EP0508109A2 - Method for screening a fine-grained material - Google Patents

Method for screening a fine-grained material Download PDF

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Publication number
EP0508109A2
EP0508109A2 EP92103817A EP92103817A EP0508109A2 EP 0508109 A2 EP0508109 A2 EP 0508109A2 EP 92103817 A EP92103817 A EP 92103817A EP 92103817 A EP92103817 A EP 92103817A EP 0508109 A2 EP0508109 A2 EP 0508109A2
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EP
European Patent Office
Prior art keywords
screening
fine
grained
coarse
substrate
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EP92103817A
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German (de)
French (fr)
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EP0508109A3 (en
Inventor
Reiner Dipl.-Ing. Schiffbauer
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Linde GmbH
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Linde GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C19/00—Other disintegrating devices or methods
    • B02C19/18—Use of auxiliary physical effects, e.g. ultrasonics, irradiation, for disintegrating
    • B02C19/186—Use of cold or heat for disintegrating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/08—Separating or sorting of material, associated with crushing or disintegrating
    • B02C23/10—Separating or sorting of material, associated with crushing or disintegrating with separator arranged in discharge path of crushing or disintegrating zone
    • B02C23/12—Separating or sorting of material, associated with crushing or disintegrating with separator arranged in discharge path of crushing or disintegrating zone with return of oversize material to crushing or disintegrating zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B9/00—Combinations of apparatus for screening or sifting or for separating solids from solids using gas currents; General arrangement of plant, e.g. flow sheets

