Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Patent
1997-11-24
1999-09-21
Husar, John M.
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
241 241, 241 2411, 241 27, 241 34, 241 38, 241171, B02C 1700, B02C 2308
Patent
active
059542764
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for grinding granular material, particularly ore material. The invention also relates to a grinding apparatus for such material.
In the prior art there is known a grate mill whereby coarse granular ore material is ground for further processing, particularly for flotation or other such concentration. It is typical of the wet grinding process realized in a grate mill that the slurry density in the process feed is of the order 50-65% by weight, i.e. the solids/water ratio in the material to be fed into the mill is equal or larger than 1, and that said slurry density is practically always the same as the steady-state density of the slurry formed in the mill. In that case the materials always proceed in the mill as a so-called plug flow, in which case water and solids proceed at the same rate through the mill. Thus it has been traditionally understood that a well-working grinding process self-evidently comprises a high volumetric filling of the mill and a high slurry density. From a grate mill, the product has been obtained as a thick flow from the output orifices of the mill.
A drawback with the above described ordinary grinding process is that the ore material is easily overground or slimed, i.e. part of the material is ground into too small particles. This brings about problems in the further processing product ground from ore material. Another drawback is that sliming uses a lot of energy; as is well known, fine grinding is a highly energy-consuming process.
In practical industrial-scale processes, the grinding of ore material almost without exception takes place in continuous operation. In laboratory-scale experiments, comminution has traditionally been carried out in a batch grinding process. However, it is a general notion that batch grinding and continuous grinding lead to different end products--the former renders more fine material in the grain size distribution than the latter. The softer the material to be ground, the bigger the difference. Consequently the grinding of experimental material in research does not necessarily give a correct prediction of the industrial-scale product.
The object of the present invention is to improve the grinding process, particularly the laboratory-scale process. It will, however, be appreciated that the method of the invention also is suited to an industrial-scale process. Another object of the invention is to introduce a new grinding apparatus for applying the method of the invention.
The method of the invention for grinding granular material, particularly ore material, as feed comprises precomminuted ore material or corresponding solids and water, which solids are ground to a mill product with a given grain size distribution. According to the invention, the grinding of the feed and the classification of the mill product into fine and coarse solids are carried out during the same step in the grinding apparatus, so that in the grinding, there is used so much water in proportion to solids that the part of the mill product that has reached a given grain size is flushed more rapidly out of the grinding chamber than the coarser part, and this coarser part remains in the grinding apparatus until it is ground to the desired grain size.
In another method according to the invention, in order to grind granular material, particularly ore material, as feed there is precomminuted ore material or similar solids and water, which are fed into a mill serving as the grinding apparatus and comprising a grinding chamber provided with a grinder charge, in which grinding chamber solids are ground, and from the grinding chamber there is obtained the mill product with a given grain size distribution. According to the invention, the solids/water ratio in the feed, i.e. its solids content or slurry density is adjusted to be such that it is of the order 45% by weight or less; now the solids content of the slurry being treated in the grinding chamber sets at a steady-state slurry density which is higher than the slurry density in the feed, advantageously within
REFERENCES:
patent: 3094289 (1963-06-01), Fahlstrom et al.
patent: 3887142 (1975-06-01), McElvain
patent: 4026479 (1977-05-01), Bradburn et al.
patent: 4119699 (1978-10-01), Kellerwessel et al.
Hintikka Vaino Viljo Heikki
Knuutinen Veli Tapio
Kuusisto Markku Elias
Morsky Pekka Parttyli
Tahvanainen Raimo Tapio
Husar John M.
Valtion teknillinen tutkimuskeskus
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