Abstract: 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.

Abstract: 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.

Abstract: An hydraulic spiral separator (10), for separating minerals, having at least one substantially helical trough (11) of a cross sectional shape comprising a base portion, an upwardly directed wall portion radially outwardly of the base portion and an upwardly directed lip radially inwardly of the base portion. The characterizing feature is that the wall portion is connected to a plurality of support members (12) positioned radially outwardly of the wall, and the lip is free and unconnected directly to any supporting means, which enables a number of spirals to be stacked coaxially thus saving floor space. Optionally the trough (11) is made of flexible material so that by varying the attachment to the support members (12) the trough may be flexed to change its pitch. Inlet pipes (16), and (18) are fitted as are conventional splitters (19) having moveable vanes (21).