EP1468742B1 - Multi-stage pusher-typ centrifuge - Google Patents

Description

The invention relates to a multi-stage pusher centrifuge according to the preamble of independent claim 1, and as this example GB-A-1 518 239 is known.

For drying wet substances or moist substance mixtures centrifuges in various embodiments are widely used and are used in a variety of fields. Thus, for example, for the drying of high-purity pharmaceutical products, discontinuously operating centrifuges, such as peeler centrifuges, are preferably used, whereas, in particular, when continuously large quantities of a solid-liquid mixture are to be separated, continuously operating pusher centrifuges are advantageously used. Depending on the requirements, one-stage or multi-stage pusher centrifuges, as well as so-called dual-pusher centrifuges, are used.

In the various types of the latter class of pusher centrifuges, a solid-liquid mixture, for example a suspension or a moist salt or salt mixture, through an inlet pipe via a mixture distributor of a rapidly rotating drum, which is designed as a filter, fed so that due the centrifugal forces acting the liquid phase is eliminated through the filter, while inside the drum wall, a solid cake is deposited. In this case, in the rotating drum is a substantially disc-shaped, arranged synchronously mitrotierender sliding floor, wherein depending on the number of screening stages either the sliding floor or a screening stage in the axial direction in the drum oscillates with a certain amplitude, so that a part of the dried solid cake is pushed out at one end of the drum. In the opposite movement of the sliding floor an adjacent to the sliding floor area of the drum is released, which can then be fed through the inlet pipe and the mixture manifold again with a new mixture. Depending on the type used with modern high-performance pusher centrifuges easily throughputs in the order of 100 tons per hour can be achieved, with drum diameter up to 1000 mm and more are quite common and typical rotational frequencies of the drum, depending on the drum diameter of up to 2000 revolutions per Minute and more can be achieved. In this case usually requires a larger drum diameter because of the strong centrifugal forces occurring a smaller maximum rotational frequency of the drum. Of course, the operating parameters, such as the rotational frequency of the drum, the amount of mixture supplied per unit time or the drum diameter or the type of pusher centrifuge used also depend on the material to be dried itself, the content of liquid and so on.

The multistage pusher centrifuges known from the prior art are generally continuous filter centrifuges. The multi-stage filter centrifuge consists of an outer sieve drum and at least one screening stage arranged in the outer sieve drum, which is likewise designed as a sieve drum. In this case, several screening stages can be arranged concentrically in one another, so that two, three and multi-stage pusher centrifuges can be realized, all screening stages being driven very quickly synchronously about a common axis of rotation. In the operating state, a solid-liquid mixture to be separated passes continuously through a stationary inlet pipe into a mixture distributor arranged in the innermost screening stage, which also co-rotates synchronously, and is uniformly distributed over its entire screen circumference at the innermost screening stage. Most of the liquid is already centrifuged off here and a solid cake is formed. In the case of a two-stage pusher centrifuge, for example, the innermost stage, which is also referred to as the first stage, carries out an oscillation movement in the direction of the axis of rotation in addition to the rotation movement about the axis of rotation. This oscillatory movement is generated, for example, hydraulically via a thrust piston with Umsteuermechanismus. As a result, the solids cake is pushed in ring sections, corresponding to the stroke length of the oscillation, from the first to the second stage and finally leaves the pusher centrifuge via an outlet opening. In practice, the solid cake in the sieve drum is washed continuously with the addition of washing liquid on the solid cake.

A known two-stage pusher centrifuge, which operates according to the previously described principle, is for example in the DT 25 42 916 A1 described in detail. In the case of two-stage and multi-stage pusher centrifuges, the first stage, ie the innermost screening stage, essentially serves for pre-dewatering of the mixture and for forming a solids cake, while the outer screening drum serves primarily as a drying stage. As a result of the pre-dewatering being possible by means of the first screening stage, multistage pusher centrifuges achieve a significantly increased liquid swallowing capacity, so that mixtures with lower inlet concentrations, ie with a higher liquid content, can be processed.

For special applications, special designs of two-stage and multi-stage pusher centrifuges, in particular for highly abrasive centrifugal goods, such. Charcoal and rock phosphate known that require special anti-wear measures, such as wear-resistant sieves. Special designs for intensive washing processes and for carrying out special washing processes, for example countercurrent washing in nitrocellulose, are also known from the prior art. Gas-tight versions of multi-stage pusher centrifuges for operation under a protective gas atmosphere are also used.

Although multistage pusher centrifuges have long been well known, as briefly outlined above, also for special applications in a wide variety of design variants, the known multistage pusher centrifuges nevertheless have different designs serious disadvantages. Although with the known multistage pusher centrifuges lower inlet concentrations, ie mixtures with increased liquid content can be better processed than with ordinary single-stage pusher centrifuges, the inlet concentration of the mixture to be processed must not be arbitrarily small. That is, if the proportion of liquid in the mixture is too high, for example, 50% or 70% or 80% or even more than 90% liquid phase, the mixture must be pre-thickened in more or less expensive processes. In fact, if the liquid content is too high, a uniform distribution of the mixture to be dried over the circumference of the sieve drum becomes increasingly difficult. On the one hand, this can lead to very damaging vibrations of the screening drum and thus to premature wear of bearings and drive; in the worst case, even become a safety issue in operation. On the other hand causes a non-uniform distributed over the circumference of the sieve drum solids cake washing problems. Therefore, for example, static thickeners, curved sieves or the well-known hydrocyclones are available for pre-drainage. It is obvious that the use of such Vorentwässerungssysteme both process technology and equipment very expensive and therefore expensive.

Another serious drawback to processing small inlet concentration mixtures is that virtually all of the liquid supplied to the mixture must be accelerated to full circumferential speed before being discharged through the filter screen of the screen drum. The same applies to the smallest particles in the mixture, which should also be separated from the solids cake by the sieve. This is energetically extremely unfavorable and affects the operating behavior of the centrifuge significantly negative.

But even in the processing of mixtures with a significantly higher solids concentration, the centrifuges known from the prior art sometimes show massive disadvantages. Thus, the mixture introduced into the mixture distributor through the inlet pipe is accelerated to the full peripheral speed of the drum in the shortest time when it strikes the screening drum. Especially with sensitive substances, this can lead to grain breakage lead, that is, that, for example, solid grains, which are distributed in a centrifuge supplied to the suspension burst in an uncontrolled manner in the abrupt acceleration process into smaller pieces, which may have a negative impact on the quality of the produced solid cake, for example, if the particle size of the grains in the End product plays a role.

The object of the invention is therefore to propose an improved multi-stage pusher centrifuge, which largely avoids the disadvantages known from the prior art.

The objects of the invention solving these objects are characterized by the features of independent claim 1.

The respective dependent claims relate to particularly advantageous embodiments of the invention.

Thus, according to the invention, a multistage pusher centrifuge is proposed for separating a mixture into a solid cake and into a liquid phase. In this case, the multistage pusher centrifuge comprises an outer screen drum rotatable about a rotation axis and at least one screening stage arranged in the outer screen drum, a mixing distributor arranged in the screen drum with a pusher bottom device, wherein either the screening step or the pusher bottom device is arranged to be movable back and forth along the rotation axis that the solids cake is displaceable by means of the pusher bottom device. The multistage pusher centrifuge further comprises a feed device with which the mixture can be introduced via the mixture distributor into an empty space which arises when the solids cake is displaced by the pusher bottom device, wherein the pusher bottom device comprises a pre-acceleration funnel which extends essentially widening in the direction of the feed device and the Pre-acceleration funnel is designed as Vorbeschleunigungssieb and the pre-acceleration funnel has a curved course and increases the pre-acceleration angle of the Vorbeschleunigungstrichters towards the feed device out.

Because the multistage pusher centrifuge according to the invention has a pre-acceleration screen arranged on the pusher bottom device, it is not necessary the entire amount of liquid phase contained in the feed mixture is accelerated to the full peripheral speed of the screen drum since a portion of the liquid phase is already deposited over the pre-acceleration screen and removable from the screen drum. Thus, mixtures with a very high liquid content are easily processed. In particular, a uniform distribution of the mixture to be dried over the peripheral surface of the screening stage or the screening drum is thus always guaranteed even with a high liquid content.

Moreover, the pre-acceleration funnel designed as a pre-acceleration screen prevents a mixture introduced into the mixture distributor by the feed device from reaching the inner circumferential surface of the screening stage directly, essentially only under the influence of gravity and without pre-acceleration. Rather, the incoming mixture is accelerated slowed down to the peripheral speed of the screen drum, whereby in particular grain breakage and other harmful influences, such as occur during abrupt acceleration in the known from the prior art multi-stage pusher centrifuges, can be prevented. Thus, by the multi-stage pusher centrifuge according to the invention a bursting of Feststoffkömer contained in the mixture can be avoided, because the acceleration process over the predeterminable Vorbeschleunigungswinkel the Vorbeschleunigungstrichters is controllable, i. that the acceleration itself is adjustable by a suitable choice of the pre-acceleration angle of the pre-acceleration funnel. As a result, the quality of the solid cake produced, in particular in products in which, for example, the particle size or the shape of the grains in the end product play a role, can be significantly increased.

The essential components and the basic mode of operation of a multi-stage pusher centrifuge are known from the prior art, so that reference may be made in the following primarily to the features essential to the invention.

The multistage pusher centrifuge according to the invention serves to separate a mixture into a solids cake and into a liquid phase and, as essential components, comprises one about an axis of rotation over a drum axis rotatable outer screen drum, which is housed in a housing. The drum axis is in operative connection with a Trömmefantrieb, so that the screen drum is set by the drum drive in rapid rotation about the axis of rotation. Within the outer screening drum at least one screening stage is arranged. Furthermore, a mixture distributor with a pusher bottom device is provided in the screen drum, wherein either the screening stage or the pusher bottom device along the axis of rotation is arranged back and forth, so that the solid cake is displaceable by means of the pusher bottom device. Both the outer screen drum and the screening stage in this case have screen openings through which liquid phase from the solid cake or from a mixture which can be applied to an inner peripheral surface of the screening stage, by the centrifugal forces occurring in the known manner can be discharged to the outside. In particular, in a particularly important example for practice, the screen drum and / or the screen stage be configured in a conventional manner as a skeletal support drum, which is lined to form the corresponding screen surfaces with special filter films on its periphery, ie the skeletal support drum can, for example be configured one or more filter screens with different or equal sized filter openings for the deposition of the liquid phase.

Within the screen drum, the mixture distributor is arranged with the pusher bottom device, which allows continuously fed through the feed device mixture to distribute to the inner peripheral surface of the screening stage by introducing into the void, which has arisen when moving the solids cake. In this case, the pusher bottom device comprises a pre-acceleration funnel, which according to the invention is designed as a pre-acceleration screen, wherein the pre-acceleration screen extends substantially widening in the direction of the feed device. At a peripheral region of the Vorbeschleunigungstrichters is designed as an annular region that is displaceable with the annular region of the deposited in the screening stage solid cake by an oscillation of the pusher bottom device or the screening stage in the screen drum or in another screening stage.

The mixture distributor is preferably coupled in a manner known per se by fastening means with the sieve drum and therefore rotates in a special embodiment synchronously with the sieve drum and the screening stage about the common axis of rotation. Depending on the number of sieving stages available, the oscillatory movement executes either the screening stage itself or the moving floor device. Thus, in the operating state there is an oscillatory relative movement between the screening stage and the sliding floor device with pre-acceleration funnel. The drive of the oscillatory movement is preferably carried out via a push rod, wherein in a first half period of the oscillatory movement with the outer ring portion of the deposited on the screening stage solid cake in ring sections whose width is determined by the stroke length of the oscillation, from the screening stage to the screen drum or a further screening stage is pushed, and in a second half-period of the oscillatory movement a deposited on the outer edge of the drum screen ring section of solid cake is pushed out of the screen drum. During the second half-period of the oscillatory motion, a void is simultaneously created at the outer ring area in the screening stage, so that new mixture can be introduced into the void space.

It is essential for the multistage pusher centrifuge according to the invention that part of the liquid phase can already be separated from the mixture in the pre-acceleration screen and the mixture can be pre-accelerated to a predefinable rotational speed in the pre-acceleration screen, so that the mixture introduced by the feed device reaches a peripheral surface of the screening stage specifiable peripheral speed can be accelerated. As a result, on the one hand not the entire amount of liquid phase contained in the mixture must be accelerated to the full peripheral speed of the drum, so that mixtures with very high liquid content can be processed easily. In particular, even at very high concentrations of liquid phase in the mixture additional facilities for pre-dewatering, such as static thickeners, curved screens or hydrocyclones are superfluous.

On the other hand, characterized in that the pre-acceleration hopper has an opening angle with respect to the axis of rotation which is smaller than 90 °, in Vorbeschleunigungstrichter the flow rate of the mixture in comparison to the speed in free fall toward the peripheral surface of the screening stage selectively adjustable so that the mixture in the region of the Vorbeschleunigungstrichters with increasing approach to the outer ring portion in both the radial direction, and in the circumferential direction of the screen drum is gradable gradually , That is, the mixture is accelerated in the region of the pre-acceleration funnel in a particularly gentle manner gradually to a predeterminable peripheral speed in order then finally reach the full rotational speed of the screening stage when reaching the peripheral surface.

In this case, both an inlet funnel, the function of which will be explained in detail below, and the pre-acceleration funnel preferably extend in a predeterminable range at a substantially constant opening angle or at a constant pre-acceleration angle in the direction of the push floor device or the feed device ,

For special applications, for example, depending on the properties of the mixture to be dewatered, however, the inlet funnel and / or the pre-acceleration funnel may also have a curved course over a predefinable range, the opening angle of the inlet funnel and / or the pre-acceleration angle of the pre-acceleration funnel being in the direction of Moving bottom device down. This may be particularly advantageous if the inlet funnel or the pre-acceleration funnel, as will be described in more detail later, is designed as a prefilter sieve or as a pre-acceleration sieve for pre-separation of liquid phase.

In a special embodiment, the pre-acceleration screen is designed as a two-stage filter with a coarse filter and a fine filter. The mixture can thereby be filtered in the region of the pre-acceleration screen in two stages. The design of the Vorbeschleunigungssiebs as a two-stage filter has the particular advantage that the fine filter is mechanically not so heavily loaded by large and / or heavy particles contained in the incoming mixture, so that the fine filter, for example, very small pores for filtering may have very small particles and in particular may also be made of mechanically less resistant materials.

In practice, it is of particular advantage if a collecting device for discharging liquid phase is provided on the mixture distributor, so that part of the liquid phase can be removed even before reaching the enormously fast rotating peripheral surface of the screening stage. This part of the liquid phase is then no longer accelerated to the full circumferential speed of the screening stage, resulting in a massive saving of energy and to relieve the components, in particular the rotating and / or oscillating components of the multi-stage pusher centrifuge. As a result, even mixtures with enormously high liquid content are easily processed.

In a further embodiment variant of the multistage pusher centrifuge according to the invention, the pre-acceleration screen is configured and arranged such that the pre-acceleration screen can be rotated by means of a rotary drive about an axis of rotation with a predeterminable rotational speed, independent of the rotational speed of the screen drum. Preferably, for controlling and / or regulating the rotational speed of the rotary drive suitable means may be provided, for example in the form of computer-aided electronic systems to control the rotary drive, for example, depending on suitable operating parameters of the multi-stage pusher centrifuge, and / or to regulate.

In another preferred embodiment of a multistage pusher according to the invention, an inlet funnel for pre-acceleration of the incoming mixture is additionally provided in the feed device. The mixture first passes through the feed device into an inlet funnel, which in one exemplary embodiment is preferably, but not necessarily, non-rotatably connected to the mixture distributor, so that the inlet funnel rotates synchronously with the mixture distributor. In this case, the inlet funnel extends in a substantially axial direction widening towards the pre-acceleration screen, so that the mixture supplied by the feed device passes directly into the inlet funnel. In this case, the inlet funnel is designed and arranged so that the mixture can be fed into the pre-acceleration screen when leaving the inlet funnel.

Due to the arrangement and design of the inlet funnel, the mixture is pre-accelerated already in the inlet funnel to a predetermined rotational speed, so that the mixture already has a certain speed in the circumferential direction of the screening stage on arrival in Vorbeschleunigungssieb and so overall even more gentle on the maximum peripheral speed of the peripheral surface of the screening stage accelerated is.

Preferably, the inlet funnel can also be designed as a prefilter screen for pre-separation of liquid phase from the mixture. In this case, collecting agents are preferably provided for the collection and discharge of separated from the prefilter liquid phase.

In this case, a value of an opening angle of the inlet funnel and / or the value of a pre-acceleration angle of the pre-acceleration funnel with respect to the axis of rotation may for example be between 0 ° and 45 °, in particular between 0 ° and 10 ° or between 10 ° and 45 °, in particular between 25 ° and 45 °, preferably between 15 ° and 35 °. Of course, it is also possible in particular that the value of the opening angle and / or the pre-acceleration angle is greater than 45 °. In general, it can be stated that an acute angle is generally advantageous with respect to the axis of rotation, wherein an optimum value of the respective opening angle and / or the pre-acceleration angle is determined inter alia by the value of a static friction angle of the product to be dehydrated.

In particular, but not only when the inlet funnel is designed as a prefilter for the pre-separation of liquid phase, it may be particularly advantageous if the inlet funnel has a curved course and the opening angle of the inlet funnel in the direction of the sliding floor device increases or decreases. Namely, it is known that different products under different operating conditions of the pusher centrifuge, for example, depending on the Komgrösse and / or the viscosity and / or other properties or parameters, such as the temperature of the mixture are different degrees of drainage.

For example, if there is a mixture that is relatively easy to dewater at given operating parameters, it may be advantageous that the inlet funnel or the prefilter has a curved course, wherein the opening angle of the prefilter increases towards the sliding floor device. This means that the inlet funnel or the prefilter sieve widens in the direction of the push floor device, much like the horn of a trumpet. Thus, the output force with which the mixture is accelerated from the inlet funnel, disproportionately larger with decreasing distance to the walking floor device, so that the mixture, which is already relatively strongly dehydrated in the prefilter and thus shows poor sliding properties in the prefilter, can leave the prefilter faster as for example in a substantially conical, with a constant opening angle expanding prefilter.

On the other hand, there may also be mixtures which are relatively difficult to dewater given operating parameters. In this case, it is advisable to use an inlet funnel or a prefilter screen with a curved course, whereby the opening angle of the prefilter screen decreases in the direction of the sliding floor device. This has the consequence that the output force with which the mixture is accelerated from the inlet funnel increases more slowly with decreasing distance to the moving floor device than, for example, at a conically widening at a substantially constant opening angle inlet funnel. As a result, a certain accumulation effect occurs in the pre-acceleration screen, so that the mixture remains longer in the prefilter screen and therefore can already be dewatered to a higher degree in the prefilter screen.

Quite analogously to the previously stated, the pre-acceleration funnel can of course also have a curved course, with the pre-acceleration angle of the pre-acceleration funnel increasing or decreasing in the direction of the feed device.

The previously explained in connection with the curved inlet funnel advantages and its operation are analogously readily transferable to the expert on a curved Vorbeschleunigungsstrichter, and therefore need not be repeated here.

In addition, in a special embodiment, the prefilter sieve can of course also be designed as a two-stage sieve with a coarse sieve and a fine sieve. The advantages are apparent. The first filter stage forms the coarse screen, which contains particles contained in the mixture which are larger than the filter openings of the coarse screen. The fine sieve retains correspondingly finer particles, while at least a portion of the liquid phase, as well as very small particles, which must also be removed, are directly drained from the screening stage. The design of the prefilter sieve as a two-stage sieve has the particular advantage that the fine sieve is not so heavily mechanically loaded by large and / or heavy particles contained in the incoming mixture, so that the fine filter, for example, very small pores for filtering very small particles and in particular may also be made of mechanically less resistant materials.

In particular, in an embodiment which is particularly important in practice, the inlet funnel and / or the pre-acceleration funnel can be designed as a skeletal support body which can be provided with special filter foils for forming the prefilter sieve and / or the pre-acceleration sieve, i. For example, the skeletal support body can be equipped with one or more filter screens, which may possibly have filter openings of different sizes for deposition in different stages.

In this case, filter screens, which may be used in particular, include slot screens or, for example, screen plates. The filter screens can be advantageously provided in different ways with filter openings of different sizes. In particular, the screen plates mentioned above may be punched, drilled, lasered, electron beam perforated or water jet cut, among other things, in principle, other techniques come into question. Depending on the requirements, the screens themselves can be made of various materials, in particular corrosion-resistant materials, such as plastics, composite materials or different steels such as 1.4462, 1.4539 or 2.4602 or other suitable materials. In addition, to protect against wear, the filter screens may be provided with suitable layers, for example hard chromium layers, tungsten carbide (WC), ceramic or otherwise hardened. The strength of the filter sheets is typically 0.2 mm to 5 mm, although significantly different sheet thicknesses are possible.

In practice, it may be of great importance to specifically control the acceleration process itself or the rotational speed to which the mixture in the inlet funnel can be accelerated. Therefore, the inlet funnel can be arranged rotatably about a drive axis and be rotatable about the drive axis by means of a drive with a predeterminable speed. For controlling and / or regulating the rotational speed of the inlet funnel, the latter is non-rotatably connected, for example, to a separate drive axle and can be driven via the drive axle by means of a drive independently of the sieve drum and / or independently of the pre-acceleration sieve with a predefinable rotational frequency. In this case, as described above for driving the Vorbeschleunigungssiebs, suitable means may be provided to control the drive, for example, depending on the mixture to be processed, certain Betriebsparametem the multi-stage pusher, etc. and / or to regulate. For this purpose, the multistage pusher centrifuge according to the invention can also comprise corresponding sensors for measuring relevant operating parameters.

It goes without saying that the features of the particularly preferred embodiment variants of the multi-stage pusher centrifuge according to the invention described above by way of example can also be combined in any advantageous manner, depending on the requirements.

Fig. 1

im Schnitt eine mehrstufige Schubzentrifuge mit Vorbeschleunigungssieb;

Fig. 2

ein weiteres Ausführungsbeispiel gemäss Fig. 1 mit Zweistufenfilter;

Fig. 3

ein anderes Ausführungsbeispiel gemäss Fig. 1 mit Auffangeinrichtung zum Abführen von Flüssigphase;

Fig. 4

eine mehrstufige Schubzentrifuge mit separat antreibbarem Vorbeschleunigungstrichter;

Fig. 5

eine mehrstufige Schubzentrifuge mit Einlauftrichter;

Fig. 5a

ein Ausführungsbeispiel eines Vorbeschleunigungstrichters;

Fig. 5b

ein weiteres Ausführungsbeispiel eines Vorbeschleunigungstrichters;

Fig. 5c

einen Einlauftrichter mit gekrümmtem Verlauf;

Fig. 5d

einen anderen Einlauftrichter gemäss Fig. 5c;

Fig. 6

ein Ausführungsbeispiel gemäss Fig. 5 mit Vorfiltersieb;

Fig. 6a

ein zweites Ausführungsbeispiel gemäss Fig. 6 mit rotierbarem Vorbeschleunigungssieb;

Fig. 6b

ein zweites Ausführungsbeispiel gemäss Fig. 6a mit Blindboden;

Fig. 7

ein zweites Ausführungsbeispiel gemäss Fig. 6 mit Grobsieb und Feinsieb;

Fig. 8

einen Einlauftrichter mit Drehantrieb.

The invention will be explained in more detail below with reference to the schematic drawing. Show it:

Fig. 1

on average, a multi-stage pusher centrifuge with pre-acceleration screen;

Fig. 2

a further embodiment according to Fig. 1 with two-stage filter;

Fig. 3

another embodiment according to Fig. 1 with catcher for removing liquid phase;

Fig. 4

a multi-stage pusher centrifuge with separately drivable pre-acceleration funnel;

Fig. 5

a multi-stage pusher centrifuge with inlet funnel;

Fig. 5a

an embodiment of a pre-acceleration funnel;

Fig. 5b

a further embodiment of a pre-acceleration funnel;

Fig. 5c

an inlet funnel with a curved course;

Fig. 5d

another inlet funnel according to Fig. 5c ;

Fig. 6

an embodiment according to Fig. 5 with prefilter screen;

Fig. 6a

a second embodiment according to Fig. 6 with rotatable pre-acceleration screen;

Fig. 6b

a second embodiment according to Fig. 6a with blindfloor;

Fig. 7

a second embodiment according to Fig. 6 with coarse sieve and fine sieve;

Fig. 8

an inlet funnel with rotary drive.

Fig. 1 shows in section in a schematic representation essential components of a first embodiment of an inventive multi-stage pusher centrifuge with pre-acceleration. In the drawings of the present applications, by way of example only, for reasons of clarity two-stage pusher centrifuges shown schematically. It is understood that the representation of two-stage pusher centrifuges is to be understood as an example and the description of course also applies to more than two-stage pusher centrifuges in an analogous manner and is correspondingly transferable.

The multistage pusher centrifuge according to the invention, which is referred to in the following by the reference numeral 1, serves to separate a mixture 2 into a solids cake 3 and into a liquid phase 4 and comprises as essential components a peripheral sieve drum 6 rotatable about a rotation axis 5 via a drum axis 51. which is housed in a housing G. The drum axis 51 is in operative connection with a drum drive 52, so that the drum 6 can be displaced by the drum drive 52 into rapid rotation about the axis of rotation 5. Within the outer screen drum 6 at least one screening stage 7 is arranged. Furthermore, a mixture distributor 8 with a pusher bottom device 9 is provided in the screening drum 6, wherein either the screening stage 7 or the pusher bottom device 9 is arranged back and forth along the rotation axis 5, so that the solid cake 3 is displaceable by means of the pusher bottom device 9. Both the outer screen drum 6 and the screening stage 7 in this case have screen openings 61, 71, through which in a known manner with rapid rotation liquid phase 4 from the Festoffkuchen 3 or from a mixture 2, which, as described in more detail below, on an inner peripheral surface 72 of the screening stage 7 can be applied, can be discharged by the centrifugal forces occurring to the outside.

Within the screen drum 6, the mixture distributor 8 is arranged with pusher bottom device 9, which allows continuously fed through the feed device 10 mixture 2 on the inner peripheral surface 72 of the screening stage 7 by introducing into a void 11, which is formed when moving the solid cake 3, too to distribute. In this case, the push floor device 9 comprises a pre-acceleration funnel 12 which is designed as a pre-acceleration screen 12, wherein the pre-acceleration screen 12 extends in a substantially conically widening direction in the direction of the feed device 10. At a peripheral region of the Vorbeschleunigungstrichters 12 is formed as an annular region 92, that with the annular region 92 of the deposited in the screening stage 7 solid cake 3 by an oscillation of the pusher bottom device 9 and / or the screening stage 7, which is described in more detail below, can be displaced into the screening drum 6 or into a further screening stage 7 (not shown here).

It is essential for the multistage pusher centrifuge 1 according to the invention that part of the liquid phase 4 in the pre-acceleration screen 12 can already be separated from the mixture 2 and the mixture 2 can be pre-accelerated in the pre-acceleration screen 12 to a predefinable rotational speed.

The mixture distributor 8 is in the in Fig. 1 shown embodiment with the sieve drum 6 rigidly coupled by fastening means 91 and therefore rotates synchronously with the screen drum 6 and the screen stage 7 about the axis of rotation 5. The oscillatory motion by the double arrow in Fig. 1 In the example shown here, however, only the screening stage 7 is performed. Thus, in the operating state there is an oscillatory relative movement between the oscillating screening stage 7 and the moving floor apparatus 9 with pre-acceleration funnel 12 which is immovable in the axial direction. The oscillatory movement of the screening stage 7 preferably takes place via a push rod 21, wherein in a first half period of the oscillatory movement with an outer ring portion 92 of the deposited on the screening stage 7 solid cake 3 in ring sections whose width is determined by the stroke length of the oscillatory movement of the screening stage 7, is pushed from the screening stage 7 to the screening drum 6, and in a second half-period of the oscillatory movement through the screening stage 7, a ring section of solid cake 3 deposited on the outer edge of the screening drum 6 is pushed out of the screening drum 6. During the second half-period of the oscillatory movement, the empty space 11 is simultaneously formed in the screening stage 7, so that new mixture can be introduced into the empty space 11.

It is essential for the multistage pusher centrifuge 1 according to the invention that part of the liquid phase 4 in the pre-acceleration funnel 12 can already be separated from the mixture 2 and the mixture 2 can be pre-accelerated to a predeterminable rotational speed in the pre-acceleration funnel 12, such that the mixture introduced by the feed device 10 2 before reaching the screening stage 7 can be accelerated to a predetermined peripheral speed. This must be done on the one hand not the entire amount of liquid phase 4, which is contained in the mixture 2, are accelerated to the full peripheral speed of the screen drum 6, since part of the liquid phase 4 is already deposited on the Vorbeschleunigungssieb 12 and directly from the sieve openings 61, 71 of sieve drum 6 is. Thus, mixtures 2 with a very high content of liquid phase 4 are easily processable. In particular, a uniform distribution of the mixture 2 to be dried over the peripheral surface 72 of the screening stage 7 or the screening drum 6 is always ensured even with a high content of liquid phase 4. In particular, even with very high concentrations of liquid phase 4 in the mixture, 2 additional devices for predewatering, such as, for example, static thickeners, curved sieves or hydrocyclones, are superfluous. Even the smallest of the particles contained in the mixture 2 can be separated much more effectively from the solid cake 3 by the effect of prefiltration.

In addition, characterized in that the Vorbeschleunigungssieb 12 has a pre-acceleration angle β, which is smaller than 90 °, the Vorbeschleunigungssieb 12, the flow rate of the mixture 2 in comparison to the speed in free fall toward the peripheral surface 72 of the screening stage 7 selectively adjustable, so that the mixture 2 in the region of the Vorbeschleunigungstrichters 12 with increasing approach to the outer ring portion 92 in both the radial direction and in the circumferential direction of the screen drum 6 is gradually graded. That is, the mixture 2 is accelerated in the region of the Vorbeschleunigungssiebs 12 in a particularly gentle manner gradually to a predetermined peripheral speed, and then on reaching the peripheral surface 72 finally reach the full rotational speed of the screening stage 7.

The value of the pre-acceleration angle β of the pre-acceleration funnel 12, as well as the value of an opening angle α of an inlet funnel 16 to be described later, can be, for example, between 0 ° and 45 ° with respect to the axis of rotation 5, in particular between 0 ° and 10 ° or between 10 ° and 45 °, in particular between 25 ° and 45 °, preferably between 15 ° and 35 °. Of course, it is also possible in particular that the value of the opening angle α and / or the pre-acceleration angle β is greater than 45 °. Quite generally, it can be stated that as a rule an acute angle is advantageous with respect to the axis of rotation 5, whereby an optimum value of the corresponding opening angle α and / or the pre-acceleration angle β is determined inter alia by the value of the static friction angle of the mixture 2 to be dehydrated is.

Due to the fact that the mixture 2, unlike the multistage pusher centrifuges known from the prior art, does not abruptly rise in the area of the pre-fuming screen 12, i. In the shortest time to the full rotational speed of the screening stage 7 is accelerated, for example, grain breakage and other harmful effects on the mixture 2 can be prevented. Thus, in the novel multi-stage pusher centrifuge 1, in particular also mechanically very sensitive substances, even at high rotational speeds of the screening drum 6 can be processed.

In Fig. 2 is a further embodiment according to Fig. 1 shown, wherein the pre-acceleration screen 12 is configured as a two-stage filter with a coarse filter 121 and a fine filter 122. The mixture 2 can thereby be filtered in the region of the Vorbeschleunigungssiebs 12 in two stages. The first filter stage forms the coarse filter 121, which contained in the mixture particles that are greater than the filter openings of the coarse filter 121 holds back, which are so introduced into the void 11. The fine filter 122 holds correspondingly finer particles back, which are also the empty space 11 and thus the solid cake 3 are fed, while at least a portion of the liquid phase 4, and very small particles that must also be removed directly through a sieve opening 61, 71 from the Screen drum 6 are discharged. The embodiment of the pre-acceleration screen 12 as a two-stage filter has the particular advantage that the fine filter 122 is not so heavily mechanically loaded by large and / or heavy particles that may be contained in the incoming mixture 2, so that the fine filter 122, for example, very small pores for Filtering can have very small particles and in particular can also be made of mechanically less resistant materials.

In practice, it is of particular advantage if, as in Fig. 3 shown schematically, a collecting device 13 for discharging liquid phase 4 is provided on the mixture manifold 8, so that a part of the liquid phase 4 is already removable before reaching the very fast circumferential surface 72 of the screening stage 7 from the screening stage 7. This part of the liquid phase 4 is no longer accelerated to the full peripheral speed of the screen stage 7, resulting in a massive saving of energy and to relieve the components, in particular the rotating and / or oscillating components of the multi-stage pusher centrifuge 1. As a result, even mixtures 2 can be processed with an enormously high proportion of liquid phase 4. It is understood that even in the Fig. 3 illustrated embodiment, the Vorbeschleunigungssieb 12 may be formed as a two-stage filter and deposited on Vorbeschleunigungssieb 12 liquid phase 4 can also be discharged according to the illustration to the right through the open side of the screen drum 6, for example, the catcher 13 over the outer ring area as shown to the right in the screening stage 7 extends, from where the liquid phase 4 deposited on the pre-acceleration screen 12 into the collecting device 13, for example, by suitable, in Fig. 3 not shown devices is sucked.

In Fig. 4 a variant embodiment of an inventive multi-stage pusher centrifuge 1 with separately drivable Vorbeschleunigungssieb 12 is shown. The Vorbeschleunigungssieb 12 is here designed and arranged so that the Vorbeschleunigungssieb 12 is rotatable by means of a rotary drive 14 about an axis of rotation 15 with a predetermined speed. In this case, the rotation axis 15, as in Fig. 4 shown by way of example, are arranged within the push rod 21 and are driven independently of this by the rotary drive 14. For controlling and / or regulating the rotational speed of the rotary drive 14 suitable, not shown here means may be provided to control the rotary actuator 14, for example, depending on suitable operating parameters of the multi-stage pusher centrifuge 1 or depending on the mixture to be processed or other factors and / or to regulate.

Preferably, but not necessarily, the pre-acceleration funnel 12, that is to say the pre-acceleration screen 12, can rotate, for example, in a direction of the oscillation movement at a different rotational speed than in the case of FIG opposite oscillation movement. Thus, for example, when moving the solid cake 3, the rotational frequency of the pre-acceleration hopper 12 can be selected so that the pre-acceleration hopper 12 rotates synchronously with the outer screen drum 6, so that between the outer ring region 92 and the solids cake 3, which is deposited on the peripheral surface 72 of the screening stage 7 is, when moving no realtivbewegung with respect to the rotation of the Dreachse 5 is present, while the return, ie in the phase of the Osillationsbewegung in which the empty space 11 is charged with new mixture 2, the Vorbeschleunigungstrichter 12, for example, slower than the outer rotating drum rotates 6 or Slower the screening stage 7.

In Fig. 5 schematically another embodiment of an inventive multi-stage pusher centrifuge 1 is shown. In this exemplary embodiment, an inlet funnel 16 for pre-acceleration of the mixture 2 is provided in the feed device 10. The mixture 2 passes through the feed device 10 first into the inlet funnel 16, which is non-rotatably connected to the mixture manifold 8, so that the inlet funnel 16 rotates synchronously with the mixture manifold 8. In this case, the inlet funnel 16 extends in a substantially axial direction and conically widening towards the pre-acceleration screen 12, so that the mixture 2 supplied by the feed device 10 passes directly into the inlet funnel 16. In this case, the inlet funnel 16 is formed and arranged so that the mixture 2 when leaving the inlet funnel 16 can be fed into the pre-acceleration screen 12.

Characterized in that the inlet funnel 16 extends in the direction of the Vorbeschleunigungssieb 12 out substantially conically widening and the inlet funnel 16 rotates synchronously, the mixture 2 is already pre-accelerated in the inlet funnel 16 to a predetermined rotational speed, so that the mixture 2 on arrival in Vorbeschleunigungssieb 12 already has a certain speed in the circumferential direction of the screening stage 7 and so overall even more gentle on the maximum peripheral speed of the peripheral surface 72 of the screening stage 7 can be accelerated.

In the Fig. 5a and 5b is exemplary and schematically each an embodiment of a Vorbeschleunigungstrichters 12 shown. In each case, a pre-acceleration funnel 12 is shown in both figures for illustration. However, as the reference numerals 12, 16 and 17 in Fig. 2b imply that refers to in Fig. 2b Example shown for the geometry of a funnel on both the inlet funnel 16 and the pre-acceleration funnel 12th

Fig. 5a shows a Vorbeschleunigungstrichter 12 with outer ring portion 92 for moving a Festoffkuchens 3. The outer ring portion 92 has a predetermined height a, depending on the mixture to be processed 2 and / or the operating conditions under which the inventive pusher centrifuge 1 is operated, about 1 % to 40% of the drum radius r, preferably about 5% to 10%, in particular 5% to 20% of the drum radius r.

It can be like in Fig. 5b shown schematically, the funnel 12, 16, 17 may be formed as a multi-stage funnel 12, 16, 17, wherein the funnel 12, 16, 17 for pre-acceleration of the mixture 2 may have a plurality of different angles φ ₁ , φ ₂ to each other inclined partial surfaces , wherein the relative size of the partial surface and their inclination angle φ ₁ , φ ₂ may depend, for example, on the mixture 2 to be processed or on the operating parameters of the pusher centrifuge 1. In this case, both the inlet funnel 16, and the pre-acceleration funnel 12 according to Fig. 5b be designed as a multi-stage funnel.

In particular, but not only when the inlet funnel 16 is formed as a pre-filter 17 for pre-separation of liquid phase 4, it may be particularly advantageous if the inlet funnel 16 has a curved course and the opening angle α of the inlet funnel 16 as in the Fig. 5c and 5d shown schematically, enlarged or reduced in the direction of the sliding bottom device 9 out. Namely, it is known that different mixtures 2 under differently operating conditions of the pusher centrifuge 1, for example, depending on the grain size and or the viscosity and / or other properties or parameters, such as the temperature of the mixture 2, are different degrees of drainage.

For example, if there is a mixture 2 which is relatively easy to dewater given operating parameters, it may be advantageous that the inlet funnel 16 or the prefilter 17 has a curved course, wherein the opening angle α of the prefilter 17 in the direction of the sliding floor device. 9 enlarged. Such a special embodiment of an inlet funnel 16 is in Fig. 5c shown schematically. That is, the inlet funnel 16 or the prefilter sieve 17 widens in the direction of the push floor device 9 similar to the horn of a trumpet. Thus, the output force with which the mixture 2 is accelerated from the inlet funnel 16, disproportionately larger with decreasing distance to the sliding bottom device 9, so that the mixture 2, which is already relatively strong in the prefilter 17 and thus poor sliding properties in the prefilter 17 shows can leave the vofilter 17 faster than, for example, at a substantially conical, with a constant opening angle α expanding prefilter 17th

On the other hand, mixtures 2 may be present which are relatively difficult to dewater given operating parameters. In this case, it is advisable to use an inlet funnel 16 or a prefilter sieve 17 with a curved course, whereby the opening angle α of the prefilter sieve 17 decreases in the direction of the push floor device 9. This has the consequence that the output force with which the mixture 2 is accelerated from the inlet funnel 16 increases slowly with decreasing distance to the sliding bottom device 9, as for example at a substantially widening at a substantially constant opening angle α inlet funnel 16. This results in Vorfiltersieb 17 a certain storage effect, so that the mixture 2 remains longer in the prefilter 17 and therefore already in the prefilter 17 is dewatered to a higher degree.

Quite analogous to the previously stated, the pre-acceleration funnel 12 or the pre-acceleration screen 12 can of course also have a curved course, the pre-acceleration angle β of the pre-acceleration funnel 12 increasing or decreasing in the direction of the feed device 10.

Preferably, the inlet funnel 16, as in Fig. 6 represented as a prefilter 17 for the pre-separation of liquid phase 4 may be formed from the mixture 2. In this case, collecting means 18 are preferably provided for collecting and discharging liquid phase 4 separated by prefilter sieve 17. In this case, the liquid phase 4, for example, through openings in the moving bottom device 9 in a separated from the solid cake 3 portion of the screening stage 7 and then discharged through the screen openings 61, 71 from the screen drum 6, or the liquid phase 4 can analogously to the in Fig. 3 illustrated embodiment are discharged directly from the screen drum, so that this part of the liquid phase is no longer accelerated to the peripheral speed of the screening stage 7 and the screening drum 6.

At the in Fig. 6a illustrated embodiment of a multi-stage pusher centrifuge 1, the inlet funnel 16 is configured as a prefilter 17 and arranged by means of one or more mounting posts 22 on the screen drum 6. The mounting posts 22 are preferably formed in the form of suitably shaped spokes 22, thin rods 22 or tubes 22, so that in the operating state of the solid cake 3 is easily removed from the screening stage 7 or from the screening drum 6. In this case, at least one of the mounting brackets 22 is formed and arranged on an outer edge of the screen drum 6, that collected in the collecting means 18 liquid phase 4 through the mounting bracket 22 in a screen opening 61 of the screen drum 6 is conveyed and separable through the screen opening 61 from the screen drum 6 is. In this case, of course, openings for discharging liquid phase 4 can also be provided on the mounting support 22 itself at a suitable location.

Of course, depending on the embodiment of the inventive pusher centrifuge 1 or as required the Vorfiltersieb 17 may be arranged by means of one or more mounting brackets 22 at a screening stage 7 or even at several screening stages 7 or at a screening stage 7 and the screen drum 6, wherein the corresponding drums preferably perform no oscillatory relative movement against each other.

Preferably, but not necessarily, the pre-acceleration funnel 12, ie the pre-acceleration screen 12, can rotate, for example, in one direction of the oscillatory movement of the screening stage 7 at a different rotational speed than in the opposite oscillation movement of the screening stage 7. Thus, for example, when the solid cake 3 is moved, the rotational frequency 12 of the pre-acceleration funnel 12 are selected such that the pre-acceleration funnel 12 rotates synchronously with the screening stage 7 so that there is no relative movement with respect to the rotation about the axis of rotation between the outer ring area 92 and the solids cake 3 deposited on the peripheral surface of the screening stage 7 5 is present, while the return, so in the phase of the Osillationsbewegung in which the empty space 11 is charged with new mixture 2, the pre-acceleration hopper 12, for example, slower than the screening stage. 7

In Fig. 6b is finally an embodiment according to Fig. 6a with a blind bottom 911 shown schematically, the pre-acceleration screen 12 is not shown for clarity as a two-stage screen. Of course, here too, both the pre-acceleration screen 12 and the prefilter screen 17 can be designed as single, double or multi-stage screen.

The embodiment according to Fig. 6b has an outer ring portion 92 designed as a blind bottom 911, which rotates synchronously with the outer screen drum 6, but is decoupled from the Vorbeschleunigungsstrichter 12 with respect to the rotational movement, so that the Vorbeschleunigungsstrichter 12, so the Vorbeschleunigungssieb 12 at a different speed than the blind bottom 911 to the Rotary axis 5 is rotatable. This can, as in Fig. 6b schematically shown, the blind base 911 via at least one attachment strut 912 rotatably connected to the outer screen drum 6, wherein the fastening strut 912 is guided through a suitably placed opening 70 in the screening stage 7, so that the fastening strut 912 is decoupled from the oscillatory movement of the screening stage 7 , Of course, the embodiment gemäs Fig. 6b also applicable to higher-level than two-stage pusher centrifuges 1 analog.

The advantages of the embodiment according to Fig. 6b are obvious. On the one hand, the Vorbeschleunigungstrichter 12 is completely independent of the speed of the outer screen drum 6 with a tunable to the processed mixture 2 rotation frequency driven and on the other hand rotates the blind bottom 911, which transports the solid cake 3 in the axial direction at the same speed as the screen drum 6 and the screening stage 7, so that between the blind bottom 911 and screening stage 7 with respect to the rotation about the rotation axis 5, no relative movement takes place. Of course, in this case too, the rotational speed can be variable, for example as a function of a current operating state of the pusher centrifuge 1, as already described above.

As in Fig. 7 As an example, the prefilter sieve 17 can of course also be configured as a two-stage sieve with a coarse sieve 171 and a fine sieve 172. The first filter stage forms the coarse sieve 171, which contains particles contained in the mixture 2 which are larger than the filter openings of the coarse sieve 171. The fine sieve 172 retains correspondingly finer particles, while at least part of the liquid phase 4, as well as very small particles, which also have to be removed, are directly dischargeable from the screening stage 7. The design of the prefilter sieve 17 as a two-stage sieve has the particular advantage that the fine sieve 172 is mechanically not so heavily loaded by large and / or heavy particles which may be contained in the incoming mixture 2, so that the fine sieve 172, for example, has very small pores Filtering can have very small particles and in particular can also be made of mechanically less resistant materials.

