THE EFFECTS OF PARTICLE SIZE, COMPACTION PRESSURE, AND TORREFACTION ON QUALITY AND THERMAL PROPERTIES OF PELLETIZED CORNCOB RESIDUES

Abstract

Torrefaction and biomass pelletization into pellets for solid fuel development are considered sustainable energy solutions to mitigate fossil fuel dependency and environmental challenges. This study investigated the effect of particle size, compaction pressure, and torrefaction on the quality and thermal properties of pelletized corncob residues. The corncob samples were collected, sorted, and pulverized before the torrefaction pretreatment. The torrefaction was achieved by placing the corncob in a furnace at a temperature and residence time of 280 °C and 30 minutes, respectively. The inert atmosphere was attained and maintained by initially purging a nitrogen gas into the torrefying chamber and passing it at 100mL/min during the processes. The raw and torrefied corncob fines were screened to 0.3 mm, 0.5 mm, and 1.0 mm grain sizes. Using starch as a binder (5% wt), pellets were produced employing their respective raw and torrefied fines at compaction pressures of 50 MPa, 75 MPa, and 100 MPa. Though all pellet samples exhibited good quality and thermal properties, the pellets from torrefied corncob are better. Also, the effects of particle size and compaction pressure are significant on the produced pellets. The compressed density varied from 760 to 1,250 kg/m3 and 637 to 920 kg/m3 for raw and torrefied corncob pellets. A maximum heating value of 25.8 MJ/kg was obtained from the torrefied pellet sample of 1.0 mm, rendering improvements of 37.2% when compared with 18.8 MJ/kg of raw corncob of the same particle size. The energy values obtained for torrefied corncob for all particle sizes compared favorably with the value obtained in coal. Investigation of particle size, compaction pressure, and torrefaction on quality and thermal properties of pelletized corncob residue proved that it can replace coal and hence could be used for energy applications.