US2567696A

US2567696A - Steam or elastic fluid generator, with positive pressure furnace

Info

Publication number: US2567696A
Application number: US73974A
Authority: US
Inventors: George W Kessler
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1949-02-01
Filing date: 1949-02-01
Publication date: 1951-09-11
Anticipated expiration: 1968-09-11

Description

Sept. 11, 1951 POSITIVE PRESSURE FURNACE 8 Sheets-Sheet 1 Filed Feb. 1. 1949 I r $3. k 0 2 s 6 8 man/o w 0 m H M T N l 2 NK R W W 0 N w 6 I, 0 A 0/ 2 M 0 2 M G m 4 2 B 1. G 0 H 42 W 38 4 2 m Sept. 11, 1951 w, KESSLER 2,567,696

STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE Filed Feb. 1. 1949 8 Sheets-Sheet 2 w a i I) "0IIIIIII/II/// k. (c INVENTO R g e'orge WKssler FIG 2 ATTORNEY G. W. KESSLER STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE Sept. 11, 1951 8 Sheet s-Sheet 5 Filed Feb. 1. 1949 .Q an:

INVENTOR George W/Cessler 'ATTORNEY Sept. 11, 1951 G. w. KESSLER 2,557,696

STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE Filed Feb. 1. 1949 8 Sheets-Sheet 4 INVENTOR 66 0596 W/fess/er ATTORNEY Sept. 11, 1951 G. w. KESSLER 2,567,696

STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE Filed Feb. 1. 1949 8 Sheets-Sheet 5 Ill 1 oooooooooooooooooooo 00oooooooooooo0ooo INVENTOR MM ATTORNEY Sept. 11, '1951 G. w. KESSLER 2,557,696

STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE Filed Feb. 1. 1949 8 Sheets-Sheet 6 INVENTOR Ggo rge W/(ew/er W ATTORNEY Sept. 11, 1951 G. w. KESSLER STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE 8 Sheets-Sheet 7 Filed Feb. 1. 1949 FIG. 9

INVENTOR Geoage W/(eaa/er B ATTORNEY Sept. 11, 1951 G. w. KESSLER STEAM OR ELASTIC FLUID GENERATOR WITH POSITIVE PRESSURE FURNACE 8 Sheets-Sheet 8 Filed Feb. 1. 1949 I iil oc o o K020020000 l NV E N To R Georye W/Qss/er BY M ATTORNEY OOOOOOOOOOOOOOOOOOO C 0000000000 Patented Sept. 11, 1951 STEAM OR ELASTIC FLUID GENERATOR, WITH POSITIVE PRESSURE FURNACE George W. Kessler, New York, N. Y., assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New J ersey Application February 1, 1949, Serial No. 73,974

11 Claims.

This invention relates to fluid heat exchange apparatus, and it i herein exemplified in va or or steam generators.

The invention is concerned with a water tube type of steam or vapor generator in which there is incorporated a furnace particularly adapted for operation at high positive pressures.

The invention involves the provision of a steam or vapor generator characterized by the arrangement of its furnace and pressure parts within a'casing which is of pressure constrainin shape in plan. More particularly, the invention involves a steam or vapor generating unit in which the pressure parts including a superheater are arranged,.with the furnace, within a circular casing adapted for effective operation at high furnace a pressures.

.Another object of the invention is to provide, in a steam or vapor generating installation of the type indicated, a plurality of furnaces one of which is operated in accordance with vapor generating requirements, and the other independently fired for maintaining an optimum superheat.

In general, the invention involves a central pressure vessel construction involving, in a unitary structure, the lower water chamber, a superposed downcomer, and an upper vapor and liquid chamber acting as a central support for the installation and having banks of fluid heating tubes and the furnace disposed in an annular arrangement around the central pressure vessel construction and within a pressure tight casing connected to the upper and lower chambers.

The objects of the invention are obtained in a structure which i illustrated in preferred forms in the accompanying drawings wherein:

Fig. 1 is a dual plane vertical section of the installation taken on the section lines l| of Fig. 3;

Fig. 2 is a vertical section through the installation on the section line 2--2 of Fig. 3;

Fig. 3 is a horizontal section on the plane of the section line 3-3 of Fig. 1;

Fig. 4 is a concentric or arcuate section through the separator on the line 44 of Fig. 1;

Fig. 5 is a detailed View showing the manner in which the exterior casing is associated with the upper part of the central pressure vessel construction;

Fig. 6 is a horizontal section illustrating a modified type of vapor generator in which there is a separately fired superheater, operated to obtain the desired steam temperature;

Fig. 7- is a horizontal section of a further modification in which a separate superheater gas pass Fig. 9 is a horizontal section of another modification in which the furnace gases are divided between a, superheater gas pass and a steam generating gas pass, the separate passes leading to a single flue with gas flow regulatin means-v therein.

The drawings illustrate a vertically extending steam or vapor generator of cylindrical form, ineluding an upper cylindrical'steam and waterv drum l0, and a lower water chamber H, the

drum and the chamber having heads I0 and I2 which are substantially semi-elliptical in cross section. The chamber l2 may also be appropriately referred to as a submerged cylindrical drum because of its shapeand because of the fact that it is normally submerged, in the sense in which that expression has been used in the-- steam generator art. It may also be referred to V as a water drum. These chambers, or drums, are integrally connected by central downcomer ll of relatively large diameter to form a unitary ressure vessel construction.

The above construction is centrally located and it is co-axial with an upright cylindrical outer wall or casing generally indicated at l6 and ineluding substantially semi-elliptical, or dished heads l6 and I6", and arranged within this wall construction are the steam generating and steam superheating tubes.

tween the downcomers l4 and the wall IS. The

bank of steam generating tubes is generally indi- Y cated at l8 in Figs. 2 and 3 and the superheater is generally indicated at 20. The steam generating tubes are arranged in radial rows as indicated in Fig. 3, most of these rows extending from the central downcomer l4 to the outer wall l6. These tubes are arranged so as to have their inlets connected to the water chamber [2 and their outlets connected to the steam and water drum In in the manner indicated in Fig. 2.

Part of the furnace gases for heating the steam generating tubes originate in a furnace 22, fired by means such as the burner 24. The

gases from this furnace pass in the direction of the arrows 252! to the flue 30, thereb'y'passin'g between and over the steam generating tubes.

These tubes. .aref. clearly shown as arranged within an annulus be 7 The steam generating tubes are also heated by gases from the furnace 60, after they have passed over the superheater 20.

Gases from the furnace 22 first contact a bank 32 (Fig. 3) of relatively large diameter steam generating tubes connected to the upper and lower chambers I2 and H3 in a manner similar to that in which the tubes 33 are so connected. This bank of steam generating tubes acts as a radiant heat screen for the main bank of steam generating tubes I8 which are of smaller diameter.

A wall for the furnace 22, at the left hand side of the burner 24 (Fig. 3) is formed by the radially spaced wall tubes 34 arranged in a radial row and being provided with a stud tube and refractory construction 36 closing the spaces only in a vertical position adjacent the burner 24. Gases from the superheater 20 can readily pass to furnace 22 above, and beneath this stud tube construction. This: construction is generally similar to the stud tube wall shown in Fig. 3 of theBailey et al. Patent 1,999,984, April 30, 1935.

The outerwall of the furnace 22 and the associated gas pass for the steam generating tubes I8 is delineated by upright wall tubes such as 40-44, these tubes being connected at their lower ends to the water chamber I2 and at their upper ends to the steam and water chamber I0, the'space's between these tubes being closed by a stud tube construction similar to that associated with the tubes 34.

The burner opening 50 for the furnace 22 is formed by an annular body of refractory 52 supported and thermally maintained by wall tubes similar'tothe tubes 40-44 and other wall tubes 545'| which are bent out of their wall formation in the zoneof the burner opening 50 to conform toand protect the burner opening.

A similarly constructed furnace for operation in accordance with the superheat requirements is indicated at 60. This furnace is fired by a burner 62; The gases generated in the furnace 60 pass generally in the direction of the arrows 64B'I, and above and beneath the stud tube construction 36, into thefurnace 22, and thence through the bank of steam' generating tubes I8, to the flue'30.

The boundaries of the furnace 6G and its associated superheater gas pass are formed by outer wall tubes such as I01I4 constructed and arranged ina manner similar to that of the outer wall tubes 4044, and a radially extending wall generally indicated at 80 and having stud tube constructions similar to those .of the radial wall. for the furnace 22, involving tubes 34. An additional boundary for the furnace 6! involves the studltube wall construction 90 extending radially from thedowncomer I4 to an arcuate wall 92 which. is similarly formed by a stud tube wall construction involving upright tubes connected into the circulation by communication with the chambers I] and I2 of the central pressure vessel construction.

Between the furnace 60 and the superheater gas pass, and between the outer casing and the inner ar'cuate wall 92 is a radiant heat screen 94 including three radially arranged rows of large diametersteam generating tubes disposed on relativelywide centers. The different rows of thesetubes are indicated at 95-98. These rows, like the radialrows of steam generating tubes i8 and the radial rowof tubes comprising the wall 80, extend inwardly to.a position closely adjacent steam generating tubes .such as 166-405 disposed,

- separator, or the whirl chamber 30.

in circular arrangement and in contiguous relation about the downcomer I4 to thereby protect the latter from overheating. The manner in which similar tubes are formed and connected to the upper and lower water chambers is indicated in Figs. 1 and 2 at H0I I3. Arcuate rows of contiguous tubes such as tubes III and III (Fig. 1) have their upper portions such as H2 disposed along the surface of the upper drum and their lower portions such as H3 similarly disposed on the surface of the lower drum I2. Tubes of the two contiguous rows (such as III and IH--Fig. 1) may have their upper ends in one circumferential row where they are connected to the large diameter portion of the upper drum, and may have their lower ends similarly connected to the lower drum I2.

The two rows of downcomer protecting tubes such as III, HI, H5 and H6 are arranged directly opposite the burner 24, and similarly arranged rows of tubes such as II'II I9, I04, and E95 are disposed opposite burner 62 (Fig. 3).

The steam generating tubes communicate at their upper ends with an annular inlet chamber I20 (Fig. 1) between the wall of the steam and water. chamber Ill and a central cylindrical con struction I22. The latter has a contracted lower portion I2- l communicating with a vortex inhibitor I26, thus providing for the flow of separated water from the. cylindrical whirl chamber I38 downwardly throughv the annular opening I32, in the. direction of the arrow I34.. The portion I24 forms a separated liquid outlet communicating with the downcomer I4 and the lower drum or chamber I2.

The steam and water mixture from the steam generating tubes passes upwardly inthe annular chamber I29 in the direction indicated by the arrows I36i38, and through tangential inlet constructions I40 to thetop of the whirl chamber I30. These constructions constitute, with their. associated. parts, means. whereby vapor and liquid mixtures from the vapor generating tubes are caused to be discharged tangentially into the The steam separated Within the whirl chamber I30 passes upwardly through an auxiliary separator I42 to the steam space of the chamber I0, whence it passes downwardly through upright tubes such as I44, I46'to extensions I50 and I52 of a superheater inlet header I54.

From the inlet header, I54 the steam passes through banks of superheater tubes II63 formed by reversely bent tubes in the manner indicated in Fig. 4. From these tubes, the steam passes to an outlet header I66, and thence through a tubular connection I68 to a pointof further treatment or use.

The specific construction of the steam and water separator of which the whirl chamber I30 is a part, is shown and claimed in the co-pending application of Ammon, Serial No. 73,985 dated February 1, 1949.

The cylindrical wall construction for the entire installation, in addition to the wall tubes such as ii2 l4 and IO-14, involves a casing including a generally cylindrical metallic shell, or upright casing, I between which and the upright Wall tubes there isa stratum I82 of thermal insulation. Exteriorly of the metallic shell I82 is outer stratum I84 of thermal insulation disposed between spaced metallic supports such as .I99I95 (Fig. 1) secured to the shell I80.

The casing has an access opening 68 and the t metallic Shell I80 is provided with an aligned opening normally closed by a closure member welded therein as indicated in the upper left hand part of Fig. 1.

Fig. 1 of the drawings clearly shows the vertically intermediate portion of the water drum I2 to have a cylindrical section, the walls of which are considerably thicker than the head of that drum. This drawing also shows a water drum as having walls which are considerably thicker than the walls of the downcomer I4. Similarly, Fig. 1 of the drawing clearly shows the vertical intermediate part of the upper drum I0 to have cylindrical section adjacent the lower part of the whirl chamber 30 of a wall thickness greater than the wall thickness of the head of that drum, and considerably greater than the thickness of the wall of the downcomer I4. The reason for these constructions involving intermediate drum sections of greater wall thickness is to provide adequate drum ligament strength, considering the greater number of steam generating tubes which are expanded into tube holes in the vertically intermediate sections of the drums.

Water is supplied to the chamber I2 through a tubular feed water inlet connection 200 including tubular element 202 passing through the lower wall of the pressure vessel element forming the chamber I2, and the installation is held in place by a circular support secured at the base of the central pressure vessel construction and including the

elements

204 and 206. Other supporting elements radially arranged about the shell I80 and fixedly secured thereto are indicated at 208 and 2I0 (Fig. 1).

The lower end of shell I80 is fixed to the lower pressure vessel I2 at I19, and the upper end of the shell is secured to the wall of the pressure vessel part forming the upper chamber I0 in the manner indicated in Fig. 5, Here, the shell I80 is welded at 220 to a collar 222 which is held in operative pressure tight relation to the wall of the steam and water chamber I0 by the metallic ring 224, associated securing devices 226228, and a gasket device 230. The purpose of this construction and a similar construction at the bottom of the casing is to provide gas-tight connections between the centrally disposed pressure vessel and the shell I80, to enable the installation to eifectively operate at positive furnace gas pres- F sures which are relatively high.

The modifications illustrated in Figs. 6 to 9, inclusive, are similar to the embodiment above described in that each includes a central drum and downcomer assembly like that shown in Figs. 1 and 2, the circumscribing casing being disposed about the assembly and joined to the upper and lower drums in a pressure tight manner. Each also includes a bank of steam generating tubes and a bank of superheater tubes disposed within the annular space between the casing and the central assembly of downcomer and drums.

The Fig. 6 modification involves two

furnaces

250 and 252 separated by a radial wall 254 which includes steam generating tubes such as 256258 with intervening stud and refractory constructions such as 260. The wall extends from the casing wall tubes such as 282 to a position adjacent the downcomer 264.

The

furnaces

250 and 252 are separately fired by burners such as those indicated at'264 and 266, these burners being arranged and constructed similar to those previously described. The burners are arranged at one side of the installation opposite the flue 268so that the gases from the furnaces must pass through opposite and substantially semi-circumferential gas passes. In the left gas pass the gases pass through the bank of superheater tubes 210 similar in construction to that previously described, this bank of tubes being disposed between the intermediate gas pass wall 212 and the adjacent part of the casing wall. The wall 212 is formed by steam generating tubes with interposed stud and refractory construction arranged in the same manner as the components of wall 254.

The superheater 210 is protected by a radially arranged bank of screen tubes 214 disposed between the burner 284 and the superheater. These tubes are relatively large diameter tubes arranged with wide spaces between them and con-- nected at the upper and lower ends to the upper and lower drums. This bank of screen tubesalso protects the bank of steam generating tubes 218 disposed between the wall 212 and the downcomer. Thus, high temperature gases in the furnace 250 pass over the tubes of the screen. 214 and are divided by wall 212, some of these gases contacting the tubes of the superheater' 210 and others passing over the steam generating tubes 216. Beyond these positions, the gases unite in passing over a part of a bank of radially arranged steam generating tubes 218 connected to the upper and lower drums and arranged between the Wall 212 and thebank of screen tubes 280 in the manner clearly indicated in the drawings.

The gases from the furnace 250, passing partially through the bank of steam generating tubes 218, unite with other furnace gases from the furnace 252 and pass from the installation through the flue 268, in which gas flow is con trolled by the damper 282. The gases proceeding from the furnace 252 first pass over the tube screen 280 and then through part of the bank of steam generating tubes 218 to juncture with the gases from the furnace 250.

In the modification shown in Fig. '1, there is a single furnace 300, the gas flow from which is divided by the semi-circumferential wall 302. All of the gases first pass over the bank of screen tubes 304 and they are then separated between the superheater gas pass 308 and the steam generating gas pass 308. The gas fiow through the gas pass 308 is controlled by the regulation of the damper 3I0 disposed in the flue 3I2. The latter is arranged adjacent a radial wall 314 which combines with the wall 302 and the radial wall 3I6 to complete the steam generating gas pass. The wall 3M is strengthened at an intermediate position by the stiffener 323, because of the wide difference in pressures on opposite sides of the wall. The steam generating tubes disposed within gas pass 308 are arranged in a semi-circumferential bank extending from the screen 304 around the downcomer 320 and to a position 322 adjacent the flue 3I2.

Within the gas pass 306 is arranged a superheater 324 constructed in a manner similar to that of the previously described superheater, and consisting of a bank of upright tubes. Beyond the superheater steam generating tubes are arranged in radial rows and disposed as a bank of tubes 321 extending from a position adjacent the screen tubes 326 to a position adjacent the flue 328. The gas flow through the superheater gas pass 308 and total steam temperature are controlled by the regulation of the damper 338 disposed across the flue 328.

Thefurnace or the Fig. 7 modification is fired by burners such as 332 and 334.

The modification shown in Fig. 8 of. the drawings involves a single furnace 350 fired by

burners

352 and 354. The gases from this furnace are divided so as'to fiow semi-rcircumferentially to the

fines

356 and 358 which are arranged at the side of the installation opposite the burners. The gas flow to the fiues is divided at a position adjacent the flues by aradial wall 360 consisting of steam generating tubes and intervening stud and refractory constructions such as those previously described.

The furnace gases moving from the furnace 358 clockwise around the downcomer 362 first pass over the bank of large diameter screen tubes 364. They are then divided by the wall 366 so that part of the gases pass over the tubes of the superheater 368 on one side of this wall. The remainder of these gases, on the other side of this wall pass over a bank of steam generating tubes 316 arranged in radial rows between the downcomer 362 and the wall 366. Beyond this wall these two divisions of the gases reunite to pass over the bank of steam generating tubes 372 to the flue 356. The gas fiow over the superheater 368, and hence the final steam temperature is controlled by the. regulation of the damper 314 disposed in flue 356, as modified by the gas flow in counter-clockwise. direction about the downcomer 362 from the furnace 356 to the hue 358. The latter gas fiow is regulated by the damper 376.

The gases. passing fromthe furnace 350 in counter-clockwise direction about the downcomer 362 first pass over and between the tubes of the bank of screen tubes 380. Beyond this screenthe gasescontact the tubes of a bank of steam generatingv tubes. 382 arranged in radial rows and substantially filling the annular space between the screen 380 and the radial wall. 35$. The latter is provided with radially extending reinforcing members 36! and 363.

In the modification shown in Fig. 9 of the drawings, there is a single furnace 406'disposed on one side of a radially positioned wall 4B2. Immediately on the other side of this wall is a single flue 404 so disposed that the gases must pass in a counter-clockwise direction almost entirely around the entire installation.

The furnace 400 is fired by burners such as 466 and 408 preferably disposed at an intermediate elevation opposite the downcomer 4H1, as in the other modifications.

The gases first contact the large diameter tubes of the bank of screen tubes 4l2 disposed in radial rows as clearly indicated in the drawings. Beyond this bank of screen tubes the gases are separated by a wall 414 between a superheater gas pass M6 and a steam generating'gas pass in which there is disposed a bank of steam generating tubes 4l8. Opposite this bank of steam generating tubes is a superheater 42 6, similar to the above described superheater.

At the outlet of the superheater gas pass M6 the gas passes over and between the large diameter screen tubes 422 and then over the major bank of steam generating tubes 424 disposed in radial rows and extending from the screen 422 to the fiue 404 as clearly shown' in the drawings.

Gas flow through the flue 404 is controlled by the damper 426.

The exterior casing, and shell I88 of each of the modifications is provided with a casing access opening 68 to thesuperheater space, this Elm-m casing opening being disposed directly above the superheater and normally closed by an appropriate cover which may be normally welded in pressure tight condition, or secured in such condition by other appropriate means. When this cover is removed, access to the annular space between the casing and the central pressure vessel construction is provided. In this manner, the amount of tube cutting necessary in the original construction and in the maintenance is minimized' because a large portion of the bent tubes of both the superheater and the steam generating surfaces may be passed through this opening.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of my invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. In a steam generator, a cylindrical metallic casing including a pressure tight cylindrical metallic shell having upper and lower heads formed with circular openings, a cylindrical steam and water drum extending through the opening in the upper head of the casing and secured thereto in pressure tight condition, a lower cylindrical drum extending through the opening in the lower head of the casing and secured thereto in pressure tight condition, a large diameter downcomer co-axial with the casing and the drums and directly connecting the latter, the annulus between the casing and the drum and downcomer assembly providing space for a furnace and space for heat absorbing surfaces, steam generating tubes forming part of said surfaces, said tubes being directly connected to the upper and lower drums, spaced tubes forming a superheater disposed within said annulus, means connecting the steam space of the upper drum to the superheater, and means including a circumferentially directed wall construction within said annulus and forming a circumferentially extending superheater gas pass adjacent the casing wall and having a radial width of less than that of the annulus, said gas pass leading from the furnace.

2. In a vapor generator, a cylindrical metallic pressure confining casing, a unitary assembly of upper and lower drums and a connecting downcomer disposed centrally of the casing with an annular space between the casing and the assembly, a furnace in said annular space, means firing the furnace, vapor generating tube directly connecting the drums and disposed within said annular space, a bank of spaced tubes forming a superheater disposed in said annular space, means including a wall construction dividing a part of said annular space into two radially positioned and circumferentially extending gas passes, the bank of superheater tubes being disposed in one of said gas passes and at least some of the vapor generating tubes in the other gas pass, and fiue means extending through the easing so as to provide for the discharge of furnace gases from said passes.

3. In a vapor generator, a cylindrical metallic pressure confining casing, a unitary assembly of upper and lower drums and a connecting downcomer disposed centrally of the casing with an pannular space between the casing and the as sembly, a furnace means in said annular space, fuel burner means, vapor generating tubes directly connecting the drums and disposed within said annular space, a bank of spaced tubes form ing a superheater disposed in said annular space, m'eansincluding a wall construction dividing the part of said annular space into circumferentially extending superheater and vapor generating gas passes, the bank-of superheater tubes being disposed in one of said gas passes and at least some of the steam generating tubes in the other gas pass, and flue means extending through the easing so as to provide for the discharge of furnace gases from said passes. V

4. In a steam generator, a casing with upper and lower heads formed with circular openings, the'casing also including a cylindrical'metallic shell connecting the heads, a cylindrical steam ating tubes forming part of said surfaces within' said annular space, said tubes being directly connected to the upper and lower drums, spaced tubes forming a superheater disposed within said annulus, means for connecting the steam space of the-upper drum to the superheater, an upright wall extending outwardly' from the downcomer to the casing, means forming a' furnace gas outlet through the casing at the side of said wall, and furnace gas supplying means communicating with said space at a position adjacent the opposite side of said wall.

5. In a vapor generator an upright tubular pressure vessel providing upper and lower fluid chambers integrally joined by a large diameter upright, downcomer, horizontally spaced upright vapor generating tubes directly connecting said chambers and disposed circumferentially of the pressure vessel, a casing circumferentially enclosing said tubesso as to provide an annular space between the downcomer and the casing, an upright wall extending from the downcomer to the casing, means forming a furnace gas outlet through the casing adjacent one side of the wall, a first combustion chamber from which furnace gases pass over some of said tubes to said outlet, said combustion chamber being disposed adjacent one side of said wall, a superheater including tubes disposed across gas flow from said combustion chamber toward said outlet, and a second combustion chamber disposed within said annular space and beyond the superheater relative to gas flow, gas from the second combustion chamber passing over others of said tubes to said outlet without passing over the superheater tubes.

6. In a vapor generator an upright tubular pressure vessel including upper and lower liquid chambers directly connected by a large diameter downcomer, horizontally spaced upright vapor generating tubes including tubes directly connecting said chambers and disposed circumferentially of the pressure vessel, a gas tight casing circumferentially enclosing said tubes and joined to said chambers in pressure tight relationship,

10 an upright wall extending from one side of the downcomer outwardly to the casing, means forming furnace gas outlets through said casing at positions on opposite sides of said wall, a com bustion chamber from which furnace gases pass through the separate gas passes over said tubes and to said outlets, a superheater including tubes disposed in one of said passes, at leastr'some of said vapor generating tubes being disposed in the other gas pass, and means in at least one of the outlets for varying gas flow over'the'superheater to control superheat.

7. In a vapor generator, an upright tubular pressure vessel including upper and lower fluid chambers directly connected by 'an upright downcomer, horizontally spaced upright vapor generating tubesdirectly connectingsaid cham-' bers and disposed circumferentially of themessure vessel, a casing circumferentially enclosing said tubes and bounding a wide annular furnace gas space around the downcomenan upright wall extending from the downcomer to the casing, means forming a furnace gas outlet on one side of said wall, a first 'combustion 'chamber from which furnace gases pass over'some of said tubes to said outlet, said combustion chamber being remote from said wall, a superheater including upright tubes disposed circumferentially between said combustion chamber and said wall and in a gas pass radially outwardly spaced from the downcomer, and a second combustion chamber disposed between the superheater and said wall and at the side of the wall opposite the furnace gas outlet, some of said vapor generating tubes being disposed within said annular. space and in a gas pass separatedfrom the gas pass in which the superheater tubes are disposed.

8. In a vapor generator; an'upright tubular pressure vessel including upper and lower fluid chambers joined by a downcomer, horizontally spaced upright vapor generating tubes directly connecting said chambers and disposed circumferentially of the pressure vessel, acasing circumferentially enclosing said tubes and forming the outer boundary of an annular furnace gas space around the pressure vessel, an upright wall extending across said space from the pressure vessel to the casing, means forming a furnace gas outlet on one side of said wall, a first combustion chamber from which furnace gases pass over some of said tubes to said outlet, an upright segmental wall intermediate the downcomer and the casing and forming a superheater gas pass along a part of the casing, a superheater including tubes disposed within said gas pass and circumferentially between said combustion chamber and said first mentioned wall, some of said vapor generating tubes being disposed in the gas pass between said segmental wall and the downcomer, and a second combustion chamber disposed between the superheater and said first wall.

9. In a vapor generator an upright tubular pressure vessel providing upper and lower fluid chambers directly joined by a large diameter downcomer, horizontally spaced upright vapor generating tubes directly connecting said chambers and disposed circumferentially of the pressure vessel, a casing circumferentially enclosing said tubes, an upright wall extending from the pressure vessel downcomer to the casing, means forming a plurality of furnace gas outlets on one side of said wall, a combustion chamber from which furnace gases pass circumferentially of the pressure vessel and over some of said tubes to one of said outlets, the combustion chamber being disposed at the side of said wall opposite said outlets, a ,superheater including tubes disposed in the path of .thegases passing from said combustion chamber .to the other of said outlets, fuel burning means oper-atively associated with thecombustion chamber, asecond wall construction combining with the pressure vessel and the casing to provide two separate gas passes leading from .a position adjacent the superheater to a position between said .gas outlets, and means associated with one ofsa'id outlets to vary the gas flow therethrough to control superheat, some of the steam generating tubes being disposed on one of .said gas passes and the superheater tubes in the other gas pass.

21.0.,In a vapor generating installation, upper and "lower ffluid chambers integrally connected byalarge diameter central downcomer, a metallic shell of larger diameter than saidchambers, said shell being secured in a gas tight relationship ,to the upper and lower chambers and provid'ing an annular space between the shell and the downcomer, a fue'lburner operating through the shell and .horizontally firing a furnace disposed in a sector of said annular space, horizontally spaced upright fluid heating tubes disposed within a convection sector of .said annular space adjacent the furnace and communicating with at'least oneo'f said-chambers. and means forming afurnace gas outlet through the shell, the furnace ,gas outletibe'ing arranged beyond said horizontally vspaced upright tubes and so disposed with reference to the fuel burner that gases flow arcuately from the furnace sector to and through the convection sector and transversely of said tubes.

'11.In a vapor generating installation, a pressure vessel structure presenting upper and lower fluid chambers integrally connected by a large 12 diameter centraldowncomer, a cylindrical metallic shell of larger diameter than said chambers, said shell .being secured in a; gas tight relationship to the upper and .lower chambers and pro= viding an annular space between the shell and the downcomer, a fuel burner operating through the shell and horizontally firing a furnace disposed in a sector of said annular space, .hori--v zontally spaced upright fluid heating tubes .dis= posed within a convectionsector of said annular space adjacent the furnace ,and communicating, with at least one ofsaid chambers. and means forming a furnace gas outlet through the side of the shell, the furnace gasoutlet-being arranged beyond said horizontally spaced upright tubes and so disposed with reference to the fuel burner that gases flow arcuately from the furnace see tor to and through the convection sector transversely of said tubes.

GEORGE W. K-ESSLER.

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

UNITED STATES PATENTS Number 'Name Date 465,533 Morse a .Dec. 22, 1891 883,852 Ballin Apr. 7, .1908

1,174,182 Rohrbacher F Mar. 7, 1916 1,766,989 Forssblad .June 24, 1930 1,917,275 Rossmanet a1., July 11, 1933, 1,999,984 Bailey et al. Apr. .30, ,1935

2,044,270 Wood .June 16, 193.6

2,102,424 Larrecq Dec. 14, 1937 2,207,247 Frisch July 9, 1940 2,271,880 Wood ,Feb. 3, 1942 2,285,442 .Kerr June '9, 1942