Torrefaction Of Spelt Husks To Increase Its Fuel Properties

Authors: Abubakar Halidu, Anh Phan,, Paul Bilsborrow

Abstract: Torrefaction is referred to as mild pyrolysis of biomass at temperatures between 200 and 300°C in an oxygen-free environment in order to increase its heating value, enhanced grindability, and storability, which can be used as a pre-treatment for other thermochemical processes. The findings from torrefaction revealed that temperature had a clear impact on torrefaction product yields. In this study, the torrefaction of spelt husks was performed at 200, 250, and 300°C under an inert nitrogen environment at a 20°C.min-1 heating rate with a residence time of 15–60 min, respectively. The effect of torrefaction temperatures and residence time was analysed. The results showed that the studied torrefaction temperatures led to an increase in the higher heating values (HHV) and an enhancement in grindability. With higher torrefaction temperatures, char yield decreased while gas and liquid yields increased. Torrefaction temperatures that are higher reduce volatiles, oxygen content and energy yield while increasing carbon content and HHV. The highest energy yield of approximately 97 % was obtained at a torrefaction temperature of 250°C and a residence time of 15 minutes. The torrefied spelt husks at 300°C with a residence time of 15 min had the highest increase in HHV of 30.88 MJ kg⁻¹ when compared to the non-torrefied spelt husks, which had an HHV of 17.56 MJ kg⁻¹. By increasing the temperature from 200 to 300°C, oxygen was removed in the form of CO2, CO, and H2O and the grindability was improved. The liquid product was predominantly water and strongly acidic with limited potential for further use in the petrochemical industry.

DOI: http://doi.org/