Reactivity prediction and mechanism analysis of raw and demineralized coal char gasification

Abstract

A series of thermogravimetric experiments were conducted to study the gasification kinetics of raw and demineralized coal char. The gasification mechanism was reveled through the kinetic analysis and the structure evolution. The systematic analyses showed that the reactivity of demineralized coal char was more sensitive to the heating rate β. The random pore model was more suitable for both raw and demineralized coal chars, where the pre-exponential factor (A) played the essential role in fitting performance. Moreover, the parameters of kinetic compensation effect were found to have a good linear relationship with lnβ, and the variations of kinetic triplet (A, Ea and f(X)) with the conversion level could be further explored accordingly. The reactivity predictions employing the integral and differential approaches were compared under the isothermal and non-isothermal conditions. The reactivity of raw coal char was more easily affected by diffusion, and the conversion-effectiveness factors increased with the conversion level at high temperatures. Finally, the local gasification mechanism was analyzed by piecewise comparing different single-step global models. The raw coal char featured the closed-pore reopening according to the distribution pore structure. The ash can act as the nuclei for gasification and affect pore growth and coalescence.