EP3849714B1 - Sifting wheel with flat sail elements and method of sifting with such a sifting wheel - Google Patents

Description

The present invention relates to a sifting wheel for a sifting device for sifting ground comminution products, in particular particulate bulk material, the sifting wheel comprising sifting wheel lamellae which are arranged in the radially outer area of the sifting wheel.

The WO 2017/067913 A1 discloses a sifting device with a rotor basket which can be rotated about a substantially vertically aligned axis of rotation and whose lateral surface is formed by rotor blades. The rotor blades are followed by a plurality of guide elements, which extend in the radial direction, in particular with a tangential component, inward in the direction of the rotor axis into the rotor basket. In some embodiments, the guide elements extend as far as the axis of rotation of the rotor basket, but not in the radially inner area near the opening of the fines discharge. The EP 0 645 196 A1 discloses a classifying wheel according to the preamble of claim 1 and a method according to the preamble of claim 11. The EP 0 983 802 A2 discloses a classifying wheel with a circular disc carrying a classifying wheel hub and an annular cover disc.

The object of the present invention is to provide an advantageous arrangement of sail surface elements in a classifying wheel, in particular with regard to separation efficiency and energy efficiency.

The invention provides, according to claim 1, a sifting wheel for a sifting device for sifting ground comminution products, in particular particulate bulk material, which comprises sifting wheel lamellae, which are arranged in the radially outer area of the sifting wheel, and sail surface elements which are radially spaced from the sifting wheel lamellae in the are arranged radially inner region of the classifying wheel. During a sifting process, an air stream carrying the ground comminution products of different particle sizes flows from radially outside to radially inside into the rotating sifting wheel and through the sifting wheel lamellae, in order to then be drawn off in the axial direction of the sifting wheel. The sail surface elements are designed to break up an otherwise generated potential vortex in the classifier wheel and thereby reduce the pressure loss in the classifying air flow. Since, in particular, a different number of canopy elements and classifying wheel lamellae is provided, the arrangement of canopy surface elements relative to the classifying wheel lamellae is not always uniform. This can lead to different flow resistances for the flow of the classifying air through the classifying wheel lamellae in the circumferential direction of the classifying wheel. Due to the radial spacing of the sail surface elements in the radial direction of the classifying wheel from the classifying wheel lamellae, a substantially rotationally symmetrical flow profile can be achieved in the classifying wheel lamellae. In particular, due to the radial spacing of the canopy elements from the classifying wheel lamellae, a gap can be created between the canopy elements and the classifying wheel elements are present, which ensures that the influence of the sail surface elements on the flow profile is kept low by the classifying wheel lamellae. As a result, a substantially rotationally symmetrical flow profile can be generated in the classifying space radially outside the classifying wheel lamellae despite the sail surface elements inside the classifying wheel, as a result of which good separation and thus in particular very high levels of selectivity can be achieved. A high selectivity ensures that ground comminution products above a certain grain size are essentially separated in the sifting chamber and can thus be fed into a new grinding process.

In particular, the particulate bulk material is ground rock material, for example limestone, gypsum, coal or claystone, mineral bulk material, for example cement or cement material, or recycled bulk material, for example recycled gypsum concrete panel material, blast furnace slag, flue gas desulfurization gypsum or fly ash.

In particular, the sifting wheel can be used for a bulk material mill, in particular for a rock mill, advantageously in a vertical roller mill. Therein, the grinding is effected in particular by rotating a grinding table relative to grinding rollers about a central axis of the grinding table, so that the grinding rollers roll on a grinding track of the grinding table about a roller axis of rotation in order to grind the particulate bulk material and reduce its grain sizes. However, other bulk material mills can also be used in combination with the classifying wheel, in particular bulk material mills that initially produce particle size distributions that do not yet correspond to the desired particle size distribution of the end product. A sifting device with the sifting wheel according to the invention is then used in order to separate particles with too large grain sizes in the comminution product and to feed them back into the grinding process. The angle of inclination of the canopy surface elements is constant relative to the axial direction of the classifying wheel in the area spanned by the axial direction and circumferential direction of the classifying wheel along the entire axial extent of the canopy surface elements. A radial turbulent flow generated by the rotation of the classifying wheel can thus be broken up more efficiently. In particular, the sail surface elements extend straight in the axial direction of the classifying wheel. In particular, the canopy surface elements extend in a surface spanned by the axial direction and radial direction of the classifying wheel.

