Coal quality and uranium distribution in Springbok Flats Coalfield samples

摘要

The presence of coal in the Springbok Flats Coalfield (SFC) has been known since the beginning of the 1900s. However, the SFC has not been mined to any degree of economic profit, mostly due to the presence of uranium in the coal. Five boreholes were drilled in the SFC (BH1 to BH5); BH5 intersected two coal zones, the other boreholes intersected one coal zone. Coal samples were collected, selected, and characterized using proximate, ultimate, and calorific value analyses. X-ray fluorescence, instrumental neutron activation analysis, and inductively coupled plasma mass spectrometry were used to determine uranium content. The BH1 intersection and the upper coal zone in BH5 had ash contents higher than 50% and were considered to be primarily carbonaceous shale. BH2 was observed to have better coal quality, resembling typical South African bituminous coal used in local electricity generation. The highest uranium content was found in BID (up to 199 mg kg~(-1), followed by BH2 and BH1. BH4, the upper coal zone in BH5, and the lower coal zone in BH5 all had uranium contents averaging less than 10 mg kg~(-1). Uranium in the SFC samples was found both hi the coal and carbonaceous shale. For all boreholes except BH5, uranium is concentrated within the uppermost 1 m of the coal zone. X-ray fluorescence was the preferred analytical technique since the analysis gave consistent results that compared well with instrumental neutron activation analysis results.