To investigate the use of biomass in the novel HIsarna technology, the reduction of FeO in the slag by chars produced from thermal coal (TC), charcoal (CC), and Bana grass char (BGC) was studied. A drop tube furnace coupled with a quadrupole mass spectrometer (DTF-QMS) was employed to study the injection of chars into pre-melted slag in the temperature range between 1450 °C and 1525 °C. The reduction rate was calculated from evolved gases and the extent of FeO reduction was confirmed by wavelength-dispersive X-ray fluorescence (WDXRF). The FeO reduction proceeds through two stages, starting with a rapid reduction, which is dependent on the carbon type, and followed by gradual leveling off. The reduction rate with the charcoal char (CC) was the highest, over 60 pct reduction was achieved in the first 500 seconds at 1500 °C, while ~ 50 and 40 pct achieved with TC and BGC chars, respectively, for the same reaction time. The kinetic analysis suggests that the first and second stages of the reaction can be described by the second-order (F2) and three-dimensional diffusion (D3) models, respectively. The apparent activation energy values for the first stage were 290, 229 and 267 kJ/mol for reactions with TC, CC and BGC chars, while 265, 369, and 282 kJ/mol were obtained for the second stage. Based on the experimental data and kinetic results, it can be concluded that the first stage is controlled by chemical reactions on the carbon surface, and the second stage is influenced by a mixed-controlling mechanism.

Al₂O₃, Al₂O₃·TiN, Al₂O₃·MgO, and CaO·2Al₂O₃ are four different types of inclusions in high Al steels. To improve the steel cleanness level, the effective removal of such inclusions during secondary refining is very important, so these inclusions should be removed effectively via inclusion dissolution in the slag. The dissolution behavior of Al₂O₃, Al₂O₃·TiN, Al₂O₃·MgO, and CaO·2Al₂O₃ in CaO-SiO₂-Al₂O₃-MgO slags, as well as the steel-slag reaction, was investigated using laser scanning confocal microscopy (LSCM) and high-temperature furnace experiments, and thermodynamic calculations for the inclusion in steel were carried out by FactSage 7.1. The results showed that Al₂O₃·TiN was observed to be completely different from the other oxides. The composite oxides dissolved quickly in the slags, and the dissolution time of the inclusions increased as their melting point increased. SiO₂ and B₂O₃ in the slag were almost completely reacted with [Al] in steel, so the slags without SiO₂ showed a positive effect for avoiding the formation of Al₂O₃ system inclusions and promoting inclusions dissolution as compared with SiO₂-rich slags. The steel-slag reaction was also found to influence the inclusion types in steel significantly. Because of the rapid absorption of different inclusions in the slag, it was found that the dissolution time of inclusions mainly depends on the diffusion in the molten slag.

Biochar has potential applications in steelmaking processes, but faces technical challenges such as low material density, high alkali content, and high reactivity compared to coal. This study explores converting the solid residue, following hydrothermal pretreatment-steam explosion (HTP-SE) of Miscanthus and other biomass feedstocks, into biochar to facilitate the replacement of coal in blast furnace and electric arc furnace operations. It is the first to demonstrate the enhanced combustion characteristics of pretreated fibre and the compatibility of the biochar for use in steelmaking. Biomass from birch, miscanthus, wheat straw, both untreated and pretreated, was evaluated. HTP-SE was conducted at 192 °C and 1.3 MPa, conditions aligned with hemicellulose extraction for application in biobased products. Biochars were produced at temperatures ranging from 300 °C to 550 °C. HTP-SE increased the carbon, hydrogen, and energy content by approximately 10%, 8%, and up to 5 MJ/kg, respectively, while reducing ash quantity by up to 45%. In addition, it reduced the alkali and phosphorus content from the solid fraction into aqueous phase. Gas analysis indicated that HTP-SE enhanced the energy content of pyrolysis syngas. Thermogravimetric studies revealed that pretreated biochars exhibited significantly lower reactivity with carbon dioxide compared to untreated counterparts, approaching the reactivity of coal. This was attributed to increased aromaticity, C=C bonding, cross-linkages enriching lignin and by the removal of hemicellulose through HTP-SE. Overall, the upgraded biochar addresses key limitations of conventional biochar and shows strong potential as a substitute to replace injection coal entirely in both blast and electric arc furnaces.