US3224749A

US3224749A - Oxygen injection lance

Info

Publication number: US3224749A
Application number: US441399A
Authority: US
Inventors: Walter V Berry
Original assignee: Berry Metal Co
Current assignee: Berry Metal Co
Priority date: 1965-03-01
Filing date: 1965-03-01
Publication date: 1965-12-21
Anticipated expiration: 1982-12-21

Description

Dec. 21, 1965 w, v. BERRY 3,224,749

OXYGEN INJECTION LANCE Original Filed April 23, 1962 INVENTOR. WALTER v. EERRY A'T'TOQMEY United States Patent f 3,224,749 OXYGEN INJECTION LANCE Walter V. Berry, Pittsburgh, Pa., assignor to Berry Metal Company, Harmony, Pa, a corporation of Nevada Continuation of application Ser. No. 189,350, Apr. 23, 1962. This application Mar. 1, 1965, Ser. No. 441,399 4 Claims. (Cl. 266--34) This invention relates to oxygen injection lances and more particularly to an improved oxygen injection lance assembly that can deliver oxygen into the interior of a furnace continuously and which will perform with a long life and a minimum of deterioration.

This is a continuation of a prior application, Serial No. 189,350, which was filed April 23, 1962, and was abandoned subsequent to the filing hereof.

In accordance with the prior art, of which I am aware, open hearth furnace operators have been shortening the tap-to-tap time by injecting oxygen over the melt in a high velocity stream from a nozzle located about four (4) inches above the material in the furnace to increase the rate of carbon removal from the molten bath in prep aration for tapping. However, in view of the high temperatures involved inside of the furnace deterioration of the nozzles of the lance has produced a difficult problem. The lance deteriorates rapidly under the combined strains of the severe requirements of high temperature environment and the presence of large volumes of pure oxygen. Cooling the lance requires co-axial piping. The unequal expansion of the multiple lengths of pipes or tubing act to tear apart the lance during operation, because the outer jackets rise to higher temperatures than the inner jackets and expand much more than the inner jackets which are surrounded by coolant. Also deterioration of the nozzle in the region of the oxygen exit ports have presented a problem.

In addition to the problems of deterioration I have recognized that there is need for means for obtaining optimum use of the oxygen injected into the furnace so that a minimum of the oxygen is carried out the chimney or wasted in oxidizing the already purified portions of the molten iron.

It is accordingly an object of my invention to provide an oxygen injection lance and nozzle assembly which will not be subject to distortion with changes in temperature.

It is another object of my invention to provide an oxygen injection lance nozzle that has a prolonged operating life within a high temperature furnace.

It is another object of my invention to provide apparatus for injecting oxygen into an open hearth furnace in such a manner as to obtain a maximum use of the oxygen and a minimum waste of oxygen, i.e., to produce a maximum use of oxygen in burning carbon and a minimum use of oxygen in oxidizing iron or in being carried off with other waste gases through the chimney.

In accordance with my invention I provide an oxygen injection lance and nozzle assembly which uniquely solves all of these problems. First, the lance comprising three concentric pipes is fastened at the upper end to a mounting assembly in such a manner that the three pipes can move axially independent of each other within the mounting assembly. This is achieved by mounting two of the three pipes in an axially sliding manner in the mounting assembly with noncorrosive junctions between the pipes and the mounting assembly, in a unique manner set forth in more detail hereinafter.

Secondly, by use of an elephants foot or bulbous nozzle head I have separated the exit ports of the oxygen by diverging each exit jet or port at least 15 from the longit-udinal axis of said nozzle so as to provide a minimum interaction between the high velocity oxygen streams and thereby minimize deterioration of the lance nozzle.

3,224,749 Patented Dec. 21, 1965 Also, I have provided a webbing between the channels for the oxygen at a distance from the face of the nozzle so as to force the cooling water to move at a higher velocity next to the surface of the nozzle face thereby carrying away any steam bubbles or solid material deposits which might mitigate the cooling effect at the nose of the nozzle. In combination with this I have indented the nose of the nozzle inward in the center thereof slightly so as to cause the water coming down the center of the lance to strike the indented portion of the nozzle and to shoot out sidewards in a rapid spray like manner so as to minimize whirlpool action and increase the cleansing effect of the water stream with respect to the inside surface of the nozzle nose. Thus by this nose design I have greatly increased the life of the nozzle.

