Pulverizing apparatus

Description

[0001] The present invention relates to pulverizing apparatus.

[0002] It has been proposed, for example, in European Patent Application EP-A-0017367 to provide a pulverizing apparatus, for example for use in the pulverizing of coal, which comprises a generally cylindrical vessel having feed means for feeding the material to the pulverizer into said vessel, a plurality of circumferentially spaced fluid injection nozzles each angled between a radius to the cylindrical vessel passing through the nozzles and a direction perpendicular to such radius, to inject fluid into the vessel and induce an axially flowing vortex in the vessel, having its axis generally centrally of the vessel, and to provide transverse wall means at a location remote from the nozzles to intercept the vortex and to deflect a portion of the fluid medium and entrained particles of material to effect a recirculation of the fluid medium within the vessel and thus to form a curtain surrounding the vortex, whereby the material is pulverized by interparticle collisions and the curtain reduces high speed particle contact with the cylindrical wall of the vessel. An outlet is provided in the transverse wall through which a fraction of the pulverized material below a predetermined mass will pass generally along the axis of the vortex, the remaining particle sizes being swept out by centrifugal force for recirculation and repulverizing.

[0003] Such an apparatus is generally satisfactory but has certain shortcomings. It is an object of the present invention to overcome, at least in part, these shortcomings.

[0004] It is now proposed, according to the present invention, that the means for feeding the material to be pulverized should be arranged to feed the material through a generally axially extending feed tube passing through the transverse wall to the point adjacent the axial centre of the vessel in the vicinity of the nozzles.

[0005] The feed tube passes through the outlet in the transverse wall, so that the outlet is made annular.

[0006] Such an arrangement of the feed means ensures that a pile of material to be pulverised is formed on the bottom of the vessel and this pile is generally symmetrical and therefore does not disturb the proper formation of the vortex, thus giving an improved pulverizing effect.

[0007] The feed tube may be surmounted by a feed hopper and the material to be pulverized can flow simply by gravity and can operate in the manner of a chicken feeder, so that the amount of material to be pulverized is controlled by the size of the pile of material on the base.

[0008] An annular shroud advantageously surrounds the outlet and the feed tube to assist in the cyclone separation of the heavier particles from those particles passing out of the vessel.

[0009] In a preferred construction, a base plate is placed within the vessel at a location below the point of feed, and on which a substantially symmetrical pile of material to be pulverized is formed, and at least one opening is provided through said base plate at or near its periphery for the passage of heavy particles, which are not taken up by the vortex. When one is pulverizing coal, for example, there is often a certain amount of stone within the coal and this tends to be heavier than the coal and one, quite clearly, does not wish to include pulverized stone in the pulverized coal. The advantage therefore arises that the heavy material tends to move outwardly from the pile and lodge near the corner of the base plate. By providing openings in the base plate at or near its periphery, this gives an opportunity for the heavier objects to fall below and they can then be conveyed from a location below the base plate. The opening may be in the form of a complete annulus with the base plate supported centrally from below, or could be in the form of a number of spaced openings or notches in the periphery of the base plate itself which is otherwise secured to the cylindrical wall of the vessel, e.g. by welding.

[0010] In order that the present invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which the sole Figure is a schematic cross-section through one embodiment of apparatus according to the invention.

[0011] The apparatus illustrated in the drawing comprises a vessel indicated by the general reference numeral 10 comprising a cylindrical wall 11, a top domed cover 12 and a bottom domed cover 13. Extending axially within the domed cover 12 is an outlet 14 having an annular shroud 15 extending within the internal volume of the vessel 10. Coaxially arranged within the outlet 14 and shrould 15 is a feed tube 16 surmounted by a hopper 17 which may be fed with material, such as coal, to be pulverized by way of a conveyor 18. The outlet 14 is provided with a number, say four, of outlet ducts 19 for feeding the pulverized material on to a point of use, for example to a boiler or further treatment zone.

[0012] Adjacent the lower end of the cylindrical wall portion 11 is a base plate 20 which is secured to the cylindrical wall, e.g. by welding and provided with a plurality of circumferentially spaced openings 21. Below the plate 20 and above the domed section 13 is an inclined ramp 22 with a discharge conveyor 23 at its lowest point.

