DK2780113T3 - Vertical roller mill - Google Patents

Description

Vertical roller mill

The invention relates to a vertical roller mill according to the preamble to claim 1. Vertical mills, or respectively vertical roller mills, are sufficiently known (WO 2005/028112 A1; DE 31 00 341 A1). The vertical mills mentioned have in the upper region of the mill housing a classifier basket, rotating about a vertical axis, for classifying the fines - gas mixture conveyed upwardly in the gas flow.

Since, in terms of processing, increasingly large throughputs are required with such vertical mills, an increasingly large dimensioning of the components such as grinding table, grinding rollers, classifier basket, etc., is carried out. The components can therefore, in part, no longer be produced as one unit but instead, due to their size, only as sub-divided units which must be put together or welded together once they have arrived at the place of use of the vertical mill.

Besides these aspects, increasingly large gas volumes and corresponding fans are also required in order for example to be able to blow in hot gas as transport and drying gas via the annular gap and in particular to be able to realise the upward conveyance of ground particles over the whole height of the vertical mill to the classifier basket .

Another vertical mill which facilitates separation and output of constituent parts of a material mixture which are difficult to disperse (DE 197 18 668 C2) has in the upper region of the mill housing a horizontal classifier which rotates about a horizontal axis and in this way facilitates an output of fines from the grinding and classifying process.

The use of one or more horizontal classifiers in vertical mills can therefore be assumed to be known.

In terms of energy, however, these configurations also have the problem of providing larger gas volumes for the transport of the over-ground grinding material particles in order to be able to convey these particles extensively over the whole height of the housing of a vertical mill to the horizontal classifiers provided in the upper region.

It is thus an object of the invention to design a vertical mill and in particular a vertical roller mill in such a way that, even with increasingly large vertical mills and higher throughputs, in particular the classifier component can be realised as one unit or with a plurality of units and a substantial increase in energy resources required for the transport and drying gas is avoided.

This object is achieved according to the invention through the features of claim 1. Advantageous embodiments of the invention are claimed in the sub-claims.

An essential core idea of the invention can be seen in considerably shortening the transport path of over-ground grinding material particles to the classifier so that a higher energy requirement does not arise having regard to the required pressure and gas volume.

This is achieved on the one hand by deviating from a classifier basket arranged in the upper region of the mill housing and instead arranging smaller classifiers in the vicinity of the rollers, in particular horizontal classifiers or such classifiers which are slightly inclined. A further essential idea of the invention can be seen in arranging a guide unit for the grinding material over-ground by the grinding roller for the finer grinding material particles conveyed upwardly in the gas flow, wherein the guide unit facilitates a spiral-like feed to the respective horizontal classifier.

The vertical roller mill designed in this way with rotating grinding table and at least two stationary grinding rollers rolling on the grinding bed thus creates a more efficient use of energy having regard to the required transport and drying gas or even energy saving as a result of the smaller structural units of horizontal classifiers or such smaller classifiers with inclined rotation axis, wherein these are arranged in the vicinity of the rollers.

The combination of the corresponding horizontal classifier with a curved guide unit for better conveyance of the grinding material particles conveyed upwardly in the gas flow reduces or respectively avoids, as the case may be, an inner recirculation of over-ground grinding material particles so that an energy reduction can also hereby be achieved. A wind classifier or horizontal classifier and a guide unit are usefully assigned to each grinding roller so that recirculation flows can be extensively avoided.

It is, however, also conceivable and possible, instead of the individual assignment of a horizontal classifier to each roller, to also bring together the ascending gas -grinding material particle flow of for example two rollers. In the case of a mill having four grinding rollers therefore a configuration with two horizontal classifiers would thus also be conceivable wherein a respective horizontal classifier is assigned to each pair of two grinding rollers brought together.

An improvement in relation to flow is also achieved by the respective wind classifier being arranged offset in front of the respective grinding roller. In structural terms, the offset of the wind classifier can be seen therefore with respect to the vertical axis guided through the centre of the respective grinding roller, as shown in Fig. 1, wherein this is carried out in the direction of the over-ground grinding material present behind the grinding roller. The arrangement of the respective wind classifier offset with respect to the corresponding grinding roller has the advantage that the grinding material particles of the over-ground grinding material which are present, so to speak, behind the grinding roller can be better taken up by the guide unit for the finer grinding material transported upwardly in the gas flow and can be fed in a more targeted way to the assigned horizontal classifier.

In order to improve the conveyance of the upwardly transported grinding material particles the guide unit is configured as a curved guide plate or as a collecting channel extending in a curved manner for the spiral feeding of the particles to the classifier basket of the wind classifier. In terms of flow dynamics, a feed of the grinding material particles with the same rotation direction as the classifier basket of the corresponding wind classifier is thereby realised over a relatively short distance so that a good classification of the grinding material particles can hereby be achieved.

