Classifier for vertical roller mills

Abstract

The invention relates to a classification device for a vertical roller mill having at least two classifiers. Each classifier has an active rotor rotatable about a rotation axis. The rotation axis is arranged at an angle of at least 50° to the vertical. The invention is characterized in that around each classifier a guide vane row is provided which at least partially surrounds the classifier and has at least one guide vane. The guide vane has an open contour towards the rotation axis. Furthermore the invention relates to a vertical roller mill having a classification device according to the invention.

Description

[Technical field]

[0001] The present invention relates to a classifying device for a vertical roller mill, comprising at least two classifiers, which may be arranged in the same spatial plane, each of which comprises an active rotor rotatable about a rotation axis, the rotation axis being arranged at an angle of at least 50° to the vertical, in particular the rotation axis being arranged horizontally. [Background technology]

[0002] Vertical roller mills usually have a rotating grinding table on which several stationary arranged rotatable grinding rollers roll. The grinding material to be ground is fed to the grinding table and is crushed or crushed by the grinding rollers. After that, the ground material after grinding needs to be classified. When doing this, a distinction is made between sufficiently ground grinding material and so-called coarse material or coarse grains, which after classification is again guided to the grinding table for a further grinding process.

[0003] The basic structure of a roller mill can be obtained, for example, from Patent Document 1 or Patent Document 2 listed below.

[0004] A typical classifier has a classifier cage, also called rotor, which actively rotates around a rotation axis. In principle, passive classifiers are also known, in which classification is achieved only by deflecting the airflow, more precisely the dust airflow. Depending on the precise design of the classifier cage and its rotation speed, for example the classification limit can be influenced. This means that the particle size, within which separation is performed in the classification process, can be influenced. Grinding material with a particle size larger than the classification limit is rejected in the classifier by the classifier cage and fed for further grinding.

[0005] A roller mill with several horizontally arranged classifiers is known, for example from US Pat. No. 5,399,636.

[0006] Due to the ever-increasing size of roller mills with higher capacities and therefore larger throughputs of ground material, partly accompanied by an increase in the number of rollers, it is also necessary to appropriately improve the classifying units used to classify the ground material after grinding, so that they can achieve higher throughputs. In addition, it must be taken into account, especially in combination with vertical roller mills operating in recirculating air mode, that the air currents or flows generated by the rotor or classifier cage can partially have a negative effect on the overall air flow. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2011 / 107124 [Patent Document 2] International Publication No. 2012 / 079605 [Patent Document 3] International Publication No. 2014 / 067688 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention is based on the object of providing an efficient and high performance classification device. [Means for solving the problem]

[0009] According to the invention, this object is achieved by a classification device for a vertical roller mill having the features of claim 1.

[0010] Advantageous embodiments of the invention are set out in the dependent claims, the description as well as in the figures and their description.

[0011] In the classifying device according to the invention, provision is made for a guide vane row arranged around each classifier, at least partially surrounding the classifier, each guide vane row having at least one guide vane, wherein each guide vane has an open contour towards the rotation axis of the classifier.

[0012] The invention is based on the basic idea that the process air used to transport the ground material crushed by the crushing rollers to the classifier is clearly guided by guide vanes to the rotor or classifier cage, in this way the flow angle of the process air and thus of the ground particles of the ground material transported therewith can be influenced so that classification can take place more efficiently.

[0013] In addition, the guide vanes are designed with a profile shape that opens towards the rotation axis of the classifier. The advantage of this is that particles rejected by the rotor because they are not yet sufficiently broken can be collected at the open profile and then guided by gravity to the area below the classifier. The advantage is thus obtained that the particles rejected in this way can be guided specifically to a specific part of the classifier or classifying device instead of being released into the entire space in which the classifier or classifier cage is located. Due to the targeted guidance of rejected particles that are too coarse, the classifier can operate more efficiently since there are fewer interfering effects.

[0014] According to the invention, the classifiers can be arranged in the same spatial plane, but also in different planes, in other words an offset arrangement is also possible, in which the classifiers are provided at different heights relative to the grinding table.

