Classifier assembly for a vertical roller mill

Abstract

The invention relates to a classifier assembly (10) for a vertical roller mill, comprising at least two classifiers (12). Each classifier (12) has an active rotor (14) which is rotatable about an axis of rotation (16). The axis of rotation (16) is oriented at least at an angle of 50° to the vertical. The invention is characterized in that, around each classifier (12), a guide-vane assembly (30) at least partly surrounding the classifier and having at least one guide vane (32) is provided. The guide vane (32) has a profile (34) which is open toward the axis of rotation. The invention also relates to a vertical roller mill having a classifier assembly according to the invention.

Description

[0001] The invention relates to a classifier arrangement for a vertical roller mill, comprising at least two classifiers. These can be arranged in the same spatial plane. Each classifier has an active rotor that is rotatable about a rotational axis. The rotational axis is oriented at least at an angle of 50° to the vertical. In particular, the rotational axis is horizontally oriented.

[0002] Vertical roller mills typically feature a rotating grinding plate on which several stationary, rotating grinding rollers roll. The material to be ground is fed onto the grinding plate and crushed or pulverized by the grinding rollers. The ground material then needs to be sifted. A distinction is made between sufficiently ground material and so-called coarse material or grit, which, after sifting, is returned to the grinding plate for further grinding.

[0003] The basic design of a roller mill can be found, for example, in WO 2011 / 107124 A1 or WO 2012 / 079605 A1.

[0004] Classifiers of this type feature a classifier basket, also known as a rotor, which is actively rotated around the axis of rotation. However, passive classifiers are also known, in which classification is achieved simply by deflecting an airflow, or more precisely, a dust-airflow. The classifying limit can be influenced by the precise design of the classifier basket and its rotational speed. This means that the particle size range within which separation occurs during classification can be controlled. Material with particle sizes larger than the classifying limit is rejected by the classifier basket and fed into a further grinding process.

[0005] A roller mill with several horizontally arranged classifiers is known, for example, from WO 2014 / 067688 or DE 38 14 458 A1.

[0006] Due to the ever-increasing size of roller mills, some with more rollers, which process higher capacities and thus greater throughput of ground material, it is also necessary to improve the classifying units used to classify the ground material accordingly, so that they too can achieve a higher throughput. Additionally, it must be considered that, especially in conjunction with vertical roller mills operating in recirculation mode, the air currents or turbulence generated by the rotors or classifier baskets can sometimes have a negative impact on the overall airflow.

[0007] The invention therefore lies in the Aufgabe The basis is to specify an efficient, high-performance classifier arrangement.

[0008] This problem is solved according to the invention by a classifier arrangement for a vertical rolling mill with the features of claim 1.

[0009] Advantageous embodiments of the invention are specified in the dependent claims, in the description, as well as in the figures and their explanation.

[0010] In the classifier arrangement according to the invention, a guide vane arrangement is arranged around each classifier, at least partially surrounding it. Each guide vane arrangement has at least one guide vane, each guide vane having a profile open in the direction of the classifier's axis of rotation.

[0011] The invention is based on the fundamental idea of ​​directing the process air, which is used to transport the ground material crushed by the grinding rollers to the classifiers, specifically onto the rotor or classifier basket by means of guide vanes. This allows the angle of attack of the process air, and thus of the crushed material particles transported with it, to be influenced, enabling more efficient classifying.

[0012] Additionally, the guide vanes are designed with an open profile in the direction of the classifier's axis of rotation. This has the advantage that particles rejected by the rotor because they are not yet sufficiently sized can be captured in the open profile and then guided by gravity to the lower section of the classifier. This allows rejected particles to be directed to specific areas of the classifier or classifier assembly instead of being scattered throughout the entire space containing the classifier or classifier basket. By guiding the rejected, overly coarse particles, the classifier can be operated more efficiently due to fewer disturbances.

[0013] According to the invention, the classifiers can be arranged in the same spatial plane or in different planes. In other words, an offset arrangement is also possible, in which the classifiers are positioned at different heights relative to the grinding plate.

[0014] In principle, each classifier can be arranged arbitrarily with respect to its axis of rotation. Preferably, however, the axis of rotation has a maximum angle of 20° to the horizontal, more preferably 10°, and can in particular be arranged horizontally. In contrast to vertically arranged classifiers, the horizontal arrangement is particularly advantageous when several classifiers are to be used. This allows for the use of smaller classifiers overall, several of which can be combined to form a safety arrangement.

