On (%FeO)–[%C] Correlation During Primary Steelmaking

Long-term global availability of steel scrap

A centralized optimization strategy is proposed to determine optimal raw material purchasing and plant operation practices as applied to primary steelmaking in the steel processing industry. Raw materials are purchased on the open market and include coal, iron ore pellets, and scrap steel. There are many raw material vendors, providing products varying in quality and price. It is desired to determine the least costly method of both purchasing and processing the raw materials to make steel of acceptable quality. A model for primary steelmaking is developed using a combination of mass balances and empirical relationships. The model, in addition to process constraints, is combined with an economic objective function and the resulting optimization problem solved using a mixed-integer nonlinear programming (MINLP) solver. Case studies illustrate the strong connection between plant sections, and the significant impact that the carbon, volatile matter, and phosphorus content of the coals and pellets have on raw ...

Steel production is a very energy-intensive process, and it requires large amounts of natural resources. In fact, energy costs account for up to 40% of the total cost in some countries. Therefore, optimizing process efficiency is one of the most effective ways to reduce energy consumption and lower costs, with the added benefit of reducing the steel industry’s impact on the environment. Iron and steel industry is the main CO2 emitter among the most CO2-intensive industrial sectors. The iron and steel industry accounts for about 19% of final energy use and about a quarter of direct CO2 emissions from the industry sector. The CO2 relevance is high due to a large share of coal in the energy mix. Unlike power plants, where CO2 is emitted from a single source, an integrated steel mill has multiple sources of CO2. The emissions are located at several stacks and occur from start to end of the iron and steel production. CCS is one of the most open fields for the reduction of greenhouse emissions in primary steelmaking. It is necessary for continuing to use fossil fuels. In the iron and steel industry, CCS faces many uncertainties regarding cost, efficiency, and technology choice. Obviously many solutions are under investigation to capture CO2 and to store it avoiding its emission in the atmosphere. Selection of capture equipment will depend on factors including CO2 capture rate, possible requirements for secondary gas treatment, energy consumption, reliability, and operational and capital costs. In the present chapter, the most innovative solutions related to energetic issues and off-gases type are described. The gas utilization depending on the plant section source and composition is underlined. The CO2 abatement potential and the various solutions costs are indicated.

FactSage has become one of the most important modeling tools in simulating the high-temperature metallurgical processes. The usefulness of the FactSage has been demonstrated in this work using several examples of steelmaking processes. Primary steelmaking (basic oxygen furnace) simulation was done with the available process data, and process charts similar to the standard ones were obtained. Ladle refining furnace process for free-cutting steels was simulated and it was observed that absolute non-equilibrium condition exists in steel during casting due to S injection. It was found that non-metallic inclusion formation is thermodynamically possible at final processing stages during Ca and S injection with variable recoveries. A significant change in the nature of non-metallic inclusions formed in re-sulfur steel causes clogging during continuous casting of liquid steel, and its influence on the process has been discussed, for mere 2 ppm of Ca difference in the liquid steel composition.

In this paper, we use a predator–prey model to simulate intersectoral dynamics, with the global steel sector as the prey that supplies inputs and the automotive sector as the predator that demands its inputs. A further prey, an additional upstream supply sector, namely the iron ore sector, is added to reflect the implications of scarcity and resource limitations for industrial development and economic prospects. We find that capacity constraints in the steel industry could limit the future supply of vehicles, a result exacerbated by the unsustainable use of iron ore reserves. The solution is not for marginal steel industries to close, but for steelmakers to adapt and move to less resource-demanding secondary steelmaking technology rather than focusing on primary steelmaking. The forecasting capabilities of the model are compared with the outputs from a neural-network model. Although the results are comparable over the short term (±10 years), over the long term, results diverge, showing that forecasting steel-industry dynamics is complex and that further work is required to disentangle the drivers of supply and demand. This study indicates the potential advantages of using predator–prey models in modelling the supply chain in economics.

