Direct Reduction Of Iron Ore Research Articles

Solar-aided direct reduction of iron ore with hydrogen targeting carbon-free steel metallurgy

Steel metallurgy accounts for about 7 % of global greenhouse gas emissions and its decarbonation is a major issue. The direct reduction of iron ore with H2 using concentrated solar heat offers a carbon-free route for the iron metallurgical process. Such a solar process for clean ironmaking has never been implemented before. This study aims to investigate the reaction characteristics of direct iron ore reduction and further proposes a first experimental demonstration of direct reduced iron production in a packed-bed solar reactor under real solar irradiation. Fe2O3 reduction with H2 was first studied by thermogravimetric analysis to unravel the effect of temperature, H2 mole fraction, and particle size. The reaction rate increased with temperature (400–800 °C) and H2 mole fraction (25–75 %), and the reaction reached completion with an initial conversion starting from 370 °C. An activation energy of 38.5 and 30.4 kJ/mol was determined for commercial Fe2O3 and iron ore, respectively. The size of iron ore particles after pellets crushing (in the range 0.25–2 mm) did not significantly affect the reaction rate. However, fine micron size powder with low bulk density showed improved conversion rates. Finally, the reduction process was demonstrated in a solar-heated packed-bed reactor up to 1000 °C, confirming the feasibility of renewable iron production from complete ore reduction at moderate temperatures (starting above 400 °C), and thus paving the way toward decarbonation of the iron and steel metallurgical industry.

A study of options to enhance the operation of a H2 direct reduction shaft furnace using a two-dimensional model

With the intent to explore techno-economically feasible options for improving the performance of the hydrogen (H2) -operated direct reduction shaft furnace for iron ores, a two-dimensional computational fluid dynamics model was applied to assess the potential of a new top gas recycling system featuring dual-row injection. A special numerical routine was developed to bridge data communication during the iterative calculation, where the composition of the gas injected in the upper (tuyere) row varies with the conditions. The results showed that a poor gas utilization is inevitable for a (conventional) single-row recycling system since it cannot properly address the strong heat demand of the process. For dual-row top gas recycling with a reduced lower-row feed rate, the in-furnace thermochemical state is inappropriate if the upper-row feed rate is low, but is gradually improved as the upper-row feed rate increases, since more thermal energy is supplied to the part of the furnace where it is needed. With an appropriate configuration of the upper- and lower-row feed rates, the overall furnace performance can be substantially improved particularly with respect to gas utilization degree. The findings of this work are expected to aid the future design of more efficient operation of H2-based direct reduction of iron ores.

Experimental investigation and CFD study of direct reduction of iron ore in the conical fluidized bed

The reduction behavior of iron ore is the fundamental process in ferrous metallurgy. Considering the gas–solid interface-structure relationship, heterogeneous transfer-reaction behavior, and multiple reaction kinetics, this work provides an effective analytical tool to investigate the fluidized reduction of iron ore. The conical fluidized bed is numerically examined to be capable of preventing de-fluidization induced by the sticking behavior, due to the steady circulation of flow pattern and full fluidization of coarse agglomerates. Compared with the hydrogen concentration, the gas velocity shows a stronger influence on the agglomerate reduction rate for the more efficient gas–solid contact. For the simulated transitions of Fe2O3 → Fe3O4 → Fe(1-x)O → Fe are assumed to overlap each other, there exist discrepancies between computed and theoretical reduction degrees. The experimental and numerical findings can be used to develop a methodology for optimizing the operational complexity and economic benefits of the fluidized reduction of iron ore.

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.

