EP0634960B1 - Foundry sand regenerating process and device - Google Patents

Foundry sand regenerating process and device Download PDF

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Publication number
EP0634960B1
EP0634960B1 EP93903831A EP93903831A EP0634960B1 EP 0634960 B1 EP0634960 B1 EP 0634960B1 EP 93903831 A EP93903831 A EP 93903831A EP 93903831 A EP93903831 A EP 93903831A EP 0634960 B1 EP0634960 B1 EP 0634960B1
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sand
air
grinding
process according
disposed
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German (de)
French (fr)
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EP0634960A1 (en
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Dietmar Prof. Dr.-Ing. Boenisch
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
    • B22C5/10—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by dust separating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
    • B22C5/02—Dressing by centrifuging essentially or additionally
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S241/00—Solid material comminution or disintegration
    • Y10S241/10—Foundry sand treatment

Definitions

  • the invention relates to a method and a device for regenerating foundry sand according to claims 1 and 11.
  • Thermal-mechanical regeneration as described for example in EP-A-0 343 272 and compared with other known processes, is currently favored.
  • the sand is annealed in a first, the thermal treatment stage at temperatures of 500 to 900 ° C and, after appropriate cooling, placed in batches in a grinder or grinder, in which the dead burnt binder residues, which do not evaporate during the annealing process, are rubbed off the sand grains by rotating cross arms and by means of the sand filling of blown compressed air is discharged and discharged from time to time.
  • thermal regeneration treatment is viewed with increasing skepticism and will have to be dropped in the future.
  • the high acquisition, operating and maintenance costs of the systems required for this overwhelm many small and medium-sized foundries and force them to cooperate or operate as a contractor, which inevitably causes additional transport.
  • Recyclable materials made from bentonite and carbon-containing constituents that are still present in the old sand are burned dead and lost. Grains of sand shatter due to the abrupt changes in temperature and become waste, so that the amount of residues increases and the grain spectrum is changed inadmissibly.
  • the global climate problem is also forcing foundries to reduce their heat and CO2 emissions and to dispense with additional furnace processes.
  • Impact cleaning consumes a relatively large amount of compressed air and generates increased quantities of residues due to grain fragmentation.
  • Rotary drums with several drives and wipers also result in large, complex constructions with increased susceptibility to wear and malfunction due to the mostly hot accumulating used sand.
  • the dedusting is carried out either by cross air, which, however, only detects and removes the whirled up dust above the material, or by means of through air.
  • cross air which, however, only detects and removes the whirled up dust above the material
  • through air if the compressed air is blown into the sand batch through a large number of nozzles in the upper machine base, as in the grinding machine according to EP-A-0 343 272, a fluidized bed is created in the area of the transverse arms, and the necessary frictional action ceases.
  • sand containing active clay this leads to inadequate abrasion, which impairs the usefulness of the regenerated material for core production.
  • the machine running times are extended and throughput reduced.
  • a significant part of the abrasion is not removed with the through-air, but settles in the dead corner formed by the floor and side wall and is removed with the regenerate when the machine is emptied.
  • the process should be so flexible that the grain-to-grain friction can be gradually increased during a regeneration batch so that the foreign matter is removed first and only then is the abrasion of the hard material Grains of sand occur, which can significantly shorten the treatment time of a batch.
  • back-referring claims 2 to 10 and 12 to 20 contain advantageous refinements of the method or the machine technology of the plant, which according to claim 21 can also be used for rounding new sand grains, which experience has shown that they can be regenerated more easily in the subsequent recycling processes.
  • the binder residues adhering to the sand grains are not only loosened by the grinding rotor, but also by grain-to-grain friction within the moving sand mass.
  • This type of friction can be promoted by blowing sharp compressed air jets into the peripheral area of the filling and is particularly effective when electrostatically adhering plastic particles have to be removed.
  • too high a degree of fluidization in the area of the sand filling near the wall can significantly impair the main grinding through the rotor blades. In order to prevent this, the compressed air should be blown in at points that are close to the floor and near the wall.
  • the vertical circulation effect can be increased if the upward and downward currents are passed separately through a partition that begins below the sand surface and ends below the grinding rotor.
  • the amount and size of the sand bubbles can be influenced if the compressed air is blown in not only at the lowest point of the machine, but also partly through its side wall, whereby the side blowing points can be angularly offset from those near the ground.
  • the change in the flow behavior of the sand filling in the course of a regeneration batch also influences the current consumption of the drive motor, by which the regeneration progress can be recognized.
  • the current consumption is used as a signal for changes in the compressed air introduction and / or the rotational speed of the grinding rotor, as a result of which the grinding intensity is changed in a desired direction.
  • the control processes can take place automatically.
  • Such signals can also be used to determine the end of a batch runtime which is not uniform.
  • the machine runtime required for the respective regenerate depends on the used sand composition, which can change frequently within a molding sand cycle.
  • Some old sands contain a relatively large amount of loose dust, which mainly consists of coal dust and bentonite. It may therefore be advantageous to remove these valuable materials before starting the grinding treatment.
  • a pre-cleaning phase is used for this, in which the grinding rotor is stationary or only rotates so slowly that the sand filling is gently stirred.
  • the discharge of the dust can be controlled by cross air blown in radially or tangentially above the sand filling, from which possibly entrained fine grain sand can be cyclone-like centrally, at the latest but separates in a funnel-shaped sand trap, is returned to the sand cycle and thus remains in the sand grain spectrum.
  • the machine shown in Figures 1 and 2 has a covered upright cylindrical container 1, which is surrounded at the lower part by a jacket 2 with a base plate 9.
  • Parts 1 and 2 delimit air chambers 3, 3a, 4 into which feed lines 5, 5a, 6 open for compressed air, which as fluidizing and dedusting air through an annular gap 7 at the bottom and through air slots or slot nozzles 8 arranged higher in the container wall in the filled Blown in sand or as cross air over its surface and discharged through the outlet line 23 becomes.
  • a speed-controllable motor 12 is mounted centrally on the cover, which drives a grinding rotor 14 via a slightly conical shaft 13 close to a base plate 24 that can be opened for sand extraction.
  • the grinding rotor can also be arranged eccentrically and, as is customary with rotary vane mixers, driven from below, in which case only the extraction opening would have to be installed.
  • the sand is introduced through a closable filler neck 16 over the inclined surface of a funnel-shaped sand trap 20 to fill level 17.
  • Figure 2 shows that the air chambers near the floor are divided by partition walls 25 into two groups of segment-shaped individual chambers 26, 27. This subdivision can also extend to the overlying air chambers 3a shown in FIG.
  • the air chambers of each group are alternatively supplied with compressed air through lines (not shown in FIG. 2), which flow out in the direction of arrow 28 into the effective area 29 and fluidize the sand here.
  • portions 30, which are not or only slightly aerated, remain in this outer area 10 between the fluidized columnar active areas, which have a firmer consistency and act as braking and support areas against the rotational force introduced by the grinding rotor 14. Its wings therefore do not work mainly in the grinding-intensive fluidized inner region 11 and penetrate at most to a limited extent into the transition region to the regions 29 which are more permeated with compressed air.
  • FIG. 3 shows a different type of device, which has a circular gap 31 or several vertical individual nozzles tapering in the bottom like a nozzle and a partition wall 34 which is held concentrically above the grinding rotor 14 by means of ribs 35.
  • this device When this device is operated, compressed air is blown into the sand from an annular chamber 32 in a sharp jet 33, an additional friction effect occurring in the outer region 10 of the sand filling, which contributes to the complete detachment of the residual material particles removed by the grinding rotor 14.
  • This device can also be operated with a pre-cleaning phase, depending on the recyclable material content of the used sand, in which the recyclable materials are only discharged by the air blown in from the annular chamber 32 before the grinding rotor is brought slowly and then to the grinding speed, so that the sand filling in the movement indicated by the arrows 15, 33, 21, 19.
  • the mixing of the sand flowing up and down is prevented by the partition wall 34 and an undesired horizontal rotation by the ribs 35.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Combined Means For Separation Of Solids (AREA)
  • Processing Of Solid Wastes (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Casting Devices For Molds (AREA)

Abstract

A foundry sand is regenerated in an upright chamber to which air is admitted at the junction between a peripheral wall and between while an abrating rotor is in a horizontal plane close to the bottom to establish a vertical line with columns of fluidized sand outwardly of the orbit of the rotor.

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Regenerieren von Gießereisand gemäß den Ansprüchen 1 und 11.The invention relates to a method and a device for regenerating foundry sand according to claims 1 and 11.

Steigende Deponiekosten und behördliche Auflagen erzwingen die Regenerierung und Wiederverwendung von Gießereisanden. Dazu sind verschiedene Regenerierungsverfahren bekannt und Regenerierungsanlagen in Betrieb.Rising landfill costs and official requirements are forcing foundry sands to be regenerated and reused. Various regeneration processes are known and regeneration plants are in operation.

Die Regenerierung von bentonithaltigen Mischsanden bereitet wegen ihrer großen Schadstoffmengen besondere Schwierigkeiten. Zur Zeit wird die thermischmechanische Regenerierung favorisiert, wie sie beispielsweise in der EP-A-0 343 272 beschrieben und mit weiteren bekannten Verfahren verglichen ist. Dabei wird der Sand in einer ersten, der thermischen Behandlungsstufe bei Temperaturen von 500 bis 900°C geglüht und nach entsprechender Abkühlung chargenweise in eine Reib- oder Schleifmaschine gegeben, in der die totgebrannten, beim Glühprozeß nicht verflüchtigen Binderreste durch rotierende Querarme von den Sandkörnern abgerieben und mittels durch die Sandfüllung geblasener Druckluft von Zeit zu Zeit ausgetragen und abgeführt werden.The regeneration of mixed sands containing bentonite presents particular difficulties because of their large quantities of pollutants. Thermal-mechanical regeneration, as described for example in EP-A-0 343 272 and compared with other known processes, is currently favored. The sand is annealed in a first, the thermal treatment stage at temperatures of 500 to 900 ° C and, after appropriate cooling, placed in batches in a grinder or grinder, in which the dead burnt binder residues, which do not evaporate during the annealing process, are rubbed off the sand grains by rotating cross arms and by means of the sand filling of blown compressed air is discharged and discharged from time to time.

