Increase In FeO Content Research Articles

Properties evaluation of electric smelting furnace slag: Viscosity and sulfide capacity under different FeO content

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO2-6wt.%MgO-10 wt%Al2O3-FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process.

Dynamic analysis of liquid permeability in the dripping zone of blast furnace and reaction behavior at the slag-coke interface

The dripping zone connects the cohesive zone and the hearth, it is one of the key areas of the blast furnace (BF). This study aims to explore the mechanism of the dripping process in BF. The dripping experiments under different conditions were carried out. Dynamics of liquid permeability in the dripping zone was analyzed, the reaction behavior at the slag-coke interface was investigated, and the consumption of coke in the dripping zone was clarified. The results show that: The retention ratio increases with the increase of Al2O3 content. The increase in retention ratio is related to the viscosity of slag. Once the Al2O3 content in slag increases, Si4+ coordination polymer ions in tetrahedra will be replaced by Al3+ cations, forming a tetrahedral structure of [AlO4]5– tetrahedron. The retention ratio decreases with the increase of FeO content. The dissociation of free oxygen ions (O)2– from FeO increases the concentration of free oxygen ions (O)2– in slag, this reduces the viscosity of slag. The presence of FeO can compensate for the increase in retention ratio caused by Al2O3. The quantitative relationship between retention ratio and Al2O3 content and FeO content in slag is obtained. The reduction reaction of FeO occurs at the slag-coke interface, the molten iron takes on the shape of small iron beads, which is the result of multiple small droplets gathering. The reduction of TiO2 is carried out by a series of reactions, the Ti exhibits a granular embedding state in molten iron, its color is darker than that of molten iron and its particles have distinct edges and corners. In the slag-coke area of retained sample, the reduction reaction occurs between coke and oxides in slag. The carbon will be consumed, resulting in a decrease in particle size. In the iron-coke area of retained sample, the carburization reaction occurs in large quantities due to the carbon content of molten iron in hearth is undersaturated, coke is further consumed.

Sulfide Capacity and Activity of Iron Oxide in CaO–SiO<sub>2</sub>–FeO Ternary System at 1573 K

The knowledge of sulfide capacities of FeO-containing slags is necessary for better understanding the resulfurization reaction in hot metal pre-treatments. In this study, copper-iron-sulfur liquid alloy was equilibrated with CaO–SiO2–FeO ternary slag to measure sulfide capacities and FeO activities simultaneously at temperature below the melting point of pure iron. The experimental result that the sulfide capacity increased with increasing FeO content could be explained by the fact that FeO was a basic oxide, and the sulfide capacity of the CaO–SiO2–FeO ternary system was significantly larger than those of the CaO–SiO2–MgO, CaO–SiO2–AlO1.5 and CaO–SiO2–CaF2 ternary systems. Although the FeO activity and oxygen potential were raised by the FeO addition, the calculated value for sulfur distribution ratio between CaO–SiO2–FeO slag and hot metal increased with an increase in FeO content.

Oxidation behavior of vanadium and phosphorus during simultaneous vanadium extraction and dephosphorization of hot metal

In this paper, the indirect equilibrium method was used to study the equilibrium distribution ratios of vanadium and phosphorus in the metal phase and the slag phase, and simultaneous vanadium extraction and dephosphorization experiments were carried out under different slag basicity (the mass ratio of CaO to SiO2) conditions to explore the oxidation behavior of vanadium and phosphorus during simultaneous vanadium extraction and dephosphorization of hot metal. The results show that with the increase of slag basicity, the equilibrium distribution ratio of V (lgLV) increases slightly and the equilibrium distribution ratio of P (lgLP) increases significantly. With slag basicity increasing from 0.5 to 2.5, lgLV and lgLP increase from 1.7 to 2.0 and 0.1 to 1.9, respectively. Both lgLV and lgLP decrease with the increase of temperature, and increase with the increase of FeO content. High MgO content is not conducive to vanadium extraction. MnO has less effect on lgLV and lgLP. lgLV increases with the increase of V2O3 content, and decreases with the increase of P2O5 content. lgLP decreases with the increase of V2O3 content, and increases with the increase of P2O5 content. Both lgLV and lgLP decrease with the increase of TiO2 content. When the slag basicity is 1.5, the oxidation rate of vanadium reaches 95% after 10 min of reaction. The total mass transfer coefficient of P is in the range of 0.0040–0.0084 cm/s, and increases obviously with the increase of slag basicity. However, the influence of slag basicity on the total mass transfer coefficient of V is not obvious. Both the rate-limiting step of vanadium extraction and dephosphorization are the mixed mass transfer in the metal phase and the slag phase.

