Synergistic effect of potassium and calcium ions on coal pyrolysis behaviors: Experimental and kinetic model investigations

Abstract

A low rank coal was first used to investigate the synergistic effect of inherent and loaded potassium and calcium ions on the pyrolysis behaviors. The non-isothermal thermal analysis with higher heating rate to medium pyrolysis temperature was carried out by thermogravimetric analyzer for the selected raw and treated coal samples. Preliminary experiments conducted show that the particle size smaller than 160 mm can eliminate heat and mass transfer effect, and the most of volatile matter was released by heating the raw coal (R-coal) to 750?C. Moreover, the effect of heating rate, inherent and loaded potassium and calcium on moisture evaporation and devolatilization is systematically investigated, and the devolatilization index is introduced to estimate the activity of pyrolysis pr?cess. A comparison among the acid pickling coal (H-coal), acid pickling coal loaded with calcium (H-coal-C), and potassium (H-coal-P) shows that potassium and calcium have improved the inner water holding capacity. Finally, the influence of inherent and loaded potassium and calcium on the kinetic characteristics of volatile matter release stage was studied with Coats-Redfern integral method.