Coal macerals separation by reflux classification and thermo-swelling analysis based on the Computer Aided Thermal Analysis

Abstract

The reflux classifier is a water based device designed for classifying and separating particles using inclined plates. Particles of sufficiently high settling rate are refluxed back to the slurry, while slow settling particles (low density vitrinites) are removed in the overflow. In this study, the reflux classifier was used to separate coal macerals less than 212μm in size. The thermo-swelling characteristics of separated macerals were evaluated on the basis of the Computer Aided Thermal Analysis (CATA) technique with extended volumetric measurements. A suite of maceral concentrates with various densities, ash contents, particle sizes and vitrinite percentages was obtained, which indicated that the reflux classifier can offer an alternative method of macerals separation/concentration without the use of dense media. The pyrolysis experiments of maceral concentrates indicated that the vitrinite-rich macerals showed a higher extent of volumetric swelling, exothermic reactions and thermal conductivity between 400 and 600°C than inertinite-rich macerals. Addition of inertinite to vitrinite concentrates showed that inertinite can suppress volumetric swelling and shift the swelling to a higher temperature during the primary devolatilization, but does not have a significant influence on high temperature contraction. Further observations about the interaction among different maceral groups were also discussed in this study.