EP0504451B1 - Process and apparatus for charging particles - Google Patents

Process and apparatus for charging particles Download PDF

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Publication number
EP0504451B1
EP0504451B1 EP19910104306 EP91104306A EP0504451B1 EP 0504451 B1 EP0504451 B1 EP 0504451B1 EP 19910104306 EP19910104306 EP 19910104306 EP 91104306 A EP91104306 A EP 91104306A EP 0504451 B1 EP0504451 B1 EP 0504451B1
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EP
European Patent Office
Prior art keywords
tube
particles
electrode
insert
charging
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EP19910104306
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German (de)
French (fr)
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EP0504451A1 (en
Inventor
Bernd Dr. Gellert
Andreas Kwetkus
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ABB Asea Brown Boveri Ltd
ABB AB
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ABB Asea Brown Boveri Ltd
Asea Brown Boveri AB
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Priority to DE59107949T priority Critical patent/DE59107949D1/en
Priority to ES91104306T priority patent/ES2090160T3/en
Priority to EP19910104306 priority patent/EP0504451B1/en
Publication of EP0504451A1 publication Critical patent/EP0504451A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C7/00—Separating solids from solids by electrostatic effect
    • B03C7/006—Charging without electricity supply, e.g. by tribo-electricity, pyroelectricity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/28—Plant or installations without electricity supply, e.g. using electrets
    • B03C3/30—Plant or installations without electricity supply, e.g. using electrets in which electrostatic charge is generated by passage of the gases, i.e. tribo-electricity

