Optimisation of Operational Parameters of A Spiral Classifier Using Design of Experiment (DOE).
Classifying Mn Ore to improve upon the grade and the properties has become a crucial activity for the Mn industry since it increases the market value of the ore. Ghana Manganese Company GMC) has renovated their oxide washing plant by integrating it with a spiral classifier to make a batch system operating process. Particle size of <3.35mm (Mn grade of 43-47%) obtained from the primary section of the plant served as feed to the classifier and with the plant condition (i.e. at 60 min washing time, 30 GHz speed of spirals and feed tonnage of 6 t) Mn grade of 49% was achieved. This paper focused on the optimization of some selected operational parameters of the classifier to obtain a Mn grade >50% using design of experiment (DOE). Series of test works were designed using the DOE for the classifier using the constraints of washing time (30-90 min), speed of spirals (20-40 GHz) and feed tonnage (6-9 t). The outcome of the test work after simulation showed that all the selected parameters had a great influence on Mn grade. The spiral speed and feed tonnage correlated negatively to the Mn grade with washing time correlating positively. Operating the spiral classifier at a feed rate, spiral speed and washing time of 6 tonnes, 25 GHz, and 30 respectively, yielded Mn grade of 52-54%. A Confirmatory test using the established conditions gave a Mn recovery of 53%, which is a 4% in increase Mn grade. Based on the outcome of the studies, the plant adhered to the newly established operational conditions and manganese concentrate with grade ranging between 52-54%.