US2212115A - Steam boiler - Google Patents

Description

Aug. 2o, 11140.4

G D. EBBETs Er Al.

STEAM 110111111l NVENTORS bbets george D1 eci g ATTORNEY.

Aug.'20, 1940. G. D. EBBr-:Ts Er Ax. 2,212,115

STEAM BOILER y Filed May 4, 1957 l5 Sheets-sheet 2 o o o o o o 5 I9 ooooooooooooocfoooooo ,r11 nrw OOOOO Aug. 20, 1940. G. D. l-:BBi-:Ts ET Al. 2,212,115

STEAM BoILER Filed May 4', 1957 5 Sheets-Sheet 3 George D Ebgg/ENTORS Cecil Gay Aug 20, 1940. G. D. EBBETs Er A1. 2,212,115

STEAM BOILER Filed May 4, 1937 5 Sheets-Sheet 4 f INVENTORS 7///////////////,'////////////////////////////////////11 1 9M/ye D Ebbs HGag/A.

ATrRNEY.

Aug. 2 0, 1940.

G. D. EBBETS ET AL STEAM BOILER Filed May 4. 1937 oooooooo oooooua Fl-c - INVENTOR5 George D. [5b/Jets i Cecil H" @my IEY.

5 Sheets-Sheet 5 Patented Aug. 20, i940 narrar orties STEAM BILER George D. llbbets, Kenilworth, N. J.; and Cecil H. @Sl-ay, Akron, hio, assignors to The Babcock @c Wilcox: @ernaar Newark, N. J., a corporation of New Jersey application May 4, 1937, Serial No. 140,724

ll) Claims.

This invention relates to the construction and operation of steam generating units, and particularly to water tube steam boilers of the Babcock & Y

cated in a zon-e in which the heating gas temper-- atures are sufciently high to secure the relatively high iinal superheat temperature desired, but yet not sufficient to cause overheating of the superheater tubes when the steam ow through the superheater tubes is within the probable operating range. The liability of such superheater tubes to be voverheated is considerably increased when the steam flow through the, superb-eater is low, as during starting-up periods before the initiation of an appreciable lsteam flow.

A further problem in steam boilers of the character described is the difficulty of maintaining a uniform iinal superheat temperature over the boiler operating range. It is known that such convection heated superheaters normally have a iinal superheat temperature curve with a rising characteristic with increase in boiler load when the amount of gases passing over the superheater surface is directly proportional to the products of combustion.

For the foregoing reasons, it is recognized as highly desirable to control the amount of heating gases passing in heat transer relation with the convection heated superheating surface. One type of such control which has been heretofore proposed consists in by-passing a variable portion of the heating gases around the superheater. Such by-pass arrangements are objectionable as they usually require a special and expensive construction of the boiler, are not readily adapted for incorporation in existing boilers of standard design, involve the loss of a considerable portion of boiler generating surface having a high rate of heat transfer when the by-pass is closed and inoperative, or require the use of control dampers in locationswhere the heating gas temperature conditions are excessive and cause overheating of the dampers or render them ineffective, to the extent that the over-all operating eiilciency of the unit may be reduced.

(ci. 12a-wisc) a double deck steam boiler of the type described which is characterized by its relatively simple and low cost of construction, effectiveness over a wide range or" boiler operating conditions, adaptability for incorporation in existing steam boilers of standard design, relatively small amount of low rate heat absorbing surface render-ed ineffective when the lay-pass is closed, improved l0- cation and construction of the bypass control dampers, and effective control of the amount of heating gases contacting Wtih the superheater tubes over a wide range of operating conditions.

The various features of novelty which characterize the 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 20 illustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a steam boiler constructed in accordance with the invention;

Fig. 2 is a half section taken on the line 2 2 of Fig. l;

. Fig. 3 is a vertical section showing the damper operating mechanism;

Fig. 4 is a view similar to Fig. 1 of a modied construction;

Fig. 5 is a partial vertical section taken on the line 5 5 of Fig. Ll;

Fig. 6 is ka horizontal section taken on the line E of Fig. 4;

Fig.. '7 is a somewhat diagrammatic sectional elevation of another modification;

Fig. 8 is a vertical half section taken on the line 3 8 of Fig. 7; `and Fig. 9 is a horizontal section taken on the line 9 5 oi Fig. 7.

