Co-firing coal and biomass offers a sustainable renewable energy option. However, slagging and fouling have been identified as some of the major operational challenges associated with co-firing. The chemistry of individual fuels can be used to determine the slagging potential of the blend. Previously, we have developed a numerical slagging index (NSI) based on the ash content in coal and the chemical properties of the coal ash. The NSI has been tested on a wide range of coals, and very good prediction results were obtained. In this paper, the slagging potential of Nigerian coal and other coals from Australia, Colombia and South Africa have been numerically evaluated. The predicted results using the NSI indicate that the Nigerian coal has relatively low slagging propensity when compared with other coals tested in this paper. One of the Australian coals seems to have lower slagging potential, and this may be attributed to the extraordinary low ash content for the coal, as reported. It has been observed that the silica-rich coal ash composition can be used to select suitable coals that could be co-fired with the alkali-rich biomass, with low operational risk. However, detail information on the chemical properties of blend and the particle-particle interaction can improve the performance of the assessment tool.

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