Direct reduction of iron-ore with hydrogen in fluidized beds: A coarse-grained CFD-DEM-IBM study

Hydrogen metallurgy technology uses hydrogen as the reducing agent instead of carbon reduction, which is one of the important ways to reduce carbon dioxide emissions and ensure the green and sustainable development of iron and steel industry. Due to the advantages of high gas-solid contact efficiency and outstanding mass and heat transfer, direct reduction of iron ore in fluidized beds has attracted much attention. Based on the three-layer unreacted shrinking core model and considering the diversity of particle structure during the reaction process, a multi-reaction path (multi-resistance network) model was established. In this study, a coarse-grained CFD-DEM-IBM solver based on hybrid CPU–GPU computing is developed to simulate the direct reduction process of two kinds of iron ore with hydrogen in fluidized beds, where the developed unreacted shrinking core model is used to model the reduction reactions, a coarse-grained model and multiple GPUs enable the significant acceleration of particle computation, and the immersed boundary method (IBM) enables the use of simple mesh even in complex geometries of reactors. The predicted results of particle reduction degree are in good agreement with the experimental values, which proves the correctness of the CFD-DEM-IBM solver. In addition, the effects of reaction kinetic parameters and operating temperature on particle reduction degree are also investigated. Present study provides a method for digital design, optimization and scale-up of ironmaking reactors.

Reduction kinetics of hematite powder using argon/hydrogen plasma with prospects for near net shaping of sustainable iron

Direct reduction of iron ore using hydrogen plasma is being explored as a potential solution to decarbonize the iron and steel sector. The current state-of-the-art demonstrated reduction of hematite pellets via hydrogen plasma using Ar + 10% H2 but had slow reduction kinetics, requiring 30 minutes of plasma exposure for complete reduction. Here we show that using hematite in a powder form, easily obtainable from beneficiated ore, results in 10× faster kinetics using plasma generated from Ar + 2% H2 shielding gas compared to the current state-of-the art. The increased kinetics using powders and a dilute hydrogen concentration can enable the use of advanced manufacturing techniques like blown powder directed energy deposition using a plasma tungsten arc welding torch to manufacture near net shape components directly from the ore concentrates. This ore to part approach will also reduce the emissions associated with downstream processes like rolling, forging, and machining, thereby further aiding in the sectorial decarbonization efforts.

Kinetics analysis of direct reduction of iron ore by hydrogen in fluidized bed based on response surface methodology

The present research investigates the efficacy of fluidized bed direct reduction of hematite ore using H2 as a metallurgical technology. The study uses response surface methodology (RSM) to obtain the optimal kinetics system for fluidized H2 reduction of hematite ore. The interaction of independent parameters, including reduction time, reduction temperature, fluidizing velocity, and H2 concentration with dependent variables comprising the reduction degree are explored. The final equation for the reduction degree can be established according to RSM analysis. Additionally, for the hematite reduction using H2 in a fluidized, the study investigates the mechanisms and kinetics of isothermal reduction. The result demonstrates that the reduction degree increases with the reduction temperature, fluidizing velocity, and H2 concentration, as well as the reduction mechanisms change with reduction conditions. For instance, an increase in fluidizing velocity and H2 content promotes the transformation of the kinetics model from D3 to D3+F1 and R3+F1 mixed control, respectively. The activation energy for the fluidized H2 reduction of hematite ore to metallic iron Fe ranges from 23.76 to 54.89 kJ/mol.

Reduction of Iron‐Ore Pellets Using Different Gas Mixtures and Temperatures

Direct reduction of iron ore (DRI) is gaining an increased attention due to the growing need to decarbonize industrial processes. The current industrial DRI processes are performed using reformed natural gas, which results in CO2 emission, although it is less than carbothermic reduction in the blast furnace. Carbon‐free reduction may be realized through the utilization of green H2 as a reducing agent, in place of natural gas. Herein, the effects of various gas mixtures and temperature on the reduction kinetics of the hematite iron‐ore pellets are focused on in this work. Pellets are reduced at 700, 800, 850, and 900 °C in hydrogen and using various gas mixes at 850 °C. Morphology of the pellets is investigated with the help of scanning electron microscopy and mercury intrusion porosimetry. The effects of temperature and gas composition on the reduction kinetics and porosity of the pellets are discussed. A notable effect of reduction rate on the internal structure of the pellets is detected, slower reduction rate yielded bigger pores offsetting the gas composition. Higher temperature results in coarser pores and higher porosity. Increase of CO content in the gas mix also leads to bigger pore size.

The Adsorption Mechanism of Hydrogen on FeO Crystal Surfaces: A Density Functional Theory Study.

The hydrogen-based direct reduction of iron ores is a disruptive routine used to mitigate the large amount of CO2 emissions produced by the steel industry. The reduction of iron oxides by H2 involves a variety of physicochemical phenomena from macroscopic to atomistic scales. Particularly at the atomistic scale, the underlying mechanisms of the interaction of hydrogen and iron oxides is not yet fully understood. In this study, density functional theory (DFT) was employed to investigate the adsorption behavior of hydrogen atoms and H2 on different crystal FeO surfaces to gain a fundamental understanding of the associated interfacial adsorption mechanisms. It was found that H2 molecules tend to be physically adsorbed on the top site of Fe atoms, while Fe atoms on the FeO surface act as active sites to catalyze H2 dissociation. The dissociated H atoms were found to prefer to be chemically bonded with surface O atoms. These results provide a new insight into the catalytic effect of the studied FeO surfaces, by showing that both Fe (catalytic site) and O (binding site) atoms contribute to the interaction between H2 and FeO surfaces.

Advanced physical model of hydrothermic reduction of iron ore pellets by dissociated 2H+ ionic gas in the shaft furnace

ABSTRACT Development of various alternative routes for the direct reduction of iron-ore (DRI) and production of sponge irons becomes a necessity today to reduce carbon dioxide (CO2) gas emissions in industrial iron & steel (I&S) making processes. Therefore, the main objective of this work is focused to reduce the carbon footprint in DRI production by eliminating fossil fuel consumption. The reduced iron could be used to melt in the electric arc furnace (EAF) to produce liquid steel by minimising direct scrap addition. Indeed, this paper shows an advanced physical model of a hydrogen fuel shaft furnace for the direct reduced iron-making process by fundamental development of technology with essential modifications in its working principle. This processing technology is hypothetically designed with knowledge of theoretical literature inputs and wisdom of iron and steel-making experience. In this model of a shaft furnace, a scientific approach is designed based on the dissociation of molecular-hydrogen gas (H2+) obtained by water electrolysis and ionisation of the hydrogen gas (2H+) and is incorporated for a high degree of gas adsorption and metallisation during chemical reduction of iron ore (Fe2O3) pellets. The steps involved in the working principle of the new design shaft furnace are simulated and modelled suitably for the existing Midrex furnace operation, which is generally used for DRI production. This approach could be tried using 100% dissociated hydrogen ionic gas (2H+, H+) for future direct reduced iron making by water electrolysis and hydrogen ionisation. Moreover, the reformed reducing gases (CH4–H2–CO) used in the Midrex process can be replaced by the ionised hydrogen gases as an advancement.

Global green hydrogen-based steel opportunities surrounding high quality renewable energy and iron ore deposits

The steel sector currently accounts for 7% of global energy-related CO2 emissions and requires deep reform to disconnect from fossil fuels. Here, we investigate the market competitiveness of one of the widely considered decarbonisation routes for primary steel production: green hydrogen-based direct reduction of iron ore followed by electric arc furnace steelmaking. Through analysing over 300 locations by combined use of optimisation and machine learning, we show that competitive renewables-based steel production is located nearby the tropic of Capricorn and Cancer, characterised by superior solar with supplementary onshore wind, in addition to high-quality iron ore and low steelworker wages. If coking coal prices remain high, fossil-free steel could attain competitiveness in favourable locations from 2030, further improving towards 2050. Large-scale implementation requires attention to the abundance of suitable iron ore and other resources such as land and water, technical challenges associated with direct reduction, and future supply chain configuration.

Review on the chemical reduction modelling of hematite iron ore to magnetite in fluidized bed reactor

Abstract Steel production is considered as one of the major backbones of many economies. Though blast furnace is the primary route of steel production, the industries are willing to alternatives technologies such as the high temperature-controlled conversion of hematite to magnetite. The geological and mineralogical characteristics of the low-grade iron ores possess difficulties in their conventional enrichment. The literature concludes the advantages of high-temperature conversion in terms of easiness in downstream operations caused by decreased hardness and increased magnetic susceptibility of magnetite. The modelling work has been primarily focused on the direct reduction of iron ore to metallic iron. The present compilation discusses the scientific and engineering developments on the reduction-roasting of iron-ore followed by the CFD–DEM modelling and simulation work performed to reduce iron ore to magnetite. It provides a comprehensive review of the experimental and industrial progress done in the area.

