US2924204A - Steam generator - Google Patents

Description

c. w. HASEK, .13., EIAL 2,924,204

Feb. 9, 1960 STEAMYGENERATOR 3 Sheets-Sheet 2 Filed Sept.'21, 1956 mmvmns Carl W. HasekJR Everefr A. Caflin ATTORNEY Feb. 9, 1960 c. w. HASEK, JR. EI'AL STEAM GENERATOR 3 Sheets-Sheet 3 Filed Sept. 21. 1966 uvmvroxs Carl W. HasekJR BY Ev'erefi A. Carlin AT TORNEY United States 2,924,204 Patented Feb. 9, 1960 STEAM GENERATOR This invention relates to a fluid heating apparatus and more particularly to an improved vapor generator having a liquid-vapor separating drum provided with novel means for channeling vapor-liquid mixtures of different qualities thereinto and separating said mixtures into their consistent parts by gravitational means.

An object of this invention is to provide in a vapor generator an improved vapor separating means. whereby the efliciency of the separation of the liquid-vapor mixtures i.e. vapor dryness is materially increased in a relatively simple, effective, and inexpensive manner.

Another object of this invention is to provide in an improved vapor generator a natural flow circulating arrangement resulting in an increased circulating head for a given heat input.

The objects and advantages of this invention are accomplished by a vapor generator having in a setting, a furnace, an associated convection gas pass and a boiler unit, the latter including an upper liquid-vapor separating drum having therein an improved liquid-vapor mixture separating means, a lower drum and connecting generating tubes. The generating tubes include a group of high duty, vapor generating tubes disposed adjacent, lining or forming a part of the walls of the furnace, the tubes being subjected to the highly heated combustion gases for generating a low-density, liquid-vapor mixture, i.e. a mixture having a high percentage of vapor by weight; a group of lower duty generating tubes disposed in the forward end or hot portion of the convection gas pass generating a higher density mixture, i.e. one having a lower percentage of vapor by weight and a group of downcomer tubes disposed rearwardly of thelow duty tubesin the cooler portion of the gas convection pass.

According to this invention, the vapor-liquid separating drum is provided with means forming a liquid compartment and a plurality of distinct, juxtaposed, circumferentially disposed compartments adjacent a wall portion of the drum, the juxtaposed compartments being arranged so as to receive respectively the discharge ends of the high duty generating tubes and the discharge ends of the low duty tubes. Thus the low density mixture of the high duty tubes are collected in one compartment and the high density mixture emanating from the low duty tubes collected in another compartment. Each of the compartments adjacent the upper end thereof is provided with means forming a discharge port through which the respective vapor-liquid mixtures are discharged, the discharge ports being in communication with the space above the level of the liquid. The discharge ports of the respective mixture receiving compartments are spaced one above the other with the high velocity, low density mixture emanating from the higher port. Further the [ports are arranged to discharge flow of the mixtures streaming out of the respective receiving compartments in a laterally, outwardly converging direction to affect gravitational separation of the liquid from the vapor in -the space above the liquid livel. The liquid thus sepa rated from the vapor is collected in the liquid compartment and the vapor separated from the liquid iscollected in the space above the liquid. As a result the liquid standing in the liquid compartment is substantially solid, i.e. free of entrained vapor, thereby allowing substantially solid liquid to flow through the downcomers.

Therefore, the fluid flowing through the downcomer has a minimum specific volume resulting in a minimurn re striction to flow. The effect is to increase the weight of liquid circulated to a maximum for a desired operating condition 'whereby the heat absorption per poundof fluid flowing in the downcomers is'minimized, Consequently for a given heat input, the velocity of the fluid in the downcomers is increased resulting in a greater circulating head on the vapor generator. To achieve desired results the discharge ports of the mixture receiving compartments are proportioned to discharge the fluid mixture'flowing outwardly therefrom at predetermined relative velocities to insure gravitational separation of the mixture into its constituent parts and to maintain the pressure drop through the port opening low enough so as to not impede the fluid circulation of the system. 7

A feature of this invention resides in the provision of an improved vapor and liquid separating drum having means for deflecting or changing the directional flow of the respective liquid-vapor mixtures as the latter aredischarged outwardly from juxtaposed, mixture receiving compartments for affecting an improved gravitational separation of the mixtures into its constituent parts, whereby the liquid because of its greater weight gravitates to the liquid compartment. 7

Another feature of this invention resides'in the provision of an improved vapor and liquid separating drum having means for discharging liquidvapor mixtures of different quality out of juxtaposed, mixture receiving compartments at relative velocities so as to prevent carryover of the liquid separating from the vapor of the low density mixture discharging outwardly from one compartment by the vapor separating from the liquid of a high density mixture which is flowing out from the juxtaposed compartment.

