Study on Entrained Flow Gasification of Coal under Ash Fusion Controlling (II)

Effect of Limestone Flux Addition on Slag Fluidity

Abstract

A laboratory scale entrained bed coal gasifier was used to study ash melting behavior and the effect of flux addition on the ash melting behavior. Blair Athol coal, Taiheiyo coal and limestone as a flux were used in this study.
Ashes produced by char gasification, mostly adhere to the surface of unreacted char particle, and flow together with char in gases flow. Ash adhension to the gasifier wall, η_{a, w} was increased with the progress of gasification, and was mostly increased around at the exit of gasifier, where char gasification was in the final stage.
By the flux addtion, slag (Blair Athol coal, FT > 1873K) melting temperature was reduced to 1613K, when CaO content is about 40wt% in slag. The ratio of flux in slag to the flux added, η was found to about 0.65 in this work.
Melting temperature change of slag with flux addition can be explained by the mineral change in slag with a phase diagram for CaO-Al₂O₃-SiO₂ compositions.