EP0792191A1

EP0792191A1 - Roller mill

Info

Publication number: EP0792191A1
Application number: EP95938404A
Authority: EP
Inventors: Horst Brundiek
Original assignee: Loesche GmbH
Current assignee: Loesche GmbH
Priority date: 1994-11-25
Filing date: 1995-11-03
Publication date: 1997-09-03
Anticipated expiration: 2015-11-03
Also published as: CA2205387C; BR9510391A; DE4442099A1; US6113015A; CN1103640C; AU3980895A; EP0792191B1; JP3668253B2; CN1166796A; DK0792191T3; CA2205387A1; MX9703803A; KR100402327B1; DE4442099C2; TW292983B; WO1996016742A1; MY129616A; ZA959149B; JPH10510749A; ES2137548T3

Abstract

The invention concerns a roller mill with a rotating pan (2), grinding rollers (6) which roll over the pan and retaining devices (10) designed to influence the movement between the grinding rollers of the material being ground. In order to raise the throughput of such a mill, while keeping capital costs low, the invention calls for efficient, wear-resistant retention devices (10) to be located between the grinding rollers (6), each device comprising a rotating wall made up of one or more retention rollers (10). The retention rollers have retention faces (12, 15) which block the movement of material outwards, thus retaining it for further grinding. In a first embodiment, one retention face (12) is the inwards-facing side of the retention roller. In another embodiment, the retention rollers are fitted with radially projecting rings (17), thus giving additional retention faces (15).

Description

Roller mill

The invention relates to a roller mill according to the preamble of claim 1.

In the case of roller mills, which are also referred to as airflow roller mills or roller bowl mills, a ground material flow of fresh material and coarse particles of a classifier, which is generally integrated into the roller mill, is fed to the center of a grinding bowl and is centrifugal to the edge of the grinding bowl and to one the blade ring surrounding the grinding bowl is moved. The centrifugal force acting on the regrind is particularly dependent on the diameter and the speed of the grinding bowl.

The throughput of a roller mill is largely determined by the available grinding surface, that is by the number and size of the grinding rollers used, and by the grinding speed. A sufficient supply of regrind to each roller is assumed.

In principle, an increase in speed could increase the throughput of a roller mill with the same, predetermined geometries and the same number of grinding rollers. As a result, a smaller roller mill could be used, which is associated with less investment.

However, an increase in speed is simultaneously associated with an increase in the centrifugal force, which leads to the

ATZBLAπ RULE 26 Grinding bowl is partially emptied or emptied in the area between two successive grinding rollers, so that the grinding rollers are no longer supplied with regrind and the desired increase in throughput cannot be achieved.

A roller mill is known from DE 36 42 814 A1, which has a retaining device between two grinding rollers for controlling the movement of the grinding material in the region of the grinding path. The retaining device is designed as an arcuate guide plate, which is attached to the housing of the roller mill via holding devices and is adjustable in height and inclination.

A roller mill described in DE-PS 1 507 579 has, compared to a material application and between two grinding rollers, a guide plate through which a sighting of the ground material moving in the direction of the bowl edge is to be achieved. The shape and height of the guide plate bring about a splitting of the ground material and a separate discharge of the fine material flow and a retention of the coarse material on the grinding path.

The disadvantages of these known devices are a relatively large friction between the ground material and the guide plate used as a retaining device, which leads to an increased need for drive power. In addition, the friction leads to high wear of the guide plates and also of the holding devices, which means that corresponding maintenance measures and armoring of the guide plates and the holding devices are necessary.

The invention is based on the object of creating a roller mill with a low-wear and efficient retention device which provides an adequate supply of grinding material to the grinding rollers in both normal and

ERSATZBL _Ä TT (REGEL26) secures even with an increased regrind speed, so that a higher throughput is guaranteed with less effort.

According to the invention the object is achieved by the characterizing features of claim 1. Appropriate and advantageous embodiments are included in the subclaims and in the description of the figures.

The invention is based on the consideration of arranging a retaining device with an extraordinarily low and significantly reduced friction between the grinding rollers of a roller mill compared to the known guide plates.

According to the invention, the roller mill has, as a retaining device between two grinding rollers, one or more accumulation rollers, which exert a jamming effect on the material to be ground moved outward on the grinding path of the grinding bowl. This accumulation effect is caused by accumulation surfaces on the accumulation rollers, which are designed approximately diametrically to the movement of the regrind, so that the regrind between the grinding rollers cannot reach the edge of the bowl due to the centrifugal force, but is retained on the grinding bed and fed to further grinding.

