US2723650A - Vapor generator - Google Patents

Description

Nov. 15, 1955 G. W. BEUTE ET AL VAPOR GENERATOR Filed NOV. 10, 1950 5 Sheets-Sheet 2 INVENTORS Gearge Wfieuze BY Zero MEzz/r 0 m..- ATTORNEY Nov. 15, 1955 G. w. BEUTE ET AL 2,723,650

' VAPOR GENERATOR Filed NOV. 10. 19553 5 Sheets-Sheet 3 INVENTO R5 George 14 Beam? 77701444 ATTO RNEY M5 /8/ HQ 4 BY [eroy/Mfink Nov. 15, 1955 G. w. BEUTE ET AL 2,723,650

VAPOR GENERATOR Filed Nov. 10, 1950 5 Sheets-Sheet 5 4: p3 in 72 /23a [23a 1M 1111i JUJJ J Fr T war :21 10 l /22 a 9 FIG. 8

INVENTORS F G. 10 George 7 1/ Beute BY Ze /0y .M Rink ATTO R N EY United States Patent 2,723,650 v'APoR GENERATOR George W. Beute, Cedar Grove, and Leroy M. Fink,

Union, N. 1., assignors to The Babcock & Wilcox Company, Rockleigh, N. L, a corporation of New Jersey Application November 10, 1950, Serial No. 194,978

13 Claims. (Cl. 122-235) The present invention relates in general to vapor generators and more particularly to the construction and operation of steam generators or steam generating boiler units of which a large proportion of the boiler heating surface is provided by water conducting tubes associated with walls of a chamber through which hot gases of 1 tion features an arrangement of steam attemperator whereby water conducted through wall cooling tubes is directed into contact with attemperator elements which serve as conductors for the steam to be attemperated. Suitably, the steam conducting attemperator elements, such as tubes, are assembled within a separate drum which is installed in or adjacent an uptake wall of the boiler unit, in a position wherein the drum is shielded from the direct heat of the combustion chamber, and wherein the necessary flow connections may conveniently be made with wall tubes and with the superheater or superheater sections. Water flowing upwardly through wall tubes is discharged into a lower portion of the attemperator drum and other wall tubes, above the drum, receive the water as it is discharged from an upper portion of the drum. The attemperator drum thus combines with wall tubes below and above the drum to form a continuous uptake fluid flow path of the boiler unit. The resulting flow path is substantially unidirectional in character and results in a minimum impedance to water flow through the drum so as to maintain an adequate rate of fluid flow therethrough and through wall cooling tubes which are connected thereto.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of our invention.

Of the drawings:

Fig. 1 is a sectional side elevation of a vapor generator constructed in accordance with our invention;

Fig. 2 is a fragmentary enlargement of Fig. 1 featuring the attemperator drum and connections thereto;

Fig. 3 is a front view of the structure illustrated in Fig. 2;

Fig. 4 is a sectional side elevation of a vapor generator embodying a modification of the invention;

Fig. 5 is a diagrammatic plan view of circulatory connections to the attemperator drum included in Fig. 4;

Figs. 6 and 7 are diagrammatic sectional end views 7 of Fig. 5, taken along lines 6-6 and 7--7, and respectively illustrating the side wall and division wall tube arrangements;

Fig. 8 is a partial sectional front view of Fig. 4 taken along line 8-8; and

Figs. 9 and 10 are fragmentary plan sections of Fig. 8 taken along lines 99 and 10-10, respectively.

As illustrated in Fig. l, the vapor generator is of the radiant type having a fuel-fired combustion chamber 50 of horizontally rectangular cross section extending throughout the height of the setting. The entire unit is suitably suspended from an overhead load supporting structure, not shown. The chamber 50 is defined by upright fluid cooled walls which include the front wall 51, the rear or burner wall 52, and opposing side walls 53 of which only one is indicated. Tubes associated with the respective walls are designated as wall tubes 51a, 52a, and 53a. The upper enclosing wall or roof 54 is suitably formed as a continuation of front wall 51 and extends rearwardly and upwardly to a position beyond an exteriorly located upper steam and water drum 55. Burners 56 are positioned in a lower portion of rear wall 52 in vertically spaced rows.

