Relationship between ash fusion temperatures of ashes from hard coal, brown coal, and biomass and mineral phases under different atmospheres: A combined FactSage™ computational and network theoretical approach

• Large set of hard coals, brown coals, and biomasses is ashed at 815 and 450/550 °C.
• Calculated mineral phases are related to the experimental ash fusion temperatures.
• Mineral phases are assigned to certain main groups with similar fusion behavior.
• Lowest HTs are found for fusion of three-component systems (oxidizing conditions).
• Lowest HT points are dominated by the melting of silicates (reducing atmosphere).

A broad set of ashes originating from national and international sources of hard coal, brown coal, and biomass is investigated under different ashing temperatures (815 °C and 450/550 °C) as well as oxidizing and reducing atmosphere conditions. In this computational study the mineral phase composition is estimated and the respective masses are not taken into account, since these approaches have been regularly less successful. The resulting mineral phases are assigned to main mineral groups and related to the experimentally determined ash fusion temperatures. On the one hand this relation is based on network theoretical considerations for the liquid slag and on the other it combines those with the fusion behavior of the residual solid mineral phases. Lowest ash fusion temperatures are addressed to the presence of low temperature melting mixtures of several mineral phases, which formed a very fragile network. Finally, the effects of different ashing temperatures and atmosphere conditions on the resulting mineral phases and respective ash fusion temperatures are studied.