Definitions

  • the invention relates to a method for charging particles according to the introductory part of claim 1 and to a device for carrying out the method.
  • Coal particles are finely ground particles in a friction charger (TRIBO charger) by collisions with solids, e.g. Walls, charged.
  • Friction chargers of this type are described, for example, in the brochure "ESB electrostatic automatic powder coating systems", page 13, from the company ESB, Meersburg (FRG), undated. This charge strongly depends on the dielectric properties of the particles.
  • a good insulator is charged differently than a bad one, so that the good insulator material can be separated from the bad one in an electrical field. For example, in the treatment of coal dust, the sulfur-containing components are separated.
  • Frictional charging and subsequent electrostatic separation also play a role in other processes in which particles are to be applied or removed, e.g. when applying powder coatings on automobile bodies or when separating dusts from exhaust gases.
  • the contact charging of solids is strongly dependent on the electrical properties of the materials.
  • the charge density that can be achieved is generally proportional to the difference the electron work function, ie the energy required to extract an electron from the solid. In the technical application of this effect in a friction supercharger, special care must be taken to choose the right materials.
  • Another important criterion is the fluidic design, since it is a two-phase flow with electrically charged particles. For example, if the particles pass through a cylindrical tube in order to be charged by wall impacts, there is a charge gradient in the longitudinal direction of the tube between the entrance of the tube, where only a few particles are loaded, and the outlet, where many are loaded. In the tube itself, this leads to mutual interference between the particles, so that the efficiency of charging can be reduced.
  • a free-fall separator is known from DE-B-1,084,246, in which gas loaded with floating particles reaches a centrifugal chamber from above. Its end is provided with a conical insert made of material generating friction electricity. At the lower end of the centrifugal chamber, a cone is fastened in an electrically insulated manner from this and the insert. The cone has a plate in which a spray electrode is attached, which extends into the interior of the centrifugal chamber. The suspended particles, which are electrically charged as a result of frictional electricity, leave the centrifugal chamber at high speed and hit the cone, where they release their electrical charge. Since it is electrically insulated, the cone and thus the spray electrode are charged with high voltage. In this way, a significant increase in separation efficiency is to be achieved.
  • electrostatic centrifugal separators as are known, for example, from GB-A-1,152,218, a type of electrostatic pre-charging of the ones to be separated has been achieved or particles to be separated from one another. There, the particle stream crosses a constant electrical field that is present between the two walls.
  • the invention is based on the object of specifying a method for separation in which the charged particles leave the frictional charging region as quickly as possible after charging. It is also an object of the invention to provide a device which is suitable for carrying out the method.
  • the method according to the invention is particularly suitable for separating ash-forming and sulfur-containing constituents in pulverized coal and is distinguished by a high separation efficiency.
  • the device for carrying out the method according to the invention is characterized by a compact structure and enables the charged particles to leave the friction charging area as quickly as possible after charging.
  • a first electrode 2 running in the longitudinal direction of the tube is arranged in a first tube 1 which is at earth potential and has a negative potential with respect to earth potential.
  • a first tube 1 which is at earth potential and has a negative potential with respect to earth potential.
  • sieve-shaped extension 3 which has a funnel-shaped end 4 with an outlet opening 5.
  • the first electrode 2 extends into the funnel-shaped end 4 of the extension 3.
  • This approach 3 is usually made of metal and is at ground potential. However, it can also consist of a dielectric material. To prevent the formation of surface charges that are too large, which would distort the field too much, however, partial areas of the screen-like attachment 3 would have to be metallized, for example in the form of strips from top to bottom.
  • a second tube 6 coaxially surrounds the sieve-shaped attachment 3 while leaving an annular gap 7 and serves as a second electrode lying at positive potential.
  • a gas stream 8 symbolized by arrows can be introduced into the annular space 7 through this annular gap 7.
  • a collecting funnel 9 is provided under the outlet opening 5.
  • a rotationally symmetrical guide device 10 is arranged at the lower end of the second pipe 6 and within the same.
  • the first tube 1 consists of a material suitable for optimal frictional charging. Alloys of metals with rare earths, such as lanthanum, cerium, cerium iron, or metal parts coated or vapor-coated with rare earths are particularly suitable. It is particularly advantageous to insert an insert 11 made of such a material into the tube 1.
  • the insert 11 consists of a spirally wound metal band, which rests everywhere on the inner wall of the tube 1 and is replaceable.
  • a spiral insert 11a with turns spaced apart from one another and thus enlarged surface made of the specified material can also be used according to FIG. Another possibility according to FIG.
  • this insert is to insert an insert 11b into the interior of the tube 1, which is distanced from the inner wall and is electrically insulated both from the tube 1 and from the inner electrode 2.
  • this insert consists of a spiral made of round wire made of the special material mentioned, the individual turns not touching one another.
  • the inner diameter of the insert 11b and its distance from the wall of the tube 1 depends on the size of the electric field and must be chosen so that no additional arcing occurs.
  • the operation of the device described above can be seen from the following:
  • the mixture containing the particles to be separated is fed at the upper end of the tube 1 in the direction of the arrow.
  • the particles are negatively charged by contact with the tube walls.
  • the low work function of the rare earths ensures a high negative charge of the particles.
  • the field is used for accelerated discharge at the end of the tribo-charger (pipe 1). Particles charged with the wall once are additionally driven to the wall by the electric field and experience multiple impacts, which leads to a higher charge especially in the case of insulating particles.
  • the field strengths used should be as high as possible and are in the range from a few kV / cm to a few 10 kV / cm.
  • the particles charged in this way are deflected in the sieve-shaped approach under the influence of the field acting between the inner electrode 1 and outer electrode 6 to the (positive) outer electrode 6 and conveyed through the stitches 12 of the sieve-like approach 3.
  • the particles Before reaching the positive electrode (tube 6), the particles are entrained and discharged by the outer gas stream 8 at a suitable flow rate.
  • Negatively charged particles that reach the positive electrode lose their charge can be removed from the electrode by suitable devices, for example tapping devices, brushes or the like, and can be fed back to the charger. The same applies to particles that have not received sufficient charging in the charger. These pass through the lower part of the funnel-shaped end 4 into the collecting funnel 9 and are also returned.
  • the present invention was explained on the basis of a coaxial arrangement of inner tube 1, inner electrode 2 and outer electrode (second tube 6).
  • plate arrangements are also conceivable.
  • the coaxial arrangement has the advantage of having a particularly homogeneous field (without edge losses).

