Insights into the role of calcium during coal gasification in the presence of silicon and aluminum.

• The interactions of Si, Al, and Ca in gasification were analyzed deeply. • The gasification rate of Ca-Si-Al coal quadrupled that of demineralized coal. • Factsage software was combined with in-situ XRD to reveal the change of minerals. • CaSiO 3 , Ca 2 SiO 4 , and Ca 2 Al 2 SiO 7 played a catalytic role in gasification. Clarifying the effect of other inert minerals on the catalytic performance of Ca in coal gasification is critical and meaningful to understand the deactivation mechanism of catalyst. In this work, four coal samples, demineralized coal (Dem-coal), coal loaded Ca (Ca + Dem-coal), coal containing Si and Al ((Si, Al)-coal), and coal loaded Ca, Si, and Al (Ca+(Si, Al)-coal), were prepared to analyze the impact of interactions on gasification reactivity. The gasification activity of coal samples with CO 2 agent at 900 °C was evaluated via thermal gravimetric analyzer (TGA). An in-situ heating stage microscope was applied to record the change of morphology of coal particles in the whole process. Besides, Factsage thermodynamic calculations were combined with in-situ X-ray diffraction (XRD) results to investigate the evolution of minerals including Ca, Si, and Al. The results indicate that Ca presenting in the form of CaO exhibits excellent catalytic performance. Si and Al existing in the form of SiO 2 crystals and amorphous structure respectively, hinder the process severely. Noticeably, the interactions of Si, Al, and Ca has a catalytic effect on coal gasification, though the gasification reactivity of Ca+(Si, Al)-coal is a bit lower than that of Ca + Dem-coal. In-situ XRD results confirmed the formation of CaSiO 3 , Ca 2 SiO 4 , and Ca 2 Al 2 SiO 7 , suggesting that these Ca complexes are catalytically active, but the catalytic performance of them is inferior to that of CaO. The evidence proved powerfully that it is not the reactions among Ca, Si, and Al which caused the deactivation of Ca catalyst. [ABSTRACT FROM AUTHOR]