Die thermische Regenerierungsbehandlung wird aber mit zunehmender Skepsis betrachtet und künftig entfallen müssen. Die hohen Anschaffungs-, Betriebs-und Wartungskosten der dafür erforderlichen Anlagen überfordern viele kleine und mittelständische Gießereien und zwingen zu genossenschaftlichem oder Lohnbetrieb, der zwangsläufig zusätzlichen Transport verursacht. Im Altsand noch vorhandene Wertstoffe aus Bentonit und kohlenstoffhaltigen Bestandteilen werden tot gebrannt und gehen verloren. Sandkörner zerspringen durch die schroffen Temperaturwechsel und werden zu Abfall, so daß die Reststoffmenge ansteigt und das Kornspektrum unzulässig verändert wird. Zudem zwingt die globale Klimaproblematik auch die Gießereien zur Verminderung ihres Wärme- und CO₂-Ausstoßes und zum Verzicht auf zusätzliche Ofenprozesse.However, thermal regeneration treatment is viewed with increasing skepticism and will have to be dropped in the future. The high acquisition, operating and maintenance costs of the systems required for this overwhelm many small and medium-sized foundries and force them to cooperate or operate as a contractor, which inevitably causes additional transport. Recyclable materials made from bentonite and carbon-containing constituents that are still present in the old sand are burned dead and lost. Grains of sand shatter due to the abrupt changes in temperature and become waste, so that the amount of residues increases and the grain spectrum is changed inadmissibly. In addition, the global climate problem is also forcing foundries to reduce their heat and CO₂ emissions and to dispense with additional furnace processes.

In neueren Druckschriften werden daher Regenerierverfahren vorgeschlagen, bei denen das Totglühen des gesamten Altsandes vermieden werden kann (DE-A-41 06 736, DE-A-41 06 737, DE-A-41 21 765 und EP-A-0 465 778).Regeneration processes are therefore proposed in more recent publications in which the dead glow of the entire old sand can be avoided (DE-A-41 06 736, DE-A-41 06 737, DE-A-41 21 765 and EP-A-0 465 778 ).

Wenn aber die thermische Regenerierungsstufe entfällt, werden an die mechanischen Regenerierungsmaschinen sehr viel höhere Anforderungen gestellt als bisher, weil sie die Reinigungsarbeit allein bewältigen müssen.However, if the thermal regeneration stage is omitted, the mechanical regeneration machines are switched on much higher demands than before because they have to do the cleaning work alone.

Untersuchungen mit den bisher gebräuchlichen Maschinen haben wesentliche Schwächen und Nachteile erkennen lassen, die die geforderte Regeneratqualität überhaupt nicht oder erst nach sehr langen Maschinenlaufzeiten erlauben.Investigations with the previously used machines have shown significant weaknesses and disadvantages which do not allow the required quality of the regenerate at all or only after very long machine running times.

Die Prallreinigung verbraucht relativ viel Druckluft und erzeugt wegen der Kornzersplitterung erhöhte Reststoffmengen. Drehtrommeln mit mehreren Antrieben und Abstreifern ergeben auch wegen der meist heiß anfallenden Altsande große aufwendige Konstruktionen mit erhöhter Verschleiß- und Störanfälligkeit.Impact cleaning consumes a relatively large amount of compressed air and generates increased quantities of residues due to grain fragmentation. Rotary drums with several drives and wipers also result in large, complex constructions with increased susceptibility to wear and malfunction due to the mostly hot accumulating used sand.

Bei den üblichen der thermischen Stufe nachgeschalteten Schleifmaschinen erfolgt die Entstaubung entweder durch Querluft, die aber nur den aufgewirbelten Staub über dem Gut erfaßt und abführt, oder mittels Durchluft. Wenn die Druckluft aber wie bei der Schleifmaschine nach der EP-A-0 343 272 durch eine Vielzahl von Düsen im oberen Maschinenboden in die Sandcharge eingeblasen wird, entsteht im Bereich der Querarme ein Fließbett, und die notwendige Reibwirkung setzt aus. Bei Aktivton-haltigem Sand führt das zu unzureichendem Abrieb, wodurch die Brauchbarkeit des Regenerats zur Kernherstellung beeinträchtigt wird. Zudem werden die Maschinenlaufzeiten verlängert und die Durchsatzmengen verringert. Außerdem wird ein erheblicher Teil des Abriebs nicht mit der Durchluft abgeführt, sondern setzt sich in der von Boden und Seitenwand gebildeten toten Ecke ab und wird beim Entleeren der Maschine mit dem Regenerat abgezogen.In the usual grinding machines downstream of the thermal stage, the dedusting is carried out either by cross air, which, however, only detects and removes the whirled up dust above the material, or by means of through air. However, if the compressed air is blown into the sand batch through a large number of nozzles in the upper machine base, as in the grinding machine according to EP-A-0 343 272, a fluidized bed is created in the area of the transverse arms, and the necessary frictional action ceases. In the case of sand containing active clay, this leads to inadequate abrasion, which impairs the usefulness of the regenerated material for core production. In addition, the machine running times are extended and throughput reduced. In addition, a significant part of the abrasion is not removed with the through-air, but settles in the dead corner formed by the floor and side wall and is removed with the regenerate when the machine is emptied.

Es stellte sich daher die Aufgabe, ein einfaches, anlage-, betriebs- und wartungskostengünstiges Verfahren zum Regenerieren von Gießereisanden, insbesondere von noch aktiven Bentonit enthaltenden Altsand zu schaffen, das unter Verzicht auf eine Glühbehandlung des Sandes auch von kleinen Gießereien selbständig betrieben werden kann. Die dazu erforderliche Anlage sollte möglichst wenig Platz beanspruchen, flexibel an die verschiedensten Reinigungsaufgaben angepaßt werden können und unkompliziert in die meist vorhandene Sandaufbereitung integrierbar sein. Das Verfahren sollte unter Vermeidung jeglicher Prallkräfte Kornzersplitterungen ausschließen, dennoch aber eine starke Korn-an-Korn-Reibung gewährleisten, damit sowohl harte, auf den Sandoberflächen aufgebackene Fremdstoffe abgerieben und auch die Körner selbst abgeschliffen und vorteilhaft gerundet werden. Das Verfahren sollte derart flexibel sein, daß die Korn-an-Korn-Reibung während einer Regenerierungscharge allmählich gesteigert werden kann, damit zuerst die Fremdstoffe abgetragen werden und erst daran anschließend der Abschliff der harten Sandkörner erfolgt, wodurch die Behandlungsdauer einer Charge wesentlich verkürzt werden kann.It was therefore the task of creating a simple, plant, operating and maintenance-economical method for regenerating foundry sands, in particular used sand containing active bentonite, which can also be operated independently by small foundries without the need for an annealing treatment of the sand. The system required for this should take up as little space as possible, be flexibly adaptable to a wide variety of cleaning tasks and be easy to integrate into the mostly existing sand preparation. The process should prevent grain splintering while avoiding any impact forces, but still ensure a strong grain-to-grain friction, so that both hard foreign substances baked on the sand surfaces are rubbed off and the grains themselves are ground and advantageously rounded. The process should be so flexible that the grain-to-grain friction can be gradually increased during a regeneration batch so that the foreign matter is removed first and only then is the abrasion of the hard material Grains of sand occur, which can significantly shorten the treatment time of a batch.

Diese Aufgabe wird durch das Verfahren nach Anspruch 1 gelöst, das sich einer Trockenschleifmaschine nach Anspruch 11 bedient. Dabei wird gewöhnlich Druckluft verwendet. Diese Betriebsweise wird auch im folgenden erörtert. Das gleiche Verfahren kann aber auch auf Saugluft eingestellt werden.This object is achieved by the method according to claim 1, which uses a dry grinding machine according to claim 11. Compressed air is usually used for this. This mode of operation is also discussed below. The same procedure can also be set for suction air.

In den jeweils rückbezogenen Ansprüchen 2 bis 10 und 12 bis 20 sind vorteilhafte Ausgestaltungen des Verfahrens, bzw. der Maschinentechnik der Anlage enthalten, die nach Anspruch 21 auch zum Runden von Neusandkörnern verwendet werden kann, die sich erfahrungsgemäß in den nachfolgenden Recyclingsprozessen leichter regenerieren lassen.In each case back-referring claims 2 to 10 and 12 to 20 contain advantageous refinements of the method or the machine technology of the plant, which according to claim 21 can also be used for rounding new sand grains, which experience has shown that they can be regenerated more easily in the subsequent recycling processes.

Wenn die Luft entsprechend der Maßnahme nach Anspruch 1 nur in den peripheren Bereich der Sandfüllung eingeblasen wird, entsteht an und über der Einblasstelle auch nur ein entlang der Seitenwand der Maschine aufsteigender Strom fluidisierten Sandes. Dabei bildet die Druckluft Blasen, die den von den Körnern abgeriebenen Staub aufnehmen und sich an der Oberfläche der Füllung deutlich sichtbar auflösen, wobei der Staub von der abströmenden Luft mitgeführt wird, die Sandkörner aber auf die Oberfläche der Füllung zurückfallen und in einem zentralen Sogtrichter um die Antriebswelle abwärts via Schleifrotor zurückgeführt werden. Dadurch entsteht ein vertikaler Kreislaufeffekt.If the air is only blown into the peripheral area of the sand filling in accordance with the measure of claim 1, only a stream of fluidized sand rising along the side wall of the machine arises at and above the blowing point. The compressed air forms bubbles that absorb the dust that has been rubbed off the grains and dissolve on the surface of the filling in a clearly visible manner, whereby the dust is carried along by the outflowing air, but the sand grains fall back onto the surface of the filling and in a central suction funnel the drive shaft can be returned downwards via the grinding rotor. This creates a vertical circulation effect.

Die auf den Sandkörnern haftenden Binderreste werden aber nicht nur durch den Schleifrotor, sondern auch durch Korn-an-Korn-Reibung innerhalb der bewegten Sandmasse gelöst. Diese Reibungsart kann durch Einblasen scharfer Druckluftstrahlen in den peripheren Bereich der Füllung begünstigt werden und ist besonders wirksam, wenn elektrostatisch anhaftende Kunststoffteilchen abgelöst werden müssen. Andererseits kann ein zu hoher Fluidisierungsgrad im wandnahen Bereich der Sandfüllung den Hauptschliff durch die Rotorflügel erheblich beeinträchtigen. Um das zu verhüten, soll die Druckluft zweckmäßig an mit Abstand voneinander liegenden boden- und wandnahen Stellen eingeblasen werden. Dadurch wird erreicht, daß sich nur an und über den Einblasstellen säulenförmige Zonen fluidisierten Sandes bilden, die durch dazwischenliegende Säulen dichteren Sandes getrennt sind. Der Zweck dieser Maßnahme ist, daß die Ausbildung eines zusammenhängenden rohrförmigen Fließbetts an der Maschinenwand verhindert wird. Durch die zwischenliegenden Säulen festerer und dichterer Sandpackung wird auch verhindert, daß bei Schleifmaschinen, die keine weiteren Einbauten im zylinderförmigen Füllraum haben, die inneren nicht fluidisierten Sandbereiche durch den ansonsten zum Rührwerk werdenden zentralen Schleifrotor wie ein Kern in einem Gleitlager in horizontale Rotation versetzt werden.The binder residues adhering to the sand grains are not only loosened by the grinding rotor, but also by grain-to-grain friction within the moving sand mass. This type of friction can be promoted by blowing sharp compressed air jets into the peripheral area of the filling and is particularly effective when electrostatically adhering plastic particles have to be removed. On the other hand, too high a degree of fluidization in the area of the sand filling near the wall can significantly impair the main grinding through the rotor blades. In order to prevent this, the compressed air should be blown in at points that are close to the floor and near the wall. It is thereby achieved that columnar zones of fluidized sand are formed only at and above the injection points, which are separated by columns of denser sand lying between them. The purpose of this measure is to prevent the formation of a coherent tubular fluid bed on the machine wall. The interposed pillars of firmer and denser sand packing also prevent the inner non-fluidized sand areas in grinding machines, which have no further internals in the cylindrical filling space, from otherwise leading to the agitator central grinding rotor will be set in horizontal rotation like a core in a plain bearing.

