Experimentation for char combustion kinetics measurements: Bias from char preparation

As an alternative to direct use in char burnout kinetics experiments, coal and other solid fuels may be devolatilized and converted to char in a separate step in order to eliminate the influence of volatile release and combustion on measured char conversion properties. In this study, the effects of char preparation conditions on char burnout characteristics during pulverized coal combustion are investigated. Untreated particles of a Colombian high-volatile bituminous coal as well as three chars from that coal, which were externally produced in three different reactors, were tested in a combustion-driven entrained flow reactor. The reactivities of the chars were quantified as pre-exponential factors for commonly employed single-film burnout models, which were estimated from optically measured temperatures and sizes of individual burning particles. The results indicate that char production with devolatilization under heating rates greater than 2 × 104 K/s yields suitable materials for experimental research on char consumption kinetics. The characteristics of high-heating-rate production methods appear to affect char reactivities only in the early stages of the consumption process (less than 20-25% conversion of the initial char mass).