Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement

By Pasquale Cavaliere

​This book describes the available technologies that can be employed to reduce energy consumption and greenhouse emissions in the steel- and ironmaking industries. Ironmaking and steelmaking are some of the largest emitters of carbon dioxide (over 2Gt per year) and have some of the highest energy demand (25 EJ per year) among all industries; to help mitigate this problem, the book examines how changes can be made in energy efficiency, including energy consumption optimization, online monitoring, and energy audits. Due to negligible regulations and unparalleled growth in these industries during the past 15-20 years, knowledge of best practices and innovative technologies for greenhouse gas remediation is paramount, and something this book addresses.

• Presents the most recent technological solutions in productivity analyses and dangerous emissions control and reduction in steelmaking plants;
• Examines the energy saving and emissions abatement efficiency for potential solutions to emission control and reduction in steelmaking plants;
• Discusses the application of the results of research conducted over the last ten years at universities, research centers, and industrial institutions.

• Language: English
• Publisher: Springer
• Release date: Jul 18, 2019
• ISBN: 9783030212094

Book preview

© Springer Nature Switzerland AG 2019

Pasquale CavaliereClean Ironmaking and Steelmaking Processeshttps://doi.org/10.1007/978-3-030-21209-4_1

1. Clean Ironmaking and Steelmaking Processes: Efficient Technologies for Greenhouse Emissions Abatement

Pasquale Cavaliere¹ 

(1)

Department of Innovation Engineering, University of Salento, Lecce, Italy

Keywords

IronmakingGreenhouse gasesGlobal warmingEnergy efficiencyBest available techniques

1.1 Introduction and Global Scenario

Steel is the base material for the global industry. In 2018, over 1.7 billion tons of steel was produced; it is expected that its demand and production will grow in the next future (Fig. 1.1). The production increase of steel is destined to continue in the future, and the only open doubt is the exact years when production level will pass the two billion ton threshold and then the three billion one (Bellevrat and Menanteau 2009). Iron and steel production has passed through many transformations and evolutions in processing during their long historical presence and their properties, as well as the technologies used for making them have transformed congruently by several orders of magnitude (Freytag 2007). If steel is an invariant of the technological growth of society, it is because of its plasticity to adapt to changing times and changing needs. This is what is called today in European Commission (EC) speech a key enabling technology (KET) – advanced materials are the relevant KET, which introduces the idea that new materials are being invented continuously but also that existing ones are being refined, reformulated, and changed just as continuously. A former expression used by the EC was that of cumulative technologies, thus emphasizing that materials like steel demonstrate a pawl and ratchet effect, where features accumulate and do not vanish, as they would in a marketing product of limited life (Birat 2016). The energy-intensive industry (EII) is responsible for two thirds of industrial carbon dioxide emissions in the EU and sometimes more in other regions. It has been recognized by both public and private stakeholders that a far-reaching transformation of these industries is required to comply with the overall emissions reduction goals stated by the European Union for 2050. Unfortunately, there is little consensus on how deep decarbonization of the EII will be achieved (Gerres et al. 2019).

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Fig. 1.1

Global crude steel production (worldsteel.​org)

From Fig. 1.2 it is clear how the highest production quantities belongs to primary metallurgy processes with a growing percentage of secondary steelmaking processes in North America and India.

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Fig. 1.2

Primary and secondary steelmaking production in the main producer countries

It should be underlined that the production in the most growing countries (China and India) increased four times in the last 10 years (Khanna et al. 2019). As a matter of fact, the China steel production is growing so fast (Duan et al. 2018) that a prevision for the future 15–20 years (Zhou et al. 2017) becomes very difficult to be defined (Fig. 1.3).

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Fig. 1.3

China crude steel production growing rate

The first 20 steelmaking companies with the relative produced tonnage are listed in Table 1.1 (the nation is relative to the company main quarter).

Table 1.1

World first 20 steelmaking companies (Worldsteel.​org)

At the present time, the European steel sector turnover is estimated around €150 billion. The sector employs 410,000 people, representing 1.25% of the total employment in EU manufacturing. Currently, 36 integrated steel plants are active (with 85 blast furnaces and 102 basic oxygen furnaces) and 222 electrical arc furnaces operating in the EU-27 (Steel Institute VDEh 2009). A large proportion of the capital stock involved in primary steelmaking in the EU was commissioned during the postwar expansion of the steel industry. More than 80% of the blast furnaces (corresponding to approximately 80% of the production capacity) were commissioned and built before 1980.

Steel is heavily traded with about 40% of production traded globally. Although such trade mainly takes place within regions, there is also some trade between different regions (Zhong et al. 2018).

The EU passed form to be an exporter to become a net importer in the very recent years. Today the EU is the world’s third biggest exporter and primary importer. China is the biggest supplier followed by Russia and Ukraine. The EU imports more than 90% of its needs of primary raw materials, iron ore, and coking coal. The exports and imports per country are listed in Table 1.2.

Table 1.2

Net export-import per country (2017)

While steel moves further into becoming a material embedded in artifacts, which are used for short or long lives and then eventually get discarded, the by-products are either used in other sectors in an industrial ecology synergy or landfilled. All may be dissipated to the environment to a small extent. Steel itself can be reused or recycled, and, indeed, steel is the most recycled material (Birat 2015).

