Direct Hydrogen Reduction Research Articles

Carburization Behavior of High-Grade Pellets After Direct Reduction in Pure Hydrogen

AbstractCarburization is a critical aspect in the iron and steel industry as it significantly affects the mechanical and chemical properties of the final product. This study provides a comprehensive analysis of the carburization potential of high-grade quality iron ore pellets after direct reduction in pure hydrogen. The results show that the porosity of the pellets has a significant impact on the efficiency and success of the direct reduction process with hydrogen. The reduction process can be completed at a lower temperature in pure hydrogen compared to carbon monoxide, with the iron carbide concentration peaking at temperatures up to 500 °C before decreasing with further temperature increases. The uniform distribution of SiO2, Al2O3, and CaO is critical to the carburizing process and affects the final properties of the steel. An increased degree of metallization and porosity are associated with an improved carburizing tendency. This study highlights the intricate interplay between temperature, carbon sources, and the resulting equilibrium concentration of iron carbides and provides insights into the complex dynamics of this phenomenon. Graphical Abstract

Preface to the Proceedings of the 5th European Academic Symposium on EAF Steelmaking

The European Academic Symposium on EAF Steelmaking (EASES) is a series of events targeted at researchers and doctoral candidates working with different aspects of electric arc furnace (EAF) steelmaking. Previously, four events were organised in 2015, 2016, 2018, and 2021 in Aachen, Germany. The 5th European Academic Symposium on EAF Steelmaking (EASES 2023) was organised jointly by the RWTH Aachen University (Department for Industrial Furnaces and Heat Engineering) and University of Oulu (Process Metallurgy Research Unit) and held at the University of Oulu in Oulu, Finland on 5-7 June 2023. A total of 29 presentations were held at the event, out of which 13 featured an accompanying full paper. After the symposium, the authors of the full papers were invited to submit their manuscripts to be included in the proceedings. The proceedings consist of a total of 12 peer-reviewed papers published in the IOP Conference Series: Materials Science and Engineering. Based on the presentations, the development of modelling and monitoring tools for process optimization, the use of biochar to replace fossil carbon for slag foaming, and the use of hydrogen as an alternative burner fuel were identified as current hot topics. In the future, the importance of the EAF process is expected to increase further due to the increasing availability of scrap and plans for ore-based production routes based on hydrogen direct reduction.

Flexible industrial power-to-X production enabling large-scale wind power integration: A case study of future hydrogen direct reduction iron production in Finland

Hydrogen Direct Reduction of Iron (HDRI) combined with renewable electricity is an attractive option for low-carbon steel production. In this paper, we present a novel and computationally efficient techno-economic power-to-x-plant optimization model which is then applied to an HDRI plant located in Finland. Plant dimensioning was carried out in several current and future power market and regulatory scenarios. We predict a production cost of 373 €/t for hot briquetted iron, and 351 €/t for a future scenario of 2025–2030. When the recently introduced EU rules for renewable fuels of non-biological origin are applied, the production costs increased by 30–46 €/t. The rules also have a significant increasing effect on the required hydrogen storage. The flexibility of the direct reduction shaft emerged as an important parameter affecting the required hydrogen storage as well as total production cost. The results of this paper hold significance for the optimal design of future low-carbon steel plants.

Multiscale modeling of non-catalytic gas-solid reactions applied to the hydrogen direct reduction of iron ore in moving-bed reactor

Direct hydrogen reduction (H-DR) is a promising technology for green ironmaking. Given the absence of commercial H-DR data, computational simulation is a powerful tool for engineering and overcoming the complexity of the system. This study develops a multiscale moving-bed reactor model to simulate non-catalytic gas-solid reactions and evaluate parameters at the pellet scale that hierarchically impact the performance at reactor scale. The reactor and solid particles are treated as coupled physical domains, enabling the computation of the solid transformations along both scales. Predictions for H-DR process highlight the substantial supply of H2 molar flow in enhancing reactor performance. A sensitivity multivariate analysis revealed the significant effect of pellet structural characteristics and gas inlet conditions on the process. Increased pellet porosity offers flexibility for process optimization, enabling the use of lower H2 percentages and temperatures. These findings provide valuable insights into optimizing H-DR process, improving energy efficiency, and better H2 utilization.

