FeO Content In Slag Research Articles

Value-added recycling of iron and titanium from bauxite residue (Red Mud) via a flux-free smelting separation process

With enriched iron and titanium elements, red mud produced by the lime-free Bayer process showing high recycling value. This work proposed a pre-reduction and flux-free smelting process to recycle Fe/Ti resources from this red mud. Considering the extraction of titanium from smelting slag, classical calcareous flux was abandoned to avoid the formation of refractory perovskite. Instead, the FeO generated by pre-reduction of red mud itself was creatively applied to regulate the subsequent smelting separation. The full melting temperature of slag can be reduced from > 1700℃ to 1450℃-1550℃, as the FeO content in slag reached 10-20 wt%. The transition from rutile to ferrouspseudobrookite contributed to this change. Since the pre-reduced sample was smelted at 1600℃ for 60 min, 93.60 wt% of the iron element in red mud can be recycled in the form of iron nugget with grade of 99.6 wt%. Titanium in red mud can be recycled as Ti-rich slag, with TiO2 content of 55.91 wt%, for titanium dioxide production. The FeO in slag also suppressed the side reactions (i.e., carbonization of titanium and iron, reduction of silicon) in smelting process, which improved slag fluidity and iron nugget purity. This technique also provides a new approach for the utilization of V-bearing titanomagnetite, ilmenite, and other similar resources.

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.

Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.

Application of MLR, BP and PCA-BP Neural Network for Predicting FeO in Bottom-Blowing O2-CaO Converter

In order to accurately predict the FeO content of slag in the bottom-blowing O2-CaO process of the dephosphorization converter, multiple linear regression model, backpropagation (BP) neural network model and principal component analysis–backpropagation (PCA-BP) combined with neural network model were established to predict the FeO content of slag. It was found that the PCA-BP combined neural network model has the highest prediction accuracy by using principal component analysis to reduce the dimension of influencing factors of FeO content in slag and eliminate the correlation between input variables. The average absolute error is 1.178%, which is 0.78% lower than that of multiple linear regression model and 0.453% lower than that of multiple linear regression model. When the prediction error range is 3.0%, the prediction hit rate of the model is 96%, and when the prediction error range is 2.0%, the prediction hit rate of the model is 78%. The prediction model has important reference value for actual production.

Correlation and Optimization of Phosphorous Content in Liquid Steel with Turndown Temperature and FeO Content in Slag for Steel Making by LD Converter by Implementing Multi-Objective Evolutionary and Genetic Algorithms

Correlation and Optimization of Phosphorous Content in Liquid Steel with Turndown Temperature and FeO Content in Slag for Steel Making by LD Converter by Implementing Multi-Objective Evolutionary and Genetic Algorithms

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.

Corrosion Behavior of MgO–C Ladle Refractory by Molten Slag

The damage of ladle refractory, which mainly occurs at the position of the slag line, results in an increasing need of maintenance and repair and can, in the worst case, lead to a breakout of melts causing potential risks for the personnel and damage of equipment. On the basis of this fact, the corrosion behavior of MgO–C refractory in contact with molten slag during the steel refining process is experimentally studied in this work. Rotating and static dipping tests of MgO–C refractory in CaO–SiO2–Al2O3–MgO–FeO slags are conducted, and the effects of composition of slag, carbon in refractory, and rotation speed on the corrosion behavior are investigated. Results show that the corrosion depth of the MgO–C refractory increases with FeO content of slag and rotation speed of MgO–C rod, whereas it decreases with an increase in slag basicity. Slag notably penetrates the surface layer of MgO–C refractory after the carbon is oxidized, causing an aggravation of the corrosion. Moreover, the corrosion mechanism of MgO–C refractory in molten slag during the refining process is studied and illustrated in this work.

Oxidizability characterization of slag system on the thermodynamic model of superalloy desulfurization

AbstractThe oxidizability characterization method of slag system has a decisive influence on the accuracy of the desulfurization model. By carrying out the balance experiments of melting system composed of CaF2–CaO–Al2O3–SiO2–TiO2–MgO–FeO slag system and Inconel 718 superalloy, the influence of Al2O3 and FeO on desulfurization distribution ratio at 1,773 K was studied. Based on the ion and molecule coexistence theory in slag, the effects of three oxidizability characterization methods, [Fe]–[O] balance, [Al]–[O] balance, and [Fe]–[Al]–[O] balance, on the accuracy of desulfurization thermodynamic model were studied. The results show that the effect of FeO on desulfurization distribution ratio is more significant than that of Al2O3 when the FeO content in slag is greater than 0.014%. When the FeO content in the slag is less than 0.014%, the effect of Al2O3 on the slag oxidizability will be greater than that of FeO. The calculated value of [Fe]–[Al]–[O] balance model is closer to the experimental-measured value compared to [Fe]–[O] balance model and [Al]–[O] balance model alone at 1,923 K.

