Torréfaction to improve biomass pellet made of oil palm empty fruit bunch

Abstract

This study aims at determining the effect of the torrefaction process on the fuel quality of biomass pellets made from oil palm empty fruit bunches (EFB). The torrefaction process was carried out using a rotary reactor, which has a cylinder with a diameter of 15 cm and a length of 15 cm made from an iron plate. The cylinder was heated externally using a horizontal heater fueled with LPG. The reactor cylinder was filled with 1.5 kg of clean sand to homogenize the heat transfer and prevent pellets from colliding during the process. The torrefaction process was conducted with a load of 300 grams of EFB pellets at temperatures around 240-310 °C at variations of reaction time (20, 30, and 45 min.) and the reactor cylinder rotation speed (16, 31, and 37 RPM). The results showed that the torrefaction process improved the quality of the EFB pellet fuel. This was reflected from the very low moisture content (0.32-0.52 %) of torrefied pellets and its calorific value, which increased from 15.82 MJ/kg (without torrefaction) to 17.59 MJ/kg (with torrefaction for 45 minutes). Torrefied pellets showed good hydrophobicity where the pellet was not broken when immersed in water for 24 hours. Pellet without torrefaction was destroyed in water just in one minute.