Iron Droplets Research Articles

Composition changes and micro explosion characteristics of burning droplets formed by combustion of micrometer iron wires

To analyze the composition changes during the combustion process of iron droplets using the energy balance equation, iron wires with diameters of tens of micrometers were burned to form temperature-stable iron droplets with diameters of hundreds of micrometers. High-speed two-color imaging pyrometry was employed to measure the spatially resolved surface temperature and volume changes of the droplets under varying oxygen concentrations. Experimental results showed that the droplet's temperature stabilized between the melting points of wüstite and iron. Quantitative analysis revealed the presence of bubbles within the droplets, primarily sourced from the oxidation of carbon in the iron to carbon dioxide. Simulation results of the droplet combustion process revealed that at the experimental combustion temperatures, the transport of oxygen in molten iron oxides was the rate-limiting step. The gas responsible for micro-explosions originates from the release of dissolved excess oxygen before the solidification of molten iron oxides, with rough estimates indicating that the mass of the released gas is only 0.02% to 0.03% of the droplet mass. The impact of reaction kinetics parameters on the simulation results, as well as the role of the micro-explosion mechanism in the self-sustained combustion of iron wires, were also discussed.

Mill Scale - Biomass Pellet as a Charged Material for EAF Steelmaking

With an aim to utilize the local-based waste materials, this research investigated the production of mill scale - biomass pellet (MBP) as an alternative charged material for EAF steelmaking. Rubber tree bark (RTB) is one of the major biomasses in Thailand, consisting of carbon and hydrogen as the main compositions. The carbon derived from RTB was mixed with coal into five different ratios. Pure coal and RTB were employed for comparison. Seven carbonaceous samples were blended with mill scale at a C/O molar ratio of 1:1 to produce MBP, namely Coal, blend#1 – blend#5 and RTB. The reduction of MBP was investigated in a horizontal tube furnace under argon atmosphere at 1550°C for 15 and 30 minutes. The obtained products were iron droplets and residual black powder of unreacted oxides. Quantities of reduced iron from the MBP of blend#1 – blend#5 was about 58 – 61 wt% after 30 minutes, while it was 62 wt% and 57 wt% for coal and RTB, respectively. Degree of metallization (DOM) for blend#1 – blend#5 was between 78.1 – 81.7%, while it was 82.7% and 83.3% for coal and RTB. This research offers the possible method to utilize mill scale and RTB biomass toward circular economy.

Innovative Transformation and Valorisation of Red Mill Scale Waste into Ferroalloys: Carbothermic Reduction in the Presence of Alumina

Primary and secondary mill scales (MSs) are waste products produced by the surface oxidation of steel during the hot (800 to 1200 °C) rolling process in downstream steelmaking. While the primary MS is comprised of FeO, Fe3O4, and Fe2O3 in a range of proportions, the secondary MS primarily contain red ferric oxide (Fe2O3) (red MS). We report a novel route for extracting iron from red MS and transforming it into ferro-aluminium alloys using carbothermic reduction in the presence of alumina. The red MS powder was blended with high-purity alumina (Al2O3) and synthetic graphite (C) in a range of proportions. The carbothermic reduction of red MS-Al2O3-C blends was carried out at 1450 °C and 1550 °C under an argon atmosphere for 30 min and then furnace-cooled. The red MS was completely reduced to iron at these temperatures with reduced iron distributed around the matrix as small droplets. However, the addition of alumina unexpectedly resulted in a significant increase in the number and sizes of iron droplets generated, much higher reactivity, and the formation of ferrous alloys. A small amount of alumina reduction into metallic aluminium was also observed at 1450 °C. There is an urgent need to identify the true potential of industrial waste and the materials within it. This study showed that red MS is a valuable material source that could be transformed into ferro-aluminium alloys. These alloys find application in a range of industrial sectors such as construction, automotive, infrastructure, etc.

