Effects of pyrolysis temperature on changes in fuel characteristics of biomass char

The fuel characteristics, the combustion profile, and the kinetic study of char that had been pyrolyzed at 300−500 °C were investigated for RH (rice husks), WC (wood chips), and WP (wood pellets). When a higher pyrolysis temperature was used, the calorific value became proportional to the fuel ratio and inversely proportional to that of the volatile matter. The pyrolysis temperature increased, the coal-band migrated toward that of coal. The number of DTG (differential thermogravimetric) peaks decreased from two to one with an increase in pyrolysis temperature. When WP was blended with coal, the unprocessed samples (WP Raw) showed two DTG peaks for all co-combustion ratios, but WP 400 (pyrolyzed at 400 °C) showed one DTG peak and a lower activation energy for all co-combustion ratios. It was observed that the combustion reaction mechanism of the WP Raw/coal-blended samples was similar to the third-order reaction model (O3) in the primary reaction (devolatilization stage), and to the diffusion model (D2–D4) in the secondary reaction (char combustion stage). On the other hand, it was thought that the secondary reaction of the WP 400/coal-blended samples had a reaction mechanism most similar to a first-order reaction (O1) at all co-combustion ratios.

► This study was to examine the effects of different pyrolysis conditions on the fuel characteristics.
► Energy yield of more than 50% could be obtained from the samples that had been pyrolyzed at 400 °C
► The pyrolysis temperature increased, the coal-band migrated toward that of coal.
► Compared with unprocessed biomasses, the burnout time of the samples decreased when pyrolyzed samples were used.