Separation by particle shape — The RecGlass device

• Equipment was developed to recover glass contained in urban waste.
• The equipment developed is to be used in dry conditions.
• The equipment explores the difference of particle shape.
• Around 70% of the stones were removed through the processing of the waste.
• About 80% of the glass contained in the feed was recovered.

Solid waste are today new ores needing innovative separation techniques or adaptations of the current ones used, for instance in mineral processing, for the recovery of materials. “RecGlass” is a device developed to separate materials with similar density but exhibiting different particle shape. It is inspired in the “vanner” and in the “Bartles cross belt” processes but it is applied in dry conditions to separate materials with specific weight slightly above 2 g/cm3 and particles in the range size 4 to 12 mm. In the work presented, it was applied to the processing of the heavy reject of Mechanical Biological Treatment of mixed Municipal Solid Waste aiming at the recovery of glass, the main constituent of this product, which is landfilled today, and to eliminate the stones, generally the second main inert constituent. The glass particles are predominantly flat while stones are sub-spherical. The core of the equipment is an inclined belt moving upwards. The particles are continuous and steadily fed by a vibrating feeder placed above the belt. Depending on the operational variables such as belt speed and slope and feed position, and also on the belt surface material, the flat particles move upwards and the round ones roll down.In the present paper the equipment is described and the physical principles of the concentration process are explained. Using samples of two different plants it was shown that it is possible to achieve a significant upgrading in glass. With a sample from one plant the glass content was increased from 88% to 92% while with a completely different sample, from another plant, the glass content in the process feed was 59%, attaining 71% in the glass concentrate. The recovery of the glass in the glass concentrate reached more than 80% by removing about 80% of the stones.