Reduction Of Ore Research Articles

The potential for hydrogen ironmaking in New Zealand

Globally, iron and steel production is responsible for approximately 6.3% of global man-made carbon dioxide emissions, because coal is used as both the combustion fuel and chemical reductant. Hydrogen reduction of iron ore offers a potential alternative ‘near-zero-CO2’ route, if renewable electrical power is used for both hydrogen electrolysis and reactor heating. This paper discusses key technoeconomic considerations for establishing a hydrogen direct reduced iron (H2-DRI) plant in New Zealand. The location and availability of firm renewable electricity generation is described, the experimental feasibility of reducing locally-sourced titanomagnetite ironsand in hydrogen is shown, and a high-level process flow diagram for a counter-flow electrically heated H2-DRI process is developed. The minimum hydrogen composition of the reactor off-gas is 46%, necessitating the inclusion of a hydrogen recycle loop to maximise chemical utilisation of hydrogen and minimize costs. A total electrical energy requirement of 3.24 MWh per tonne of H2-DRI is obtained for the base-case process considered here. Overall, a maximum input electricity cost of no more than US$80 per MWh at the plant is required to be cost-competitive with existing carbothermic DRI processes. Production cost savings could be achieved through realistic future improvements in electrolyser efficiency (∼ US$5 per tonne of H2-DRI) and heat exchanger (∼US$3 per tonne). We conclude that commercial H2-DRI production in New Zealand is entirely feasible, but will ultimately depend upon the price paid for firm electrical power at the plant.

Lithium Enrichment by the Carbothermal Reduction of Spodumene Ore and the Preparation of Manganese-Silicon Alloy

To increase the low utilization rate of spodumene ore during lithium extraction, spodumene ore was subjected to carbothermic reduction to enrich lithium and prepare a manganese-silicon alloy. The experimental results showed that during thermal reduction, lithium was volatilized and collected in the condensation zone. The Li2O content in the lithium condensate was 41.72%, which was 10.85 times higher than that of the raw material. The effects of varying reduction temperatures and times on the lithium volatilization rate and direct yield of Mn5Si3 alloy were investigated. The best process conditions were 1873 K for 6 h. Under these conditions, the lithium volatilization rate was 97.65%, and the direct yield of Mn5Si3 was 86.47%.

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.

Softening and melting performance of mixed burden under the simulated hydrogen-rich blast furnace atmosphere

ABSTRACT The effects of the application of iron coke in hydrogen-rich blast furnace atmosphere on the softening and melting performance of burden were studied.The results indicated that with the increase in hydrogen content, the cohesive zone of mixed burden became narrower and the permeability of charge was improved, and the suitable hydrogen content was 10vol.-%. The application of iron coke could promote the iron ore reduction and carburizing of iron, decrease the melting temperature by 1–10°C, decrease the dripping temperature by 5–16°C, narrow the cohesive zone, improve the air permeability with S value decrease of 3.19–13.87 kPa °C, and reduce the dissolution loss of coke and ensure the skeleton function of coke. The suitable burden structure was confirmed as follows, i.e. the ratio of pellets and sinter is 4:6, and the ratio of iron coke and coke is 2:8.

Prospects and challenges of the electrochemical reduction of iron oxides in alkaline media for steel production

Steelmaking industries have been facing strict decarbonization guidelines. With a net zero carbon emissions target, European policies are expected to be accomplished before 2050. Traditional steelmaking industry still operates by the carbothermic reduction of iron ores for steel production. Consequently, the steel sector is responsible for a large amount of CO2emissions, accounting for up to 9% of the CO2worldwide emissions. In this scope, the electrochemical reduction or electrolysis of iron oxides into metallic iron in alkaline media arises as a promising alternative technology for ironmaking. Significant advantages of this technology include the absence of CO2emissions, non-polluting by-products such as hydrogen and oxygen gases, lower temperature against the conventional approach (∼100°Cversus2000°C) and lower electric energy consumption, where around 6 GJ per ton of iron manufactured can be spared. The present minireview discusses the progress on the electrochemical reduction of iron oxides in alkaline media as a green steelmaking route. A historical overview of the global steelmaking against recent developments and challenges of the novel technology is presented, and the fundamental mechanisms of iron oxide reduction to iron and alternative iron feedstocks are discussed. Factors affecting the Faradaic efficiencies of the alkaline electroreduction of iron oxide suspensions or iron oxide bulk ceramics are also explored, focusing on the concurrent hydrogen evolution reaction. Overall, if scrutinized, this technology may become a breaking point for the steel industry sector.