Numerical Simulation of the Hydrogen-Based Directly Reduced Iron Melting Process

In the context of carbon reduction and emission reduction, the new process of electric arc furnace (EAF) steelmaking based on direct hydrogen reduction is an important potential method for the green and sustainable development of the steel industry. Within an electric furnace for the hydrogen-based direct reduction of iron, after hydrogen-based directly reduced iron (HDRI) is produced through a shaft furnace, HDRI is melted or smelted in an EAF to form final products such as high-purity iron or high-end special steel. As smelting proceeds in the electric furnace, it is easy for pieces of HDRI to bond to each other and become larger pieces; they may even form an “iceberg”, and this phenomenon may then worsen the smelting working conditions. Therefore, the melting of HDRI is the key to affecting the smelting cycle and energy consumption of EAFs. In this study, based on the basic characteristics of HDRI, we established an HDRI melting model using COMSOL Multiphysics 6.0 and studied the HDRI melting process, utilizing pellets with a radius of 8 mm. The results of our simulation show that the HDRI melting process can be divided into three different stages: generating a solidified steel layer, melting the solidified steel layer, and melting HDRI bodies. Moreover, multiple HDRI processes are prone to bonding in the melting process. Increasing the spacing between pieces of HDRI and increasing the preheating temperature used on the HDRI can effectively reduce the aforementioned bonding phenomenon. When the melting pool temperature is 1873 K, increasing the spacing of HDRI to 10 mm and increasing the initial HDRI temperature to 973 K was shown to effectively reduce or eliminate the bonding phenomenon among pieces of HDRI. In addition, with the increase in the melting pool temperature, the time required for melting within the three stages of the HDRI melting process shortened, and the melting speed was accelerated. With the increase in the temperature used to preheat the HDRI, the duration of the solidified steel layer’s existence was also shortened, but this had no significant impact on the time required for the complete melting of HDRI. This study provides a theoretical basis for the optimization of the HDRI process within EAFs.

Comparative Technical and Economic Analyses of Hydrogen-Based Steel and Power Sectors

Decarbonizing the current steel and power sectors through the development of the hydrogen direct-reduction iron ore–electric arc furnace route and the 100% hydrogen-fired gas turbine cycle is crucial. The current study focuses on three clusters of research works. The first cluster covers the investigation of the mass and energy balance of the route and the subsequent application of these values in experiments to optimize the reduction yield of iron ore. In the second cluster, the existing gas turbine unit was selected for the complete replacement of natural gas with hydrogen and for finding the most optimal mass and energy balance in the cycle through an Aspen HYSYS model. In addition, the chemical kinetics in the hydrogen combustion process were simulated using Ansys Chemkin Pro to research the emissions. In the last cluster, a comparative economic analysis was conducted to identify the levelized cost of production of the route and the levelized cost of electricity of the cycle. The findings in the economic analysis provided good insight into the details of the capital and operational expenditures of each industrial sector in understanding the impact of each kg of hydrogen consumed in the plants. These findings provide a good basis for future research on reducing the cost of hydrogen-based steel and power sectors. Moreover, the outcomes of this study can also assist ongoing, large-scale hydrogen and ammonia projects in Uzbekistan in terms of designing novel hydrogen-based industries with cost-effective solutions.

