Solid material comminution or disintegration – Processes – By utilizing kinetic energy of projected or suspended material
Reexamination Certificate
1999-10-21
2001-05-15
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
By utilizing kinetic energy of projected or suspended material
C241S024140, C241S029000, C241S039000, C241S152200, C241S155000
Reexamination Certificate
active
06230995
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention refers to a micronizing device and a method for micronizing solid particles fluidized in a pressurized power gas.
All industrial fields from medical industry to mine and building material industry use as raw materials a continuously increasing amount of different types of finely ground or micronized powder like dry products. The micronizing/fine-grinding of these products is nowadays generally carried out in jet mills, in which highly pressurized air or overheated water vapor is generally used as grinding energy. Depending on the final product and the fineness thereof tho energy consumption of these grinding and classifying processes is about 100 to 3000 kWh/ton.
An effective and relatively economical micronizing method is a technique operating according to the opposed jet mill principle. The opposed jet mill technique was developed during the 1980:ies and the 1990:ies substantially by the Finnish company Oy Finnpulva Ab, by means of which technique the energy economy and the grinding effectiveness of the fine grinding have been improved considerably. However, a wider utilization and application of the developed opposed jet mill technique has been considerably disturbed by the lack of effective auxiliary techniques applicable in connection with that technique and/or their low efficiency and high energy costs.
In fine-grinding/micronizing a high-energy power gas, most often pressurized air, is used as grinding energy. The micronizing devices will need industrial compressor effects ranging from 100 kw to 1000 kW depending upon application.
A drawback of previously known minronizing devices and methods is the considerably increasing energy consumption if the counter jet mill is adjusted to concentrate the grinding to eliminate particles having a particle size over 10 &mgr;m. Further the pressure of the power gas has to be considerably high because an elevated pressure must be maintained in the jet mill in order to force the ground solid-gas suspension to a classifier and further treatment steps.
It is, therefore, an object of the present invention to eliminate the above drawbacks by providing a new and improved micronizing device.
It is another object of the present invention to provide a new and improved method for micronizing solid particles fluidized in a pressurized power gas having no one of the above drawbacks.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a micronizing device comprising a grinding housing with an outlet opening at one end, two coaxial positioned rotatable driven hollow axles entering the grinding house through two opposite side walls thereof, each of said axles having an inner end provided with a conical enlarging disc defining a grinding chamber, a circumferential outlet gap being formed between said discs, each disc being provided with at least one concentrically positioned ring of axially directed taps and/or wings near the circumference of the disc, the rings having different diameters, so that the discs can be driven to rotate in opposite directions. Two acceleration nozzles are brought into said grinding chamber through said hollow axles, said nozzles being directed towards a common point in the grinding chamber away from a center point of said grinding chamber.
By means of such a micronizing device the pressure of the fluidized gas-solid suspension can be lowered without affecting the grinding result because the pressure in the grinding chamber is lowered due to a fan effect of the appositely rotating wings and taps at the discs. Further said taps and wings can be adjusted to mechanically grind possible coarser particles, having a particle size over 10 &mgr;m, passing the gap between the two discs, with considerably smaller energy consumption as required in a conventional opposed jet mill technique. In a micronizing device according to the present invention the gas volume to be circulated is considerably smaller than in a conventional opposed jet mill resulting in still improved energy economy.
In accordance with the invention there is also provided a method for micronizing solid particles fluidized in a pressurized power gas comprising the steps of accelerating a fluidized solid-gas suspension through two opposedly directed acceleration nozzles into a grinding chamber, wherein the solids are ground on colliding against one another between two opposed conical discs rotating in different directions, during escaping from the grinding chamber through a circumferential gap between the discs the thus ground gas/solid suspension is mechanically further ground by means of taps and/or wings extending axially from a circumferential inner surface of both oppositely rotating discs, arid such a further ground solid-gas suspension will then leave a grinding house surrounding said discs through an outlet opening.
Further features of the invention will appear from the attached dependent claims.
REFERENCES:
patent: 2839253 (1958-06-01), Yellott
Ilmasti Veikko
Niemi Jouko
Suominen Hannu L.
Connolly Bove Lodge & Hutz
Micropulva Ltd Oy
Rosenbaum Mark
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