Ashes of four different fuels - comprising a hard coal, a brown coal, a refuse-derived fuel (RDF), and a biomass - are investigated in the present study. The ashes were generated by different methods of a plasma treatment with a low temperature of around 200 degrees C as well as in a classical ashing oven under respective medium and high temperatures of 450 and 815 degrees C. All ash compositions are analyzed by XRF. The mineral phases obtained by those three ashing methods are compared as well as their formation and transformation are illustrated as a function of temperature. These results are reproduced by thermochemical calculations using the software package FactSageTM. Experimental and calculated mineral phases are in agreement. Subsequently, the ash fusion behavior is studied under oxidizing conditions. A solely reduction of the deformation temperature is detected for an ashing temperature of 450 degrees C compared to 815 degrees C. The determined flow temperatures can already be predicted by means of the composition of mineral phases in the ash produced at 815 degrees C under consideration of the melting point of those minerals. Finally, an influence of different ashing temperatures on the resulting ash fusion interval is ascertained for all investigated fuels. (C) 2017 Elsevier Ltd. All rights reserved.