EP3677348B1 - Centrifugal separator with special separator wheel - Google Patents

Description

The invention relates to a centrifugal separator.

TECHNICAL BACKGROUND

Centrifugal separators are known in various designs in the prior art.

The heart of every centrifugal separator is a separator drum rotating at high speed within a drum-shaped separator chamber.

The sifter drum is perforated, perforated or otherwise provided with a sieve structure on the casing side. Classifier air is sucked in from the fines outlet. This creates a continuous sifter air flow. This usually enters the sifter room together with the sifted material via the sifted material inlet. There, the sifter air flow loaded with the sifted material is swirled by the high-speed sifter drum to form a kind of cyclone flow. This initially circulates around the outside of the classifier drum and finally enters the interior of the classifier drum through the perforated casing. From there, the sifter airflow flows into the fines outlet which is connected to at least one end face of the sifter wheel.

In this process, the centrifugal classifiers take advantage of the fact that the larger, more massive particles of the classifying material are finally separated by the centrifugal forces thrown outwards when the sifted material circulates in the cyclone-like flow in the sifter room. In contrast, smaller, lower-mass particles, which are therefore only exposed to lower centrifugal forces at the same angular velocity, are detached from the cyclone-like flow by the classifier air flowing inwards and sucked into the inside of the classifier drum, in order to then be discharged together with the classifier air flow.

The market is increasingly demanding classifiers with increased throughput, whereby the classifying quality should also be increased or at least maintained if possible.

One way of increasing the throughput of a centrifugal classifier of this type is to increase the diameter of the classifier wheel and, as a result, to rotate the classifier wheel at a higher speed - since the mere increase in the classifier wheel diameter at the same nominal speed means that the fines that can be obtained are coarser becomes.

However, the increase in speed means that the systems are technically more complex, have to be balanced even more precisely and are more complex to maintain.

The EP 1 004 366 A2 shows a vertically running centrifugal classifier with two separate classifier rotors arranged opposite one another at the end, with a radial flow gap being formed in which the material to be classified is dispersed.

The EP 0 369 399 A2 shows a vertically running wind sifter with only one sifting drum.

THE PROBLEM UNDERLYING THE INVENTION

The invention addresses the problem of creating a centrifugal classifier that is easier to balance and easier to maintain, and that offers the possibility of achieving better classifying quality.

THE SOLUTION ACCORDING TO THE INVENTION

According to the invention, the solution is achieved by means of a centrifugal separator with the features of the first main claim.

It is a centrifugal classifier with a classifier housing—usually fixed relative to the foundation—and a classifier wheel that rotates in the classifier housing. The sifter housing has at least one sifting material inlet, at least one sifting air inlet, at least one coarse material outlet, and at least one fine material outlet, usually a first and a second fine material outlet. The sifter air, which is sucked in or fed in at least via the inlet for the sifting material, is usually also drawn off via the latter(s). The sifter air is preferably drawn through the centrifugal sifter by means of an external blower, which sucks in on the side of the fines outlet.

The classifier wheel is formed by a classifier drum and a classifier wheel shaft carrying the classifier drum. Ideally, the classifier wheel shaft rotates around an imaginary horizontal axis.

The lateral surface of the sifter drum is perforated in such a way that during operation it causes the sifted material that strikes the sifter drum on the outer side of the casing to rotate, with other aids possibly being present to generate the rotation. As a rule, one can say that the material to be classified is set in rotation by the classifier drum, or is further accelerated. The material to be classified already has a certain basic translational speed when it enters the machine, with the direction changing in this respect as it enters. The outer surface of the classifier drum is perforated in such a way that the classifying air flows through it in a radially inward direction.

The fines outlets are arranged at the two front ends of the sifter drum, with the mixture of fines and sifting air flowing out of the interior of the sifter drum into the respective fines outlet via the respective free end face of the sifter drum. The same applies analogously if only one fines outlet is provided.

According to the invention, it is provided that the sifter wheel shaft consists of two parts which are not directly connected to one another in a load-bearing manner. The first part of the sifter wheel shaft extends outwards from a first hub, which carries the sifter drum in the region of its first end face, away from the sifter drum. The second part of the sifter wheel shaft extends from a second hub, which carries the sifter drum in the region of its second end face, outwards in the opposite direction, also away from the sifter drum.

For clarification of the term, the following should first be noted:
The term "not directly connected" means in the context of the invention that there is no direct flow of force from one shaft part to the other - unlike in the case of directly flanged, sleeved or z. B. by means of a Hirth gearing directly coupled to each other shaft parts. The two shaft parts are therefore arranged at a spatial distance from one another. Between them is the separator drum. The distance between the two shaft parts is usually at least 80% of the length of the separator drum. This is self-supporting and bridges the gap between the two shaft parts by acting there as a kind of hollow shaft.

The term "fine goods" in its broader sense initially has no inherent size limitation. However, the term "fines" also has a narrower meaning - currently optional - and then designates such material made of ultrafine particles in which 98% of the particles have an average diameter of less than 6 μm and ideally even less than 3 μm.

The configuration according to the invention has the following consequences:
The fact that inside the classifier drum no longer rotates a shaft whose imbalance is different from the imbalance of the classifier drum, the classifier wheel can be fine-balanced more easily and better. It is therefore predestined for higher speeds and has less tendency to vibrate.

In addition, with the elimination of the classifier wheel shaft that previously ran centrally inside the classifier drum, a significantly larger clear flow cross section is available for the mixture of classifier air and fines. While the freighted with the fines sifter air with a speed of 13 to 17 m/s through the sieve structure of the sifter roller into the interior of which, the measure according to the invention slows down the flow speed of the sifter air loaded with the fines to 2 to 6 m/s immediately in front of the fines outlet. This reduces the tendency of the fines to agglomerate, ie to clump, due to turbulence in the sifter air.

