US1969405A - Steam boiler - Google Patents

Description

' Aug; 7, 1934. H J, KERR 1,969,405

STEAM BOILER Filed April 13, 1932 2 Sheets-Sheet 1 INVENTOR Howard J Kerr- ATTORNEY STEAM B ER Aug 7 1 Filed April 13, 1932 2 Shem- 2 Howard J p ATTORNEY Patented Aug. 7, 1934 STEAM BOILER,

' H'o'wa'rdJ. Kerr, Westfield, N. J assignor to The Babcock '& Wilcox Company, Bayonne; :N; J.,

. a corporation of New Jersey f Application A ril 13, 1932, Serial No. 604,977

7 Claims.

w presentinvention relates in general to watertubesteam boilers, and more particularly tothe construction and operation of water tube steam boilers which are characterized by the a? cation of, a steam andwaterseparating drum or drums at a distance above the highest point of Steam generation in a bank of natural circulation steamgenerating elements which is great as compared to the vertical distance between the highest and lowest points, of steam generation in that bank- 1 The general object of my invention is the provision'of a water tube boiler having an improved construction and arrangement of the fluid heating surface thereof. A more specific object of my invention is the provision of a high drum twostage watertube boiler with an improved arrangement and proportioning of the fluid conduit elements constituting the forced circulation steam generating stage. V a

,The various features of novelty which characterize my invention are pointed out with particularityinthe claims annexed to and forming a partJof 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 I have illustrated and described preferred embodiments .-.?9 of my invention.- 1

Of the drawings, Fig. 1 is a sectional elevation, partly diagrammatic, of a water tube boiler constructed in accordance with my invention; and Fig. 2 is a sectional elevation of a portion of the boiler shown inFig. 1, illustrating a modifiedarrangement of the heating surface.

The embodiment of the. inventionillustrated in Fig. 1 consists of a Water tube boiler unit having a fluid cooled furnace 10 of substantial fuel burning capacity and into which fuel is introduced and burned by a pair of oppositely positioned underfeed :stokers 11. The upper end of the furnace chamber is substantially in alignment with the lower end of a vertical heating gas pass 12.v A relatively shallow bank of natural circulation steam generating tubular elements 13 is positioned across the lower end of the gas pass 12. The tubes 13 receive preheated water from a transversely extending steam and water drum 14 located at a vertical distance above the highest point of steam generation in the tube bank 13 which is great as compared to the vertical distance between the highest and lowest points of steam generation in the tube bank. .Downtake circulators 15 connect the bottom .of the drum 14 to downtake headers 16 at the lower ends of the tubes 13. The steam generated in the tubes 13 passes through uptake headers 17 and uptake circulators 18 to the drum 14. I a I As shown in Fig. 1 the do. ntake circulators are bent laterally to define a portion of the gas pass. A vertical wall 19, having a lower ofist portion 20, extends vertically from the down take headers 16 to a heating gas outlet 21 at the upper end of the gas pass. The wall 19in; 5 eludes and is supported by the wall defining per tions of the downtake circulators. The opposite wall 22 of the gas passextendsupwardly from the uptake headers 17 at an inclination towards the wall 19 until the gas outlet 2l is reached. The uptake'circulators 18 line the wall substan-'- tially throughout its extent, and have horizontal portions 18 extending across the tapering gas pass directly below the gas outlet 21. i

It will be noted that in the above described con '7 5 struction only a small portion of thegas passis occupied by fluid heating surface. The remain ing portion of the gas pass is advantageously utilized for a compact and thermally efficient arrangement therein of a convection heated (superheater and a steamingfeconomizer. The s1i-, perheater consists of a series of return bend tubes 23 arranged in parallel vertical planes, and providing parallel fiow paths between the super!- heater inlet header 24 and outlet header 25. The legs of the tubes 23 are preferably arranged par,- allel to the tube bank 13 and between the wall portion 20 and the tube bank U Substantially all of the remaining portion ,of the gas pass 12 is occupied by the steaming economizer, which, as shown, isdivided into four super: posed tube sections 26, 27,. 28 and 29, each of which is formed by a horizontal series of return bend tubes 30 arranged in parallel vertical planes and provid ng parallel flow paths through these'c; .95 tion. Each tube of the economizer sections is formed in a. plurality of horizontal tube legs connected by vertical return bends. It will be noted that the available space is fully utilized bypro-v portioning the lengths of thetube legs to the hon- 1 zontal extent of the available space. Forexample, in the econo-mizer section 26, the lowermost tube leg is quite short, while the remaining tube legs progressively increase in length in accordanceiwiththe varying horizontal distance be- 10.5 tween the wall 19 and the uppermost row of superheater tubes 23. The tubes of the economizer sections 2'7, 28 and 29in the tapering p'ortion of the gas pass have tube legs progressively decreasing in length upwardly. 1-10 The economizer sections form part of a forced circulation steam generating stage of the boiler. Feed water is delivered under pressure to the tubes of the economizer section 29 through a header 31 by means of a suitable boiler feed pump (not shown) and passes through the parallel flow paths formed by the tubes into corresponding tubes in-tlie economizer section 28. Flow resistor elements may be incorporated, if desirable, at the inlet portions of economizer tubes in the bank 29. Each pair of corresponding tubes is connected by a detachable return bend member 32 located externally of the gas pass wall 19. The

return bend connections of adjacent tubes are preferably nested as indicated in Fig. 1. downfiow of water takes place in the economizer sections 29 and 28, and the heating surface of these sections is so proportioned that under all' normal conditions of operation the feed wateri temperature will not be raised to the corresponding saturated steam temperature before leaving these sections. a

"Ihe' lowermostv tube legs in the economizer section 28 pass through the wall 19 and are conhave passedover the superheater tubes. The heated water passes upwardly from the header 34 through the economizer sections 26 and 27 through parallel flow paths, corresponding tubes in sections 26 and 27 being connected by external return bends 36.

, The water flowing through the tubes of the secterposition of the mixing header 34. of "steam generation in all of the tubes of the tion 26 is rapidly heated to the saturated steam temperature and at some point therein steam is generated, the point of steam generation in each tube being substantially the same due to the in- The point lower economizer sections will vary with different conditions of operation. The heating surface in the several economizer sections is desirably so proportioned relative to the heat transfer surfacein said natural circulation bank and the heat output of the furnace chamber that no steam will be generated until after the lower legs of the tubes in the section 26 have been passed. The

. discharge ends of the tubes in the economizer 1 section. 27 are connected to the drum 14 by uptake and downtake circulators 37, which extend along the outer side of the inclined portion of the wall 22, and then horizontally across the gas passinto, the side of the drum 14. Steam separated. in the drum 14 passes from the drum throughsteam circulators 41 to the superheater inlet header 24.

'The'superheater and economizer sections are preferably supported from the uptake and downi take circulators 15 and 18 by means of cooper ating lugs 42 welded on the tube return bend portions and circulators 15 and 18. The circulators in turn are carried by hangers 43 depending from the steel framework surrounding the upper sections of the boiler and welded to the circulators 15 and 18, as indicated.

In operation, the heating gases generated in the furnace chamber 10 pass successively over the natural circulation'tube bank, superheater,

' economizer sections and the-horizontal portions of the circulators 37 and 18 to the gas outlet 21. The described arrangement of the fluid heating surface in the gas pass presents a substantially maximum amount of heating surface to the heating gases flowing through the gas pass. The absence of flow bafi'les in the single vertical pass avoids the presence of dead gas zones'and 'requires only a relatively 'small amount .of fan power because of the low draft loss present in the boiler. The rate of heat transfer in all portions of the gas pass is maintained high by the increased mass flow per unit area of heating surface the cooler portions of the pass provided by the tapered formation of the gas pass walls .in that section.

high thermalefficien'cy. In constructions however intended to carry varying boiler loads, a wholly countercurrent circulation of water throughthe economizer sections wouldbe disadvantageous, since whenever the supply-of feed water to-the unit was decreased substantially-i the steam generated in the lower sections of the its which the steam is generated are arranged for an upfiow of fluid therein parallel to the heating gas flow. With this flow arrangement all of the steam generated may freely pass upwardly to the drum 14 without affecting the water flow through the economizer. The heat transfer sur-' face in the tube bank 13, s'uperheater 23,- and economizer are proportioned relative to one another and to the heat output of the furnace cham her to insure that the heating gases contacting with the economizer will be of such quantity and temperature that no water will be evaporated in the economizer prior to entering theeconomizer section 26. The very slight loss in thermal'eificiency due to this arrangement is more than oli-setby the practical circulation advantages attained by its use. 1'

In the modification illustrated in Fig. 2, the pass is non-tapering and the tube legs on the banks 27, 28 and 29 are all of the same length and extend the full width of the pass. In this .-ar.- rangement, the economizer section 2'7 and the lower portion of the section 26. form a part of the water heating surface of the forced circulation stage, and all of the steam-generation in this stagewill occur in the upper portion of the sec-' tion 26. The use of special return bends 32 and 36 is avoided by an integral formation'of corresponding tubes in the several sections. Further-1' more, the junction header 34 between the down: flow and upfiow sections is also eliminated. The uptake circulators 37' connecting the section '26 with the drum 14 are. arranged within the heating gas pass rather than externally thereof, as in Fig. 1. The modification shown in Fig. 2 is other-; wise similar in construction and mode of operation to the construction shown in Fig. 1. While in accordance with the provisions of the statutes I have illustrated-and described herein the best form of my invention now known to those skilled in the art will understand that changes may be made in the'for'm of-the apparel tus 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. l

Iiclaim:

1. A water tube boiler comprising a furnac'e chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in the lower portion of said gas pass, a steam and water drum positioned above said bank, uptake and downtake circulators connecting said tube bank and drum, a forced flow economizer having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed economizer sections, each formed by a series of return bend tubes arranged in parallel and having parallel tube leg portions extending horizontally across said gas pass in the portion thereof bounded by said natural circulation tube bank, uptake and downtake circulators and drum, means interconnecting said economizer sections and providing a downfiow through a section in the upper portion of said gas pass and an upflow through a section in the lower portion of said gas pass, and a conduit connecting said last mentioned section to said drum.

2. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation bank of steam generating tubes positioned in the lower portion of said gas pass, a steam and water drum positioned a substantial distance above said bank, uptake and downtake circulators connecting said tube bank and drum, and a forced flow steam generating stage having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising a plurality of superposed water heating and steam generating sections, each formed by a series of return bend tubes arranged in parallel and having parallel tube leg portions extending horizontally across said gas pass in the portion thereof bounded by said natural cirulation tube bank, uptake and downtake circulators and drum, means interconnecting said sections and providing a downflow through water heating sections in the upper portion of said gas pass and an upflow through a steam generating section in a lower portion of said gas pass, and a conduit connecting said steam generating section to said drum.

3. A water tube boiler comprising a furnace chamber, a vertical heating gas pass in communication with said furnace chamber, a natural circulation steam generating stage comprising a bank of horizontally inclined tubes extending across said gas pass, a steam and water drum located a substantial distance above said tube i bank, uptake and downtake circulators connecting said tube bank and drum, a plurality of superposed economizer sections arranged in said gas pass in the portion thereof bounded by said tube bank, uptake and downtake circulators and drum, each of said economizer sections being formed by a series of return bend tubes arranged in parallel and having tube legs extending horizontally across said gas pass, means interconnecting said economizer sections for a serial flow therethrough, and. the tubes in the economizer section nearest said tube bank having tube legs progressively increasing in length upwardly;-

4."A water tube-boiler comprising-a furnace chamber, a vertical heating gas' pass incommunication witli -saidfurnace chamber,- anatural circulation steam generating stage compr'ising a bank" of horizontally inclined tubes- -extending across said gas pass, a steam and water dr'uiii located a substantial-distance {above said tiibe bank, uptake and downtake circulators coi'irie'cte ing said tube bank and drum, '2. convection-heat ed superheater comprising steain tubesPin-said gas pass above and extending'parallel to said tube bank, a plurality of superposed economizer sections arranged in saidgasip'as's in: the portion thereof 11 bounded by said superheater tubes, dip take and downtake circulators and drum, each of said economizer sections being formed by a series of return bend tubes arranged in parallel and having tube legs extending horizontally across said gas pass, means interconnecting said economizer sections for a serial flow therethrough, the economizer section nearest said superheater having tube legs at one side of and below the level of the upper ends of the uppermost superheater tubes and progressively increasing in length upwardly.

5. A water tube boiler comprising a furnace chamber, a vertical heating gas pass having a tapered upper section and in communication with said furnace chamber, a natural circulation steam generating stage comprising a bank of horizontally inclined tubes extending across said gas pass, a steam and water drum located a substantial distance above said tube bank, uptake and downtake circulators connecting said tube bank and drum, and a forced flow steam generating stage having a fluid flow therein independent of the fluid flow in said natural circulation tube bank and comprising superposed economizer sections arranged in said gas pass in the portion thereof bounded by said tube bank, uptake and downtake circulators and drum, each of said economizer sections being formed by a series of return bend tubes arranged in parallel and having tube legs extending horizontally across said gas pass, means interconnecting said economizer sections for a serial flow therethrough, the economizer section nearest said tube bank having tube legs progressively increasing in length upwardly, and the economizer section in the tapered portion of said gas pass having tube legs progressively decreasing in length upwardly.

6. A water tube boiler comprising a furnace chamber, a vertical heating gas pass having a tapered upper section and in communication with said furnace chamber, a natural circulation steam generating stage comprising a bank of horizontally inclined tubes extending across said gas pass, a steam and Water drum located a substantial distance above said tube bank, uptake and downtake circulators connecting said tube bank and drum, a convection heated superheater comprising steam tubes in said gas pass above and extending parallel to said tube bank, and a forced flow steam generating stage comprising superposed economizer sections arranged in said gas pass in the portion thereof bounded by said superheater tubes, uptake and downtake circulators and drum, each of said economizer sections being formed by a series of return bend tubes arranged in parallel and having tube legs extending horizontally across said gas pass, means interconnecting said economizer sections and providing a downfiow in a section in the tapered portion of said gas pass and an upflow in the section nearest said superheater, the economizer section nearest said superheater having tube legs atone sideof and below the levelof the upper ends of the uppermost superheater tubes and progres sively increasing in length upwardly, and the economizer section in the tapered portion of said gas pass having tube legs progressively decreasing in length upwardly, I v I ,7, In a steam boiler comprising a furnace chamben ayertical heating gas pass arranged for anupward flow of heating gases therethrough from said furnace chamber, and a st eam and water drum, a steaming economizer having an upper water heating section and a lower steam: ing section superimposed in said gas pass, each of said sections having a multiplicity of vertically spaced tubes connected in series and forming con; tinuous predeterminedflow paths insuring pro; gressive fluid heating from the inlet thereto ,to the discharge therefrom, means fonsupplying feed water under pressure to theinlet endiof the

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