Mathematical modelling of wooden biomass torrefaction

Torrefaction is used for initial biomass valorisation prior to energetic utilization. The produced biocarbon is characterized by high energy density, and high calorific value. Moreover, it contains less moisture, and has hydrophobic character. Due to that, this technology is being found perspective, but the relation between process parameters, and biomass, and biocarbon properties should be still optimized. The presented work shows the mathematical modelling of torrefaction of the wooden biomass particle. The dependence between technological parameters (process temperature, and retention time), and biomass properties (density, calorific value of the biomass), and calorific value of biocarbon has been examined. The parameters of IInd degree polynomial functions, allowing the estimation of the required retention time or required process temperature to achieve desired calorific value of biocarbon have been determined. The modelling showed, that the process temperature and retention time are the most significant factors influencing the torrefaction efficiency. Also, the calorific value of biocarbon may be an important parameter, but biomass properties are not significant, with recommendation to neglect the biomass density.