科研之友
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摘要
Torrefaction is being widely investigated for improving the quality of wood and agricultural residues for gasification and combustion applications. Torrefaction is thought to increase the energy density of biomass and decrease the energy required for grinding as well as reducing the moisture content of the material. However, torrefaction is endothermic and in addition involves loss of mass and therefore energy is removed from the biomass. Therefore, a balance has to be achieved between the advantages and disadvantages of torrefaction. In this paper, several systems were modelled including torrefaction - gasification and torrefaction - combustion in both on-site and off-site scenarios. The aim was to determine the optimum temperature at which torrefaction should be carried out if greenhouse gas emissions are to be minimized. It was found that all the systems investigated gave lower greenhouse gas emissions when torrefaction was used compared to an identical reference system where no torrefaction was used. The ideal torrefaction temperature was determined to be 280 and 300 degrees C for hardwood and softwood respectively when the latent heat of the syngas was used to heat the torrefaction process. When the torrefaction volatiles were used to provide the heat for torrefaction, then the optimum temperature dropped to 240 and 260 degrees C for hardwood and softwood respectively. Torrefaction was found to have little impact in reducing transportation greenhouse gas emissions.
- 出版日期2012-4
