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Description
The paper describes the commissioning of a conduction-cooled NbTi magnet system for Superconducting Magnetic Density Separation (SMDS), as well as its preliminary field tests on-location at the industrial end-user. MDS is a relatively new sorting technology that allows to sort multiple non-magnetic materials simultaneously, based on their mass density. A ferrofluid carries a mixed particle stream through the vertical magnetic field gradient of a flat-bed magnet, causing different materials to float at different heights. By using flat race-track type coils and minimizing their distance to the room-temperature ferrofluid, the magnetic field gradient can be maximized.
The magnet system with a flat-bed size 1.1 x 1.4 m$^2$; stored energy 0.74 MJ; operational current 300 A; and 5.2 T peak magnetic field in the windings was designed and constructed at the University of Twente. Key design choices were the use of a conduction-cooled dry magnet - allowing for a single-walled cryostat - and the use of stay rods that support the flat top plate of the D-shaped cryostat – allowing to minimize its thickness. The three 0.3 x 1.4 m$^2$ racetrack coils are shrink-fitted side-by-side in an aluminum alloy cassette that provides both thermal pre-stress and cooling. The coils are cooled to 4.5 K with a 1.5 W @4.2 K GM cryocooler and generate a maximum gradient of 20 T/m at the fluid bed.
We present the cryogenic performance, EM test results and quench protection of the magnet, that reaches nominal operation both with and without the ferro-fluid present. In addition, the first successful separation test with the system at the end-user’s premises are reported, including sorting campaigns with various waste materials.
| Submitters Country | Netherlands |
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