Minpro Pty. Limited

Murray H Pryor

Jeremy James Lees

John R Andrews

Andrew J Dalzell

A process for the recovery of coal particles having a maximum dimension of less than 2 mm from coal tailings including the steps of forming a slurry (101) of tailings having a pulp density of from 10 to 30% by weight; feeding the slurry into a hydrocyclone (103) to produce an underflow second stream which contains the tailing particles over a predetermined size and some of the gangue particles smaller than that size and an overflow stream containing the coal particles smaller than the predetermined size and the balance of the gangue particles, the hydrocyclone (103) being operated such that the underflow stream has a pulp density of from 40% to 60% by weight; adjusting the pulp density of the second stream, if required, to from 20 to 50% by weight; passing the repulped second stream over a rapped or vibrated sieve screen deck (105) having a wedge wire sieve screen with a radius of less than 2 m, an arc angle of from 45.degree. to 60.degree. and a slot aperture of from 80 microns to 500 microns to form a stream of coarse particles substantialy all having a particle size greater than 65 microns; and passing the course particle stream from the sieve screen deck, after repulping to a pulp density of from 20 to 50% by weight, to a spiral separator (108) for fractionation according to density to separate the coal from the gangue.

Process for recovering course particles from tailings

A multi-start spiral separator for separating particles in a stream of such particles according to their respective densities and/or sizes comprises a plurality of substantially helical troughs arranged around a common axis which is substantially vertical, each trough including at an upper end an upwardly-facing open fluid-receiving portion and at a lower end an outlet, and a fluid delivery pipe which delivers fluid to the spiral separator so that fluid is distributed to the receiving portions of the helical troughs uniformly.

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Roseville, Australia

Murray H Pryor