PROPERTIES OF INERTINITE MACERALS

Much of the published data on the properties of the inertinite macerals show a continuous change across the semifusinite/fusinite range. For example, reflectance and density increase while volatile matter and combustion reactivity, decrease. However other properties especially fusibility show a discontinuous relationship across the semifusinite/fusinite range. The nature of this change has importance in coal utilization including combustion and coking. The overall objective of this study was to analyze the nature of the change in thermal properties across the density and reflectance range of the inertinite macerals. In this work the inertinite macerals from demineralized samples the Herrin No. 6 and Murphysboro coal seams and their associated fusain lithotypes were isolated by sink/float methods and the inertinite concentrate was separated into twenty-six density fractions using density gradient centrifugation techniques. The thermal properties of the fractions were analyzed by thermogravimetric (TGA) methods. This study is the first time that such detailed analysis of samples across the the semifusinite/fusinite density range has been attempted. The preliminary results show in general that the thermal properties for the inertinite macerals from both the whole coal and fusain lithotype samples change in a discontinuous manner across the semifusinite/fusinite range. Specifically, the temperature and rate of chemisorption, the maximum combustion rate, the temperature of 50% burnoff, mean activation energy, and the temperature of char burnout all show a discontinuous relationship. Interestingly, the discontinuous transition between semifusinite and fusinite in this study occurred at the density minimum between the two types of macerals. This suggests that there may be a marked structural difference or “phase” change between these two macerals.