Note: Descriptions are shown in the official language in which they were submitted.
WO 99/54660 PCT/HU99/00028
MODULAR CERAMIC COMBUSTION REACTOR
Technical Fietd
The invention relates to a ceramic combustion reactor. The reactor of the
invention
s has a tubular body, consisting of modules. The modules are fixed to each
other with
rigid connection means.
Background Art
US patent No 5,041,268 discloses a combustion reactor having an elongated
tubular
to body. The tubular body is enclosed in a steel outer shell. During the
combustion
process, the tubular body is heated up to high temperatures. Only materials
which
are suitably heat-resistant can be considered as materials for the tubular
body of this
type of reactor. Hereafter we will refer to this special type of reactor as a
complete
combustion reactor. It has been found that the reactor type disclosed in the
US
is patent No. 5,041,268 performs best if the wall of the tubular body is
relatively thin,
preferably less than 10 mm, so that the heat generated in the combustion
process is
quickly dissipated through intense IR radiation of the tubular wall. It has
also been
found that these reactors are functioning very satisfactorily in large
dimensions, but
the wall of the tubular body still must remain relatively thin. It has been
shown that
2o reactors with a length of more than five meters and a diameter of about a
meter are
fully feasible, and the combustion process remains very efficient and clean.
The only suitable material for the production of the above-mentioned reactor
so far
found is high-grade ceramics. However, the manufacture of such reactors on
larger
scale poses several problems.
2s It is very complicated to manufacture large tubular bodies of ceramics with
a
relatively thin wall. Firstly, the die to produce the necessary ceramics body
is very
expensive, due to the large size. Secondly, the transport of the tubular body
is also
very complicated, because the ceramics material is very rigid, and thus breaks
very
easily.
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lllso, with extensive use, sarlte cracking in tile ceramics rzlaterial is
almost
unavoidable. Large, one-niece rcact.ors are very cxrensive to chrrnge, so
there is
needed a reactor which may be repaired for a relatively low cost.
S ~E-OS 29 40 245 A1 discloses a ceramic yrs flame reactor with an essentially
tubular body, which ifi used in a heating system. 'fhe l;as flarnc reactor has
a ceramic
central flarnc tube, which GOIISISt c~f ring-shaped elements and longitudinal
connection means, which together act a.~ corlnectiern means to hold together
the wall
elements of the flame tube. Il is a problem of this constructiolt that it can
not be
to taken apart into smaller piecc:~, and once assembled, itc Parts can Pal be
replaced.
Lame Si~Cd certrmics ovens and kilos for the burning of clay sod porcelain are
known in the art. TItcSC c~;rallW s ow'tlls taro uiutslly vinrstmclcd of
scvc;ral Liocks of
ceramics, which are encased by a ~tccl frame or box, In these known ovens the
is blocks constituting the walls of ihc oven arc very thick, and arc thcroforc
self
supporting. Hut due to the thickness of tl~G wails, this structuro in not.
practical for
the inner combustion reactor, became the generated heat can not dissipate
through
the thick walls.
U5 patcm No. x,687,572 teaches a thin wall combustnr with backside impingement
cooling. This carnbustor is used for a gas turbine engine having a thin-walled
nnnporous ceramic liner whose backside is irnpingemcnt cooled. 'fl:c ccrarnic
shell
is supported by a porous outer metallic shell. Thls coolln g is necessary in
order to
protect the outer mehll.lic: shell from the high ielnperaturcs. The nac:essity
of the
2s cooling system n131:es this type of ceramic shell unusable in the complete
combustion reHetor, because the Glean burning process needs the presence of
the
high temperature wall.;, where the ca talytic oxidation and rcdusrtion of the
combustion rr~ducts takes plsce.
AMENDED SHEET
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Therefor, it is the object of the invention to provide a thin-walled ceramics
combustion reactor, which may be manufactured cheaply and relatively easily
also
in large sizes. It is a further object to provide a reactor which is easy to
transport.
and may be repaired with simple and cheap methods, or where the faulty part
may
be replaced without having to change the whole reactor. It is a further goal
to
produce a reactor where the fault part may be replaced in a manner so that the
whole
reactor need not be taken apart.
Summary of the Invention
According to the invention, the objects above are achieved with a reactor
consisting
of drum-shaped modules connected by rigid connection means, where the drum-
shaped modules are comprising several segments together forming a drum-shaped
module, the segments and/or the modules are connected together by connection
means.
is
In the preferred embodiment, the connection means are comprising connection
plates and connection clamps, where
a, the connection plates are positioned on the segments in the vicinity of the
corners
of the segments and extending radially outwards, and
2o b, the connection clamps are provided with at least one recess receiving at
least two
connection plates.
