Influence of Water Balance and Classifier Choice on Energy Efficiency of Milling Circuit

A Hinde, E. Ford, J. Makola, A. Jain

Copper Cobalt Africa, 10-12 July 2018, Livingstone, Zambia


A large contributor to the energy consumption of metallurgical plants is the mill circuit. A popular circuit configuration is one involving a primary open-circuit semi-autogenous mill followed by a secondary ball mill operating in a close circuit with hydrocyclones.

The objective of the secondary circuit is not only to minimise the energy required to liberate the valuable mineral species but also to yield a product that optimises the residence time of the downstream leach tanks and/or floatation cells. Unfortunately, the energy-efficient operation of the milling circuit implies that the hydrocyclones must be fed at low pulp densities (corresponding to about 20% solids by volume). This results in a very dilute circuit product, leading to sub-optimal residence times for the leaching tanks or flotation cells, which should also be fed at pulp densities of about 20% by volume. Accordingly, the hydrocyclone overflow product should be dewatered and thickened before it can be treated downstream.

It is shown how high classification and overall plant efficiencies can be achieved by using in-circuit dewatering hydrocyclones and by replacing the classifying hydrocyclones with modern fine screening technology.


A Hinde (1), E. Ford (2), J. Makola (3), A. Jain (4)

  1. Independent Comminution Consultant, Johannesburg, South Africa. Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
  2. Mintek, Randburg, South Africa
  3. Derrick Solutions International, Johannesburg, South Africa
  4. Derrick Corporation, Buffalo, New York, USA


CEEC acknowledges and thanks SAIMM for organising Copper Cobalt Africa, incorporating the  9th Southern African Base Metals Conference. Conference paper can be found here.