US2544600A - Multiple tube gas heating furnace - Google Patents

Description

March 6, 1951 c. KELLER MULTIPLE TUBE GAS HEATING FURNACE 2 Sheets-Sheet 1 Filed Nov; 8, 1948 Inuerflzor Curt Keller March 6, 1951 c. KELLER 2,544,600

MULTIPLE TUBE GAS HEATING FURNACE Filed Nov. 8, 1948 2 Sheets-Sheet 2 2 [l U U 31 27 32 30 30 29 27 I I 8 i a y R N t Invzntor Curc Keller y f7" Aiiornegs Patented Mar. 6, 1951 Curt Keller, Kusnacht, Switzerland, assignor .to Aktiengesellschaft Fuer Technische Studien,

Zurich, Switzerland, a corporation I land of Switzer- Application November 8,.19:48.,-'SerialiNo. 59,01 1

:In'Switzerland November 21, I947 11 Claims. (01. "126-109) This invention relates to a'tu'bular gasheaiterr more especially to .a heater of this kind for, in-

, corporation in agas turbine plant with an indirec't supply of heat to the working medium.

One object of the said invention is to provide of construction for a tubular heater which is suitable for heating air used as the working medium in a thermal power plant of the well known kind in which such .Working medium operates in a tubular gas heater in which the heating tubes though arranged in as 'com'pacta system as possible, are yet easily accessible. This last-named .feature is particularly valuable when the tubular .gas heater is incorporated in aga turbine plant with an indirect supply of heat to the working medium, as, in such caseqthe heater tubes are subjected to severe stresses, on account of 'the high temperatures attained; thus it is important to be able, when necessary, to repair thetu'b'es or to change them andto clean any 'foul'ed tubes.

Another "object-of this invention is toprovide a tubular gas heater in which flue walls and dei'iiector walls -'(which do not participate directly in the heat exchange but only cause pressure losses a closed circuit.

Fig. 2 .as regards its right hand .half, is a plan view of the heater shown in Fig. 1, while the left hand .half of Fig. '2 is a sectionta'ken in the horizontal planes whose positions are indicated b theIineII-JI in Fig. '1.

Fig. 3 is a view similar to Fig. .1 showing another (form of construction for a tubular heater adapted to serve the same purpose as that menon the heating gas side of the heat exchange system 'arereduced to 'a minimum. ffurther object of the invention is to provide a tubular 'gas f'h'eatermeeding comparatively :litt-l'e headroom "for dismantling and having the smallest diameter.

possible :but in "which the parts :subjected to the highest temperatures shall besable to m'ove'ireely, while the absolute expansions are slight :and the :relative -positions :of the necessary Connecting points :remain practically unchanged.

.Inrord'er to secureaall :these advantages, 1a tubul'a'r "gas heater according to the present invention is provided with a removable combustion "cham- 'ber, which is .co-axial with the: longitudinal axis of said heater, and is in direct communication,

with 'at least onezsystem of heating tubes likewise "arrangedwcoaxially with respect to the said longitudinal axis so that its tube :nests are traversed externally, from the inside to the outside "of the system and mainly ;-in transverse directions, by.

the heating gases issuing iirom the said combus- -tion chamber. In-such agas beaten-a distributing chamber .-for the gas to be heated may surround, within a double-walled structural member, .a collecting chamber for the gas brought to the temperature and the pressure needed, I or .in stance, .attheinlet .tora first .expansionstage- The r distributing chamber and 'the coljlecting chamber may, likewise, be coaxial with the longitudinal axis of the heater.

itioned in connection with the first example, 'While j f Fig.4 is a plan view, half .in section, oi'the heater of Fig. 3., the section being taken on 'line IVIV of Fig.3. g

In Figs. 1 and 2, which show an oil-fired tubu- '1ar heater, suitable for heating air, as aforesaid, the reference I denotes a casing element whichis coaxial with the'longitudinal axis of the heater .and is insulated internally. This casing element embodies and contains a co-axial combustion chamber 3 and also carries 'the'burner 2 which work in the said combustion chamber. Reference 4 denotes a second or lower casing element, which is likewise insulated internally and arranged co-axially with .respect 'to the longitudinal axis of theheater. The casing element l'is connected detachably .(but in gastight fashion) to the'cas'in'g element 4 which latter surrounds a itubul'arfheating system 5 comprising a number of lengths of tubing arranged as compactly as possible, with the avoidance, so far as this isjposs'ib'le, of dead spaces and bypasses for the heating gases. This heatingsystem 5, also arranged cpaxial'ly with 'respe'ct to the longitudinal axis 'of the heater, is provided immediately beyond the combustion chamber '3 so that its tube nests are system 5 and given up heatto the tubes, escape fromthe heaterthrough a'branch B of the-casing element 4. .Reference .1 denotes a double-walled structural member provided at the lower part ofthe heater and, again, co-axial with the'lon- .gitudinal axis of the latter. This-member "I is 'cletachabl connected at the seating 4 to the casing element '4. Reference 1 denote a distributing chamber provided 'in the member 1 for the air which *isfto be ,Fheated and which flows branch 8. This air may, for instance, come from the heat exchanger of a thermal power plant, in which air, serving as the working medium, flows in a closed circuit. The inlet ends of the tubes of the system open into this distributing chamber 1 which concentrically surround a collecting chamber 9 for the air brought to the required temperature in the said heating tubes and this heated air flows through apipe It) to a point ofconsumption such, for example, as a turbine in a thermal power plant of the kind above referred to.

It will be observed that, in the heater con structed as above described, those parts of the heating tube system 5 throughwhich flows the 'i coldest part of the air to be heated are located nearest to the longitudinal axis of the heater.

coldest Waste gases impinge upon them.

The air which is required for combustion and i which is preferably preheated, enters the casing element I through a branch ll, passing first into a chamber i2 which co-axially surrounds the combustion chamber 3'. From the chamber l2,

part of the combustion air then flows directly into the combustion chamber 3 through slots .|3 in a partition wall [4 which surroundsthe said combustion chamber; the other part of said combustion air flows along the external surface of said partition wall and hereupon into the heating chamber I6. Additional air for the support of combustion also flows directly into the combustion chamber 3 through a branch [5 right at the top of the heater. This additional combustion air may be preheated.

These guide plates l1 and [8 are disposed convergently, in such a Way that they impart the desired velocity to the fire gases and waste gases flowing between them through the heating system 5. For instance, the velocity of these gases may be kept constant. The heater may be supported in any convenient manner, for instance, on stanchions as at I9 r If the casing element be detached from the 65 casing element 4 it will bring with it the burners 2 and the partition wall l4 surrounding the combustion chamber 3 so exposing the tube nests of the system 5, and rendering them easily accessible from inside for such purposes as cleaning, overhauling or replacing. Moreover, when necessary, the whole of the tube system 5 together with the structural part 1 and the plate 18 and Wall 19 can be lifted bodily out of the casing element 4, the headroom needed for this dismantling operation being substantially less than in the case of tubular gas heaters of the longitudinal flow type in which the wall surrounding the combustion chamberextends far deeper into the heating chamber.

Owing to the symmetrical arrangement of the nests of tubing in the system 5 and of the chambers I and 9 relatively to the longitudinal axis of the heater, free movement ofthese tube nests and of the structural part I "surrounding these 4 said chambers in permitted; thus the relative positions of the connecting flanges on the parts in question remain unchanged, because all radial expansions proceed outwards from the longi- 5 tudinal axis aforesaid.

The tubular heater shown in Figs. 3 and 4 is intended for a hot air turbine plant in which the expanding air is re-heated at least once. Two systems of tube nests 20 and 2| each as compact it) as possible, ar therefore provided, both systems being arrangedco-axially in relation to the longitudinal axis of the heater. The system 2| surrounds the system 20 for the greater part of the length of the latter. The high pressure air to be heated flows through a branch 22 into a distributing chamber 23 in a double-walled struc- --tural member 23, which is arranged co-axially inrelation to the longitudinal axis of the heater, and the inlet ends of the tube nests comprised in the system 2| open into the said chamber 23 The air, brought to the required temperature in the system 2|; passes into a collecting chamber 24 which is locatedin, the innermost part of the structural member 23 and is surrounded con- 25 centrically by the aforesaid distributing chamber 23 From the collecting chamber 24 the heated air flows through a pipe 25 to a high pressure turbine (not shown) in which it expands to a certain extent, cooling down as it does so. This expanded air then flows through a branchfl26 into a distributing header 2'! belonging to. the

. s econd system 20 of heating tubes. From said header the air passes into and through the individual tubes of the system 2!] and is thus reheated and delivered into a collecting header 28,

out of which it passes through a branch 29 and a pipe (not shown) to a low pressure turbine (likewise not shown) in which machine it expands still further.

The distributor 21 and the collector 28, on

. which the tube nests of the system 20 hang, are

arranged inside an upper casing element 30, being movably connected thereto, as is indicated by dot and dash lines 3| and 32 in Fig. 3. The upper casing element30 of the heater is detachably mounted on'a lower casing element 33 to which also the structural member 23 is detachably secured. A hood 34, which contains the burners 6o 35 and surrounds a combustion chamber 36 is detachably connected tothe casing element 30. By a suitable inclined arrangement of guide plates 3-8 and 39 (whereof the guide plate 38 is detachably fixed to the element 33 while the guide plate 39 is connected to the structural part 23), it is possible to impart to the fire gases and waste 1 gases passing, in the main, transversely through the systems 20 and 2|, a desired velocity at all points of the path in question.

In the type of construction last described the two heating tube systems 20 and 2| are'also in direct communication with the combustion chamber 36. At the same time, the combustion chamber 36 and the systems 20, 2| and the structural 55 member 23 are all arranged in co-axial relation to the longitudinal axis of the heater. The tube nests of the two systems 20 and 2| are, as aforesaid, traversed,'in the main, transversely from the inside to the outside bythe fire gases and waste gases, the latter passing out through a branch 31.

On disconnecting the hood 34 from the casing element 30 the combustion chamber 36, toget her withthe burners 35, canbe lifted out in the 'upward direction and the tube nests of the "system ,5 :20 are then accessible from the inside "of the heating "ch-amber. Kfter liavin'g 'separated the "casing elements 3 6 "and 3 3, the heating "tube system 2!! can be lifted out upwards, quit-e independently'of-the system 2'! this renders the tube nestsof the said system 2i freely accessible from thehealtin'g'c'l'iairnber. Finally, after-breaking the jdintbe'tw'een the structural member 23 and the casingelementtt, the second heating tub'e system 2i and, with it, the "structuralpart "23 may "alsobedrawn out'upward's. The' headr'oom necessary for the removal of these various pafts is comparatively small.

The -fact that, in both the heaters above described, a comparatively small amountcf space z'is' requiredto make the heating tube systems "accessible from the heating chamber, and to en- :a'ble themto be removedfif necessaryis o'f'par- "ticfilar importanceinthe case of tubular heaters I "installed in ships, in'which'a's a rule'spaceis very 's'tfictly limited.

Instead of the oilfurnaces show'n inthe'fi ures, furnaces for other fuels, such "for example, as Ipulverised coal or gases maybe used.

"Under certain circumstances, waste gases which escape from the heating chambers of the beater. may be returned to the combustion chamberin order to help to support combustion. Thus in the case of a heater construction as in Figs. 1 and 2, for example, such waste gases will bein- "troduced'through"thebranch i l, while preheated fresh air can be introduced through the branch I5. With the h'elp difii'e'turn'ed flue gases or fresh cooling air flowing over the external surfaceof :1 a

L for r'einovailupo'n 'sep'ara'tion'of said parts.

"the partition wall bounding the combustion -chamber,-it is possible to produce, in the heat ng chamber, which is always indirect communication with the combustion chamber, such a temperature that the radiant heat emanating from the said heating chamber shall not be dangerous to the tube nests of the heating system or heating systems.

Since, in a tubular gas heater according to the present invention, the pressure losses on the heating gas side can, as already stated, be kept comparatively low, a heater of this kind is particularly well suited for cases in which the heating chamber is supercharged, that is to say, where a pressure higher than atmospheric pressure is maintained in this chamber. Under such working conditions it is important to be able to operate with low pressure losses in the heating chamber, because the output of the turbine which drives the supercharging compressor and is itself driven by the waste gases from the heating chamber will be greater the greater the residual pressure of the waste gases.

What is claimed is:

l. A heater intended for heating gases and comprising in combination a generally cylindrical casing, closed at its ends and divided transversely into first and second normally connected but separable parts, the first of said casing parts having a ported, open-ended, tubular projection extending inward from its closed end and dividing a combustion chamber within said tubular projection from an annular combustionair chamber which encircles the same, and the second of said casing parts enclosing a heating chamber into an unobstructed axial portion of which combustion products may flow in an axial direction from said combustion chamber; com bustion burners arranged to operate in said combustion chamber; a connection for supplying air 6 to *said annurar chamber; tubular 'he'alt transfer units arranged within-said heating*charnb'er anrl surrounding said unobstructed axial portion;

two annular --generally conical baffles-so mounted 5 'in saidheating chamberasto converge-outward and to lap corresponding opposite end portions of said tubular heat tra ns-fer units, the first of said "baiiie'sextending from the peripheralwall of the cylindrical casing nearly to the ppen end of "the "tubular-combustion chamber from which it is spaced "to "afford "an annular entrance passage '"for secondary "air, and the second of "said "baiiles extending nearly but not quite to "the --peripheral wall *of'said casingto define "behind the battle an "dfft'ake space "to which products 'of combustion can flow ast the "periphery of the baiile after 'svieeping'thesurface of said heat transfer units;

means providing an outlet from said o'fitake "spa e"; and connections for leading gas to be heated to and from said tubular heat transfer units.

