The effect of slag basicity on spinal inclusion wettability

Steel cleanness is an important and growing research area driven by the demands to produce high quality steel. Inclusion content in steel is an important criterion to assess clean steel. MgO.Ah03 spinel inclusions cause problems in steel processing and are generally deleterious to steel products due to their high melting point and high hardness. Jnclusions are generally r· moved by rea ting with slag. This is primarily achieved by optimizing lhe PI\u27 \u27ess omliLions to promote contact and reaction between the inclusion and S,l,lg \u27. or efticient rem val from the steel the inclusions must attach to and dissolve in the slag pba~e. If this atta hment is weak, then local fluid conditions are likely to result in the shearing of this attachment and the inclusions re-cntrapment in the . tee!. The strength of attachment (reactivity) between the inclusion and tJle slag phase can be characteri zed by the wettability of the slag on inclusions 2-3. Research on inclusion removal in steel refining is principally divided into categories of flotation of juclusion Lo the steel/slag interi\u27ace 4-5 modification to improve reactivity/separation wilh the sJag phase (j and dissoluti n in lhe s lag phase

The behavior of manganese in oxygen steelmaking

Manganese serves as an important alloying element in commercial grades of steel and high levels of Mn can improve the mechanical properties of steel. [1] The chemical behavior of Mn in Oxygen Steelmaking is complex because the element is readily oxidised in conditions found in steelmaking but the stability of its oxide is a strong function of temperature and slag chemistry, and the oxide can readily revert back to elemental Mn in steelmaking conditions. In many steel plants, manganese ore has been added to achieve high Mn at the end blow. This approach means that the use of relatively expensive ferromanganese (FeMn) can be reduced in the subsequent secondary steelmaking process. [1] Steel plants can also face the problem of high Mn (>1 wt pct) in the hot metal due to the use of lean iron ores with high MnO in the blast furnace, and this can cause operational issues in the steelmaking process.[2

Investigation into the cause of spontaneous emulsification of a free steel droplet : validation of the chemical exchange pathway

Small Fe-based droplets have been heated to a molten phase suspended within a slag medium to replicate a partial environment within the basic oxygen furnace (BOF). The confocal scanning laser microscope (CSLM) has been used as a heating platform to interrogate the effect of impurities and their transfer across the metal/slag interface, on the emulsification of the droplet into the slag medium. The samples were then examined through X-ray computer tomography (XCT) giving the mapping of emulsion dispersion in 3D space, calculating the changing of interfacial area between the two materials, and changes of material volume due to material transfer between metal and slag. Null experiments to rule out thermal gradients being the cause of emulsification have been conducted as well as replication of the previously reported study by Assis et al.[1] which has given insights into the mechanism of emulsification. Finally chemical analysis was conducted to discover the transfer of oxygen to be the cause of emulsification, leading to a new study of a system with undergoing oxygen equilibration

Volume shrinkage during carbothermic reduction of low-grade iron ore containing goethite and coal composite

The volume shrinkage and reduction behavior of low-grade iron ore goethite during the solid-state carbothermic process was studied and compared to synthetic goethite. The carbothermic reduction process using low-grade coal as a reducing agent was carried out in the temperature range 1000-1200 °C up to 60 min of reaction time. The results demonstrated that the volume shrinkage, reduction degree, and metallization degree of reduced samples increase with increasing temperature and reaction time. Compared to the reduced samples using synthetic goethite, the volume shrinkage, reduction degree, and metallization degree of the reduced samples using iron ore are lower due to the presence of impurities in Sebuku iron ore concentrates, which include Mg, Mn, Al, and Si. The highest volume shrinkage observed at 1200 °C for 60 min reaction time for the reduced samples using iron ore and synthetic goethite was 63.57±0.57 and 76.51±1.53%, respectively. The observed phases at this point were metallic iron (Fem) and spinel (Fe,Mg)Al2O4. The volume shrinkage of the reduced samples was caused primarily by the weight loss due to carbon, oxygen, and combined water evaporation, as well as the sintering of gangue oxides and metallic iron particles, and partial melting of these phases