Modeling the First Hydrogen Direct Reduction Pilot Reactor for Ironmaking in the USA Using Finite Element Analysis and Its Validation Using Pilot Plant Trial Data

Direct reduction of hematite pellets with hydrogen (H2) was used to produce directly reduced iron (DRI) in a pilot scale reactor at a pellet feed rate of 21.4 kg/h. At a steady state, operational parameters of the pilot plant (gas recycling rate and inlet temperature) along with key reactor output parameters, the pellet metallization, and the internal temperature profile of the reactor were reported for two scenarios with high recycle and low recycle rate of H2. Scenario 1, with a high recycle rate of 400 L/min H2 along with external heating of 870 °C, gave an average metallization of 91.8%, while Scenario 2, with low recycle rate of 100 L/min H2 and external heating of 850 °C gave a metallization of 67.8% due to the higher moles of H2 available for reduction and the external energy required for the endothermic reduction reaction in Scenario 1 as compared with Scenario 2. Finite element analysis was used to build a model of the shaft reactor, which was validated against the metallization and internal temperature profile data. The average metallization values predicted by the model were very close to the metallization values obtained from the pilot plant samples, with 90.9% average metallization for Scenario 1 and 65.6% average metallization for Scenario 2. The internal temperature profiles in the lower region of the reactor obtained from the model were very close to these pilot plant data, with a maximum difference of 52.7 °C and 67.6 °C for Scenarios 1 and 2, respectively. The pilot plant reactor model was used extensively in the commissioning of the pilot plant and to predict the startup outcomes for a given set of operating parameters.

The perspective of hydrogen direct reduction of iron

The work proposes a perspective on the direct reduction of iron (DRI) using hydrogen. Typically, iron is produced in blast furnaces (BFI) by the reduction of iron ore with carbon-rich materials such as coal or coke. Greenhouse emissions may be drastically reduced by introducing DRI coal/oil-based, and further reduced by using methane-based DRI. By increasing the share of hydrogen in the reducing gas by the addition of green hydrogen, the GHG emission further reduces. While hydrogen DRI becomes competitive for GHG emission with methane-based DRI once the electricity indirect emissions of GHG fall below 120 g CO2 per kWh, the full potential of hydrogen DRI is achieved phased with the complete uptake of green hydrogen, which is an essential component of a zero-emission stable electric grid fed with non-dispatchable renewables, as well as zero-emission non-electric total primary energy uses. The market perspective for hydrogen DRI in the short term is quite promising, and it is gaining significant attention and interest within the iron and steel industry. Key factors contributing to its market perspective are decarbonization and climate goals, policy support and incentives, investor interest, industry collaboration, technological advancements, sustainability, and brand value.

Decarbonization strategies for steel production with uncertainty in hydrogen direct reduction

The steel industry remains difficult to decarbonize because of its high dependence on coal. This industry plans to use hydrogen instead of coal via hydrogen direct reduction. Although this technology reduces steel emissions significantly, considerable uncertainty remains. This study aimed to explore how internal and external uncertainties in hydrogen direct reduction affect uncertainties in steel decarbonization using an energy system model and Monte Carlo simulation. This study assumed that the investment cost of hydrogen direct reduction, hydrogen price, and emission coefficient of hydrogen are uncertain. The uncertainty in hydrogen prices was the most important factor affecting hydrogen use, emissions, and emission reduction costs. Moreover, the probability of steel emissions deviating from their target level was highest when hydrogen price was uncertain. This study contributes to the development of strategies for steel decarbonization and assists policymakers in probabilistic decision making with uncertainty regarding hydrogen direct reduction. Policymakers should understand the relationship between the steel, power, and hydrogen sectors and manage external uncertainties in the power and hydrogen sectors because steel decarbonization largely depends on renewable electricity and electrolyzer costs.

Hydrogen direct reduction and reoxidation behaviour of high-grade pellets

High grade pellets with basicity index close to 0.5 were directly reduced in pure hydrogen atmosphere. The reduction experiments were performed in the temperature range 800–1000 °C at the pressure of 8 bar. The pellets internal structure was analysed through micro tomography observations in the unreduced and reduced conditions. After reduction, the pellets showed a variation of porosity up to more than 15% with a remarkable change in the pore dimensions and aspect. Given the pores aspect variations, tortuosity strongly varied. This is believed to have large influence on the pellets reduction kinetics depending on the reduction conditions. After reduction, the pellets were re-oxidized in the temperature range 200–700 °C for different times. Up to 500 °C the weight increase due to oxidation resulted very slow, for higher temperatures the re-oxidation behaviour showed a very remarkable acceleration.

