Steam pre-treatment and leaching for the production of high quality oil palm residue pellets

It is estimated that about 26 million metric tons of oil palm oil residues are produced annually in Malaysia. The oil palm residues contain high ash content, high alkali metals and low lignin content. Ash and alkali metals lead to slagging in a combustion reactor and fouling of surfaces in convective tubes of heat exchangers. Low lignin content leads to disintegration of pellets during pellet handling and storage. This research thesis investigated the pelletization performance and the ash reduction on Empty Fruit Bunches (EFB) and Palm Kernel Shell (PKS) of oil palm residues by two different pre-treatment processes: steam explosion and water leaching. Steam explosion for increasing binding ability was performed by reacting EFB/PKS with saturated steam ranging from 120 to 220℃ for 5 minutes in a batch reactor. Water leaching for reducing the ash and alkali metals of EFB and PKS was investigated by immersing the samples in water from 25 to 55℃. The immersion time ranged from instantaneous to 240 minutes. Single pellets were made from water treated and steam treated samples. A significant ash reduction from 5.47 to 2.47 % was found for the EFB pellet due to water leaching. A slight reduction of pellet’s porosity and a significant reduction in ash content suggested that water leaching may be used to improve the quality of EFB as a biofuel. On the other hand, pre-treatment processes were not necessary for PKS, considering low binding ability and no ash reduction after pre-treatments. Kinetic models of EFB and PKS leaching were developed. A mass balance of cross flow process was investigated for evaluating the number of stages for a continuous leaching system of EFB and PKS. The techno-economic analysis showed that the additional leaching process costs $25.75 per tonne in a pellet making line.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat