Accuracy of kinetic parameters in multiple methods for separating multi-step thermal degradation reactions of biomass into single-step reactions

Biomass can provide value-added fuels through thermal degradation technologies. However, their thermochemical processes are complicated and involve multi-step reactions. Due to the fact that traditional kinetic methods are only applicable to single-step reactions, multi-step reactions of biomass should be divided into single-step reactions to obtain accurate kinetic parameters. Therefore, some improved methods have been applied. There are three widely used methods for separating multi-step reactions, including fluctuating activation energy (FAE), peak-differentiating analysis (PDA) and First Order Pseudo Bi-component Separate-stage Model (PBSM-O1) methods. In this study, representative biomass (Chinese fir) was measured through thermogravimetry at multiple heating rates. Subsequently, its multi-step thermal degradation reactions were divided into multiple single-step reactions by FAE, PDA and PBSM-O1 methods. Next, the kinetic parameters of these single-step reactions were estimated by the Distributed Activation Energy Model method. The Shuffled Complex Evolution method was adopted to optimize these kinetics. Finally, the optimization accuracy based on the three methods was compared. The results showed that different single-step reactions could be obtained using different methods. The kinetics based on the FAE method were the highest. The accurate kinetics determined by this study contributed to the design and optimization of the biomass conversion system, thereby promoting large-scale industrial applications.