Ore beneficiation methods
Ore beneficiation methods:
are used to increase the metal content in the ore. This is achieved by removing most of the waste rock, as well as selective enrichment with subsequent production of concentrate. If the ore contains secondary elements of interest and economic value, then this problem is solved by collective enrichment (collective flotation) with subsequent separation of each metal into a separate product suitable for further enrichment or processing. For example, non-ferrous metal ores are characterized by a multi-component composition; as a result of enrichment of such ores, up to 5-6 concentrates of various elements are obtained. Conditionally, enrichment methods can be divided into the following stages:
- Ore crushing. Crushing is performed for the most complete opening of intergrowths, as a result of which valuable ore components are separated from waste rock as much as possible, however, crushing is a rather knowledge-intensive process, as it requires careful analysis of the ore to select the required crushing size. Over-crushing can significantly worsen subsequent enrichment processes.
- The processes that are mainly used for primary enrichment include magnetic separation processes, gravity enrichment, etc.
- The most widespread and efficient enrichment processes are provided by flotation processes.
Preliminary enrichment of ore raw materials provides the following advantages:
- Increases the complexity of using raw materials by separating valuable components into separate concentrates suitable for further independent metallurgical processing.
- Reduces the cost of subsequent metallurgical operations and lowers the cost of the final product primarily by reducing the volume of processed materials.
- Allows processing of poor ores that are not suitable for direct metallurgical processing.
Flotation is a method of enrichment based on the selective adhesion of mineral particles suspended in the pulp to air bubbles. Mineral particles that are poorly wetted by water adhere to air bubbles and rise with them to the surface of the pulp, forming mineralized foam on the surface of the pulp. Particles that are well wetted by water remain in the internal volume of the pulp. However, such separation is only possible with the use of flotation reagents - organic and inorganic compounds. Reagents, depending on their purpose, are divided into collectors, foaming agents, depressors, activators and environmental regulators.
Collectors are reagents that selectively reduce the wettability of certain mineral particles with water. These include potassium (less often sodium) xanthates.
The most commonly used foaming agents are aliphatic alcohols, phenols, cresol and a number of other synthetic compounds based on propylene and ethylene oxides. The main effect of foaming agents is to reduce the interfacial tension at the liquid-air boundary, resulting in the formation of smaller air bubbles in the pulp, which in turn leads to the formation of a strong and stable foam.
Depressants delay the flotation of any mineral, as if suppressing it. They promote the formation of a well-wetted surface on the mineral.
Activators have the opposite effect to depressants, restoring the floatability of depressed materials.
Environmental regulators are used to create an environment with specific physical and chemical properties.
Flotation is carried out in devices called flotation machines.
Each element in the ore can be matched with a reagent that either enhances the floatability of the element or worsens it. The entire spectrum of reagents and their basic properties can be found in special reference books on flotation.
