Combining wet torrefaction and pyrolysis for woody biochar upgradation and structural modification

This study investigated the effect of wet torrefaction (WT) on biochar property derived from softwood (PIW) and hardwood (POW) pyrolysis. The biochar gasification was performed in a thermogravimetric analyzer, followed by kinetic modelling. The biochar structure was analyzed, including inherent metals, pore structure and carbon structure. The results showed that WT affected reactivity and structure of PIW-derived biochar more than that of POW-derived biochar. The critical WT temperature determined the reactivity changes together with kinetic parameters. The WT affected the inorganic and organic component in biochar simultaneously. As results of WT, more than 70 and 50% ion-exchanged AAEMs in PIW-derived biochar and POW-derived biochar were removed. Nevertheless, the organic structure had essential effect on the gasification reactivity. More pronounced structure evolution of PIW-derived biochar was observed, including lower mesopore surface area, more graphite structure and small rings. This research provides new insights into the structure-reactivity correlation for biochar utilization.