Magnetic Separator

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.

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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].

Benefits

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

Application

  • Waste management applications - to remove the ferrous portion from different waste materials such as:
    • Dry Recyclables/DMR (mixed and twin streams)
    • MSW
    • C&I Waste
    • C&D Waste/Skip Waste
    • Waste Derived Fuel - to ensure reduction of metal in RDF and SRF to meet end specification
  • Scrap Metal Separation - to remove ferrous from mixed metal streams
  • Fridge Recycling Plants- to remove ferrous from mixed metal, plastic and glass stream
  • Tyres Recycling- to remove ferrous from rubber stream
  • Incinerator Bottom Ash - to remove ferrous from ash as part of production of IBAA
  • Biomass - to remove ferrous from Wood Waste to ensure purity for onward use
  • WEEE Processing - to remove ferrous from mixed metal and plastic streams
  • Window Frame Recycling - to remove ferrous from plastic streams

The Process

There are two primary types of Magnetic Separator

Types

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

  1. Inline Overband Magnets - where the magnet and extracting conveyor are aligned with the transporting conveyor
  2. 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

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Key to Diagram  

  1. The feed material is fed onto the conveyor belt and is transported under the magnet. 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

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Key to Diagram  

  1. The feed material is fed onto the conveyor belt and is transported towards the magnetic pulley end.
  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:

  1. Magnetic Separation
  2. Magnetic Separation: A Review of Principles, Devices, and Applications
  3. Magnetic and Electrical Separation
  4. Based on Information within Magnapower Website accessed Dec. 2021
  5. Developments in the physical separation of iron ore: magnetic separation

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