EP1080326A1

EP1080326A1 - Modular ceramic combustion reactor

Info

Publication number: EP1080326A1
Application number: EP99915963A
Authority: EP
Inventors: Allan Inovius; Carlo P. A. Inovius; Lili Madeleine Inovius
Original assignee: Reactor Combustion World Organisation SA
Current assignee: Reactor Combustion World Organisation SA
Priority date: 1998-04-17
Filing date: 1999-04-16
Publication date: 2001-03-07
Also published as: ZA200005672B; NO320092B1; HK1042335A1; HUP9800902A1; SK15402000A3; HU9800902D0; NO20005134L; PL192179B1; CZ20003816A3; JP2002512355A; CA2328717A1; AU3437599A; KR20010042792A; CZ300872B6; CN1305575A; PL343568A1; NO20005134D0; UA54589C2; WO1999054660A1; IL139033A0

Abstract

The invention relates to a ceramic combustion reactor (1) with a tubular body, consisting of several ceramic drum-shaped modules (2) and top (3) and bottom modules. The modules (2, 3) are fixed to each other with rigid connection means (5). According to the invention, the drum-shaped modules (2, 3) are comprising several segments (6, 61) together forming a drum-shaped module (2, 3), the segments (6, 61) and/or the modules (2, 3) being connected together by connection means (5).

Description

- 1 -

MODULAR CERAMIC COMBUSTION REACTOR

Technical Field

The invention relates to a ceramic combustion reactor. The reactor of the invention 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 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 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 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. 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. - 2 -

Also, with extensive use, some cracking in the ceramics material is almost unavoidable. Large, one-piece reactors are very expensive to change, so there is needed a reactor which may be repaired for a relatively low cost.

US patent No. 4,416,619 discloses a ceramic combustion reactor with a tubular body, which is used in a heating system. In this case the combustion is not on the inside, but on the outside of the reactor. The outer surface of the reactor has a plurality of indentations to break up the surface continuity. Thereby the heat- induced stresses in the ceramics material are substantially reduced, and scaling and cracking of the surface is prevented. However, this reactor is of a small size only, and therefor the problem of size need not be solved.

Large sized ceramics ovens and kilns for the burning of clay and porcelain are known in the art. These ceramics ovens are usually constructed of several blocks of ceramics, which are encased by a steel frame or box. In these known ovens the blocks constituting the walls of the oven are very thick, and are therefore self- supporting. But due to the thickness of the walls, this structure in not practical for the inner combustion reactor, because the generated heat can not dissipate through the thick walls.

US patent No. 5,687,572 teaches a thin wall combustor with backside impingement cooling. This combustor is used for a gas turbine engine having a thin-walled nonporous ceramic liner whose backside is impingement cooled. The ceramic shell is supported by a porous outer metallic shell. This cooling is necessary in order to protect the outer metallic shell from the high temperatures. The necessity of the cooling system makes this type of ceramic shell unusable in the complete combustion reactor, because the clean burning process needs the presence of the high temperature walls, where the catalytic oxidation and reduction of the combustion products takes place. - 3 -

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.

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 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 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 the most preferred embodiment, the connection plates and/or the connection clamps are made of ceramic material. 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 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. 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, 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 ribs. It has been found most practical if the connection plates are integral with the segments.

Brief Description of Drawings

The invention will now be described in more detail below with reference to the 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. 1, - 5 -

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. 1, Fig. 4e is top view of a modified connection clamp used as connection means for certain parts of the reactor of Fig. 1, FIG. 5a-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 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 , Fig. 8 is a cross-section of a further reactor module made of universal segments.

Best Mode for Carrying out the Invention

Fig. 1 shows a perspective view of the reactor 1 of the invention. This reactor is a 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 NOCO 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 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.

1, for better illustration of the inside of the reactor 1. As it is clearly seen in Fig. 1, four segments 6 form each center module 2, and four segments 61 form the top module 3. - 6 -

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 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. 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 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 the edges 1 1 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 - 7 -

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 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 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, 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 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 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 ceramic material, preferably with identical or similar properties to the ceramic material of the reactor. Especially, the suggested material for the segments is high- - 8 - 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 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.

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 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 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 51 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 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 - 9 - 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.

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.

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 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 81, 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 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 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 - 10 - 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 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 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 1, 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 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.

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 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 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 - 11 - 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.

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 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 manufacturing the segments and the connection means.

Claims

- 12 - Claims:

1. Ceramic combustion reactor with a tubular body, consisting of several ceramic drum-shaped modules and top and bottom modules, the modules being fixed to each other with rigid connection means, wherein the drum-shaped modules are comprising several segments together forming a drum-shaped module, the segments and/or the modules being connected together by connection means.

2. The reactor according to claim 1, wherein 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 b, the connection clamps are provided with at least one recess receiving at least two connection plates.

3. The reactor according to claim 2, wherein the connection plates and/or the connection clamps are provided with retention means for preventing the connection clamps from falling off from the connection plates.

4. The reactor according to claim 3, wherein the retention means comprise ceramic pins insertable into openings in the connection plate and the connection clamp.

5. The reactor according to claim 4, wherein the ceramic pins are provided with oval end-plates, and the connection plates are provided with oval openings for receiving the oval end-plates.

6. The reactor according to claim 3, wherein the connection clamps comprise cooperating flanges on the edge of the connection plates and in the recess of the connection clamps. - 13 -

7. The reactor according to claims 2 to 6, wherein the connection plates and/or the connection clamps are made of ceramic material, preferably with identical or similar properties to the ceramic material of the reactor.

8. The reactor according to claim 1 to 7, wherein one drum-shaped module consists of two to eight segments.

9. The reactor according to claims 1 to 8, comprising a cone-shaped flame-retarding insert, the insert having radially extending supports, and the segments of at least one module being provided with recesses receiving the supports of the insert.

10. The reactor according to claims 2 to 9, wherein the connection clamp is provided with two symmetric recesses, each recess receiving two connection plates of two neighbouring segments.

1 1. The reactor according to claims 2 to 10, wherein the recess of a connection clamp is formed as an elongated slit, with the plane of the slit containing the central axis of the reactor.

12. The reactor according to claim 1 1 , wherein the elongated slit of a connection clamp has an arrow-like cross section.

13. The reactor according to claims 2 to 12, wherein the connection clamp is provided with stiffening ribs.

14. The reactor according to claims 2 to 13, wherein the connection plates are integral with the segments.

15. The reactor according to claims 1 to 14, comprising a domed end module. - 14 -

16. The reactor according to claims 9 to 15, wherein the supports of the flame- retarding insert are provided with separate supports inserted into the recess of the segments.

17. The reactor according to claims 9 to 15, wherein the supports of the flame- retarding insert are integral with the cone, and the supports are formed as rods with a hollow or U-shaped cross section, and the rods are resting in co-operating cradles formed on the segments.

18. The reactor according to claims 1 to 17, wherein the segments are formed so that any number thereof may be connected to form an essentially circular module.