Front wall tubes 51a are extended along the roof to provide roof tubes 54a which are connected at their upper ends to drum 55. The lower portion of chamber 50 is formed as an ash hopper having oppositely inclined front and rear walls 57 and 53 which diverge downwardly toward an ash discharge opening 59. The lower ends of front and rear wall tubes 51a and 52a are connected to headers 61 at the bottom of the unit. The lower ends of side wall tubes 53a are connected to lower side wall headers 62, 63 and 64, and their upper ends to upper side wall headers 65 and 67 from which suitable connections, including tubes 68, are made to the upper drum 55. Water is supplied to the lower headers 61, 62, 63 and 64 through means including external cylindrical downcomers 69 which extend downwardly from opposite ends of drum 55 to which their upper ends are connected, only one downcomer 69 being indicated. Suitable supply connections including tubes 71 and header 72 are utilized to conduct water from the lower portions of downcomers 69 to the respective lower wall headers.

A reverse arch 73 extends forwardly from rearwall 52 and, with front wall 51, defines a throat passage 74 of reduced cross section through which heating gases are directed into the upper chamber space 75. The lower arch portion 76 is inclined forwardly and upwardly to direct gases into the throat passage 74, .while the upper arch portion 78 is inclined rearwardly and upwardly in downwardly spaced relation to roof 54 so as to define a gas outlet passage 79 of progressively decreasing gas flow area in the direction of gas flow therethrough. The gas outlet passage 79 also serves as a superheater chamber and in order to accommodate an adequate amount of superheater surface, the boundaries of the passage are extended rearwardly to provide communication with an upright economizer flue 80 which is rearwardly spaced from the rear furnace wall 52. The upper flue wall 81 is formed as a continuation of the combustion chamber roof 54, while the front and rear flue walls 82 and 83 are arranged substantially parallel to the rear furnace wall 52. It may be assumed that the economizer in flue 80 comprises serially connected tube sections 84 which discharge into an upper header or headers 85 from which suitable discharge connections, not detailed, extend to drum 55. Gases discharging from the flue 80 are directed through an angular duct 86 into an air heater 87, herein represented as an air heater of the regenerative type having a gas outlet 88. Air to' be heated enters the air heater through inlet 89 and the heated air is discharged through an air outlet 91 into 3 a windbox structure 92 which is associated with burners 56'.

The superheater 93 in chamber '79 comprises a primary section 94 having inlet and outlet headers 95 and 96 respectively, and a secondary section 97 having inlet and outlet headers 98 and 99 respectively, each section being of the pendant continuous-tube type having multiple loopcoils or platens arranged in planes parallel to side walls 53. Steam from drum 55 is initially directed into the primary section 94 through tubes -1 which lead to inlet header 95. superheated steam from the primary section is directed through pipes 102 which extend from opposite ends of header 96 to corresponding ends of any attemperator 103 disposed within a drum 104 which is positioned rearwardly of arch 73, the at" temperator comprising horizontally extending Ll-tubes which are arranged longitudinally of drum 104- in bundles as indicated in Figs. 1 and 2. Atternperated steam is discharged from the attemperator through pipes 106 which extend from opposite ends of the attemperator to opposite ends of inlet header 98 of the secondary superheater section 97. The bundles of attemperator tubes 105 are arranged in two separate groups within the respective end portions of drum 104, with each. group of tube bundles forming a separate atternperator section of which the U-tubes have their inlet ends connected in parallel to a single steam inlet pipe 102 and their outlet ends connected in parallel to a single steam outlet pipe 106. Each attemperator section is thus similar in construction and arrangement to the single attemperator section disclosed in the copending application of l. L. Langvand, Serial No. 653,843, filed March 12, 1946, now U. S. Patent No. 2,561,875, granted July 24, l95l, except for the provision of three tube bundles per section instead of a total of two bundles.

A bypass valve 107 is positioned in each pipe 10.2 and provides a bypass connection 108 to pipe 106 whereby a controllable portion of superheated steam from the primary superheater section 94 may be caused to mix with attemperated steam in pipe 106 and the resulting mixture caused to flow to the secondary superheater section 97. Valve 107 is suitably of the construction disclosed in U. S. Patent 2,444,942, B. H. Miller, July 13, 1948.

The attemperator drum 104 is included in the circulatory system of boiler wall tubes whereby water is caused to pass through the drum in contactwith the steam conducting attemperator tubes 105. For convenience in making the necessary water connections, drum 104 is horizontally positioned within the reentrant angular recess 109 formed between the lower and upper arch walls 76 and 78, with its longitudinal centerline in a common vertical plane with the rear wall cooling tubes 52a. The recess or space 109 is closed at the rear, below drum 104, by a rear wall section 115, and above the drum, by a rear wall section 116 which extends to the lower boundary 78 of the gas outlet passage. The drum 104' extends to the exterior of opposite side walls 53 where opposite ends of the drum are provided with suitable manhole openings, and removable closures therefor, so as to permit access to the interior of the drum and to the atternperator equipment therein. In the particular arrangement shown in Figs. 2 and 3, the rear wall tubes 52a are suitably of 3" outside diameter and are tightly spaced in a single row at 3 center-to-center. Of the tubes 52a, every fourth tube 52b is extended upwardly and connected to the lowermost portion of drum 104 at 12" center-to-center. The remaining tubes 520 are extended along the arch 73, as a part of its lower wall portion 76. One tube 52d of every three tubes 52s is extended upwardly from the nose of the arch, on 12" centers, across the entrance to the combined gas outlet passage and superheater chamber 79, the tubes 52d having their upper ends connected to the steam and water drum 55. The remaining tubes 522 are continued along the upper arch wall portion 78 to a point above the centerline position of drum 55 where alternate tubes 52) are extended horizontally to enter drum 104, while the remaining alternate tubes 52g are continued along the upper arch wall portion 78. Interspersed with tubes 52g are tubes 111 and 112 which have their lower ends connected to drum 104 to form fluid outlets or risers therefrom, the'lower end portions of riser tubes 112 lying in a common vertical plane with the rear wall water inlet tubes 52b. Tubes 52g, 111 and 112 are connected at their upper ends to drum 55 and, at an intermediate location, beyond superheater 93, are arranged in two rows 113 to provide adequate. gas flow area therebetween. Other riser tubes 114 having their lower ends connected to drum 104 are vertically arranged in single transverse rows adjacent the respective ends of the drum, in vertical alignment with the rows of side wall tubes 53a, the tubes 114 having suitable discharge connections, not shown, to the upper drum 55 and furthermore having suitable overhead support means, not shown, whereby the riser tubes- 114, of 4" outside diameter, for example, serve as suspension supports for the attemperator drum 104. As thus described, certain of the rear wall tubes 52:: serve to supply cooling water to drum 104 while other tubes 111, 112 and 114 serve to conduct the heated water therefrom, all such water inlet and water outlet tubes 111 and 112 having their connections to drum 104 longitudinally distributed in rows throughout the greater part of the length of the drum, and outlet tubes 114 having connections circumferentially distributed in rows adjacent opposite ends of the drum.

In the modification illustrated in Figs. 4 to 10 inclusive, the vapor generator is of the radiant type having a fuel fired combustion chamber which is defined by upright fluid cooled front and rear walls 121 and 122, respectively, and by upright fluid cooled side walls 123, the upper end of the chamber being closed by a roof 124. Chamber 120 is fired by means of vertically spaced burners 125 located in a lower portion of front wall 121. The entire unit is suitably suspended from an overhead load supporting structure, not shown. At an elevation above burners 125, an upper section of rear wall 122 is extended forwardly in the form of a reverse arch 126 having lower and upper inclined portions 127 and 128, respectively, similar to the structure shown in Fig. 1. Arch 126 terminates in spaced relation to front wall 121 so as to define therewith a throat 129 through which heating gases are directed into the up per chamber space 130. The upper arch portion 128 is inclined rearwardly and upwardly in downwardly spaced relation to roof 124 so as to define a combined gas outlet passage and superheater chamber 131 of progressively decreasing gas flow area in the direction of gas flow therethrough. The gas discharge end of passage 131 is connected to an upright flue 132 which is defined in part by an upright rear wall 134 arranged parallel to wall 122, and by an upright front Wall portion 135 which also serves as an enclosing wall for the reentrant angular recess 136 which is formed reaiwardly of arch 125 between upper and lower portions thereof. The upper flue wall 137 is formed as a continuation of roof 124. Gases are discharged from the flue through a gas outlet 138 to an air heater, not shown, whereby air for combustion may be heated for delivery to burners 125.

The combustion chamber 120 is laterally divided into sections 140, 140 by means of an upright fluid cooled partition or division wall 141, each section 140 having a hopper bottom portion 142 as defined by downwardly converging side wall portions 143 and 145 which are continuations of a main side wall 123 and division wall 141 respectively. Each hopper bottom portion 142 terminates in a throat 146 through which ash accumulations are discharged into an integral ash hopper 147, of a construction which is more fully disclosed, and is claimed, in the copending application of R. J. Boyer and. C. L. Marquez, Ir., Serial No. 199,265, filed Dec. 5, 1950. Burners 125 are arranged in horizontally successive sets so that each combustion chamber section 140 may be fired by a separate set of vertically spaced burners 125 which are positioned in front wall 121 at an elevation between arch 126 and the bottom end of division wall 141. Air for combustion is supplied to each set of burners through a hot air duct 148 and windbox 149.

All upright fluid cooled walls of the setting include wall tubes which are arranged for natural circulation of water therethrough. Accordingly, an elevated steam and water drum 150 is provided at or above the uppermost part of chamber 121) and water is supplied from drum 150 to the lower ends of all wall tubes through suitable downcomer means including downcomer tubes 151, for example, which at their upper ends are connected to opposite ends of the drum. Vapor generated within the wall tubes is discharged into drum 150 through suitably arranged upflow connections which are made to drum 150 from the upper ends of the tubes.

Feed water is delivered to drum 150 from a tubular economizer 152 located in the lower portion of flue 132 and having water inlet and water outlet headers 153 and 154 respectively. The heated water is discharged from opposite ends of header 154 through pipes 156, of which one only is shown, to opposite ends of drum 150.

Vapor such as steam is conducted from drum 150 through successive superheaters or superheater sections 157 and 158 of the continuous-tube type, and the superheated vapor finally discharged through pipe 159 to a point of use; the primary superheater 157 having tubes formed in continuous lengths and connected at opposite ends to inlet and outlet headers 161 and 162, respectively, the tubes being arranged in vertically spaced banks a and b in flue 132 and having horizontally extending tube lengths connected to form horizontally spaced multiple loop coils which are disposed parallel to side walls 123; the 'secondary superheater 158 having tubes formed in continuous lengths and connected at opposite ends to inlet and outlet headers 163 and 164 respectively, the tubes being arranged in horizontally spaced-banks c and d in the tapered gas passage 131 and having vertically extending tube lengths connected to form horizontally spaced multiple loop coils which are disposed parallel to side walls 123. Vapor is conducted from drum 150 to the primary inlet header 161 through fluid connections which include tubes 165 which lead from drum 150 to a header 167 above the setting, the vapor then passing through sets of tubes 168 and 169 to a header 171 located adjacent the top end of flue wall 134, portions of which tubes 168 extend along the flue roof 137, and thence through tubes 172 which extenddownwardly along flue wall 134 to inlet header 161 of the primary superheater section. Vapor superheated in the primary section 157 is discharged therefrom through pipes 173 which extend from opposite ends of the primary outlet header 162 to corresponding ends of an attemperator 174 located interiorly of a drum 175 which is horizontally positioned rearwardly of arch 126 within the angular recess 136. As hereinafter described, the attemperator drum 175 is included in the circulatory system of boiler wall tubes whereby water is caused to pass through the drum in contact with steam conducting elements of the attemperator. For this purpose, the attemperator 174 is formed of steam conducting tubes suitably arranged and connected substantially as described for attemperator 103 in reference to the embodiment illustrated in Figs. 1 to 3. Attemperated steam is discharged from the attemperator through pipes 176 which extend from opposite ends of the attemperator to opposite ends of secondary superheater inlet header 163. A bypass valve 107, as previously identified, provides a steam flow connection between pipes 173 and 176 whereby a controllable portion of superheated steam may be caused to bypass the attemperator 175 and mix with attemperated steam discharging from the attemperator before entering the secondary superheater 158.

In order to maintain a supply of water to wall cooling tubes in each of the combustion chamber walls, downcomer connections are made from drum to the lower ends of all such wall tubes through headers to which the lower ends of downcomer tubes 151 are connected. In front and rear walls 121 and 122, for example, wall tubes 121a and 122a of the respective walls are connected at their lower ends to headers 178 and 179 arranged at different elevations due to the provision of ash hoppers 147, with alternate groups or panels of tubes 121a and 122a being connected to lower headers 178 located at approximately the elevation of threats 146, and the two remaining intermediate panels of tubes 1211a and 122a being connected to lower front and rear wall headers 179 located adjacent the bottom ends of hoppers 147. In partition wall 141, tubes 141a are connected at their lowermost ends to headers 181 located at the bottom ends of hoppers 147. In side walls 123, tubes 123a are connected to lower headers 182, also associated with hoppers 147 but located at a higher elevation than the bottom hopper headers 181, the headers 182 being connected to bottom headers 181 by inclined tubes 183 which extend along the hopper outlet wall 184 between horizontally spaced ash removal openings 135. Although the specific arrangement of downcomers 151 is only partially illustrated, it is to be understood that the complete arrangement may be entirely conventional so as to provide a suitable distribution of water supply from drum 150 to the respective lower Water wall headers 178, 1-79 and 181. Hopper headers 182 are supplied with water from the bottom hopper headers 181 through tubes 183.

In order to complete the natural circulation flow paths through the various wall tubes described, upflow connections are made from the upper ends of wall tubes to the steam and water drum 150, in some instances these connections being direct, and in other instances indirect, as hereinafter described. Thus in front wall 121, the tubes 121a extend upwardly from headers 178 and 179 and, at their upper ends, are directly connected to upper drum 151).

In rear wall 122, the tubes 122a are suitably of 3" outside diameter and are tightly spaced in a single row at 3" center-to-center. Tubes 122a extend vertically from headers 178 and 179 to the lower end of arch 126 where'a majority of such tubes are extended along the lower inclined arch portion 127 to the nose of the arch, at which location selected tubes 122b are continued vertically at 12" centers to form a screen across the entrance to superheater chamber 131. Upper end portions of tubes 1221) are extended along roof 124 and are connected to drum 150 in a common row with front wall tubes 121a. Other rear wall tubes 1220, at 6" centers, extend upwardly along the upper inclined arch portion 127 and thence upwardly across passage 131 as indicated. Upper end portions of tubes 1220 also extend along roof 124 and are connected to drum 150. The remaining rear wall tubes 122d, at 12" centers, are connected to vertically disposed tubes 12212 from which upflow connections are made to drum 150, the tubes 122a preferably being of larger diameter than tubes 122d, of 4" outside diameter for example, and being suitably supported by means not shown, whereby in addition to forming riser connections for tubes 122d, the tubes 122a constitute a top suspension means or support for rear wall 122.

In side walls 123, the tubes 123a arearranged in front and rear sections or panels, as determined by their positions along walls 123 relative to a vertical plane A, for example, which extends parallel to front and rear walls 121 and 122, at a position between the attemperator drum and the nose of arch 126; the front tube panel in each side wall comprising tubes 123b which are disposed forwardly of plane A, and the rear tube panel comprising tubes 123a which are disposed rearwardly of plane A. The front panel tubes 12312 extend from the hopper headers 182 to an elevation above roof 124 where their upper ends are connected to upper side wall headers 186 from. which: riser connections, not shown, are made to drum 150. The rear panel tubes 1230 extend upwardly from. hopper headers 132 to an elevation above the lower arch portion 127 where their upper ends are suitably arranged and connected to the attemperator drum 175 in a manner to be later described, with reference to Figs. and 6.

In division wall 1 11, at elevations below arch 126, the tubes 141a are tightly spaced in a single row as indicated in Fig. 10, the tubes 141a being suitably of 3" outside diameter and arranged at 3" center-to-center spacings. Above throat 129, and forwardly of arch 126 and screen tubes 1221), a front panel of tubes 141a is arranged so that every fourth tube 141a is continued upwardly in its original vertical plane, whereas intermediate tubes 141b, in groups of three, for example, are bent out of the original plane and are continued upwardly in vertical planes disposed at opposite sides of the original plane, as indicated in Fig. 9. In an intermediate panel of tubes 141a, between plane A and the nose of the arch, the tubes 141a are continued upwardly through the arch and, above the arch, extend between platens of tubes forming the front tube bank c of the secondary superheater 158. In a rear panel of tubes 141a, between plane A and rear wall 122, the tubes 141:! are connected at their upper ends to the attemperator drum 175, as diagrammatically illustrated in Figs. 5 and 7. All division wall tubes 1410, except those which discharge into drum 175, are joined at their upper ends, above roof 124, to suitable riser means, not shown, by which fluid conducted therethrough is discharged into the boiler drum 150.

As indicated in Figs. 5 and 6, each rear panel of side wall tubes 123a is composed, for example, of twenty-nine tubes which, for convenience of identification, are numbered 1 to 29 inclusive, from front to rear. All odd numbered tubes 1, 3, 5, etc., except tube 29, are maintained in their original vertical plane and are connected at their upper ends to drum 175 at circumferentially spaced locations about the lower half of the drum as seen in Fig. 6. The majority of the odd-numbered rear panel tubes 1, 3, 5, 29 have their upper ends suitably bent so as to be directed radially of the drum. Tubes 11, 13, 15, and 17, are straight tubes which extend vertically in non-radial relation to drum 175, and serve as supports for lower side wall portions rearwardly of plane A. All evennumbered rear panel tubes 2, 4, 6, 28, and the single odd-numbered tube 29 heretofore mentioned, are bent at their upper ends so as to provide radial connections with drum 175 at longitudinally spaced locations therealong, as diagrammatically represented by solid lines in Fig. 5. It. is to be understood that these solid lines represent tube length portions which extend from tube positions in side wall. 123 to the correspondingly numbered points of connection to drum 175. They are not to be construed as illustrating the specific tube length formations for this purpose. These side wall tube connections to the lower half of drum 175, for both side walls, are symmetrically arranged with respect to the center of length of the drum.

The corresponding riser connections from the upper half of drum 175, for each side wall, are composed of tubes 30 to 41 inclusive which, at elevations above arch 126 are disposed in substantially the same vertical plane as side wall tubes 1 to 29 below the arch. Tubes 33 to 37 inclusive, which constitute an intermediate group, are straight tubes of larger diameter than the remainder of the tubes and serve as suspension supports for drum 175, similar to riser tubes 114 which support drum 104 of the first described embodiment. The remaining side wall risers, such as tubes 30 to 32 which form a front group, and tubesi38 to 41 which form a rear group, are bent at their lower ends within space 136 so as to extend radially of drum 175 at their respective longitudinally spaced points of connection. thereto. Tubes 38 to 41, in the respecttve side walls, are connected at their upper ends to headers 186,, from which suitable riser connections are provided to drum 150, as heretofore mentioned.

In division wall 141', as indicated in Figs. 5 and 7, the rear panel of tubes 141a is composed, for example, of twenty-nine tubes which for more specific identification, are numbered 1D to 29D inclusive, from front to rear. All odd-numbered tubes 1D, 3D, 5D 27D have their upper ends connected to drum 1'75 at circumferentially spaced locations Within the lower half of the drum, and in the original plane of the wall. The majority of such tubes are bent at their upper ends so as to extend radially of the drum at their respective points of connection. Tubes 11D, 13D, 15D and 17D, which form an intermediate group and provide support for a lower wall portion, are substantially straight and vertical throughout and thus provide non-radial connections. T he upper end of tube 29]), and the upper ends of all even-numbered tubes 2D, 4D, 6D 28D are bent out of the plane of Wall 141 and extended to correspondingly numbered points of connection along the lower half of drum 175, as represented in Fig. 5 by dotted lines. Riser tubes 36D to 42D inclusive extend upwardly from drum in sub stantially the same vertical plane as divisional wall tubes 1D to 29D below the drum. The lower ends of tubes 30D to 42D, within arch space 136, are bent so as to extend radially of drum 175 at circumferentially spaced locations, as seen in Fig. 7, whereas the upper portions of tubes 30D to 42D, above the upper inclined arch portion 128,. are arranged vertical and parallel in a single plane intermediate tube coil platens of superheater 158. The upper ends of division wall tubes 30D to 42D inclusive are connected to the upper drum 156 by suitable uptake or riser conductors such as a header and tubes, not shown.

In each form of vapor generator herein disclosed, the superheat attemperating device is made an integral part of the unit. and occupies a space which otherwise would serve no useful purpose. Thus, the overall space occupied by the entire vapor generating unit, including the attemperator, is no greater than the space heretofore required for vapor generating units of comparable output capacities, without an attemperator. Moreover, applicants provide an attemperator located adjacent the combustion chamber but nevertheless in a position where the attemperator is completely shielded from the direct heat of the chamber. In the position selected, the attemperator drum forms a conductor for fluid in the upflow section of a natural circulation flow circuit wherein the flow of fluid is induced by thermo-siphonic action as a result of the heating of tubes through which fluid enters and leaves the attemperator drum. With the attemperator drum arranged horizontally as shown, the inlet and outlet connections for cooling fluid may be made at locations distributed throughout the'length of the drum, so as to result in active circulation of cooling fluid throughout the interior of the drum, with minimum impedance to cooling fluid flow through the drum due to the relatively short and generally unidirectional path of travel therethrough. Furthermore,,the attemperator drum is top supported in common with all vapor generatingand vapor superheatingelements of the unit, and thus obviates the necessity of compensating for differential movement which otherwise might take place between different parts of the structure.

While in accordance with the provision of the statutes we have illustrated and described herein the best forms of our invention now known to us, 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 our claims, and that certain features of our invention'rnay sometimes be used to advantage without a corresponding use of other features.

We claim:

1. In a top-supported vapor generator of the type having; upright walls forming outer walls of a chamber through. which; hot gaseous products of combustion are directed and from which said gases are discharged through an upper gas outlet passage, said generator having a superheater positioned in the path of said gases, an attemperator comprising fluid conducting elements arranged to receive vapor from said superheater, and an attemperator drum enclosing said attemperator elements and horizontally positioned exteriorly of said chamber in parallel spaced relation to one of said walls so as to be shielded from the heat of said gases, the improvement which comprises wall cooling tubes associated with at least two of said walls and in one of said two walls comprising a lower row of upright wall cooling tubes below said drum and an upper row of upright wall cooling tubes above said drum, said tubes in said respective rows having upper and lower ends connected respectively to lower and upper portions of said drum so as to provide a support for said drum from tubes in said upper row and a continuous fluid flow path through said drum. and the tubes thus connected thereto, and fluid supply means connected to the lower ends of tubes in said lower row for causing cooling liquid to flow upwardly in series through said rows of tubes and said drum.

2. In a vapor generator, the improvement as claimed in claim 1 wherein tubes of said upper row are extended upwardly along a wall of said passage.

3. In a vapor generator, the improvement as claimed in claim 2 wherein the one wall with respect to which said attemperator drum is arranged parallel is formed in part as an arch having vertically spaced lower and upper inclined wall portions diverging outwardly from said chamber and defining an exterior recess within which said attemperator drum is supported clear of said arch wall portions.

4. In a vapor generator, the improvement as claimed in claim 3 wherein said gas outlet passage extends horizontally from said chamber and the upper wall portion of said arch forms the lower wall of said gas outlet passage, and wherein the wall providing said arch includes wall cooling tubes arranged in continuous lengths along said lower and upper arch wall portions.

5. In a vapor generator, the improvement as claimed in claim 4 and further comprising substantially straight and vertical tube lengths arranged above said drum in transverse rows adjacent opposite ends of said drum and having lower ends connected to said drum to form suspension means therefor in addition to forming fluid outlets therefrom.

6. In a vapor generator, the improvement as claimed in claim 5 wherein at elevations below said arch said tubes of said lower row are interspersed with said tubes providing said continuous tube lengths, and wherein said tubes of said upper row are interspersed with said continuous tube lengths along the upper wall portion of said arch.

7. In a vapor generator, the improvement as claimed in claim 1 wherein the one wall with respect to which said attemperator is arranged in parallel spaced relation includes an upper portion formed as an arch having vertically spaced lower and upper inclined wall portions diverging outwardly from said chamber and defining an exterior recess within which said attemperator drum is suspended clear of said arch portions, said walls with which said wall cooling tubes are associated including opposing side walls arranged transversely with respect to said wall having said upper arch portion, each of said side walls including rows of upright tubes respectively below and above said drum and having ends connected respectively to lower and upper portions of said drum at longitudinally distributed locations therealong.

8. In a vapor generator, the improvement as claimed in claim 7 wherein said lower and upper rows of side wall tubes are disposed in substantially vertical planes at ele vations below and above said arch, said tubes in said rows including tubes having end portions bent within said recess 10 for connection to said drum'at said longitudinally distributed locations.

9. In a vapor generator, the improvement as claimed in claim 8 wherein each upper row of said side wall tubes includes a group of substantially straight and vertical tube lengths symmetrically arranged with respect to the longitudinal axis of the drum and constituting suspension means for said drum. Y r

10. In a top-supported vapor generator having pairs of opposing upright walls forming outer walls of a combustion chamber from which gases are discharged through a gas outlet passage extending horizontally from an upper portion of said chamber, one of said walls having an upper portion formed as an arch projecting inwardly of said chamber, said arch having lower and upper inclined wall portions diverging outwardly from said chamber and defining an angular recess exteriorly of said chamber, said upper arch wall portion forming the lower wall of said gas outlet passage, an attemperator drum supended within aid exterioor recess in spaced relation throughout to said diverging arch wall portions, wall cooling tubes associated with a pair of said walls and in one wall of said pair including a lower row of upright wall cooling tubes below said drum having upper ends connected to a lower portion of said drum, an upper row of upright drum-supporting wall cooling tubes above said drum in substantially a common vertical plane with said lower row of tubes and having lower ends connected to an upper portion of said drum, an upper drum disposed above said gas outlet passage, and means for maintaining an upward flow of cooling liquid through said attemperator drum comprising fluid supply conduits connecting said upper drum to the lower ends of tubes of said lower row.

11. In a vapor generator, the combination as claimed in claim 10 wherein said wall cooling tubes are associated with a pair of upright walls arranged transversely with respect to said attemperator drum and forming opposing side walls of said chamber, and further comprising an upright division wall arranged intermediate said side walls and defining laterally adjoining sections of said chamber, said division wall comprising upright wall tubes which at elevations below said arch include a panel of tubes beneath said attemperator drum having upper ends connected to a lower portion of said attemperator drum at longitudinally distributed locations therealong, said panel of division wall tubes including tubes having end portions bent within said exterior recess for connection to said attemperator drum at said longitudinally distributed locations.

12. A vapor generator having upright walls forming opposing side walls of a combustion chamber and defining in part a gas outlet passage through which gases are discharged from an upper portion of said chamber, means defining an upright flue arranged exteriorly of said chamber and having its upper portion arranged to receive gases discharging from said passage, said chamber having an upright boundary wall arranged transversely with respect to said side walls and formed with an arch having lower and upper inclined wall portions diverging outwardly from said chamber toward the position of said flue, a superheater having a primary section and a secondary section disposed in the path of said gases with said secondary superheater section disposed upstream of said primary section at a location within said passage, conduit means connecting said superheater sections and arranged for vapor flow through said sections in series, an attemperator drum arranged exteriorly of said chamber between said diverging arch wall portions, vapor conducting attemperator elements disposed within said drum and forming part of said conduit means connecting said superheater sections, upright wall cooling tubes associated with each of said walls and in one of said walls comprising a lower row of said tubes having upper ends connected to a lower portion of said drum and an upper row of said tubes having lower ends connected to an upper portion of said drum, :said upright wall cooling tubes including tubes associated with said transversely arranged boundary wall and extending upwardly in continuous lengths from a position below said drum to positions above said drum along said upper arch wall portion which forms the lower wall of said gas outlet passage, and means including said lower and said upper row of tubes for maintaining an upward flow of cooling liquid throughsaid attemperator drum.

13. The combination with a top-supported vapor generating and superheating unit having rows of substantially upright vapor generating tubes in the walls of a heating gas pass, :of an attemperator drum positioned intermediate the height of said vapor generating tubes, at least some of said tubes opening to the lower portion-of said :drum and discharging fluid into the drum substantially at the saturation temperature of said vapor, tubes of said tube rows opening to the upper portion of .said drum arranged to-receive the fluid discharged to said drum, fluid conduct- References Cited in the file of this patent UNITED STATES PATENTS 1,757,343 Steinmuller May 6, 1930 2,305,611 Frisch Dec. 22, 1942 2,424,476 Marshall July 22, 1947 2,602,433 Kuppenheimer July 8, 1952 2,647,495 Moore Aug. 4, 1953 FOREIGN PATENTS 690,526 Germany Apr. 27, 1940

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