[0015] The classifiers, especially their rotors, can have essentially identical shapes. These can be, for example, essentially cylindrical. However, other shapes, such as a conical base, are also possible. Using identical classifiers simplifies the overall design as well as spare parts management.

[0016] In a preferred embodiment, the rotation axes of the classifiers are aligned with each other and have a common point of intersection. It is also possible for the point of intersection to be slightly enlarged, thus creating a cutting area if the axes are not exactly aligned. Such an arrangement has proven advantageous because it improves the classifying result and / or reduces the energy required to drive the classifiers.

[0017] Advantageously, the guide vanes are arranged in a ring around the axis of rotation or the rotor. In other words, in the case of a cylindrical rotor, the guide vanes form a second cylindrical shell-shaped arrangement around the rotor itself.

[0018] A guide vane arrangement can have at least three guide vanes. Preferably, significantly more, up to twelve or twenty guide vanes, are provided. The distance between adjacent guide vanes can be the same. This distance is chosen to provide a gap through which the process air, carrying the ground material particles, can flow. In another embodiment, the distance varies. For example, it can decrease or increase from the outside, i.e., the area of ​​the mill housing, to the inside, i.e., the center of the mill.

[0019] As previously described, the guide vanes have an inwardly open profile, open towards the rotor, which can have a V- or U-shaped cross-section. The tip or rounded side of the V- or U-shaped cross-section points outwards, away from the axis of rotation of the classifier. This allows incoming air to be divided and efficiently guided past the guide vanes, directing it in a desired direction. Additionally, this design simplifies the inwardly open profile, enabling it to capture and redirect rejected particles. According to the invention, it is not essential that the cross-section or profile of a guide vane be uniform along its entire length. The cross-section or profile can vary. Furthermore, the cross-section or profiles of the guide vanes used can differ.

[0020] In principle, the guide vanes can have different leg shapes in cross-section. If the guide vanes are designed with a V- or U-shaped cross-section, for example, they usually have two legs, which do not have to be identical; one can also be longer than the other. This allows the carrier air or process air flowing through the guide vane assembly to be directed towards the rotor of the classifier in a desired direction.

[0021] It is advantageous if the guide vanes of the guide vane assembly have a break in their ring-shaped form. This allows the particles rejected by the classifier to fall out of the open profiles and be reground.

[0022] Guide vanes can also be arranged within this interruption. These are preferably arranged transversely to the direction of the guide vanes. The guide vanes serve, firstly, to further guide the incoming carrier air. Secondly, they provide a means of directing the rejected particles falling from the guide vanes in a controlled direction.

[0023] Furthermore, the invention relates to a vertical rolling mill with a classifier arrangement according to the invention.

[0024] The number of classifiers in the classifier arrangement can correspond to the number of rollers intended for active grinding. For the purposes of the invention, active rollers can be understood to be, in particular, rollers used for comminuting the material to be ground. Roller mills are also known that have both larger and smaller grinding rollers, the smaller grinding rollers often being referred to as preparation rollers and being used primarily for preparing the grinding bed. They do not primarily serve to comminute the material to be ground.

[0025] Providing the same number of classifiers as active grinding rollers has proven to be a good solution for achieving energy-efficient classifying, as this avoids the need for many small classifiers or a few large classifiers.

[0026] Depending on the material being ground and the available space in the housing, the number of classifiers can be greater or less than the number of active rollers.

[0027] It is preferred that the classifiers of the classifier assembly are arranged in a star shape within the mill housing of the vertical mill. This means that they each have the same radial or angular distance to one another. Such a uniform distribution provides good classification results, since in a roller mill, especially in recirculating air operation, the ground particles are transported throughout the entire mill housing by the carrier airflow. This arrangement also allows for optimal utilization of the available space within the mill housing. In certain embodiments, it may also be advantageous to provide the classifiers with different angular distances to one another.

[0028] A common semolina hopper can be provided for all classifiers in the classifier arrangement, and chutes can be arranged below the breaks in the guide vane arrangement to guide the rejected particles into the common semolina hopper. In this context, it is preferred that the breaks in the guide vane arrangement are oriented towards the grinding chamber, so that the rejected particles fall downwards towards the grinding plate or, if a common semolina hopper is provided, into it by gravity, thus eliminating the need for additional transport.