[0015] Basically, each classifier can be arranged with any desired axis of rotation. Preferably, however, the axis of rotation has a maximum angle of 20°, more preferably 10°, to the horizontal, in particular arranged horizontally. In contrast to vertically arranged classifiers, a horizontal arrangement is particularly suitable when several classifiers are to be used. As a result, classifiers with a small overall size can be used, several of which are combined into a classifier device.

[0016] The classifiers, and more particularly their rotors, may have a substantially identical shape. By way of example, this may be substantially cylindrical. However, other shapes are also possible, such as a conical basic shape. The arrangement of identical classifiers facilitates the overall construction as well as the storage of spare parts.

[0017] In a preferred embodiment, the rotation axes of the classifiers are aligned with one another and have a common intersection point. If the axes are not precisely aligned with one another, it is also possible for the intersection point to be slightly enlarged so that an intersection area exists. Such an arrangement has proven to be advantageous, since it improves the classification result and can reduce the energy required to drive the classifiers.

[0018] Advantageously, the guide vanes are arranged in the shape of a ring around the axis of rotation or around the rotor, in other words, in a cylindrical rotor, the guide vanes form a second cylindrical shell-shaped structure around the rotor itself.

[0019] In conjunction with this, the guide vane row may have at least three guide vanes. Preferably, a much larger number of guide vanes, up to 12 or 20, is provided. Here, the distance between adjacent guide vanes may be the same for each adjacent guide vane. This distance is selected so that there is an intermediate space through which the process air with the ground particles of the ground material can flow. In different embodiments, said distance is designed in a different way. For example, it may decrease or increase from the outside, i.e. the area of ​​the mill housing, towards the inside, i.e. the center of the mill.

[0020] As described above, the guide vanes may have a V-shaped or U-shaped cross section with a profile that opens inwardly towards the rotor. In this case, the tip or curved side of the V-shaped or U-shaped cross section faces outward, i.e. opposite to the direction towards the rotation axis of the classifier. The incoming air is thus divided and easily guided by the guide vanes, which direct it in the desired direction. In addition, it is easy to design the inward opening profile so that it can serve to collect and return the rejected particles. According to the invention, it is not absolutely necessary that the shape of the cross section or profile of the guide vanes is the same over their entire length. The shape of the cross section or profile may vary. In addition, the shape of the cross section or profile of the guide vanes used may be varied.

[0021] Basically, the guide vanes here can have various flanks in cross section, for example if they are designed with a V-shaped or U-shaped cross section, they usually have two flanks, both of which do not necessarily have to be designed the same, one may be designed longer than the other, and this allows the conveying air or process air flowing through the guide vanes of the guide vane row to be guided in the desired direction to the rotor of the classifier.

[0022] It is advantageous if the guide vanes of the guide vane row have an interruption in the shape of a ring, which serves the purpose that the particles rejected by the classifier can fall through an open contour and be transported to be crushed again.

[0023] Guide plates can also be arranged in the interruptions. These are preferably arranged transversely to the direction of the guide vanes. On the one hand, the guide plates serve to further guide the incoming conveying air. On the other hand, it is thus possible to discharge the rejected particles that have fallen from the guide vanes in the guiding direction.

[0024] Furthermore, the present invention relates to a vertical roller mill comprising a classifying device according to the present invention.

[0025] Here, the number of classifiers of the classifier may correspond to the number of rollers provided for grinding purposes (active rollers). In the sense of the present invention, active rollers may in particular be understood as rollers that are used to grind the grinding raw material. Rolling mills are also known which have smaller grinding rollers as well as larger grinding rollers, in which case the smaller grinding rollers are often called preparation rollers and are mainly used to prepare the grinding bed. They do not primarily serve to grind the grinding raw material.

[0026] Providing as many classifiers as active grinding rollers has proven to be a good solution to achieve energy-efficient classification, since in this case a large number of small classifiers as well as a small number of large classifiers are used.

[0027] Depending on the raw material to be ground and the space available in the housing, the number of classifiers may be more or less than the number of active rollers.

[0028] Preferably, the classifiers of the classifying device are arranged in a star-shaped manner in the mill housing of the vertical mill. This means that they have the same radial or angular distance (angular interval) from each other. Such an even distribution leads to good classification results, especially in roller mills operating in recirculating air mode, since the ground particles are transported throughout the mill housing by the conveying air flow. Furthermore, in this way the space available in the mill housing can be utilized in an optimal manner. In some embodiments, it can also be advantageous to provide classifiers with different angular distances from each other.

