AU620620B2 - Device for the removal of non-combustibles from mills - Google Patents

Description

4i 62062,0 6206 2& Ref: 60731 FORM 10 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int. Class

P

0 0 Application Number: Lodged: PI8479 27 May 1988 Priority: Related Art: Name and Address Accepted: Published: 84 08 8 0 8 of Applicant: ICAL Limited 38-46 South Street Rydalmere New South Wales 2116

AUSTRALIA

Actual Inventor: Thomas James Dring Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market S'reet, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Device For The Removal Of Non-combustibles From Mills The following statement is a full description of this invention, including the best method of performing it known to me/us 5815/2 i;i i JLH/96U 1 -1- The present invention relates to mills for the processing of coal.

Coal has a percentage of non-combustible material in it as well as mixed with it. Frequently this material is comparatively hard and takes longer to reduce to an acceptable size for transfer to the next stage of processing (normally transferred to a furnace) thus effectively reducing mill capacity. Additionally, this hard material is normally a significant contributor to erosion of the mill and subsequent process equipment.

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a vertical spindle mill for the treatment of coal, said mill comprising a hollow body, a mill table supported in the body and rotatable about a generally vertical axis, said mill table being generally radially extending relative to its rotational axis, at least one grinding roller engaging said table to crush coal delivered to said table, means to create an upward travelling airstream within said body to carry 2 of" coal from said table to an outlet in said body, and means to remcd at least a portion of non-combustibles delivered to the interior of said body with said coal, said means to remove said non-combustibles comprising a chute attached to the interior of said body at a position -stream of said table in the direction of flow of said airstream.

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 vertical spindle mill with a vane wheel; Figure 2 is a schematic part sectioned perspecti' e view of a portion 4"0'0* of the mill of Figure 1; Figure 3 is a schematic part sectioned side elevation of a vertical spindle mill with air ports and a separator body liner; Figure 4 is a schematic plan view of a hopper employed in the mill of f 30 Figures 1 and 3; Figure 5 is a schematic front elevation of the hopper of Figure 4; Figure 6 is a schematic side elevation of the hopper of Figure 4; Figure 7 is a schematic side elevation of a screen employed with the hopper of Figure 4; and Figure 8 is a schematic plan view of a portion of the screen of Figure 7 in Figure 1 there is schematically depicted a vertical spindle mill RA: tO-ftr-the treatment of coal. The mill 10 comprises a hollow body 11 with tDG: 3jo.

-2central feed pipe 12 to deliver coal to the interior of the mill Surrounding the lower extremity of the feed pipe 12 is a cone 13 having an aperture 14 through which the input coal is delivered to a mill table The cone 13 has side apertures 16 which communicate with an outlet pipe 17 through which processed coal may be delivered to a furnace. The table is rotatably supported by means of a shaft 18 which in turn is supported by bearings 19. Fixed to the shaft 18 is a gear 20 engaged by a worm gear 21 to rotate the shaft 18. The worm gear 21 rotates the shaft 18 at an approximate speed of 50 rpm. The gear 20 is contained in a gear box 22 provided with oil and an oil cooler 23. 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 body 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.

o a0 Extending between the body 11 and the roller body 27 is a spring 29 biasing 0, the roller 25 to a crushing position engaged with the crushing surface 24.

The table 15 is provided with a vane wheel 30 (as best seen in Figure 2) which causes air to circulate upward through the interior space 31 0400 0 o 0 °2D enclosed by the body 11. Hot primary air is delivered to the air inlet 32, a0 wherefrom the air is then delivered to the vane wheel Located below the table 15 are scrapers 33 which deliver reject o, material to a reject chute 34. It has been found that heavier material will often fall past the vane wheel 30, which heavier material is gathered by the scrapers 33 and delivered to the chute 34.

C

In operation of the above described mill 10, the table 15 is caused to rotate, coal is delivered via the feed pipe 12 to the grinding surface 24. The coal delivered to the surface 24 is engaged by the roller 25 and thereby is reduced in size. The coal of reduced particle size is picked up by the upward travelling airstream and is delivered to the slots 16.

Therefrom, the coal is delivered to the outlet 17. Oversized particles are collected by the cone 13 and are again delivered to the crushing surface 24. Additionally, oversized particles too heavy for the airstream travelling upward to the cone 13 are again circulated and delivered to the surface 24.

Located on the internal surface of the body 11 is at least one chute to collect at least a percentage of the recirculating heavier material.

This recirculating heavier material will often be silica, which is too DG:0131t

I

-3heavy for the airstream and tends to circulate around the lower portions of the space 31. During this recirculation of the heavier material, at least a portion will be collected by the chute.

It should be appreciated that normally the mill 10 would be provided with three of the rollers 25 equally spaced around the vertical axis of the mill 10. Additionally three equally spaced chutes 35 would also be provided.

The above described preferred form of the present invention, that is the mill 10, is intended to remove a percentage of the non-combustible material from the mill 10, most of it before it has been reduced significantly in size. By doing this the recirculating load in the mill is reduced, the percentage of highly errosive material recirculating in the S mill is reduced and the percentage of erosive material passed on to subsequent equipment is reduced. The net result is lower mill load 00 00 °o o5 (reduced recirculating load), subsequent increased mill capacity, lower 000 a mill erosion, less mill maintenance and lower erosion of subsequent plant.

GOo Turning now to Figure 3 wherein an alternative configuration of the mill 10 is depicted. The mill 10 of Figure 3 is of substantially similar construction to the mill 10 of Figure 1 except that the table 15 is not 0000 0° provided with a vane wheel. Surrounding the table 15 is a sealing member 00 0 36 provided with a plurality of air ports allowing air to pass from the hot air inlet 32 to the space 31. Each of these ports is provided with a 0 00 S0 plurality of vanes which direct the air to circulate as best seen in Figure 3. There is also provided at spaced locations about the internal surface of the body 11 deflector liners 37. The vanes in the air ports co-operate with the deflector liners 37 to again cause recirculation of the heavier material. Some of this heavier material is collected by the chute In Figures 4, 5 and 6, the chute 35 of Figures 1 and 3 is more fully depicted. The various parameters in respect of the size and location of the chute 35 are also indicated and are listed in the table to follow. The chute 35 is provided with an outlet tube 38 through which the rejected material is drained while additionally there is provided a selective screen hood 39. The screen hood 39 is more fully depicted in Figures 7 and 8 and comprises a plurality of spaced bars 40 as best seen in Figure 8. Again the various parameters governing the size of the screen hood 39 are listed in the following table.

DG:0131t iK [-i

PARAMETER

e h a b c to 30 Deg -4 PREFERRED RANGE 10 to 20 Deg 800 to 1100 mm 0 to 200 mm 200 to 700 mm 40 to 700 mm 25 Deg 17'

OPTIMUM

13 Deg 900 mm 0 mm 500 mm 500 mm 1359 mm t a car Ir I 'aS 25 r Ir I

U.

A 20 to 75 mm 30 to 50 Deg 45 Deg p 2.5 to 5 mm w 1.0 to 2.4 mm B 0 to 50 mm C 10 to 65 mm cc 30 to 50 Deg p 2.5 to 5 mm w 1.0 to 2.4 mm Figures 5 to 8 the following parameters are indicated 55 mm 2.5 mm 2.0 mm 0 0 by the In following:

A.B.C.

w, w p, pl h a and b 0

R

c Angle of incline top screen.

Angle of incline bottom screen.

Height geometry of hood.

Width of respective screen rods.

Pitch of respective screen rods.

Horizontal reference angle from datum.

Vertical reference height from datum.

Height geometry of collection hopper.

Anglor width of collection.

Wall radius.

Depth of collection hopper.

;i I j aW j

Claims (5)

1. A vertical spindle mill for the treatment of coal, said mill comprising a hollow body, a mill table supported in the body and rotatable about a generally vertical axis, said mill table being generally radially extending relative to its rotational axis, at least one grinding roller engaging said table to crush coal delivered to said table, means to create an upward travelling airstream within said body to carry coal from said table to an outlet in said body, and means to remove at least a portion of non-combustibles delivered to the interior of said body with said coal, said means to remove said non-combustibles comprising a chute attached to the interior of said body at a position 4stream of said table in the direction of flow of said airstream.

S2. The vertical spindle mill of Claim 1, wherein said chute has an upwardly open face to receive said non-combustibles, which open face extends angularly for 10 to 20 degrees about said vertical axis. c

3. The vertical spindle mill of Claim 2, wherein said open face extends for approximately 13 degrees about said vertical axis.

4. The vertical spindle mill of Claim 2 or 3, further including a selective screen hood covering said open face, which hood consists of a plurality of spaced rods.

5. A vertical spindle mill, substantially as hereinbefore described with reference to the accompanying drawings. DATED this FIRST day of JUNE 1989 ICAL Limited Patent Attorneys for the Applicant SPRUSON FERGUSON DG 0 ©rT