The
aim of the study was to address the challenge - in a particular plant - of the high (FeO) content in slag in Electric Arc furnace (EAF) steelmaking, adopting a high ratio of hot metal to scrap, ...which uses the operation mode of adding hot metal and smelting simultaneously, the oxygen blowing process was optimised through a combination of industrial practice and theoretical calculation. Specifically, the start time of oxygen blowing was delayed, and the C content of the molten steel at the smelting endpoint was increased; furthermore, an oxygen blowing method was performed with a C content of 0.6-0.8% for the molten bath during the smelting process. After the oxygen blowing method was optimised, the oxygen consumption per ton of steel decreased by 7.96 Nm
3
, and the (FeO) content of slag decreased by 11.85% on average.
Steel slag is one of the most common waste products from the steelmaking industry. Conventional methods of slag disposal can cause negative impacts on humans and the environment. In this paper, the ...process of steel and steel slag production, physical and chemical properties, and potential options of slag recycling were reviewed. Since steel is mainly produced through an electric arc furnace (EAF) in Malaysia, most of the recycling options reviewed in this paper focused on EAF slag and the strengths and weaknesses of each recycle option were outlined. Based on the reports from previous studies, it was found that only a portion of EAF slag is recycled into more straightforward, but lower added value applications such as aggregates for the construction industry and filter/absorber for wastewater treatments. On the other hand, higher added value recycling options for EAF slag that are more complicated such as incorporated as raw material for Portland cement and ceramic building materials remain at the laboratory testing stage. The main hurdle preventing EAF slag from being incorporated as a raw material for higher added value industrial applications is its inconsistent chemical composition. The chemical composition of EAF slag can vary based on the scrap metal used for steel production. For this, mineral separation techniques can be introduced to classify the EAF slag base on its physical and chemical compositions. We concluded that future research on recycling EAF slag should focus on separation techniques that diversify the recycling options for EAF slag, thereby increasing the waste product’s recycling rate.
In steelmaking slag, phosphorus is distributed between liquid phase and solid solution of 2CaO·SiO2 and 3CaO·P2O5 at refining temperature. Using the difference in water solubility of the solid ...solution and the other phases, we are developing the process to separate phosphorus by acid leaching. In this paper, the optimum condition of leaching by nitric acid by the control of valency of Fe in slag was investigated and the recovery of phosphorus from leachate was also conducted. To dissolve the solid solution, pH has to be decreased to 3 and the solid solution containing FeO showed lower dissolution ratio. To suppress the dissolution of other phases in slag at this pH, slow cooling to avoid the formation of glassy phase was necessary. The artificially steelmaking slag with the appropriate composition was made and subjected to the leaching experiment. The dissolution ratio of phosphorus has reached about 91% and the phosphorus content in the residue was enough low. After the separation of residue, pH of the leachate increased to precipitate phosphate. At pH=7, 80% or more of the phosphorus in the leachate was precipitated and the phosphate content of the precipitate was about 25% after calcination.
A comprehensive model of oxygen steelmaking that includes the kinetics of scrap melting, flux dissolution, slag chemistry, temperature profile of the system, formation and residence of metal droplets ...in the emulsion, and kinetics of decarburization reaction in different reaction zones was developed. This paper discussed the development and the application of the model into an industrial practice. The results from the model were consistent with the plant data from the study of Cicutti et al. The model suggested that 45% of the total carbon was removed via emulsified metal droplets and the remaining was removed from the impact zone during the entire blow. It was found that the residence time of droplets as well as decarburization reaction rate via emulsified droplets was a strong function of bloating behavior of the droplets. This model is the first attempt in the open literature that allows for the decarburization kinetics of the impact zone to be predicted separately from decarburization kinetics of the emulsion.
The need of a strong improvement of productivity and reliability led the adoption of advanced modeling techniques in the design of steelmaking plants components. In this work a procedure based on a ...finite element simulation is proposed in order to perform a durability analysis of an anode for electric arc furnace. This component undergoes cyclic thermal loads, which also produce a partial melting of one part, meanwhile the other is maintained at almost constant temperature by a cooling system. A simplified, but effective, procedure is developed to take into account steel melting during the heating phase. Considering the cyclic loading conditions, several material cyclic plasticity models, and their effect on the thermal fatigue behavior, are also systematically investigated. The proposed approach permits the component fatigue life to be assessed by a simple and fast uncoupled thermo-mechanical simulation in steady-state conditions.