In addition, the periodic maintenance of the classifier wheel is significantly easier. There no longer exists a one-piece shaft which is extremely cumbersome because of its great length - particularly when it must be manipulated to remove a one-piece or multi-piece classifier bowl and re-slide and position the replacement part, to finally release it by tightening a bolting, which is usually difficult to access in the annular gap between the classifier drum and the classifier shaft.

In addition, the quality of the sifting is usually improved by the configuration according to the invention, because the clear flow cross section within the sifter drum becomes larger. An effect that usually goes hand in hand with this is that the transport of the fine particles is improved. After passing through the sieve-like drum shell, the fine particles have more space inside the classifier drum, so there is less agglomeration after classifying.

ANOTHER PROBLEM UNDERLYING THE INVENTION

In addition to what has been said above, the invention is also dedicated to the problem of creating a centrifugal separator which achieves a qualitatively further improved sifting result.

THE FURTHER SOLUTION ACCORDING TO THE INVENTION

According to the invention, the solution is achieved by means of a centrifugal separator with the features of the second main claim. On the one hand, independent protection is claimed for this, without reference to other claims. On the other hand, protection is also claimed for it in combination with the first main claim, making it a dependent claim.

In its broadest form, the aforementioned claim proposes a centrifugal separator as a solution, in which a one-part or multi-part guide element is arranged in the area of the at least one coarse material outlet. The guide element is arranged at a minimum distance X from the inner lateral surface of the classifier housing section surrounding the classifier drum. It is designed in such a way that sifted material, which flows along the aforesaid inner lateral surface with a radial distance ≦X, runs under the guide element and is then discharged centrifugally into the coarse material outlet. In addition, the guide element is designed in such a way that at least part of the material to be classified, which flows along the said inner lateral surface with a radial distance >X, is deflected in a radially inward direction towards the classifier drum and thus approaches the classifier wheel, usually more than just insignificantly.

For clarification of the term, the following should first be noted:
The minimum distance X is measured in the radial direction. It designates the distance that the front edge of the guide element, which is first reached by the inflowing sifted material when it hits the guide element, keeps from the inner lateral surface delimiting the sifter space.

An underflow in the sense of the invention occurs when the material to be screened passes the guide element on its radially outward side without receiving an impulse from the classifier wheel that changes the trajectory or changes it significantly.

The configuration according to the invention has the following consequences:
Sifted material, which flows along said inner lateral surface with a radial distance ≦X, is coarse material that has already been separated from the fine material in the best possible way and is therefore ripe for separation from the sifting process. It runs under the guide element and reaches the coarse material outlet undisturbed. Since there is no supporting effect of the inner lateral surface here, the incoming coarse material is discharged into the coarse material outlet by the centrifugal forces acting on it. Since the coarse material reaches the coarse material outlet on the side with calmer flow, ie on the leeward side of the guide element, there is no risk of part of the coarse material being unintentionally carried back into the sifter room due to turbulence.

On the other hand, the part of the material to be classified that flows along said inner lateral surface at a radial distance >X is deflected in the direction of the classifier drum 14 and flung back. This prevents the material to be classified, which has already come relatively close to the clear opening that leads to the coarse material outlet, but has not yet qualitatively completed the sifting process, from being prematurely thrown into the Grobgutauslass is discharged. As a result, fines that could actually still be separated would be withdrawn from the sifting process, which would worsen the sifting result. Instead, a further sifting of the sifted material thrown back in the direction of the sifter drum takes place, in the course of which the fine material that was previously entrained by the coarse material is given the opportunity to separate from it.

OPTIONAL FURTHER DEVELOPMENT POSSIBILITIES OF THE INVENTIONS

The guide element preferably partially covers the coarse material outlet or the clear cross-section that branches off to the coarse material outlet. Preferably more than 35% and better still more than 50% of said clear cross-sectional area are covered.

In this way, the guide element gives the leeward area, already mentioned above, an extremely effective size and essentially prevents classified material from being discharged prematurely into the coarse material outlet.

Constructions are particularly preferred in which additional sifter air is fed in at the coarse material outlet, which flows out via the sifter drum into the fine material outlet. You could use this additional sifter air as in the area of the coarse material outlet designate acting supporting air which--particularly in conjunction with said guide element--ensures that the material to be classified is not discharged prematurely into the coarse material outlet. It is particularly preferred if said sifting air is not only sucked in passively, but is actively blown in by means of a corresponding blower or from a compressed air network.

It is favorable if the ratio NL/ND between the usable length NL of the classifier drum and the maximum usable diameter ND of the classifier drum is ≧2 and ideally ≧2.3. If the optimal case is NL/ND = 2.5, then a classifier drum with a useful length of 2,000 mm has a useful diameter of 800 mm. The usable length of the sifter drum is the length over which it extends freely parallel to the axis of rotation L through the sifter space. The useful diameter is the maximum outer diameter of the drum. Flow-technically insignificant, purely a locally further outward protruding structures (e.g. flanges) are not included in the calculation of the maximum outer diameter.

The throughput can be increased by constructing an extremely long classifier drum without increasing its nominal diameter. With increasing length, the area through which the fines can be sucked in from the sifter chamber into the interior of the sifter drum increases. As the nominal diameter of the sifter drum is not increased, the sifting result is not negatively influenced. In particular, there is no increased entry of coarser grains into the fines obtained, which would have to be compensated for by other measures.