Definitions

  • the particularly difficult to sieve powders include, in particular, electrostatically charging substances such as plastic powders (e.g. PVC, polystyrene, polyethylene, polypropylene etc.). Also fabrics with a fibrous grain shape, e.g. Tobacco dust, tea, leaf drugs, etc., cause difficulties when sieving. Materials with a low specific weight, such as carbon powder and natural graphite, are also problematic.
  • plastic powders e.g. PVC, polystyrene, polyethylene, polypropylene etc.
  • fabrics with a fibrous grain shape e.g. Tobacco dust, tea, leaf drugs, etc.
  • Materials with a low specific weight such as carbon powder and natural graphite, are also problematic.
  • the screening aids include e.g. Tapping balls that hit the underside of the screen deck or brushes that pass the screenings through the mesh of the screen.
  • the present invention has for its object to provide a screening method with which an effective screening, in particular difficult to screen screenable material is ensured without the disadvantages of conventional methods.
  • This object is achieved in that a coarse-grained substrate is added to the screenings before and / or during the screening process.
  • the coarse-grained substrate has a grain size that is well above the mesh size of the screen fabric, so that it is not itself subjected to screening.
  • the much larger substrate particles act as a sieve aid for the very fine sieve particles and drive them through the sieve meshes, unaffected by electrostatics and drafts.
  • a coarse-grained substrate for example, granulate comes into question, the particle size of which is many times larger than the mesh size of the screen fabric.
  • a substance specific to the material to be screened is used as the coarse-grained substrate.
  • the screening process is integrated into a process for comminuting coarse-grained substrate.
  • the coarse-grained substrate for example coarse-grained granules such as plastic particles, spice grains, nuts etc.
  • the fine-grained powder is fed into a simple mesh screen in order to obtain a powder with a defined upper grain limit.
  • the coarse-grained substrate is mixed with the fine-grained powder, preferably in a mixer provided, for example, with a screw drive. The many times larger particles of the coarse-grained substrate drive the fine powder particles through the sieve mesh.
  • the comminution of the coarse-grained substrate is preferably carried out downstream of the screening, the fine-grained screenings resulting from the comminution being returned to the screening.
  • the coarse-grained substrate to be shredded is first mixed with the material to be screened before and / or during the sieving process, is then removed from the sieve and finally fed to the shredding.
  • the coarse-grained substrate is expediently comminuted in a cold grinding system, the coarse-grained substrate being cooled by means of a cryogenic refrigerant before and / or during the comminution.
  • This produces cold exhaust gas which is preferably used at least partially to purge the sieve and / or the mixer.
  • a sieving of very fine powders is achieved with the advantage of an exactly defined upper grain limit and a very low proportion of missing grains.
  • pre-cooling of the coarse-grained substrate to be shredded and a reduction in the refrigerant consumption are additionally achieved.
  • Standard vibrating, circular vibrating, tumbling or drum sieves can be used as sieves without special additional devices, e.g. Brushing or tapping devices are used.
  • the cold grinding plant shown in FIG. 1 is for the comminution of coarse-grained substrate, in particular from granules, such as plastic granules, to fine-grained powder.
  • the granules are fed via a feed line 1 and a cell wheel 2, which is switched into the feed line 1 and serves for dosing, to a mixer 3 which has, for example, a worm drive.
  • the mixer 3 the granulate is homogeneously mixed with the fine-grained powder which is obtained in the comminution of the granulate in a downstream mill 4 and which is to be fed to the sieving as sieving material.
  • the resulting mixture is fed via a feed 5 of a screening machine 6.
  • the screening machine 6 can be, for example, a standard vibrating, circular vibrating, tumbling or drum screen.
  • the many times larger granulate particles serve as a sieving aid for the fine-grained powder and drive the very fine powder particles through the sieve meshes, unaffected by electrostatics and drafts.
  • the fine material driven through the sieve mesh which has a precisely defined upper grain limit, is drawn off via line 7 for further use.
  • the granules which do not pass through the sieve mesh are first fed to an intermediate container 9 via line 8 and then fed via a metering cell wheel 10 to a cooling screw 11 which is charged with a cryogenic refrigerant, in particular liquid nitrogen.
  • the frozen and embrittled granules are fed via line 12 to the mill 4, which can be designed, for example, as a hammer mill.
  • the frozen granulate is ground into very fine powder with grain sizes in the micrometer range.
  • the powder is drawn off via line 13 and fed to a cyclone 14, in which fine dust is separated off.
  • the fine dust is extracted from the cyclone 14 by means of a fan 17 and passed through a filter 15.
  • the resulting filter dust is drawn off via line 16.
  • the powder intended as screenings is fed to the mixer 3 via line 18, in which it is homogeneously mixed with the granules to be comminuted.
  • the regrind is also pre-cooled, as a result of which the consumption of cryogenic refrigerant during cold grinding is reduced.
  • Cold exhaust gas occurring in the cooling screw 11 is drawn off via an exhaust gas line 19 and partly led via a flushing gas line 20 to the mixer 3 and to the screening machine 6 in order to purge these parts of the system with cold gas, which likewise results in pre-cooling of the ground material.
  • the rest of the exhaust gas is released to the atmosphere together with the exhaust air drawn off from the filter 15 via line 21 and an interposed throttle valve 22.
  • Figure 2 shows a comparison of the sieving results of test sieving with polyester powder.
  • a 125 mm mesh screen was used, which worked as a circular oscillator.
  • the diagram shows the distribution of fine and coarse material (whereby “fine material” means particles with a particle size below a defined upper grain limit, which is determined by the mesh size of the sieve; while “coarse material” denotes such particles, whose size is above the upper grain limit).
  • Graph I shows the result of a screening according to the prior art, i.e. without adding granules.
  • the graphs 11 and 111 show the results of the screening according to the invention, wherein in case 11 a granulate content of 50% was set in the fine material, while in case III the granulate content was 33%.
  • the effective coarse material fraction (G) i.e. the fraction of particles that cannot pass through the sieve mesh due to their size
  • G the effective coarse material fraction
  • FG coarse material
  • F the proportion of the fine material discharge

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  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combined Means For Separation Of Solids (AREA)
  • Disintegrating Or Milling (AREA)

Abstract

A screening method is described which permits a very fine powder to be reliably screened. A large-grained substrate is added to the material for screening before and/or during the screening process. The substrate particles which are many times larger act as a screening aid for the very fine particles of material for screening and drive said particles through the screening meshes, uninfluenced by electrostatics and air draughts.

