US3477411A

US3477411A - Heat recovery boiler with bypass

Info

Publication number: US3477411A
Application number: US692836A
Authority: US
Inventors: Frank Gething
Original assignee: Aqua Chem Inc
Current assignee: Aqua Chem Inc; Coca Cola Co
Priority date: 1967-12-22
Filing date: 1967-12-22
Publication date: 1969-11-11
Anticipated expiration: 1986-11-11

Description

Nov. 11, 1969 F.GETH1NG HEAT RECOVERY BOILER WITH BYPASS 2 Sheets-Sheet 1 Filed Dec. 22, 1967 N w )NN ANN NNVJ MN RNs www Nw www (lvl www/WM w I (VWM (Will um Nov. 11, 1969 F. GETHING HEAT RECOVERY BOILER WITH BYPASS 2 Sheets-Sheet 2 Filed Dec. 22. 1967 United States Patent O 3,477,411 HEAT RECOVERY BOILER WITH BYPASS Frank Gething, Milwaukee, Wis., assignor to Aqua-Chem, Inc., a corporation of Wisconsin Filed Dec. 22, 1967, Ser. No. 692,836

Int. Cl. F22b 9/12 U.S. Cl. 122-7 25 Claims ABSTRACT OF THE DISCLOSURE A boiler connected to an external source of heated medium, such as the exhaust of a turbine or engine; and including means for bypassing the heated medium around the heat exchange tubes. The bypassing means is in the form of an insulated furnace drum extending through the heat exchange chamber; and the furnace drum and the heat exchange tubes contain means for silencing the sound of the source of heated medium. A converging nozzle is provided at the entrance end of the furnace drum for drawing cooling air in through the heat exchange tubes during a bypassing operation to compensate for any heat given to the heat exchange chamber through the furnace drum.

Background of the invention This invention relates in general to heat exchange apparatus, and more particularly to a boiler wherein water in a heat exchange chamber is converted into steam by having a heated medium flow through a plurality of heat exchange tubes in the heat exchange chamber.

One of the most common types of boilers is the socalled fretube boiler, and such structures have usually included a furnace tube or drum in the heat exchange chamber, with a burner or the like being provided at one end of the iretube, and with baffle means being provided for directing the products of combustion in one or more passes through the heat exchange tubes. Many suggestions have been made in the past for irnproving the efficiency of such boilers, and one such solution has been to utilize the products of combustion from an external source, such as from a turbine or engine, as the heat exchange medium. This suggestion obviates the necessity of providing a self-contained burner unit within the boiler, and also makes use of the heat carried in the exhaust gases, which would normally flow to atmosphere.

One of the chief drawbacks of the above suggestion is that the demands for steam from a boiler are usually sporadic, and do not necessarily coincide with the period during which the external source of heat exchange medium is used. In many installations, prime movers such as engines and turbines are operated continuously, and if the products of combustion were continuously circulated to a boiler, there would be an obvious wastage of steam, during periods when there was no demand for steam. One solution to this problem is to physically disconnect the external source of heat exchange medium from the boiler during periods when steam is not needed, but this is obviously a time consuming and undesirable step. Applicant has solved this problem in a unique manner by providing means within the boiler itself by which the heated medium can bypass the heat exchange tubes. While this solution has obviated the necessity of disconnecting the source of heat exchange medium from the boiler, it has created a further problem, in that the heat exchange medium flowing in the bypass path through the boiler also gives up heat to the water within the boiler, which may produce steam when it is not needed.

