Recovery of silicon metal from dross

Summary

This project developed a separation process that would allow recovery of silicon from dross, for sale at a greatly enhanced value.

To recover the silicon metal two objectives had to be realised:

1. Development of a suitable mineral flotation technique to recover entrained silicon metal from dross; and
2. Development of a furnace melting process in which molten flotation concentrate is separated into a >99% Si product and a waste slag.

The flotation process produced a silicon-rich concentrate and a silicon-slag tailing, achieving a concentrate grade and recovery of greater than 90% from a dross feed containing 58 weight percent silicon.

The second stage of the two-part separation process involved melting the flotation concentrate, to upgrade the silicon to a saleable product with a grade of 99 weight percent silicon.

Large furnace trials produced silicon metal in excess of 98 weight per cent silicon when corrected for iron contamination.

Keywords: silicon metal, recovery from dross, mineral flotation