The basic rudiments of mineral beneficiation have not changed for many years. The techniques have been improved, but are still essentially the same, using either a materials weight, density, shape or magnetic susceptibility to enable separation. For removing impurities from non-metallic minerals, such as silica sand, typical methods include Flotation, Gravity and Magnetic separation.
Magnetic separation offers mineral processors many key advantages over other technologies. Environment issues and costs continue to dominate the thoughts of mineral processors, especially in Europe and North America. Some projects are simply not proceeding because of the environmental costs. Fortunately, magnetic separation is a clean technology as no chemicals are required resulting in no chemical waste to dispose of. In many dry processes, permanent magnets are used but in wet processes, the magnetic field is produced using electromagnets which means maintenance is minimal, operation is simple and costs are reduced.
There are some limitations to using magnets. For instance, magnetic separators will only separate particles that are magnetically susceptible. However, higher magnetic fields and changes in the way the materials are processed, means that the range of minerals that can now be influenced by a magnetic separator has widened substantially. Also, when compared to other technologies such as flotation, there were concerns about the ability to handle large capacities, with several banks of magnetic separators being potentially required.
With the latest developments, these concerns are no longer valid.
Magnets: A viable alternative to flotation for sand producers