Numerical simulation and prediction of fast pyrolysis behavior of biomass pellet based on the coupling of heat and mass transfer characteristics and component reaction kinetics

Fast pyrolysis of biomass pellets is an effective means of large-scale utilization of biomass resources. This paper simulated and predicted the fast pyrolysis weight loss behavior of biomass pellets by using a comprehensive model coupling the temperature-varying thermal properties as well as the stepwise reaction mechanism of three biomass components. Results showed that the heat transfer limitation caused by temperature-varying thermal properties increased the inner-particle temperature difference from 288 °C to 376 °C under the heating rate of 100 °C/min when considering heat transfer characteristics, and the difference was more obvious at higher heating rates. Compared with one-step reaction kinetics, adopting the three-component stepwise reaction kinetics reduces the average simulation error of pyrolysis at 100 °C/min from 4.42 % to 0.68 %. Furthermore, based on the optimized three-component five-reaction model, the TG curves at low heating rates are used to predict the TG results at higher heating rates. The deviation of the TG curves at 200–500 °C/min for the same biomass predicted by the kinetic parameters at 100 °C/min was less than 1 %. With the introduction of ash content correction, the model can also be used to predict the behavior of different biomass species with an error of less than 2 %.