US3137486A - Burner construction - Google Patents

Description

Jun 16, 96 w. R. KEOUGH 3,137,486

BURNER CONSTRUCTION Filed Nov. 28, 1962 2 Sheets-Sheet l INVENTOR.

Mam/1 A. KEQUGH BY 0/1. jO/V, 557715 & Gen/6 A'TTo'e/vE v.5

J n 1 19 4 w. R. KEOUGH 3,137,486

BURNER CONSTRUCTION Filed Nov. 28, 1962 2 Sheets-Sheet 2 I NVEN TOR.

41m MM R. KEOUGH BY Mgm; 527745 42 C4l6 ,QTTO/QNE v.5

United States Patent 3,137,486 BURNER CONSTRUCTION William R. Keough, 124 S. Williamsbury, Birmingham, 'lVlich., assignor of forty-five percent'to Multifasten'er Company, Redford, Mich, apartnership Filed Nov. 28, 1962, Ser. No. 240,544 5 Claims. (Cl. 263-42) The present invention relates to a burner construction and more particularly to a burner of the radiant tube type for use inheat treating'furnaces or the like.

The desirability of radiant tube heating in heat treating furnaces, such as annealing furnaces, lehrs, controlled atmosphere furnaces and the like, has long been'recognized. However, conventional radiant tube burners leave much to be desired in several respects, e.g. the combustion efliciency is low, severe limitations are normally placed on the maximum temperatures which can be attained, difiiculties are" encountered in sealing the tubes aganst loss of atmosphere in a controlled atmosphere furnace, and satisfactory structural designs have not yet been accomplished to permit the usage of high temperature ceramic materials as radiant tubes.

The present invention proposes a new and useful'burner construction which solves these difliculties.

More particularly, this invention provides an improved radiant tube burner composed of three basic components, i.'e. the radiant burner *tube, a combustion burner through which combustible fuel is supplied to the 'tube, and a means for providing additional combustion air or other combustion medium to the tube independently bustion burner. r

This last means preferably is in the form of a casting closing one end of'the burner tube, the casting receiving the combustible burner therethrough and'supplying addiof the comtional combustion mediumysuch as air, in a peripheral direction for flow in a helical path about the burner. As a result of the helical air flow throughthe casting, combustion occurs in a helical path throughout the length of the burner tube, with the combustible gas and'the products of combustion scrubbing the interior periphery of the burner tube throughout substantially the length of the burner to provide an elongated,-swirling path of-flow which 3,137,486 Pa tented June 15,1964

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2 hereafter fully described, compression arrangement may be utilizedto retain'the tube in position under compression and withoutsubiecting the tube to any material tensile load.

It is, therefore, an important object of the presentin-v vention to provide a new and improved burner of the radiant tube type 'for'utilization in a heat treating furnace or the like. a I

Another important object 'of the :present invention is to provide an improved radiant tube burner structure wherein the flow of combustion gases and combustion products is'accomplished in a swirling helical'pathetfectively scrubbing the'inten'or surface of the burner'tubeand increasing the heating efiiciencyof the complete burner structure. I g V It is a fu'rtherobject of thisinventiontq provide an improved "burner construction for a heat treat furnace or the like and in which a controlled atmosphere is maintained, the burner tube being sealed to the furnace to retain the controlled atmosphere therein.

Yet another, and no less important, object of the present invention is the provision of an improved radiant tube burner for a heat treating furnace or the like utilizing a high temperature ceramic material to form "the radiant tube, the ceramic tube being retained in the furnace under a compression load to avoid structuralfailure of the'tube. It is still another important object of thepresent invention to provide a radiant tube construction'for a furnace wherein a metallic tube is-suspended'in'the furnaceto be supplied at its lower end with acombustible fuel and ing description and appendedfcl'airns, referencebeing had to the accompanying 'drawings forming a part of this specification wherein like reference charactersdesi'gnate corresponding parts in the several views.

maintained, for example a reducing atmosphere, such as hydrogen; a treating atmosphere, such as hydrogen cy- On the drawings I FIGURE 1 is a vertical sectional 'view taken through a. 'heat treating furnace and illustrating "one form of radiant tube burner construction of thep'resent invention; FIGURE 2 is a' sectional viewtaken along the plane 2-2 of FIGURE 1; V Q n FIGURE 3 is a view similar to FIGURE lilIustrating a differentfform jof radiant tube burner construction 'of the present invention; and

' "FIGURE 4 is 'a view taken along the plain 4 '4"in FIGURE 3. I V

Before explaining the presentinvention injdetail, it is to be understood that the invention is not limited in its application to the details of 'c'onstruction and arrangement of parts illustrated initlie accompanying drawings,

within the casting maintains the casting at substantially in several different structural arrangements, the specific arrangement being dependent upon the specific, type of tube desired. When the tube is metallic, as for example,a chromium-nickel-steel alloy, the tube may merely be suspended from the roof of the furnace and the casting secured .to the lower end of the tube by conventional means, such as threads. Wherethe tube is ceramic and does not haveall of the structural strength of a metallic element, the tube may be mounted undercompres'sion between'the roof and thefloor of'thefur'nacejand a specific,

since the invention is capable of other embodiments and of beingpracticed or carried out 'in variousways, Also, it is to be understood thatthe phraseologycr terminology employed 7 herein is 'forthe purpose of description and not of limitation. Y As shown on'the drawingsz' n In FIGURE 1, reference numeral 10 refers] generally to aihat treating. {furnacehaving an upper wall or roof 11 and alower wall .01 floor Several layers 'or courses Of refractory brick; indicated generally at 1 3, are utilized to line'the furnace, as is conventional.

The furnace '10 may be any desired heat treating furnace utilized/for any desired purpose, the invention ceramic, such asgglassware, or *the like.- -In-any event,

the structural'elements,inamelythe roof 11 andthe fioor 12 and the several courses of refractories 13 enclose an interior heat treating space indicated generally at 15.

It will be noted that the roof 11 and the floor 12 are provided with vertically aligned apertures 16, 17, respectively, and the refractory linings 13 are also provided with similar apertures 13 to accommodate installaroof plate 11 by suitable means, as by nuts 24. Abutting the undersurface of the flange is a generally cylindrical bushing or stub 25, preferably'formed of refractory material, such as mullite. Muliite is a conventional re fractory material of somewhat variant composition and containing alumina and silica in varying relative proportions. isprovided with an upper shoulder 26 abutting the under- It will be noted that the mullite stub 25 surface of the pipe flange 21, with a cylindrical interior bore27 and with a radially enlarged lower recess 23 concentric with the bore 27 and defining therewith a down-. wardly facing shoulder 23.

Seated against the shoulder 29 and snugly received within the recess 28 is a cylindrical radiant burner tube indicated generally at 30. This tube 30, in that form of the invention illustrated in FIGURE 1 of the drawings, is preferably ceramic and is formed of pure silicon carbide fired at a temperature of 2900 C., such material being available commercially from the Carborundum Company of Perth Amboy, New Jersey, under the trade name KT. Such material is suitable for utilization in radiant tube furnaces, since it is capable of withstanding the 7 maximum temperature of all gas fired fuels utilizing air in admixture with the fuel for combustion, i.e. up to a temperature of about 3700 F. However, as will be later explained, this material is of low tensile strength and can be utilized as a radiant tube only when subjected only to compression loads, by the structure to be hereafter more fully described. I The lower end of the radiant tube 39 is received i a lower mullite stub 31 which is also generally cylindrical in configuration and of the sameor substantially the same composition as the stub 25. This lower stub 31 is provided with an upper radially enlarged recess 32 providing a lower shoulder 33 abutting the free lower end 'of the radiant tube 30, the stub 31 being of sufficient length to extend completely through the lower courses of the refractory 13 and to project freely downwardly be yond the floor 12 of the furnace.

V The stub 31 is provided, at its lower end, with a downwardly facing shoulder 34 abutting a lower metallic casting 35. This casting 35 is provided with generally cylindrical side walls 36 smoothly blending, as at 37, into a lower or end wall 38 having located centrally thereof an axially projecting embossment 39 which is internally threaded, the embossment projecting both above and below the end wall 38. An internal mounting shoulder. 41B isprovided in the casting side wall 36, the shoulder being annular to receive thereagainst the extreme lower end of the stub 31. i

Secured to the floor 12 of the furnace by suitable means, as by welding, is an annular, downwardly projecting wall 41 peripherally enclosing the lower end of the stub 31 and the upper portions of the casting side walls 36, this wall 41 cooperating with the exterior peripheral portions of the stub 31 and the exterior periphery as at 44. The wall 41 is provided with one or more conj i ventional grease fittings, commonly known as zerk fit-. tings 45 by means of which the sealant space 42 may be filled with grease or a similar sealant.

rods 46 to receive the rods therethrough. The lower ends of the rods 46 are threaded, as at 49, to receive thereon; securing nuts 5%. Compression springs 51 are interposed between the lower surface of the plate47 and each of the nuts 59 to urge the plate 47 upwardly relative tothe furnace 10. The plate is centrally apertured, as at '52.

to receive the threaded embossment 39 projecting beyond the bottom wall 3 8 of the casting 35, those portions of the plate surrounding the aperture 52 abutting the exposed lower surface of thecasting, so that the springs 51 urge the casting upwardly. p

These springs 51 serve to maintain in removable assembly the casting 35, the stub 31, the radiant rtube 30, the stub 25, against the metallic pipe flange 21. By virtue of the telescopic assembly of the various elements, it is not necessary to cement, grout or otherwise fixedly secure the elements to one another, although such fixed securing may be utilized if desired.

As best illustrated in FIGURE 1 of the drawings, the threadedembossment 39 of the casting 35 threadedly receives therethrough and secures in position within the stub 31 a burner assembly indicated generally at 55 and comprising a burner head 56 of any desired design surmounting a pipe 57 threaded into the casting portion 39.

As best illustrated in FIGURES 2 and'4 of the drawings,

the casting 35 is provided with an aperture 58 which is located tangentially of the side wall 36 of the casting in the area 37 of the casting joining the side walls 36 and This aperture communicates with an embossment 59 integral with the casting and projecting therebeyond to receive therein a supply pipe 6% connected to a suitable source of combustionsupporting gas, such as air. 'A flow of a combustionthe bottom wall 33 thereof.

57 of the burner assembly 55, ignition of this combustible mixture occurring exteriorly of the burner head 56,v i.e. I

somewhere within the upper'regions of the stub 31 or the lower regions of the radiant tube 30. The air or other gas flowing spirally through the stub31 provides additional combustion atmosphere for the mixture introduced through the burner assembly 55 and ignited therebeyond. The additional combustion atmosphere increases the combustion efiiciency of the burner 55 and the swirling or helical path of the air induces a similar swirling or helical path of the combustion gases, so that the entire inner periphery of the radiant tube 30 is contacted by the burning mixture, this burning'm'ixture effectively scrubbing the interiorsurface of the radiant tube and imparting heat thereto for radiant dissipation into the furuacespace 15. After substantially complete combustion has occurred within the radiant tube 33, and the tube has been heated by such combustion, the products of combustion escape upwardlythrough the upper stub 25 to exit through the aperture 22 of the flange 21. d j

.It will be specifically noted that there is neither combustion nor heat of combustion within the casting 35, any

such combustion necessarily occurring at or above the upper end of the burner assembly 55. Further, the swirling .of combustionair through thecasting 35 will continually cool :the interior surface of this casting'and of the lower :extremityof the stub 31. :Asa consequence, the sealant chamber '42 will :remain relatively :cool, ie in actual practice, the exposed lower end of the casting 35 and 'the walls flare cool 'to the touch. As a result, the grease .or other sealant the chamber '42 remains viscous and .in its original condition, so .as to effectively seal the atmosphere within the furnace interior from the exterior atmosphere, despite :the possibility of the escape of the furnace atrnosphere' through the refractory apertures :18ian'd the floor aperture 17 whichare necessarilyspaced peripherally from :the exterior surface: of-the st1ib31. Thus, teifective:sealing of'the furnace atmosphere is obtainedby'theutilization ofa'conventional, cheap and readilyzavailablesealant suhasa :common grease.

In that embodiment of the :invention illustrated in FIGURES 3 and 4,-the structurezfor supporting aradiant tube internally of a:furnace'is substantially simplified by the utilization of a metallic .radiant'tube. Reference numerals in FIGURES 3 and 4 identical with reference nmncrals'inJFIGURES 11 and Z-referxto identicalportions of the apparatus. 1

It will be noted that the furnace. structure 10 is substantially the same, including the furnace roof 11, the furnace :floor 12, and the {refractory linings :13 for these elements. A similar form of pipefiangeis utilized, this flange being identified by reference numeral 70. The,

flange 70 is suhstantiallythe same as that utilized in the embodiment of EIGURES .1 .and 2, the flange having a straight-throughaxial aperture .71. Again, the flange is secured to-thefnrnace. roof by suitable'means, ias by bolts Projecting through the flange aperture 71 is" a metallic radiant tube 75 having an out-turned upper marginal flange 76 overlying the upper surface of the standard flange 70. Of course, the flange 76 may be either integral with the radiant tube 75 (as illustrated) or may be secured thereto by suitable means, as by welding.

The radiant tube 75 is preferably a high temperature resistant steel alloy, such as a chrome-nickel alloy, such alloys being well known and being capable of withstanding temperatures on the order of 1850 F. without distortion and without loss of tensile strength to an extent such as to endanger their utilization in the manner shown in FIGURES 3 and 4. Thus, although the metallic radiant tube 75 illustrated in FIGURES 3 and 4 is not capable of withstanding the temperatures to which the ceramic tube of the embodiment of FIGURES 1 and 2 may be subjected (on the order of 3700 F.) the simplification of the structure indicates the desirability of utilization of such metallic tubes where undue temperatures, on the order of 1850 F. or less, are encountered.

The tube 75 projects vertically downwardly from the flange 70 and terminates in an externally threaded lower end 77 which is threadedly received by the threaded upper end 78 of a lower casting 35 substantially identical with the casting illustrated and heretofore described in connection with the embodiment of FIGURES l and 2. It will be noted that the complete radiant tube-casting assembly is suspended vertically from the flange 70, inasmuch as the tube is ceramic) or to pure tensile-loads -(in the-event that the tube is metallic). In either event, the atmosphere within the :furnace iscompletely sealed from the exterior atmosphere by means of a'conventional, readily available, inexpensive sealant, such as grease, which .'is maintained at substantially an ambient or normal air temperature completely divorced from the; temperature .interiorly of the furnace. .In each form of the invention the upper-end'of thetube is alsosealed-from the furnace atmosphere and the flange 2:1, 70 :se alsthe roof aperture the metallic tube 75 is capable of withstanding the tensile assembly projects freely vertically directly into the metallic radiant tube 75. One again, the surrounding sealant space is utilized, such space being cool by virtue of the fact that combustion occurs well above the casting 35 and the casting 35 is continuously swept at its interior periph- Having thus described my invention, I claim:

1. In a heat=treat furnace havingtop-and bottom wall means defining a treating space therebetWeen, .a' substantially cylindrical radiant tube disposed interiorly of said-furnace and traversing said treating space, upper and lower hollow elements having annular inner :wall surfaces registering with :said tube-and carried by said wall meansi-to support-said tube therebet-wcen, means defining asealant chamber disposed exteriorlyof said treating'space and supported bysaid bottom w'al-l means to surround said lower hollow element means for supplying a'combustion mixture. to thetubefor combustion therein, means for supplying additional combustion-supporting fluid to the lower of said'hollow element beneaththe bottom wall I means and means for flowing said additional fluid tangentially of the annular inner wall surface of said element for travel therethrough in a helical path to maintain said lower hollow element and said sealant space at a temperature substantially less than the temperature interiorly of said furnace.

2. In a heat treating furnace having roof and floor elements defining therebetween an interior treating space containing a treating atmosphere, a radiant tube burner assembly comprising a radiant tube verticallyv traversing said treating space and projecting downwardly'through an aperture in said floor element, means fixing the upper end of said tube to said roof element and providing an exit for combustion products from said tube, afitting located beneath said floor element closing the lower end of said tube and carrying a burner for supplying a combustible mixture to the tube for combustion therein, said burner projecting upwardly from said fitting into the interior of said tube, and a conduit tangential to the inner wall surface of said fitting for supplying air under pressure tangentially to the interior of said fitting for up wardly spiralling passage therethrough into said tube to' be admixed in said tube with said combustible mixture, the upwardly spirilling flow of air through'the fitting and the tube cooling the fitting exposed beneath said floor element, and sealing means disposed between said floor element and the exterior of said fitting at a region of said fitting cooled by the upwardly spiralling flow of air for sealingthe aperturein saidfloor element.

3; In a heat treating furnace having an aperture therein, a radiant tube burner assembly for imparting radiant heat to an enclosed treating space interiorly of said furnace, comprising a radiant tube in said treating space having one end projecting freely through said aperture to the exterior of said furnace and open at its opposite end, a fitting located exteriorly of said furnace closing said one end of said tube, means traversing said fitting for supplying a combustion mixture to the interior of said tube for combustion therein, the products of combustion escaping from the open opposite end of said tube, means for supplying air under pressure to said fitting in spaced relation from said oneend of said tube, and means defining a sealant chamber at least partially surrounding said fitting and enclosing said aperture,-and means in said air-supplying means for introducing air from said supplying means into said fitting in a direction tangential to the inner periphery of said tube so that the'fiow of air through said fitting cools said sealant chamber during the resultant spiral How of air through said fitting into said tube 4. 111a heat treating furnace having roof and floor elemerits defining therebetween an interior treating space 7 containing a treating atmosphere, a radiant tube burner assembly comprising a metallic radiant tube vertically traversing said treating space, an annular collar secured to said root element and suspending said tubetherefrom, said collar providing an exit for combustion products from said tube, a fitting secured to the lower end of said tube and carrying a burner for supplying a combustible mixture to the tube for combustion therein, means for supplying air under pressure to said fitting for passage therethrough in an upwardly spiralling path into said tube to be admixed in said tube with said combustible mixture, said fitting being located beneath said furnace floor element, said floor element being apertured to receive said burner assembly therethrough, a depending wall secured to the under-surface of said floor element and surrounding said floor element aperture and at least a portion of said fitting, said Wall and said fitting portion defining therebetween a sealant chamber, and means for filling said sealant chamber with sealant, the flow of air through said fitting chilling said chamber despite the free communication of said fitting with said radiant tube.

5. In a heat treating furnace having roof and floor elements defining .therebetween an interior treating space containing a treating atmosphere, a radiant tube burner assembly comprising a ceramic radiant tube vertically 1 traversing said treating space, upper means traversing said roof element and abutted by said .tube to provide an exit for combustion products from said tube, a lower fitting means sealingly abutting the lower end of said tube and carrying a burner for supplying a combus-' tible mixture to the tube for combustion therein, means for supplying air under pressure to" said fitting means for v I upwardly spiralling passage therethrough into said tube to be admixed in said tube with said combustible mixture,

said fitting means projecting beyond said furnace floor element, said floor element being apertured to receive said burner assembly therethrough, a depending wall secured to the undersurface of said floor element and surrounding said floor element aperture and at least a portion of said fitting means, said wall and said fitting means portion de r fining therebetween a sealant chamber, meansfor filling said sealant chamber with sealant, the upwardly spiralling flow of air through said fittingrneans chilling said chamber despite the free communication of said fitting means with said radiant tube, and means biasing said fitting means and said tube upwardly toward said upper means to maintain said tube in position under a compression load only.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN A HEAT TREAT FURNACE HAVING TOP AND BOTTOM WALL MEANS DEFINING A TREATING SPACE THEREBETWEEN, A SUBSTANTIALLY CYLINDRICAL RADIANT TUBE DISPOSED INTERIORLY OF SAID FURNACE AND TRAVERSING SAID TREATING SPACE, UPPER AND LOWER HOLLOW ELEMENT HAVING ANNULAR INNER WALL SURFACES REGISTERING WITH SAID TUBE AND CARRIED BY SAID WALL MEANS TO SUPPORT SAID TUBE THEREBETWEEN, MEANS DEFINING A SEALANT CHAMBER DISPOSED EXTERIORLY OF SAID TREATING SPACE AND SUPPORTED BY SAID BOTTOM WALL MEANS TO SURROUND SAID LOWER HOLLOW ELEMENT, MEANS FOR SUPPLYING A COMBUSTION MIXTURE TO THE TUBE FOR COMBUSTION THEREIN, MEANS FOR SUPPLYING ADDITIONAL COMBUSTION-SUPPORTING FLUID TO THE LOWER OF SAID HOLLOW ELEMENT BENEATH THE BOTTOM WALL MEANS AND MEANS FOR FLOWING SAID ADDITIONAL FLUID TANGENTIALLY OF THE ANNULAR INNER WALL SURFACE OF SAID ELEMENT FOR TRAVEL THERETHROUGH IN A HELICAL PATH TO MAINTAIN SAID LOWER HOLLOW ELEMENT AND SAID SEALANT SPACE AT A TEMPERATURE SUBSTANTIALLY LESS THAN THE TEMPERATURE INTERIORLY OF SAID FURNACE.

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