[0013] Projecting inwardly into the cylindrical wall 11 of the vessel 10 are a plurality of circumferentially spaced injection nozzles 24 which are arranged to point upwardly somewhat and also at an angle to the radius passing through the nozzle. These nozzles, therefore, induce within the vessel 10 a vortex comprising a central upwardly axially flowing vortex portion 25 which impinges against the transverse wall formed by the upper domed cover 12 so that the stream of fluid flows downwardly to provide a curtain 26 which is peripheral to the core zone defined by the vortex portion 25. At the lower end of the downward flow 26, the flow splits into a portion 27 which is recirculated through the upwardly flowing vortex portion and a further circumferential portion 28 which flows upwardly to rejoin the downwardly flowing part 26 adjacent the transverse wall formed by the cover 12.

[0014] In operation, material to be pulverized, for example coal, is introduced into the hopper 17 by the conveyor 18 and fills up the feed tube 16 to form a pile 30 which is generally symmetrical because the feed tube is central. The coal particles are picked up by the vortex and swirled around in the manner indicated and there is a considerable amount of interparticle collision which produces a grinding effect. The heavier particles move outwardly in the vortex which is thus in a form of a cyclone separator and pass down the stream 26, while the lighter portions exit through the shroud 15 and outlet 14 to discharge through the outlet ducts 19.

[0015] Very heavy particles, for example, stones, are not taken up by the vortex and pass downwardly through the openings 21 onto the ramp 22 for discharge by the conveyor 23.

Claims

1. Pulverizing apparatus comprising a generally cylindrical vessel (10), feed means (16) for feeding the material to be pulverized into said vessel, a plurality of circumferentially spaced fluid injection nozzles (24) each angled between a radius of the cylindrical vessel passing through the nozzles and a direction perpendicular to said radius, to inject fluid into the vessel and induce an axially flowing vortex (25) in the vessel having its axis generally centrally of the vessel, transverse wall means (12) at a location remote from the nozzles to intercept the vortex and to deflect a portion (26) of the fluid medium and entrained particles of material to effect a recirculation of the fluid medium within the vessel and thus to form a curtain surrounding the vortex, whereby the material is pulverised by interparticle collisions and the curtain reduces high speed particle contact with the cylindrical wall of the vessel, and an outlet (14) in said transverse wall through which a fraction of the pulverised material below a predetermined mass will pass generally along the axis of the vortex, characterised in that the means (16) for feeding the material to be pulverised comprise a generally axially extending feed tube (16) passing through the transverse wall (12) to a point adjacent the axial centre of the vessel in the vicinity of the nozzles and in that said feed tube (16) passes through said outlet (14) in the transverse wall, so that the outlet is thus made annular.

2. Apparatus according to claim 1, characterised in that an annular shroud (15) surrounds said outlet and said feed tube.

3. Apparatus according to claim 1 or 2 characterised in that a feed hopper (17) is mounted on top of said feed tube and material to be fed passes through the feed tube under gravity.

4. Apparatus according to any preceding claim, characterised in that a base plate (20) is placed within said vessel at a location below said point on which a substantially symmetrical pile (30) of material to be pulverised is formed and in that at least one opening (21) is provided through said base plate at or near its periphery for the passage of heavy particles which are not taken up by the vortex.

5. Apparatus according to claim 4, characterised in that a conveyor (23) is provided to remove said heavy particles from a location below said plate.

Ansprüche

1. Prallzerkleinerer mit einem allgemein zylindrischen Behälter (10), mit einer Zufuhreinrichtung (16) zur Zufuhr des zu zerkleinernden Materials in den Behälter, mit einer Mehrzahl von in Umfangsrichtung beabstandeten Fluid-Einblasedüsen (24), von denen jede unter einem Winkel zwischen einem durch die Düsen verlaufenden Radius des zylindrischen Behälters und einer zu diesem Radius rechtwinkligen Richtung angeordnet ist, um Fluid in den Behälter einzublasen und eine axial gerichtete Wirbelströmung (25), deren Achse sich allgemein im Zentrum des Behälter befindet, im Behälter hervorzurufen, mit einer querliegenden Wandeinrichtung (12) an einem von den Düsen entfernten Platz, um die Wirbelströmung abzufangen und einen Teil (26) des Fluidmediums sowie mitgeführter Materialpartikel abzulenken und eine Rezirkulation des Fluidmediums innerhalb des Behälters zu erlangen sowie auf diese Weise einen die Wirbelströmung umgebenden Schleier zu bilden, so daß das Material durch Kollision der Partikel untereinander zerkleinert wird und der Schleier eine Berührung der Partikel mit der zylindrischen Wand des Behältes unter hoher Geschwindigkeit vermindert, und mit einem Auslaß (14) in der querliegenden Wand, durch den ein Anteil des zerkleinerten Materials unter einer vorbestimmten Masse im allgemeinen längs der Achse der Wirbelströmung treten wird, dadurch gekennzeichnet, daß die Einrichtung (16) zur Zufuhr des zu zerkleinernden Materials ein allgemeinen axial verlaufendes Zufuhrrohr (16), das sich durch die querliegende Wand (12) zu einer der axialen Mitte des Behälters in der Nachbarschaft der Düsen nahegelegenen Stelle erstreckt, umfaßt und daß das Zufuhrrohr (16) den Auslaß (14) in der querliegenden Wand durchsetzt, so daß der Auslaß damit ringförmig ist.

