Recycling of abrasives from wasted slurry by superconducting magnetic separation

Abstract

Abrasives have been recovered from the slurry wasted of the factory where the silicon wafers for solar battery are processed. The slurry consists of oil and abrasives and is used in the wire saw. The viscosity of the slurry is carefully controlled to maintain a high cutting performance though it tends to be high as the silicon powder is accumulated in the slurry. The cutting performance of the slurry decreases as the amount of the silicon powder increases. The abrasives, however, still have enough performance to cut the silicon wafers. Iron segments of the wire saw were found to attach to the SiC abrasives. The iron segments magnetize the abrasives in the mechanochemical process and thus reduce the cutting performance of the abrasives. Due to the iron segments presence the abrasives with poor cutting performance could be separated from the slurry by means of superconducting magnetic separator. After the magnetic separation a centrifugal separator was used to separate the silicon powder. It was confirmed that the superconducting magnetic separation is applicable to this practical application.