EP2633917A2 - Thrust centrifuge and method for operating same - Google Patents

Abstract

The push centrifuge (1) has a filter drum (3) with a longitudinal axis, around which the filter drum is rotatable, and a filter drum body (7) which comprises an inner circumferential surface (9) and an outer circumferential surface (11). The inner circumferential surface is defined by a filter unit (33). Another filter drum body (13) comprises another inner circumferential surface (15) and another outer circumferential surface (17), where the latter inner circumferential surface is defined by another filter unit (47). A push floor (25) is arranged in the filter drum. The former filter drum body is arranged radially directly adjacent to the push floor. A relative movement mechanism (27) is provided by which the push floor and the two filter drum bodies are moved axially to and fro relative to each other in the direction of the longitudinal axis (5) of the filter drum. An independent claim is included for operating a push centrifuge.

Description

The invention relates to a pusher centrifuge and a method for operating a pusher centrifuge in filter operation.

For pusher centrifuges, e.g. an effort to increase the solids content in the material to be filtered which is e.g. a suspension from which the solid contained therein is to be filtered / separated, before a main filtration to increase, thereby increasing the efficiency of the pusher centrifuge.

From the EP 1 468 742 A1 . EP 1 468 743 A1 and DE 1 079 551 A It is known to direct a filling distributor, via which material to be filtered is passed into a filter drum of a pusher centrifuge, directly downstream of a conical filter drum. In the DE 32 26 247 A1 are formed in a sliding bottom sieve bags, and at the DE 1 209 507 is formed in a moving floor a sieve. In the DE 195 46 019 C1 is arranged on the radial outer periphery of a sliding floor a ring cup, which may be combined with a screen formed in the sliding floor. From the GB 1 518 239 A and the DE 1 087 979 A Multi-stage pusher centrifuges are known.

According to the invention there is provided a pusher centrifuge comprising a filter drum having a longitudinal axis about which the filter drum is rotatable, a first filter drum body having an inner circumferential surface defined by a first filter means and an outer peripheral surface, and a second filter drum body containing one of a second filter means defined inner circumferential surface and an outer peripheral surface, a pusher bottom disposed in the filter drum, the first filter drum body being disposed radially adjacent the pusher bottom, and a relative movement mechanism of which the pusher bottom and the second filter drum body are common and the first filter drum body is relatively in the direction of the longitudinal axis of the filter drum axially reciprocally movable (to thereby, for example, on the inner peripheral surface of the first filter drum body adhering material in the direction of the longitudinal axis of the filter drum (forward) on the inner peripheral surface of the second filter drum body to push or displace and, for example, on the inner peripheral surface of the second filter drum body adhering material in the direction of the longitudinal axis successively to push further forward or displace), seen in the direction of the longitudinal axis, the second filter means has an axial extent which is greater than the axial Erst stretching the first filter means, wherein the relative movement mechanism is designed such that the push floor under axial displacement of adhering to the inner peripheral surface of the first drum body filter material in the relative reciprocal motion at least to half, or eg to at least two thirds or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95% or up to 100%, of the axial extent of the first filter means being axially relatively movable. is relatively moved), and wherein the outer peripheral surface and / or the outer circumferential wall of the first drum body substantially (and / or for example largely) parallel to the longitudinal axis and / or, in the longitudinal axis extending through the cross section of the first filter drum body seen, a straight line through the two axially and radially outermost end points of the cross section of the first filter drum body is substantially parallel to the longitudinal axis and the first filter drum body mostly, optionally completely or altogether, (seen in this cross section or cross-sectional profile) does not protrude radially over the straight line ,

As a rule, the sliding floor as a rule extends transversely across the longitudinal axis of the filter drum acting as the axis of rotation. The outer circumferential surface and / or the outer circumferential wall of the first filter drum body generally extend substantially concentric with the longitudinal axis.

Between the inner peripheral surface and the outer circumferential surface of the first filter drum body, e.g. a drainage gap may be formed, which is bounded radially outward with respect to the filter drum by a (radially outer) inner boundary surface, which extends substantially parallel (and usually concentric) to the longitudinal axis of the filter drum.

The inner circumferential surface of the first filter drum body generally extends (also) parallel (and eg concentric) to the longitudinal axis of the filter drum and thus substantially parallel to the outer circumferential surface of the first filter drum body. The inner diameter of the first filter drum body is smaller than the inner diameter of the second filter drum body, wherein due to the substantially parallel to the longitudinal axis of the filter drum designed outer peripheral surface of the first filter drum body or due to the substantially parallel to the longitudinal axis of the filter drum, extending radially outer radial boundary surface of the drainage gap of the first filter drum body with a radially flachwandigen or radially thin-walled outer peripheral wall can be produced, whereby the radial distance between the inner peripheral surface of the first filter drum body and the inner peripheral surface of the second filter drum body can be kept small.

Thus, a radial step or a radial step between the inner circumferential surface of the first filter drum body and the inner peripheral surface of the second filter drum body can be kept small, or the difference between the inner diameter of the first filter drum body and the inner diameter of the second filter drum body can be made small.

The first filter drum body, which is upstream of the second filter drum body in the material flow of a material to be filtered introduced into the filter drum, e.g. is immediately upstream, thus forming a pre-filtration stage or pre-main filtration stage with an available for filtration inner peripheral surface per axial length (in the direction of the longitudinal axis of the filter drum), which is approximately equal to or slightly smaller than that (further) to ( Main) filtration available per inner circumferential surface (in the direction of the longitudinal axis of the filter drum) of the second filter drum body.

The first and the second filter means may be, for example sieves, such as bar screens, which are composed of mutually parallel and arranged in the circumferential direction of the filter drum spaced apart rods. The filter means can also be mesh and / or mesh screens, for example, or in the form of another suitable filter screen be educated. The first and second filter means may be structurally identical or may be different filter media.

