US2936752A - Furnace structure - Google Patents

Description

May 17, 1960 J. w. THRocKMoR-roN ET AL FURNACE STRUCTURE 2 Sheets-Sheet 1 Filed Feb. 27, 1957 ATTORNEY May 17, 1960 J. w. THRocKMoRToN ETAL 2,936,752

FURNACE STRUCTURE Filed Feb. 27, 1957 2 Sheets-Sheet 2 @www 2,936,752 FURNACE STRUCTURE John W, Thro'ckm'orton and John S. Wallis, New York,

N.Y.,7assignors, by mesne assignments, to Yuba Consolidated Industries, Inc., San Francisco, Calif., a corporation of Delaware Application Fehmarym, i957,seria1.N.64z,soo

40mm. (ci. 12e-109) This invention is concerned with heaters in general. More specifically, the invention pertains to tall, cylindrical, upright furnaces of the pressure fired type having a single cylindrical bank of vertical heat exchange tubes spaced near the inner wall of the combustion chamber and forming a circle of large diameter.

It has been found that with thls typev of furnace, therel are set up, within .anyupright portion of 1the` furnace,

down drafts of the products ofV combustion.v These down drafts are causedV by atemperature gradient that, is lset up as the heat is transferredfrom the products `f y combustion to `the heat exchange tubes by radiation.-

United Safes P atented May17, .19.60

burner located in the center of the bottom area vof the" furnace, vwith flue gas exit openings locatedv near the4 periphery of the'bottom ,outside of the burner. The

furnace also has an air intake duct that is adjacent to a ue gas removal duct for convenient connection of the two ducts to the proper passages of a heat exchanger, inorder to Vprovide convenient and easy heat transfer for lowering thetemperature of the stack"gases and preheat-` ing ofthe intake air. i

Briefly, this invention combustion chamber. addition the furnace com? prises means for receiving heat from the-jcombustionof fuel in said chamber, andy at/leastl one "burner located near thei bottom of said chamber and directed upwardLv The furnace also comprises means for forcing the prod-' Such down drafts have a tendency tofunduly' c`o o1'thef v Therefore much of the potential heat is not transferred..`

In addition, the top ringmethodfcrfeates. the necessity forproviding duct work that Iextends the full Yheight ofy the furnace in order to b e able top m'ake use of a preheat exchange for preheating the intake air to the burners'. L Suchlengthy duct work, to say nothing of the more complicated structure-for mounting va burner at the top. o f the furnace, creates a relatively expensive vaddition toY the necessary structure.

.Consequently, it is an object Aof this invention to provide an improved heaterfth'a't .overcomes the above indicated disadvantages and difficulties.

Furth'ermore,1t1s an object of this 1nven'tion toprovide a heater V that has a furnace chamberthatis red at one end-thereof and has its ue gases discharged near the .Another object Vof this invention is to provide a vertical furnace lhaving one or more pressure type burners at the bottom thereof that forces the ame and hot combustion products centrally to the full height of the furnace ichamber`, and that has the flue gases withdrawn'from the chamber'ne'a'r the periphery at the bottom.

lStill another object of the invention is to'provide a vertical typefurnace which employs a single bank of vertical heat exchange tubes therein. The furnace being centrally vfire'dat the bottom ofthe furnace with the burner directed axially within the furnace chamber." The furnace also includes aconical baffleat the toplof the closed chamber, and has flue gas'exitopenings loy voo cated Vat the bottom of the furnace chamberfandspacedy.

radially vfrom the burner or burners; v

Still another object of the inventionjis to provide a vertical type-furnace having a` singlebank of vvertical;

heat exchange tubes near the furnace wall and an upshot ucts of combustion from said burners with sufficient ve# locity to cause them to circulate substantially the full,

height'of the chamber, and comprises flue gas exit means:

located near the bottom of said chamber spaced from said burner.

Certain embodiments of the invention are, described below, byway of illustration thereof, and illustrated in the drawings in which:

Fig. l is an elevation showing y the furnace largely in' longitudinal cross section;

Fig. 2 is an enlarged transverse cross section of thef furnace takenl on theline 2 2 of Fig. l looking rin the direction of the arrowsg.

Fig 3 is. an elevation of cross section; v Fig. 4 is an enlarged cross section view o f the Fig. 3v

embodiment taken along the line 4`4 of Fig. looking` in the direction of the arrows; and

jFig. 5 is a fragmentary elevation with the furnaceLl largely in longitudinal cross section, showing an addi-- tional embodiment of the invention employing the same features asthat shown in Fig. 3,- but including a preheat'l element in addition to a blower for additionally inducingthe'ilowof ue gases v out of the furnace.

there is a stack 11 to which the nfurnace is connected for may be clamped or bolted to the under furnaceV above the oor level. The'furnace shell 12 may within shell 12 there is a closed top structure 18` that surrounds va centrally located inverted cone bafe.1 9. Baiie 19 is preferably supported from the cross beam 14 b y means of a vertical cylindrical extension 20. Batlle, 19 has asolid surface construction, so that there is -no exit at the top of the furnace for any ofA the ilue',g ases ..-l Around the periphery of the top member 1 8 thercz. iS n support for'the upper ends, `of a cylindrical..banl o vertical heat exchange tubes 21. supportstructur is `not shown in detail asit is of .a conventional-nature The-furnace chamber is formed within acylindrifcalside/ wall of heat resistant material 22. This wal l 22 isformed l. on the'inside of shell12 in the usual manner for provid 1. ing a tire resistant, heat reecting 1iner on the insidg q ff the furnace chamber.

includes acver'tical'- type furnace i which comprises, among other elements, a'closed top anotherjembodime'ntiof the.T v invention, showing the furnacelargcly in longitudinal` Referring to Figs. 1 and 2, it will be observedthat@Y be attached .to` the I 13in any convenient manner (not shown) such. as by. clamping or bolting. Integrally attached to the lining;Y

At the bottom of the furnace chamber there is a floor structure 25 which is supported' within a peripheral tubesupporting annular structure. 26 that is attached to the outer. shell, 12Al ofthe furnace in any convenient manner (not shown). Centrally located in the hoor 251 there is. agroup of four burners 27 that are-directed; axially upward withinl the. Afurnace chamber.

N The construction ofthese burners is conventional' and; the details thereof' are not shown. It may, be noted that they are constructed to, be in the naure. of high velocity,L oli j et burners, such that the ilame and hotl products of combustion are forcibly ejected' 'upward' inthe unobstructedvv central portion of the furnace to the full; height ofjthe furnace chamber. i

' Underneath. the floor member25 ofthe furnace therel isattaohed" a. closed housing: 28, which surrounds and" encloses the side 'of' the burners 27' beneath oor 25.'. Leading` from Vone corner of housing 2S there is an intake air duct 29;. Duct 29Y is directly connected to the; output ofi a forced draft blower 33t, There, is included' in this connection via duct 29, a preheat heat-exchange. ulnit` 311. By this arrangement the intake air for burners- 27v is, supplied under pressure in order to create the necessary high velocity action required; There is afuel supplypipe 34 connected to. each burner 27; at the bottom thereof. These pipes are'connected' to asource Vof supply for the fuel', in any convenient manner (notshown).

'Thereis an annular hue gas exit opening 3S at the periphery of the furnace chamber near the hoor level. Thisv opening is formed by an annular flange 37 of--a ring or bathe ofl heat' resistant material-36. vThe bathe 36j stands vertically upward, from. the Hoor-25 and the hori# Zontal'flange 37; asviewed in cross section extends radially outward from the vertical baille 36 toward the Vtubes 21 near the base thereof, but leaves an adequate annular open; space around the tubes 21 for passage of the flue gases.' Batlle 36' together with its ange 37 thus forms anv annular manifold 38 atthe lower peripheral cornersof. the combust-ion chamber. Connected to this manifold 38- there is al ue gas exit conduit 39 that carries the flue gases 4leaving the -furnace chamber, Ythrough the heat' exchange element 3,1 and on finto thestack 11 for disposal. The baille 36 extends only a short distance upwardly and covers small portions at the bottom of the heat exchange tubes 21.

It will be observedv from Fig. 2 that there are empl'o'yed four; burners 27. However, itwill be clear to any one skilled intheart that a single burner of adequate size might be` employed instead of the four smaller burnersv shown.

The embodiment" illustrated in Figs. 3- and 4 is quite` similarto thatof--Figs 1 and 2. The majordiiference inn this; embodiment of the invention, over that-of Figs'. l andj,l lies in the use of-diiferent-heatexchange tubes 4'7.A Tubes 47.' include both a long upper smooth portion 47a and a short lower portion -having extended surfaces 4,7bthereon. The elements ofl the furnace which are, unchanged over; corresponding elementsin- Figs. 1 endlare giveni the samereference numerals, so that-no furtherexplanation t-hereoff need be given here.

By employing the structure of the furnace illustrated in Figs. 3` and- 4', the heat transfer to the circular bankof tubes 47 is carried out in the form of a radiant heat exchange from the ame and hot gases forced upwardly from the burners plus convection heat effects from the downwardly owing cooler gases, over the smooth upper portion 47a of the tubes. Then at the lower portion 47b of the tubes 47, Vi.e., within the annular ue gas exit space radially between wall 4S and the furnace chamber side walls22, there isa heat exchange by convection only. Such heat exchange is aided by the use of tins or extended surfaces 47b.

As clearly indicated in the drawings, the heat exchange tubes-are exposed throughout a` large percentage of their entire length to direct radiation from the central column of ame and hot combustion gases, and the relatively short cylindrical bales 36 and 48 form outlet manifolds in all4 of the; drawings. 48 additionally forms a short convection section in Figs. 3, 4 and 5'.

The ue` gases are carried off (as was the gas in the earlier modification). via the hue gas exit duct 39. It will. be noted' that in this embodiment there is not shown any heat exchange unit for preheat exchange purposes. In some instances the omissionof a preheat exchangel unit may be. permissible.

In Figure. 5,v an additional embodiment of the invention is illustrated'. It will be noted that the furnace structure lis the same as that used' in the Figures 3 andv 4v lembodiment. Consequently, the same reference numerals apply to 'the similar elements and no additionalv explanation thereof' is necessary.

` In'the Figure 5 embodiment thereA is shown an addiy than would be the case with only the pressurizing forced In the Figs; 3 and 4 embodiment'a bathe 48 which is' constructed of heat resistant material, extends vertical# ly upward,r from the floor-25. This baffle 48 extends to` a height substantially level with the lowest part of the smooth 'portion 47h-of the heatexchange tubes. Thus; the extended surface section 4'-7b ofthe tubes` 47, fillsv up aconsiclerable amount of-A the radial spacev which lies between the-baffle 48v andthe heat resistant side wall 22 ofthe furnace chamber. i

'Phocas-tended' surface sections 47bofv the tubes 47 stop somewhat above the tube supportingannular structuregztglso4 in effect a manifold'space 49 is formedAv ina: simi-lar as wasmanifold" 38 of the Figs. l

2 embodiment:

draft blower 30 on the air" 4intake side. Thus, the degree of negative pressure on the-exhaust end of the furnace.

may be separately regulated or controlled. At the sametime the degree of. intake pressure applied is controlled by blower 30.

It i's to vbe noted that although there areonly threeV different embodiments of the invention illustrated, it will be clear to one skilled in theV art that various other arrangements might readily suggest themselves.V Furthermore, theindividual elements of these embodiments may be combined .in other and dierent ways without falling-V outside the scope of this,l invention. For example the furnace illustrated in Figs. 1 and 2i might additionally inolude a blo-wer on the exhaust duct,. or it mightnotemploy any preheat'heat exchanger. Similarly, the furnace illustrated in Figs. 3 and 4 might include a preheat i' heat exchanger but notemploy `anyexl'laust draft blower, Gag,

' Operation Referring first, to Figure -l inV particular, the operation of a furnace according tothis invention will be described the ilameand hotcombustion gases in their upward flow accenna do not contact the heat exchange tubes. Since the top of the furnace chamber is completely enclosed the hot gases cannot escape, but are all returned down along the side walls of the furnace chamber in the vicinity of the tubes 21. Some of this reverse flow or recirculation would take place even though the ue gases were to bez the base of tubes 21. These flue gases are then drawn out through the conduit 39 and via Vthe intake heat exchange unit 31 to the stack 11 for disposal of the spent gases.

obstructed cylindrical shell, a single cylindrical bank of vertical heat exchange tubes spaced from one another and located close to but spaced from the inner surface of the cylindrical shell and exposed to the axis of said shell throughout the major portion of their height, a bottom plate closing the lower end of said shell, one or more upshot burners mounted near the'center of the bottom i plate, means for closing the furnaceshell at the top,

It is pointed out that the conical battle 19 is not absolutely necessary. However, it has a double function in use. First the turning back ofthe products of combustion is aided with a minimizing of eddy currents etc. to disturb a smooth flow. Second the battle l9becomes `heated by the products of combustion which strike against it so that it acts as a secondary source and reradiates heat to the smooth portion of the primary heat exchange tubes, e.g., tubes 21 or 47.

It is to be particularly noted that by reason of the withdrawal of liuc gases at the bottom of the furnace, they are prevented from being turned back into the stream of gases being ejected from the burners. For this reason there is no harmful quenching action applied to the flames of the burners. Furthermore, it is to be noted that the ue gas exit duct 39 .is radially located close to the intake air duct 29, sothat there is necessary v bodiment according to Figures 3 and 4. The only differ-Y ence is the fact that `withdrawal of the `flue gases begins somewhat higher from the iloor of the furnace and for a distance vertically including the length of the extended surface elements 47b. Also there is an additional primary heat exchange carried out between the heat exchange tubes 47 and the products of combustion, by

means of convection action only.`

It will be noted that the ue gas exit opening 3S might take different forms without departing from the spiritof the invention. For example, there might be individual openings surrounding each of the heat tubes 21.

- While various embodiments of the invention have been described in considerable detail in accordancev with the applicable statutes, this is not to be taken as in any way 4limiting the invention, but merelyV as being descriptive thereof. f

It s claimed: A j j l. A vertical furnace comprising a tall hollow unvmeans operatively associated with said burners for'forcing the flame and hot combustion gases upwardly fromthe burners through the central unobstructed space in the shell of the furnace out vof contactwith said cylindrical tube bankmeans forming a short cylindrical exhaust manifold surrounding the lower ends of the tubes near the bottom ofthe furnace shell at its periphery, said manifold being coaxial with said shell and open at its top, and means for creating a draft withdrawing the relatively cool combustion gases from said cylindrical manifold at the bottom of the furnace, the parts being so arranged that the cylindrical bank of heat exchange tubes is directly exposed to radiant heat only from the flame and hot combustion gases moving upwardly near the axis of the furnace shell and thatV said tubes are subjected to convection heat fromthe relatively coolY combustion gases flowing downwardly near the cylindrical Afurnace wall into said` manifold.

V2. A vertical furnace, in accordance with claim 1,

l furthercomprising extended surface means on the surfaces of the tubes within the manifold where the tubes are subjected only to convection heat from the down flowingv combustion gases.

3. A vertical furnace, in accordance with claim 1,

further comprising an inverted conical baffle suspended from and projecting centrally downward from the furnace topadapted to absorb heat from the hot gases and to reradiate heat to thetubes near their upper ends and adapted Vto assist the hot ilue gases to be returned downwardly behind and around the tubes.

4. A vertical furnace, in accordance with'clairn l,

further comprising .extended surface means on the sur- .i faces of the tubes within the manifold Vwhere the tubesv are subjected only to convection heatk from the down owing combustion gases and an inverted conical -balle suspended fromfand projecting centrally downward from the furnace top adapted to absorb heat'from the hot gases and vto reradiate heat to the tubes near their upper ends and adapted to assist the hot ue gases to be returned downwardly behind and around the tubes.

References Cited inthe le of this patent UNITED STATES PATENTS v1,599,613 -Fahrenwald Sept. 14, 1926 2,276,527 Throckmorton et al Mar. v17, 1942 2,294,254 Throckmorton et al Aug. v25, 1942 2,630,789 ySmith ...Q Mal'. 10, 1953 2,648,599

Throckmorton et al Aug. 11, 1953

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