Radial distribution of iron oxide and silica particles in the reject flow of a spiral concentrator

• A specific splitter is used to divide the reject flow of a spiral classifier into 6 streams.
• Coarse iron carrier particles are found in the inner and outer zones of the reject stream.
• Coarse silica carrier particles are not concentrated in the inner stream bands of the reject.

Spiral concentrators are used in the iron ore industry to separate heavy iron oxide carrier particles from the light silica ones. Losses of iron occur mainly in the fine (− 75 μm) and coarse (+ 600 μm) size fractions. This paper analyzes the radial distribution of iron oxide and silica particles in the reject of a 7 turn spiral. A splitter divides the reject flow into six (6) streams that can be sampled individually. Results show that coarse iron carrier particles settle mainly in the inner part of the spiral trough. Although fine iron particles are mostly concentrated in the outer part of the spiral trough, a significant proportion of these particles remain captive close to the concentrate ports. Coarse silica particles (+ 600 μm) are not concentrated in the innermost part of the spiral trough, while a significant concentration of silica particles in the size range of 75 to 212 μm is found close to the concentrate ports. This observation is coherent with the size of the silica particles that contaminate the spiral concentrate.