Description

Besonders feinkörnige Pulver, wie sie beispielsweise beim Kaltmahlen von Granulat anfallen, können mittels eines einfachen Maschensiebes nicht ohne zusätzliche Maßnahmen gesiebt werden. Aufgrund der geringen Korngröße des Pulvers und der damit verbundenen geringen Masse der einzelnen Körner sind die beim Siebvorgang ausgenutzten Massenkräfte sehr klein, so daß Störeinflüsse, wie z.B. elektrostatische Aufladung oder Luftströmungen, die Siebung extrem behindern können. Falls die Massenkräfte so klein sind, daß die Störeinflüsse überwiegen, so ist eine Siebung herkömmlicher Art völlig undurchführbar.Particularly fine-grained powders, such as those obtained when cold-grinding granulate, cannot be screened without additional measures using a simple mesh screen. Due to the small grain size of the powder and the associated low mass of the individual grains, the inertial forces used during the sieving process are very small, so that interfering influences, e.g. electrostatic charge or air currents that can extremely hinder screening. If the mass forces are so small that the disturbing influences predominate, sieving of a conventional type is completely impractical.

Zu den besonders schwer siebbaren Pulvern gehören insbesondere elektrostatisch aufladende Stoffe, wie Kunststoffpulver (z.B. PVC, Polystyrol, Polyäthylen, Polypropylen etc.). Auch Stoffe mit faseriger Kornform, z.B. Tabakstaub, Tee, Blattdrogen etc., bereiten beim Sieben Schwierigkeiten. Problematisch sind auch Stoffe mit geringem spezifischen Gewicht, wie Kohlepulver und Naturgraphit.The particularly difficult to sieve powders include, in particular, electrostatically charging substances such as plastic powders (e.g. PVC, polystyrene, polyethylene, polypropylene etc.). Also fabrics with a fibrous grain shape, e.g. Tobacco dust, tea, leaf drugs, etc., cause difficulties when sieving. Materials with a low specific weight, such as carbon powder and natural graphite, are also problematic.

Man versucht, durch geerdete, metallische Siebgewebe, durch eine luftzugarme Siebdeckbewegung und durch diverse Siebhilfen die Probleme zu bewältigen. Zu den Siebhilfen gehören z.B. Klopfbälle, die gegen die Unterseite des Siebdecks stoßen, oder Bürsten, die das Siebgut durch die Maschen des Siebes passieren.Attempts are being made to overcome the problems by using grounded, metallic sieve mesh, a low-draft screen movement and various sieve aids. The screening aids include e.g. Tapping balls that hit the underside of the screen deck or brushes that pass the screenings through the mesh of the screen.

Die bisherigen Methoden sind jedoch mit wesentlichen Nachteilen verbunden. So können ausgefallene Borsten der Bürsten oder Abrieb der Klopfbälle das Siebprodukt verunreinigen. Auch können die anstreifenden Bürsten das Siebgewebe zerstören. Außerdem läuft nach wie vor ein hoher Anteil Feingut ins Grobgut über, d.h. der sog. Fehlkornanteil ist sehr hoch.However, the previous methods are associated with significant disadvantages. Fancy bristles on the brushes or abrasion of the tapping balls can contaminate the sieve product. The brushes can also destroy the screen mesh. In addition, a large proportion of fine material continues to flow into the coarse material, i.e. the so-called false grain fraction is very high.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Siebverfahren bereitzustellen, mit dem eine effektive Siebung insbesondere schwer siebbaren Siebgutes gewahrleistet wird, ohne daß die Nachteile herkömmlicher Verfahren auftreten.The present invention has for its object to provide a screening method with which an effective screening, in particular difficult to screen screenable material is ensured without the disadvantages of conventional methods.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß dem Siebgut vor und/oder während des Siebvorgangs ein grobkörniges Substrat zugegeben wird.This object is achieved in that a coarse-grained substrate is added to the screenings before and / or during the screening process.

