Characteristics of Different Sized Slag Particles from Entrained-Flow Coal Gasification

Gasification slags are byproducts of the coal gasification process, including fine slags (slags from filter) and coarse slags (slags from lock hopper). The characteristics of gasification slags with different particle sizes were investigated by the loss-on-ignition (LOI) method, scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), pore structure analysis, X-ray diffractometry (XRD), and X-ray fluorescence spectrometry (XRF). The relationships between the particle size and the characteristics of slags, which include residual carbon content, surface characteristics, pore structure, crystal mineral content, and ash composition, were analyzed and obtained. For fine slags, carbon content, specific surface area, porosity, and crystal content increase with particle size. For coarse slags, medium sized (105–280 μm) particles contain the most residual carbons and crystal minerals, followed by the smaller (0–105 μm) particles. Si/Al/Ca/Mg/K tends to concentrate in larger coarse slags, while Fe/S/P tends to concentrate in smaller particles. Different characteristics of different sized slags are mainly due to their different processes experienced in the gasifier. It is considered that particle fragmentation, ash agglomeration, and slag deposition should be taken into account.