Ironmaking and Steelmaking Processes

The raw materials for an integrated steelworks can be classified into four categories, which are iron ores, fluxes, fuels, and reverts. The characteristics of these raw materials strongly affect the metallurgical properties of iron ore sinter and sinter plant performance. An optimal ore blend design is therefore essential to produce low cost and high quality hot metal. Without doubt, some hazardous components are brought into the production process, and therefore, there are some associated pollutants. A good preparation of raw materials is the first step for in-process anti-pollution action. This chapter will introduce the common materials used in iron ore sintering and the handling procedures in an integrated steelworks.

This chapter is focused on the multiphase multicomponent model development and prediction of common hazardous compounds produced during the industrial iron ore sintering process within an integrated steelworks. The iron ore sintering process is a key technology in the steel industry due to its possibility of recycling waste solids or powders internally produced during the raw materials handling or subsequent process of steel production. However, this process is also recognized as one of the most critical unit with regard to the polychlorinated dioxins and furans (PCDD/F) emissions. In addition, as fossil fuels are used, the emissions of SO_x and NO_x are significant and must be strictly controlled. The process is dynamic and involves the cross flow of gas through the bed which can carry the fine particles. The outlet gas treatment involves the cleaning with electrostatic precipitator and filter bags. New technologies, however, have been introduced in order to treat PCDD/F and SO_x–NO_x compounds, which introduce significant increase in the cost of the production. New process concepts and technologies have been proposed such as gas recycling, fuel gas injection, and biomasses fuels. However, testing these technologies are expensive. In this context, comprehensive mathematical models based on transport phenomena are efficient tools to study and indicate new possibilities for designing operational conditions as well as resizing the machines for minimizing the hazardous emissions. In this chapter, the model principles and analysis cases are presented and discussed. The impacts of four technological proposal on the hazardous emissions of PCDD/F, NO_x, SO_x , and particulates are analyzed, as follows: (a) effect of fuel gas injection; (b) effect of gas recycling and oxygen injection; and (c) effect of using biomass and biogas replacing the fossil fuel (coke breeze). The analysis is carried out comparing the actual operation of the industrial iron ore sintering machine with the new concepts proposed based on their specific hazardous emissions.

Sintering operations in steelmaking is one of the main sources of production of PCDD (polychlorinated dibenzo-p-dioxins), PCDF (polychlorinated dibenzo-furans), NOx, and SOx. The precise operating conditions through which a reduction of greenhouse emissions is described and analyzed by experimental-numerical approach. The goal is the recognition of optimized design as a function of the strong reduction of dioxins, furans, NOx, and SOx coupled with high productivity of the plant. Following the proposed approach, it was possible to reduce the emissions close to the legal limits with a high level of productivity and efficiency of the plant.

The sintering process is an important part of iron and steel production. In the process of sintering, large amounts of SOx, NOx, HF, dioxins, particulate matters and other gaseous pollutants are produced. In order to control the sintering flue gas pollutants, the emission standard for iron and steeling sintering flue gas in China was published in 2012 and the control application of source, process and end treatment were applied. Based on a systematic description of relevant purification technologies, this chapter reviews the current situation for control of sintering flue gas in China and the trend of technology development. Aplication cases are described, with the purpose of providing an important reference for the choice of sintering flue gas emission control technology for domestic and international steel corporations.

This article presents an outline of the iron ore sintering process, which introduces the blast furnace slag-forming requirements to allow an understanding of the required adjustments to flux addition in the sintering process; some basic concepts of the sintering reactions are also introduced. The recovery of miscellaneous wastes using high S, N, Cl content materials in sinter plants has been associated with some hazardous emissions, such as dust, NOx, SOx, and dioxins. The formation mechanism of these hazardous pollutants and some practical countermeasures are discussed.