Coupled Typical Coke Gasification and Sintering Ore Reduction in CO-N2-H2.

Through thermodynamic calculation and high-temperature simulation experiments, the coupling behavior between gasification of high- and low-reactivity cokes and reduction of sintering ore in CO–N2–H2 mixed gas with 25% H2 volume fraction was studied, and the evolution of the coke carbon structure and the pore structure was analyzed. The results show that the reaction rate of the two cokes increases with the increase in temperature after the coupling reaction, and the strength after drumming decreases with the increase in temperature. The strength of low-reactivity coke after the reaction is higher than that of high-reactivity coke, and the reduction degree of sintering ore after the coupling reaction with low-reactivity coke is higher than that with high-reactivity coke. At high temperatures and high hydrogen-rich atmospheres with φ(H2) of 25%, the strength of high-reactivity coke after drum rotation is greater than 60.4%. The graphitization degree and carbon structure order of low-reactivity coke are higher than those of high-reactivity coke.

Hydrogen reduction of low-grade banded iron ore

The current study investigates hydrogen reduction of low-grade iron ore (∼37 % Fe) containing dispersed bands of hematite and jasper/quartzite phases. Gaseous hydrogen reduction is carried out at isothermal conditions in a custom-made tubular furnace, followed by magnetic separation. The reduction temperature (300–600 °C), time (30–90 min), particle size (0.5–3.3 mm), and hydrogen flow rate (0.5–1.5 LPM) were optimized by statistical design of experiments to maximize the saturation magnetization, degree of reduction and metallization. Complete reduction of hematite was achieved in 2 h at 600 °C; however, the separation of quartz from reduced ferrite was inefficient evidenced by the lower saturation magnetization. The association of impurities with hematite does not affect the reduction rate; however, the trapped quartz particles in the reduced phases deteriorate the magnetic separation efficiency. Temperature and time synergize the reduction rate, improving reduction and metallization degree; meanwhile, flow rate and particle size have minimal effect. Reduction below 450 °C restricted the reduction to magnetite, and the optimal conditions; 600 °C, 60 min, 0.5 LPM H2, and 3.3 × 2 mm particle size yielded ferrite concentrate possessing saturation magnetization of 134.6 emu/g (68 % FeM) with 97.9 % DOR, 88.8 % DOM and 47.3 % yield. The reduction of hematite results in generation of micro cracks and porous morphology of the ferrite. Iron oxide reduction follows the Fe2O3 → Fe3O4 → Fe, evidenced by the absence of wustite (FeO) or fayalite (FeO.SiO2) phases in the product. The ferrite particles form a fused and porous layer trapping the silica particles.

Fluidization behavior and reduction kinetics of pre-oxidized magnetite-based iron ore in a hydrogen-induced fluidized bed

The influence of different pre-oxidation temperatures and pre-oxidation degrees on the reduction and fluidization behaviors of magnetite-based iron ore was investigated in a hydrogen-induced fluidized bed. The raw magnetite-based iron ore was pre-oxidized at 800 and 1000°C for a certain time to reach a partly oxidation and deeply oxidation state. The structure and morphology of the reduced particles were analyzed via optical microscope and scanning electron microscopy (SEM). The reaction kinetic mechanism was determined based on the double-logarithm analysis. The results indicate that the materials with higher oxidation temperature and wider particle size range show better fluidization behaviors. The lower oxidation temperature is more beneficial for the reduction rate, especially in the later reduction stage. The pre-oxidation degree shows no obvious influence on the fluidization and reduction behaviors. Based on the kinetic analysis, the reduction progress can be divided into three stages. The reduction mechanism was discussed combing the surface morphology and phase structure.

