Note: Descriptions are shown in the official language in which they were submitted.
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REFRACTORY DIFFUSOR FOR INDUSTRIAL HEAT SOURCE
Background of the Invention
Large scale heat sources are used for a variety of
applications in industry, including sulfur recovery units,
waste incinerators, and the like. Such heat sources
typically have a construction as shown in Fig. l, wherein a
large-scale heating vessel 1 has a burger 2 oa one end and
a waste heat boiler 3 on the other end.
Waste heat boilers are commonly used with many types of
industrial heat sources to extract heat from waste gases of
an industrial process. It may be necessary to extract heat
from the waste gas to cause a component thereof to condense.
or it may be advantageous to extract heat from the waste gas
and use that heat in another process or eves to provide heat
for the industrial facility.
Generally speaking, a waste heat boiler includes a
plurality of metal boiler tubes 4 supported by opposed metal
tube sheets 5 (only one tube sheet ie depicted in Fig. 1).
The tube sheets define a vessel for holding water or some
other form of heat transfer medium. Hot waste gas passes
through the boiler tubes arranged in the inlet tube sheet
and heat is extracted therefrom via heat transfer from the
hot gas to the heat transfer medium contained within the
confines of the tube sheets.
There are several concerns associated with such
industrial heat sources, e.g., incinerators. One concern is
the corrosive nature of the heat and gas produced by the
3 0 incinerator f lame, and the damage that such heat and gas can
inflict on the metal components of the waste heat boiler.
In an effort to deal with this problem, the present
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inventors disclosed. in u.s. Patent ~o. 5,65,432,
a new refractory ferrule to protect the metal
components of the waste heat boiler from the corrosive
nature of the incinerator heat/flame. A plurality of
refractory ferrules are arranged to form protective wall 7.
Another concern is making use of the full heat exchange
capability of the waste heat boiler. That ia, the vessel Z
shown in Fig. 1 typically has a length of about 20-30 feet
and a diameter of about 6-10 feet. The incinerator flame,
however, is typically not as long or wide as the vessel. As
a result, only the central tubes of the waste heat boiler
receive the main thrust of the incinerator flame and a hot
spot is created at the center of the tube sheet.
In as attempt to spread the heat of the incinerator
flame across the satire face of the tube sheet of the waste
heat boiler. it has become industry praatiae to erect a
diffusor wall 6 between burger a cad tube sheet 5 of waste
heat boiler 3, as shown is Fig. l~ is as attempt to spread
the inaiaerator flame over the full surface of tubs sheet 5.
Such diffusor walls have been fozmed of standard refractory
brick, typically 9" x 4.5~ x 4.5"~ is the shape of a
standard wall, except that alteraatiaQ briake were omitted
to give the appearaaae of a checkerboard (these walls are
sometimes referred to as "aheakes~ralls' ) . The holes formed
is the wall allow passage of the incinerator gas cad provide
more uniform heat distribution across the satire face of the
tube sheet of the waste heat boiler.
This type of wall. however, has several drawbacks.
First, the open frontal area of this type of diffusor wall
is only about 35%. so that the presence of the wall
substantially disrupts the volume flow of heated gas through
the waste heat boiler.
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Another drawback is that the bricks that make up the
wall are mortared is place to withstand the force of the gas
passing through the vessel. The service entrance of the
vessel is near the burner, and thus the checkerwall, if not
equipped with a ~maaway"'. must be dismantled each time the
tube sheet of the waste heat boiler needs to be serviced or
replaced.
Another type of checkerwall has been constructed from
a plurality of refractory cylindrical tubes stacked one on
top of the other like a pile of firewood. This structure
provides greater open frontal area, but still must be
dismantled whoa the tube sheet needs to be serviced. If the
refractory tubes are assembled without the use of mortar in
order to facilitate disassembly for tube sheet maintenance
and repair, then the overall wall is highly unstable in the
axial direction of the vessel, cad the force of the gas
emitted from the burner tends to displace the tubes in the
direction of gas flow and collapse the wall.