Uvarovite from Reduced Native Fe-Bearing Paralava, Hatrurim Complex, Israel

Abstract A new genetic type of chromium garnet—uvarovite with the simplified formula Ca3(Cr,Al,Ti4+,V3+)2(Si,Al)3O12—was detected in unusual wollastonite-gehlenite-bearing paralava within the Hatrurim Complex in Israel. The pyrometamorphic rocks of that Complex usually formed in the sanidinite facies (low pressure and high temperature) and, as a rule, under oxidized conditions. This paralava contains nodules and grain aggregates of native Fe, usually distributed linearly in the rock or located close to gaseous voids. The presence of native iron droplets in association with the “meteoric” phosphide—schreibersite, suggests that the formation of paralava occurred under high-reducing conditions and high temperature, reaching 1500°C. Uvarovite forms xenomorphic grains either randomly distributed within the rock or flattened crystals on the walls of gaseous voids. Analyzed uvarovite indicates a significant enrichment in Ti4+ (up to 8 wt.% TiO2) and V3+ (up to 4.5 wt.% V2O3), the highest concentrations documented for uvarovite. Unlike known uvarovite from different localities, uvarovite from this study does not contain Fe3+, and Fe2+ is present in insignificant amounts. The obtained structural data reveal that the high contribution of hutcheonite, Ca3Ti4+2SiAl2O12 (up to 18%), and goldmanite, Ca3V3+2Si3O12 (up to 11%), end-members increases the lattice parameter a to >12.00 Å. The crystallization of uvarovite occurs in the narrow interval of oxygen fugacity, a little above the iron-wüstite buffer ƒO2 ≥ ΔIW. Uvarovite xenomorphic grains formed due to the decomposition of wollastonite and chromite, including H2S from the intergranular melt/fluid according to the following reaction: Ca3Si3O9 + Fe2+Cr3+2O4 + H2S → Ca3Cr2Si3O12 + FeS + H2O, while the flattened crystals grew from specific melt that formed on the walls of the voids as a result of exposure of hot gas flow. The comparison of the obtained results with available chemical data from previous studies reveals a gap in the natural isomorphic series between andradite and uvarovite.

The nature of some Late Bronze Age iron-bearing artefacts of the Ural-Kazakhstan region

The problem of the beginning of iron production in the Late Bronze Age of the Ural-Kazakhstan region is dis-cussed. For this, 13 iron-bearing artefacts from nine settlements that functioned in the 2nd mil. BC were studied using the SEM-EDS and LA-ICP-MS methods: metal objects, metallurgical slags, and a bimetallic droplet. Most of the studied artefacts are not related to the iron metallurgy. High ferric impurities in copper metal products of the Late Bronze Age on the territory of the Southern Trans-Urals are caused by the use of iron-rich ore concentrates. The raw materials for these products were represented by mixed oxidized-sulphide ores from the cementation subzone of the volcanogenic massive sulphide and skarn copper deposits. Iron droplets, frequently found in the Late Bronze Age copper slag in the Ural-Kazakhstan region, are not directly related to iron metallurgy. They are by-products of the copper metallurgy formed in the process of copper extraction from the iron-rich components of the furnace charge or fluxes (brown iron ore, iron sulphides). The only artefacts that indicate direct smelting of metal from iron ore are the slag fragments from the Kent settlement. Presumably, oxidized martitized ore of the Kentobe skarn deposit or its nearby analogues was used to extract iron at the Kent settlement. Rare finds of iron slags from the Late Bronze Age, known only in the territory of Central Kazakhstan, confirm an extremely small scale of iron production. Iron ore had been already deliberately used for these experiments. However, iron metal-lurgy in the Ural-Kazakhstan region developed into a mature industry much later. The discovery of iron metallurgy based on the smelting of copper-sulphide ores in the Ural-Kazakhstan steppes is doubtful. The use of sulphide ores here is known from the 20th c. BC, and it was widespread. In the meantime, the first iron slags and products appear much later, and their finds are sporadic. The development of iron metallurgy on the basis of experiments with iron ores seems more likely.

Falling Angle of Fe‐C‐Based Alloy Droplet on Coke and Graphite

The hold‐up of molten pig iron and slag melt in the coke packed bed of blast furnace (BF) causes a decrease of void between coke lumps and inhibits gas permeability. Smooth dripping of those liquids in the coke bed is desirable to keep the productivity of BF. Herein, the conditions for smooth flowing of molten iron on coke surface are calrified, and the falling angles of Fe‐C and actual pig iron droplets on coke and graphite are measured at high temperature. It is found that Fe‐C droplet easily slids down on coke because of small falling angle, and the falling angle of actual pig iron is even smaller, while those droplets adhere to a graphite substrate. The carbon in iron has only a small effect on the static contact angle with coke, but has a great influence on the falling angle. From the viewpoint of the roughness of coke surface, the variation of static contact angle and falling angle is discussed.