Das grobkörnige Substrat besitzt eine Korngröße, die deutlich über der Maschenweite des Siebgewebes liegt, so daß es selbst nicht der Siebung unterworfen wird. Die um vieles größeren Substratpartikel wirken als Siebhilfe für die sehr feinen Siebgutpartikel und treiben diese, unbeeinflußt von Elektrostatik und Luftzug durch die Siebmaschen. Als grobkörniges Substrat kommt beispielsweise Granulat in Frage, dessen Partikelgröße um ein Vielfaches über der Maschenweite des Siebgewebes liegt. Vorzugsweise wird als grobkörniges Substrat ein in Bezug auf das Siebgut arteigener Stoff verwendet.The coarse-grained substrate has a grain size that is well above the mesh size of the screen fabric, so that it is not itself subjected to screening. The much larger substrate particles act as a sieve aid for the very fine sieve particles and drive them through the sieve meshes, unaffected by electrostatics and drafts. As a coarse-grained substrate, for example, granulate comes into question, the particle size of which is many times larger than the mesh size of the screen fabric. Preferably, a substance specific to the material to be screened is used as the coarse-grained substrate.

In einer besonders bevorzugten Ausführungsform der Erfindung ist das Siebverfahren in ein Verfahren zur Zerkleinerung grobkörnigen Substrats integriert. Das grobkörnige Substrat, beispielsweise grobkörniges Granulat wie Kunststoffpartikel, Gewürzkörner, Nüsse etc., wird z.B. in einer Hammermühle zu feinkörnigem Pulver zermahlen. Das feinkörnige Pulver wird einem einfachen Maschensieb zugeführt, um ein Pulver mit definierter Kornobergrenze zu erhalten. Vor und/oder während des Siebvorgangs wird das grobkörnige Substrat dem feinkörnigen Pulver, bevorzugt in einem beispielsweise mit einem Schnekkenantrieb versehenen Mischer, zugemischt. Die um ein Vielfaches größeren Partikel des grobkörnigen Substrats treiben die feinen Pulverpartikel durch die Siebmaschen.In a particularly preferred embodiment of the invention, the screening process is integrated into a process for comminuting coarse-grained substrate. The coarse-grained substrate, for example coarse-grained granules such as plastic particles, spice grains, nuts etc., is e.g. grind to a fine grain powder in a hammer mill. The fine-grained powder is fed into a simple mesh screen in order to obtain a powder with a defined upper grain limit. Before and / or during the screening process, the coarse-grained substrate is mixed with the fine-grained powder, preferably in a mixer provided, for example, with a screw drive. The many times larger particles of the coarse-grained substrate drive the fine powder particles through the sieve mesh.

Vorzugsweise ist die Zerkleinerung des grobkörnigen Substrats der Siebung nachgeschaltet, wobei das bei der Zerkleinerung anfallende feinkörnige Siebgut zur Siebung zurückgeführt wird. Das zu zerkleinernde grobkörnige Substrat wird zunächst dem Siebgut vor und/oder während des Siebvorgangs zugemischt, wird anschließend vom Sieb abgezogen und schließlich der Zerkleinerung zugeführt.The comminution of the coarse-grained substrate is preferably carried out downstream of the screening, the fine-grained screenings resulting from the comminution being returned to the screening. The coarse-grained substrate to be shredded is first mixed with the material to be screened before and / or during the sieving process, is then removed from the sieve and finally fed to the shredding.

