Solid material comminution or disintegration – Apparatus – Including means applying fluid to material
Patent
1987-01-29
1989-02-28
Rosenbaum, Mark
Solid material comminution or disintegration
Apparatus
Including means applying fluid to material
241152R, 241300, B02C 1906
Patent
active
048078158
DESCRIPTION:
BRIEF SUMMARY
FIELD BACKGROUND OF THE INVENTION
The object of the invention is an energy-saving internal sizing air-jet mill having a pregrinding chamber for fine grinding of preferably various carbides, silicates, oxides, ores, pigments or elastic materials, as well as for surface treatment and/or cryogenic grinding of the same.
The air-jet mills known according to the present state of art, could be divided into five basic types. The first type is characteristic of the situation where grinding comes about by accelerating the material to high speed through a nozzle and impacting it against a so-called anvil. This apparatus provides adequate grinding; however, due to high specific energy consumption its operation is not economical and the lining experiences much wear thereby causing high contamination of the ground product.
In order to eliminate such contaminating effect, it is often the practice to use linings from the same basic material as the material which is to be ground. The best known version of this type now in use is the air-jet mill of the Vortex system provided with an outer sizer or separator, ceramic lining and anvil. The other type of the air-jet mill widely used is the so-called Majec mill. Here, comminution takes place by the autogenous grinding effect of grains impacting against each other by the acceleration generated through two nozzles facing one another. This operation, however, exhibits energy losses and thus very poor comminution efficiency. The nozzles can carry comparatively small amounts of grains and vortices occur also due to the effect of the opposite air jets thus fairly reducing the number of collision of grains. Known examples of this type are: West German Patents DE No. 2543691 C2 and DE No. 2523471 C2.
The third air-jet mill, the so called Micronizer type is the one which has been used most predominantly. The essence of its operation is that grinding takes place in the discusshaped grinding chamber under the effect of pressurized gas issuing from peripheral jet pipes. The gas jets first contact a circle in the outer third part or half of the grinding area. Material to be ground enters the grinding space in a vertical plane crossing the tangent of this circle, however, at an angle of 60.degree. to the vertical passing through the top of the grinding space.
According to the theory of the designers, the grains greater in size than a predetermined dimension are circulating along this tangential circle, the smaller grains, that is, the ground end product discharge from the facility past obstructing dam entrained in the exhaust and, the coarser grains, under the effect of the pressurized gas from the peripheral nozzles, collide with each other and circulates until their dimensions are reduced to or below the required level. Under actual working conditions the operation of the facility does not meet the conditions of the above theoretical operation, yet the type is widely used as the unit presenting the best efficiency. Several patented inventions exist on the above apparatus, e.g. U.S. Pat. No. 3,726,484, SF-33960, DE No. 3201778 C1. These technical solutions represent the combination of the double-jet mill, the anvil type and the micronizer, where the coarse product is returned to the grinding space, or by applying a anvil-type pregrinder an attempt is made, with little success, to improve the fineness of grinding. Therefore, up to now, the unchanged basic type provided with some kind of liner is most frequently used in the industry.
With the fourth type of the air-jet mills, the goal was the increase of mill output by a method which did not cause the shortening of the path of free movement of particles.
In favour of this, the volume of grinding space and the number of nozzles has been increased, increasing thereby the output of mill relative to its unit volume, however, the efficiency of energy utilization has been decreased and the extent of wear also increased. This type of mill is known as the Jet-O-Mixer or Reductionizer. Addressed to the reduction of wear, the design of the Double-Imp
REFERENCES:
patent: 3559895 (1971-02-01), Fay
patent: 4504017 (1985-03-01), Andrews
Csillag Zsolt
Czafit Sandor
Kalman Tibbr
Lajtai Bela
Legat Tibor
Magyar Aluminiumipari Troszt
Rosenbaum Mark
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