Fundamental Research on Gasification Dephosphorization with Coke Powder Reducing Converter Molten Slag

In order to realize the gasification dephosphorization process in converter slag splashing stage for avoiding the P enrichment, and the dephosphorized slag can be left for recycling in subsequent furnaces. The experiment of reduction of converter slag by coke powder in laboratory was carried out, The results show that with the increase of the experimental temperature, the gasification dephosphorization rate of coke powder gradually increases, and the gasification dephosphorization rate reaches up to 82.35% at 1900K. The gasification dephosphorization rate decreases with the increase of slag basicity. When the coke powder is added in a sufficient amount, increasing properly the FeO content of slag is favorable for the gasification dephosphorization reaction; when the coke particle size is between 0.5 and 2.5 mm, the gasification dephosphorization rate changed little, about 58%, but when the coke particle size between 2.5 and 3.5mm, the gasification dephosphorization rate dropped to 52%. The results provide some theoretical guidance for industrial development.

Distribution of P2O5 between solid solution and liquid phase in dephosphorization slag of CaO–SiO2–FeO–P2O5–Na2O system

A multi-phase slag containing Na2O is potential to efficiently dephosphorize high-P hot metal. After dephosphorization, the generated slag with high P2O5 content is regarded as a P resource. Because P2O5 was mainly concentrated in the 2CaO·SiO2–3CaO·P2O5 solid solution, the recovery of P from dephosphorization slag primarily depends on the separation of the solid solution from other phases. The distribution ratios of P2O5 between solid solution and liquid phase in the CaO–SiO2–FeO–P2O5–Na2O slag system were investigated. The results indicated that the addition of Na2O facilitated the enrichment of P2O5 in the solid solution because it increased not only the distribution ratio of P2O5 but also the mass fraction of the solid solution. The distribution ratio of P2O5 was independent of the P2O5 content in slag. A higher P2O5 content in slag resulted in higher P2O5 and Na2O contents in the solid solution. The distribution ratio of P2O5 increased with the total Fe content in the liquid phase, regardless of the valence of Fe. An increase in the FeO content in slag brought a higher P2O5 content in the solid solution. As slag basicity increased, the distribution ratio of P2O5 increased, but the P2O5 content in the solid solution decreased.

Effects of FeO and CaO/Al2O3 Ratio in Slag on the Cleanliness of Al-Killed Steel

The slag composition plays a critical role in the formation of inclusions and the cleanliness of steel. In this study, the effects of FeO content and the C/A (CaO/Al2O3) ratio in the slag on the formation of inclusions were investigated based on a 10-minute slag–steel reaction in a MgO crucible. The FeO content in the top slag was shown to have a significant effect on the formation of MgO·Al2O3 spinel inclusions, and critical content exists; when the initial FeO content in the slag was less than 2 pct, MgO·Al2O3 spinel inclusions formed, and the T.O (total oxygen) was 20 ppm; when the initial FeO content in the slag was more than 4 pct, only Al2O3 inclusions were observed and the T.O was 50 ppm. It was clarified that the main source of Mg for the MgO·Al2O3 spinel inclusion formation was the top slag rather than the MgO crucible. In addition, the cleanliness of the steel increased as the initial FeO content in the top slag decreased. As regards the effects of the C/A ratio, the MgO amount in the observed inclusions gradually increased, whereas the T.O content decreased gradually with the increasing C/A ratio. Slag with a composition close to the CaO-saturated region had the best effect on the inclusion absorption.

Three-Dimensional Mathematical Model of Oxygen Transport Behavior in Electroslag Remelting Process

A transient three-dimensional model has been proposed to investigate the oxygen transport behavior in electroslag remelting process. The electromagnetism, heat transfer, multiphase flow, and species transport were calculated simultaneously by finite volume method. The volume of fluid approach was adopted to trace the metal–slag–air three-phase flow. Based on the necessary thermodynamics of oxygen transport behavior, a kinetic model was established to predict the mass source terms in species transport equation. The kinetic correction factor was proposed to account for the effect of the oxide scale formed on the electrode on the FeO content in slag. Finally, the effect of applied current on the oxygen transfer was studied. The predicted result agrees well with the measured data when the kinetic correction factor is set to be 0.5. The temperature distribution that affects the thermodynamics differs at the interfaces. The oxygen in air is absorbed into slag due to the oxidation at the slag/air interface. The Fe2O3 in slag and the oxide scale contribute to the increase of FeO content in slag, and the latter one plays the leading role. The oxygen transfer from slag to metal mainly occurs during the formation of the droplet at the slag/metal droplet interface. With the current increasing from 1200 to 1800 A, the oxygen content increases from 76.4 to 89.8 ppm, and then slightly declines to 89.2 ppm when the current increases to 2100 A.