Der vertikale Kreislaufeffekt kann verstärkt werden, wenn die aufwärts und abwärts verlaufenden Ströme durch eine oben unter der Sandoberfläche beginnende und unten über dem Schleifrotor endende Trennwand separat geführt werden. Die Menge und Größe der Sandblasen kann beeinflußt werden, wenn die Druckluft nicht nur an der tiefsten Stelle der Maschine, sondern teilweise auch durch deren Seitenwand eingeblasen wird, wobei die seitlichen Einblasstellen gegenüber denen in Bodennähe winkelversetzt sein können.The vertical circulation effect can be increased if the upward and downward currents are passed separately through a partition that begins below the sand surface and ends below the grinding rotor. The amount and size of the sand bubbles can be influenced if the compressed air is blown in not only at the lowest point of the machine, but also partly through its side wall, whereby the side blowing points can be angularly offset from those near the ground.

Im Verlauf der Regenerierbehandlung ändert sich mit der Zusammensetzung und weiteren Eigenschaften auch das Fließverhalten des Sandes, so daß die Änderung verschiedener Betriebsparameter zweckmäßig wird. Zu Beginn der Behandlung tritt ein Temperaturausgleich in der Sandfüllung ein, der besonders deutlich beim Einsatz frisch ausgeleerten und erst noch schwach durchmischten Altsandes zu beobachten ist. Dabei wird zuerst der auf den Sandkörnern haftende Aktiv-Bentonit getrocknet, abgerieben und zusammen mit den Kohlenstoffteilchen verstärkt ausgetragen. Diese Wertstoffe werden zweckmäßig getrennt aufgefangen, weil sie in der Sandaufbereitung wiederverwendet werden können.In the course of the regeneration treatment, the flow behavior of the sand changes with the composition and other properties, so that the change in various operating parameters becomes expedient. At the beginning of the treatment, a temperature equalization occurs in the sand filling, which can be observed particularly clearly when freshly emptied and only slightly mixed old sand is used. The active bentonite adhering to the sand grains is first dried, rubbed off and discharged together with the carbon particles. These recyclables are appropriately collected separately because they can be reused in sand processing.

Die Änderung des Fließverhaltens der Sandfüllung im Verlauf einer Regenierungscharge beeinflußt auch die Stromaufnahme des Antriebsmotors, an der der Regenerierfortschritt erkannt werden kann. In einer vorteilhaften Ausgestaltung der Erfindung wird die Stromaufnahme als Signal für Änderungen der Drucklufteinleitung und/oder der Drehzahl des Schleifrotors herangezogen, wodurch die Schleifintensität in einer gewünschten Richtung verändert wird. Die Regelprozesse können selbsttätig erfolgen. Mit Hilfe derartiger Signale ist auch das Ende einer Chargenlaufzeit bestimmbar, die nicht einheitlich ist. Die für das jeweilige Regenerat erforderliche Maschinenlaufzeit hängt von der Altsandzusammensetzung ab, die sich innerhalb eines Formsandkreislaufs häufig ändern kann.The change in the flow behavior of the sand filling in the course of a regeneration batch also influences the current consumption of the drive motor, by which the regeneration progress can be recognized. In an advantageous embodiment of the invention, the current consumption is used as a signal for changes in the compressed air introduction and / or the rotational speed of the grinding rotor, as a result of which the grinding intensity is changed in a desired direction. The control processes can take place automatically. Such signals can also be used to determine the end of a batch runtime which is not uniform. The machine runtime required for the respective regenerate depends on the used sand composition, which can change frequently within a molding sand cycle.

Manche Altsande enthalten relativ viel losen Staub, der hauptsächlich aus Kohlenstaub und Bentonit besteht. Es kann daher vorteilhaft sein, diese Wertstoffe vor Beginn der Schleifbehandlung abzuziehen. Dazu dient eine Vorreinigungsphase, in der der Schleifrotor steht oder sich nur so langsam dreht, daß die Sandfüllung schonend umgerührt wird.Some old sands contain a relatively large amount of loose dust, which mainly consists of coal dust and bentonite. It may therefore be advantageous to remove these valuable materials before starting the grinding treatment. A pre-cleaning phase is used for this, in which the grinding rotor is stationary or only rotates so slowly that the sand filling is gently stirred.

