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The potential of CO2 utilization through its injection into blast furnace (BF) tuyeres is studied using the 1D steady‐state zonal model. Scenarios with the injection of CO2, hydrogen, and their co‐injection at various H2/CO2 mass ratios are analyzed. The impacts on factors affecting vertical temperature patterns and the position of the cohesive zone in the BF are identified. A life cycle assessment for several scenarios with various carbon emissions intensities of hydrogen production, carbon capture, and grid electricity generation is performed. Injection of CO2 without the addition of hydrogen increases the coke rate, reduces productivity, and increases direct CO2 emissions; however, thanks to producing top gas with higher calorific value, injection of CO2 may reduce the global warming potential (GWP) if the electric grid carbon intensity is above 654 kg‐CO2 kWh−1, while carbon capture is powered by green electricity. Although the injection of hydrogen alone would result in a more substantial reduction of GWP from the baseline than the injection of H2/CO2 mix at any mass ratio, considering the identified impacts on heat exchange and the position of the cohesive zone in the BF, co‐injection might be an enabling solution for the adoption of hydrogen injection. [ABSTRACT FROM AUTHOR]

While blast furnaces remain the dominant ironmaking technology, there is growing interest in using hydrogen to partially replace coke and pulverized coal to reduce CO2 emissions in this hard‐to‐decarbonize process. However, significant discrepancies in modeling the tuyere injection of hydrogen are noted in the literature, which can challenge the scale‐up from modeling predictions and pilot trials to actual blast furnace operations. To address this, the impact of uncertainties in the assumptions of the temperature in the thermal reserve zone and the ratio of H2 and CO utilization on the results of blast furnace process modeling are evaluated using a 1D steady‐state zonal model. The study indicates that variations in the assumed value of thermal reserve zone temperature significantly impact the estimation of optimal hydrogen injection rate, coke replacement ratio, and direct CO2 emissions reductions. In contrast, the same parameters are much less affected by the variations in the assumed value of the proportion between H2 and CO utilization ratios, which, however, affect the top gas composition. A need for further research to determine the range of the difference in temperatures of gas and solid in the thermal reserve zone tolerable for smooth blast furnace operation is highlighted. [ABSTRACT FROM AUTHOR]

Softening and melting behaviour of the iron ore materials was studied towards understanding the mechanism of formation of liquid slag and metal phases in the pre-reduced sinter and pellets. Wide range of the sinter and pellets samples was investigated revealing the effect of gangue amount and composition on temperature indices corresponding to gas permeability loss in the bed (T1) and to the largest portion of liquid products dripping (T2). For both sinter and pellets, the growth of bacisity is followed by T1 increase which is explained by raised temperature of primary liquid phase appearance during the heating-reduction treatment. Relationship of T2 with the bacisity corresponds to the basicity effect on slag liquidus temperature. Both slag and metal phases were only partially evacuated from the crucible with essential portions of both phases captured in the coke bed. Growing divergence of the basicities of effluent slag and of slag captured in crucible was observed with the increase of sinter basicity. Increased share of the effluent metal with the sinter bacisity growth is explained by the decreased adhesion of slag to iron surface which assists carburization. Growth of melt-down temperature with the increase of gangue amount is explained by less active carburization owing to larger quantity of slag minimising direct contact of sponge with carbonaceous materials.

The accumulation of impurities in the recycling of steel impacts the quality of secondary steel. Understanding impurity levels is crucial in the context of the proliferation of circular economy policies, expected high recycling rates, and growth of scrap consumption. By assuming the accumulation of impurities to be equal worldwide, the understanding of the extent and variation of the mixing and accumulation was limited in previous studies, and the factors influencing those variations were not considered. This is a first cross‐national comparison of impurity accumulation in recycled steel. In this study, the copper, tin, nickel, chromium, and molybdenum content was analyzed in over 500 samples of electric arc furnace rebars from China, Japan, Vietnam, Ukraine, and the Netherlands (representing northwestern Europe) with an optical emission spectrometer. The impurity content in rebars represents the content of impurities accumulated in steel scrap in the countries studied. The measured content of impurities was then used to determine the factors influencing the accumulation of those impurities. It was revealed that the recycling technology, the presence of a market for recovered metals, the quality of the material input, steelmaking practices, and the management of byproducts derived from a legislative or economic context played a role in the impurities content. By communicating on scrap chemical content, the collaboration between the recycling and steel industries could be enhanced in terms of matching the demand and supply and facilitating an increase in the scrap share in steelmaking. [ABSTRACT FROM AUTHOR]

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Selective extraction of valuable elements (such as V, Cr, Mn, etc.) and their compounds from metallurgical slag is in a focus of many researchers. Although vanadium may be present in slag as oxides and/or complex spinels with Fe, Mn, etc. during an alloyed steel production, the majority of vanadium in metallurgical slags typically exists as V2O5, which comprises up to 3-5 wt% of the slag in some cases. Due to the vanadium toxicity, these slags are forbidden in many civil engineering applications. As a result, hundreds of thousand tonnes of V2O5-bearing slags are landfilled every year. In the present work, the formation of vanadium ferrites (FeV2O4 and Fe2VO4) in synthesized CaO-SiO2-FeO-V2O5 slags containing 5 wt% V2O5 was examined under different partial pressures of oxygen. For the current slag chemistry range, an XRD analysis confirmed the presence of vanadium ferrite in slag samples treated at 1773 K in an argon atmosphere ( PO2 = 10−1-10−2 Pa) while no solid was noted in samples treated in air. Results were discussed based on thermodynamic consistency. [ABSTRACT FROM AUTHOR]

Integrated tailings utilization of metallic ore is an overall situation associated with additional resourse storage, cleaning exploitation of mine, and environmental concerns. The purpose of the present work is to study and develop several corresponding recycling routes for tailings in accordance with chemical component and paragenesis state of minerals. Four typical gangues are collected from Chinese western dominant mine, discharged after mill run from rare earth metal ore, iron ore containing titanium and vanadium, nonferrous paragenetic ore (Pb, Zn, Sn, Sb, and other nonmetallic elements), and multimetal bonanza ore, respectively. To meet the demands for national recycling economics, it is necessary to design for recycled materials involving recovery of metal and preparation of advanced ecological ceramics through several novel approaches. Experimental results indicate that Ce, Y, and Nb rare metals have been leached from those tailings, and high performance Ca-Sialon can be synthesized from the as-discarded residues. A newly metal bonded ceramic eco-material, identified as Fe3Si-TiCN-MgAl2O4 by XRD are discovered, whose fracture tougness is 12 MPa·m1/2, which is successfully prepared by Carbonothermal Reduction Nitride route using iron-titanium tailing ore based on thermodynamics calculation. Zinc oxide and lead oxide powders can be extracted from nonferrous mineral tailings by hydrometallurgy process, regarded as fresh precursory powders for Pb(Zn1/3Nb2/3)O3 functional ceramics, whereas magnetic Fe3O4 nanopowders are refined, originated from multimetal tailing ore by leaching-separating-precipitation. In addition, a practicing software, Search and Analysis System on Recycling of Solid Waste, has been developed to promulgate common knowledge to worldwide readers (Web site: http://recycling.net.cn). [ABSTRACT FROM AUTHOR]