US3045997A - Porous oxygen lance - Google Patents

Description

July 24, 1962 E. B. HUDSON POROUS OXYGEN LANCE 5 Sheets-Sheet 1 Filed March 2. 1959 INVENTOR. fan MAB, f/uasa/v,

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United States Patent 3,@45,997. Patented July 24, 1962 ice Ohio

Filed Mar. 2, 1959, Ser. No. 796,343 7 Claims. (Cl. 266-34) This invention relates to apparatus for discharging a gas into an open hearth furnace or a converter type vessel, and relates more particularly to the provision of a lance by means of which oxygen may be injected onto the top of a molten iron charge in an oxygen process converter.

In the oxygen converter method of steel making, which is sometimes referred to as the L-D (Linzer Dusen Verfahren or Linz-Donawitz) process, pig iron is converted into steel by directing a stream of oxygen downwardly into a bath of metal from above. The apparatus generally used for this purpose is a structure or lance having a discharge nozzle positioned near the surface of the molten metal. Such lances are constructed from a metal having high heat conductivity, such as copper, and are provided with water cooling passageways to prevent the metal from melting or burning away during use. However, since the temperatures of the molten metal during the oxygen operation are exceptionally high, ranging up to 6000-8000" F., the Water cooled lances currently in use fail in a very short time.

The principal cause of lance failure lies in the fact that the conductivity of the metal from which the lance is made is far below that required to remove excess heat from the external surfaces of the lance to the cooling water. This is indicated by the relatively low temperature rise of the cooling water in view of the high temperature on the heat exposed outer surfaces of the lance. Copper, which has a very high rate of heat conductivity, melts at 1982" F. and there are indications of melting or burning of the outer surfaces of a copper lance after a relatively short period of use. Readily available metals other than copper provide an even more acute problem in that their conductivity or K values are less than that of copper. While there are some metals available which have a higher K value, their cost is prohibitive.

In accordance with the instant invention, I eliminate the foregoing difficulties by conducting the coolant directly to the exposed surfaces of the lance. This is accomplished by providing a lance having a porous wall structure through which the coolant may be passed, the coolant thus being brought into direct con-tact with the outermost or hot surfaces of the lance, thereby maintaining the temperature'of the lance structure at approximately the same temperature as the coolant. With the porous wall structure, it is no longer necessary to transmit heat through the wall structure to the coolant and the K value is no longer a problem. For a coolant I prefer to employ steam which may be readily supplied under pressure and forced through the porous wall structure of the lance. The temperature of the steam, even if super heated under high pressure, will nevertheless be well below the melting point of porous metal and will cool it sufficiently to prevent melting or burning.

In addition to protecting the lance structure from excessive heat, the instant invention also solves other problems encountered in basic oxygen processing. When blowing molten metal with oxygen, the nozzle of the lance will normally become heavily encrusted with splashes of molten slag and metal which serve to diminish the heat transfer efliciency of the lance, thereby further decreasing its useful life. In accordance with the instant invention, the escaping steam or other cooling fluid as it passes through the walls of the lance under pressure will prevent the splashes of slag in metal from sticking to the lance. However, if by accident a burn does occur on the lance surface, thereby reducing its wall thickness, then at this point the decreased wall thickness will increase the steam velocity at the point of damage, thereby arresting further lance deterioration.

in this connection, it may be observed that another advantage in the invention lies in the fact that a wide range of lance protection to meet most of any temperature conditions encountered can be provided by varying the velocity of the coolant as it leaves the outside surface of the nozzle structure. For example, where the coolant fluid is steam having a pressure of 40 p.s.i.a. and a temperature of 276 F., the steam velocity will be approximately 10 fps. as it leaves the outside surface of a /2" porous wall. By varying the velocity of the cooling fluid, whether it be steam, an inert gas, or compressed air, in accordance with the temperatures encountered, a wide range of lance protection can be provided.

The instant invention also solves another problem encountered in basic oxygen processing, namely, the fumes which are given off by the molten metal during the blowing operation. These fumes are contaminated with various impurities which must be cleaned before being released to the atmosphere. The use of a gaseous coolant and its release in the furnace or converter results in the formation of a blanket or layer which completely surrounds the oxygen jet between the nozzle and the surface of the molten metal, thereby providing an additional control of the fumes which is not possible in the conventional lance construction. Where the coolant is steam a further advantage is realized in that the steam increases the particle sizes of the impurities in the fumes and makes the use of bag filters possible for filtering purposes.