In a particularly expedient and simple embodiment, a storage roller has a storage surface on an inner end face facing the longitudinal axis of the roller cooler. One or more accumulation rollers are expediently arranged and dimensioned in such a way that their end faces form a rotating storage surface wall or a rotating weir to prevent the ground material from flowing off.

In an advantageous manner, the accumulating rollers rotating on the grinding bed between two grinding rollers

BLAH RULE26) Rotating accumulation surface wall or a rotating weir is formed in that the individual rollers have their end faces almost adjoining one another and are arranged as close as possible to the adjacent grinding roller.

The accumulation rollers generally have no grinding action and are therefore generally not subjected to force or only to such an extent that they do not "jump". As a result, the friction is kept extremely low with a very good accumulation effect, which has an advantageous effect on the energy balance.

For the intended accumulation effect or for the effect of a weir to prevent the regrind from draining off with particularly low friction, it makes sense to design the accumulation rollers with the lowest possible weight. The accumulation roller does not require a defined additional force for its own weight, since grinding work should not be carried out by the accumulation roller. A spring damping system can expediently be provided, with which the accumulation roller is held on the grinding bed.

If a hold-down force is provided, for example by means of a spring damping system, jumping of the accumulation rollers can be avoided.

It is advantageous to limit the free mobility of the accumulation rollers down to the grinding path of the grinding bowl with the aid of a device. A particularly simple limitation device provides a lever with a stop, an adjusting screw or a buffer.

In order to achieve a weir that is as dense as possible or a dense storage surface wall, the accumulation rollers are arranged in such a way that their axes of rotation are at a lead angle or a caster! related to a radial arrangement.

ERSATZBLAH (REGEL26) Depending on the design of the accumulation rollers, for example as a conical accumulation roller, as a cylindrical or as a spherical accumulation roller, the accumulation rollers are arranged in such a way that their extended axes of rotation form an intersection with the axis of rotation of the grinding bowl or with the longitudinal axis of the roller mill form.

The accumulation rollers can be arranged in dependence on the mill geometry, the material to be ground and the desired throughput capacity in such a way that the storage surfaces of the inner end faces have a different radial distance and / or a different inclination to the axis of rotation of the grinding bowl or to the longitudinal axis of the roller mill and and / or the grinding rollers overlap.

In a further development of the invention, the accumulation rollers are provided with more than one storage area. The further stowage surfaces are formed on the inside of the stowage rings, the stowage rings projecting radially from the outer surface of a stowage roller. The storage surfaces of the storage rings expediently form almost a right angle with the aid of the axis of rotation or the lateral surface of the storage roller.

These additional storage areas increase the retention effect of a storage roller. Grist, which is moved as a result of the centrifugal action of the grinding track in the direction of the storage rim of the grinding bowl, this movement taking place on a spiral track, is first blocked by the storage area on the inside end face of the storage roll and then on one or more further storage areas of the Restraining rings held back. The baffle rings thus act as a weir or as a blocking device, with the rotating design of the baffle wall showing extremely low friction.

ERSATZBL _Ä TT (REGEL26) In a particularly advantageous embodiment, a storage roller has, in addition to an inner storage area in the area of the inner face, at least on the outer face facing the housing wall of the roller mill, a storage ring which forms an outer weir or an outer storage area.

The baffle rings can expediently be applied subsequently to the baffle rollers. A detachable arrangement enables the storage surfaces of the storage rings to be adapted to the respective requirements.

The storage rings are expediently made of a wear-resistant material and roll on the grinding bed with a lateral surface of a relatively small radial width.

As an alternative to the pure rolling movement or a rolling movement superimposed on a sliding movement, depending on the arrangement of the accumulation rollers and the intersection of the axes of rotation with the axis of rotation of the grinding bowl below or above the level of the grinding track, the accumulation roller can also be driven in rotation to the grinding bowl. In addition, a leveling or, in addition, smoothing and pre-compression of the grinding bed can be carried out from the lateral surface areas of the accumulation roller formed between the accumulation rings if the accumulation roller has a corresponding weight or is additionally subjected to force.

The advantages of the roller mill according to the invention with accumulation rollers as retention devices are an extremely effective retention of regrind between the milling rollers. By preventing the material to be ground from reaching the bowl rim and into the area of the blade ring, disadvantageous loading of the sifting air stream with insufficiently ground material is avoided. This relieves the mill cycle and requires less work, what

ERSATZBLAH (REGEL26) leads to an improved energy balance. Since the accumulation rollers hold back the regrind extremely effectively, there is the possibility of increasing the speed of rotation of the grinding bowl and of increasing the throughput. Associated with this is the advantageous possibility of using smaller _> investment-friendly mills. Additional armor as wear protection is not necessary, especially if the accumulation rollers only rest on the grinding bed with their own weight and roll along.