At the same time, a classifier drum that is longer in the axial direction with otherwise the same parameters (diameter, speed and air volume) tends to lead to finer classification, since the radial passage speed of the air through the sieve-like casing of the classifier drum decreases due to the larger flow inlet cross section. As a result, only finer particles tend to be sucked in while overcoming the centrifugal forces acting on them.

It is particularly favorable to design the centrifugal classifier in such a way that at least one, preferably both, parts of the classifier wheel shaft are mounted outside of the compartment for the materials to be classified. The roller bearings, which were previously located in the sifter room itself, had to be protected from the turbulent and therefore highly invasive and abrasive atmosphere in the sifter room at great expense. Even an arrangement outside of the sifter room, e.g. B. in the area of the far less turbulent flow through the fines outlet, brings an improvement here. The maximum improvement is achieved when the bearings are arranged completely outside any fine dust-laden atmosphere, i.e. also outside the fines outlet, easily accessible on its side facing away from the sifter room. Here they achieve significantly longer average service lives, which is a decisive advantage at the high speeds.

It has proven to be particularly favorable if blades protrude radially inwards from the inner lateral surface of the classifier drum and influence the movement of the classifying air, in particular directing the classifying air and its rotation strengthen. In this context it should be considered that the rotation of the safety air inside the sifter bowl reduces the pressure that is necessary to convey the fine product in the direction of the front-side outlets.

It is particularly favorable if the intermediate ring, which will be discussed in more detail later and is intended in particular for the middle of the sifter drum, has blades of the type mentioned which protrude radially inwards from its inner lateral surface.

Ideally, self-contained support rings protrude radially inward from the inner lateral surface of the classifier drum in the circumferential direction. Such support rings support the often quite long and yet comparatively thin-walled sifter drum at certain intervals and thus prevent it from expanding outwards like a drum at extremely high speeds and possibly even being overloaded or even failing.

It is particularly expedient if said support rings are formed in pairs from radially inwardly projecting flanges with which the separator drum elements discussed in the next paragraph are flanged to one another.

The sifter drum preferably consists of several, preferably at least four, sifter drum elements. These are arranged one behind the other along the common axis of rotation and are connected to one another, preferably screwed together.

It is particularly favorable if the several sifter drum elements consist of two groups of identical sifter drum elements, since the production costs can be reduced by using identical parts. In some cases it is even possible Achieve cost-efficient modularization for entire series, for example by equipping larger centrifugal separators with a separator drum that consists of two sets of two and three identical separator drum elements instead of two sets of two identical separator drum elements.

Ideally, an intermediate ring is installed between two classifier drum elements in the middle of the classifier drum. The intermediate ring has—preferably on its outer lateral surface—one or more depressions for receiving a balancing mass body, usually in the form of at least one balancing groove.

Such an additional support ring can very effectively support the central area of the separator drum, which is particularly stressed by the centrifugal forces, and protect it from overloading.

Another possible development of the invention is that the sifter drum has a deflector lip at its front ends, directly at the transition to the fines outlet. This extends obliquely radially inward—preferably at an angle of 35° to 50°. The deflector lip prevents an undesired sifter air flow from occurring in the shortest possible way, almost in a kind of "short circuit", which flows at the front side of the sifter drum, directly from its jacket into the fines outlet. This is because such an undesired sifter air flow may, under certain circumstances, drag only incompletely sifted sifted material into the fines outlet and thus lead to a kind of partial "short circuit".

Preferably, the wheel discs, which connect the classifier drum with the classifier wheel shaft, consist of a wheel rim which has at least two, better at least three spokes are connected to a hub shell.

It is particularly favorable if the rim forms an inner lateral surface that widens conically towards the fines outlet - and not just in the sense of a chamfer customary in mechanical engineering, but over at least 25%, better at least 45% of the extension of the rim in the direction of the axis of rotation . This improves the guidance of the sifter air loaded with the fines, where it exits from the face of the sifter drum at high speed into the fines outlet. This prevents strong turbulence from occurring here due to an excessively abrupt change in the clear flow cross section or abrupt deflection if the flow speed is too high. Excessive turbulence at this point could lead to a part of the fines carried along by the outflowing sifter air falling out prematurely and cumbersomely piling up instead of being completely discharged by the outflowing sifter air.

As part of a particularly preferred development, it is provided that the length of the hub sleeve in the direction of the axis of rotation is greater than the length of the rim of the wheel disc. In this way, a particularly strong and rigid anchoring of the classifier wheel shaft parts according to the invention that does not tend towards permanent vibrations or at least temporary imbalances (e.g. when passing through the subcritical speed range during start-up) can be achieved. Ideally, the length of the hub shell in the direction of the axis of rotation should be at least 30%, better still at least 50%, greater than the corresponding length of the rim rim.

Another, particularly favorable option is that the first and the second part of the sifter wheel shaft each form a radially outwardly projecting disk flange. This disk flange in each case preferably rests over its entire surface against the end ring surface, which faces the interior of the classifier drum, of the hub sleeve assigned to this part of the classifier wheel shaft. The disc flange is preferably screwed to the hub shell, which last but not least provides additional flexural rigidity.

Further configuration options, further technical effects and further advantages result from the exemplary embodiment which is described below with reference to the figures.

