Oxidation reactivity and kinetic analysis of bituminous coal char from high-temperature pyrolysis: Effect of heating rate and pyrolysis temperature

Non-isothermal thermogravimetry (TGA) is conducted at four heating rates to determine the kinetic parameters and oxidation reactivity. The ignition (T_i), peak (T_p) and burnout (T_e) temperature and reactivity index S are calculated. Isoconversional method is adopted to determine the activation energy (E_α) and frequency factor (A_α). The rate constant (k(T)) is obtained by the kinetic parameters. The results show that S is strongly dependent on the TGA heating rate, while T_i, T_p and T_e are independent of the heating rate. With the increase of pyrolysis temperature, T_i monotonically increases, while the reactivity evaluated at T_p, T_e and k(T) ranks as char-1000< char-1200< char-800< char-600. A significant variation in T_i, T_p, T_e and k(T) is observed between char-800 and char-1000. The compensation effect between thermal annealing and surface structure evolution determines the reactivity with the pyrolysis temperature. The mass loss at a higher heating rate is predicted based on E_α and A_α.