Steel for the hydrogen economy

At OCAS, we’re focusing on the assessment of actual and future infrastructure for the storage and transport of hydrogen in relation to the energy transition required to solve global warming.

Nuria Sanchez

At OCAS, we consider our expertise developed in our hydrogen lab to be one of our strongest assets for future solutions. Hydrogen is a clean energy carrier and will be increasingly used for renewable power energy storage or fuel-cell-powered cars and trucks. Moreover, hydrogen plays a major role in the decarbonisation of the steel-making industry.

OCAS AND HYDROGEN, A LONG TRACK RECORD

Over the past 17 years, OCAS has been building experience and competences concerning hydrogen-microstructure interactions, hydrogen embrittlement, and design of microstructures resistant to hydrogen environments. Those competences have been developed to support steel grade and coating development for industry and the energy and automotive markets. Some examples of OCAS’s research on hydrogen embrittlement are: line pipe grades resistant to H2S, high-strength steels with increased resistance to hydrogen delayed cracking, enamelling grades with higher resistance to fish-scale, new coatings acting as hydrogen barrier, etc. OCAS has a dedicated H-lab, industrial simulators and characterisation tools to support these studies and developments. In addition, the competences available at OCAS are used for industrial quality control of steel grades sensitive to hydrogen embrittlement. During the past few years, OCAS has established the methodology to control the hydrogen absorbed by highstrength steels during their production (pickling, electro-galvanising, etc.). Production control, and its link to the properties and process parameters, is key for further product optimisation.

HYDROGEN, FUTURE ENERGY VECTOR

As stated in the EU Hydrogen Strategy, it is crucial that hydrogen becomes a part of the energy system. Hydrogen can be used as a feedstock, a fuel, or to carry and store energy – and it has many possible applications across industry, transport, power and building sectors. The EU strategy also calls for a hydrogen logistical infrastructure that needs to be developed in order to distribute, transport, store and expand the use of hydrogen across Europe, which will lead to great opportunities for steel. In the Global Energy Transition framework, and looking to

steel opportunities, OCAS has continued to further develop its competences for the H2 economy. For this, a complete gap analysis on the necessary competences and experimental capabilities was finalised, concluding in an action plan for present and future deployment. Furthermore, the acquired competences from other markets have been used to initiate the developments of steel solutions for H distribution (H2 pipelines) and H storage (H2 highpressure vessels).

TRANSPORTING HYDROGEN SAFELY ACROSS EUROPE

In April 2021, in their EU Hydrogen backbone document, major European transmission system operators (or TSO companies) highlighted the need for new pipeline stretches across Europe to connect hydrogen hubs and countries in order to create a European hydrogen transmission network similar to what exists for Natural Gas today, over the coming 20 years. This document estimates the steel volume needs at about 5.5 million tonnes. Therefore, OCAS started to assess the compatibility of existing line pipe grades with hydrogen gas.

PRESSURISED HYDROGEN STORAGE

In the same context, increased capacity for H2 distribution and storage – including hydrogen refuelling stations – will be needed, leading to a critical demand for storage capacity: larger tank capacity, higher storage pressure and competitive costs. In this framework, growing markets for hydrogen steel vessel applications have been identified: — Mobility, industrial (truck, bus, forklift,…): this market consists of on-board tanks targeting minimum H2 pressure of 350 bar. Hydrogen forklifts are already in the industrialisation phase. — Mobility, refuelling stations: this market application is generally divided into low H2 pressure (<350 bar), middle H2

pressure (500 bar to 700 bar) and high H2 pressure (1000 bar) stations. — Distribution, trailers: this market focuses mostly on transportation of hydrogen at 200-300 bar and 300 kg per delivery.