FIGURE LIST

• The figure 1 shows a perspective view obliquely from above and outside of a centrifugal separator according to the invention.
• The figure 2 shows a central longitudinal section perpendicular to the axis of rotation through the centrifugal separator according to FIG figure 1 .
• The figure 3 shows a section along the axis of rotation through the centrifugal separator according to FIG figure 1 .
• The figure 4 shows a front view of the cut surface of the figure 3 .
• The figure 5 shows a frontal view of the cut surface of the figure 2 .
• The figure 6 shows an overall view of the centrifugal separator according to the invention.
• The figure 7 shows a detail enlargement from the figure 2 in the central area, although here the intermediate ring is optionally equipped with blades.
• The figure 8 shows a detail enlargement from the figure 5 .
• The figure 9 shows a section of what a seal according to the invention can look like.
• The figure 10 shows the same as that figure 9 , frontal from the front.

EXEMPLARY EMBODIMENT THE FUNCTIONAL PRINCIPLE OF THE CENTRIFUGAL SEPARATOR

The basic functional principle of a centrifugal separator, according to which the centrifugal separator according to the invention also works, has already been explained in the introduction to the description. Reference is made to this to avoid repetition.

THE SEPARATOR HOUSING

The figure 1 provides a first overview of a preferred embodiment of the centrifugal separator 1 according to the invention.

The classifier housing 2 can be seen clearly here 1 classifier wheel not shown.

The separator housing 2 is preferably divided by a horizontal flange 3 into an upper part 2a and a lower part 2b. The upper part 2a can then preferably be detached as a whole and either removed completely or at least folded up about the hinges 4 and their hinge pivot axis S. This gives you easy maintenance access to the sifter room, which should advantageously be cleaned on a regular basis or in batch operation after each batch.

In the sifter chamber 10, which the sifter housing 2 delimits in its interior, a sifter wheel, which is to be described in more detail immediately, rotates about the axis of rotation L. The sifter wheel is well in the figure 3 recognizable, it is marked there with the reference numeral 7.

As can be seen, the centrifugal separator is preferably designed as a horizontal separator. This means that the axis of rotation L, around which the sifter wheel 7 rotates, runs horizontally in the operational state.

This reduces the load on the rolling bearings on which the classifier wheel of this centrifugal classifier is mounted in order to keep the classifier wheel completely or essentially free of play. This is important given the high speeds to which the roller bearings are subjected, since the classifying wheel preferably rotates at an outer peripheral speed of between 50 m/s and 150 m/s. The reason for this is that when the axis of rotation L runs horizontally, the roller bearings inherently carry essentially the same load on each side of the classifier wheel. In contrast, a uniform bearing load is more difficult to achieve when the classifier wheel rotates about a vertical axis.

Above the sifter wheel, the sifter housing 2 has a sifting material inlet 5. Via this sifting material inlet 5 (large black arrow), the sifting material consisting of mixed coarse and fine material is fed to the sifter room. As a rule, the sifting material inlet 5 functions at the same time as a sifting air inlet. Thus, at least the predominant part of the sifting air also enters the sifting chamber via this sifting material inlet 5 . Due to the design of the classifier wheel according to the invention, which is to be described in more detail and which is particularly favorable in terms of flow technology, it is possible for the first time within the scope of the invention to Increase product to air ratio. For classifiers according to the invention, it is ideally at least 0.5 kg, even better at least 0.75 kg of material to be classified per cubic meter of classifying air. The optional upper limit is 1 kg of sifted material per cubic meter of sifted air. Said mixture of sifting material and sifting air preferably flows in in a substantially tangential direction. Such a directed entry supports the circling of the sifted material in the sifter room, which generates the sifting effect. As can be seen, viewed in the direction of the axis of rotation L, the sifting material inlet 5 extends over the predominant part of the length of the sifting chamber.

The sifter housing 2 has a fines outlet 6 at each end of the sifter chamber. The discharge usually takes place with the help of the sifter air, which is also drawn off via the fines outlet 6 . As you can see, the fines are preferably discharged in a tangential direction, which is symbolized by the two small white arrows.

The classifier housing 2 has a coarse material outlet 8 which is generally arranged completely below the classifier wheel 7 . This coarse material outlet is figure 1 symbolized by the large white arrow.

A certain proportion of sifter air is preferably additionally blown into the sifter space via the coarse material outlet 8 or the auxiliary air supply 9 arranged there, by means of a blower not shown in the figure. This auxiliary air supply is in figure 1 symbolized by the small black arrow. In particular, fines that accidentally get into the area of the coarse material outlet has fallen or threatens to fall unintentionally into this area, transported back into the sifter room. This leads to a significant improvement in the quality of the screening result.

More details are very good based on the figure 2 to recognize, which shows a section in the vertical direction through the central area of the classifier and in conjunction with the figure 3 is to be considered.

The cut part of the classified material inlet 5, the fine material outlet 6 located behind it in the direction of the axis of rotation L and the coarse material outlet 8 located below, into the clear opening of which the guide element 28 protrudes, can be clearly seen here. It is also easy to see how the classifier housing 2 forms a classifier chamber 10 in the form of an essentially cylindrical drum, which here runs horizontally. In this drum, the sifter wheel 7 rotates at a considerable distance from the inner lateral surface A of the drum. The distance A is preferably between 25% and 65% of the outer diameter of the classifier wheel 7.

In particularly preferred cases, it is between 32% and 40% of the outer diameter of the classifier wheel 7.

THE CLASSIFIER WHEEL

The classifier wheel 7 according to the invention and its precise structure can best be illustrated by the figures 6 and 7 explain.

The classifier wheel 7 consists essentially of a classifier drum 14 with a classifier wheel shaft 11, which forms its axis of rotation.