Advantageously, the connection plates and/or the connection clamps are
provided
with retention means for preventing the connection clamps from falling off
from the
25 connection plates. The retention means may be made of ceramic pins, which
are
insertable into openings in the connection plate and the connection clamp.
It is especially advantageous if the connection clamps comprise co-operating
flanges
on the edge of the connection plates and in the recess of the connection
clamps. In
3o the most preferred embodiment, the connection plates and/or the connection
clamps
are made of ceramic material.
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It has been found that one drum-shaped module may consist of as much as eight
segments, but smaller numbers are also applicable. As a general rule, fewer
segments are sufficient for smaller reactors, while reactors with larger
diameters
s may require the use of more segments.
In a special embodiment, the tubular reactor body comprises a cone-shaped
flame-
retarding insert. This insert is of principal importance for the proper
functioning of
those complete combustion reactors which are disclosed in the US patent no.
~ 0 5,041,268, among others. In order to properly position and attach the
insert, the
insert is provided with radially extending supports, and the segments of at
least one
module being provided with recesses receiving the supports of the insert.
Advantageously, the connection clamp is provided with two symmetric recesses,
1 s each recess receiving two connection plates of two neighbouring segments.
Thereby
one connection clamp is holding together four segments at their corners, so
the
number of connection clamps used may be kept low.
For better mechanical properties, the connection clamp is provided with
stiffening
2o ribs. It has been found most practical if the connection plates are
integral with the
segments.
Brief Descriution of Drawings
The invention will now be described in more detail below with reference to the
2s accompanying drawings, which, by way of example only, illustrate a
preferred
embodiment of the reactor according to the invention.
In the drawings
FIG. 1. is a perspective view of the reactor in the preferred embodiment of
the
invention,
FIG.2a-c is a perspective, side, and front view of a segment in the center
modules of the reactor of Fig. l,
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FIG. 3a-c is a perspective, side, and front view of a segment in the top
module of
the reactor of Fig. 1,
FIG. 4a-d is a perspective, an upside-down perspective, side, and top view of
a
connection clamp used as connection means for the reactor of Fig. l,
s Fig. 4e is top view of a modified connection clamp used as connection means
for certain parts of the reactor of Fig. 1,
FIG. Sa-d is a perspective, side, top, and front view of a retention pin for
the
connection clamp of Figs. 4a-e, and
FIG. 6 is another perspective view of the reactor in the preferred embodiment
to of the invention, with two segments taken away for showing the
interior of the reactor with the flame retardation insert in position,
Fig. 7 is a perspective view of a modified embodiment of the cone-shaped
insert used in the modules of a reactor having a similar structure to
that shown in Fig. 1,
is Fig. 8 is a cross-section of a further reactor module made of universal
segments.
Best Mode for CarrvinE out the Invention
Fig. 1 shows a perspective view of the reactor 1 of the invention. This
reactor is a
2o so-called complete combustion reactor. Smaller versions of this reactor are
manufactured by the RCWO Complete Combustion Reactor Bureau Ltd. of
Hungary, under the brand name hJOCO Reactor ~. These previous smaller reactors
are made of one piece of material. The reactor 1 in Fig. 1 depicts a larger
version,
which consist of two drum-shaped center modules 2 and one top module 3. The
25 modules 2 and 3 are fixed to each other with rigid connection means 5. On
the right
side, a top module 3 having a domed end 31 is visible. The reactor 1 is
supported on
the U-shaped rail 9, which receives the connection means 5 on the underside of
the
reactor 1. The reactor also comprises a bottom module, which is not shown in
Fig.
l, for better illustration of the inside of the reactor 1. As it is clearly
seen in Fig. l,
3o four segments 6 form each center module 2, and four segments 61 form the
top
module 3.
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The segments 6 and 61 are made of high-grade ceramics, usually a silica-based
compound. The bottom module need not tolerate such high temperatures as the
other modules, hence it may be manufactured of high-grade steel, but ceramics
may
s also be used as material for the bottom module.
The connection means 5 are comprising connection plates 51 (see also Fig. 2
and 3)
and connection clamps 52 (see also Fig. 4.). The connection plates 51 are
positioned
on the segments 6 and 61 in the vicinity of the corners 53 of the segments 6
and 61.
to The connection plates 51 are extending radially outwards, so that the plane
of the
touching surface 62 of the connection plates 51 is containing the central axis
of the
reactor 1. The connection plates 51 are integral with the segments, and they
have the
same thickness as the thickness of the wall of the segments. As it is best
seen in
Figs. 2a and 3a, the connection plates are formed as a part of a wide edge 65,
which
i5 is "folded out" on the straight sides of the segments, perpendicularly to
the arched
wall of the segments 6 and 61. Comparing Figs. 2a and 3a, it is also clear
that the
segments 6 and 61 have an almost identical construction, except for the domed
end
31 on the segments 61. The form of the domed end 31 plays an important part in
forming the proper turbulence conditions within the cavity of the reactor 1.