In practice, it may be of great importance to specifically control the acceleration process itself or the rotational speed to which the mixture 2 in the inlet funnel 16 can be accelerated. This is for example with the in Fig. 8 shown further embodiment of an efindungsgemässen multi-stage pusher centrifuge 1 reachable. In the embodiment according to Fig. 8 the inlet funnel 16 is mechanically decoupled from the mixture manifold 8. For controlling and / or regulating the rotational speed of the inlet funnel 16, this is rotatably connected to a separate drive shaft 19 and via the drive shaft 19 by means of a drive 20 regardless of the screen drum 6 with a predetermined Rotational frequency drivable. In this case, suitable, not shown, means may be provided to control the drive 20, for example, depending on suitable operating parameters of the multi-stage pusher centrifuge 1 and / or to regulate.

Moreover, it goes without saying that the previously explained embodiments and variants shown schematically in the figures can also be combined as desired with one another to form further exemplary embodiments in order to meet specific requirements in practice.

By using the multi-stage pusher centrifuge according to the invention, the introduced mixture can be pre-accelerated to a predeterminable peripheral speed by the pre-acceleration screen arranged on the pusher bottom device, so that the mixture does not fall from a circumferential speed close to zero to the full peripheral speed of the inner screening stage in a very short time when hitting the screen drum is accelerated. As a result, inter alia, grain breakage is avoidable, so that in particular substances which are particularly sensitive to abrupt changes in a centrifugal acceleration, are processed in compliance with the highest quality standards.

In the various preferred embodiments, in particular also particularly lower inlet concentrations can be processed, for example, corresponding to 50% or 70% or 80% or even more than 90% proportion of liquid phase, since a significant portion of the liquid phase contained in the mixture already separated in Vorbeschleunigungssieb becomes. In particular, by additional use of Vorfiltersiebs it is possible to process mixtures with almost any large liquid content, without the mixture must be pre-thickened in complex procedures. So even with high liquid content is always guaranteed that a uniform distribution of the mixture to be dried on the inner peripheral surface of the inner screening stage or the screen drum takes place. Thus, on the one hand very damaging vibrations of the drum and thus the premature wear of bearings and drive are prevented and safety problems during operation is effectively prevented. In addition, problems in washing the solid cake by the uneven distribution over the peripheral surface of the screen drum largely avoided. The use of both process engineering and equipment very expensive pre-dewatering systems is also avoided, which of course leads to significant cost savings in operation.

When using the aforementioned filter systems, it is no longer necessary to accelerate the entire amount of liquid phase supplied with the mixture to the full circumferential speed of the screen drum. This is extremely favorable, especially with regard to the energy consumption of the multi-stage pusher centrifuge according to the invention, and, moreover, has a clearly positive overall effect on the operating behavior of the centrifuge.

By appropriate different design of the different filter surfaces or by the use of Vorbeschleunigungstrichters and / or the inlet funnel with its own drive, it is possible to process even very mechanically sensitive mixtures, even at high speeds of the drum while maintaining the highest quality standards.

Claims (14)

1. A multi-stage pusher centrifuge for the separation of a mixture (2) into a solid cake (3) and into a liquid phase (4), including an outer screen drum (6) rotatable about an axis of rotation (5) and at least one screen stage (7) arranged in the outer screen drum (6), a mixture distributor (8) arranged in the screen drum (6) with a pusher base apparatus (9), with either the screen stage (7) or the pusher base apparatus (9) being arranged movably to and fro along the axis of rotation (5) such that the solid cake (3) is displaceable by means of the pusher base apparatus (9), and including an infeed device (10) with which the mixture (2) can be introduced via the mixture distributor (8) into an empty space (11) which arises on the displacement of the solid cake (3) by the pusher base apparatus (9), with the pusher base apparatus (9) including a pre-acceleration funnel (12) which extends in a substantially divergent manner in the direction towards the infeed device (10), characterised in that the pre-acceleration funnel (12) is designed as a pre-acceleration screen (12) and the pre-acceleration funnel (12) has a curved extent and the pre-acceleration angle (β) of the pre-acceleration funnel (12) becomes larger in the direction towards the infeed device (10).
2. A multi-stage pusher centrifuge in accordance with claim 1, wherein the pre-acceleration funnel (12) extends at a substantially constant pre-acceleration angle (β) in a conically divergent manner in the direction towards the infeed device (10).
3. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the pre-acceleration funnel (12) has a curved extent and the pre-acceleration angle (β) of the pre-acceleration funnel (12) becomes smaller in the direction towards the infeed device (10).
4. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the pre-acceleration screen (12) is designed as a two-stage filter with a coarse filter (121) and a fine filter (122).
5. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein a collection device (13) is provided at the mixture distributor (8) for the draining of liquid phase (4).
6. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein a value of the pre-acceleration angle (β) of the pre-acceleration screen (12) with respect to the axis of rotation (5) lies between 0° and 45°, specifically between 0° and 10° or between 10° and 45°, in particular between 25° and 45°, preferably between 15° and 35°.
7. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the pre-acceleration funnel (12) is designed and arranged such that the pre-acceleration screen (12) is rotatable at a pre-settable speed of rotation about an axis of rotation (5) by means of a rotational drive (14).
8. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein, at the infeed device (10), an inlet funnel (16) is arranged which extends at a substantially constant opening angle (α) in a conically divergent manner in the direction towards the pusher base apparatus (9).
9. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the inlet funnel (16) has a curved extent and the opening angle (α) of the inlet funnel (16) becomes larger in the direction towards the pusher base apparatus (9).
10. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the inlet funnel (16) has a curved extent and the opening angle (α) of the inlet funnel (16) becomes smaller in the direction towards the pusher base apparatus (9).
11. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the inlet funnel (16) is designed as a pre-filter screen (17) for the pre-separation of liquid phase (4) from the mixture (2).
12. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the pre-filter screen (17) is designed as a two-stage screen with a coarse screen (171) and a fine screen (172).
13. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein collection means (18) are provided for the collection and draining of the liquid phase (4) from the pre-filter screen (17).
14. A multi-stage pusher centrifuge in accordance with any one of the preceding claims, wherein the inlet funnel (16) is rotatably arranged about a drive axis (19) and can be rotated at a pre-settable speed of rotation about the drive axis (19) by means of a drive (20).

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