Mechanism study on gas-based reduction swelling behavior of ultra-high grade pellets

Utilizing super-concentrate for direct hydrogen reduction in pelletizing which decrease energy consumption and improve smelting quality are critical steps towards achieving the dual carbon goal. The reduction swelling behavior and its corresponding mechanism of ultra-high-grade pellets were studied from multi-dimensions combing visualization detection, micromorphological analysis, and first-principles molecular dynamics simulation in present work. The results showed that for the reduction no matter in CO or H2 atmosphere, the ultra-high grade pellets expand abnormally. Whereas the increase of SiO2 content and the selection of H2 atmosphere can effectively inhibited the reduction swelling behavior of pellets, while Al2O3 content had only a slight effect. The cause of catastrophic expansion was related to the various formation of new-born iron that it exhibited angular during CO reduction while became flatter with SiO2 addition or by H2 reduction. The simulation results were validated the accuracy since the structure and energy changes during iron oxide reduction were corresponding to the experimental observations. C and Fe mainly formed chemical bonds while H and Fe primary produced physical adsorption during FexO reduction. Combing the comprehensive effect of adsorption energy, electrostatic force, and energy change, it was tended to create iron whiskers by CO reduction contrary to H2 reduction. It was conductive to generate iron whisker after Si doped in FexO. However, the decrease of pellets RSI with SiO2 addition in H2 reduction was caused by the increase of pellet porosity, which provided space for the growth of iron whisker. With the increase of Si doping amount in CO reduction, iron whiskers gradually changed from thin to chunky, resulting in more uniform growth of iron whiskers and uniform stress, which brought about a decrease in pellet reduction expansion rate contrarily.

Hydrogen direct reduction ironmaking process for zero CO2 emission: A study on the effect of particle properties changes during the multiple non-catalytic gas-solid reactions

Direct hydrogen reduction (H-DR) is one of the most attractive technologies for decarbonization in the iron and steelmaking industries. Improvements in process efficiency depend on a multi-scale evaluation since the industrial performance is significantly affected by transient non-catalytic gas–solid reactions at the pellet scale. This study investigated the effect of temperature-dependent morphological changes in industrially produced pellets during isothermal reduction temperatures from 600 to 900 °C. A 2D axisymmetric pellet grain model using the finite element method and considering the three reduction reactions and the mass and heat transfer phenomena was developed to evaluate the evolution of the solid transformations along the pellet radius during the reduction time. Based on the experimental results, structural properties of the pellets, such as grain size, tortuosity, and transient porosity, were incorporated into the proposed pellet model. The simulation results under different conditions show good agreement with experimental data when changes in the pellet tortuosity are considered, particularly at higher temperatures. Furthermore, predictions of solid and gas concentration and temperature profiles over the pellet radius during the reduction process evidenced the transient behavior of the process. The findings represent an important contribution to the degree of knowledge on the H-DR process application by providing information on the effect of structural parameters of the pellets for the current status of mathematical models of the process.

Techno-economic analysis of wind-powered green hydrogen production to facilitate the decarbonization of hard-to-abate sectors: A case study on steelmaking