How to use the immediately 6 recognizes, the classifier wheel shaft 11 is characterized in that it does not completely traverse the classifier wheel 7 . Instead, the interior of its sifter drum 14 remains free of it over at least 80% of its length, measured in the direction of the axis of rotation L. In this area, the sifter drum 14 takes on the supporting function of the section of the sifter wheel shaft 11 that is saved here, which will be discussed in more detail shortly.

As can be seen, the sifter wheel shaft 11 consists of a first and a second sifter wheel shaft part 12, 13. The two sifter wheel shaft parts each end in a wheel disk 15. This wheel disk 15 consists of a hub sleeve 16 which is connected to a rim rim 18 via at least three spokes 17 , preferably in one piece. The hub sleeve 16 has a length in the direction of the axis of rotation L that is greater than the corresponding length of the rim rim 18.

As can be seen clearly, each classifier wheel shaft part 12, 13 forms a disk flange 19 at its end facing the inside of the classifier drum. This disk flange 19 rests against the inner face of the hub sleeve 16 assigned to it. The respective disk flange 19 thus prevents the relevant classifier wheel shaft part 12, 13 from being pulled out of the hub sleeve 16 to the outside. In addition, the disk flange 19 is preferably screwed to the hub sleeve 16 . The bolt heads 35 of the corresponding, preferably at least six studs are in figure 6 can be seen on the disk flange 19 of the first classifier wheel shaft part 12 .

As has already been mentioned briefly above, the classifier drum 14 assumes the supporting function in the area in which the classifier wheel shaft 11 is exposed. For this purpose, the lateral surface of the separator drum is thick-walled. Its wall thickness can essentially correspond to the wall thickness of a hub shell 16 . It is particularly favorable when its wall thickness is greater than 20 mm and ideally in the range between 30 mm and 48 mm, +/- 0.3 mm. The sifter drum is additionally reinforced by the inwardly projecting annular disc-shaped support rings, several of which are provided at a distance from one another on the inner surface of the sifter wheel and which will be discussed in more detail in a moment. The predominant part of the peripheral surface of the classifying drum is perforated. It then forms a sieve-like or preferably grid-like or perforated structure through which suction can take place. A lattice-like structure can be distinguished in particular by the fact that its openings in the direction parallel to the longitudinal axis are longer by a factor of at least 7.5 and better by a factor of at least 10 than in the circumferential direction, which can improve the intake characteristics.

Each classifier wheel shaft part 12, 13 is preferably equipped as a stepped shaft with different diameters. The hub shell 16 preferably overlaps where this stepped shaft (apart from the disk flange 19) has its greatest diameter.

As can be seen, the rim rim 18 of the wheel disc 15 is designed as a ring that is completely closed in on itself in the circumferential direction. One end face of this ring rests against a corresponding end face of the separator drum 14 and is screwed to it. The screwing preferably takes place from the outside of the wheel disk 15 . Accordingly, the receiving bores 20 for the bolt head in the rim rim 18 can be seen here, compare figure 6 .

The figure 6 shows how the inner lateral surface 21 of the rim 18 widens conically towards the fines outlet. This extension is more than just a chamfer that is usual in mechanical engineering. In the present case, it extends over the majority of the length of the rim in the direction of the axis of rotation L.

On its outer peripheral surface, each wheel rim carries a type of toothing 22 or other blade-like structures. Together with the housing enclosing them, these form a type of impeller and/or mechanical deflector, which is arranged in the direction of flow in front of the sealing gap, for which it is functionally responsible, cf. 6 combined with 10 . Despite the air flushing of the gap between rotor and housing, it keeps particles from getting into this space.

The rim rim is preferably provided with one or more sealing grooves 23 on its outer peripheral surface, which form part of the labyrinth-like seal with which the classifier wheel is sealed off at its end faces from the fines outlet 6 - which will be discussed in more detail later.

The preferred embodiment of the spokes 17 can be based on the rear part of the figure 6 comprehend. The spokes 17 preferably extend in a purely radial direction from the hub shell 16 to the rim rim 18. Each spoke 17 is where it is connected to the hub shell 16, just as long as this, measured in the direction of the axis of rotation L. Each spoke tapers 17 towards the wheel rim 18. This means that each of the spokes generally protrudes into the interior of the sifter drum 14 and protrudes outwards on its opposite side in the direction of the axis of rotation L over the rim rim 18 . In this way, the spokes have a relatively large area and can therefore contribute effectively to causing the sifter air to rotate.

The classifier drum is preferably composed of several separately manufactured classifier drum elements 14a and 14b. These are arranged one behind the other along the common axis of rotation L and connected to one another, preferably screwed. Ideally, the sifter drum elements have a "effective length (NL) to effective diameter (ND) ratio" that satisfies the following equation: NL/ND = 0.5 to 0.8. The useful length corresponds to the total extension parallel to the axis of rotation L. A sifter drum element that extends 500 mm along the axis of rotation L then has a diameter of 1,000 mm.

It is particularly favorable if each of the sifter drum elements 14a, 14b carries a fastening flange 24a, 24b, 24c in the form of an annular disk on each of its two end faces. This extends in the radially inward direction by an amount H in relation to the inner lateral surface of the separator drum element. Ideally, the following applies: H ≥ 30 mm, cf. 7 , where that Dimension H is drawn. Viewed from a different perspective, it can be said that the free area through the clear diameter XX (see 7 ), depending on dimension H, must provide enough space for the flow rate to fall below 30 m/sec here. Nevertheless, the construction must of course have sufficient mechanical strength.