Summary The present invention provides a unique arrangement whereby any heat imparted to the water during the bypassing of heat exchange medium through the boiler may be compensated by drawing cooling ambient air through the heat exchange tubes during the bypassing operation. To achieve this, the plenum chamber at the exhaust end of the boiler is divided into two compartments, one communicating with the exhaust end of the heat exchange tubes, and the other communicating with the exhaust end of a furnace drum that is used to bypass the heat exchange medium through the boiler. The entrance end of the furnace drum is in communication with the plenum chamber at the opposite end of the boiler, which also communicates with the entrance end to the heat exchange tubes. A converging nozzle is provided in the entrance of the furnace drum, and during a bypassing operation, the heat exchange medium that is accelerated by the converging nozzle draws cooling air through the heat exchange tubes, with the cooling air passing through the furnace drum with the heat exchange medium. The furnace drum includes a damper, which may be closed during normal heating operation of the boiler, so that the heated medium will flow through the heat exchange tubes. During a bypassing operation, the damper may be opened to a selected position wherein the cooling effect of the ambient air drawn through the heat exchange tubes will balance the heating elfect due to the heat exchange medium owing through the furnace drum. To minimize the heating effect of the heat exchange medium during a bypassing operation, an insulating liner or sleeve is provided within the furnace drum, and conveniently the sleeve may include silencing means for muiiiing any noises emanating from the source of heat exchange medium.

Brief description of the drawings FIG. 1 is a vertical section through. a boiler that is formed in accordance with the principles of the present invention;

FIG. 2 is a view taken generally along line 2-2 of FIG. 1;

FIG. 3 is a view taken generally along line 3-3 of FIG. 1; and

FIG. 4 is a view taken generally along line 4-4 of FIG. 1.

Desecript-ion of the preferred embodiment While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawings in detail, the boiler of the present invention is indicated in its entirety at 10 in FIG. l, and the boiler 10 is supported on legs 12 that extend upwardly from base 11. Boiler 10 includes substantially cylindrically shaped shell 13 having outwardly extending

flanges

14 and 15 at opposite ends thereof, and end caps 16 and 17 have outwardly extending flanges 18 and 19, respectively, secured to

shell flanges

14 and 15 by suitable means, such as by bolts or by welding. End caps 16 and 17 each include suitable refractory or insulating material 20 and 21, respectively, and plenum chambers 22 and 23 are provided inwardly of the end caps 16 and 17 at opposite ends of the boiler.

A `pair of

spaced tube sheets

24 and 25? extend generally transversely with respect to the axis of shell 13, and

tube sheets

24 and 25 are secured to the shell 13 in water tight fashion to provide a heat exchange chamber 26 therebetween. A plurality of openings 27 are provided in tube sheet 24, and a plurality of openings 28 are provided in tube sheet 25, with each opening 27 being aligned with an opening 28. A plurality of heat exchange tubes 29 are provided in chamber 26, with one end of each tube 29 being secured in water tight fashion around an opening 27 and the other end of tube 29 being secured in water tight fashion around opening 28. Boiler includes a conventional steam nipple 30 for withdrawing steam from chamber 26, and the boiler may also include pressure relief valves such as those shown at 31.

Tube sheets

24 and 25 include enlarged openings 32 and 33 adjacent the lower end thereof that are aligned with one another. A cylindrical furnace tube or drum 34 extends through the lower portion of chamber 26, and the right hand end (as viewed in FIG. l) of drum 34 is secured in water tight fashion to tube sheet 25 outwardly of opening 33, while the opposite end of drum 34 is secured in water tight fashion within opening 32 in the tube sheet 24. As is clear from FIG. l, drum 34 includes an end portion 34a that extends outwardly of tube sheet 24 into plenum chamber 22, and the purpose of this will be hereafter explained.

A generally U-shaped baille 35 extends outwardly from tube sheet 24 into plenum chamber 22, and baille 35 surrounds the end 34a of furnace drum 34, as can be best seen in FIG. 3. A generally vertically extending baille 36 extends upwardly from baille 35 in plenum chamber 22, divides the plenum chamber into two compartments 37 and 38. An annular ring of refractory or insulating material 39 extends around plenum chamber 22, and an opening 40 in the upper end of refractory material 39 establishes communication between plenum chamber 22 and an exhaust stack 41, which communicates with atmosphere. An outwardly extending flange 42 on stack 41 is joined to an outwardly extending flange 43 on a chimney 44 by suitable fastening means, such as bolts or the like, and a partition 45 extends through stack 41 and chimney 44, with the lower end of partition 45 being secured to the upper end of partition 36. Partition 45 divides stack 41 and chimney 44 into compartments 46 and 47 which communicate, respectively, with compartments 37 and 38 of plenum chamber 22. A further baille 48 may extend inwardly from end cap 16 into compartment 38 of plenum chamber 22, for diverting gases emanating from the furnace drum 34 through a tortuous ow path.

Boiler 10 includes means for connecting the boiler to an external source of heated medium, such as the exhaust from a turbine or engine, and said means may include a tubular member 50 that is connected to the exhaust of the external heated medium source, with an outwardly extending flange 51 on member 50 being secured to the outer face of end cap 17. The flow of heated medium from the external source in represented by the arrow 52 in FIG. 1, and the boiler 10 includes means for accelerating the flow of heated medium into the furnace durm 34, with the accelerating means being illustrated in the form of a converging nozzle 53 in FIG. 1. Nozzle 53 may have an outwardly extending flange 54 secured to the outer surface of end cap 17, and illustratively, the flange 54 on nozzle 53 may be positioned under the flange 51 on member 50, with common fasteners securing both flanges to the end cap 17. As is evident from FIG. 1, the nozzle 53 extends entirely through plenum chamber 23, and the end portion 53a of nozzle 53 extends slightly inwardly of furnace tube 34 through the opening 33 in tube sheet 25.

As can be best seen in FIG. 1, a generally cylindrically shaped liner or sleeve 55 is positioned in furnace drum 34, and sleeve 55 extends outwardly through opening 33 in tube sheet 25, with an outwardly extending flange 56 of sleeve 55 being secured to the tube sheet 25 around opening 33 by suitable fasteners. As is evident from FIG. l, sleeve 55 is effectively a cantilevered member, in that it is supported entirely by having its flange 56 secured to the tube sheet 25. This creates an annular air gap 57 between sleeve 55 and furnace drum 34, which serves to insulate the furnace drum from the heated medium flowing through sleeve 55, as will hereinafter appear. While sleeve 55 is illustrated in FIG. 1 as a cylindrical member unsupported throughout its length, the present invention contemplates that other forms of insulating liners may be used, and one such means would be a corrugated tubular member with the outer surface of the corrugation either being spaced from the furnace drum wall, or resting thereagainst to create a series of spaced air pockets. Furthermore, the present invention also contemplates that one or more simple supports may be provided for the sleeve 55 to enable the sleeve 55 to move slightly relative to the furnace drum 34 in response to the differences in temperature therebetween.

Means is provided for silencing or mullling any noises emanating from the external source of heated medium during a bypassing operation, and said means includes a plurality of sound deadening llow impediments positioned at longitudinally spaced positions within sleeve 55. As can be seen in FIG. 1, the flow impediments include a plurality of spaced discs 58 having a diameter less than the diameter of sleeve 55, with the discs 5S being disposed generally transversely with respect to the flow of heated medium through the sleeve 55, and being secured thereto by a plurality of rods, not shown. A disc 59 is interposed between discs 58, and disc 59 includes a central opening 59a substantially the same diameter as discs 58, so that the heated medium must flow through a tortuous path past the impediments 58 and 59. A further llow impediment is carried upon a disc 6l) that is disposed generally transversely with respect to the flow of heated medium through the sleeve 55, and this latter impediment takes the form of a plurality of tubes 61, three in the illustrated embodiment, with the tubes 61 being secured to disc 69. The axes of tubes 61 are disposed generally parallel with respect to the axis of sleeve 55, and the entrance end of tubes 61 is positioned in alignment with the adjacent disc 58, so that the heated medium must tlow through a tortuous path in entering the tubes 61. A further disc 58 is positioned in alignment with the outlet end of tubes 61, as is clear from FIG. 1, so that the heated medium must llow around the outer periphery of disc 58 in passing outwardly of the end of sleeve 55, which is disposed somewhat inwardly of tube sheet 24.