The filtration regions (in which the material to be filtered is still in a substantially liquid form) are essentially formed by those regions or portions of the inner circumferential surface of the first and second filter drum bodies which are periodically spaced during relative reciprocation essentially completely freed of material adhering thereto (on the inner circumferential surface) by means of the pushing bottom (with respect to the inner circumferential surface of the first filter drum body) or by means of the first filter drum body (with respect to the inner circumferential surface of the second filter drum body). Since the pusher bottom is displaced from material adhering (to be filtered) adhered to the inner peripheral surface of the first drum body up to at least the axial center or eg at least two-thirds or at least 75% or at least 80% or at least 85% or Up to at least 90% or at least up to 95% or up to 100% of the axial extent of the first filter means (and thus the axial extent of the defined by the first filter means inner peripheral surface of the first filter drum body) is axially relatively movable or axially relatively moved, can be achieved be that the defined by the first filter means inner peripheral surface of the first filter drum body is periodically substantially completely freed from it adhering (to be filtered) material, without risk of channeling. (With too short axial sweeping of the inner peripheral surface of the first filter drum body through the sliding floor channels could form between remaining adherent material, which Channels can be generated by the flow of material flowing into the filter drum to be filtered material via rinsing.) The sliding floor can in its relative movement relative to the first filter drum body, for example, from a rear reversal point, in which a maximum for receiving material to be filtered inner peripheral surface of the first filter drum body is present in front of the sliding floor, to be movable relative to a front reversal point, where the sliding floor as described above is relatively axially moved to at least half of the axial extent of the first filter means. The rearward reversal point of the push floor may be located adjacent to a corresponding rear axial end portion of the first filter means. The rear reversal point can also be arranged further forward, for example, already at the axial center of the axial extension of the first filter means (or even further forward), the front reversal point then correspondingly still further forward towards the front (away from the sliding floor) end of the first Filter drum body is arranged and the sliding floor accordingly over half of the axial extent of the first filter means addition, for example at least two-thirds or at least 75% or at least 80% or at least 85% or at least 90% or at least 95% or up to 100% of the axial extent of the first filter means, is relatively movable. The relative movement mechanism is, for example, designed and / or set up such that at least half or at least two-thirds or at least 75% or at least 80% or at least 85% or at least 90% of the moving floor in the context of its relative reciprocating movement or at least 95% or 100% of the maximum axial extent of the first filter means present in front of the sliding floor (or present before the rear reversal point) can be painted over or painted over axially. The maximum axial extent of the (first) filter means present in front of the sliding floor defines, for example, the effective area of the first filter drum body available for filtering, so that the relative movement mechanism is designed and / or set up, for example, by the sliding floor in the context of its relative back and forth -Her movement at least half or eg at least two-thirds or at least 75% or at least 80% or at least 85% or at least 90% or at least 95% or 100% of this useful surface are overspread or be painted over.

Further, since the axial extent of the second filter means (and thus the axial extent of the second filter means defined / formed inner peripheral surface of the second filter drum body) is greater, for example at least 50% larger or at least 60% larger or at least 100% larger (ie For example, at least twice as large as), as the axial extent of the first filter means (and thus the axial extent of the first filter means defined / formed inner peripheral surface of the first filter drum body), for example, the relative movement mechanism can be formed / be such that the first filter drum body with the or about the entire axial length of its first filter means (and thus with the (or around) the entire axial length of its inner peripheral surface) is relatively movable or relatively moved over the inner peripheral surface of the second filter drum body, while still an axial end portion (in the direction away from the sliding floor ) the inner peripheral surface of the second filter drum body remains in front of the first filter drum body, which axial end portion is not cleared periodically, so that on this axial end portion a permanent filter cake can form or form, which is only partially further forward (away from the moving floor) is moved on and which is (further) dehumidified by the rotation of the filter drum. Thus, according to the invention, at the first filter drum body, substantially only a filtration region and at the second filter drum body both a filtration region (in the axial portion of the inner circumferential surface of the second filter drum body between the first filter drum body and approximately at that point to which the first filter drum body maximally over the inner circumferential surface the second filter drum body is axially relatively moved) and a dehumidifying region (in the axial end portion of the inner peripheral surface of the second drum body between the front (away from the sliding bottom) axial end of the second drum body and in about (the above) that point to which the first filter drum body is axially relatively movable or relatively movable over the inner peripheral surface of the second drum body). The inventors have further recognized that a further improved efficiency can be achieved if, for example, the dewatering area on the second filter drum body is at least as large as the filtration area on the second filter drum body and / or if, for example, the area size of the axial end portion of the inner circumferential surface of the second filter drum body is between front (away from the thrust floor) axial end of the second filter drum body and in about (the above) that point to which the first filter drum body axially over the inner peripheral surface of the second filter drum body axially (forward) relatively moved or is relatively movable, at least as large like the area size of the maximum ago and the axial extent of the axial end portion of the inner peripheral surface of the second filter drum body between the front (from the sliding bottom) axial end of the second filter drum body and in about (the above) that of the thrust bottom portion of the defined by the first filter means inner peripheral surface of the first filter drum body The maximum extent to which the first filter drum body is axially (forwardly) relatively movable or relatively movable across the inner peripheral surface of the second drum body is at least as large as the axial extent of the portion of the inner peripheral surface defined by the first filter means first filter drum body.

The relative movement mechanism is, for example, formed such that the first filter drum body is relatively movable with the entire axial length of its first filter means via the inner peripheral surface of the second filter drum body defined by the second filter means, an axial end portion of the inner circumferential surface of the second filter drum body not facing the first filter drum body (from the first filter drum body) Filter drum body) is painted over or painted over. For example, the axial end portion of the second filter drum body defined by the second filter means does not have the same or larger area than the inner peripheral surface of the first drum body defined by the first filter means, or has an axial extent equal to or greater than, for example the axial extent of the defined by the first filter means inner peripheral surface.

The relative movement mechanism is e.g. in such a way that the first filter drum body can sweep or sweep the inner circumferential surface of the second filter drum body only axially so far in the direction away from the push floor, that the end portion of the remaining from the first filter drum body and a front end of the second filter drum body facing away from the sliding bottom second filter means defined inner peripheral surface of the second filter drum body, which end portion is not axially painted over the filter drum body / swept, has an axial extent equal to or greater than the axial extent of the present before the push floor portion of the defined by the first filter means inner peripheral surface of the first Filter drum body and / or which is equal to or greater than the axial extent of the inner peripheral surface of the first filter drum body and / or that between the first filter drum body r and a front end remote from the sliding bottom of the second filter drum body end portion defined by the second filter means inner peripheral surface of the second filter drum body, which end portion is not axially painted over by the filter drum body, an area size that is equal to or greater than the area size of the maximum present in front of the sliding floor Portion of the inner circumferential surface defined by the first filter means of the first filter drum body and / or equal to or greater than the surface area of the inner peripheral surface of the first filter drum body.

According to the invention, the total filtering surface available to the (main) filtration is considerably increased, eg substantially doubled, whereby the filtering efficiency is correspondingly increased, the Filter conditions on both the inner peripheral surface of the first filter drum body and at the filtration available portion of the inner peripheral surface of the second filter drum body are substantially equal. Due to the flat and / or thin-walled possible design of the first filter drum body, it is easier, for example, the operation (volume and / or mass flow rate of the material to be filtered, stroke length and optional speed of the filter drum and optional frequency of the reciprocating motion) to provide such that on the inner peripheral surface of the first filter drum body separating filter cake or the material there has a same or barely smaller radial distance from the longitudinal axis of the filter drum as or as the on the inner peripheral surface of the second filter drum body separating material or as the filter cake separating there, wherein for example a liquid of the material to be filtered, eg a suspension, is still above (radially further inside) both filter cakes (filter cakes zugewan on the inner peripheral surface of the first filter drum body and filter cake on a first filter drum body That is, as for the inner peripheral surface of the first filter drum body and the filtration-available portion of the inner circumferential surface of the second drum body, approximately equal filter conditions can be obtained in this regard, without additional measures such as variably controlling the supply of the material to be filtered (volume and / or mass flow rate) to make 0. That is, the volume and / or mass flow rate can be kept substantially constant in the filter operation of the pusher centrifuge. Such additional Although measures do not have to be taken, they are not excluded.

