Effects of coal drying on the pyrolysis and in-situ gasification characteristics of lignite coals

Pyrolysis behaviors of two lignite coals with different drying conditions were determined by a thermogravimetric analyzer coupled with mass spectrometer (TG-MS) and a high-frequency furnace. An in-situ heating stage microscope was adopted to observe the morphological changes during char-CO2 gasification process. It is concluded that the effects of moisture contents in coals on the gaseous release process during coal pyrolysis mainly depend on coal type, final pyrolysis temperature and heating method. The in-situ heating stage experiments indicate that the shrinking particle mode is suitable to illustrate the gasification reaction mechanism in the initial and midterm reaction stages of all the lignite char samples. Although drying conditions have significant effects on coal pyrolysis process under rapid heating, these dewatering conditions result in little noticeable reactivity loss of the char during the subsequent char-CO2 gasification reaction. The measuring results of catalytic active sites can well explain the similar reactivity of lignite coals with different drying conditions.