The iron- and steelmaking is the largest energy consuming in the industrial sectors. The high energy consumption is associated with emission of CO₂ and other pollutants. The most common ironmaking process used in the world is the blast furnace which contributes around 70 % of the world’s steel production. Recently, blast furnace has undergone tremendous modifications and improvements to reduce the energy consumption and CO₂ emissions. The modifications are being focused on two main approaches: (1) development of top charging materials and (2) injections of auxiliary fuels through blast furnace tuyeres. The present chapter will discuss the recent modifications and development in the top charging burden and how it could participate in minimizing the energy consumption and CO₂ emissions for more efficient and sustainable iron and steel industry. The injection of auxiliary fuels will be discussed in details in another chapter. The enhancement of burden material quality and its charging mode into the blast furnace has resulted in a smooth and efficient operation. Recently, the usage of nut coke in the modern blast furnace is accompanied by higher production and lower reducing agent rates. An efficient recycling of in-plant fines by its conversion into briquettes with proper mechanical strength is applied in some blast furnaces to exploit the iron- and carbon-rich residues. Nowadays, novel composite agglomerates consist of iron ores and alternative carbonaceous materials represent a new trend for low-carbon blast furnace with lower dependence on the conventional burden materials. The recent investigations demonstrated that the novel composites are able to reduce the thermal reserve zone temperature in the blast furnace and consequently enhance the carbon utilization through its higher reactivity compared to fossil fuels. The top charging of bio-reducers and hydrogen-rich materials into the blast furnace is one of interesting innovations to mitigate the CO₂ emissions. Although some of previous approaches are recently applied in the modern blast furnace, others are still under intensive discussions to enhance its implementations.

Blast furnace smelting is the dominant ironmaking method around the world. Blast furnace operations cover not only blast furnace smelting but also a set of auxiliary processes and equipments, including molten slag granulation, hot stoves and off-gas treatment systems. Dangerous emissions of SO₂ and H₂S are found in molten slag granulation sites; NOx are found from the hot stoves; heavy metals (mainly Zn and Pb) are found in the sludge and dust from off-gas treatment systems; fluorides are found in the off-gas. These emissions are generally in low concentrations. However, since the production of blast furnace is huge, the mass are still appreciable. The heavy metal emissions are mostly safely treated or recycled. However, few processes have been installed to treat emissions of H₂S, SO₂, NOx and fluorides.

This chapter deals with possibilities of mathematical modeling of blast furnace operation. This chapter summarizes various attitudes for evaluation of blast furnace operation. The chapter is aimed at modeling of kinetics of reduction processes. It presents a methodology developed at VŠB—Technical University of Ostrava—for interpreting of laboratory tests carried out according to international standards such as ISO 4695:2007. The designed model uses laboratory test results as inputs for mathematical simulation of the material processing in blast furnace aggregate. The model calculates kinetic constants of changes in iron oxides concentration during nondirect reduction and estimates coke consumption for it. It presents simulation of reduction gas consumption regarding the ratio of direct reduction in time. It carries out simulation for one-component and two-component blast furnace feedstock to find easily the optimum of production process.

Blast furnace (BF) represents the dominant hot metal-making process all over the world and one of the main energy-consuming processes. Modern research in the field focuses on the increase in plant productivity through energy saving and on the greenhouse emission reduction compatible with legal limits. The iron and steel industry is one of the biggest industrial emitters of CO₂. It is estimated that between 4 and 7 % of the anthropogenic CO₂ emissions originate from this industry in EU-27, which generated 252.5 million tons of CO₂ emissions on average during the period 2005–2008. Productivity is mainly governed by relevant input parameters such as material rates, material properties, and operating conditions. All the dominant input parameters and their variation have been analyzed in the present study, and they have been optimized in order to increase the plant productivity and reduce the greenhouse emissions. The study suggests new solutions in all processing parameters in order to improve plant productivity and to reduce the dangerous emissions.

Minimizing the coke consumption in the blast furnace is the key to achieve both ecological and economic aspects by reducing the CO₂ emissions and the overall hot metal production cost. Complementary injection of cheaper auxiliary fuels and waste materials into the blast furnace via tuyeres has been greatly modified in the recent years to reduce the expensive coke consumption. Nowadays, most of the blast furnaces all over the world use pulverized coal at different injection rates. The greatest influence of coal injection on lowering the production cost and enhancement of hot metal production rate has led to further investigations on the injection of various other auxiliary materials including coke oven gas, converter gas, blast furnace dust, waste plastics, charcoal and torrefied biomass. In addition, trials on the injection of iron ore fines, low reduced iron and BOF slag have been recently studied. The injection rate of auxiliary materials into the blast furnace should be optimized to attain the minimum coke consumption and stable operation. The present chapter will discuss the influence of various materials injection on the blast furnace operation. The injection limit and changing of the blast furnace operating conditions, hot metal quality and coke consumption will be explained based on the experimental trials and mathematical modelling.