In the relative movement, the push floor sweeps the inner peripheral surface of the first drum body to thereby push the material to be filtered adhered to the inner circumferential surface of the second drum body, and the first drum body sweeps the inner peripheral surface of the second drum body around the filter adhered there (in the overlined portion) Move material in a more forward (in the direction away from the sliding floor) portion of the inner peripheral surface of the second filter drum body, in which more forward section is permanently (in filter operation) forms a filter cake, which is further dehumidified / dried by the rotation and which in Frame of the relative movement is periodically pushed forward periodically towards an outlet or a discharge end of the filter drum.

In a pusher centrifuge, the (main) filtration of the material to be filtered usually takes place on that filter drum body which is closest to a feeder which feeds material to be filtered into the filter drum in the material flow, and also substantially only at that portion this filter drum body whose inner peripheral surface is cleared of the sliding bottom in periodically spaced by the relative reciprocating motion of the material to be filtered adhering thereto. On the other hand in the material flow subsequent sections of the inner peripheral surface of the aforementioned filter drum body and on the / the inner peripheral surface (s) of / from a further downstream filter drum body / n remains in the filter operation always or permanently a filter cake on the local inner peripheral surface (which filter cake is periodically moved further in the longitudinal direction of the filter drum to an outlet or discharge end or pushed), so there usually only one further dehumidification of the local filter cake material, however no actual filtering out of solid from a liquid suspension occurs anymore. In the pusher centrifuge according to the invention, on the other hand, the (main) filtration can take place both on the inner circumferential surface of the first filter drum body and on the portion of the inner circumferential surface of the second filter drum body swept by the first filter drum body because the first drum body is substantially complete can be freed from adhering to filtering material. This is because the pusher bottom can cover at least 50% of the inner circumferential surface of the first filter drum body, wherein the remaining 50% of the inner circumferential surface can be substantially flushed free by means of a sufficiently high throughput of material to be filtered without risk of channeling. Furthermore, due to this periodic sweeping, only a relatively thin layer, for example still under liquid, of material to be filtered forms on the portion of the inner circumferential surface of the second filter drum body defined by the second filter medium on the filter drum body, so that it is separated from the first Filter drum body periodically swept over section of the defined by the second filter means inner peripheral surface of the second filter drum body still filtering the material takes place, the dehumidifying only from the axially following (in the direction away from the sliding floor) portion of the inner peripheral surface of the second Filter drum body is formed. Thus, the filtration area in the pusher centrifuge according to the invention is considerably increased and is composed, for example, of a pre-filtration area formed by the inner circumferential surface of the first filter drum body and a main filtration area formed by a first axial section (the moving floor closer axial section) of the inner peripheral surface of the second filter drum body.

The first and second filter drum bodies are respectively provided on their inner circumferential surface with the first and second filter means and the first and second filter media, such as a screen such as a slotted screen, and the first and second filter drum bodies have, for example, a radially perforated or perforated filter ., Provided with radial through openings peripheral wall through which liquid passing through the filter medium / filter medium can pass radially outward to be discharged from there away from the filter drum. The respective filter medium / filter medium may be a separate component which is releasably attached to the respective filter drum body. The respective filter medium / filter medium can also be an integral part of the respective filter drum body. The respective filter drum body may comprise an integrally formed cylindrical drum body portion having an outer peripheral wall integral therewith or formed as an integral cylindrical drum body. The respective filter drum body may also be formed of assembled individual components, such as two spaced apart axially spaced (in the longitudinal direction of the filter drum) retaining rings with interposed screen bars, which are arranged with their longitudinal direction in the longitudinal direction of the filter drum and the are circumferentially spaced from each other along the circumference of the filter drum body and which, for example, form an outer peripheral wall of the respective filter drum body from which the outer circumferential surface of the respective filter drum body is formed.

The drainage gap of the first filter drum body is e.g. formed between the first filter means / filter medium and an outer peripheral wall of the first filter drum body. In the second filter drum body, a drainage gap may be formed which has a structure corresponding to the drainage gap of the first filter drum body.

The first filter drum body may have an integral outer peripheral wall which defines radially outward the outer surface of the first drum body and in which radially extending through holes or through holes are formed.

The first filter drum body may comprise a plurality of elongated rods (eg, screen bars) disposed along the circumference of the first filter drum body and extending with its longitudinal direction in the direction of the longitudinal axis of the filter drum, and may comprise a first and a second retaining ring, wherein the rods arranged in the longitudinal direction between the first and the second retaining ring and secured to the retaining rings, and wherein the radial outer sides of the rods together define the outer peripheral surface of the first drum body.

The drainage gap may be bounded in radial direction with respect to the filter drum by radially opposed inner boundary surfaces that are substantially parallel to each other, optionally, the radial distance between the two inner boundary surfaces is less than or equal to 30mm or smaller than 25mm or smaller than or equal 20mm or smaller than or equal to 15mm or smaller than 10mm or less than or equal to 5mm smaller than 2mm.

The outer circumferential surface of the first filter drum body is seen in the cross section taken through the longitudinal axis of the filter drum, e.g. formed substantially straight. The same applies, for example, for the inner circumferential surface of the first filter drum body and for the respective inner boundary surface of the drainage gap. The respective inner boundary surface also extends e.g. essentially parallel to the longitudinal axis of the filter drum.

For example, between the sieve bars and the retaining rings of the respective (eg the first) filter drum body holding them, there may be a shoulder radially outward, which does not prevent the outer circumferential surface of the first filter drum body from being substantially rectilinear, for example (for the most part) and straps extending parallel to the longitudinal axis are formed, substantially or largely straight, and extending parallel to the longitudinal axis of the filter drum. The retaining rings may for example be welded directly to the screen bars, and / or the retaining rings may also be axially connected to each other by radially outwardly of the screen bars axially extending bolts. In the event that only a few such bolts are provided, such as less than ten bolts, then the outer circumferential surface of the first filter drum body, for example, will still be substantially formed by the outer surfaces of the screen bars. In the case of a large number of such bolts, for example, more than ten, so that the bolts in a small Circumferentially spaced from each other, the outer peripheral surface of the first filter drum body may also be formed (largely) of the radially outer surfaces of the bolts.

The first filter drum body may e.g. also be one piece. For example, For example, the retaining rings and the screen bars may be in one piece, e.g. be worked by laser cutting or by other Materialabtragungsart from a single piece of material.

The term "substantially parallel to the longitudinal axis of the filter drum" or "substantially parallel to one another" is herein incorporated by reference. the meaning "parallel", with which certain usual tolerances are included, and / or the meaning of further smaller angles of e.g. less than or equal to 15 ° or from e.g. less than or equal to 10 ° or from e.g. less than or equal to 5 ° or from e.g. less than or equal to 3 ° or from e.g. less than or equal to 2 ° or from e.g. less than 1 ° are detected. As used herein, the term "substantially rectilinear" includes the meaning "straight-line within normal tolerances" and / or "mostly straight-line" (ie, a single paragraph (such as those discussed above for the retaining rings and the mesh bars) for straightness do not exclude.

The inner circumferential surface and the outer circumferential surface of the first filter drum body and possibly the respective inner boundary surface of the drainage gap extend, for example, substantially parallel to one another. With regard to a design of the first filter drum body which is as flat as possible or thin-walled, the outer peripheral surface and, if applicable, the respective inner boundary surface of the element extend Drainage gaps, for example parallel to the longitudinal axis of the filter drum and / or parallel to each other.

The pusher centrifuge also has e.g. a feed device for feeding material to be filtered (eg suspension) into the filter drum, the feed device having a filling distributor device which is arranged inside the filter drum and which has an outlet which is designed and oriented in such a way that the material to be filtered of the outlet with respect to the longitudinal axis of the filter drum is output obliquely in the direction of the sliding bottom and radially outwardly on the inner circumferential surface of the first filter drum body.

The second filter drum body is seen in the direction of the longitudinal axis of the filter drum, e.g. more than twice as long as the first filter drum body. It can thus be achieved that, even if the first filter drum body with its entire axial length (viewed in the longitudinal direction of the filter drum) axially overstretches the inner circumferential surface of the second filter drum body, an axial end portion of the inner peripheral surface of the second filter drum body is not overstretched, so that at this axial end portion the inner circumferential surface of the filter drum body can form a filter cake, whereby the axial end portion of the second filter drum body forms a (first) dehumidifying region for further dehumidifying the filter cake (from solid material of the material to be filtered).

The radial distance between the outer peripheral surface and the inner peripheral surface of the first filter drum body is, for example, less than or equal to 70mm or less than or equal to 60mm less than or equal to 50mm, or less than or equal to 40mm, or less than or equal to 30mm, or less than or equal to 20mm, or less than or equal to 10mm, or less than or equal to 5mm.

The radial distance between the inner circumferential surface of the first filter drum body and the inner peripheral surface of the second filter drum body is e.g. less than 70mm or e.g. less than or equal to 60mm or e.g. less than or equal to 50mm, e.g. less than or equal to 40mm, e.g. less than or equal to 30mm or e.g. less than or equal to 20mm or e.g. less than or equal to 10mm, e.g. less than 5mm

In the event that the second filter drum body no additional filter drum body is connected downstream, the pusher centrifuge quasi one-stage pusher centrifuge with e.g. The pusher centrifuge may also have one or more additional stages and thus one or more additional filter drum body, which are connected downstream of the second filter drum body and of which the material is further dehumidified or dried.

For example, the pusher drum of the pusher centrifuge may have a third filter drum body having an inner peripheral surface (and an outer peripheral surface) downstream of the second filter drum body, the relative movement mechanism being such that the moving bottom mechanism and the second filter drum body are common and the first and second filter drum bodies third filter drum body together in the direction of the longitudinal axis of the filter drum relative to each other axially movable back and forth to push material adhering thereto to the inner circumferential surface of the second drum body in the direction of the longitudinal axis of the filter drum on the inner circumferential surface of the third drum body and from the inner circumferential surface of the third drum body toward a solids discharge line.

In the pusher centrifuge, e.g. the sliding floor may be axially reciprocally movable together with the second filter drum body, and the first filter drum body may be axially fixed, or vice versa. In the pusher centrifuge, e.g. the push floor together with the second filter drum body axially reciprocally movable, and the first filter drum body and the third filter drum body may be axially fixed, or vice versa.

The available for filtration inner peripheral surface of the filter drum, which is composed for example of the sum of the area size of before the (in the direction of the longitudinal axis of the filter drum to the material Ausschiebe- or Ausförderrichtung out facing) the sliding bottom portion of the inner peripheral surface of the first filter drum body and the area size of the portion of the inner circumferential surface of the second drum body prior to the first filter drum body up to the point at which the first drum body can sweep axially the second drum body (per stroke), eg during filter operation (or back and forth) Agitation mode) is not (or never) less than, for example, 75% or 80%, or 85%, or 90% of the maximum size of this filter drum inner circumferential surface available for filtration.

According to the invention there is further provided a method of operating a pusher centrifuge in filter operation, the pusher centrifuge comprising a filter drum having a longitudinal axis about which the filter drum is rotatable, a first filter drum body having an inner circumferential surface defined by a first filter means, and a second filter drum body comprising an inner circumferential surface defined by a second filter means, a pusher tray disposed in the filter drum, the first filter drum body being radially adjacent to the pusher tray, and a relative movement mechanism of which the pusher tray and the second filter drum body are common and the first filter drum body in the direction of the longitudinal axis of the filter drum by a stroke length and with a stroke frequency relative to each other are axially reciprocally movable, thereby adhering to the inner peripheral surface of the first filter drum body the material to be filtered in the direction of the longitudinal axis of the filter drum on the inner circumferential surface of the second filter drum body, optionally for operating a pusher centrifuge as described herein, wherein the material to be filtered on the inner peripheral surface of the first filter drum body having such a substantially constant volume and supplied and / or mass flow rate and the relative movement mechanism can be adjusted to such a stroke length and / or controlled that the inner peripheral surface of the first filter drum body is freed in determined by the stroke frequency periodic distances substantially completely attached thereto to be filtered material and that the radial distance from at the Inner peripheral surface of the second filter drum body permanently adhering filter cake to the longitudinal axis of the filter drum is smaller than the radial distance of the inner peripheral surface of the first filter drum body to the longitudinal axis of the filter drum.

The relative movement mechanism may be adjusted and / or controlled to such a stroke length as viewed from the pusher bottom in the direction of the longitudinal axis of the filter drum, at intervals of at least 50% or e.g. at least 60% or e.g. at least two-thirds or e.g. at least three quarters or e.g. at least 80% or e.g. at least 85% or e.g. At least 90% of the (defined by the first filter means) inner peripheral surface of the first filter drum body are swept from the sliding floor.

The relative movement mechanism may e.g. is adjusted to such a stroke length and / or controlled that is of the first filter drum body defined by the second filter means inner peripheral surface of the second filter drum body is only axially overlapped so far that the remaining before the first filter body not swept (from the first filter drum body) surface portion of the inner peripheral surface of the second filter drum body is equal to or greater than the maximum present before the sliding floor surface portion of the first filter means formed inner peripheral surface of the first filter drum body.

The invention further provides a method for operating a pusher centrifuge in filter operation, the pusher centrifuge comprising a filter drum having a longitudinal axis about which the filter drum is rotatable, a first filter drum body having an inner peripheral surface defined by a first filter means, and a second filter drum body. one of a second Filter means defined inner peripheral surface, a sliding floor, which is arranged in the filter drum, wherein the first filter drum body is disposed radially adjacent the push floor, and a relative movement mechanism, of which the push floor and the second filter drum body in common and the first filter drum body in the direction of the longitudinal axis of the filter drum axially reciprocally movable at a stroke frequency relative to each other to thereby slide material to be filtered adhered to the inner peripheral surface of the first drum body toward the inner circumferential surface of the second drum body in the direction of the longitudinal axis of the filter drum, optionally for operating one as herein Pusher centrifuge described, wherein the relative movement mechanism is set to such a stroke length and / or controlled that seen from the sliding floor in the direction of the longitudinal axis of the filter drum, in by the stroke Frequency determined periodic intervals each at least 50% of the defined by the first filter means inner peripheral surface of the first filter drum body are swept by the sliding bottom, and wherein the relative movement mechanism is set to such a stroke length and / or controlled that of the first filter drum body defined by the second filter means inner peripheral surface of the second filter drum body is only swept over axially so far that the surface portion of the inner circumferential surface of the second filter drum body not covered by the first filter drum body is equal to or greater than the maximum surface area of the inner circumferential surface of the first filter medium formed before the first filter medium first filter drum body.

• Figur 1 einen schematischen Längsschnitt einer Schubzentrifuge gemäß einer Ausführungsform der Erfindung, wobei ein Schubboden in einer hinteren Umkehrposition gezeigt ist,
• Figur 2 einen schematischen Längsschnitt der Schubzentrifuge von Figur 1, wobei der Schubboden in einer vorderen Umkehrposition gezeigt ist,
• Figur 3 einen schematischen Längsschnitt einer Schubzentrifuge gemäß einer anderen Ausführungsform der Erfindung, wobei ein Schubboden in einer hinteren Umkehrposition gezeigt ist, und
• Figur 4 einen schematischen Längsschnitt der Schubzentrifuge von Figur 3, wobei der Schubboden in einer vorderen Umkehrposition gezeigt ist.
• Figuren 5-8 jeweilige Querschnitte eines ersten Filtertrommelkörpers gemäß Ausführungsformen der Erfindung.

The invention will be explained below with reference to embodiments with reference to the drawings. In the drawings show:

• FIG. 1 a schematic longitudinal section of a pusher centrifuge according to an embodiment of the invention, wherein a moving floor is shown in a rear reversing position,
• FIG. 2 a schematic longitudinal section of the pusher centrifuge of FIG. 1 wherein the walking floor is shown in a front reversing position,
• FIG. 3 a schematic longitudinal section of a pusher centrifuge according to another embodiment of the invention, wherein a sliding floor is shown in a rear reversing position, and
• FIG. 4 a schematic longitudinal section of the pusher centrifuge of FIG. 3 , wherein the sliding floor is shown in a front reversing position.
• Figures 5-8 respective cross sections of a first filter drum body according to embodiments of the invention.

In the FIG. 1 Pusher centrifuge 1 schematically illustrated in longitudinal section according to an embodiment of the invention comprises: a filter drum 3 having a longitudinal axis 5 about which the filter drum 3 is rotatable, a first filter drum body 7 having an inner peripheral surface 9 and an outer circumferential surface 11, a second filter drum body 13, which has an inner circumferential surface 15 and an outer peripheral surface 17, and a third filter drum body 19 having an inner circumferential surface 21 and an outer circumferential surface 23, a sliding floor 25, the is disposed in the filter drum 3 and fixedly connected to the second filter drum body 13, wherein the first filter drum body 7 is disposed radially adjacent to the sliding floor 25, and a relative movement mechanism 27 which is formed, for example in the form of axial guides and an axial drive device 29, of which the push floor 25 and the second filter drum body 13 are movable relative to each other axially relative to the first filter drum body 7 and the third filter drum body 19, both of which are fixed axially, in the direction of the longitudinal axis 5 of the filter drum 3 relative to each other axially (arrow P) to thereby slide on the inner peripheral surface 9 of the first filter drum body 7 adhering / adhering material / filter cake 31 in the direction of the longitudinal axis 5 of the filter drum 3 forward on the inner peripheral surface 15 of the second filter drum body 13, wherein the relative movement mechanism 27 is formed such that from the Schubbo 25 seen in the direction of the longitudinal axis 5 of the filter drum 3 (in the context of the to-and-fro movement) each (at each stroke) more than three quarters of the inner peripheral surface 9 of the first filter drum body is swept over, and wherein the outer peripheral surface 11 of the first filter drum body. 7 extends substantially parallel to the longitudinal axis 5 of the filter drum 3 and extends.

The first filter drum body 7 has a first filter medium or first filter means 33 in the form of a screen, from which the inner peripheral surface 9 of the first filter drum body 7 is defined or formed. The first filter drum body 7 further has an outer peripheral wall 35, here an integral outer peripheral wall, from which the outer circumferential surface 11 of the first filter drum body 7 is defined, wherein between the Outer peripheral wall 35 and the first filter means 33 a drainage gap 37 is formed (the drainage gap 37 is shown for reasons of clarity with an oversized radial width dimension) of a radially outer inner boundary surface 39 which is defined by the outer peripheral wall 35, and a radially inner inner boundary surface 41 defined by the first filter means 33 is radially defined. The inner peripheral surface 9, the radially outer inner boundary surface 41 and the radially inner inner boundary surface 39 of the first filter drum body 7 also extend parallel to the longitudinal axis 5 of the filter drum 3 and parallel to each other and parallel to the outer peripheral surface 11 of the first filter drum body 7th

In the outer peripheral wall 35 of the first filter drum body 7, through holes 43 penetrating radially through the outer peripheral wall 35 are formed.

The second filter drum body 13 has a second filter medium or second filter means 47, eg a sieve, which defines or forms the inner peripheral surface 15 of the second filter drum body 13. The second filter drum body 13 further has an outer peripheral wall 49, here an integral outer peripheral wall, in which radially through-holes 51 are formed. Between the outer peripheral wall 49 and the second filter means 47, a drainage gap 53 is formed (the drainage gap 53 is shown with an excessively large radial dimension for clarity) defined by a radially outer inner boundary surface 55 defined by the outer peripheral wall 49 is, and a radially inner Inner boundary surface 57, which is defined by the second filter means 47, radially limited or defined. The outer peripheral surface 17, the inner peripheral surface 15, the radially outer inner boundary surface 55 and the radially inner inner boundary surface 57 of the second filter drum body 13 also extend parallel to the longitudinal axis 5 of the filter drum 3 and parallel to each other.

The third filter drum body 19 comprises a third filter medium or third filter means 59, e.g. a screen, which defines the inner circumferential surface 21 of the third filter drum body 19. The third filter drum body 19 further has an outer peripheral wall 61, here an integral outer peripheral wall, in which radially through-holes 62 are formed. Between the outer peripheral wall 61 and the third filter means 59, a drainage gap 63 is formed (the drainage gap 63 is shown with an excessively large radial dimension for clarity) defined by a radially outer inner boundary surface 65 defined by the outer peripheral wall 61 and a radially inner inner boundary surface 67 defined by the filter means 59 is radially defined. The outer peripheral surface 21, the inner peripheral surface 23, the radially outer inner boundary surface 65 and the radially inner inner boundary surface 67 of the third filter drum body 19 also extend parallel to the longitudinal axis 5 of the filter drum 3 and parallel to each other.

The pusher centrifuge 1 further comprises a feed device 69 for feeding material 71 to be filtered, which is, for example, a suspension, into the filter drum 3 and which comprises: one from outside the filter drum 3 into the filter drum 3 Filtering drum 3 in-feed line 73 and a Füllverteilervorrichtung 75 with an outlet 77, from which via the outlet 77, the supplied from the feeder to be filtered material 71 is discharged into the filter drum 3. The Füllverteilervorrichtung 75 is formed in the context of the back-and-forth movement of the sliding floor 25 axially with the sliding floor 25 back and forth with movable. The outlet 77 is designed and aligned in such a way that the material 71 to be filtered is output from the outlet 77 with respect to the longitudinal axis 5 of the filter drum 3 obliquely in the direction of the sliding floor 25 and radially outwards onto the inner peripheral surface 9 of the first filter drum body 7.

At the front axial end 79 of the third filter drum body 19, the pusher centrifuge 1 has a solids discharge line 81, via which the solid material 83 filtered out of the material 71 to be filtered is removed from the pusher centrifuge 1. The liquid contained in the material 71 to be filtered and separated from the solid material 83, which is discharged radially out of the filter drum 3 through the radial through-holes 43, 51, 62, is further removed via a liquid discharge line 85.

The filter drum 3 is attached to a drive shaft 87, which is driven in rotation by a rotary drive 89, for example an electric motor. The axial drive device 29 is, for example, a pneumatically or hydraulically or electrically operating device. The rotary drive 89 and the axial drive device 29 are controlled by an electronic control unit, not shown, for controlling the rotational speed or the axial stroke frequency and / or the axial stroke size. The control unit may also be connected to the feeder to control the flow rate / flow rate to control the filter drum 3 supplied to be filtered material.

The filter drum 3 is further accommodated in a housing 89.

In filter operation, the material 71 to be filtered discharged via the filling distributor device 69 into the filter drum 3 first reaches the front side of the sliding floor 25 and the inner peripheral surface 9 of the first filter drum body 7, which is immediately downstream of the filling distributor device 69. Due to the inner circumferential surface 9 extending parallel to the longitudinal axis of the filter drum 3, an already large centrifugal force is exerted on the material 71 thereon (due to the rotation of the filter drum 3) so that liquid is already efficiently removed from the material 71 and the material 71 is effectively thickened thereby , In the context of the constant axial reciprocating movement of the sliding floor 25 relative to the first filter drum body 7, the material 71 is pushed in the stroke frequency of the relative movement between the sliding floor 25 and the first filter drum body 7 certain time intervals on the inner peripheral surface 15 of the second filter drum body 13, and in the context of the constant axial reciprocating movement of the first filter drum body 7 relative to the second filter drum body 13, the material 71 is at the time determined by the stroke frequency of the relative movement between the first filter drum body 7 and the second filter drum body 13 on the inner surface 23 of the third filter drum body 19 pushed, and in the context of the constant axial reciprocating movement of the second filter drum body 13 relative to the third filter drum body 19 is ultimately from the material to be filtered 71 remaining solid material 83 in pushed by the stroke frequency of the relative movement between the second filter drum body 13 and the third filter drum body 19 certain time intervals to the solids discharge line 81 out.

The actual filtration or main filtration are available here in front of the sliding bottom 25 lying axial portion of the inner peripheral surface 9 of the first filter drum body 7 and that axial (in the direction of the longitudinal axis 5) (start) portion 97 of the inner peripheral surface 15 of the second filter drum body 13, which extends from (immediately) in front of the first filter drum body 7 up to that axial point 100, up to which the first filter drum body 7 relative to the second filter drum body 13 in its stroke can reach maximum forward, so that the axial initial portion 97 of the inner peripheral surface 15 of the second filter drum body 7 is substantially completely freed from adhering material at periodic intervals. That axial end portion 98 of the inner circumferential surface 15 of the second filter drum body 13 extending from the aforementioned axial location 100 to the front axial end 102 (which is then followed by the inner peripheral surface 21 of the third filter drum body 19) of the second filter drum body 13 constitutes (FIG. first) dehumidifying area, where in filter operation there is always a filter cake, which is periodically moved on sections of the inner peripheral surface 21 of the third filter drum body 19, which inner peripheral surface 21 forms a further dehumidification area.

The in the FIGS. 1 and 2 illustrated pusher centrifuge 1 thus provides in principle a combination of a conventional two-stage pusher centrifuge, the two conventional Steps are formed by the second and third filter drum body 13, 19, with a pre-filtration stage, which is formed by the first filter drum body 7 connected between the two conventional stages and the feeder 69. The axial extension or length (in the direction of the longitudinal axis 5) of the second filter means 47 or the inner circumferential surface 15 defined by the second filter means 47 is more than twice the axial extension or length of the first filter means 33 or defined by the first filter means 33 Inner peripheral surface of the first filter drum body 7, so that although the first filter drum body 7 is moved by almost its entire axial length or almost the entire axial extent of the first filter means 33 relative to the second filter drum body 13 and sweeps the second filter means 47 by this extension / length, still remains the above-described axial end portion 98 of the inner circumferential surface 15 of the second filter drum body 9, on which can permanently deposit filter cake and which is greater than the axial initial portion 97 of the inner peripheral surface 15 of the second filter drum body and as the inner peripheral surface 9 of the first F filter drum body 7.

Although according to the embodiment of FIGS. 1 and 2 it is also possible that the sliding floor 25 and the second filter drum body 13 are held axially fixed and that the first filter drum body 7, for example, together with the third filter drum body 19, is moved axially ,

In the Figures 3 and 4 a pusher centrifuge 1 according to another embodiment of the invention is shown schematically in longitudinal section.

The pusher centrifuge 1 according to the Figures 3 and 4 is identical to the one in the FIGS. 1 and 2 Pusher centrifuge shown, with the only difference that in the Figures 3 and 4 illustrated pusher centrifuge 1 has no third filter drum body. Otherwise, in view of the structure and function of the pusher centrifuge according to Figures 3 and 4 to the above description of the pusher centrifuge 1 according to FIGS. 1 and 2 directed.

Accordingly, the material to be filtered 71 passes through the feed device 69 into the filter drum 3 and there first to the front of the sliding floor 25 and on the inner peripheral surface 9 of the first filter drum body 7. Due to the axial (in the direction of the longitudinal axis 5 of the filter drum 3) relative Hin- and-fro movement between the pusher tray 25 and the first filter drum body 7, the material 71 is pushed from the inner peripheral surface 9 of the first filter drum body 7 on the inner peripheral surface 15 of the second filter drum body 13, and due to the axial relative reciprocating motion between the First filter drum body 7 and the second filter drum body 13, the resulting from the material to be filtered 71 solid material 83 is pushed by the inner peripheral surface 15 of the second filter drum body 13 in the solids discharge line 81.