Der Austrag des Staubes kann durch oberhalb der Sandfüllung radial oder tangential eingeblasene Querluft gesteuert werden, aus der eventuell mitgerissener Feinkornsand sich zyklonartig zentral, spätestens aber in einem trichterförmigen Sandfang abscheidet, wieder in den Sandkreislauf zurückgeführt wird und damit dem Sandkornspektrum erhalten bleibt.The discharge of the dust can be controlled by cross air blown in radially or tangentially above the sand filling, from which possibly entrained fine grain sand can be cyclone-like centrally, at the latest but separates in a funnel-shaped sand trap, is returned to the sand cycle and thus remains in the sand grain spectrum.

Die Erfindung ist anhand einiger Prinzipskizzen beispielhaft erläutert. Dabei zeigen:

Figur 1:
eine von einem Mantel teilweise umgebene zylindrische Sandschleif- und Regeneriermaschine,
Figur 2
einen Schnitt durch Figur 1 entlang der Linie A-A,
Figur 3
eine zylindrische Sandschleif- und Regeneriermaschine mit einer rohrförmigen Trennwand im Füllraum.
The invention is explained by way of example with the aid of some basic sketches. Show:
Figure 1:
a cylindrical sanding and regeneration machine partially surrounded by a jacket,
Figure 2
2 shows a section through FIG. 1 along the line AA,
Figure 3
a cylindrical sanding and regeneration machine with a tubular partition in the filling chamber.

Die in den Figuren 1 und 2 dargestellte Maschine hat einen abgedeckelten aufrechtstehenden zylindrischen Behälter 1, der am unteren Teil von einem Mantel 2 mit Bodenplatte 9 umgeben ist. Teile 1 und 2 begrenzen Luftkammern 3, 3a, 4, in die Zuleitungen 5, 5a, 6 für Druckluft münden, die als Fluidisierungs- und Entstaubungsluft durch einen Ringspalt 7 am Boden und durch höher in der Behälterwand angeordnete Luftschlitze oder Schlitzdüsen 8 in den eingefüllten Sand oder als Querluft über dessen Oberfläche eingeblasen und durch die Austrittsleitung 23 abgeführt wird. Auf dem Deckel ist im dargestellten Fall ein drehzahlregelbarer Motor 12 zentrisch gelagert, der über eine leicht konische Welle 13 einen Schleifrotor 14 nahe über einer zum Sandabzug zu öffnenden Bodenplatte 24 antreibt. Der Schleifrotor kann aber auch exzentrisch angeordnet und wie bei Drehflügelmischern üblich von unten angetrieben werden, wobei dann nur die Abzugsöffnung zu verlegen wäre. Der Sand wird durch einen verschließbaren Einfüllstutzen 16 über die geneigte Fläche eines trichterförmigen Sandfanges 20 bis zur Füllhöhe 17 eingebracht.The machine shown in Figures 1 and 2 has a covered upright cylindrical container 1, which is surrounded at the lower part by a jacket 2 with a base plate 9. Parts 1 and 2 delimit air chambers 3, 3a, 4 into which feed lines 5, 5a, 6 open for compressed air, which as fluidizing and dedusting air through an annular gap 7 at the bottom and through air slots or slot nozzles 8 arranged higher in the container wall in the filled Blown in sand or as cross air over its surface and discharged through the outlet line 23 becomes. In the case shown, a speed-controllable motor 12 is mounted centrally on the cover, which drives a grinding rotor 14 via a slightly conical shaft 13 close to a base plate 24 that can be opened for sand extraction. However, the grinding rotor can also be arranged eccentrically and, as is customary with rotary vane mixers, driven from below, in which case only the extraction opening would have to be installed. The sand is introduced through a closable filler neck 16 over the inclined surface of a funnel-shaped sand trap 20 to fill level 17.

Figur 2 zeigt, daß die bodennahen Luftkammern durch Zwischenwände 25 in zwei Gruppen segmentförmiger Einzelkammern 26, 27 unterteilt sind. Diese Unterteilung kann sich auch auf die in Figur 1 dargestellten darüberliegenden Luftkammern 3a erstrecken. Die Luftkammern jeweils einer Gruppe werden durch in Figur 2 nicht dargestellte Leitungen alternativ mit Druckluft beschickt, die in Pfeilrichtung 28 in den Wirkbereich 29 ausströmt und den Sand hier fluidisiert. Wie dargestellt verbleiben in diesem Außenbereich 10 zwischen den fluidisierten säulenförmigen Wirkbereichen aber auch noch nicht oder nur schwach mit Luft durchsetzte Abschnitte 30, die eine festere Konsistenz haben und als Brems- und Stützbereiche gegen die vom Schleifrotor 14 eingebrachte Drehkraft wirken. Dessen Flügel arbeiten mithin hauptsächlich im schleifintensiven nicht fluidisierten Innenbereich 11 und dringen höchstens begrenzt in den Übergangsbereich zu den stärker mit Druckluft durchsetzten Bereichen 29 ein.Figure 2 shows that the air chambers near the floor are divided by partition walls 25 into two groups of segment-shaped individual chambers 26, 27. This subdivision can also extend to the overlying air chambers 3a shown in FIG. The air chambers of each group are alternatively supplied with compressed air through lines (not shown in FIG. 2), which flow out in the direction of arrow 28 into the effective area 29 and fluidize the sand here. As shown, portions 30, which are not or only slightly aerated, remain in this outer area 10 between the fluidized columnar active areas, which have a firmer consistency and act as braking and support areas against the rotational force introduced by the grinding rotor 14. Its wings therefore do not work mainly in the grinding-intensive fluidized inner region 11 and penetrate at most to a limited extent into the transition region to the regions 29 which are more permeated with compressed air.

