CA2062405C - Liquid cooled boiler door - Google Patents

Abstract

A liquid-cooled boiler door for use with a boiler having a flooded liquid section and a storage liquid section. The liquid-cooled boiler door includes an interior wall having an interior surface and an exterior surface and an exterior wall having an interior surface and an exterior surface. The exterior wall is spaced from said interior wall to define a circulation space therebetween. A first connector fluidly connects the flooded liquid section of the boiler to the circulation space defined between the interior wall and the exterior wall of the liquid-cooled boiler door. A second connector fluidly connects the storage liquid section of the boiler to the circulation space defined between the interior wall and the exterior wall. Liquid contained within the boiler circulates from the flooded liquid section, through the circulation space defined between the interior wall and the exterior wall, and into the storage section of the boiler.

Description

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LIQUID COOLED BOILER DOOR

TECHNICAL FIELD OF THE lNV~.~lON
The present invention relates to a door for use in conjunction with a firetube boiler. In particular, the invention relates to a firetube boiler door which is S cooled by internal liquid circulation.

BACRGRO~JND OF THE 1N V~;N 110N
Firetube boilers are commonly used to heat water for a variety of purposes. Firetube boilers typically are formed by a cylindrical vessel capped at each end. A
plurality of parallel or substantially parallel heating tubes are disposed within the vessel. A main furnace tube is also defined within the vessel. A stream of high temperature gases is directed down the furnace tube from a main flame source. Upon reaching the opposite end of the vessel, i.e., the turnaround chamber, the heated gases are reflected through the parallel heating tubes of the firetube boiler. The number of times that these heated gases are reflected defines the number of "passes"
employed by the boiler. Thus, if the stream of heated gases is reflected once, the boiler is considered to be a two-pass boiler. If the stream of heated gases is reflected twice, the boiler is considered to be a three-pass boiler.
In order to effect the desired magnitude of heating of the liquid within the boiler, very high levels of heat are directed through the furnace tube and the heating tubes of the boiler. As a result, it has been found that the internal surfaces of the turnaround chamber, in particular the rear wall of the turnaround chamber, are subjected to great erosion from the heated gases. In order to minimize the detrimental effects of the heated gases on the turnaround chamber, two alternative approaches have been developed.
Some boilers employ a ceramic refractory lining within the turnaround chamber in order to minimize erosion. Such boilers are sometimes referred to as "dryback" boilers. Boilers employing such a refractory lining have proven to be somewhat successful in reducing erosion of the turnaround chamber.
In some dryback boilers, the refractory-lined wall of the turnaround chamber is a door which permits access to the interior of the boiler, thereby facilitating service of the interior of the boiler. It has been found, however, that there is a significant level of heat loss realized through the ceramic refractory material due to its relatively poor insulating characteristics. In addition, the ceramic refractory material is also subject to the erosive effects of the hot gases over extended periods of use, thereby requiring replacement or repair of the door.
An alternative approach to resolving the erosion problems has given rise to what is known as a "wetback boiler." Rather than employing a refractory material to limit erosion of the turnaround chamber, the wetback boiler utilizes a body of water contained within the boiler to cool the walls of the turnaround chamber. The body of water "surrounds" the turnaround chamber on three sides, and thus essentially ~submerges" the turnaround chamber. The presence of water around the turnaround chamber provides greater insulation than the refractory material discussed above, thereby minimizing heat loss from the boiler.
Although providing better resistance to erosion and better insulation characteristics as compared to the "dryback" firetube boiler, there are certain disadvantages associated with the wetback boiler. The wetback design often significantly reduces access to the interior of the boiler through the rear wall of the turnaround chamber.
Although most wetback boilers include a small porthole through the cooling chamber, these portholes are typically .~
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2eB2~0s very small in dimension, thereby reducing access to the interior of the boiler. Thus, it has been found to be considerably more difficult to service the interior of a wetback boiler as compared to dryback boilers having a larger access door disposed at the rear wall of the turnaround chamber.

