Molten Iron Oxide Research Articles

Co-wetting behavior of molten slag and iron on carbon materials in blast furnace

The interaction between molten slag, liquid iron, and carbon is one of the most typical and complex multiphase flow behaviors in the high-temperature zone of blast furnace. The wetting behavior among these phases is the most fundamental characteristic that determines their interactions. This research focuses on the co-wetting behavior of molten slag and iron on graphite, using high-temperature experiments and atomistic simulations. The results revealed that the multiphase cooperative reaction wetting process is influenced by multiple factors. The wettability of molten iron is mainly affected by its initial carbon content, while the wettability of slag is influenced by both the initial carbon content of the molten iron and its own compositional changes. The initial carbon content in molten iron affects the carburizing reaction, which in turn influences the wetting mechanism between molten iron and graphite. Additionally, it alters the reaction of FeO in the slag, thereby modifying the properties of the slag-carbon interface and affecting the overall co-wetting process. Meta-dynamic calculations showed that the reduction of molten iron oxide by dissolved carbon is significantly more effective than that by solid graphite carbon, demonstrating that the behavior of carbon between iron and slag is a key factor in the multiphase cooperative reaction process.

Deciphering diffuse scattering with machine learning and the equivariant foundation model: the case of molten FeO

Bridging the gap between diffuse x-ray or neutron scattering measurements and predicted structures derived from atom–atom pair potentials in disordered materials, has been a longstanding challenge in condensed matter physics. This perspective gives a brief overview of the traditional approaches employed over the past several decades. Namely, the use of approximate interatomic pair potentials that relate three-dimensional structural models to the measured structure factor and its’ associated pair distribution function. The use of machine learned interatomic potentials has grown in the past few years, and has been particularly successful in the cases of ionic and oxide systems. Recent advances in large scale sampling, along with a direct integration of scattering measurements into the model development, has provided improved agreement between experiments and large-scale models calculated with quantum mechanical accuracy. However, details of local polyhedral bonding and connectivity in meta-stable disordered systems still require improvement. Here we leverage MACE-MP-0; a newly introduced equivariant foundation model and validate the results against high-quality experimental scattering data for the case of molten iron(II) oxide (FeO). These preliminary results suggest that the emerging foundation model has the potential to surpass the traditional limitations of classical interatomic potentials.

Reproduction of I‐type cosmic spherules and characterization in an Fe‐Ni‐O system

AbstractThe chemical composition and texture of cosmic spherules are influenced by atmospheric conditions and the characteristics of their parent interplanetary particles. The objective of this study was to reproduce I‐type cosmic spherules, which consist mainly of Fe oxide and Fe‐Ni metal, and compare their textural characteristics with those of natural I‐type cosmic spherules. Thus, a series of rapid heating and quenching experiments were performed on free falling iron meteorite powders obtained from Canyon Diablo, in the United States. The experiments were conducted using a high‐temperature furnace with controlled gas flow rates at oxygen fugacities of FMQ + 2.4, FMQ, and FMQ − 2.5 log unit. The resulting Fe‐Ni metal and oxide phases showed the nonequilibrium state of the melted spherules formed during quenching. Two types of magnetite crystals in different orientations were found in iron oxide. As temperatures decreased, the molten metal was oxidized to form immiscible molten iron oxide that then covered the former. As the oxide melt increased at the expense of metal, magnetite began to crystallize from the iron oxide melt, as the liquidus phase, either on the surface or within the melt phase. The characteristics of the run products obtained under different oxygen fugacities were similar to those of natural I‐type cosmic spherules, which have textures and compositions that may contain information regarding the oxygen content of the upper atmosphere. Our study suggests that CO2‐bearing molecules in the atmosphere could form iron oxide with a texture similar to natural I‐type cosmic spherules. During this process, rapid crystallization of magnetite plays an important role in texture formation in disequilibrium states.

Competitive Oxidation of O2 and CO2 in Fe–C Melts Using Isotope Tracing Method

The application of an O2–CO2 mixture gas in the steel industry makes an important contribution to energy savings and emissions reduction. To clarify the reaction mechanisms of this gas mixture, isotope gases (18O2 and 13CO2) are used to study the competitive oxidation of O2 and CO2, for Fe–C melts at 1873 K. Changes in gas mix composition during the decarburization of Fe–C melts with O2–CO2 are monitored using an online mass spectrometer. The results show that when the O2/CO2 ratio at the inlet is 4:1, the O2 oxidation rate is approximately four times that of CO2. O2 and CO2 decarburization abilities are found to be basically the same, even when the O2 supply is more than sufficient. As for the ability to oxidize Fe in molten steel, when the ratio of O2/CO2 at the inlet is 4:1, the O2 oxidation rate is approximately seven times that of CO2, allowing us to conclude that CO2 is less able to compete with molten iron oxide.