Wetting and interfacial tension of molten CaO–Al2O3–MgO–FeO slag and BN substrate

The interface characterization is one of the important properties of molten slag, which has a significant influence on the interface phenomenon of molten slag and the reaction between slag and metal. The wettability of molten CaO–Al2O3–MgO–FeO slag on BN substrate was investigated in a wide range of temperatures from 1673 to 1773K. The FeO content was varied from 0 to 15 wt%. The contact angle was measured by the sessile drop method, the surface tension and interfacial tension were calculated by Dorsey method and Young's equation, respectively. The effects of the FeO content and temperature on the contact angle, surface tension and interfacial tension were discussed. The results indicated that the initial contact angle decreases with the increase of temperature and FeO content. And the wetting reaction between BN substrate and the selected molten slag is non-reactive wetting. The surface tension of the selected molten slag is in the range of 586–616 mN/m, and the surface tension decrease with the increase of FeO content and temperature. The value of interfacial tension between the selected molten slag and BN substrate is close to that of the surface tension, and the interfacial tension is 211–375 mN/m. The trend that the interfacial tension changes with the FeO content and temperature was the same as the trend that surface tension changes with the FeO content and temperature. Changes in the interfacial tension were correlated with modifications in the slag structure when FeO is added. The interfacial tension linearly decreases with increasing the optical basicity, which can provide a global measure of the concentrations of free oxygen ion in molten slag.

Mechanism of Phosphorus Enrichment in Dephosphorization Slag Produced Using the Technology of Integrating Dephosphorization and Decarburization

In order to better understand and develop the technology of integrating dephosphorization and decarburization in a single converter (abbreviated as IDDSC), the relevant thermodynamic issues were discussed by calculation. Based on the thermodynamic calculation, the bridges between the phosphorus distribution ratio, temperature, and slag composition were constructed. Besides, the connections between the dephosphorization behavior and the microstructure of slag were also established by investigating four heats of hot metal smelt using IDDSC technology. As a result, the mechanism of phosphorus enrichment in the dephosphorization slag was revealed. Also, the results show that the dephosphorization efficiency increases gradually with increasing slag basicity. While the dephosphorization efficiency increases first and then decreases with the increase of FeO content in slag. There is a competition relationship between P2O5 and FeO in reacting with CaO and SiO2. When CaO/FeO is relatively high, not enough FeO is provided. Thus P2O5 is in priority to react with CaO and SiO2 through [3n + 2](CaO) + 2SiO2 + n(P2O5) = n(3CaO·P2O5)-2CaO·SiO2(s), generating P2O5-rich nC2S-C3P solid solution which promotes the removal of [P] from the hot metal. When CaO/FeO is relatively low, FeO competes over P2O5 in reacting with CaO and SiO2 through a(CaO) + b(SiO2) + c(FeO) = aCaO·bSiO2·cFeO(s), generating CaFeSiO4 instead of P2O5-rich solid solution. As a consequence, the slag with low CaO/FeO shows a poor dephosphorization ability.

Modeling Viscosity of High Titania Slag

TiO2-FeO-Ti2O3 slag system is the dominant system for industrial high-titania slag production. In the present work, viscosities of TiO2-FeO and TiO2-FeO-Ti2O3 systems were experimentally determined using the concentric rotating cylinder method under argon atmosphere. A viscosity model suitable for the TiO2-FeO-Ti2O3 slag system was then established based on the modification of the Vogel-Fulcher-Tammann (VFT) equation. The experimental results indicate that completely melted high-titania slags exhibit very low viscosity of around 0.8 dPa s with negligible dependence on temperature and compositions. However, it increases dramatically with decreasing temperature slightly below the critical temperature. Besides, the increase in FeO content was found to remarkably lower the critical temperature, while the addition of Ti2O3 increases it. The developed model can predict the viscosities of the TiO2-FeO-Ti2O3 and TiO2-FeO systems over wide ranges of compositions and temperatures within experimental uncertainties. The average relative error for the present model calculation is < 18.82 pct, which is better than the previously developed models for silicate slags reported in the literature. An iso-viscosity distribution diagram was made for the TiO2-FeO-Ti2O3 slag system, which can serve as a roadmap for the Ilmenite smelting reduction process as well as the high titania slags tapping process.