The steam boiler illustrated in Figs. 1 to 3 of the drawings is of the Babcock 8l Wilcox double deck cross drum type comprising a lower bank of horizontally inclined steam generating tubes lil eX- tcnding between vertically arranged sectional downtake anduptake headers il and i2 respectively, and arranged acrossI the upper end of a i water cooled furnace i3 adapted for the burning of fluid fuel, such as pulverized coal, oil or gas, in suspension at high rates of heat release.

As shown in Figs. l and 2, the lowermost rows lila of the tube bank are arranged to form a boiler slag screen, while the remaining rows are arranged in vertical alignment. The headers II and I2 are connected by nipples I4 and I5 respectively, to corresponding downtake and uptake headers I 6 and I 'I respectively, between which extend staggered rows of horizontally inclined steam generating tubes I8 forming an upper steam generating bank. The headers I'I and I6 are connected, by horizontal circulator tubes I9 and downtake tubes 20 respectively, to a steam and water drum 2l .extending transversely of and above the tube banks. A space 22 is thus provided between and extending the full length of the tube banks.

The steam generating surface described is provided with a baille system which in conjunction with the boiler setting defines a single upflow heating gas pass across the lower tube bank, and a plurality of serially connected upilow and downow gas passes across the upper tube bank. As shown, a refractory baffle 23 extends from the downtake headers II along the uppermost row of tubes I of the lower bank for a portion of their length, thence vertically and forwardly through the interdeck space 22 and vertically across the tubes I8 of the upper bank. A second transverse baille 24 extends downwardly and rearwardly from one side of a gas outlet 25 to the upper bank and vertically across the same. The described baille system is well known in steam boilers ofthis type, and in conjunction with the boiler setting provides a single upflow heating gas pass 30 across the lower tube bank I2 which communicates through a tapering portion of the interdeck space 22 with an upflow gas passf3I at the uptake end of the upper tube bank. The gas pass 3I is serially connected over the upper end of the baillle 23 with a downilow g-as pass 32 which in turn communicates below the lower end of the baille 24 with a second upilow gas pass 33 leading to the gas outlet 25. The heating gases leaving through the gas outlet 25 may be passed through a feed water economizer, or air heater, o-r both, before reaching the stack.

In steam boilers of the character described the interdeck space 22 is ordinarily utilized for a convection heated steam superheater, as the gas temperatures in this section are sufficient to effect the high nal superheat temperatures now required in high capacity units, while the superheating tubes are protected from excessive heating gas temperatures in normal operation. by the lower tube bank. As shown, the uptake .end of the interdeck space 22 is occupied by a bank of multiple looped horizontally extending superheating tubes 35 arranged in flat side-by-side unitary coils for the full width of the boiler. 'I'he lowermost tube leg of each coil is connected to a superheater inlet header 36 at the downtake side of the baille 23, receiving steam from the drum 2I through tubes 31. The uppermost tube leg of each coil has a portion extending downwardly along and supporting an inclined portion of the baille 23 with its lower end connected to a steam outlet header 38. The uptake end of each superheater tube coil has an expansible supporting connection with Aa corresponding nipple I5. With the described boiler construction the heating gases pass upwardly across the lower tube bank, thence upwardly across the superheater tubes 35, and successively through the heating gas passes 3|, 32, and 33 to the gas outlet.

In accordance with the invention, a heating gas by-pass around the superheater is provided by terminating the downtake ends of the superheater tube loops forwardly of the baille 23 and embedding the same in the refractory baille 40 extending the full width of the interdeck space 22 and defining the uptake side of a relatively narrow by-pass 4I between the baille 40 and the baille 23. The baille 40 and the downtake end of the superheater tubes are supported from an auxiliary header 42 extending transversely below the upper bank, and receiving a supply of water from certain tubes I Ila in the lowermost row of the upper bank. 'I'he header 42 is connected by spaced supporting tubes 43 extending upwardly intermediate the tubes I8 to the drum 2I. The tubes 43 are supported by vertical hanger rods 44 carried by the external steel work. A vertical baille 45 extends across the upper tube bank alongside the tubes 43 from the header 42 to the uppermost row of the bank to dene the uptake side of the bly-pass 4I across the tube bank. With the by-pass 4I open a substantial portion of the heating gases leaving the lower tube bank would pass upwardly across the upper tube bank without contacting with the superheating tubes except for the relatively small portion thereof formed by the connections to the inlet and outlet headers. On reaching the top of the by-pass, the by-passed gases join the heating gas stream which has passed over the superheater tubes and the combined gas streams pass over the upper end of the baille 23 and downwardly through the gas pass 32.

'I'he heating gas flow through the by-pass is eiectively controlled in the present construction by means of a row of dampers 50 extending across the upper end thereof. Each of the dampers 50 is formed by a shallow rectangular box of heat resistant alloy steel filled with heat insulating material. Each damper is pivotally supported as indicated at I on the upper end of the baille 45, and when in its closed position extends along the uppermost row of tubes I8 with its downtake end resting on the upper end of the baille 23. Each damper extends across a plurality of the tubes I8 in the uppermost row of the upper bank substantially in contact therewith, so that a substantial cooling effect is effected by these tubes on the damper when the damper is in its closed position. Even when the damper is in its fully open position, indicated by the broken lines in Fig. 1, the subjacent tubes I8 will exert a substantial cooling effect.

The damper operating mechanism illustrated comprises an adjustable link rod 52 pivotally connected to the downtake end of the damper and to a lever 53 carried by an operating shaft 54 and having an adjustable counterweight 55. The shaft 54 is a common operating shaft for a number of dampers and is actuated by a reversible electric motor 56 through a speed reducer 5'I. A sliding seal 58 is provided in the top of the boiler setting to permit vertical and lateral movements of each link 52.

In the modified steam boiler construction illustrated in Figs. 4 to 6 the interdeck superheater 60 extends horizontally in the interdeck space the full length of the upilow heating gas pass, with its downtake end supported from a downwardly and rearwardly inclined extension 6I of the uppermost superheater tube leg of each coil, which in turn is supported from the upper tube bank at Gla. The main boiler baille 62 is formed by tile extending between the tube legs 6I and a row of water tubes 63 extending parallel to the tube legs 6I, with their upper ends engaging a transverse header 64 to which spaced groups of tubes in the lowermost row of the upper bank are connected. The upper portion 62a of the balile 62 extending-across the upper tube bank is inclinedto provide tapering gas passes across the upper bank. The lower ends of. the tubes 63 are connected to a header 59 ,incorporated in the downtake nipples. Hanger rods S1 provide a support for the tubes 63. The transverse baiiie section 62a divides the space occupied by the upper tube bank into an upflow gas pass 65 and a downflow gas pass 66. The downtake corner portions of the downlow pass are occupied by the upiiow superheater by-passes 'lll hereinafter described.

The front wall of each superheater` ,by-pass `'iii is defined by a refractory baiile @il which is supported on and extends upwardly, from the tubes 53 at a point adjacent the lower end of the superheater. The portion of each baiile 68 extending across the upper tubebankisof poured refractory, and extends the full height of the upper tube bank. rEhe inner side wall of each by-pass, as shown in Fig. 5, is defined by a re-brickand plastic refractory wall 69 carried by the tubes S3 and extending throughout the space at the rear of and above the baiiie 52 between the baille 68 and the rear wall of the setting. As indicated in Fig. 5, the portion of the baille S2 which would be below each by-pass 'it is omitted to permit an uplow of heating gases through the 1:2y-passes.

The control mechanism for regulating the heating gas flow through each by-pass consists of three pivoted dampers 'li similar to those shown in Figs. l to 3, movable between the full line closed positions and theV broken line open positions indicated in Fig. 4. Each of the dampers `is operated by an adjustable rod 'l2 of heat resistant alloy steel connected to a common operating shaft i3 by a lifting arm iii. rlhe shaft i3 is osoillated by a bell crank lever 'l5 carrying a counterweight 'i6 and connected to a suitable external oscillating mechanism (not shown) e With the described construction the main path of heating gas flow from the furnace chamber will be upwardly across the lower tube bank, superheater, and the'portion of the upper tube bank at the uptake side of the baie 62e. `The gases then turn over the upper ,end ofthe baffle 5E@ and pass downwardly through the portion of the downflow gas pass l@ between the by-passes 'lll to a gas outlet "it, The arrangement of the bfi-passes and their control dampers in the downtake corners of the setting vsubstantially reduces the heat transfer to the dampers when in their closed position. When the by-pass dampers are partly or fully open, a portion of the heating gases-leaving the lower tube bank will by-pass the superheater and iiow vertically past thesides of the balie t2 into each .by-pass.` rI'he gases iiowing through the lay-passes passover the upper ends of the baies 63 and 59 and join the gas stream ilowing downwardly through the surrounding downlow gas pass 5 to the gas outlet 18.

In the modiied construction diagrammatically illustrated in Figs. 7 to 9, the superheater tube coils Sil extend the full length of the space between the main boiler b aiie Q33 and theuptake nipples, but as shown in Fig. 8, terminate short of the side walls ofthe setting. A vertical .baffle 82 extends along each side of the superheater between the tubes i8 of the upper bank tothe uppermost tube row of the upper bank to denne a vertically extending superheater b-,y-pass B3 at the uptake side of the baffle 23 between one of the baffles s2 and the adjacent side wall of the setting. A row of externally operated control dampers 8i is located at the `upper end of each bY-pass along the top row of the upper bank. With the described construction the by-passed gaseswill now upwardly at each side of the gas streamthrough the upow pass at the uptake end, merging with that stream to ow through the subsequent downow and upflow gas passes of the upper bank. ,f

. In all of the boiler constructions illustrated the superheater by-pass or .by-passes are formed by vertical non-tortucus upflow gas passages. The pressure drop through these passages. is conse, quently utilized for heat transfer purposes rather than in effecting changes in .direction of the gas ow. The pressure drop through each by-pass will obviously be lower than through the gas pass containing the superheater, andconsequently an effective control of the hea-ting gas ow across the superheater canv be maintained even at low boiler ratings. The only heat absorbing surface included in each yby-pass is part of the upper 'bank of generating tubes which operate with a substantially lower rate oi? heat absorption than the surface in the lower bank, thus utilizing secondary heating surface of the boiler to secure adequate protection of the by-pass control dampers and reduce .the gas temperature sufficient to maintain overall unit thermal efficiency. The construction and location of `these dempers and their operating .mechanism not only insures a long life in operation but also the absence Iof any warping of the dampers lpermits the control mechanism to be maintained fully eective. The tube and baffle support o the dampers in their closed position reduces the stresses on the damper operating mechanism. An eiiective control of the heating gas ow across the superheater is thus provided which can be employed to by-pass a major portion of the heating gases around the superheater during starting-up periods to avoid overheating -of the superheater tubes, and during normal `operation to control the nal superheat temperature 'as desired. i

While in accordance with. the provisions of the statutes we have illustrated and described herein the preferred forms of thev invention now known to us, those skilled in the art will understand that changes may .be made in the form of theI apparatusdisclosed without departing from the spirit of the invention covered by the claims, and that certain features of the invention may sometimes be used to'advantage without a correspon-ding use of other features. i

We claim: i.

1. Av steam boiler having upper and lower vertically; spacedfbanks of horizontally inclined steam generating tubes, a steam superheater having a plurality of steam superheating tubes occupying a portion oi the space between said tube banks adjacentcneend thereof, bafiie means arranged to denne a plurality of serially connected up-lowV and downow gas passes across said upper bank with .said superheater arranged directly below the first upflow gas pass, sbaflie means arranged to define `an upiiow heating gas by-pass about said su-perheater tubes extending substantially vertically'across said space and `said upper bank and at one side of said superheater, and damperineans at the upper end of said by-pass for controlling the gas flow through saidgby-p-ass.

2. A steam boiler having upper and lower vertically spaced banks of horizontally inclined steam generatingtu'bes,- a steam superheater having a pluralityof steam superheating tubes occupying a portion4 of the space between vsaid tube banks adjacent one end thereof, baille means arranged to dene a plurality of serially connected upflow and downow gas passes across said upper bank with said superheater arranged directly below the rst upilow gas` pass, baille means arranged to define an upilow heating gas by-pass about said superheater tubes extending substantially vertically across said up-per bank and at one side of said superheater, and damper means for controlling the gas flow through said lby-pass extending along lthe uppermost tube row of said upper bank.

3. A steam boiler having upper and lower vertically spaced banks of horizontally inclined steam generating tubes ha-ving uptake and downtake connections to the upper and lower ends thereof respectively, .a steam superheater having a plurality of steam superheating tubes occupying a portion lof the space between said tube banks adjacent the uptake end thereof, baille means arranged to .denne an upilowheating gas by-pass about said superheater tubes extending substantially vertically across said upper bank and at one side of said superheater, and ldamper means for controlling the gas flow through said by-pass extending Ialong the uppermost tube row of said upper bank.

. 4. A steam :boiler having upper and lower vertically spaced banks of horizontally inclined steam generating tubes, a steam superheater having a pluralityV of steam superheating tubes. occupying a portion of the space between said tube banks adljacent one end thereof, baille means arranged to dene a single upflow heating gas pass across said lower bank and a plurality of serially connected upilow and downlow gas passes across said upper bank with the iirst upilow pass across Said upper bank opening to the upflow pass across said lower bank and said superheater arranged in said upilow gas stream, baille means arranged to deiine an upflow heating gas `:by-pass about said superheater tubes extending substantially vertically across said upper bank at oneside oi said superheater, and pivotally mounted damper means for controlling the gas flow through said by-pass extending along the uppermost tube row of said upper bank.

5. A steam boiler having upper and lower vertically spaced banks of horizontally inclined steam generating tubes having uptake and downtake connections to the upper and lower ends thereof respectively, a steam superheater having a plurality of steam superheating tubes occupying .a portion of the space between said tube banks adjacent one end thereof, baille means arranged to define an upflow heating gas pass across said lower bank and a serially connected upilow gas pass across .the uptake end of said upper bank with said superheater arranged between said baffle means and the uptake end of the boiler, baille means arranged to defme an upflow heating gas by-pass between said superheater and said ilrst mentioned baille means and extending across said upper bank, and damper means at the upper end ofA said by-pass for controlling the gasV rality of steam superheating tubes occupying a portion of the space between said tube banks adjacent the uptake end thereof, baille means arranged to define an upflow heating gas pass across said lower bank and a serially connected upflow gas pass across the uptake end of said upper bank with said superheater arranged between said baille means and the uptake end of the boiler, baille means arranged to deiine a substantial vertical heating gas by-pass .between said superheater and said rst mentioned baille means and extending across said upper bank, and damper means for controlling the gas flow through said by-pass extending along the uppermost tube row of said upper bank.

7. A steam boiler having upper and lower vertically spaced banks of horizontally inclined steam generating tubes having uptake and downtake connections rto the upper and lower ends thereof respectively, a steam superheater having a plurality of steam superheating tubes occupying a portion of the space between said tube banks adjacent the uptake end thereof, baille means arranged along one side of said superheater and defining a plurality of serially connected upflow and downflow gas passes across said upper bank, baille means arranged to deiine an upflow heating gas by-pass about said superheater tubes extending substantially vertically across said upper bank at the downilow side of said rst mentioned baille means, and damper means at the upper end of said by-pass for controlling the gas flow through saidby-pass.

8. A steam boiler having a setting rectangular in horizontal cross-section and including upper and lower'vertically spaced banks of horizontally inclined steam generating tubes having uptake and downtake connections to the upper and lower ends thereof respectively, a steam superheater having a plurality of steam superheating tubes occupying a portion of the space between said tube banks add acent the uptake end thereof, baille means arranged along fthe downtake side of said superheater 'and deming a single upilow heating gas pass across said lower bank and a plurality of serially connected upilow and downflow gas pas-ses across said upper bank, baffle means arranged to define an upflow heating gas by-pass about 'said superheater tubes extending substantially vertically across one corner portion of said setting and said upper bank at the downtake side of said ilrst mentioned baille means, and damper means for controlling the gas ilow through said by-pass.

9. A steam boiler having upper and lower vertically spaced banks of horizontally inclinedy steam generating tubes having uptake and downtake connections to the upper and lower ends thereof respectively, a steam superheater having a plurality of steam superheating tubes occupying a portion of the space between said tube banks adjacent the uptake end thereof and spaced from the remaining opposite sides of said boiler, baille means arranged to dene upfloW heating gas bypasses extending substantially vertically across said upper bank at said opposite sides of said superheater, and damper means for controlling the gas ilow through said :by-passes.

10. A steam boiler having upper and lower vertically spaced ibanks of` horizontally inclined steam generating tubes having uptake and downtake connections to the upper and lower ends thereof respectively, a steam superheater having a plurality of steam superheating -tubes occupying a portion of the space between said tube banks adjacent the uptake end thereof and spaced from the remaining opposite sides of said boiler, baille means arranged along the downtake side of said superheater and defining a single upflow heating gas pass across said lower bank and separating upiioW and doWnfloW gas passes across said upper bank, other baHe means arranged to dene upow heating gas Iby-passes about said 4superheater tubes extending substantially vertically across said upper bank at the upflow side of said rst mentioned baffle means and at said opposite sides of said superheater, 'and' damper means for controlling the gas flow through said by-passes.

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