In the changing global market scenario for raw materials for the steel industry, a number of novel iron and steelmaking process technologies are being developed to provide the steel companies with economically sustainable alternatives for iron- and steelmaking (Ghanbari 2019). In addition, the steel industry is also focusing on reduction of energy consumption as well as greenhouse gas (GHG) emissions to address the crucial subject of climate change (Pardo and Moya 2013). Climate change is presenting new risks to the high-energy and carbon-intensive iron and steel industry. The industry needs to focus on reduction of energy consumption as GHG emissions to address climate change (Bataille et al. 2018). Development of alternate iron and steelmaking process technologies can provide steel companies with economically sustainable alternatives for steel production (Gordon et al. 2015). A very recent study from Voestalpine analyzes the scenario of potential decarbonization in Europe through the energy issues (Voestalpine 2018). The study underlines how the EU steel industry committed to substantial reduction of CO2 emissions. Being the limits of existing production techniques (mainly coal-based) reached, the development and implementation of new breakthrough technologies together with supportive energy infrastructure and services are required. The EU steel companies have intensely explored a number of possible emissions reduction approaches leading to the global conclusion that coordinated and comprehensive energy and funding strategy on EU level is the key. In addition, there is no short-term solution. The general indications are related to CDA (carbon direct avoidance) and CCU (carbon capture and usage) , directly avoiding CO2 emissions through an increased use of renewable electrical power in basic steelmaking (e.g., hydrogen replacing carbon in metallurgical processes) and chemical conversion of CO2 captured from industrial processes and using the CO2 as a raw material, respectively. Voestalpine indicates that breakthrough technologies for decarbonization (e.g., on hydrogen basis) will not be available before ~2035. In addition, transformation has to be technically and economically feasible. This is because the fully renewable transformation nearly results in a doubling of the production costs basing on the current situation. The ETC is confident that a complete decarbonization of the steelmaking industry is achievable by mid-century, with a modest impact on end-consumer prices and cost to the overall economy, although an uneven transition on a global scale may create competitiveness issues (ETC 2018). The last report suggests that given that the two main routes for primary steel production decarbonization will almost certainly be CCS and hydrogen-based reduction, public and private R&D spending, as well as investment in pilot plants, should focus on driving down the cost and increasing the efficiency of electrolysis equipment, piloting and driving down the cost of hydrogen-based reduction, ensuring the feasibility and driving down the cost of innovative BF-BOF designs which would reduce CCS costs, and helping to increase the feasibility and reduce the cost of CCS – in those locations where storage capacity is available and where higher electricity prices are likely to make the hydrogen route a more expensive option. The report also gives useful indications on the actual and future R&D priorities, driving down the cost of energy efficiency and carbon efficiency technologies that can drive down carbon emissions from existing plants, developing iron electrolysis as a potentially lower-cost solution in the very long term, and developing innovations that enable higher-quality and higher-value recycling of steel, also indicating the governmental priorities to this end, supporting specific pilot projects designed to achieve early decarbonization of a country’s steel industry, supporting early-stage R&D in technologies which are currently further away from commercial readiness – such as electrochemical approaches to iron ore reduction – and supporting the development of shared CO2 transportation networks which may be required to make CCS a feasible solution in those locations where it is likely to be significantly cost advantaged.

1.2 Main Approaches to the Problem

A popular and contemporary concept describing how materials life and resources can be optimized in the future is named circular economy. Circular economy is obviously based on the materials recycling and on energy saving. Materials are recovered from the collection of end-of-life (EoL) investment or consumer goods. The key word is therefore recycling of EoL goods, materials, metals, minerals, residues, and by-products and also dangerous emissions, like CO or CO2 (carbon capture use and storage, CCUS) . Resource efficiency is an instrumental mitigation option in the steel industry, but existing studies have failed to provide a global analysis of the sector’s energy and material use. Despite the interactions between energy and materials in steelmaking, recent studies investigate each of these resources in isolation, providing only partial insight into resource efficiency. Gonzalez Hernandez et al. (2018) analyze the latest, most comprehensive resource data on the global steel industry and quantify the savings associated with reducing this through energy- and material-saving measures. The sector’s resource efficiency – accounting for energy and materials – is expressed in exergy and measured at two levels, that of production routes and plants. The results show that the sector is 32.9% resource-efficient and that secondary steelmaking is twice as efficient (65.7%) as ore-based production (29.1%). Energy-saving options, such as the recovery of off-gases, can save about 4 EJ/year (exergy). Material saving options, such as yield improvements, can deliver just under 1 EJ/year extra (Chowdhury et al. 2018). A global shift from average ore-based production to best available operation can save up to 6.4 EJ/year, a 26% reduction in global exergy input to steelmaking (An et al. 2018). Shifting to secondary steelmaking can save 8 EJ/year, limited only by the need to still produce half of steel from ore in 2050.

Recycling procedures bring materials savings consequently reducing the need for virgin resources (primary raw materials). When materials are recycled to the same material, additional environmental benefits and credits can contemporarily be collected, like energy savings, greenhouse gas emissions reduction, and a smaller environmental footprint in general. The optimal route will consequently be the one capable of favoring all this aspects at the same time in order to reach the highest efficiency. This is the basis of the holistic ironmaking optimization (Bettinger et al. 2017). While process optimization systems have been widely introduced in many facilities of ironmaking plants, in a lot of cases, there is no overall automation system, supporting coordination and through-process optimization of all ironmaking facilities in place. This approach allows for automated production control systems to achieve standardized operation throughout all ironmaking facilities by coordinating the individual aggregates, such as raw material management, coke oven plants, sintering, pelletizing, direct reduction, pulverized coal injection plant, and blast furnace operation. Holistic ironmaking optimization enhances the performance of ironmaking plants by the consistent, methodical, and comprehensive consideration of the global optimum rather than aiming at local optima for each plant. The resulting traceable production decisions and the increase in transparency allow for thorough process optimization, which leads to reduced conversion costs and more consistent quality, higher efficiency, and increased production. As an example, ore-based ironmaking generates a variety of residues, including slags and fines such as dust and sludges. Recycling of these residues within the integrated steel plant or in other applications is essential from a raw material efficiency perspective. The main recycling route of off-gas dust is to the blast furnace (BF) via sinter, cold-bonded briquettes, and tuyere injection. However, solely relying on the BF for recycling implicates that certain residues cannot be recycled in order to avoid buildup of unwanted elements, such as zinc. By introducing a holistic view on recycling where recycling via other process routes, such as the desulfurization (deS) station and the basic oxygen furnace (BOF), landfilling can be avoided (Andersson et al. 2018). The holistic approach considered a compromise between energy efficiency and raw material efficiency for the process system including the BF, BOF, and deS station. Furthermore, the approach accounted for tramp elements, mainly zinc, while maintaining the production of high-quality steel. The study suggested that the off-gas dust could be recycled, minimizing the amount of non-recycled residues.

The circular economy should be described material by material, in order to analyze in detail what is already being done and what can still be improved: the various materials achieve very different levels of recycling, and thus policies for going beyond present achievements will differ according to each material. The circular economy has an important time dimension, as many materials are stocked in the economy for long times, sometimes half a century or more. The life span of the material stocks means that high recycling rates today will be translated into high-recycled contents only in the future, sometimes in the long time. The circular economy is a long-time endeavor! A first step towards capturing the broader impacts – environmental, social, or otherwise – in complex systems is to trace the impacts of consumption up the supply chain. Well-established methods such as life cycle analysis (LCA) and MFA (materials flow analysis) address precisely this issue, their core aim being to estimate environmental impacts throughout supply chains – extraction, manufacture, transport, etc. – and reallocate these to final materials or products (Millward-Hopkins et al. 2018). LCA is an important tool in implementing the environmental management system (EMSy). LCA is a technique for assessing the environmental aspects and potential impacts associated with the product or technology. LCA is an environmental assessment tool for evaluation of impacts that a technology or product has on the environment over the entire period of its life – from the extraction of the raw material through the manufacturing, packaging, and marketing processes and the use, reuse, and maintenance of the product to its eventual recycling or disposal as waste at the end of its useful life. It is important to integrate environmental assessment and results of LCA with other economic methods into product design at an early stage to improve the environmental and economic performance of the product or technology and to eco-efficiency analysis. Environmental life cycle assessment study in iron and steel industry is widely developing in the world. This method can be used for selecting new optimal technologies or products. LCA is an important method used for environmental impact assessment of current, alternative, and future technologies in ironmaking (Burchart-Korol 2011).

LCA and MFA incorporate the cycle time of recycling but need to be expanded into dynamic LCA and MFA in order to become fully time-dependent. The complexity of MFA of iron can be viewed in Fig. 1.4 (Allwood et al. 2012).

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Fig. 1.4

MFA of iron in the world for year 2000 presented as a standard MFA diagram (Allwood et al. 2012)

Policies founded on LCA at a microeconomic scale and MFA at a macroeconomic scale are the most apt to mirror how the socioeconomic system works and thus to avoid negative rebound effects. Fostering the use of these tools is an important element in encouraging the circular economy. But it is also important to understand that the rationale for moving in this direction is environmental and political, not necessarily economical (Hellweg et al. 2014). Thus it will not be enough to foster technological R&D (research and development) and to achieve R&I (research and innovation): tools to internalize these externalities in the market economy will need to be introduced more widely.

The complexity of this scheme is obvious but is compounded by the fact that steel is not simply iron but contains other elements, either originating from the initial raw materials or added as alloying and similar elements. These have a different fate in the recycling loop from irons: some are also recycled, often co-recycled with iron, while others are simply lost. Steel is thus not simply identical to element iron, even if carbon steel is one of the simplest alloys in metallurgy (Dente et al. 2019). Steel is a complex mixture of elements, a complex alloy, and a complex set of phases, NMI, depending on temperature and kinetics histories. Steel is mainly a binary alloy of iron and carbon, but many more elements are part of its composition. Some remain as a memory of the raw materials and reactants used in the iron and steelmaking processes, while some more have been added voluntarily, since it was understood in the Neolithic that properties could be changed greatly by adding some small amounts of alloying elements. Another conceptual dimension is related to how useful or perturbing the minor components are: the minor elements/components that bring positive value or usefulness to steel have been given specially positive names, like alloying elements, additions, precipitates, or, more recently, nano-features. Those that bring negative value are given negative names, like tramp elements, inclusions and non-metallic inclusions, impurities, third phases, slag particles, etc.

Raw materials for steel production – iron ore and coal mostly – are neither rare nor scarce, except for a very few alloying and reactant elements, for the fundamental reason that iron is the most abundant element in the Earth and a fairly common one as well in the Earth crust. This does not mean, however, that they will be used indiscriminately in the future, because steel is presently already recycled to a high level (83% and 36 years of average life), and, when peak steel production is reached, probably towards the end of this century, a full circular economy will take over, except, possibly at the margin for a small number of niche applications (Babich and Senk 2019).

Among several greenhouse gases with different impact on the air quality, CO2 is the main contributor accounting for about 60% of the greenhouse effect because of its huge and broad emission levels. Among all the industrial sectors, ironmaking and steelmaking one is calculated and measured to be the largest emitter of carbon dioxide (over 160 Mt. CO2/year in 2017) and one of the users with largest energy demand (over 25 EJ/year in 2017). It accounts for an estimated 5.2% of total global greenhouse gas emissions and 21% of total EU industrial emissions. Taking into account the emissions of the only ironmaking and steelmaking sector, about 80–90% of the emissions are related to the blast furnace-converter process. The World Steel Association estimates an average energy intensity of 18.68 GJ/tCS for the integrated steel route with an average CO2 intensity of 1.77 tCO2/tCS (Janjua 2017).

