Torrefaction Time and Environment Dependence of Miscanthus Elephant Grass Properties

摘要

Miscanthus x giganteus (commonly known as Miscanthus or elephant grass) is a potential bioenergy crop to displace fossil fuels and provide a more rapidly renewable alternative to wood biomass. Pretreatment of this energy crop via torrefaction or mild pyrolysis can further optimize storage, handling and, ultimately, improve combustion performance of the resource for energy generation. Typically, torrefaction in laboratory studies is executed using nitrogen (N_2) as a carrier gas. Fewer studies have explored torrefaction using carbon dioxide (CO_2), a potentially more representative environment gas since industrial torrefaction processes might combust product gases for process heat to improve overall system efficiency. Additionally, few studies have examined the torrefaction time dependence on biomass handling and conversion characteristics. Torrefaction in pure N_2 and CO_2 at three temperatures (250, 275 and 300°C) was explored in this study for a range of residence times (0.25 to >1 hour) using a custom batch reactor. The effect of residence time on mass loss was further explored using thermogravimetric analysis. The effects of the torrefaction environment and the time dependence on mass loss, grindability, and combustion behavior were assessed.