GRINDING BOOM

Field of the Invention

This invention relates to a grinding method and apparatus. It relates particularly but not exclusively to a grinding boom which can be used in high temperature situations such as grinding scale from exhaust systems of high temperature furnaces. It also relates to sealing methods and devices for allowing equipment such as a grinding boom to operate in a closed environment.

Background of the Invention

Off gases from furnaces are often loaded with, components which solidify and form scale in exhaust systems for such furnaces. This is particularly true of flash furnaces generating nickel matte or other metals, particularly non-ferrous metals.

Typically such furnaces have a vertical section for taking off hot gas. The vertical section communicates with a quench chamber or waste heat boiler via a transition member. The hot gases may be cooled by a shower of water in the quench chamber or the heat recovered via a plurality of boiler tube bundles.

With the rapid cooling of gas as it moves from the vertical flue to the quench chamber or waste heat boiler, there tends to be a build up of scale or particles in the transition.

As a result, it is generally necessary to periodically scrape the scale or other deposits from the transition to prevent it becoming blocked. However, with current practices, because of the high temperature usually present in the transition during operation of the furnace and the pressure differential to outside air, operation of the furnace must be interrupted to remove scale or other unwanted deposits from the transition or from other parts of the furnace construction. Typically, this may mean that a furnace is not operating for as much as one hour in every twenty-four.

Given that there is an enormous loss of revenue associated with interrupting the operation of a furnace on a regular basis, there is clearly a very real need for an alternative approach which can successfully remove scale without interrupting the furnace operation.

Disclosure of the Invention

The invention provides in one aspect a grinding boom comprising, a rotatable grinding head having a grinding surface and an underside surface, a support arm for mounting the grinding head, and a cooling fluid conduit extending coaxially through the support arm, wherein the arrangement is such that cooling fluid can pass through the cooling fluid conduit to cool the undersize surface of the grinding head.

By having a grinding head construction which allows the head to be cooled while in use, it should be possible to grind away scale or other materials in certain situations without stopping operation of the furnace.

Where there is a pressure differential between the outside air and the region where scale is being ground away, the use of a sealing arrangement for the grinding boom may be appropriate to maintain the pressure differential.

Of course, given the high temperatures involved, it is highly desirable for the cooling fluid eg. water to be kept separate from contact with the hot gases and accretion materials evolved by the furnace.

Thus, the cooling fluid may be directed through the boom to impinge upon the underside of the grinding head without ever actually coming into contact with the hot gases and accretion materials and furnace walls.

The cooling fluid conduit may be arranged so that it directs cooling fluid against the underside surface.

The underside surface may be provided with an arrangement of channels which direct the cooling fluid over a predetermined region of the underside surface. It may direct the cooling fluid in spiral fashion over the underside surface. The channel arrangement may comprise a cup shaped to fit against the underside surface. The cup may have a spiral divider in the form of a ridge or vane which creates a flow channel for the cooling fluid. Suitably the flow channel may be spiral.

The cooling fluid conduit may be rotatable with the grinding head.

A return gallery coaxial with the cooling fluid conduit may be arranged to return cooling fluid to an exit point from the grinding boom. The return gallery may be rotatable with the cooling fluid conduit.

The grinding head may comprise a generally hemispherical shell. It may comprise a plurality of grinding elements. The grinding elements may be set in recesses formed in the grinding head. The grinding elements may comprise tungsten carbide. They may be arranged at an acute angle with respect to a tangent taken on the spherical head at the location of the grinding element. The acute angle may be between 15° and 70°, it may be between 35° and 50°.

A secondary cooling circuit may be provided for the grinding boom. The secondary cooling circuit may be arranged so as to cool the support arm. It may comprise one or more water galleries for cooling the support arm. The water galleries may be arranged so as to cause water to spiral in contact with and along the support arm.

The grinding boom may be arranged so as to be movable into and out of a transition member for a smelter exhaust. The transition member may be arranged to direct hot gases into a quench chamber or waste heat boiler. The arrangement of grinding boom and quench chamber or waste heat boiler may be such that the grinding boom is arranged to penetrate through the quench chamber so that it may reach the transition member. For this purpose, the grinding boom may be mounted via a trackway so that it is movable along the trackway. It may be mounted via a robot. The robot may be

arranged to move the grinding boom so as to bring the grinding head into contact with scale in the transition member. The grinding boom may pass through a sealing device in a wall of a chamber or enclosure so as to maintain any pressure differential between the outside and the interior of the chamber or enclosure.

In another aspect, the invention provides a method of grinding a surface in an enclosure maintained at a pressure differential to outside air comprising extending an arm Of a grinding apparatus from a region of normal outside air pressure through a seal assembly provided at a wall of the enclosure so as to impinge a grinding head of the grinding apparatus against the surface, wherein the seal assembly is constructed so as to allow the arm to move with respect to the wall whilst maintaining a seal between the wall and arm.

The seal assembly may be mounted on a carriage arranged to bring the seal assembly into an out of registry with an access port provided on the wall of the enclosure. The access port may have a movable cover to allow closing of the access port when the seal assembly is moved away from the access port.

Li another aspect, the invention provides a seal assembly for allowing a grinding apparatus such as the grinding boom hereinbefore described to extend through the wall of an enclosure comprising, a hollow member having a part spherical outer surface, an outer opening and an inner opening for the hollow member, a collar for holding the hollow member about the part spherical outer surface whereby the hollow member may be swivelled with respect to the collar, and seating means for providing a seal between the seal assembly and an arm of the grinding apparatus extending through the hollow member from the outer opening to the inner opening and into the enclosure.

The seal assembly may include roller members for allowing the arm of the grinding apparatus to be slidable through the hollow member.

Preferred aspects of the invention will now be described with reference to the accompanying drawings.

Brief Description of the Drawings

5

Figure 1 shows an elevational view of a grinding boom constructed in accordance with the invention;

Figure 2 shows a fragmentary magnified section A-A taken through Figure 1;

Figure 3 shows a further magnified partial sectional view of a front portion of i o the grinding boom of Figure 1 ;

Figure 4 shows a side on elevational view of a grinding head;

Figure 5 shows apian view of a grinding head;

Figure 6 shows section A-A taken on Figure 5;

Figure 7 shows section B-B taken on Figure 4; 15 Figure 8 shows an isometric view of a grinding boom and quench chamber;

Figure 9 shows a fragmentary magnified view of a portion of the quench chamber of Figure 8;

Figure 10 shows a partially cut away view of a swivel seal; and

Figure 11 shows section A-A taken on Figure 10. 0

Detailed Description of the Preferred Embodiments

The various elements identified by integers in the drawings are listed in the following integer list. 25

Integer List

1 Grinding boom

2 Water galleries

30 3 Water galleries

4 Water galleries

5 Grinding head

6 Grinding elements

7 Fluid conduit

8 Head space

9 Connecting assembly

10 Bearing assembly

11 Bearing assembly

12 Seal assembly

13 Support arm

14 Extension member

15 Extension member

16 Drive shaft member

17 Seal (high temperature)

18 Cavity

19 Intermediate member

20 Spiral cup

21 Open end

22 Spiral divider

25 Spiral divider

26 Spiral divider

27 Spiral divider

28 Outer surface

29 Underside surface

30 Tubular wall

32 Jjnternal cavity

33 Inlet pipe

34 Outlet pipe

36 tniet

38 Outlet

39 Rotary union

40 Drive unit

42 Mounting assembly

44 Recess

45 Dome

47 Screw thread

50 Quench chamber

51 Transition member

52 Gas inlet

54 Outlet

56 Mounting platform

58 Trackway

59 Robot

62 Trackway

64 Swivel seal assembly

66 Carriage

68 Access port

70 Movable cover

72 Cool gas exhaust

74 Semi-spherical casting

75 Outer opening

16 Inner opening

78 Mounting collar

79 Low friction packing

80 Roller

82 Cover piece

83 Annular element

84 Cover piece

85 Annular element

86 Annular element

87 Spacer element

88 Spacer element

89 Spacer element

92 Scraper element

94 Bolts

Referring to Figures 1 to 3, there is shown a grinding boom according to the invention generally designated 1.

It comprises a tubular elongate support arm 13 at the end of which is mounted a tubular extension member 14 in a manner which allows relative rotation between these two members. The rotating portions of the grinding boom are identified by hatching in Figure 3 for clarity. .

A grinding head 5 is mounted on the extension member 14. The grinding head is hollow and has a generally hemispherical outline.

A number of grinding elements 6 comprised of high temperature high hardness material such as tungsten carbide are provided on the grinding outer surface 28 of the head in a manner which will be described in more detail hereinafter.

A fluid conduit 7 which extends coaxially within the support arm 13 is arranged to deliver cooling fluid such as water to the grinding head. The water flows in the direction indicated by the arrows in the water galleries 2. The fluid conduit is arranged to deliver fluid to the head space 8. From there it flows through the open end 21 of the spiral cup 20 to impinge on the inner underside surface 29 of the grinding head 5. It then flows into a number of water galleries 2 defined by the spiral cup 20 which nests against the underside surface of the grinding head. A spiral divider 22 in the form of a ridge spiralling around the outer surface of the spiral cup directs the water to move spirally through water galleries 2 around the spiral cup along the underside surface of the grinding head and then through a further number of water galleries 2 defined between the intermediate member 19 and extension member 14.

A spiral divider 25 between the telescopic extension 14 and intermediate member 19 defines a spiral water gallery 2 for return of cooling fluid from the grinding head 5 after it has passed through the spiral galleries defined by the spiral cup 20.

The extension member 15 and intermediate member 19 are joined at the connecting assembly 9 formed at the forward end of the intermediate member by appropriately located connecting bolts. In turn, the extension member is mounted on a drive shaft

member 16. The water gallery 2 for water returning from cooling the grinding head is defined between the drive shaft member 16 and fluid, conduit 7.

A cavity 18 is defined between the telescopic drive shaft 16 and fluid conduit 7 for return of water after it has cooled the grinding head 5. This constitutes a further water gallery 2.

The fluid conduit, extension member 15 drive shaft 16 intermediate member 19, extension member 14 and grinding head 5 are jointly mounted. They are all driven to rotate with respect to the support arm 13 by a rotary-drive assembly operating through the end assembly 39.

Bearing assemblies 10 and 11 allow relative rotation, between these components and the support arm. The bearing assemblies 10 and 11 are mounted between the tubular wall 30 and extension member 15. The seal assembly 12 aizd high temperature seal 17 ensure water tightness of the water flow through the various galleries.

The tubular wall with drive shaft 16 defines an internal cavity 32.

Spiral dividers 26 and 27 are provided between the support arm 13 and tubular wall 30 to provide spiral water galleries 3 and 4 for flow of cooling water to cool the support arm.

The water galleries 3 and 4 are arranged so that water flows counter current through • adjacent galleries so that it moves forward to cool the support arm and then returns with water to the galleries being supplied by the inlet pipe 33 and being discharged through the outlet pipe 34.

Cooling water for the fluid conduit 7 and water galleries 2 is supplied by the inlet 36 and exits via the outlet 38 shown more clearly in Figure 2.

A rotary union 39 is provided for mounting the inlet and outlet 36 and 38 and connects to the drive unit 40 for the grinding boom. The grinding boom is mounted on a robot 59.

The connecting arm and grinding boom are in turn joined together by the mounting assembly 42.

Referring to Figures 4 to 1, it can be seen that the grinding head 5 comprises a hollow dome 45 usually formed of a heat resistant material such as steel. A large number of recesses 44 are formed on the outer surface-of the dome. These recesses are used for mounting of the tungsten carbide grinding elements 6 which may typically be mounted so that they project forward at an angle of about 45° with respect to the tangent to the dome.

The direction of the grinding elements 6 is such that they point forward in the direction of rotation of the grinding head. Typically, they may be arranged in rows of grinding elements as illustrated.

A screw thread 47 is provided on the interior surface of the dome to facilitate attachment to the corresponding screw thread formed on the telescopic extension member 14.

Referring to Figures 8 and 9, there is shown a typical exhaust gas arrangement for a nickel smelter which incorporates a quench chamber 50.

As discussed previously, the quench chamber may include an arrangement for spraying water down through the chamber to cool hot exhaust gases from a nickel matte furnace.

The hot gases after passing through a vertical flue above the furnace, are transferred via the transition member 51 through a gas inlet 52 in the side of the quench chamber 50.

An outlet 54 at the bottom of the quench chamber is provided for excess water and/or solids and a cool gas exhaust 72 is provided at the side of the quench chamber.

A mounting platform 56 provided level with the quench chamber includes a trackway 58 on which the robot 59 is mounted.

The robot is arranged to hold and move the grinding boom 1 so as to grind away scale which accumulates in the transition member.

The grinding boom is long enough to allow it to be moved forward by the robot along trackway 58 so that it extends through the swivel seal assembly 64 in the side of the quench chamber. The scope of movement will be sufficient to allow the cutting head to be appropriately positioned in the transition member 51 and moved as required to grind off scale in the transition member. A second trackway 62 having a movable carriage 66 is arranged so as to be able to move the swivel seal assembly 64 into and out of registry with the access port 68 of the quench chamber.

When the grinding boom and swivel seal assembly 64 are fully retracted, the access port 68 may be covered by the movable cover 70 as and when required.

Referring to Figures 10 and 11, the swivel seal assembly 64 comprises a semi-spherical casting 74 having an outer opening 75 for insertion of the arm of a grinding boom, and an inner opening 76 which extends through the access port 68 of an enclosure such as a quench chamber.

The semi-spherical casting is mounted in a mounting collar 78 which is mounted on the carriage 66 described with reference to Figure 8.

Low friction packing 79 is provided between the mounting collar and outer surface of the semi-spherical casting 74, ' The packing conforms to the circular surface of the semi-spherical casting allowing the semi-spherical casting to swivel with respect to the collar.

A number of rollers 80 are provided proximate the inner and outer openings 76 and 75. The rollers have a generally dished or concave surface to facilitate smooth sliding of the tubular arm of a grinding boom through the swivel seal assembly.

Cover pieces 82 and 84 are provided on the outer and inner openings covering the roller assemblies, hi the case of cover piece 84, it also secures an annular element 83 to the outlet of the inner opening 76.

A pair of annular elements 86 are secured in front of the cover piece 84.. Spacer elements 87, 88 and 89 are provided between these annular elements, and a scraper element 92 for purposes to become apparent

The scraper element 92 is mounted forward of one of the two annular elements 86 and is spaced therefrom by the spacer element 87. Finally, the annular element 85 is provided forward of the scraper element.

The assembly of annular elements, spacer elements and scraper element together with the cover piece are held by the bolts 94,

The annular elements 83, 85 and 86 may be formed of a resilient material such as a tough rubber or plastic material which provides a seal with the arm of the grinding boom. They snugly surround the arm of a grinding boom and act to wipe off loose detritus which may accumulate on the arm. The spacer elements create a gap between the annular elements through which detritus which has been wiped off may freely fall into the chamber or enclosure into which the arm extends.

The scraper element 92 has a forwardly protruding edge which serves to perform an initial cutting or slicing operation on detritus accumulating on the arm of the boom when the arm is retracted. The annular element 85 acts as a washer to assist with holding the scraper element securely in position.

With this type of arrangement, it can be seen that the cooled grinding boom may be used to grind away scale formed in the transition member even when the furnace is

operating and hot gas is passing through the transition member. Thus the furnace can be operated continuously. Furthermore, the swivel seal assembly and boom/robot are retractable, the boom, robot and swivel seal assembly may be removed for servicing with closing of the movable cover 70 without interrupting the operation of the furnace.

Whilst the above description includes the preferred embodiments of the invention, it is to be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spirit or ambit of the invention.

It will be also understood that where the word "comprise", and variations such as

"comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of another feature or features.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge in Australia,