US2840362A - Apparatus for heating gases - Google Patents

Description

June 24, 1958 E. L. KRIEBLE ETAL 2,840,362

APPARATUS FOR HEATING GASES Filed June 4, 1954 2 Sheets-Sheet 1 FIG. 2.

INVENTORS ELVIN L. KRIEBLE EUGENE J. HOUDRY ATTORNEY n 95 E. L. KRMIEBLE ETAL 2,840,362

APPARATUS FOR HEATING CASES 2 Sheets-Sheet 2 Filed June 4, 1954 INVEN TORS ELVIN L. KRIE E EUGENE J. HOUDRY ATTORNEY United States Patent APPARATUS FOR HEATING GASES Elvin L. Krieble, Newtown Square, and Eugene J. Houdry, Ardmore, Pa., assignors to Oxy-Catalyst, Inc.

Application June 4, 1954, Serial No. 434,576 1 Claim. (Cl. 263-19) the gas stream. Where these gases are non-combustionsupporting, it has heretofore been difficult, if not impossible, to heat them in this way using a conventional fluid fuel burner of the type which will operate efficiently only .in a combustion supporting atmosphere. The term "non-combustion-supporting atmosphere is herein employed with reference to those gaseous atmospheres which are incapable of supplyingoxygen to a flame in such quantities as to permit efficient and relatively complete combustion. By way of example, the atmosphere may be non-combustion-supporting by reason of its being so deficient in free oxygen as to be incapable of supplying the oxygen required for the maintenance of a flame; As a further example, the atmosphere may contain a high concentration of combustible. constituents, such asCO and Atmospheres of smoke, along'with some free oxygen. the latter type are non-combustion-supporting for the reabustion-supporting atmosphere with relative ease. How-' ever, the solution of providing a pressure type aspirator burner is not always acceptable because of the added ex-' pense and complexity of the equipment. For installations of this nature the present invention permits the use of a! conventional burner of the type which requires a combustion-supporting atmosphere for efiicient operation, and thereby obviates the need for complex or in any way expensive equipment.

' It is one of the objects of the present invention to provide a method and apparatus for heating non-combustiom supporting gases flowing under negative draft in a con-' fined passageway.

-It is"a further object of the present invention to provide a method and apparatus for operating a burner of the" type which requires "a combustion-supporting atmosphere within a confined passageway in which non-combustionsupporting gases areflowing under negative draft.

Further objects of the invention will be apparent from the following description and from the annexed drawings in which: i

Fig.1 is a cross-sectional view of an embodiment of the present invention taken along the lines 1--1 of Fig. 2..

'Fig. 2' is a viewtaken along the lines 2-2 of Fig; 1.

'Fig. 3 is aperspective view, with parts broken away, showing the embodiment illustrated in Figs.1 and 2.

Fig. 4 is a sectional view of an alternative embodiment of the invention.

According to the invention, considered in its broad'er' aspects,*the eflicient operation of a burner located int a stream of non-combustion-supporting gases flowing ina passageway under negative draft is made possible by operating the burner in an enveloping streamof aim drawn into thepassageway from the atmosphere by virtue of the negative draft existing therein. Theproducts of combustion from the'burner, of course, are subsequently intermixed with the stream of gases to be heated,

and thereby rais e the't'emperatu're of; the gases to the desired level.- With the provisionin' 'such manner of a" source of air independent of the flue gases, it is possible 'to operate inexpensive burners which require a' com- 'bustion-supporting atmosphere in any gas stream which son that if it is attempted to maintain a flame therein from n a fluid fuel burner, the flame will tend to ignite the combustible constituents in the atmosphere and the resulting combustion of these constituents will consume the supply.

of oxygen in the atmosphere to the extent that insufficient quantities willremain for theflame from the burner.

Atmospheres which are non-combustion-supporting by reason of oxygen deficiency exist, for example, in heat treating ovens and the like in which it is necessaryto maintain a neutral or mildly reducing atmosphere. Such atmospheres do not, of course, contain oxygen, and cannot therefore support a flame from a burner. Atmospheres which are non-combustion-suppor'ting by reason of the presence of combustible constituents along with some free oxygen exist, for example, in flue gases from an incomplete combustion process such as might be carried out in an incinerator. With either type of non-combustion-supporting atmosphere, it is virtually impossible to eflicently operate a burneriof'the type which produces a flame that takespart' of its oxygen from the surrounding.

gaseous mediumat the point and time of combustion.

In industrial installations or other installations war ranting relatively expe'nsiveand complex equipment, it is possible to provide a high pressureaspirator mixer type burner for the purpose of burning a gaseous fuel in a stream of non-combustion-supporting gases. With such pressure type aspirator burners, suflicient quantities of. oxygen or air are premixed with the fuel prior'to de livery to the burning ports; As a result, no secondary is required and a flame can be maintainedin a non-comflows under a negative draft regardless of the composition of the gas stream. As'-'will be apparent, the presentinvention has the additional advantage that the burnin'gfof I the gaseous mixture of fuel and air-takes place-in a relatively quiet atmosphere, that is, an atmosphere un-' disturbed by turbulence such as may sometimes 'existfi'n a flue or other gas' conducting passage. By virtue of this aspectof the invention, the flame of the burner can readily be maintained, and is not-subject to extingiiishment by virtue of the moving gas'stream being heated. v In the embodimerlt of Figs. 1-3 there is provided a conventional inspirator type burner designated by the reference numeral 10 which 'is mounted within apa'ssage way (such as a flue) 12.-'Ahousing, broadly'designated j .by'.the reference numeral14,"is secure'dto the inside of" the flue '12 by means of fasteners 16, and encloses the? head 18 of the burner." A gasfuel line ZO'enters the burner through a plate 26 and terminatesin a restricted f orifice 22 contained within the delivery tube 24 of the} burner. The end ofthis delivery tube is 'closed'by plate;.

26 which is provided 'with ports: 28 therein which admit;

primary air into the interior of the delivery tube 24. The;

delivery tube is constricted as at 25 to permit inspiration of air through ports 28 on the venturi princip1e. T he delivery tube 2 4 conducts .the mixture of primary air and 1 gaseous fuel to the burner head 18, whichas noted above,-, is disposed within the housing 14. -The head 18' (shown inphantom in Fig. 3) icomprises a, generally rectangular? member having centrally..located apertures.:30,' and "is;

v V Patented June 24,

provided on its upper surfaces with burning ports or nozzles 32.

The housing 14 as shown in Figs. 1 to 3 is in the disclosed embodiment of the invention rectangular inshape,

and provided with sides 34 and a base 36, The top of the housing 14 is openas shown clearly in Fig. 3, so that the housing in effect comprises an open top vessel or container for the burner head. The open end of housing 14 faces downstream with reference to the flow of gases within the passageway 12 as indicated by the arrows and a battle .44 in the form of a canopy supported as by supports 46 above this month contributes to the intermixing of gases flowing frorn the housing 14 and gasesflqwing in the flue 12. One wall of the housing is. provided with an air inlet 38 shown in Figs. l-3,'which communicates from the interior of the housing with the atmosphere. This inlet permits the entryof; air intothe interior of the housing 14 at a point preferably below the burner head 18.. A secondopening 40 is provided for the purpose of lighting theburner head 18 from the outside of the passageway 12. This opening is provided with a hinged closure 42 or other such device.

-Within the opening 40 therc is mounted a pilot burner 58'and a control element 60 (often referred to as a pilotstat). The burner 58 andcontrol element 60 are provided with lines. 59 and 61 respectively which are connected to a control valve. 62 in fuel line 20. Line 59 provides a continuous supply of fuel to pilot burner 58 from fuel line 20; however, if the pilot flame 56 shonldv be extinguished, valve 62 will be automatically closed by virtue of pilotstat 60. Valve 62fis, provided with a plunger 63manual1y depressibleto permita flow of,fuel in line 59to pilot burner 58 duringinitial lighting of the pilot flame. Once started, the pilot flame maintains pilctstat 60 at the requisite temperature to permit a continuing flow of fuel to the pilot burner.

For. the purpose of controlling the main burner there is providedan on-off. valve .54 in line located downstream from valve 62, This valve is actuated'by a solenoid 52 which is controlled ,by a thermalswitch 48 acting through a source of electrical power50. As

shown in Fig. 3 thermal switch 48. is disposed downstream within passageway 12 with reference to housing 14. This switch can be adapted to cut off the supply of fuel to burner '10 in the event that the temperature of the non-combustion-supporting gases exceeds a predetermined ,rninimum' level] such that the operation of burnerv 10 is not necessary. g

A manually controlled valve 64 is provided in fuel line 20 forthe-purpose of cutting ,off' the supply of fuel to both the main'burner .10 and pilot burner 58,. This valve is closed only when it is desired to. render the apparatus completely. inoperative. Thebprner 10 of the "embodiment of Figs. 1-3 is of the conventional inspirator type which is adapted to operatewithgaseous fuel under relatively low. pressure, for example the fuel commonly supplied for domestic use which is usually under a pressure of less than 1 p. s. i. gage. In the operation of such burners the fuel issues as a jet into the venturi throat and inspirates air (commonly termedprimary air) from theatrnosphere. The amount of primary air so inspirated isnot, however, sufficientto supply the needs for efficient and complete combustion of the fuel. This fuel-primary air mixture flows through.

the delivery tube 24. of the burner and is delivered to.

the burner ports or noz'zles,32 where combustion takes place. This combustion must of necessity takes place in an atmosphere i capable of supplying the remainder of the air (commonly termed secondary air) necessary. for complete and eflicient. burning. For this reason it is impossible or at leasfimpractical'to utilize such burnersin non-combustion-supporting atmospheres.

existing in passageway 12, and the housing 14 maintains In the practice of the present invention the operation of the inspirator type burner lo in the confined passage- Way 12, in which..n n-combustion-supporting gases are the air stream separate from the stream of non-combustion-supporting gases. The air stream flows upwardly within housing 14 around theburner head 18 and through the openings 30 so that the flame at ports 32 is at all times enveloped in a stream of fresh air from the atmosphere.

The products of combustion of this burning flow upwardly, as indicated by the arrows, and are deflected by the baflle 44 into the stream of gases flowing in the passageway 12. The combustion products from the burning'will, of course, raise the temperature of the gases flowing in passageway 12 to a level. which will be dependent upon the initial temperature of the gases, the temperature of the combustion products, and the ratio of the volumes'of the gases and the combustion products.

The. non-combustion-supporting gases are diverted around and kept out of contact with the burner head by the housing 14 as indicated by the arrows in the drawings. As a result, the mixture of fuel and primary air is burned at the burner head under substantially ideal conditions since the burner head is shielded from the turbulence of the flue, and the flame itself is supplied with. its oxygen requirements by the air stream flowing through flue 38. The baflle member 44 of the instant invention provides for eflicient mixing of the combustion, products. with the gases flowing within the confined passageway 12. As indicated by the arrows in the drawings, this baflie deflects the combustion products into the path of. the gases, and thereby prevents stratification of the combustion products on the one hand and the flue gases on the other. This baflle, therefore, assures uniform mixing and a uniform temperature inthe heated flue gases.

The amount of air admittedthrough the inlet 33 should beregulated to provide sufficient secondary air for eflicient burning of the fuel, but should not be excessive since its diluting elfect will otherwise militate against the desired purpose of effecting a temperature increase in the gas stream flowing within the confined passageway 12. The amount of air drawn through inlet 38 will be determined in part by the size of this inlet, and in part bythe amount ofnegative draft existing in the passageway including the draft generated by the flames from burner ports 32. The amount of air from this source required for eflicient operation of the burner will be dependent upon such factors as the amount of primary air inspiratcd and the composition of the particular fuel suppliedby the fuel line 20. In view of the large number of variable factors involved in the determination of the proper amount of secondary air which should be admitted through inlet 38, it will be most convenient to determine this empirically. If desired, an adjustable shutter may be provided over inlet 38. for the purpose of permitting adjustment of the amountiof secondary air admitted.

.It should be mentioned that where the gaseous fuel is initially under a relatively high pressure (c. g. 5 to 10 p. s.. i. gage) it maybe possible to inspirate a high percentage of the airrequired for burning the fuel. Under these circumstances the secondary air provided by the present inventioncan be correspondingly reduced. However, burning should, in any event, take place in an environment of combustion supporting gas to assure efficient burning, particularly where the gas stream to be heated contains combustible matter-suchas CO and ,smoke for the reason that atmospheres of this type ,will

In most instances gas supplied for domestic use is, of course, under a relatively low positive pressure, usually less than 1 p. s. i. gage. In these circumstances, the amount of primary air inspirated is ordinarily insufficient to provide for efiicient combustion of the fuel, or even to sustain a flame in a non-combustion-supporting atmosphere, and accordingly relatively large quantities of secondary air must be provided.

The present invention is applicable to virtually any circumstances where gases are flowing within a confined passageway under a negative draft. The term negative draf as herein employed is intended to include those situations where the non-combustion-supporting gases are flowing under a pressure less than atmospheric pressure, and to exclude those situations where the gases are flowing under a pressure greater than atmospheric pressure. Obviously the operation of the invention depends upon a flow of suificient secondary air through the inlet 38 and around the burner head 18 in order to provide the proper environment for the burning of the flame. If the gases flowing within the confined passageway 12 were under a positive pressure, that is, a pressure above atmospheric pressure, these gases would flow downwardly into the housing 14 and out of the inlet 38. Under these circumstances, of course, burning of a gaseous mixture at the burner ports of the head 18 would not be possible for the reason that the burner head would be enveloped by the non-combustion-supporting gases from the passageway. On the other hand, where there is a negative draft in passageway 12, air from the atmosphere will flow through inlet 38 as described above because of the pressure differential between the atmosphere and the interior of passageway 12. The present invention is applicable then where the non-combustion-supporting gases are flowing either under the influence of natural draft or under the influence of a fan disposed downstream in passageway 12 from the burner. The invention would not be operative, of course, if the fan were placed upstream in passageway 12 with reference to the burner since a fan so placed would raise the pressure in the vicinity of the burner above atmospheric pressure.

Fig. 4 discloses an alternative embodiment in which both the primary and secondary air is admitted into the interior of the housing 14a. In the interest of clarity and facility of description, the reference numerals employed in the following description of the embodiment of Fig. 4 are the same as the numerals used in the embodiment of Figs. 1-3 with the addition of the letter a. Corresponding numerals in the two embodiments refer to corresponding parts. As is apparent from the drawing, the housing 14a surrounds a burner 10a; however, as contradistinguished from the embodiment of Figs. 1-3, the burner of Fig. 4 generally comprises burner head in the form of a toroidal tube 1811 provided with burning ports 32a. Branch lines 24a conduct fuel from the throat 27a of the burner to the toroidal head 18a. The throat is constructed to effect inspiration of primary air, on the venturi principle, through ports 28:: provided on a plate 26a which closes the lower end of the throat. Fuel line 20a terminates in a nozzle 22a disposed within this throat. The entire burner 10a is mounted within the housing by braces 65a which are secured as by welding or bolting to the housing walls 34a. The embodiment of Fig. 4 is in other respects similar to the embodiment of Figs. 1-3 in the provision of the mouth 38a, lighting port 40a, baflle 44a and other elements common to both embodiments. In the interest of clarity the fuel controls and pilot lighting system are not shown, although these components can, of course, be provided.

The operation of the embodiment of Fig. 4 differs from the operation of the embodiment of Figs. l-3 in that all of the air required for burning (both primary and secondary) is admitted through the inlet 38a. The primary air is, of course, inspirated within the housing by 6 means of the inspirator of the burner 10a, .while the secondary air by-passesthe inspirator and flows upwardly in enveloping relationship to burnerhead 18a. The embodimentof Fig. 4, as is apparent from the drawings, is more compact than the embodiment of Figs. 1-3, and, moreover, precludes the necessity for having an inspirator disposed exteriorly of the passageway 12.

While we have disclosed preferred embodiments of our invention, obvious modifications thereof within the scope of the appended claims will be apparent to those skilled in the art to which it appertains. For example, the housings 14 (Figs. l3), 14a (Fig. 4) might be provided with curved rather than flat surfaces. A housing having such curved surfaces would offer less resistance to the stream of non-combustion-supporting gases flowing within the fine, and would have less tendency to cause turbulence or in any other manner interfere with the draft within the passageway. While we have disclosed an inspirator type burner, it is understood that the principles of the invention are applicable with other types of burners V which can be efficiently operated only in a combustionsupporting atmosphere.

Other modifications within the scope of the appended claim will be apparent to those skilled in the art.

We claim:

Apparatus for heating a stream of non-combustionsupporting gases flowing under negative draft within a confined passageway comprising an inspirator type burner, said burner having a burner head disposed within said passageway, said burner head being provided with a plurality of burner ports, a fuel supply line for supplying a gaseous fuel to said burner head, air supply ports opening into said fuel supply line permitting the inspiration of primary combustion air into said fuel line, a housing surrounding said burner head and having external surfaces adapted to divert said stream of non-combustion supporting gases around said burner head whereby flames issuing from said burner head are shielded from said stream of non-combustion-supporting gases, at least one opening communicating with the interior of said housing adjacent said burner head and permitting the flow of a separate stream of air from the atmosphere to the interior of said housing, said air opening being located down-stream from said burner head with respect to the flow of air through said housing whereby said air flows into said housing and around said burner head in enveloping relationship thereto and thus supplies secondary air to the flame at said burner ports whereby suflicient quantities of secondary air are provided for burning of said mixture of fuel and primary air to produce a stream of hot combustion products, said housing being provided with portions opening into the interior of said passageway, said portions being located downstream from said burner head, baflle means adjacent said open portions in such manner that said stream of combustion products flows within said housing, through said open portions of said housing against said baffle means and is intermixed with said stream of non-combustion-supporting gases, said bafile means eflecting complete and intimate intermixing of said streams whereby said stream of oxygen-deficient gases is heated to a temperature greater than its temperature prior to intermixture.

References Cited in the file of this patent UNITED STATES PATENTS 1,301,324 Schlatter Apr. 22, 1919 1,528,816 Cummings Mar. 10, 1925 1,773,256 Breitwieser Aug. 19, 1930 1,863,391 Bluemel June 14, 1932 2,066,524 Gehnrich Ian. 5, 1937 2,231,445 Grapp Feb. 11, 1941 2,444,588 Bassinger et a1. July 6, 1948 2,583,736 Hess Jan. 29, 1952

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