Study of the Viscosity of a La2O3-SiO2-FeO Slag System

Abstract The viscosity and break temperature of La2O3–SiO2-FeO slag was investigated to develop low-Al2O3 or Al2O3-free slag for the effective recovery of rare-earth metals. When La2O3 content is fixed (45, 50 and 55 mass%), the viscosity and break temperature of La2O3–SiO2-FeO slag decrease with an increase in FeO content and a decrease in SiO2 content. A higher La2O3 content in the La2O3-SiO2-FeO ternary slag yields a lower slag viscosity but a higher break temperature. Individual minor components of Al2O3, MnO and B2O3 does not affect, or decreases slightly the viscosity of La2O3–SiO2-FeO slag, whereas the slag break temperature is reduced so that the reduction ability order is ranked as B2O3 &gt; Al2O3 &gt; MnO. A small amount of two components Al2O3 + MnO and Al2O3 + B2O3 has little effect on the viscosity of the slag but it has an additive effect on the slag break-temperature reduction.

Effect of MgO/Al2O3Ratio on Viscosity of Blast Furnace Primary Slag

AbstractThe effects of MgO, Al2O3, C/S (CaO/SiO2) and FeO on the viscosity and the liquidus temperature (TLQ) of blast furnace (BF) primary slag were analyzed by using multiphase equilibrium. The results show that theTLQof primary slag exhibits a minimum value at 12 wt% Al2O3and 14 wt% Al2O3when MgO contents are 8 wt% and 10 wt%, respectively. It can be suggested that the content of MgO in primary slag is prone to be retained at different value when Al2O3is different for smooth operation. The suitable value of MgO/Al2O3ratio increases with the increase of Al2O3content from 10 wt% to 18 wt% in the primary slag and the proper MgO/Al2O3ratio is 0.4–0.55. TheTLQof the slag increases with the increase of C/S when Al2O3content is lower than 14 wt%, while it decreases with the increase of the C/S when Al2O3is higher than 14 wt%. The slag viscosity decreases with the increase of FeO content. The isoviscosity curves become closer and closer when FeO is in a low level. In the condition of the high Al2O3content, improving the reduction degree of iron ore in the upper area of the BF can achieve a lowerTLQand have a smooth operation.

Viscosity of TiO2-FeO-Ti2O3-SiO2-MgO-CaO-Al2O3 for High-Titania Slag Smelting Process

The present study demonstrates the dependence of viscosity on chemical composition and temperature of high-titania slag, a very important raw material for producing titanium dioxide. The results indicated that completely molten high-titania slag exhibits a viscosity of less than 1 dPa s with negligible dependence on temperature. However, it increases dramatically with decreasing temperature slightly below the critical temperature, i.e., the solidus temperature of the slag. Above the critical temperature, the slag samples displayed the same order of viscosity at 0.6 dPa s, regardless of their compositional variation. However, the FeO, CaO, and MgO were confirmed to decrease viscosity, while SiO2 and Ti2O3 increase it. The apparent activation energy for viscosity-temperature relation and liquidus temperature based on experiments and thermodynamic calculations are also presented. Conclusively, the critical temperatures of the slags are on average 15 K below their corresponding calculated liquidus temperatures. The increase in FeO content was found to considerably lower the critical temperature, while the increase in both Ti2O3 and TiO2 contents increases it. The main phases of the slag in solid state, as indicated by X-ray diffraction, are (Fe, Mg)xTiyO5 (x + y = 3, pseudobrookite) and rutile.

Viscosity and structure evolution of the SiO2-MgO-FeO-CaO-Al2O3 slag in ferronickel smelting process from laterite

The SiO2 fractions in laterite-nickel ores are quite high, thus certain amount of lime should be used as fluxing material to achieve good fluidity and desulfurization capacity in industrial smelting process. However, this operation leads to an additional cost of lime. In addition, the increase of slag volume decreases the effective furnace volume. To avoid such problem, partial reduction of FeO has been suggested. Therefore, the high SiO2, low MgO and FeO and very little CaO slag is formed, which was less studied in the previous literature. Therefore, the viscosity and slag structure are investigated in the present study through FT-IR and Raman analysis methods. Experimental results show that the slag is a mixture of liquid and solid phases under the experimental temperature. The FT-IR and Raman spectra show that the fractions of the complex polymerization structure decrease significantly with the increase of FeO content and slag basicity, resulting in the decrease of apparent viscosity.

