Fusion Properties of Gasified Fine Ash at High Temperature under Reducing Atmosphere. Part 2: Influence of Fe_2O_3

摘要

The slag blocking may occur during the equipment normal operation because of the iron phase separation in coal gasifier. However, as a kind of common fluxing material, the iron-based fluxes are always applied to change the ash fusibility temperature (AFT). Therefore, it is very important to analyze the migration and transformation of iron element in the fusibility process from mineral transformation and microstructure. The fusibility and flow properties of the gasified fine ash greatly differ from the raw coal and the semichar. In this paper, two kinds of gasified fine ash from industrial circulating fluidized bed gasifier are chosen as the samples. The effect of Fe2O3 flux agent on the fusibility properties especially the AFTs was investigated, in conjunction with the XRD, SEM, and ash fusion determinator from the aspects of mineral transformation, microstructure, and morphology, respectively. The AFTs greatly and monotonically decrease with gradual increase in Fe2O3 content. The change of the ash fusibility characteristics is owing to the formation of minerals such as hercynite, anorthite, and fayalite, which can produce the low-temperature eutectic with silicate minerals. Moreover, the formation of refractory minerals such as mullite is inhibited. The microstructure and micromorphology analyses from SEM images just verify the above results. The small particles adhered to the surface of the ash during the melting process gradually decrease, and the bonding phenomenon occurs due to the low-temperature eutectic.