Introduction to Mineral Processing

Sometimes, during introductions to mineral processing we consider it only as an art and not as a science. The statement mentioned is partially true due the fact that many times practical aspects determine the success of a particular process, however never must be forgotten that basic and technical information related to mineral processing is founded on a variety of engineering and science areas.

The mineral processing industry depends to a large extent on energy costs. Such as that economics and the environment are closely linked. The most energy intensive operation in the minerals industry is the pyrometallurgical operation of smelting and it is the objective of mineral processing to reduce the bulk of material which has to be smelted. Improved efficiencies and optimization not only reduce losses of material, but also let operations more selective which reduces smelter feed weights in relation to throughput of a mine. So mineral processing has an important role in minerals industry economics and environmental aspects.

Once the ore is extracted from the mine is sent to the processing plant where the objective is to obtain a concentrate of a valuable mineral. There is a sterile part called tailings which are many times an issue very important at the moment of beginning any metallurgical project. The processing plant employs essentially two operations: comminution and concentration. The comminution has as unique objective to liberate the valuable particles from the no valuable minerals (gangue). This operation involves crushing and grinding steps. It is believed that grinding is often the greatest energy consumer in a mineral processing plant. As it is this process which achieves particles liberation, it is also important to obtain a good separation between particles. Thus, in order to obtain clean concentrates is necessary to grind the ore fine enough to liberate the associated minerals. So grinding is a compromise between high grade concentrates and operating costs.

The concentration processes are variable and must be chosen according to the type of ore to be treated. The main processes are gravimetric which makes use of settling velocity; electrical and magnetic which are based on the ore behaviour through a electric or magnetic field, and froth flotation which employ chemical reagents to create special conditions on the mineral surface. The latter one is perhaps the most polemical process due to the diversity of options and choices at the moment of selecting and design a flotation circuit.

The mineral processing industry has done a big important improvement in their results after adopting some advanced computer based tools for designing, optimization and control strategies. For example in a comprehensive system, with a variable speed drive and classifier feed flow and density control, circulating load and slurry density are calculated on line. Product sizing is estimated from overflow and flotation parameters can be ready to receive any change.

As can be observed, nowadays the mineral processing industry trends to work under the most optimal conditions which give the best metallurgical results and also lead to reduce the operative costs so that the revenues can be optimal. However, many times concentration operations are no simple and the real actors are the skilled workers.