US3175817A - Burner apparatus for refining metals - Google Patents

Description

March 30, 1965 G. H. sMrrH ETAL BURNER APPARATUS FOR REFINING METALS` F'iled NOV. 28, 1960 3 Sheets-Shea?l 1 R. J m O r 0 R E T T NHS W a WMA r IQNE. f HD 4 EN mm OY.. EA GR w Y B March 30, 1965 G. H. SMITH ETAL BURNER APPARATUS FOR REFINING METALS 3 Sheets-Sheet 2 Filed Nov. 28, 1960 INV EN TORS G W N um m mm .W

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w Y B March 30, 1965 s. H. sMrrH ETAL 3,175,617

BURNER APPARATUS FoR REFINING METALS Filed Nov. 28, 1960 I5 Sheets-Sheet 3 www@ INVENTORS GEORGE H. SMITH RAYMOND E. ARMSTRONG,JR.

BY Lm 3,175,8l7 BURNER APPARATUS FOR REFINNG NETALS George H. Smith, Berkeley Heights, and Raymond E. Armstrong, lr., Clark, NJ., assignors to Union Carbide Corporation, a corporation of New York Filed Nov. 28, 1960, Ser. No. 72,034 2 Claims. (Cl. 266-34) The present invention relates to an improved jet device and process for directing separate flows of a treating fluid and a combustible gas mixture toward the charge in a metallurgical furnace. It further relates more particularly to a novel construction and method for cooling such a device when exposed to the hot molten bath formed therein.

The use of oxygen by the steel industry to speed up production is increasing every year. Not only are oxygen and other treating gases used extensively in the final stages of the open hearth method to refine the steel, but they are used also in the initial stages of the process to speed up melting of the charges by flame enrichment with oxygen. lt has also been found that refining periods may be greatly reduced especially in the open hearth type of furnace, by supplementing the normally present end positioned burners, with burners which may be suspended from the furnace roof thereby permitting heating flames to be directed at close range upon the upper surface of the furnace charge and on the subsequently formed molten bath.

In order to fully and most economically utilize the lances which conduct the treating fluids, or direct the heating flames onto the molten bath surface, it is necessary to provide such lances with adequate means for countering the effects of high temperatures, furnace atmospheres, and molten material splash. Generally such lances, or jets as they are frequently referred to, consist of a plurality of vertically and concentrically disposed elongated tubes which are so associated as to provide a flow of the treating material from the lance lower face, which face is normally spaced Within the range of a few inches to a few feet from the bath surface. It is of course necessary to incorporate into such devices a cooling system of some sort which most generally embodies, a passage for conducting a flow of coolant liquid toward the lance face, and a return channel which brings the liquid into contact with the heated outer casing of the lance. This method of removing heat, by a circulatory coolant flow, is found to be satisfactory up to a certain point after Which it is impossible to achieve a sufficiently high coolant rate of flow to overcome the damages re- :sulting from exposure to the furnace heat and from rnetal slag buildup on the lance outer surface due to vfurnace splash.

In the instance of roof burners used in open hearth installations for the purpose of increasing the scrap melt down rate, the prior art has proposed devices in which the fuel gas composition is pre-mixed within some portion of the burner end thence ignited at the discharge face to form heating flames. A notable disadvantage to this method of flame generation is the susceptibility of the combustible mixture to being ignited within the confines of the burner thereby resulting in flash back or burn back of the gas. `Since flashback often results in damage to the burner itself, or parts associated therewith, it is'highly desirable to prevent such a reaction.

It is therefore a primary object of the present invention to provide an apparatus for treating the charge in a metallurgical furnace, said apparatus being particularly adapted to resist the detrimental effects of excessive furnace temperatures and molten splatter.

A further object is to provide a device of the type den l t scribed in which a liquid coolant material is provided as a heat transfer medium for protecting the surfaces of said device which are exposed to the molten metal bath.

Still another object is to provide a combination oxygen roof jet and roof burner of the postmixed gas flame type, including means for protecting the forward exposed surface thereof with La flow of coolant fluid.

ln the drawing:

FIG. l is a longitudinal View in cross section of a combination oxygen jet and roof burner apparatus embodying the novel features of the invention;

FIG. 2 is a plan view of the apparatus shown in FIG.

l; and

FIG. 3 is an enlarged cross sectional view illustrating the lower portion of the apparatus shown in FIG. 1.

FIG. 4 is an enlarged view of the front end discharge face of the apparatus shown in FIG. l.

in brief, the device contemplated by the present invention includes the combination of a roof lance for introducing flows of a treating gas such as oxygen to a molten bath, and a roof burner for impinging heating flames onto the unmeltcd furnace charge and against the bath surface in a single apparatus. The combustion jet, as the device will be hereinafter referred to, consists of an inner elongated tube extending the burner length, the forward end of said tube being terminated at the burner face in a nozzle portion. A plurality of concentrically disposed tubes surrounding the inner tube, define an nular passages for separately conducting flows of the treating gas, a fuel gas, and a coolant fluid respectively to the nozzle portion which fixedly positions the lower end of said tubes relative to each other. A manifold engaging the tube upper ends provides a closure thereto and also afford means for communicating with the said annular passages. The burner inner tube is provided at the upper end with means for simultaneously introducing at a high pressure, a fuel gas, and a non-combustible, heat vaporizable fluid additive substance; a deflector interposed at the lower end of said inner tube deflects the high velocity composite stream of said fuel gas and additive, outwardly toward the burner wall where the latter may adhere to and flow toward the exposed burner face. The fuel gas thereafter is discharged from the burner face, to mix with an oxygen stream and thence burn as a heating flame.

Referring to FIG. 1, a preferred embodiment of the present combustion jet is shown at 10 and comprises a centrally located inner tube 12, the forward end of which terminates in a discharge opening 14 at the exposed burner face. The upper end of said tube is slideably enclosed by a cap 16 which constitutes a removable segment of the manifold 18. A resiliently sealed opening in said cap 16, including the 0 ring 20 retained in a groove therefore, provides a fluid tight connection with the outer surface of tube 12 in spite of relative movement between the sealing surface of said tube and cap due to thermal expansion Iand contraction of the respective burner parts in the course of operation. The cap 16 is provided with a port 22 for introducing to the inner tube 12 a flow of fuel gas such as methane, or natural gas. According to the invention, this gas is ordinarily delivered to the inner conduit 12 at a sufficiently high pressure to achieve a rate of delivery to the furnace of about 20,000 to 60,000 cubic feet per hour. Such a volume of gas in passing through the relatily-small diameter of the inner conduit 12 will of course form a high velocity stream.

lnto the high velocity gas stream thus formed, there is injected a relatively small amount of vaporizable coolant fluid preferably water or steam, which is introduced through a second port 24 positioned down stream of port 22, so that the injected fluid will be aspirated, substantially atomized, and conveyed as minute droplets in the gas stream toward the burner discharge opening 14. While not presently shown in the drawings, the port 24 may be provided with suitable flow metering means such as a valve, for proportioning the proper amount of liquid or steam into the gas stream.

The lower or discharge end of tube 12 as previously noted, is generally positioned in an open hearth or other type furnace, a matter of a few inches above the molten bath or scrap charge surface and therefore subject to severe abuse both from the bath heat and from molten splatter. In addition, as the stream of fuel gas emerges from the discharge port 14, it will then mix with a stream of oxygen also emitting from the burner to form a cornbustible mixture and be ignited into an intensly hot flame which tends to further heat the burner face.

Also, since it has been found desirable to introduce the oxygen to a molten bath in the form of a large number of high velocity jets, a further problem has often been encountered. Since the orifices which form the high velocity jets are positioned at the lance face, they are subjected to particular abuse from molten splatter, as are the web sections 85 which separate the respective orifices. In order to obtain the maximum number of oxygen streams, the lateral spacing therebetween is usually quite limited and consists in many instances of no more than a thin web 85. Since it is quite difficult to adequately cool the web section, burning out at this vital point is one of the most common causes for lance failure.

In accordance with the invention, much of the heretofore frequently occuring damage to roof lances of the type described has been overcome by interposing in the lower end of tube 12, at a point slightly to the rear of the discharge opening 14, a fuel stream diffuser element 26. This diffuser in effect separates the tube 12 into respective upper and lower portions. The primary purpose of the deflector is to intercept the downwardly flowing composite fluid stream and urge said stream laterally toward the conduit wall. As illustrated in FIG. 3, a preferred embodiment of said element 26 is provided with a generally helicoid configuration characterized by gradually sloping surfaces disposed to meet the high velocity, composite fuel gas and coolant stream, and to redirect said stream into a substantially lateral direction with respect to the burner center axis.

The centrifugal force thereby imparted to the fluid particles making up the composite stream, will impinge said particles against the smooth inner wall of the conduit 12 at a glancing angle with the result that the heavier liquid particles of water will tend to cling to the wall while the lighter gas particles will merely be guided into a swirling path. When steam is employed in lieu of entrained water, the steam will be guided into a swirling path along with the fuel gas but since the inner wall surfaces are maintained at a temperature below the condensing point of steam, the steam will condense on the wall surfaces forming droplets of water whereas the fuel gas will leave the jet as aforementioned. During the decarburizing phase of the steelmaking process, the use of steam without fuel gas is employed, as the fuel gas would create a reducing atmosphere. Referring to FIG. 3, an embodiment of the novel deflecting element 26 consists of a screw like member having a peripheral channel 23 formed thereon defined by a spiral land 30. This land is provided with an outer diameter approximating the inside diameter of the tube 12 so as to contact the inner wall of said tube or be contiguous thereto. A smoothly tapered rearwardly projecting portion 32 of the deflector 26, minimizes the actual blocking force exerted by said member against the rapidly moving composite stream so that the high forward velocity component of the gas stream will be maintained along with the swirling component.

The defiector axial length is preferably minimized in order to reduce back drag on the swirling stream and also to permit the formation of aforwardly advancing thin liquid film on the conduit wall. We have found that in a tube having a diameter of about 2 inches, a suitable length for the deflector from forward to rear end would be about 4 inches. Said member 26 may be positioned by welding or other suitable means at the desired location in conduit 12 or it may be adjustably disposed. It has been determined that a high degree of cooling is effected when the deliector is positioned about 6 inches in from the burner lower face.

As illustrated in the figures, the centrifuging effect on the composite fuel gas stream will cause a thin film of water to form along the cylindrical wall of tube 12 from tne downstream end of deiiector 26 to the forward opening 14. The high velocity swirling gas stream, together with the gravitational force acting thereon, then will continue to urge the water film forward along the outwardly (divergent) throat 40 and thence in a lateral direction onto the recessed plane face portion 42 of the burner. It has been found that not only does the thin water layer cool the exposed burner surfaces by an evaporation pro"- ess, but said layer also serves to prevent metallic particles ejected from the bath, from clinging to said surfaces. Actually, there is both a wetting of the exposed surfaces for cooling purposes and also a slight explosive effect when the hot bath particles form steam on striking the liquid film. Such cooling is particularly effective for protecting the previously mentioned web sections intermediate the oxygen orifices.

Under actual operating conditions, we have found that when the burner is operated as a heating device, with natural gas as the fuel, a proper mixture would constitute 60,000 to 160,000 c.f.h. of oxygen to 30,000 to 80,000 c.f.h. of fuel gas, with about l0 to 50 gallons per hour of water entrained in the fuel stream. In the subsequent refining step where only oxygen was introduced to the bath, about 80,000 c.f.h. of oxygen was injected while l0 to 70 gallons per hour of water was carried through the burner by a nominal ow of fuel gas. When steam rather than water is utilized as the cooling medium, for the abovenoted fuel and coolant mixtures, about 30 to 100 pounds per hour of steam are required.

Again referring to FIGS. 1 and 3 of the drawings the inner tube 12 is surrounded by a second tube 44 outwardly spaced therefrom to define an annular passage 45 for conducting a treating gas such as oxygen toward the burner forward end. The lower end of said tube engages the burner nozzle in a gas tight seal and the upper end is enclosed by a cylindrical ring portion 46 of the manifold 18 to define a annular chamber 48. Said chamber is maintained fluid tight with respect to tube 44 and with the adjacent manifold chambers, by resilient seal rings 20, 50, and 52 respectively, which are confined in grooves therefor at the respective ends of said ring 46. As noted previously with respect to seal ring 20; the sliding joints so 'formed by the companionate surfaces of the tubes and resilient seal rings, permits a degree of longitudinal expansion of the burner tubes without the consequence of fluid leakage. t An inlet 54 communicates with chamber 48 for providing oxygen to the lance, and may be coupled to a supply of said gas by a iiexible hose or other suitable form of conduit. The lower end of passage 45 terminates at the burner nozzle into which a plurality of small bore oxygen orlfices 56 are formed. The oxygen orifices as shown in FIG. 3, are disposed in circular fashion about the center opening 14 and are slightly outwardly biased from the burner longitudinal axis to form divergent streams. On emerging at a relatively high velocity from the circularly spaced orifices the oxygen streams at a point forward of the nozzle face, will impinge against the spiral stream of fuel gas emerging from the center discharge opening 14 and thereby provide a combustible mixture which is immediately ignited to form an elongated conical flame.

It has also been found that, rather than employing the circularly spaced oxygen orifices as presently shown, an annular orifice disposed outwardly of and substantially concentric with opening 14 will also provide an efficient mixing of oxygen and fuel gas after both of said gases leave the burner face. The orifices 56 as shown in FIGS. l-3 are directed in a generally divergent pattern not only for the purpose of proper mixing with the fuel gas stream but also for accomplishing a dispersed treating area on the molten bath surface when the streams of oxygen are being introduced thereto without a heating flame, as for example in a deoxidizing step.

In normal furnace operation, the presently disclosed combined roof lance and burner would first be utilized in a heating capacity by directing Oxy-fuel gas flames onto the unmelted scrap metal charge. As the molten bath is formed, the flow of fuel gas is substantially abated until only the oxygen flow is continued. In order to sustain the above mentioned wetting of the exposed lower Wall portion of the center tube, as well as the exposed burner face, a limited fiow of fuel gas may be provided merely to act as a carrier for the water additive. It should be noted though that when `steam rather than water is utilized, the former would not require a carrier and may be introduced alone. Therefore, it is possible to eect the desired burner protection during all steps of the metal refining process. Especially beneficial in this respect is the distinct advantage realized that there will be absolutely no mixing of the fuel and combustion supporting gases prior to their exiting from the burner. This will of course preclude the possibility of flashback in the burner body or in the gas equipment associated therewith. i

Referring to FIGS. l and 3 of the drawings, the internal cooling system employed in the present burner consists of a pair of elongated cylindrical conduits 66 and 62 which are disposed outwardly of tube 44 in substantially concentric relationship therewith to define respective coolant inlet passage 63 and coolant return passage 64. As illustrated in the figures, said conduits extend substantially the length of the burner and are engaged at the upper end with a circumferential collar 66 which forms an integral portion of the manifold .18, The lower end of conduit 66 terminates at the burner nozzle, at a point rearwardly adjacent to an annular coolant chamber 67 formed therein. Said chamber 67 is provided with a curved forward surface which constitutes the rear wall of the exposed nozzle face 42 such that circulating coolant liquid, which is generally Water, will be received from the water inlet passage 63 and then ire-directed into the outer coolant return passage 64.

It has been found that a more efficient cooling of the burner may be achieved by the provision of a baflie member 68 disposed in passage 63, and a similar baffle mem- 'ber 70 positioned in passage 64. The respective baffles as shown comprise a spiral shaped member which, when interposed in the annular coolant passages, urge the coolant stream into a confined spiral channel. By so doing the velocity of the water is increased and a smooth fiow is obtained, both of which characteristics improve the rate of heat transfer from the burner. These bafiies are So constructed and arranged that cooling water passing downwardly through passage 63 will be given a swirling motion in, for instance, a clockwise direction. On passing through the annular chamber 67, the swirling motion will be continued and the stream will be thence directed into the channels formed in passage 64. These latter channels are likewise arranged to continue the stream in a swirling path so as to maintain a rapid velocity throughout the lance.

As mentioned above, collar 66 engages the respective upper ends of conduits 60 and 62, said collar is adapted to threadably engage the outermost conduit 62 and to slideably, fluid tightly engage conduit 69 and tube 44 respectively. A water hose, or similar fiexible conduit not shown on the drawings, but connected to a suitable water d supply, may be coupled at inlet port 72 to provide a HOW of the coolant liquid to an annular chamber 74 and thence to the coolant inlet passage 63. Likewise, the outer coolant return passage 64 terminates in an annular passage 76 which is provided with a port 7S for communication with a second hose for coolant iiuid.

The nozzle or discharge end of the -burner is provided as shown in FIG. 3 with a smooth outer surface which terminates at the forward end in the recessed face 42. It has been found that much of the burner damage, usually caused by blocking of the oxygen orifices with splashed molten metal particles, may be avoided by preventing said molten particles from fiowing down `the burner exposed outer wall and then being aspirated into the high velocity gas stream. Iln this respect, a peripheral lip or ring 80 formed on said face and spaced radially outwardly of the circularly disposed orifice 56, permits the down owing molten metal on `the lance outer surface to drip back into the bath.

A circumferential plate 82 fixed to the outer surface of conduit 62 immediately below the manifold 18, provides means for supporting the burner in operating position, within a furnace. A metal bail 84 formed to be positioned above cap 22, supportably engages said plate 82. Normally the burner may be transported and positioned in an open hearth furnace by an overhead traveling crane of the type peculiar to steel mills, which crane is provided with a downward extending hook for engaging the burner bail.

In view of the operating hazards which normally accompany any metal refining process, it will be readily appreciated that the construction of the present burner which obviates the necessity for flashback precautions is highly desirable. Furthermore, not only is the lance a safe Working tool, but by virtue of the external cooling feature, it has exhibi-ted a useful life that is prolonged considerably over similar jets or burners utilizing the conventional circulatory cooling means.

Of particular advantage are means by which oxygen may be introduced to the bath. As suggested by prior art devices, the web portion of the nozzle lbetween oxygen orifices had to be maintained at a certain thickness. The greater this thickness, the less would be the number of orifices which could be formed into any particular lance nozzle. The unique cooling method presently disclosed permits a greatly reduced web thickness limited only by machining tolerances. Therefore, with a greater number of orices, metal and slag splash is substantally reduced for a given oxygen flow.

It is understood that the presently disclosed combination treating lance and roof `burner constitutes a preferrd embodiment of the novel apparatus, and that certain changes and alterations may be made by one skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. Apparatus for use in a metallurgical furnace having a forward end adapted to withstand the effects of bath heat and splatter, said apparatus including an inner conduit for conducting a fiuidized material containing stream consisting of a gas component and a non-gaseous component, an outer conduit spaced from, and extending substantially the length of the said inner conduit defining an annular passage therebetween for conducting a second uid, a closure engaging the upper ends of said respective inner and outer conduits to position the lower ends thereof approximately adjacent each other thereby defining a forward discharge face, said face having a fiat annular surface with a plurality of orifices therein for the discharge of said second fluid and a large central orifice for the discharge of the components of said fiuidized stream, defining web sections between said orifices, means for introducing flows of the fiuidized material and said second fiuid to said inner conduit and annular passage respectively, and a defiector disposed in the lower portion of said inner conduit positioned rearwardly of the forward discharge face, said deector being so arranged to substantially occupy the cross-sectional area of the inner conduit and to divide said inner conduit into upper and lower portions of substantially constant free and unobstructed cross-sectional area whereby the uidized stream passing therethrough will be deflected into a spiral stream and the non-gaseous component of said uidized stream will be impinged against the inner conduit wall forward of said deector and thence be urged along said wall and onto the web sections of said face by the spiralling gas component of the stream thereby providing a non-gaseous layer on said wall and said forward discharge lface.

2. An elongated jet burner for use in steelmaking to direct a stream of fuel gas and a stream of oxygen from the exposed face of said burner toward a charge of steelmaking materials, said burner comprising an elongated central conduit having upper and lower ends, the lower end terminating in a central discharge opening at the burner forward face, said face having an annular surface with a plurality of orifices therein and defining web sections between said orices, a second elongated conduit surrounding said central conduit defining an annular passage therebetween, means for communicating said annular passage with said plurality of orifices in said face, means for introducing a pressurized flow of oxygen into said annular passage for discharge at high velocity through said plurality of orifices, means for introducing a pressurized ow of fuel gas into said central conduit for discharge from said central opening at said burner face, means for entraining water into said fuel gas flow in said central conduit, and a spiral shaped deector positioned within said central conduit adjacent its lower end, said deflector dividing said central conduit into upper and lower portions,

.3 said lower portion having a face and unobstructed crossseetional area substantially equal to that of said upper portion whereby the water in said fuel gas will be thrown against and deposited upon the lower portion wall of said central conduit and thence be urged onto the web sections of said face as the fuel gas is discharged ythrough said central opening for admixture with said discharged oxygen.