Green hydrogen is among the most promising energy vectors that may enable the decarbonization of our society. The present study addresses the decarbonization of hard-to-abate sectors via the deployment of sustainable alternatives to current technologies and processes where the complete replacement of fossil fuels is deemed not nearly immediate. In particular, the investigated case study tackles the emission reduction potential of steelmaking in the Italian industrial framework via the implementation of dedicated green hydrogen production systems to feed Hydrogen Direct Reduction process, the main alternative to the traditional polluting routes towards emissions abatement. Green hydrogen is produced via the coupling of an onshore wind farm with lithium-ion batteries, alkaline type electrolyzers and the interaction with the electricity grid. Building on a power generation dataset from a real utility-scale wind farm, techno-economic analyses are carried out for a large number of system configurations, varying components size and layout to assess its performance on the basis of two main key parameters, the levelized cost of hydrogen (LCOH) and the Green Index (GI), the latter presented for the first time in this study. The optimal system design and operation logics are investigated accounting for the necessity of providing a constant mass flow rate of H2 and thus considering the interaction with the electricity network instead of relying solely on RES surplus. In-house-developed models that account for performances degradation over time of different technologies are adapted and used for the case study. The effect of different storage technologies is evaluated via a sensitivity analysis on different components and electricity pricing strategy to understand how to favour green hydrogen penetration in the heavy industry. Furthermore, for a better comprehension and contextualization of the proposed solutions, their emission-reduction potential is quantified and presented in comparison with the current scenario of EU-27 countries. In the optimal case, the emission intensity related to the steelmaking process can be lowered to 235 kg of CO2 per ton of output steel, 88 % less than the traditional route. A higher cost of the process must be accounted, resulting in an LCOH of such solutions around 6.5 €/kg.

Promoting the reduction reactivity of magnetite by introducing trace-K-ions in hydrogen direct reduction

Hydrogen metallurgy exhibits considerable potential for application in the steel industry. However, it is restricted by the low utilization efficiency of hydrogen owing to the poor kinetic conditions and low reduction efficiency, which limit the development of ironmaking via hydrogen direct reduction. Therefore, improving the reduction efficiency of hydrogen direct reduction is critical. In this study, the reactivity of magnetite was considered. The impregnation of trace K+ (0.8 wt%) was found to significantly promote the reduction efficiency, and a possible mechanism was proposed. The increase in the metallization ratio from 88.51% to 99.43% indicated that the 0.8 wt% K+-promoted magnetite exhibited an improved reaction efficiency due to its higher reactivity. Furthermore, modified magnetite reacted under a broader range of gas conditions, e.g., the partial pressure of hydrogen could be reduced to 57%. According to the refined X-ray diffraction patterns, the promotion of the reduction reactivity could mainly be attributed to the increased Fe–O bond polarities, in addition to the solid-state diffusion of O2−, due to the formation of more oxygen vacancies. An enhanced reduction efficiency during hydrogen direct reduction was realized, which could provide promising guidance for the green, sustainable development of hydrogen direct reduction.

Low-carbon reorientation in a declining industry? A longitudinal analysis of coevolving contexts and company strategies in the UK steel industry (1988–2022)

To assess the speed and directionality of low-carbon transition processes in the UK steel industry, this article makes a longitudinal analysis of changing external pressures and company response strategies over the last 34 years. Using the Triple Embeddedness Framework and a five-phase model of reorientation, the study finds that the steel industry's low-carbon reorientation strategies moved from inaction (phase 1 in our model) and incremental change (phase 2) in the 1988–1997 period, to hedging and exploration of technical alternatives (phase 3) in the 1997–2007 period, back to incremental change in the 2007–2015 period (phase 2), and then forward again to hedging and exploration of technical alternatives (phase 3) in the 2015–2022 period. The reason for this oscillation pattern is that economic decline and successive retrenchment strategies reduced managerial attention and organizational resources for low-carbon orientation, especially after the 2007/8 financial crisis which led to a survival-focus. In recent years, UK steelmakers have started to explore three decarbonisation pathways (scrap/electric arc furnaces, carbon-capture-and-storage, and hydrogen direct reduction) but have not yet committed to their deployment, which is why reorientation speed is limited. New economic headwinds in 2021/2 threaten the implementation of low-carbon visions and roadmaps, leading steelmakers to ask for more government support. Future shifts to phase 4 (deployment and diversification) and phase 5 (full reorientation) in our conceptual model will depend on the outcome of currently ongoing political negotiations.