The invention is explained below with reference to a drawing; in this show a schematic representation

Fig. 1 is a plan view of a grinding bowl

Roller mill with grinding rollers and with accumulation rollers as retention devices;

2 shows a partially sectioned view of a roller mill in the region of a damming roller rolling on a grinding bowl;

Fig. 3 is a view of an alternative embodiment of a storage roller according to Fig. 2 and

Fig. 4 is a view of a cylindrical accumulation roller.

The schematic representation acc. 1 shows a grinding bowl 2 which is set in rotation by a drive. The regrind fed from above or from the side onto a grinding path 8 of the grinding bowl is comminuted between resiliently pressed grinding rollers 6 and the grinding path 8 of the grinding bowl 2. The resilient pressing is usually carried out via a rocker arm and a hydraulic cylinder device (not shown) which interacts with it.

ERSATZBLAπ RULE26 The grinding rollers 6 are usually driven solely by frictional engagement with the grinding bed 7 present on the grinding track and have no separate drive. A fluid, usually air, is supplied via a blade ring 4 (see also FIG. 2) via a feed channel. The fluid flowing in via the blade ring 4 conveys from the grinding path 8 after being rolled over by the grinding rollers 6 as a result of the centrifugal force, the ground material mixture of fine material and coarse grain thrown outwards into the area of a classifier (not shown). Fine material is discharged from the airflow mill, while the coarse grain is fed to the center of the grinding bowl via a coarse material outlet, not shown. As a result of the centrifugal movement, the coarse grain comes together with fresh material onto the grinding track 8 and forms the grinding bed 7. The coarse grain can also be at least partially removed from the classifier or the mill and fed in via feed devices after an external circuit in front of the grinding rollers 6.

In order to avoid that, at a correspondingly high rotational speed, the grinding bowl 2 is inadequately comminuted ground material between the grinding rollers 6 over the grinding bowl edge 11 to the blade ring 4, retaining rollers 10 are arranged as retaining devices. In contrast to the grinding rollers 6, the accumulation rollers 10 rest on the grinding bed 7 solely due to their own weight and possibly due to a spring damping system. The accumulation rollers 10 are not involved in the comminution of the ground material. The jam rollers 10 primarily have the task of "sealing" the free space between the grinding rollers 6 in order to prevent insufficiently comminuted grinding material from being thrown off the grinding path 8 and loading the mill circuit.

1 shows a first embodiment of the accumulation rollers 10, which only have a storage surface 12 on an inner end face 14. The total storage areas 12

REPLACEMENT SHEET (RULE 26) In the area of the inner end faces 14 form an almost dense storage surface wall 13 or a weir, by means of which the ground material is retained between the grinding rollers 6 and fed to the next grinding roller 6 on the grinding path 8. Only in the area of the grinding rollers 6 and thus after the comminution process can the ground material be moved in the direction of the blade ring 4 and be transported into the classifying chamber. Fig. 1 shows that the accumulation rollers 10 are arranged with a lead or trailing angle in order to achieve an efficient accumulation effect for the regrind moving on a spiral path.

2 shows a second, particularly effective storage roller 10 in a longitudinal section, the axis of rotation 20 of which, in extension, intersects the axis of rotation 3 of the roller bowl 2 at the level of the roller bowl 2. The storage of the accumulation roller 10, which is not shown, can be carried out analogously to the storage of the grinding rollers 6. If several accumulation rollers 10 are arranged and each have a particularly low weight compared to the grinding rollers, there is also the possibility of attaching the accumulation rollers 10 to the housing. 2 has a storage surface 12 on an inner end face 14 and a storage ring 17. This retaining ring 17 runs in the region of an outer end face 18 facing the housing wall 5 of the roller mill and, with a further storage surface 15, faces the axis of rotation 3 of the grinding bowl. Identical features have been given the same features. The accumulation roller 10 according to FIG. 2 has a truncated cone shape and, due to the two accumulation surfaces, namely the inner 12 and the external accumulation surface 15 formed on the accumulation ring 17, has a particularly good retention effect.