In order to promote a desired uniform flow condition in the axial direction in the sifting chamber and within the sifting wheel, it is particularly advantageous if the radial distance between the radially inner end of the sifting wheel lamellae and the radially outer end of the sail surface elements is constant along the entire axial extent of the sifting wheel.

In a preferred embodiment, the radial distance between the radially inner end of the classifying wheel lamellae and the radially outer end of the sail surface elements is at least 3% of the diameter of the classifying wheel, advantageously at least 5%. In particular, the radial distance is at most 30%, advantageously at most 20%, of the diameter of the classifying wheel. These proportions represent an advantageous compromise between a reduction in the potential vortex and an essentially rotationally symmetrical flow profile in the classifier wheel gap.

In one embodiment, the sail surface elements extend straight in the radial direction of the classifying wheel.

In a preferred embodiment, the sail surface elements are at least partially curved and/or inclined with respect to the radial direction of the classifying wheel. In particular, the radially outer edge of the canopy element is set back in relation to the intended direction of rotation of the classifying wheel, ie in particular in the circumferential direction counter to the direction of rotation. The curved and/or inclined design of the canopy elements enables the flow behavior to be optimized in order to reduce the flow resistance in the direction of the discharge opening of the classifier wheel. In particular, potential vortices can be further reduced as a result.

In one embodiment, the classifying wheel lamellae are at least partially curved and/or inclined relative to the radial direction of the classifying wheel, with the inclination of the canopy surface elements relative to the radial direction at least at their radially outer edge being greater than the inclination of the classifying wheel lamellae relative to the radial direction at least on their radially inner edge edge. As a result, an advantageous flow profile can be generated between the classifying wheel lamellae.

In one embodiment, the radially outer edge of the sail surface elements is at least partially curved and/or inclined with respect to the axial direction of the classifying wheel. In this way, the flow in the direction of the discharge opening can be promoted or reduced in the axial direction in order to provide the desired flow condition in the sifting chamber and inside the sifting wheel.

The canopy elements are in particular formed from a rigid, flat material, for example sheet steel. However, the sail surface elements can also have a varying thickness along their extent, for example in order to optimize the flow conditions thereon.

In particular, the sail surface elements can be arranged at least partially at their radially inner end on a central shaft in the classifying wheel. In particular, the classifying wheel can be mounted on the central shaft. The central shaft can be solid or hollow. The provision of the central shaft and the direct connection of the canopy elements to it has the effect, in particular, that no vortices can arise in the center of the classifying wheel.

In one embodiment, the sail surface elements can be guided up to the radial center of the classifying wheel. This allows the size of the sail surface elements to be maximized.

Alternatively, a distance can be provided between a centrally arranged shaft and the sail surface elements. A flow between the areas separated by the sail surface elements in the radially inner area of the classifying wheel can thus be made possible.

Advantageously, the canopy elements are distributed uniformly in the circumferential direction in the classifying wheel. As a result, uniform flow conditions can be achieved in the sifter wheel, which in turn promotes uniform flow conditions in the sifting chamber.

In particular, at least four canopy elements are provided. In some embodiments, more than 6, 8, 10, 12, 14 or 16 canopy elements can also be provided. The larger the diameter of the classifying wheel, the more canopy elements make sense.

In one embodiment, the sail surface elements extend at least partially over the entire height of the interior of the classifying wheel. As a result, the formation of vortices can be prevented, particularly in the area of the axial discharge opening.

Advantageously, the distance between the radially inner end of the classifying wheel lamellae and the radially outer end of the sail surface elements is adjustable. This can be made possible in particular by a radial displaceability of the classifying wheel lamellae and/or canopy surface elements. In particular, the classifying wheel lamellae and/or sail surface elements can be slidably provided in slots in support plates at the axial ends of the classifying wheel. In particular, it can be attached by screwing. In some embodiments, it is also possible to adjust the classifying wheel lamellae and/or canopy elements in the circumferential direction.

In particular, the sail surface elements can only extend as far as an area of the classifying wheel that is adjacent to a discharge opening.

The invention also provides a sifting device for sifting ground comminution products, in particular for sifting particulate bulk material, which has the sifting wheel according to the invention and a vane ring, within which the sifting wheel is rotatably arranged, with a sifting space being formed between the vane ring and the sifting wheel. In the sifting room, coarse material is primarily separated from the sifting air, in that it falls out of the sifting air flow under the influence of gravity.

The invention further provides a plant for grinding feed material in the form of particulate bulk material, comprising a bulk material mill, in particular a vertical roller mill, and a sifting device, as defined above. The sifting device is arranged in particular above the bulk material mill, with particulate bulk material being transported from the bulk material mill to the sifting device by means of the sifting air.

