THE EFFECTS OF PARTICLE SIZE, COMPACTION PRESSURE, AND TORREFACTION ON QUALITY AND THERMAL PROPERTIES OF PELLETIZED CORNCOB RESIDUES
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Date
2022
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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.