Extractive Metallurgy Principles

Nowadays, native metals practically have disappeared, and it’s necessary each day to apply basic extractive metallurgy principles and techniques to the treatment of ores or concentrates in order to get a particular metal. Many times, people are used to consider the metal extraction as mechanical processes that involve only routine operations. However, this statement is not exact because each operation is done considering chemical and physical principles. Then, to know, to understand and to find out the concepts to be used in each extraction process is very important because each metal is extracted following a particular route which can not be avoided.

Sometimes, can be necessary to concentrate the valuable minerals employing a process like froth flotation which is founded on chemical and physical laws such as superficial tension, wetting, collision, and kinetics. Well, each mineral can be concentrated according to a special process. The concentrate is sent to the next step where the metal will be obtained after several processes such as roasting, leaching and electrowinning. These processes belong to the Pyrometallurgy, Hydrometallurgy, and Electrometallurgy, respectively. The latter ones are built on chemical and physical laws, and again each metal is extracted following a particular route. Thus, try to find out the best process and its parameters are the key aspect to consider.

Other possibility is to treat the ore directly without a previous concentration step, so any extractive process can be used. Perhaps, the simplest example is the treatment of gold ores using a hydrometallurgical process like heap leaching, and later the pregnant solution can be treated by a Merryl-Crowe process, and finally will be used a smelting process. One more time, each process is done under particular parameters which are founded on chemical and physical principles. Evaluate the ore and find the best parameters are the initial steps of the ore treatment.

Also, when the ore is concentrated, smelters give an appropriate range to consider at the moment of treating any concentrate. For example, if an ore deposit contains a copper mineral as chalcopyrite. The final concentrate must not have a specific amount of bismuth, because the metallic copper to be obtained will be brittle. Then, will be necessary to investigate and understand how to reduce the bismuth content in the final concentrate.

Knowledge of the basic parameters lead to the formulation of several processes to be used which can be correlated and thus choose the more appropriate. This stage is done during the research step and no project can avoid this step. Avoid the research step can create a serious problem in the future because a process was selected randomly without any study. So, a well understanding of chemical and physical principles will let to get a good panorama of the treatment to be used.

With the basic principles we can distinguish the parameters that have influence in the process. The parameters are also involved in the plant design and the equipments to be used. A process design involves the preparation of a flowsheet that shows the main equipment, operating conditions, flow quantities, control instrument, heat and material balance. The process engineer and the metallurgist must work closely on those aspects so that the process can be real and effective.