References Cited in the tile of this patent UNITED STATES PATENTS 1,399,006 Cunetry Dec. 6, 1921 1,410,942 Mann Mar. 28, 1922 1,491,318 Shearer et al Apr. 22, 1924 1,501,849 Johnson July 15, 1924 1,564,064 Hannah Dec. 1, 1925 1,569,163 Waldron Jan. 12, 1926 1,830,574 Thwing Nov, 3, 1931 2,446,511 Kerry et al Aug. 3, 1948 `2,454,892 Sprow Nov. 30, 1948 2,669,511' Whitney Feb. 16, 1954 2,819,891 Graef Ian. 14, 1958 2,829,960 Vogt Apr. 8, 1958 2,836,411 Auer May 27, 1958 2,851,351 Cuscoleca et al Sept. 9, 1958 2,905,234- Scholz Sept. 22, 1959 2,937,864 Kesterton May 24, 1960 3,043,577 Berry July 10, 1962 FOREIGN PATENTS 400,793 Great Britain Nov. 2, 1933 542,347 Great Britain I an. 5, 1942 559,408 Canada June 24, 1958

Claims (1)

1. APPARATUS FOR USE IN A METALLURGICAL FURNACE HAVING A FORWARD END ADAPTED TO WITHSTAND THE EFFECTS OF BATH HEAT AND SPLATTER, SAID APPARATUS INCLUDING AN INNER CONDUIT FOR CONDUCTING A FLUIDIZED MATERIAL CONTAINING STREAM CONSISTING OF A GAS COMPONENT AND A NON-GASEOUS COMPONENT, AN OUTER CONDUIT SPACED FROM, AND EXTENDING SUBSTANTIALLY THE LENGTH OF THE SAID INNER CONDUIT DEFINING AN ANNULAR PASSAGE THEREBETWEEN FOR CONDUCTING A SECOND FLUID, A CLOSURE ENGAGING THE UPPER ENDS OF SAID RESPECTIVE INNER AND OUTER CONDUITS TO POSITION THE LOWER ENDS THEREOF APPROXIMATELY ADJACENT EACH OTHER THEREBY DEFINING A FORWARD DISCHARGE FACE, SAID FACE HAVING A FLAT ANNULAR SURFACE WITH A PLURALITY OF ORIFICES THEREIN FOR THE DISCHARGE OF SAID SECOND FLUID AND A LARGE CENTRAL ORIFICE FOR THE DISCHARGE OF THE COMPONENTS OF SAID FLUIDIZED STREAM, DEFINING WEB SECTIONS BETWEEN SAID ORIFICES, MEANS FOR INTRODUCING FLOWS OF THE FLUIDIZED MATERIAL AND SAID SECOND FLUID TO SAID INNER CONDUIT AND ANNULAR PASSAGE RESPECTIVELY, AND A DEFLECTOR DISPOSED IN THE LOWER PORTION OF SAID INNER CONDUIT POSITIONED REARWARDLY OF THE FORWARD DISCHARGE FACE, SAID DEFLECTOR BEING SO ARRANGED TO SUBSTANTIALLY OCCUPY THE CROSS-SECTIONAL AREA OF THE INNER CONDUIT AND TO DIVIDE SAID INNER CONDUIT INTO UPPER AND LOWER PORTIONS TO SUBSTANTIALLY CONSTANT FREE AND UNOBSTRUCTED CROSS-SECTIONAL AREA WHEREBY THE FLUIDIZED STREAM PASSING THERETHROUGH WILL BE DEFLECTED INTO A SPIRAL STREAM AND THE NON-GASEOUS COMPONENT OF SAID FLUIDIZED STREAM WILL BE IMPINGED AGAINST THE INNER CONDUIT WALL FORWARD OF SID DEFLECTOR AND THENCE BE URGED ALONG SAID WALL AND ONTO THE WEB SECTIONS OF SAID FACE BY THE SPIRALLING GAS COMPONENT OF THE STREAM THEREBY PROVIDING A NON-GASEOUS LAYER ON SAID WALL AND SAID FORWARD DISCHARGE FACE.

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