Low-carbon production of iron and steel: Technology options, economic assessment, and policy

Production of iron and steel is an energy-intensive manufacturing process. In 2006, the iron and steel industry accounted for 13.6% and 1.4% of primary energy consumption in China and the U.S., respectively (U.S. DOE/EIA, 2010a; Zhang et al., 2010). The energy efficiency of steel production has a direct impact on overall energy consumption and related carbon dioxide (CO2) emissions. The goal of this study is to develop a methodology for making an accurate comparison of the energy intensity (energy use per unit of steel produced) of steel production. The methodology is applied to the steel industry in China and the U.S. The methodology addresses issues related to boundary definitions, conversion factors, and indicators in order to develop a common framework for comparing steel industry energy use. This study uses a bottom-up, physical-based method to compare the energy intensity of China and U.S. crude steel production in 2006. This year was chosen in order to maximize the availability of comparable steel-sector data. However, data published in China and the U.S. are not always consistent in terms of analytical scope, conversion factors, and information on adoption of energy-saving technologies. This study is primarily based on published annual data from the China Iron & Steel Association and National Bureau of Statistics in China and the Energy Information Agency in the U.S. This report found that the energy intensity of steel production is lower in the United States than China primarily due to structural differences in the steel industry in these two countries. In order to understand the differences in energy intensity of steel production in both countries, this report identified key determinants of sector energy use in both countries. Five determinants analyzed in this report include: share of electric arc furnaces in total steel production, sector penetration of energy-efficiency technologies, scale of production equipment, fuel shares in the iron and steel industry, and final steel product mix in both countries. The share of lower energy intensity electric arc furnace production in each country was a key determinant of total steel sector energy efficiency. Overall steel sector structure, in terms of average plant vintage and production capacity, is also an important variable though data were not available to quantify this in a scenario. The methodology developed in this report, along with the accompanying quantitative and qualitative analyses, provides a foundation for comparative international assessment of steel sector energy intensity.

Exploring the spatiotemporal evolution of energy intensity in China by visual technology of the GIS

Given the urgent need for transitions towards global net zero emissions, decarbonisation of the iron and steel industry is critical. Deep decarbonising this sector requires a breakaway from current blast furnace-basic oxygen furnace (BF-BOF) technologies that largely depend on fossil resources. Biosyngas is considered to be a promising alternative to fossil energy and reductants used in existing ironmaking due to its renewability, technological maturity and compatibility for use in existing furnaces. The present work assesses the environmental impacts of biosyngas-based direct reduced iron production followed by electric arc furnace (DRI-EAF) routes for crude steel production. Further, the proposed routes are compared with the other steelmaking routes, including BF-BOF, natural gas (NG)-based and hydrogen-based direct reduction routes by performing life cycle assessment (LCA). The results indicate that the global warming potential (GWP) value for the biosyngas-based DRI-EAF system is 75% lower than the existing NG-based DRI-EAF route and 85% lower than the BF-BOF route. Moreover, the proposed system possibly has lower GWP values than the renewable hydrogen-based DRI-EAF route. The proposed system has an estimated cradle-to-gate GWP of 251 kg CO2 eq./t crude steel, of which 80% is from upstream emissions. Combined with CO2 storage, the GWP of the proposed system is a net negative, estimated at −845 kg CO2 eq./t crude steel for the selected system boundary. In addition to GWP, other non-climate impact indicators are also evaluated to identify potential burden shifting. The results highlight the emissions reduction potential of the novel biosyngas DRI production route. Large-scale deployment, however, requires sustainable forest management and adequate CCS infrastructure, along with a strong, long-term policy framework to incentivise the transitions.

Cost and life cycle analysis for deep CO2 emissions reduction of steelmaking: Blast furnace-basic oxygen furnace and electric arc furnace technologies

On the relationship between energy intensity and industrial structure in China

Steel is an alloy of iron and one or more element(s), namely carbon, nickel, chromium, manganese, vanadium, molybdenum, tungsten, and so on. Chemically, steels may be classified in two groups: plain carbon steels and alloy steels. The former comprises the alloys of iron and carbon, whereas the latter contains one or more elements in addition to carbon. The alloying elements improve the mechanical, magnetic and electrical properties, as well as the corrosion resistance of steels. Impurities like Si, Mn, S, P, Al, and O are invariably present in steels due to their association in pig iron obtained by reduction smelting of iron ore with coke and lime in the blast furnace. Essentially, steelmaking is the conversion of molten pig iron (hot metal) containing variable amounts of 4.0–4.5% carbon, 0.4–1.5% silicon, 0.15–1.5% manganese, 0.05–2.5% phosphorus (normally between 0.06 and 0.25%), and 0.15% sulfur (normally between 0.05 and 0.08%) to steel containing about 1% of controlled amount of impurities by preferential oxidation. Alternatively, steel can be produced from solid sponge iron obtained by solid-state reduction of iron ore in the shaft furnace or retort. Thus, basically two routes are adopted in the production of steels. The first one employs the basic oxygen furnace (BOF – LD/Q-BOP/Hybrid converters) for treatment of hot metal, and the second route uses the electric arc furnace (EAF) to treat steel scrap/sponge iron or direct reduced iron (DRI). Electric arc or induction furnaces are generally used in the production of alloy steels. Pig iron contains a total of about 10% of C, Si, Mn, P, S, and so on as impurities, whereas sponge iron contains gangue oxides of iron ore, such as Al2O3, SiO2, CaO, and MgO. The amount and number of impurities depend on the quality of the iron ore, coke, and lime stone used in smelting. The molten pig iron is refined to molten steel under oxidizing conditions using iron ore and/or oxygen. On the other hand, scrap and sponge iron are melted in electric furnaces and refined for steel production.

