Journal of Korean Society of Agricultural Engineers ISSN:1738-3692(Print) 2093-7709(Online) 한국농공학회논문집

Torrefaction is considered as a promising pre-treatment for thermochemical utilization of biomass. Torrefaction temperature and time are the critical operation parameters. In this study, investigated were the effects of reaction temperature and time on product composition of torrefaction. scanning electron microscope (SEM) images and thermo gravimetric analyzer (TGA) results were also compared for the effects of the operating parameters. SEM images showed that the pores were observed at the temperature of 250 ℃ for 30 minutes. Rapid decreases in weight were observed the temperature between 200 and 400 ℃. Higher heating value of the torrefied biomass was over 5,000 kcal/kg at the temperature of 250 ℃ for 45 minutes. Energy density, which is defined as the ratio of the energy yield over the mass yield was 1.36 at the temperature of 250 ℃ for 45 minutes. The energy density was higher up to 1.6 at the temperature of 280 ℃, which indicates greater loss in mass. The major components of the gas produced in the torrefaction were CO₂ and CO, with traces of methane. The total amount of gas was 31.54 l/kg and the calorific value of the gas was 1,164.4 Kcal/Nm³ at the temperature of 250 ℃ for 30 minute reaction time. Based on the results of this study, the temperature of effective torrefaction is about 250 ℃ for 30 to 45 minutes of reaction time. Considering the heating value, it is desirable to utilize the gas for efficient process of torrefaction.