Attrition mill

Details Attrition mill Attrition mill

1996-10-11

1998-08-25

Rosenbaum, Mark

Solid material comminution or disintegration

Apparatus

Loose grinding body comminutor

241172, B02C 1714

Patent

active

057975507

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an attrition mill and a method of, and apparatus for, classifying fine particles in a slurry of coarse and fine particles. More particularly, the invention relates to a classification system and a separation system for an attrition mill which permits outlet of ground mineral fines and a small quantity of spent grinding media from the mill while retaining useful grinding media in the mill for further attrition.


BACKGROUND OF THE INVENTION

Hitherto, attrition mills have been mainly used for high value low throughput applications (e.g. below about 10 cubic meters per hour). The present invention was developed for use in mineral beneficiation in the mining industry which requires higher throughput volume than other industries in which attrition mills have previously been used.
Although the invention is herein described with particular reference to its use in a mill, it is not limited to that use and may have more general application in particle separation.
The term "attrition mill" is herein used to include mills used for ultra-fine grinding for example, stirred mills in any configuration such as bead mills, peg mills; wet mills such as ball mills, colloid mills, fluid energy mills, ultrasonic mills, petite pulverisers, and the like grinders. In general, such mills comprise a grinding chamber and an axial impeller having a series of mainly radially directed grinding elements such as arms or discs, the impeller being rotated by a motor via a suitable drive train. The grinding elements are approximately equally spaced along the impeller by a distance chosen to permit adequate circulation between the opposed faces of adjacent grinding elements and having regard to overall design and capacity of the mill, impeller speed and diameter, grinding element design, mill throughput and other factors.
Such mills are usually provided with grinding media and the source material to be ground is fed to the mill as a slurry. Although the invention is herein described with particular reference to the use of exogenous grinding media, it will be understood that the invention may be applied to mills when used for autogenous or semi-autogenous grinding. In the case for example of a stirred mill used for grinding pyrite, arseno-pyrite, or the like, the grinding medium may be spheres, cylinders, polygonal or irregularly shaped grinding elements or may be steel, zircon, silica-sand, slag, or the like. In the case of a bead mill used to grind a sulphide ore (for example galena, pyrite) distributed in a host gangue (for example, shale and/or silica) the gangue may itself be sieved to a suitable size range, for example 1-6 millimeters or 1-4 millimeters, and may be used as a grinding medium. The media size range is dependant on how fine the grinding is required to be. From about 40% to about 95% of the volume capacity of the mill may be occupied by grinding media.
It should be recognized that in the grinding process, grinding media undergoes size reduction as does source material to be ground. Grinding media which is itself ground to a size no longer useful to grind source material is referred to as "spent" grinding media. Grinding media still of sufficient size to grind source material is referred to as "useful" grinding media.
A source material to be ground, for example a primary ore, mineral, concentrate, calcine, reclaimed tailing, or the like, after preliminary size reduction by conventional means (for example to 20-90 microns), is slurried in water and then admitted to the attrition mill through an inlet in the grinding chamber. In the mill, the impeller causes the particles of grinding media to impact with source material, and particles of source material to impact with each other, fracturing the source material to yield fines (for example 0.5-25 microns). It is desirable to separate the coarse material from the fines at the mill outlet so as to retain useful grinding media and unground source material in the mill while permitting the fines and spent grinding media to exit

REFERENCES:
patent: 4784336 (1988-11-01), Lu
patent: 5312051 (1994-05-01), Preisser
patent: 5333804 (1994-08-01), Liebert
patent: 5566896 (1996-10-01), Stehr et al.
patent: 5597126 (1997-01-01), Frommherz et al.
patent: 5620147 (1997-04-01), Newton
patent: 5630557 (1997-05-01), Barthelmess
Derwent Abstract, Accession No. 94-133115/16 Class P41, SU 1793962 A3 (Teckhnoint Stock Co) 7 Feb. 1993.

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