Said fastening flange is therefore completely inside the separator drum. It carries the screw connection that fixes two adjacent classifier drum elements together. It usually also forms a centering groove or a centering projection 36 complementary thereto, via the interaction of which adjacent classifier drum elements are positioned precisely relative to one another. A detailed representation of such a centering groove and a centering projection identified by the reference numeral 36 can be found in figure 7 right, middle.

In this exemplary embodiment, a pair of annular disk-shaped fastening flanges 24a, 24b, 24c screwed together forms one of the support rings already mentioned briefly above. These support rings prevent the classifier drum 14 from expanding outward in a barrel shape in its middle area under the influence of the strong centrifugal forces caused by the high operating speed or from being even overloaded and failing.

According to the figure 6 a special intermediate ring 25 is installed between two classifier drum elements 14a in the middle of the classifier drum. This intermediate ring 25 has one or more indentations on its outer lateral surface for receiving a balancing mass body, preferably in the form of at least one balancing groove 37, cf. Figure 7 .

In addition, this intermediate ring 25, together with the annular disk-shaped fastening flanges 24a locked to it by the screw connection, creates a wider and therefore particularly heavy-duty support ring of the type already explained above lies.

Optionally, the intermediate ring 25 can be equipped with blades 26 that protrude even further inwards in the radial direction and serve to move the sifter air without disturbing the pressure equalization explained below, compare figure 7 .

In earlier designs, for reasons of strength, the sifter drum was supported by the safety shaft in the area of today's intermediate ring 25 with a disc wheel with narrow openings or turbulent spokes. In contrast, the construction according to the invention results in a significantly better equalization of the instantaneous pressure between the left half of the classifier drum, which communicates with the first fines outlet, and the right half of the classifier drum, which communicates with the second fines outlet on the other side, over its maximum flow cross section .

The resulting lower pressure pulsations inside the sifter drum improve the sifting result, if only because fewer agglomerations occur.

As can be seen, the radially inward end of each mounting flange 24a, 24b, 24c is beveled over its entire width, approximately in the manner of a pent roof, as shown in FIG figure 6 shown. Because of this, two fastening flanges screwed together form a gable roof-like configuration, which functionally represents a sliding slope for the visible material. This reliably prevents a slightly heavier part of the sifted material from being permanently deposited at this point during operation and being held in place by centrifugal forces - as could be the case with a surface running parallel to the axis of rotation L due to a missing sliding slope.

For the same reason, the radially inward end of the intermediate ring 25 is beveled in the manner of a gable roof and, where present, the inner ends of the blades 26.

Easily recognizable by the figure 6 is that the sifter drum elements consist of two groups of identical sifter drum elements. As can be seen, the two classifier drum elements 14a meeting in the middle of the classifier drum 14 are structurally identical and the two classifier drum elements 14b which close off the classifier drum 14 on the outside are also structurally identical.

Finally shows the figure 6 that the sifter drum has at its two front ends, directly at the transition to the fines outlet 6, a deflector lip 27 that extends radially inward and at the same time obliquely towards the center of the sifter drum 14. This has the function mentioned in the introduction to the description.

It is contemplated that the classifier bowl elements 14a and 14b could be cast parts, such as ductile iron, which would then be subsequently precision turned. In this way, the large number of openings in the outer lateral surface of the classifier drum 14 can be produced particularly efficiently. Irrespective of whether the sifter drum has one or more parts, these openings are required for the sifter air to enter the inside of the sifter drum. They are also preferably the sole or at least predominant means in the one-piece or multi-piece classifier wheel to bring the safety air entering the classifier space and the material to be classified in the classifying chamber to circulate in such a way that the centrifugal forces can develop their separating effect.

THE GUIDE BODY CONTROLLING THE COARSE OUTLET

The guide element 28 according to the invention, which controls access to the coarse material outlet, can best be based on the figures 2 , 5 and 8th recognize and explain.

The guiding element 28 according to the invention can be a shovel or—in an optionally broader interpretation of the term shovel—a guiding element similar to a shovel. Its main guide surface 29 is curved in such a way that material to be classified that strikes this main guide surface 29 is deflected or thrown back inwards towards the classifier drum 14 . Fine material that may have been mixed in with the sifting material hitting the blade 26 and was entrained radially outwards by it, thus has the chance to separate from it to be separated from the coarse material and then taken along by the sifting air flowing into the interior of the sifter drum 14 and entered into the interior of the sifter drum 14 . This significantly improves the classification quality.

It should be noted that said curvature is preferably a continuous concave curvature sloping towards classifier bowl 14 . The main guide surface 29 is preferably designed as a correspondingly curved sheet metal, which is kept in shape at least by two edge plates 30 bordering it on both sides, cf. figure 5 and 8th . The main guide surface 29 is often also stabilized in its center (measured in the direction along the axis of rotation L) by an edge plate 30 of the type mentioned, which is welded on here as a rib-like reinforcement. Preferably, the vane is designed in such a way that it does not cause turbulence - at least not significantly.

In the direction parallel to the axis of rotation L, the extent of the preferably one-piece guide element 28 according to the invention is generally so large that it covers the entire coarse material outlet in the direction along the axis of rotation L. Viewed in the direction of rotation, the extension of the guide element 28 according to the invention is preferably so large that the guide element covers more than 45% and better 60% to 70% of the clear surface with which the coarse material outlet opens into the inner lateral surface of the drum designed as part of the classifier housing, which Classifier room 10 limited.

It when the position of the guide member is adjustable in and against the direction of rotation, ideally continuously adjustable, so that it is more or less the when needed is particularly favorable covers clear surface with which the coarse material outlet opens into the inner lateral surface of said drum, which is not shown separately here in the drawing. In this way, the guide element according to the invention can be adjusted to the maximum mean grain diameter of the fines currently required by the sifter.