The ongoing increase in world steel demand means that this industry’s energy use and CO2 emissions will continue to grow, so there is significant industrial and governmental incentive to develop, commercialize, and adopt emerging energy efficiency and CO2 emissions reduction technologies for steel production (Otto et al. 2017). New developments will obviously include different processes and materials as well as technologies that can economically capture and store the industry’s CO2 emissions. Deployment of these new technologies in the market will be critical to the industry’s climate change mitigation strategies for the mid and long term. As a matter of fact, it should be noted that the technology adoption in regions around the world is driven by economic viability, raw materials availability, energy type used and energy cost, as well as regulatory regime (Perkins 2017).

Anyway, steel is not particularly energy-intensive as compared to other materials; indeed materials are in essence all energy intensive, which is the price to pay for the functions they provide to society. Moreover, the energy involved is mainly exergy, not simply heat dissipated as is the case for combustion processes (Birat et al. 2013).

In 2013, the world total industry final energy consumption was 113,131 PJ, of which the consumption of the iron and steel sector accounted for 18%. Figure 1.5 shows the shares of different fuels used in the world iron and steel industry.

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Fig. 1.5

World total industry final energy consumption of the iron and steel sector in 2013 (IEA 2016)

As shown in the figure, coal is the major resource for power generation, accounting for over 60% of the final energy use; 21% of the final energy use is from electricity, 11% is from natural gas, and approximately 8% is from other energy sources (such as oil, biofuels, waste, and heat).

Now, as shown in Fig. 1.6, 52% of the energy input is employed, and 48% represents wasted energy.

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Fig. 1.6

Energy employed and wasted in the BF-BOF-CC route

This shows the broad potential for energy recovery and reuse in an integrated steel plant. The situation is clarified also for all the sections of the integrated steel plant (Fig. 1.7).

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Fig. 1.7

Wasted energy in the integrated route (all the numbers refer to GJ/ton steel)

A big effort has been conducted by all the producing companies in order to improve energy efficiency to sustain reduction in specific energy consumption; among these they have to be generally mentioned: utilization of by-product gases for steam and power generation, phasing out old and energy-inefficient units, enhancing by-product gas recovery and optimization of operating practices, regular energy audit and implementation of its recommendations, coal injection at blast furnaces, waste heat recovery from waste gas of blast furnace stoves, installation of top recovery turbine, the use of regenerative burners at hot strip mill for maximizing fuel efficiency, coke dry quenching, application of V/F drives, upgraded centralized energy management center, large size BFs with higher energy efficiency, use of pellets and shift to alternate fuel for utilizing lean by-product gases, promoting use of renewable energy in operations, and coal injection (Chittrey 2016). Thanks to the continuous development and implementation of incremental technologies, the steel industry has largely improved its energy efficiency and deeply reduced its specific energy consumption by about 60% over the past 50–60 years. Actually, the unit energy consumption for iron and steel production differs greatly depending on the country because of energy supply and cost issues. In those countries where energy prices are high, relevant levels of energy saving by various advanced technologies have been already developed and applied (Kan et al. 2016). The close linkage between energy consumption and CO2 emission has resulted in a similar reduction in specific CO2 emission, where currently about 2.2 tCO2 is produced per ton of crude steel manufactured through efficient integrated blast furnace and BOF plants. The very fast production growth in the global steel industry encounters new and increased problems related to raw material quality and availability, industry structure, and pricing and environmental issues impacting the preferred ironmaking route in different regions of the world (Cavaliere 2016). Better targets could be achieved if radical changes in the steel production processes are introduced (thus reaching 15–25% of energy efficiency increase). However the business model for introducing these changes is still elusive, which means that the cost of introducing more energy savings is far higher than the value of the energy saved (Birat 2010). The energy transition, which is taking place now and especially in Europe with different flavors in each country, is also a challenge for the steel sector (Rootzén and Johnsson 2013; Madureira 2012).

1.3 Technological Issues

The integrated steelworks is a complex system in which huge quantities of coal and other fossil materials are consumed as reducing agents and energy resources in the upstream process, that is, the ironmaking process centering on the blast furnace, and the gases generated by the ironmaking process are supplied to downstream processes as energy. These systems have been highly optimized to produce steel products from the viewpoint of energy utilization. However, in order to address the issues of global warming and energy security, the steel industry must now deeply review its utilization of carbon and energy (Shatoka 2016a). Since the steel industry depends on coal as the main reductant in the production of steel products, efforts to decrease carbon consumption are being pursued from the mid- and long-term viewpoints on global warming (Sato et al. 2015). Obviously, CO2 emissions are related to the growing of steel needing; this aspect becomes particularly crucial in those countries where population and economic growing is relevant (Fig. 1.8).

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Fig. 1.8

CO2 emissions levels from the Chinese iron and steel industry

Based on current climate change forecast, it is predicted that the steel industry will face greater challenges which cannot be solved with the past incremental technologies in the future. Thus, a more comprehensive social system to support clean steel production will be required. Climate change is a global issue which requires a global response and responsibility. There still exist many subjects to be considered. The optimal solutions cannot be seen, and the discussions to find a better pathway to attain the long-term goal have just started (Ariyama et al. 2019). Industries and scientists are all aimed to reduce emissions and energy consumptions by 30% (400 Mt. and 5 EJ/year, respectively) in the next 30 years. Ironmaking and steelmaking involves various processes and technologies that can be operated and organized in different combinations depending on the charging materials properties and the final required products. Different raw materials, energy requirements, and investments can vary as a function of the different plant configurations and the chosen advanced technologies employed for the emissions reductions (He and Wang 2017). The main processing routes can be summarized as (schematically described in Fig. 1.9):

Blast furnace (BF)/basic oxygen furnace (BOF) route. Here pig iron is obtained by employing primarily iron ore and hydrocarbons (mainly carbon coke) by iron oxide reduction at high temperatures in the blast furnace. In the blast furnace, coke, ores, and limestone are continuously charged from the top of the furnace; the hot blast is injected through the tuyeres in order to allow the reducing reactions to take place as the charging materials move down. The molten metal and the slag are concentrated at the bottom of the furnace, while the flue gases are eliminated from the top. The material is then converted into steel in the basic oxygen furnace. Due to sintering operations and coke making, this route is highly energy expensive and subjected to the problem of high-impact greenhouse emissions (dioxins, furans, CO2, SOx, and NOx).