In recent years, the CO₂ emission in China is the highest all around the world, accounting for about 30 %. China’s 15 % CO₂ emission is produced from iron and steel companies, where blast furnace contributes more than 60 %. Therefore, blast furnace is the key to reduce CO₂ emission for iron and steel companies. Blast furnace is a countercurrent reactor between descending burdens and ascending gas. The higher the CO utilization ratio is, the lower the CO₂ emission. There are two main measures to improve CO utilization ratio—upper adjustment and lower adjustment. The upper adjustment is mainly about the burden distribution which includes adjusting batch weight, charging mode, stock line and so on. The lower adjustment is mainly about the gas distribution in the lower part of the blast furnace, which includes adjusting the gas volume, gas temperature, gas humidity and so on. The paper presents the upper and lower adjustments to improve CO utilization ratio in China’s blast furnaces.

Steel production through electric arc furnaces has strongly increased in the past decade. Dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are the main type of greenhouse emissions in such kind of plants. The main factors influencing the emissions levels are the composition of raw materials, the processing conditions employed during melting, and the adsorbent effects of additional compounds added before filtering. Many techniques have been experienced in the recent past to improve the abatement of emissions levels. In the present chapter, the greenhouse emissions belonging to an industrial steel electric arc furnace are monitored in different processing condition setups. The effect of lignite and CuCl addition on the dangerous emission levels have been deeply investigated.

The present chapter describes the determination of emissions of high toxic airborne pollutants (dioxins, dibenzofurans, polycyclic aromatic hydrocarbons, and polycyclic carbonyl biphenyls) from electric arc furnaces during the production of steel. By using the European Standard method CEN 1948 for dioxin-like compound sampling and measurement, it was possible to determine the characteristic fingerprint of these micropollutants emitted by this particular stationary source.

Cementitious materials are the most popular binding agents used in the treatment of hazardous waste to convert it from an unstable to a more stable form. The use of ordinary Portland cement (PC) or other hydraulic binders (such as pozzolanic power plant fly ash) in the solidification/stabilisation (S/S) process is one of the best available methods for the treatment of waste that cannot be reduced, destroyed or recycled.

There are many other studies and researchers who agree that PC is the main binder being used to solidify and immobilise pollutants into a solid form (Li et al., J Hazard Mater 82:215–230, 2001). In addition to cement, pozzolanic materials are also used for this purpose. These mainly include PFA, blast furnace slag, silica fume, natural or modified clays and sand (Poon et al., Waste Manage Res 3:127–142, 1985). Although cement was selected as the main binder in the S/S technique, it was realised in the past century that it has detrimental effects on the environment and human health. The production of cement causes large amounts of carbon emissions to be released into the environment and involves an overuse of natural resources (Middendorf et al., Lime pozzolan binders: an alternative to OPC, 2005).

This has incited the use of different types of additives and binders as substitutes for cement. Many different formulations have been developed for the S/S process mainly based on the type of waste or heavy metals it might include. It has been proved that PC can be modified and/or replaced using fly ash, hydrated lime, steel slag, soluble silicates, clay and magnesium oxide (MgO) for suitable S/S process (Mayers and Eappi, Laboratory evaluation of stabilization/solidification technology for reducing the mobility of heavy metals in New Bedford Harbour superfund site sediment, stabilization of hazardous radioactive and mixed wastes, 1992; Singh and Garg, Cem Concr Res 29:309–314, 1999; Fernandez et al., J Environ Eng 129:275–279, 2003; Turkel, J Hazard Mater 137:261–266, 2006; Tsakiridis et al., J Hazard Mater 152:805–811, 2008; Fernandez-Pereira et al. Fuel 88(7):1185–1193, 2009; Zhang et al., Cem Concr Res 41:439–442, 2011).

An industrial by-product may be used in the cement manufacturing process in two different ways. One could be the use of the by-product as the raw material feed to the kiln in the manufacture of PC in place of coal. Alternatively, by-products could be used together with PC by mixing slag cements or PFA as pozzolans (Gutt, Manufacture of cement from industrial by-products, 1971; Tsakiridis et al., J Hazard Mater 152:805–811, 2008). Alternative binding agents to cement are discussed in detail with the aim of achieving the most sustainable material that could be used in the treatment of industrial wastes as binding agents which would allow them to be used as construction materials. The S/S treatment is based on binders and waste mixtures where the binders used in these systems are most likely alkaline materials that reduce the leachability of the metals in a high-pH matrix.

