CH714933B1 - Refractory wall, especially for an incinerator. - Google Patents

Abstract

A fireproof wall, in particular for an incinerator, comprises a base element (1), in particular a metallic one, and a fireproof protective cladding (2) made of fireproof panels (21) in front of the base element (1). To protect against smoke gases that have passed through the protective cladding (2), the base element (1) has a ceramic corrosion protection layer (10) on at least one side facing the protective cladding (2).

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 incineration furnace in practical use and walls that are arranged e.g. suspended inside the incineration furnace in practical use and exposed to flue gas on several sides. Typical representatives of such walls are described, for example, in CH 699 406 A2 and WO 2016/109903 A1.

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 intended use, the protective cladding is only arranged on one side of the pipe wall (e.g. CH 699 406 A2) or the protective casing surrounds the pipe wall all around (e.g. WO 2016/109903 A1).

Basic elements protected by protective cladding are also used, for example, in fluidized bed furnaces, 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 plates 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 getting through the protective cladding and attacking the basic element behind it, e.g. 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 smoke 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 described, for example, in CH 699 406 A2 or WO 2016/109903 A1 and also in EP 2 754 961 A2.

[0007] Actively rear-ventilated systems are relatively complex in terms of construction because of the required supply of protective gas. In addition, energy is used to pump the protective gas through under excess pressure.

The present invention is therefore intended to improve a fireproof 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 from the corrosive effect of flue 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 15 defines a method for producing 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. 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 anti-corrosion layer preferably has a proportion of tricalcium aluminate and SiC which is at least 60% by weight. A high temperature resistance and protective effect can be achieved in this way.

The corrosion protection layer is advantageously a hardened or hydraulically set ceramic paste. As a result, the corrosion protection layer can be applied relatively easily as a paste to the (usually metallic) at least one base element.

Preferably, the ceramic paste is a mixture of solid constituents and water and immediately after mixing its constituents, based on the totality of its solid constituents, contains a proportion of 20-80% by weight, preferably 35-75% by weight, SiC and additionally a proportion of 10-50% by weight Al2O3, 5-30% by weight SiO2 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 remains securely adhered 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 fireproof protective cladding is advantageously 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. Smoke gases that have penetrated through the protective cladding can escape through this space.

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 an incinerator, the protective cladding advantageously surrounds the at least one base element all around, so that the at least one base element is essentially protected from flue gases 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.

The application of 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.

In the following, the invention is described in more detail with reference to the embodiments shown in the drawings. 1 shows a detail of a first exemplary embodiment of a refractory wall according to the invention in a plan view; FIG. 2 shows a longitudinal section of the detail in FIG. 1 along the line II-II in FIG. 3; FIG. 3 shows a cross section of the detail in FIG. 1 along the line III-III in FIG. 1; FIG. 4 shows an enlarged detail from FIG. 3; FIG. 5 shows a detail of a second exemplary embodiment of a refractory wall according to the invention in a plan view; 6 shows a longitudinal section of the detail in FIG. 5 along the line VI-VI in FIG. 7; 7 - a cross section of the detail from FIG. 5 according to the line VII-VII in FIG. 5 and FIG. 8 - an enlarged detail from 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.

Designations of position and direction, such as, for example, top, bottom, side by side, one above the other, side, vertical, horizontal, height and width relate 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.

The first embodiment of a refractory wall according to the invention shown in FIGS. 1-4 represents, in practical use, part of a boundary wall of an incinerator, its protective covering being aligned with the interior of the incinerator. 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 4) through which air can flow.

The pipe wall 1 forming the base element consists of a plurality 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. The plates are, for example, ceramic SiC plates, preferably SiC 90 plates with an SiC content of approximately 90% by weight. in production, which 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 the AISI standard or material no.1.4845 according to DIN 17440. Corrosion-resistant CrNi alloys, in particular with additives such as molybdenum, are also suitable. 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 widened grooves 21 a (FIG. 4) of the plates 21 and define 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, with the plates 21 resting on the plate holders 13 with bridge elements (not shown) arranged on them. 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 formation of the plate edges (not in detail shown).

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 described, for example, in CH 699 406 A2, WO 2016/086322 A1 and WO 2016/109904 A1 in all details, in particular also with regard to the formation of the refractory panels are described. 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 coated with a ceramic corrosion protection layer 10. The corrosion protection layer 10 can best be seen in detail FIG. 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 means that active rear ventilation (pumping through a gas, e.g. air, under overpressure through the space 3 of the wall), which is complex in terms of construction, can be dispensed with. 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 its solid constituents have been mixed and before the addition of water, the paste contains 20-80%, preferably 35-75%, SiC as the most important constituent. Further components at this point are 10-50% Al2O3, 5-30% SiO2 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 (H2O) is added (so that the total amount is about 106%), which results in a pasty-liquid state of aggregation. All percentages are percentages by weight.

