US2612144A - Steam boiler with equalized water level - Google Patents

Description

D. M. SCHOENFELD I I STEAM BOILER WITH EQUALIZED WATER LEVEL Filed Sept. 16, 1947 Sept. 30, 1952 2 SHEETS-SHEET l INVENTOR.

I David M. Schoenfeld BY KM Patented Sept. 30, 1952 UNITED- STATES V norhiiitasgglig zuulzsn WATER I I I} 16, 19W; Seridl N ;":7714;219

Apphcstion -September i3'i3la1inis. (0151222328) This invention refers -to-stea'm generating boilers and particularly to' such boilers that are-associatedwith furnaces -in which the distributionof the iproducts of combustion from the fu-rnace through i the boiler is substantially uneven r The --major-ity 'of bent tube boilers have their vfuel burners located sothat the flames are direntedtransversely to the axes of the-drums. This of course results insubstantially uniform distribution of the-products of combustion :and consequent substantially-uniform-steam generation-"across the-widthof the boiler.- As a result downeomersare usuallyarranged at theends of the-drums, the arrangement and numbers beingsy-rnn etrieal However, in many instances espe ci'ally aboard ships and-naval yessels -in particu la rit is advisable toarran-ge. the tuel firingequipment so that firingbccurs substantially--parallel toihe axes of the drums. .ln boilers 01" the lat- 'teritypefthatare.operated at eXtremeIyThighIateS, orare fbrced,"it lhas 'be'en-iound that-(a temperature gradient exists in'the flue gasesuflo'wing over- "the-tube bank. This temperatureegradient inere'a'si'as frcihfthe fro'i' t'of the he boiler, which its the sidewlie'rein the burners are "located, .to the rear or'--op'positeside remote from the 'bu-rners. This largertemperature'oifierehtime ists be; tweentheifiueigasesand the' Wat" n' the tubes attherearthanat thefror'it; hatuia11 y resulting in-higher rates of steam getterationinithosetubes adjabeht'therear of'theboiler. v

j Furthermore; in' boiierstperated "at high rates; it hasbeen noted that the gases tend 'tolfp'ii'e up at the rear of the furnace and the ressure'iof the ases; is higher there" than" toward the front. This results in increased rates offiowbf the gases 52 i which are set forth in detail. the- -preferrednems bodiment of theinvention I I Figure 1 is a cross -section.,-in elevation, taken onlineJ-l of Fig. 2, throughva steam-boiler embodying one-formof the'invention; 1 H Figure 2 isa cross section in plan taken online 2- "2efmg. 1.

I v igure3 is'anend view of the right -sid oi Fig.1. Thei boiler unit illustrated combri'ses steam and watervdrum l andallowertwater di 2 i'hteroonhecte'diby a main'barik.bfi'tubS SI sooiated with theiboilerisfurnaoe'd. Crlbh side of the furnace opposite the main bank 'of" tubes 3 is a secon'clbank of 'tubes i onnectedatitshbt: tom end to a second Water drum' B andlatits top end' with the steam and waterldrium-"l. downcomers 1 and rear .ldowncomersl-fl .1 terodfi nect th'e's'team .and. water drum 1 Withth bottom drums '2 and I5. TThese downcomers arfilocated adjaceht the front and rear-ends ofth'e as shoWn-ffor a purpose later-to be madeevide it thereare'more downcoi-nersadjacent the rearind than there are adjacent the front'erfcl'. I. v The re resented furnace is enclosed hyfliront and 'rearwe'iis 9 audio and an end wa11;"'|'i', t1i front sidewall 9 being providedtwith "burner openings I 2 "through" which theiburners' iiizlsueh as oil burners; project-the fuel'andiair to? com? bustion'into therurnace towardtherearrwali"In; The "main bank of boiler tubes 3- fboundeii by the furnace walls 13, ur and is (best'shownin overthe'tubes in'therear'portiorrofthe tube-hank anth-"from the' 'known laws-"of heat transfefi in creaseii'rates 'of'-*'heat-' t-ransfer 'from the gases to the boiler tubes, and hence*increasedwatesof steam generation in those tubes.

Fig. -2) Side walls "I 3iand1'4whichjoin'th fur= nace walls 9 and l 0 respectively," arein'efietta o0ritinuation thereof and direct. thef'flow ofj'gaises fro'rrithe furnace through the bank. Wttilfi rearward'tf the hankwithrespect" to gas ow Y through th bank, joins said-walls l3 and to direct the gases leaving the m'ain 'bank- 3 into Oif= take 16; "The furnace '4 is further-pro 'rideti'lw-ith The net result of these phenomena is a rate of from "the followi-ngdescription :and-drawinghdn -downcomers -1' and+8 and the-burnerzopenings 2 3 .A super-heater 2 0: m yh o i w th n; we

