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• 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]

• 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]