Project Title:Re-purposing acid generating fine coal waste: an assessment and analysis of opportunitiesr
Supervisors: Prof Sue Harrison; A/Prof Jenny Broadhurst
Current Research Overview/Abstract
The coal industry in South Africa is currently both imperative for South Africa’s immediate energy security and a contributor to South Africa’s significant acid rock drainage (ARD) problems. ARD in coal mining is generated in the mines themselves, and in deposits of coarse discards and ultra-fine tailings produced in coal washing operations. Researchers at the University of Cape Town’s department of Chemical Engineering have developed a two-stage separation process which separates ultra-fine coal tailings into a recovered coal stream, a sulfide-lean stream which is nonacid generating, and a sulfide-enriched stream. The sulfide-enriched stream, which has a relatively low volume and is acid generating, can potentially be reallocated as feedstock for other uses. In this way, the longterm pollution risks associated with ARD generation from the coal tailings deposits are effectively eliminated, whilst simultaneously increasing recovery of mined resources.
This paper focuses on the opportunities for the re-purposing of the separated sulphide-rich tailings fraction. The approach used in this study was based on the innovation value chain and included identification and preliminary analysis of alternatives, multi-criteria performance assessment of selected alternatives, and a scenario analysis of the two preferred options to achieve a better understanding of the implications of these applications in the South African context. The analysis and assessment of application alternatives was consistent with early stage design in terms of accuracy and details, and used value theory as a decision-making tool. This work highlighted that there are several potential applications for sulfidic coal waste, seven of which were screened and selected for performance assessment based on a comprehensive set of technical, economic, social and environmental criteria. This evaluation indicated that cemented paste backfill and soil amelioration were the preferred options. However, a more detailed scenario analysis showed that further developmental work would be required to establish