2019 Volume 98 Issue 3 Pages 35-43
A new concept for modeling the overlap between devolatilization and char oxidation was extended to various coal types. Quasi-steady mass transfer analysis around a single coal particle with devolatilization was performed, and the overlap between devolatilization and char oxidation was modeled with a semi-parallel reaction model. The semi-parallel reaction model can capture the differences in the char oxidation rates of each coal by a single fitting parameter called the inhibition factor. The combustion simulation of the single coal particle indicated the superiority of the semi-parallel reaction model over the previously reported modeling concepts because the semi-parallel reaction model could describe the decrease in char oxidation rate during devolatilization, which is not represented by other reaction models. Although the inhibition factor is not correlated with the proximate analysis of the volatile matter, it is correlated with the temperature at which the rate-controlling step of char oxidation shifts. This is because the proximate analysis does not include information on char reactivity. Therefore, it is suggested that the inhibition effect of devolatilization on char oxidation strongly correlates with the parameter that describes the sensitivity of char oxidation to the mass transfer processes of the oxidant.