Energy & Fuels, Vol.29, No.8, 4893-4901, 2015
Thermo-swelling Properties of Particle Size Cuts of Coal Maceral Concentrates
A suite of coal maceral concentrates were prepared from a single coal using a water-based method for two discrete particle size fractions. Coal macerals were produced with the vitrinite content varying from 91.2% to 26.1% for the 106-212 mu m particle size fraction and 96.0% to 38.2% for the 212-500 mu m particle size fraction. Thermo-swelling of coal maceral concentrates were evaluated by the Computer Aided Thermal Analysis (CATA) technique with extended volumetric measurements. This novel CATA technique allows the apparent specific heat, thermal conductivity, and transient volumetric swelling of the coal sample to be measured simultaneously, as a function of temperature. The experimental results indicated that the maximum swelling (similar to 510 degrees C) and high-temperature contraction (600-1000 degrees C), as well as exothermic heat during primary devolatilization and thermal conductivity at maximum swelling all increased with vitrinite content, with the data inferring a linear relationship, and was independent of particle size, when coal maceral concentrates contain more than 63% vitrinite. A hypothesis for intragranular (within particles) and intergranular (between particles) swelling was used to explain the association of swelling with vitrinite content and particle size. Optical microscopic results of the final pyrolytic residues of different coal maceral concentrates support this hypothesis.