Um ein besonders feinkörniges Pulver zu erhalten, erfolgt die Zerkleinerung des grobkörnigen Substrats zweckmäßigerweise in einer Kaltmahlanlage, wobei das grobkörnige Substrat vor und/oder während der Zerkleinerung mittels eines kryogenen Kältemittels gekühlt wird. Dabei fällt kaltes Abgas an, das vorzugsweise zumindest teilweise zur Spülung des Siebes und/oder des Mischers verwendet wird.In order to obtain a particularly fine-grained powder, the coarse-grained substrate is expediently comminuted in a cold grinding system, the coarse-grained substrate being cooled by means of a cryogenic refrigerant before and / or during the comminution. This produces cold exhaust gas, which is preferably used at least partially to purge the sieve and / or the mixer.

Mit dem erfindungsgemäßen Verfahren wird eine Absiebung sehr feiner Pulver mit dem Vorteil einer exakt definierten Kornobergrenze und einem sehr geringen Fehlkornanteil erreicht. Bei Anwendung des Verfahrens in einer Kaltmahlanlage wird zusätzlich eine Vorkühlung des zu zerkleinernden grobkörnigen Substrats sowie eine Reduzierung des Kältemittelverbrauchs erzielt. Als Siebe können standardmäßige Vibrations-, Kreisschwing-, Taumel- oder Trommelsiebe ohne besondere Zusatzeinrichtungen, wie z.B. Bürst- oder Klopfeinrichtungen, zur Anwendung kommen.With the method according to the invention, a sieving of very fine powders is achieved with the advantage of an exactly defined upper grain limit and a very low proportion of missing grains. When using the method in a cold grinding system, pre-cooling of the coarse-grained substrate to be shredded and a reduction in the refrigerant consumption are additionally achieved. Standard vibrating, circular vibrating, tumbling or drum sieves can be used as sieves without special additional devices, e.g. Brushing or tapping devices are used.

Im folgenden soll die Erfindung anhand eines Ausführungsbeispiels näher erläutert werden.

  • Figur 1 zeigt ein Fließschema einer Kaltmahlanlage mit vorgeschalteter Siebmaschine.
  • Figur 2 zeigt eine graphische Darstellung des Siebergebnisses in Abhängigkeit von der zugegebenen Menge an grobkörnigem Substrat zum Siebgut.
In the following, the invention will be explained in more detail using an exemplary embodiment.
  • FIG. 1 shows a flow diagram of a cold grinding plant with an upstream screening machine.
  • FIG. 2 shows a graphic representation of the screening result as a function of the amount of coarse-grained substrate added to the screenings.

Die in Figur 1 dargestellte Kaltmahlanlage ist für die Zerkleinerung von grobkörnigem Substrat, insbesondere von Granulat, wie z.B. Kunststoffgranulat, zu feinkörnigem Pulver vorgesehen. Das Granulat wird über Zuleitung 1 und ein in die Zuleitung 1 eingeschaltetes, zur Dosierung dienendes, Zellrad 2 einem Mischer 3 zugeführt, der z.B. einen Schneckenantrieb aufweist. Im Mischer 3 wird das Granulat mit dem bei der Zerkleinerung des Granulats in einer nachgeschalteten Mühle 4 anfallenden feinkörnigen Pulver, das als Siebgut der Siebung zugeführt werden soll, homogen vermischt. Die entstehende Mischung wird über eine Zuführung 5 einer Siebmaschine 6 aufgegeben. Die Siebmaschine 6 kann z.B. ein standardmäßiger Vibrations-, Kreisschwing-, Taumel- oder Trommelsieb sein. Die um ein Vielfaches größeren Granulatpartikel dienen als Siebhilfe für das feinkörnige Pulver und treiben die sehr feinen Pulverpartikel, unbeeinflußt von Elektrostatik und Luftzug, durch die Siebmaschen. Das durch die Siebmaschen getriebene Feingut, das eine exakt definierte Kornobergrenze aufweist, wird über Leitung 7 zur weiteren Verwendung abgezogen. Das nicht durch die Siebmaschen gehende Granulat wird über Leitung 8 zunächst einem Zwischenbehälter 9 zugeführt und anschließend über ein Dosierzellrad 10 einer Kühlschnecke 11 aufgegeben, die mit einem kryogenen Kältemittel, insbesondere flüssigem Stickstoff beaufschlagt wird. Das gefrorene und versprödete Granulat wird über Leitung 12 der Mühle 4, die beispielsweise als Hammermühle ausgebildet sein kann, zugeführt. In der Mühle 4 wird das gefrorene Granulat zu sehr feinem Pulver mit Korngrößen im Mikrometerbereich zermahlen. Das Pulver wird über Leitung 13 abgezogen und einem Zyklon 14 zugeführt, in dem eine Abtrennung von Feinstaub erfolgt. Der Feinstaub wird mittels eines Gebläses 17 vom Zyklon 14 abgesaugt und über ein Filter 15 geleitet. Der anfallende Filterstaub wird über Leitung 16 abgezogen. Das als Siebgut vorgesehene Pulver wird über Leitung 18 dem Mischer 3 zugeführt, in dem es mit dem zu zerkleinernden Granulat homogen vermischt wird. Durch die Vermischung des aus der Mühle 4 abgezogenen kalten Pulvers mit dem Granulat, also dem Mahlgut, erfolgt auch eine Vorkühlung des Mahlgutes, wodurch der Verbrauch an kryogenem Kältemittel bei der Kaltmahlung reduziert wird.The cold grinding plant shown in FIG. 1 is for the comminution of coarse-grained substrate, in particular from granules, such as plastic granules, to fine-grained powder. The granules are fed via a feed line 1 and a cell wheel 2, which is switched into the feed line 1 and serves for dosing, to a mixer 3 which has, for example, a worm drive. In the mixer 3, the granulate is homogeneously mixed with the fine-grained powder which is obtained in the comminution of the granulate in a downstream mill 4 and which is to be fed to the sieving as sieving material. The resulting mixture is fed via a feed 5 of a screening machine 6. The screening machine 6 can be, for example, a standard vibrating, circular vibrating, tumbling or drum screen. The many times larger granulate particles serve as a sieving aid for the fine-grained powder and drive the very fine powder particles through the sieve meshes, unaffected by electrostatics and drafts. The fine material driven through the sieve mesh, which has a precisely defined upper grain limit, is drawn off via line 7 for further use. The granules which do not pass through the sieve mesh are first fed to an intermediate container 9 via line 8 and then fed via a metering cell wheel 10 to a cooling screw 11 which is charged with a cryogenic refrigerant, in particular liquid nitrogen. The frozen and embrittled granules are fed via line 12 to the mill 4, which can be designed, for example, as a hammer mill. In the mill 4, the frozen granulate is ground into very fine powder with grain sizes in the micrometer range. The powder is drawn off via line 13 and fed to a cyclone 14, in which fine dust is separated off. The fine dust is extracted from the cyclone 14 by means of a fan 17 and passed through a filter 15. The resulting filter dust is drawn off via line 16. The powder intended as screenings is fed to the mixer 3 via line 18, in which it is homogeneously mixed with the granules to be comminuted. By mixing the cold powder withdrawn from the mill 4 with the granules, ie the regrind, the regrind is also pre-cooled, as a result of which the consumption of cryogenic refrigerant during cold grinding is reduced.

In der Kühlschnecke 11 anfallendes kaltes Abgas wird über eine Abgasleitung 19 abgezogen und teilweise über eine Spülgasleitung 20 zum Mischer 3 und zur Siebmaschine 6 geführt, um diese Anlagenteile mit Kaltgas zu spülen, wodurch ebenfalls eine Vorkühlung des Mahlgutes erfolgt. Der Rest des Abgases wird gemeinsam mit der vom Filter 15 abgezogenen Abluft über Leitung 21 und eine zwischengeschaltete Drosselklappe 22 an die Atmosphäre abgegeben.Cold exhaust gas occurring in the cooling screw 11 is drawn off via an exhaust gas line 19 and partly led via a flushing gas line 20 to the mixer 3 and to the screening machine 6 in order to purge these parts of the system with cold gas, which likewise results in pre-cooling of the ground material. The rest of the exhaust gas is released to the atmosphere together with the exhaust air drawn off from the filter 15 via line 21 and an interposed throttle valve 22.

