LAUSR

Abstract The release of alkali and alkaline earth metallic species (AAEMs) and their effects on char gasification reactivity in different atmospheres were investigated. Chars from a bituminous coal pyrolysis were gasified under 30% H 2 O, 30% CO 2 , and 15% CO 2  + 15% H 2 O atmospheres at 800 °C to obtain a series of gasified chars with different carbon conversions. The AAEM content and morphology of the gasified chars were analyzed by atomic absorption spectroscopy and scanning electron microscopy, respectively. The physicochemical structural features of gasified chars were characterized by Raman spectroscopy and N 2 adsorption. The reactivities of the gasified chars were determined using a thermogravimetric analyzer. The release behavior of Na and K is insensitive to the change in atmosphere, whereas the release of Ca in CO 2 atmosphere is obviously higher than that in H 2 O or mixed H 2 O/CO 2 atmosphere. Ca compounds agglomerated and sintered during the char-CO 2 gasification, whereas they maintained good dispersion in the presence of H 2 O. Gasification under CO 2 atmosphere produced micropores, whereas that under H 2 O atmosphere favored the formation of mesopores. The water-soluble Na and K species showed a better catalytic activity in the gasified char, leading to a higher reactivity of gasified char than the raw coal char.