Study on mineralogical structure of dephosphorisation slag at the first deslagging in BOF steelmaking process

The mineralogical structure of dephosphorisation slag at the first deslagging was studied by SEM–EDS, XRD and FactSage 7.0. The results show that the slag which is favourable for the enrichment of Si, Ca and P has good dephosphorisation ability. While the slag that is favourable for the enrichment of Fe and O show poor dephosphorisation ability. The main mineralogical structure in liquid slag phase is 2CaO·SiO2 and 2CaO·SiO2–3CaO·P2O5, which is favourable for dephosphorisation. The values of and increase with increasing the mole fraction of P2O5 in the solid solution phase and in the liquid slag phase, and increasing the temperature of the first deslagging. The value of increases with the increase of FeO content and slag basicity, but decreases with the increase of FeO content and basicity of solid solution phase.

Adoption of Sinter Addition in Steelmaking Converter to Control Spitting

Steel Melting Shop-I, Rourkela Steel Plant, Rourkela, produces 0.5 MT of various special steels through BOF-VAR/VOR-LF-CC route. One of the most serious problems in BOF operations was lance skulling, hood jamming, and build-up of metal in the mouth and cone of the furnace due to spitting and slopping. As spitting occurring during blowing increases, these particles of metal are deposited inside the mouth and cone and affect badly BOF productivity. In the present work, control of spitting has been established by addition of sinter during the period of spitting. It also helped to improve the slag formation and fluidity of slag through increase of FeO content during peak decarburisation period.

Structural, Mechanical and Magnetic Properties of FeO Added Zirconia

ZrO2 is one of the most studied transition-metal oxides in biological field. Because of the excellent mechanical properties (high value of hardness, high fracture toughness etc.) it is used in protective coatings. The applications area of ZrO2 can be increased by the addition of metal oxide. Aim of this study is to determine the effects of FeO doping on ZrO2 thin films. FeO doped zirconia is synthesized by sol gel route. Different samples are prepared by varying iron oxide concentrations in the range of 2-10wt%. Sols of FeO doped ZrO2 are spun on glass substrate at 3000rpm for 30seconds and annealed at 300°C for 1 hour. X-ray diffraction results confirm the formation of tetragonal phase of ZrO2 along with low intensity peak of FeO. Crystallite size of FeO doped zirconia increases with increase in FeO content. Relatively low dislocation density is observed at 10wt% of FeO. Hardness of the sample, determined by micro Vickers hardness tester, lies is in the range of 400HV to 1000HV. FeO doped ZrO2 thin films show ferromagnetic behaviour with saturation magnetization of 2emu/g with 10wt%.

Numerical simulation of slag foaming on bath smelting slag (CaO–SiO2–Al2O3–FeO) with population balance modeling

A computational fluid dynamic (CFD) model has been developed for the simulation of slag foaming on bath smelting slag (CaO–SiO2–Al2O3–FeO) by considering foam as a separate phase. The CFD model has been used to predict the foam height, bubble number density and the multiphase flow phenomena in the system. The height of foam is dynamically balanced by the formation of foam due to transformation of both gas and liquid into foam and its destruction due to liquid drainage and bursting of bubbles, transforming foam back to liquid and gas. The bubble break-up and coalescence were considered in gas–liquid dispersion whereas in the foam layer, the bubble coalescence due to film rupture was incorporated. A population balance modeling was used to track the number density of different bubble classes and fixed pivot method was used to discretize the population balance equation. The model predicted the foam height of the slag system (CaO–SiO2–Al2O3–FeO). The content of FeO was changed and its effect on the foam height predicted. The foaming index was calculated and the results from the model predict that the foaming index decreases with increase of FeO content in slag. The CFD model also predicts that the foaming index of a slag with Al2O3 is higher than that of slag without Al2O3. Dimensionless analysis was performed based on the model available in the literature to correlate the foaming index with the physical properties of the slag. The predicted results from the present study are in reasonable agreement with available experimental data.

Recycling MgO–C refractories and dolomite fines as slag foaming conditioners: experimental and thermodynamic evaluations

Abstract The slag foaming process is currently applied in the steel production due to its greater benefits, i.e., reduction of energy losses, enhancement of the refractory service life and productivity, etc. Lime/dolomite, oxygen and carbon are usually added during an electric arc furnace (EAF) operation to adjust the liquid basicity and saturation and also provide suitable conditions for foam generation. Considering the high concentration of MgO and C contained in spent MgO–C refractories and dolomite fines (derived from rotary kilns), one good alternative consists of recycling those materials as slag conditioners. In this work, experimental tests and thermodynamic calculations (phase equilibrium, viscosity and isothermal solubility diagrams) were carried out in order to define the impact of some mixtures (comprised mainly of ground MgO–C spent bricks, dolomite fines and coke) on the foaming behavior of a molten synthetic slag at 1700 °C. Based on the attained results, recycling MgO–C bricks and dolomite fines led to faster slag saturation and provided suitable conditions for foam formation. Furthermore, the increase in FeO content in the liquid portion of the slag compositions presented a clear correlation with the measured foam height, indicating that this oxide plays a major role in the foaming phenomenon.

