Ca-Si-Al interactions induced char structure and active site evolution during gasification–A comparative study based on different gasifying agent.

• The difference of Ca-Si-Al interactions on CO 2 and H 2 O gasification was analyzed systematically. • The well dispersed SiO 2 particles cannot adsorb gasifying agent molecule to transfer oxygen. • Newly generated minerals in H 2 O have no ability to prompt the generation of active site. • CaO in Ca+Dem-coal favors mesopore formation, especially in H 2 O. Catalytic steam gasification, as a promising technology for producing hydrogen-enriched syngas, has been a hotspot in recent studies. This study aims to analyze the role of calcium-silicon-aluminum (Ca-Si-Al) interactions in char gasification and distinguish the difference of the interaction in different gasifying agent. The gasification reactivity of coal char was closely linked with the physiochemical structure and the mineral interactions. It was found that whether in CO 2 or H 2 O, the calcium oxide (CaO) has function to promote the generation of mesopores, which is beneficial to the diffusion of reactant and product gases. The scanning electron microscopy (SEM) images showed that no SiO 2 particles agglomerated in coal char containing silicon-aluminum ((Si-Al)-coal), which was a good reason why Si-Al inhibited gasification severely; the well dispersed SiO 2 particles have no function to adsorb the gasifying agent molecular to transfer oxygen. New minerals including Ca 2 Al 2 SiO 7 , Ca 2 SiO 4 and CaSiO 3 were formed in CO 2 and H 2 O, while CaAl 2 Si 2 O 8 only was detected in H 2 O. These new minerals exert a positive effect on active site in CO 2 but negative effect in H 2 O. While in H 2 O, compared with active sites, the mesopores dominate the reaction more. Overall, the interactions catalyze gasification to a moderate degree whether in CO 2 or H 2 O. [ABSTRACT FROM AUTHOR]