EP3561385B1 - Refractory wall with anti-corrosive layer - Google Patents

Description

The invention relates to a refractory wall, in particular for an incinerator, according to the preamble of claim 1 and a method for producing such a refractory wall.

Such refractory walls are used, for example, in combustion chambers for the recovery of thermal energy from the hot flue gases. In principle, a distinction must be made between walls that form part of the boundary walls of an incinerator in practical use, and walls that, in practical use, are arranged hanging inside the incinerator and are exposed to flue gas on several sides. Typical representatives of such walls are, for example, in the CH 699 406 A2 or. WO 2016/109903 A1 described.

The usually metallic base element of the wall is often designed as a pipe wall and usually consists of pipes connected by webs. The fireproof protective cladding is placed in front of the pipe wall and is intended to protect the pipe wall from corrosion by smoke gases. The fireproof protective cladding is usually formed from panels arranged in rows and columns next to or one above the other. Depending on the application, the protective covering is only arranged on one side of the pipe wall (e.g. CH 699 406 A2 ) or the protective cladding encloses the pipe wall all around (e.g. WO 2016/109903 A1 ).

Basic elements protected by protective cladding are also used in fluidized bed furnaces, for example, where the aim is to protect a metallic boiler wall from corrosion by flue gases. In this case the base element is formed by the boiler wall.

The panels of the protective cladding are usually mutually sealed by various measures to a certain extent in order to prevent the passage of smoke gases. However, in practice this alone cannot completely prevent corrosive smoke gases from passing through the protective cladding and can attack the underlying base element, for example the pipe wall or boiler wall.

So-called actively rear-ventilated systems counter this problem in that a protective gas - generally air - is pumped through the space between the base element and the protective cladding, which is placed in front of it at a distance. The gas or air is under a slight overpressure in relation to the combustion chamber of the incineration furnace, which prevents the flue gases from the combustion chamber from penetrating into the wall space and attacking the metallic base element. Typical examples of such rear-ventilated systems are, for example, in CH 699 406 A2 or. WO 2016/109903 A1 as well as in the EP 2 754 961 A2 described.

Actively rear-ventilated systems are relatively complex in terms of construction because of the necessary protective gas supply. In addition, energy is used to pump the protective gas through under excess pressure.

In the WO 2004/068050 A1 describes a fireproof wall with a metallic pipe wall and a protective covering in front of it. The protective cladding is attached to the pipe wall using a ceramic-based cement.

In the AT 43703 B describes a refractory wall with a metallic pipe wall and a protective covering in front, the parts of which are fastened to the pipe wall by means of holding elements. The holding elements are protected by means of a covering made of refractory material, which also causes an adhesive connection between the parts of the protective covering and the holding elements.

The present invention is intended to improve a fire-resistant wall in such a way that, on the one hand, active rear ventilation can be dispensed with and, on the other hand, reliable protection of the at least one base element against the corrosive effect of smoke gases is achieved.

This object on which the invention is based is achieved by the refractory wall according to the invention, as it is defined in independent patent claim 1. Claim 14 defines a method for manufacturing such a refractory wall. Particularly advantageous developments and refinements of the invention emerge from the dependent claims.

The essence of the invention consists in the following: A refractory wall, in particular for a combustion furnace, comprises at least one base element and a refractory protective cladding made of refractory panels in front of the at least one base element. The at least one base element has a ceramic corrosion protection layer on at least one side facing the protective cladding. The fireproof protective cladding is arranged at a distance from the at least one base element, with an intermediate space being present between the at least one base element and the protective cladding through which the smoke gases that have penetrated through the protective cladding can escape.

Due to the ceramic corrosion protection layer, aggressive smoke gases that have penetrated through the protective cladding cannot attack the at least one base element, so that active rear ventilation can be omitted.

The ceramic corrosion protection layer can cover the at least one base element on a side facing the protective cladding entirely or only in certain areas, for example if a different corrosion protection is provided for certain areas or if none at all is required.

The ceramic corrosion protection layer preferably has a proportion of tricalcium aluminate and SiC which is at least 60% by weight. In this way, a high temperature resistance and protective effect can be achieved.

The corrosion protection layer is advantageously a hardened or hydraulically set ceramic paste. This allows the corrosion protection layer as Apply paste relatively easily to the (usually metallic) at least one base element.