The steelmaking in the electric arc furnaces (EAFs) is in the category of industrial processes with high degree of pollution. In the air environmental factors are transferred the following dangerous substances: carbon oxides, sulphur dioxide, nitrogen oxides, volatile organic compounds, polychlorinated dibenzodioxins, polychlorinated dibenzofurans and particulate matter. This chapter presents the categories of dangerous emissions generated from the steelmaking in the EAFs; potential sources that generate the dangerous emissions from the steelmaking in the EAFs; generation mechanisms of dangerous emissions from the steelmaking in the EAFs; methods of minimizing the dangerous emissions from the steelmaking in the EAFs.

In this chapter, electric steelmaking is introduced with a short review: share, raw materials, operation, typical equipment, off-gas treatment, emissions. Electric-based steelmaking enjoys a much comfortable position than integrated classical blast furnace—oxygen steelmaking facilities, regarding greenhouse emissions. This is compared both for regions and for the world. For instance, the mostly EAF-based NAFTA countries are nowadays the region where the production of steel generates lower specific emissions. This said (and detailed), the chapter continues with a discussion of the CO₂ emissions of the electric arc furnaces. A reference is be made to the use of alternative raw materials, as DRI/HBI, pig iron and hot metal. In relation with the EAF design, factors to be analyzed are the effects of different furnace designs on emissions: conventional, twin shell, conveyor scrap preheating, and shaft scrap preheating are considered. The use of chemical energy is reviewed, as well as the effect of an external factor: how electric energy is generated.

BOF process is one of the most productive ways of steel manufacturing. Byproducts of this process are metallurgical slag, gases (volatile-rich oxide and other chemical compounds), metallurgical dust, and excessive heat. Nevertheless there are developed a large number of waste gas cleaning systems and recycling technologies, these factors still have negative impact on whole biosphere. The greatest effect it makes on the atmosphere since during melting, a substantial amount of carbon and nitrogen oxides are released into the environment. The steelmaking dust can be classified by its origin. The main types of waste dust include: fragments of the raw material (as a result of technological overload and crushing of the raw materials), products of evaporation and condensation (vaporized molten slag and graphite ripe). For their capture in conditions of Ukrainian manufacturing developed a number of specific technological schemes involving precipitation of dust component in special units (Venturi tubes, cyclones, and scrubbers). Their use can reduce the concentration of hazardous substances and to the regulated legal framework limit.

In integrated steel mills, the sinter plant is one of the major sources of emissions to the atmosphere, whereas the emissions of waste water and solid residues from the sinter plant are usually less significant. Therefore, state-of-the-art emission control technology for off-gas treatment is essential in order to comply with stringent emission limits. In the first part of this chapter, the sinter process is described, the resulting emissions are characterized and primary measures to reduce the off-gas volume and the emission of various pollutants are presented. The second part gives an overview of the state-of-the-art emission control technologies applied in sinter plants for the reduction of particulate emissions, emissions of SO₂ and other acid gases, NOx emissions and emissions of dioxins. In the third part, methods of treating and recycling the residues from sinter plant off-gas cleaning are described. The last part describes some possible future developments in air pollution control for sinter plants.

Processing of raw materials to valuable products results in the formation of undesired compounds due to feedstock impurities and process inefficiencies. During the iron and steelmaking process, iron ore is converted to iron and steel at high temperatures using carbon energy sources. As the iron ore and carbon sources contain minor and trace element impurities and the combustion of carbon is incomplete, certain undesirable compounds may be formed that can be detrimental if emitted to the environment. These emissions can pose significant risks to humans and to the health of the ecosystem. This chapter outlines the various emissions associated with ironmaking, the risks these emissions pose to the environment and the technologies employed to minimise or eradicate the pollutants.

CO emissions have become a serious problem in China because of the country’s heavy reliance on fossil fuels as an energy source. The iron and steel industries, the energy consumptions of which are high compared to the rest of the world, are confronted with an increasing demand to reduce CO emissions. Data on CO emissions from iron and steel industries is a basic requirement for a certificate of CO reduction. By analyzing the production process and the influence factors of CO emissions during iron and steel production process, the scope of CO emissions were defined. Material Flow Analysis (MFA) was used to analyze carbon flow from iron and steel production process, and the CO emissions of a typical enterprise were calculated. The existing processing CO emissions reduction technologies were also analyzed, such as blast furnace top gas pressure recovery turbine (TRT), sintering waste heat power generation, converter low pressure saturated steam generation and so on. The technologies including blast furnace stock gas circulation technology, coke oven gas injection technology after reforming, carbon capture and storage technologies and so forth are considered to have a better prospect of application for CO emissions reduction.