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  • Electrostatic Separation (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren zur Aufladung von Partikeln gemäss dem einleitenden Teil des Anspruchs 1 sowie auf eine Einrichtung zur Durchführung des Verfahrens.The invention relates to a method for charging particles according to the introductory part of claim 1 and to a device for carrying out the method.

TECHNOLOGISCHER HINTERGRUND UND STAND DER TECHNIKTECHNOLOGICAL BACKGROUND AND PRIOR ART

Bei der elektrostatischen Separation von Partikeln, z.B. Kohleteilchen, werden in einem Reibungsauflader (TRIBO-Auflader) fein gemahlene Partikel durch Stösse an Festkörpern, z.B. Wänden, aufgeladen. Reibungsauflader dieser Art sind beispielsweise im Prospekt "ESB Elektrostatik-Automatik-Pulverbeschichtungs-Systeme", Seite 13, der Firma ESB, Meersburg (BRD), undatiert, beschrieben. Diese Aufladung hängt stark von den dielektrischen Eigenschaften der Partikel ab. Ein guter Isolator wird dabei anders als ein schlechter aufgeladen, sodass man das gute Isolatormaterial vom schlechten in einem elektrischen Feld trennen kann. So können z.B. bei der Behandlung von Kohlestaub die schwefelhaltigen Bestandteile abgetrennt werden.In the electrostatic separation of particles, e.g. Coal particles are finely ground particles in a friction charger (TRIBO charger) by collisions with solids, e.g. Walls, charged. Friction chargers of this type are described, for example, in the brochure "ESB electrostatic automatic powder coating systems", page 13, from the company ESB, Meersburg (FRG), undated. This charge strongly depends on the dielectric properties of the particles. A good insulator is charged differently than a bad one, so that the good insulator material can be separated from the bad one in an electrical field. For example, in the treatment of coal dust, the sulfur-containing components are separated.

Die Reibungsaufladung und nachfolgende elektrostatische Trennung spielt aber auch bei anderen Verfahren eine Rolle, bei denen Partikel appliziert oder entfernt werden sollen, z.B. bei der Auftragung von Pulverlacken auf Automobilkarossen oder der Abtrennung von Stäuben aus Abgasen.Frictional charging and subsequent electrostatic separation also play a role in other processes in which particles are to be applied or removed, e.g. when applying powder coatings on automobile bodies or when separating dusts from exhaust gases.

Die Kontaktaufladung von Festkörpern ist stark abhängig von den elektrischen Eigenschaften der Materialien. Die erreichbare Ladungsdichte ist im allgemeinen proportional der Differenz der Elektronenaustrittsarbeit, d.h. der Energie, die benötigt wird, um ein Elektron aus dem Festkörper herauszulösen. Bei der technischen Anwendung dieses Effektes in einem Reibungsauflader ist daher besonders auf die geeignete Wahl der Materialien zu achten. Ein weiteres wichtiges Kriterium ist die strömungstechnische Auslegung, da es sich hier um eine Zweiphasenströmung mit elektrisch geladenen Partikeln handelt. Durchlaufen die Partikel z.B. ein zylindrisches Rohr, um darin durch Wandstösse aufgeladen zu werden, so kommt es in Rohrlängsrichtung zu einem Ladungsgefälle zwischen dem Eintritt des Rohres, wo noch wenige Teilchen geladen sind, und dem Austritt, wo sehr viele geladen sind. Im Rohr selbst kommt es dadurch zu gegenseitigen Beeinflussungen der Teilchen, sodass die Effizienz der Aufladung vermindert werden kann.The contact charging of solids is strongly dependent on the electrical properties of the materials. The charge density that can be achieved is generally proportional to the difference the electron work function, ie the energy required to extract an electron from the solid. In the technical application of this effect in a friction supercharger, special care must be taken to choose the right materials. Another important criterion is the fluidic design, since it is a two-phase flow with electrically charged particles. For example, if the particles pass through a cylindrical tube in order to be charged by wall impacts, there is a charge gradient in the longitudinal direction of the tube between the entrance of the tube, where only a few particles are loaded, and the outlet, where many are loaded. In the tube itself, this leads to mutual interference between the particles, so that the efficiency of charging can be reduced.

