(19)
(11) EP 0 298 777 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
07.02.1990 Bulletin 1990/06

(43) Date of publication A2:
11.01.1989 Bulletin 1989/02

(21) Application number: 88306282.0

(22) Date of filing: 08.07.1988
(51) International Patent Classification (IPC)4: B02C 23/12, B02C 21/00, B02C 23/36
(84) Designated Contracting States:
AT BE CH DE FR GB IT LI NL SE

(30) Priority: 09.07.1987 GB 8716213

(71) Applicant: ALCAN INTERNATIONAL LIMITED
Montreal Quebec H3A 3G2 (CA)

(72) Inventors:
  • Askew, Herbert Frank
    Weston Turville Aylesbury Bucks HP22 5TG (GB)
  • Brown, Stephen Clifford
    Northolt Middlesex (GB)

(74) Representative: Lightfoot, Robert Oscar et al
Raworth, Moss & Cook 36 Sydenham Road
Croydon Surrey, CR0 2EF
Croydon Surrey, CR0 2EF (GB)


(56) References cited: : 
   
       


    (54) Method of producing fine particles


    (57) This invention relates to a method of reducing the particle size of solid particles and is applicable to the production of very fine particles of a wide variety of solids, includuing relatively hard solids.
    The method comprises milling a liquid suspension of solid particles in an agitated media mill (13), pumping the milled suspension through a particle size classification device (16) to separate the slurry into a coarse fraction (17) and a fine fraction (18), the particles of the coarse fraction having a greater median particle size than the particles of the fine fraction, recycling the coarse fraction (17) from the particle size classification device to the input of the mill (13), and recycling the fine fraction (18) by pumping (15) it to the classification device, wherein recycling of both coarse and fine fractions are continued until solid particles of the desired reduced particle size are produced.
    Preferably a single classification device and a single mill can be used, and particles having a median particle size of 0.3 microns or less and a relatively narrow particle size distribution can be produced, even using a hydrocyclone as the classification device.







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