A special feature is that the guide element 28 is attached at a distance X from the inner lateral surface of the drum, which delimits the sifter space 10 . The distance X meant here is preferably between 3 mm and 12 mm. Ideally, it can be adjusted, usually steplessly. In this context, the distance depends on the number of coarse particles contained in the sifted material. If there are many coarse particles, the separation must be faster. The distance will then tend to be set larger, resulting in faster ejection.

This positioning of the guide element 28 means that classified material (coarse material), which flows along the aforesaid inner lateral surface with a radial distance ≦X, runs under the guide element 28 and is then discharged into the coarse material outlet by the centrifugal forces. Only that part of the sifted material that flows along said inner lateral surface with a radial distance >X and <Y is deflected in the direction of the sifter drum 14 . For the distance Y, preferably (DSK-DSR)/2 applies, where DSK is the inner diameter of the sifter space and DSR is the outer diameter of the sifter drum. Alternatively, it can be said that the distance Yʺ should be in the absolute range between 1/2 DSR and 2/6 DSR

It is also noteworthy that the guide element 28 is particularly effective in conjunction with the auxiliary air supply 9, since these two improvements together develop a synergistic effect.

This can be done quite well using the figure 5 recognize.

The guide member 28 forces the auxiliary air blown in via the auxiliary air supply 9 to enter the sifter chamber 10 oriented in a tangential direction. It prevents or reduces the tendency of the auxiliary air to impinge unbraked at an obtuse angle on the classifying air rotating at high speed in the classifying chamber 10 and thus to produce undesired turbulence.

At the same time, the guide element 28 calms the air flow in the area in which the coarse material falls out after it has passed under the guide element 28 . This is because in this area the guide element 28 creates a leeward space, at least essentially, in relation to the classifying air circulating at high speed in the classifying room.

All this leads to a significant improvement in the quality of vision.

THE FRONT SEAL OF THE CLASSIFIER WHEEL

Within the scope of the invention, the focus is also on sealing the transition between the sifter chamber 10 and the fines outlet 6 on the end face of the sifter drum 14 as effectively as possible. This is significant, because sealing errors on this one This means that the fine material, which has already been obtained with a high degree of classification, is contaminated with material that has not yet been classified or not completely classified. This is to be avoided.

A non-contact seal is provided for this purpose.

In order to be able to implement such a seal, the classifier housing 2 is designed as a double-walled area in the area of the sealing point between the classifier chamber 10 and the fines outlet 6 . This double-walled range is in figure 3 identified by the reference character D.

Compressed air is fed to the sealing point via this double-walled area D.

The actual sealing point shows the figure 10 in an enlarged view. A section of the rim rim 18 can be seen here. On its outside, it carries several, in the present case preferably three, circumferential sealing grooves 23, as have already been mentioned briefly above, see again 6 .

The double-walled area carries a sealing insert 31 at its end, near the sealing point, see again 10 . Although the seal operates at least essentially without contact, the sealing insert 31 is preferably designed to be replaceable, since in the long term it is a wear part in an atmosphere polluted with fine dust. This sealing insert forms three raised, circumferential sealing rings 32 .

Each of these sealing rings 32 engages in a sealing groove 23 assigned to it on the wheel rim 18 .

Since the seal works without contact, the raised, circumferential sealing rings 32 and the sealing grooves 23 assigned to them form a kind of labyrinth. In order to give this seal a real blocking effect, the sealing insert 31 is equipped with one or preferably several compressed air injection openings 34, via which compressed air is blown into the distribution channel 33 for the said sealing labyrinth, which has been brought to the sealing point via the double-walled area, cf. 10 .

From the distribution channel 33, the greater part of the compressed air that is blown in flows out into the sifting chamber 10 and keeps the path over which it flows out free of penetrating sifted material. The smaller part of the compressed air that is blown in flows out into the fines outlet 6 . The latter because this part of the injected compressed air is blocked by two baffles formed by sealing rings 32 and sealing grooves 23, and not just one, which is why the flow rate is correspondingly lower.

Such a non-contact seal is of great advantage for controlling the high speeds occurring on the classifier wheels according to the invention.

REFERENCE LIST

1

centrifugal classifier

2

classifier housing

2a

Upper part of the separator housing

2 B

Lower part of the classifier housing

3

horizontal flange

4

Hinge for swinging open the separator housing, which was previously detached in two halves

5

visible material inlet

6

fines outlet

7

classifier wheel

8th

coarse material outlet

9

auxiliary air supply

10

classifier room

11

classifier wheel shaft

12

first classifier wheel shaft part of classifier wheel shaft 11

13

second classifier wheel shaft part of classifier wheel shaft 11

14

separator drum

14a

Classifier drum element, type 1

14b

Classifier drum element, type 2

15

Wheel disc made of hub shell, spoke and rim rim

16

hub shell

17

spoke

18

wheel rim

19

disc flange

20

Location hole bolt head

21

Inner lateral surface of the rim rim

22

gearing

23

sealing grooves

24a

washer-shaped mounting flange

24b

washer-shaped mounting flange

24c

washer-shaped mounting flange

25

intermediate ring

26

shovel

27

deflector lip

28

governing body

29

Main Conductor

30

edge plate

31

sealing insert

32

sealing ring

33

distribution channel

34

compressed air injection openings

35

bolt heads

36

centering projection

37

balancing groove

A

Radial distance between the inner lateral surface of the classifier chamber and the outer lateral surface of the classifier drum.