Aus der DE-B-1.084.246 ist ein Freifallscheider bekannt, bei welchem mit Schwebeteilchen beladenes Gas von oben in eine Schleuderkammer gelangt. Ihr Ende ist mit einem konischen Einsatzstück aus Reibungselektrizität erzeugendem Material versehen. Am unteren Ende der Schleuderkammer ist von dieser und dem Einsatzstück ein Konus elektrisch isoliert befestigt. Der Konus weist eine Platte auf, in welcher eine Sprühelektrode befestigt ist, die in das Innere der Schleuderkammer reicht. Die infolge Reibungselektrizität elektrisch geladenen Schwebeteilchen verlassen mit hoher Geschwindigkeit die Schleuderkammer und treffen auf den Konus, an dem sie ihre elektrische Ladung abgeben. Da derselbe elektrisch isoliert ist, wird der Konus und damit die Sprühelektrode mit hoher Spannung aufgeladen. Auf die Weise soll eine wesentliche Erhöhung der Abscheideleistung erzielt werden.A free-fall separator is known from DE-B-1,084,246, in which gas loaded with floating particles reaches a centrifugal chamber from above. Its end is provided with a conical insert made of material generating friction electricity. At the lower end of the centrifugal chamber, a cone is fastened in an electrically insulated manner from this and the insert. The cone has a plate in which a spray electrode is attached, which extends into the interior of the centrifugal chamber. The suspended particles, which are electrically charged as a result of frictional electricity, leave the centrifugal chamber at high speed and hit the cone, where they release their electrical charge. Since it is electrically insulated, the cone and thus the spray electrode are charged with high voltage. In this way, a significant increase in separation efficiency is to be achieved.

Auch bei sogenannten elektrostatischen Zentrifugalscheidern, wie sie beispielsweise aus der GB-A-1,152,218 bekannt sind, wurde eine Art elektrostatische Voraufladung der abzuscheidenden bzw. voneinander zu trennenden Partikel angewandt. Dort durchquert der Partikelstrom ein elektrisches Gleichfeld, das zwischen den beiden Wänden anliegt.Also in the case of so-called electrostatic centrifugal separators, as are known, for example, from GB-A-1,152,218, a type of electrostatic pre-charging of the ones to be separated has been achieved or particles to be separated from one another. There, the particle stream crosses a constant electrical field that is present between the two walls.

KURZE DARSTELLUNG DER ERFINDUNGSUMMARY OF THE INVENTION

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Separation anzugeben, bei welchem die geladenen Teilchen möglichst schnell nach der Aufladung den Reibungsaufladungsbereich verlassen. Aufgabe der Erfindung ist es ferner, eine zur Durchführung des Verfahrens geeignete Einrichtung zu schaffen.The invention is based on the object of specifying a method for separation in which the charged particles leave the frictional charging region as quickly as possible after charging. It is also an object of the invention to provide a device which is suitable for carrying out the method.

Diese Aufgabe wird bei einem Verfahren der eingangs genannten Gattung durch die im Anspruch 1 gekennzeichneten Merkmale gelöst.This object is achieved in a method of the type mentioned by the features characterized in claim 1.

Das erfindungsgemässe Verfahren eignet sich insbesondere zur Abtrennung aschebildender und schwefelhaltiger Bestandteile in pulverisierter Kohle und zeichnet sich durch hohe Abscheideleistung aus.The method according to the invention is particularly suitable for separating ash-forming and sulfur-containing constituents in pulverized coal and is distinguished by a high separation efficiency.

Die Einrichtung zur Durchführung des erfindungsgemässen Verfahrens, wie sie in den Patentansprüchen 2 bis 7 gekennzeichnet ist, zeichnet sich durch einen kompakten Aufbau aus und ermöglicht es, dass die geladenen Teilchen möglichst schnell nach der Aufladung den Reibungsaufladungsbereich verlassen.The device for carrying out the method according to the invention, as characterized in claims 2 to 7, is characterized by a compact structure and enables the charged particles to leave the friction charging area as quickly as possible after charging.

Die Erfindung sowie weitere mit ihr erzielbare Vorteile werden nachstehend anhand eines in der Zeichnung dargestellten Ausführungsbeispiels näher erläutert.The invention and further advantages which can be achieved with it are explained in more detail below with reference to an embodiment shown in the drawing.

KURZE BESCHREIBUNG DER ZEICHNUNGENBRIEF DESCRIPTION OF THE DRAWINGS

In der Zeichnung ist in schematisierter Form eine Einrichtung zur elektrostatischen Separation von Partikeln dargestellt. Dabei zeigt

Fig.1
einen vereinfachten Längsschnitt durch einen feldunterstützten Reibungsauflader;
Fig.2
ein Detail aus dem Wandbereich des Rohres aus Fig.1 mit einem auf der Innenwand aufliegenden spiraligen Einsatz;
Fig.3
ein Detail aus dem Wandbereich des Rohres aus Fig.1 mit einem von der Innenwand distanzierten spiraligen Einsatz.
In the drawing, a device for electrostatic separation of particles is shown in schematic form. It shows
Fig. 1
a simplified longitudinal section through a field-assisted friction supercharger;
Fig. 2
a detail from the wall area of the tube of Figure 1 with a spiral insert lying on the inner wall;
Fig. 3
a detail from the wall area of the tube of Figure 1 with a spiral insert spaced from the inner wall.

DETAILLIERTE BESCHREIBUNG DER ERFINDUNGDETAILED DESCRIPTION OF THE INVENTION

Gemäss Fig.1 ist in einem auf Erdpotential liegenden ersten Rohr 1 eine in Rohrlängsrichtung verlaufende erste Elektrode 2 angeordnet, die gegenüber Erdpotential Negativ-Potential aufweist. Am unteren Ende des Rohres 1 schliesst sich ein siebartiger Ansatz 3 an, der ein trichterförmiges Ende 4 mit einer Austrittsöffnung 5 aufweist. Die erste Elektrode 2 ragt bis in das trichterförmige Ende 4 des Ansatzes 3 hinein. Dieser Ansatz 3 besteht normalerweise aus Metall und liegt auf Massepotential. Er kann aber auch aus einem dielektrischen Material bestehen. Damit sich keine zu grossen Oberflächenaufladungen bilden, wodurch das Feld zu stark verzerrt werden würde, müssten Teilbereiche des siebartigen Ansatzes 3 jedoch metallisiert sein, z.B. streifenförmig von oben nach unten.According to FIG. 1, a first electrode 2 running in the longitudinal direction of the tube is arranged in a first tube 1 which is at earth potential and has a negative potential with respect to earth potential. At the lower end of tube 1, it closes sieve-shaped extension 3, which has a funnel-shaped end 4 with an outlet opening 5. The first electrode 2 extends into the funnel-shaped end 4 of the extension 3. This approach 3 is usually made of metal and is at ground potential. However, it can also consist of a dielectric material. To prevent the formation of surface charges that are too large, which would distort the field too much, however, partial areas of the screen-like attachment 3 would have to be metallized, for example in the form of strips from top to bottom.

Ein zweites Rohr 6 umgibt unter Belassung eines Ringspaltes 7 koaxial den siebförmigen Ansatz 3 und dient als zweite, auf Positiv-Potential liegende zweite Elektrode. Durch diesen Ringspalt 7 ist ein durch Pfeile symbolisierter Gasstrom 8 in den Ringraum 7 einleitbar.A second tube 6 coaxially surrounds the sieve-shaped attachment 3 while leaving an annular gap 7 and serves as a second electrode lying at positive potential. A gas stream 8 symbolized by arrows can be introduced into the annular space 7 through this annular gap 7.