The ceramic paste is preferably a mixture of solid constituents and water and, immediately after the mixing of its constituents, contains a proportion of 20-80% by weight, preferably 35-75% by weight, of SiC and an additional proportion, based on the totality of its solid components of 10-50% by weight Al ₂ O ₃ , 5-30% by weight SiO ₂ and 1-5% by weight CaO. With these compositions, on the one hand, a high temperature resistance and protective effect can be achieved and, on the other hand, the coefficient of thermal expansion can be adapted to that of the at least one base element, so that the corrosion protection layer adheres securely to the at least one base element when exposed to thermal stress. Advantageously, the coefficient of thermal expansion of the anti-corrosion layer does not differ by more than 10% from the coefficient of thermal expansion of the at least one base element.

The corrosion protection layer advantageously has a thickness of 0.1-3 mm, preferably 0.9-1.1 mm. This is an advantageous compromise between the anti-corrosive protective effect and the required amount of ceramic paste and the optimal heat transfer.

The at least one base element is preferably metallic.

The at least one base element expediently comprises tubes for the passage of a fluid medium.

The at least one base element is advantageously designed as a tube wall with tubes connected by webs. Such pipe walls have proven themselves in known refractory walls.

The refractory plates are expediently attached to the at least one base element via at least one plate holder each.

The fireproof panels of the protective cladding are preferably arranged in rows and columns next to and one above the other. Such an arrangement facilitates the assembly of the protective cover and also the replacement of defective panels.

For the use of the refractory wall in the interior of a combustion furnace, the protective cladding advantageously encloses the at least one base element all around, so that the at least one base element is protected from flue gases essentially on all sides.

In an advantageous embodiment variant, the at least one base element is a boiler wall.

With regard to the method for producing a refractory wall, the essence of the invention consists in the following: By mixing solid components and water, a hydraulically setting ceramic paste is produced. The ceramic paste is applied to at least one base element of a refractory wall as a corrosion protection layer, in particular painted on or sprayed on, and the ceramic paste is then caused to harden or set. After the ceramic paste has been applied, a refractory protective cladding made of refractory plates is placed in front of the at least one base element.

Applying a ceramic paste is much easier and cheaper than, for example, welding on protective alloys.

The design variants and advantages mentioned with regard to the refractory wall according to the invention also apply accordingly to the method for producing such a refractory wall.

Fig. 1 -

einen Ausschnitt eines ersten Ausführungsbeispiels einer erfindungsgemässen feuerfesten Wand in Aufsicht;

Fig. 2 -

einen Längsschnitt des Ausschnitts der Fig. 1 gemäss der Linie II-II der Fig. 3;

Fig. 3 -

einen Querschnitt des Ausschnitts der Fig. 1 gemäss der Linie III-III der Fig. 1;

Fig. 4 -

einen vergrösserten Detailausschnitt aus Fig. 3;

Fig. 5 -

einen Ausschnitt eines zweiten Ausführungsbeispiels einer erfindungsgemässen feuerfesten Wand in Aufsicht;

Fig. 6 -

einen Längsschnitt des Ausschnitts der Fig. 5 gemäss der Linie VI-VI der Fig. 7;

Fig. 7 -

einen Querschnitt des Ausschnitts der Fig. 5 gemäss der Linie VII-VII der Fig. 5 und

Fig. 8 -

einen vergrösserten Detailausschnitt aus Fig. 7.

The invention is described in more detail below with reference to the exemplary embodiments shown in the drawings. Show it:

Fig. 1 -

a detail of a first embodiment of a refractory wall according to the invention in plan view;

Fig. 2 -

a longitudinal section of the section of the Fig. 1 according to line II-II of Fig. 3 ;

Fig. 3 -

a cross section of the detail of the Fig. 1 according to line III-III of Fig. 1 ;

Fig. 4 -

an enlarged detail section Fig. 3 ;

Fig. 5 -

a section of a second embodiment of a fire-resistant wall according to the invention in plan view;

Fig. 6 -

a longitudinal section of the section of the Fig. 5 according to the line VI-VI of Fig. 7 ;

Fig. 7 -

a cross section of the detail of the Fig. 5 according to the line VII-VII of the Fig. 5 and

Fig. 8 -

an enlarged detail section Fig. 7 .

The following definition applies to the following description: If reference symbols are given in a figure for the purpose of clarity of the drawing, but not mentioned in the directly associated part of the description, reference is made to their explanation in the preceding or following parts of the description. Conversely, in order to avoid overloading the drawings, less relevant reference symbols for direct understanding are not entered in all figures. Reference is made to the other figures in each case.