2. The'com'bination defined in claim l'in which the tubular heat transfer units are in the form "of tubes bent "to form .radi'ally arranged flat "coils having passes which are approximately parallel with the axis or the heating chamber, and the course of gas to beheated through 'said 00115 is that it first traverses a 'passadjacent said unobstructed axialportion of "the heating cham- "her and next traverses a pass adjacent "the wall "the CSISl'l'l'g.

The combination d'efined'i'n claimlfinwlii'ch the first pane "is retained in the joint between the *two separable casing-'partsso as to be freed 4. The combinationdefinedin "claiml in which the tubular heat transfer units, and the second -ba'file-are constructed as a unit with and are supported by a manifold arranged to serve "as "the connections forleading the gas to be heated to and from the tubular units, the unit structure so formed being removably mounted in said cylindrical casing.

5. The combination defined in claim 1 in which the tubular heat transfer units, and the second baffle are constructed as a unit with and are supported by a manifold arranged to serve as the connections for leading the gas to be heated to and from the tubular units, the unit structure so formed being removably mounted in the second of said casing parts and the first baffie is retained in the joint between the two separable casing parts so as to be freed for removal upon separation of said parts.

6. The combination defined in claim 1 in which the connections for leading gas to be heated to and from the tubular heat transfer units comprise a double walled unit affording two manifold spaces, one enveloping the other, to which spaces the tubular heat transfer units are connected in parallel.

7. The combination defined in claim 1 in which the connections for leading gas to be heated to and from the tubular heat transfer units comprise a double walled unit affording two manifold spaces, one enveloping the other, to which spaces the tubular heat transfer units are connected in parallel, said double walled unit serving as the sole support for said tubular units and being bodily removable from the casing therewith,

8. A heater intended for heating gases and comprising in combination a generally cylindrical casing, closed at its ends and constructed in separable parts, one end part being formed with a ported open-ended tubular projection ex- -tending inward from its closed end and dividing a combustion chamber within said tubular projection from an annular combustion-air chamber which encircles the same, and the other end part enclosing a heating chamber into the unobstructed axial portion of which combustion products may flow in an axial direction from said combustion chamber; combustion burners arranged to operate in said combustion chamber;

a connection for supplying air to said annular chamber; supply and collection manifolds adja- I cent said annular chamber; a plurality of looped heat exchange tube-passes connecting said manifolds and projecting into said heating chamber in circular series around said unobstructed axialportion thereof; an annular group of tubular heat transfer units also in said heating chamber I around said circular series of heat exchange passes; two annulangenerally conical bafiles so I mounted in said heating chamber as to converge outward and to lap corresponding end portions vof the tubular heat transfer units, the first of 'said baffles extending from the peripheral wall I of the cylindrical casing nearly to the open end 'of said combustion chamber and the second of said baffles extending nearly but not quite to 'said ofitake chamber; and connections for leading gas to be heated to and from said supply and collection manifolds and to and from said tubular heat transfer units.

9. The combination defined in claim 8 in which the cylindrical casing comprises two end parts and an intermediate part and the joint between an end part and the intermediate part is so 40 located that when these parts are separated the supply and collection manifolds and the looped heat exchange tube-passes connecting them may be withdrawn as a unit.

10. The combination defined in claim 8 in which the cylindrical casing comprises two end parts and an intermediate part and the joints between said parts are so located that separation of the three parts frees for removal said supply and collection manifolds and the looped heat exchange tube-passes connecting them, and also said first baflie.

11. The combination defined in claim 8 in which the connections for leading gas to be heated to and from the tubular heat transfer units comprise a double walled unit affording two manifold spaces, one enveloping the other,

to which spaces the tubular heat transfer units are connected in parallel, said double walled unit serving to support said tubular units and being bodily removable from the casing therewith, said casing comprising two end parts and an intermediate part and the joints between said parts being so located that separation of the parts frees for removal said supply and collection manifolds with the looped heat exchange tube passes connecting them and also said first baflle.

CURT KELLER.

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

UNITED STATES PATENTS Number Name 7 Date 2,119,817 Keller June 7, 1938 2,224,544 Keller Dec. 10, 1940 2,409,801 Ruegg Oct. 22, 1940 2,411,294 Ruegg Nov. 19, 1946

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