ZBBs have a high open circuit voltage (1.82 V), a high theoretical energy (> 400 W h-1 kg-1) and high demonstrated power densities (> 100 mW cm-2). Typically, ZBBs adopt a redox flow design involving the use of a Nafion membrane to separate aqueous zinc bromide anolyte and catholyte solutions [1]. In this study, the use of a membrane-free non-flow design was investigated for the purposes of recovering zinc from scrap and waste steel resources [2]. The rationale for this work stems from the greenhouse gas emissions produced by the iron and steel industry, which accounts for between 4-7 % of the anthropogenic CO2 emissions globally [3]. Blast furnace technology is likely to account for most stainless steel production in the coming decades, and therefore a transition to low-carbon and green steel production will require increased steel recycling rates and significantly improved waste and scrap management. To the best of our knowledge, this is the first time a zinc-bromine battery has been investigated for the recovery of materials rather than energy storage.Galvanization of steel is required to prevent rusting and degradation and involves coating the surface of steel in a protective layer of zinc. Galvanization processes account for over 50 % of global zinc consumption and by 2050 the demand for zinc will be 2.7 times greater than that of 2012 [4]. In order to enable recycling of scrap steel directly into blast furnaces, zinc is removed and recovered via mineral acid leaching. This method of recovery has a high zinc extraction efficiency but creates problematic waste streams and has poor energetic efficiency.In this work, the use of a membrane-free zinc-bromine battery has been studied for the purposes of extracting zinc from steel substrates and subsequently re-electroplating onto a conventional carbon foam electrode. The electrical performance of the cell was characterised by charge-discharge profiles and I-V curves. Zinc removal and recovery onto electrodes was characterised using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The work successfully demonstrates that ZBB technology could enable efficient and clean recovery of zinc from metal and waste substrates including scrap steel, slurries generated from basic oxygen steelmaking processes, and secondary vent dust from the primary steelmaking off gas streams. The cell studied in this work enabled dipping of zinc-containing steel substrates directly into the electrolyte solution without disassembly of the battery housing. In addition, the design involved the use of low-cost materials and reagents and potentially offers low balance-of-plant costs.The results show that zinc could be removed from steel surfaces during cell discharge with greater than 99.9 % yield. The Figure shows the extracted zinc could subsequently be re-electroplated onto a standard carbon foam electrode upon re-charging the cell. When a 0.5 V cut-off voltage was used upon discharge, the zinc was recovered selectively from the steel (see Fig. (a)); the surface elemental composition of the carbon electrode measured by EDS after charging was: carbon (26.79 wt%), oxygen (18.06 wt%), zinc (30.03 wt%) and bromine (25.11 wt%). Using a lower cut-off voltage (0.2 V) resulted in the co-extraction of iron from the substrate as well as zinc (see Fig. (b)); in this case, the elemental composition of the carbon electrode after charging was: carbon (27.53 wt%), oxygen (22.65 wt%), iron (4.72 wt%), zinc (24.44 wt%) and bromine (20.65 wt%). Provided a cut-off voltage of no less than 0.5 V was used for discharging, high purity zinc was recovered, and the cell showed good initial durability, with 30 cycles of charge-discharge demonstrated in this work.[1] S. Suresh, M. Ulaganathan, N. Venkatesan, P. Periasamy, P. Ragupathy, High performance zinc-bromine redox flow batteries: Role of various carbon felts and cell configurations. J. Energy Storage, 2018. 20: pp. 134-139.[2] S. Biswas, A. Senju, R. Mohr, T. Hodson, N. Karthikeyan, K. Knehr, A.G. Hsieh, X. Yang, B.E. Koel, D.A. Steingart, Minimal architecture zinc-bromine battery for low-cost electrochemical storage. Energy Environ. Sci., 2017. 10: pp. 114-120.[3] Iron and Steel Technology Roadmap: Towards More Sustainable Steelmaking, Energy Technology Perspectives, International Energy Agency, IEA Publications, Paris, 2020. https://www.iea.org/reports/iron-and-steel-technology-roadmap [accessed 12 April 2022].[4] K.S. Ng, I. Head, G.C. Premier, K. Scott. E. Yu, J. Lloyd, J. Sadhukhan. A multilevel sustainability analysis of zinc recovery from wastes. Resour. Conserv. Recycl., 2016. 113: pp. 88-105.Figure. SEM images showing the carbon foam zinc electrodes after charging the cell. (a) is an electrode when a discharge cut-off voltage of 0.5 V was used, (b) is an electrode when a discharge cut-off voltage of 0.2 V was used. Figure 1