Numerical simulation of Marangoni effect induced by species transfer across iron droplet–molten slag interface

Numerical simulation of Marangoni effect induced by species transfer across iron droplet–molten slag interface

Laser-assisted reduction of iron ore using aluminum powder

This study reports on the laser-assisted reduction of iron ore waste using Al powder as a reducing agent. Due to climate change and the global warming situation, it has become of paramount importance to search for and/or develop green and sustainable processes for iron and steel production. In this regard, a new method for iron ore utilization is proposed in this work, investigating the possibility of iron ore waste reduction via metallothermic reaction with Al powder. Laser processing of iron ore fines was performed, focusing on the Fe2O3–Al interaction behavior and extent of the iron ore reduction. The reaction between the materials proceeded in a rather intense uncontrolled manner, which led to the formation of Fe-rich domains and alumina as two separate phases. In addition, a combination of Al2O3 and Fe2O3 melts, as well as transitional areas such as intermetallics, was observed, suggesting the occurrence of incomplete reduction reaction in isolated regions. The reduced iron droplets were prone to acquire a sphere-like shape and concentrated mainly near the surface of the Al2O3 melt or at the interface with the iron oxide. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and wavelength-dispersive x-ray spectroscopy analyses were employed to analyze the chemical composition, microstructure, and morphological appearances of the reaction products. High-speed imaging was used to study the process phenomena and observe differences in the movement behavior of the particles. Furthermore, the measurements acquired from x-ray computed microtomography revealed that approximately 2.4% of iron was reduced during the laser processing of Fe2O3–Al powder bed, most likely due to an insufficient reaction time or inappropriate equivalence ratio of the two components.

Utilization of rubber tree bark as a carbon source for electric arc furnace steelmaking: Carbon/slag interaction at 1550℃

Rubber tree bark (RTB) is a biomass that consists of wood and rubber parts, with high volatile and ash contents. This research reports the utilization of RTB as a carbon source in Electric Arc Furnace steelmaking processes. RTB was mixed with coal at a ratio of 1:1 by weight, and heated at 1000℃ under an argon atmosphere for 1 h. The chars were brought to contact with Electric Arc Furnace slag (37.86 wt% Fe2O3) at 1550℃ for 15 min to investigate their interaction and compared to coal. Coal showed short slag foaming behavior with a foaming time of 4 min, while complete FeO reduction was seen thereafter with the DOM of 65.14%. For RTB, slag foaming sustains over 15 min, but small extent of FeO reduction was observed with the DOM of 42.57%. For the Mixture, foaming time was 8 min, while iron droplets were seen since 8 min with the DOM of 54.63%. It was likely that interaction between the mixture and slag was due to the synergistic effect between coal and RTB. This research unlocks the potential of using RTB biomass for steelmaking process and the consumption of coal could be deducted by up to 50 wt%.

Tulp1 deficiency causes early-onset retinal degeneration through affecting ciliogenesis and activating ferroptosis in zebrafish

Mutations in TUB-like protein 1 (TULP1) are associated with severe early-onset retinal degeneration in humans. However, the pathogenesis remains largely unknown. There are two homologous genes of TULP1 in zebrafish, namely tulp1a and tulp1b. Here, we generated the single knockout (tulp1a−/− and tulp1b−/−) and double knockout (tulp1-dKO) models in zebrafish. Knockout of tulp1a resulted in the mislocalization of UV cone opsins and the degeneration of UV cones specifically, while knockout of tulp1b resulted in mislocalization of rod opsins and rod-cone degeneration. In the tulp1-dKO zebrafish, mislocalization of opsins was present in all types of photoreceptors, and severe degeneration was observed at a very early age, mimicking the clinical manifestations of TULP1 patients. Photoreceptor cilium length was significantly reduced in the tulp1-dKO retinas. RNA-seq analysis showed that the expression of tektin2 (tekt2), a ciliary and flagellar microtubule structural component, was downregulated in the tulp1-dKO zebrafish. Dual-luciferase reporter assay suggested that Tulp1a and Tulp1b transcriptionally activate the promoter of tekt2. In addition, ferroptosis might be activated in the tulp1-dKO zebrafish, as suggested by the up-regulation of genes related to the ferroptosis pathway, the shrinkage of mitochondria, reduction or disappearance of mitochondria cristae, and the iron and lipid droplet deposition in the retina of tulp1-dKO zebrafish. In conclusion, our study establishes an appropriate zebrafish model for TULP1-associated retinal degeneration and proposes that loss of TULP1 causes defects in cilia structure and opsin trafficking through the downregulation of tekt2, which further increases the death of photoreceptors via ferroptosis. These findings offer insight into the pathogenesis and clinical treatment of early-onset retinal degeneration.

