Screening device for vertical drum mills

Abstract

This invention relates to a screening device (10) for a vertical drum mill, having at least two screening units (12). Each screening unit (12) has an active rotor (14) rotatable about a rotation axis (16). The rotation axis (16) is oriented at an angle of at least 50° relative to a vertical line. The invention is characterized by a guide vane device (30) that at least partially surrounds each screening unit (12), the guide vane device having at least one guide vane (32). The guide vane (32) has a profile (34) that opens toward the direction of the rotation axis. Furthermore, this invention relates to a vertical drum mill having a screening device according to the invention.

Description

Technical Field

[0001] This invention relates to a screening device for a vertical drum mill, comprising at least two screening devices. These screening devices can be arranged in the same spatial plane. Each screening device has an active rotor capable of rotating about a rotation axis. The rotation axis is oriented at an angle of at least 50° relative to the vertical. In particular, the rotation axis is horizontally oriented. Background Technology

[0002] Vertical drum mills typically feature a rotating grinding disc on which multiple rotatable grinding rollers, fixed in position, roll. The material to be ground is added to the grinding disc and crushed or squeezed by the grinding rollers. Subsequently, it is necessary to screen the ground material. Here, a distinction is made between sufficiently crushed material and so-called coarse material or coarse particles, which, after screening, are returned to the grinding disc for further crushing.

[0003] The principle and structure of the roller mill can be found in, for example, WO 2011 / 107124 A1 or WO 2012 / 079605A1.

[0004] The type of screener described above has a screening basket, also known as a rotor, which actively rotates about a rotational axis. However, passive screeners are also known in principle, where screening is achieved solely by redirecting an airflow, or more precisely, a dust-airflow. The screening limit can be influenced, for example, by the precise structure of the screening basket and its rotational speed. This means that particle size can be affected, and separation occurs during screening within a certain particle size range. Abrasive material with particle sizes larger than the screening limit is rejected by the screener by means of the screening basket and is conveyed to a further grinding process.

[0005] A rotary drum mill having multiple horizontally arranged screening units is known, for example, from WO 2014 / 067688.

[0006] As drum mills become increasingly larger, and in some cases, have more and more drums (which handle higher capacities and thus larger throughputs of abrasive material), it is equally necessary to correspondingly improve the screening units used to sieve the abrasive material being sifted, so that they can also achieve higher throughputs. Additionally, it should be considered that, in conjunction with vertical drum mills operating in a recirculating air mode, the airflow or air vortices generated by the rotor or screening basket may partially negatively impact the overall airflow. Summary of the Invention

[0007] Therefore, the objective of this invention is to describe an effective and efficient screening device.

[0008] This task is accomplished according to the invention by a screening device for a vertical drum mill having the features of claim 1.

[0009] Advantageous embodiments of the invention are described in the dependent claims, in the specification, and in the drawings and their explanations.

[0010] In the screening device according to the invention, a guide vane assembly is arranged around each screening unit, at least partially surrounding it. Each guide vane assembly has at least one guide vane, wherein each guide vane has a profile that opens toward the axis of rotation of the screening unit.

[0011] This invention is based on the fundamental concept of guiding process air, used to transport abrasive material crushed by a grinding drum to a screening device, onto a rotor or screening basket via guide vanes. This influences the inflow angle of the process air and the inflow angle of the crushed abrasive particles transported by it, thereby enabling more efficient screening.

[0012] Furthermore, the guide vanes are designed with an open profile toward the axis of rotation of the screen. This has the advantage that particles rejected by the rotor due to insufficient pulverization are captured in the open profile and then guided by gravity to the lower region of the screen. This provides the advantage that rejected particles are thus guided specifically at certain locations within the screen or screen assembly and are not thrown through the entire space containing the screen or screening basket. By guiding the rejected, overly coarse particles in a targeted manner, the screen can operate more efficiently due to less interference.

[0013] According to the present invention, the screening devices can be arranged in the same spatial plane, but also in different planes. In other words, staggered arrangements are also possible, in which the screening devices are set at different heights relative to the grinding disc.