[0029] A common coarse funnel can be provided for all classifiers of the classifying device, and below the interruption of the guide vane row a chute can be arranged for guiding the rejected particles to the common coarse funnel. In conjunction with this, it is preferred if the interruption of the guide vane row is positioned towards the grinding chamber so that the rejected particles fall downwards in the direction of the grinding table or, if a common coarse funnel is provided, fall there by gravity, making additional transport unnecessary.

[0030] In certain embodiments, it may also be advantageous if the classifier coarse particles of each classifier are guided in an individual chute also to the grinding table or further towards the outside of the grinding chamber, in the latter case removing the classified coarse particles from the further grinding process in order to be fed to a different type of further treatment.

[0031] In the following, the invention is explained in more detail by means of schematic and exemplary embodiments with reference to the figures. [Brief description of the drawings]

[0032] [Figure 1] 1 is a highly schematic, partially cross-sectional view of a vertical roller mill equipped with a classifying device according to the invention; [Diagram 2] 3 is a highly schematic, partially cross-sectional view of a roller mill equipped with a classification device according to the invention in another embodiment; FIG. [Diagram 3] FIG. 2 shows a guide vane array with guide plates. [Figure 4] 1A-1C illustrate various profiles for guide vanes of a guide vane row according to the present invention. [Diagram 5] FIG. 1 shows a coarse funnel with a chute. [Figure 6] FIG. 1 shows a coarse funnel with three guide vane rows. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] In the following, with reference to FIG. 1, on the one hand the basic principle of a vertical roller mill is described and on the other hand the concept according to the invention is presented.

[0034] In Fig. 1 a rather simplified view of a vertical roller mill 20 is shown. It has a grinding table 23 on which several grinding rollers 22 roll. In operation, the grinding table 23 rotates. The material to be ground is fed to said table and is ground by the grinding rollers 22 which are rotatably mounted in a fixed position. In the embodiment shown here, only two grinding rollers 22 are shown.

[0035] Above each of the crushing rollers 22, a classifier 12 of the classifying device 10 according to the present invention is installed.

[0036] Each classifier 12 has a rotor 14 rotatable about an axis of rotation 16. In the embodiment shown here, the axes of rotation 16 of the two classifiers 12 are arranged in the same plane and intersect approximately above the center of the grinding table 23.

[0037] Surrounding the rotor 14, which may also be referred to as a classifier cage, is a guide vane array 30 having eight guide vanes 32 in the embodiment shown.

[0038] In Fig. 3, the guide vane rows 30 are shown separately. As can be seen, the guide vanes 32 are designed in the shape of a ring, with an interruption in which the guide plate 36 is arranged in the embodiment shown in Fig. 3. In essence, the guide vanes 32 describe a full circle or even a ring. Overall, the guide vane rows 30 have a shape similar to a cylindrical shell. They are arranged around the rotor 14 of each classifier 12, which may also have a cylindrical shape. If the rotor 14 has a different external shape, this external shape may be reproduced by the guide vane rows 30.

[0039] In Fig. 4 various possible cross sections of the guide vane 32 are depicted by way of example. In this case the cross section has a U-shaped or V-shaped shape. In the mounted state the open side of the contour 34 faces inwards, i.e. towards the rotor 14. In the embodiment shown here the cross section of the guide vane 32 has essentially two side surfaces 35. As can be seen, the side surfaces can be designed with the same size, but they can also be of different size or length. Likewise, it is not absolutely necessary that the cross section has a symmetrical design, but it can also be designed with one side surface 35 that is rather long. As shown in Fig. 4, it is also possible that the cross section has a triangular shape.

[0040] As can be seen especially in the general views of Figures 1 and 2, the guide vanes 32 may be arranged in different ways, for example with their inclined sides facing towards the grinding table 23, as in Figure 1, or facing away, as shown in Figure 2. Together with the various contours 34 depicted in Figure 4, this may have various effects on the flow of process gas present inside the roller mill 20.

[0041] In FIG. 3, guide plates 36, the function of which will be explained in more detail below, are disposed in recesses or interruptions in the guide vanes 32 of the guide vane row 30.

