Sedimentation and electro-osmotic dewatering of coal-washery slimes

✍ Scribed by Neville C. Lockhart

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 620 KB
• Volume: 60
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(81)90086-7

✦ Synopsis

Dewatering of three samples of fine-tailings from two Australian coal washeries, where the clay content of the tailings is predominantly either the swelling or the non-swelling type, is examined on the laboratory scale. Thixotropic slurries of ~55 wt% solids are achieved by sedimentation of the crude or prethickened tailings. Electra-osmotic treatment of these slurries yields a moist but load-bearing material ~67 wt% solids up to a relatively dry, hard, and compact cake M 80 wt% solids, at a power consumption equivalent to 5-8 and 40-50 kWh, respectively, per tonne of the 55 wt% slurries. The corresponding cost per tonne of particulate matter present, at 2.2 cents kWh_', is 20-32 cents for 67 wt% solids and $1.6& $2.00 for 80 wt% solids. (To express these costs per tonne of moisture removed, multiply by 5.6 and 3.2 respectively). The only mechanical process currently used at Australian coal washeries is centrifugal dewatering of thickener underflow after conditioning with polyelectrolyte.

A wet, non-load bearing product (37 wt% solids in the one sample tested) is obtained at a cost in the range $I-$2 per tonne of particulate matter present. If an efficiency similar to that for the laboratory electroosmotic treatment can be realised on the industrial scale, then the comparison favours the electro-osmotic treatment, particularly considering that the drier product could be saleable as a fuel.