Evaporation of As and Sn from Liquid Iron: Experiments and a Kinetic Model during Top-Blown Oxygen Steelmaking Process.

Evaporation kinetics of tramp elements (M = As and Sn) in liquid iron were investigated by high-temperature gas–liquid reaction experiments and a phenomenological kinetic model. Residual content of As or Sn in the liquid iron ([pct M]) during the evaporation was measured in the temperature range of 1680 C to 1760 C. [pct As] and [pct Sn] decreased faster as the reaction temperature and [pct C] increased. Assuming first-order reaction kinetics, the apparent rate constants () were obtained at each reaction temperature and [pct C]. [pct M] in a liquid iron during the top-blown oxygen steelmaking process was simulated, with an emphasis on enlarging the reaction surface area by forming a large number of liquid iron droplets. The surface area and the droplet generation rate were obtained based on the oxygen-blowing condition. The whole surface area increased up to ∼163 times the initial liquid iron (bath) surface area, due to the generation of the droplets. Using the obtained in the present study, the evaporation of M during the top-blown oxygen steelmaking process for 200 tonnes of liquid iron was simulated. For a condition of [pct M] = 0.005 (M = As and Sn), As and Sn could be removed from the liquid iron, which was seen to be much improved by the consideration of the droplet generation. However, additional actions are required to improve the evaporation rate, as the evaporation rate in the BOF process was not fast enough to be practically considered.

Modeling and Parameterization of the Evaporation and Thermal Decomposition of an Iron(III) Nitrate Nonahydrate/Ethanol Droplet for Flame Spray Pyrolysis

Flame spray pyrolysis (FSP) is a promising approach to generate nanoparticles from precursor solutions, where the convective droplet heating and evaporation of the single precursor solution droplet play a key role. Depending on the precursor solution under consideration, reactions inside the liquid may occur. The present numerical study concerns the heating, evaporation, and thermal decomposition of single droplets of iron(III) nitrate nonahydrate (INN) and ethanol at an initial temperature of 293.15 K in hot convective air at atmospheric pressure. If the ambience is below the thermal decomposition temperature (Tth) of the INN, iron nitrate particles are directly formed inside the particle, whereas at ambient temperatures beyond Tth, the iron nitrate thermally decomposes into gaseous Fe2O3 and N2O5. Vaporization and thermal decomposition govern the process, depending on the droplet surface temperature. If the ambient temperature is larger than a specific value T+, thermal decomposition is very fast and vaporization dominates the total process time, whereas at lower ambient temperatures, the vaporization is slower, which causes a lower final droplet surface temperature, leading to considerably longer thermal decomposition, which dominates the total process time under that condition. The ambient temperature at which this reversed behavior occurs depends on initial INN loading of the particle and the relative velocity but is largely independent of the initial droplet size. These new results are very useful in choosing the process temperature, which is recommended to lie beyond the ambient air temperature of T+ to assure that the total process time is kept short. The numerical results are parameterized for use in more complex simulations of FSP.