Beim Betrieb dieser Vorrichtung stellt sich ein aufsteigender Strom 18 fluidisierten, mit Staub durchsetzten Sandes ein, wobei Aufwärtsbewegung und Durchlüftung durch Luftströme aus den Schlitzen 8 unterstützt werden können. Je nach Druck und Menge tritt die Luft mehr oder weniger heftig vor allem im Außenbereich 10 in Form zerplatzender Blasen oder aus der nur leicht sprudelnden Sandoberfläche aus. Sie trifft auf den Sandfang 20 und strömt unter Mitnahme der leichten Staubpartikel in der durch die Pfeile 22 angedeuteten Richtung zur Austragsleitung 23 und weiter zu einem nicht dargestellten Abscheider, während mitgerissener schwerer Sand von der Unterseite des Sandfanges 20 in Richtung 21 zurückgeführt wird oder als Feinkorn von der Trichterfläche zurückrollt und im Innenbereich 11 in Pfeilrichtung 19 abwärts wieder in den Arbeitsbereich des Schleifrotors gelangt, von dem er in Pfeilrichtung 15 erneut in den vertikalen Kreislauf gefördert wird. Da sich im Eckbereich vor den gerade nicht blasenden Kammern Abrieb und Staub absetzt, wird im Chargenverlauf die aktive Kammergruppe mehrmals gewechselt, so daß Staubansätze aus den Totzonen immer wieder ausgeblasen werden.During the operation of this device, an ascending stream 18 of fluidized sand interspersed with dust occurs, whereby upward movement and aeration can be supported by air currents from the slots 8. Depending on the pressure and quantity, the air escapes more or less violently, especially in the outside area 10 in the form of burst bubbles or from the only slightly bubbling sand surface. It hits the sand trap 20 and flows along with the light dust particles in the direction indicated by the arrows 22 to the discharge line 23 and further to a separator, not shown, while entrained heavy sand is returned from the underside of the sand trap 20 in the direction 21 or as fine grain rolls back from the funnel surface and in the inner region 11 in the arrow direction 19 down again into the working area of the grinding rotor, from which it is conveyed again in the arrow direction 15 into the vertical cycle. Since abrasion and dust settle in the corner area in front of the non-blowing chambers, the active chamber group is changed several times in the course of the batch, so that dust deposits are blown out of the dead zones again and again.

Figur 3 zeigt eine andersartige Vorrichtung, die im Boden einen sich düsenartig verjüngenden ringsumlaufenden Spalt 31 oder mehrere vertikale Einzeldüsen und eine über dem Schleifrotor 14 mittels Rippen 35 konzentrisch gehalterte Trennwand 34 hat. Beim Betrieb dieser Vorrichtung wird Druckluft aus einer Ringkammer 32 in scharfem Strahl 33 in den Sand geblasen, wobei im Außenbereich 10 der Sandfüllung eine zusätzliche Reibwirkung auftritt, die zur vollständigen Ablösung der vom Schleifrotor 14 abgetragenen Reststoffteilchen beiträgt. Auch diese Vorrichtung kann je nach Wertstoff gehalt des anfallenden Altsandes mit einer Vorreinigungsphase betrieben werden, in der die Wertstoffe ausschließlich durch die aus der Ringkammer 32 eingeblasene Luft ausgetragen werden, bevor der Schleifrotor erst langsam und dann auf Schleifdrehzahl gebracht wird, so daß die Sandfüllung in die durch die Pfeile 15, 33, 21, 19 angedeutete Bewegung gerät. Die Vermischung des auf- und abwärts strömenden Sandes wird dabei durch die Trennwand 34 und eine unerwünschte Horizontaldrehung durch die Rippen 35 unterbunden.FIG. 3 shows a different type of device, which has a circular gap 31 or several vertical individual nozzles tapering in the bottom like a nozzle and a partition wall 34 which is held concentrically above the grinding rotor 14 by means of ribs 35. When this device is operated, compressed air is blown into the sand from an annular chamber 32 in a sharp jet 33, an additional friction effect occurring in the outer region 10 of the sand filling, which contributes to the complete detachment of the residual material particles removed by the grinding rotor 14. This device can also be operated with a pre-cleaning phase, depending on the recyclable material content of the used sand, in which the recyclable materials are only discharged by the air blown in from the annular chamber 32 before the grinding rotor is brought slowly and then to the grinding speed, so that the sand filling in the movement indicated by the arrows 15, 33, 21, 19. The mixing of the sand flowing up and down is prevented by the partition wall 34 and an undesired horizontal rotation by the ribs 35.