Position and directional designations, such as above, below, side by side, one above the other, side, vertical, horizontal, height and width refer to the usual vertical position of use of the refractory wall shown in the drawings.

In connection with the invention, a base element is understood to mean any type of, in particular metallic, construction. In particular, this can be a metallic boiler wall or an arrangement of (e.g. parallel) pipes through which a fluid medium (e.g. water) can be passed. The base element is to be understood in particular as a pipe wall consisting of a plurality of pipes connected to one another or a single pipe.

That in the Figures 1-4 The illustrated first embodiment of a refractory wall according to the invention represents, in practical use, part of a boundary wall of an incineration furnace, its protective cladding being aligned with the interior of the incineration furnace. One side of the wall is exposed to hot smoke gases.

The refractory wall designated as a whole with W comprises a base element designed as a metallic pipe wall 1 and a refractory protective cladding 2, which is placed in front of the pipe wall 1 at a distance so that there is a gap 3 between the protective cladding 2 and the pipe wall 1 ( Figures 2 and 4th ) through which air can flow.

The pipe wall 1 forming the base element consists of a large number of pipes 11 which are vertical in practical use and which are held together by webs 12 at a mutual distance (see in particular Fig. 4 ). The tubes 11 and the webs 12 are usually made of steel.

The protective cladding 2 consists of a large number of refractory plates 21 arranged next to and on top of one another, in rows and columns that are fire-resistant up to over 1000 ° C.

The plates 21 of the protective cladding 2 are fastened to the pipe wall 1 by means of plate holders 13. The plate holders 13 consist, for example, of heat-resistant steel, e.g. steel no. 310 according to AISI standard or material no. 1.4845 according to DIN 17440. Corrosion-resistant CrNi alloys are also suitable, in particular with additives such as molybdenum. The plate holders 13 essentially each comprise a screw bolt welded to a web 12 and a nut seated on the screw bolt. The plate holders 13 engage in vertically continuous, inwardly expanded grooves 21a ( Fig. 4 ) of the plates 21 and determine the distance between the plates 21 and the pipe wall 1. The plate holders 13 also serve to support the plates 21 in the vertical direction, the plates 21 with bridge elements (not shown) arranged on them resting on the plate holders 13. The plates 21 are movable to a certain extent in the vertical direction in order to allow thermally induced expansion and contraction movements.

Vertical parting lines 23 run between the panels 21 arranged next to one another and horizontal parting lines 24 are located between the panels 21 arranged one above the other. The parting lines are sealed in a manner known per se by inserted sealing elements and / or an overlapping design of the panel edges (not shown in detail).

To this extent, the refractory wall according to the invention corresponds in its basic structure and in its mode of operation to conventional walls of this type, as for example in FIG CH 699 406 A2 , WO 2016/086322 A1 and WO 2016/109904 A1 are described in detail, in particular with regard to the design of the refractory panels. The person skilled in the art does not therefore need any further explanation.

The essential difference between the refractory wall according to the invention and conventional refractory walls of this type is that the pipe wall 1 or generally the (in particular metallic) base element is covered with a ceramic corrosion protection layer 10. The corrosion protection layer 10 is best in the detail Figure 4 recognizable. The anti-corrosion layer 10 prevents that smoke gases that have penetrated into the space 3 between the protective lining 2 and the pipe wall 1 through leaks in the protective lining 2 cannot attack the pipe wall 1. This enables a structurally complex active rear ventilation (pumping through a gas, e.g. air, under overpressure through the Gap 3 of the wall) are omitted. The smoke gases that have penetrated can escape through the space 3.

The ceramic corrosion protection layer 10 here covers the entire pipe wall 1 including the webs 12 between the individual pipes 11. It consists of a hardened or (hydraulically) set ceramic paste, which consists of a mixture of various solid components and water. Immediately after mixing its solid components and before adding water, the paste contains 20-80%, preferably 35-75%, SiC as the most important component. Further components at this point are 10-50% Al ₂ O ₃ , 5-30% SiO ₂ and, as a binder, 1-5% CaO. The proportions of these solid constituents (without taking water into account) are always chosen so that they add up to 100%. Then about 6% water (H ₂ O) is added (so that a total amount of about 106% results), whereby a pasty-liquid state of aggregation is achieved. All percentages are percentages by weight.