This chapter describes the emission and control of primary particulate matter (PM) in iron and steelmaking plants. The organized and unorganized emission sources of total suspended particulates (TSP) are presented and their emission amounts are reported. Considering the increasingly strict environmental air quality requirements, the emissions of inhalable particles (PM₁₀) and fine particles (PM_2.5) during the iron and steelmaking processes are further discussed. For a sustainable and green iron and steel production, effective dust removal technologies adopted at present and should be developed and promoted in the future are also presented in this chapter.

Iron and steel manufacturing is one of the most energy-intensive and CO₂ emitting industries in the world. In order to contribute to the prevention of global warming, the reduction of CO₂ from the steel works becomes a major issue imposed on the steel industry. A number of technologies have been developed in the past decade under worldwide CO2 breakthrough program for the reduction of carbon emissions. This chapter focuses on present needs, recent progress, and future trends of energy efficient new iron and steelmaking technologies. This study presents a comparative analysis of CO₂ breakthrough programs including the present technological development and effects of application, economic feasibility, and environmental impact assessment. In addition, a brief analysis on ULCOS innovative ironmaking technologies has been done. Finally, significant CO2 reductions can be achieved by combining a number of the available energy efficient technologies with Bio-CCS.

Manganese emission from pyrometallurgical furnaces is becoming an important issue with more and more stringent environmental restrictions on hazardous air pollutant (HAP) metals across the globe. Manganese is going to become the next pollutant in focus from 2016 onward. Mn emission from steelmaking or ferromanganese furnaces mainly depend on factors such as input load, gas flow rate, blowing practice, and finally the operating conditions of the dust capture systems which control particulate matter emissions. In the present study, several mechanisms of dust formation have been reviewed, and a manganese mass balance was performed to understand the distribution of Mn between liquid metal, slag, and dust for a few BOFs in operation. Operational parameters such as oxygen flow rate, blowing time, hot metal (HM) Mn content, scrap Mn content, end blow Mn%, and conditions of the electrostatic precipitator (ESP) were considered and correlated to plant measurements of Mn emission. Issues related to emissions from EAFs, ferromanganese furnaces, and high-Mn steels have been discussed as well.

Transition to a low-carbon economy requires modernisation of the iron and steel industry. Improvement of energy efficiency of blast furnace ironmaking, development of new and rapid commercialisation of currently developed innovative ironmaking technologies and deployment of carbon capture and storage/utilisation technologies are required to reach sustainability targets. Four scenarios with various combinations of energy efficiency enhancement and different market penetration of breakthrough ironmaking technologies have been developed and analysed. Deployment of the best available technologies is indispensable though not sufficient for cutting CO₂ emissions to an extent required by the climate change mitigation targets established by the International Energy Agency. Increased share of secondary steel produced via EAF method using gradually decarbonised electricity also is a prerequisite for substantial cutting of CO₂ emissions. Rapid and wide commercialisation of currently developed innovative ironmaking technologies after 2020 allows for reaching emission levels consistent with the targets up to 2030–2040, depending upon the market penetration. However, in the following years even in the most radical modernisation scenario, new impulse is needed to align CO₂ emissions with sustainability targets. Hydrogen-based ironmaking, enhanced material efficiency, greater share of secondary steel production and CCS/CCU technologies can play the role of such impulse. Delayed and limited mitigation actions will result in much greater amounts of CO₂ emitted to atmosphere with unavoidable impact on climate.

The emissions of greenhouse gases (GHG), mainly carbon dioxide, and energy consumption levels of a number of ironmaking processes including several new technologies that are currently under development worldwide are analyzed and compared. In terms of total emissions of greenhouse gas, energy consumption is important because the production of fuels and energy indirectly adds to the total amount of emissions. The relevant levels of emissions and energy requirements are compared with those of an average blast furnace, which is currently the dominant ironmaking process. The article will also discuss the needs for alternate ironmaking processes and present the descriptions of major alternate ironmaking processes, including important novel technologies under development. Finally, different methods for calculating process energy vs total energy requirement in ironmaking will be discussed.