A study on the reactivity of various chars from Turkish fuels obtained at high heating rates

This work investigates the reactivity of chars produced from Turkish biomass and lignite fuels using a wire mesh reactor at high temperature and high heating rate. The fuels studied were olive residue, almond shell, and Soma lignite. Blends of Soma lignite-olive residue and Soma lignite-almond shell were prepared in proportions of 75:25 and 50:50 wt%, respectively. A wire mesh reactor is used for the pyrolysis of the samples in a controlled inert atmosphere at a uniform temperature of 1600 °C and at a heating rate of above 103 °C s−1. The resulting volatile yields from the wire mesh reactor were compared with those from the proximate analyses. Volatile yield of Soma lignite obtained from wire mesh reactor (53 wt%) was higher than that of the proximate analysis (31 wt%); however, biomasses showed similar yields from both techniques. The morphology and structural changes of the chars were investigated using Scanning Electron Microscopy. Biomass chars displayed a high level of macro-porosity. Combustion reactivity and burnout times of the char samples were determined from thermogravimetric analysis. Biochars had about three times shorter burnout times and three times higher reactivity values compared to those of Soma lignite. First-order kinetic rate constants were determined for all individual chars and blends. Rate constants of the blends showed minor synergistic effect with an increase in the olive residue content, and a pronounced deactivation effect observed with an increase in almond shell content. •Volatile yields from fast pyrolysis were greater than those from proximate analysis.•Reactivities of the biomass chars were higher when compared to those of the lignite.•Blends with 25% biomass displayed a combustion behavior similar to neat lignite char.•Blends with 50% olive – 50% lignite showed a synergistic effect.•Blends with 50% almond – 50% lignite presented a deactivation effect.