Due to the parallel orientation of the outer peripheral surface 11 of the first filter drum body 7 and due to - in the cross section of the filter drum 3 through the longitudinal axis 5 of Filter drum 3 seen - rectilinear formation of the outer peripheral surface 11 of the first filter drum body 7 can already be a relatively flat-building thin-walled first filter drum body 7 can be achieved. Any optional additional measures (which may be considered individually or in any combination and, for example, individually or in any combination, may be added to the subject-matter of the independent claims also in combination with the respective dependent claims) are of the flat and thin-walled construction of the first filter drum body 7 For example, that the radially outer inner boundary surface 41 of the drainage gap 37 is aligned parallel to the longitudinal axis 5 of the filter drum 3 and - seen in cross section of the filter drum 3 through the longitudinal axis 5 of the filter drum 3 - eg rectilinear and / or that the radially inner interior Boundary surface 39 of the drainage gap 37 is aligned parallel to the longitudinal axis 5 of the filter drum 3 and - seen in cross-section through the longitudinal axis 5 of the filter drum 3 - eg rectilinear and / or that inner peripheral surface 9 of the first filter drum body 7 parallel to the longitudinal axis 5 of the filter drum 3 au is srichtichtet and - seen in the cross section of the filter drum 3 through the longitudinal axis 5 of the filter drum 3 - for example rectilinear and / or that the outer peripheral wall 35 of the first filter drum body 7 is aligned parallel to the longitudinal axis 5 of the filter drum 3 and - in cross section of the filter drum 3 through seen the longitudinal axis 5 of the filter drum 3 - for example, is rectilinear and / or and that the drainage gap 37 - seen in cross section of the filter drum 3 through the longitudinal axis 5 of the filter drum 3 - in the direction of the longitudinal axis 5 of the filter drum 3 is substantially elongated rectangular.

As in the embodiment of FIGS. 1 and 2 is also in the embodiment of Figures 3 and 4 the axial extension / length (in the direction of the longitudinal axis 5) of the second filter means 47 of the second filter drum body 13 is more than twice the axial extension / length of the first filter means 33 of the first filter drum body 7, so that although the first filter drum body 7 around the entire Axial length of its first filter means 33 is relatively moved relative to the second filter drum body 13 via the inner peripheral surface 15, nor the above-mentioned large axial end portion 98 of the inner peripheral surface 15 of the second filter drum body 9 between that axial point 100, to the first filter drum body 7 relative to the second filter drum body 13 in its stroke can reach maximum forward, and the front axial end 102 of the second filter drum body 13 remains on which can permanently deposit filter cake, so that this axial end portion 98 forms a dehumidifying area.

In FIG. 5 an embodiment of a first filter drum body 7 is shown in passing through the longitudinal axis 5 cross-section. Hereinafter, the first filter drum body 7 has an integral drum-shaped body 104, which forms the outer peripheral wall 35 and the outer peripheral surface 11 thereon and which at both axial ends 106, 108 each have a radially inwardly extending, circumferential collar 110, 112. Siebsticks 114 are arranged between the two peripheral collars 110, 112, which with their longitudinal direction in the direction of the longitudinal axis 5 of the filter drum 3 (see Figures 1-4 ), wherein the screen bars 114 are arranged at a circumferential distance from one another, so that in each case a screen gap 116 is formed between adjacent screen bars 114 (FIGS Sieve gaps 116 are oversized). A (imaginary) straight line G connecting the two axially and radially outermost ends 118, 120 of the first filter drum body 7 runs parallel to the longitudinal axis 5 of the filter drum 3, and the filter drum body 7 extends circumferentially (ie in the cross-sectional profile) with no section radially beyond this straight line outside. The screen bars 114 forming the first filter means 33 further define the inner circumferential surface 9 of the first filter drum body 7.

FIG. 6 shows an embodiment of a first filter drum body 7 in a passing through the longitudinal axis 5 of the filter drum 3 cross-section. Thereafter, the first filter drum body 7 at its axial ends 110, 112 each have a circumferentially extending in the circumferential direction of the first filter drum body 7 retaining ring 122, 124 and screen bars 114, which are arranged between the retaining rings 122, 124 and which held by the retaining rings 122, 124 are. Further, the first filter drum body 7 has tethers 126, 128 extending along the outer periphery of the first drum body 7 in radial contact with the screen bars 114 around the first drum body 7 to radially support the screen bars 114. The inner circumferential surface 9 of the first filter drum body 7 is formed by the screen bars 114 forming the first filter means 33. For example, in the case where the tethers 126, 128 and the retaining rings 122, 124 have a smaller radial outer surface than the screen bars 114, the radially outer surface formed by the screen bars 114 may be considered the outer circumferential surface 11 of the first filter drum body 7. In the case that the holding straps 126, 128 and the retaining rings 122, 124 have a larger radial outer surface compared to the straining bars 114, for example, that of the holding rings 122, 124 and the screen bars 114 formed radially outer surface as the outer peripheral surface 11 'of the first filter drum body 7 are considered. A straight line G, which connects the axially and radially outermost ends (end points) 118, 120 of the first filter drum body 7, extends substantially parallel to the longitudinal axis 5 of the filter drum 3, wherein (in the cross-sectional profile) no portion of the first filter drum body 7 radially extends outwardly beyond this straight line G.

FIG. 7 shows an embodiment of a first filter drum body 7 in a passing through the longitudinal axis 5 of the filter drum 3 cross-section. Thereafter, the first filter drum body 7 at its axial ends 110, 112 each have a circumferentially extending in the circumferential direction of the first filter drum body 7 retaining ring 122, 124 and screen bars 114, which are arranged between the retaining rings 122, 124 and which held by the retaining rings 122, 124 are. Further, the first filter drum body 7 holding bolts 130 which connect the two retaining rings 122, 124 together and which are arranged along the circumferential direction of the first filter drum body 7 at a distance from each other. For example, in the case that the retaining bolts 130 and the retaining rings 122, 124 have a smaller radial outer surface than the screen bars 114, the radially outer surface formed by the screen bars 114 may be considered as the outer peripheral surface 11 of the first filter drum body 7. In the case that the retaining bolts 130 and the retaining rings 122, 124 have a larger or slightly smaller radial outer surface compared to the screen bars 114, for example, the radial outer surface formed by the retaining rings 122, 124 and the screen bars 114 may be referred to as the outer peripheral surface 11 'of the first Filter drum body 7 are considered. A straight line G, which the axially and radially outermost ends (end points) 118, 120 of the first filter drum body 7 extend substantially parallel to the longitudinal axis 5 of the filter drum 3, wherein (in the cross-sectional profile) no portion of the first filter drum body 7 radially outward on this straight line G. extends beyond. The screen bars 114 form the first filter means 33, which defines the inner circumferential surface 9 of the first filter drum body 7.

FIG. 8 shows an embodiment of a first filter drum body 7 in a passing through the longitudinal axis 5 of the filter drum 3 cross-section. Thereafter, the first filter drum body 7 at its axial ends 110, 112 each have a circumferentially extending in the circumferential direction of the first filter drum body 7 retaining ring 122, 124 and screen bars 114, which are arranged between the retaining rings 122, 124 and which held by the retaining rings 122, 124 are. The screen bars 114 are, for example, welded directly to the retaining rings 122, 124 and form the outer peripheral surface 11 and the inner circumferential surface 9 of the first filter drum body 7, which peripheral surfaces 9, 11 are both arranged parallel to the longitudinal axis 5 of the filter drum and are seen in cross section of the filter drum body 7 rectilinear , The first filter drum body 7 may for example also be in one piece. For example, the retaining rings 122, 124 and the screen bars 114 may be made in one piece, for example, by laser cutting or by any other Materialabtragungsart be made of a single piece of material. The retaining rings 122, 124 and the screen bars 114 may, for example, be welded together.