Thermodynamic potential of high temperature chemical looping combustion with molten iron oxide as the oxygen carrier

The thermodynamic potential of a chemical looping combustion (CLC) system using molten iron slag as the oxygen carrier (OC) for the combustion of methane is reported. A configuration of two inter-connected bubbling column reactors is proposed as a plausible configuration for the air and fuel reactors to facilitate the heating of a pressurised hot gas stream to an estimated temperature of 1350°C. This approach has potential to avoid the technical challenges associated with the use of the solid OC employed in conventional CLC systems such as particle breakage, attrition, agglomeration and structural change that arise from successive reduction and oxidation (Red-Ox) cycles. However, it brings alternative challenges associated with the handling of molten metal oxides such as proper material selection and solidification of the LOC, which will require further work to full identify and resolve. The process has been modelled using codes developed with MATLAB and HSC Chemistry 7.0 software and compared with published data. The model was used to estimate that a fuel conversion efficiency of more than 97% can be achieved with molten iron oxide as the oxygen carrier, together with a mole fraction of the iron and iron oxides in the product gas of less than 10−6. A sensitivity to molar ratios of liquid oxygen carrier, steam to fuel flow rate and the operating pressure is also reported.

Iron production electrified

Scientists have long dreamt of converting molten iron oxide to iron and oxygen using electricity. An anode material that withstands the high temperatures and corrosive chemicals involved brings the dream closer to reality. See Letter p.353 Metals production is the largest industrial source of greenhouse gases, with steel the main culprit. Traditional methods of extracting iron from its ore require a carbon-based reductant and produce large quantities of CO2. Molten oxide electrolysis is a promising alternative, but until now it has required anode materials that are either consumable or prohibitively expensive. This paper reports the development of a new chromium-based aluminium alloy electrode that is relatively cheap and, thanks to its three-layered structure (metal oxide/mixed oxide/electrolyte), is protected from dissolution. This technology must now be scaled up and its long-term performance assessed.

Electrolysis of Molten Iron Oxide with an Iridium Anode: The Role of Electrolyte Basicity

Molten oxide electrolysis (MOE) is a carbon-free, electrochemical technique to decompose a metal oxide directly into liquid metal and oxygen gas. From an environmental perspective what makes MOE attractive is its ability to extract metal without generating greenhouse gases. Hence, an inert anode capable of sustained oxygen evolution is a critical enabling component for the technology. To this end, iridium has been evaluated in ironmaking cells operated with two different electrolytes. The basicity of the electrolyte has been found to have a dramatic effect on the stability of the iridium anode. The rate of iridium loss in an acidic melt with high silica content has been measured to be much less than that in a basic melt with high calcia content.

Production of Oxygen Gas and Liquid Metal by Electrochemical Decomposition of Molten Iron Oxide

Molten oxide electrolysis (MOE) is the electrolytic decomposition of a metal oxide, most preferably into liquid metal and oxygen gas. The successful deployment of MOE hinges upon the existence of an inert anode capable of sustained oxygen evolution. Herein we report the results of a program of materials design, selection, and testing of candidate anode materials and demonstrate the utility of iridium in this application. An electrolysis cell fitted with an iridium anode operating at 0.55 A cm−2 produced liquid metal and oxygen gas by the decomposition of iron oxide dissolved in a solvent electrolyte of molten MgO–CaO–SiO2–Al2O3. The erosion rate of iridium was measured to be less than 8 mm y−1. The stability of iridium is attributed to a mix of mechanisms including the electrochemical formation and simultaneous thermal decomposition of a surface film of iridium oxide.

