Solid material comminution or disintegration – Apparatus – Loose grinding body comminutor
Patent
1986-10-06
1988-05-17
Goldberg, Howard N.
Solid material comminution or disintegration
Apparatus
Loose grinding body comminutor
241284, B02C 1700
Patent
active
047445254
DESCRIPTION:
BRIEF SUMMARY
The device of the invention is in preference intended for regulating the retention time of the material, for the grinding of mineral ores with single chamber, autogenous, semi-autogenous of ball grinding mills in wet grinding mode.
In these mills the discharge of the material from the grinding chamber is effected either by overflowing or through an outlet grate.
Grinding mills with overflow discharge generally retain the material for too long a period in the grinding chamber, which has the effect of producing undesirably fine particles; the grinding mill is overfilled on account of the excessive retention time, with the result that the load tends to slip and the mill's output is reduced.
Grinding mills equipped with a grate discharge the material more rapidly, are not subject to overfilling, and have a higher output. However, the retention time in these mills is often too short, they contain too little material and the mill does not function at its optimum efficiency. In ball mills--in which it is an advantage to use cast balls in treated alloys for greater hardness and better resistance to wear--, the hard balls tend to scale, with the result that their resistance to wear is seriously affected.
Various outlet grate devices have been designed, to optimize the retention time of the material in the grinding mills.
Said devices generally consist of a frame, the upstream face of which is open and covered by grids provided with a number of apertures which allow ground material to pass, but retain insufficiently ground material, and the grinding media if any; the upstream face of the device is spaced apart from the downstream face, which is solid except for a central discharge opening; the space between the two said faces forms a small discharge chamber to receive the material which has passed the grids. Lifting elements fixed within the discharge chamber raise, by the rotation of the mill, the material above the centre line of the mill, and let it fall on to a deflector which directs it towards the central discharge outlet.
In an attempt to control the retention time of the material, efforts have been made to regulate the passage of the material through the apertures in the grids, for example by progressively blocking these apertures as in patents DE-420 049 and U.S. Pat. No. 1,787,897. All of these blocking mechanisms are nevertheless rapidly jammed by particles and all kinds of waste passing through the grids, with the result that regulation becomes inoperative.
Patents DE-477 135 proposed a deflector in the form of a mobile cone integral with the mill; this would partially or totally return the material coming from the lifting elements (paddles in this case) back into the compartment upstream of the discharge compartment, in order to re-grind coarse particles which had entered the discharge compartment. With this system, the recirculated material passes again into the grid, which should theoretically give some control over the retention time in the mill. However, as the cone is integral with the mill, a major part of the regulating mechanism functions within the mill itself; this device is therefore very vulnerable on account of wear and jamming caused by the presence of ore particles and steel scrap.
Patent GB-812 320 describes a system by means of which the lifting paddles can be progressively neutralized using adjustable-angle chutes. These adjustable chutes and a major part of the control mechanism are also integral with the mill and have to function in the material. The invention described in patent GB-812 320 is intended for the dry grinding of selflubricating carbonaceous material. Such a system could not function on a long-term basis in a wet process and/or with materials such as mineral ores which would cause it serious abrasion and jamming.
Patent CA-884 866 describes a mill discharge launder, which can be disposed in an operative position within the mill discharge trunnion, to receive material from the lifting members of the mill discharge chamber, and to deliver said material from the mill. Said
REFERENCES:
patent: 2482740 (1949-09-01), Brown, Jr.
patent: 3180581 (1965-04-01), Velcheff
Goldberg Howard N.
Gorski Joseph M.
Slegten Societe Anonyme
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