Steel production accounts for approximately 8% of all global CO2 emissions, with the primary steelmaking route using iron ores contributing approximately 80% of those emissions, mainly due to the use of fossil-based reductants and fuel. Hydrogen-based reduction of iron oxide is an alternative for primary synthesis. However, to counteract global warming, decarbonization of the steel sector must proceed much faster than the ongoing transition kinetics in primary steelmaking. Insufficient supply of green hydrogen is a particular bottleneck. Realizing a higher fraction of secondary steelmaking is thus gaining momentum as a sustainable alternative to primary production. Steel production from scrap is well established for long products (rails, bars, wire), but there are two main challenges. First, there is not sufficient scrap available to satisfy market needs. Today, only one-third of global steel demand can be met by secondary metallurgy using scrap since many steel products have a lifetime of several decades. However, scrap availability will increase to about two-thirds of total demand by 2050 such that this sector will grow massively in the next decades. Second, scrap is often too contaminated to produce high-performance sheet steels. This is a serious obstacle because advanced products demand explicit low-tolerance specifications for safety-critical and high-strength steels, such as for electric vehicles, energy conversion and grids, high-speed trains, sustainable buildings, and infrastructure. Therefore, we review the metallurgical and microstructural challenges and opportunities for producing high-performance sheet steels via secondary synthesis. Focus is placed on the thermodynamic, kinetic, chemical, and microstructural fundamentals as well as the effects of scrap-related impurities on steel properties.

Concern about the growing carbon dioxide content in the atmosphere has induced increasing research activities in the search for means to suppress the emissions of CO2 in primary steelmaking. Blast furnace top gas recycling, combined with CO2 stripping, has been proposed as a promising concept. The paper presents a numerical analysis of top gas recycling under massive oxygen enrichment of the blast based on a simulation of the process chain from coal and ore to liquid steel. Because of the conflicting goals of reducing both production costs and emissions, the task is formulated as a multi-objective optimization problem. The optimal states of the system studied were found to vary significantly on the Pareto frontier, which demonstrates that fundamentally different states of operation may be selected to strongly reduce the emissions, still keeping the steelmaking economically feasible. The findings stress the importance of selecting a proper state of operation for achieving a cost-efficient production of steel with reduced environmental impact. The results also show how emissions can be “artificially” reduced by minimizing the arising emissions within the system boundary.

Syngas production through multi-cycle chemical looping of chromite mines waste: A sustainable approach to mitigate CO2 emissions

Limited natural resources and a growing concern about the potential effect of carbon dioxide emissions on the world's climate have triggered a search of ways to suppressing the emissions of CO2 in primary steelmaking. A possible future solution is to strip CO2 from the blast furnace top gas, feeding back the gas to the tuyere level. The work reported in this article explores states of an integrated steel plant that arise if both production costs and emissions are simultaneously minimized. This multiobjective problem is tackled by genetic algorithms using a predator–prey strategy for constructing the Pareto-frontier of nondominating solutions. Four alternative ways of treating the top gas recycling problem are explored, and the resulting solutions are analyzed with respect to the two objectives and to the internal states of the plant they correspond to. Conclusions are drawn concerning the solutions in terms of technical feasibility and complexity.

Excess heat-driven carbon capture at an integrated steel mill – Considerations for capture cost optimization

The ever increasing demands of consumers towards superior quality steel products urged steelmakers to consider the implementation of various relatively new metallurgical technologies into the classical operations. The necessity to produce high quality steels led to the use of two stage steel production processes, one is the primary steelmaking and the other stage is the outside furnace treatment through which many metallurgical functions can be achieved like degassing, stirring and inclusion removal, Inclusion modification, desulphurization, deoxidation, decarburization, heating and alloying. In this research a trial was done to optimize the performance and usage of 30tons-ladle refining system during production of X65-pipeline steel as final product-Aluminium killed steel melts through controlling the mass flow contour using optimized modelling, optimum usage of Al2O3 and Sulphide modifiers and enhancing removal of non-metallic inclusions by altering their morphologies and hence floatation speed. Assessment of fine clusters of inclusions in the final steel product has been industrially correlated to the cleanness of melt before refining, to the slag composition and to the parameters of materials flow rates as well as their effects on the mechanical properties of final X65-steel product. Scanning-EM+DX analyzing unit and metallurgical microscopes were used to emphasis qualitatively and quantitatively the characters of non-metallic inclusions.