[0042] In Fig. 5 a coarse funnel 40 is shown, which in this embodiment has three chutes 41. By means of the coarse funnel 40 the coarse particles rejected by the classifier, also called under-ground particles, can also be guided to the grinding table 23. Openings or interruptions in the guide vane rows 30 can be used for this purpose. For this reason a coarse funnel 40 with three guide vane rows 30 arranged thereon is shown in Fig. 6, which have openings that end in the area of ​​the chutes 41.

[0043] In the following, with particular reference to FIG. 1, the basic functioning of the roller mill 20 will be described taking into account the classification device 10 according to the invention.

[0044] The material to be ground is fed to the grinding table 23 and ground by the grinding rollers 22. The ground material that falls on the grinding table 23 is conveyed to the classifier 10 by a process air flow that is directed upwards towards the classifier 12. Through an air flow, which may also be called a conveying air flow, the ground material passes through a guide vane array 30 and advances to the classifier 12, which comprises a rotor 14.

[0045] The rotation of the rotor 14 classifies the ground particles or the ground raw material after grinding. The ground raw material that is sufficiently ground is further transported by the process gas flow and leaves the vertical roller mill 20 through an outlet provided above the classifier 10.

[0046] Under-ground material is rejected by the rotor 14. It is literally thrown out of the rotor 14. These under-ground particles are collected by the profile of the guide vanes 32 and slide under the force of gravity down the inside of the guide vanes and towards the grinding table 23, i.e. the lower area of ​​the vertical roller mill 20. Depending on the precise profile of the guide vanes 32, the direction of the process gas flow into the rotor 14 can be influenced.

[0047] In the embodiment shown here, the guide vanes 32 of the guide vane row 30 have openings in the lower area, through which the rejected particles, which correspond to insufficiently ground raw material, are conveyed via a chute 41 to the coarse grain funnel 40, from where they are again guided to the grinding table 23, where they are again ground and once again guided by the process gas flow to the classifier 10.

[0048] Additionally, or optionally, guide plates 36 may be provided at the interruptions in the guide vane array 30. These guide plates serve to guide the process gas flow exiting the interior of the mill and to achieve optimal entrance flow to the rotor 14 at the recesses or interruptions in the guide vane array 30.

[0049] Thus, the classification device according to the present invention enables efficient classification of the pulverized raw material after pulverization.

Claims

1. A classification apparatus for a vertical roller mill having at least two classifiers, Each classifier has an active rotor that can rotate around its axis of rotation. The rotation axis is positioned such that the angle it makes with the vertical line that is 90° or less is at least 50°. Guide vane arrangements are provided around each classifier, at least partially surrounding the classifier. Each of the above guide vane arrangements has at least one guide vane, The guide vanes are arranged in a ring shape around the axis of rotation, The guide vane has an open contour facing the rotation axis of the classifier, The guide vanes in the aforementioned guide vane arrangement have an intermediate portion, and a guide plate is arranged in the intermediate portion in a direction transverse to the guide vanes. Multiple rotation axes are aligned with each other and have a common intersection or crossing area, Classifying device.

2. The classification apparatus according to claim 1, wherein at least two of the classifiers are identical and have a cylindrical shape.

3. The classification apparatus according to claim 1, wherein the axis of rotation has a maximum angle of 20° with respect to the horizontal plane.

4. The classification apparatus according to claim 1, wherein the guide vane has a V-shaped or U-shaped cross-section.

5. The classifier according to claim 1, wherein the guide vane is designed to have at least two sides, one of which is longer.

6. The classification apparatus according to claim 1, wherein at least three guide vanes are provided for each of the guide vane arrangements, and there is a distance between each of two adjacent guide vanes.

7. A vertical roller mill comprising the classification apparatus described in claim 1.

8. The vertical roller mill according to claim 7, wherein the number of classifiers in the classification device corresponds to the number of rollers provided for the purpose of crushing.

9. The vertical roller mill according to claim 7, wherein the classifiers of the classification apparatus are arranged in a star shape within the mill housing at equal distances from one another.

10. A vertical roller mill according to claim 7, further comprising a common coarse grain funnel having a chute for each classifier.

11. The vertical roller mill according to claim 7, wherein the interrupted portion of the guide vane arrangement is positioned toward the grinding chamber.

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