D

double wall area

DSK

Inner diameter of the sifter room or the drum delimiting it

DSR

Outer diameter of classifier drum

H

amount of extension

L

axis of rotation

ND

Useful diameter of the classifier drum

NL

Usable length of the classifier drum

S

Hinge pivot axis of the hinge pair 4

X

smallest radial distance between the guide element 28 and the inner lateral surface of the sifter space.

Y

maximum radial distance that the sifted material rotating in the sifter space may have from the inner lateral surface of the sifter space in order to still come into direct contact with the guide element 28

Yʺ

radial clearance between guide element 28 and the classifier wheel

XX

Clear diameter inside a ring-shaped mounting flange

Claims (14)

1. Centrifugal separator (1) comprising a separator housing (2) and a separator wheel (7) which rotates in the separator housing (2),

   wherein the separator housing (2) has at least one inlet for the material to be separated (5), at least one coarse material outlet (8) and at least one first fine material outlet (6),

   wherein the separator wheel (7) is formed by a separator drum (14) and a separator wheel shaft (11) supporting the separator drum (14), and the circumferential jacket surface of the separator drum (14) is perforated in such a way that it sets the material to be separated, which hits the separator drum (14) on the outer jacket side, into rotation during operation and the air flow within the separator is designed in such a way that a separation air loaded with fine material flows through the circumferential jacket surface of the separator drum in a radially inward direction,

   wherein the at least one fine material outlet (6) is arranged on the end of the separator drum (14) and fine material is discharged from the interior of the separator drum (14) into the at least one fine material outlet (6) via the free front face of the separator drum (14), on the outside past the separator wheel shaft (11),

   characterized in that

   the separator wheel shaft (11) consists of two parts (12, 13) which are not directly connected to one another in a supporting manner,

   and the first part (12) of the separator wheel shaft (11) extends outwards from a wheel disc (15) which supports the separator drum (14) in the region of its first front face, away from the separator drum (14),

   and the second part (13) of the separator wheel shaft (11) extends outwards from a wheel disc (15) which supports the separator drum (14) in the region of its second front face, away from the separator drum (14).
2. The centrifugal separator (1) according to claim 1, characterized in that the separator wheel shaft (11) rotates about a horizontal axis.
3. The centrifugal separator according to one of the preceding claims, characterized in that at least one, preferably both parts (12, 13) of the separator wheel shaft (11) are mounted outside the separator chamber (10), wherein the two parts of the separator wheel shaft (12, 13) preferably also pass through the respective fine material outlet (6) and are only mounted outside the fine material outlet (6), on the side facing away from the separator chamber (10).
4. The centrifugal separator (1) according to one of the preceding claims, characterized in that the at least one coarse material outlet (8) is arranged below the separator drum (14) and separation air which flows off via the separator drum (14) is fed in at the coarse material outlet (8).
5. The centrifugal separator (1) according to one of the preceding claims, characterized in that the ratio NL/ND between the usable length (NL) of the separator drum (14) and the maximum usable outer diameter (ND) of the separator drum (14) is ≥ 2 and ideally ≥ 2 .3.
6. The centrifugal separator (1) according to one of the preceding claims, characterized in that blades (26) project radially inwards from the inner jacket surface of the separator drum (14).
7. The centrifugal separator (1) according to one of the preceding claims, characterized in that supporting rings which are closed in the circumferential direction project radially inwards from the inner jacket surface of the separator drum (14).
8. The centrifugal separator (1) according to one of the preceding claims, characterized in that the separator drum (14) consists of several, preferably at least four separator drum elements (14a; 14b) which are arranged one behind the other along the common axis of rotation (L) and connected to one another, preferably are screwed together, wherein the plurality of separator drum elements (14a; 14b) ideally consist of two groups of identical separator drum elements (14a; 14b).
9. The centrifugal separator (1) according to claim 8, characterized in that each separator drum element (14a; 14b) forms an annular disk-shaped fastening flange (24a; 24b; 24c) on each of its front faces which extends, in relation to the inner jacket surface of the separator drum element (14a; 14b), by an amount (H) in the radially inward direction, wherein preferably at least one fastening flange (24) of each separator drum element (14a; 14b) is bevelled over at least 25% of its radial extent.
10. The centrifugal separator (1) according to one of claims 8 or 9, characterized in that an intermediate ring (25) is installed in the middle of the separator drum (14) between two separator drum elements (14a, 14a), wherein the intermediate ring (25) preferably has on its outer jacket surface one or more recesses for receiving a balancing mass body, preferably in the form of at least one balancing groove.
11. The centrifugal separator (1) according to one of claims 8 to 10 in conjunction with claim 6, characterized in that the intermediate ring (25) has blades (26) that project radially inwards from its inner jacket surface.
12. The centrifugal separator (1) according to one of the preceding claims, characterized in that each of the wheel discs (15) consists of a wheel rim (18) which is connected to a hub sleeve (16) via at least two, better at least three spokes (17), wherein the wheel rim (18) preferably forms an inner jacket surface which widens conically towards the fine material outlet (6).
13. The centrifugal separator (1) according to claim 12, characterized in that the first part and the second part of the separator wheel shaft (11) each form a radially outwardly projecting disc flange (19) which rests against the end ring surface of the hub sleeve (16) associated with this part of the separator wheel shaft (11), which end ring surface faces the interior of the separator drum (14), wherein the disc flange (19) is preferably screwed to the hub sleeve (16).
14. The centrifugal separator according to one of the preceding claims, characterized in that the nominal speed of the separator drum is such that the target value of 160 m/s at the outer diameter of the separator drum is reached or exceeded.

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