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.

Coarse-grained rCFD-DEM analysis of coke gasification and iron ore reduction in the shaft region of an ironmaking blast furnace

Understanding the fundamentals of iron ore reduction and coke gasification in the shaft region of an ironmaking blast furnace (BF) is the key to improving iron productivity and stability, yet the particle-scale understanding is hindered by the huge computational cost. In this paper, a coarse-grained reacting CFD-DEM (rCFD-DEM) model is implemented to investigate the complex thermochemical behaviours inside a simplified BF shaft. The results show that, in comparison to the CFD-DEM approach, the coarse-grained rCFD-DEM approach can have a similar accuracy but reduces computational cost by ~89.01% in this study. The typical thermochemical behaviours in respective coke and iron ore layers can be captured at particle scale. Then the effect of key operating parameters is studied quantitatively at particle scale. It is indicated that the inlet velocity increasing from 1.7 m/s to 2.3 m/s improves the reduction degree of iron ore by 16%, but the coke consumption is reduced by 5.51%. The operating temperature increasing from 1200 K to 1250 K increases the coke consumption by 44.92%, but the reduction degree of iron ore only increases slightly. When CO mass fraction in the inlet gas increases from 0.25 to 0.30, the coke consumption increases by 12.68% and the reduction degree of iron ore increases by 16.88%. The findings shed light on the fundamentals of coke gasification and iron ore reduction in the BF shafts. • A coarse-grained reacting CFD-DEM model is developed to investigate the blast furnace shaft. • Compared to previous CFD-DEM approach, the approach have a similar accuracy but reduces computational cost by ~89%. • The typical thermochemical behaviours and the effect of key operating parameters are quantified. • The findings shed light on the fundamentals of coke gasification and iron ore reduction in blast furnace shafts.

The Effect of Pre-Oxidation on the Reducibility of Chromite Using Hydrogen: A Preliminary Study

The majority of ferrochrome (FeCr) is produced through the carbothermic reduction of chromite ore. In recent years, FeCr producers have been pressured to curve carbon emissions, necessitating the exploration of alternative smelting methods. The use of hydrogen as a chromite reductant only yields water as a by-product, preventing the formation of carbon monoxide (CO)-rich off-gas. It is however understood that only the Fe-oxide constituency of chromite can be metalized by hydrogen, whereas the chromium (Cr)-oxide constituency requires significantly higher temperatures to be metalized. Considering the alternation of chromite’s spinel structure when oxidized before traditional smelting procedures, the effects on its reducibility using hydrogen were investigated. Firstly, the effect of hydrogen availability was considered and shown to have a significant effect on Fe metallization. Subsequently, spinel alternation induced by pre-oxidation promoted the hydrogen-based reducibly of the Fe-oxide constituency, and up to 88.4% of the Fe-oxide constituency was metallized. The Cr-oxide constituency showed little to no reduction. The increase in Fe-oxide reducibility was ascribed to the formation of an exsolved Fe2O3-enriched sesquioxide phase, which was more susceptible to reduction when compared to Fe-oxides present in the chromite spinel. The extent of Fe metallization of the pre-oxidized chromite was comparable to that of unoxidized chromite under significantly milder reduction conditions.