Claims (21)

  1. A process for regenerating foundry sand in an upright dry grinding machine having at least one horizontally rotating grinding tool (14) and compressed air supply device, characterised in that only outside the rotary circle of the blades of the grinding tool is air blown in or drawn in through the floor and/or the side wall into the outer region of the sand charge in the grinding machine, which in cooperation with the rotating blades produces a layer (18) of fluidised sand flowing upwardly in the peripheral region, in that the dust-charged air (22) is drawn off above the charging level and the denser sand, which is then no longer fluidised, is conveyed in the central flow (19) downwardly to the grinding tool (14) rotating just above the floor.
  2. A process according to Claim 1, characterised in that the air is blown or drawn into the sand charge at locations (7,8;31) disposed horizontally close to the walls and floor and spaced from one another.
  3. A process according to Claim 1 or 2, characterised in that the peripherally upwardly (18) and the centrally downwardly (19) directed streams of sand are conveyed separately from one another by a partition (34) open at the top and bottom and disposed above the grinding tool (14).
  4. A process according to Claim 1, 2 or 3, characterised in that the rotational speed of the grinding tool (14) and/or pressure, quantity, blowing-in location and blowing-in direction of the air alter in the course of the regenerating treatment and are adapted to the cleaning progress of the grains of sand and dust discharge.
  5. A process according to Claim 4, characterised in that the cleaning progress is monitored by means of the current or power consumption of the driving motor (12) and the change therein is used as a signal to control further operating parameters in the charging operation.
  6. A process according to one or more of Claims 1 to 5, characterised in that the air is blown in or drawn in through locations (8) disposed at various wall heights.
  7. A process according to one or more of Claims 1 to 6, characterised in that the dust-charged exhaust air is conveyed through a funnel-shaped sand trap (20) in the grinding machine to a discharge line (23).
  8. A process according to one or more of the preceding Claims 1 to 7, characterised in that the removal of the dust-charged exhaust air is assisted and/or controlled by means of suction through the discharge line (23) and/or injection of transverse air beneath the sand trap.
  9. A process according to one or more of the preceding Claims 1 to 8, characterised in that the unburnt valuable substances strongly accumulated in the exhaust air (22) particularly in the initial period of the regenerating treatment are collected separately for reutilisation.
  10. A process according to Claim 9, characterised in that the grinding rotor (14) is not driven or is only driven slowly in a precleaning phase.
  11. A device for regenerating foundry sand, consisting of an upright dry grinding machine having closable sand supply (16) and discharge opening (24), compressed air and/or suction air supply (5,5a,6) and exhaust air discharge line (23), and also at least one horizontally rotating grinding tool (14), characterised in that the inlet lines (7,8) for the fluidisation air are disposed outside the rotary circle of the blades of the grinding rotor (14) rotating just above the base plate (9).
  12. A device according to Claim 11, characterised in that the grinding rotor (14) has at least two curved blades, which are driven by a speed-controllable motor (12).
  13. A device according to Claim 11 or 12, characterised in that the inlet lines (7) are disposed in the corner region formed by base plate (9) and container wall (1).
  14. A device according to Claim 13, characterised in that the inlet lines (7) consist of at least two groups of segment-shaped individual chambers (26,27).
  15. A device according to one or more of the preceding Claims 11 to 14, characterised in that the container wall (1) is surrounded by one or more air chambers (3,3a,4), which have supply lines (5,5a,6) controllable independently of one another.
  16. A device according to one or more of Claims 11 to 15, characterised in that the inlet lines are constructed as self-cleaning annular gaps (7,31) having annular gap segments or air passages (8) disposed spaced from one another.
  17. A device according to Claim 16, characterised in that the inlet lines have sand-tight inserts of porous sintered metal or sand filters.
  18. A device according to one or more of Claims 1 to 17, characterised by at least one tubular partition (34) disposed in the charging chamber of the grinding machine above the grinding rotor (14) and beneath the charging level (17).
  19. A device according to one or more of Claims 11 to 18, characterised by a funnel-shaped sand trap (20) disposed between charging pipe (16) and charging level (17).
  20. A device according to Claim 19, characterised in that injection nozzles for transverse air are provided in the container wall (1) between the under side of the sand trap (20) and the charging level (17).
  21. Use of a device according to one or more of Claims 11 to 19 to round off the new sand by rough grinding.
EP93903831A 1992-04-10 1993-02-17 Foundry sand regenerating process and device Expired - Lifetime EP0634960B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4212097 1992-04-10
DE4212097A DE4212097A1 (en) 1992-04-10 1992-04-10 Method and device for regenerating foundry sand
PCT/DE1993/000168 WO1993020964A1 (en) 1992-04-10 1993-02-17 Foundry sand regenerating process and device

Publications (2)

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EP0634960A1 EP0634960A1 (en) 1995-01-25
EP0634960B1 true EP0634960B1 (en) 1996-04-17

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EP (1) EP0634960B1 (en)
JP (1) JPH08504131A (en)
AT (1) ATE136826T1 (en)
AU (1) AU3491793A (en)
BR (1) BR9306220A (en)
CA (1) CA2117787A1 (en)
CZ (1) CZ248194A3 (en)
DE (2) DE4212097A1 (en)
HU (1) HUT70816A (en)
WO (1) WO1993020964A1 (en)

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JPH08504131A (en) 1996-05-07
AU3491793A (en) 1993-11-18
BR9306220A (en) 1998-06-30
DE4212097A1 (en) 1993-10-14
CA2117787A1 (en) 1993-10-11
CZ248194A3 (en) 1996-02-14
US5439044A (en) 1995-08-08
ATE136826T1 (en) 1996-05-15
WO1993020964A1 (en) 1993-10-28
DE59302276D1 (en) 1996-05-23
DE4212097C2 (en) 1994-01-27
US5520341A (en) 1996-05-28
EP0634960A1 (en) 1995-01-25
HUT70816A (en) 1995-11-28
HU9402907D0 (en) 1995-02-28

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