AU624266B2 - Pulverizing mill - Google Patents

Description

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624 2 66 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION S F Ref: 108007

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number: Lodged: PJ6468 20 September 1989 Accepted: Published: Priority: Related Art: Name and Address of Applicant: ICAL Limited 38-46 South Street Rydalmere New South

AUSTRALIA

Wales 2116 6 Actual Inventor: Address for Service: Thomas James Dring Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Pulverizing Mill The following statement is a full description of this invention, including the .t method of performing it known to me/us 8 017013 030990 5815/4 i i i 2 Field of the Invention The present invention relates to mills for the processing of coal.

Background of the Invention A mill with a static classifier is apt to reject too many fine particles, returning rejected fine particles into the recirculating load in the mill. This tends to restrict the capacity of the mill.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate the above disadvantage.

Summary of the Invention There is disclosed herein an appartus for a pulverizing mill, comprising: an inverted conical collector having a large upper opening and a smaller lower opening, the conical collector having an interior surface; o S.5 the lower opening having located within it a body return cone with a tapered outside surface; there being an annular passageway between the lower opening and the tapered outside surface of the body return cone; the 0o0 body return tapering downward,,, and outwardly with respect to the annular passageway.

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a schematic part sectioned side elevation of a mill according to the prior art; 4- 0 Figure 2 is a schematic part sectioned perspective view of a mill according to the present invention.

Best Mode and Other Embodiments of the Invention 949t I In Figure 1 there is schematically depicted one type of commercially available vertical spindle mill 10 for the treatment of coal. The mill comprises a hollow body 11 with central feed pipe 12 to deliver coal to the 3d interior of the mill 10. The interior of the mill body 10 is defined by an inner periphery 100. Surrounding the lower extremity of the feed pipe 12 is a conical collector or cone 13 having an aperture 14 through which the input coal and classifier returns are delivered to a mill table 15. The cone 13 includes a static classifier with apertures 16 which communicate with an outlet pipe 17 through which classified processed coal may be delivered to a furnace.

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i r a r~ ii 1 I 3- The table 15 is, for example, rotatably supported by means of a shaft which in turn is supported by bearings. Fixed to the shaft is a gear engaged by a worm gear. The worm gear rotates the shaft at an approximate speed of 50 rpm. The gear is contained in a gear box provided with oil and an oil cooler. The table 15 has a slightly inclined grinding surface 24 engaged by a crushing roller 25. The crushing roller 25 is rotatably supported so as to be rotatable about an axis 26. The axis may be horizontal or inclined. The journal 27 supporting the roller 25 is pivotally supported by means of a pin 28 so that the roller 25 may also be pivotally moved about an axis extending generally transverse of the axis 26 but spaced therefrom. Extending between the body 11 and the roller journal 27 is a spring 29 biasing the roller 25 to a crushing position engaged with the crushing surface 24.

The table 15 is encircled with an airport 30 through which air o 01\5 circulates upward through the interior space 31 enclosed by the body 11.

o° In operation of the above described mill 10, the table 15 is caused oo0 o to rotate, coal is delivered via the feed pipe 12 to the grinding surface 0 24. The coal delivered to the surface 24 is engaged by the roller crushed and thereby is reduced in size. The crushed coal of reduced 0 0 0 particle size is picked up by the upward travelling airstream 101 from the airport 30 and is delivered to the slots 16. Therefrom, the fine coal is delivered to the outlet 17. Oversized particles fall into and are collected by the cone 13 and are again delivered to the crushing surface 24.

S m* *It should be appreciated that normally the mill 10 would be provided o.O°2J with two or more rollers 25 equally spaced around the vertical axis of the mill 10. Further design criteria of mills adapted to utilize the teachings of the present invention may be found in Australian Patent Application No.

35971/89 in the name of ICAL Limited.

The problem with the type of mill described with reference to Figure 3i 1 3d 1, particularly with reference to coal mills, is that the static classifier is not entirely effective. Thus, fine particles which should enter the outlet pipe 17, do not. These rejected fine particles are reintroduced onto the mill table 15 through the collecting cone aperture 14 and are pulverized again. This reduces the potential efficiency of the mill and may create mechanical problems when fine particles accumulate on the mill table.

rhk/0206E ii, i L: i:B, -4- The problem is solved by providing a device as depicted in Figure 2.

Note that in Figure 2 a mill is shown having a flat table 115, it being acceptable to utilize the teachings of the invention with a variety of vertical spindle arrangements, with flat or inclined tables. As shown in Figure 2, the collecting cone 113 has a lower opening 114. An optional tapered deflector 150 forces falling pulverized material through a first narrow annular passageway 151 between the lower edge of the deflector and the interior surface 152 of the cone 113. This material, including fine particles rejected by the static classifier 153, are forced through a second annular passageway 154 located between the lower periphery of the classifier cone 113 and the tapered outside surface 155 of a body return cone 156. The dispensing skirt is preferably an extension of the central feed pipe 112 which flares downwardly and outwardly as it descends away from the second annular passageway 154. The central feed pipe may be replaced by a side feed, so long as the body return cone is suspended so o o that the second annular passageway 154 and body return cone remain ooo functional. The body return cone 156 terminates at a terminal edge 160 :o which is near the inner periphery 200 of the mill body, closer to the periphery than is the second annular passageway 154. This location for the 0 4:30 body return cone 156 ensures that particles leaving the classifier 113 directed towards the rising flow of heated air 165 emanating from the airport 170 around the mill table rather than being directed directly back 0 onto the mill table with incoming raw coal as shown in Figure 1. This Sinteraction re-suspends the rejected fine particles before they reach the O.2) mill table 115. Coarser particles will fall to the table. Re-suspended fine particles rise with the air flow 165 toward the static classifier, 000 where once again they are either admitted 190 into the outlet pipe 117 or re-admitted 191 into tile cone 113 and dispensed again by the body return cone 156 into the air flow 165. This acts to both increase the capacity of S36 the mill and reduce the unwanted accumulation of fine particles on the mill table. The location of the lower or terminal edge 160 of the body return cone 156 may be above the level of the crushing rollers 25, as shown in Figure 2 or below the upper extremity 125 of the rollers, with the roller extremities 125 located within the cone 156. The terminal edge 160 preferably extends radially as far as, or past the upper extremity 125 (with reference to the centerline 210 of the table 115). In the rhk/0206E rhklO206E L i u, i: d~ alternative, the slope of the outside surface 155 should be such that the particles which travel down the outside surface 155 acquire a trajectory which takes them radially past the upper extremity 125 and into the rising flow of heated air 165 from the airport 170.

While the present invention has been described with reference to particular applications and methods of construction, these should be taken as examples and not limitations to the scope or spirit of the invention.

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Claims (9)

1. An appartus for a pulverizing mill, comprising: an inverted conical collector having a large upper opening and a smaller lower opening, the conical collector having an interior surface; the lower opening having located within it a body return cone with a tapered outside surface; there being an annular passageway between the lower opening and the tapered outside surface of the body return cone; the body return~tapering downwardly and outwardly with respect to the annular passageway.

2. The apparatus of claim 1 further comprising: a conical deflector located above the body return cone and within the conical collector, the deflector tapering downwardly and outwardly to a lower edge; there being a second annular passageway formed between the interior 'L surface of the conical collector and the lower edge of the deflector.

03. The apparatus of either of claims 1 or 2, wherein: 4aP cone f the body returntcomprises an extension of a lower end of a central S" feed pipe. opp

4. A pulverizing mill having a static classifier, the mill also having a hollow body with an inner periphery, a mill table supported in the body and rotatable about a generally vertical axis, at least one grinding roller engaging said table, means for creating an upward travelling Sairstream from around a perimeter of the mill table, characterized by: 4, aO an inverted conical collector having a large upper opening and a smaller lower opening, the conical collector having an interior surface; the lower opening having within it a body return cone with a tapered outside surface; there being an annular passageway oetween the lower opening and the Stapered outside surface of the body return cone; the body return cone tapering downwardly and outwardly with respect to the annular passageway; the body return cone adapted to dispense particulate matter deposited into the conical collector into said upward travelling airstream.

The pulverizing mill of claim 4 further comprising: a deflector located above the body return cone and within the conical collector, the deflector tapering downwardly and outwardly to a lower edge; *r 2.i4l^ I -7 therebeing a second annular passageway formed between the interior surface of the conical collector and the lower edge of the deflector.

6. The pulverizing mill of either of claims 4 or 5 wherein: the body return cone comprises an extension of a lower end of a central feed pipe. One

7. The pulverizing mill of any of claims 4-6, wherein: the grinding rollers are characterized by an upper extremity; the body return cone extending in a radial direction at least as far as, or beyond the upper extremity.

8. A body return cone, substantially as hereinbefore described with reference to Figure 2.

9. A pulverizing mill, substantially as hereinbefore described with reference to Figure 2. DATED this THIRTY-FIRST day of AUGUST 1990 ICAL Limited Patent Attorneys for the Applicant SPRUSON FERGUSON 4 II I) II 0~ O v-J 0 I BO 0 O'I 0Q 0 00 4d 0440I 0 0 0040)~ 4'00 o 008 0 O 0s 0 rhk/0206E