S~marv of the Invention
The present invention was developed is view of the
above-discussed problems with the prior art.
aspect of the present invention is to provide a
refractory brick particularly suited for use in constructing
a diffusor wall of as industrial heat source. The brick
includes a substantially tubular body having a first end, a
second end opposed to the first end, as inner surface
defining a passageway extending is a longitudinal
direction of the body from the first end to the second end,
and as outer peripheral surface extending from the first end
to the second end. The outer peripheral surface has a
complementary shape that allows mating of a plurality of the
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bricks to form cooperatively a diffusor wall . Mating structure
is formed oa or in the outer peripheral surface for engaging
corresponding mating formed oa or is outer peripheral
surfaces of adjacent bricks when assembled as a diffusor
wall.
Another aspect. of the present invention is to provide
a diffusor wall that overcomes the problems associated with
the above-discussed prior art diffusor walls. The diffusor
wall of the present invention includes a plurality of
refractory bricks each comprising (i) a substantially
tubular body having a first cad, a second cad opposed to the
first end, an inner surface defining a passageway extending
in a longitudinal direction of the body from the first cad
to the second end, and as outer peripheral surface extending
from the first end to the second cad. The outer peripheral
surface has a complementary shape that allows mating of a
plurality of the bricks to form cooperatively the diffusor
wall.(ii) A plurality of mating structures is formed on or in the outer
peripheral surface for engaging corresponding mating structures formed on or
in outer peripheral surfaces of adjacent bricks when
assembled as the diffusor wall. The bricks ara stacked one
upon aaothsr such that the passageways of all the bricks are
aligned is substantially a common direction.
A diffuaor wall formed of the refractory brick of the
present invention overcomes the problems associated with
prior art diffusor walls, ia~that the wall can be assembled
without the use of mortar. Accordingly, the wall is very
easy to disassemble to allow access to the tube sheet.
Additionally, the mating means provided on each brick allows
tha bricks to be "tied" together, such that the overall
stability of the diffusor wall is sufficient to stand up to
the force of the exhaust gas emitted by the burger. Still
further, when the bricks are formed in the shape of hexagons
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with a circular passageway formed therethrough, the open
frontal area of the overall diffusor wall can reach about
50%, thereby allowing higher volume flow of exhaust gas to
pass therethrough.
Yet another aspect of the present invention is to
improve the heat transfer efficiency of a waste heat boiler
associated with an industrial heat source. The present
invention provides a system that accomplishes this goal by
arranging a refractory wall adjacent an upstream side of the
waste heat boiler and s diffusor wall upstream from the
refractory wall. The refractory wall has a plurality of
openings formed therethrough in alignment with tubes formed
in the waste heat boiler. This arrangement directs all of
the exhaust gas into and through the tubes of the waste heat
boiler, as opposed to heating the upstream face of the waste
heat boiler itself. Heat transfer through the tubes is much
more efficient thaw heat transfer through the upstream face
of the waste heat boiler.
The diffusor wall is positioned upstream from the
refractory wall and is designed to spread the intensity of
the exhaust gas across the entire surface of the upstream
face of the waste heat boiler. If the diffusor wall ware
omitted. the central tubes of the waste heat boiler would
receive the majority of the heat from the exhaust gas and
less heat transfer would occur through the perimeter tubes.
The diffusor wall is designed to make use of the heat
transfer capability of all the tubes in the waste heat
boiler.