Figur 2 zeigt einen Vergleich der Siebergebnisse von Versuchssiebungen mit Polyesterpulver. Dabei wurde ein Plansieb mit einer Maschenweite von 125 mm verwendet, der als Kreisschwinger arbeitete. In dem Diagramm ist jeweils die Verteilung von Feingut und Grobgut angegeben (wobei unter "Feingut" Partikel mit einer Partikelgröße zu verstehen sind, die unterhalb einer definierten Kornobergrenze liegt, die durch die Maschenweite des Siebes bestimmt wird; während "Grobgut" solche Partikel bezeichnet, deren Größe oberhalb der Kornobergrenze liegt).Figure 2 shows a comparison of the sieving results of test sieving with polyester powder. A 125 mm mesh screen was used, which worked as a circular oscillator. The diagram shows the distribution of fine and coarse material (whereby “fine material” means particles with a particle size below a defined upper grain limit, which is determined by the mesh size of the sieve; while “coarse material” denotes such particles, whose size is above the upper grain limit).

Die Graphik I zeigt das Ergebnis einer Siebung nach dem Stand der Technik, d.h. ohne Zugabe von Granulat. Die Graphiken 11 und 111 zeigen die Ergebnisse bei der erfindungsgemäßen Siebung, wobei im Falle 11 ein Granulatanteil von 50% im Feingut eingestellt wurde, während im Falle III bei einem Granulatanteil von 33% gearbeitet wurde.Graph I shows the result of a screening according to the prior art, i.e. without adding granules. The graphs 11 and 111 show the results of the screening according to the invention, wherein in case 11 a granulate content of 50% was set in the fine material, while in case III the granulate content was 33%.

Wie aus einem Vergleich der Graphiken I, 11 und III hervorgeht, liegt der effektive Grobgutanteil (G) (d.h. der Anteil an Partikeln, die wegen ihrer Größe nicht durch die Siebmaschen hindurchtreten können) bei allen Versuchen bei ca. 10%. Bei der Siebung nach dem Stand der Technik (Graphik I) ist jedoch ein hoher Anteil von Feingut im Grobgut (FG) von 55% vorhanden (d.h. es geht Feingut, das eigentlich aufgrund der geringen Partikelgröße durch die Siebmaschen hindurchtreten könnte, nicht durch die Siebmaschen hindurch, sondern sammelt sich im Grobgut als sog. Fehlkorn an). Bei den Siebversuchen gemäß der vorliegenden Erfindung (Graphik 11, 111) geht dagegen kein Feingut in das Grobgut über, der Anteil des Feingutaustrages (F) liegt in beiden Fällen bei ca. 90%.As can be seen from a comparison of the graphs I, 11 and III, the effective coarse material fraction (G) (i.e. the fraction of particles that cannot pass through the sieve mesh due to their size) is approx. 10% in all tests. In the screening according to the prior art (graphic I), however, there is a high proportion of fine material in the coarse material (FG) of 55% (ie fine material that could actually pass through the sieve mesh due to the small particle size does not pass through the sieve mesh through, but accumulates in the coarse material as so-called faulty grain). In contrast, in the sieve tests according to the present invention (graphic 11, 111), no fine material passes into the coarse material, the proportion of the fine material discharge (F) is approximately 90% in both cases.

Diese Versuchssiebungen zeigen, daß mit dem erfindungsgemäßen Siebverfahren eine Absiebung sehr feiner Pulver mit dem Vorteil einer exakt definierten Kornobergrenze und eines sehr geringen Fehlkornanteils (im vorliegenden Fall praktisch 0) erreicht wird.These test sieves show that the sieving process according to the invention achieves a sieving of very fine powders with the advantage of a precisely defined upper grain limit and a very low proportion of missing grains (practically 0 in the present case).