Scrap/electric arc furnace (EAF) route. Here, selected steel scraps are used as input for the EAF processing to obtain a product of the required composition. The energy requirements are lower if compared to the blast furnace (BF)/basic oxygen furnace (BOF) route thanks to the absence of coke making and sintering operations.

Smelting reduction route. Smelting basically employs reducing agents at high temperatures to decompose the iron ores. Gases and slags are eliminated, and the molten metal is lived at the end of the smelter. The reducing agent is mainly the charcoal so eliminating the necessity to use coke. The carbon reduces the oxygen from the ore, and then it is oxidized to CO and CO2. Other impurities are separated from the iron through the injection of reducing substances that, once reacted, are collected in the slag.

Direct reduced iron (DRI)/EAF route. Iron ores are reduced through the employment of natural gas. The energy intensity of these processes is similar or slightly lower with respect to the blast furnace (BF)/basic oxygen furnace (BOF) route.

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Fig. 1.9

Ironmaking and steelmaking processes

The employed raw materials and the different processes belonging to the various routes are schematically described in Fig. 1.10.

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Fig. 1.10

Schematic of the different processing routes

In the integrated steel plant , carbon enters mainly as coal and in a minor percentage as limestone, and then it is emitted (under the form of different compounds) by various routes described schematically in Fig. 1.11.

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Fig. 1.11

Major carbon flow in the integrated still mill

Given the different sectors of an integrated steel plant indicating the raw materials, the different types of the produced dangerous compounds are shown in Fig. 1.12.

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Fig. 1.12

Emissions type in the integrated steel mill

The sinter plants are responsible for the 50% of dust emissions in the integrated steel plant. Other relevant emissions are heavy metals, SO2, HCl, HF, PAHs, and persistent organic compounds such as PCB and PCDD/PCDFs (Cavaliere et al. 2011; Cavaliere and Perrone 2013). Many of the emissions to be taken into account from the coke oven operations are the coal storing, handling, crushing, and blending. VOC emissions to air come from the oven batteries along with toluene, benzene, ammonia, and xylene. CO2 and SO2 are the more impacting greenhouse emissions of these plants. The many environmental problems related to the BF operations are related to dust, wastewater, SO2, and H2S as well as CO2 (Kuramochi 2016). A recent estimation of the main off-gases generated in a 6 Mt. steel/year is shown in Table 1.3.

Table 1.3

Volumetric flow rates, lower heating values, and composition of the steelwork off-gases after cleaning of a modern steel plant producing 6 Mt. steel/year (Uribe Soto et al. 2017)

These off-gases have a reasonable LHV, implying that the current main utilization of these off-gases is the thermal use. But, these off-gases contain also valuable compounds that may be used as reducing agents, such as CH4, H2, and CO in order to synthetize a high-added value product. For this reason, the thermochemical processing of these gases is an option to use them. Many products may be synthesized from the steelwork off-gases. To do this, several processes have been proposed. In particular, H2 recovery schemes may be mentioned. The water-gas shift reaction applied to the CO-rich streams (BFG and BOFG) and methane reforming applied to the COG may increase the amount of available H2. In this case, the recovery of H2 contained in the COG using gas permeation or a PSA system is needed as well as CO from the BFG and the BOFG using a chemical absorption process or a PSA system (Nestler et al. 2018).

By focusing on CO2 emissions, the quantification for a typical steel mill is shown in Fig. 1.13.

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Fig. 1.13

CO2 emissions in the integrated steel mill

The emissions of EAFs to air are inorganic compounds and persistent organic compounds.

Regarding GHG emissions, the ambition of the UNFCC is to cut emissions by 80% by 2050 in order to avoid a surface temperature increase of more than 2 °C. This cannot be achieved in the steel sector by implementing energy efficiency solutions, which fall short of the target by a factor 6. New breakthrough processes are needed (Holappa 2017). Engaging in these major changes for making steel with greatly reduced CO2 emissions is similar to engaging in the energy transition. The change will only happen when R&D is finished and confirmed and when a business model is developed in connection with the world governance of climate change policies – as any climate-related transformation is today still an externality in the market economy.

A very recent report from the European Commission affirms that the current changes in our planet’s climate are redrawing the world and magnifying the risks for instability in all forms. The last two decades included 18 of the warmest years on record (Fig. 1.14).

