US2507260A - Air-cooled burner for furnaces - Google Patents

Description

May 9, 1950 F. H. Lor-Tus AIR-COOLED BURNER FOR FURNACES llll l Il. Il

lllllll/l flllllllll//llllI/l/ l INVENTOR.

Fred H. Loftus M MM www Filed Jan. 29, 1947 May 9, 1950 F. H. LQFTUS AIR-COOLED BURNER FOR FURNACES Filed Jan. 29, 1947 2v Sheets-Sheet 2 INVENTOR. Fred H. Loftus Patented May 9, 1950 UNITED STATES TENT FFICE AIR-COOLED BURNER FOR FURNACES Fred H. Loftus, Mount Lebanon, Pa.

Application January 29, 1947, Serial No. 725,009

3 Claims. (Cl. 158-7) This invention relates to the construction of burners, particularly to burners for the combustion of fluid fuel in industrial furnaces. The burner of this invention is more particularly, though not exclusively, adapted for firing furnaces used in the heat treatment and/or anhealing of metal products, such, for example, as sheet steel which is ordinarily treated in boxtype or cover-type furnaces.

A burner of the sort to which this invention is especially directed comprises an elongate duct having a plurality of outlets for the release of jets of fuel at points spaced apart longitudinally on the burner body.

The iiuid fuel used with burners of the type in mind is a hydrocarbonaceous gaseous or vaporous fuel, which, under the effect of the heat to which the burner is subjected to in service, deposits carbon upon the surfaces of the burner body, and tends to plug the orifices or passages through which the fuel flows. With this circumstance in mind, it will be understood that this invention consists in certain new and useful improvements in burner construction, whereby the fuel-conducting portions of the burner body are screened from extreme furnace temperatures. Additionally, the burner structure is such that the portion or portions thereof which tend to become fouled with accumulations of carbon may be readily removed from the '1 burner structure, and a spare portion substituted. In consequence, it becomes possible to maintain the burner, and the furnace in which it ls used, in substantially continuous operation; that is to say, it is no longer necessary to withhold the furnace from service in order to permit the removal of accumulated carbon from the `burner or burners of the furnace.

The invention will be understood upon reference to the accompanying drawing, in which:

Fig. 1 is a fragmentary view showing a burner embodying the invention in side elevation. By way of example, this view shows the burner in position of service within the burner chamber of a box-type annealing furnace, the refractory walls of the chamber in the furnace structure being indicated fragmentarily in vertical section;

Fig. 2 is a fragmentary view of the burner structure as seen in plan from above;

Fig. 3 is a fragmentary sectional view of the burner installation to larger scale, as seen on the plane III-III of Fig. 1; and

Fig. 4 is a fragmentary view of the burner, partly in longitudinal vertical section and partly in side elevation. This view shows the burner on larger scale than Figs. 1 and 2, but on smaller scale than Fig. 3.

Referring to the drawings the burner comprises an elongate fuel duct 2 and an air duct 3. The air duct is positioned immediately above the fuel duct, and is substantially coextensive in length therewith. In service the burner is usually arranged within an elongate tunnel-like chamber, such as the chamber 50 within refractoryv body 5 of the furnace fragmentarily indicated in Figs. 1 and 3. Angle members 4 are welded to the fuel duct, providing feet upon which the burner structure is supported upon the floor of the chamber 50. The roof of the chamber 50 is provided with a series of ports 6 through which the burner is adapted to deliver burning jets of fuel and air into the combustion chamber or zone located in the furnace above the roof or top wall 5 of the burner chamber 50.

The fuel duct 2 of the burner is advantageously formed of an inner tube 'I telescopically assembled Within and encased by an outer tube 8; the inner tube I is substantially smaller in diameter than the tube 8 and is provided with lugs 9 which support the inner tube in concentric relation with respect to the outer tube 8, with a substantial thermal insulating space I0 provided between the walls of the inner and outer tubes. The burner structure at one end (the right-hand end, Fig. 1) extends beyond the walls of the furnace structure, where an inlet is provided for delivering fuel to the inner tube of the fuel duct 2, and an inlet for delivery of combustion air to the air duct 3.

More particularly, the outer tube of the fuel duct is equipped with a flange I I through which the inner tube l extends to a threaded terminal, by means of which connection is made to a fuel supply pipe I2. The inner tube 'I carries a flange I3. The flanges II and I3 are bolted together, detachably securing the tubes 1 and B in assembly.

The air duct 3 is positioned immediately abov the fuel duct 2, with the axes of the two ducts located in the same vertical plane. The air duct is of substantially larger diameter than the fuel duct, and in this case rests upon the top of the fuel duct. An inlet for air is provided at the end of the burner where the fuel inlet is located. The air inlet is formed by a vertical pipe section I4 welded upon the end 0f air duct 3, and the pipe section I4 is flanged at its upper end, Whereby it may be detachably bolted to the flanged end of a pipe I5 which supplies the combustion air to the burner. Preferably the inlet pipe section I4 extends downward below the air duct 3, and is ported for the passage of the fuel duct 2 through it, the lower end of the section I4 thus forming an additional supporting member for the burner structure. Blanking plates or bulkheads I6 are welded across the bore of pipe section I4 above and below the fuel duct, as shown in Fig. 4.

At points spaced apart longitudinally of the fuel duct radially extending jet pipes I'I are provided. These jet pipes are welded in hermetic seams I8 to the outer tube 8 of the fuel duct, and in the burner shown ithegjetipipes rise in a vertical line, projecting upwardly through the air duct 3. The wall of the 'airduct'is orificcd, as at 20 and 2I, to permit -the passage through of the jet pipes. The jet pipes are united to the wall of the air duct by continuous hermetic welds in the upper orices 20, and, if desired, by intermittent tack welds'in `the-lower -orificesiZI. .Removable -nozzle sleeves I9 (Fig. 3) are positioned upon the projecting upper ends of the jet pipes. -As shown, these jetpipes 'are sevverally aligned with `the ports :6 kin the top wall oftheburner chamber D. Passages-Rand 22 are fformed in the walls 'ofthe innereand outer tubes 'J1 and 8, respectively, of theffuel duct, and through 'such passages 'communication is established beltween'the fuel-deliveringttube 'I and the jet-.pipes severally. :'Eachof the'passages 23 inithe inner ftube comprises a relatively small orifice, whose fsize is determined "to give the desired ow lvof "fuel into -the 4associate jet pipe, v.while .the Acorresponding passage 22 in :the outer tube Il is' comparatively large. The "function of "the pas- Isage A22 is primarily to provide .unrestrictedzpas- 'sage of the fuel jetdelivered'by the associate `orifice 23 into the jet pipe above.

The jets of fuel are directed upwardly from .the `jet lpipes and nozzles .through .the ports 6, and air is released from the air duct V3'to furnish combustion air 4for thefuel jets projected into the furnace chamber or combustion zones above the 'top .wall of theburner chamber. .This combustion air is released by thefuel duct at .dis-

tributed points inthe extent of the iburnenand advantageously the ainreleaseis effected by forming the orifices .2l in the wall ofthe air ;duct 'larger than the bodies 4'0f the jetpipes, as :may be understood upon lreference to Fig. 3. Around each of the jet pipes, therefore, a clearance is provided, through which Lair 'is delivered Yinto ythe 'burner chamber 5D, and Vfrom this chamber the air is aspirated by the action fof A.the Vfuel jets "flowing upwardly through .ports :6. A com- `bustiblemixture of^fuel and airis thus .delivered ,upwardlyfrom each of the'ports 6.

[As noted in the introduction to this speciication a problemin the voperation'o'f 'burners fir- ,ing fluid 4hydrocarbon fuels 'hasiheretofore been r.caused by the deposition'of carbon Vupon the body and in the passages of the burner, thiscleposition/of carbon *being created-by theheat to vwhich the lbody of the burner lis subjected in service. jln'Fig. 3 the arrows-indicate the directions .in which thegreatest quantity'of lheatllows or'radifates into the chamber. It will'be understood, Yof course, that when the furnace is Vin fservice all Vof 'the refractory 'rwalls 5 -which `.define the burner chamber 50 heat up, but theA highest temperatures are developed in the upper wall portions `of the chamber, and greatest heat is radiated vdownwardlyinthe directionof the ai-rows.

EIf the :portion :of any .burner carrying a hydrocarbon fuel is prevented from becoming excessively hot, the problem in question is practically solved. The structure of the burner of this invention is particularly effective to this end.

The inner tube 'I of the fuel duct is the more critical element of the burner structure, since it is this tube which carries the fuel, and it is this tube which includes the relatively small ori- .ces (23) which tend to become clogged with accumulations of carbon. It will be noted that the tube I is housed or encased within the outer `tube 8, and thus receives primary protection against excessive heat. Additionally, the dead space IIl, while filled with the gaseous fuel, provides a thermal screen for the fuel-conducting tube The position and the relatively large diameter of the air duct 3 are important, since the -air duct shades the fuel duct from the most acute heat radiated in .lthe directions of the arrows. Furthermore, the duct 3, conningafcontinuously flowing stream of relatively cool fair, exerts a `cooling as well as a shading" effect uponthe fuel duct. Also, it is importantto .note

clean the relatively small oriiices23of the burner,

irrespective of the degree to which the deposition of carbon is inhibited. Hitherto, burners of ythe class herein under consideration had to-beremoved from the furnace to permit cleaning, or in some cases the furnace has been removedffrom service and the burner cleaned, after the furnace has been cooled down -to the point -where vworkmen could enter.

In the burner structure of this invention, such furnace lshutdowns Iare avoided. It is merely necessary to :remove the bolts which secure the flanges II .and I3 -together, vdisconnect the coupling |20 in theffuel supply line, and then Withdraw ythe innergtube uTI of the fuel duct from the burner structure. 4A spare inner tube I is then quickly assembled 1in place of the inner tube removed, and furnace operation can proceed without undueinterruption. The removed inner tube can be cleaned .at leisure, and held in readinessas aspare.

Theappended claimsdeiine :the invention with the understanding thatmany variations orzmodifications maybe made in the structure described without departing from the spirit of the invention.

I claim:

1. A burner structure comprisingan elongate fuel duct in the form-of an outer cylindrical 'tube having an inner cylindrical tube removably positioned therein, an inlet vfor vthe introduction @of fuel to said inner tube, an elongate cylindrical air duct of greater ,diameter than the fuel duct, said air duct being superimposed upon-said -fuel duct in position to screen the fuel duct from heat radiated downwardly from points above the burner structure, an inlet for the introduction of air to said air duct, and ya plurality of jetpipes extending from said fuel duct `at spaced-.apart points longitudinally Athereof vand "projecting transversely'through said air'duct, the vwalls of said inner and .outer tubes of the fuelductincluding passages for the flow of fuel from said inner tube into said jet pipes severally, and the wall of said air duct including in its bottom wall portion a plurality of outlet passages spaced apart longitudinally of the air duct for the delivery of air over the external wall of the outer tube of said fuel duct,

2. A burner structure comprising an elongate fuel duct in the form of an outer cylindrical tube having an inner cylindrical tube removably positioned therein, an inlet for the introduction of fuel to said inner tube, an elongate cylindrical air duct of greater diameter than the fuel duct, said air duct being superimposed upon said fuel duct in position to screen the fuel duct from heat radiated downwardly from points above the burner structure, an inlet for the introduction of air to said air duct, and a plurality of jet pipes extending from said fuel duct at spaced apart points longitudinally thereof and projecting transversely through said air duct, the walls of said inner and outer tubes of the fuel duct including passages for the flow of fuel from said inner tube into said jet pipes severally, and the wall of said air duct including in its bottom wall portion at the points where said jet pipes project therethrough passages for the delivery of air over the external Wall of the outer tube of said fuel duct.

3. In combination, a tunnel-like chamber provided with openings at its top for upwardly directed jets of burning fuel, a burner structure mounted to extend longitudinally of said chamber, said burner structure comprising an elongate fuel duct in the form of an outer cylindrical tube having an inner cylindrical tube removably positioned therein, an inlet for the introduction of fuel to said inner tube, an elongate cylindrical air duct of greater diameter than the fuel duct, said air duct being superimposed upon said fuel duct in position to screen the fuel duct from heat radiated downwardly through said openings and from the upper wall portions of said chamber, an inlet for the introduction of air to said air duct, and a plurality of jet pipes extending from said fuel duct at spaced-apart points longitudinally thereof and projecting transversely through said air duct in line with said openings at the top of said burner chamber, the Walls of said inner and outer tubes of the fuel duct including passages for the iiow of fuel from said inner tube into said jet pipes severally, and the wall of said air duct including in its bottom wall portion a plurality of outlet passages spaced apart longitudinally of the air duct for the delivery of air over the external wall of the outer tube of said fuel duct.

FRED H. LOFIUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 322,791 Chess July 21. 1885 328,914 Ashcroft Oct. 27, 1885 1,758,828 Fisher et al. May 13, 1930 2,130,165 Warren Sept. 13, 1938

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