The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadropole magnet. The open gradient magnetic field further segregates the paramagnetic particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin.

Apparatus for magnetic separation of paramagnetic and diamagnetic material

A large bore, high gradient superconducting quadrupole magnet has been fabricated and tested which generates a gradient of 60 T/m in a cold bore 12.7 cm in diameter and 2.8 m long. The magnet operates safely without active quench protection and the unwanted multipole fields of the magnet sum to four parts per thousand at a bore radius of 5.0 cm. The magnet has been exposed to a neutral secondary beam at Fermilab produced by targeting a 400 GeV/c primary proton beam on a 30 cm Be target. When operated at a gradient of 52.5 T/m (86% of short sample) the magnet is quenched at a primary beam intensity of 6 x 1011 protons per one second spill. The corresponding energy deposition in the magnet coils has been calculated to be 2 mJ/cm3.

Performance Results of a Low Current, High Gradient Superconducting Quadrupole Magnet

A superconducting quadrupole magnet has been fabricated and tested that generates a gradient of 60 T/m at a peak operating current of 1100 amperes. The cold bore of the magnet is 12.7 cm in diameter and 2.8 m long, and the unwanted field multipoles sum to 4 parts per thousand of the quadrupole field at a bore radius of 5.0 cm. The magnet operates safely without quench protection and peak coil temperatures following quenches deliberately induced at full field do not exceed 50 K. Testing at the design gradient of 50 T/m indicates a beam energy deposition quench threshold of approximately 5 mJ/cm3.

D. Underwood

Papers

A safe, low current, high gradient, superconducting quadrupole magnet for high energy physics beam transport