Unter der Austrittsöffnung 5 ist ein Auffangtrichter 9 vorgesehen. Am unteren Ende des zweiten Rohres 6 und innerhalb desselben ist eine rotationssymmetrische Leiteinrichtung 10 angeordnet.A collecting funnel 9 is provided under the outlet opening 5. A rotationally symmetrical guide device 10 is arranged at the lower end of the second pipe 6 and within the same.

Das erste Rohr 1 besteht aus einem für optimale Reibungsaufladung geeigneten Material. In Frage kommen dabei besonders Legierungen von Metallen mit seltenen Erden, wie Lanthan, Cer, Cer-Eisen, oder mit seltenen Erden beschichtete oder bedampfte Metallteile. Besonders vorteilhaft ist es, in das Rohr 1 einen Einsatz 11 aus einem derartigen Material einzusetzen. Im Beispielsfall besteht der Einsatz 11 aus einem spiralig gewundenen Metallband, das überall an der Innenwand des Rohres 1 anliegt und auswechselbar ist. Anstelle eines an der Innenwand des Rohres 1 anliegenden und diese vollständig bedeckenden Einsatzes mit glatter Oberfläche kann gemäss Fig.2 auch ein spiraliger Einsatz 11a mit voneinander distanzierten Windungen und damit vergösserter Oberfläche aus dem genannten speziellen Material verwendet werden. Eine andere Möglichkeit besteht gemäss Fig.3 darin, in das Innere des Rohres 1 einen Einsatz 11b einzubringen, der von der Innenwand distanziert und elektrisch sowohl vom Rohr 1 als auch von der Innenelektrode 2 isoliert ist. Dieser Einsatz besteht im Beispielsfall aus einer aus Runddraht hergestellten Spirale aus dem genannten speziellen Material, wobei sich die einzelnen Windungen nicht berühren. Der Innendurchmesser des Einsatzes 11b und sein Abstand von der Wand des Rohres 1 hängt von der Grösse des elektrischen Feldes ab und muss aber so gewählt sein, dass keine zusätzlichen Ueberschläge entstehen. Durch Verwendung eines Einsatzes wird generell der Abrieb des speziellen Materials verringert und die Wartungsfreundlichkeit der Anlage erhöht. Bei einem spiraligen Einsatz mit distanzierten Windungen - sei es ein an der Wand anfliegender oder von ihr distanzierter, wird darüber hinaus noch die für die Reibungsaufladung wirksame Oberfläche vergrössert.The first tube 1 consists of a material suitable for optimal frictional charging. Alloys of metals with rare earths, such as lanthanum, cerium, cerium iron, or metal parts coated or vapor-coated with rare earths are particularly suitable. It is particularly advantageous to insert an insert 11 made of such a material into the tube 1. In the example, the insert 11 consists of a spirally wound metal band, which rests everywhere on the inner wall of the tube 1 and is replaceable. Instead of an insert with a smooth surface which lies against the inner wall of the tube 1 and completely covers it, a spiral insert 11a with turns spaced apart from one another and thus enlarged surface made of the specified material can also be used according to FIG. Another possibility according to FIG. 3 is to insert an insert 11b into the interior of the tube 1, which is distanced from the inner wall and is electrically insulated both from the tube 1 and from the inner electrode 2. In the example, this insert consists of a spiral made of round wire made of the special material mentioned, the individual turns not touching one another. The inner diameter of the insert 11b and its distance from the wall of the tube 1 depends on the size of the electric field and must be chosen so that no additional arcing occurs. By using an insert, the abrasion of the special material is generally reduced and the ease of maintenance of the system is increased. In the case of a spiral application with distant windings - be it against the wall or at a distance from it, the surface that is effective for frictional charging is also increased.