Ferruginous lime—i.e. burnt lime coated with dicalcium ferrite (2CaO.Fe2O3)—has attractive properties as a steelmaking flux. Work was undertaken to assess the feasibility of producing ferruginous lime in a rotary kiln-type reactor and to determine the operating conditions favourable for both the formation of a hydration-resistant product and the minimization of such problems as accretion and agglomeration within the reactor. The trials indicated that a period of 45 min at temperatures in excess of 1200°C with a peak reaction temperature of 1260°C provides appropriate conditions for the production of ferruginous lime. The optimal oxide addition is 10% by weight of the limestone charge to the rotary lime kiln. When subjected to hydrating conditions of short duration, i.e. 30 min in contact with steam at 100°C (in accordance with ASTM specification X6), the product exhibited good resistance to hydration relative to pure CaO and moderate physical degradation. Laboratory tests demonstrated the significantly enhanced rate and degree of dissolution of ferruginous lime in a steelmaking slag relative to that of uncoated lime.

Until the recent past, the mechanical properties and surface quality of steel produced by conventional processes, for example, open hearth, LD, OBM, and so on were up to the satisfaction of consumers in meeting their general requirements. However, in recent years, there has been a steadily increasing demand for better quality steels in terms of lower impurity contents, better surface finish, better internal quality (i.e., inclusion-free), and specific grain size as well as in their mechanical properties in terms of strength, toughness, and workability under extreme forming conditions. In order to fulfill the stringent demand of consumers it has become essential on the part of steel producers to drastically lower down the impurity level in steel, in some cases to a few parts per million. For example, alloy steel forgings, line-pipe steel, and HIC-resistant steel need ultralow sulfur, as low as 0.001% S (10 ppm). It is important to note that secondary treatment reduces the concentration of sulfur, oxygen, nitrogen, hydrogen, and nonmetallic inclusions. Thus, modern steelmaking is classified into two categories: “primary and secondary.” The first category includes the major bulk of steelmaking processes that carry out total refining and melting (if required). In fast (primary steelmaking) processes where operations are completed within 60 min, the resulting steel may not always meet the desired specifications. Hence, the primary steelmaking processes are nowadays restricted to bulk steel production of ordinary quality steels for construction purposes. In order to adhere to the specific composition, molten steel from these units is processed in ladles. This ladle treatment is known as “secondary steelmaking,” which in fact is the second stage of refining that is carried out for the final refining and finishing. By controlling the composition in this way, the deleterious effect of impurities on the mechanical properties is avoided and steel with better internal quality and ultralow carbon/sulfur/phosphorus can be produced. Nowadays, secondary steelmaking units have become an essential part of the integrated steel plants to supply sophisticated grade of steel for continuous casting. In recent years, a large number of research investigations [1–6] have been conducted on secondary refining to produce inclusion-free steels containing ultralow carbon, silicon, and phosphorus.

The electric arc furnace (EAF) generates dust containing about 21% Zn during primary steelmaking at Uddeholm Tooling AB. Research work on upgrading of the dust has been carried out jointly by Uddeholm Tooling AB and MiMeR, Minerals and Metals Recycling Research Centre, at Luleå University of Technology. The work included laboratory studies and plant trials. The laboratory studies, with 6 dust smelting tests at temperatures around 1650°C, demonstrated that the smelting had no negative effects on qualities of the steel and slag. It was also shown that both carbon and silicon could be used to reduce the oxides in the dust, leading to high metal recoveries. Based on the study results, plant trials were performed at Uddeholm Tooling AB. The trials consisted of 100 EAF heats, recycling dust at a rate of 925 kg/heat. No negative impact has been found on the furnace products and production. The Zn content of the obtained dust increased by 11% and the weight of the generated dust decreased by 42%. The material costs for the dust recycling during the trials were rather low, $0.4 (4–5 SEK)/tonne steel. Some of the test results are interpreted by virtue of mass and energy balances of the dust smelting calculated using the computer software “Chemsage.” By utilizing results from the tests and calculations, the energy consumption for dust smelting was estimated.