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• Biomass utilisation in iron and steelmaking processes does offer a solution to decrease the environmental impact of steelmaking. • Potentials for biomass application in different parts of (BF-BOF) integrated steelmaking process reviewed. • Biomass upgrading technologies to produce suitable biochar for iron and steelmaking are evaluated. • Insights and recommendations for effective use of biochar as a reducing agent are suggested. This study provides a fundamental literature review of biomass characterisation and application for utilisation as a reducing agent and fuel in an integrated steelmaking process. This review contains and evaluates the existing literature concerning the properties of different biomass sources and available pre-treatment technologies for upgrading biomasses to have similar characteristics to fossil coal. The suitability of biofuels in different operating units including Brazilian mini blast furnaces, cokemaking, larger blast furnace injection, sintering and production of carbon composite agglomerates are analysed. There is a considerable opportunity to reduce CO 2 emissions in the integrated steelmaking process by using biomass-based reducing agents. The literature reports that charcoal optimisation in the integrated steel plant can achieve reduction in net CO 2 emissions of 31–57%, depending on the substitution rate. Although, some level of pre-treatment is also necessary for efficient use of biomass, the pre-treatment requirement will depend on the unit operation where the biomass material is added. Solid biofuels are considered the most suitable form of biomass-based reducing agents due to similarities in the physical properties with the injected coals; this will make coal replacement more straightforward and lower the costs required for plant modifications. [ABSTRACT FROM AUTHOR]

• Effect of rapid devolatilization on carbonaceous materials investigated for the HIsarna alternative ironmaking process. • Chars produced under high temperature and rapid heating via drop tube furnace (DTF) • Explained the reactivity behaviour of chars from different carbon sources produced under rapid heating. • Revealed the effect of temperature on the physical structure for coal and biomass materials. • To measure the real-time structural changes via high temperature confocal scanning laser microscope (HT- CSLM) To evaluate the potential of using renewable biomass in the novel HIsarna technology, reactivity of thermal coal (TC), charcoal (CC), Bana grass char (BGC) before and after rapid devolatilization at 1500 °C in a drop tube furnace (DTF) was investigated. Thermogravimetric (TG) was used for CO 2 gasification study, and high temperature confocal scanning laser microscope (HT-CSLM), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) were used to characterise the morphology of all three raw carbonaceous materials and their chars produced by rapid devolatilization. CC has fastest gasification reaction before and after rapid heat treatment, and BGC raw is more reactive than TC raw but BGC 1500 °C and TC 1500 °C have very similar gasification behaviour. The reactivity index of the rapidly devolatilized char is reduced to 84.21% (BGC), 92.11% (TC) and 94.23% (CC) compared to their raw materials. This shows that BGC is more severely affected by the rapid devolatilization, and this behaviour is likely to be governed by the high ash content which will melt and cause pore blockage during heat treatment. According to HT-CSLM results the average particle sizes decreased by 28%, 24% and 20 % for TC, CC and BGC respectively. While the SEM images shown that TC has gone through significant structural changes during the rapid devolatilization, but CC and BGC maintained their parent structural shapes. The BET results indicate that TC is non-porous, but both CC and BGC contain a large number of constricted micropores with significantly larger surface area. [ABSTRACT FROM AUTHOR]

• Rapid devolatilization of carbonaceous materials investigated for HIsarna technology. • Rapid heating via drop tube furnace with quadrupole mass spectrometer (DTF-QMS). • Explained the effect of temperature on variation of light gases in the rapid devolatilization. • Revealed the effect of temperature on the rate of carbon conversion for coal and charcoal. • R-factor obtained to give solid residual efficiency for different carbon sources. A drop-tube furnace coupled with quadrupole mass spectrometer (DTF-QMS) was employed to simulate rapid heating conditions that carbonaceous materials experience during HIsarna injection with the measurement of gas composition change as a result. A devolatilization study for thermal coal (TC) and charcoal (CC) samples was carried out at three temperatures of 1000, 1250 and 1500 °C under an initial high purity Ar gas environment. The volatiles released were measured online by QMS, while the char yield was determined directly by the weight of particles collected and the deficit was calculated by subtracting the gas yielded from the total weight loss. The study reveals that working temperature has a strong impact on the devolatilization rate, the maximum weight loss and the variation in gas species produced. Due to intensification in the carbon oxidation and secondary reactions at higher temperatures, there was an increase in the weight loss, which led to a greater yield of H 2 and CO but less yield of hydrocarbons, CO 2 and H 2 O. Despite lower volatile matter content in charcoal, the weight loss for charcoal (29%) was higher than that for thermal coal (23%) at 1500 °C. Although the amount of H 2 produced for both materials is similar, the amount of CO produced by charcoal is twice of that by thermal coal, and accounts for 79% of the total gas weight formed by charcoal. This suggests that a higher rate of carbon oxidation takes place through O 2 containing groups within the charcoal, which results in lower char efficiency. It was found that thermal coal produces a significant amount of tar, while a large number of particles in the form of soot/dust escaped from the bulk material during charcoal injection but no tar formation was observed. [ABSTRACT FROM AUTHOR]

• Devolatilisation behaviours of different carbon sources investigated for HIsarna alternative ironmaking process. • Maximum peaks of evolved gases from VTF-QMS corresponded well to DTG curves. • The kinetic parameters for coal and biomass samples were determined. • Biomass pre-treatment temperature suggested to produce chars with similar properties to coal injected in HIsarna. HIsarna process offers a novel low CO 2 emission alternative to the blast furnace for primary iron production. This new smelting ironmaking technology is flexible in raw material usage such as the substitution of biomass for coal as a reductant. Reduction is conducted through multiple mechanisms within the smelting vessel including gaseous reaction products from thermal decomposition of volatile matters reacting directly with iron oxide containing slags and injected iron ore. In this study, four coals with notable differences in volatile matter content along with two biomass samples sourced from wood and grass origins were investigated for the selection of suitable fuel mix. Thermogravimetric analysis (TGA) was used to measure the weight loss of the carbonaceous materials and a vertical tube furnace coupled with a quadrupole mass spectrometer (VTF-QMS) was employed for off-gas analysis during the devolatilisation. During TGA tests the samples were heated under a 99.9999% argon atmosphere to 1500 °C at three different heating rates to investigate the kinetics of thermal decomposition for these materials. Through use of the Kissinger– Akahira–Sonuse model an average activation energy was determined as a function of the conversion degree. The furnace experiments were carried out under a 99.999% Ar atmosphere to a peak temperature of 1500 °C, at a heating rate of 10 °C/min. The wt% of reducing gases e.g. H 2 , CO, and hydrocarbons, and the temperature required for these gases to evolve was notably different for each materials, but the respective maximum peaks of evolution of these gases corresponded well to the maximum rate of mass loss. Furthermore, the off-gas analysis reveals torrefied grass contains large amount of water and carbon dioxide which will be released at very low temperature, therefore pre-treatment to the temperature of ~400 °C is necessary to produce chars with similar properties to coal injected in HIsarna. [ABSTRACT FROM AUTHOR]