new experimental data obtained by the authors.

This article is part of the themed issue ‘The challenges of hydrogen and metals’.

Link to document download on Royal Society Website

This study proposed a strategy for selecting an optimal propulsion system of a liquefied hydrogen tanker. Four propulsion system options were conceivable depending on whether the hydrogen BOG (boil-off gas) from the cryogenic cargo tanks was used for fuel or not. These options were evaluated in terms of their economic technological and environmental feasibilities. The comparison scope included not only main machinery but also the BOG handling system with electric generators. Cost-benefit analysis life-cycle costing including carbon tax and an energy efficiency design index were used as measures to compare the four alternative systems. The analytic hierarchy process made scientific decision-making possible. This methodology provided the priority of each attribute through the use of pairwise comparison matrices. Consequently the propulsion system using LNG with hydrogen BOG recovery was determined to be the optimal alternative. This system was appropriate for the tanker that achieved the highest evaluation score.

Hydrogen mixed natural gas for combustion can improve combustion characteristics and reduce carbon emission which has important engineering application value. A casing swirl burner model is adopted to numerically simulate and research the natural gas hydrogen mixing technology for combustion in gas boilers in this paper. Under the condition of conventional air atmosphere and constant air excess coefficient the six working conditions for hydrogen mixing proportion into natural gas are designed to explore the combustion characteristics and the laws of pollution emissions. The temperature distributions composition and emission of combustion flue gas under various working conditions are analyzed and compared. Further investigation is also conducted for the variation laws of NOx and soot generation. The results show that when the boiler heating power is constant hydrogen mixing will increase the combustion temperature accelerate the combustion rate reduce flue gas and CO2 emission increase the generation of water vapor and inhibit the generation of NOx and soot. Under the premise of meeting the fuel interchangeability it is concluded that the optimal hydrogen mixing volume fraction of gas boilers is 24.7%.

The influence of the previous electrolytic hydrogenation on the micromechanical properties and tribological behavior of the surface layers of iron and carbon steels has been studied. The concentrations of diffusion-moving and residual hydrogen in steels are determined depending on the carbon content. It is shown that the amount of sorbed hydrogen is determined by the density of dislocations and the relative volume of cementite. After desorption of diffusion-moving hydrogen the microhardness increases and materials plasticity decreases. The change of these characteristics decreases with the increase of carbon content in the steels. Internal stresses increase and redistribute under hydrogen desorption. Fragmentation of ferrite and perlite occurs as a result of electrolytic hydrogenation. Ferrite is characterized by the structure fragmentation and change of the crystallographic orientation of planes. The perlite structure shows the crushing of cementite plates and their destruction. The influence of hydrogen desorption on the microhardness of structural components of ferrite-perlite steels is shown. Large scattering of microhardness is found in perlite due to different diffusion rates of hydrogen because of the unequally oriented cementite plates. It was found that the tendency of materials to blister formation is reduced with the increase of carbon content. The influence of hydrogen on the tribological behaviour of steels under dry and boundary friction has been studied. It is shown that hydrogen desorption intensifies the materials wear. After hydrogen desorption tribological behaviour is determined by the adhesion interaction between the contacting pairs.

While most hydrogen research focuses on the technical and cost hurdles to a full-scale hydrogen economy little consideration has been given to the geopolitical drivers and consequences of hydrogen developments. The technologies and infrastructures underpinning a hydrogen economy can take markedly different forms and the choice over which pathway to take is the object of competition between different stakeholders and countries. Over time cross-border maritime trade in hydrogen has the potential to fundamentally redraw the geography of global energy trade create a new class of energy exporters and reshape geopolitical relations and alliances between countries. International governance and investments to scale up hydrogen value chains could reduce the risk of market fragmentation carbon lock-in and intensified geo-economic rivalry.

Since early 2020 Turkey has been considering the role of hydrogen in its energy future with a view to producing a hydrogen strategy in the next few months.  Unlike many other countries considering the role of hydrogen Turkey has only recently (October 2021) ratified the Paris Agreement addressing climate change and its interest is driven more by geopolitical strategic and energy security concerns.   Specifically with concerns about the high share of imported energy particularly gas from Russia it sees hydrogen as part of a policy to increase indigenous energy production.   Turkey already has a relatively high share of renewable power generation particularly hydro and recent solar auctions have resulted in low prices leading to a focus on potential green hydrogen production.  However it still generates over half of its electricity from fossil fuel including over 25% from coal and lignite.  Against that background it provides an interesting case study on some of the key aspects that a country needs to consider when looking to incorporate low-carbon hydrogen into the development of their energy economy.

The research paper can be found on their website