Single-step and multi-step thermokinetic study - Deconvolution method as a simple pathway for describe properly the biomass pyrolysis for energy conversion

The kinetic pyrolysis is often studied as a global process (single-step mechanism), but this method is inadequate since it does not adequately describe the biomass pyrolysis. In this context, the purpose of this study is to present a simple pathway to describe the kinetic parameters of pyrolysis properly. Sugarcane bagasse waste and cashew nut shell waste were chosen because each presented high bioenergetic potential, based on preliminary physicochemical characterizations. Pyrolysis was performed at a range from room temperature to 1073 K under heating rates of 5, 10, 20, and 30 K min(-1). The activation energy, frequency factor and reaction model were obtained from isoconversional methods, compensation effect and master plot, respectively. For the study of the single-step mechanism, a temperature range of 408-723 K and 398-873 K was used for sugarcane bagasse waste and cashew nut shell waste, respectively. For study of the multi-step mechanism study, the algorithm process of deconvolution was used as a simple pathway. The results obtained for single-step mechanism suggest that the kinetic parameters are only applied for decomposition processes with only one decomposition stage. Overlap curves reduce the accuracy between the simulated and experimental curves for sing-step mechanism and unable to describe the biomass pyrolysis process. On the other hand, the multi-step mechanism using deconvolution associated with isoconversional methods can provide a good approximation of the experimental data independent of the thermal behavior of the biomass. In addition, the algorithm provides suitable values of kinetic parameters, which do not require advanced programming or software.