Study on the Desulphidation in Basic Electrode Welding

The behaviors of desulphidation during manual metal arc welding have been studied by means of experimental and theoretical analysis. The results indicated that the relationship curve between the distribution of sulphur in slag and deposited metal (Ls) and coating basicity of elect rode ( B1) was a parabolic shape with a maximum value. With the increase of FeO content in slag, Ls decreased and the sulphur content in deposited metal increased. With increasing coating basicity , the activity of oxygen ion in slag , FeO content in slag and oxygen potential of arc atmosphere increased. In teraction of them made that relationship between sulphur content in deposited metal and B1 had a minimum value.

Numerical Simulation of Slag Foaming in High Temperature Molten Metal with Population Balance Modeling

Abstract A computational fluid dynamic (CFD) model has been developed for the simulation of slag foaming on bath smelting slag (CaO-SiO-Al 2 O 3 -FeO) by considering foam as a separate phase which is comprised of a mixture of gas and liquid. The model accounts for the formation of foam due to transformation of both gas and liquid into foam and it's destruction due to liquid drainage and bursting of bubble. The bubble break-up and coalescence was considered in gas-liquid dispersion whereas in the foam layer, the bubble coalescence due to film rupture was incorporated. Population balance modelling was used to track the number density of different bubble class. The model predicted the foam height of the slag system (CaO- SiO-Al 2 O 3 -FeO). The foam height was found to increase with the increase of superficial gas velocity. The content of FeO was changed and its effect on the foaming index was observed. The results from the present model show that foaming index decreases with increase of FeO content in slag. The results from the CFD model also show that the foaming index of a slag with Al 2 O 3 is higher than that of slag without Al 2 O 3 . The predicted results from the present study are in reasonable agreement with the experimental data.

Recycling of steel plant mill scale via iron ore sintering plant

During the processing of steel in steel mills, iron oxides will form on the surface of the metal. These oxides, known as mill scale, occur during continuous casting, reheating and hot rolling operations. Mill scale is a valuable metallurgical raw material since it contains 65–70% iron. JSW Steel Ltd is a 7 Mtpa integrated steel plant and generates 270 t of mill scale per day. Most of the materials of steel plant wastes are recycled through sinter making in most of the countries. Because of its physical, chemical and mineralogical properties, it can be used as a raw material in a process like sintering. The mill scale contains high amounts of Fe and low amounts of silica and alumina. Thus, recycling it through the sintering process helps in the saving of raw materials like iron ore and limestone. This paper presents preliminary findings of a study that investigates the potential for recycling steel mill scale in the sintering process. Experiments were conducted using the mill scale in sinter making from 0 to 70 kg/t of sinter. The total Fe and FeO contents of the sinter increased with the increase in mill scale addition. The sinter productivity decreased with the increase in mill scale addition due to a decrease in sinter bed permeability. The sinter strength and sinter mean size initially increased and reaches a maximum at mill scale addition of 40–50 kg/t of sinter and afterwards declines with the increase in mill scale addition. Sinter reduction degradation index and reducibility decreased with the increase in mill scale addition due to the increase in FeO content. Except sinter productivity, other desired sinter properties can be obtained with the use of 40–50 kg mill scale per tonne of sinter.

Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags

Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags were determined at 1 673 K by electrochemical measurements of the solid electrolyte cell: Mo |Mo+MoO2|ZrO2(MgO)|Fe+(CaO-SiO2-Al2O3-MgO-FeO)+Ag|Fe. The influences of slag compositions and basicity on FeO activities were analyzed. The results reveal that, for slags of fixed (%CaO)/(%SiO2) ratio, MgO and Al2O3 content, there was an increase of FeO activities with increase of FeO content. For slags with constant {(%CaO)+ (%MgO)}/(%SiO2) ratio, fixed FeO and Al2O3 content, FeO activities decreased when MgO content increased from 5% to 10%, and increased with the increase of MgO content when it was over 10%. The FeO activities increased when (%CaO)/(%SiO2) ratio changed from 1.03 to 1.30 in the slags of constant MgO, FeO and Al2O3 content.