Insofar as a curved collecting channel is provided for the upwardly transported grinding material particles, the channel cross-section is reduced in the direction towards the wind classifier so that, on account of the increased flow speed in this region and the centrifugal force acting there, a type of pre-classification for coarse material is realised. This coarse material is moved, in addition to the coarse particles rejected by the classifier basket of the wind classifier, to a recirculating unit arranged below the wind classifier and fed once again to the grinding process. The recirculating unit is usefully formed as a funnel-like cone, whereby rejected coarse material is fed back on the recirculating unit inclined towards the centre, preferably approximately in the middle of the grinding table.

The arrangement of the wind classifiers or horizontal classifiers can be connected in a constructively simple manner via a common inner, central discharge line for the gas - fines flow, so that a feed pipe suffices for conveying the gas - fines flow to downstream units such as cyclone or dust filter.

Depending upon the design of the whole vertical mill the respective wind classifiers can be equipped with separate discharge lines outwardly for the classified gas - fines mixture. By means of this division, separate preparation of the grinding material particles into different, desired fractions can be carried out.

In spite of the integration of a plurality of wind or horizontal classifiers, in this configuration of the vertical mill a central grinding material feed can be realised so that increased cost resources do not appear necessary in spite of a plurality of wind classifiers.

Such a designed vertical mill with wind classifiers arranged horizontally or inclined and which are in particular each assigned to a grinding roller thus facilitates shortened transport paths for the over-ground grinding material particles. The grinding process and the energy resources required for this can be considerably improved with the solution according to the invention, especially since the overall height of the vertical mill is smaller and lower and also a recirculation of over ground grinding material particles is avoided as extensively as possible. The wind classifiers used horizontally or inclined improve the classification of fine material particles in comparison with static classifiers in the upper region of a vertical mill. Due to the shortened transport paths for over-ground grinding material particles upwards, even in the case of a blade ring within the annular gap around the grinding table, the gas volume and the required pressure can be reduced so that energy savings can be achieved.

The invention is explained in greater detail below using a schematic embodiment.

The single Fig. 1 shows a partial cut-out of a vertical mill in the region of a grinding table and grinding rollers provided thereon and also horizontal classifiers arranged in the vicinity of the rollers. The cut-out shown corresponds approximately to a 90° cut-out which can also be approximately 140° having regard to the outer contours of the grinding rollers. A grinding roller with a view of the inner side thereof is shown in the rotation axis of the grinding table, whereas in the left region of Fig. 1 a side view of a second grinding roller with schematic rocker arm arrangement in the region of the grinding table edge and the annular gap is shown.

Fig. 1 shows a vertical roller mill 1 according to the invention schematically and in partial section.

The detailed section shows a vertical roller mill 1 in a circular segment-form cutout of approximately 90° between the vertical axes of two adjacent grinding rollers 4 offset approximately by this angle. The whole circular segment cut-out is therefore somewhat greater and approximately 140°.

In the lower region a grinding table 2 is shown with a rotation direction D about its rotation axis 3. Two grinding rollers 4 are provided on the grinding table 2, wherein the grinding roller 4 lying in the drawing plane in the rotation axis 3 is shown as looking in the direction outwardly from inside. The grinding roller 4 arranged in the left region or the left half of the roller mill 1 is shown in the side view with a view towards the conical roller shell and the suspension of the grinding roller via a rocker arm.

An annular gap 17 is provided around the radially outer edge of the grinding table 2, said annular gap 17 normally having a blade ring and being intended for blowing in the transport and drying gas 19 as a gas flow.

The grinding material 13 to be comminuted and ground which can be centrally introduced is fed through the rotation D of the grinding table 2 to the grinding rollers 4 and comminuted through the pressure of the grinding roller and shear forces thereby produced so that an over-ground grinding material is present behind the grinding roller 4 (left).

The newly introduced grinding material 13 and the over-ground grinding material 14 form, in the actual grinding process, a mixture constituting the grinding bed 15 in the outer region of the grinding table 2.

In order to avoid repeated over-rolling or respectively over-grinding of comminuted grinding material, provision is made according to the process for a volumetric portion of fines and grinding material particles which is as large as possible to be fed through the blown-in gas flow 19 in the ascending gas - grinding material particle mixture 21 behind the respective grinding roller 4 immediately to the corresponding wind classifier 7.

The grinding rollers 4 arranged in a stationary manner carry out, due to the force and friction locking with the grinding bed 15, a rotational movement Dw in the same direction with the grinding table 2.

Provision is made according to the invention to provide in the vicinity of each grinding roller 4, above it, offset approximately in the rotation direction D of the grinding table 2, a smaller wind classifier 7 with horizontal axis 9, possibly also inclined axis. The corresponding horizontal classifier 7 with a rotationally driven classifier basket 8 thus obtains the over-ground grinding material, upwardly conveyed in the gas flow 19, over a relatively short distance.