Trends in the global steel industry: Evolutionary projections and defossilisation pathways through power-to-steel

Steel production is a carbon and energy intensive activity, releasing 1.9 tons of CO2 and requiring 5.17 MWh of primary energy per ton produced, on average, globally, resulting in 9% of all anthropogenic CO2 emissions. To achieve the goals of the Paris Agreement of limiting global temperature increase to below 1.5 °C compared to pre-industrial levels, the structure of the global steel production must change fundamentally. There are several technological paths towards a lower carbon intensity for steelmaking, which bring with them a paradigm shift decoupling CO2 emissions from crude steel production by transitioning from traditional methods of steel production using fossil coal and fossil methane to those based on low-cost renewable electricity and green hydrogen. However, the energy system consequences of fully defossilised steelmaking has not yet been examined in detail. This research examines the energy system requirements of a global defossilised power-to-steel industry using a GDP-based demand model for global steel demands, which projects a growth in steel demand from 1.6 Gt in 2020 to 2.4 Gt in 2100. Three scenarios are developed to investigate the emissions trajectory, energy demands, and economics of a high penetration of direct hydrogen reduction and electrowinning in global steel production. Results indicate that the global steel industry will see green hydrogen demands grow significantly, ranging from 2809 to 4371 TWhH2 by 2050. Under the studied conditions, global steel production is projected to see reductions in final thermal energy demand of between 38.3% and 57.7% and increases in total electricity demand by factors between 15.1 and 13.3 by 2050, depending on the scenario. Furthermore, CO2 emissions from steelmaking can be reduced to zero.

Copper‐Zinc Oxide Catalysts for Aldehyde Hydrogenation by Direct Reductive Activation of Precursors

AbstractBulk copper‐zinc oxide hydrogenation catalysts are generally prepared by calcination of co‐precipitated precursors followed by reduction. This study reports the direct reduction in hydrogen of co‐precipitated oxy/hydroxy‐carbonate precursors omitting calcination. Dried and incompletely calcined precursors are compared with calcined catalysts. The reduction reactions in hydrogen were monitored in situ by XRD and TGA‐MS. Direct activation of precursors led to higher copper dispersions and increased catalytic activity in the hydrogenation of butyraldehyde to butanol as test reaction.

A Liquid Metal Encapsulation for Analyzing Porous Nanomaterials by Atom Probe Tomography

Abstract Analyzing porous (nano)materials via atom probe tomography has been notoriously difficult. Voids and pores act as concentrators of the electrostatic pressure, which results in premature specimen failure, and the electrostatic field distribution near voids leads to aberrations that are difficult to predict. In this study, we propose a new encapsulating method for porous samples using a low melting point Bi–In–Sn alloy, known as Field's metal. As a model material, we used porous iron made by direct-hydrogen reduction of single-crystalline wüstite. The complete encapsulation was performed using in situ heating on the stage of a scanning electron microscope. No visible corrosion nor dissolution of the sample occurred. Subsequently, specimens were shaped by focused ion-beam milling under cryogenic conditions at −190°C. The proposed approach is versatile and can be applied to provide good quality atom probe datasets from micro/nanoporous materials.

Comprehensive study on the reduction of biomass embedded self-reducing pellets (SRP) under H2 involved conditions by TG-DTA

Application of biomass embedded self-reducing pellets (SRP) in the Hydrogen direct reduction (H-DR) process is expected to solve the problem of low/zero carbon content in the DRI product of H-DR. In this study, reduction of biomass embedded SRP by N2/H2/CO at different temperatures was conducted by using Thermogravimetric/Differential Thermal Analyzer (TG/DTA), Scanning electron microscopy (SEM) was used to characterize the microstructure, porosity, and remaining biomass of the reduction product. Results show that: the reduction of iron ore by biomass starts at about 400 °C; the activation energies of H2 reduction in the initial and final stages are 2.54–4.68 kJ/mol and 56.69–85.36 kJ/mol, respectively; addition of biomass in pellets could ensure the carbon content and porosity of the reduction product; besides, reduction of 12% biomass pellets at 950 °C and 40% H2–60% N2 atmosphere is considered as the optimal reduction condition in this study, the final relative mass loss is 97.90%.

Nanoarchitectonics of Ni/CeO2 Catalysts: The Effect of Pretreatment on the Low-Temperature Steam Reforming of Glycerol.

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition.