TECHNICAL FIELD

The invention relates to a centrifugal separator.

BACKGROUND

Centrifugal separators are known in different embodiments in the prior art.

A separator drum revolving inside a drum-shaped separator chamber at high speed forms the centerpiece of every centrifugal separator.

The separator drum is perforated, interrupted or provided with a sieve structure on the jacket side in another way, respectively. Separation air is sucked in from the fine material outlet. A continuous separation air flow forms thereby. The latter enters into the separator chamber, usually together with the material to be separated, via the inlet for material to be separated. There, the separation air flow, which is loaded with the material to be separated, is swirled by the high-revving separator drum into a type of cyclone flow. The latter initially circles around the separator drum on the outside and finally enters through the perforated jacket of the separator drum into the interior thereof. From there, the separation air flow flows into the fine material outlet, which is adjacent to at least one front face of the separator wheel.

In the case of this process, the centrifugal separators take advantage of the fact that the larger particles of the material to be separated, which have more mass, are finally centrifuged to the outside by means of the centrifugal forces, when the material to be separated circles in the cyclone-like flow in the separator chamber. In contrast, smaller particles, which have a smaller mass and are thus only subjected to lower centrifugal forces at the same angular speed, are released from the cyclone-like flow by the separation air, which flows off to the inside, and are sucked into the interior of the separator drum, so as to then be discharged together with the separation air flow.

The market increasingly demands separators comprising an increased throughput, whereby the separation quality is to simultaneously also be increased or at least maintained, if possible.

One option for increasing the throughput of a generic centrifugal separator lies in increasing the diameter of the separator wheel and, associated therewith, in allowing the separator wheel to rotate at a higher speed because the mere increase of the separator wheel diameter at consistent nominal speed has the result that the obtainable fine material becomes coarser.

The speed increase has the result, however, that the systems become technically more complex, need to be balanced even more exactly, and require a more complex maintenance.

SUMMARY

The invention is dedicated to the problem of creating a centrifugal separator, which can be balanced more easily or better, respectively, and can be maintained more easily and provides the option of achieving a better quality of the separation.

According to the invention, the solution takes place by means of a centrifugal separator comprising the features of the first main claim.

It is a centrifugal separator comprising a separator housing which, as a rule, is stationary relative to the foundation and a separator wheel, which revolves in the separator housing. The separator housing has at least one inlet for material to be separated, at least one separation air inlet, at least one coarse material outlet, as well as at least one, usually a first and a second fine material outlet. Via the latter, the separation air, which is sucked in or fed in, respectively, at least via the inlet for material to be separated, is also removed, as a rule. The separation air is preferably pulled through the centrifugal separator by means of an external blower, which sucks in on the side of the fine material outlet.

The separator wheel is formed by a separator drum and a separator wheel shaft supporting the separator drum. Ideally, the separator wheel shaft rotates around an imaginary horizontal axis. The jacket surface of the separator drum is interrupted in such a way that it sets the material to be separated, which hits the separator drum on the outer jacket side, into rotation during operation, wherein further aids for creating the rotation can possibly be present. As a rule, it can be said that the material to be separated is set into rotation or is further accelerated, respectively, by the separator drum, among others. The material to be separated already has a certain translatory base speed upon entering into the machine, whereby the direction changes in this respect as part of the entering. The jacket surface of the separator drum is interrupted in such a way that the separation air flows through it in the radially inwards direction.

The fine material outlets are thereby arranged on the two front face ends of the separator drum, wherein fine material-separation air mixture flows out of the interior of the separator drum into the respective fine material outlet via the respective free front face of the separator drum. The same applies analogously, when only one fine material outlet is provided.

It is provided according to the invention that the separator wheel shaft consists of two parts, which are not directly connected to one another in a supporting manner. The first part of the separator wheel shaft thereby extends outwards from a first hub, which supports the separator drum in the area of its first front face, away from the separator drum. The second part of the separator wheel shaft extends outwards, in the opposite direction, from a second hub, which supports the separator drum in the area of its second front face, also away from the separator drum.

The following should initially be noted with regard to the conceptual clarification:

In terms of the invention, the term “not directly connected to one another” means that no direct power flow takes place from one into the other shaft part—in contrast to shaft parts, which are directly flanged to one another, sleeved or directly coupled to one another, e.g., by means of a serration. The two shaft parts are thus arranged at a spatial distance from one another. The separator drum is located between them. The distance between the two shaft parts is usually at least 80% of the length of the separator drum. The latter is self-supporting and bridges the distance between the two shaft parts in that it acts quasi as a hollow shaft there.

The term “fine material” in its broader sense inherently does not initially include a size limitation. The term “fine material”, however, also has a narrower meaning—currently optionally—and then identifies such material of ultra-fine particles, in the case of which 98% of the particles have an average diameter of less than 6 μm and ideally even of less than 3 μm.

The embodiment according to the invention has the following consequences:

Due to the fact that a shaft, the imbalance of which is different from the imbalance of the separator drum, no longer revolves in the interior of the separator drum, the separator wheel can be fine-balanced easier and better. It is thus predestined for higher speeds and has less of a tendency to oscillate.

In addition, a significantly larger clear flow cross section is available for the mixture of separation air and fine material in the interior of the separator drum with the elimination of the separator wheel shaft, which centrally passes through. While the separation air, which is loaded with the fine material, enters with a speed of 13 to 17 m/s through the sieve structure of the separator roller into the interior thereof, the flow speed of the separation air, which is loaded with the fine material, slows down to 2 to 6 m/s directly in front of the fine material outlet due to the measure according to the invention. The tendency of the fine material to agglomerate, i.e. to clump, by swirls in the separation air is reduced thereby.

Moreover, the periodic maintenance of the separator wheel becomes much easier. A one-piece shaft no longer exists, which is extremely unwieldy due to its long length—in particular when it has to be manipulated in order to take or remove a one- or multi-piece separator drum and to slide on and position the replacement part again, so as to finally fix it by tightening a screw connection, which is located, often difficult to access, in the annular gap between the separator drum and the separator shaft.

In addition, the quality of the separation is usually also improved by means of the embodiment according to the invention, because the clear flow cross section inside the separator drum becomes larger. An effect, which is usually associated therewith, is that the transport of the fine particles is improved. After passing through the sieve-like drum jacket, the fine particles have more space in the interior of the separator drum, less agglomeration thus occurs after the separation.

Beyond the above statements, the invention is also dedicated to the problem of creating a centrifugal separator, which reaches a separating result, which is qualitatively further improved.

According to the invention, the solution takes place by means of a centrifugal separator comprising the features of the second main claim. On the one hand, independent protection is claimed for said centrifugal separator, without dependency on other claims. On the other hand, protection is also claimed for it in combination with the first main claim, thus turning it into a subclaim.

In its broadest form, the above-mentioned claim proposes a centrifugal separator as solution, in the case of which a one- or multi-piece guide member is arranged in the area of the at least one coarse material outlet. The guide member is arranged at a minimal distance X from the inner jacket surface of the separator housing section surrounding the separator drum. It is designed in such a way that material to be separated, which flows along said inner jacket surface at a radial distance <X, circumvents the guide member and is then centrifugally discharged into the coarse material outlet. The guide member is furthermore designed in such a way that at least a portion of the material to be separated, which flows along said inner jacket surface at a radial distance>X, is deflected in the radially inwards direction towards the separator drum, and thus approaches the separator wheel, usually more than only insignificantly.

For the conceptual clarification, the following should initially be noted:

The minimal distance X is measured in the radial direction. It identifies the distance, which the leading edge of the guide member, which the inflowing material to be separated reaches first, when it hits the guide member, holds from the inner jacket surface, which defines the separator chamber.

A circumventing in terms of the invention is present when material to be separated of the guide member passes on the radially outer side thereof, without receiving an impulse from the separator wheel, which changes or significantly changes the trajectory, respectively.