A discharge line is advantageously arranged centrally above the classifying wheel. Advantageously, the sifting wheel has a discharge opening in its radially inner region, so that the interior of the sifting wheel is connected to the discharge line and the sifting air can convey fines out of the sifting wheel into the discharge line. In alternative embodiments, the discharge line can also be arranged under the sifting wheel.

The invention provides a method for classifying ground comminution products, in particular particulate bulk material, wherein ground comminution product is fed into a classifying chamber surrounding a rotating classifying wheel, and an air flow is provided which flows radially inwards into the rotating classifying wheel and then in the axial direction is discharged through a discharge opening in the classifying wheel, with the air flow in the region of the classifying wheel adjacent to the discharge opening carrying part of the comminution product along in the axial direction along canopy surface elements, with the angle of inclination of the canopy surface elements relative to the axial direction of the classifying wheel being in a direction spanned by the axial direction and circumferential direction of the classifying wheel area is constant. In particular, sail wheel surfaces are provided in the area of the classifying wheel adjacent to the discharge opening, so that no vortices can arise within the classifying wheel that would impair the removal of the fines in the classifying air from the classifying wheel.

In the method, the radial distance between the radially outer end of the canopy surface elements and the radially inner end of classifying wheel lamellae of the classifying wheel can optionally be adjusted as a function of the speed and/or diameter of the classifying wheel. This can be done by automatically adjusting the canopy surface elements and/or the classifying wheel lamellae in the radial and/or circumferential direction by actuators controlled by a controller. This can take place in particular during operation and as a function of the operating states, in particular the speed and/or the flow rate. Alternatively, an adjustment can also be made manually during breaks in operation.

In a preferred embodiment, the air flow between the classifying wheel lamellae is rotationally symmetrical. In particular, there is an identical flow condition in each case in all intermediate spaces between separating wheel lamellae arranged next to one another at the same distance. This enables an even separation of coarse material in the sifting chamber.

• Fig. 1 eine seitliche Schnittansicht einer Sichteinrichtung gemäß eines Ausführungsbeispiels der vorliegenden Erfindung;
• Fig. 2 eine horizontale Schnittansicht durch das Sichtrad gemäß Figur 1;
• Fig. 3 eine Schnittansicht durch ein Sichtrad gemäß einer Ausführungsform der Erfindung;
• Fig. 4 eine Schnittansicht durch ein Sichtrad gemäß einer weiteren Ausführungsform der Erfindung;
• Fig. 5 eine Schnittansicht durch ein Sichtrad gemäß einer weiteren Ausführungsform der Erfindung;
• Fig. 6 eine seitliche Schnittansicht durch eine Sichteinrichtung gemäß einer weiteren Ausführungsform der Erfindung.

The invention is explained in more detail below using exemplary embodiments which are illustrated in the following figures. It shows:

• 1 a side sectional view of a viewing device according to an embodiment of the present invention;
• 2 a horizontal sectional view through the classifying wheel according to FIG figure 1 ;
• 3 a sectional view through a classifying wheel according to an embodiment of the invention;
• 4 a sectional view through a classifying wheel according to a further embodiment of the invention;
• figure 5 a sectional view through a classifying wheel according to a further embodiment of the invention;
• 6 a side sectional view through a viewing device according to a further embodiment of the invention.

In figure 1 a viewing device 1 according to an embodiment of the invention is shown. The sifting device 1 enables coarse material to be separated from fine material in a sifting air stream, the coarse material to be resupplied to a grinding process and the fine material to be transported away for further processing. A classifying wheel 2 is provided for this purpose, which can be rotated about a vertical axis by means of a motor 3 . The classifying wheel 2 is arranged within a ring of guide vanes 4 . An outer ring of classifying wheel lamellae 5 of the classifying wheel is spaced radially from the guide vane ring 4 so that a classifying space 6 is formed between the classifying wheel lamellae 5 and the guide vane ring 4 . A ground crushed product, in particular particulate bulk material, is entrained by an air flow from radially outside through a ring of guide vanes 4 and then enters the classifying chamber 6. The rotation of the classifying wheel lamellae 5 together with the classifying wheel 2 creates flow conditions in the classifying chamber that cause coarse Portions of the ground comminution products fall down and only comminution products that have at least a certain degree of fineness are transported radially inward into the sifting wheel 2 . The sifting air flows through the sifting wheel lamellae 5 into the inside of the sifting wheel and then through a discharge opening 7 into a downstream processing device. The downstream processing device can simply consist in the fact that the fines are heaped up, transported further and/or packaged.