Therefore, a gas flow 19 which is high in terms of pressure and volume is not required in order to transport the gas - grinding particle mixture over the whole grinding chamber of the vertical mill as far as a classifier basket arranged in the upper region of the housing of the mill.

According to the invention, besides the shortening of the distance through the arrangement of the wind classifier 7 in the vicinity of the grinding roller 4, a guide unit 25, for example as a guide plate 26 or as a collecting channel 27, is additionally provided. The ascending gas particle flow can thus be collected through this guide unit 25 and guided in a targeted manner, wherein a curved design in the direction of and around the wind classifier 7 further improves the spiral feed. The decreasing cross-section of the guide channel 27 also contributes to this. The feed of the ascending gas - grinding particle mixture 21 to the wind classifier 7 thus takes place in the same rotation direction as the wind classifier itself so that a good classification into fines and rejected coarse material can be realised at the classifier basket 8.

Fines classified in the classifier basket 8 can then, as shown in the left part of Fig. 1, be guided outwards as fines 29, in particular being pneumatically guided, and fed there in a central feed pipe or with decentralised individual lines to downstream units such as a cyclone or filter.

The wind classifiers 7 shown have a horizontal rotation axis. An inclined rotation axis is also possible, wherein an inclination of the rotation axis inwardly towards the centre of the grinding table also encourages the discharge of fines outwards. An inclination of the rotation axis of the wind classifier 7 in the direction of the suspension and the rocker arm of the corresponding grinding roller 4 encourages on the other hand the output of classified fines into the central, upper region of the roller mill so that a central discharge can be created for the fines. A funnel-like cone 31 is provided for the recirculation of rejected coarse material 32 as a recirculating unit for the material approximately into the central region of the grinding table 2.

The structure according to the invention of the vertical roller mill with the arrangement of wind classifiers 7 in the vicinity of the grinding rollers 4 and in combination with the guide unit 25 thus allows a highly efficient grinding process, as a recirculation of over-ground particles is extensively prevented. In addition there is a lower transport gas volume and a low gas pressure due to the short path between the grinding bed and existing wind classifiers 7. Likewise, a lower level of investment is required for the overall installation of a roller mill according to the invention due to the lower mode of construction of this vertical roller mill in comparison with convention vertical mills.

Claims (12)

A vertical roller mill (1) with a driven mill surface member or disc (2) and at least two rolling mill stationary rollers or rollers (4) rolling on the grinding surface (15) of the grinding material (13), with an annular slot (17), surrounding the mill face member or disc (2), for blown air (19) for transport and / or for drying the particles (21) of the milled milling material of the milled milling material, with at least one classifying air screen (7) which classifies the particles (14) transported upwards in the air stream (19) into fine material (29) and recycled coarse material (32), and wherein the classifying air screen (7) is arranged with a substantially horizontal (9) or inclined oriented classification screen axis, characterized in that that several classifying air sieves (7) are provided and where they are disposed in the vicinity of the mill rollers or rollers (4) and that each mill roll or roll is arranged e (4) includes at least one guide device (25) for spirally extending supply of grinding material particles (14) upwardly transported in the air stream (21) to the classifying air screen (7). Rolling mill according to claim 1, characterized in that a classifying air sieve (7) and a guide device (25) are respectively provided for each mill roll or roller (4). Rolling mill according to claim 1 or 2, characterized in that the respective classifying air screen (7) in the direction of the milled grinding material (14) is positioned arranged relative to the vertical axis (3) through the respective mill roll or rolls (4). center (5). Rolling mill according to claim 1, 2 or 3, characterized in that the guide device (25) has an arcuate extending guide plate (26) or an arcuate extending trapping channel (27) for supplying a grinding material particles (14) to the air screen (7). classification screen basket (8). Rolling mill according to claim 4, characterized in that the arc-shaped catch channel (27) is formed with decreasing channel cross-section in the direction of or around the classifying air screen (7). Rolling mill according to claim 1, 2, 3, 4 or 5, characterized in that the guide device (25) has an inflow area of the grinding channel (27) for grinding material particles (approximately) in height with the upper region of the mill rollers or rollers (4). , 19) and in the rear region of the present mill roller or roller (4). Rolling mill according to claim 1, 2, 3, 4, 5 or 6, characterized in that the direction of flow of grinding material particles (14, 19) in the region of the guide device (25) corresponds to the direction of rotation of the classifying air sieves (7). Rolling mill according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that each classifying air screen (7) has a reclining device (31) inclined towards the center of the mill surface or disc (2). rejected coarse material (32). Rolling mill according to claim 8, characterized in that the return device (31) is designed as a funnel-shaped cone. Rolling mill according to claims 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that the classifying air sieves (7) are connected to the classified air-fin material extracted from the classifying air sieves (7). mixture (29). Rolling mill according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that the classifying air screens (7) outwardly exhibit separate discharges for the classified air-fine material mixture (29). Rolling mill according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, characterized in that a central painting material delivery section is arranged.