An adjustable flow control device is provided in furnace drum 34, and in the illustrated embodiment, the flow control device is in the form of a butterfly damper 62 that is carried on a pivotally mounted control rod 63. Since furnace drum 34 has an extension 34a that extends outwardly of tube sheet 24, control rod 63 is positioned in the dry portion of the boiler outwardly of chamber 26. Damper 62 is movable from a maximum heating position shown in full lines in FIG. l wherein the flow of heated medium through furnace drum 34 is blocked, and a maximum heat compensating position shown in broken lines in FIG. 1, wherein the damper offers substantially no retardation to the flow of heated medium through the furnace drum 34.

During a heating operation, and assuming damper 62 to be in the full line position of FIG. 1 completely blocking tlow of heated medium through furnace drum 34, it will be apparent that the heated medium will flow through the annular passage 64 between the end 53a of nozzle 53 and sleeve 55 into plenum chamber 23. The ilow of heated medium in a heating operation is represented by the full line arrows 65, and it will be noted that the heated medium flows from plenum chamber 23 through tubes 29 in heat exchange relationship with the fluid in chamber 26 into compartment 37 of plenum chamber 22, and thence into compartment 46 of stack 41 and chimney 44. While only a single pass boiler has been illustrated and described herein, that is, a boiler wherein the heated medium flows directly from one end of the boiler through the heat exchange tubes to the other end of the boiler and thence to atmosphere; it will be apparent to those skilled in the art that suitable baffling means may be provided in plenum chamber 23 and in compartment 37 of plenum chamber 22 for directing the heated medium in plural passes through the heat exchange tubes 29. Each of the heat exchange tubes 29 includes means for mullling or silencing any noises emanating from the source of heated medium, and in the illustrated embodiment, the silencing means takes the form of a plurality of dimples 29a provided at spaced positions along each of the tubes 29. Dimples 29a may take the form of those described in Cleaver et al. Patent 3,230,936 and Loebel et al. Patent 3,232,280;

The dimpled tubes 29 provide a llow path for the heated medium having a pressure drop which is greater than the pressure drop presented by a llow path through sleeve '55. Thus, when it is desired to bypass the heated medium around heat exchange tubes 29, the damper 62 is adjusted to a position unblocking furnace drum 34 to an extent where the pressure drop through furnace drum 34 is less than the pressure drop through heat exchange tubes 29. This damper position will be intermediate the full and broken line positions illustrated in FIG. l, and with the damper in this position, the heated medium llowing into sleeve 55 from nozzle r53 will follow the path represented by the broken line arrows 66 around the silencing impediments 58-61 outwardly of sleeve 55, around damper `62, outwardly of furnace drum 34, around baille 35, into compartment 38 of plenum chamber 22, around baille 48, into compartment 47 of stack 41 and chimney 44 and to atmosphere.

When the damper 62 is in the maximum heat compensating position shown in broken lines in FIG. 1, the heated medium accelerated by nozzle 53 will apply a suction to annular area 64 and plenum chamber 23, thus drawing cooling ambient air into the boiler. The path of the cooling air is represented by the broken line arrows 67, and it will be noted that the cooling air flows downwardly in compartment 46 of stack 41 and chimney 44 into compartment 47 of plenum chamber 22, through heat exchange tubes 29 thereby cooling the lluid within chamber 26, and into the plenum chamber 23, Where the cooling air then flows through annular opening 64 into the liner 55 where it passes with the heated medium in its llow path to atmosphere. It will be appreciated that the insulating air gap 57 between sleeve 55 and furnace drum 34 effectively prevents a great deal of heat from passing to the fluid within chamber 26 through the walls of drum 34, and that the damper 62 may be adjusted to a position wherein the flow of ambient air through the tubes 29 off-sets any heat that is imparted to the fluid within chamber 26 through the wall of furnace drum 34. It will further be apparent that during a heating operation, the damper 62 may be adjusted to a position wherein a portion of the heated medium flows through the heat exchange tubes 29 and a further portion of the heated medium flows through the furnace drum 34 to thereby modulate the heating effect.

I claim:

1. A boiler comprising: means defining a casing having a chamber therewith adapted to contain a fluid; a tube sheet closing each end of the chamber; a plurality of spaced tubes in said chamber and opening outwardly of said tube sheets, said tubes being adapted to be in heat exchange relationship with the lluid in said chamber; an exhaust stack; and alternatively selective means, for either directing a heated medium in a first path through said tubes in heat exchange relationship with said fluid, or for directing said heated medium in a second path toward the exhaust stack to bypass said tubes.

2. A boiler as set forth in claim 1 wherein said means for directing a heated medium through said tubes includes means for establishing communication between a source of said heated medium and one end of at least some of said tubes, and means for establishing; communication between atmosphere and the other end of at least some of said tubes.

3. A boiler as set forth in claim 2 wherein said means for directing heated medium toward the exhaust stack to bypass said tubes includes means for establishing communication between said source of heated medium and said exhaust stack, said last named means including an alternatively selective device that is movable to a maximum heating position blocking communication between said source of heated medium and said exhaust stack, whereby said heated medium will tlow through said tubes and thence to atmosphere.

4. A boiler as set forth in claim 3 wherein said device is movable to a heat compensating position establishing communication between said source of heated medium and said exhaust stack, said means for establishing communication between said source of heated medium and said one end of at least some of said tubes cooperating with at least a portion of said means for establishing communication between said source of heated medium and said exhaust stack when said device is in said heat compensating position to apply a suction to said one tube ends, whereby cooling air is drawn inwardly through said tubes and flows with said heated medium through said means establishing communication between said source of heated medium and said exhaust stack.

5. A boiler as set forth in claim 4 wherein the pressure drop of heated medium flowing through the means establishing communication between the source of heated medium and the exhaust stack is less than the pressure drop of heated medium flowing through the means establishing communication between the source of heated medium, tubes and atmosphere.

6. A boiler as set forth in claim 4 in which said source of heated medium is external of said boiler, and wherein means is provided in both said first and second paths for deadening sound from said source of heated medium.

7. A boiler as set forth in claim 6 wherein the sound deadening means in said first path includes a series of dimples in each of said tubes.

8. A boiler as set forth in claim 6 wherein said means for establishing communication between said source of heated medium and said exhaust stack includes a furnace drum extending through said chamber and communieating at one end with said source of heated medium and communicating at the other end with said exhaust stack, sound deadening means in said second path being provided in said furnace drum.

9. A boiler as set forth in claim 8 wherein a portion of said furnace drum extends outwardly beyond the tube sheet closing the end of the casing remote from said source of heated medium.

10. A boiler as set forth in claim 9 wherein said alternatively selective device is positioned in the outwardly extending portion of said furnace drum.

11. A boiler as set forth in claim 8 wherein a generally tubular sleeve is positioned in said furnace drum, at least a portion of said sleeve being spaced from said furnace drum to define an insulating space therebetween.

12. A boiler as set forth in claim 11 wherein said sleeve extends into said furnace drum from the end of the furnace drum adjacent the source of heated medium, said sleeve being spaced from said furnace drum throughout its length.

13. A boiler as set forth in claim 11 wherein the sound deadening means in said second path includes a series of impediments to the flow of heated medium at longitudinally spaced locations in said sleeve.

14. A boiler as set forth in claim 12 wherein said means for establishing communication between said source of 7 heated medium and said exhaust stack further includes a nozzle communicating with said source of heated medium and having a convergent portion extending into said sleeve.

15. A boiler as set forth in claim 14 wherein said nozzle portion is spaced from said sleeve to define an annular area therearound.

16. A boiler comprising: a generally cylindrical shell; a pair of spaced tube sheets adjacent opposite ends of said shell and defining a chamber therebetween that is adapted to contain a fluid; means defining a first plenum chamber outwardly of one tube sheet; means defining a second plenum chamber outwardly of the other tube sheet; partition means dividing said second plenum chamber into first and second compartments, each of said compartments communicating with atmosphere; a plurality of spaced tubes extending between said tube sheets in said chamber, said tubes communicating at one end with said first plenum chambers and at the other end with the first compartment of said second plenum chamber; a furnace drum in said chamber and communicating at one end with said first plenum chamber and with a source of heated edium, the other end of said furnace drum communicating with the second compartment of said second plenum chamber; and an adjustable control member selectively movable between (a) a maximum heating position blocking said furnace drum so that said heated medium flows into said first plenum chamber, through said tubes to the rst compartment of said second plenum chamber, and thence to atmosphere, (b) a maximum heat compensating position unblocking said furnace drum so that said heated medium bypasses said tubes and cooling air is drawn into the first compartment of said second pienum chamber, said cooling air owing through said tubes into said first plenum chamber, and thence flowing with said heated medium through said furnace drum into the second compartment of said second plenum chamber and thence to atmosphere, (c) and a series of heat modulating positions intermediate of said maximum heating position and said maximum heat compensating position.

17. A boiler as defined in claim 16 wherein a converging nozzle communicates with said source of heated medium and extends through the first plenum chamber with the end of the nozzle being positioned inwardly of the end of said furnace drum, the end of said nozzle being spaced from said furnace drum to define an annular space therebetween establishing communication between said furnace drum and said first plenum chamber.

18. A boiler as dend in Claim 16 wherein a single exhaust stack communicates with said second plenum charnber, said exhaust stack including partition means therein dividing the interior of the exhaust stack into a first compartment that communicates with the first compartment of said second plenum chamber and a second compartment that communicates with the second compartment of said second plenum chamber.

19. A boiler connected to an external source of heated medium, such as the exhaust of a turbine or engine, comprising: means defining a casing having a chamber therewithin adapted to contain a fluid; a pair of tube sheets closing each end of the chamber; a plurality of spaced tubes in said chamber, said tubes being adapted to be in heat exchange relationship with the fluid in said chamber; an exhaust stack communicating with one end of said tubes; means establishing communication between said source of heated medium and the other end of said tubes; and means for silencing sound emanating from said source of heated medium.

20. A boiler as set forth in claim 19 wherein said sound silencing means is associated with said tubes.

21. A boiler as set forth in claim 18 including means for bypassing heated medium away from said tubes, said sound silencing means being associated with said bypassing means.

22. A boiler connected to an external source of heated medium, such as the exhaust of a turbine or engine, comprising: means defining a casing having a chamber therewithin adapted to contain a uid; a pair of tube sheets closing each end of the chamber; a plurality of spaced tubes in said chamber, said tubes being adapted to be in heat exchange relationship with the fluid in said chamber; an exhaust stack communicating with one end of said tubes; means establishing communication between said source of heated medium and the other end of said tubes; and means for bypassing heated medium around said tubes to said exhaust stack.

23. A boiler as set forth in claim 22 wherein said bypassing means includes a drum in said chamber and extending from end to end thereof, said drum communicating at one end with said source of heated medium and at the other end with said exhaust stack.

24. A boiler as set forth in claim 23 including means in said drum for insulating the drum from the flow of heated medium.

25. A boiler as set forth in claim 24 wherein a sleeve is provided in said drum, with at least a portion of said sleeve being spaced from said drum to define said insulating means.

References Cited UNITED STATES PATENTS 1,734,310 11/1929 Taylor 122-149 1,994,026 3/1935 Pierce 122-23 2,080,404 5/1937 Hunter et al 122-149 2,576,053 11/1951 Toner 122-149 XR 3,231,016 1/1966 Stewart et al. 122-7 XR 3,269,360 8/1966 Adams 122-7 FOREIGN PATENTS 774,799 5/ 1957 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner U.S. Cl. X.R. 122-135, 149