Effect of slag composition on steel cleanliness in interstitial-free steel

Ladle slag affects steel cleanliness at the end of the Ruhrstahl-Hereaeus (RH) and holding process. The relationship between composition of ladle slag, total oxygen (TO) and inclusions was investigated using X-ray fluorescence (XRF), infrared absorption, and SEM + EDS methods. The results indicate that TO in steel at the end of RH increases linearly with increasing FeO content in slag. TO is lower when ωCaO/ωAl2 O3(C/A)=1. 5-2. 0 than that of C/A = 1.0–1.4 under an approximate content of FeO. During the holding process, irregular Al2O3 inclusions are newly generated due to slag reoxidation. Additionally, Al2O3-Tix O inclusions are newly generated in the steel when the content of FeO is higher. By combining experimental and thermodynamic calculation results, it is determined that the slag has a good melting property within the zone of C/A=1.2–1.8 and adsorption capacity of Al2O3 when the content of SiO2 in slag is controlled at 4%–6%. The increase in the C/A ratio and the decrease of FeO content in slag can slow down the reoxidation rate.

Effect of FeO content in Slag on formation of MgOfflAl2O3inclusion for Al-killed steel

In this study, experiments are carried out to investigate the effects of FeO content in slag on formation of MgOfflAl2O3 inclusion for Al-killed steel, and thermodynamic and kinetics analysis are made to explain the experimental phenomena. Result shows that the dissolved [Mg] in steel is supplied from the reduction of MgO in slag by [Al] in steel after deoxidation with Al. However, the specific [Mg] content in steel is affected largely by FeO content rather than MgO content in slag. At low FeO content, the dissolved [Mg] in steel in equilibrium with FeO in slag is enough to transform most of the Al2O3 into MgOfflAl2O3 inclusions; at high FeO content, the dissolved [Mg] in steel can be expended by FeO in slag at the slag/metal interface and the formation of MgOfflAl2O3 can be restrained. In present work, FeO content in slag should be controlled at about 5 wt-% to avoid the formation of MgOfflAl2O3 as well as minimize the reoxidation between steel and slag as much as possible.

Vapor pressure measurement of lead and lead chlorides in FeOT–CaO–SiO2–Al2O3 system

Vapor pressure of lead and lead chlorides from FeOT–CaO–SiO2–Al2O3 slag system was measured by using Knudsen effusion method. The results suggest that the vapor pressures of lead and lead chlorides increase with increasing temperature. For the slag systems without chlorine, the logarithm of vapor pressure (lnp) shows highly linear dependency on the reciprocal of temperature (1/T), and higher vapor pressure is observed in the condition where more metallic lead vapor is formed. In this case, the vapor pressure of lead increases with increasing slag basicity (w(CaO)/w(SiO2)), increasing FeO content and w(Fe2+)/w(Fe3+) ratio. For the case of slag system with chlorine addition, the total pressures of PbCl2 and PbCl increase with decreasing basicity and FeO content of slag.

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.

Dephosphorization by Slag Pour out in the Smelting for High Carbon 70 Steel

Dephosphorization is one of key goals for converter to smelt high carbon steel. The chemical equation of dephosphorization reaction and the expression of phosphors distribution between slag and steel were deduced on fundamental of metallurgical thermodynamics and the steelmaking situation of Shougang Shuicheng Iron and Steel (Group) Co. Ltd. The rerults showed that the dephosphorus capcaty of slag increases with the increase of the content of FeO in slag, but decreases with the increase of temperature. Compared with the single slag operation, the total weight of slag met the dephosphorus requirement by the double slag process for high carbon 70 steel in 100t convert can be decreased to 80%.

The Control and Prediction of End‐Point Phosphorus Content during BOF Steelmaking Process

AbstractRemoval of phosphorus is a reaction, which plays an important role in combined converter steelmaking process, and the precise control of end‐point phosphorus content during BOF steelmaking process would greatly improve the quality of liquid steel. Therefore, the relation between dephosphorization ratio and temperature of liquid steel, FeO content of slag, slag basicity is clearly clarified through thermodynamic analysis of dephosphorization process in this paper. Besides, by means of combining the methods of multivariate regression analysis and multi‐level recursive completely, the multi‐level recursive regression model, which is used to complete the prediction of end‐point phosphorus content during BOF steelmaking process, is established based on large amount of production data. The verification of the model with the data taken from three steel plants indicates that the hit rate of the multi‐level recursive regression model is above 84% when predictive errors of the model are within ±0.005%, and it could provide a relatively good reference for real production.

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.