US2579559A - Steam generator - Google Patents

Description

Dec. 25, 1951 L. M. FlNK 2,579,559

' STEAM GENERATOR Filed Dec. 19, 1946' '4 Sheets-Sheet 1 v54 290 I52 I56 INVENTOR Patented Dec. 25, 1951 STEAM GENERATOR Leroy M. Fink, Union, N. J assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New J ersey Application December 19, 1946, Serial No. 717,109-

4 Claims, (01.122-235) This invention relates to improvements in steam generators.

More particularly, the invention concerns improvements in steam generators of a radiant type in which thepredominating proportion of the steam is generated in closely arranged walltubes I which define the boundaries of a large volume combustion chamber.

The invention includes, in combination with the large volume combustion chamber, a superheater, economizer, an airheater, constructed and arranged in such a manner as to reduce costs of original installation and promote a high avail ability factor. To this :end, the superheater, economizer, and airheater consist of separate banks of upright and parallel tubes disposed in succession in the gas flow, rearwardly of an upright bank of tubes which constitute part of, the total steam generating surface. 1

The invention also includes the above arrangement of installation components in succession beneath a top steel-work frame from which the upright tubes of all of the various components are successively suspended from a common datum position.

' An object or the invention is to provide, in

such a combination as that above indicated, a

vertical tube cross-flow two-drum economizer which effectivelyutilizes the vertically extended space alongside a high combustion chamber.

It is also an object of the invention to provide a steam generator with the above indicated successive components arranged and constructed in such a manner that the heatexchange surfaces can be effectively maintained in good, heatexchange condition because of the minimization of horizontally inclined surfaces upon which deposited solids .can collect.

It is a further. object of the invention to pro,-

vide a steam generating installation of the above indicated type constructed and arranged with a wide dust hopper below both the economizer gas outlet and the airheater air inlet so, as to provide ample gas turning space and thereby give the installation a low draft loss characteristic while providing for the gravity separation of dust particles from gases for collection in, and periodic discharge from, a single hopper.

It is also an object of the invention to provide, in a steam generator having an economizer and airheater construction which markedly decreases installation costs, increases the accessibility of the tubes, and improves maintenance conditions. Installation costs are minimized by a construction and arrangement of the steam generator components which decreases the required amount of tube bends and requires a minimum amount of thermal insulation for the installation.

Further objects of the invention include the provision of a steam generator installation which facilitates cleaning of the tubes and their replacement when necessary.

The invention will be described by reference to the accompanying drawings in which a preferred embodiment of the invention has been illustrated.

In the drawings:

Fig. l is a vertical section through. the steam generator installation, showing the arrangement of the combustion chamber, upright banks of steam generating tubes, superheater, economizer, and airheater;

Fig. 2 is an enlarged vertical section of part of the installation, particularly showing the relationships of the tubes in the economizer construction, with its multiple gas pass provisions. This figure also shows the relationship of the economizer to the superheater and the airheater. This figure further indicates the manner in which the successive components of the installation are arranged and suspended in succession in from a common datum position and supported by a top frame of the heavy steel-work supporting the pressure parts of the installation;

Fig. 3 is a sectional plan of one-half of the symmetrical installation on line 3-3 of Fig. 1;

Fig. 4 is a view in the nature of partial plan showing the arrangement of the drums, headers and tubes to the top steelwork and the pressure part suspension means; and

5. is a diagrammatic view illustrating the construction and operation of the air preheater.