[0014] In principle, each screener can be arranged arbitrarily along its axis of rotation. However, it is preferable that the axis of rotation has a maximum angle of 20°, preferably 10°, relative to the horizontal line, and it is particularly suitable for horizontal arrangement. Compared to vertically arranged screeners, horizontal arrangement is especially suitable when multiple screeners should be used. Thus, it is possible to use smaller screeners overall, in which multiple screeners are combined into a single screener device.

[0015] Here, the screens, especially their rotors, can have essentially the same shape. This shape can be, for example, essentially cylindrical. However, other shapes, such as a basic conical shape, are also possible. The arrangement of identical screens facilitates overall design and also makes spare parts storage easier.

[0016] In a preferred embodiment, the rotation axes of the screens are aligned with each other and have a common intersection point. It is also possible that if the axes are not precisely aligned, the intersection point is slightly enlarged, thus creating an intersecting area. This arrangement has proven advantageous because it can improve screening results or reduce the energy required to drive the screens.

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

[0018] Here, the guide vane assembly can have at least three guide vanes. More, even twelve or twenty, are preferred. The spacing between adjacent guide vanes can be made identical. This spacing is chosen to create gaps through which process air, along with the pulverized abrasive particles, can flow. In another embodiment, the spacing can be made differently. Thus, the spacing can, for example, decrease or increase from the outside, i.e., the area of ​​the mill housing, towards the inside, i.e., the center of the mill.

[0019] As already described, the guide vanes have an inwardly opening profile toward the rotor, which can have a V-shaped or U-shaped cross-section. The pointed end or rounded side of the V-shaped or U-shaped cross-section points outward, i.e., away from the rotation axis of the screen. This allows for the distribution of incoming air and, more effectively, guidance of the air from beside the guide vanes, directing it in the desired direction. Furthermore, this inwardly opening profile can be easily manufactured so that it can be used to capture and guide rejected particles. According to the invention, it is not mandatory that the cross-section or profile of the guide vanes be the same throughout its entire trajectory. The cross-section or profile can also vary. The cross-section or profile of the guide vanes used can also be different.

[0020] In principle, the guide vanes can have different legs in their cross-section. If the guide vanes are constructed with a V-shaped or U-shaped cross-section, they usually have two legs, which are not necessarily made identically, but one can be constructed to be longer than the other. This allows the carrier air or process air flowing through the guide vanes of the guide vane assembly to be guided in the desired direction to the rotor of the screen.

[0021] Advantageously, the guide vanes of the guide vane device have an interruption in their annular shape. This interruption allows particles rejected by the screener to fall out of the open profile and be re-grinded.

[0022] Guide plates can also be arranged in this interruption section. These guide plates are preferably arranged transversely to the direction of the guide vanes. The guide plates serve two purposes: firstly, to further guide the incoming carrier air; and secondly, to provide a feasible solution for discharging rejected particles that have fallen from the guide vanes in the guided direction.

[0023] Furthermore, the present invention relates to a vertical drum mill having a screening device according to the present invention.

[0024] Here, the number of screens in the screening device can correspond to the number of rollers provided for active grinding. In the context of this invention, "active roller" specifically refers to a roller used to crush the abrasive material. Drum mills with both large and small grinding rollers are also known, wherein the smaller grinding rollers are often referred to as preparation rollers and are primarily used for preparing the grinding machine. They are not primarily used for crushing the abrasive material.

[0025] Setting up the same number of screens as the active grinding drum has proven to be a good solution for achieving energy-efficient screening, as it eliminates the need for many small screens, but also eliminates the need for fewer large screens.

[0026] The number of screens can be greater than or less than the number of active rollers, depending on the supply of abrasive material and positional space within the housing.

[0027] Preferably, the screeners of the screening device are arranged in a star shape within the mill housing of the vertical mill. This means that the screeners each have the same radial or angular spacing. Such a uniform distribution provides good screening results because, especially in rotary mills operating with recirculating air, the particles being ground throughout the mill housing are transported by the carrier airflow. This also allows for optimal utilization of the available space within the mill housing. In certain embodiments, it is also advantageous to arrange the screeners with different angular spacings relative to each other.

