Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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F I E LD OF THE I NVENT I O~l
2 The present invention relates to boiler tube
3 supports and particularly to process tube supports for
4 hybrid boilers.
BACKGROUND OF TIHE INVENTION
.
6 There are a nunnber of techniques disclosed in
7 the art for locating process tubes within high tempera-
8 ture boilers, Illustrative of such techniques are those
g disclosed in U.S. Patent 3,385,271; U.S. Patent 3,552,362
and U.S. Pa~ent 4,244,606. In actual practice, how-
11 ever, it is most common to have the process tubes
12 which are located in boilers suspended by tube supports
13 from a superstructure external the boiler roof casingO
14 Thus, the process tubes located in the boiler have
upper portions which extend through the boiler roof
16 casing, form a ~end, and return back down through the
17 boiler roof casing. The tubes are suspended by tube
13 supports attached to the bend of the tube and super-
19 structure over the roof casing. Experience has shown
that these precautions are necessary to avoid mechanical
21 failure of the tube supports which would occur if the
22 supports were located within the boiler where temper-
23 atures are generally above at least 1000F and often
24 are as high as about 2000F and a corrosive atmosphere
exists,
26 There are a number of disadvantages to the
27 common tube support technique in practice; not the least
2~ of which is the difficulty associated with providing
29 appropriate expansion joints in the region where the
process tubes penetrate the casing of the boiler. Thus,
31 there remains a need for a very simple and economical
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1 technique for supporting process tubes in a boiler
2 chamber,
3 SUMMARY OF THE INVENTI ON
4 sriefly stated, a vertically disposed serpen-
tine tubular c~il is s~lspended within the convection
6 section of a boiler chamber from the upper return bends
7 of the tubular Iroil by means of metal supports which are
8 in thermal cont3ct with and attached to the upper return
g bends of the tubular coiil. The supports pass through
the insulation of the boiler roof and also are in
11 thermal contact with and attached directly to the metal
12 roof casing. The metal suppor~s are sufficiently short
13 thab, under conditions of use, the supports are cooled
14 by means of conduction oE heat to the metal roof casing
and the process tubes.
1~ In one embodiment of the invention, a metal
17 sleeve and insulation are provided around that portion
18 of the support which extends from the upper return bend
19 of the tubular coil to the boiler roof insulation.
In another embodiment, the support is a metal
21 tube which has an opening above the roof casing and has
22 a plurality of orifices in the tube wall within the
23 boiler such that air from outside the boiler is aspirat-
24 ed from external the boiler through the tube and into
the boiler thereby providing for additional cooling of
26 the support.
27 In yet another embodiment, a liquid, such as
28 water, is sealed within the tubular supports so that
29 under conditions of use, the liquid in contact with that
portion of the support within the boiler is heated and
31 vaporized. The vaporized liquid is then condensed at
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1 the cooler portion of the support which is in contact
2 with the roof casing. Thereafter!~ condensed liquid
3 returns by gravity to portions of the support within the
4 boiler ther~by cooling the support.
Thes,e and otber features of the present
6 invention will be better understood by reading a de-
7 tailed description of the invention in connection
8 with the drawings.
g THE DRAWINGS
Figure 1 is a schematic diagram illus~rating
11 the support of process tubes in a hybrid boiler in
12 accordance with the prese~nt invention.
13 Figure 2 is a cross-section of a view taken
14 along lines 2,2 of Figure 1.
Figure 3 is a schematic illustration of an
16 alternate embodiment of the present invent;on.
17 Figure 4 is a schematic illustration of yet
18 another embodiment of the present inven~ion.
19 DETAILED DESCRIPTION OF THE INVENTION
.
Referring particularly to Figures 1 and 2 of
21 the drawings, there is shown a metal roof casing 10 of a
22 hybrid boiler. The boiler, of course, is provided with
23 side walls and a floor (not shown) defining a convection
24 section of the boiler. Preferably, roof casing 10 is
2S provided with a plurality of upwardly directed channels
26 12 which extend along the length of the boiler roof~ As
~7 can be seen in Figure 2t an insulating material 14 is
28 located within each of the upwardly directed channels
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1 12. The insulating material is selected from typical
2 boiler insulating materials such as refractory materials,
3 ceramic fibers and the like.
4 Arranged within the convection section of the
furnace are a plurality of serpentine tubes 1~) for the
6 passage theretlhrough of process fluid to be heated in
7 the boiler. A~; shown in Figures 1 and 2, the serpentine
8 process tube 16 has upper bend portions 17, lower bend
g portions 18 and straight: run portions 15. The serpen
tine tube 16 is suspended in the boiler in accordance
11 with the practice of the present invention as will be
12 described herein in greal:er detail.
13 At substantial]Ly the mid-portion of each upper
14 bend portion 17, there is provided a circular metal ring
19.
16 Ring 19 may be similar, for example, to a half
17 socket welding pipe coupling. In any event, ring 19 is
18 adapted to receive in engaging relationship and be in
19 thermal contact with one end of supporting stud 20. As
is shown in the drawings, stud 20 is attached by welding
21 to ring 19; however, it should be readily appreciated
22 that ring 19 and stud 20 may be threaded so that stud 20
23 can be screwed into ring 19.
24 In the practice of the present invention
supporting stud 20 preferably is either a cyclindrical
26 metal rod or tube. In any event, supporting stud 20
27 extends upwardly from ring 19 through the insulation 14
28 of channel 12 and through an opening in the roof casing
29 10 and roof casing reinforcing plate 21. The opening in
the roof casing 10 and the reinforcing plate 21 are just
31 sufficient to accommodate the passage of supporting stud
32 20. As can be seen in the figures, the supporting stud
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1 20 is welded to the casing reinforcing plate 21 and the
2 casing rein~orcing plate 21, i~ turn, is welded to the
3 roof casing 10. Thus, the support stud 20 is in thermal
4 contact with and attached to both the ~etal roof casing
10 and the serpentine tube 16.