A radial distance 100 is provided between the sail surface elements 8 and the classifying wheel lamellae 5 . As a result, the effect of the sail surface elements 8 on the flow of the sifting air through the sifting wheel lamellae 5 can be reduced, so that a more uniform flow profile is present in the sifting chamber 6 . Nevertheless, the canopy elements prevent unwanted potential vortices from developing inside the classifying wheel 2 and can advantageously contribute to energy recovery with regard to the flow of classifying air by reducing the necessary drive power of the motor 3 .

In particular, the sail surface elements 8 are attached to the shaft 9 of the classifying wheel or at least connected to it. A fines removal line 10 is provided above the discharge opening 7, with which the fines with the desired grain sizes are transported away in an air stream. The discharge line 10 is arranged in particular above the sifting wheel.

A hopper 11 can be arranged under the sifting wheel 2, which collects coarse material falling from the sifting chamber 6 and feeds it to a grinding process. In particular, a grinding table can be arranged centrally under the funnel 11 so that the material to be ground is fed centrally to the rotating grinding table and then crushed again by grinding rollers before it is gripped again by a sifting air stream and fed to the sifting device 1 . The material to be ground or the comminution products is thus guided through the sifting device 1 until the desired comminution stage is reached, so that the corresponding fine material can pass through the sifting chamber 6 into the interior of the sifting wheel and can then be discharged via the discharge line 10 .

As in figure 1 is shown, the canopy elements 8 extend right up to the discharge opening 7 of the classifying wheel 2. The classifying air flow in the classifying wheel 2 is thus guided through the canopy surface elements 8 up to its discharge opening 7. This prevents the emergence of unwanted air turbulence in the classifying wheel 2 and improves energy recovery from the visual airflow. The sail surface elements 8 extend over the entire height of the sifting wheel 2.

In figure 2 is the in figure 1 Drawn horizontal sectional view AA represented by the embodiment of the classifying wheel 2 according to the invention. The classifying wheel 2 has a central shaft 9 with sail surface elements 8 extending therefrom in the radial direction. The classifying wheel lamellae 5 are arranged at a radial distance 100 from the radially outer ends 8 of the canopy surface elements 8 . The classifying wheel lamellae 5 are slightly inclined here in pairs in opposite directions with respect to the radial direction. Furthermore, a higher number of classifying wheel elements 5 than of sail surface elements 8 is provided.

In figure 3 another embodiment of a classifying wheel 2 is shown in a horizontal sectional view. Here the sail surface elements 8 are designed with a corrugated profile. The canopy elements 8 are curved counter to the intended direction of rotation. That is, the canopy elements each have different angles to the radial direction over their extent. Furthermore, the classifying wheel lamellae 5 are inclined relative to the radial direction. The angle 200 of the radially outer end of the sail surface element 8 with respect to the radial direction is greater than the angle 300 of the classifying wheel lamellae 5. This enables an advantageous flow profile in the classifying chamber 6, i.e. radially outside of the classifying wheel lamellae 5.

Vortices can still arise between the sail surface elements 8, as in figure 3 is shown as an example. However, these vortices are locally limited and thus cause a significantly lower pressure loss than the vortices in classifier wheels according to the prior art.

In figure 4 an increased number of sail surface elements 8 is provided in order to further reduce the formation of vortices inside the classifying wheel 2 . Furthermore, in figure 4 shown by way of example how the sail surface elements can be guided up to the radial center of the sifting wheel. This is possible in particular if no shaft 9 is provided in this area, but instead the shaft is only flanged axially outside of the classifying wheel 2 .

In figure 5 a classifying wheel 2 is shown, in which a radial distance between the centrally arranged shaft 9 and the sail surface elements 8 is provided. The canopy elements arranged in the radially central area nevertheless enable an effective reduction of vortices, but it can be advantageous if the canopy elements 8 are guided at least in the area adjoining the discharge opening 7 up to the central shaft 9 .

The sail panel elements 8 in Figures 2 to 5 each extend straight in the axial direction of the classifying wheel 2.