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Fig. 1.14

Temperature anomaly May 2018 (NASA.​gov)

The trend is clear. Immediate and decisive climate action is essential (European Commission 2018). The Intergovernmental Panel on Climate Change (IPCC) issued in October 2018 its Special Report on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways (Bataille et al. 2018). Based on scientific evidence, this demonstrates that human-induced global warming has already reached 1 °C above pre-industrial levels and is increasing at approximately 0.2 °C per decade. Without stepping up international climate action, global average temperature increase could reach 2 °C soon after 2060 and continue rising afterwards. Irreversible loss of the Greenland ice sheet could be triggered at around 1.5–2 °C of global warming. This would eventually lead to up to 7 m of sea level rise affecting directly coastal areas around the world including low-lying lands and islands in Europe. The Paris Agreement, ratified by 181 parties, requires strong and swift global action to reduce greenhouse gas emissions, with the objective to hold global temperature increase to well below 2 °C and to pursue efforts to limit it to 1.5 °C. It also has the goal to achieve a balance between emissions by sources and removals by sinks of greenhouse gases on a global scale in the second half of this century. All parties are to present long-term low greenhouse gas emission development strategies by 2020 that deliver on its objectives. CCS plays a major role in decarbonizing the industry sector in the context of 1.5 °C and 2 °C pathways, especially in industries with higher process emissions, such as cement, iron, and steel industries. In 1.5 °C-overshoot pathways, CCS in industry reaches 3 GtCO2/year by 2050, albeit with strong variations across pathways. Given the projected long-lead times and need for technological innovation, early scale-up of industry-sector CCS is essential to achieving the stringent temperature target (Rogelj et al. 2018).

The estimated sinter energy intensity is in the range 0.70 MMBtu/ton (0.82 GJ/ton)–1.32 MMBtu/ton sinter (1.54 GJ/ton). US coke making energy values, estimated to be 3.83 MMBtu/ton coke (4.45 GJ/ton), are specific to coke making facilities at integrated steel plants (US Department of Energy 2015). Blast furnace ironmaking energy intensity is estimated at 11.72 MMBtu/ton of hot metal (13.63 GJ/ton). Steelmaking in the basic oxygen furnace (BOF) with subsequent refining operations (ladle metallurgy, vacuum treatment, slag management, etc.) can have a fairly wide range of energy use. Energy intensity for BOF steelmaking is estimated at 0.58 MMBtu/ton of liquid steel (0.67 GJ/ton). Final energy intensity for EAF steelmaking is estimated at 1.86 MMBtu/ton liquid steel (2.16 GJ/ton).

A range of technologies and measures exist for lowering CO2 emissions including minimizing energy consumption and improving energy efficiency, changing to a fuel and/or reducing agent with a lower CO2 emission factor (such as wood charcoal), and capturing the CO2 and storing it underground. Significant CO2 reductions can be achieved by combining a number of the available technologies. If carbon capture and storage is fitted, then steel plants could become near-zero emitters of CO2 (Jahanshahi et al. 2016).

In terms of CO2 emissions levels, the provisional scenario is given in Fig. 1.15.

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Fig. 1.15

CO2 emissions depending on the technological structure

With the present technological routes, the CO2 emissions are destined to increase of 50% by 2050. The 2 °C scenario will be possible only if the emissions will be reduced by 50% (Delasalle 2019).

The book will describe the main available technologies employed in the traditional or innovative routes capable of reducing the energy consumption and the dangerous greenhouse emissions. Obviously the energy topic will be described taking into account the direct and indirect energy consumption per each analyzed technology. The methods to improve the energy efficiency are the energy consumption optimization, the online monitoring, and the energy audits. To give a preliminary idea, Table 1.4 describes the energy consumption ranges for the indicated main routes.

Table 1.4

Energy consumption for the different ironmaking routes

As a summary, at the end of each chapter, we’ll indicate the potential of the main greenhouse emissions abatement per each described technology. The data will be related to the energy consumption/saving and, once available, an estimation of the costs related to the introduction of the innovation.

As a matter of fact, many of the industrial choices are related to a scenario finalized to reduce the global CO2 emissions in order to avoid global warming .

The key emissions abatement options in the steel industry include:

Improved energy efficiency; the steel industry has managed to improve considerably the energy efficiency of the production process over the last decades. However, a multitude of measures, both in primary and secondary steelmaking, could be implemented that would reduce significantly energy use and associated CO2 emissions (Mohsenzadeh et al. 2019).

Fuel shift; the blast furnace is the single most energy-consuming process in the production of steel. Coke, which is derived from coal, often functions as both a fuel and reducing agent. Replacing coke with natural gas or biofuel could potentially reduce CO2 emissions from the blast furnace process (Ng et al. 2018).

Carbon capture and storage; opportunities for CO2 capture in the steel production vary depending on the process and the feedstock used. The largest flow of CO2 in a conventional integrated steel mill is generated in the blast furnace. Recovery of CO2 from blast furnace gas is a feasible capture option for the steel industry (Mandova et al. 2019). Applying current end pipe technologies to existing blast furnaces, ~30% of the overall CO2 emissions from a conventional integrated steel plant could be captured. Capture could be applied to other gas flows in the production process, although the costs are likely to be higher, since the volumes and concentrations CO2 are lower. One of the most promising opportunities for CO2 capture in the steel industry is to replace or retrofit conventional blast furnaces with top gas recycling blast furnaces (TGR-BF). In a TGR-BF, the CO2 is separated from the BF gas, and the remaining CO-rich gas stream is recirculated back into the furnace (Liu et al. 2018). Simultaneously replacing the preheated air with pure oxygen would ensure that the blast furnace gas stream was free of N2, thereby simplifying CO2 capture. It has been estimated that 70% of the CO2 emitted from an integrated steel plant could be recovered if TGR-BF with CO2 capture was introduced (Rootzén et al. 2011).

Structural change; secondary steelmaking in electrical arc furnaces is expected to continue to gain market share at the expense of primary steelmaking in integrated steel plants, thereby lowering the carbon intensity of steel production.

New steelmaking processes; the steel companies and associations identified a number of process technologies that could reduce CO2emissions by at least 50% compared to the current best routes (often in combination with CCS).