[0029] In certain embodiments, it can also be advantageous to convey the classifying grit from each classifier back to the grinding bowl in individual chutes or to the outside, outside the grinding chamber. In the latter case, the classifying grit is removed from the further grinding process in order to be used for other processing.

[0030] The invention is explained in more detail below with reference to schematic embodiments and the figures. These show: Fig. 1 a highly schematic view of a vertical roller mill with a classifier arrangement according to the invention, in a partially cutaway view; Fig. 2 a highly schematic view of a roller mill with a classifier arrangement of a further embodiment according to the invention, in a partially cutaway view; Fig. 3 a guide vane arrangement with guide plates; Fig. 4 various profiles for guide vanes of the guide vane arrangement according to the invention; Fig. 5 a semolina hopper with chutes; and Fig. 6 a semolina hopper with three guide vane arrangements.

[0031] The following refers to Fig. 1 Firstly, the basic principle of a vertical rolling mill is described, and secondly, the idea according to the invention is explained.

[0032] In Fig. 1 Figure 1 shows a highly simplified representation of a vertical roller mill 20. This mill has a grinding plate 23 on which several grinding rollers 22 roll. During operation, the grinding plate 23 rotates. Crushed material is fed onto it and crushed by the stationary, rotatably mounted grinding rollers 22. In the embodiment shown here, only two grinding rollers 22 are indicated.

[0033] Above each grinding roller 22 is a classifier 12, a classifier arrangement 10 according to the invention.

[0034] Each classifier 12 has a rotor 14 that can be rotated about its 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 plate 23.

[0035] A guide vane arrangement 30 surrounds the rotor 14, which can also be called a classifier basket, and in the embodiment shown here has eight guide vanes 32.

[0036] A guide vane arrangement 30 is in Fig. 3 shown separately. As can be seen, the guide vanes 32 are ring-shaped and have in the Fig. 3 The illustrated embodiment features a break in which guide vanes 36 are arranged. In principle, the guide vanes 32 could also describe a complete circle or ring. Overall, the guide vane arrangement 30 has a cylindrical shape. It is arranged around the rotor 14 of each classifier 12, which can also have a cylindrical shape. If the rotor 14 has a different outer contour, this outer contour can also be replicated by means of the guide vane arrangement 30.

[0037] In Fig. 4 Several possible cross-sections of guide vanes 32 are shown as examples. The cross-section has a U- or V-shaped form. In the assembled state, the open side of the profile 34 faces inwards, i.e., towards the rotor 14. In the embodiment shown here, the cross-section of the guide vanes 32 can essentially have two legs 35. As can be seen, the legs can be of the same size, but they can also be of different sizes or lengths. It is also not necessary for the cross-section to be symmetrical; it can have one leg 35 that is significantly longer. It is also possible, as shown in Fig. 4 shown that the cross-section has a triangular shape.

[0038] As especially in combination between Fig. 1 and Fig. 2 As can be seen, the guide vanes 32 can be arranged differently. For example, as in Fig. 1 with an inclined side of the guide vanes 32 pointing towards the grinding plate 23 or as in Fig. 2 shown, in the opposite direction. This can be seen together with the various profiles 34, as shown in Fig. 4 shown, have different influences on the process gas flows present within the roller mill 20.

[0039] In Fig. 3 Guide plates 36 are arranged in a recess or interruption of the guide vanes 32 of the guide vane arrangement 30, the function of which will be discussed in more detail below.

[0040] In Fig. 5 A semolina hopper 40 is shown, which in this embodiment has three chutes 41. Semolina that has been rejected by the classifiers and is also referred to as insufficiently ground particles can be returned to the grinding plate 23 by means of the semolina hopper 40. The opening or break in the guide vane arrangement 30 can be used for this purpose. For this reason, in Fig. 6 The grit hopper 40 is shown with three arranged guide vane assemblies 30. These in turn have an opening which ends in the area of ​​the chutes 41.

[0041] The following will now be discussed, in particular with reference to the Fig. 1 The basic operating principle of a roller mill 20 is described, taking into account the classifier arrangement 10 according to the invention.

