An Integrated Design Methodology for CO2 Emission Reduction Based on Industrial Metabolism: Hybrid Carbon Hydrogen Metallurgy Manufacturing Process (HCHMP)

The iron and steel industry (ISI) is one of the basic industries of all industrialized countries in the world and plays an important role in the national economy. Per capita steel production is even considered an important indicator of a country's economic strength. However, the rapid development of ISI has resulted in serious environmental pollution and climate change due to massive consumption of fossil fuels and non-renewable energy (Zhang et al., 2021). The blast furnace-base oxygen furnace (BF-BOF) route needs to consume about 1.37 t of iron ore, 0.78 t of coal, 0.27 t of limestone and 0.125 t of steel scrap to produce 1.0 t of crude steel and 2, Emitting 1 t of carbon dioxide. The average consumption can reach 0.586 t of steel scrap/crude steel, 0.15 t of coal/crude steel, 88 kg of limestone/crude steel and 2.3 GJ of electricity/crude steel in the electric arc furnace (EAF) route (WSA, 2021). Furthermore, with the increase in crude steel yield, carbon emissions have become one of the major challenges. Sustainable development has become a significant strategy for a country's development. China has formulated a long-term plan to peak carbon emissions in 2030 and achieve carbon neutrality by 2060 to achieve green, low-carbon and sustainable development (Ren et al., 2021). The research and development of hydrogen metallurgy technologies and resource optimization technologies is of great importance to the sustainable development and low-carbon transition of steel companies.

The “Carbon Neutral Vision and Low Carbon Technology Roadmap for the Iron and Steel Industry” points out that reducing demand, improving energy efficiency, innovating processes and optimizing resources are the paths to low-carbon development in China's iron – and steel companies are. The most important thing is that the innovation process technology is realized in the first place. Currently, hydrogen metallurgy technology is preferred by steel companies around the world for its ability to achieve zero emissions (Patnaik et al., 2023; Rukini et al., 2022; Sun et al., 2023; Wang et al., 2022). Hydrogen metallurgy projects abroad include, for example, the following: the ULCOS project proposed by the EU and the H2FUTURE project proposed by voestalpine as well as the HYBRIT project jointly initiated by SSAB, LKAB and Vattenfall as well as the SALCOS project in Germany and POSCO. COURSE50 project, etc. In China, several documents have been proposed to support and research pilot demonstrations of hydrogen metallurgy. Baowu Group, Jiuquan Iron and Steel Group, HBIS Group, Jianlong Group and others have invested heavily in the research of hydrogen metallurgy and direct reduced iron (DRI) technology. Now the theory of hydrogen metallurgy is preferred by researchers and preliminary theoretical studies have been carried out. Guo developed an ideal model for the redox of hydrogen metallurgy based on stoichiometry and free energy minimization, and conducted an analysis of reduction efficiency and theoretical energy consumption (Guo, 2024). The results show that adding hydrogen to BF increases carbon consumption. Shatokha used a one-dimensional model to simulate the effects of hydrogen injection on BF operation and CO₂ Emissions (Shatokha, 2022). The decarbonization potential of hydrogen injection was estimated in the range of 9.4 t CO₂/t by H₂ up to 9.7 t CO₂/t by H₂. Feng et al. investigated the behavioral analysis and mechanistic evolution of titanium binding to hydrogen metallurgical (SF) furnace pellets (Feng et al., 2023; Feng et al., 2024). The results showed that the adhesion index decreased linearly with increasing TiO₂ Addition. Zhang et al. investigated the influence of hydrogen metallurgy (PP) process parameter on energy utilization and the environment based on heat and mass balance. The results showed that increasing H₂ Volume fraction and process temperature can effectively reduce carbon emissions (Zhang, Y. et al., 2022). Due to the lack of comprehensive and in-depth analysis of energy exergy based on the second law of thermodynamics, Qiu et al. developed a numerical computational model of hydrogen metallurgy for material-energy exergy to better evaluate the effect of each PP (Qiu et al., 2023a; Qiu et al., 2024; Qiu et al., 2023b). The research results can be used to select practical operating parameters in hydrogen metallurgy. To carefully assess the impact of hydrogen metallurgy on carbon emissions from a broad perspective and at each production stage, Wan et al. used the Long Range Energy Alternatives Planning (LEAP) model to study the impact of hydrogen metallurgy on carbon reduction in steel production (Chang et al., 2023; Wan and Li, 2024). The results tend to focus on the environmental impact of different hydrogen production routes. The rapid development of hydrogen metallurgy shows the enormous potential for energy saving and emissions reduction in iron and steel manufacturing systems. Metallurgical mechanisms, material consumption, gas consumption and energy intensity of hydrogen metallurgy are hot topics and challenges, and theoretical research can provide appropriate PP for actual operation. However, these hydrogen metallurgy projects are still in the research and experimental stage and have not yet been widely applied.

