Grindability, thermogravimetric characteristics, and kinetics analysis of semi-biochar from coarse wood pyrolyzed in a fluidized bed

For the utilization of leftover materials from furniture factory, a two-step pyrolysis, an initial treatment at mild temperature followed by a fast pyrolysis step, in a fluidized bed reactor was proposed in this study. The grindability of semi-biochar samples after the mild temperature pyrolysis was studied. The fast pyrolysis characteristics and kinetics parameters of the semi-biochar samples were also investigated by thermogravimetric analysis. Results showed that an improvement in the grindability characteristics was observed. The grinding of semi-biochars that do not completely devolatilize mainly produces a mixture of fine particles and small fragments, whereas the semi-biochars that completely devolatilize have good grinding characteristic, and the main ground products are short and round particles. Most differential thermogravimetric (DTG) curves of the semi-biochar samples presented two peaks and four common stages. With increase of the temperature or residence time in mild temperature treatment process, the decomposition intensity of hemicellulose and cellulose in grinding residues decreased gradually, while the decomposition intensity of lignin changed little. Peak DTG value ranging from 4%/min to 6%/min can be adopted to estimate the optimal operation condition for mild temperature pyrolysis. Three-dimensional diffusion model can accurately describe the fast pyrolysis of semi-biochar.