Geochemistry Of The Majuba Underground Coal Gasification Geo-Reactor

Underground coal gasification (UCG) is an unconventional mining method that gasifies coal in situ to produce a synthetic gas that can be used for industrial purposes. This mining method is still to go commercial and one of the challenges to its sustainable development is the potential risk to groundwater pollution. There is therefore a need to quantify the environmental risks associated with UCG in order for authorities to regulate this emerging sector. The knowledge attained through this work has provided for a simple but comprehensive groundwater risk assessment of a spent UCG chamber via an integrated model. The model follows the source-pathway-receptor model where the sources are identified as ash, char, roof and floor. The risk to groundwater pollution is then assessed by subjecting these sources to the following tests; mineralogical and element analysis, petrography and chemical assessment, leaching tests and acid generation assessments. Groundwater was identified as the only natural medium that can access the spent geo-reactor and transport contaminants to secondary locations. The pathways that pollution from the UCG geo-reactor can be transmitted through were identified as; natural faults, heat induced fractures, boreholes, local aquifers. This research has laid a firm foundation in understanding groundwater contamination from UCG operations.