Resource optimization and efficient management are important ways for steel companies to achieve environmentally friendly and low-carbon production (Gong et al., 2024b; Xiao et al., 2021). The material flow analysis (MFA) method is widely used to create models of material consumption, energy consumption and carbon emissions, and to develop low-carbon production strategies through analysis and summary of the laws. Na et al. developed an optimization model for energy efficiency, energy consumption and CO₂ Iron and Steel Manufacturing Process Emissions (ISMP) to assess and improve energy efficiency. The results showed that BF coal injection ratio, BF charge structure, steel interface and casting and rolling interface have a greater influence on energy efficiency (Na et al., 2021), energy consumption and CO2 emissions₂ Emission of ISMP (Na et al., 2022). Zhang et al. proposed an integrated and complete ISMP model for evaluating energy utilization and CO₂ -Emissions that can reduce the site's optimal total energy consumption (SEC) and the site's total direct CO emissions₂ emissions (DCE) by 14.07% and 6.65%, respectively (Zhang et al., 2019). Zhang et al. developed an integrated material-energy-carbon hub for carbon flow tracking and carbon accounting. In addition, the connection between carbon flows, material flows and energy flows and the effects of material flows and energy flows on CO are examined₂ Emissions are being investigated (Zhang, H. et al., 2022). Zhang et al. determines energy consumption and CO₂ Emissions modeling through a comprehensive assessment method based on dynamic material flow to investigate the energy saving and emission reduction potential of China's ISI (Zhang et al., 2018b). Xin et al. developed an integrated model based on steel demand and scrap recycling, energy consumption, carbon emissions and air pollutant emissions to explore the roadmap for maximum carbon emissions at the provincial level (Xin et al., 2023). To study the effects of carbon emissions in BF, BF-BOF, e-waste furnaces and hydrogen metallurgy, Na et al. has developed an industrial structure prediction model to predict future CO emissions₂ Volume of the ISI and analyzed the key factors of CO₂ Emissions (Na et al., 2023). Industrial metabolism, the branch of MFA, can be used to describe the connection between the mechanisms of material and energy metabolism and carbon emissions. Zhao et al. used the industrial metabolism method to establish the metabolic system between material-energy metabolism and equipment, which can effectively improve the accuracy of carbon accounting (Zhao et al., 2019). Chen et al. used the industrial metabolism approach to model the material energy input and output of a BF for carbon emissions prediction (Chen et al., 2022). In addition, a material-energy-carbon emission model of the pure carbon metallurgy manufacturing process (PCMP) is presented, and the low-carbon development trend of various crude steel production is realized (Chen et al., 2023), which provides valuable assistance for the production study in this article.

Numerous studies have established different optimization models for different steel mills and provide valuable information on carbon reduction. However, the research object is PCMP. Typically, most BFs only have a lifespan of around 30 to 40 years, and the transition from PCMP to hydrogen metallurgy will incur higher costs. In particular, it is impossible to completely replace PCMP with hydrogen metallurgy in the short term. With the rapid development of hydrogen metallurgy, hybrid carbon-hydrogen metallurgy manufacturing process (HCHMP) will be a future stage of hydrogen metallurgy applications in ISI. However, optimizing materials, energy and carbon emissions for HCHMP is a research gap.

The remaining sections of this paper are organized as follows. In Section 2, the metabolic mechanism of HCHMP is described, a three-layer design optimization framework is proposed, and mathematical material-energy models are presented. Section 3 presents a case study of HCHMP. Section 4 shows the results and discusses the carbon emission law of HCHMP. Finally, Section 5 summarizes the results and contributions of the study.