Kinetic Study of Torrefaction Process of Oil Palm Biomass

Torrefaction is thermal pretreatment process for biomass at temperature range from 200 to 300°C which carried out at under inert atmosphere. This process is aiming to produce solid fuel which increased energy density, lowered moisture content and easy to comminute into small particle size by decomposing hemicellulose. In this study, three types of oil palm biomass namely empty fruit bunch (EFB), palm mesocarp fiber (PMF) and palm kernel shell are torrefied by using thermogravimetric analyzer (TGA) at different particle sizes, i.e. 250-355μm and 355-500μm. Two steps reaction are found out to give description about decomposition for EFB, PMF and PKS. For two steps, activation energies, Ea of 58267 kJ/mol and -34247 kJ/mol, respectively and pre-exponential factors, A of 11x103 and 1.24x10-6, respectively for EFB with particle size 250-355 μm are found. During the process, only hemicellulose decomposition takes place. The hemicellulose decomposition is more significant compare to cellulose and lignin during torrefaction of oil palm biomass since temperature decomposition of hemicellulose between 225-325°C. TGA process conditions are replicated using tube furnace to determine energy yield and ultimate analysis for torrefied samples. Energy yield is found increasing with torrefaction temperature. Meanwhile, kinetic model is created and verified for predicting amount of torrefied solid. As conclusion, four main parameters give significant towards torrefaction process which are type of biomass, particle size, torrefaction temperature and reaction time.