CZ498A3 - Milling process of material within a circular mill with a roller - Google Patents

Abstract

The present invention relates to a ring roller mill operating at a subcritical speed and comprising at least one grinding ring and at least one roller fitted inside the grinding ring. Such a mill can be used in connection with the manufacture of cement for grinding of mineral clinker materials, slags, and similar materials. The objective of the present invention is to provide a ring roller mill in which undesirable vibrations or skewrunning of the roller do not occur during operation and this is achieved by mounting internal fittings in the form of impact and distribution units in the mill. These units are placed in the path where the compacted material falls off the ring, descending towards the draw-in zone. During the grinding process the impact and distribution units will break down agglomerates, if any, while distributing the loosened material down over the draw-in zone in an even layer. The maximum degree of impact is attained when the material hits the unit at an angle between 60 DEG and 110 DEG .

Description

Technical field

The invention relates to a method of grinding a material in a roller mill with a roller, which comprises at least one grinding ring, at least one roller mounted within the grinding ring and at least one unit mounted between the roller and the grinding ring.

For example, this mill can be used in conjunction with cement production, for grinding mineral clinker materials, clinker and the like.

BACKGROUND OF THE INVENTION

European Patent Application Publication No. 486371 discloses a circular mill with a roller. In this mill, the feed material is fed into the space upstream of the grinding path where it is subjected to centrifugal action. Furthermore, the material and air are transferred axially through the mill. The grinding ring in this mill operates at a grinding pressure in the range of 10-40 MPa and at a supercritical speed, which means that the material subjected to the grinding action is maintained on the grinding ring for the entire duration of the rotation. Thus, it is possible and necessary to place scrapers and guide plates inwardly in the ring to release material during transverse passage into the grinding ring and guide the material forward along the roll in the direction of flow.

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In a circular mill with a cylinder that is operated at a subcritical speed, the ground material will only be held on a portion of the grinding ring. In the area of the grinding ring, depending on the rotational speed of the ring, the roughness of the ring and the properties of the material being processed, the milled material will be separated from the ring while continuing to fall along the path down towards the feed zone in front of the roller.

The uniform distribution of material into the feed zone and the grinding bed is the most important for the mill operation. Significant fluctuations in the thickness of the grinding bed will cause irregular operation or vibrations in the mill and a considerable variation in the torque of the drive assembly. Uneven loading of the roller can also cause damage to the friction segments that protect the grinding ring surface and the roller.

The intensity of the grinding pressure applied and the type of material being milled are determining factors with respect to the shape that the compacted material will have after passing under the roller in the mill. High grinding pressure and sticky material will result in the formation of clumps that maintain their shape upon discharge of material from the grinding ring, while lower grinding pressure will result in the outgoing material being relatively free flowing and friable material. Both the size and the hardness of the clusters will have an effect on balancing the bed with the material that is deposited in the inlet zone and in the grinding bed itself.

The roller mill operating at subcritical speed has a lower rotational speed than the roller mill operating at supercritical speed. In order to increase production in the mill operating at subcritical speed to the same level as in a similar mill operating at

• The modified side of the supercritical speed is necessary to increase the grinding pressure. Normally, the grinding pressure in the mill operating at a subcritical speed will be greater than 50 MPa.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for grinding material in a circular mill with a roller, wherein the agglomerates formed during operation are crushed and distributed along the feed zone and the roller in such a way that no undesirable vibrations or misalignment of the roller occurs.

This is achieved according to the invention in a surprisingly simple manner by mounting the unit at a certain distance from the point P on the ring. The unit is placed in a path where the compressed material falls off the circle, dropping towards the inlet zone in such a way that the clusters formed during operation at an angle α between 60 ° and 120 ° fall on the unit, where α is the angle between the surface material.

During the grinding process, the impact and distribution units disrupt the agglomerates, distributing the loosened material downward through the pull-in zone into a leveled layer. The maximum degree of impact is achieved when the material strikes the unit at an angle between 70 ° and 110 °.

The units need not have a solid surface, it may be advantageous if the units have a perforated surface or consist of grilles.

If the material is fed symmetrically through the openings at both ends of the grinding ring, material agglomeration may occur mainly in the center of the grinding ring and thus the impacting and modified fines of the distribution unit may be appropriately designed to disrupt the agglomerates while evacuating most of the material towards the sides of the grinding ring.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a circular mill with a cylinder; FIG. 2 shows the different shapes of the impact and distribution units shown both on the side where the material strikes the plate and the cross section; arms 8.

DETAILED DESCRIPTION OF THE INVENTION

The mill in Figure 1 has a grinding ring 1 and a roller 2. The roller 2 and the grinding ring 1 rotate by means of an undiscovered drive mechanism and the roller 2 is pressed against the grinding ring 1 by a tensioning system. Between the roll 2 and the grinding ring 1, the partially crushed material forms a grinding bed 4 and a space 4a in front of the roll, which is designated as a feed zone and from which the feed material is drawn in for compression.

