US2204350A

US2204350A - Steam generator

Info

Publication number: US2204350A
Application number: US111638A
Authority: US
Inventors: Frisch Martin
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1936-11-19
Filing date: 1936-11-19
Publication date: 1940-06-11
Anticipated expiration: 1957-06-11

Description

June 1l, 1940. M. FRlscH STEAM GENERATOR FilAed Nov. 19, 1936 5Sheets-Sheet ATTORN EY June ll, 1940. M. FRlscH l 2,204,350

- y STEAM GENERATQR I v Filed Nov. 19, 1936 5 SheetsrSheet 3 June l1, 1940. M. Freisml STEAM GENERATOR Filed Nov. 19, 193e 5 Sheets-*Sheet 4 INVENTOR /V/l/r//v /fws ATTORNEY June l1, 1 940. M. FRlscH 2,204,350

` STEAM GENERATOR Fviled Nov. 19, 1936 5 Sheets-Sheet 5 INVENTOR Patented June 11, 1940 UNITED PATENrroFFlCE I STEAM GENERAToR' Martin Frisch, Cranford, N. J., assigner to Foster l, Wheeler Corporation, New York,` N. Y., a corporation of N ew York Appiieation NovemberL 19, 1936, serialvNo.A 111,638

' 13 claims; (o1. 12a- 336iv This4 invention relates to steam generators andv more particularly pertains to steam generators of the vertical straighttubeftype.

The general object of the invention is to pros vide a steam generator of the vertical straight tube type which incorporates the most desirable features of modern practice with; the various component parts thereof so varrangedthat the generator maybe readily adapted to meet lo very small, very large and all intermediate steam out any changein the width or length, "andwith the arrangement such Aas to requireonly vvery low head room for small unitsand less than the '.71 usual head room for large units than isA now required by units of conventional designand com,-l

parable capacity. v v i Further objects of the invention are To provide a vertical, straight tube type gen- 3i erator which requires l'esshead room, than confI ventional steam generators, and lessspace by reason of the eliminationv of vthe necessity for side aisles between generator units and thenecessity for tube Withdrawal .spaces aroundtheunit. fifi To provide a steam generator ofthe type in, dicated Which-includes all essentials'necessary for high availability,reliability7 low maintenance and high. efiiciency butI with the elimination, 'or the reduction to a minimum, of all costly ,details so' of design and construction such as outside` water conventional designs. o

To provide a steam ygenerator of the type -indicated, having more radiant heat absorbing sur- 45 face per cubic foot of furnacevolume than in conventional units and in which maximum heat absorption in the boiler proper is obtained with a lower draft lossthanfis customary in conven-` tional types of generator units.

im To reduce the cost of field erectionof vertical straight tube steam generators.gbyly designing the unit so that a` larger proportion thereofm'ay be assembled inthe shop than is now customary. To simplify the ysupportingframework kof a` indicated, in which superheat. control maybe the cost Wall connectionsvwhich are required by the usual.

steam generator of the type mentioned, so that a minimumamount Will be required.y

To provide a steamgenerator of theftypefmen-v l o tioned, which will be suitable for outdoorlopera- `tion and such that no'building ror protecting ).5

structure Will be required. o

To provide a steam generator of thev type designated, in Whichvit is possible to increase the load range obtainable by arranging the furnace' volume with respect to the unit so that low 10 ratingA operation need not result in excessive cooling .of the flame. v

yTo .provide a steam generator of the character readilyeffected. l

To provide a `verticalstraight tube steam generator in which the convection superheater is so arranged with respect to therother x heating surface thatthere will bano directame impingementv on the superheater and the gases,

' particularly where the unit is fired with pulverizedcoal, Will make an abrupt change kin direction of flow before entering' the superheater so that alargev proportion of the ashcarried thereby will be thrown out into the furnace before the gases enter the superheater..A

To provide a steam generator of the character indicated having Aa furnace so arranged with respect tothe boiler'that every part of thelfurnaceV Volume is effective, thus permitting when neces- .30

sary, higher rates of heat yliberation than is now customary in practice.r`

To provide `a verticalstraight tube steam generator which may be constructed Without any f' brick Work, if necessary, or if brick work is -de- 3,5

sirable, to havetheamount thereof a minimum andof very simple design. v Y

y To provide a steam generator of the character A mentioned, the overall cost of which isless than of conventional unitsvof .equal surface 4,0`

and reliability. f In l,the preferred embodiment of thevinvention Kherein disclosed, vthese and .other objects are attain'ed'gby providing a steam generator having' a vertical, straight tube boiler throughwhich the 45 gas-flow is substantially parallel to `the drums,

'disposed between and flanked `by two Watercooled furnaces of standard but minimum Width required for the best performance with pulveri'zed, liquid lor gaseous fuel, f thereby providing the boiler with ,at leasttwoexposures to radiant heat.

o In the other formrof .the invention herein disclosed, Vthe vertical straight` .tube boiler"is.,pro vided with a single laterally disposedjfurnace.

l The furnaces 1n schijfrems are `ventirely .water-1 si;

cooled or may be water-cooled except for the ring end and the opposite end, if desired. The furnaces are red from the front of the boiler by burners disposed adjacent the top or bottom or both top and bottom of the front walls and thegases flow tothe rear of each of the furnaces where they turn vertically through the separate upper and lower streams combine, mix and return to the front ends of the furnaces where they make a change in their horizontal direction of `iow of 180 to enter the boiler tube bank. These tur'ns separate from the gas a substantial proportion of fly ash and cause it to deposit in the furnaces. A superheater is disposed at the inlet end of the boiler and by virtue of this location, possesses the characteristics of Aboth a radiant and a convection superheater. After passing through the superheater, the gases flow through the boiler in a direction parallel to the boiler drum and across all of the boiler tubes, which are arranged in staggered rows from front to rear, with the result that maximum heat absorption in the boiler proper is obtained with a lower draft loss than in conventional units. The gases leave the boiler at the central portion of the rear of the boiler and flow to additional heat recovery apparatus such as an econoinizer and/or an air heater and thence into an induced draft fan. The boiler tubes are staggered but are readily removable into the furnaces and the water wall and superheater tubes are also readily removable into the furnaces.

The nature, objects and advantages of the invention will be understood from the following description considered in connection with the accompanying drawings forming a part thereof and in which:

Fig. 1-is a transverse vertical sectional view of steam generating apparatus embodying the invention, taken substantially on line I-I of Fig. 3;

Fig. 2 is a horizontal sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a longitudinal vertical sectional View, taken on line 3-3 of Fig. 1;

Fig. 4 is a side elevational View with parts in section;

Fig. 5 is a horizontal, partial sectional View, on an enlarged scale, of the area designated A in Fig. 2;

Fig. 6 is a partial vertical sectional view, on an enlarged scale, of the boiler header arrangement;

Fig. '7 is a transverse vertical sectional view of another `form of boiler embodying the invention; and

Fig. 8 is a horizontal sectional view, taken on line 8-8 of Fig. 'l'.

Like characters of reference indicate the` same or similar parts in the several views.

Referring to Figs. 1 to 6 inclusive of the drawings, the steam generator illustrated has a rectangular casing or setting including a front wall I0, a rear wall II and side walls l2 and I3. The generator is provided with two spaced parallel furnaces I4 and I5 which are disposed adjacent the side walls I2 and I3 respectively of the setting. The generator is also provided with a steam generating section or boiler I6, which is disposed intermediate the spaced furnaces but is somewhat shorter in length. The furnaces and boiler are of rectangular configuration and are disposed in parallel relationship, as shown.

The boiler consists of straight vertically disposed tubes I1 arranged in rows extending transversely to the axis of the boiler with the tube rows arranged in spaced pairs or groups of two rows each, with the tubes in the rows of each group arranged in staggered relationship, as clearly in dicated in the drawings, particularly in Fig. 5. The lower ends of these tubes are rolled into a plurality of square headers I8 which are spaced somewhat from each other so that ash which separates from the combustion gases in the boiler may drop lfreely into the soot hopper i9 below. The upper ends of the boiler tubes I1 are rolled into square headers 20 which are arranged in two spaced rows extending longitudinally of the boiler. The headers I8 and 20 are arranged in staggered relationship, as shown more clearly in Fig. 6, that is to say, alternate headers are disposed at higher elevations than the other headers. Downcomers 2| connect the lower end oi the boiler drum '22 with the central portions of the lower square headers I8. These downcomers extend through the central part of the boiler but are segregated from' the boiler tubes and are protected from contact with the combustion gases by suitable refractory or other material 23. If desired, a passage between the downcomers may be provided for access. Headers 20 are connected to headers 24 through upcomers 25 and headers 24 are connected to the upper portion of drum 22 through a plurality of risers 26. The boiler tube bank also includes a plurality of rows, ve rows in the form shown, of boiler tubes 21 which are larger than the tubes I1. Tubes 21 may conveniently be 3%, inches O. D., whereas tubes I1 may be 2 inches O. D. A superheater 28 consisting of a plurality of rows of 2 inch O. D. loop tubes as shown, is disposed at the inlet end of the boiler I6 ahead of the boiler tubes 21 with respect to the path of flow of the gases through the boiler. 'The

side walls

29 and 30 of the boiler have a row of 31/4 inch boiler tubes 3| disposed along the boiler side of these walls for their entire lengths. These tubes 3I are connected into the headers I8 and 20. A plurality of rows of 31A inch O. D.

tubes

32 and 33 are disposed between the front ends of the

side walls

29 and 30 of the boiler and the front wall I0 of the boiler setting to provide slag screens for the gases entering the boiler trom the furnaces I4 and I5. These

tubes

32 and 33 may be disposed, as indicated in Fig. 2, or one or more rows of these tubes may be disposed in front of the superheater 28, if desired.

The boiler drum 22 is provided with a steam washer and drier 35 which is more fully disclosed and claimed in the copending application of Martin Frisch and Walter F. Keenan, Jr., Serial No. 110,310, led November l1, 1936.

A plurality of steam risers 3B connect the upper end of boiler drum' 22 with a steam drum 31 disposed above drum 22 and transversely with respect thereto. A steam line 38 connects steam drum 31 with the inlet header of superheater 28.

In the form of invention disclosed in Figs. 1 to 6 inclusive, the steam generating section or boiler I6 is suspended from supporting framework. This framework includes vertically disposed columns 39, one of which is placed at each corner of the boiler section I6, spaced longitudinally disposed girders 40 and 4I which are secured to the upper ends of the columns 39 and transverse girders 42 which extend between and are secured to the girders 40 and 4I. The boiler drum is suspended by spaced cradles 43 which are supported by the spaced girders 42. The boiler circulating tubes and headers to which they are connected are suspended by a plurality of hanger rods 44 which are secured at their upper 'ends to the girders 40 and 4I. The steam drum 31 issupported in cradles 45 which rest upon the upper surface of girders 40 and 4I. With this arrangement it will be seen that the steam gener ating or boiler section in its entirety,excepting the `steam drum 31, is supported by being suspended from `points or supporting members above the boiler section.

The furnaces cooled. However, for low capacity installations the firing wall and the rear wall may be installed Without water cooling. Thewater wall tubes for each furnace are designated 46 and these tubes' a're suitably connected by headers which are connected into the circulating system. The furnaces are supported by columns 41, auxiliary columns 48 vwhich aredisposed at the outerside walls of the furnace, main girders 49vwhich are supported by the

columns

41 and 39 and by a plurality of auxiliary girders or beams 50 which extend between the columns 48. As maybe seen in Fig. 1, a plurality of hanger rods 5I whichvare connected at their upper ends to the girders 40 and 4l aid in supporting portions of the furnaces and the water walls thereof.

rods 52 from a beam 53 extending between the main girders 40 and 4|. o'

Each of the furnaces I4 and I5 isired byv a plurality of spaced fuel burners disposed in .the front wall I IJ of veach furnace. The burners 55 are located adjacent the upper ends of the front walls I0 of the furnaces and, burners 56 are disl posed adjacent the lower ends of the front walls or pulverizing mill.

I0 of the furnaces as clearly shown in Figs. l, 3 and 4 of the drawings. These burners are arranged to project streams ,of fuel and air through the spaces between the water wall tubes 46 and may be arranged similarly 'to the burners disclosed in the copending application `of Martinv Frisch, Serial No. 444,906, filed April `1*'1, 1930. Fuel and primary air are supplied tof the burners through conduits 51 to which the fuel is supplied from any suitable source such as a storagev bin Secondary airv for the burners is supplied through an air yconduitl 58 which connects with an air casing E9 disposed outwardly of the front wall I 0 of the boiler casing. Air

vfrom the casing 59 is supplied to air ducts 60 and 6I disposed respectively above and below' the fuel Anozzles, of the burners 55and. 56. With the .burner arrangement disclosed, th-e stream of products of combustion producedby each of the burners may be directed horizontally throughout the lengths of the furnaces or may be directed vertically upward or `vertically downward depending upon the quantity and velocity of the air streams supplied through the air ducts 6I) and 6I. '

I'he fuel burners

55 and 56 direct separate spaced `streams ofA products of combustionV to-` ward the rear walls II of thelfurnace, adjacent to which the upper `stream turns downwardly and then forwardly through an angle of 180 and the lower stream turns upwardly and then forwardly through approximately thesame angle. The two streams impinge upon and mix with keach other at points near the rear walls II of the furnace and substantially midway between the top and bottom walls of the furnace, after whichV they flow toward the, front `of the furnace as indicated in Figs. 3 and 4. Upon reaching the front end of each of the furnaces, the returning streams of products -of combustion' turn horizontally `through anangle V,0 '18Q and pass over the slag screens 32'ahd 33 and flow I4 and I5 are entirely water v The superheater tubes as* .may be seenin Fig. 3, are suspendedk by hanger into the chamber 62 disposed between the two furnaces and the front end of the boiler section rvI6 and' impinge upon and mix with each other. These streams then makeanother horizontal turn through an angle of 90 and flow over the superheaterl tubes 28, boiler tubes 21 and there-v after flow over vall of the boiler tubes I1 after which 'they enter a iiue 63 disposed at the rear end of the boiler section I6. `The gases flow downwardly in the ue 63v through .the return bend vsection 64 and upwardly through the vertically disposed lsection 65 ywhich delivers the gases to an induced draft fan 66l which lin turn delivers them to a stack 61. In the form shown in Figl, an air heater 68 is disposed inthe flue section 65 and air is supplied to this air heater by a forced draft fan 69. Ifdesired, an economizer may be disposed in the return bend section 64 preferably at its inlet portion 10. l'

rlhe firing arrangement disclosed and the method of firing carried out thereby accomplishes several desirable results. Among these lmay be mentioned the fact that all o f the furnace volume of each furnace is fully utilized. This will beapparent fromr an inspection of Figs. 3 and 4, particularly wherein the lines designating the flow of the stream-s of products of combustion indicate that the gases flow through substantially all portions of each of the furnaces. At the points or vzones where the upper and lower streams of products of combustion impinge Vupon each other, intensive mixing occurs which accelerates combustion to a vmaximum and reduces stratification of the gases to a minimum. Inasmuch as the gases and burning fuel `are forced to makertwo changes in directionof approximately 180/1 each prior to their entering the superheater and boiler, a larger proportion of suspended ash will be precipitated within the furnaces thanin conventional units.

, The method -of ring disclosed herein is dis-` closed and claimed in a appending application of Martin Frisch, Serial ber 19,1936-, l

' The boilerr maybe fitted with a plurality of No. 111,639, filedNQverwrt' suitable -soot4 blowers disposed so as to face the superheater andwith several soot blowers placed under the superheater and with a plurality of stationary pipe dust blowers 1I which are dis- `posed so that their nozzles open up into the main bank of yboiler tubes in the clearances between the lower headers I8. Additional soot blowers may be provided to serve the economizer vand lancing doors may be provided for cleaning advantages over the usual method of removing tubes from straight tubey boilers. These advantages are first, complete `elimination "of any danger of scoring the tube holes when .attempting to remove bagged or blist-ered boiler tubes andcse'cond, no tube removal spaces in the front or rear of `the/boiler need be provided which means that a straight tube steam generator may be installed in spaces where the installation of standard straight tube boilers would be entirely out of the question. Additionally with this arrangement, the boiler drum may be thinner than is required for benttube types of boilers because of the higher ligament efficiency. For this reason and because the cost of the simple square headers used will be lessnthan the cost of a mud drum, the cost of this type of boiler will be less for high pressures than for conventional types.

It will be perceived that each steam generating tube will have the full circulating head acting upon it. In this respect the boiler arrangement disclosed herein is superior to conventional straight tube boilers in which the circulating head progressively decreases from row to row toward the top of the boiler. As a result, circulation difiiculties with the type of boiler herein disclosed should be non-existent.

In the forms of the invention shown, the gases from both furnaces flow over the superheater 28.. However, if desired, the superheater may be so arranged that the gases from one furnace may pass over the entire superheater and the gases from the other furnace may by-pass or pass only over a part of the superheater. This arrangement may be effected without the necessity of employing dampers or of by-passing any of the steam generating surface.

Figs. 7 and; 8 illustrate more or less diagrammatically the invention embodied in a boiler having a single furnace disposed laterally of the steam generating section. In its essentials, this form of the invention is the same as the form shown in Figs. 1 to 6. The boiler section includes a plurality of vertical straight tubes 80 connected to a plurality of square headers 8| arranged in the manner shown in Fig. 6, with a plurality of downcomers 82 disposed along side wall 83. A single drum 84 is disposed longitudinally of the boiler section at its upper portion thereof. The furnace 85 is entirely water cooled as shown, and burners 86 and 81 are disposed in the front wall 88 of the furnace adjacent the upper and. lower portions thereof as shown in Fig. 7. ',Ihe streams of products of combustion from these burners flow through the furnace and the boiler section as described in connection with Figs. 1 to 6. After the gases have mixed and have returned to the front end of the furnace B5, they turn through an angle of 90 and pass over slag screen 89, after which they make another turn of 90 and ow over the superheater 90, thence over the group of larger steam generating tubes 9|,` after which they flow over the smaller steam generating tubes 80. The gases pass out of the boiler at the rear end of the steam generating section through a flue 92.

, The downcomers 82 may be shielded from contact with the combustion gases. The boiler tubes 80 and 9i are grouped similarly to the tube arrangement shown in Figs. 1 to 6 and each of these tubes is readily withdrawn through the furnace 85 in the same manner as described in connection with the other form of invention herein disclosed.

With these arrangements of component parts of a steam generator, it will be perceived that a change in the vertical dimension only of the generator and the several component parts thereof will result in a proportional increase in furnace volume and heating surface, in consequence of which steam generating units may be provided for any steam output requirements whether large or small, by merely varying the height of the unit without changing either the width or length thereof. In consequence, the same design may be utilized for `all steam output requirements, thereby eliminating the necessity for separately designing generators for every new use. By the use of a plurality of Water cooled furnaces, it is possible to maintain the desirable ratio of watercooled surface to the furnace volume or to the rate of fuel firing, as the size of the generator is at an end of the row of units or at some intermediate point which will permit access to the rear of the row of units. However, such aisles as may be necessary to the rear may be much narrower than in conventional arrangements because no access to any part of the units through the sides thereof is necessary for any purpose.

The heat recovery devices, such as air heaters and economizers as well as the fans, may be disposed below the boiler and furnaces if desired, and may be located either on the operating oor or on a basement floor. Such an arrangement entirely eliminates the necessity for overhead supporting structures for these devices.

Any essential auxiliary equipment may be located at the front of the units on the operating aisles and all parts of the boiler are accessible for repairs from within the furnace. For removing the ash when pulverized coal firing is used, a simple and low cost ejector system may be installed with several openings connecting to the furnaces and with Valves which are readily controllable from the front of the boiler. Such ash as may stick to the ash receiving hoppers at the bottom of the boiler and which cannot be blown away by the soot blowers can be similarly removed.

With the arrangement disclosed, it is apparent that the furnaces may be built in sections by sectionalizing the headers and that they may be shop assembled and shipped as units complete with insulation and casing.

Steam generating units embodying the invention are suitable for outdoor operation without any housing means therefor since all of the component parts are included within or below the casing of the unit.

Although the invention has been disclosed in connection with steam generating units having one and twofurnaces respectively, which are disposed in parallel relationship with each other and with the boiler section, it will be understod that more than two furnaces may be utilized in a unit without transcending the principles of the invention. It will also be understood that various changes may be made in the location and arrangement of the several component parts of the steam generating units without departing from the invention. Accordingly, it will be understood that no intention is entertained to limit the invention except by the scope of the claims appended.

What is claimed is:

1. A steam generator comprising a setting, a steam generating section in the setting, an undivided furnace in the setting laterally disposed With respect to the steam generating section and steam generating section in `the setting, anvundi-V separated'therefrom', a gas passage at one end of the furnace connecting .the furnaceand said secA tion, and meansat saidone end l' of the furnace for producing astream of products of combustion which ows throughthe'ffurnace toward the other end thereof and then returns to said. one end and-thereafter flowsrthroughsaid gas passage andv throughthe steamgenerating section.

2. A steam generator comprising a setting, a steam generatingsection in the setting, an undivided furnace in the'setting laterally disposed with respect tothe steam generating section and separated therefrom,.a gas passage at one end of the furnace connecting the-furnace and said sec tion, and means, at said one end of the furnace for producing a pluralityl of spaced streams of products of combustionjwhich ow through the furnace toward the otherend thereof and then return to said one end and thereafter flow through said gas p-assagevand through the steam generating section. v

3. Asteam generator comprising a setting having enclosing Walls, a steam generating section in the setting, a furnace inthe setting laterally disposed withrespect to the steam generating section and separated therefrom by wall means, a gas passage at one end of the furnace connecting the furnace and said section, and burners at the upper and lower portions of said one end of the through said gas passage and'through the steam generating section.k i

4. A steam generator comprising a setting," a

steam generating section in the setting, an lundivided furnace in the setting'at each vside of the .steam generating section and separated from the latter, a gas passage at one end of each furnace y through which gases flow into the same end of the steam generatingv section, and means at said one end of each furnace for producing a stream of products of combustion which flows through the furnace toward the other end thereof and then returnslto said oneend and thereafter flows i' through the gas passage and the steam generating section. f

5. A steam generator comprising a setting, a steam generating section in the setting, an 11n-- divided furnace in the setting at each side of the steam generating section and separated from ther latter, a gasv passage at one end of each furnace f tion in the setting, a furnace in the setting atA l each side of the steam-generating section and separated from' the latter by wall means, a gas 'gas passage and through the vided furnace in' the settinglaterally disposed "with respect to the steam generating section and separated therefrom', a gas'pas'sage at one end'of the furnace connecting the furnaceand said secltion,1a superheater disposed inthepath of flow of the gases between saidngas passage and the steam generating section, and means at said one end of the furnace for .producing a stream of .products of combustion which rflows through the furnace toward :the other end thereof andthen returns yto said one end and thereafter flows through said gaspassage andv through the steam generating section.

8.1A steam steam generating section in the setting, an undigenerator comprising a setting, a fvided furnace in thesetting at yeach side of the end thereof and thenreturns to said one end and thereafter flows through the gasfpassage and the steam generating section. f i

9. A steam generator comprising a setting, a steam vgenerating section in the setting, an undivided furnace in the setting laterally disposed with respect to the steam generating section and separated therefrom, a gas passage at onev end of the furnace connecting the furnace and said sec tion, a. plurality of tubes forming a slag screen in the path of the gasesl flowing from the furnace to said section, and means at said one end of the furnace for producing a stream'of products of combustion which flows through the furnace to ward the other end thereof and then returns to said one end and vthereafter flows through said steam generating section. y y

10.7A steam generator comprising a. setting, a

`steam generating section in the zsetting, anundividedfurnace inthe setting at each side of the steamgenerating section and separated from the latter, a gas passage at one end of each furnace through which gases flow `into the same end of the steam generating section, a plurality of tubes forming a slag screen in the path of the gases y flowing from each furnace to said section, and

` meansat saidone end of each furnace for producing a stream of products of combustion which flows through the furnace toward the other end thereof and then.y returns to "said rone end and thereafter flows through the gas passageand the steam generating section, y

' 11. A steam generator comprising a setting, a steam generating section in the setting including a bank of steam generating tubes having their major portions at least extending substantially transversely of the longitudinal axis of said sec tion, a furnace` in the setting separated from said section and wherein gases are produced for flow through said section, the path of flowof the gases through said sectionbeing transverse to the steam generating tubes therein, downcomers within said ban-k of steam generating tubes, and means for shielding the downcomers fromv contact with the gases, said downcomers and shielding means being disposed to divide the gases flowing through said section into a plurality of paths.

12. A steam generator comprisingavsettng, a

steam generating section in the setting including a bank of steam generating tubes having their major portions at least extending substantially transversely of the longitudinal axis of said section, a furnace in the setting separated from and at substantially the same elevation as said section and wherein gases are produced for flow through said section, the path of oW of the gases through said section being transverse to the steam generating tubes therein, dovvncomers disposed intermediate the side Walls of the steam generating section, and means for shielding the downcorners from contact With the gases flowing through said section.

13. A steam generator lcomprising a setting, a

steam generating section in the .setting including a. bank of steam generating tubes having their major portions at least extending substantially transversely ofthe longitudinal axis of saidsection, a furnace in the setting separated from and at substantially the same elevation as said section and wherein gases are produced for flow through said section, the path of flow of the gases through said section being transverse to the steam generating tubes therein, downcomers disposed intermediate the side Walls of the steam generating section, and means for completely shielding the downcomers from contact withl the gases flowing through said section.

MARTIN FRISCH.