Optimisation and stabilisation of coal rejects at the Peabody Metropolitan Mine using Acti-Gel~R 208

摘要

The Peabody Energy Metropolitan Mine in New South Wales produces about two million tons of metallurgical-grade coal annually through an underground longwall mining operation, producing about 450 ktpa of coarse-grained rejects and ultra-fine tailings that require co-disposal. Currently, ~100 ktpa of these materials are processed to form high-density slurry that is pumped up to 2 km as backfill into underground voids. The balance of the waste is trucked and dumped, but the mine has a mandate to pump 100% of the rejects underground by the end of 2015 and to extend the pumping distance to at least 7 km.We conducted field trials to optimise and stabilise the slurry using Acti-Gel~R 208, a highly-purified Mg-aluminosilicate rheology modifier and suspending agent, at the Metropolitan Mine using the 100 mm NB pipe loop connected to the backfill pilot plant. Coal rejects used for the demonstration were comprised of a typical mix of ultra-fine, fine and coarse particles ranging to ~15 mm with the percent solids and process water adjusted to a target range of between 74-76% and a starting yield point of at least 100 Pa. To determine how the treatment affected the properties of each mix, baseline pipeline pressure data was collected for a period of about two hours prior to adding Acti-Gel. Slurry samples were taken at regular intervals thereafter to measure yield stress, specific gravity and other parameters in both treated and untreated mixes. Pumping tests were also conducted by varying the flow rate of each mix through the pipe loop from about 0.2-2.0 m/s and by ramping pump speed up and down with 15 minutes of stable operation at each speed in order to obtain pipeline pressure data.