EP0711607B1 - Process for operating a screw centrifuge - Google Patents
Process for operating a screw centrifuge Download PDFInfo
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- EP0711607B1 EP0711607B1 EP95116855A EP95116855A EP0711607B1 EP 0711607 B1 EP0711607 B1 EP 0711607B1 EP 95116855 A EP95116855 A EP 95116855A EP 95116855 A EP95116855 A EP 95116855A EP 0711607 B1 EP0711607 B1 EP 0711607B1
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- centrifuge
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
- B04B—CENTRIFUGES
- B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
- B04B1/20—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl
- B04B1/2016—Driving control or mechanisms; Arrangement of transmission gearing
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- the invention relates to a method for operating screw centrifuges for the separation of solid-liquid mixtures into heavy substances (Solids) and light substances (liquid), consisting of a cylindrical centrifuge drum with a conically tapering Drum end, which is rotatably mounted about its longitudinal axis and their Drum wall a coaxially arranged, rotatably mounted about its longitudinal axis Screw conveyor encloses, with facilities for feeding the separating mixture into the centrifuge drum and outlet openings for the discharge of the separated light and heavy substances, the radial distance of the outlet openings from the centrifuge drum axis is less than the radial distance of the centrifuge drum wall from the centrifuge drum axis, so that when the screw centrifuge is operating under the influence of the centrifugal force inside the centrifuge drum forms a liquid ring from which the heavy substances with With the help of the screw conveyor, which rotates in the same direction as the centrifuge drum, but with a different speed (differential speed) rotated, lifted out and over the
- the heavy substances (solids) are discharged in screw centrifuges by the difference in speed between the screw conveyor and the Centrifuge drum, depending on the direction of rotation of the centrifuge drum the speed of the screw conveyor leading (the speed of the screw conveyor is greater than the speed of the centrifuge drum) or lagging (the speed of the screw conveyor is less than the speed of the centrifuge drum) is set.
- the light substances like the liquid flow to the opposite, for example End of the centrifuge drum to outlet openings arranged there, being carried out by the screw augers of the screw conveyor formed channels at least partially against the conveying direction of the screw conveyor flow.
- a screw centrifuge which not continuously, but cyclically using a complex control system is operated by time-controlled two different work phases always alternate, namely a sedimentation phase in which the centrifuge drum and the screw conveyor should run synchronously, so that no solid is discharged and a solid discharge phase, in which by actuating one acting on the centrifuge drive Eddy current brake a differential speed between the drum and screw set and the sedimented solid discharged is, the inlet of the solid suspension in this working phase interrupted in the centrifuge.
- the centrifuge drum wall are favored. The problem of Switching off and restarting a continuously at continuous operating speed operated screw centrifuge is not addressed.
- the object of the invention is therefore to operate Screw centrifuges to create a process with which avoided will that when turning off and restarting the screw centrifuge a too moist solid phase is discharged from the drum becomes.
- the speed n of the centrifuge drum is shown as a function of the time Z.
- the centrifuge drum speed (11) increases almost linearly up to the operating speed (10).
- This operating speed (10) is now maintained throughout the entire duration of normal operation (15) of the screw centrifuge (time Z 2 to Z 3 ).
- the screw centrifuge is switched off.
- the speed (12) of the centrifuge drum slows steadily from the normal operating speed (10) until the centrifuge drum comes to a complete standstill at time Z 5 .
- the speed of the screw conveyor changes in relation to the speed of the centrifuge drum in such a way that starting from zero the normal operation of the screw centrifuge sets the required differential speed (17). Separated solid is now discharged. This differential speed (17) is initially maintained even after switching off the screw centrifuge at time Z 3 .
- the start-up or shutdown phase can ensure the differential speed the screw briefly for a few seconds relative to the drum speed be turned on and then turned off again without being inadequate dewatered solid is discharged at the cone.
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Abstract
Description
Die Erfindung ist auf ein Verfahren zum Betrieb von Schneckenzentrifugen für die Trennung von Feststoff-Flüssigkeitsgemischen in schwere Stoffe (Feststoffe) und leichte Stoffe (Flüssigkeit) gerichtet, bestehend aus einer zylindrischen Zentrifugentrommel mit einem sich konisch verjüngenden Trommelende, die um ihre Längsachse drehbar gelagert ist und deren Trommelwand eine koaxial angeordnete, um ihre Längsachse drehbar gelagerte Förderschnecke umschließt, mit Einrichtungen zum Zuführen des zu trennenden Gemisches in die Zentrifugentrommel sowie Auslaßöffnungen für den Austrag der voneinander getrennten leichten und schweren Stoffe, wobei der radiale Abstand der Auslaßöffnungen von der Zentrifugentrommelachse geringer ist als der radiale Abstand der Zentrifugentrommelwand von der Zentrifugentrommelachse, so daß sich beim Betrieb der Schneckenzentrifuge unter dem Einfluß der Zentrifugalkraft innerhalb der Zentrifugentrommel ein Flüssigkeitsring ausbildet, aus dem die schweren Stoffe mit Hilfe der Förderschnecke, die in gleicher Drehrichtung wie die Zentrifugentrommel, aber mit von dieser abweichender Drehzahl (Differenzdrehzahl) rotiert, herausgehoben und über das konische Trommelende zur Auslaßöffnung transportiert werden.The invention relates to a method for operating screw centrifuges for the separation of solid-liquid mixtures into heavy substances (Solids) and light substances (liquid), consisting of a cylindrical centrifuge drum with a conically tapering Drum end, which is rotatably mounted about its longitudinal axis and their Drum wall a coaxially arranged, rotatably mounted about its longitudinal axis Screw conveyor encloses, with facilities for feeding the separating mixture into the centrifuge drum and outlet openings for the discharge of the separated light and heavy substances, the radial distance of the outlet openings from the centrifuge drum axis is less than the radial distance of the centrifuge drum wall from the centrifuge drum axis, so that when the screw centrifuge is operating under the influence of the centrifugal force inside the centrifuge drum forms a liquid ring from which the heavy substances with With the help of the screw conveyor, which rotates in the same direction as the centrifuge drum, but with a different speed (differential speed) rotated, lifted out and over the conical drum end to the outlet opening be transported.
Der Austrag der schweren Stoffe (Feststoffe) erfolgt bei Schneckenzentrifugen durch die Differenzdrehzahl zwischen der Förderschnecke und der Zentrifugentrommel, wobei je nach Drehrichtung der Zentrifugentrommel die Drehzahl der Förderschnecke voreilend (die Drehzahl der Förderschnecke ist größer als die Drehzahl der Zentrifugentrommel) oder nacheilend (die Drehzahl der Förderschnecke ist kleiner als die Drehzahl der Zentrifugentrommel) eingestellt ist. The heavy substances (solids) are discharged in screw centrifuges by the difference in speed between the screw conveyor and the Centrifuge drum, depending on the direction of rotation of the centrifuge drum the speed of the screw conveyor leading (the speed of the screw conveyor is greater than the speed of the centrifuge drum) or lagging (the speed of the screw conveyor is less than the speed of the centrifuge drum) is set.
Der in der Schneckenzentrifuge unter dem Einfluß der durch die Drehung der Zentrifugentrommel hervorgerufenen Zentrifugalkraft sich ausbildende Flüssigkeitsring, dessen Innendurchmesser durch die radiale Anordnung der Austragsöffnung für die leichten Stoffe bestimmt ist, besteht vorwiegend aus bereits abgetrennter Flüssigkeit, in der sich die schweren Stoffe (Feststoffe) am äußeren Rand des Ringes, also an der Zentrifugentrommelwand, absetzen.The one in the screw centrifuge under the influence of the rotation the centrifugal force caused by the centrifuge drum Liquid ring, the inside diameter of which is determined by the radial arrangement of the The discharge opening for which light fabrics are intended mainly consists of already separated liquid, in which the heavy substances (solids) settle on the outer edge of the ring, i.e. on the centrifuge drum wall.