Die Wirkungsweise der im Vorstehenden beschriebenen Einrichtung geht aus folgendem hervor:
Das die zu trennenden Partikel enthaltende Gemenge wird am oberen Ende des Rohres 1 in Pfeilrichtung zugeführt. Die Partikel werden durch Kontakt mit den Rohrwänden negativ aufgeladen. Die niedrige Austrittsarbeit der seltenen Erden gewährleistet eine hohe negative Aufladung der Partikel. Das Feld dient zum beschleunigten Austrag am Ende des Triboaufladers (Rohr 1). Durch einmaligen Stoss mit der Wand aufgeladene Partikel werden zusätzlich vom elektrischen Feld verstärkt zur Wand getrieben und erfahren Mehrfachstösse, was speziell im Fall von isolierenden Teilchen zu höherer Aufladung führt. Die dabei angewandten Feldstärken sollen so hoch wie möglich sein und liegen im Bereich von einigen kV/cm bis einigen 10 kV/cm. Die so aufgeladenen Teilchen werden im siebförmigen Ansatz unter Einfluss des zwischen der Innenelektrode 1 und Aussenelektrode 6 wirkenden Feldes zur (positiven) Aussenelektrode 6 abgelenkt und durch die Maschen 12 des siebartigen Ansatzes 3 befördert. Vor dem Erreichen der positiven Elektrode (Rohr 6) werden die Teilchen durch den äusseren Gasstrom 8 mit geeigneter Strömungsgeschwindigkeit mitgerissen und ausgetragen. Negativ geladene Teilchen, welche die positive Elektrode erreichen, verlieren ihre Ladung, können durch geeignete Vorrichtungen, z.B. Klopfvorrichtungen, Bürsten o.ä., von der Elektrode entfernt und dem Auflader erneut zugeführt werden. Gleiches gilt für Partikel, die im Auflader keine ausreichende Aufladung erhalten haben. Diese gelangen durch den unteren Teil des trichterförmigen Endes 4 in den Auffangtrichter 9 und werden ebenfalls zurückgeführt.The operation of the device described above can be seen from the following:
The mixture containing the particles to be separated is fed at the upper end of the tube 1 in the direction of the arrow. The particles are negatively charged by contact with the tube walls. The low work function of the rare earths ensures a high negative charge of the particles. The field is used for accelerated discharge at the end of the tribo-charger (pipe 1). Particles charged with the wall once are additionally driven to the wall by the electric field and experience multiple impacts, which leads to a higher charge especially in the case of insulating particles. The field strengths used should be as high as possible and are in the range from a few kV / cm to a few 10 kV / cm. The particles charged in this way are deflected in the sieve-shaped approach under the influence of the field acting between the inner electrode 1 and outer electrode 6 to the (positive) outer electrode 6 and conveyed through the stitches 12 of the sieve-like approach 3. Before reaching the positive electrode (tube 6), the particles are entrained and discharged by the outer gas stream 8 at a suitable flow rate. Negatively charged particles that reach the positive electrode lose their charge, can be removed from the electrode by suitable devices, for example tapping devices, brushes or the like, and can be fed back to the charger. The same applies to particles that have not received sufficient charging in the charger. These pass through the lower part of the funnel-shaped end 4 into the collecting funnel 9 and are also returned.

Die vorliegende Erfindung wurde anhand einer koaxialen Anordnung von Innenrohr 1, Innenelektrode 2 und Aussenelektrode (zweites Rohr 6) erläutert. Daneben sind auch Plattenanordnungen denkbar. Die koaxiale Anordnung hat jedoch den Vorteil, ein besonders homogenes Feld (ohne Randverluste) aufzuweisen.The present invention was explained on the basis of a coaxial arrangement of inner tube 1, inner electrode 2 and outer electrode (second tube 6). In addition, plate arrangements are also conceivable. However, the coaxial arrangement has the advantage of having a particularly homogeneous field (without edge losses).

