Effect and mechanism of short time ball milling on physicochemical characteristics and pyrolysis kinetics of Pennisetum giganteum

This study investigated the variation of biomass pyrolysis kinetics with changes in ball milling (BM) intensity. Pennisetum giganteum was used as the pyrolysis sample, and different BM times were set to alter the BM intensity. A comprehensive analysis was carried out, combining physicochemical property measurements and pyrolysis experiments. The results showed that BM could change the sample's particle size (1770-30.80 mu m), specific surface area (0.0291-0.7554 m2/g), and pore volume (0.103-2.207 mm3/g) within a very short time (>= 2 min). Interestingly, only a long BM duration (20 min) significantly reduced the sample's crystallinity. The activation energy vs. conversion rate curve of the samples transitioned from being tangential to being parabolic as the duration of BM increased, with a notable change in the average activation energy observed after BM 20 min (152.65-135.50 kJ/mol). This was caused by the destruction of crystalline cellulose into amorphous cellulose, which reduced the thermal stability of the sample. Furthermore, changes in other physicochemical properties had no significant impact on the pyrolysis average activation energy. This study provided valuable references for the optimization of pretreatment parameters in pyrolysis production.