In figure 6 Finally, an embodiment is shown in which the radially outer edge of the sail surface elements is inclined with respect to the axial direction. In particular, the area of the sail surface elements 8 increases toward the discharge opening, so that in these areas where a increased air flow is present, effective suppression of air vortices is possible. As shown above, the canopy elements 8 can not only be used to suppress eddy currents, but can also be driven by the air flow, and thus at least reduce the power input via the motor 3 for driving the classifying wheel. In addition, by spacing the canopy surface elements 8 from the classifying wheel lamellae 5, a reaction of the canopy surface elements on the classifying space 6 can be reduced. In particular, it can be prevented that there is an uneven air flow in the circumferential direction depending on the canopy elements 8 in the viewing space 6 .

Claims (15)

1. Classifier wheel (2) for a classifier device for classifying milled comminuted products, in particular particulate bulk material, comprising:

   classifier wheel blades (5), which are arranged in the radially outer region of the classifier wheel (2), and vane surface elements (8), which are arranged radially spaced apart from the classifier wheel blades (5) in the radially inner region of the classifier wheel (2),

   characterized in that

   the angle of inclination of the vane surface elements (8) is constant with respect to the axial direction of the classifier wheel (2) in an area spanned by the axial direction and the circumferential direction of the classifier wheel (2).
2. Classifier wheel according to claim 1, wherein the vane surface elements (8) extend linearly in the axial direction of the classifier wheel (2).
3. Classifier wheel according to one of the preceding claims, wherein the radial distance between the radially inner end of the classifier wheel blades (5) and the radially outer end of the vane surface elements (8) is constant along the entire axial extension of the classifier wheel (2).
4. Classifier wheel according to one of the preceding claims, wherein the radial distance between the radially inner end of the classifier wheel blades (5) and the radially outer end of the vane surface elements (8) is at least 3%, preferably at least 5%, and at most 30%, advantageously at most 20%, of the diameter of the classifier wheel (2).
5. Classifier wheel according to one of the preceding claims, wherein the vane surface elements (8) are designed to be at least partially curved and/or inclined with respect to the radial direction of the classifier wheel (2).
6. Classifier wheel according to one of claims 1, 2, 4 or 5, wherein the radially outer edge of the vane surface elements (8) is designed to be at least partially curved and/or inclined with respect to the axial direction of the classifier wheel (2).
7. Classifier wheel according to one of the preceding claims, wherein the vane surface elements (8) are at their radially inner ends at least partially arranged at a central shaft (9) in the classifier wheel (2).
8. Classifier wheel according to one of claims 1 to 6, wherein the vane surface elements (8) extend up to the radial center of the classifier wheel (2).
9. Classifier wheel according to one of the preceding claims, wherein the vane surface elements (8) only extend to a region of the classifier wheel (2) adjacent to a discharge opening (7).
10. Classifier device for classifying milled comminuted products, in particular for classifying particulate bulk material, comprising:

    a classifier wheel (2) according to one of the preceding claims,

    a vane ring (4) inside of which the classifier wheel (2) is rotatably arranged, wherein a classifying space (6) is arranged between the vane ring (4) and the classifier wheel (2).
11. Method for classifying milled comminuted products, in particular particulate bulk material, including the steps of

    - feeding the milled comminuted product into a classifier space (6) surrounding a rotating classifier wheel (2), and

    - providing an airflow which flows radially inward into the rotating classifier wheel (2) and is then discharged in the axial direction through a discharge opening (7) in the classifier wheel (2), wherein the airflow carries along a portion of the comminuted product in the axial direction along vane surface elements (8) in the region of the classifier wheel (2) adjacent to the discharge opening (7),

    characterized in that
    the angle of inclination of the vane surface elements (8) is constant with respect to the axial direction of the classifier wheel (2) in an area spanned by the axial direction and the circumferential direction of the classifier wheel (2).
12. Method according to claim 11, wherein the radial distance between the radially inner end of the classifier wheel blades (5) and the radially outer end of the vane surface elements (8) is constant along the entire axial extension of the classifier wheel (2).
13. Method according to claim 11 or 12, wherein the vane surface elements (8) extend linearly in the axial direction of the classifier wheel (2).
14. Method according to one of claims 11 to 13, wherein the classifier wheel (2) comprises classifier wheel blades (5), the classifier wheel blades (5) are arranged in the radially outer region of the classifier wheel (2), and the vane surface elements (8) are arranged radially spaced apart from the classifier wheel blades (5) in the radially inner region of the classifier wheel (2), and wherein the radial distance between the radially outer end of the vane surface elements (8) and the radially inner end of classifier wheel blades (5) of the classifier wheel (2) is adjusted depending on the rotational speed and/or diameter of the classifier wheel (2).
15. Method according to one of claims 11 to 14, wherein the airflow between the classifier wheel blades (5) is designed to be rotationally symmetrical.

Images