Thermal decomposition study and pyrolysis kinetics of coal and agricultural residues under non-isothermal conditions

Abstract

In this work thermal decomposition along with pyrolysis kinetics of two coals namely Chamalang Coal (CC) and Dukki Coal (DC) and four agricultural residues i.e. Rice Husk (RH), Corn Husk (CH), Sunflower Disc (SD) and Falsa Stick (FS) were investigated under non-isothermal conditions. Four different parameters were used to evaluate the reactivity of fuels. These were peak temperature, average rate of weight loss, maximum rate of weight loss and pyrolysis factor. All these parameters were evaluated at four heating rates 10, 20, 30 and 40 °C/min. The average rates of weight loss were found higher in devolatilization region compared with char formation region of degradation. It was found from reactivity analysis that the fuels could be ranked in following order of reactivity CH > FS > RH > SD > DC > CC. It was observed that increasing heating rate shifted the reaction zone to higher temperature and increased the peak temperatures, rate of average and maximum weight loss that increased the reactivity and pyrolysis factor. Coals showed low reactivities and high activation energies compared to agricultural residues. The activation energy has been estimated using Friedman differential isoconversional model and it was found that the activation energy varied with fractional conversion. The estimated average values of activation energy (kJ/mol) for CC, DC, RH, CH, SD, and FS were found to be 134.54, 129.81, 109.43, 98.24, 113.25, and 103.64 respectively.