A further, alternative accumulation roller 10 is shown in FIG. 3. This conical storage roller 10 is formed with three storage rings 17. These can also be removably attached to the jacket surface 19 of the accumulation roller 10. The too corresponding storage surfaces 15 extend radially outward from the lateral surface 19 of the accumulation roller 10 and are each arranged parallel to one another. The accumulation surfaces 15 formed on the accumulation rings 17 run almost at right angles to the axis of rotation 20 of the accumulation roller 10, so that the ground material moved to the bowl edge 11 of the grinding bowl 2 is blocked and retained.

The gap distance between the grinding track 8 and the lateral surfaces 19 of the accumulation rollers 10 can advantageously be adjusted with the aid of a device (not shown) and can be measured in such a way that the lateral surfaces 19 contribute to leveling or compaction of the grinding bed. The stowage rings 17 are made of a wear-resistant material. The storage surfaces 15 of the storage rings 17 can be flat, concave or convex.

A cylindrical accumulation roller 10 of FIG. 4 has an axis of rotation 20 which runs parallel to the grinding track 8. The accumulation roller 10 is provided with two accumulation rings 17, so that a total of three accumulation areas 12, 15 are formed together with a storage surface 12 on an inner end face 14. Even with a grinding bowl 2 rotating at high rotational speed, with an almost adjacent arrangement of accumulation rollers 10 and grinding rollers 6, efficient retention and grinding are ensured, so that an airflow roller mill equipped in this way has a high throughput capacity with a reduced energy requirement, has less wear on the restraint device and reduced maintenance outlay.

Claims

claims

1. Rolling mill with an almost horizontal grinding path (8) on a rotating grinding bowl (2), with stationary grinding rollers (6) which roll on a grinding bed (7) formed by ground material on the grinding path (8) of the grinding bowl (2), and with retaining devices (10) which are arranged between the grinding rollers (6) to influence the movement of the regrind, characterized in that retaining rollers (10) are provided as retaining devices (10) which roll on the milling bed (7) and at least one storage area (12 , 15) which retain the ground material between the grinding rollers (6) on the grinding track (8) for further grinding.

2. Rolling mill according to claim 1, characterized in that the accumulation rollers (10) on an inner, the axis of rotation (3) of the grinding bowl (2) facing end face (14) with the storage surface (12) are provided and that between the grinding rollers (6 ) one or more accumulation rollers (10) are arranged and dimensioned in such a way that their end faces (14) form a rotating accumulation surface wall (13) for holding back the ground material on the grinding track (8).

REPLACEMENT SHEET (REGEL2G)

3. Rolling mill according to claim 1 or 2, characterized in that the accumulation roller (10) has at least one further accumulation surface (15) and that the additional accumulation surface (15) is formed by means of at least one accumulation ring (17) which is radial protrudes from a lateral surface (19) of the accumulation roller (10).

4. Rolling mill according to claim 3, characterized in that an accumulation ring (17) is formed on an outer end face (18) of the accumulation roller (10) facing the mill housing (5).

5. Rolling mill according to one of the preceding claims, characterized g e k e n n z e i c h n e t that the lateral surface areas (19) between the retaining rings (17) and the internal storage surface (12) level or compress the retained regrind.

6. Rolling mill according to one of the preceding claims, characterized in that the accumulation rollers (10) rest on the grinding bed (7) solely by their own weight.

7. Rolling mill according to one of the preceding claims, characterized in that the accumulation rollers (10) have their own weight, which represents a fraction of the weight of the grinding rollers (6).

8. Rolling mill according to one of the preceding claims, characterized in that the accumulation rollers (10) can be acted upon with a hold-down force.

9. Rolling mill according to one of the preceding claims, characterized in that a device is provided with which the gap height between the lateral surface areas (19) of the accumulation roller (10) and the grinding bed (7) is adjustable and / or limited.

10. Rolling mill according to one of the preceding claims, characterized in that the accumulation rollers (10) and the grinding rollers (6) are arranged such that the extended axes of rotation each form an intersection with the axis of rotation (3) of the grinding bowl (2).

11. Rolling mill according to one of the preceding claims 1 to 9, characterized in that the accumulation rollers (10) with a reserve or

Caster angle to the grinding rollers (6) are arranged, the elongated axes of rotation (20) of the accumulation rollers

(10) lie outside the axis of rotation (3) of the grinding bowl (2).

12. Rolling mill according to one of the preceding claims, characterized in that the retaining rings (17) are formed from a wear-resistant material.

13. Rolling mill according to one of the preceding claims, characterized in that the retaining rings (17) have flat or curved storage surfaces (15).

14. Rolling mill according to one of the preceding claims, characterized in that the retaining rings (17) are detachable and / or subsequently applied.