In a preferred form of the present invention. the
refractory wall is built up from a plurality of refractory
ferrules positioned is the tube openings of the waste heat
boiler and each of the ferrules includes (i) a head portion
having a first cad defining as inlet of the ferrule, a
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second end opposed to the first end. as inner surface
defining a passageway extending from the first end ,to the
second end, and an outer peripheral surface extending from
the inlet first end to the second end. The outer peripheral
surface has as outer shape that allows mating of a plurality
of the ferrules to form cooperatively a substantially gas-
tight barrier between outer peripheral surfaces of adjacent
ferrules. A groove is formed in the outer peripheral
surface and extends around the circumference thereof. The
ferrule also includes a tube portion having a first end
joined to the head portion, a second end defining the outlet
of the ferrule which is positioned is the opening of each
tube is the waste heat boiler, and as inner surface defining
a passageway extending from the first end to the outlet
second end and merging with the passageway of the head
portion.
Brief Description of the Drawiaas
Fig. 1 illustrates the arrangement of a burner, waste
heat boiler and diffusor wall in an industrial incinerators
Fig. 2 is a longitudinal cross-sectional view of a
ceramic ferrule used to protect the tube sheet of the waste
heat boilers
Figs. 3A and 3B are plan views of as array of ceramic
ferrules at room temperature sad at the working temperature
of the industrial incinerator, respectivelys
Fig. 4A is a cross-sectional view. taken along line I-I
of Fig. 4B, of a refractory brick used to build a diffusor
wall is accordance with the present invention:
Fig. 4B is a longitudinal cross-sectional view, taken
along line II-II of Fig. 4A, of the refractory brick shown
in Fig. 4A~
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Fig. 5 is a plan view of a half-brick that is otherwise
the same as the brick depicted is Figs. 4A sad 4H=
Fig. 6 is as cad play view of a diffusor wall formed of
the bricks shows in Figs. 4A-5: sad
Fig. 7 is an cad play view of a diffusor wall formed of
the bricks shown is Figs. 4A-5, with the addition of a
manway.
Detailed Deseri~tioa of the Invention
Fig. 1 shows as industrial heat source, e.g.. as
l0 incinerator. including a heating vessel 1 that is typically
cylindrical is shape having a length ranging from 20' to 30'
and a diameter of about 6' to 10'. A bursar 2 is arranged
at a leading cad of vessel l, sad, typically, a waste heat
boiler 3 is arranged at the exit cad of vessel 1. A service
entrance (sot shows) is typically arranged proximate the
inlet end of vessel 1. In aasordaaae with the invention
disclosed sad claimed in u.s. Patent rro. 5,657,432,
refrastory ferrules are used to form a
refractory wall 7 to protest tube sheet 5 of waste heat
boiler 3. Ia aaaordaase with the present invention, a
diffusor wall 6 is disposed between burger 2 sad waste heat
boiler 3 is order to spread the heat of the incinerator gas
along the satire face of tube sheet 5 of waste heat boiler
3.
Fig. 2 is a cross-sectional view of one embodiment of
the refractory ferrule 21 used to protest tube sheet 5 of
waste heat boiler 3. The ferrule iaaludes a head portion 22
sad a tube portion 26.
The head portion 22 of ferrule 21 has a first cad 22a
defining as islet of the ferrule, a second end 22b opposed
to first cad 22a, an inner surface 23 defining a passageway
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24 extending from first sad 22a to second end 22b, and an
outer peripheral surface 25 extending from first end 22a to
second end Z2b. The tube portion 26 of ferrule 21 has a
first end 26a joined to head portion 22. a second end 26b
defining the outlet of the ferrule, sad as inner surface 23'
defining a passageway 24' extending from first end 26a to
seaoad end 26b sad merging with passageway 24 of head
portion 2Z.
The outer peripheral surface 25 of head portion 22 has
as outer shape that allows mating of a plurality of the
ferrules to form cooperatively a substantially gas-tight
(with respect to the interfaces between adjacent ferrules)
refractory barrier wall. The outer shape, whea~viewed is a
transverse plane of the ferrule (Fig. 3A). can be polygonal
(a. g., square or hexagonal).
Fig. Z shows that head portion 22 includes a groove 27
formed is the outer peripheral surface thereof. Groove 27
preferably extends around the satire airaumfersace of head
portion 2Z, although partial circumfereatial grooves could
be employed.
The manner is which the ferrule engages the tubes of
the tube sheet is the waste heat boiler is described in
detail in u.s. Patent rro. 5,657,432 and thus will not
bs repeated herein.
Fig. 311 is a plea view shoving as array of ferrules 21
installed is boiler tubes of as inlet tube sheet. The
boiler~tubes sad inlet tube sheet are not shown in Fig. 3A
because they are shielded by the head sad tubs portions of
the ferrules. The outer peripheral shapes of the ferrules
shows is Fig. 3A are hexagonal. such that outer surfaces of
adjacent ferrules will abut each other at the operating
temperature of the industrial heat source. More
specifically, the ferrules are dimensioned such that the
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outer peripheral surfaces thereof are spaced from one
another when cold (i.e., when the industrial heat source is
inoperative) (Fig. 3A), and abut one another at the
operating temperature of the industrial heat source (Fig.
3B). The mated ferrules act as a cast refractory wall by
shielding the inlet tube sheet from the heat of the waste
gas.
Fig. 4A is a cross-sectional view of one embodiment of
the refractory brick in accordance with the present
invention. Fig. 48 is a longitudinal cross-sectional view
takes along line I-I of Fig. 4A. The cross-sectional view
of Fig. 4A is taken along line II-II of Fig. 4B.
The refractory brick 30 has a substantially tubular
body 31. When used herein, the term '"tubular" describes
bodies that are generally tubular in nature, although the
inner and outer peripheral surfaces thereof are not
necessarily cylindrical. In a preferred form of the
invention as shows in Fig. 4A. the inner surface 32 of
tubular body 31 is cylindrical, while the outer peripheral
surface 33 of tubular body 31 is hexagonal. Fig. 5,
described below, also depicts a substantially ~tubular°
body.
Body 31 has a first end 34 and a second opposed end 35.
The inner surface 32 defines a passageway 36 that extends in
the longitudinal direction of body 31 from first end 34 to
second end 35. The hot exhaust gas emitted from burner 2
passes through passageways 36 of each refractory brick when
a plurality of bricks are assembled to form diffusor wall 6.
While the outer peripheral surface 33 of the refractory
brick can have a shape other than hexagonal, that shape
preferably should be complementary, such that a plurality of
bricks can be stacked one upon another in such a manner that
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the outer peripheral surface of each brick meets smoothly
with the outer peripheral surfaces of adjacent bricks.
Mating means 37 are formed on or in outer peripheral
surface 33 of body 31. The mating means preferably are
formed as corresponding male and female parts. such as the
tongue 37A and groove 37B structures depicted in Figs. 4A
and 4B. The mating mesas preferably extend in a direction
substantially perpendicular to the longitudinal direction of
body 3l. as shown is Fig. 4B. In the case of a hexagonal-
shaped brick as depicted in the drawings it is preferred to
have corresponding male and female mating means oa all sides
of the outer peripheral surface of the body. such that each
refractory brick will interlock with all bricks adjacent
thereto. While Figs. 4A and 4H show the male and female
mating parts as alternating along the outer peripheral
surface of the refractory brick it is possible to use any
combination of male sad female mating parts depending upon
the particular application.
Fig. 4B shows that the male and female mating parts are
arranged in roughly the same axial plane of body 31. The
male and female parts preferably extend around the entire
outer peripheral surface of the body and collectively form
a group that is positioned on substantially a single axial
plane of the body. Fig. 4B shows that a plurality of such
groups can be arranged along the body spaced from one
another in the axial direction thereof.
The respective dimensions of the tongue and groove
structures depicted in Fig. 4A show that it is preferred to
leave a space between the interlocking male and female
mating structures. That is~ the tongue while having the
same general shape as the groove is dimensioned slightly
smaller than the groove. This space simply facilitates
assembly of the diffusor wall. in that it is easier to
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assemble the bricks one upon another if there is a certain
degree of "play' between the interlocking structures.
The refractory bricks can be made of nay type of
refractory material. Many types of ceramic materials are
often used in these types of applications. A preferred
material is alumiaa is view of cost sad ease of manufacture.
In this regard, the refractory bricks aaa be made by any one
of several conventional ceramic maaufaaturiag processes such
as slip casting. injection molding, extrusion followed by
machining. or the like. A preferred method by which the
refractory bricks are made is the freese cast process
described is U.B. Patent 4,Z46,Z09.
Fig. 5 shows a half-brick 38 that is easeatially oae-
half of the brisk shown in Figs. 4A sad 4H with the addition
of a closure portion 39. The brick depicted is Fig. 5 is
particularly helpful is filling peripheral holes of the
diffusor wall and defining maaways through the diffusor
wall, as described is greater detail below with reference to
Figs. 6 sad 7.
Fig. 6 is as sad plan view of the diffusor wall 6
mounted is the vessel 1, all depicted is Fig. 1. Fig. 6
shows that, due to the aomplemaatary shape of tha outer
peripheral surface of each refractory brick, a structurally
sound diffusor wall can be formed by simply ataakiag the
refractory bricks one upon another. It can be understood
very easily from viewing Fig. 6 how the mating mesas of each
refractory brick interlocks with the mating manna of
adjacent refractory bricks. Fig. 6 shows how the half-
bricks 38 are employed to fill peripheral holes is the
refractory wall. It is unnecessary to use mortar to bond
the bricks together since the cooperating mating means
provide sufficient structural integrity.
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Although the dimensions of each refractory brick can be
selected at random, 9" is the preferred length (ia the axial
direction depicted in Fig. 48) for each refractory brick,
since this is the length of standard refractory bricks used
to form the lining 40 of industrial heat sources. In a
preferred method of assembling the diffusor wall in
accordance with the present invention. the standard
refractory bricks are removed from lining 40 to provide an
angular slot in the refractory lining of vessel 1. The
refractory bricks 30,38, having the same length as the
standard refractory bricks removed from the lining 40, are
then placed in the angular slot formed is the lining 40.
This ties the entire diffusor wall 6 to the overall lining
40 of the vessel 1. And, the mating means foz~ed on each
refractory brick ties the bricks to one another to avoid
axial displacement of diffusor wall 6 by the force of the
exhaust gas emitted from burner 2.
Fig. 6 shows that some additional peripheral voids 41
might exist in the diffusor wall. Those voids can be filled
with a standard refractory packing material such as GREENPAK
94.
Fig. 7 shows the same refractory wall as Fig. 6 with
the addition of a manway 42 formed by six half-bricks 38.
Even though the entire diffusor wall 6 can be easily
disassembled since it is unnecessary to use mortar to attach
the bricks to one another. it ~ is sometimes preferable to use
a maaway 42 so that personnel can access the downstream tube
sheet for maintenance and service.
The diffusor wall depicted in Fig. 6 has an open
frontal area of about 50%. thus allowing a substantial
amount of exhaust gas to flow therethrough, as compared to
the conventional ~cheekerwall" formed of standard refractory
bricks having as open frontal area of only about 30%.
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Another advantage of the refractory bricks and diffusor
wall of the present invention is that the wall can be
assembled without the need for mortar between adjacent
refractory bricks. The mating means formed on the outer
surface of each refractory brick ensure that the diffusor
wall as a whole will not be shifted axially by the force of
the exhaust gas during operation of burner 2. The mating
mesas, in combination with the method of anchoring
peripheral refractory bricks is the lining of the heating
l0 vessel all but guarantee that the diffusor wall will not
collapse wader the force of the exhaust gas emitted from
burner 2.
While the present invention has been described with
reference to preferred embodiments thereof, it ie understood
that one skilled is the art could make various modifications
to the present invention as disclosed herein without
departing from the spirit and scope of the claims appended
hereto.