A research on rigid polyurethane foam resistibility to ignition from an electric arc welding spark

Introduction. A fire investigation assumes that electric arc welding sparks (hereinafter referred to as “sparks”) are effective sources of ignition. However, the spark ignition of a combustible material depends on the contact time. This work has experimentally proven that a smooth vertical wall, made of combustible rigid polyurethane foam (PUF), is not subjected to spark ignition. To explain this fact, the author calculated the time of contact between the spark and the wall τint, and compared it with the minimal estimated contact time τmin required to ignite the wall.The sample and the testing procedure. Sparks (the arc power up to 6 kW, the current up to 160 A) reached the PUF wall located at a distance of 0.1–0.15 m from the arc. An everyone experiment was continued until the electrode was burned down.Research results and discussion. Neither attempt to inflame the PUF sample by a spark was successful. Sparks bounced off the PUF sample and fell down. The characteristic dimensions of cooled iron droplets ranged from 0.2 to 3 mm.An evaluation of τint. The authors applied a model of elastic interaction between a drop of molten iron and a rigid wall, assuming that the sum of the potential energy of the drop, associated with its surface, and the kine­tic energy of a spreading drop, if flattened, is conserved. The longest contact time is achieved for drops, featuring the maximum diameter of 3 mm: τint ≈ 0.004 s.Estimation τmin. The authors applied the experimental modeling of the process, whereby the effect of an iron drop on PUF was replaced by the time-controlled effect, produced by a wooden cylinder (6 mm in diameter), inflamed at one edge. τmin ≈ 0.3 s. The ratio τint << τmin explains the inability of electric arc welding sparks to ignite the PUF wall.Conclusions. Electric arc welding sparks, having a diameter of up to 3 mm, cannot ignite a vertical wall, made of rigid combustible polyurethane foam, in case of a side impact. The lack of ignition is explained by the short-term contact between the spark and the surface of the polyurethane foam.

Flux‐Mediated Wetting of Alumina by Liquid Fe–Ti–Csat

In article 2100068, S. T. Britt and P. C. Pistorius study liquid titanium-bearing iron (saturated with carbon) wets alumina crucibles. Wetting is caused by reaction between dissolved titanium and alumina; it can be prevented by pre-treating the alumina crucible with a liquid flux containing alumina and calcium fluoride. By avoiding wetting, clear images of titanium carbide formation on the iron droplet can be obtained, during confocal scanning laser microscopy.

Phenomenon of Whiskers Formation in Al2O3−C Refractories

Pure alumina (Al2O3) and carbon‐bonded alumina (Al2O3−C) are used to investigate their interaction with iron (Armco) at 1625 °C, applying the sessile drop method. The investigations are conducted inside a heating microscope for 1 h under argon atmosphere with low oxygen partial pressure. No whiskers formation is observed from the experiments with pure Al2O3 and molten iron. In the case of Al2O3−C/Fe system, several phenomena including the decarburization of Al2O3−C, Al2O3−C dissolution in molten iron, Al2O3 layer formation on the iron droplet, and Al2O3 whiskers formation are observed. To clarify the possible influence of iron on Al2O3 whiskers formation, blank Al2O3−C samples without the presence of iron are heated and held in a half‐sealed platinum crucible at 1550 °C for 2 h. Thereby, the Al2O3 whiskers formation is detected. Finally, the experimental investigations are supported with thermodynamic simulations.

Redox Hysteresis of Super-Earth Exoplanets from Magma Ocean Circulation

Abstract Internal redox reactions may irreversibly alter the mantle composition and volatile inventory of terrestrial and super-Earth exoplanets and affect the prospects for atmospheric observations. The global efficacy of these mechanisms, however, hinges on the transfer of reduced iron from the molten silicate mantle to the metal core. Scaling analysis indicates that turbulent diffusion in the internal magma oceans of sub-Neptunes can kinetically entrain liquid iron droplets and quench core formation. This suggests that the chemical equilibration between core, mantle, and atmosphere may be energetically limited by convective overturn in the magma flow. Hence, molten super-Earths possibly retain a compositional memory of their accretion path. Redox control by magma ocean circulation is positively correlated with planetary heat flow, internal gravity, and planet size. The presence and speciation of remanent atmospheres, surface mineralogy, and core mass fraction of primary envelope-stripped exoplanets may thus constrain magma ocean dynamics.

