Thomas, AD, Cowper Snr, NT & Whitton, S 2015, 'Recycling fine slurry – an alternative to paste for coarse rejects co-disposal in Queensland coal mines', in R Jewell & AB Fourie (eds), Proceedings of the 18th International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 419-432, https://doi.org/10.36487/ACG_rep/1504_32_Thomas
Conventional co-disposal of coarse rejects (minus 50 mm) and fine thickener underflow tailings (minus
2 mm) is practised at a number of Queensland coal mines. The two streams are combined and pumped together to disposal. However, with the ratio of coarse rejects to tailings typically being about 70:30 on a dry mass basis, it is necessary to add large quantities of water to reduce the volume concentration of coarse rejects to an acceptable pumpable level. At the disposal site, the low concentration fines wash through the coarse rejects, forming a pond at the toe of the deposit. Water needs to be recovered from the pond and pumped back to the plant, and some water is lost through evaporation. The deposit also requires significant management with earthmoving equipment.
An alternative co-disposal system is described, in which no dilution water is required. By recycling some of the minus 2 mm thickener underflow in a recycle pipeline, the required reduction in volume concentration of rejects in the mixture is achieved without water dilution. With a thickener underflow concentration of 50% by weight (w/w), the total mixture concentration discharged to disposal is up to 75% w/w, and the discharged mixture is essentially homogeneous with minimal separation of fines. The emplacement can take the form of a cone-shaped deposit, thereby greatly reducing the earthworks required. The net effect is that total costs are about half of that required for the current co-disposal systems.
The 75% w/w concentration achieved by recycling fines is similar to the concentration likely to be delivered by proposed laminar flow paste pipeline systems, and is achieved with more reliable turbulent flow operation, avoiding the uncertainties associated with laminar flow.
Jolin, M, Burns, D, Bissonnette, B, Gagnon, F & Bolduc, L-S 2009, ‘Understanding the pumpability of concrete’, in F Amberg &
KF Garshol (eds), Proceedings of Shotcrete for Underground Support XI, Engineering Conferences International, New York, viewed 9 February 2015,
Miura, H & Mase, S 1979, ‘Operation and maintenance of slurry transportation system at hydraulic coal mine’, in D Lambert (ed.), Proceedings of the 4th International Technical Conference on Slurry Transportation, Slurry Transport Association, Washington DC, pp. 43-50.
Morris, PH & Williams, DJ 1997, ‘Results of field trials of co-disposal of coarse and fine coal wastes’, Transactions of the Institution of Mining and Metallurgy, vol. 106, pp. A38-A41.
Paterson, AC & Watson, N 1979, ‘The NCB pilot plant for solids pumping at Horden Colliery’, in HS Stephens & L Gittins (eds), Proceedings of the Hydrotransport 6 conference, British Hydromechanics Research Association, Cranfield,
Prettlin, W & Gaessler, H 1976, ‘Bases of calculation and planning for the hydraulic transport of run-of-mine coal in pipelines according to the results of the hydraulic plants of the Ruhrkohle AG’, in HS Stephens, M Streat, J Clark & NG Coles (eds), Proceedings of the Hydrotransport 4 Conference, British Hydromechanics Research Association, Cranfield, pp. E213-E236.
Siebert, H, Kortenbusch, W & Harzer, H 1980, ‘Further experience with horizontal and vertical hoisting of coarse run of mine coal at Hansa hydromine’, in HS Stephens & L Gittins (eds), Proceedings of the Hydrotransport 7 Conference, British Hydromechanics Research Association, Cranfield, pp. 41-54.
Thomas, AD 1977, ‘A rational design philosophy for long distance slurry pipelines’, Chemical Engineering in Australia, pp. 22-33.
Thomas, AD 1979, ‘Pipelining of coarse coal as a stabilized slurry – another viewpoint’, in D Lambert (ed.), Proceedings of the 4th International Technical Conference on Slurry Transportation, Slurry Transport Association, Washington DC,
Wilson, KC & Thomas, AD 2006, ‘Analytic model of laminar-turbulent transition for Bingham plastics’, The Canadian Journal of Chemical Engineering, vol. 84, no. 5, pp. 520-526.