Aica's'in'g :3l8 encloses ail of the wa'iis of the tui nace, the boil'er and theibottom lhefthe'rurnaee antitis spaced trom -saidlwallss-and bottom tovideta conduitiliila'fortlie flow of enter-comma tionto' slotted-openings ll2b-leading to the burfir openings: 1 2; An inlet l Siifor 'the i-r for combos: tion is providediadjae'ent thewaiiio op esi te tiie burner wall il. Where the drums pase through the casing an air tight :se'al is:provided so' that air :underpressure may: .b'eIconveyew-th rdugli the casing. The casing :may:-be"constructe&= tions so :as tobe removable and provide accessi'to the war-ions partswith-in the roasingrsuohzias' the main boiler bank 3 comprising a bundle of U-shaped tubes connected to inlet and outlet headers 21 and 22 (see Fig. 2) which in turn are connected to inlet and outlet connections 23 and 24 passing through the casing l8 by way of seals 25 and 26. The return bends of the superheater extend into a pocket in the side wall 9, and wall 9 is corbelled inwardly on the furnace side of the 7 superheater to deflect the furnace leaving gases away from said pocket.

As mentioned above, in a boiler in which a bank of steam generating tubes receives a predominant portion of heat from products of combustion or hot gases adjacent one end thereof, the tubes adjacent said end will generate steam at higher rates than the remaining tubes of the. bank. This condition prevails particularly at high rates of steaming or under forced rates, at which a distinct temperature gradient exists in the flue gases flowing over the tube bank; the gas temperature decreasing from the end of the bank receiving the predominant portion of the heat toward the other end. This unequal distribution of heat to the bank of steam generating tubes may be caused by a number of influences, such as flow of the products of combustion longitudinally of the drum or bank, whereby the products impinge against a Wall and pile up there to be deflected therefrom into the adjacent end of the tube bank resulting in a greater proportion of the products passing through said end of the bank than through the remaining portion. As shown in the drawings the burners 12d mounted in openings 12 direct the flame through the front furnace wall 9 into the furnace in direction longitudinal to the steam drum 1 and to'th'e 'banks of tubes 3 and and toward the rearfurnace wall H3. The products of combustionpile' up against wall In and the pressure of the products is higher there than toward the burner wall 9. This results in relatively increased rates of flow of the products over each tube bank portion adjacent wall Ill, and from the known laws of heat transfer, increased rates of heat transfer occur from products to boiler tubes at that location and hence increased rates of steam generation in those tubes. Obviously the same unbalanced heat flow to the main tube bank will occur if the furnace leaving gases are directed'as by baflling to enter the bank at one end thereof, or if a conduit delivers hot gases to enter the bank at one end thereof.

The result of the increased steam and water discharge from the steam generating tubes receiving the greater proportion of the heat of the products, is to raise the level of the Water in the steam and water drum l above these tubes while the water level above the remaining tubes is at a substantially lower level. The resulting water level in the drum may conceivably be shown approximately by the dashed line 2'! in Fig. 3. The location within the drum where the greatest proportionate steam release occurs then has the least steam space above the water level for the separation of steam from water. For reasons earlier indicated this is objectionable.

. To overcome this objection I provide, according to the invention, the end of the steam drum l experiencing the greatest proportional steam generation with a downcomer area to the water drum or drums (2 and B) therebelow which is greater than the downcomer area at the opposite end of the steam drum. In the drawing hereof the former area is represented by the three rows of downcomer tubes 8 at the boiler rear while the latter is represented by the single row of downcomers l at the boiler front (see Figs. 2 and 3). Such greater downcomer area 8 withdraws a proportionately greater amount of water from the overloaded rear end of the steam drum and thereby lowers the water level adjacent that end. and by proper choice of the two downcomer areas 8 and 1, the Water level in the steam drum I may be caused to be substantially the same from one drum end to the other.

In this manner a greater average steam releasing space becomes available, which is most desirable. Furthermore, the greater amount of water Withdrawn from the most active portion of the steam drum will be delivered to the most active portion of the water drum, thereby assuring ample supply of water to the tube bank where th circulation is most rapid. Also there will be a substantial reduction in the longitudinal flow of water through the steam drum 1 from the overactive to the underactive end. In the lower water drums 2 and 6) a minimum end flow is desirable since the water in it is thus quieter and increases the tendency for solids to settle out. In the upper drum, the improvement here disclosed contributes to the maintenance of a more nearly horizontal water level, since for flow to occur requires a gradient or head.

The larger number of downcomer tubes 8 at the rear of the boiler adjacent wall In, results in a deeper rear casing. Since in the normal arrangement air for combustion enters at the upper portion of the rear casing, flows down'through the rear casing, thence underneath the boiler and upward in the front casing to the fuel burners in wall 9, the friction loss of the air flowing down the rear casing is reduced. Although the depth of the front casing (housing downcomer tubes 1) is reduced in the same increment dimension that the depth of the rear casing is increased, the effect on the friction loss of flow in the front casing is minimized as the required quantity of flow upward in the front casing is diminishing by vir v tue of the quantities entering the fuel burning devices in opening I2. This beneficial effect is achieved without increase in the weight or overall dimensions (or box volume) of the boiler unit. In fact, if downcomer tubes are arranged in equal numbers front and rear, generally the resulting depth of front casing is greater than required or desirable.

While the preferred embodiment of my invention has been shown and described, it will be understood that changes in construction, combination and arrangement of parts may bemade without departing from the spirit and scope of the invention as claimed.

I claim: I

1. In a steam boiler unit, an associated furnace having four sides, burners in a first side wall of the furnace projecting the fuel to be burned toward the opposite or second side wall with greatest concentration in released heat adjacent thereto, a steam and water drum arranged with its axis transversely to said first and second furnace walls, spaced water drums below and parallel to said steam drum, two banks of steam generating tubes interconnecting said water drums with the steam drum for discharge of steam and water mixture into the steam drum, one of the banks facing a third side wall, the other bank forming the remaining side of the furnace; walls enclosing said last named bank of tubes and joining said first and second furnace Walls for directing the flow of gases from the furnace through said last named bank transversely to the steam drum, and downcomer tubes for a flow of water therethrough of substantially constant density, said tubes interconnecting the ends of the steam drum and the water drums and located outside of the bank-enclosing walls, the total cross-sectional inside area of downcomer tubes adjacent said second furnace wall being greater than the total cross-sectional inside area of the downcomer tubes adjacent said first furnace wall in substantial proportion to the ratio of the heat that is absorbed by the half of each of said banks adjacent said second furnace wall to the heat that is absorbed by the half of each of said banks adjacent said first furnace wall, whereby to provide for faster outflow of water from the steam drum end that connects with the most highly heated portions of said banks of steam generating tubes in order substantially to equalize the water level throughout the length of said steam drum.

2. In a steam boiler unit, an associated furnace,

burners in a first wall of the furnace projecting the fuel to be burned toward the opposite or second wall with greatest concentration in released heat adjacent thereto, -a steam and water drum arranged with its axis transversely to said first and second furnace walls, a water drum below the steam drum, a bank of steam generating tubes interconnecting the drums and discharging steam and water mixture into the steam drum; boiler walls enclosing said bank of tubes and joining said first and second furnace walls for directing the flow of gases from the furnace through the bank; a further wall on the upstream side of the bank with respect to, gas fiow and joining said boiler walls and a bottom under the furnace; downcomer tubes for a flow of water therethrough of substantially constant density, said tubes interconnecting the ends of the steam drum and the water drum and located outside of the bank-enclosing walls, all of the downcomer tubes being of the same diameter and the number thereof adjacent said second wall being greater than that adjacent said first wall in substantially the same proportion that exists between the greater heat concentrated adjacent said second wall and the lesser heat concentrated adjacent said first wall, whereby to provide for faster outfiow of water from the steam drum end that connects with the most highly heated portion of said steam generating tube bank in order substantially to equalize the water level throughout the length of said steam drum; and a casing enclosing the walls of the furnace, bank and bottom and spaced therefrom to form a conduit for flow of air for combustion from said second wall via 6 the bottom conduit to said first wall, the spacing from said second wall being greater than the spacing from said first wall; and means in said burners for receiving said air for combustion.

3. In combination with a steam boiler having an upper steam and water drum, a lower mud drum arranged substantially parallel thereto, and a substantially uniform and generally upright bank of tubes extending longitudinally of and connected between said upper drum and said lower drum for generation of steam and for delivering said steam to the upper drum; a furnace arranged in heat exchange relation with said tube bank and having a first and a second side wall, said walls being spaced apart and positioned normal to the longitudinal axes of said drums; said first side wall being arranged adjacent one vertical end of said tube bank and said second side wall being arranged adjacent the other opposite end of said tube bank; burner means positioned in said first side wall only for discharging a stream of fuel into said furnace for combustion therein, said combustion of fuel causing a greater heat release in a region adjacent the second furnace side wall than in a region adjacent the first furnace side wall; first and second conduit means located outside the furnace and connecting the upper drum with the lower drum for feeding water to said lower drum of substantially constant density, said first conduit means being positioned adjacent said first side wall, said second conduit means being positioned adjacent said second side wall and having a cross-sectional fiow area which is substantially greater than the cross-sectional flow area of said first conduit means, the cross-sectional fiow area of said first and second conduit means being substantially proportional to the ratio of heat absorption of that half of said tube bank that adjoins said first side wall to the other half that adjoins said second side wall, whereby to provide for faster outflow of water from said upper steam and water drum end that connects with the most highly heated portions of said bank of steam generating tubes in order substantially to equalize the water level throughout the length of said steam drum.

DAVID M. SCHOENFELD.

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

UNITED STATES PATENTS Number Name Date 525,614 Normand Sept. 4, 1894 1,128,700 Lovekin Feb. 16, 1915 2,232,935 Bailey Feb. 25, 1941 2,374,818 Jacobs May 1, 1945

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