Influence of Interface Electric Field on Wettability Between Molten Iron and Submerged Entry Nozzle Interface

The study of submerged entry nozzle clogging dynamics mainly focuses on the interface wetting behavior. So as to understand the effect of the interface electric field on the wetting behavior between the immersion nozzle and the molten steel, electrowetting experiments and field industrial tests were performed. The results show that the wettability between the iron droplet and the nozzle constituent material can be improved by applying an electric field, and the solid–liquid wetting angle decreases with increasing voltage. There is an electric field at the interface between the submerged entry nozzle and molten steel during continuous casting, and the resulting electrowetting effect significantly changes the wetting behavior between the molten steel and the nozzle, which promotes the interaction between the two phases resulting in a large amount of deposits on the inner surface of the submerged entry nozzle, causing nozzle clogging.

Observations of FeO Reduction in Electric Arc Furnace Slag by Aluminum Black Dross: Effect of CaO Fluxing on Slag Morphology

The effect of CaO fluxing on slag morphology was investigated during the reduction of FeO in electric arc furnace slag by aluminum black dross (ABD). Macro- and microscopic observations, by evaluating entrapped gas bubbles and reduced iron droplets related to gas evolution, apparent slag morphologies, and vertical section of slag at different initial CaO contents and reaction times, confirmed that both aluminothermic (dominant reaction) and carbothermic (minor) reduction occurred. Thus, the production of CO(+CO2) gas caused swelling-shrinking phenomena with repeated expansion and collapse of the slag pellet. In addition, macroscopic observation of slag morphologies as a function of the initial CaO content is well associated with quantitative consideration of the apparent viscosity as well as spinel ([Mg,Fe]Al2O4) activity. Consequently, appropriate CaO fluxing is necessary to control the composition of highly fluid slag by changing the slag from a high-alumina system to calcium–aluminosilicate melts when utilizing ABD as a reducing agent.

Optimization of Basicity of High Ti Slag for Efficient Smelting of Vanadium Titanomagnetite Metallized Pellets

Slag basicity (mass ratio of CaO to SiO2) is an important index to ensure smooth operation and efficient separation between the metal and slag within the metallurgical industry. Effects of basicity of the high titanium slag on the recovery of iron and vanadium, the separation behaviors between iron and slag, as well as the slag foaming behavior during the smelting process with the operating temperature of 1550 °C have been experimentally investigated. The results show that the recovery ratios of iron and vanadium increase with higher slag basicity. The amount of dispersed metallic iron droplets in the slag decreases sharply when the basicity increases from 0.5 to 0.8, then decreases slowly when the basicity is from 0.8 to 1.1. Furthermore, the perovskite (CaTiO3) phase appears when the basicity is above 0.8. The foaming height is at a high level when the basicity is from 0.5 to 0.6, then it decreases when the basicity is increased from 0.6 to 0.7, whereas it slowly increases with higher slag basicity. Finally, the optimum basicity range of titanium slag for efficient smelting of vanadium titanomagnetite is proposed to be 0.8 to 1.1 by considering the combined effects on the recovery, foaming, and minimization on the retention of the metal droplets within the slag.

Preparation of iron powders using rotary cup atomizer with water curtain

A novel atomization process based on a rotary cup atomizer (RCA) was proposed to manufacture iron powders using semisteel as the raw material. To achieve rapid cooling of iron droplets and efficient separation of iron powders from cooling water, a circle of water curtain was set around the RCA in the experimental setup. The effects of rotating speed, cup diameter, slope angle, and cup depth on the particle size of iron granules were investigated to meet the size requirement of iron powders applied as reductive agent during the sulfate process. Results indicated that the optimal conditions for the atomization of semisteel were a rotating speed of 1800 rpm, a cup diameter of 150 mm. Under such conditions, the accumulative fraction of the obtained iron granules that measured less than 0.45 mm reached a maximum of 93.12 wt% when the slope angle and cup depth were 45° and 50 mm. Thus, this novel preparation process for iron powders with semisteel using RCA basically achieved the required particle size. The median diameter of the obtained iron granules decreased with an increase in rotating speed, cup diameter, slope angle, and cup depth. The disintegration mechanism of semisteel was determined, and the result indicated that the atomization process probably followed the ligament formation mode. A modified correlation that considered the influences of slope angle and cup depth was proposed to predict median granule size. An analysis on atomizer design was conducted based on these findings to provide a good insight for industrialization. As with RCA design for the treatment of molten semisteel rating up to 3.5 t/h, the minimum diameter of the rotary cup decreased from 1.36 m to 1.10 m as the rotary speed increased from 1200 rpm to 1800 rpm.