1.4 Main Solutions

Meeting the targets will require rapid and comprehensive implementation of mitigation technologies and measures that are commercially available today and emerging technologies that are still in the early phases of development. Preliminary results and evaluations through simulations indicate that some 60–75% of the emissions could be avoided annually if the full potential of emerging CCS technologies was to be realized. Furthermore, several regions were identified as being particularly suitable to facilitate integrated networks for the transportation and storage of the captured CO2. The most promising prospects for early deployment of CCS are found in the regions bordering the North Sea. Other evaluations illustrate how the access to infrastructures, such as district heating networks, natural gas grids, chemical industries, and possible CCS storage sites, which could facilitate CO2 abatement in the petroleum refining industry, is optimal. Furthermore, it is shown that the potential for currently available mitigation measures in the refining industry is relatively limited and that the potential for CO2 capture varies widely depending on which sub-process is targeted. Near-term targets for emissions reductions can probably be met through measures that are already available, such as increased energy efficiency, optimization of production processes, and shifts in the usage of fuel and feedstock mixes. To realize the goals of future, stricter, emission targets, more radical alterations to production processes are required. In the iron and steel manufacturing sector, in which breakthrough technologies are still in their infancy, to enable significant reductions in emissions up to year 2050, the ongoing efforts to develop new steelmaking processes must be accelerated considerably (Quader et al. 2016a). As emphasized above, the technological transition required to reduce radically the CO2 emissions in less than four decades involves both the phasing out of current carbon-intensive technologies and the phasing in of new zero- or low-carbon technologies (Ökvist et al. 2017).

A CO2 price set at a level significantly higher than it is today is a prerequisite for incentivizing near-term mitigation measures, as well as for stimulating investments aimed at further developing emerging technologies and processes. However, developing and phasing in new zero- or low-carbon technologies, at scale, will require complementary policy interventions, including R&D funding, support for niche markets, and adaptation of infrastructure policies (Wilson and Grubler 2011). While policy support plays an important role in the development and deployment of many low-carbon technologies, it is especially crucial for CCS. This is because, in contrast to, e.g., renewable energy or applications of energy efficiency, CCS generates no income nor other market incentives, so long as the cost of emitting CO2 remains low. Shifting away from conventional processes and products will require a number of developments including education of producers and consumers, new standards, aggressive research and development to address the issues and barriers confronting emerging technologies, government support and funding for development and deployment of emerging technologies, rules to address the intellectual property issues related to dissemination of new technologies, and financial incentives (e.g., through carbon trading mechanisms) to make emerging low-carbon technologies, which might have a higher initial costs, competitive with the conventional processes and products. The authors suggest how different policy mechanisms may generate outcomes over different timescales (Table 1.5).

Table 1.5

Illustrative technology innovation and diffusion policy approaches matched to realistic timescales of outcomes

In future scenarios, a lack of credibility in international climate policy imposes significant costs on climate stabilization as investment decisions in energy plant and infrastructure become increasingly myopic. Alongside stability and credibility, innovation policy needs to be aligned. Policies to support innovations through early research and development can be undermined by an absence of support for their demonstration to potential investors and their subsequent deployment in potential markets (e.g., promoting energy-efficient building designs without strengthened building codes or CCS development without a price on carbon). Alignment means an integrated approach, stimulating both the development and the adoption of energy technologies. R&D initiatives without simultaneously incentivizing users to adopt the outcomes of innovation efforts risk not only being ineffective but also precluding the market feedbacks and learning that are critical for continued improvements in the technologies. Incentives can also be perverse. Support for low-carbon innovations is undermined by diffusion subsidies for carbon-intensive technologies. Policies promoting the demand for mobility mean efficiency improvements are swamped by rising activity levels. Static innovation incentives can undermine continual improvement. By comparison, dynamic technology standards can spur a continuous innovation recharge. Aligned policies are also systemic policies. The innovation system comprises not just technologies and infrastructures but also actors, networks, and institutions. Technology policies supporting market deployment can support a build-out of numbers of units or an upscaling of unit capacity or both. Policies to support growth in numbers of units might diversify market niches, promote modularity, or advance flexibility and adaptability to different contexts. Policies to support upscaling might co-fund demonstration projects and field trials, streamline the licensing process for retrofits (or support leasing business models for process technologies), or provide testing infrastructure. Timing, however, is important. The importance historically of a formative phase of building out large numbers of units over an often extended period strikes a cautionary note for policies acting too early in a technology’s commercial life cycle to support upscaling. More broadly, managing expectations among the many innovation system actors is important. Ill-timed policies or stop-start policies, if short-term objectives are not being met, can undermine long-term innovation investments.

The IEA developed a BLUE scenario examining the implications of a policy objective to reduce CO2 by 2050; these subjects are specified in Table 1.6.

Table 1.6

Emissions trend in the BLUE scenario

This scenario provide also the potential of direct emissions reduction, indicating that more than 50% of reduction will be ensured by the development of CCS technologies (Fig. 1.16).

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Fig. 1.16

Direct emissions reduction potential

It is globally believed that the short- to medium-term approach is mainly focused on the energy efficiency and on the energy-saving/recovering technologies as well as the quick development of technologies such as CDQ and TRT. The long-term approaches are mainly devoted to deeply include the use of renewables and CCS technologies and their combination with pure oxygen top gas recycled blast furnace (Xu and Cang 2010).

The exiting steel technologies are based on fossil fuels, i.e., mostly on carbon, natural gas, mix of carbon and hydrogen, and electric arc furnaces. For CO2-lean process routes, three major ways of solutions have been identified: decarbonizing whereby coal would be replaced by hydrogen or electricity in hydrogen reduction or electrolysis of iron ore processes, CCS technology introduction, and the use of sustainable biomass (Fig. 1.17).

