Beneficial Utilisation of Sasol Coal Gasification Ash

Sasol utilises low grade coal in a Lurgi gasification process to produce synthesis gas from which ash is an inevitable co-product. Gasification ash, referred to as coarse ash, is a clinker ash with heterogeneous texture varying from fine material to large irregularly shaped aggregates. Ash utilisation opportunities can be separated into off-site use as a product replacement or on-site through the utilisation of ash dumps to treat waste products. The large scale opportunities for the off-site use of gasification ash is in brick making, as road fill and other construction applications. As a commodity input its market penetration is very price sensitive due to transport costs. Geographical location of the ash source largely determines off-site ash utilisation opportunities. Within large ash disposal sites there exists significant opportunities to beneficially utilise on-site the top layer of an ash dump for the treatment and disposal of wastes such as bio-solids. This in turn can improve the ash properties to make it more suitable for rehabilitation and research in this area is being pursued. Environmental risks associated with ash utilisation include leachate (surface and ground water contamination), dust and loss of arable land. These risks are definable and in most cases low and controllable. Gasification ash remains a valuable under utilised co-product and its responsible use is encouraged particularly in exploiting its unique properties.