By separating the streams of oxygen exiting from the nozzle ports through the use of the bulbous construction I have produced an entirely different reaction between the oxygen and the bath. If the exit ports are close together, as was the case in the prior art, the oxygen streams tend to merge and to produce one large center of activity within the bath. Thus in view of the high velocities of oxygen used, if the oxygen ports are close together the molten iron in the furnace near the nozzle tends to be turned over and over repeatedly so that the iron in the immediate region of the lance nozzle is thoroughly oxidized so as to remove all of the carbon from it and the iron in other portions of the bath does not receive the oxygen which it needs. The iron which has been purified in the region of the nozzle, having no further carbon to give up to the oxygen, proceeds to become oxidized itself. This production of iron oxide is obviously an undesirable effect.

I have found, however, that in accordance with the present invention by separating these oxygen ports in the nozzle in the manner taught herein, I produce a plurality of separated reaction pockets in the furnace bath which operating independently give a much better distribution of oxygen throughout the molten bath than was possible with the other methods of the prior art. Also this pattern of oxygen flow deflects the concentrated shower of steel and slag particles away from the body of the lance thus preventing scarping, erosion and burning of the outer pipe and also reduction of the splashing retards destruction of the refractory linings and the roof of the furnace.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing in which:

FIGURE 1 is a showing in cross section of the entire oxygen lance assembly in accordance with the preferred embodiment of my invention.

FIGURE 2 is an end view of the lance nozzle in accordance with the preferred embodiment of my invention.

FIGURE 3 is a showing in cross section of a portion of the lance nozzle so as to show the webbing, taken along the line III-III of FIGURE 2.

In accordance with the preferred embodiment of my invention I provide an oxygen head or nozzle 6 which contains a plurality of passageways or jets 3 for oxygen. These oxygen passageways 8 are diverted within the oxygen nozzle so that they exit from the exterior surface of the nozzle face at positions well removed from the center of the nozzle head and from each other. The exit jets 8 lie in a circle on the exterior surface of the head.

In the preferred embodiment of my invention the head 6 is bulbous in shape, that is, the outside surface has increasingly larger diameters as it extends from its base toward its extremity. This provides a large nozzle face which permits spacing the exit jets 8 a large distance from each other which in turn permits both a greater distance between the adjacent oxygen exit jets 8 and also makes the central interior portion of the nozzle head available to unrestricted flow of coolant water.

About halfway along the projection of the nozzle head toward its face, the surface of the head curves gradually inward to the said area where the exit jets 8 exit out from the head. Such an exterior peripheral shape approximates the nearest approach to the spherical enclosure as can be accommodated by the limitations of matching with the mounting pipes and providing the widely-separated, and angled exit jets 8 for the oxygen. The quality this provides is derived from the efficiency of a sphere. A sphere encloses the most volume per unit of surface area. Thus this bulbous arrangement provides large coolant volume within the head compared to the exterior surface area exposed to the high temperature within the furnace.

A dent, or dimple 12, is provided at the center of the face so as to introduce a smoothly-contoured inward projection at the center of the incoming stream of coolant water which helps divert the coolant stream from its central path, out across the interior of the face. Without'this interior projection, water would tend to whirlpool within the central nose of the nozzle head and have a reduced velocity in this central region. Maintaining the coolant stream velocity against the interior surface scrubs vapor bubbles and debris off the surface and maintains good heat flow from the hot nozzle head metal to the coolant stream. If debris and bubbles were allowed to collect they would form an insulation layer that would permit formation of a hot spot in the center of the nozzle head. The exterior dimple at the center 12 is necessary to maintain a uniform wall thickness. A uniform wall thickness assures that the temperatures gradient through the metal from the exterior surface, which is exposed to the furnace environment, to the interior surface, which is exposed to the coolant water, will be similar across the face of the head. This assures a uniform thermal stress in the metal.

In the preferred embodiment of my invention, cooling is enhanced by sizing apertures provided between adja cent jets 8 for the flow of cooling water from the central interior region 20 to the peripheral return passageway 22. Webbing 26 connecting between the exit jet chambers 8 are opened near the front surface of the nozzle head providing a proportioned opening 24 for the flow of cooling water between the exit chambers 8 at the face of the nozzle head. The total area of all of these proportioned openings 24, through which the cooling water flows out from the central region 20 of the head, is made approximately equal to the interior cross-sectional area of the central tubing 30, described hereinafter, down which the cooling water arrives at the nozzle. Thus the velocity flow along the interior metal surface within the nozzle head rinses away any air bubbles that may have a tendency to cling to the interior surface and inhibit cooling, and also rinses free any particles of foreign matter or oxides that may insulate the metal from the cooling water and thus inhibit cooling.

The main portion, or shank of the lance comprises three coaxial tubes, or

pipes

30, 36, 38. The tubes have different diameters, providing three

separate passageways

32, 34, 4t). Cooling water flows down to the nozzle head 6 within the inside passageway 32. Oxygen flows down to the nozzle head 6 in the annular space 34 which is outside of the center tube 30, and within the intermediate tube 36. The annular space that is outside of the intermediate tube 36, and inside of the exterior tube 38 provides a passageway 22 for the return of the cooling water. The end of each tube is welded to concentric surfaces on the nozzle head. These joints must be made tight and remain tight to prevent the oxygen and water streams from mixing.

The upper end of the lance is terminated by a brass casting 44. The casting is provided with a cored opening 46 to provide passageways for the return stream. of cooling water 34. The casting is provided with a longitudinal core with the upper end thereof having a smoothwall cylindrical bore 63 that is adapted to receive fittings through which the oxygen is introduced, and through which the cooling water passes on leaving the casting.

A collar 52 stands between the central pipe 30 and the casting 44 at the upper end of the casting. This collar is attached to the inner pipe 30 and makes an axially slidable, O-ring sealed junction with the casting 44.

The annular space thus provided around the central pipe 30 and the inside of the casting receives the oxygen, which then flows down this annular space toward the nozzle.

A face plate 56 of steel is machined across its face and is welded to the upper end of the exterior tube 38. This face plate 56 engages the casting 44. O-ring 62 is compressed in the face joint between the face plate 56 and the brass casting 44 to assure a seal at the joint, in this case sealing in the return stream of cooling water. The face plate 56 is held to the brass casting 44 by bolts which extend parallel to the axis of the shank thereby connecting the casting 44 to the outer pipe 38. Note that only the exterior tube 38 is joined rigidly to the brass casting 44 (via the face plate 56).

The external tube 38 is exposed to the high-temperature atmosphere within the furnace, and will rise to a much higher temperature than will the intermediate tube 36 and the central tube 30. The external tube 38 will expand much more when the lance is in the furnace than will the intermediate and central tubes. If the external, intermediate, and central tubes are all joined rigidly to the brass casting 44 (as they are all rigidly joined to the nozzle 6), the

inside tubes

36, 30 would be in severe tension when the external tube 38 expands in length within the furnace. Thus in accordance with my invention the intermediate tube 36 and the central tube 30 are provided with slip joints to permit their movement with respect to the brass casting 44. As was pointed out above, the central tube 30 passes entirely through the brass casting 44. The collar 52 is welded to the central tube 30. O-rings 64 are provided in the collar 52. The O-rings 64 are compressed by the interior surface of the brass casting 44, sealing in the oxygen while permitting lengthwise movement of the central tube 38 relative to the brass casting 44.

A fitted sleeve 68 of non-corrosive metal such as stainless steel is coupled to the intermediate tube 36, said fitted sleeve 68 extending up around a downward extension 66 of the brass casting 44. The downward extension 66 has two annular grooves around it in which are fitted two O- rings 70 that form a junction or contact between the sleeve 68 and the extension 66 to permit lengthwise movement of the intermediate tube 36 relative to the extension 66 of the brass casting 44 while keeping a seal which prevents mixing of the oxygen and coolant water.

Use of the lance that I provide permits the open-hearth furnace operator to insert the nozzle through the roof of the open hearth and lower it down to a position approximately four (4) inches from the surface of the bath. The nozzle, in effect, establishes multiple jets of oxygen fanning out in the shape of a cone down to and out into the bath. Each of these jets from the nozzle are suificiently separated so that they set up independent regions of activity in the bath so as to provide a maximum distribution of the oxygen throughout the bath.

Thus, the enlarged bulbous shape of the head, the expansion feature, the separated oxygen jets and the other contributing factors thus described cooperate to provide both an improved life expectancy of the lance assembly within the furnace, and an improved and more efficient use of the oxygen supplied to the furnace.

Although I have shown and described specific embodiments of my invention, I am aware that other modifications thereof are possible; my invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and the spirit of the invention.

I claim as my invention:

1. An oxygen lance comprising a nozzle head that projects down into the furnace, three concentric tubes joined to the nozzle head and running up to a mounting assembly, said mounting assembly comprising a casting cored and tapped to provide separated entrances for oxygen and water and an exit for return water, the face of said casting being machined for union with a face plate, said face-machined surface being cut with a continuous circular groove to receive an O-ring to assure seal with said face plate, said mounting assembly cored throughout to provide for through passage of the central tube of said concentric tubes, said coring being machined at the upper end to provide a smooth-wall cylindrical bore, said central tube being fitted with a metal, elongated ring having grooves around its exterior surface that receive O-rings that effect a seal with said smooth-wall cylindrical bore of said mounting assembly while permitting linear displacement of said central tube relative to said mounting assembly, said mounting assembly having a projected lower cylindrical extension also having grooves around it to receive O-rings that effect a seal against the interior surface of a cylindrical fitting that is joined to "the intermediate tube of said concentric tubes, said seal permitting linear displacement of said cylindrical fitting and intermediate tube relative to said mounting assembly, said nozzle head cored to receive coolant water from said central tube of said concentric tubes and passageways to communicate said coolant water to the annular space between said intermediate tube and the external tube of said other passageways provided for said oxygen, said oxygen passageways receivingsaid oxygen from the annular space between said central tube and said intermediate tube and carrying said oxygen down through said nozzle through a plurality of exit jets, said exit jets diverging from each other, the angle of divergence from the longitudinal axis of said nozzle being at least 15, thus providing a large volume in the interior central region of said nozzle for coolant flow, said divergent passageways having openings between each but not communicating therewith, said openings situated at the front internal surface of said nozzle to permit flow of said coolant from the central internal region out around said oxygen passageways, said openings having a total area approximately equal to the internal area of said central coolant tube, said nozzle head having a bulbous external shape wherein the largest diameter is significantly larger than the diameter of said external tube so that the exit jets for oxygen are approximately opposite the region between the outer tube and the intermediate tube, said nozzle head being curved gradually to the face region, which is recessed at its center to project an intrusion into the internal central region to divert and maintain flow velocity of said coolant water while maintaining a uniform thickness of the wall of said nozzle head.

2. An oxygen lance comprising a nozzle head that projects down into a furnace, three concentric tubes joined to the nozzle head and running up to a mounting assembly, said mounting assembly comprising a casting cored and tapped to provide separated entrances for oxygen and water and an exit for return water, the face of said casting being machined for union with a face plate attached in a watertight junction to the outer of said concentric tubes, said face-machine surface being cut with a continuous circular groove to receive an O-ring to assure seal with said face plate, said mounting assembly being cored throughout to permit through passage of the central tube of said concentric tubes, said coring being machined at the upper end to provide a smooth-wall cylindrical bore, said central tube being fitted with a metal, elongated ring having grooves around its exterior surface that receive O-rings that effect a seal with said smoothwall cylindrical bore of said mounting assembly while permitting linear displacement of said central tube relative to said mounting assembly, said mounting assembly having a projected lower cylindrical extension that effects an axially slidable seal against the interior surface of a cylindrical fitting that is joined to the intermediate tube of said concentric tubes, said seal permitting linear displacement of said cylindrical fitting and intermediate tube relative to'said mounting assembly, said nozzle head being cored to receive coolant water from said central tube of said concentric tubes and passageways to communicate said coolant water to the annular space between said intermediate tube and the external tube of said concentric tubes, without leaks of said coolant water to other passageways provided for said oxygen, said oxygen passageways receiving said oxygen from the annular space between said central tube and said intermediate tube and carrying said oxygen down through said nozzle through a plurality of exit jets, said exit jets diverging from each other, the angle of divergence from the longi tudinal axis of said oxygen nozzle being at. least 15, thus providing a large volume in the interior central region of said oxygen. nozzle for coolant flow, said divergent passageways having openings between each but not communicating therewith and situated at the front internal surface of said nozzle to permit fiow of said coolant from the central internal region out around said oxygen passageways, said openings having a total area approximately 'equal to the internal area of said central coolant tube, said -to project an intrusion into the internal central region to divert and maintain flow velocity of said coolant water while maintaining a uniform thickness of the wall of said nozzle head.

3. An oxygen lance comprising a nozzle head that projects down into a furnace, three concentric tubes joined to the nozzle head and running upto a mounting assem- --bly, said mounting assembly comprising a casting cored and tapped to provide separated entrances for oxygen and water and an exit for return water, the face of said casting being machined for union with a face plate, said facemachined surface being cut With a continuous circular groove to receive an O-ring to assure seal with said face plate, said mounting assembly being cored throughout to permit through passage of the central tube of said concentric tubes, said coring being machined at the upper end to provide a smooth-wall cylindrical bore, said central tube being fitted with a metal elongated ring having grooves around its exterior surface that receive O-rings that effect a seal with said smooth-wall cylindrical bore of said mounting assembly while permitting linear displacement of said central tube relative to said mounting assembly, said mounting assembly having a projected lower cylindrical extension also having grooves around it to receive O-rings that effect a seal against the interior surface of a cylindrical fitting that is joined to the intermediate tube of said concentric tubes, said seal permitting linear displacement of said cylindrical fitting and intermediate tube relative to said mounting assembly, said nozzle head being cored to receive coolant water from said central tube of said concentric tubes and passageways to communicate said coolant water to the annular space between said intermediate tube and the external tube of said concentric tubes, without leaks of said coolant water to other passageways provided for said oxygen, said oxygen passageways receiving said oxygen from the annular space between said central tube and said intermediate tube and carrying said oxygen down through said nozzle through a plurality of exit jets, said exit jets diverging from each other, the angle of divergencc from the longitudinal axis of said nozzle being at least 15, thus providing a large volume in the interior central region of said oxygen nozzle for coolant flow, said divergent passageways having openings between each but not communicating therewith, said openings situated at the front internal region out around said oxygen passageways, said openings having a total area approximately equal to the internal area of said central coolant tube, said nozzle head having a bulbous external shape wherein the largest diameter is significantly larger than the diameter of said external tube and so that the centers of the exit jets are approximately on an extension of a line through the outer tube, in the direction of its length, said oxygen nozzle head being curved gradually to the face region, which is recessed at its center to project an intrusion into the internal central region to divert and maintain flow velocity of said coolant water while maintaining a uniform thickness of the wall of said nozzle head.

4. An oxygen lance comprising a nozzle head that projects down into the furnace, three concentric tubes joined to the nozzle head and running up to a mounting assembly, said mounting assembly comprising a casting cored and tapped to provide separated entrances for oxygen and water and an exit for return water, the face of said casting being machined for union with a face plate, said facemachined surface being cut with a continuous circular groove to receive an O ring to assure seal with said face plate, said mounting assembly being cored throughout to permit through passage of the central tube of said concentric tubes, said coring being machined at the upper end to provide a smooth-wall cylindrical bore, said central tube being fitted with a metal, elongated ring of the same materials of said casting having a groove around its exterior surface that receives on O ring that eflects a seal with said smooth-wall cylindrical bore of said mounting assembly while permitting linear displacement of said central tube relative to said mounting assembly, said mounting assembly having a projected lower cylindrical extension also having grooves around it to receive O-rings that effect a seal against the interior surface of a cylindrical fitting that is joined to the intermediate tube of said concentric tubes and is of a non-corrosive material, said seal permitting linear displacement of said cylindrical fitting and intermediate tube relative to said mounting assembly, said nozzle head cored to receive coolant water from said central tube of said concentric tubes and passageways to communicate said coolant water to the annular space between said intermediate tube and the external tube of said concentric tubes, without leaks of said coolant water to other passageways provided for said oxygen, said oxygen passageways receiving said oxygen from the annular space between said central tube and said intermediate tube and carrying said oxygen down through said nozzle through a plurality of exit jets, said exit jets diverging from each other, the angle of divergence from the longitudinal of said oxygen nozzle being at least 15, thus providing a large volume in the interior central region of said oxygen nozzle for coolant flow, said divergent passageways having openings between each but not communicating therewith and situated at the front internal surface of said oxygen nozzle to permit flow of said coolant from the central internal region out around said oxygen passageways, said openings having a total area approximately equal to the internal area of said central coolant tube, said nozzle head having a bulbous external shape wherein the largest diameter is significantly larger than the diameter of said external tube, said oxygen nozzle head being curved gradually to the face region, which is recessed at its center to project an intrusion into the internal central region to divert and maintain flow velocity of said coolant water while maintaining a uniform thickness of the wall of said nozzle head.

References Cited by the Examiner UNITED STATES PATENTS 2,828,956 4/1958 Bienivsek et al. 26641 2,863,656 12/1958 Cox 26641 2,979,270 4/1961 Hutton 239-132 3,043,577 7/1962 Berry 26634 3,118,608 1/1964 Berry 239132 3,170,016 2/1965 Grace 26634 3,170,977 2/1965 Obenchain 26634 WHITMORE A. WILT Z, Primary Examiner.

J. C. HOLMAN, Assistant Examiner.

Claims

1. AN OXYGEN LANCE COMPRISING A NOZZLE HEAD THAT PROJECTS DOWN INTO THE FURNACE, THREE CONCENTRIC TUBES JOINED TO THE NOZZLE HEAD AND RUNNING UP TO A MOUNTING ASSEMBLY, SAID MOUNTING ASSEMBLY COMPRISING A CASTING CORED AND TAPPED TO PROVIDE SEPARATED ENTRANCES FOR OXYGEN AND WATER AND AN EXIT FOR RETURN WATER, THE FACE OF SAID CASTING BEING MACHINED FOR UNION WITH A FACE PLATE, SAID FACE-MACHINED SURFACE BEINAG CUT WITH A CONTINUOUS CIRCULAR GROOVE TO RECEIVE AN O-RING TO ASSURE SEAL WITH SAID FACE PLATE, SAID MOUNTING ASSEMBLY CORED THROUGHOUT TO PROVIDE FOR THROUGH PASSAGE OF THE CENTRAL TUBE OF SAID CONCENTRIC TUBES, SAID CORING BEING MACHINED AT THE UPPER END TO PROVIDE A SMOOTH-WALL CYLINDRICAL BORE, SAID CENTRAL TUBE BEING FITTED WITH A METAL, ELONGATED RING HAVING GROOVES AROUND ITS EXTERIOR SURFACE THAT RECEIVE O-RINGS THAT EFFECT A SEAL WITH SAID SMOOTH-WALL CYLINDRICAL BORE OF SAID MOUNTING ASSEMBLY WHILE PERMITTING LINEAR DISPLACEMENT OF SAID CENTRAL TUBE RELATIVE TO SAID MOUNTING ASSEMBLY, SAID MOUNTING ASSEMBLY HAVING A PROJECTED LOWER CYLINDRICAL EXTENSION ALSO HAVING GROOVES AROUND IT TO RECEIVE O-RINGS THAT EFFECT A SEAL AGAINST THE INTERIOR SURFACE OF A CYLINDRICAL FITTING THAT IS JOINED TO THE INTERMEDIATE TUBE OF SAID CONCENTRIC TUBES, SAID SEAL PERMITTING LINEAR DISPLACEMENT OF SAID CYLINDRICAL FITTING AND INTERMEDIATE TUBE RELATIVE TO SAID MOUNTING ASSEMBLY, SAID NOZZLE HEAD CORED TO RECEIVE COOLANT WATER FROM SAID CENTRAL TUBE OF SAID CONCENTRIC TUBES AND PASSAGEWAYS TO COMMUNICATE SAID COOLANT WATER TO THE ANNULAR SPACE BETWEEN SAID INTERMEDIATE TUBE AND THE EXTERNAL TUBE OF SAID CONCENTRIC TUBES, WITHOUT LEAKS OF SAID COOLANT WATER TO OTHER PASSAGEWAYS PROVIDED FOR SAID OXYGEN, SAID OXYGEN PASSAGEWAYS RECEIVING SAID OXYGEN FROM THE ANNULAR SPACE BETWEEN SAID CENTRAL TUBE AND SAID INTERMEDIATE TUBE AND CARRYING SAID OXYGEN DOWN THROUGH SAID NOZZLE THROUGH A PLURALITY OF EXIT JETS, SAID EXIT JETS DIVERGING FROM EACH OTHER, THE ANGLE OF DIVERGENCE FROM THE LONGITUDINAL AXIS OF SAID NOZZLE BEING AT LEAST 15*, THUS PROVIDING A LARGE