Understanding beneficiated coals using organic petrology: mineral and maceral partitioning in Highveld coals, South Africa

Coal is a heterogeneous material, posing challenges in predicting its behavior during beneficiation and utilization. The effectiveness of beneficiation is linked to the modes of occurrence of minerals, and the separation of minerals from organic matter is challenging.Organic petrography enables the identification of modes of occurrence of observable minerals and quantification of organic-mineral associations using microlithotype analysis. Five (5) No. 4 Seam samples (termed “parent”) were collected from five (5) collieries in the Highveld Coalfield (South Africa) with the aim of understanding the behavior of organic and inorganic matter during density fractionation at 1.7 and 1.9 g/cm³.Organic petrography (macerals, microlithotype, and rank), proximate analysis, and X-Ray Diffraction (XRD) were undertaken. The coals are medium rank, borderline D and C bituminous. The parent samples are variably enriched with inertinite. Some sink samples from the 1.7 g/cm³ relative density RD are of a better quality compared to the float samples obtained at 1.9 g/cm³ from the other locations. This suggests further beneficiation of selected 1.7 sink products may likely produce medium ash feedstock with a suitable yield. These observations are supported using statistical analysis. The data presented suggest that a one-size beneficiation plan does not apply to all sources.