2. Prallzerkleiner nach Anspruch 1, dadurch gener nach Anspruch 1, dadurch gekennzeichnet, daß ein ringförmiger Mantel (15) den Auslaß sowie das Zufuhrrohr umgibt.

3. Prallzerkleinerer nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß am oberen Ende des Zufuhrrohres ein Speisetrichter (17) angebracht ist und zuzuführendes Material sich durch das Zufuhrrohr unter der Schwerkraft bewegt.

4. Prallzerkleinerer nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß eine Bodenplatte (20) innerhalb des Behälters an einem Platz unterhalb der Stelle, an der ein im wesentlichen symmetrischer Haufen (30) von zu zerkleinerndem Material gebildet wird, angeordnet ist und daß wenigstens ein Durchlaß (21) in der Bodenplatte an oder nahe deren Außenumfang für den Durchtritt von schweren, von der Wirbelströmung nicht mitgenommenen Partikeln vorgesehen ist.

5. Prallzerkleinerer nach Anspruch 4, dadurch gekennzeichnet, daß ein Förderer (23) für den Austrag der schweren Partikel von einer Stelle unterhalb der Bodenplatte vorgesehen ist.

Revendications

1. Appareil de pulvérisation comprenant un récipient de forme générale cylindrique (10), des moyens d'amenée (16) pour amener le matériau à pulvériser dans ce récipient, une multiplicité de buses d'injection de fluide (24) circonférentielle- ment espacées, chaque buse étant orientée entre un rayon du récipient cylindrique passant à travers les buses et une direction perpendiculaire à ce rayon, pour injecter du fluide dans le récipient et induire un tourbillon (25) se déplaçant axialement dans le récipient et ayant son axe généralement au centre de celui-ci, des moyens de paroi transversale (12) situés à un endroit éloigné des buses pour intercepter le tourbillon et dévier une portion (26) du fluide et des particules de matériau entraînées pour recycler le fluide à l'intérieur du récipient et former ainsi un rideau entourant le tourbillon, d'où il résulte que le matériau est pulvérisé par des collisions entre les particules et que le rideau réduit les impacts des particules à grande vitesse sur la paroi cylindrique du récipient, et une sortie (14) dans cette paroi transversale à travers laquelle une fraction du matériau pulvérisé en dessous d'une masse prédéterminée passe généralement selon l'axe du tourbillon, caractérisé en ce que les moyens (16) pour amener le matériau à pulvériser comprennent un tube d'amenée (16) s'étendant de façon générale axialement et passant à travers la paroi transversale (12) jusqu'à un point adjacent au centre axial du récipient à proximité des buses et en ce que le tube d'amenée (16) passe à travers la sortie (14) dans la paroi transversale, de sorte que cette sortie devient annulaire.

2. Appareil selon la revendication 1, caractérisé en ce qu'une enveloppe de protection annulaire (15) entoure cette sortie et ce tube d'amenée.

3. Appareil selon la revendication 1 et la revendication 2, caractérisé en ce qu'une trémie d'alimentation (17) est montée sur le sommet du tube d'amenée et que le matériau à amener passe à travers le tube d'amenée par gravité.

4. Appareil selon l'une quelconque des revendications précédentes, caractérisé en ce qu'une plaque de base (20) est placée à l'intérieur du récipient à un endroit situé en dessous du point où se forme un monceau pratiquement symétrique (30) du matériau à pulvériser et en ce qu'au moins une ouverture (21) est prévue à travers la plaque de base sur ou au voisinage de sa périphérie pour laisser passer les particules lourdes qui ne sont pas entraînées par le tourbillon.

5. Appareil selon la revendication 4, caractérisé en ce qu'un convoyeur (23) est prévu pour enlever ces particules lourdes depuis un emplacement situé sous la plaque de base.

Drawing