Comparison of Combustion Behavior of Pulverized Torrefied Biomass under Different Severity Conditions using Computational Fluid Dynamics

This research investigated the combustion behavior of pulverized biomass
under different degrees of severity during the torrefaction processes. The fuel studied in
this work was natural rubber trees and in the torrefaction process varied from 0.4 to 1
solid yield. The fuel has been grounded by a cutting mill using a 1 mm sieve. Torrefied
biomass from the grinding process had an average particle size of 216 to 394 μm. The
combustion behavior was studied using Computational Fluid Dynamics (CFD) through
a numerical modeling and simulation of an industrial pulverized biomass furnace with
the thermal capacity of 1 MW. Heat transfer, fluid flow, reaction kinetics, species
transport and discrete phase particle movement were carried out by using commercial
CFD software Ansys Fluent to study the conversion of chemical energy to thermal
energy and pollution released during combustion. Simulation results showed that
torrefied biomass provided a higher temperature than raw biomass (25.9%) because of
better hydrophobic properties and lower composition of hydrogen and oxygen. In
emissions of combustion, torrefied biomass tends to lower carbon monoxide emissions,
whereas nitrogen dioxide and carbon dioxide emissions tend to increase due to more
intense combustion compared to raw biomass. Carbon monoxide decreased up to
86.5%, Nitrogen dioxide and carbon dioxide increased by a maximum of 74.8% and
34.7%, respectively, for sulfur dioxide emissions decreased by up to 26.5% due to the
sulfur components in the fuel were released during the torrefaction process.