Modeling of droplet generation in a top blowing steelmaking process

Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modeling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work, a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by Subagyo et al. on the basis of dimensionless blowing number (N B). The blowing number was re-evaluated at the impingement point of jet with taking into account the temperature effect of change in density and velocity of the gas jet. The result obtained from the work shows that the modified blowing number N B,T at the furnace temperature of 1873 K (1600 °C) is approximately double in magnitude compared to N B calculated by Subagyo and co-workers. When N B,T has been employed to the Subagyo’s empirical correlation for droplet generation, a wide mismatch is observed between the experimental data obtained from cold model and hot model experiments. The reason for this large deviation has been investigated in the current study, and a theoretical approach to estimate the droplet generation rate has been proposed. The suitability of the proposed model has been tested by numerically calculating the amount of metals in slag. The study shows that the weight of metals in emulsion falls in the range of 0 to 21 wt pct of hot metal weight when droplet generation rate has been calculated at ambient furnace temperature of 1873 K (1600 °C)

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : modelling of manganese removal

In the earlier work, a dynamic model for the BOF process based on the multi-zone reaction kinetics has been developed. In the preceding part, the mechanism of manganese transfer in three reactive zones of the converter has been analyzed. This study identifies that temperature at the slag-metal reaction interface plays a major role in the Mn reaction kinetics and thus a mathematical treatment to evaluate temperature at each reaction interface has been successfully employed in the rate calculation. The Mn removal rate obtained from different zones of the converter predicts that the first stage of the blow is dominated by the oxidation of Mn at the jet impact zone, albeit some additional Mn refining has been observed as a result of the oxidation of metal droplets in emulsion phase. The mathematical model predicts that the reversion of Mn from slag to metal primarily takes place at the metal droplet in the emulsion due to an excessive increase in slag-metal interface temperature during the middle stage of blowing. In the final stage of the blow, the competition between simultaneous reactions in jet impact and emulsion zone controls the direction of mass flow of manganese. Further, the model prediction shows that the Mn refining in the emulsion is a strong function of droplet diameter and the residence time. Smaller sized droplets approach equilibrium quickly and thus contribute to a significant Mn conversion between slag and metal compared to the larger sized ones. The overall model prediction for Mn in the hot metal has been found to be in good agreement with two sets of different size top blowing converter data reported in the literature

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : model derivation and validation

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the BOF operation. The three reaction zones, (i) jet impact zone (ii) slag-bulk metal zone (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process

Challenges of metal recovery from low grade and urban ores for resource efficiency

The presentation briefly discusses the general challenges (with focus on technical point of views) in unlocking alternative resources of lower grade and above ground (urban) metal ores for resource efficiency. The low concentration of the targeted metals and more complex composition of these alternative sources provide challenges in processing and recovering all the valuable metals. There is limited thermodynamic information and the lack of understanding of the behavior of the elements during processing. A comprehensive approach addressing both the technical and non-technical barriers needs to be applied for maximising resource efficiency and wealth generation. In this presentation, a number of activities in Australia including researches within the Wealth from Waste Cluster and Swinburne University of Technology will be also briefly discussed. Wealth from Waste Cluster is a multi-disciplinary international research cluster between CSIRO, University Technology Sydney, Swinburne University of Technology, University of Queensland, Monash University and Yale University. The researches within the Cluster aim to explore ways to harness value from above ground stocks of metals with a focus on industrial ecology and circular economy, considering the size and value of the available resources, the socio-technical systems needed to overcome barriers and to develop new business models which would facilitate the harnessing of wealth from waste. In Swinburne University of Technology a Research Group with theme focusing on the Resource Efficiency is being developed. This multidisciplinary research area within Swinburne is supported by the existing research infrastructures and laboratories, as well as the new Design for Resource Efficiency Studio within the Factory of the Future to be opened in mid 2015. Researches within Swinburne, associated with the theme are also discussed in the presentation, which include electrically enhanced boron impurities removal from metallurgical grade silicon, selective sulfidation for removal of impurities in weathered ilmenite (FeTiO3), and studies on thermodynamic behavior of valuable metals