MSc Project title A systemic approach for the optimization of water usage in zinc processing
(Supervisors: Prof A Lewis, Prof D Deglon) Graduated: 2009
This project involved a systemic optimisation of the water balance of the Skorpion Zinc refinery, with the aim of reducing water consumption. A simulation was performed using the Aspen Plus simulation package, and a number of water minimisation scenarios were presented, as informed by process design heuristics. Unit operational changes and circuit configuration changes were formulated with the aim of retaining water in the process. The simulations were compared to date obtained from the plant, with good agreement.
The scenarios leading to the largest reduction in water use all required the full recycle of treated effluent water which resulted in water savings of up to 23%. Recycling of untreated water was prohibited by the build-up of trace elements, which affect final product purity. It was concluded that the Skorpion process already features a highly optimised water balance, with the unit operational changed merely resulting in a shift in the water balance. Consequently, the largest area for improvement is through the recovery and re-use of effluent water to supplement the fresh water input.
Peer-reviewed journal publications
Bhikha, H., Lewis, A.E. and Deglon, D.A. 2011. Reducing water consumption at Skorpion Zinc. Journal of the South African Institute of Mining and Metallurgy, 111: 437-442.