Iron particles are automatically separated by the rotation of the drum. These devices are also employed to control finished mixtures. The drum is housed in a robust casing and can thus be readily integrated into an existing tube system. The iron particles contained in the product are attracted by the permanent magnets through the rotating drum casing until they drift out of the magnetic field. They then fall into the discharge funnel for magnetic waste. The product should be spread evenly across the entire working length before it enters the device. This can be facilitated by connecting a distribution box or feed device.