SIEVE SCREEN DECK AND SEPARATION METHOD

摘要

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 substantially all having a particle size greater than 65 microns; and passing the coarse 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.