Von den Schneckenwendeln der Förderschnecke, die in gleicher Drehrichtung wie die Zentrifugentrommel und je nach Drehrichtung der Zentrifugentrommel von der Trommeldrehzahl nacheilend oder voreilend in Drehung versetzt ist, werden die an der Zentrifugentrommelwand angeordneten Feststoffe erfaßt und zu einem Ende der Zentrifugentrommel transportiert. Dieses Ende ist konisch ausgebildet, so daß an diesem Ende die Feststoffe mit Hilfe der Förderschnecke aus dem Flüssigkeitsring entgegen der Richtung der Zentrifugalkraft herausgehoben und über diesen Trommelkonus zu einer oder mehreren Auslaßöffnungen für den Feststoff transportiert werden.From the screw spirals of the screw conveyor, which rotate in the same direction like the centrifuge drum and depending on the direction of rotation of the centrifuge drum trailing or leading in rotation from the drum speed is offset, the solids arranged on the centrifuge drum wall detected and transported to one end of the centrifuge drum. This End is conical so that the solids at this end Help the screw conveyor out of the liquid ring against the direction the centrifugal force lifted out and over this drum cone to a or more outlet openings for the solid are transported.
Die leichten Stoffe wie die Flüssigkeit fließen beispielsweise zum entgegengesetzten Ende der Zentrifugentrommel zu dort angeordneten Auslaßöffnungen, wobei sie durch die aus den Schneckenwendeln der Förderschnecke gebildete Kanäle zumindest teilweise entgegen der Förderrichtung der Förderschnecke fließen.The light substances like the liquid flow to the opposite, for example End of the centrifuge drum to outlet openings arranged there, being carried out by the screw augers of the screw conveyor formed channels at least partially against the conveying direction of the screw conveyor flow.
Beim Abstellen der Schneckenzentrifuge verringert sich die Drehzahl der Zentrifugentrommel bis zum Stillstand und damit verringert sich auch die Zentrifugalkraft. Es wird dann beim Auslaufen der Zentrifugentrommel eine Drehzahl erreicht, bei der die Zentrifugalkraft niedriger wird als die Gravitationskraft mit der Folge, daß der in der Zentrifugentrommel sich ausbildende Flüssigkeitsring zusammenbricht und der Füllstand der Flüssigkeit innerhalb der Zentrifugentrommel über die Auslaßöffnung für die schweren Stoffe hinausreicht, so daß an diesen Öffnungen, wenn auch nur kurzfristig, schwallartig auch die leichten Stoffe ausgetragen werden. When the screw centrifuge is switched off, the speed of the Centrifuge drum to a standstill and thus the Centrifugal force. It then becomes a when the centrifuge drum runs out Speed reached at which the centrifugal force becomes lower than the gravitational force with the result that the developing in the centrifuge drum Liquid ring collapses and the level of the liquid inside the centrifuge drum through the outlet opening for the heavy ones Substances extends so that at these openings, even if only for a short time, The light fabrics are also gushed out.
In der älteren, nicht vorveröffentlichten DE 43 21 964 wird deshalb vorgeschlagen, die Drehzahl der Zentrifugentrommel und/oder die Drehzahl der Förderschnecke kurzfristig schlagartig so zu ändern, daß der Flüssigkeitsring, der aufgrund seiner Massenträgheit dieser Drehzahländerung nicht folgt. Durch die träge Masse der Flüssigkeit zwischen den Schneckenwendeln werden die leichten Stoffe bei schlagartiger Drehzahländerung zur Austragsöffnung für die leichten Stoffe geschraubt.In the older, unpublished DE 43 21 964 it is therefore proposed the speed of the centrifuge drum and / or the speed of the Suddenly change the screw conveyor so that the liquid ring, the due to its inertia this speed change not follows. Due to the inert mass of the liquid between the screw spirals the light fabrics become a sudden change in speed Screwed discharge opening for the light fabrics.
Ein weiterer Nachteil, der bereits vor dem Zusammenbrechen des Flüssigkeitsrings beim Erreichen einer kritischen niedrigeren Drehzahl auftritt, wird durch die Verringerung der Zentrifugentrommeldrehzahl bewirkt.Another disadvantage that occurs even before the liquid ring collapses occurs when a critical lower speed is reached, is caused by the reduction of the centrifuge drum speed.
Durch die Relativbewegung der Förderschnecke zur Zentrifugentrommel in Drehrichtung erfaßt die Förderschnecke die an der Zentrifugentrommelwand angeordneten schweren Stoffe und schiebt sie über den Konus entgegen der Zentrifugalkraft in Richtung Drehachse nach innen zur dort angeordneten Auslaßöffnung. Bei diesem Transport der schweren Stoffe außerhalb der abgetrennten Flüssigkeit über den Konus der Zentrifugentrommel erfolgt eine weitergehende Abtrennung der noch anhaftenden leichten Stoffe. Mit fallender Drehzahl und somit fallender Zentrifugalkraft wird dieser "bergaufwärts" gerichtete Transport der schweren Stoffe zunehmend erleichtert, d. h. auch die Entwässerung wird zunehmend verschlechtert.Due to the relative movement of the screw conveyor to the centrifuge drum in Direction of rotation detects the screw conveyor on the centrifuge drum wall arranged heavy fabrics and pushes them against the cone Centrifugal force in the direction of the axis of rotation towards the inside Outlet opening. During this transport of heavy substances outside of separated liquid takes place over the cone of the centrifuge drum a further separation of the still adhering light substances. With falling speed and thus falling centrifugal force becomes this "uphill" transport of heavy materials increasingly easier, d. H. drainage is also deteriorating.
Wird nun beim Abstellvorgang zunächst die Gemischzufuhr abgestellt, so trägt die Förderschnecke aus dem gespeicherten Feststoffvorrat innerhalb der Zentrifugentrommel noch eine gewisse Zeit entwässerten Feststoff aus, der aber bei der noch anstehenden Solldrehzahl dann ganz aufhört. Wird nun im Verlauf des Abstellvorgangs die Drehzahl der Zentrifugentrommel verringert, beginnt die Schneckenzentrifuge trotz abgestellter Gemischzufuhr erneut mit einem Feststoffaustrag, der nun aber wegen der geringeren Zentrifugalkräfte nicht mehr den gewünschten Entwässerungsgrad aufweist und teilweise "verklumpt" ist. If the mixture supply is turned off during the shutdown process, then carries the screw conveyor out of the stored solid material within dewatered solid from the centrifuge drum for a certain time, which then stops completely at the target speed that is still pending. Becomes now the speed of the centrifuge drum during the shutdown process reduced, the screw centrifuge starts despite the mixture feed being switched off again with a solids discharge, but now because of the lower Centrifugal forces no longer have the desired degree of dewatering and partially "clumped".
Dieser Austrag von zu feuchtem Schwergut findet auch beim Wiederanfahren einer noch teilweise mit Feststoff gefüllten Schneckenzentrifuge statt, da dann auch hier ein Bereich niedriger Zentrifugalkraft durchfahren wird.This discharge of heavy goods that are too moist also takes place when restarting a still partially filled with solid screw centrifuge instead then a range of low centrifugal force is also passed through here.
Durch die nachteilige Entwässerung der schweren Stoffe während des Abstellvorganges und während des Wiederanfahrens der Schneckenzentrifuge wird nicht nur das Trennergebnis insgesamt verschlechtert, sondern es sind auch verfahrenstechnische Störungen bei der weiteren Verarbeitung der abgetrennten schweren Stoffe durch z. B. Verklebungen an nachfolgenden Transport-Trockner- oder Verbrennungseinrichtungen zu erwarten.Due to the disadvantageous dewatering of the heavy substances during the parking process and while restarting the screw centrifuge not only does the separation result deteriorate overall, but it does also procedural disturbances in the further processing of the separated heavy substances such as B. bonds to subsequent Transport dryer or incinerators to be expected.
Aus der DE-A-1925001 ist eine Schneckenzentrifuge bekannt, die nicht kontinuierlich, sondern mittels einer aufwendigen Steuerung zyklisch betrieben wird, indem zeitgesteuert zwei verschiedene Arbeitsphasen immer abwechseln, nämlich eine Sedimentationsphase, in der die Zentrifugentromel und die Förderschnecke synchron laufen sollen, so daß kein Feststoff ausgetragen wird, und eine Feststoffaustragsphase, in der durch Betätigung einer am Zentrifugenantrieb angreifenden Wirbelstrombremse eine Differenzdrehzahl zwischen Trommel und Schnecke eingestellt und der sedimentierte Feststoff ausgetragen wird, wobei in dieser Arbeitsphase der Einlauf der Feststoffsuspension in die Zentrifuge unterbrochen wird. Mit der bekannten Steuerung soll eine ungestörte Sedimentation der Suspensions- Feststoffe an die Zentrifugentrommelwand begünstigt werden. Die Problematik des Abstellens und Wiederanfahrens einer kontinuierlich mit Dauerbetriebsdrehzahl betriebenen Schneckenzentrifuge ist dabei nicht angesprochen.From DE-A-1925001 a screw centrifuge is known which not continuously, but cyclically using a complex control system is operated by time-controlled two different work phases always alternate, namely a sedimentation phase in which the centrifuge drum and the screw conveyor should run synchronously, so that no solid is discharged and a solid discharge phase, in which by actuating one acting on the centrifuge drive Eddy current brake a differential speed between the drum and screw set and the sedimented solid discharged is, the inlet of the solid suspension in this working phase interrupted in the centrifuge. With the well-known control should undisturbed sedimentation of the suspension solids the centrifuge drum wall are favored. The problem of Switching off and restarting a continuously at continuous operating speed operated screw centrifuge is not addressed.
Der Erfindung liegt daher die Aufgabe zugrunde, zum Betrieb von Schneckenzentrifugen ein Verfahren zu schaffen, mit dem vermieden wird, daß beim Abstellen und Wiederanfahren der Schneckenzentrifuge eine zu feuchte Feststoffphase aus der Trommel ausgetragen wird.The object of the invention is therefore to operate Screw centrifuges to create a process with which avoided will that when turning off and restarting the screw centrifuge a too moist solid phase is discharged from the drum becomes.
Die gestellte Aufgabe wird gelöst durch die Maßnahmen des Kennzeichnungsteils des Anspruchs 1. Vorteilhafte Ausgestaltungen der Erfindung sind in den Unteransprüchen angegeben.The task is solved by the measures of the labeling part of claim 1. Advantageous embodiments of the invention are specified in the subclaims.
Durch die erfindungsgemäße Maßnahme, während der beim Anfahr- und Auslaufvorgang durchlaufende Phase mit gegenüber der Betriebsdrehzahl niedrigerer Drehzahl der Zentrifugentrommel und entsprechend niedrigerer Zentrifugalkraft ab einer Mindestdrehzahl der Zentrifugentrommel die Drehzahl der Förderschnecke der Drehzahl der Zentrifugentrommel anzugleichen (d. h. die Differenzdrehzahl geht gegen Null), wird während dieser Betriebsphase zunächst weniger und dann überhaupt kein Feststoff durch die Förderschnecke mehr ausgetragen. Bei richtiger Anpassung der Differenzdrehzahl an die Zentrifugalkraft entspricht der in dieser mit niedrigerer Differenzdrehzahl noch ausgetragene Feststoff in seiner Konsistenz, d. h. seinem Entwässerungsgrad, dem beim normalen Betrieb der Schneckenzentrifuge ausgetragenen Feststoff, so daß Störungen durch den Austrag von z. B. zu nassem Feststoff nicht mehr auftreten können. By the measure according to the invention, during the start-up and Stopping phase in phase with compared to the operating speed lower speed of the centrifuge drum and correspondingly lower Centrifugal force from a minimum speed of the centrifuge drum Adjust the speed of the screw conveyor to the speed of the centrifuge drum (i.e. the differential speed approaches zero), during this Operating phase initially less and then no solid at all through the Screw conveyor carried out more. With correct adjustment of the differential speed to the centrifugal force corresponds to that with a lower differential speed Solid matter still discharged in its consistency, d. H. his Degree of drainage, that during normal operation of the screw centrifuge discharged solid, so that interference from the discharge of z. B. can no longer occur in wet solids.
Um bei hydraulisch angetriebenen Schneckenzentrifugen, bei denen die Zentrifugentrommel und die Förderschnecke durch separate hydraulische Antriebe in Drehung versetzt werden, und bei denen während der Anlauf- bzw. Abschaltphase der Antrieb der Förderschnecke in einfacher Weise zeitweise stillgesetzt werden kann, um die Drehzahl der Förderschnecke der der Zentrifugentrommel anzugleichen, eine nachteilige Erwärmung des hydraulischen Antriebs, der nun zwangsweise über Kraftschluß mit Hilfe des vorhandenen Feststoffs mit der Drehzahl der Zentrifugentrommel mitrotierenden Förderschnecke zu vermeiden, wird ein Teilölkreislauf zur Kühlung im Antrieb der Förderschnecke aufrechterhalten.In order for hydraulically driven screw centrifuges, in which the Centrifuge drum and the screw conveyor by separate hydraulic Drives are set in rotation, and where during start-up or shutdown phase of the drive of the screw conveyor in a simple manner can be temporarily stopped to the speed of the screw conveyor the centrifuge drum, an adverse heating of the hydraulic Drive, which is now forcibly with the help of the existing solid co-rotating with the speed of the centrifuge drum Avoiding the screw conveyor becomes a partial oil circuit for cooling in the drive of the screw conveyor.
Weitere Einzelheiten und Merkmale der Erfindung werden anhand einer schematischen Darstellung des Betriebszustandes einer Schneckenzentrifuge beispielhaft näher erläutert.Further details and features of the invention are based on a schematic representation of the operating state of a screw centrifuge exemplified in more detail.
In dieser Darstellung ist die Drehzahl n der Zentrifugentrommel als Funktion der Zeit Z dargestellt. Während der Anfahrphase (14) (vom Startpunkt Z0 bis zur Zeit Z2) steigt die Zentrifugentrommeldrehzahl (11) annähernd linear stetig bis zur Betriebsdrehzahl (10). Diese Betriebsdrehzahl (10) wird nun während der gesamten Dauer des normalen Betriebs (15) der Schnekkenzentrifuge (Zeitpunkt Z2 bis Z3) konstant aufrechterhalten. Zum Zeitpunkt Z3 erfolgt das Abschalten der Schneckenzentrifuge. Während der nun folgenden Auslaufphase (16) (Zeitpunkt Z3 bis Z5) verlangsamt sich die Drehzahl (12) der Zentrifugentrommel von der normalen Betriebsdrehzahl (10) stetig bis auf den völligen Stillstand der Zentrifugentrommel zum Zeitpunkt Z5.In this illustration, the speed n of the centrifuge drum is shown as a function of the time Z. During the start-up phase (14) (from the starting point Z 0 to the time Z 2 ) the centrifuge drum speed (11) increases almost linearly up to the operating speed (10). This operating speed (10) is now maintained throughout the entire duration of normal operation (15) of the screw centrifuge (time Z 2 to Z 3 ). At time Z 3 , the screw centrifuge is switched off. During the subsequent phase-out phase (16) (time Z 3 to Z 5 ), the speed (12) of the centrifuge drum slows steadily from the normal operating speed (10) until the centrifuge drum comes to a complete standstill at time Z 5 .
Erfindungsgemäß wird beim Wiederanfahren einer bereits teilweise noch mit Feststoff gefüllten Schneckenzentrifuge (also nicht bei ihrem ersten Anfahren) bei Erreichen der Mindestdrehzahl (13) zum Zeitpunkt Z1 die Drehzahl der Förderschnecke gegenüber der Drehzahl der Zentrifugentrommel so verändert, daß von Null ausgehend sich die zum normalen Betrieb der Schneckenzentrifuge erforderliche Differenzdrehzahl (17) einstellt. Es wird nun abgetrennter Feststoff ausgetragen. Diese Differenzdrehzahl (17) wird zunächst auch nach dem Abschalten der Schneckenzentrifuge zum Zeitpunkt Z3 aufrechterhalten. Wenn aber die Zentrifugentrommeldrehzahl auf die Mindestdrehzahl (13) zum Zeitpunkt Z4 abgefallen ist, erfolgt ein Regeleingriff, der die Drehzahl der Förderschnecke nun der Drehzahl der Zentrifugentrommel angleicht, beispielsweise durch Abschalten des Antriebs der Förderschnecke, wodurch nun diese mit der Drehzahl der Zentrifugentrommel mitrotiert. Die Differenzdrehzahl ist nun gleich null und ein Austrag von Feststoff erfolgt nicht mehr.According to the invention, when restarting a screw centrifuge that is already partially filled with solid matter (i.e. not when starting up for the first time) when the minimum speed (13) is reached at time Z 1, the speed of the screw conveyor changes in relation to the speed of the centrifuge drum in such a way that starting from zero the normal operation of the screw centrifuge sets the required differential speed (17). Separated solid is now discharged. This differential speed (17) is initially maintained even after switching off the screw centrifuge at time Z 3 . If, however, the centrifuge drum speed has dropped to the minimum speed (13) at time Z 4 , a control intervention takes place, which now adjusts the speed of the screw conveyor to the speed of the centrifuge drum, for example by switching off the drive of the screw conveyor, which now rotates with the speed of the centrifuge drum . The differential speed is now zero and solid matter is no longer discharged.
Um beispielsweise die Kühlung und Schmierung einiger Bauteile während der Anfahrt- oder Abstellphase sicherzustellen, kann die Differenzdrehzahl der Schnecke relativ zur Trommeldrehzahl kurzzeitig für einige Sekunden eingeschaltet werden und dann wieder ausgeschaltet werden, ohne daß unzureichend entwässerter Feststoff am Konus ausgetragen wird.For example, during the cooling and lubrication of some components the start-up or shutdown phase can ensure the differential speed the screw briefly for a few seconds relative to the drum speed be turned on and then turned off again without being inadequate dewatered solid is discharged at the cone.
Claims (5)
- A method for the operation of screw centrifuges for the separation of fluid-solid material mixtures into fluid and heavy material, comprising a cylindrical centrifuge drum with a conically tapering drum end, which is mounted so as to be rotatable about its longitudinal axis and whose drum wall encloses a screw conveyor, mounted rotatably about its longitudinal axis, with arrangements for the supply of the mixture to be separated into the centrifuge drum and outlet openings for the extraction of the light and heavy materials separated from each other, whereby the radial separation of the outlet openings from the axis of the centrifuge drum is less than the radial separation of the centrifuge drum wall from the centrifuge drum axis, so that in operation of the screw centrifuge a fluid ring forms inside the centrifuge drum under the influence of centrifugal force, out of which the heavy materials are lifted with the aid of the screw conveyor, which rotates in the same direction as the centrifuge drum, but at a different rate of rotation from it, and transported via the conical drum end to the extraction openings, characterised in that in the running down (16) of the screw centrifuge following its disconnection, whereby the rate of rotation of the centrifuge drum (12) reduces from the operating rate of rotation (10) of the normal centrifuge operation (15) from the time-point (Z3) of the disconnection of the screw centrifuge onwards, from a least rate of rotation (13), which is less than the operating rate of rotation (10), the rate of rotation of the screw conveyor so nearly approaches the rate of rotation of the centrifuge drum, i.e. the difference rate of rotation (17) is adjusted close to null, that the extraction of the heavy material ceases, and that on again running up (14) of the screw centrifuge the rate of rotation of the screw conveyor and of the centrifuge drum is at first equally high, i.e. the difference rate of rotation (17) is maintained equal to null and only on reaching the least rate of rotation (13) of the centrifuge drum at a time-point (Z1) is the required difference rate of rotation (17) for the normal continuous operational rate of rotation (10) set in.
- A method according to Claim 1, characterised in that in screw centrifuges with hydraulic drive during the period in which the rate of rotation of the screw conveyor is being equalised to the rate of rotation of the centrifuge drum, a sector oiling circuit is maintained for cooling in the drive to the screw conveyor.
- A method according to Claim 1, characterised in that on renewed running up the screw centrifuge the difference rate of rotation is increased in dependency on the rate of rotation of the drum in accordance with a pre-programmable function.
- A method according to Claim 1, characterised in that on running down the screw centrifuge the difference rate of rotation is changed steadily or abruptly in dependency on the rate of rotation of the drum in accordance with a prescribed function.
- A method according to Claim 1, characterised in that below an adjustable least rate of rotation of the centrifuge drum the difference rate of rotation of the screw is null and takes up a final value only short term for a few seconds duration.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4439938 | 1994-11-09 | ||
| DE4439938A DE4439938A1 (en) | 1994-11-09 | 1994-11-09 | Process for operating screw centrifuges |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0711607A1 EP0711607A1 (en) | 1996-05-15 |
| EP0711607B1 true EP0711607B1 (en) | 2000-07-12 |
Family
ID=6532826
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95116855A Expired - Lifetime EP0711607B1 (en) | 1994-11-09 | 1995-10-26 | Process for operating a screw centrifuge |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0711607B1 (en) |
| JP (1) | JPH08323240A (en) |
| AT (1) | ATE194507T1 (en) |
| DE (2) | DE4439938A1 (en) |
| ES (1) | ES2151574T3 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015073951A (en) * | 2013-10-09 | 2015-04-20 | 神鋼環境メンテナンス株式会社 | Operation method of organic wastewater treatment facility |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3494542A (en) * | 1968-05-27 | 1970-02-10 | Pennwalt Corp | Centrifuging process and apparatus |
| DE2551788A1 (en) * | 1975-11-18 | 1977-06-02 | Flottweg Werk Bruckmayer | FULLY-SLEEVED SCREW CENTRIFUGE WITH DIFFERENTIAL SPEED-VARIABLE COUPLING BETWEEN SHEATH PART AND SCREW PART |
| US4978331A (en) * | 1989-07-11 | 1990-12-18 | Alfa-Laval Ab | Method and apparatus for cleaning in place of a decanter centrifuge |
| DE4321964A1 (en) | 1993-07-01 | 1995-01-12 | Kloeckner Humboldt Deutz Ag | Process for operating screw centrifuges |
-
1994
- 1994-11-09 DE DE4439938A patent/DE4439938A1/en not_active Withdrawn
-
1995
- 1995-10-26 AT AT95116855T patent/ATE194507T1/en not_active IP Right Cessation
- 1995-10-26 ES ES95116855T patent/ES2151574T3/en not_active Expired - Lifetime
- 1995-10-26 DE DE59508557T patent/DE59508557D1/en not_active Expired - Fee Related
- 1995-10-26 EP EP95116855A patent/EP0711607B1/en not_active Expired - Lifetime
- 1995-11-09 JP JP7315905A patent/JPH08323240A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE59508557D1 (en) | 2000-08-17 |
| ES2151574T3 (en) | 2001-01-01 |
| ATE194507T1 (en) | 2000-07-15 |
| DE4439938A1 (en) | 1996-05-15 |
| EP0711607A1 (en) | 1996-05-15 |
| JPH08323240A (en) | 1996-12-10 |
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