20S2~05 SUMMARY OF THE lNv~NlION
The liquid-cooled boiler door of the present invention includes an interior wall and an exterior wall which define a water circulation space therebetween. The circulation space of the boiler door is fluidly connected at one end to a flooded section of the boiler. The circulation space of the boiler door of the present invention is also fluidly connected at a second end to a storage section of the boiler such that water circulates naturally from the flooded section of the boiler, through the circulation space of the liquid-cooled boiler door, and into the storage section of the boiler.
In an alternative embodiment of the present invention, a liquid-cooled baffle is formed on the interior wall of the liquid-cooled door. The liquid-cooled baffle includes plurality of substantially parallel liquid tubes fluidly connected to the circulation space of the liquid-cooled boiler door.

BRIEF DESCRIPTION OF THE DRA~INGS
For a more complete understanding of the present invention, and for further details and advantages thereof, reference is now made to the following Detailed Description read in conjunction with the accompanying drawings in which:
FIGURE 1 is a cross-sectional view of a known three-pass "dryback" firetube boiler;
FIGURE 2 is a cross-sectional view of a known two-pass "wetback" firetube boiler;
FIGURE 3 is a cross-sectional view of a boiler incorporating the liquid-cooled boiler door of the present invention;
FIGURE 4 is an exploded view of one embodiment of the liquid-cooled boiler door of the present invention; and FIGURE 5 is a detailed view of the liquid tubes of a baffle disposed on the liquid-cooled boiler door of one embodiment of the present invention.
FIGURE 6 is a detailed view of an alternative embodiment of the liquid-cooled boiler door of the present invention.
FIGURE ? is a detailed view of a boiler door constructed in accordance with one embodiment of the present invention in use with a firetube boiler.
FIGURE 8 is a perspective view of the interior of a liquid-cooled boiler door constructed in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION
Referring to FIGURES 1 and 2, known dryback and wetback Scotch firetube boilers are illustrated. A double pass boiler having a liquid-cooled door constructed in accordance with the present invention is generally indicated at 10 in FIGURE 3. Boiler 10 is generally defined by cylindrical outer wall 12. A furnace tube 14 is disposed within boiler 10 as depicted in FIGURE 3 and extends from first end 16 to second end 18 of boiler 10. A
flooding water section 20 and a storage water section 22 are defined within boiler 10 as depicted in FIGURE 3.
Tubes 38, 38a, 38b are disposed within boiler 10 as depicted in FIGURE 3. Water spaces 21a, 21b, 21c are defined between tubes 38, 38a, 38b. As the heated gases pass through passageways 38, 38a, 38b, as discussed in detail below, there is a transfer of heat from the gases within tubes 38 to the liquid within spaces 21a, 21b, 21c.
A liquid-cooled door constructed in accordance with the present invention is generally indicated at 24 in FIGURE 3. Door 24 includes interior wall 24a and exterior wall 24b. Circulation space 26 is defined between interior wall 24a and exterior wall 24b. In a preferred embodiment of the present invention depicted in FIGURE 4, door 24 is substantially hemispherical in shape in order to provide greater structural integrity. In this embodiment, door 24 includes interior wall 24a, exterior wall 24b, and connecting wall 24c in order to define circulation space 26. It is to be appreciated, however, that door 24 can have any shape with~out departing from the scope of the present invention.
In an alternative embodiment of the present invention, door 24 has an irregular shape such as depicted in FIGURE 6. In this embodiment, second end 32 of door 24 .~
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2~624~5 serves a dual function. First, second end 32 provides cooling of turnaround chamber 34. Second, second end 32 essentially isolates turnaround chamber 34 from the upper portions of boiler 10. The desirability of isolating turnaround chamber 34 from the upper portions of boiler 10 is discussed in detail below with respect to the inclusion of baffles 36 on interior wall 24a.
As depicted in FIGURE 3, circulation space 26 fluidly connects flooding section 20 and storage section 22.
~irst end 28 of circulation space 26 is fluidly connected to flooding water section 20 through first connector 30.
Second end 32 of circulation space 26 is fluidly connected to storage water section 22 through second connector 33.
Storage water section 22 may be used to store either water or steam. Connectors 30, 33 preferably provide a watertight connection between door 24 and the remainder of boiler 10. Connectors 30, 33' can bè constructed of a flexible tubing or a plurality of pivotable elbow joints interconnected by gaskets. Other known devices can be used as connectors 30, 33 to achieve the desired effect.
Heated liquid witnin circulation space 26 will naturally tend to circulate due to the loss of hot liquid and steam through second connector 33. As a result, additional liquid is drawn into circulation space 26 from flooding section 20. Simultaneously, additional liquid will be drawn into flooding section 20 from the remaining sections of boiler 10. The circulation of liquid through circulation space 26 thus is achieved naturally and does not require the use of a pump. Further, this natural circulation is achieved using the flooding section and storage section of existing firetube boilers.
Accordingly, the liquid-cooled door 24 of the present invention can be added to firetube boilers currently in use or can be installed as original equipment in new firetube boilers.
It will be appreciated that the flow of liquid through circulation space 26 will cool interior wall 24a of door 24, thus reducing the effect of erosion created by the flow of heated gases on interior wall 24a. In addition, it will be appreciated that the presence of liquid within circulation space 26 will provide a significant degree of insulation between the interior of boiler 10 and its external environment. Finally, liquid flowing through circulation space 26 will be heated as a result of the transfer of heat from interior wall 24a.
In another alternative embodiment of the present invention, door 24 is constructed of a plurality of liquid transfer tubes 135. Liquid transfer tubes 135 are preferably configured as depicted in FIGURE 7. In this embodiment, outer tube 135a is essentially donut-shaped.
Major cross tube 135b is in fluid communication with outer tube 135a and divides door 24 substantially into two halves. A plurality of tubes 135c fluidly connect outer tube 135a and major cross tube 135b as shown in FIGURE 7.
Regions 137 defined between tubes 135 are preferably constructed of a web of material that is resistant to the erosive effects of the heated gases within turnaround chamber 34. In an alternative configuration of this embodiment, tubes 135 are disposed in tangential relation to one another such that web 137 is not needed. It will be appreciated that liquid will flow from flooded water section 20, through tubes 135, and into storage water section 22 in the manner discussed in reference to other embodiments of the present invention. In this way, door 24 is cooled, thereby reducing the erosive effects of the flow of heated gases on the wall of turnaround chamber 34.