Assessment of utilization potential of biomass volatiles and biochar as a reducing agent for iron ore pellets

ABSTRACT India is an agricultural country and near about 500 MT of agricultural wastes are generated each year. India has huge reserves of low-grade iron ore fines. Therefore, considering the availability of these two, the present study mainly focuses on utilization of solid waste in iron and steel industry; also, biomass being carbon-neutral fuel, promotes mitigation of environmental issues. To carry out this study, agricultural wastes like groundnut shell and corn cob which contain more than 70% of volatile matter were considered. Hence, an attempt has been taken to utilize this volatiles as well as char (prepared at 350°C) of corn cob and groundnut shell as a reducing agent for reduction of iron ore pellets. Maximum reduction percentage was achieved at 1000°C and 75 min using corn cob as a reductant, i.e. 78.38% with its volatile and 92.01% using its char. Higher intensity of elemental iron is also reflected by X-ray Diffraction analysis of reduced pellets. Further, cost estimation of reduction of iron ore pellets was also done using both the reducing agents, which signifies that the reduction process using biomass volatiles is much more economical than biochar. The total cost of producing DRI from corn cob volatiles is 56% less than coal followed by groundnut shell volatiles 53.36% and minimum in the case of groundnut shell char 36.17%. Highlights Effects of biomass volatiles and char on iron ore pellets reduction @ 1000°C at different time interval of 15, 30, 45, 60 & 75 min. Comparative assessment of iron ore pellets reduction through XRD and FESEM analysis. Economic evaluation of iron ore reduction using volatiles and char of biomass.

Effect of rice husk volatiles in iron ore reduction and its kinetic study

ABSTRACT India is an agricultural country, whose main crop is rice. Processing and milling of rice crops generate waste which is not yet potentially utilized, at most, it can be used for combustion purposes only. Hence, this research attempts to utilize rice husk volatiles (RHv) as a reducing agent for iron ore pellets in iron and steel making. Selected rice husk (RH) consists of approximately 72% volatile matter. The reduction process was carried out at different temperatures at 800, 900, 1000, and 1100°C and time intervals of 15, 30, 45, 60, and 75 min in a double chamber vertical furnace, using RHv as a reducing agent. It has been observed that the reduction percentage of iron ore obtained in case of RHv is 79.01% at 1100°C in 75 min. Field Emission Scanning Electron Microscope (FESEM) and X-ray diffraction (XRD) analysis show the reduced pellets’ morphological characteristics and phase transformation, respectively. Kinetic analysis was done using the shrinking core model and it shows that at lower temperatures, that is, 800, 900, and 1000°C, reduction was diffusion control and followed by chemical reaction control at 1100°C. The activation energy obtained for diffusion and chemical control was 159 KJ/mol and 83.93 KJ/mol, respectively.

A New Methodological Approach to the Characterization of Optimal Charging Rates at the Hydrogen Plasma Smelting Reduction Process Part 1: Method.

The development of a carbon lean steel production process following the concept of direct carbon avoidance is one of the most challenging tasks the iron and steel industry must tackle in just a few decades. The necessary drastic reduction of 80% of the process’s inherent emissions by 2050 is only possible if a new process concept that uses hydrogen as the primary reductant is developed. The Hydrogen Plasma Smelting Reduction (HPSR) of ultra-fine iron ores is one of those promising concepts. The principle was already proven at a lab scale. The erection of a bench-scale facility followed this, and further scaled-ups are already planned for the upcoming years. For this scale-up, a better understanding of the fundamentals of the process is needed. In particular, knowledge of the kinetics of the process is essential for future economically feasible operations. This investigation shows the principles for evaluating and comparing the process kinetics under varying test setups by defining a representative kinetic parameter. Aside from the fundamentals for this definition, the conducted trials for the first evaluation are shown and explained. Several differences in the reduction behavior of the material at varying parameters of the process have already be shown. However, this investigation focuses on the description and definition of the method. An overall series of trials for detailed investigations will be conducted as a follow-up.

Towards more efficient control of the ironmaking blast furnace: modelling gaseous reduction of iron ores in H2-N2 atmosphere

Abstract The fraction of hydrogen (H2) in the blast furnace (BF) shaft gas containing a notable portion of nitrogen (N2) is expected to increase. For more efficient control of the BF, it is therefore desirable to conduct more rigorous studies on gaseous reduction of iron ores especially in H2-N2 atmosphere. In this paper, an unreacted shrinking core model (USCM) with multicomponent gas diffusion for iron ore reduction in H2-N2 atmosphere is developed. The resultant nonlinear equations are solved using the 4th order Runge-Kutta method. The present model and the original USCM are compared based on a series of pertinent experimental data.