Thermodynamic analysis and experimental verification of the direct reduction of iron ores with hydrogen at elevated temperature

Thermodynamic analysis and experimental verification of the direct reduction of iron ores with hydrogen at elevated temperature

Kinetic Analysis of Isothermal and Non-Isothermal Reduction of Iron Ore Fines in Hydrogen Atmosphere

Direct reduction of iron ore with H2 has become an alternative technology for iron production that reduces pollutant emissions. The reduction kinetics of iron ore fines in an H2 atmosphere under isothermal and non-isothermal conditions were studied by thermogravimetric analysis. X-ray diffraction and scanning electron microscopy were used to measure the mineral composition and analyse the morphology of the reduced fines, respectively. In the isothermal reduction experiment, it was found that the final reduction time was shorter, the higher the temperature, and the metallic iron particles formed a dense matrix structure. It is likely that the initial stages reduction process is the result of a combination of gaseous diffusion and interfacial chemical reaction mechanisms, and that the later stages a combination of interfacial chemical reaction and solid diffusion is the rate control mechanism. In the non-isothermal experiment, the heating rate had a significant effect on the reaction rate. The results show that the non-isothermal reduction proceeded through three stages: mixing control model, two-dimensional diffusion, and three-dimensional diffusion.

Carbon Utilization Combined with Carbon Direct Avoidance for Climate Neutrality in Steel Manufacturing

AbstractThe European steel industry faces the challenge of transformation to climate neutral steel making over the next decades. A combination of hydrogen‐based direct reduction of iron ore with melter and chemical usage of steel mill gases is discussed. This transformation path allows to reach the climate goals economically with minimized effects on production network and steel quality, additionally providing sustainable feedstocks for the chemical industry.

Development of electrolysis technologies for hydrogen production: A case study of green steel manufacturing in the Russian Federation

The article reviews a list of solutions to reduce the carbon intensity of the Russian fuel and energy complex. The technological scheme of green hydrogen production that is the most optimal for the Russian Federation has been determined. It is shown that by 2040, the net present value of hydrogen production units by the alkaline electrolysis method will amount to US $ 35 thousand/ kW while the cost of plants with a solid polymer or a solid-oxide electrolyzer will be at US$30 thousand/ kW and US $ 26 thousand/ kW accordingly. This paper presents a feasibility study of green hydrogen production from wind-powered electrolysis with further direct reduction of iron ore for green steel manufacturing. According to the analysis, the difference in cash flows between standard steelmaking technology and direct reduction of iron ore with hydrogen is 20% which in the long term could be reduced to 5%. Compared to the European Carbon Border Adjustment Mechanism, companies will be able to save about 3% of the present value. To achieve the commercial attractiveness of hydrogen production by electrolysis, the minimum amount of government subsidies should be at least 10% of capital expenditures from 2021 with a gradual increase to 20% by 2040 to support the emerging market.

Designing the technological transformation toward sustainable steelmaking: A framework to provide decision support to industrial practitioners

Climate change and the resultant requirement to reduce greenhouse gas emissions have become one of society’s main challenges. High emissions occur in the industrial sector and particularly in steelmaking. Due to energy-intensive carbon-based production processes, there is a significant potential to reduce greenhouse gas emissions in the steel industry. In this context, a promising technology is the hydrogen-based direct reduction of iron ore that can be used instead of coal-based blast furnaces. However, the transformation toward sustainable steelmaking implies various regulatory, technological, and economic challenges. For example, decision-makers must decide about strategic investments in the context of an uncertain political environment and unpredictable development pathways of future technologies. These courses have a direct impact on the competitiveness of steelmaking corporations. Consequently, decision-makers in industrial practice waver to design and evaluate advantageous transformation pathways for their corporations. We propose a framework of a decision support tool to design and evaluate the transformation toward sustainable steelmaking. To this end, we model the relevant steelmaking processes based on activity analysis and link them to optimization packages. Decision-makers can evaluate alternative future market scenarios and determine the optimal transformation pathway for their corporation. We discussed our framework with decision-makers from steelmaking. They confirm the effectiveness of our approach to support them in evaluating advantageous transformation pathways for their corporation.

