Magnetic Separator

From Wikiwaste

A Magnetic Separator is a machine that is used to separate and recover ferrous, magnetic metals such as iron and steel from the non-magnetic fraction in the waste stream. This is achieved by passing waste materials, via a conveyor, over or under strong magnets.

Crossbelt Overband Magnet on MSW - Magnapower Image all rights reserved
Crossbelt Overband Magnet on MSW - Magnapower Image all rights reserved


Overview

A Magnetic Separator separates out the ferrous portion of the waste stream from the non-ferrous. The separation process extracts strongly magnetic (ferromagnetic) and even weekly magnetic (paramagnetic) materials by passing the waste stream over (or under) powerful magnets[1]. The conventional use of magnetic separation can be placed into two categories: the purification of feeds with magnetic components (with the desired product being non-magnetic) and the concentration of magnetic materials (with the desired product being magnetic)[2]. Close control of the speed of passage through the magnetic field is essential for efficient sorting/recovery rates[3].

Applications[4]

Benefits

  • Large capacity
  • High efficiency
  • Continuous process
  • Low operating cost[5]

The Process

There are two primary types of Magnetic Separator:

  • Overband Magnets (which include electromagnetic overband magnets) - where the waste is passed under a magnet and a rotating conveyor belt pulls the ferrous metal away from the transporting conveyor. There are two types of configuration for overband magnets
    • Inline Overband Magnets - where the magnet and extracting conveyor are aligned with the transporting conveyor
    • Crossbelt Overband Magnets - where the magnet is at right angles to the transporting conveyor
  • Drum Magnets where the waste is passed over a rotating magnet to pull the ferrous metal away from the transporting conveyor belt

Overband Magnet

Overband Cross Belt Schematic - Magnapower Image - all rights reserved
Overband Cross Belt Schematic - Magnapower Image - all rights reserved

Schematic Diagram of a Crossbelt Magnetic Separator[4]
1. The feed material is fed onto the conveyor belt and is transported under the magnet.
Crossbelt Overband Magnet - Magnapower Image - all rights reserved
Crossbelt Overband Magnet - Magnapower Image - all rights reserved
2. The ferrous material is drawn up towards the magnet from the waste stream.
3. A rotating conveyor with paddles carries the ferrous material over the side of the transporting conveyor where it drops out of the magnetic field into a separate bin.
4. The non-magnetic material continues on the transporting conveyor unaffected by the process.

Drum Magnet

Magnetic Separator Diagram. All Rights Reserved.
Magnetic Separator Diagram. All Rights Reserved.

Schematic Diagram of a Drum Magnetic Separator[1]
1. The feed material is fed onto the conveyor belt and is transported towards the magnetic pulley end.
Drum Magnet - MangnaPower Image, all rights reserved
Drum Magnet - MangnaPower Image, all rights reserved
2. The waste stream falls off the end of the pulley and travels downward by the combined action of gravitational and frictional forces.
3. Magnetic forces produced by the stationary magnets within the pulley hold the ferrous material against the rotating drum and deposit them in the ferromagnetic bin.
4. The diamagnetic (non-magnetic) material falls into a separate bin as they are repelled from the magnetic field[1].

References