Roller mill

Details Roller mill Roller mill

1997-07-22

2000-09-05

Rosenbaum, Mark

Solid material comminution or disintegration

Apparatus

Plural rotary or oscillatory surfaces cooperate with common...

B02C 1500

Patent

active

06113015&

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a roller mill with a virtually horizontal grinding path on a rotary grinding bowl, having stationary grinding rollers, which roll on a grinding bed formed by the grinding material on the grinding path of the bowl, and with retaining devices, which are located between the grinding rollers for influencing the grinding material movement.


BACKGROUND OF THE INVENTION

In roller mills, which are also known as air-swept roller mills or roller bowl mills, a grinding material flow supplied to the centre of a grinding bowl and containing fresh material and coarse particles from a classifier, which is generally integrated into the roller mill, is moved by centrifugal force to the edge of the grinding bowl and to a blade ring surrounding the latter. The centrifugal force acting on the grinding material is in particular dependent on the diameter and speed of the grinding bowl.
The throughput of a roller mill is essentially determined by the available grinding surface, i.e. the number and size of the grinding rollers used and the grinding speed. This assumes an adequate supply of grinding material to each roller.
In principle, by a speed increase the throughput of a roller mill can be increased for the same, predetermined geometries and the same number of grinding rollers. Consequently a smaller roller mill can be used, which leads to lower costs.
However, a speed increase is simultaneously associated with a centrifugal force increase, which leads to the grinding bowl being partly or completely emptied in the area between two successive grinding rollers, So that the latter are no longer supplied with grinding material and the sought throughput increase cannot be achieved.
DE 36 42 814 A1 discloses a roller mill, which is provided with a retaining device between two grinding rollers for controlling the grinding material movement in the vicinity and on the grinding path. The retaining device is constructed as an arcuate baffle or deflector, which is fixed by means of holding devices to the roller mill housing and is adjustable as regards height and inclination.
A roller mill described in German patent 1 507 579 has facing a material feed and between two grinding rollers a deflector, through which it is intended to bring about a classification of the grinding material moved in the direction of the bowl edge. The shape and height of the deflector bring about a splitting up of the grinding material and a separate carrying off of the fine material flow and a retention of the coarse material on the grinding path.
The disadvantages of these known means are a relatively high friction between the grinding material and the deflector used as retaining device, which leads to an increased drive power requirement. As a result of the friction increased wear takes place to the deflectors and also the holding devices, which requires corresponding maintenance measures and hard surfacing of the deflectors and holding devices.
DE 39 21 986 C1 discloses a roller mill with precompacting or smoothing rollers. These precompacting or smoothing rollers are provided for equalization and levelling of the grinding bed and are in each case positioned upstream of a grinding roller. The smoothing or precompacting rollers are not constructed as retention devices for the grinding material moved outwards on the grinding path of the grinding bowl, but instead for venting and smoothing of the grinding material to be supplied to a grinding roller and in particular for eliminating a "bow wave" of an air-dust mixture. For obtaining this sought effect a precompacting or smoothing roller is positioned upstream of a grinding roller. However, this document does not disclose constructing and arranging the precompacting or smoothing rollers for retaining the grinding material on the grinding path. Thus, a retention effect of the smoothing or precompacting roller is only possible to a limited extent over the end face of such a roller.
The object of the invention is to provide a roller mill with a low-wear, and in par

REFERENCES:
patent: 4611765 (1986-09-01), Shimojima et al.
patent: 4981269 (1991-01-01), Koga et al.

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