Solid material comminution or disintegration – Processes – With classifying or separating of material
Patent
1998-09-21
2000-03-28
Rosenbaum, Mark
Solid material comminution or disintegration
Processes
With classifying or separating of material
241 29, 241 791, 241 80, 241 97, B02C 2312
Patent
active
060420324
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a process and a continuously operating plant for comminuting a mineral material to grains of different sizes and dividing the ground product into several granulometric fractions each constituted by grains the dimensions of which range between a predetermined upper and a predetermined lower limit.
BACKGROUND ART
In many applications, it is necessary to produce, from a mineral material, grains, the dimensions of which are contained within clearly determined limits. When the grains are relatively large (between one millimeter and several tens of millimeters), it is known to produce them by breaking and to classify them according to different grades by screening. When the starting material has to be comminuted to powder (between one micron and several tens of microns), crushing is carried out, generally after several stages of breaking and grinding, followed by grading, for example by means of one or more pneumatic separators.
To produce relatively large grains and powder simultaneously, at least two comminuting apparatus have to be used: a breaker and a grinder.
The object of the invention is to permit the simultaneous production of several fractions of different grain sizes, ranging from a fraction the grains of which are of a size of possibly up to several tens of millimeters to a fraction the grains of which are of a size in the order of one micron to several hundreds of microns, by means of a single fragmenting apparatus and of grading apparatus.
SUMMARY OF THE INVENTION
The process to which the invention relates is characterized in that, starting from a raw product in the form of pieces, the pieces being, for example, of dimensions less than, or at the most, equal to, 150 mm, the product is subjected to grinding by material layer crushing, the ground products are divided into several fractions comprising at least one coarse fraction the grains of which are of a size ranging, for example, between 0.5 and several tens of millimeters, and a fine fraction having an upper limit ranging, for example, from 300 .mu.m to several tens of .mu.m, the parameters of the grinding operation possibly being selected in such a way that, in the case of all the fractions, the throughput produced is greater than, or at least equal to, the throughput desired, and those grains the dimensions of which are above the upper limit of the coarse fraction, and possibly all or part of the fractions the grains of which have dimensions contained between the lower limit of the coarse fraction and the upper limit of the fine fraction, are returned to the input of the grinder.
The fine and coarse fractions are thus directly usable after a single grinding step. As to the intermediate fraction, it can also be sub-divided.
The advantage of grinding by material layer crushing is that it makes it possible, within a single fragmentation step, to produce a mixture having a wide grain size spectrum containing both large-sized grains (ranging, for example, from 0.5 mm to several tens of millimeters) and grains forming powder (the size of which is, for example, less than 300 .mu.m).
In addition, by choosing to grade or classify the grains obtained, apart from the oversize grains, according to at least three grain size fractions, and by choosing to recycle the grains of the intermediate fraction in preference to those of the coarse fraction, grinding is optimised.
The expression grinding by material layer crushing refers to those grinding processes in which a multi-granular layer of product to be ground is compressed between two surfaces using a pressure that is sufficient to cause fragmentation of the grains, which are comminuted to form smaller grains. The known apparatus for implementing these processes are edge runner type grinders, vertical small ball or pebble grinding mills, ring grinders, roll presses and vibrating cone grinders.
These are, for example, apparatus permitting the application of a fragmenting pressure several times to the material in the course of its processing.
The invention also
REFERENCES:
patent: 2072063 (1937-02-01), Alton
patent: 2461089 (1949-02-01), Smidth
patent: 2554450 (1951-05-01), Ayers
patent: 5379948 (1995-01-01), Teppo
SALA Mining Equipment, Canadian Mining Journal, Dec. 1960.
FCB Societe Anonyme
Rosenbaum Mark
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