Magnetic Separation and Iron Ore Beneficiation Oct04

Magnetic Separation and Iron Ore Beneficiation...

Magnetic Separation and Iron Ore Beneficiation Magnetic separation is an old technique for the concentration of iron ores and for the removal of tramp iron. Since 1849, a number of patents on magnetic separation have been issued in USA, and texts of some of the patents before 1910 describe a variety of magnetic separators for mineral processing. Magnetic separation methods are used to take the advantage of the difference in the magnetic properties for separating iron ore from the non-magnetic associated gangue materials. Magnetic separation can be conducted either in a dry or in a wet environment, although wet systems are more in use. Magnetic separation is a physical separation of discrete particles based on the three way competition between tractive (i) magnetic forces, (ii) gravitational, hydro-dynamic drag, frictional, or inertial forces, and (iii) attractive or repulsive inter-particle forces. These forces combine to act differentially on particles of differing magnetic properties in the feed material. Fig 1 shows the principle of the magnetic separation. Fig 1 Principle of magnetic separation The forces in the magnetic separators which compete with the magnetic forces and act on all of the particles which travel through the separator are those of gravity, hydrodynamic drag, friction, and inertia. Depending on the type of magnetic separator, certain of these forces can have higher or lesser importance. The gravitational force is significant for large particles while the hydrodynamic drag force is significant for the small particles. Thus in the magnetic separator which treats large particles in dry form, the feed material passes through the force of gravity. The magnetic forces need to be sufficient to hold the magnetic particle against the competing force of gravity. In a wet separator for small particles, the magnetic force need to be larger than the...