Claims (5)

1. Verfahren zum Sieben eines feinkörnigen Siebgutes, dadurch gekennzeichnet, daß dem Siebgut vor und/oder während des Siebvorgangs ein grobkörniges Substrat zugegeben wird.1. A method for sieving a fine-grained screenings, characterized in that a coarse-grained substrate is added to the screenings before and / or during the screening process. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß als grobkörniges Substrat ein in Bezug auf das Siebgut arteigener Stoff verwendet wird.2. The method according to claim 1, characterized in that is used as a coarse-grained substrate with respect to the material to be screened substance. 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß das feinkörnige Siebgut durch Zerkleinerung des grobkörnigen Substrats hergestellt wird.3. The method according to claim 2, characterized in that the fine-grained screenings are produced by crushing the coarse-grained substrate. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß die Zerkleinerung des grobkörnigen Substrats der Siebung nachgeschaltet ist und das bei der Zerkleinerung anfallende feinkörnige Siebgut zur Siebung zurückgeführt wird.4. The method according to claim 3, characterized in that the comminution of the coarse-grained substrate of the sieving is downstream and the fine-grained screenings obtained in the comminution is returned to the sieving. 5. Verfahren nach Anspruch 3 oder 4, dadurch gekennzeichnet, daß das grobkörnige Substrat vor und/oder während der Zerkleinerung mittels eines kryogenen Kältemittels gekühlt wird und dabei anfallendes kaltes Abgas zumindest teilweise zur Spülung während des Siebvorgangs verwendet wird.5. The method according to claim 3 or 4, characterized in that the coarse-grained substrate is cooled before and / or during comminution by means of a cryogenic refrigerant and cold exhaust gas is used at least partially for purging during the screening process.
EP19920103817 1991-03-12 1992-03-06 Method for screening a fine-grained material Withdrawn EP0508109A3 (en)

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DE4107872 1991-03-12
DE19914107872 DE4107872A1 (en) 1991-03-12 1991-03-12 METHOD FOR SEVENING A FINE-GRAINED MATERIAL

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DE102010007004A1 (en) 2010-02-05 2011-08-11 Linde AG, 80331 Method for filtering or screening of goods, involves glazing cryogenic medium to goods before filtering to cool goods, where nitrogen or carbon dioxide, particularly in form of carbon dioxide pallet or snow is used as cryogenic medium

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB863093A (en) * 1958-04-01 1961-03-15 Beteiligungs Uend Patentverwal Oscillating sieve for greasy material
US4249906A (en) * 1979-12-17 1981-02-10 Howell Phillip C Method and apparatus for handling flux fines
EP0044506A1 (en) * 1980-07-18 1982-01-27 TYCZKA GmbH & Co. Gesellschaft für Gase, Wassertechnik, Engineering Separation method for different plastic materials
EP0221377A2 (en) * 1985-11-02 1987-05-13 Fried. Krupp Gesellschaft mit beschränkter Haftung Method of finely grinding mineral material and device for carrying out the method
EP0238432A2 (en) * 1986-02-14 1987-09-23 Nordberg Inc. Method and apparatus for energy efficient comminution

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB863093A (en) * 1958-04-01 1961-03-15 Beteiligungs Uend Patentverwal Oscillating sieve for greasy material
US4249906A (en) * 1979-12-17 1981-02-10 Howell Phillip C Method and apparatus for handling flux fines
EP0044506A1 (en) * 1980-07-18 1982-01-27 TYCZKA GmbH & Co. Gesellschaft für Gase, Wassertechnik, Engineering Separation method for different plastic materials
EP0221377A2 (en) * 1985-11-02 1987-05-13 Fried. Krupp Gesellschaft mit beschränkter Haftung Method of finely grinding mineral material and device for carrying out the method
EP0238432A2 (en) * 1986-02-14 1987-09-23 Nordberg Inc. Method and apparatus for energy efficient comminution

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