6 It shlDuld be readily appreciated that stud 20
7 may be attachedl to roof casing 10 by other techniques
8 such as providillg a threaded portion on the upper end of
9 stud 20 and using a nut to retain stud 20 in position
against reinforcing plate 21.
11 As is shown in the figures, the hybrid boiler
12 includes horizontally dispo~ed water tubes 22 which
13 generally are arranged so as to run transverse to the
14 direction of the serpentine tubes 16; however, water
tubes 22 optionally may run parallel to the direction of
16 the serpentine tubes 16. Also, as is shown, a plurality
17 of support bars 23 are welded to the roof casing 10.
18 Generally U-shaped connectors 24:, which are welded
19 to ~he tubular water pipes 22, hang from the support
bar 23 so that the pipes 22 are suspended immediately
21 below the roof casing 10 of the boiler.
22 In a preferred embodiment of the present
23 invention, the water tubes 22 also are provided wi~h
24 horizonatally arranged fins 25 which serve to enhance
the heat transfer efficiency of water tubes 22.
26 Heat loss to the exterior of the boiler is
27 minimized by means of insulation 28 located, in general~,
28 between the top half of tubes 22 and the roof casing
29 10.
An extremely important feature of supporting
31 stud 20 is that it be sufficièntly short that when the
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1 furnace is in use, heat is conducted from stud 20 to
2 roof casing 10 and process tube 16 so that the tempera-
3 ture of stud 20 will not exceed 1400F and preferably
4 1000F. Thus, while the gases within the boiler and in
contact with stud 20 may be as high as 2000F, and even
6 higher-, stud 21D is cooled by conduction since it is in
7 thermal contacl: with the process tube 16 and the roof
8 casing 10, earh of which are at considerably lower
9 temperatures.
In a preferred embodiment, the protection of
11 the support stud 20 by conductive cooling is enhanced by
12 providing a metal sleeve 30 which extends downwardly
13 from a position interme~3iate channel member 12 to the
14 top surface of the upper bend portion 17 of tubes 16 and
an insulating material 3~!, such as refractory insulation,
16 ceramic fibers and ~he like, is located within the tubu-
17 lar sleeve 30. In this way, contact of the stud 20 with
18 hot gases is minimized and heat transfer by conduction
19 to the roof casing 10 is facilitated.
~0 In an alternate embodiment of the present
21 invention, shown in Figure 3, support stud 20 is a
22 hollow tu~e which is open at one end to the atmosphere
23 immediately above the roof of the boiler. Located
24 along the circumference of the tube support stud 20 near
the other end boiler within the boiler are a plurality
26 of orifices. Since during operation of a hybrid boiler,
27 the convection chamber tends to be at a pressure lower
28 than atmospheric pressure, air will enter into the
29 furnace chamber by passing downwardly through the
tubular support stud 20 through orifices 34 and then
31 through the porous insulating material 32. In this way,
32 the support stud 20 also is cooled by convection, as
33 well as by conduction to the roof casing 10 and tube 16.
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1 In yet another embodiment of the present
2 invention, shown in ~igure 4, a liquid charge, shown
3 as reference numeral 34 in Figure 4, is sealed within
4 support 20 by tube sealing members 35. Any non-
corrosive liquid which will reflux under conditions of
6 use of the boiler can b~e employed. One such liquid is
7 mineral free deareated water. Also, the amount of
8 liquid employecl is not critical. In general, the liquid
9 will be sufficient to substantially fill that portion of
the support 20 which exltends below the water tubes 22.
11 Typicall~, the liquid charge will be at atmospheric
12 pressure at room temperature; however, the liquid may
13 optionally be at reduced pressure.
14 Optionally, support 20 may also be provided
with a small needle valve (not shown) for maintaining a
16 check on the condition of the support.
17 In operation, the support 20 is cooled not
18 only by heat being conducted by the metal support 20 to
19 the relatively cooler roof casing 10 and the serpentine
tube }6, but also by vaporization of the liquid in
21 contact with the portion of the support 20 within the
22 boiler which liquid-, after vapori~zation, condenses at
23 the end of the support 20 outside the boiler and in
24 contact with the roof casing 10, where it gives up
its heat to the atmosphere and returns by gravity to the
26 portion of the support 20 for repeat of the cycle.
27 As will be readily appreciated, there are many
28 benefits to be gained by the practice of the present
29 invention. For example, since the process tubes 16 are
supported within the convection section of the boiler,
31 the entire process tube surface serves as a heat input
32 surface, In boiler designs such as that set forth in
33 U.S. Patent 3,385,271, where the process tubes penetrate
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l the roof casing for external support, the effective heat
2 input surface area of the tubes are significantly
~ reduc~sd. Consider also that tube surfaces located
4 outside of the boiler provide a means for increased heat
loss, Then too expansioJI joints are not required in the
6 casing when thls process tub~ss are suppor~ed in accord-
7 ance with the present invention, thereby avoiding the
8 problem of air leakage i.rom or into the boiler. More-
9 over, fabrication and erection are simplifled because
roof penetrations are eliminated or simplified, except
ll for the inlet and outlet connections of the process
12 tubes. Veey importantl~, since the support studs are
13 fabricated from common pipe components, the need for
14 unusually designed parts: with their associated higher
costs is avoided.
