Thermomechanical analysis of coal ash: The influence of the material for the sample assembly

Concerns over the characterization of the thermal properties of coal ash us ing thermomechanical analysis (TMA) in carbon assemblies (crucible and pene trating ram) has led to a study which critically examines the effect of sam ple assembly materials on thermomechanical analysis measurements. This stud y quantifies the influence of the sample assembly material on the TMA trace s. For temperatures up to 1600 degrees C and in inert conditions, ash chemi stries were identified where the slag reacts with a range of sample assembl y materials [molybdenum (Mo), platinum (Pt), carbon (C), zirconia (ZrO2), a lumina (Al2O3), and boron nitride (BN)], Only ZrO2 and Pt sample assemblies were found to be unreactive to ash samples during the tests. Iron-containi ng ashes were found to react with C assemblies, so that previous TMA data p ublished for such assemblies and inert gases is not characteristic of ash f usibility alone. The implications of the reactions to the interpretation of this TMA data are outlined. For ashes that contain iron, TMA results in gr aphite sample assemblies may be considered to have been obtained under stro nger reducing conditions than those used in the standard AFT test.