However, the trend is moving upward, with the pressure and some new designs achieving 500 bar. However, hydrogen embrittlement, hydrogen diffusion, and the high cost of hydrogen storage vessels are outstanding problems that hinder the scale-up of the hydrogen economy. The severity of hydrogen embrittlement usually increases with increasing hydrogen pressure. For instance, in order to refuel a 700 bar onboard hydrogen storage cylinder in about 3 minutes, the pressure of a stationary hydrogen storage vessel may exceed 900 bar, which makes it challenging to reach a balance between the mitigation of hydrogen embrittlement and cost.

For more than a decade, OCAS has been building up hydrogen research competence to serve the needs related to tomorrow’s technological developments.

Dennis van Hoecke

The most abundant element in the universe, hydrogen, is also a promising source of clean fuel. At OCAS, we believe we are well armed to thoroughly tackle its technological challenges in multiple applications.

Marc-Antoine Thual

UNDERSTANDING HYDROGEN PICK-UP BY METALS

The pick-up of hydrogen by metals has been studied extensively in this context, primarily focusing on two aspects: the diffusibility of hydrogen inside the metal (‘how mobile it is’) and the solubility (‘how much can be stored’), i.e. how does hydrogen behave once it’s in the metal substrate. Less is known, however, about another key aspect of the occurrence of hydrogen embrittlement: at which rate can hydrogen enter through the surface into the metal in the first place? If the entrance rate can be hindered – or, ideally, even blocked – by a proper surface treatment or surface condition, then the subsequent degradation process will be slowed down and the lifetime of the metal component extended.

HYDROGEN AND STEEL PROPERTIES

Despite the vast number of articles that have been published related to hydrogen embrittlement, and the multiple attempts to explain the governing mechanisms, it is evident that hydrogen’s effect on mechanical properties in steel is still a challenging topic, and our understanding of the embrittlement mechanisms needs further deepening. Based on current knowledge, special implications for the design of steels for H2 distribution and storage are in place, with a focus on fatigue loading, fracture toughness, and potentially increased axial stress levels. In addition, implications for potentially large-deformation failure modes – such as burst, running ductile fractures, and (external) damage – are also addressed. How hydrogen embrittlement is affecting those design laws is still to be defined.

LINKING HYDROGEN TO MICROSTRUCTURE FOR FUTURE GRADES MATCHING INDUSTRY’S NEEDS

OCAS’s key competences on materials’ hydrogen embrittlement focus on bridging the structural design needs with metallurgical concepts of the materials’ microstructure and properties. Those process-structure-properties (P-S-P) links are being studied by means of determining hydrogen trapping and distribution among the microstructural features, and hydrogen embrittlement tests under relevant environments and modelling. For an unequivocal determination of the hydrogen microstructure interactions, deuterium (isotope hydrogen tracer) is being used.

NUMERICAL SIMULATION OF HYDROGEN INTERACTIONS

Finite element analysis models capable of describing hydrogen interactions with steel are key to assisting the interpretation of microstructure-hydrogen in-use properties. The scientific community is working on different approaches, from nano- to macroscale. OCAS is focusing on the micro-level to describe the hydrogen microstructure interactions – with the ultimate goal of assessing the risk of failure in metal components for the hydrogen economy.

OCAS’S INTERNATIONAL RECOGNITION

The OCAS hydrogen team is actively participating in drafting the Strategic Research and Innovation Agenda and the Annual Work Plans of Horizon Europe Clean Hydrogen Partnership. OCAS’s expertise is welcomed in many research consortia, such as FORGE, INiTiAl, and joint industry projects, such as DNV’s H2Pipe. OCAS experts contribute to standardisation bodies, including NACE, ISO, EFC and API. Our hydrogen research has been published in multiple scientifi c peer-reviewed journals and international conferences. Currently, OCAS is preparing its 4th edition of the International Conference on Metals and Hydrogen – ‘SteelyHydrogen 2022’ – attracting academic participants as well as participants from industry globally.

‘SteelyHydrogen’ combines high-level scientifi c contributions with to-the-point industrial applications, all in the pleasant, picturesque setting of Ghent’s city centre

Laura Moli Sanchez