Effect of Torrefaction Conditions on Physicochemical Properties of Empty Fruit Bunches

Abstract

Empty fruit bunches (EFB) in current bulky form are low in energy density and highly moist making them unsuitable as a solid fuel. Pre-treatment of EFB via thermochemical process i.e. torrefaction is required in order to improve its energy density via reduction of moisture and oxygen contents, which eventually will lead to an increased calorific value (CV). This study investigated the effects of temperature (225 °C, 250 °C and 300 °C) and retention time (20, 40 and 60 min) on the torrefaction products distribution (solid, liquid and gas) and physicochemical properties including proximate and ultimate (elemental) compositions and energy content of torrefied EFB. The results indicated that an increased temperature and retention time led to lower mass of torrefied EFB yield. The highest yield (90.44%) was attainable after 20 min of torrefaction at the lowest deployed 225 °C. However, the CV of torrefied EFB increased with increasing temperature and retention time, reaching a maximum 25.73 MJ/kg at 300 °C for 60 min, i.e. up to 46% higher than its raw form. The resulting improved physicochemical properties indicated suitability of the torrefied EFB for bioenergy processes such as combustion, gasification, pyrolysis and peptization.