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This study investigates the potential of utilizing industrial by-products—mill scale (MS) and aluminum dross (AD)—as sources of Fe2O3 and Al2O3, respectively, for hercynite (FeAl2O4) production. Through combustion of MS-AD-graphite systems at 1550 °C under air atmosphere, hercynite-based refractory materials were synthesized. Results confirm the viability of this upcycling approach for hercynite synthesis. During the formation of hercynite, the development of a dendritic structure can be observed, which subsequently fuses into a grain shape. XRD phase analysis using the Rietveld method revealed that the major components of the product with a C/O ratio of 1 were 85.11% FeAl2O4, 10.99% Al2O3, and 3.9% C. For the product with a C/O ratio of 2, the composition was 82.4% FeAl2O4, 13.0% Al2O3, and 4.6% C. The combustion of raw pellets with a C/O ratio of 1 at 1550 °C for 1 h in a normal air atmosphere is economically viable for producing hercynite, yielding 85.11 wt%. This approach presents a sustainable and eco-friendly alternative to using commercial raw materials, potentially eliminating the need for virgin alumina and iron ore. By repurposing waste materials from the steel and aluminum industries, this study contributes to the circular economy and aligns with the goal of zero waste. [ABSTRACT FROM AUTHOR]

Driven by the rising demand for glass, metals, and plastics in industrial and household sectors, there was a substantial increase in waste and by-products generated. This study presents a method for repurposing waste glass, mill scale, and plastics as raw materials for ferrosilicon alloy production. This process entails reducing SiO2 and Fe2O3 using carbon derived from polystyrene/polypropylene mixtures. The glass, scale, and carbon powders were blended to achieve a C/O molar ratio of 1 (Blends A to F). The thoroughly mixed samples were then shaped into pellets and subsequently heated at 1550 °C in a tube furnace for 60 min. Ferrosilicon was successfully synthesized, with the reaction generating numerous metal droplets along with a slag layer in the crucible. The metallic yield for Blends A to F ranged from 16.65 wt% to 21.39 wt%, with the highest yield observed in Blend D. The bulk metal primarily consists of the FeSi phase, with Blend D exhibiting the highest Si concentration of 13.51 wt% and the highest hardness of 649.55 HV. Mechanism steps for ferrosilicon formation may vary with carbon dissolution rates. This work supports fossil fuel reduction and carbon neutrality, benefiting zero wastes practice and promoting sustainable material processing. [ABSTRACT FROM AUTHOR]

Carbon dissolution from blends of metallurgical coke with high-density polyethylene (HDPE) into liquid steel at 1823 K is investigated in-depth. HDPE is blended with metallurgical coke into three different ratios (blends H1, H2, and H3) and used as a carburizer. Compared to coke, a significant improvement in carbon dissolution is observed in the case of blend H3 with the carbon picked up by liquid steel after 60 min of reaction and the dissolution rate ( K) is 4.5 wt% and 15.2 × 10−3 s−1, respectively. For coke alone, the melt carbon content is 0.8 wt% and the dissolution rate of 0.3 × 10−3 s−1. SEM micrographs and corresponding off-gas analysis reveal that the gasification of HDPE/coke blends slow down the coverage of ash oxides at the Fe-C interface and modify morphology of the ash layer. The associated reactions of volatiles generated during the thermal degradation of the polymer can aid the carburization of liquid steel to some extent. However, the amount of gas generated must be high enough to overcome the effect of ash oxides at the Fe-C interface. This study has strong implications in enhancing the potential of recycling waste polymers for sustainable steelmaking. [ABSTRACT FROM AUTHOR]

With an aim to recycle waste polymers as a carbon resource in steelmaking, in-depth investigations have been carried out on polymer/coke blends and molten steel at 1823 K. Three polymers, namely high density polyethylene (HDPE), polyethylene terephthalate (PET), and bakelite were blended with metallurgical coke and devolatilized at 1473 K using a drop tube furnace. High temperature interactions of various chars with molten steel were investigated at 1823 K using the sessile drop technique in argon atmosphere; the influence of polymers on the interfacial phenomena and carbon dissolution was determined. While the residual volatiles from HDPE did not affect the chemical composition of interfacial products, the coverage of the interfacial region was somewhat slower than metallurgical coke. Oxygen present in PET was found to oxidize liquid steel leading to the formation of FeO at the interface modifying both the chemical composition and the morphology of the interfacial region. CaCO3, present as a filler impurity in bakelite was found to act as a fluxing agent and lowered the melting point of the ash layer at the metal/carbon interface. The addition of polymers improved the overall carbon dissolution into molten steel by a small extent as compared to metallurgical coke. This study has shown that a variety of waste polymers can be utilized to partially replace metallurgical coke in steelmaking. [ABSTRACT FROM AUTHOR]