1. Institute of Applied Materials, Department of Chemical Engineering, University of Pretoria, Private Bag X20, Hatfield, 0028 Pretoria, South Africa
2. Data Science, Sasol Operations Improvement, P.O. Box 1, Sasolburg 1947, South Africa
3. School of Industrial Engineering, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa