GB1364474A - Waste treatment and paper fibre reclamation system - Google Patents

Abstract

1364474 Wet separating BLACK CLAWSON FIBRECLAIM Inc 19 April 1971 [26 Feb 1970 12 March 1970 1 Dec 1970] 24356/71 Heading B2H [Also in Division Dl] Fibres of papermaking length are recovered from municipal refuse comprising mixed waste paper, some admixed with inorganic and other organic material. In its broadest aspect, the recovery process comprises (a) treating the mixed refuse with an aqueous (liquid) medium to form a suspension, (b) mechanically treating, e.g. by agitation, the suspension of (a) to reduce the frangible portion of the refuse to particles of less than a predetermined size, (c) treating the slurry product of (b) in a centrifugal separator to divide it into acceptable material including all organic material and rejected material including most inorganic particles and (d) screening accepted material from (c) so as to reject the (relatively coarse) organic particles whilst retaining at least the major portion of the fibres of papermaking size ranges therein. In the process represented in Fig. 1, a conveyor 14 continuously deposits refuse in a vessel 10 to be treated by a rotor 11 with flail or hammers 13 in a liquid supplied by a line 18 through a junk remover 15 and conduit 16 (the former removing infrangible materials such as iron castings or metal cans) and large particles of frangible materials are extracted through holes in an extractor plate 17. The material extracted from vessel 10 as aqueous slurry is forced by pump 20 to a centrifugal cleaner 22 which "accepts" material mainly composed of paper and some other organic materials which pass to a holding tank 23 whence the slurry is delivered by a pump 24 to coarse screening apparatus 25 and accepted slurry thereferom passes to a fine screen 26. The screen's separate a portion of reusable papermaking fibres from the other constituents, such as a major part of the wood and other vegetation, textiles, plastics, food waste, metal foil, rubber, leather and undefibred wet strong paper, which are carried by a conduit 29 to a secondary screen 30 accepted material from which returns to holding tank 23 for recirculation through screens 25, 26, whilst "rejects" pass to agitator chest 31. A holding tank 32 receives "accepts" from screen 26 and topping-up water from supply 33, pump 34 forces material therefrom to a centrifugal cleaner 35 which removes all of the inorganic materials such as glass, metal, dirt and sand and also odd-shaped organic particles, such rejects being pumped through a common line 37 to secondary centrifugal cleaner 39 from which the accepts are recirculated through line 40 to tank 32 and rejects pass by line 41 to chest 31. Accepted slurry from cleaner 35 is delivered by line 36 to fibre selecting apparatus 42, e.g. of-a construction described in U.S. Patent Specification 1,786,973, retained acceptable shock passing to dewatering devices 43 and 50 and rejects passing to a clarifier chest 44. Dewatered material passes by line 53 to a feeding device, e.g. screw feeder, for delivery to a digester 55 which subjects the material to heat and/or supersteaan to disperse grease, asphalt, printing ink, and digest any remanent food waste and/or vegetable contaminants. Discharged material is conveyed to a holding tank 56 thence by a pump 57 to a washer 60 to which washing liquid is supplied at 59. Washed material is dewatered in a press 61 then passes to a station 62, e.g. a papermaking machine or a fibre baler, and wash liquid passes to a holding chest 63 from which some liquid is returned by a pump 64 to tank 56 and the balance removed from the system at 65 for disposal. Liquid removed by press 61 may be recycled, e.g. to vessel 10. Solids in suspension withdrawn from chest 31 by a pump 66 are passed to a dewatering device 67 (screw thickener type) thence by a conduit 68 to additional dewatering presses 70 in preparetion for final disposal, e.g. by fluidised bed reactor 71 in combination with a blower 72. Clarified liquid from clarifier 44 is conveyed to water chest 75 thence by pump 77 through conduit 78 to inlet 18 to vessel 10: additional liquid (probably containing some solids) bled off at 80 is forced by pump 82 to a filter 83, the removed solid material passing by line 84 to presses 70 and liqiud return by line 85. In a modification, Fig. 2 (not shown) line 53 conveys' fibrous materials and contaminants to screw feeder 54 while a volatile solvent, e.g. trichloroethylene, is fed through an additional line 88 into digester 55: material therefrom passes to a blow tank (90) from which the solvent may be recovered. Large particles of light weight materials, e.g. grass and shrubbery clippings, which tend to become entrapped with papermaking fibres, may be removed at any appropriate stage by directing slurry containing such materials to refining apparatus (100), Fig. 3 (not shown), e.g. of the disc type operating with minimum clearance between refining plates, thence to a froth flotation tank (102) and/or centrifugal cleaner (104). Paper fibres may be recovered for reuse in selected fractions, Fig. 5 (not shown).