Physicochemical analysis of South African metamorphosed coal

Abstract

An in-depth understanding of the physico-chemical nature of coal is required in order to meet ever-increasing energy demands and environmental legislature. New and classical coal analysis techniques were used on thermally-affected coals from a working coalfield in Secunda, South Africa. The study area has ubiquitous dolerite intrusions that have large-scale impacts on the minable coal resource. A combination of five modern and classical analysis techniques, namely Schmidt hammer testing, three-dimensional X-ray tomography, proximate analysis, petrographic analysis with reflectance analysis, and two-dimensional gas chromatography time of flight mass spectrometry (GC*GCTOFMS) were used to model the mechanics of metamorphism of coal intruded by an igneous body. Freshly exposed coalface with an intersecting dolerite was analysed. The data produced from GC*GCTOFMS, reflectance, and tomographic analysis produced no strong linear correlations. Thermal dolerite influence was capped at approximately 5m from the dolerite intrusion and of note was a secondary trend that identified peaks throughout the transect correlating across GC*GCTOFMS, reflectance, and tomographic analysis. To reconcile the non-linear correlation a model using a combination of hydrothermal and thermal influences was produced to explain the mechanics of the metamorphic environment.