SiO ₂ , Al ₂ O ₃ and CaO react together with H ₂ O, whereby _{a large part of H 2} O is broken down (chemically bound). The rest of the H ₂ O evaporates during operation at the latest. The SiC reacts only minimally. The SiO ₂ contributes, among other things, to the strength of the corrosion protection layer. During hydration (setting), so-called calcium silicate hydrate fibers (Ca ₃ S ₂ H ₃ ) are created (grow), which combine with the three components SiO ₂ , Al ₂ O ₃ and CaO, resulting in the hardened product "tricalcium aluminate". The SiC is only an additive that is embedded by the tricalcium aluminate and solidifies to form the actual ceramic mortar after it has set. After setting, there is a ceramic corrosion protection layer in which the proportion of tricalcium aluminate and SiC is at least 60% by weight.

Specific examples for the composition of only the solid components of the ceramic paste are (data in percent by weight): SiC SiO ₂ Al ₂ O ₃ CaO 38 17th 42 3rd 49 15th 33 3rd 57 12th 28 3rd 63 10 24 3rd 72 8th 17th 3rd

The grain size of the SiC in the ceramic paste is preferably <2 mm, more preferably <1 mm. The thickness of the anti-corrosion layer 10 is preferably 0.1-3 mm, more preferably 0.9-1.1 mm. The corrosion protection layer 10 adheres to the surface roughness of the metallic pipe wall 1.

During the manufacture of the wall, the corrosion protection layer 10 is painted or sprayed onto the pipe wall 1 as a paste and then hardens or sets hydraulically. Usually paste is mixed together and then applied within 5 minutes to 1 hour. After that, it is already hardened to the point where it can hardly be applied.

The composition of the ceramic paste is also selected so that the anti-corrosion layer in the cured or set state has a thermal expansion coefficient that is as similar as possible (deviating at most 10%) to the pipe wall or, in general, the base element. The composition of the paste can advantageously be based on the expected temperature range that the base element (in this case the metallic pipe wall 1) reaches in use. At higher expected temperatures of the base element, the SiC proportion is reduced and the (highly heat-resistant) Al ₂ O ₃ proportion is increased, as the following table shows, for example (percentages by weight here including water): SiC SiO ₂ Al ₂ O ₃ CaO Fe ₂ O ₃ H ₂ O 300 ° C 57 10 25th 1 1 6th 280 ° C 60 10 22nd 1 1 6th 260 ° C 63 10 19th 1 1 6th

In the examples in the table above, the paste also contains a small amount of Fe ₂ O ₃ , which supports the formation of nitrides and thereby the hardening. However, this portion is not absolutely necessary and can therefore also be omitted.

That in the Figures 5-8 The illustrated second embodiment of the refractory wall according to the invention is intended to be arranged in practical use as a heat exchanger inside a combustion furnace, the wall being acted upon by hot flue gases on more than one side. In principle, it has a similar structure to the fireproof wall of the Figures 1-4 but with the difference that its base element, i.e. the pipe wall, is protected on four sides or all around by a fireproof protective cladding.

The fireproof wall again comprises a base element designed as a metallic pipe wall 1 and a fireproof protective lining 20, which is placed in front of the pipe wall 1 on four sides at a distance so that there is a gap 3 between the protective lining 20 and the pipe wall 1 ( Figures 6 and 8th ).

The pipe wall 1 forming the base element again consists of a large number of pipes 11 which are vertical in practical use and which are held together by webs 12 at a mutual distance (see in particular Fig. 8 ).

The protective cover 20 is analogous to that in the Figures 1-4 The illustrated embodiment consists of a plurality of refractory plates 21 and 22 arranged next to one another and one above the other, in rows and columns, which are fastened to the pipe wall 1 by means of plate holders 13. In contrast to the first exemplary embodiment, in this exemplary embodiment the protective cladding 20 encloses the pipe wall 1 all around. As in the first exemplary embodiment, essentially flat plates 21 are arranged on the two opposite longitudinal sides of the pipe wall 1 and, in addition, plates 22 which are essentially U-shaped in cross section are arranged along the lateral end edges of the pipe wall 1, which surround the lateral end edges of the pipe wall 1, see above that the protective cladding 20 forms a closed shell around the pipe wall 1, a space 3 remaining around the pipe wall 1 between the pipe wall and the protective casing 20. The plates 22 are also fastened to the pipe wall 1 by means of plate holders 13, these plate holders being in vertically continuous, inwardly expanded grooves 22a ( Fig. 8 ) of the plates 22 engage.

