Assessing different coal combustion residue backfill scenarios in opencast coal mines, Mpumalanga, South Africa

Abstract

Coal-fired power stations produce large volumes of coal combustion residues (CCRs), which are disposed of in hold ponds or landfill sites. These ash storage facilities are limited in space and are approaching the end of their capacities, thus additional land is required for extensions. If new land is not sourced, power plants will be forced to cease operations, resulting in increased expenditure costs and environmental liability. A proposed disposal solution is to backfill opencast coal mines with CCR monoliths. However, there is limited knowledge on the hydraulic behaviour of CCRs in an opencast coal mine environment. This leads to an inability to assess this applications feasibility and determine whether this activity will have a positive, negligible or negative effect on groundwater quality. This study aims to address this gap in knowledge by assessing the flow and transport properties of CCRs under numerous theoretical backfilling conditions.