Measurement and determination of main kinetic parameters of medium temperature pyrolysis bituminous coal char

The oxidation reaction order (n) and activation energy (Ea) are the primary parameters in the global carbon/oxygen reaction model. However, these parameters continue to be a subject of argument due to the problems of experimental technology and kinetic analysis methods. This paper used a micro fluidized bed reaction analysis system to study the reaction kinetics of bituminous coal char with a median particle size of 75 μm at 923–1223 K and 2%–21% oxygen concentration. The effects of temperature and oxygen concentration on the combustion characteristics of char were analyzed emphatically. Measured the real n value and main kinetic parameters in the nth-order Arrhenius model and determined the transition temperatures of the combustion control zone. Results showed that the position of the maximum combustion reactivity is in the range of 20–30% of carbon conversion, which decreased slightly with the increase of temperature and increased slightly with the increase of oxygen concentration. The intrinsic reaction zone is below 1023 K, the intrinsic reaction order is between 0.64 and 0.71, and the intrinsic activation energy is about 106 kJ/mol. This study contributes to improve the precision and practicality of the nth-order Arrhenius model. •Proposes a better method to determine the order n and activation energy Ea•As temperature rises, Xmax slightly drops, contrary to the oxygen ratio rises•The intrinsic reaction zone is below 1023 K•Zone I n = 0.64–0.71, Ea = 97–117 kJ/mol, and A0 = 130–836 mol/(s·m2·atmn)•Intrinsic reaction zone activation energy of medium temperature pyrolysis bituminous coal char are reported for the first time in the literature.•Higher pyrolysis temperatures produce chars with higher reactivity.•Biomass char has higher intrinsic reactivity than the coal char in T > 973 K.•Ash content of Vietnamese coal plays a negative role in pyrolysis, but a positive role in the char combustion.•A new correlation of the char surface area and density with the fuel properties and temperature.