The O/C (oxygen to carbon) ratio is reduced due to the liberation of water during the drying process and oxygen released during torrefaction. As a consequence the heating value increases, i.e. the H/C (hydrogen to carbon) ratio increases . Pyrolysis peaks in Table 2 indicate that the thermal degradation is intensified at this temperature. Lignin has been shown to be highly resistant to thermal degradation Figure 6. The 230˚C torrefaction process primarily releases moisture and light volatiles, improving the quality of the biomass slightly . The 260˚C torrefaction process partially the hemicellulose fraction which results in a large improvement in biomass quality for “pyrolyses” combustion . At 290˚C, the torrefaction process produces a large degradation of hemicellulose and cellulose. This is not desirable as it significantly reduces the solid mass yield and as such severe torrefaction is not recommended. However, it should be noted that the duration of torrefaction as well as the particle size are also influencing factors when it comes to mass loss, e.g. Willow torrefied for 17 minutes at 280˚C was shown to have a mass yield of 87.5% (daf) with an energy yield of 94.9% (LHVdaf).
The O/C (oxygen to carbon) ratio is reduced due to the liberation of water during the drying process and oxygen released during torrefaction. As a consequence the heating value increases, i.e. the H/C (hydrogen to carbon) ratio increases . Pyrolysis peaks in Table 2 indicate that the thermal degradation is intensified at this temperature. Lignin has been shown to be highly resistant to thermal degradation Figure 6. The 230˚C torrefaction process primarily releases moisture and light volatiles, improving the quality of the biomass slightly . The 260˚C torrefaction process partially “pyrolyses” the hemicellulose fraction which results in a large improvement in biomass quality for combustion . At 290˚C, the torrefaction process produces a large degradation of hemicellulose and cellulose. This is not desirable as it significantly reduces the solid mass yield and as such severe torrefaction is not recommended. However, it should be noted that the duration of torrefaction as well as the particle size are also influencing factors when it comes to mass loss, e.g. Willow torrefied for 17 minutes at 280˚C was shown to have a mass yield of 87.5% (daf) with an energy yield of 94.9% (LHVdaf).
Arbor+Report+-+An+overview+and+inventory+of+current+biomass+upgrading+technology+for+energy+use+%28Final%29.docx