Solid material comminution or disintegration – Processes – Miscellaneous
Patent
1997-09-17
1999-10-05
Rosenbaum, Mark
Solid material comminution or disintegration
Processes
Miscellaneous
241254, 2412571, B02C 1900
Patent
active
059610565
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for fine comminution of mill feed material, wherein the mill feed material in a granular mass is subjected to a pressure of over 50 MPa by pressing once between two opposing surfaces.
BACKGROUND OF THE INVENTION
The method for fine comminution is known for example from DE-B-27 08 053. In order to carry out this method so-called material bed roll mills may be considered which consist of two rolls which are pressed against one another with high pressure and are driven in opposite directions.
However, the efficiency of these roll mills is limited by the fact that the grinding tools, i.e. the rolls, have to transport the mill feed material into the pressing zone. In this case the "transport speed" is highly dependent upon the friction conditions of the as yet unpressed granular mass of material on the roll surface and upon how stable the material bed is in order to transfer the pressure. Thus the mill feed material is drawn into the grinding gap by the roll surfaces. The actual pressing begins at an angle of nip which is set automatically. The pressing speed at the beginning of the compression stress may be calculated on the basis of the peripheral speed of the grinding rolls. The pressing speed is understood here to mean the speed at which the distance between two opposing points on the surface of the two rolls is decreased.
The pressing speed at the start of the compression stress is in direct relation to the throughput of the roll mill. An increase in the efficiency of such mills is possible through an increase in the peripheral roll speed only in so far as the material feed through the roll transport before the pressing can keep pace with the pull-through speed in the pressing zone at the desired pressing density. Otherwise an interruption of the material flow is to be expected and the consequence is a high instability of the pressing operation. For this reason roll mills can only be operated at initial pressing speeds of about 0.5 m/s.
The object of the invention, therefore, is to improve the known method in such a way that the throughput is increased.
SUMMARY OF THE INVENTION
According to the invention the pressing of the material once between two opposing surfaces should take place in such a way that in the region of the pressing the distance between opposing points on the two surfaces at the start of the compression stress decreases at an initial speed of at least 1 m/s. In a preferred embodiment of the invention this method is implemented by the use of a ring mill, such as is known for example from DE-A-42 27 188. With regard to the construction of the ring mill reference is made to DE-A-42 27 188.
With the method according to the invention a very high energy efficiency and energy conversion is possible in the material bed comminution. Furthermore, it is possible to comminute very fine feed material and materials with a high voids fraction in the granular mass (inclusions of gas, air) as well as moist material and such material in which the voids fraction in the granular mass is filled with a fluid. The apparatus which operate by the method according to the invention are enormously efficient and can be operated with the highest throughput.
THE DRAWINGS
Further advantages and embodiments of the invention are explained in greater detail with the aid of the following description with reference to the drawing, in which:
FIG. 1 shows a schematic sectional representation of a ring mill ;
FIG. 2 shows a sectional representation along the line II--II in FIG. 1;
FIG. 3 shows a representation of the vertical movement over the angle of rotation and
FIG. 4 shows a representation of the vertical speed over the angle of rotation.
THE PREFERRED EMBODIMENT
FIG. 1 shows a schematic sectional representation of a ring mill 1. Essentially it comprises a stationary first grinding track 2, a second grinding track 3 which is disposed below this first grinding track and is capable of wobble motion relative thereto, and a wobble plate 4 which can be driven by a suitable rotary dri
REFERENCES:
patent: 4199113 (1980-04-01), Genev
patent: 4721260 (1988-01-01), Genev
patent: 5673860 (1997-10-01), Heinemann et al.
Krupp Polysius AG
Rosenbaum Mark
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