US2879752A

US2879752A - Steam generator

Info

Publication number: US2879752A
Application number: US544513A
Authority: US
Inventors: Edward G Hutchings
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1955-11-02
Filing date: 1955-11-02
Publication date: 1959-03-31
Anticipated expiration: 1976-03-31

Description

March 31, 1959 E. G. Hu'rHlNGs 2,879,752.

STEAM GENERATOR l Filed Nov. 2. 1955 4 sheets-sheet 1 ooooooooooooo JNVENToR. Edward G. Hufchings Wwf ATTORNEY March 31, 1959 E. G. HUTcHlNGs 2,879,752

STEAM GENERATOR ATTORNEY March 31, 1959 K E. G. HuTcHlNGs 2,879,752

STEAM GENERATOR Filed Nov.v 2. 195:5- Y 4 sheets-sheet s FIG. 3

INVENTOR. Edward G. Hu'rchings BY ATTORNEY Max'ch 31, 1959 E. G. HUTcHlNGs STEAM GENERATOR 4 Sheets-Sheet 4 Filed Nov. 2. 1955 INVENTOR.

g,Edward G. Hurchings ATTORNEY STEAM GENERATOR Edward G. Hutchings, Whitton, Twickenham, England, assignor to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Application November 2, 1955, Serial No. 544,513

6 Claims. (Cl. 122-480) This invention relates in general to steam generators, and more particularly, to steam generating and superheating units of the type especially adapted for use in marine installations and including provisions for regulating the ow of heating gases over the steam superheating surface to control the heat absorption thereof.

`In a steam generating and superheating unit of the type of the invention, the amount of convection heated steam superheating surface is proportioned and arranged to provide a predetermined nal steam temperature at the steam outlet at a predetermined load. As the prime mover associated with such a unit is generally designed for operation with a maximum steam temperature at the predetermined load, provisions are normally made for maintaining the steam temperature at the desired value at loads in excess of the predetermined load by controlling the llow of heating gases over the steam superheating surface.

Heretofore, the practice in effecting superheat control in marine installations has been to provide parallel damper-controlled gas passages and to confine the steam superheating surface wholly or substantially wholly to one of the gas passages. However, the provision of parallel gas passages results in restriction of the width of each pass and with the usual form of superheater comprising looped tubes extending between upright headers, the surface available for superheating may be inadequate for attainment of the degree of superheat desired. Moreover, the restriction of the cross-sectional area of each passage results in a relatively high draft loss.

In accordance with the present invention a steam gen` erating and superheating unit of the general character described islconstructed with a particular arrangement of convection heated steam superheating surface, whereby the unit can be operated to maintain a relatively low draft loss and a substantially constant degree of superheat over a relatively wide steam generating load range.

The present invention provides a steam generating and superheating unit having a furnace chamber disposed at one side of a steam generating tube bank, and a superheater disposed within a superheater gas passage and at the side of the steam generating tube bank remote from the furnace chamber, while a substantially u nobstructed or open gas passage is arranged to receive gases from the furnace chamber. Gases leaving the open gas passage normally llow partly to the space including the steam generating tube bank and partly to the superheater gas passage, which is of greater width than the open gas passage, in proportions determined by the steam load and the degree of superheat required. Means are also provided for variably proportioning the ilow of gases to the steam generating tube bank and to the superheater surface.

The various features of novelty which characterize my 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, refl 2,879,752 Patented Mar. 31, 1959r CCy erence should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

In the drawings:

Fig. 1 is a sectional elevation of a steam generating unit embodying my invention.

Fig. 2 is a sectional plan taken on the line 2 2 of Fig. 1.

Fig. 3 is a sectional elevation taken on the line 3--3 of Fig. l.

Fig. 4 isa sectional elevation taken on the line 4 4 of Fig. 1.

Fig. 5 is a sectional elevation taken on the line 5--5 of Fig. l.