Claims (7)

  1. Method for electrostatically charging particles by leading a stream of particles through a friction charger, the charging of the particles in the friction charger being supported by an electric field, characterized in that the charging in the friction charger is supported by an externally applied first electric field and the charged particles are separated from as yet uncharged particles after leaving the friction charger by the effects of a second externally applied electric field of reverse polarity and under the influence of this field are deflected outwards, and in that [lacuna], by an additional air stream (8) that is led outside the friction charger (1) and that does not affect the charged particles until after frictional charging, causing the deflected particles to be removed.
  2. Device for carrying out the method according to Claim 1, characterized by essentially an earthed cylindrical tube (1) having at least one first electrode (2) that is at a negative potential and extends in the longitudinal direction of the tube and at least one second electrode (6) that is at a positive potential and is arranged downstream of said tube (1) seen in the direction of flow of the particles, the lower part of said tube being constructed as a sieve or having a sieve-like attachment (3) that act as a separating zone, said separating zone being arranged in the sphere of action of the electric field between the first (2) and second electrode (6), and in that a gas auxiliary flow (8) in the direction of flow of the particles can be introduced into the annular space (7) between the two tubes (1, 6).
  3. Device according to Claim 2, characterized in that the cylindrical tube (1) consists of a material having a low work function, preferably of rare-earth elements, or is coated or vapour-deposited inside with such a material.
  4. Device according to Claim 2, characterized in that in the cylindrical tube (1) an insert (11, 11a), preferably in the shape of a helix, consists of a material having a low work function, preferably of rare-earth elements, or is coated or vapour-deposited with such a material, which insert (11) bears against the inner wall of the tube (1).
  5. Device according to Claim 2, characterized in that in the cylindrical tube (1) an insert (11b), preferably in the shape of a helix, consists of a material having a low work function, preferably of rare-earth elements, or is coated or vapour-deposited with such a material, which insert (11b) is distanced from the inner wall of the tube (1).
  6. Device according to one of Claims 3 to 5, characterized in that said material is lanthanum, cerium or cerium/iron or an alloy containing these substances.
  7. Device according to one of Claims 2 to 6, characterized in that the first electrode (2) is arranged in the central region of said tube (1), and in that the second electrode (6) is likewise constructed in the shape of a tube having a diameter larger than that of the first tube (1) and is directly joined to the end of the first tube (1) on the downstream side.
EP19910104306 1991-03-20 1991-03-20 Process and apparatus for charging particles Expired - Lifetime EP0504451B1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE59107949T DE59107949D1 (en) 1991-03-20 1991-03-20 Method and device for charging particles
ES91104306T ES2090160T3 (en) 1991-03-20 1991-03-20 PROCEDURE AND DEVICE FOR LOADING PARTICLES.
EP19910104306 EP0504451B1 (en) 1991-03-20 1991-03-20 Process and apparatus for charging particles

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19910104306 EP0504451B1 (en) 1991-03-20 1991-03-20 Process and apparatus for charging particles

Publications (2)

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EP0504451A1 EP0504451A1 (en) 1992-09-23
EP0504451B1 true EP0504451B1 (en) 1996-06-19

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EP19910104306 Expired - Lifetime EP0504451B1 (en) 1991-03-20 1991-03-20 Process and apparatus for charging particles

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DE (1) DE59107949D1 (en)
ES (1) ES2090160T3 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001052998A1 (en) * 2000-01-21 2001-07-26 The University Of Western Ontario Tribocharging and electrostatic separation of mixed electrically insulating particles
CN106000654B (en) * 2016-05-23 2017-10-27 中国矿业大学 A kind of particle reversely feeds friction electrical selection separator

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE829132C (en) * 1944-05-10 1952-01-24 Metallgesellschaft Ag Process and device for the electrostatic separation of two or multiple substances
DE1084246B (en) * 1956-03-08 1960-06-30 Otto Schmid Dr Ing Centrifugal separator in cyclone design
FR1505476A (en) * 1965-10-25 1967-12-15 Electrostatic separator device

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DE59107949D1 (en) 1996-07-25
ES2090160T3 (en) 1996-10-16
EP0504451A1 (en) 1992-09-23

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