Phase transformations during fluidized bed reduction of New Zealand titanomagnetite ironsand in hydrogen gas

Direct reduction of iron ore in a fluidized bed reactor is usually limited by the onset of particle sticking at temperatures ≳ 800 °C. This paper examines the phase and microstructural evolution of New Zealand titanomagnetite (TTM) ironsand during fluidized bed reduction by hydrogen gas at temperatures ranging from 750 °C to 1000 °C. All samples were characterized using quantitative X-ray diffraction and scanning electron microscope/energy dispersive spectroscopy. No sticking was observed at any point during this series of experimental reduction reactions. At higher temperatures sticking appears to be prevented by the formation of a Ti-rich oxide shell around each partially-reduced particle. At lower temperatures, no shell is observed to form, but temperatures are not high enough to drive particle sticking/agglomeration.The reduction mechanism appears to vary within different temperature regimes. At high temperatures (950 °C and 1000 °C), the reduction of TTM proceeds via the wüstite phase during the initial reduction stage, although the TTM is not completely converted to wüstite. The formation of wüstite results in an enrichment of Ti within the residual TTM phase. This is observed as an increase in the TTM lattice parameter, which is stretched by Ti substitution into the spinel. For reactions at low temperatures (750 °C and 800 °C), the TTM is directly reduced to metallic iron without any evidence of the appearance of the wüstite phase. At ‘intermediate temperatures’ (850 °C and 900 °C), a mixed behaviour is observed with the appearance of low levels of short-lived wüstite during the reduction reaction. Overall, these results indicate that the fluidized bed processing of NZ TTM ironsand in hydrogen can be completed over a wide temperature range without incurring sticking.

The Direct Reduction of Iron Ore with Hydrogen

The steel industry represents about 7% of the world’s anthropogenic CO2 emissions due to the high use of fossil fuels. The CO2-lean direct reduction of iron ore with hydrogen is considered to offer a high potential to reduce CO2 emissions, and this direct reduction of Fe2O3 powder is investigated in this research. The H2 reduction reaction kinetics and fluidization characteristics of fine and cohesive Fe2O3 particles were examined in a vibrated fluidized bed reactor. A smooth bubbling fluidization was achieved. An increase in external force due to vibration slightly increased the pressure drop. The minimum fluidization velocity was nearly independent of the operating temperature. The yield of the direct H2-driven reduction was examined and found to exceed 90%, with a maximum of 98% under the vibration of ~47 Hz with an amplitude of 0.6 mm, and operating temperatures close to 500 °C. Towards the future of direct steel ore reduction, cheap and “green” hydrogen sources need to be developed. H2 can be formed through various techniques with the catalytic decomposition of NH3 (and CH4), methanol and ethanol offering an important potential towards production cost, yield and environmental CO2 emission reductions.

Physics and Chemistry of Solid State Direct Reduction of Iron Ore by Hydrogen Plasma

Presently, Iron is produced from iron ores by using carbon from coal. The production process is consisting of many stages. The involvement of multi-stages needs high capital investments, large-scale equipments, and produces large amounts of carbon dioxide (CO2) responsible for environmental pollution. There have been significant efforts to replace carbon with hydrogen (H2). Although H2 is the strongest reductant, it still also has thermodynamic and kinetic limitations. However, these thermodynamic and kinetic limitations could be removed by hydrogen plasma (HP). HP comprises rovibrationally excited molecular, atomic, and ionic states of hydrogen. All of them contribute to thermodynamic advantage by making the Gibbs standard free energy more negative, which makes the reduction of iron oxides feasible at low temperatures. Apart from the thermodynamic advantage, these excited species increase the internal energy of HP, which reduces the activation energy, thereby making the reduction easier and faster. Apart from the thermodynamic and kinetic advantage of HP, the byproduct of the reaction is environmentally benign water. This review discusses the physics and chemistry of iron ore reduction using HP, emphasizing the solid-state reduction of iron ore. HP reduction of iron ore is a high potential and attractive reduction process.