Investigation on Saprolitic Laterite Ore Reduction Process using Palm Kernel Shell Charcoal: Kinetics and Phase Transformation

The performance and kinetic of saprolitic laterite reduction using palm kernel shell charcoal and anthracite were studied. The anthracite coal represents the conventional high-grade carbon content matter, and palm kernel shell charcoal represents

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%.

Relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed reduction

The relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed hydrogen reduction were systematically investigated at 600–800 °C in a laboratory fluidized bed. First, the reduction kinetics were studied, and the results showed that hydrogen reduction of granulated iron ore was controlled by reduction reaction, and the activation energy was approximately 88.4 kJ/mol. The reduction rate of granulated iron ore with a diameter of 200 μm could be increased by 10 times as the reduction temperature rose from 600 to 800 °C. Then, a modified force balance model was established to distinguish the critical sticking point of granulated iron ore during high temperature fluidized bed hydrogen reduction, and it indicated that the defluidization temperature could be raised from 630 to 790 °C as the particle size was enlarged from 100 to 200 μm with a fluidization number of 10. Eventually, coupling the kinetic model and modified force balance model, the maximum gas utilization rate of fluidized bed hydrogen reduction was estimated, and it indicated that at reduction temperatures of 650–750 °C with particle sizes of 200–300 μm, the optimal gas utilization rate could be achieved, which was consistent with the experimental results. Contradictory to traditional understandings of chemical reaction engineering, due to the interaction of reduction performance and sticking behavior, too high of a reduction temperature or too small of a particle size might not be preferable for fluidized bed hydrogen reduction, and this study provided valuable references for industrial operation.

Assessment of variable solar- and grid electricity-driven power-to-hydrogen integration with direct iron ore reduction for low-carbon steel making

Power-to-gas (PtG) technologies offer a promising approach for decarbonization of energy-intensive industries, particular the iron and steel (I&S) sector, which depends on specific chemical feedstock and processes that are not currently directly electrifiable. However, PtG implementation faces challenges in the medium term related to the carbon footprint of electricity networks, decoupling process applications from variable renewable energy inputs, and economic feasibility. In this study, the design, energy, emissions, cost, and hourly operation of a power-to-hydrogen (PtH2)-based direct reduction of iron (DRI)-electric arc furnace (EAF) system, are investigated for solar energy-rich conditions in the near- to medium term (2030) with the intent to facilitate the deployment of low-carbon DRI-EAF steel making. A plant hourly operating and sizing methodology is developed based on PtH2 and use of renewable, low-cost solar photovoltaic (PV) electricity and H2 storage to counteract grid emissions and cost. The analysis approach is generically applicable to different solar-rich locations and other variable renewable electricity sources. For base-case system design/operating conditions, the emission intensity of the PtH2-I&S process is found to be abated from 890 to 567 kgCO2/tLS (∼36%), in absence of EAF scrap steel use, relative to the use of grid electricity only with no H2 storage, with a slight reduction in the levelized of cost steel (CLS) at 618 USD/tLS. Relative to conventional natural gas (NG)-DRI-EAF and blast/oxygen furnace (BF-BOF) processes, emission intensity is reduced by ∼43–60% and ∼53–74%, respectively. At off-base case PV and water electrolysis capacities, steel making emission intensity reductions of ∼40% relative to conventional NG DRI-EAF are achievable at normalized PV capacities, α = 3, relative to the plant nominal hourly electricity demand, and normalized electrolysis capacities, β ≥ 1.3, relative to the nominal hourly capacity requirement, while maintaining CLS within less than +25% of NG DRI-EAF. Based on the performance improvement and cost reduction potential for electrolysis and solar PV, the sub-space of normalized PV and electrolysis capacities yielding a ∼40% reduction in emission intensity within the above CLS limit would be significantly enlarged towards lower PV capacities (α ≥ 2) and electrolysis capacities (β ≥ 1.2).