lO 2062405 Heated gases directed through furnace tube 14 from main flame source 100 will impact interior surface of interior wall 24a of door 24. The stream of heated gases will be reflected by interior wall 24a as generally indicated by arrows 102 in FIGURE 3 into tubes 38, 38a, 38b.
The boiler depicted in FIGURE 3 is a double pass boiler. In a double pass boiler, heated gases passing through passageways 38, 38a, 38b enter vent chamber 50 and are subsequently removed from boiler 10 through vent 52. In some instances, it has been found to be desirable to protract the time during which the heated gases flow through boiler 10 in order to maximize the quantity of heat transferred from the gases to the liquid within boiler 10. For example, FIGURE 1 depicts a three-pass dryback firetube boiler having a second turnaround chamber disposed at the first end of the boiler.
In a second alternative embodiment of the present invention constructed for use with a three-pass boiler of the type depicted in FIGURE 1 or four-pass boiler, door 24 includes baffle 36 disposed along interior wall 24a, as shown in FIGURE 8. Baffle 36 serves to direct heated gases passing through turnaround chamber 34 into second pass 38. In other words, baffles 36 partitions turnaround space 34 into two smaller turnaround spaces 34a, 34b. In this way, heated gases entering second pass 38 do not commingle with heated gases passing into three-pass venting chamber 50a, thereby reducing heat loss through venting chamber 50a. It is to be appreciated that additional baffles 36 can be disposed along interior wall 24a for use with boilers having more than four passes.
Baffle 36 is preferably constructed of a plurality of substantially parallel water tubes 35 arranged in the manner depicted in FIGURE 5. Tubes 35 can be disposed tangentially to one another. In an alternative configuration, tubes 35 can be connected by web 37. It is to be appreciated that tubes 35 can be U-shaped or have various other configurations without departing form the scope of the present invention.
In a preferred embodiment of baffle 36 of the present invention depicted in FIGURE 8, first ends 42 of tubes 40 are fluidly connected to manifold 45 and second ends 44 of tubes 40 are fluidly connected to circulation space 26 of door 24. As seen in FIGURE 8, manifold 45 is mounted on internal wall 24a of door 24 such that the interior of manifold 45 is in fluid communication with circulation space 26. Water circulating within circulation space 26 will thus circulate within manifold 45 and water tubes 40 in order to provide cooling of baffles 36.
Although the present invention has been described in detail with reference to certain preferred embodiments, it is to be appreciated that certain modifications can be made to the disclosed liquid-cooled boiler door without departing from the true spirit and scope of the present invention.

Claims (20)

1. A liquid-cooled boiler door for use with a boiler having a flooded liquid section with a firetube submerged therein and a storage liquid section, said liquid-cooled boiler door comprising:
an interior wall having an interior surface and an exterior surface;
an exterior wall having an interior surface and an exterior surface, said exterior wall being spaced from said interior wall whereby a circulation space is defined between said exterior surface of said interior wall and said interior surface of said exterior wall;
a first connector fluidly connecting said flooded liquid section of said boiler to said circulation space defined between said interior wall and said exterior wall of said liquid-cooled door;
and a second connector fluidly connecting said storage liquid section of said boiler to said circulation space defined between said interior wall and said exterior wall, whereby liquid is permitted to circulate from said flooded liquid section, through said circulation space defined between said interior wall and said exterior wall, and into said storage section of said boiler.

2. The liquid-cooled boiler door of Claim 1 wherein said interior wall and said exterior wall are hemispherically shaped, said liquid-cooled boiler door further comprising:
an annular wall, said interior wall and said exterior wall being mounted to said annular wall whereby a circulation space is defined within said annular wall, said interior wall, and said exterior wall.

3. The liquid-cooled boiler door of Claim 1 wherein a manifold and a plurality of liquid tubes are disposed on said interior surface of said interior wall, said manifold having a first end and a second end, said manifold defining a channel therethrough, said first end and said second end of said manifold being fluidly connected to said circulation space defined between said interior wall and said exterior wall whereby said circulation space is in fluid communication with said channel defined through said manifold, each of said liquid tubes having a first end and a second end, said first end of said liquid tubes being fluidly connected to said manifold and said second end of said liquid tubes being fluidly connected to said circulation space defined between said interior wall and said exterior wall.

4. The liquid-cooled boiler door of Claim 3 wherein said liquid tubes are disposed in tangential contact to one another.

5. The liquid-cooled boiler door of Claim 3 wherein said liquid tubes are spaced from one another and wherein adjacent liquid tubes are connected by a web.

6. The liquid-cooled boiler door of Claim 1 wherein a baffle is disposed on said interior surface of said interior wall whereby said baffle directs the movement of heated gases within said boiler.

7. The liquid-cooled boiler door of Claim 6 wherein said baffle comprises a plurality of liquid tubes.

8. The liquid-cooled boiler door of Claim 7 wherein said liquid tubes are disposed in tangential contact to one another.

9. The liquid-cooled boiler door of Claim 7 wherein said liquid tubes are spaced from one another and wherein adjacent liquid tubes are connected by a web.

10. The liquid-cooled boiler door of Claim 7 wherein a plurality of baffles are disposed on said interior surface of said interior wall.

11. The liquid-cooled boiler door of Claim 1 wherein said first connector is a flexible conduit connected in a fluid-tight manner to said flooded liquid section and to said circulation space defined between said interior wall and said exterior wall, and wherein said second connector is a flexible conduit connected in a fluid-tight manner to said circulation space defined between said interior wall and said exterior wall and to said storage liquid space.

12. A liquid-cooled boiler door for use with a boiler having a flooded liquid section with a firetube submerged therein and a storage liquid section, said liquid-cooled boiler door comprising:
an interior wall having an interior surface and an exterior surface, said interior wall having a hemispherical shape;
an exterior wall having an interior surface and an exterior surface, said exterior wall having a hemispherical shape;
an annular wall, said interior wall and said exterior wall being mounted on said annular wall whereby a fluid circulation space is defined within said annular wall, said interior wall, and said exterior wall;
a first connector fluidly connecting said flooded liquid section of said boiler to said circulation space defined within said annular wall, said interior wall, and said exterior wall of said liquid-cooled door; and a second connector fluidly connecting said storage liquid section of said boiler to said circulation space defined within said annular wall, said interior wall, and said exterior wall of said liquid-cooled door, whereby liquid is permitted to circulate from said flooded liquid section, through said circulation space defined within said annular wall, said interior wall, and said exterior wall, and into said storage section of said boiler.

13. The liquid-cooled boiler door of Claim 12 wherein a baffle is disposed on said interior surface of said interior wall whereby said baffle directs the movement of heated gases within said boiler.

14. The liquid-cooled boiler door of Claim 13 wherein said baffle comprises a plurality of liquid tubes and a manifold whereby liquid circulating through said circulation space defined between said interior wall and said exterior wall also circulate through said liquid tubes and through said manifold.

15. The liquid-cooled boiler door of Claim 14 wherein said liquid tubes are disposed in tangential contact to one another.

16. The liquid-cooled boiler door of Claim 14 wherein said liquid tubes are spaced from one another and wherein adjacent liquid tubes are connected by a web.

17. The liquid-cooled boiler door of Claim 13 wherein a plurality of baffles are disposed on said interior surface of said interior wall.

18. The liquid-cooled boiler of Claim 12 wherein a manifold and a plurality of liquid tubes are disposed within said interior surface of said interior wall, said manifold having a first end and a second end, said manifold defining a channel therethrough, said first end and said second end of said manifold being fluidly connected to said circulation space defined between said interior wall and said exterior wall whereby said circulation space is in fluid communication with said channel defined through said manifold, and wherein each of said liquid tubes has a first end and a second end, said first end of said liquid tubes being fluidly connected to said manifold and said second end of said liquid tubes being fluidly connected to said circulation space defined between said interior wall and said exterior wall.

19. A liquid-cooled boiler door for use with a boiler having a flooded liquid section with a firetube submerged therein and a storage liquid section, said liquid-cooled boiler door comprising:
an interior wall having an interior surface and an exterior surface, said interior wall having a substantially hemispherical shape;
an exterior wall having an interior surface and an exterior surface, said exterior wall having a substantially hemispherical shape;
an annular wall, said interior wall and said exterior wall being mounted on said annular wall whereby a fluid circulation space is defined within said annular wall, said interior wall, and said exterior wall;
a first connector fluidly connecting said flooded liquid section of said boiler to said circulation space defined within said annular wall, said interior wall, and said exterior wall of said liquid-cooled door;
a second connector fluidly connecting said storage liquid section of said boiler to said circulation space defined within said annular wall, said interior wall, and said exterior wall of said liquid-cooled door, whereby liquid is permitted to circulate from said flooded liquid section, through said circulation space defined within said annular wall, said interior wall, and said exterior wall, and into said storage section of said boiler; and at least one baffle disposed on said interior surface of said interior wall whereby said baffle directs the movement of heated gases within said boiler.

20. The liquid-cooled boiler door of Claim 19 wherein a manifold and a plurality of liquid tubes are disposed on said interior-surface of said interior wall, said manifold having a first end and a second end, said manifold defining a channel therethrough, said first end and said second end of said manifold being fluidly connected to said circulation space defined between said interior wall and said exterior wall whereby said circulation space is in fluid communication with said channel defined through said manifold, each of said liquid tubes having a first end and a second end, said first end of said liquid tubes being fluidly connected to said manifold and said second end of said liquid tubes being fluidly connected to said circulation space defined between said interior wall and said exterior wall.