The Effect of Biomass on Fluidity Development in Coking Blends Using High-Temperature SAOS Rheometry

The addition of biomass to coking blends has the potential benefits of reducing the amount of expensive coking coals and reducing carbon emissions. However, there is little research in the use of biomass as additive in coking blends. The easily available biomass samples pine wood, sugar beet, and miscanthus have been chosen to study the effect of these additives on the fluidity properties of coal. High-temperature small-amplitude oscillatory-shear (SAOS) rheometry was used to determine the fluidity of the samples as a function of temperature. TGA and solid-state 13C NMR were also used to determine the thermal stability and compositional changes in the samples during pyrolysis. Sugar beet can be added in coking blends up to 5 wt % without altering the viscoelastic properties of the coal, whereas pine wood and miscanthus reduce the fluidity even with 2 wt % additions. No solid–solid interactions were observed in the blends, but there were differences in viscoelastic behavior that were attributed to gas–solid interactions. Fast heating (i.e., 180 °C/min) can facilitate the incorporation of pine wood and miscanthus in coking blends. The use of fast heating increases the fluidity of the coal and preserves the fluid material in the biomass at higher temperatures. As a result, the biomass acts as a regulator of fluid material development in the coal, and the viscoelastic properties of the blend are identical to those of prime coking coals. Although fast heating could also be used to produce good coking blends by combining biomass with high volatile matter, high fluidity coals, the amount of biomass required (>5 wt %) is expected to be detrimental for coke strength.