Torrefaction pretreatment of lignocellulosic biomass for sustainable solid biofuel production
2022
Ivanovski, Maja | Goricanec, Darko | Krope, Jurij | Urbancl, Danijela
Torrefaction can upgrade the properties of biomass by reducing its oxygen content. In this study, the effects of torrefaction pretreatment on four different lignocellulosic biomass materials at three different temperatures (200 °C, 250 °C, and 300 °C) were studied using a Bosio EUP 6/1200 electric furnace. The results of proximate and ultimate analyses showed that the oxygen content is reduced with a higher torrefaction temperature, while the heating values increased, with 260 °C being the optimal temperature for the process. Among the torrefied products, oak waste wood (OWW, torrefied at 200 °C) had the highest solid yield, 93.2%, while the energy yield was 95.7%, fixed carbon (FC) content 11.8%, volatile matter (VM) content 80.9%, ash content 0.8%, and HHV 19.1 MJ/kg. The TGA/DTG experiments confirmed typical thermal properties for all lignocellulosic biomaterials, while the FTIR and XRD patterns for miscanthus and OWW indicate that the molecular chains of cellulose are broken (damaged) at temperatures higher than 300 °C. Porous ovals were observed at all temperatures in all biomass materials using SEM. SEM images showed that at higher temperatures the ovals started to crack, leading to materials with better grindability than the raw materials. Therefore, we conclude that solid biofuels with properties similar to coal can be produced with torrefaction.
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