Search Results (2)

Hydrogen-based fluidized bed direct reduction (H-FBDR) is an important and promising route for fossil-free ironmaking. In this study, to achieve the optimal operation state of energy use and exergy efficiency, the influences of the metallization process and the ratios of H₂ injected on the energy and exergy flows in the H-FBDR process are studied. The results show that the thermodynamically designed two-stage reduction process (first: Fe₂O₃→FeO; second: FeO→Fe) requires a smaller H₂ quantity than other metallization processes. According to the mass, energy, and exergy balance analyses, variations in the H₂ consumption, exergy destruction, and energy/exergy losses of the overall system, iron ore preheater (F1), fluidized bed reactor system (R), heat exchanger (E), and gas preheater (F2) with different ratios of H₂ injected (η) are derived. The total H₂ consumption, total exergy destruction, and energy/exergy losses rise with increasing η, and sharp increases are observed from η = 1.3 to η = 1.8. The exergy efficiencies (φ) can be ranked as φ_R > φ_E > φ_F1 ≈ φ_F2, and the exergy destruction in components F1 and F2 is mainly caused by the combustion reaction, whereas physical exergy destruction dominates for components R and E. The performances of components F1, E, and F2 degrade from η = 1.0 to η = 1.8, and significant degradation arises when η exceeds 1.3. Thus, considering the H₂ consumption, thermodynamic efficiency, and energy/exergy losses, the ratio of H₂ injected should be set below 1.3. Notably, although the energy loss in the H-FBDR system is 2 GJ/h at η = 1.3, the exergy loss is only 360 MJ/h, in which the recycled gases from component E occupy 320 MJ/h, whereas the total exergy destruction is 900 MJ/h. Therefore, improving the performance of operation units, particularly the components F1 and F2, is as important as recovering the heat loss from component E for optimizing the H-FBDR process. Full article

The Swedish and Finnish steel industry has a world-leading position in terms of efficient blast furnace operations with low CO₂ emissions. This is a result of a successful development work carried out in the 1980s at LKAB (Luossavaara-Kiirunavaara Aktiebolag, mining company) and SSAB (steel company) followed by the closing of sinter plants and transition to 100% pellet operation at all of SSAB’s five blast furnaces. However, to further reduce CO₂ emission in iron production, a new breakthrough technology is necessary. In 2016, SSAB teamed up with LKAB and Vattenfall AB (energy company) and launched a project aimed at investigating the feasibility of a hydrogen-based sponge iron production process with fossil-free electricity as the primary energy source: HYBRIT (Hydrogen Breakthrough Ironmaking Technology). A prefeasibility study was carried out in 2017, which concluded that the proposed process route is technically feasible and economically attractive for conditions in northern Sweden/Finland. A decision was made in February 2018 to build a pilot plant, and construction started in June 2018, with completion of the plant planned in summer 2020 followed by experimental campaigns the following years. Parallel with the pilot plant activities, a four-year research program was launched from the autumn of 2016 involving several research institutes and universities in Sweden to build knowledge and competence in several subject areas. Full article