Impact of Torrefaction Process in Elevating the Fuel Properties of Selected Herbaceous Biomass Solid Waste

Abstract

Thermal pretreatment of biomass is a process that promotes an increase in its energy quality, making it a more efficient energy generation for combustion and co-firing applications. This research presents reports on the torrefaction of selected herbaceous biomass solid waste, coconut shells (CS). The torrefaction was carried out using a 79.8-liter capacity fixed bed reactor designed to carbonize 5kg of biomass per batch. Solid fuel was produced at varying torrefied temperatures (TT) of 275°C and 285°C and residence time (RT) effect at 30 minutes and 1 hour respectively. The torrefied biomass was collected and assays for their energy content characterization. The result from this study showed an increase in total carbon content, whereas the hydrogen, oxygen, and moisture content decreased, this behavior is found to be more pronounced with the increase in torrefaction temperature (TT). Compared to raw biomass, the carbon content of torrefied biomass increases 26-33 wt.% with an increase in (TT) and (RT). Analysis of the energy yield of the torrefied CS biomass sample was found to be higher than that of its mass yield as expected, Similarly, the obtained bulk density content of the torrefied biomass sample (CS) is observed to increase with increment in (TT). Findings from this study showed that torrefied products exhibited up to a 32% higher heating value compared to raw biomass and the highest calorific value of about 16 MJ/kg was also achieved. Overall, this research yields solid fuel that could contribute to reducing the emission of contaminants into the atmosphere compared with the use of fossil fuels.