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Fig. 1.17

Pathways of technologies for GHG emissions abatement

This triangle matrix explains how reducing agents and fuels can be selected from three possibilities such as carbon, hydrogen, and electrons. The mock ternary diagram represents all existing energy sources where coal is near to carbon on the carbon-hydrogen line, natural gas is near to hydrogen, hydrogen from electrolysis of water is on the hydrogen-electricity line, etc.

Minimizing energy consumption and improving energy efficiency offer the greatest scope for cutting CO2 emissions in the short term, as well as lowering costs. The principal measures for improving energy efficiency include enhancing continuous processes to reduce heat loss, increasing the recovery of waste energy and process gases, and efficient design. Recycling wastes generated within and outside the steelworks can help reduce overall CO2 emissions per ton of steel produced (Gonzalez Hernandez et al. 2018). Thus increasing the recycling rate of steel scrap will lower CO2 emissions. There is still room to increase scrap recycling rates as only around 40% of the steel produced globally is recycled steel.

Over the years the iron and steel industry has made significant efforts to reduce energy consumption and lower CO2 emissions by improving energy efficiency, reducing coke and coal consumption, utilization of by-product fuels, increasing the use of biomass and renewable energy, and other techniques (Suopajärvi et al. 2018). But the scope for further reduction by these means is limited in state-of-the-art facilities. Further significant reductions will depend on the development of carbon capture and storage (CCS) technologies. One of the largest sources of CO2 emissions is from the use of carbon-based agents to reduce the iron ore to iron. The production of steel is a complex process incorporating a variety of process technologies with different plant layouts. These processes interact with one another, and a change in one process can affect other upstream or downstream processes. A systematic study of the steelworks as a whole should first be carried out to assess the energy balance and CO2 emissions before any abatement measures are introduced. This includes an energy audit to identify points of energy loss and how to minimize them. Not all of the BATs are necessarily suitable for all installations or can be retrofitted, and the cost-effectiveness of the technologies will vary from plant to plant (Shatoka 2016b).

Blast furnace is the most energy-consuming process in integrated steel plants. So it is essential to reduce fossil CO2 emissions from this process. Top gas recycling blast furnace is a blast furnace gas separation technology for clean steel production. Top gas used to absorb CO2 inside blast furnace acts as a reducing agent. It effectively reduces carbon emission around 50%. The integrated use of TGR-BF and CO2 capture and storage (CCS) technologies is helpful to remove nitrogen from the TGR-BF, and oxygen injection into BF can also effectively recover CO2 (Kumar Sahu et al. 2016). After extraction of CO2 from recycled gas by using VPSA CCS technology, the cryogenic technique is applied to store.

Smelting technologies are employed for coal preheating and partial pyrolysis in a reactor, melting cyclone for ore melting, and melter vessel for final ore reduction and iron production. By removing sintering and coking processes, it reduces CO2 emission. Moreover, by using biomass or natural gas instead of coal, processing combustion gases, storing CO2, and recycling heat energy, the technology reduces almost 70% CO2 emission (Kitamura et al. 2019).

To produce direct-reduced iron (DRI) for sending to electric arc furnace, the reducing agent such as natural gas or biomass gas is used in a reactive level for the iron ore sintering process. In gas purification process, traditional reducing agent is replaced by natural gas. Top gas recycling and preheating processes reduce natural gas consumption (Perato et al. 2018). Obviously, the DRI production is related to the fuel supply and price as shown in Table 1.7.

Table 1.7

DRI production in 2016 (Worldsteel.​org)

The principle of the direct electrolysis of iron ore has been applied to produce iron and oxygen with zero-carbon emission (Wiencke et al. 2018).

By hydrogen-based steelmaking route, CO2 emissions would be reduced by more than 80%. Hydrogen steelmaking will depend profoundly on the availability of green hydrogen. It can be generated from natural gas by steam reforming or from water by electrolysis. Today hydrogen-based steelmaking is a potential low carbon and economically attractive route in a few countries where natural gas is cheap (Xing et al. 2019).

Carbon capture and storage presents one of the most promising options for large-scale CO2 emissions reduction for the future. Iron and steel plants are suitable for CCS because emissions are generated from single fixed and easily accessible points. In order to capture CO2 from emissions, carbon dioxide must be separated from flue gases and then compressed and/or cooled and transported by pipeline network for underground storage. TGR-BF experiments show that chemisorption technologies such as amine scrubbing, physisorption, the VPSA or PSA, and cryogenics have different fields of optimality. The level of CO2 concentration of the gas stream to be treated in the TGR-BF for physisorption systems is the best in terms of technical performance and economical operation (Quader et al. 2016b).

An increasing number of countries around the world are taking economic measures to reduce their CO2 emissions through emission trading schemes (e.g., the EU and South Korea), carbon taxes, or energy efficiency initiatives. Steelmakers are involved in many programs to transfer technologies and best practices, thereby improving or replacing existing processes or reducing process steps. Steel producers are researching and investing in low-carbon technologies that would radically reduce their environmental impact (worldsteel.​org). The targets set out by governments and international bodies require breakthrough technologies via innovation and exploration of new production processes (Table 1.8).

Table 1.8

Breakthrough programs

The programs identify steelmaking technologies most likely to succeed in reducing CO2 emissions. Feasibility studies are carried out on various scales – from lab work to small pilot plant and eventually commercial-sized implementation or testing the improvement at an existing plant. There are no restrictions placed on the scope of the projects, and the output is intended to be aspirational and develop breakthrough technologies that can reduce the GHG emission to atmosphere by at least 50%, potentially revolutionizing the way steel is made. Each regional initiative explores the solutions that seem best suited to local constraints, energy generation sources, and raw materials.

Four possible directions are under examination:

Carbon will continue being used as a reducing agent, but the CO2