SiO2, Al2O3 and CaO react together with H2O, whereby a large part of H2O is broken down (chemically bound). The rest of the H2O evaporates during operation at the latest. The SiC reacts only minimally. The SiO2 contributes, among other things, to the strength of the corrosion protection layer. During hydration (setting) so-called calcium silicate hydrate fibers (Ca3S2H3) arise (grow), which combine with the three components SiO2, Al2O3 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 constituents of the ceramic paste are (data in percentages by weight): 38 17 42 3 49 15 33 3 57 12 28 3 63 10 24 3 72 8 17 3

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.

The anti-corrosion layer 10 is painted or sprayed onto the pipe wall 1 as a paste during the production of the wall 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 chosen so that the corrosion protection layer in the cured or set state has a thermal expansion coefficient that is as similar as possible (differing at most 10%) to the pipe wall or the base element in general. 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) Al2O3 proportion increased, as the following table shows, for example (weight percent here including water): 300 ° C 57 10 25 1 1 6 280 ° C 60 10 22 1 1 6 260 ° C 63 10 19 1 1 6

In the examples in the table above, the paste also contains a small amount of Fe2O3, which supports nitride formation and thereby hardening. However, this portion is not absolutely necessary and can therefore also be omitted.

The second exemplary embodiment of the refractory wall according to the invention shown in FIGS. 5-8 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 in FIGS. 1-4, 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 an intermediate space 3 between the protective lining 20 and the pipe wall 1 (FIGS. 6 and 8 ).

The pipe wall 1 forming the base element again consists of a plurality 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).

Similar to the embodiment shown in FIGS. 1-4, the protective cladding 20 consists of a large number of refractory plates 21 and 22 arranged next to and on top of one another, 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 completely surrounds the pipe wall 1. 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 gap 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 engaging in vertically continuous, inwardly widened grooves 22a (FIG. 8) in the plates 22.

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 the conventional wall described, for example, in WO 2016/109903 A1. 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 coated with a ceramic corrosion protection layer 10, which prevents leaks in the protective cladding 20 Flue gas that has penetrated into the space 3 between the protective lining 20 and the pipe wall 1 can attack the pipe wall 1. The anti-corrosion layer 10 can best be seen in the detail FIG. 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 not connected by webs, the tubes again being covered with the ceramic anti-corrosion layer already mentioned. Metallic base elements consisting of unconnected pipes (without a corrosion protection layer) are described, for example, in EP 2 754 961 A2.

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 (15)

1. Refractory wall (W), in particular for an incinerator, with at least one base element (1) and a refractory protective cladding (2; 20) made of refractory panels (21, 22) in front of the at least one base element (1), characterized in that the at least one base element (1) has a ceramic corrosion protection layer (10) on at least one side facing the protective cladding (2; 20). 2. Refractory wall (W) according to claim 1, characterized in that the ceramic corrosion protection layer (10) has a proportion of tricalcium aluminate and SiC which is at least 60% by weight. 3. Refractory wall (W) according to claim 1 or 2, characterized in that the corrosion protection layer (10) is a hydraulically set ceramic paste. 4. Refractory wall (W) according to one of the preceding claims, characterized in that the corrosion protection layer (10) has a thickness of 0.1-3 mm, preferably 0.9-1.1 mm. 5. Refractory wall (W) according to one of the preceding claims, characterized in that the corrosion protection layer (10) has a thermal expansion coefficient which does not deviate by more than 10% from the thermal expansion coefficient of the at least one base element (1). 6. Refractory wall (W) according to one of the preceding claims, characterized in that the at least one base element (1) is metallic. 7. Refractory wall (W) according to one of the preceding claims, characterized in that the at least one base element (1) comprises tubes (11) for the passage of a fluid medium. 8. Refractory wall according to one of the preceding claims, characterized in that the at least one base element (1) is designed as a pipe wall with pipes (11) connected by webs (12). 9. Fireproof wall (W) according to one of the preceding claims, characterized in that the fireproof protective cladding (2; 20) is arranged at a distance from 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 (3). 10. Refractory wall (W) according to one of the preceding claims, characterized in that the refractory plates (21, 22) are fastened to the at least one base element (1) via at least one plate holder (13) each. 11. Refractory wall according to one of the preceding claims, characterized in that the protective cladding (20) encloses the at least one base element (1) all around. 12. Refractory wall (W) according to one of the preceding claims, characterized in that the at least one base element (1) is a boiler wall. 13. A method for producing a refractory wall (W) according to one of the preceding claims, characterized in that a hydraulically setting ceramic paste is produced by mixing solid components and water, that this paste is applied as a corrosion protection layer to the at least one base element (1) , in particular painted on or sprayed on, and then caused to harden, and that the at least one base element (1) is placed in front of the at least one base element (1) after the ceramic paste has been applied, a refractory protective cladding (2; 20) made of refractory plates (21, 22). 14. The method according to claim 13, characterized in that the paste is a mixture of solid components and water and immediately after mixing its components, based on the totality of its solid components, a proportion of 20-80% by weight, preferably 35-75% by weight .%, Contains SiC. 15. The method according to claim 14, characterized in that the paste immediately after the mixing of its constituents, based on the totality of its solid constituents, has a proportion of 10-50% by weight Al2O3, 5-30% by weight SiO2 and 1-5% by weight Contains CaO.