GB1288016A - - Google Patents

Abstract

1288016 Separating and drying coal BIRD MACHINE CO 2 June 1971 [9 July 1970] 18645/71 Heading B2H Coal containing refuse is converted to a usable coal product having a predetermined maximum moisture content by (a) separating wet, refuse-containing coal into fractions according to particle size, including a finest fraction and at least one larger fraction; (b) removing refuse at least from said larger fraction; (c) dewatering said larger fraction to a moisture content below said predetermined moisture content; (d) mechanically dewatering said finest fraction in a continuous centrifuge of the screen bowl-type to provide a finest coal output of a moisture content above said predetermined maximum which when the said fractions are recombined, will provide a confined moisture content within said predetermined maximum; and (e) recombining the dewatered fractions to form the desired product. In one embodiment, Fig. 1, raw coal is screened at 12 into a first coarse fraction which is dewatered into an oscillating centrifuge dryer 14 and into a second fraction which passes with effluent from centrifuge 14 to a cleaner 18, e.g. concentrating table, cyclone or jig, which removes refuse particles. The cleaned coal fraction from 18 is screened at 20 into a medium fraction which is dewatered in an oxillating centrifuge dryer 24 or a thermal dryer and a finest fraction which passes to a froth flotation apparatus 30 for removal of further refuse particles. The cleaned coal slurry from 30 is dewatered in a continuous screen bowl centrifuge 34. The fractions from 14, 24 and 34 are delivered to a bin 16 where they are mixed to give the desired product. Instead of the froth flotation apparatus 30 a hydrocyclone may be used. Refuse from cleaner 18 is dewatered on a screen 40 and delivered to a container 42. Effluent from the downstream screen portion of centrifuge 34 is returned to flotation apparatus 30 while effluent from its upstream imperforate portion is directed with effluent from screen 40 and refuse from apparatus 30 to a thickener 48 of which the overflow may be recirculated, e.g. for initial wetting of coal, and the underflow is sent to a solid bowl centrifuge 50. The solids from the latter are discharged into container 42 whereas the effluent is recirculated to thickener 48.