Still another feature of this invention resides in. the provision that theseparation of the mixtures into its constituent parts by gravitational means above the normal liquid level of the drum eliminates undesirable fiuxation in the level of the liquid within the drum. 7 A

Otherfeatures and advantages will be readily apparent when considered in view of the drawings and accompanying description in which:

Fig. 1 is a front elevation sectional view of a vapor generator including a furnace with walls defined by vapor generating tubes and a two drum vapor generating convec'tion section heated by gases from the furnace,

Fig. 2 is a detailed longitudinal sectional view having portions thereof broken away of an improved vapor and liquid sparating drum according to this invention,

Fig. 3 is a left end sectional view of the drum taken along line 33 of Fig. 2,

Fig. 4 is a right end sectional view of the drum taken along line 44 of Fig. 2,

Fig. 5 is an intermediate sectional view of the drum taken along line 55 of Fig. 2.

1 While the instant invention is directed to vapor generator generally, for the purpose of illustration and description, particular reference is made to a steam generator having particular utility as a marine boiler. Referring to Fig. l, the steam generator according to this invention consists of a setting 10 comprising a furnace cavity 11 fired by suitable burners 12 and an associated gas convection pass 13. Housed within this'setting'ltl are the pressure parts of the boiler unit.

steam and water drum 14, which according to this invention and as will be hereinafter described is provided with means for improving the quality of steam separation, i.e. steamdryness, as well as for affecting an increase in the circulatin'g head on the boiler unit; a lower liquid or water driim15 anda plurality of vapor or steam generating tubes in communication with the upper and lower drum'sr" According to thisinvention the vapor generating tubeSare made'up of a group ofhigh-duty tubes 16 andagroupof low duty tubes 17. a

t The high duty vapor or steam generating tubes 16 consist ar a bank of staggered screen tubes 16A extending from-front to rear of the setting and separatesthe furnace cavity 11 from the convection gas pass 13, the screen tubes 1 6A being directly connected to drums 14 and 15. Included also as high'duty-tubes are the furnace wall tubes, which as shown includea group of furnace rear-wall-tubes 16B, furnace sidewall tubes 16C and roof tubes 16D, the latter forming a continuation of the side wall tubes1'6C. The furnace rear wall riser tubes 16B lead u'p wardly from a rear wall lower header 18, the latter being connected to the water drum 15 by tubes 19, and-connect intoan upper rear wall header 20 which is appropriately connected to the main steam drum 14 by a series'of tubes 16E. If desired, the upper header 20 is providedwith suitable diaphragms (not shown) to protvide-a plurality of compartments from which a plurality of outlet tubes-16E discharge a steam-water mixture to longitudinal spaced positions along the drum 14. The sidewall riser .tubes 16C lead upwardly from alower sidewall head 21 which is connected to the water drum 15*by-a seriesof tubes .22, the upper portions of. the sidewall tubes 16C being bent to follow the slope of the roof portion 23 of the setting and have the discharge ends thereof connected directly to the steam drum 14.

According to this invention the low duty group of vapor or steam generating tubes 17 are disposed in the gas convection pass 13, i.e. to the left of the screen tubes 16Aas viewed in Fig. 1, and spaced therefrom to provide a setting for a bank of superheater tubes 24 disposed in "thespace therebetween. As shown the low duty tubes 17' consist of a ten row, inclined bank of tubes which i are directly connected to the drums 14 and 15.

To the left of the low duty tubes 17and disposed in the cooler portion of the gas convection pass 13 is a bank of inclined downcomer tubes 25 connecting the main steam drum14 to the lower water drum 15; the bank of downcomers consisting often rows of tubes extending across the setting. i

t According to this invention the main steam drum 14 is provided with partitioning means 26 and 27 extending substantially the length of the drum dividing the same into a liquid or water space or compartment 28 and into a plurality of distinct and separate, juxtaposed, circumferentially extending compartments 29 and 30, the latter compartments 29 and 30 forming independent outlet manifolds for receiving the mixture of steam and water formed in the high duty and low duty generating tubes 16 and17 respectively.

Referringzparticularly to Figs. 2 to 5, the improved 7 adjacent wall portion 15A of the drum-andcQ-operates 1 therewith to form the manifold compartments 29 which As shown, two manifold compartments are formed between a pair of end plates 34 and 35 connected to the interior wall surface of the drum adjacent the ends thereof and extend inwardly therefrom a distance equal to approximately 25 percent of the diameter of the drum.

Connected to and extending therebetween are a pair of. spaced partition means 26: and 27, shown diagrammaticah eral plate sectionswhich are supported in a line extending substantially the length of the drum by intermediate supporting plates 36 longitudinally spaced between the and support plates 34 and 35.

As shown in Figs. Z'and 5, partition means 26 includes a plurality of plate sections 26A, 26B, 26C and 26D connected by suitable means, such as bolts 26Eand the like. It is to be noted that the plates 26A-D are tied together in a manner to simulate the curvature ofy the terminate in an upwardly diverted opening 37. 'If desired the intermediate support plates36 are providedwith a cutout notch 36Ato provide means whereby eachsectionof the manifold compartment may be rendered in communication with each other -A second partition means-27 spaced from partition '26 1 and connected to a projected portion 34A,1'35A ofthe support plates 34, 35 respectively form therewith a second manifold compartment; The second partition 27 likewise is made-up of. a plurality of plate sections 271M273, and 27C which are disposed in spaced relationship'tothe plates 26AD of partition 26 to form therewith the second manifold compartment 30.. As shown in Figsal and 1 5 the second compartment30 terminates in an opening 38' a which is spaced below that of the opening 37 of comsteam drum 15 of this invention consists of a closed end cylindrical shell .31 having internally disposed along the top thereof a perforated steam 'pipe' 32, Figs. 3 to 5, which communicates with the steam outlet 33. To divide the interior of the drum into a water compartment 28 and into a plurality of separate and distinct. manifold compartmentsextending substantially the length of the drum, suitable dividing means such as haffles and/or partitioning plates are utilized which co-operate with the walls of the drum and with each other to form the distinct compartments. While the partitioning means 26 and 27 may be integrally formed, in the illustrated'form of the .invention the said means are formed of severalseparately connected plate members;

partment 29. As noted from Fig. 1,-both openings are "disposed above the normal level of the waterfin'thewater 1 compartment 28, thelatter being formed between the;

second described partition 27 and the opposite wall 39 0f the drum'15. K

According to this invention baffle means '40 and 41 spaced above the openings 37and 38,*respectively,' are provided to form therewith discharge ports 42, 43 through which a liquid and vapor mixture is adapted to be discharged outwardly from the respective compartments as it will be hereinafter described. As shown the upper bafile means 40 consist of aplate disposed between the steam dry pipe 32 and opening 37 and is sealed welded to the drum to incline downwardly and inwardly to form the discharge port 42,'the inner 'end of the bathe being provided with an upturned flange 40A. Spaced there.- from and connected to platesections 26A and projecting substantially perpendicular thereto (i.e. "extending in a.

substantially horizontal direction-substantially parallel.

to the liquid level) is a secondbaffie means 41spaced above opening 38 and forming therewith the discharge port 43 ofthe secon'dcompartment.

As best seen in Fig. 1 it will be n'oted that the high duty tubes 16, i.e.the screendhbes 16A, roof tube's16D and tubes 16E have their discharge ends incommhnication with compartment; 29. The-lower duty tubes'g17 discharge into thesecond compartment 30 and the downcomers25 connect thewatercompartment 28 with the Thus in operation with the burners- 12" firing in the furnace cavity, the screen tubes, 16Ayand furnace wall tubes 16B, 16CIandfI6D- exposed to the hot gases of combustion become' highly heated thereby "and generate a predominent portion of the steam ofgthe unit which is dischargedinto compartment 29 as a low density mix-.

ture of steam and *water at.relatively.high velocities.

:. As thegases flowthrough the convection pass 13, the. lower,.duty...tube's 17. become h ated- ,1 Howeve 93% 'of-the heat of the gases has already been absorbed by the superheater 24 etc., these tubes do not absorb as much heat as the screen and furnace wall tubes and therefore the amount of steam generated therein is less. Accordingly, the ratio of steam to water in tubes 16 is greater than the ratio of steam to water in tubes 17, the latter discharging into the second compartment 30 at a comparative lower velocity thanthat of the mixture discharging into compartment 29. As indicated in Figs. 1 and 5, the high ratio and low ratio steam and water mixtures stream into its separate compartment 29, 3t) and is deflected outwardly therefrom through the ports 42, 43 by the baflles 40 and 41 respectively. By changing the direction of flow as the mixtures are discharged and due to the greater weight of the water, a gravitational separation of the mixture occurs. According to the invention, it had been discovered that by diverting the mixture having the higher velocity downwardly, as indicated by the arrows in Figs. 2 and 5, entrainment of the water by the steam as the latter rises to seek the steam outlet 33 is substantially eliminated.

The mixture discharging from the compartment 30 has a relative lower velocity and gravity effectively separates this mixture into its liquid and vapor parts. By properly proportioning of the port openings 42 and 43, the velocities of both mixtures can be controlled so that the water separating from. the mixture of the higher port 42 will not be entrained or carried over by the vapor separating from the mixture discharging from the lower port 43.

It will be further noted that the improved drum arrangement herein discussed provides for an improved boiler circulation. Because the mixtures from the high duty and low duty tubes are discharged into separate and distinct compartments and separated above the normal water level, the water standing in the drum is substantially solid. For this reason, the water flows through the downcomer 25 substantially free of any entrained vapor. Therefore, since the water flowing through the downcomer has a minimum specific volume, the weight of water circulated is greater and the heat absorbed per pound of water flowing in the downcomer is reduced. Thus as the velocity of the water in the downcomer is increased, the circulating head on the boiler is increased. To maintain this advantage the ports 42 and 43 are proportioned to maintain the pressure drop through the port opening sufficiently low so as to not impede this circulation.

It will be further noted that the improved arrangement of this invention eliminates fluxation of the water level within the drum in that the specific volume of the water is maintained at an absolute minimum since it is substantially free of vapor.

Further, it will be apparent that the instant invention provides means for affecting an improved quality of steam separation in a relatively simple, efiicient and expedient manner, while at the time provides an increased circulating head for the boiler.

While the instant invention has been disclosed in accordance to a particular embodiment thereof, it is to be appreciated that the invention is not to be taken as limited to all of the details thereof as modifications and variations thereof may be made without departing from the spirit or scope of the invention.

What is claimed is:

1. In a vapor generator, a vapor liquid separting drum normally having a liquid level therein separating a liquid space from a vapor space and normally having a high density and low density liquid vapor mixture simultaneously discharged thereinto, a dry vapor pipe within the drum extending longitudinally along the top thereof, gravity means for separating each of said mixtures into its respective vapor and liquid constituents, said gravity separating means including a first partition spaced from a circumferential wall portion of the drum and forming 6 therewith a circumferentially extending compartment adapted to enclose the ends of generating'tubes discharg ing the low density liquid-vapor mixture into said drum,

' said compartment having an upper open end above the liquid level, a second partition spaced from said first partition and forming therewith a second compartment adapted to enclose the ends of generating tubes. discharging the high density liquid-vapor mixture into said drum, said second compartment having. an open upper end positioned above the liquid level and below the open upper end of said first compartment, a first downwardly inclined bafile means positioned between the dry pipe and the upper open end of said first compartment, said baffie means co-operating with said open end of said first compartment to form therewith a discharge port, a second substantially horizontally disposed bafile means connected to said first partition, said second bafile means being spaced above the opening of said second compartment and forms therewith the discharge port of said second compartment, the port of said first compartment being disposed above the port of said second compartment, said ports discharging the liquid-vapor mixtures of their respective compartments into the free vapor space above the liquid level, said first bafiie means directing the low density liquid-vapor mixture emanating from said first compartment angularly downwardly towards the liquid level and said second bafile means directing the high density mixture emanating from said second compartment in a direction substantially parallel to the liquid level at a position above the liquid level and below the discharge port of the low density mixture whereby said high density liquid-vapor mixture discharging substantially parallel to the liquid level blankets the downwardly directed low density mixture from direct impingement on said liquid level, said blanketing effect enhancing the dryness of the separating vapor by minimizing foaming and moisture carry-over due to direct impingement of the separating vapors of the respective mixtures on the liquid level.

2. In a vapor generator, a vapor liquid separating drum normally having a liquid level therein separating a liquid space from a vapor space and normally having a high density and low density liquid vapor mixture simultaneously discharged thereinto, means forming a steam outlet at the top of said drum, gravity means for seperating each of said mixtures into its respective vapor and liquid constituents, said gravity separating means including a first partition spaced from a circumferential wall portion of the drum and forming therewith a circumferentially extending compartment adapted to enclose the ends of generating tubes discharging the low density liquid-vapor mixture into said drum, said compartment having an upper open end above the liquid level, a second partition spaced from said first partition and forming therewith a second compartment adapted to enclose the ends of generating tubes discharging the high density liquid vapor mixture into said drum, said second compartment having an open upper end positioned above the liquid level and below the open upper end of said first compartment, a first downwardly inclined bafile means positioned between said steam outlet means and the upper open end of said first compartment, said baffle means co-operating with said open end of said first compartment to form therewith a discharge port, a second substantially horizontally disposed bafile means connected to said first partition, said second bafiie means being spaced above the opening of said second compartment and forms therewith the discharge port of said second compartment, the port of said-first compartment being disposed above the port of said second compartment, said-ports discharging the liquid-vapor mixtures of their respective compartments into the free vapor space above the liquid level, said first bafile means directing the low density liquid-vapor mixture emanating from said first compartment angularly downwardly towards thq liquid level a nd said second baffle. means dire qing thq] high density Tmixtiire emanating; from said sabnd dqnipar tm'ent in a direction substantially parallel to the nli zing foaming moisture carry-over due to direct

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