Macroeconomia

Chapter 2

2.3 Mineral processing techniques
The purpose of mineral processing is to turn the raw ore from the mine into a marketable product.

2.3.1

Equipment

The following information isall taken from [105, Wotruba, 2002]. 2.3.1.1 Comminution

Comminution is an essential element of mineral processing. It requires a great deal of expenditure in terms of energy consumption andmaintenance. In comminution, the particle size of the ore is gradually reduced. This is necessary for many reasons, e.g.:

   

to liberate one or more valuable minerals from the gangue in an orematrix to achieve the desired size for later processing or handling to expose a large surface area per unit mass of material, thus aiding some specific chemical reaction (e.g. leaching) to satisfymarket requirements relating to particle size specifications.

Comminution is composed of a sequence of crushing and grinding processes. After grinding, the ore, often in slurry form, ‘contains’ the nowliberated ore particles and the tailings material which need to be separated in later process steps. The characteristics of the ore, in combination with the equipment used for the crushing andgrinding, determine the physical properties of the tailings, such as the particle shape and particle size distribution.
2.3.1.1.1 Crushing

Crushing is the first stage in the comminution process. This isusually a dry operation, which involves breaking down the ore by compressing it against rigid surfaces or by impacting it against hard surfaces in a controlled motion flow. This process step preparesthe ore for further size reduction (grinding) or for feeding directly to the classification and/or concentration separation stages. Tailings are usually not generated in this process step. Typicaltypes of crushers are:

    

jaw crushers gyratory crushers cone crushers roll crushers impact crushers.
Grinding

2.3.1.1.2

Grinding is the final stage in the comminution process and...