The embodiment according to the invention has the following consequences:

Material to be separated, which flows along said inner jacket surface at a radial distance <X, is coarse material, which has already separated as best as possible from the fine material and which is thus ready for separation from the separating process. It circumvents the guide member and reaches the coarse material outlet without interruption. Due to the fact that the support effect of the inner jacket surface is eliminated here, the arriving coarse material is then discharged into the coarse material outlet by means of the centrifugal forces acting on said coarse material. Due to the fact that the coarse material reaches the coarse material outlet on the slow-flow side, i.e. on the leeward side of the guide member, there is no risk that a portion of the coarse material is unintentionally carried back into the separator chamber again by means of swirls.

In contrast, the portion of the material to be separated, which flows along said inner jacket surface at a radial distance>X, is deflected in the direction of the separator drum14and is thrown back. It is prevented thereby that material to be separated, which has already come relatively close to the clear opening, which leads to the coarse material outlet, but which has nonetheless not yet qualitatively concluded the separating process, is prematurely discharged into the coarse material outlet by the centrifugal forces and the swirls occurring in the vicinity of said clear opening. This is so, because fine material, which can actually still be separated, would be removed from the separating process thereby, which would impair the separating result. Instead, a further separation of the material to be separated, which is thrown back in the direction towards the separator drum, takes place, as part of which the fine material, which is still being entrained by the coarse material so far, gets the chance to separate therefrom.

The guide member preferably partially covers the coarse material outlet or the clear cross section, respectively, which branches to the coarse material outlet. Preferably, more than 35% and more preferably even more than 50% of said clear cross sectional surface are covered.

The guide member provides the leeward area, which has already been mentioned above, with an extremely effective size in this way and it essentially prevents that material to be separated is prematurely discharged into the coarse material outlet takes place.

Constructions, in the case of which additional separation air, which flows off into the fine material outlet via the separator drum, is fed in on the coarse material outlet, are particularly preferred. This additional separation air could be referred to as support air acting in the area of the coarse material outlet, which—in particular in conjunction with said guide member—ensures that material to be separated is not prematurely discharged into the coarse material outlet. It is particularly preferred, when said separation air is not only sucked in passively, but is blown in actively by means of a corresponding blower or from a compressed air network.

It is favorable, when the ratio NL/ND between the useable length NL of the separator drum and the maximum useable diameter ND of the separator drum is >2 and ideally >2.3. If the optimal case of a NL/ND=2.5 is at hand, a separator drum, the useable length of which is 2.000 mm, has a useable diameter of 800 mm. The useable length of the separator drum is thereby the length, across which it extends freely through the separator chamber parallel to the axis of rotation L. The useable diameter is the maximum outer diameter of the drum. Fluidically insignificant structures, merely standing locally farther to the outside (e.g. flanges) are thereby not included in the calculation of the maximum outer diameter.

The throughput can be increased by the construction of a very long separator drum without increase of the nominal diameter thereof. This is so, because the passage surface, via which fine material can be sucked from the separator chamber into the interior of the separator drum, increases as the length increases. Due to the fact that the nominal diameter of the separator drum is not increased, the separating result is not negatively impacted. In particular, an increasing input of coarser grains into the obtained fine material, which has to be compensated by other measures, does not occur.

A separator drum, which is longer in the axial direction, with otherwise identical parameters (diameter, speed and air quantity) simultaneously tends to lead to a finer separation, because the radial passage speed of the air through the sieve-like jacket of the separator drum decreases due to the larger flow entry cross section. As a result of this, there is a tendency that only finer particles can be sucked in by overcoming the centrifugal forces acting thereon.

It is particularly favorable to embody the centrifugal separator in such a way that at least one, preferably both parts of the separator wheel shaft are mounted outside of the chamber of the material to be separated. The roller bearings arranged in the separator chamber itself until now had to be protected at great expense against the turbulent and thus highly invasive and abrasive atmosphere in the separator chamber. An arrangement outside of the separator chamber, e.g. in the area of the fine material outlet, which is flown through far less turbulently, brings an improvement here. The maximum improvement is reached, when the bearings are arranged completely outside of every fine dust-loaded atmosphere, thus also outside of the fine material outlet, easily accessible on the side thereof facing away from the separator chamber. Here, they reach significantly longer average service lives, which is a significant advantage in the case of high speeds.