Claims (13)

Pusher centrifuge (1), comprising
a filter drum (3) having a longitudinal axis (5) about which the filter drum (3) is rotatable, a first filter drum body (7) having an inner peripheral surface (9) defined by a first filter means (33) and an outer peripheral surface (11) , and a second filter drum body (13) having an inner peripheral surface (15) defined by a second filter means (47) and an outer peripheral surface (17),
a pusher tray (5) disposed in the filter drum (3), the first filter drum body (3) being disposed radially adjacent the pusher tray (25), and
a relative movement mechanism (27) from which the pusher bottom (25) and the second filter drum body (13) together and the first filter drum body (7) are axially reciprocally movable relative to each other in the direction of the longitudinal axis (5) of the filter drum (3)
in the direction of the longitudinal axis (5) seen the second filter means (47) has an axial extent which is greater than the axial extent of the first filter means (33), wherein the relative movement mechanism (27) is formed such that the sliding floor (25) below axial displacement of material adhering to the inner circumferential surface (9) of the first filter drum body (7) is relatively axially movable relative to the relative reciprocating motion at least to half the axial extent of the first filter means (33), and wherein the outer peripheral surface (11) and / or the outer peripheral wall (35) of the first filter drum body (3) extends substantially parallel to the longitudinal axis (5)
and / or, in the cross section of the first filter drum body (7) extending through the longitudinal axis (5), a straight line the two axially and radially outermost end points of the cross section of the first filter drum body (7) extend substantially parallel to the longitudinal axis (5) and the first filter drum body (7) for the most part does not project radially beyond the straight line. Pusher centrifuge (1) according to claim 1, wherein between the inner peripheral surface (9) and the outer peripheral surface (11) of the first filter drum body (7), a drainage gap (37) is formed, which in radial direction relative to the filter drum (3) radially outwardly an inner boundary surface (41) is limited, which is substantially parallel to the longitudinal axis (5) of the filter drum (3). Pusher centrifuge (1) according to claim 2, wherein the drainage gap (37) in radial direction relative to the filter drum (3) is bounded by radially opposed inner boundary surfaces (39, 41) which are substantially parallel to each other, optionally the radial distance between the two inner boundary surfaces (39, 41) is less than or equal to 30mm. Pusher centrifuge (1) according to one of claims 1 to 3, wherein the relative movement mechanism (27) is formed such that the first filter drum body (7) with the entire axial length of its first filter means (33) on the inner circumferential surface defined by the second filter means (47) (15) of the second filter drum body (13) is relatively movable, wherein an axial end portion (98) of the inner peripheral surface (15) of the second filter drum body (13) in front of the first filter drum body (7) from the first filter drum body (7) can not be painted over. Pusher centrifuge according to claim 4, wherein the axial end portion (98) of the second filter means (47) defined by the second filter means (47) inner circumferential surface (15) of the second filter drum body (13) has a larger surface area than that of the first filter means (7) 33) defined inner peripheral surface (9) of the first filter drum body (7). Pusher centrifuge (1) according to one of claims 1 to 5, wherein the axial extent of the second filter means (47) is at least twice as large as the axial extent of the first filter means (33). Pusher centrifuge (1) according to one of claims 1 to 5, wherein the relative movement mechanism (27) is formed such that from the first filter drum body (7) the inner peripheral surface (15) of the second filter drum body (13) at most only in the direction away from the walking floor ( 25) can be painted over axially to the front, that the end portion (98) remaining between the first filter drum body (7) and a front end (102) of the second filter drum body (13) facing away from the push floor (25) is defined by the second filter means (47) Inner peripheral surface (15) of the second filter drum body (13), which end portion (98) is not axially painted over from the filter drum body, an axial extent equal to or greater than the axial extent of the maximum before the sliding floor (25) present portion of the first filter means (33) defined inner peripheral surface (9) of the first filter drum body (7) or the same or greater is as the axial extent of the inner peripheral surface (9) of the first filter drum body (7). Pusher centrifuge (1) according to one of claims 1 to 7, further comprising a feed device (69) for feeding material (71) to be filtered into the filter drum (3), wherein the feed device (69) has a filling distributor device (75) which in the Inside the filter drum (3) is arranged and which has an outlet (77) which is designed and aligned such that the material to be filtered (71) from the outlet (77) with respect to the longitudinal axis (5) of the filter drum (3) obliquely in the direction of the sliding floor (25) and radially outwardly on the inner peripheral surface (9) of the first filter drum body (7) is output. Pusher centrifuge (1) according to one of claims 1 to 8, wherein the second filter drum body (13) seen in the direction of the longitudinal axis (5) of the filter drum is more than twice as long as the first filter drum body (7). Pusher centrifuge (1) according to one of claims 1 to 9, wherein the radial distance between the outer peripheral surface (11) and the inner peripheral surface (9) of the first filter drum body (7) is less than or equal to 70mm and / or wherein the radial distance between the inner peripheral surface (9 ) of the first filter drum body (7) and the inner peripheral surface (15) of the second filter drum body (13) is less than or equal to 70mm. Method for operating a pusher centrifuge (1) according to any one of claims 1 to 10 in the filter operation, wherein the material to be filtered (71) supplied to the inner peripheral surface of the first filter drum body (7) having such a substantially constant volume and / or mass flow rate and the relative movement mechanism (27) is adjusted to such a stroke length and / or controlled that the inner circumferential surface (9) of the first filter drum body (7) in substantially free of adhering material to be filtered by the stroke frequency and that the radial distance from the inner circumferential surface (15) of the inner peripheral surface (15) of the second filter drum body (13) permanently adhering filter cake to the longitudinal axis (5) of the filter drum (3) is smaller than the radial distance of the inner peripheral surface of the first filter drum body (7) to the longitudinal axis (5) of the filter drum (3). A method according to claim 11, wherein the relative movement mechanism (27) is adjusted and / or controlled to such a stroke length as seen from the sliding floor (25) in the direction of the longitudinal axis (5) of the filter drum (3) at periodic intervals determined by the stroke frequency in each case at least 50% of the inner circumferential surface (9) of the first filter drum body (7) are covered by the sliding floor. Method according to one of claims 11 to 12, wherein the relative movement mechanism (27) is set and / or controlled to such a stroke length that of the first filter drum body (7) of the second filter means (47) defined inner peripheral surface (15) of the second filter drum body (13) is swept only axially so far that the not swept surface portion of the inner circumferential surface of the second filter drum body (13) remaining in front of the first filter body (7) is equal to or greater than the maximum surface area of the first filter medium (33) present in front of the sliding bottom. formed inner peripheral surface (9) of the first filter drum body (7).

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