In steam generating installations, and more particularly installations of high capacity for operating electric power stations, reliability of operation, or a high availability factor, is of paramount importance, and those skilled. in the art will readily appreciate the prior art problems which have arisen from unclean heat exchange surfaces. These problems have been of particular concern with reference to economizer construction and operation. In many cases collections of solids from furnace gases upon the economizer tubes have not only involved high maintenance costs occasioned by the periodic removal of such solids, but have resulted in ultimate loss of efliciency of absorption capacity of the tubes between tube cleaning operations. These difliculties and others have resulted, in many cases, from the use of complicated economizer structures in which the tubes have had thereon a multiplicity of elements providing surfaces on which undesired deposits were made. The present invention avoids such difficulties by providing a simplified construction eliminating a multiplicity of tube bends in the original construction and enhancing maintenance by its increased accessibility of the tubes for cleaning or replacement. 7

The economizer I is shown in Fig. 1 cross baffled at E2 and It for the transverse flow of furnace gases across thetubes in gas passes It, (8 and 20 of large free flow'areal" The cross baiiies are steeply inclined, and for long life they are supported and cooled by some of the economizer tubes; For example, the upper cross baiile l2 of the economizer is supported upon the inclined mid-portions 22 of the front tubes of the economizer and is extended forwardly'from a position 24 in the economizer bank. "The front economizer tubes extend along the bailled position and then downwardly along the front wall 26 of the economizer to the lower economizer drum 28. The upper parts (it of these tubes extend forwardly from the upper economizer drum 32 and downwardly to a position adjacent the superheater to support and maintain the refractory and thermal casing insulationshown at 34 and 36.

The upper cross bafiie l2 of the economizer is also so arranged as to constitute a' substantialcontinuation of the downwardly inclined wall 40 beneath the superheater 32. This Wall is cooled. and supported by the downwardly inclined sections 44 of the rear row of steam generating tubes which constitute circulators connecting the main steam and water drum of the installation with the submerged drum. These tubesalso have upper roof sections 46 extending 'rearwardly over the superheater to a position adjacent theupper parts 30 of the front row ofjeconomizer tubes adjacent the upper economizer drum 32, From that position mid-portions 48 'of' the circulators extend downwardly toward the upper economizer bafiie l2.

With this construction the heating gases pass through the upper part of the economizer to a position rearwardly of the main bank 50 of economizer tubes where ample space is provided for the turning ofthe gases rearwardly of the main bank of economizer tubes and forwardly of the rearrow 52 of the economizer tubeswhich are disposed vertically between the air heater and the economizer above the lower cross baflle M of the economizer. From this position-"intermediate sections 56 of these tubes are inclined downwardly to afford fluid cooling elements and supports for the lower economizer baffle M. This. baflle consists of appropriate refractory material closing the spaces between the tube sections 55 and extending downwardly at a sharp angle of the order of the inclination of the upper economizer battle !2.

The gas turning space at the rear of the first economizer gas pass I 6 is continued to a position justabove the lower economizer cross baflie I d and at the entrance of the second economizer pass it, in the interests of low draft loss.

- Below the lower economizer cross bafiie ample gas turning space is provided at 6B for the gases turning from the outlet of the second economizer gas pass 18 to the inlet of the third gas pass 20, this turning space being provided by the spacing of the lower sections 52 of the front row economizer tubes considerably forwardly of the main bank 50 of economizer tubes.

From the gas turning space 60 below the upper economizer cross baflie, gases pass rearwardly over the lower sections of the economizer tubes and into the lower gas turning space 64 beneath the lower economizer cross baflie. From this turning spac the gases pass downwardly to a position above the large dust hopper construction 66 which extends entirely across the gas outlet 68 of the economizer as well as the gas inlet HI-for the air heater. In this gas turning space, several factors contribute to the separation of suspended solids'ffro'm the furnace gases. One

' of these is the downward flow of the gases from the last economizer pass into the dust hopper. A second is the change in direction of the gases in the ample turning space provided in the dust hopper construction, and a third factor is the further turning of the gases as they move to process 'to' 'passbpwardlythrough the tubes of the air heater. 1 Thea'ir heater'54 consists ofa banklZof upright and horizontally'spaced'tubes fixed at their lower ends to 9, lower'tub'esheetH and 'attheir upper'endsto anupperv tube sheet 'lfi'at aposition'clo'se' to theupp'er rectangular 'frame 'IBof the steel-work. Appropriate "transverse baffles BIL-83 (-Figl 5) across said tubes provide for air flow'dnthe multiple passes 85-40 externally of the tubes "for' the purpose'of effectively heating air-to-b"d ivered tothe furnaceor' combustion .chamb J The economizer and as heater are separated by'the common wali 92 closely adjacent the rear tubes5 2 of; tlie economizer and the front tubes olf 'th anteater as clearly indicated 'in" Fig'.' 2.

a marked simplicity 'inbonstruction is attained with attendant decreased upkeep and in original installation costs 'the'w'all '92 being cooled bythe economizer 'tub'ef52, on one sidelyand by the 'front' row or air" preheatei" tubes on the other side? up U V.

It is to b'notdthat' the top tube sheet 16 of the airheater is disposed at a position ad- 'jaqnt'tne' eta gunrrdp frame l8 of the steelworkfAs indicatd'in Figl l, this tube sheet is in position to be directly secured "to rearwardly dissoseaibesins'sueh as the beam 94 (Fig. 1)) of the top"fframe:work"which are disposed in the "s me horiz' ntal tale with zhorizon'tally disposed d. fixe'. ...i 'i r'amslb the te sr portin the .e qnqm z t r e ter. widths ste m nerat n -l Just, iorward o he bn are Shbwn a ser or s spens n ro s: 2 an 1 by which the tubes, headers and otherpressure parish: \theh u erhhea r co s r s ipn. ar s po e it mth lx l a ylbeamso the t p a e: T c ol .mizer 1 is s m a y supp rt dby th drum straps I l 4 Eorwardly of the 1 superheater usp n in stru t a e, the e v -sh rs str p 1.16 for su po th v ea d water dru n l lg. A These extend upwardly, through t he top frame work components such as I20,

of heavyconstructionr,

Forwardly oi the steam and water drum H8, there are a nuinber of suspension rods (not shown) for similar suspension of the headers, tubes and pther pressure parts of the combustionchamber l30 se'ction of the installation.

Thus, the pressure parts of the combustion chamber, upright bank of steam generating tubes I32, upright banks of superheater tubes, economizer, and airheater, are top suspended from a unitary frame at the top; oi the steel-work In this manner, not only are expansion and construction" problems simplified, but maintenance problems and'costs are materially reduced.

"The "combustion chamber illustrated in the drawings is of a height of the order of 100 feet. Its other dimensions being indicated by the proportions of Fig. 1. The lower part of the combustion chamber involves a hopper construction I34, the downwardly converging hopper walls I36 and I 31 of which are defined by the lower sections of the front and rear wall steam gencrating tubes I40 and I42. Alternate tubes at their lower ends are bent downwardly to the positions indicated at I50 and 'I 52 and are connected to the lower headers I56 and I53 which in turn are in communication with the water space of the steam and water drum H8 through the agency of suitable tubular connections not shown.

' The steam space of the steam and water drum H8 isin communication with the superheater 42 through the agency of a series of tubes having roof sections such as I 60 and I62 leading horizontally to a position toward the rear of the superheater where they have vertical sections such as I68, downward extensions of which constitute the rear tubes I!!! of the superheater. From this position at the rear of the superheater, the steam flow from these tubes continues through connections including the successive multiple loop return bend tube sections I8llI88 which lead to the rearward upper (and intermediate) superheater header 200. The flow is upward through the upright tube sections I81), I82, I84, I86, and I88, and downward through the alternately disposed sections I8II83, I85 and I81, it being understood that these sections are serially connected at their upper and lower ends by the return bends ISO-I98. With this construction, the tubular sections I88 act as pendant supports from the header 200, with this part of the superheater balanced on either side thereof. From this header, the steam flows through appropriate connections to an attemperator and returns from the attemperator to the header 202. From the superheater header 202, the steam flows successively through the similar upright tubular sections 2III-2I3 which are disposed as a bank of tubes, just rearwardly of the access space 2I4. These tube sections are connected for continuous steam flow by the return bends 22ll222. Beyond this position, the steam flow is through the wide return bends 230, and then successively through the upright tube sections 2-39233, connected for series flow by the return bends 23Ii238, these elements constituting the forward bank 240, of superheater tubes, pendantly supported through the hangers I03, the header 242 and the tube sections 233. From the header 242 the steam flows to a point of use.

The illustrative arrangement of the steam generator installation components minimizes the refractory material and thermal insulating material required forcasing construction, and further reduces original installation costs by the simplification of the casing construction. For example, the successive elements such as the superheater, eoonomizer, and airheater tubes are arranged alongside each other and in parallel vertical positions so that a minimum of refractory material is required between those successive components. Again, the construction of the economizer is such that its bafiles require a minimum of refractory materialy. the disposition of the various steam generating installation components described above in successive vertical positions simplifies the casing construction at the top of the installation and materially reduces the amount of refractory material and thermal insulation material required at that position. These factors are not only of importance with respect to the original installation costs, but they are also of considerable importance with respect to subsequent maintenance in which access must frequently be had to the tubes of the components of the installation. In such cases, and when the construction and arrangement of the components is such that a minimum amount of casing materials is required, the amount of such materials to be removed and replaced for repairs on any single component are obviously markedly reduced.

The arrangement ofthe components of the illustrative installation is also such as to afford the optimum use of a given horizontal area. This not only results from the closely arranged banks of vertical tubes which constitute the different components, but also from the particular construction of the combustion chamber I30 which permits the disposition of the vertical bank of steam generating tubes I32 and a substantial part of the superheater surface within the up wardly extended confines of the main part of the combustion chamber. This point will be clear from. an inspection of Fig. 1 wherein the upper part 259 of the combustion chamber forwardly of the bank of tubes I32 is much. narrower than the ignition zone of the combustion chamber adjacent the burners 252-254. The upper parts 256 of the rear wall tubes I42 are upwardly inclined toward front wall tubes I40, and these parts extend inwardly for a distance greater than one-third the depth of the combustion. chamber from which point they extend to a direct connection with the submerged drum 2%.

The burners 252-254 are supplied with preheated air through the duct-work which includes a burner casing 258 connected with a transversely extending lower duct 260. The latter is connected on either side of the furnace by a rearwardly extending duct such as 262 with an upwardly extending duct 264which leads to the airheater inlet 266 (Fig. 5).

Fig. 1 also discloses the upright tubular memher 270 providing the attemperator chamber with its outlet connected by the conduit 2'32 with the intermediate superheater 202. This attemperator is preferably of a type such as that illustrated in. the pending application of Fletcher and Huge, filed on August 17, 1946, S. N. 691,274, Patent Number 2,550,683.

Referring again to the economizer, its lower drum 28 is connected with a source of feed water by appropriate connections (not shown). and the upper drum of the economizer is in communication with the steam and water drum H8 by the tubular connections 280 and 282. These connections preferably lead to a drum inlet chamber from which the steam and water mixture passes to steam and water separating devices from which steam and water separately pass to the respective steam and water spaces of the drum. Such an inlet chamber associated with such steam and water separating devices is indicated in Fig. 2 of the U. S. patent to Fletcher et al.,2,271,634, February 3, 1942.

With reference to the circulatory connections for such a steam generator as that shown in the drawings, it will of course be understood that there are appropriate and preferably external tubular connections between the water space of the drum I l8 'andthe'msubmerged drum :8. Similar down'c-orne'rs will'also connect the water space of the d-ru mllt'with-the'lower headers for the wall tubes of the combustion chamber, such headers as those shown at I54 and I56. The lower headers for the combustion chamber wall confronting the observer in Fig. 1 of the drawings are indicated at 290', 252, and 294 at the lower part of this figure. It will alsobe understood that the tubes of this wall may be connected to a similar header or headers at a level above that or the cornbustionchamber and that these top headers may be in communication with the steam and water inlet chamber of the drum H8 by appropriate circulators.

The economizer tubes of the main bank of tubes 50 arearranged" in front to rear rows as indicated in Fig. 3. This enhances the functioning of the soot blowers 300-303 (Fig. 2), the jets of which are aligned with the spaces between the rows of tubes. 'The general downfiow of gases and the arrangement of upright tubes also further enhance the removal Of solids from the tubes by the action'of the soot blower jets. The larger gas turning spaces on either side of the main bank of economizer tubes as well as the cavity between the superheater'and the economizer further improve the removal of solids from the tubes by the soot blower. These spaces also facilitate'access to the tubes, and to take advantage of this construction large access doors are provided as indicated at 3 i 0-,3 I 3.

I claim:

1. In a steam generating installation of high capacity, upright and closely arranged steam generating wall tubes constructed and disposed to define boundaries of a vertically elongated combustion chamber, steelwork including a top frame above the combustion chamber, a steam and water drum suspended from said frame and having said tubes connected thereto, said combustion chamber havinga lateral gas outlet leading to a rearwardly tapering gas pass at a level below that of the drum, a submerged drum, a steam generating convection section including upright tubes extending across said gas pass and directly connecting said steam and water drum and said submerged drum, a superheater including a bank of upright multiplelocp tubes disposed transversely of the gas fiow in said gas pass, superheater headers, means suspending the superheater headers and tubes from said frame, circulator tubes connected to said drums and extending around the superheater in vertical planes and having sharply downwardly inclined portions disposed beneath the superheater and leading toward the-submerged drum and combining withbafile forming material to define the lower boundary wall of said rearwardly tapering gas pass, a two drum bent tube economizer including long upright tubes extending from an upper position nearthe level of the top of the convection section and the superheater to a position below ,the level of the superheater, the upright extent of the economizer being a substantial part of the height of said combustion chamber and the entire installation, an air heater including long uprigh tubes disposed in a bank in parallelism with the economizer tubes and of a vertical extent of the order of that of the economizer, the main part of said economizer bank being spaced substantially rearwardly of said superheater and substantially forwardly of the air heater to present cavities at said positions of spacing, front tubes of the economizer bank having interm'ediate parts inclined sharplyrdowne wardly in a substantial continuation of -the-mclined parts of said circulator portions and-supporting an upper cross-baffle for theeconomizer, said upper cross-baflie extending over'a gas turning space in front of the economizer bankand terminating forwardly of the rear'of the'economizer to separate the first two cross passe,s.;(gas) of the economizer, the upper cross-bafiie disposed as a substantial continuation of the lower boundary wall of the tapering gas pass, rear tubes of the economizer having upper parts spaced ,rearwardly of the main part of the economizer bank extending downwardly alongside the air heater to a level intermediate the level of said crossbaffle and the level of the lower economizer drum and then having sharply downwardly inclined parts extending from'that position forwardly to the main part of the economizer bank, baffle forming material supported by said-last men'- tioned inclined parts to form an economizer lower cross-baffle, and a dust hopper extending across the gas outlet of the economizer and the gas inlet of the air heater.

2. In a vapor generating installation of "the type having heating gases passing from a com.- bustion chamber across and externally of the spaced upright tubes of a convection vapor generating section, a vapor and liquid drum to which the upper ends of the tubes are connected, and a submerged drum connected to the lower ends of the tubes; the combination therewith'of a convection superheater including multiple loop upright tube sections disposed in a'bank rearwardly of the convection section, fluid circulators directly connecting said drums and extending around the superheater in vertical planes with their lower portions sharply inclined downwardly beneath the superheater toward said submerged drum and disposed in wall alignment, a main bank of upright economizer tubes spacedre'ar wardly of the superheater and having their up per portions forming an upright gas flow screen subject to a continuation of the gas flow'from the superheater, upper and lower economizer drums to which the economizer tubes are directly connected, the economizer also having a rear row of upright tubes with parts spaced substantially rearwardly of said main bank of tubes near its upper portion and having their intermediate portions sharply downwardly inclined toward a position intermediate said main bank to constitute a support for a lower economizer crossbafiie, said tubes extending alongside the tubes of the main bank below said cross bafile, others of said upright economizer tubes having portions sharply inclined downwardly and forwardly of said main bank to'constitute supports for an upper economizencross-bafiie, the lower parts of the latter tubes being spaced substantially forwardly of the main bank of economizer tubes to provide a gas turning space of large volume at the outlet of the second gas pass of the economizer and inlet of the third gas pass below said lower baffle, an air heater including a vertically elongated bank of tubes disposed alongside the upright economizer tubes, and a dust hopper below the economizer gas outlet and air heater gas inlet.

3. In a vapor generating unit of the type having means constituting a source of heating gases, at superheater and an air heater; the combination therewith of a fluid heating component of said unit interposed relative to the air heater and superheater and having upper and lower drums and a bank of upright tubes directly connecting said drums and disposed in the path of said gases, first wall means extending upwardly from said lower drum adjacent the forward side of said bank and terminating in downwardly spaced relation to said upper drum to form the lower limit of a gas inlet into said bank from the super heater, and second wall means extending down wardly from said upper drum along the front surface of the air heater and adjacent the rearward side of said bank and having a part terminating in upwardly spaced relation to said lower drum to separate lower cross tube gas passes leading to a gas outlet from said bank to the air heater, each of said wall means having a portion substantially spaced from the majority of tubes of said bank to form a wall of upper and lower substantially unobstructed gas turning spaces opposite said inlet and said outlet respectively, said second wall means having a part terminating within said bank in a lower end portion inclined downwardly toward said lower gas turning space, said bank of tubes including a forward row of tubes having intermediate portions inclined forwardly from the majority of tubes of said bank and disposed along an intermediate inclined portion of said first wall means in cooling and supporting relationship thereto, said bank of tubes also including a rearward row of tubes having intermediate portions inclined upwardly and rearwardly from the majority of tubes of said bank and disposed along said inclined portion of said second wall means in cool ing and supporting relationship thereto, said tubes in said rows having end connections to said drums at the same side of said bank from which said tubes are respectively inclined.

4. In a vapor generating unit of the type having means constitutin a source of heating gases,

a superheater and an air heater; the combination therewith of a fluid heating component of said unit interposed relative to the superheater and the air heater and having upper and lower drums and a bank of upright tubes directly connecting said drums and disposed in the path of said gases, first wall means extending upwardly from said lower drum at a position forwardly of the main part of said bank and terminating in downwardly spaced relation to said upper drum to form the lower limit of a gas inlet into said bank from the superheater, and second wall means extending downwardly from said upper drum along the front surface of the air heater and adjacent the rearward side of said bank and having a part terminating in upwardly spaced relation to said lower drum to separate lower cross tube gas passes leading to a gas outlet from the lower part of said bank to the air heater, each of said wall means having a portion substantially spaced from the majority of tubes of said bank to form a wall of upper and. lower substantially unobstructed gas turning spaces opposite said gas inlet and said gas outlet respectively, said second wall means having a part terminating within said bank in a lower end portion inclined downwardly toward said lower gas turning space, an upright flat metal air heater wall constitutin a part of the second wall means, said bank of tubes including a forward row of tubes having intermediate portions inclined downwardly and forwardly from the majority of tubes of said bank and disposed along an intermediate inclined portion of said first wall means in cooling and supporting relationship thereto, said bank also including a rearward row of tubes having intermediate portions inclined upwardly and rearwardly from the majority of tubes of said bank and disposed along said inclined portion of said second wall means in cooling and supporting relationship thereto, the rearward row of tubes including parts extending in wall cooling relationship alon said upright flat metal wall, said tubes in said rows having end connections to said drums at the same side of said bank from which said tubes are respectively inclined.

LEROY M. FINK.

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

UNITED STATES PATENTS Number Name Date 1,704,132 Jones Mar. 56, 1929 1,862,367 Connelly June 7, 1932 2,158,509 Kuhner May 16, 1939 2,293,040 Baile Aug. 18, 1942 2,354,059 Rehm July 18, 1944 2,416,053 Grossman Feb. 18, 1947 2,515,443 Ebbets July 18, 1950 OTHER REFERENCES Page 126 of the November 26, 1929, issue of Power, a magazine published by McGraw-Hill Co., New York city.

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