It turned out to be particularly favorable, when blades protrude radially inwards from the inner jacket surface of the separator drum, which influence the movement of the separation air, in particular guide the separation air and intensify the rotation thereof. It is important to consider in this context that the rotation of the separation air in the interior of the separator drum reduces the pressure, which is necessary to convey the fine product in the direction of the outlets on the front face.

It is particularly favorable thereby, when the intermediate ring, which will be discussed in more detail later, which is in particular designated for the separator drum center, has blades of the mentioned type, which protrude radially to the inside from its inner jacket surface.

Ideally, support rings, which are closed in the circumferential direction, protrude radially to the inside from the inner jacket surface of the separator drum. The separator drum, which is often quite long and nonetheless comparatively thin-walled, is supported at certain intervals by such support rings, and is thus prevented from widening to the outside in a drum-like manner in the case of extremely high speeds, and from thereby possibly even being overloaded or even from failing.

It is particularly advantageous, when said support rings are formed in pairs of flanges protruding radially to the inside, by means of which the separator drum elements, which will be discussed in the next paragraph, are flanged to one another.

The separator drum preferably consists of a plurality of, preferably of at least four separator drum elements. They are arranged one behind the other along the joint axis of rotation and are connected to one another, preferably screwed to one another.

It is particularly favorable, when the plurality of separator drum elements consist of two groups of identical separator drum elements each, because the production costs can be lowered as a result of identical parts. A cost-efficient modularization can possibly even be attained for entire series, for instance in that larger centrifugal separators are equipped with one separator drum, which plurality of separator drum elements consist of two sets of two identical separator drum elements on the one hand and of three identical separator drum elements on the other hand, instead of two sets of two identical separator drum elements each.

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

Such an additional support ring can support in particular the central area of the separator drum, which is particularly loaded by the centrifugal forces, highly effectively and can protect it against overload.

Another further development option of the invention is that the separator drum has a deflector lip on its front face ends, directly at the transition to the fine material outlet. Said deflector lip extends radially inwards at an incline—preferably at an angle of 35° to 50°. The deflector lip prevents that an unwanted separation air flow appears via the shortest route, almost in a type of “short-circuit”, which, at the front face of the separator drum, flows directly from the jacket thereof into the fine material outlet. This is so, because such an unwanted separation air flow may drag only incompletely separated material to be separated into the fine material outlet and thus leads to a type of partial “short-circuit”.

The wheel disks, which connect the separator drum to the separator wheel shaft, preferably consist of a rim, which is connected to a hub sleeve via at least two, preferably at least three spokes.

It is particularly favorable, when the rim forms an inner jacket surface, which widens conically towards the fine material outlet—namely not only in terms of a chamfer, which is common in mechanical engineering, but to at least 25%, preferably at least 45%, of the extension of the rim in the direction of the axis of rotation. The guidance of the separation air loaded with the fine material is improved thereby at the location, where it escapes from the front face of the separator drum into the fine material outlet at high speed. It is thus prevented that this leads to strong swirls as a result of an overly brusque change of the clear flow cross section or a brusque deflection, respectively, at an excessive flow speed. This is so, because swirls, which are too strong at this location, could have the result that a portion of the fine material, which is guided along by the separation air, which flows out, falls out prematurely and accumulates in an obstructive manner, instead of being completely discharged by the separation air, which flows out.

As part of a particularly preferred further 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 disk. A particularly firm and rigid anchoring of the separator wheel shaft parts according to the invention, which does not tend to persistent oscillations or at least temporary imbalances (for instance when passing through the subcritical speed range during the startup). Ideally, the length of the hub sleeve in the direction of the axis of rotation is at least 30%, preferably at least 50% larger than the corresponding length of the rim.

Another, particularly favorable option is that the first and the second part of the separator wheel shaft each form a disk flange, which protrudes radially to the outside. This disk flange in each case preferably bears completely against the front ring surface of the hub sleeve assigned to this part of the separator wheel shaft facing the interior of the separator drum. The disk flange is preferably screwed to the hub sleeve, which not least ensures additional bending stiffness.

Further embodiment options, further technical effects, and further advantages result from the exemplary embodiment, which will be described below by means of the figures.