After the bulk material from the feed zone has passed under the cylinder, the material will normally be compressed into a solid mass that is held on the ring up to the point P where the material begins to fall towards the feed zone.

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The position P will depend inter alia on the speed of the grinding ring and the type of material to be ground.

The unit 3a is located in a mill on the way where the compressed material sinks towards the feed zone. For example, the unit may be fixed by means of an arm across the mill in such a way that it is possible to adjust the vertical position of the unit and the angle at which the milled material strikes the surface of the unit, for example by tilting or rotating the unit. The position of the unit and the angle to the vertical can be adjusted from the outside, which means that the position of the unit can be adjusted while the material is ground in a mill. In order to optimally fulfill its purpose, the impact unit or the first of the impact units should be located at least 1/4 x d, preferably more than 1/3 x d, from P, where d is the inside diameter of the grinding ring.

The unit 3a will disrupt the clusters and distribute the bulk material across the cylinder 2 and the inlet zone 4a.

The units 3b and 3c show alternative positions in the mill and, if appropriate, it is possible to install several units at the same time, either side-by-side or vertically tilted, thereby improving the distribution accuracy of the ground material.

In Fig. 2A there is shown a unit formed as a flat plate 6 which does not distribute the material in any particular direction, but merely scatters the material and disrupts the clusters.

Figure 2B shows a unit formed as a flat plate 6 with end portions 5. The end portions ensure that the dispersion of the material that strikes the unit is axially limited, and that the material is directed downwardly into the feed-in.

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A A zone. The axial size of such a plate will typically correspond to the width of the cylinder.

Figures 2C and 2D show a unit formed with a raised area 7, which in Figure 2C has a shape that is roughly similar to the shape of a roof ridge. In this arrangement, the material is distributed from the center of the grinding ring and outwardly towards the sides, which is useful if there is a tendency for the material to deposit in the center of the grinding ring during the grinding process.

Unit size, cf. FIG. 2C or 2D, i. The axial dimension is a contributing factor in determining what the final curve of the finished material will look like, as the size will be important with respect to the number of material cycles in the mill. Thus, a small roof ridge will cause a flat particle distribution curve, since the same material will be subjected to several rolling passes without intermediate separation, while a wider roof ridge will result in more mixing and therefore more effective separation and a steeper particle size distribution curve.

If, in a circular mill with a cylinder such as the mill shown in FIG. 1, material is to be milled according to the invention, the material is fed to the mill by one or more feed lines by one or both fixed units installed at the end of the grinding ring 7; directed to the drawing zone where it is drawn under the cylinder 2 and subjected to a crushing action. Gradually, as the amount of milled material increases, the material is ejected over the edge of the grinding ring 1 where it is collected and either put back into circulation for re-grinding in the mill, or directed, e.g. mills for re-processing wherever appropriate.

• UŘra \ erjá «§tpa’ «and’

Represented by:

Dr. Miloš Všetečka v.r.

Claims (9)

H Fl H PATENT CLAIMS A method of grinding a material in a roller mill with a roller comprising at least one grinding ring, at least one roller mounted in a grinding ring and at least one unit mounted between a roller and a grinding ring, characterized in that the mill operates at subcritical speed and at a grinding pressure of more than 40 MPa that the unit is placed in a path where the compressed material is released from the circle at a certain distance from the point P, which is the point on the circle where the material is released, in such a way as at an angle α between 60 ° and 120 °, where α is the angle between the surface of the unit and the direction of incidence of the material after being released from the grinding ring, and that the released material is distributed through the draw zone upstream and through the cylinder. Method according to claim 1, characterized in that the grinding pressure is between 60 MPa and 100 MPa. Method according to claim 1 or 2, characterized in that the angle α is between 70 ° and 110 °. Method according to claim 1, 2 or 3, characterized in that the distance between point P and the unit is at least d / 4, where d is the inner diameter of the circle. Method according to claim 1-4, characterized in that the unit is formed as one or more solid or perforated plates. The method according to claim 5, characterized in that 9 9 9 9999 9 9 9 9 9 • Wrinkled beam • 9 · 9 · 9 9 9 9 9 9 The unit consists of a number of vertically curved plates. The method of claim 1-6, wherein the at least one region on one or more units is raised relative to the surface of the plate such that most of the material that strikes the unit is directed towards the feed zone and the cylinder axially bent relative to point of material impact per unit. Method according to claim 7, characterized in that the raised area has a shape resembling the shape of a roof ridge or the like. Method according to claims 1-8, characterized in that the unit is provided with end portions which are located at the very edge of the unit, pointing in the direction of the fixed end walls.