1. School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa
2. DSI/NRF Clean Coal Technology Research Group, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa
3. Department of Mining and Metallurgical Engineering, University of Namibia, Windhoek, Namibia
4. School of Mining Engineering, University of the Witwatersrand, Johannesburg, South Africa