One arched side of the segment 6 and 61 comprise an arched band 66, which
forms
a part of an annular ring 10 when the segments are assembled into a tubular
body.
The ring 10 has a larger inner diameter than the outer diameter of the drum
modules
20. When the modules 20 are assembled into the tubular body, the rings 10
overlap
2s the edges 11 of the segments 6.
Referring to Fig. 4 and 5, the connection clamps 52 are provided with at least
one
recess 54 receiving two connection plates 51. For preventing the connection
clamps
52 from falling off the connection plates 51, it is foreseen that the
connection plates
51 and/or the connection clamps 52 are provided with retention means 7. In the
suggested best mode of the invention, the retention means 7 comprise ceramic
pins
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70, which are insertable into openings 55 in the connection plate 51 and the
connection clamp 52.
Further, to the ceramic pins 70 are provided with oval end-plates 71. The
openings
55 on the connection plates 51 and the connection clamps 52 are shaped oval,
so
s that their size and shape corresponds to the oval end-plates. After
insertion into the
oval openings, the retention pins 70 are rotated 90°, so that the oval
end-plates 71
will keep the retention pins 70 from falling out.
The mechanical connection between the modules 2 is provided by form locking of
~o the connection means 5. Therefore, the connection means 5 comprise flanges
56 on
the edge of the connection plates 51, and co-operating flanges 57 in the
recess 54
of the connection clamps 52. It is the flanges 56 and 57 which provide the
connecting force between the modules 20 and the segments 6 and 61. The
dimensions of the parts constituting the connection means 5, especially the
flanges,
~ s are made somewhat loosely, in order to leave room for some dilatation or
displacement of the different parts. This dilatation is necessary, due to the
differences in the thermal expansion and the rigidity of the ceramics
material. The
pins 70 are also allowed to move sideways in the oval openings 55, and thus
allow
some degree of displacement of the segments 6 and 61 relative to the other
segments
2o in the adjoining module. This arrangement prevents the thermally induced
mechanical stresses between adjoining modules 2 and 3. It must be noted that
the
relative movement between the segments must not be too large either. Since
there is
no sealing between the segments and modules, small gaps are unavoidable. The
efficiency of the combustion process within the reactor will decrease if too
much of
2s the gases escape through the gaps between the modules or segments.
Due to the high thermal load on the tubular body of a complete combustion
reactor,
the connection means 5 must be made of a heat-resistant material. It has been
found
best if the connection plates 51 and/or the connection clamps 52 are made of
o ceramic material, preferably with identical or similar properties to the
ceramic
material of the reactor. Especially, the suggested material for the segments
is high-
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grade SiSiC. This is an expensive type of ceramics, but it is heat resistant
until 1800
C°. An alternative material for the segments is SiC, which is slightly
cheaper, but
may be used only for combustion temperatures below 1300 C°. The
suggested
material for the connection clamps is Corderite, which is cheap to manufacture
by
s pressing. Corderite is also preferred because it slightly more resilient,
and therefor
less likely to break under stress. However, for special applications it is
suggested to
manufacture the connection clamps from SiC or SiSiC as well. For most
applications, however, the connection clamps made of Corderite are fully
acceptable. It is also more economical, because larger quantities are cheaper
to
manufacture by pressing. On the other hand, SiC and SiSiC need expensive die-
fabrication procedures. The invention therefore .provides the important
advantage,
that broken parts of a reactor 1 may be replaced easily, without the expense
of
replacing the entire reactor. Alternatively, the segments may be manufactured
of
Corderite as well, if the combustion process is kept at relatively low
temperatures.
is
Further referring to Fig. 4d, the connection clamp 52 is provided with two
symmetric recesses 54. Each recess 54 receives two connection plates 51 of two
neighbouring segment 6 or 61, i. e. one connection clamp 52 connects four
segments
6 or 61 at their corners. Fig. 4e shows a connection clamp 52', which has only
one
2o recess 54. The connection clamp 52' is practically one half of a connection
clamp
52, and it is used for connecting the connection plates 51' adjacent to the
domed end
31 part of the segments 61. The bottom module (not shown), or a support plate
of
the bottom module is equipped with similar connection plates as the connection
plates 51, and therefore may be fixed to the adjoining drum-shaped module 2 by
25 ordinary connection clamps 52.
As it is best seen in Fig. 4d and 4e, the recess 54 of a connection clamp 52
and 52'
is formed as an elongated slit. The slit receives two connection plates S 1
with
appropriate tolerance, so that the connection clamp 52 may slide smoothly on
the
connection plates 51, without being too tight or too loose. The elongated slit
has an
3o arrow-like cross section. The widening at the head of the arrow forms the
flange 56,
which engages the flange 57 of the connection plate 51. To improve the
mechanical
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strength of the connection clamps 52, they are equipped with stiffening ribs
58. The
underside of the clamp is provided with a recess 59, which leaves room for
band 66
forming the ring 10.
s Generally, it is contemplated that one drum-shaped module consists of two to
eight
segments. From a designing and manufacturing point of view, even numbers are
preferred, but there is nothing preventing the manufacturing of modules
consisting
of three, five, seven or even greater number of segments within one module.
1o A speciality of the complete combustion reactor is a a cone-shaped flame-
retarding
insert 8. This insert is shown in Fig. 6. The insert 8 divides the reactor
cavity into
two chambers. The special turbulence caused by the insert 8 increases the
efficiency
of the reactor, and produces a complete, soot-free burning of the fuel. In
order to
accommodate the proper positioning and mechanical support of the cone-shaped
is insert 8, it is suggested to provide the insert 8 with radially extending
supports 80.
The segments 6 of at least one module 2 or 3 are provided with recesses 81
receiving the supports 80 of the insert 8. However, to keep the manufacturing
costs
low, it is advisable to keep the number of different parts at a minimum level.
Therefore, it is foreseen that all segments 6 and 61 are provided with the
recesses
20 $1, as it is shown in Fig. 1 and Fig. 6. The recesses 81 are created by two
indentations 82 on the walls of the segments. With this solution the material
thickness remains largely uniform in all parts of the segments, and the
thermal
stresses are lower. The supports 80 are integral with the cone of the insert
8. It is
also contemplated that with larger versions of the reactor 1 the supports of
the
?s flame-retarding insert 8 are provided with separate supports (not shown).
The
separate supports are properly attached to the cone by one end, and the other
end or
the separate supports are inserted into the recess 81 of the segments. In this
case the
separate supports have corresponding recesses in the cone of the insert 8. In
another
possible embodiment, the separate supports of the insert are constructed as
hollow
3o rods, where the hole of the rod receives pins extending from the cone
insert on one
end and pins extending from the segments towards the cone on the other end. In
a
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further, not illustrated embodiment the recesses receiving the supports 80 are
formed between the connection plates of the segments.
Fig. 7 shows a further advantageous realisation of the cone-shaped flame
retarding
s insert 8. Here the insert 8 is also integral with the supports 83, similar
to the
embodiment in Fig. 6, but here the supports 83 have an annular or U-shaped
cross
section. The insert 8 and the supports 83 are cast together. There are cradles
85
integral with the wall of the segments 61, which cradles 85 receive the outer
end of
the hollow tube shaped or half tube-shaped supports 83. There are openings 84
at
to the base of the supports 83, connecting the cavity within the supports 83
with the
space surrounded by the cone of the insert 8. These openings 84 contribute to
the
turbulence within the reactor l, and the hollow structure of the supports 83
ensures
increased mechanical strength. This type of insert 8 is especially suitable
for use in
reactors combined with gas turbines, where the gas pressure on the cone of the
is insert 8 is much greater. This is an important application, because the gas
turbines
are used for the burning of low cost fuels and waste. The hollow support
structure is
able to prevent the breaking of the supports even in the presence of minor
casting
faults. This specific embodiment is shown with reference to a segment 61 for a
top
module 3, but the very same construction may be realised on the segments 6 as
well.
?o
Fig. 8 illustrates how larger modules with different diameters may be
constructed
using the same type of universally applicable segments. In Fig. 8, there is
shown a
reactor module 90, which is made up of eight segments 91. Actually, only four
or
six segments 91 would constitute a perfect circular module, depending on the
design
?s of the universal segment 91. However, with appropriately designed
connecting
means, more segments 91 may be connected to form a module with larger
diameter.
(It must be noted that smaller modules still must be made of two to four
segments)
The segments 91 are designed so that any number (in practice at least four)
thereof
may be connected together to form modules with different diameters. In this
manner
o modules with a flower-like cross section are created, as shown in Fig. 8.
The
working principle of the complete combustion reactor is essentially unaffected
by
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the slight deviation from the circular cross-sectional form. This solution has
obvious
economic benefits, because only one type of segment is needed to make reactors
of
widely different dimensions. In this manner the universal segments 91 may be
mass-
produced, at a lower cost per segment.
s
While the reactor of the invention has been shown with reference to the
preferred
embodiment shown in the attached figures, other modified embodiments which are
obvious for the person skilled in the art also fall within the scope of the
invention. E.
g. it is not necessary to form all modules from the same number of segments.
It is
to fully feasible to construct the domed end module of fewer segments, e. g.
from two
semi-circular segments, and connect such an end module to a central drum-
shaped
module consisting of four quarter-arch segments. Also, other novel, high-
temperature resistant materials can be considered for manufaeW ring the
segments
and the connection means.
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