[0042] The material to be ground is fed onto the grinding plate 23 and ground by means of the grinding rollers 22. A process airflow directed upwards towards the classifiers 12 carries the ground material, which falls over the grinding plate 23, towards the classifier assembly 10. The ground material is then carried by this airflow, which can also be referred to as the carrier airflow, through the guide vane assemblies 30 into the classifiers 12 with their rotors 14.

[0043] The rotation of the rotors 14 separates the comminuted particles or the ground material. Sufficiently comminuted material can be transported further by the process gas stream and exits the vertical roller mill 20 through an outlet located above the classifier assembly 10.

[0044] Insufficiently ground material is rejected by the rotors 14. It is literally flung away from the rotors 14. These flung, insufficiently ground particles can be captured by the profile shape of the guide vanes 32 and slide back within the guide vanes towards the grinding plate 23, i.e., the lower part of the vertical roller mill 20, due to gravity. Depending on the exact design of the guide vane profile 32, the direction of the process gas flow onto the rotor 14 can be influenced.

[0045] In the embodiment shown here, the guide vanes 32 of the guide vane assemblies 30 have an opening in their lower region through which the rejected particles, which do not represent sufficiently ground material, pass via the chutes 41 into the grit hopper 40 and from there are guided back onto the grinding plate 23. Here they are ground again and once more conveyed by means of the process gas flow to the classifier assembly 10.

[0046] Additionally or optionally, guide vanes 36 can be provided in the interruption of the guide vane arrangement 30. These serve to guide the process gas flow present in the mill interior and to achieve optimal flow to the rotor 14 even in the recess or interruption of the guide vane arrangement 30.

[0047] Thus, the classifier arrangement according to the invention makes it possible to efficiently classify crushed material.

Claims

1. Classifier arrangement (10) for a vertical roller mill (20), having at least two classifiers (12), wherein each classifier (12) has an active rotor (14) that is rotatable about an axis of rotation (16), wherein the axis of rotation (16) is aligned at least at an angle of 50° to the vertical, wherein around each classifier (12) a guide vane arrangement (30) is provided at least partially surrounding the said classifier, wherein each guide vane arrangement (30) has at least one guide vane (32), characterized in that the guide vane (32) has an open profile (34) towards the axis of rotation (16) of the classifier, in that the axes of rotation (16) are aligned with respect to each other and in particular have a common point of intersection or intersection area.

2. Classifier arrangement (10) according to claim 1, characterized in that the classifiers (12) have a substantially identical, in particular cylindrical shape.

3. Classifier arrangement (10) according to any one of claims 1 or 2, characterized in that the axis of rotation (16) has a maximum angle of 20° to the horizontal.

4. Classifier arrangement (10) according to any one of claims 1 to 3, characterized in that the guide vanes (32) are arranged in a ring-like manner around the axis of rotation (16).

5. Classifier arrangement (10) according to any one of claims 1 to 4, characterized in that the guide vanes (32) have a V- or U-like cross section.

6. Classifier arrangement (10) according to any one of claims 1 to 5, characterized in that the guide vanes (32) have at least two flanks (35), one of which is of longer design.

7. Classifier arrangement (10) according to any one of claims 1 to 6, characterized in that the guide vanes (32) of the guide vane arrangement (30) have an interruption and in that in this interruption guide plates (36) are arranged substantially transversely to the guide vanes (32).

8. Classifier arrangement (10) according to any one of claims 1 to 7, characterized in that at least three guide vanes (32) per guide vane arrangement (30) are provided which each have a distance between two adjacent guide vanes (32).

9. Vertical roller mill (20) characterized by a classifier arrangement (10) according to any one of claims 1 to 8.

10. Vertical roller mill according to claim 9, characterized in that the number of classifiers (12) of the classifier arrangement (10) corresponds to the number of rollers (22) provided for active grinding.

11. Vertical roller mill (20) according to claim 9 or 10, characterized in that the classifiers (12) of the classifier arrangement (10) are arranged in a star-shaped manner in the mill housing, in particular at the same distance to each other.

12. Vertical roller mill (20) according to any one of claims 9 to 11, characterized in that a common grit funnel (40) is provided which has chutes (41) for each classifier (12).

13. Vertical roller mill (20) according to any one of claims 9 to 12, characterized in that the interruptions in the guide vane arrangement (30) are aligned towards the grinding chamber.

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