Forward and Backward Reaction Rate Constants of the Reaction of C+O=CO (g) on Fe–C Melts

It is known that the molten iron oxide reduction by Fe–C melt shows quite different behavior depending on whether the surface of Fe–C melts is fully covered with molten iron oxide or not. There have been only two studies of the molten iron oxide reduction by Fe–C melt with the existence of free surface. In both studies, the reduction appears to be controlled by the reaction of C+O→CO (g). The rate of this reaction has not been fully established. In the present study, based on the reexamination of overall reaction rates of previous two studies by Dancy and Lloyd et al., the forward and backward reaction rate constants of the reaction C+O→CO (g) at 1873 K have been evaluated by applying the order of magnitude evaluation method. The forward rate constant, in the unit of mol/m2 s, is given by: k=1.33×108 exp(−250000/RT), and the backward rate constant, in the unit of mol/m2 s, is deduced to: kCO=2.4×1011 exp(−277000/RT).

Natural gas based direct steelmaking using melt circulation: technoeconomic feasibility

Steelmaking based on natural gas rather than coal is proposed as a logical solution to concerns about climate change and global warming. Highly preheated iron ore fines are fed onto the surface of the molten iron carrier medium in a single loop melt circulation reactor. A thin layer of liquid iron ore is formed and reduction occurs as the molten iron oxide containing melt is transported along the length of the reduction arm countercurrent to natural gas in situ generated reducing gases flowing at high velocity. Issues relating to Kelvin–Helmholtz instability are addressed and detailed consideration is given to soot formation and its subsequent gasification in the bulk gas phase. Key parameters for 1 Mtpa liquid steel are evaluated based on thermal decomposition of methane by convective heat transfer and reduction of ferrous oxide controlled by gaseous diffusion. A breakdown of capital and operating costs indicates the relative importance of key elements.

Interfacial reaction between CO2-CO gas and molten iron oxide containing P2O5

The interfacial reaction between CO2-CO gas and molten iron oxide containing P2O5 was investigated by the 13CO2-CO isotope exchange technique at 1773 K with CO2/CO=1.0. The apparent rate constant rapidly decreased with the addition of P2O5 up to 2.86 mol pct PO2.5 and the Fe3+/Fe2+ ratio kept constant at approximately 0.2. By the classic site blockage model, in which the reaction only occurs on the vacant sites, and the modified site blockage model, in which the reaction occurs on the vacant sites and the sites occupied by phosphorus simultaneously, the effect of the addition of P2O5 was analyzed and the reaction mechanism of CO2 dissociation was discussed. It may be concluded that the dissociation of the adsorbed CO2 molecule is reasonable as a rate-determining step and that the effect of phosphorus on the interfacial reaction is caused by the decrease in the number of active sites with the increase of phosphorus content as a surface active element in molten iron oxide.

｀１８´Ｏを含むＣＯ‐ＣＯ２気体質量分析によるガス‐溶融酸化鉄間の酸素交換反応速度測定

Reaction between molten oxide containing iron oxide and CO-CO2 gas is the essential reaction in numerous metallurgical smelting processes and the refining speed depends on this reaction rate. Therefore, the mechanism and kinetics for this reaction give us important information for the analysis, simulation and control of processes, and development of new refining systems. Many investigations have been done for clarification of reaction mechanisms between molten oxide containing iron oxide and CO-CO2 gas, however the direct measurement of oxygen exchange rate controlled by chemical reaction has not been conducted because of experimental difficulties. In the present work, oxygen exchange reaction rate between molten iron oxide and CO-CO2 gas has been measured by means of isotope exchange technique using C18O2-enriched CO2 gas. Isotope exchange technique is a useful method because the chemical reaction rate between gas and liquid phases could be measured directly without any influence of mass transfer in gas or liquid phases. The effects of temperature and CO2/CO ratio on the exchange rate have been investigated. It was clarified that the exchange rate was determined by interfacial reactions at first, and then by diffusion of 18O in liquid iron oxide.

“In Situ” Observation of Smelting Reduction and Carburization of Iron Ore with Carbonaceous Materials by Laser Scanning Microscope

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The Solubility of Oxygen in Liquid Iron Oxide During the Combustion of Iron Rods in High-Pressure Oxygen

The combustion of pure iron rods in oxygen is characterized by excess oxygen in the molten products. The amount of oxygen dissolved in the molten mass exceeds that required for stoichiometric haematite, Fe2O3, the highest oxidation state for solid iron oxide. Oxygen mass-balance calculations and post-test product analysis suggest that the average oxygen-to-iron molar ratio of the molten oxide product is as high as 2.1 and possibly higher. This corresponds to an increase in oxygen solubility in the molten iron oxide (over that of molten iron metal), which is compatible with the existence of various forms of ferrite ions such as FeO2−1, Fe2O5−4, FeO3−3, and Fe2O7−8. The presence of this excess oxygen confirms the proposed heterogeneous mechanism for the burning of iron, that is, that primary oxidation takes place at an interface between liquid iron and the molten combustion products containing the excess oxygen.