In the past, there has been some reluctance to use oxygen lances in the conventional open hearth furnace, since considerable roof damage occurs, reducing the availability of the furnace. With the use of a fluid-cooled lance, the escaping fluid provides a heat barrier, thereby providing added protection to the open hearth roof.

In accordance with the foregoing, it is a principal object of my invention to provide for enhanced lance protection by conducting a coolant fluid into direct contact with the outermost or hot surfaces of the lance.

A further object of the invention is the provision of a lance structure wherein the coolant is transmitted directly through the walls of the lance, the lance structures themselves embodying various novel features of construction and arrangement of parts inclusive of a wholly steamcooled lance and a lance incorporating a steam-cooled nose and water-cooled walls.

The foregoing together with other objects of the invention which will appear hereinafter or which will be apparent to the skilled worker in the art upon reading these specifications I accomplish by those constructions and arrangements of parts, and by those procedures of which I shall now describe certain exemplary embodiments.

Reference is now made to the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a lance constructed in accordance with the invention.

FIGURE 2 is a side elevational view with parts broken away of a water and steam-cooled lance.

FIGURE 3 is a vertical sectional view through the porous nose of the lance, illustrating the use of a plurality of grades of porous metal.

FIGURE 4 is a side elevational view with. pants broken 'away of a modified form of lance structure.

FIGURE 5 is -a sectional view taken along the line 5-5 of FIGURE 4.

FIGURE 6 is a partial elevational view of another modification of the lance.

FIGURE 7 is an end view of the lance shown in FIG- URE 6.

FIGURE 8 is an enlarged partial sectional view taken along the line 88 of FIGURE 7.

FIGURE 9 is a sectional view taken along the line 99 of FIGURE 8.

FIGURE is an enlarged sectional view of a mounting ring forming a part of the nozzle structure illustrated in FIGURE 8.

FIGURE l l is an enlarged sectional view of the inner nose member forming a part of the nozzle structure.

In accordance with my invention the solid walls and/ or the nose of a conventional lance are replaced by a porous structure wherein the coolant fluid passes through interstices in the porous material. A preferred material is porous bronze which is commercially available and is produced by bonding together, metal-to-metal, small bronze spheres which are carefully graded to the same size and then sintered by powder metallurgy methods. The grades are determined by the size of the spheres, which in turn control the size and number of flow passages or interstices per square inch of metal. For example, porous bronze manufactured by the Moraine Products Division of General Motors Corporation under the trademark Moraine Porous Metal is currently available in four grades, ranging from coarse to very fine. The porous metal is graded on a particle stopping basis and ranges from .0O2.005" (coarse) to .000 1.0005" (very fine). As will be explained more fully hereinafter, various parts of the lance structures may be formed hrom different grades of the porous metal so as to proportion the coolant flow to suit the temperatures encountered. For example, the tip or nose of the lance which is nearest the molten metal can be made from a more porous grade of metal, whereas the more remote parts of the nozzle can be made from less porous grades, thereby restricting the coolant lflow in areas where lesser temperatures are encountered.

Referring now to FIGURE 1 of the drawings, I have therein illustrated a lance having a body or head 1, an elongated tubular nozzle 2 terminating at its free end in a tip or nose 3, the entire structure being adapted to be suspended within a furnace or converter by means of a removable eye ring 4 threaded into the upper end of the lance body.

In the embodiment illustrated in FIGURES l and 2 the body or head 1 of the lance is composed of a plurality of body sections, the uppermost section 5 having an oxygen chamber 6 to which oxygen is supplied through an inlet passageway 7 from a source not shown. A centrally disposed conduit -8 extends downwardly from the oxygen chamber and serves to deliver the oxygen to the nose 3 of the lance where it is discharged directly onto the surface of the molten metal 9 as a stream 10.

A second body section 11 is secured immediately beneath body section 5, the section 11 being provided with a hub portion 12 which surrounds the upper end of cond-uit 8, the conduit being conveniently secured in place by means of a nut 13. The conduit 8 is preferably provided with an annular shoulder 14 which engages an O ring 15 positioned to make sealing contact with the outer surface of the conduit. The body section 11 defines a steam chamber 16 to which steam is delivered through inlet passageway 17. A second conduit 18 extends downwardly from chambers 16 to the nose of the lance, the conduit 18 surrounding conduit 8 and defining an annular passageway 19 therebetween through which steam from the chamber 16 may flow to the nose of the lance. At its lower end the conduit 18 is preferably flared outwardly, as at 20, and is secured to the lower end of nozzle 2.

A third body section 21 is secured immediately beneath body section 11 and provided with a hub 22 surrounding the upper end of conduit 18, the hub mounting a stufiing box 23 which provides a tight seal between the hub and the conduit. The third body section provides a water inlet chamber 24 to which water is supplied through inlet orifice 25. A third conduit 26 extends downwardly from chamber 24, the conduit 26 surrounding the second conduit 18 and defining an annular passageway 27 therebetween. The conduit 26 also lies in spaced relationship with respect to the Wall surfaces of tubular nozzle 2 to define an annular passageway 28 therebetween. At its lower end the conduit 26 terminates short of the flared lower end of conduit 18, thereby providing a connection between passageways 27 and 28 so that water flowing downwardly through passageway 27 will reverse its direction and flow upwardly through passageway 28 wherein it will be in heat exchange relationship with the walls of nozzle 2. At its upper end, the passageway 28 opens into a discharge chamber 29 formed in a fourth body section 30, the chamber having an outlet orifice 3'1. A stuffing box 32 provides a tight seal between the conduit 26 and the walls of body section 30.

In this embodiment of the invention, the tubular nozzle 2 is preferably formed from centrifugally cast copper to insure high heat conductivity and, as already indicated, the walls of the nozzle are cooled by means of water flowing through inlet chamber 24, down passageway 27 and then upwardly along passageway 28. The nose of the lance is, however, cooled by steam flowing downwardly through passageway 19, the nose 2 being constructed of porous bronze material of the character already described. As best seen in FIGURE 3, the nose 3 has a central bore 33 which receives the lowermost end of oxygen conduit 8, the oxygen flowing through the conduit being expelled through orifice 33a in the nose. The orifice 33a is machined, and the machining acts to seal the interstices at the machined surface, thereby preventing the exchange of oxygen or steam through oxygen bore 33a. The nose is also provided with an annular cavity 34 which is in communication with the passageway 19, so that steam flowing downwardly through the passageway will enter the cavity 34 and pass through the porous walls 35 of the nose. If desired, the entire nose structure may be formed from the same grade of porous bronze, or, where the temperatures encountered permit it, the lowermost portion of the nozzle, which is indicated at 36, may be formed from a first relatively coarse grade of porous metal whereas the remainder of the nozzle, indicated by the reference numeral 37, may be formed from a second and less coarse grade of metal, thereby permitting a greater flow of the coolant through the portion of the nose nearest the molten metal. As will be evident from FIGURE 2, spacers 38 may be provided to support the lowermost free end of conduit 26.

In FIGURES 4 and 5 of the drawings there is illustrated an embodiment of the invention wherein the entire nozzle structure is formed from porous metal. In this embodiment, the eye ring 4 suspends a unitary hollow body 40 having an oxygen chamber 41 in communication with an inlet passageway 42, there being a centrally disposed oxygen conduit 43 extending downwardly to the nose of the lance, the conduit being secured to the body by means of a fitting 44. The body 40 is also provided with a steam chamber 45 in communication with an annular passageway 46 defined between the outer surface of conduit 43 and a second conduit 47 the lower end of which terminates short of the nose 2 so as to provide communication to a return passageway 48 formed between the walls of conduit 47 and the inner surfaces of nozzle 50. In this instance the entire nozzle 50 is formed from porous metal. If desired, the same grade of metal may be used throughout the length of the nozzle or, as illustrated, it may be composed of a plurality of sections 50a, 50b and 500 composed of diflerent grades of porous metal progressing upwardly from a relatively coarse section adjacent the nose to a relatively fine uppermost section adjacent the body, thereby controlling the rate of coolant flow in accordance with the proximity of the lance to the molten metal. As seen in FIGURE 5, spacers 51 may be provided to support the concentric conduits 43 and 47.

Referring again to FIGURE 4, the protective boundary layer of steam is shown at 52, the layer completely surrounding the external surfaces of both the nose 3 and the walls of nozzle 5%, thereby both cooling these surfaces and protecting them from splashes of molten metal. The blanket of steam also completely surrounds the oxygen jet which impinges upon the molten metal, the surrounding layer of steam forming a blanket over the fumes which are generated by the molten metal. Slag is indicated at 53.

FIGURES 6 and 7 illustrate still another modification of the invention wherein the nose 55 is provided with a plurality of oxygen outlets 56 arranged to diffuse the oxygen stream and thereby minimize splashing. In this embodiment, the nozzle is composed of a plurality of juxtaposed rings 57 which may be formed from either porous material or from conventional refractory materials.

As best seen in FIGURE 8, the centrally disposed oxygen conduit 58 is provided at its lower end with an inner nose member 59 (see also FIGURE 11) having a plurality of openings 60 therein corresponding in position and number to the openings 56in the nose 55. The inner nose member 59 may be conveniently threaded on the lower end of conduit 58. As seen in FIGURE 10, inner nose 5 9 also supports a mounting ring 61 having an inner sleeve 62 adapted to surround the upper portion of the inner nose with lower edge seated on the shoulder 63 of the inner nose. The mounting ring also has an outer sleeve 64 which is spaced from the inner sleeve by means of webs 65; and, as seen in FIGURE 8, the outer sleeve lies in prolongation of the steam conduit 66. It will be noted that the lower end of the outer sleeve 64 turns inwardly, as at 67, so that steam flowing downwardy through conduit 66 will flow into the chamber 68 between the nose 55 and the inner nose member 59, whereupon it will pass outwardly around the inturned end of sleeve 67 and flow upwardly through annular passageway 69. Tubes 70 extend between the openings 56 in the outer nose and the openings 60 in the inner nose member through which the oxygen flows.

The mounting ring 61 also includes a series of Webs 71 which support an annular shoulder 72 against which the lowermost refractory ring 57 is seated. The several refractory rings are notched, as at 73, so that they will fit together. If the refractory material is of imperforate character, the notches or joints 73 provide spaces through which steam may escape, as indicated by the arrows 74, thereby again enclosing the nozzle by steam. It will be understood, of course, that the outer nose 55 will be formed from porous material through which the coolant steam will pass. If desired, one or more of the rings 57 may also be formed from porous material.

As should now be readily apparent to the skilled worker in the art, the problem of heat conductance in an oxygen lance is substantially eliminated by conducting the fluid coolant directly to the outermost or hot surfaces thereof. By using a wide range of fluid pressure, the invention provides protection to the lance even though the temperatures of the molten metal range up to 600045000 F. At the same time fumes from the blowing operation are blanketed with the coolant and hence may be more readily controlled and removed.

Modifications may, of course, be made in the invention without departing from the spirit and purpose of it. Thus, while steam has been disclosed as the preferred coolant, other cooling fluids may be readily employed without departing from the spirit of the invention. Similarly, while porous bronze has been disclosed as a preferred material from which to form the nose and wall surfaces of the nozzle, other porous metals and porous refractories may be employed. It will also be obvious that modifications may be made in the construction of the lances, and the porosity of the nose and wall parts thereof may be varied as required.

Having, however, described my invention in certain exemplary embodiments what I desire to secure and protect by Letters Patent is:

1. A lance for use under conditions of high temperature, said lance having an elongated tubular nozzle structure terminating in a nose, said nozzle structure comprising a plurality of porous sections formed from porous material having minute interstices therein through which a fluid coolant such as steam may be transmitted, said porous sections being of varying degrees of porosity, and means within said nozzle structure for delivering a fluid coolant to the inner surfaces of said porous sections, whereby said coolant may pass through the interstices therein so as to envelope the exterior surfaces of said nozzle structure in a protective blanket of the coolant fluid.

2. The structure claimed in claim 1 wherein the said porous sections progress from a relatively coarse section adjacent the nose of said nozzle to a relatively fine section at the end of said nozzle remote from said nose, whereby to control the rate of coolant flow in accordance with the proximity of the lance to a source of heat such as molten metal in an open hearth furnace in which said lance is suspended.

3. An oxygen lance for use under conditions of high temperature, said lance having an elongated tubular nozzle structure terminating at one end in a nose, at body member secured to the opposite end of said nozzle structure, an oxygen chamber in said body, an oxygen discharge orifice in said nose, a first conduit centrally disposed in said tubular nozzle structure and having one end thereof in communication with said oxygen chamber and the opposite end thereof in communication with said orifice, a coolant chamber in said body, a second conduit surrounding said first conduit in spaced relation thereto and having one end in communication with said coolant chamber and its opposite end positioned so that a coolant fluid passing therethrough will impinge upon the inner surfaces of said nose in an area surrounding the orifice therein, said last named area of said nose being formed from a porous metal having interstices therein through which the coolant fluid may be transmitted from the inner to the outer surfaces of said nose, said second named conduit being surrounded by and lying in spaced relation to the wall surfaces of said tubular nozzle, the wall surfaces of said nozzle being composed of a plurality of tubular sections formed from porous material having interstices therein through which the coolant fluid may be transmitted, said tubular sections having varying degrees of porosity, the space between said second conduit and said tubular nozzle being in communication with the end of said second conduit at a point adjacent said nose, whereby coolant flowing through said second conduit to said nose will then flow through said space in reverse direction for contact with the inner surfaces of the tubular nozzle.

4. An oxygen lance for use in the oxygen converter method of steel making, said lance having an elongated nozzle structure including a generally conical nose, a plurality of oxygen discharge orifices in said conical nose, the conical wall surfaces at least of said nose being formed from porous metal having interstices therein through which a coolant fluid may be transmitted from the inner to the outer surfaces thereof, a first conduit extending through said nozzle structure, said first conduit terminating at its lower end in an inner nose member lying in spaced relation to said conical nose to form a cavity therebetween, said inner nose member having a plurality of openings therein corresponding in number to the orifices in said conical nose, tubes in said cavity connecting the orifices in said conical nose and the opening in said inner nose member, a second conduit within said tubular nozzle surrounding said first conduit, said second conduit lying in spaced relation both to said first conduit and to the wall surfaces of said tubular nozzle to provide annular passageways therebetween, said passageways at their lower end being in communication with the cavity between said conical nose and said inner nose member, whereby a fluid coolant will flow through said annular passageways and said cavity, said nozzle structure being composed of a plurality of concentric rings formed from a refractory material and loosely fitted together one upon the other so as to permit the escape of the fluid coolant therebetween at spaced apart intervals along the length of said nozzle structure, and a mounting ring surrounding said inner nose for supporting said concentric rings.

5. An oxygen lance for use in the oxygen converter process of steel making, said lance having a plurality of fluid delivery chambers at one end and an elongated nozzle depending therefrom, a centrally disposed oxygen delivery tube extending downwardly through said nozzle from one of said chambers but terminating short of the bottom of said nozzle, a porous nose piece having at least an outer wvall and a bottom wall extending downwardly below said oxygen delivery tube and outwardly beyond the periphery thereof, said porous nose piece having at least one orifice therein connected to said oxygen tube for the delivery of a jet of oxygen downwardly :from the end of said lance, a first concentric tube srrounding said oxygen delivery tube and connected to a second of said fluid delivery chambers and coacting with said oxygen delivery tube to form a passageway for steam, said first concentric tube terminating downwardly in an open end within said porous nose piece so as to deliver steam to the interior of said nose piece, the exterior surface of said elongated nozzle being defined by an outer casing concentric with and spaced from said first concentric tube to define a passageway therebetween connected to one of said chambers, and supplementary cooling means in conjunction with said outer casing for cooling it throughout its length.

6. The lance structure claimed in claim 5 wherein said supplementary cooling means comprises an outer casing of perforate character, and wherein the passageway between said outer casing and said first concentric ring is connected to the chamber supplying steam to said nose piece.

7. The lance structure claimed in claim 5 wherein said supplementary cooling means comprises water cooling means connected to a third of said fluid delivery chambers.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,231 Avery et al. Feb. 6, 1951 2,807,506 Gehring Sept. 24, 1957 2,828,956 Bieniosek et al. Apr. 1, 1958 2,829,960 Vogt Apr. 8, 1958 2,863,656 Cox Dec. 9, 1958 FOREIGN PATENTS 755,416 Great Britain Aug. 22, 1956

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