GB2144055A - Apparatus for and method of spraying refractory-forming material - Google Patents

Abstract

Apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprises a lance 1 having a lance head 2 mounted at the distal end of a feed tube 4 and a cooling jacket 5 surrounding at least part of the length of that tube. The lance head 2 is mounted for rotation relative to the cooling jacket 5, and comprises at least one discharge orifice 6 whose axis is, when viewed in a direction along the bore of the feed tube 4 at its distal end, radial of or chordal to that bore. For repairing a refractory or refractory-lined flow passage, the lance head is moved axially along the passage and is rotated to discharge the particulate material against the wall of the passage so that the combustible material burns with the evolution of heat to form a coherent refractory mass adhering to the wall. <IMAGE>

Description

SPECIFICATION Apparatus for and method of spraying refractory-forming material This invention relates to apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprising a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of that tube. The invention extends to a method of spraying such material.

Apparatus of such a kind and a process using such apparatus are described in British Patent Specifications Nos 1,530,895 and 1,350,894 to Glaverbel. In such processes, a mixture of refractory-forming particles and refractory particles is projected against a surface in a gas stream containing oxygen. Examples of refractory materials cited are particles of silica, alumina, zircon, zirconia and magnesia, and mixtures of two or more of these materials. Examples of refractory-forming materials are particles of silicon, aluminium, zirconium and magnesium, and mixtures of two or more of these materials. The refractoryforming particles burn in the presence of oxygen to form a corresponding refractory material and to evolve heat to melt at least the surfaces of the refractory particles they are sprayed with, so that a coherent refractory mass is formed.

Such a process and apparatus are useful for forming in situ repairs on hot refractory linings and other parts of laboratory or industrial furnaces or ovens, for example glass or steel melting furnaces or coking ovens, where the part to be repaired is within a chamber of sufficient size that the lance can easily be manipulated within it. However problems arise when there is not sufficient room for the lance to be manipulated easily to direct material against the surface to be repaired.

Such a problem arises in particular in connexion with basic oxygen steel making furnaces, otherwise known as LD or Linz-Donawitz steelmaking furnaces. The basic oxygen steelmaking furnace comprises a barrelshaped steel shell with a refractory lining which is supported on trunnions so that it can be tilted. A taphole is located in the side of the furnace, below the mouth, so that on tilting the molten steel contained in the furnace can be poured from beneath the floating slag. The refractory lining is usually formed of magnesite and/or dolomite bricks while the taphole leading through it typically has a length of about Im and a diameter of about 200 mm. The taphole is usually formed using hollow magnesia bricks.In order to pour steel from the furnace in a smooth stream, the taphole must have a good cylindrical form, but it will be appreciated that pouring even a single load which may be up to 400 tonnes will erode the magnesia bricks defining the taphole. It is accordingly desirable to make good the taphole after each pour.

In the usual working cycle, the furnace is charged with scrap and then with molten iron, an oxygen lance is then introduced into the furnace and the charge is blown with oxygen whereafter the steel is poured off through the taphole. Slag is then poured off and the furnace is cleaned ready for the next cycle. In a 200 tonne furnace such a cycle usually takes about 50 minutes and it is generally desirable that the furnace should be recharged within a further 10 or 20 minutes. This is the only time available for carrying out repairs to the taphole without disrupting production.

It is an object of the present invention to provide an apparatus and a method which enables such a repair to be effected in the time available and which is also suitable for use in repairing other refractory or refractorylined flow passages.

According to the present invention, there is provided apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprising a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of that tube, characterised in that the lance head is mounted for rotation relative to said cooling jacket for discharging sprayed material at an angle to the axis of such rotation.

The invention also provides a method of repairing a refractory or refractory-lined flow passage for the conveyance of hot fluid material, which method comprises spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas via a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of the feed tube, characterised in that the lance head is moved axially along the flow passage and is caused to rotate about such axis in order to discharge the particulate material against the wall of the passage so that the combustible material burns with the evolution of heat to form a coherent refractory mass adhering to such wall.

By using the apparatus or method of this invention, a refractory or refractory-lined flow passage, for example a basic oxygen furnace taphole, may easily and rapidly be provided with a smooth continuous surface of refractory material formed in situ.

In the most preferred embodiments of the invention, the lance head comprises at least one discharge orifice whose axis is, when viewed in a direction along the bore of the feed tube at its distal end, radial of or chordal to that bore. The adoption of this feature enables a stream of particles to be ejected with but a single change in direction within the lance head, and this contributes to reducing wear of the lance head by the refractory particles which are, in particular, strongly abrasive.

The adoption of this feature is of considerable practical value, and according to a further aspect of the present invention, there is provided apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprising a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of that tube, characterised in that the lance head comprises at least one discharge oriffice whose axis is, when viewed in a direction along the bore of the feed tube at its distal end, radial of or chordal to that bore.

In such apparatus, it is especially preferred that the lance head is mounted for rotation relative to said cooling jacket.

Preferably, the lance head is fixed to the distal end of said feed tube and said feed tube is rotatable in said cooling jacket. By causing the feed tube to rotate relative to the cooling jacket during performance of the method of the invention, such performance is made more reliable, and the construction of the apparatus is simpliffied. The cooling jacket itself serves as a bearing for the rotating lance head. As a result of this, the bearing is cooler, and thus less liable to jam, than would be the case if for example the lance head were mounted for rotation on the distal end of the feed tube.

Because the apparatus can be arranged with a non-rotating cooling jacket, supply of coolant to the jacket is simplified.

Advantageously, the lance head comprises at least one discharge orifice whose axis is substantially perpendicular to that of the distal end of the feed tube. The discharge of particulate material from the lance head perpendicular to the bore of the feed tube at its distal end tends to promote adherence of the in situ formed refractory mass to the wall of a refractory or refractory-lined passage in which such discharge takes place.

In preferred embodiments of the invention the feed tube is substantially straight and concentric with the axis of rotation of the lance head. By the adoption of this feature, especially if the feed tube is moved so that its axis coincides with the axis of the flow passage, unifformity of deposition of sprayed material is enhanced.

Such uniformity of deposition of sprayed material is further enhanced when the lance head comprises a plurality of discharge orifices symmetrically located with respect to its axis of rotation, as is preferred.

Preferably the cooling jacket extends substantially to the lance head. This enables the feed tube to be cooled over a length which extends substantially to the lance head where the feed tube would, in the absence of such cooling, be hottest.

It is preferred for the cooling jacket to be fixed to a carriage which is movable for advance and withdrawal of the lance head.

Preferred embodiments of the present invention will now be described in greater detail, and by way of example only, with refer ence to the accompanying diagrammatic drawings, in which: Figure 1 is a detail sectional view of a distal end of a lance feed tube bearing a lance head; Figure 2 is a section on the line ll-ll of Figure 1; Figure 3 is a section corresponding to that of Figure 2, showing a modified lance head; and Figure 4 is a general view of apparatus according to this invention.

A lance 1 for spraying particulate refractoryforming combustible material, particulate refractory material and a comburent gas has a lance head 2 mounted by a screwthread at the distal end 3 of a feed tube 4, and a cooling jacket 5 which surrounds at least part of the length of that tube. The lance head 2 includes a plurality of discharge orifices 6, of which two are shown in Figure 1, their axes being coincident with the line ll-ll of that Figure. The lance head is provided with a heat-resistant thermally-insulating cover (not shown), which, together with the flow of gas through the lance head in use, ensures that the temperature of the lance head does not rise too much. The cooling jacket 5 comprises two concentric tubes 7,8 for the counter flow of coolant which surround the feed tube 4 and extend almost to the distal end 3 of that tube.The outer cooling jacket tube 7 is connected to the feed tube 4 by a sealing bearing 9, for example a graphoil bearing, at the distal end of the cooling jacket 5.

The axis of rotation of the lance head 2, which is coincident with the axis of the bore 10 of the feed tube 4, is indicated at 11.

As will be seen from Figure 2, there are four discharge orifices 6 which are located symmetrically of the axis 11. Those orifices are radial of the bore 10 when viewed in a direction along that bore at the distal end 5 of the feed tube 4, and as will be seen from Figure 1, they are perpendicular to that bore.

In a particular practical example, the radius of the bore 10 of the feed tube was 0.5 inch (1 2.7mm) while the radius of each discharge orifice was 0.575 inch (9.5mm).

Figure 3 illustrates a second form of lance head 2 which has been modified in that the discharge orifices 6 are chordal to the bore 10 of the feed tube, rather than radial to it.

Figure 4 illustrates a lance 1 having a head 2 mounted at the distal end of a feed tube 4 for rotation relative to a cooling jacket 5, the lance 1 being carried by a carriage 1 2 having wheels 1 3 running on tracks 14 under the control of a hydrauiic jack 1 5 whose cylinder 1 6 is fixed with respect to the tracks 1 4 and whose control rod 1 7 is attached to a bracket 1 8 mounted on the carriage 1 2. The jack 1 5 is shown offset for clarity in Figure 4, but would normally be mounted centrally.

The cooling jacket 5 of the lance 1 is fixed to the carriage 1 2 by means of a bracket 1 9.

The feed tube 4 of the lance 1 projects from the proximal end of the cooling jacket 5, through a bearing 20 mounted on the carriage 12 and past a drive mechanism 21 for rotating that tube, and terminates in a coupling 22. The coupling 22 permits sealing between the rotatable feed tube 4 and a stub tube 25 fixed in a bracket 24 on the carriage.

The stub tube 23 is connected to a source of material to be sprayed via a flexible pipe 25.

Means 26 is provided for the ingress and egress of coolant at the proximal end of the cooling jacket 5.

The tracks 1 4 are slung from a gantry (not shown) for bodily movement, tilting and rotation, so that the lance carried thereby may readily be aligned with the part to be repaired.

In operation, for repairing a taphole of a basic oxygen furnace, the furnace and the tracks 1 4 are appropriately relatively positioned, for example with the lance 1 pointing downwardly at an angle of 45 . The lance head is caused to rotate by the mechanism 21, for example at a rate of between 1 and 20 rpm, and material sprayed from the head 2 is ignited. The jack 1 5 is actuated to advance the lance head rapidly into the taphole to the extent necessary, and then to withdraw the lance more slowly so as to deposit the desired new refractory lining.

By way of example, the particulate material sprayed to repair a hot refractory body of magnesia may consist of, by weight, 88% magnesia refractory particles and 12% combustible particles made up of 10% silicon and 2% aluminium. If desired, the proportions of silicon and aluminium could be altered to increase the amount of aluminium used.

Claims (18)

1. Apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprising a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of that tube, characterised in that the lance head is mounted for rotation relative to said cooling jacket for discharging sprayed material at an angle to the axis of such rotation.

2. Apparatus according to claim 1, wherein the lance head comprises at least one discharge orifice whose axis is, when viewed in a direction along the bore of the feed tube at its distal end, radial of or chordal to that bore.

3. Apparatus for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas comprising a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of that tube, characterised in that the lance head comprises at least one discharge orifice whose axis is, when viewed in a direction along the bore of the feed tube at its distal end, radial of or chordal to that bore.

4. Apparatus according to claim 3, wherein the lance head is mounted for rotation relative to said cooling jacket.

5. Apparatus according to any of claims 1, 2 and 4, wherein the lance head is fixed to the distal end of said feed tube and said feed tube is rotatable in said cooling jacket.

6. Apparatus according to any preceding claim, wherein the lance head comprises at least one discharge orifice whose axis is substantially perpendicular to that of the distal end of the feed tube.

7. Apparatus according to any preceding claim, wherein the feed tube is substantially straight and concentric with the axis of rotation of the lance head.

8. Apparatus according to any preceding claim, wherein the lance head comprises a plurality of discharge orifices symmetrically located with respect to its axis of rotation.

9. Apparatus according to any preceding claim, wherein the cooling jacket extends substantially to the lance head.

10. Apparatus according to any preceding claim, wherein the cooling jacket is fixed to a carriage movable for advance and withdrawal of the lance head.

11. A method of repairing a refractory or refractorylined flow passage for the conveyance of hot fluid material, which method comprises spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas via a lance having a lance head mounted at the distal end of a feed tube and a cooling jacket surrounding at least part of the length of the feed tube, characterised in that the lance head is moved axially along the flow passage and is caused to rotate about such axis in order to discharge the particulate material against the wall of the passage so that the combustible material burns with the evolution of heat to form a coherent refractory mass adhering to such wall.

1 2. A method according to claim 11, wherein the lance head is caused to rotate relative to the cooling jacket.

1 3. A method according to claim 11 or 12, wherein the particulate material is discharged from the lance head radially of or chordally to the bore of the feed tube at its distal end.

14. A method according to any of claims 11 to 13, wherein said feed tube is caused to rotate relative to the cooling jacket.

1 5. A method according to any of claims 11 to 14, wherein the particulate material is discharged from the lance head perpendicular to the bore of the feed tube at its distal end.

1 6. A method according to any of claims 11 to 15, wherein the feed tube is straight and is withdrawn so that its axis coincides with the axis of the flow passage.

1 7. A method according to any of claims 11 to 16, wherein the particulate material is discharged symmetrically about the axis of rotation.

18. A method according to any of claims 11 to 17, wherein the feed tube is cooled over a length which extends substantially to the lance head.