To this extent, this exemplary embodiment of a wall according to the invention corresponds in its basic structure and in its mode of operation to that in FIG WO 2016/109903 A1 described conventional wall. With regard to the design of the refractory plates and the plate holders, what has been said in connection with the first exemplary embodiment applies. The person skilled in the art therefore does not need any further explanation with regard to the second exemplary embodiment.

The main difference between the inventive fire-resistant wall and conventional fire-resistant walls of this type is that the pipe wall 1 or generally the base element is covered with a ceramic corrosion protection layer 10, which prevents leaks in the protective lining 20 from entering the space 3 between the protective cladding 20 and the pipe wall 1, smoke gas that has penetrated the pipe wall 1 can attack. The corrosion protection layer 10 is best in the detail Figure 8 recognizable. With regard to the corrosion protection layer 10 and the ceramic paste on which it is based, what has been explained in connection with the first exemplary embodiment applies again.

The at least one base element can also comprise an arrangement of two or more tubes that are not connected by webs, the tubes again being covered with the ceramic corrosion protection layer already mentioned. Out Unconnected pipes existing metallic base elements (without a corrosion protection layer) are, for example, in the EP 2 754 961 A2 described.

The at least one base element can also be formed by a metallic boiler wall, the protective cladding being placed in front of this boiler wall at a distance. In this case, the boiler wall only has a ceramic corrosion protection layer on its side facing the protective cladding.

Claims (14)

1. Refractory wall (W), in particular for an incinerator, comprising at least one base element (1) and a refractory protective cladding (2; 20) comprising refractory panels (21, 22) and disposed in front of the at least one base element (1), wherein the at least one base element (1) has a ceramic corrosion protection layer (10) at least at one side towards the protective cladding (2; 20), characterised in that the refractory protective cladding (2; 20) is arranged at a spacing relative to the at least one base element (1), wherein between the at least one base element (1) and the protective cladding (2; 20) there is an intermediate space through which flue gases which have penetrated through the protective cladding (2; 20) can be withdrawn.
2. Refractory wall (W) according to claim 1, characterised in that the ceramic corrosion protection layer (10) has a proportion of tricalcium aluminate and SiC which is at least 60 wt-%.
3. Refractory wall (W) according to claim 1 or claim 2, characterised in that the corrosion protection layer (10) is a hydraulically set ceramic paste.
4. Refractory wall (W) according to claim 3, characterised in that the paste is a mixture of solid constituents and water and immediately after mixing of its constituents in relation to the total of its solid constituents contains a proportion of 20-80 wt-%, preferably 35-75 wt-% of SiC.
5. Refractory wall (W) according to claim 4, characterised in that immediately after mixing of its constituents in relation to the total of its solid constituents the paste has a proportion of 10-50 wt-% of Al₂O₃, 5-30 wt-% of SiO₂ and 1-5 wt-% of CaO.
6. Refractory wall (W) according to one of the preceding claims, characterised in that the corrosion protection layer (10) is of a thickness of 0.1 - 3 mm, preferably 0.9 - 1.1 mm.
7. Refractory wall (W) according to one of the preceding claims, characterised in that the corrosion protection layer (10) has a coefficient of thermal expansion which differs by not more than 10% from the coefficient of thermal expansion of the at least one base element (1).
8. Refractory wall (W) according to one of the preceding claims, characterised in that the at least one base element (1) is metallic.
9. Refractory wall (W) according to one of the preceding claims, characterised in that the at least one base element (1) includes tubes (11) for passing a fluid medium.
10. Refractory wall (W) according to one of the preceding claims, characterised in that the at least one base element (1) is in the form of a tube wall with tubes (11) connected by bars (12).
11. Refractory wall (W) according to one of the preceding claims, characterised in that the refractory panels (21, 22) are fixed to the at least one base element (1) by way of at least one respective panel holder (13).
12. Refractory wall according to one of the preceding claims, characterised in that the protective cladding (20) surrounds the at least one base element (1) all around.
13. Refractory wall (W) according to one of the preceding claims, characterised in that the at least one base element (1) is a boiler wall.
14. Method of producing a refractory wall (W) according to one of the preceding claims, characterised in that a hydraulically setting ceramic paste is produced by mixing solid constituents and water, the paste is applied as a corrosion protection layer to the at least one base element, in particular being painted or sprayed thereon, and is then caused to harden, and after application of the ceramic paste the refractory protective cladding (2; 20) comprising refractory panels (21, 22) is disposed in front of the at least one base element (1).

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