In oxygen steelmaking, one important aspect is to depict the splashing induced by the impingement of multiple jets quantitatively. In this paper, experiments were conducted to investigate the splash ...sheets. The results demonstrated that with the decrease of lance height, the sheet area increased, while the sheet height decreased. The sheet diameter was much less affected by the gas flow rate compared to the sheet height. The cavity width-to-depth ratio is a critical parameter affecting the sheet shape. The sheet area produced by the 5-nozzle jet was larger than that produced by the 6-nozzle jet. Taking the sheet area reduction as the critical condition where the cavity mode changes from splashing to penetrating, the critical lance height was investigated under various ejecting conditions. This was further represented by the blowing number as a normalized formula. At last, curve fitting illustrating the conditions that lead to the penetrating mode was conducted.
The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag ...foaming behavior was studied. The slag’s composition was set to FeO-CaO-Al2O3-MgO-SiO2, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe2MgO4) and magnetite (Mg0.4Fe2.96O4). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca2(Al(AlSi)O7) and two spinels: magnesium aluminate (MgAl2O4) and magnesium iron oxide (Fe2MgO4).
In the Basic Oxygen Steelmaking (BOS) process, a heterogeneous emulsion‐solid mix will form, consisting of an emulsion of liquid slag and metal droplets, in which 2nd phase particles of undissolved ...fluxes and solid in‐blow precipitates are suspended. When the carbon in the metal droplets reacts with iron oxide, small bubbles of CO gas are formed. If the upward movement of these bubbles is obstructed by the physical properties of the emulsion‐solid mix, foaming will occur. Certain process conditions may lead to an excessive foam growth, in the worst case forcing foam out of the vessel. This undesired process event is known as “slopping”. Extensive studies during recent decades have shown that emulsion characteristics strongly connected to foaming are: viscosity, surface tension, and density. The extent of foaming is also dependent on bubble size; foaming increasing with smaller bubble size. However, investigations into the influence of the mineralogy and morphology of the emulsion‐solid mix on foaming in basic oxygen steelmaking are scarce. In this work, samples from trials in a 6‐tonne pilot plant BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology at different stages of the oxygen blow. The study confirms the importance of tight process control in order to minimize the emulsion‐solid mix apparent viscosity and, hence, the foam height, but this without over‐oxidizing the liquid slag phase, which would result in increased gas generation within the slag‐metal emulsion.
Samples from a 6‐tonne pilot BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology. The study confirms the importance of minimizing the emulsion‐solid mix apparent viscosity, but this without over‐oxidizing the liquid slag phase, which would cause an increased gas generation within the slag‐metal emulsion, increasing the risk of slopping.
•Experimental Investigation of the heat transfer coefficients.•Coefficients achieved approx. 10x smaller than calculated with Nusselt correlations.•Explicit numerical model for heat transfer in scrap ...melting was developed.
Dynamic modelling of the Linz-Donawitz oxygen steelmaking process (LD) is one of the most challenging tasks in the current economic situation for the optimization of integrated steel plants. One of the main influencing parameters is the melting and dissolution behaviour of scrap. Scrap is used as an iron source and coolant for the exothermic reactions inside the LD converter. Literature-based dissolution equations are commonly used in modelling. As a basis for developing a new numerical model for scrap melting with coupled heat and mass transfer, laboratory-scale experiments were conducted. The aim of the experiments was the determination of the heat transfer coefficient between scrap and liquid hot metal through a combination of thermocouple measurements with analytical and numerical solutions. The heat transfer coefficients achieved were in the range between 4.5 and 6.2 kW/m2 K. The heat transfer coefficients estimated in the present work are approximately 10 times smaller than those evaluated through existing Nusselt correlations. These discrepancies may be explainable through specific effects of scrap dissolution, e.g. shell freezing and successive melting or air-gap formation between solidified shell and mother scrap increasing the heat transfer resistance at the solid scrap to melt interface. The numerical solution to the heat transfer problem shows identical results to the analytical solution of the problem and provides a feasible basis for further research and development.
The way to decarbonization will be characterized by the huge production of hydrogen through sustainable routes. Thus, the basic production way is water electrolysis sustained by renewable energy ...sources allowing for obtaining “green hydrogen”. The present paper reviews the main available technologies for the water electrolysis finalized to the hydrogen production. We describe the fundamental of water electrolysis and the problems related to purification and/or desalinization of water before electrolysis. As a matter of fact, we describe the energy efficiency issues with particular attention to the potential application in the steel industry. The fundamental aspects related to the choice of high-temperature or low-temperature technologies are analyzed.
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