高炉融着帯・滴下帯領域での溶融酸化鉄によるコークスの劣化

高炉融着帯・滴下帯領域での溶融酸化鉄によるコークスの劣化

Studies for the Staggered Pans Core Catcher

Special devices (core catchers) might be required in the future to prevent containment failure by basemat erosion after reactor pressure vessel melt-through during a core meltdown accident. Quick freezing of the molten core masses is desirable to reduce the release of radioactivity. A configuration is investigated that consists essentially of a stack of vertically superimposed melt-resistant ceramic pans and that makes use of the vertical extension of small-diameter cavities to provide a sufficiently large spreading area such that the core melt freezes quickly. Tests with {approximately}100 kg of molten iron and aluminium oxide generated by the thermite reaction give some information on the resistance of various materials against the mixed metal/oxide melt and on the flow and distribution of metallic and oxide melts in such a core-catcher configuration.

溶融酸化鉄の還元速度におよぼす石炭中の揮発分の影響

溶融酸化鉄の還元速度におよぼす石炭中の揮発分の影響

Reducing Rates of Molten Iron Oxide by Solid Carbon or Carbon in Molten Iron

In order to collect basic data on the smelting reduction process which consists of blowing powder iron ore and powder coal into molten iron bath with oxygen gas for a partial combustion, the reduction rates of molten iron oxide by the solid carbon or the carbon in molten iron were measured. Molten iron oxide in a steel or an alumina crucible was reduced by a rotating carbon rod. The carbon in molten iron in an alumina crucible was reacted with molten iron oxide which was melted in a steel container beforehand. The reduction rates were calculated from the amount of CO gas evolved. The following results were obtained:(1) The reduction rates of molten iron oxide by the solid carbon were 0.21-0.82×10-4mol-FeO/cm2•s at 1420-1620°C, and the activation energy of the reaction were 75 and 31kcal/mol for a steel and an alumina crucibles, respectively.(2) The reduction rates of molten iron oxide by the carbon in molten iron were 1.1-3.3×10-4mol-FeO/cm2•s at 142O- 1620°C, and the activation energy of the reaction was 44kcal/mol.(3) It was concluded that the reaction rate between the solid iron oxide and the carbon in molten iron was the highest among reactions between the solid or the molten iron oxide and the solid carbon, the carbon in molten iron, CO, or H2 gas based on the results so far.

溶融酸化鉄の固体炭素および溶銑中炭素による還元速度

溶融酸化鉄の固体炭素および溶銑中炭素による還元速度

Reduction of Molten Iron Oxide and FeO Bearing Slags by H2-Ar Plasma

(I) Reduction of molten iron oxide and FeO bearing slag by H2-Ar plasma was studied using water cooled Cu crucible. The sample weights were 25 to 75g, the flow rate of mixture-gas was 20l/mm and DC electric power of plasma was 8.3kW. Results obtained were as follows:(1) The reduction of molten iron oxides proceeds linearly with time and the reaction rate is proportional to the partial pressure of atomic hydrogen. Therefore, it is considered that the rate determining step is the chemical reaction between FeO and the atomic hydrogen formed by thermal dissociation in the plasma.(2) The rate of reduction of FeO bearing slag is lower than that of molten iron oxide and is proportional to the FeO concentration in slag. It is presumed that the reduction rate is controlled by both the chemical reaction rate of FeO with atomic hydrogen at the gas-solid interface and the mass transport rate of FeO across the boundary layer between the interface and the molten slag bulk.(3) The reduction of molten iron oxide and FeO bearing slag by H2-Ar plasma takes place only on the cavity formed at the surface of melt by the momentum of plasma jet gas.(II) Continuous melting of pre-reduced ore powder, obtained by a fluidized bed reduction was examined using MgO crucible and H2-Ar plasma.Following results were obtained:(1) Carry-over loss of the pre-reduced ore powder during the melting in plasma arc furnace was small, when the condition of powder feeding and plasma arc were properly chosen.(2) Reduction of FeO in slag, accompanied in fed material, by H2-Ar plasma, could be described by a simple model of continuous melting and reduction, based on experimental results of the reduction of FeO bearing slag as described (1-2).With this model, the rate of reduction during continuous melting was determined.