Abstract
KHD Humboldt Wedag AG developed an improved version of a drum–type magnetic separator PERMOS with special magnetic field configuration for the NdFeB permanent magnets which is giving the magnetic field strength of 0.7 Tesla and a wide working range outside the drum. The magnet system within the PERMOS unit is no longer made of relatively large magnet blocks of alternate radial magnetisation; the system is now made up of a multitude of small NdFeB bars with a specially oriented magnetisation. This open-gradient magnetic separator can be used for dry magnetic separations in “top–feed” or “free–fall” feed configuration as well as in the conventional wet “drum–type” feed mode. It allows high throughput rates of up to 40 tonnes of solids per hour per meter of the drum length without any dogging problems in case of higher magnetite content in the feed material. Important design features and the actual machine characteristics of the improved PERMOS units for dry and wet magnetic separation are described and typical examples for their commercial application for industrial minerals and for martitic iron ores are presented.