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Reducing CO 2 emissions of the iron and steel industry, a typical heavy CO 2 -emitting sector, is the only way that must be passed to achieve the 'dual-carbon' goal, especially in China. In previous studies, however, it is still unknown what is the difference between blast furnace-basic oxygen furnace (BF-BOF), scrap-electric furnace (scrap-EF) and hydrogen metallurgy process. The quantitative research on the key factors affecting CO 2 emissions is insufficient. There is also a lack of research on the prediction of CO 2 emissions by adjusting industrial structure. Based on material flow analysis, this study establishes carbon flow diagrams of three processes, and then analyze the key factors affecting CO 2 emissions. CO 2 emissions of the iron and steel industry in the future is predicted by adjusting industrial structure. The results show that: (1) The CO 2 emissions of BF-BOF, scrap-EF and hydrogen metallurgy process in a site are 1417.26, 542.93 and 1166.52 kg, respectively. (2) By increasing pellet ratio in blast furnace, scrap ratio in electric furnace, etc., can effectively reduce CO 2 emissions. (3) Reducing the crude steel output is the most effective CO 2 reduction measure. There is still 5.15 × 108-6.17 × 108 tons of CO 2 that needs to be reduced by additional measures. [ABSTRACT FROM AUTHOR]

Revealing the life-cycle CO 2 emissions of steel products is of great significance for mitigating CO 2 emissions. However, previous studies did not conduct comparative analysis for steel products produced by different technological pathways, resulting in considerable confusion in the setting of carbon reduction pathways. By using the material flow analysis method, this study revealed the life-cycle CO 2 emissions associated with various technological pathways. The results shows that life-cycle CO 2 emissions per metric ton of steel are: 3620.78 kg for shaft furnace (SF)-electric furnace (EF) routes, 2598.54 kg for blast furnace (BF)- basic oxygen furnace (BOF), 1868.16 kg for Scrap & Molten Iron-EF and 1330.22 kg for scrap-EF. The energy structure (e.g. coal blending mode, power generation mode) material structure (e.g. iron ore matching mode, matching mode of scrap and molten iron), and transportation mode have a significant impact on CO 2 emissions. Undoubtedly, low-carbon or zero-carbon electricity is more effective in reducing CO 2 emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

Energy efficiency is an extremely important indicator for exploring energy conservation and consumption reduction. The traditional energy efficiency assessment methods for process industry lack an in-depth thinking on energy utilization of the whole system. Based on the proposed required energy, this paper established an energy efficiency assessment method for process industry. By establishing material and energy flow networks, energy efficiency of typical iron and steel manufacturing process (ISMP) is analyzed and its influencing factors are discussed. The results found that the required energy of coking, sintering, pelletizing, blast furnace iron-making, basic oxygen furnace steel-making and steel rolling are 2626.2 MJ/t-coke, 1122.9 MJ/t-sinter, 992.3 MJ/t-pellet, 9781.5 MJ/t-hot metal, 393.95 MJ/t-molten steel and 445.3 MJ/t-steel products, respectively. The energy efficiency of typical ISMP is 66.9%. The energy efficiency of the ISMP can be effectively improved by adjusting the steel ratio, recovering waste heat and residual energy, and developing interface technologies. • Energy efficiency assessment method of process industry is proposed and established. • The material and energy flow networks of iron and steel manufacturing process are established. • The required energy of iron and steel manufacturing process is analyzed and given. • Energy efficiency of typical iron and steel manufacturing process is evaluated and given. • The influencing factor of energy efficiency is discussed. [ABSTRACT FROM AUTHOR]

The development of hydrogen metallurgy holds enormous significance in facilitating the low-carbon and environmentally sustainable transition of iron and steel industries. However, there is a lack of research on the impact of implementing hydrogen metallurgy on the downstream process and even the whole process. To fill this research gap, a model that considers specific internal reactions of steelmaking process was developed utilizing the bottom-up approach. Subsequently, by integrating the hydrogen metallurgy process with the traditional long process and short process, the energy intensity, exergy intensity and carbon emission intensity were quantitatively analyzed from multiple viewpoints. The results of the basic oxygen furnace (BOF) and electric arc furnace (EAF) exhibit a degree of similarity, with an increase in directly reduced iron (DRI) addition, resulting in an insufficient heat and an increase in process energy consumption, exergy loss, and carbon emissions. But there are also some subtle differences, such as oxygen consumption. Following the integration of hydrogen metallurgy, the energy intensity and exergy intensity of the BF-BOF process increase 11.984 kgce/t-CS and 3.083 × 102 MJ/t-CS, respectively. However, the carbon emission intensity decreased by 46.514 kg/t-CS. The integrated Chinese-style short process has the lowest carbon emission intensity of 879.664 kg/t-CS at 40% DRI and 60% scrap. Nevertheless, the energy intensity and exergy intensity have increased by 27.383 kgce/t-CS and 42.012 × 102 MJ/t-CS respectively compared to their initial values. It is noteworthy that the process of hydrogen production plays a significant role in mitigating the exergy intensity and carbon emission intensity. [Display omitted] • The white box model based on material-energy-exergy flow of furnace are created. • The material–energy–emission nexus model of integration processes is proposed. • Energy intensity, exergy intensity and carbon emission intensity are introduced as indicators. • Impacts of direct reduced iron addition on variation in indicators are discussed. • Hydrogen production process has an important impact on the indicators. [ABSTRACT FROM AUTHOR]