Comparison of iron and steel production energy use and energy intensity in China and the U.S.

ABSTRACTAs an energy-intensive industry, iron and steel production are suffering from the resource and environmental issues. Blast furnace—basic oxygen furnace (BF-BOF) process and electric arc furnace (EAF) process are the two most common routes of steel production. Therefore, it is very important to quantify the industrial metabolism for the two routes. In this work, material flow analysis is used to comparatively investigate the energy efficiency, material efficiency, and emissions intensity at the enterprise level. The results show that the total energy consumption and material consumption per ton of steel of the BF-BOF route are 2.8 and 11 times larger than those of the EAF route, respectively. In addition, the emission intensities of dust, CO2, SO2, NO2 and CO of the BF-BOF route are 7.7, 2.6, 92.6, 33.5, and 12.0 times greater than those of the EAF route, respectively. To achieve a more sustainable steel industry, some policy recommendations are put forward finally.

The heterogeneous impacts of interregional green technology spillover on energy intensity in China

The main goal of this study was to model the evolution of energy intensity in China by using the four-parameter logistic model and the artificial neural network technique to determine the future level of energy intensity in China. In this study, a back-propagation network with one hidden layer was used. The two models were compared for degree of fit to the historical data on energy intensity in China for the period of 1980 to 2009. The selected statistical measures include SSE, RMSE, MAPE, R2 and residual plots. The comparison indicates that the better modelling of the evolution of energy intensity in China is given by the developed artificial neural network model. According to the results forecast by it, energy intensity in China in the future will slowly decrease.

To achieve net-zero iron and steel production by 2050, many iron and steel producers are turning to direct reduced iron (DRI)—electric arc furnace (EAF) steel production as an opportunity to achieve significant CO2 emissions reductions relative to current levels. However, additional innovations are required to close the gap between DRI and net-zero steel. Pressurized chemical looping-DRI (PCL-DRI) is a novel technology explored to meet this target, in which the reformer firebox and fired process gas heaters are replaced with PCL combustion units. Captured CO2 is conditioned and compressed for pipeline transportation and storage/utilization. The performance of two different PCL-DRI configurations relative to traditional DRI processes was explored via process simulation: a Midrex-type process and an Energiron-type process. The PCL-DRI processes were shown to have equivalent or lesser total fuel consumption (8% reduction) compared to the base cases, and greater process water production (170–260% increase), with minimal or no loss in thermal efficiency. PCL-DRI is a strong competitor to alternative methods of reaching net-zero DRI due to lower energy penalties for carbon capture, no required changes to stream chemistry in or out of the EAF, and no requirement for hydrogen infrastructure.

The process of mini steel mills using oxidized pellets as a feedstock includes production of metallized pellets, which are used further for the production of direct reduction iron (DRI), production of steel in electric arc furnaces (EAF), and its continuous casting and rolling. Companies that are importing large amounts of iron ore pellets annually for DRI production and also during the course of the transportation, stockpiling, and charging of the pellets into metallization reactors, as well as the discharging of the metallized pellets, generate tens of thousands of tons of fine materials containing iron every year. Pellets fines and DRI sludge are usually dumped in piles and EAF dust and mill scale are sold to a third party. The results of a preliminary analysis indicate that the recycling of such materials in the form of briquettes would help to produce additional quantities of steel, and would also free up a significant area occupied by dumped wastes. Recovery of these wastes would generate additional revenues, surpassing revenue from direct sales of wastes.

Phasing out the blast furnace to meet global climate targets

The global steel industry is integral to the development of modern infrastructure, yet it stands as one of the most significant contributors to greenhouse gas (GHG) emissions worldwide. This dichotomy brings forth the imperative for an in-depth analysis of GHG inventory practices and the pursuit of sustainable production methods. This mini-review paper addresses the current methodologies for GHG accounting within the steel sector, emphasizing the critical role of accurate and transparent emissions data as the basis for effective climate change mitigation strategies. Evaluating the prevalent carbon-intensive blast furnace-basic oxygen furnace (BF-BOF) production route, this paper contrasts traditional practices with innovative reduction initiatives, particularly those aligned with the emergence of green steel. We delve into the advancements in electric arc furnace (EAF) technology, direct reduced iron (DRI) processes utilizing green hydrogen, and the potential of carbon capture, utilization, and storage (CCUS) systems. The analysis extends to a critical examination of the challenges and opportunities these technologies face, including economic viability, scalability, and the readiness of energy infrastructure to support such a transition. Further, this review highlights the significance of verification and validation in reinforcing the credibility of GHG inventories. We scrutinize the materiality of reported emissions in the context of evolving regulatory frameworks and stakeholder expectations, stressing the need for standardized and rigorous assurance practices.Graphical

Assessment of low-carbon iron and steel production with CO2 recycling and utilization technologies: A case study in China