Experimental study of the mechanical and thermal behaviour of pellets produced from oil palm biomass blends

The production of bio-pellets is an alternative to add value to the residual biomass of the oil palm-extraction process. In this work, an experimental study of the pelletising process of oil palm residual biomass blends is presented. An experimental full factorial design that uses as factors the binding agent content, the moisture content and the mass content of palm kernel shell in the biomass blends is performed. The moisture content of the raw biomass material influences remarkably the durability index of the pellets. These results indicate that high moisture contents in biomass hinder the process of extrusion and linking among the oil palm biomass particles. An increase in the palm kernel shell mass fraction in biomass leads to an increase in the pellets apparent density value. The pellets durability index behaviour study leads to the conclusion that the moisture content is the parameter that exerts the major influence. If the moisture content increases, the durability index decreases. Further, no standard bending tests at 3-points on the pellets are made with the purpose of evaluating the mechanical strength of the densified biomass. Additionally, the produced pellets maintain the quality and durability criteria after being carbonised by means of a thermo gravimetric analysis. The best quality characteristics of the pellets were obtained for a raw biomass material with 10% of moisture content, 4% of binding agent content and 40% by mass of palm kernel shell in the overall biomass respectively.