Fig. 6 is a sectional plan view similar to Fig. 2 of a modified form of the invention. y

The boiler unit illustrated comprises a setting of rectangular cross-section having upright front and

rear walls

10 and 12, respectively,

upright side walls

14 and 16,

an upper enclosing wall or roof 18 and a lower enclos-i ing Wall or floor 20. The space within the setting is divided by a partition wall 22 to provide a boiler tube space 24 laterally adjoining a furnace chamber 26. The pressure parts of the boiler include upper and

lower drums

28 and 30, respectively, which extend the full length of the setting in parallel ollset relation, and are connected by a bank of upright boiler tubes 32 disposed within the boiler tube space 24 and having their ends radially connected to the drums. The drum 28 is also interconnected to the drum 30 by

downcomer pipes

34 and 36 located externally of the front and

rear walls

10 and 12, respectively.

` The partition wall 22 is formed by a row of tubes 3S which are partially studded to support refractory closing the intertube spaces throughout their extent. This wall extends from the rear wall 12 to a location spaced from the front wall 10 whereby a gas outlet 40 is provided for heating gases flowing from the furnace chamber 26 into the boiler tube space 24. Tubes 42 are spaced and arranged to provide a screen across the gas outlet 40.

The furnace chamber 26 is lluid cooled by a row of tubes 44 extending along the floor 20, side wallll and roof 1S between the upper and lower drums 28 and fill, respectively; a row of tubes 46 extending along the rear wall 12 between a lower header 48 and an upper header 50, the lower header being connected to the dru'm 30 through supply tubes (not shown) and the upper header being connected to the drum 28 through riser tubes (not shown); and a row of tubes 52 extending along the front wall 10 between headers (not shown) connected into the circulation system in the same manner as that described for the rear wall. The furnace chamber portions of all these wall tubes are studded and covered with refractory.

Transverse baille walls

54 and 56 extending partially across boiler tube space 24 and a partition wall 58 provide serially connected gas ypasses 60, 62, and 64 through which ya substantially horizontal flow of heating gases is maintained from the furnace chamber 26, the gases from the final pass 64 being discharged from the setting through a boiler gas outlet 66 which terminates at damper 68.

The portion of wall 10 defining the front section of the open gas passage 60 is lluid cooled by a row of studded and refractory covered tubes 70. The baille wall r54 extends downwardly throughout the height of the boiler tube space 24 and laterally from the front end of the partition wall 22 to-a point spaced from the partition wall 58. The baffle wall 56 is positioned rearwardly of the baille wall 54 and extends from the rear wall 16 across the boiler tubes 32 to a position spacedfrom the partition wall 22. Some of the boiler tubes 32 .are formed with intermediate bowed parts to provide the gas turning space between gas passes 62 and 64. The partition wall 58 extends longitudinally between an intermediate portion of the baiile wall 56 and the front wall 10.

Each of the

bale walls

54, 56, and the partition wall 58 is formed by at least one row of fluid cooled

tubes

72, 74, and 76, respectively, which, with the exception of the lower portion of tubes 76, are studded to support refractory closing the intertube spaces. The intertube spaces of the lower part of wall S8 are left open to form a gas inlet 78 into an upright superheater gas passage 80. The baiiie wall 56 and the partition wall 58 also serve to separate the boiler tube space 24 from the laterally adjoining superheater gas passage 80.

Wall tubes

38, 70, 72, 76 and screen tubes 42 are connected to

drums

28 and 30, to provide natural circulation flow paths in parallel with the boiler tubes 32. The upper portions of some of the partition wall tubes 76 are formed with lateral extensions to screen the drum from radiation from the gases owing through the boiler boiler tube space 24. A part of the bale wall tubes 74 are connected to

drums

28 and 30, and the remainder extend from a lower header 82 to the drum 28, the header being connected to the drum 30 through a tubular connection 83.

The upright superheater gas pasage 80 is of rectangular cross-section, and has boundary surfaces including portions of

walls

10, 16, 56 and 58. The portion of the setting occupied by the gas passage 80 is advantageously employed for the location of the convection heated superheater surface of the unit. The superheater is of the drainable type and includes vertically spaced banks of multiple-looped horizontally arranged longitudinally extending tubular elements 84 disposed across the upward flow of gases and connected between horizontally arranged upper and

lower headers

86 and 88, respectively. The superheater tubular elements 84 are suspended from structural steel work, adjacent loops being connected by means permitting differential expansion. The gases leaving the superheating gas passage 80 are discharged from the setting through a boiler gas outlet 90 which terminates at dampers 92.

As shown in Fig. 2, the superheater gas passage 80 extends outwardly beyond the front wall of the open gas passage 60, thus permitting installation of superheater tubes of substantial length and thereby facilitating the attainment of a high degree of superheat. Moreover, with the above described superheater gas passage and superheater construction and arrangement exibility of design is permissible since the space available for the superheater may readily be varied by changing the distance between the partition wall 58 and the side wall 16.

Access to the tubes located adjacent the gas turning space between the gas passes 62 and 64 may be had through a door 94 situated in the rear Wall 12. Access to the superheater gas passage 80 may be had through a door 96 located at the bottom of the front wall 10. In order to permit access also to the boiler tube space 24, three adjacent tubes 76a of the partition wall 58 areformed with lower end portions displaced laterally in the direction toward the rear wall 16. An access door 98 to the rear end of the gas pass 64 is provided in the side wall16.

The unit is provided with an outer casing 100 which encloses the downcomer tubes and the superheater headers and deines a space for the flow of combustion air to burners 102.

Burners 102 of any suitable type are installedin association with the front wall 10 to provide a source of heating gases. The gases rst pass substantially horizontally and rearwardly toward the rear wall 12 and then turn and flow forwardly to the outlet 40. The heating gases leave the furnace chamber 26 through the outlet 40 and then ow horizontallyover the screen tubes 42 to the open gas passage 60. `Gases leaving the open tube space 24 in proportions determined by adjustment of dampers68 and 92.

Gases entering the boiler tube space 24 flow horizontally over the boiler tubes 32 disposed in the gas passes 62 and 46 and then ow upwardly through the gas outlet 66 to the dampers 68. The gases which enter the superheater gas passage have been cooled only to a limited degree and spread out in the space below the superheater, thus assuring uniform heating gas distribution to the superheater. Gases entering the superheater continue their upward ow across the tubes 84 and through the gas outlet to the dampers 92. The

dampers

68 and 92 control the gas flow through the superheater gas passage and through the boiler tube space, permitting variable proportioning of the gas flow to each section to provide an eiective superheat control over a wide load range. These dampers may be automatically controlled for the purpose of maintaining a predetermined superheat temperature, by a control system which regulates the damper in accordance with the variations in the steam ow from the superheater outlet and also in response to variations in the superheat temperature from a predetermined value.

Header 86 receives steam from the drum 28 through tubular connections (not shown). The steam then ows from the header 86 through the superheater tubular elements 84 to the outlet header 88, and thence through a conduit (not shown) to the point of use.

Fig. 6 illustrates another form of the invention in which the baie arrangement of Fig. 2 is modiiied so that the heating gases from the furnace chamber 26 make only a single pass over the tube bank 32. In this embodiment the partition Wall 22 of Fig. 2 is omitted; the tube bank 32 and the superheater 84 are in the same relative positions as in Fig. 2; battle wall 56A extends from the rear wall 16 to the rear end of baille wall 58; baffle wall 54A extends transversely of the tube bank 32 adjacent the front end thereof; and a baie wall 55 forms an angular continuation of bale wall 56A and closes the space between

baffle walls

56A and 54A. The baille arrangement of Fig. 6 provides two parallel gas passes 60, 63 receiving gases from

outlets

39 and 41, respectively, of the furnace chamber 26 and through which a substantially horizontal llow of heating gases is maintained from the furnace chamber 26. Each of the

baffle walls

54A, 55, 56A is formed by at least one row of tiuid cooled

tubes

72A, 73, and 74A, respectively, which are studded to support refractory closing the intertube spaces. Tubes 43 are spaced and arranged to provide a screen across the

gas outlets

39 and 41. The

baffle wall tubes

72A and 73 and screen tubes 43 are connected at their opposite ends to

drums

28 and 30 to provide natural circulation flow paths in parallel with the boiler tubes 32; and the baie wall tubes 74A extend from the header 82 to the drum 28. Except for the features of diterence mentioned above, and any necessary consequences thereof, the modied unit is to be assumed to be similar to the arrangement of Figs. l through 5.

The part of the superheater gas passage 80 containing the superheater 84 overlapsthe part of the gas pass containing the tube bank 32. Although the cross-sectional area for gas ow of the open gas pass 60 is limited by the presence of the tube bank 32 to the rear thereof,v which limits the length of the open gas pass 60, the cross-sectional area for gas ow of the superheater gas passage 80 is not limited for such a reason, and the cross-sectional area thereof has without diliculty been made relatively large, so that the draft loss through -the unit due to the superheater is small having regard to the size of the superheater. Correspondingly, although the cross-sectional area for gas flow of the portion of the gas pass 63 to the rear of the superheater gas passage 80 is limited by the presence forwardly thereof of the superheater 84, which limits the length of said portion, the cross-sectional area for gas ow of the tube bank 32 is not limited for such a reason, and the cross-sectional area thereof for gas iiow has therefore been made relatively large, so that the draft loss through the unit due to the tube bank is small having regard to the size of the tube bank.

In operation gases leaving the furnace chamber 26 flow in parallel paths to the gas passes 60 and 63. The `portion of the gases entering gas pass 63 iiow in a generally horizontal iiow path over screen tubes 41 and boiler tubes 32 and then upwardly to the dampers 68; and the portion of the gases directed to the open gas pass 60 flow in a generally horizontal iiow path over the screen tubes 41 and through the open gas pass 60 to the inlet 78 of the superheater gas passage 80 and thence upwardly across the superheater tubes 84 to the dampers 92. The proportions of the gases entering the gas passes 60, 63 are determined by adjustment of

dampers

68 and 92.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

l. A vapor generating and superheating unit comprising walls forming a setting containing pressure parts including horizontally disposed upper and lower drums and a bank of upwardly extending vapor generating tubes connected to said drums along the length thereof, some of said walls defining a furnace chamber laterally adjacent one side of the space containing said tube bank and communicating therewith at one end, means forming an upwardly extending superheater gas passage laterally adjacent the opposite side of the space containing said tube bank, a superheater disposed in said superheater gas passage and extending longitudinally of and in overlapping relation with said tube bank, baiiie means including uid cooled tubes arranged to divide the space containing said tube bank into a plurality of serially connected gas passes extending transversely of said tube bank and including an open gas pass between said drums opening to said superheater gas passage and receiving gases from said furnace chamber and to provide parallel gas iiow paths from the open gas pass to the remainder of the serially connected gas passes and to the superheater gas passage, means for burning fuel in said furnace chamber and generating heating gases therein, and means for variably controlling the portion of the heating gases contacting with said superheater tubes to regulate the superheater heat absorption.

2. A vapor generating and superheating unit comprising walls forming a setting containing pressure parts including horizontally disposed upper and lower drums and a bank of vertically extending vapor generating tubes connected to said drums along the length thereof, some of said walls including uid cooled tubes and defining a furnace chamber laterally adjacent one side of the space containing said tube bank and communicating therewith at one end, means forming an upright superheater gas passage laterally adjacent the opposite side of the space containing said tube bank, a bank of superheater tubes disposed across the flow of gases in said superheater gas passage and extending longitudinally of and co-extensively with a substantial portion of said tube bank, baflie means including uid cooled tubes arranged to divide the space containing said tube bank into a plurality of serially connected gas passes extending transversely of said tube bank and including a substantially unobstructed gas pass between said drums opening to the lower portion of said superheater gas passage and receiving gases from said furnace chamber and to provide parallel gas ow paths from the open gas pass to the remainder of the serially connected gas passes and to the superheater gas passage, means for burning fuel in said furnace chamber and generating heating gases therein, and means for variably controlling the portion of the heating gases contacting with said superheater tubes to regulate the superheater heat absorption.

3. A vapor generating and superheating unit comprising walls forming a setting containing pressure parts including horizontally disposed upper and lower drums and a bank of upwardly extending vapor generating tubes connected to said drums along the length thereof, some of said walls defining a furnace chamber laterally adjacent one side of said tube bank and arranged to discharge gases thereto, means forming an upwardly extending superheater gas passage laterally adjacent the opposite side of said tube bank and having a gas inlet, a superheater disposed in said superheater gas passage and extending longitudinally of and in overlapping relation with said tube bank, wall means including iiuid cooled tubes arranged to divide the space containing said tube bank into a plurality of gas passes and forming parallel gas flow paths to said tube bank and to said superheater, said gas passes including a substantially unobstructed gas pass extending between said drums and opening at 'one end to said furnace chamber and at its opposite end to said superheater gas inlet, means for burning fuel in said furnace chamber and generating heating gases therein, and means for variably controlling the portion of the heating gases contacting with said superheater tubes to regulate the superheater heat absorption.

4. A vapor generating and superheating unit comprising walls forming a setting containing pressure parts including horizontally disposed upper and `lower drums and a bank of upwardly extending vapor generating tubes connected to said drums along the length thereof, some of said walls including fluid cooled tubes and defining a furnace chamber laterally adjacent one side of the space containing said tube bank and arranged to discharge gases thereto, means forming an upwardly extending superheater gas passage laterally adjacent the opposite side of the space containing said tube bank and having a gas inlet, a bank of superheater tubes disposed across the iiow of gases in said superheater gas passage and extending longitudinally of and co-extensively with a substantial portion of said tube bank, wall means including tiuid cooled tubes arranged to divide the space containing said tube bank into a plurality of gas passes and forming parallel gas flow paths to said tube bank and to said superheater, said gas passes including a substantially unobstructed gas pass extending between said drums and opening at one end to said furnace chamber and at its opposite end to said superheater gas inlet, means for burning fuel in said furnace chamber and generating heating gases therein, and means for variably controlling the portion of the heating gases contacting with said superheater tubes to regulate the superheater heat absorption.

5. A vapor generating and superheating unit comprising walls `forming a setting containing pressure parts including horizontally disposed upper and lower drums and a bank of vertically extending vapor generating tubes connected to said drums along the length thereof, some of said walls including tiuid cooled tubes and defining a furnace chamber laterally adjacent one side of the space containing said tube bank and arranged to discharge gases thereto, means forming a vertically extending superheater gas passage laterally adjacent the opposite side of the space containing said tube bank and having a gas inlet in the lower portion thereof, a superheater including a bank of vertically spaced tubes disposed across the ow of gases in said superheater gas passage and extending in overlapping relation with a substantial portion of the length of said tube bank, wall means including iiuid cooled tubes arranged to divide the space containing said tube bank into a plurality of gas passes and forming parallel gas flow paths to said tube bank and to said superheater, said gas passes including a substanltially unobstructed gas pass extending between said drums and opening at one end to said furnace chamber and at its opposite end to said superheater gas inlet, means for burning fuel in said furnace chamber and generating heating gases therein, and means for variably controlling the portion of the heating gases contacting with said superheater tubes to regulate the superheater heat absorption.

6. The vapor generating unit of claim 3 in which said iluid cooled wall means divides the space containing said tube bank into two gases passes and forms parallel gas flow paths to said tube bank and to said superheater,

aseefrsa one of said gas passes being substantially unobstructed and extending between said drums and opening at one end to said furnace chamber and at its opposite end to said superheater gas inlet.

References Cited in the tile of this patent UNITED STATES PATENTS 2,048,039 Stillman July 21, 1936 10 2,243,862 Heller June 3, 1941 FOREIGN PATENTS 939,608 France Apr. 26, 1948 551,483 Great Britain Feb. 24, 1943