[0028] A common coarse-graining funnel can be provided for all the screens in the screening device, and a schuren can be arranged below the interrupted portion of the guide vane device to guide rejected particles into the common coarse-graining funnel. Preferably, the interrupted portion of the guide vane device is oriented towards the grinding chamber, so that rejected particles fall downwards towards the grinding disc, or if a common coarse-graining funnel is provided, they fall into it due to gravity, and additional transport is unnecessary.

[0029] In certain embodiments, it is also advantageous to guide the coarse particles from each screen into the grinding bowl via individual chutes, or, however, to the outside of the grinding chamber. In the latter case, the coarse particles are subjected to an additional grinding process in order to convey them to other subsequent processing steps. Attached Figure Description

[0030] The invention will now be explained in detail with reference to the accompanying drawings and illustrative embodiments. Herein:

[0031] Figure 1 A very schematic view of a vertical drum mill having a screening device according to the invention is shown in a partially sectional illustration.

[0032] Figure 2 A very schematic view of a drum mill having a screening device according to the invention is shown in a partially sectional illustration.

[0033] Figure 3 A guide vane device with a guide plate is shown;

[0034] Figure 4 Different profiles of guide vanes for a guide vane device according to the present invention are shown;

[0035] Figure 5 A coarse-grained funnel with a chute is shown; and

[0036] Figure 6A coarse-grained funnel with a three-guide vane assembly is shown. Detailed Implementation

[0037] The following reference Figure 1 On the one hand, the basic principle of the vertical drum mill is described, and on the other hand, the concept according to the invention is explained.

[0038] exist Figure 1 A greatly simplified illustration of a vertical drum mill 20 is shown. The vertical drum mill has a grinding disc 23 on which multiple grinding drums 22 rotate. During operation, the grinding disc 23 rotates. The abrasive material to be pulverized is added to the grinding disc and pulverized by means of the fixed-position, rotatably mounted grinding drums 22. In the embodiment shown here, only two grinding drums 22 are depicted.

[0039] A sieve 12 of the sieve device 10 according to the invention is present on top of each grinding drum 22.

[0040] Each sieve 12 has a rotor 14 that is rotatable about its axis of rotation 16. In the embodiment shown here, the axes of rotation 16 of the two sieves 12 are arranged in the same plane and intersect approximately above the center point of the grinding disc 23.

[0041] A guide vane device 30 is arranged around the rotor 14, which can also be referred to as a screening basket. In the embodiment shown here, the guide vane device has eight guide vanes 32.

[0042] Guide vane device 30 in Figure 3 Shown separately. As can be seen, the guide vane 32 is formed in an annular shape and... Figure 3 The illustrated embodiment has an interruption section in which a guide plate 36 is arranged. However, in principle, the guide vanes 32 can also trace complete circles or rings. In short, the guide vane device 30 has a shape similar to a cylindrical shell. It is arranged around the rotor 14 of each screener 12, which can also have a cylindrical shape. If the rotor 14 has other outer contours, these contours can also be imitated by means of the guide vane device 30.

[0043] exist Figure 4Different possible cross-sections of the guide vane 32 are exemplarily shown. Here, the cross-section has a shape similar to a U or V. In the installed state, the open side of the profile 34 points inward, i.e., toward the rotor 14. In the embodiment shown here, the cross-section of the guide vane 32 can have substantially two legs 35. The legs can be made to the same size as can be seen, but can also be made in different sizes or lengths. It is not mandatory that the cross-section be made symmetrically, and the cross-section can be made with significantly longer legs 35. Figure 4 As shown, it is also possible that the cross-section has a triangular shape.

[0044] Especially in Figure 1 and Figure 2 As can be seen from the overview, the guide vanes 32 can be arranged in different ways. For example, as in Figure 1 The guide vane 32 is tilted towards the grinding disc 23, or as shown in the image. Figure 2 As shown, it points in the opposite direction. This is possible with, as in... Figure 4 The different profiles 34 shown together have different effects on the process airflow present inside the drum mill 20.

[0045] exist Figure 3 In the above, a guide plate 36 is arranged in the gap or interruption of the guide blade 32 of the guide blade device 30. The working principle of the guide plate 36 will be discussed in more detail below.

