Effects of Temperature and Concentration of Oxygen on Torrefaction of Empty Fruit Bunches

抄録

A huge amount of underutilised empty fruit bunches (EFB) are produced in Malaysia. The abundance of EFB has gained much attention, as they are seen as a potential resource for solid fuel production. However, EFB cannot be directly fed to existing combustion systems due to its undesirable properties. Hence, pre-treatment such as torrefaction is usually conducted to address these limitations. Torrefaction is a thermochemical pre-treatment method that upgrades biomass properties at mild temperatures. The purpose of this study is to investigate the effects of varying oxygen concentrations and temperatures on EFB (0.375 mm particle size) during the torrefaction process. The experiment was conducted at 220 °C, 260 °C, and 300 °C in oxygen concentrations ranging from 0 to 21 vol.% using a vertical tubular reactor. The torrefied EFB was found to turn dark as the torrefaction temperature and oxygen concentration increased. The density of the torrefied EFB was also seen to decrease with increasing temperature. It was also observed that the presence of oxygen lowered the density of the torrefied EFB compared to that of inert conditions. From this work, it was found that solid yield decreased with increasing temperature and oxygen concentration. The solid yield of torrefied EFB ranged from 74-89%, 63-79%, and 51-72% at 220 °C, 260 °C, and 300 °C, respectively, under different oxygen concentrations. The results also reveal an increase in heating values with increasing temperature and oxygen concentrations, ranging from 18.8 to 24.6 MJ/kg. In conclusion, oxygen torrefaction can potentially be a feasible option for biomass pre-treatment.