Rumbidzaishe Chipakwe

Abstract

The coal sector has increased its contribution to the South African economy over the years and consequently there has been an increase in waste generation. Historically, depending on the particle size of the waste it is either disposed of by tipping over onto dumps or pumping into slurry ponds. This method of waste disposal is accompanied by environmental pollution through spontaneous combustion, acid rock drainage (ARD) and dust generation, which subsequently affects aquatic life, human health, livestock and crop production. Recently there has been increased emphasis on the development and integration of large-volume waste management practices that reduce these impacts and maximise resource efficiency through value recovery and repurposing of the benign fractions.

Researchers at UCT have been working on the development of integrated approaches to mitigate long-term risks as well as re-purposing of and value recovery from the wastes. This work includes the development of a 2-stage flotation process generating sulphide-lean tailings, sulphide-rich concentrate and recovering coal, soil fabrication and co-disposal using desulphurised tailings. Whilst a number of opportunities for the downstream utilisation of coal processing wastes have been identified, application and pre-processing requirements will depend largely on the characteristics of the waste. However, the focus has largely been on the characterisation of coal waste for assessment of characteristics of environmental significance with little consideration for characterisation for the purposes of downstream management. Therefore, this project aims to develop a matrix of key coal processing waste properties related to various re-purposing options, through a desktop study. The matrix is generated in accordance with currently available data and information on South African coal waste characteristics. A quality function deployment type matrix has been used in this project, relating the technical requirements (i.e. coal waste properties) to the selected re-purposing option target specifications.