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

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 CO2 agent at 900 degrees 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 SiO2 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 CaSiO3, Ca2SiO4, and Ca2Al2SiO7, 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.

Automated summary

Clarifying the effects of inert minerals on the catalytic performance of Ca in coal gasification is crucial. The presence of CaO showed excellent catalytic performance, while Si and Al hindered the process. Interactions among Si, Al, and Ca had a catalytic effect on coal gasification, although slightly lower in reactivity compared to Ca-only coal. The evidence suggested that the deactivation of Ca catalyst was not caused by reactions among Ca, Si, and Al.