[0046] exist Figure 5 The image shows a coarse-grained funnel 40, which in this embodiment has three chutes 41. By means of the coarse-grained funnel 40, coarse particles rejected by the sieve and also referred to as insufficiently crushed particles can be guided back onto the grinding disc 23. For this purpose, an opening or interruption in the guide vane device 30 can be used. For this reason, in Figure 6 The image shows a coarse-grained funnel 40 with three arranged guide vane devices 30. These guide vane devices also have openings that terminate in the region of the chute 41.

[0047] Now, especially refer to the following Figure 1 The principle of operation of the drum mill 20 is described in principle with reference to the screening device 10 according to the present invention.

[0048] The abrasive material to be crushed is added to the grinding disc 23 and crushed by means of the grinding roller 22. The crushed abrasive material falling onto the grinding disc 23 is carried towards the screening device 10 by a process airflow pointing upward toward the screening device 12. The crushed abrasive material is squeezed into the screening device 12 along with its rotor 14 by the airflow, which can also be called the carrier airflow, through the guide vane device 30.

[0049] The rotation of the rotor 14 sieves the crushed particles or abrasive material. Sufficiently crushed abrasive material can be further transported by process airflow and exit the vertical drum mill 20 through an outlet located above the screening device 10.

[0050] Insufficiently pulverized abrasive material is rejected by rotor 14. It is effectively flung off rotor 14. These flung, insufficiently pulverized particles can be captured by the profile of guide vanes 32 and slide back towards the grinding disc 23, i.e., towards the lower region of the vertical drum mill 20, due to gravity within the guide vanes. Depending on the precise implementation of the profile of the guide vanes 32, the inflow direction of the process airflow onto rotor 14 can be influenced.

[0051] In the embodiment shown here, the guide vanes 32 of the guide vane device 30 have an opening in the lower region. Particles that are rejected, representing insufficiently ground abrasive material, pass through this opening via the chute 41 into the coarse particle funnel 40 and are then guided back onto the grinding disc 23. Here, the particles are re-ground and then guided to the screening device 10 by means of the process airflow.

[0052] As a supplementary or optional solution, guide plates 36 can be provided in the interruption section of the guide vane device 30. These guide plates are used to guide the process airflow present in the internal space of the mill and also to achieve optimal inflow to the rotor 14 in the empty or interrupted section of the guide vane device 30.

[0053] Therefore, by means of the sieving device according to the invention, effective sieving of crushed abrasive materials can be achieved.

Claims

1. A screening device for a vertical drum mill. It has at least two screening devices. Each of the screens has an active rotor that can rotate about a rotation axis. The axis of rotation is oriented at an angle of at least 50° relative to the vertical line. A guide vane device is arranged around each screen, at least partially surrounding the screen. Each guide vane assembly has at least one guide vane. The guide vanes have a profile that opens toward the axis of rotation of the screen. The rotation axes thereon are aligned with each other.

2. The screening device according to claim 1, The sieves described therein have essentially the same shape.

3. The screening device according to claim 1, The rotation axis has a maximum angle of 20° relative to the horizontal line.

4. The screening device according to claim 1, The guide vanes are arranged in a ring around the axis of rotation.

5. The screening device according to claim 1, The guide vane has a cross-section similar to a V-shape or a U-shape.

6. The screening device according to claim 1, The guide vane has at least two legs, one of which is constructed to be longer.

7. The screening device according to claim 1, The guide vane of the guide vane device has an interrupted portion, and In this interrupted section, the guide plate is arranged substantially transversely to the guide blade.

8. The screening device according to claim 1, Each guide vane device is provided with at least three guide vanes, and the guide vanes are spaced apart between two adjacent guide vanes.

9. Vertical roller mill, Its features are, The vertical drum mill includes a screening device according to any one of claims 1 to 8.

10. The vertical roller mill according to claim 9, The number of screens in the screening device corresponds to the number of rollers configured for active grinding.

11. The vertical roller mill according to claim 9, The screening devices are arranged in a star shape within the mill housing.

12. The vertical roller mill according to claim 9, A common coarse-grained funnel is provided, which has chutes for each screener.

13. The vertical roller mill according to claim 9, The interrupted portion of the guide vane device is oriented toward the grinding chamber.

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